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 applies when a single @code{break} command
4347 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4351 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4352 disabled within a @var{command-list}.
4354 You can use breakpoint commands to start your program up again. Simply
4355 use the @code{continue} command, or @code{step}, or any other command
4356 that resumes execution.
4358 Any other commands in the command list, after a command that resumes
4359 execution, are ignored. This is because any time you resume execution
4360 (even with a simple @code{next} or @code{step}), you may encounter
4361 another breakpoint---which could have its own command list, leading to
4362 ambiguities about which list to execute.
4365 If the first command you specify in a command list is @code{silent}, the
4366 usual message about stopping at a breakpoint is not printed. This may
4367 be desirable for breakpoints that are to print a specific message and
4368 then continue. If none of the remaining commands print anything, you
4369 see no sign that the breakpoint was reached. @code{silent} is
4370 meaningful only at the beginning of a breakpoint command list.
4372 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4373 print precisely controlled output, and are often useful in silent
4374 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4376 For example, here is how you could use breakpoint commands to print the
4377 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4383 printf "x is %d\n",x
4388 One application for breakpoint commands is to compensate for one bug so
4389 you can test for another. Put a breakpoint just after the erroneous line
4390 of code, give it a condition to detect the case in which something
4391 erroneous has been done, and give it commands to assign correct values
4392 to any variables that need them. End with the @code{continue} command
4393 so that your program does not stop, and start with the @code{silent}
4394 command so that no output is produced. Here is an example:
4405 @c @ifclear BARETARGET
4406 @node Error in Breakpoints
4407 @subsection ``Cannot insert breakpoints''
4409 If you request too many active hardware-assisted breakpoints and
4410 watchpoints, you will see this error message:
4412 @c FIXME: the precise wording of this message may change; the relevant
4413 @c source change is not committed yet (Sep 3, 1999).
4415 Stopped; cannot insert breakpoints.
4416 You may have requested too many hardware breakpoints and watchpoints.
4420 This message is printed when you attempt to resume the program, since
4421 only then @value{GDBN} knows exactly how many hardware breakpoints and
4422 watchpoints it needs to insert.
4424 When this message is printed, you need to disable or remove some of the
4425 hardware-assisted breakpoints and watchpoints, and then continue.
4427 @node Breakpoint-related Warnings
4428 @subsection ``Breakpoint address adjusted...''
4429 @cindex breakpoint address adjusted
4431 Some processor architectures place constraints on the addresses at
4432 which breakpoints may be placed. For architectures thus constrained,
4433 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4434 with the constraints dictated by the architecture.
4436 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4437 a VLIW architecture in which a number of RISC-like instructions may be
4438 bundled together for parallel execution. The FR-V architecture
4439 constrains the location of a breakpoint instruction within such a
4440 bundle to the instruction with the lowest address. @value{GDBN}
4441 honors this constraint by adjusting a breakpoint's address to the
4442 first in the bundle.
4444 It is not uncommon for optimized code to have bundles which contain
4445 instructions from different source statements, thus it may happen that
4446 a breakpoint's address will be adjusted from one source statement to
4447 another. Since this adjustment may significantly alter @value{GDBN}'s
4448 breakpoint related behavior from what the user expects, a warning is
4449 printed when the breakpoint is first set and also when the breakpoint
4452 A warning like the one below is printed when setting a breakpoint
4453 that's been subject to address adjustment:
4456 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4459 Such warnings are printed both for user settable and @value{GDBN}'s
4460 internal breakpoints. If you see one of these warnings, you should
4461 verify that a breakpoint set at the adjusted address will have the
4462 desired affect. If not, the breakpoint in question may be removed and
4463 other breakpoints may be set which will have the desired behavior.
4464 E.g., it may be sufficient to place the breakpoint at a later
4465 instruction. A conditional breakpoint may also be useful in some
4466 cases to prevent the breakpoint from triggering too often.
4468 @value{GDBN} will also issue a warning when stopping at one of these
4469 adjusted breakpoints:
4472 warning: Breakpoint 1 address previously adjusted from 0x00010414
4476 When this warning is encountered, it may be too late to take remedial
4477 action except in cases where the breakpoint is hit earlier or more
4478 frequently than expected.
4480 @node Continuing and Stepping
4481 @section Continuing and Stepping
4485 @cindex resuming execution
4486 @dfn{Continuing} means resuming program execution until your program
4487 completes normally. In contrast, @dfn{stepping} means executing just
4488 one more ``step'' of your program, where ``step'' may mean either one
4489 line of source code, or one machine instruction (depending on what
4490 particular command you use). Either when continuing or when stepping,
4491 your program may stop even sooner, due to a breakpoint or a signal. (If
4492 it stops due to a signal, you may want to use @code{handle}, or use
4493 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4497 @kindex c @r{(@code{continue})}
4498 @kindex fg @r{(resume foreground execution)}
4499 @item continue @r{[}@var{ignore-count}@r{]}
4500 @itemx c @r{[}@var{ignore-count}@r{]}
4501 @itemx fg @r{[}@var{ignore-count}@r{]}
4502 Resume program execution, at the address where your program last stopped;
4503 any breakpoints set at that address are bypassed. The optional argument
4504 @var{ignore-count} allows you to specify a further number of times to
4505 ignore a breakpoint at this location; its effect is like that of
4506 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4508 The argument @var{ignore-count} is meaningful only when your program
4509 stopped due to a breakpoint. At other times, the argument to
4510 @code{continue} is ignored.
4512 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4513 debugged program is deemed to be the foreground program) are provided
4514 purely for convenience, and have exactly the same behavior as
4518 To resume execution at a different place, you can use @code{return}
4519 (@pxref{Returning, ,Returning from a Function}) to go back to the
4520 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4521 Different Address}) to go to an arbitrary location in your program.
4523 A typical technique for using stepping is to set a breakpoint
4524 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4525 beginning of the function or the section of your program where a problem
4526 is believed to lie, run your program until it stops at that breakpoint,
4527 and then step through the suspect area, examining the variables that are
4528 interesting, until you see the problem happen.
4532 @kindex s @r{(@code{step})}
4534 Continue running your program until control reaches a different source
4535 line, then stop it and return control to @value{GDBN}. This command is
4536 abbreviated @code{s}.
4539 @c "without debugging information" is imprecise; actually "without line
4540 @c numbers in the debugging information". (gcc -g1 has debugging info but
4541 @c not line numbers). But it seems complex to try to make that
4542 @c distinction here.
4543 @emph{Warning:} If you use the @code{step} command while control is
4544 within a function that was compiled without debugging information,
4545 execution proceeds until control reaches a function that does have
4546 debugging information. Likewise, it will not step into a function which
4547 is compiled without debugging information. To step through functions
4548 without debugging information, use the @code{stepi} command, described
4552 The @code{step} command only stops at the first instruction of a source
4553 line. This prevents the multiple stops that could otherwise occur in
4554 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4555 to stop if a function that has debugging information is called within
4556 the line. In other words, @code{step} @emph{steps inside} any functions
4557 called within the line.
4559 Also, the @code{step} command only enters a function if there is line
4560 number information for the function. Otherwise it acts like the
4561 @code{next} command. This avoids problems when using @code{cc -gl}
4562 on MIPS machines. Previously, @code{step} entered subroutines if there
4563 was any debugging information about the routine.
4565 @item step @var{count}
4566 Continue running as in @code{step}, but do so @var{count} times. If a
4567 breakpoint is reached, or a signal not related to stepping occurs before
4568 @var{count} steps, stepping stops right away.
4571 @kindex n @r{(@code{next})}
4572 @item next @r{[}@var{count}@r{]}
4573 Continue to the next source line in the current (innermost) stack frame.
4574 This is similar to @code{step}, but function calls that appear within
4575 the line of code are executed without stopping. Execution stops when
4576 control reaches a different line of code at the original stack level
4577 that was executing when you gave the @code{next} command. This command
4578 is abbreviated @code{n}.
4580 An argument @var{count} is a repeat count, as for @code{step}.
4583 @c FIX ME!! Do we delete this, or is there a way it fits in with
4584 @c the following paragraph? --- Vctoria
4586 @c @code{next} within a function that lacks debugging information acts like
4587 @c @code{step}, but any function calls appearing within the code of the
4588 @c function are executed without stopping.
4590 The @code{next} command only stops at the first instruction of a
4591 source line. This prevents multiple stops that could otherwise occur in
4592 @code{switch} statements, @code{for} loops, etc.
4594 @kindex set step-mode
4596 @cindex functions without line info, and stepping
4597 @cindex stepping into functions with no line info
4598 @itemx set step-mode on
4599 The @code{set step-mode on} command causes the @code{step} command to
4600 stop at the first instruction of a function which contains no debug line
4601 information rather than stepping over it.
4603 This is useful in cases where you may be interested in inspecting the
4604 machine instructions of a function which has no symbolic info and do not
4605 want @value{GDBN} to automatically skip over this function.
4607 @item set step-mode off
4608 Causes the @code{step} command to step over any functions which contains no
4609 debug information. This is the default.
4611 @item show step-mode
4612 Show whether @value{GDBN} will stop in or step over functions without
4613 source line debug information.
4616 @kindex fin @r{(@code{finish})}
4618 Continue running until just after function in the selected stack frame
4619 returns. Print the returned value (if any). This command can be
4620 abbreviated as @code{fin}.
4622 Contrast this with the @code{return} command (@pxref{Returning,
4623 ,Returning from a Function}).
4626 @kindex u @r{(@code{until})}
4627 @cindex run until specified location
4630 Continue running until a source line past the current line, in the
4631 current stack frame, is reached. This command is used to avoid single
4632 stepping through a loop more than once. It is like the @code{next}
4633 command, except that when @code{until} encounters a jump, it
4634 automatically continues execution until the program counter is greater
4635 than the address of the jump.
4637 This means that when you reach the end of a loop after single stepping
4638 though it, @code{until} makes your program continue execution until it
4639 exits the loop. In contrast, a @code{next} command at the end of a loop
4640 simply steps back to the beginning of the loop, which forces you to step
4641 through the next iteration.
4643 @code{until} always stops your program if it attempts to exit the current
4646 @code{until} may produce somewhat counterintuitive results if the order
4647 of machine code does not match the order of the source lines. For
4648 example, in the following excerpt from a debugging session, the @code{f}
4649 (@code{frame}) command shows that execution is stopped at line
4650 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4654 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4656 (@value{GDBP}) until
4657 195 for ( ; argc > 0; NEXTARG) @{
4660 This happened because, for execution efficiency, the compiler had
4661 generated code for the loop closure test at the end, rather than the
4662 start, of the loop---even though the test in a C @code{for}-loop is
4663 written before the body of the loop. The @code{until} command appeared
4664 to step back to the beginning of the loop when it advanced to this
4665 expression; however, it has not really gone to an earlier
4666 statement---not in terms of the actual machine code.
4668 @code{until} with no argument works by means of single
4669 instruction stepping, and hence is slower than @code{until} with an
4672 @item until @var{location}
4673 @itemx u @var{location}
4674 Continue running your program until either the specified location is
4675 reached, or the current stack frame returns. @var{location} is any of
4676 the forms described in @ref{Specify Location}.
4677 This form of the command uses temporary breakpoints, and
4678 hence is quicker than @code{until} without an argument. The specified
4679 location is actually reached only if it is in the current frame. This
4680 implies that @code{until} can be used to skip over recursive function
4681 invocations. For instance in the code below, if the current location is
4682 line @code{96}, issuing @code{until 99} will execute the program up to
4683 line @code{99} in the same invocation of factorial, i.e., after the inner
4684 invocations have returned.
4687 94 int factorial (int value)
4689 96 if (value > 1) @{
4690 97 value *= factorial (value - 1);
4697 @kindex advance @var{location}
4698 @itemx advance @var{location}
4699 Continue running the program up to the given @var{location}. An argument is
4700 required, which should be of one of the forms described in
4701 @ref{Specify Location}.
4702 Execution will also stop upon exit from the current stack
4703 frame. This command is similar to @code{until}, but @code{advance} will
4704 not skip over recursive function calls, and the target location doesn't
4705 have to be in the same frame as the current one.
4709 @kindex si @r{(@code{stepi})}
4711 @itemx stepi @var{arg}
4713 Execute one machine instruction, then stop and return to the debugger.
4715 It is often useful to do @samp{display/i $pc} when stepping by machine
4716 instructions. This makes @value{GDBN} automatically display the next
4717 instruction to be executed, each time your program stops. @xref{Auto
4718 Display,, Automatic Display}.
4720 An argument is a repeat count, as in @code{step}.
4724 @kindex ni @r{(@code{nexti})}
4726 @itemx nexti @var{arg}
4728 Execute one machine instruction, but if it is a function call,
4729 proceed until the function returns.
4731 An argument is a repeat count, as in @code{next}.
4738 A signal is an asynchronous event that can happen in a program. The
4739 operating system defines the possible kinds of signals, and gives each
4740 kind a name and a number. For example, in Unix @code{SIGINT} is the
4741 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4742 @code{SIGSEGV} is the signal a program gets from referencing a place in
4743 memory far away from all the areas in use; @code{SIGALRM} occurs when
4744 the alarm clock timer goes off (which happens only if your program has
4745 requested an alarm).
4747 @cindex fatal signals
4748 Some signals, including @code{SIGALRM}, are a normal part of the
4749 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4750 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4751 program has not specified in advance some other way to handle the signal.
4752 @code{SIGINT} does not indicate an error in your program, but it is normally
4753 fatal so it can carry out the purpose of the interrupt: to kill the program.
4755 @value{GDBN} has the ability to detect any occurrence of a signal in your
4756 program. You can tell @value{GDBN} in advance what to do for each kind of
4759 @cindex handling signals
4760 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4761 @code{SIGALRM} be silently passed to your program
4762 (so as not to interfere with their role in the program's functioning)
4763 but to stop your program immediately whenever an error signal happens.
4764 You can change these settings with the @code{handle} command.
4767 @kindex info signals
4771 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4772 handle each one. You can use this to see the signal numbers of all
4773 the defined types of signals.
4775 @item info signals @var{sig}
4776 Similar, but print information only about the specified signal number.
4778 @code{info handle} is an alias for @code{info signals}.
4781 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4782 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4783 can be the number of a signal or its name (with or without the
4784 @samp{SIG} at the beginning); a list of signal numbers of the form
4785 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4786 known signals. Optional arguments @var{keywords}, described below,
4787 say what change to make.
4791 The keywords allowed by the @code{handle} command can be abbreviated.
4792 Their full names are:
4796 @value{GDBN} should not stop your program when this signal happens. It may
4797 still print a message telling you that the signal has come in.
4800 @value{GDBN} should stop your program when this signal happens. This implies
4801 the @code{print} keyword as well.
4804 @value{GDBN} should print a message when this signal happens.
4807 @value{GDBN} should not mention the occurrence of the signal at all. This
4808 implies the @code{nostop} keyword as well.
4812 @value{GDBN} should allow your program to see this signal; your program
4813 can handle the signal, or else it may terminate if the signal is fatal
4814 and not handled. @code{pass} and @code{noignore} are synonyms.
4818 @value{GDBN} should not allow your program to see this signal.
4819 @code{nopass} and @code{ignore} are synonyms.
4823 When a signal stops your program, the signal is not visible to the
4825 continue. Your program sees the signal then, if @code{pass} is in
4826 effect for the signal in question @emph{at that time}. In other words,
4827 after @value{GDBN} reports a signal, you can use the @code{handle}
4828 command with @code{pass} or @code{nopass} to control whether your
4829 program sees that signal when you continue.
4831 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4832 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4833 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4836 You can also use the @code{signal} command to prevent your program from
4837 seeing a signal, or cause it to see a signal it normally would not see,
4838 or to give it any signal at any time. For example, if your program stopped
4839 due to some sort of memory reference error, you might store correct
4840 values into the erroneous variables and continue, hoping to see more
4841 execution; but your program would probably terminate immediately as
4842 a result of the fatal signal once it saw the signal. To prevent this,
4843 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4846 @cindex extra signal information
4847 @anchor{extra signal information}
4849 On some targets, @value{GDBN} can inspect extra signal information
4850 associated with the intercepted signal, before it is actually
4851 delivered to the program being debugged. This information is exported
4852 by the convenience variable @code{$_siginfo}, and consists of data
4853 that is passed by the kernel to the signal handler at the time of the
4854 receipt of a signal. The data type of the information itself is
4855 target dependent. You can see the data type using the @code{ptype
4856 $_siginfo} command. On Unix systems, it typically corresponds to the
4857 standard @code{siginfo_t} type, as defined in the @file{signal.h}
4860 Here's an example, on a @sc{gnu}/Linux system, printing the stray
4861 referenced address that raised a segmentation fault.
4865 (@value{GDBP}) continue
4866 Program received signal SIGSEGV, Segmentation fault.
4867 0x0000000000400766 in main ()
4869 (@value{GDBP}) ptype $_siginfo
4876 struct @{...@} _kill;
4877 struct @{...@} _timer;
4879 struct @{...@} _sigchld;
4880 struct @{...@} _sigfault;
4881 struct @{...@} _sigpoll;
4884 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
4888 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
4889 $1 = (void *) 0x7ffff7ff7000
4893 Depending on target support, @code{$_siginfo} may also be writable.
4896 @section Stopping and Starting Multi-thread Programs
4898 @cindex stopped threads
4899 @cindex threads, stopped
4901 @cindex continuing threads
4902 @cindex threads, continuing
4904 @value{GDBN} supports debugging programs with multiple threads
4905 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
4906 are two modes of controlling execution of your program within the
4907 debugger. In the default mode, referred to as @dfn{all-stop mode},
4908 when any thread in your program stops (for example, at a breakpoint
4909 or while being stepped), all other threads in the program are also stopped by
4910 @value{GDBN}. On some targets, @value{GDBN} also supports
4911 @dfn{non-stop mode}, in which other threads can continue to run freely while
4912 you examine the stopped thread in the debugger.
4915 * All-Stop Mode:: All threads stop when GDB takes control
4916 * Non-Stop Mode:: Other threads continue to execute
4917 * Background Execution:: Running your program asynchronously
4918 * Thread-Specific Breakpoints:: Controlling breakpoints
4919 * Interrupted System Calls:: GDB may interfere with system calls
4923 @subsection All-Stop Mode
4925 @cindex all-stop mode
4927 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
4928 @emph{all} threads of execution stop, not just the current thread. This
4929 allows you to examine the overall state of the program, including
4930 switching between threads, without worrying that things may change
4933 Conversely, whenever you restart the program, @emph{all} threads start
4934 executing. @emph{This is true even when single-stepping} with commands
4935 like @code{step} or @code{next}.
4937 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4938 Since thread scheduling is up to your debugging target's operating
4939 system (not controlled by @value{GDBN}), other threads may
4940 execute more than one statement while the current thread completes a
4941 single step. Moreover, in general other threads stop in the middle of a
4942 statement, rather than at a clean statement boundary, when the program
4945 You might even find your program stopped in another thread after
4946 continuing or even single-stepping. This happens whenever some other
4947 thread runs into a breakpoint, a signal, or an exception before the
4948 first thread completes whatever you requested.
4950 @cindex automatic thread selection
4951 @cindex switching threads automatically
4952 @cindex threads, automatic switching
4953 Whenever @value{GDBN} stops your program, due to a breakpoint or a
4954 signal, it automatically selects the thread where that breakpoint or
4955 signal happened. @value{GDBN} alerts you to the context switch with a
4956 message such as @samp{[Switching to Thread @var{n}]} to identify the
4959 On some OSes, you can modify @value{GDBN}'s default behavior by
4960 locking the OS scheduler to allow only a single thread to run.
4963 @item set scheduler-locking @var{mode}
4964 @cindex scheduler locking mode
4965 @cindex lock scheduler
4966 Set the scheduler locking mode. If it is @code{off}, then there is no
4967 locking and any thread may run at any time. If @code{on}, then only the
4968 current thread may run when the inferior is resumed. The @code{step}
4969 mode optimizes for single-stepping; it prevents other threads
4970 from preempting the current thread while you are stepping, so that
4971 the focus of debugging does not change unexpectedly.
4972 Other threads only rarely (or never) get a chance to run
4973 when you step. They are more likely to run when you @samp{next} over a
4974 function call, and they are completely free to run when you use commands
4975 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4976 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
4977 the current thread away from the thread that you are debugging.
4979 @item show scheduler-locking
4980 Display the current scheduler locking mode.
4983 @cindex resume threads of multiple processes simultaneously
4984 By default, when you issue one of the execution commands such as
4985 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
4986 threads of the current inferior to run. For example, if @value{GDBN}
4987 is attached to two inferiors, each with two threads, the
4988 @code{continue} command resumes only the two threads of the current
4989 inferior. This is useful, for example, when you debug a program that
4990 forks and you want to hold the parent stopped (so that, for instance,
4991 it doesn't run to exit), while you debug the child. In other
4992 situations, you may not be interested in inspecting the current state
4993 of any of the processes @value{GDBN} is attached to, and you may want
4994 to resume them all until some breakpoint is hit. In the latter case,
4995 you can instruct @value{GDBN} to allow all threads of all the
4996 inferiors to run with the @w{@code{set schedule-multiple}} command.
4999 @kindex set schedule-multiple
5000 @item set schedule-multiple
5001 Set the mode for allowing threads of multiple processes to be resumed
5002 when an execution command is issued. When @code{on}, all threads of
5003 all processes are allowed to run. When @code{off}, only the threads
5004 of the current process are resumed. The default is @code{off}. The
5005 @code{scheduler-locking} mode takes precedence when set to @code{on},
5006 or while you are stepping and set to @code{step}.
5008 @item show schedule-multiple
5009 Display the current mode for resuming the execution of threads of
5014 @subsection Non-Stop Mode
5016 @cindex non-stop mode
5018 @c This section is really only a place-holder, and needs to be expanded
5019 @c with more details.
5021 For some multi-threaded targets, @value{GDBN} supports an optional
5022 mode of operation in which you can examine stopped program threads in
5023 the debugger while other threads continue to execute freely. This
5024 minimizes intrusion when debugging live systems, such as programs
5025 where some threads have real-time constraints or must continue to
5026 respond to external events. This is referred to as @dfn{non-stop} mode.
5028 In non-stop mode, when a thread stops to report a debugging event,
5029 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5030 threads as well, in contrast to the all-stop mode behavior. Additionally,
5031 execution commands such as @code{continue} and @code{step} apply by default
5032 only to the current thread in non-stop mode, rather than all threads as
5033 in all-stop mode. This allows you to control threads explicitly in
5034 ways that are not possible in all-stop mode --- for example, stepping
5035 one thread while allowing others to run freely, stepping
5036 one thread while holding all others stopped, or stepping several threads
5037 independently and simultaneously.
5039 To enter non-stop mode, use this sequence of commands before you run
5040 or attach to your program:
5043 # Enable the async interface.
5046 # If using the CLI, pagination breaks non-stop.
5049 # Finally, turn it on!
5053 You can use these commands to manipulate the non-stop mode setting:
5056 @kindex set non-stop
5057 @item set non-stop on
5058 Enable selection of non-stop mode.
5059 @item set non-stop off
5060 Disable selection of non-stop mode.
5061 @kindex show non-stop
5063 Show the current non-stop enablement setting.
5066 Note these commands only reflect whether non-stop mode is enabled,
5067 not whether the currently-executing program is being run in non-stop mode.
5068 In particular, the @code{set non-stop} preference is only consulted when
5069 @value{GDBN} starts or connects to the target program, and it is generally
5070 not possible to switch modes once debugging has started. Furthermore,
5071 since not all targets support non-stop mode, even when you have enabled
5072 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5075 In non-stop mode, all execution commands apply only to the current thread
5076 by default. That is, @code{continue} only continues one thread.
5077 To continue all threads, issue @code{continue -a} or @code{c -a}.
5079 You can use @value{GDBN}'s background execution commands
5080 (@pxref{Background Execution}) to run some threads in the background
5081 while you continue to examine or step others from @value{GDBN}.
5082 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5083 always executed asynchronously in non-stop mode.
5085 Suspending execution is done with the @code{interrupt} command when
5086 running in the background, or @kbd{Ctrl-c} during foreground execution.
5087 In all-stop mode, this stops the whole process;
5088 but in non-stop mode the interrupt applies only to the current thread.
5089 To stop the whole program, use @code{interrupt -a}.
5091 Other execution commands do not currently support the @code{-a} option.
5093 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5094 that thread current, as it does in all-stop mode. This is because the
5095 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5096 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5097 changed to a different thread just as you entered a command to operate on the
5098 previously current thread.
5100 @node Background Execution
5101 @subsection Background Execution
5103 @cindex foreground execution
5104 @cindex background execution
5105 @cindex asynchronous execution
5106 @cindex execution, foreground, background and asynchronous
5108 @value{GDBN}'s execution commands have two variants: the normal
5109 foreground (synchronous) behavior, and a background
5110 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5111 the program to report that some thread has stopped before prompting for
5112 another command. In background execution, @value{GDBN} immediately gives
5113 a command prompt so that you can issue other commands while your program runs.
5115 You need to explicitly enable asynchronous mode before you can use
5116 background execution commands. You can use these commands to
5117 manipulate the asynchronous mode setting:
5120 @kindex set target-async
5121 @item set target-async on
5122 Enable asynchronous mode.
5123 @item set target-async off
5124 Disable asynchronous mode.
5125 @kindex show target-async
5126 @item show target-async
5127 Show the current target-async setting.
5130 If the target doesn't support async mode, @value{GDBN} issues an error
5131 message if you attempt to use the background execution commands.
5133 To specify background execution, add a @code{&} to the command. For example,
5134 the background form of the @code{continue} command is @code{continue&}, or
5135 just @code{c&}. The execution commands that accept background execution
5141 @xref{Starting, , Starting your Program}.
5145 @xref{Attach, , Debugging an Already-running Process}.
5149 @xref{Continuing and Stepping, step}.
5153 @xref{Continuing and Stepping, stepi}.
5157 @xref{Continuing and Stepping, next}.
5161 @xref{Continuing and Stepping, nexti}.
5165 @xref{Continuing and Stepping, continue}.
5169 @xref{Continuing and Stepping, finish}.
5173 @xref{Continuing and Stepping, until}.
5177 Background execution is especially useful in conjunction with non-stop
5178 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5179 However, you can also use these commands in the normal all-stop mode with
5180 the restriction that you cannot issue another execution command until the
5181 previous one finishes. Examples of commands that are valid in all-stop
5182 mode while the program is running include @code{help} and @code{info break}.
5184 You can interrupt your program while it is running in the background by
5185 using the @code{interrupt} command.
5192 Suspend execution of the running program. In all-stop mode,
5193 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5194 only the current thread. To stop the whole program in non-stop mode,
5195 use @code{interrupt -a}.
5198 @node Thread-Specific Breakpoints
5199 @subsection Thread-Specific Breakpoints
5201 When your program has multiple threads (@pxref{Threads,, Debugging
5202 Programs with Multiple Threads}), you can choose whether to set
5203 breakpoints on all threads, or on a particular thread.
5206 @cindex breakpoints and threads
5207 @cindex thread breakpoints
5208 @kindex break @dots{} thread @var{threadno}
5209 @item break @var{linespec} thread @var{threadno}
5210 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5211 @var{linespec} specifies source lines; there are several ways of
5212 writing them (@pxref{Specify Location}), but the effect is always to
5213 specify some source line.
5215 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5216 to specify that you only want @value{GDBN} to stop the program when a
5217 particular thread reaches this breakpoint. @var{threadno} is one of the
5218 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5219 column of the @samp{info threads} display.
5221 If you do not specify @samp{thread @var{threadno}} when you set a
5222 breakpoint, the breakpoint applies to @emph{all} threads of your
5225 You can use the @code{thread} qualifier on conditional breakpoints as
5226 well; in this case, place @samp{thread @var{threadno}} before or
5227 after the breakpoint condition, like this:
5230 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5235 @node Interrupted System Calls
5236 @subsection Interrupted System Calls
5238 @cindex thread breakpoints and system calls
5239 @cindex system calls and thread breakpoints
5240 @cindex premature return from system calls
5241 There is an unfortunate side effect when using @value{GDBN} to debug
5242 multi-threaded programs. If one thread stops for a
5243 breakpoint, or for some other reason, and another thread is blocked in a
5244 system call, then the system call may return prematurely. This is a
5245 consequence of the interaction between multiple threads and the signals
5246 that @value{GDBN} uses to implement breakpoints and other events that
5249 To handle this problem, your program should check the return value of
5250 each system call and react appropriately. This is good programming
5253 For example, do not write code like this:
5259 The call to @code{sleep} will return early if a different thread stops
5260 at a breakpoint or for some other reason.
5262 Instead, write this:
5267 unslept = sleep (unslept);
5270 A system call is allowed to return early, so the system is still
5271 conforming to its specification. But @value{GDBN} does cause your
5272 multi-threaded program to behave differently than it would without
5275 Also, @value{GDBN} uses internal breakpoints in the thread library to
5276 monitor certain events such as thread creation and thread destruction.
5277 When such an event happens, a system call in another thread may return
5278 prematurely, even though your program does not appear to stop.
5281 @node Reverse Execution
5282 @chapter Running programs backward
5283 @cindex reverse execution
5284 @cindex running programs backward
5286 When you are debugging a program, it is not unusual to realize that
5287 you have gone too far, and some event of interest has already happened.
5288 If the target environment supports it, @value{GDBN} can allow you to
5289 ``rewind'' the program by running it backward.
5291 A target environment that supports reverse execution should be able
5292 to ``undo'' the changes in machine state that have taken place as the
5293 program was executing normally. Variables, registers etc.@: should
5294 revert to their previous values. Obviously this requires a great
5295 deal of sophistication on the part of the target environment; not
5296 all target environments can support reverse execution.
5298 When a program is executed in reverse, the instructions that
5299 have most recently been executed are ``un-executed'', in reverse
5300 order. The program counter runs backward, following the previous
5301 thread of execution in reverse. As each instruction is ``un-executed'',
5302 the values of memory and/or registers that were changed by that
5303 instruction are reverted to their previous states. After executing
5304 a piece of source code in reverse, all side effects of that code
5305 should be ``undone'', and all variables should be returned to their
5306 prior values@footnote{
5307 Note that some side effects are easier to undo than others. For instance,
5308 memory and registers are relatively easy, but device I/O is hard. Some
5309 targets may be able undo things like device I/O, and some may not.
5311 The contract between @value{GDBN} and the reverse executing target
5312 requires only that the target do something reasonable when
5313 @value{GDBN} tells it to execute backwards, and then report the
5314 results back to @value{GDBN}. Whatever the target reports back to
5315 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5316 assumes that the memory and registers that the target reports are in a
5317 consistant state, but @value{GDBN} accepts whatever it is given.
5320 If you are debugging in a target environment that supports
5321 reverse execution, @value{GDBN} provides the following commands.
5324 @kindex reverse-continue
5325 @kindex rc @r{(@code{reverse-continue})}
5326 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5327 @itemx rc @r{[}@var{ignore-count}@r{]}
5328 Beginning at the point where your program last stopped, start executing
5329 in reverse. Reverse execution will stop for breakpoints and synchronous
5330 exceptions (signals), just like normal execution. Behavior of
5331 asynchronous signals depends on the target environment.
5333 @kindex reverse-step
5334 @kindex rs @r{(@code{step})}
5335 @item reverse-step @r{[}@var{count}@r{]}
5336 Run the program backward until control reaches the start of a
5337 different source line; then stop it, and return control to @value{GDBN}.
5339 Like the @code{step} command, @code{reverse-step} will only stop
5340 at the beginning of a source line. It ``un-executes'' the previously
5341 executed source line. If the previous source line included calls to
5342 debuggable functions, @code{reverse-step} will step (backward) into
5343 the called function, stopping at the beginning of the @emph{last}
5344 statement in the called function (typically a return statement).
5346 Also, as with the @code{step} command, if non-debuggable functions are
5347 called, @code{reverse-step} will run thru them backward without stopping.
5349 @kindex reverse-stepi
5350 @kindex rsi @r{(@code{reverse-stepi})}
5351 @item reverse-stepi @r{[}@var{count}@r{]}
5352 Reverse-execute one machine instruction. Note that the instruction
5353 to be reverse-executed is @emph{not} the one pointed to by the program
5354 counter, but the instruction executed prior to that one. For instance,
5355 if the last instruction was a jump, @code{reverse-stepi} will take you
5356 back from the destination of the jump to the jump instruction itself.
5358 @kindex reverse-next
5359 @kindex rn @r{(@code{reverse-next})}
5360 @item reverse-next @r{[}@var{count}@r{]}
5361 Run backward to the beginning of the previous line executed in
5362 the current (innermost) stack frame. If the line contains function
5363 calls, they will be ``un-executed'' without stopping. Starting from
5364 the first line of a function, @code{reverse-next} will take you back
5365 to the caller of that function, @emph{before} the function was called,
5366 just as the normal @code{next} command would take you from the last
5367 line of a function back to its return to its caller
5368 @footnote{Unless the code is too heavily optimized.}.
5370 @kindex reverse-nexti
5371 @kindex rni @r{(@code{reverse-nexti})}
5372 @item reverse-nexti @r{[}@var{count}@r{]}
5373 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5374 in reverse, except that called functions are ``un-executed'' atomically.
5375 That is, if the previously executed instruction was a return from
5376 another function, @code{reverse-nexti} will continue to execute
5377 in reverse until the call to that function (from the current stack
5380 @kindex reverse-finish
5381 @item reverse-finish
5382 Just as the @code{finish} command takes you to the point where the
5383 current function returns, @code{reverse-finish} takes you to the point
5384 where it was called. Instead of ending up at the end of the current
5385 function invocation, you end up at the beginning.
5387 @kindex set exec-direction
5388 @item set exec-direction
5389 Set the direction of target execution.
5390 @itemx set exec-direction reverse
5391 @cindex execute forward or backward in time
5392 @value{GDBN} will perform all execution commands in reverse, until the
5393 exec-direction mode is changed to ``forward''. Affected commands include
5394 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5395 command cannot be used in reverse mode.
5396 @item set exec-direction forward
5397 @value{GDBN} will perform all execution commands in the normal fashion.
5398 This is the default.
5402 @node Process Record and Replay
5403 @chapter Recording Inferior's Execution and Replaying It
5404 @cindex process record and replay
5405 @cindex recording inferior's execution and replaying it
5407 On some platforms, @value{GDBN} provides a special @dfn{process record
5408 and replay} target that can record a log of the process execution, and
5409 replay it later with both forward and reverse execution commands.
5412 When this target is in use, if the execution log includes the record
5413 for the next instruction, @value{GDBN} will debug in @dfn{replay
5414 mode}. In the replay mode, the inferior does not really execute code
5415 instructions. Instead, all the events that normally happen during
5416 code execution are taken from the execution log. While code is not
5417 really executed in replay mode, the values of registers (including the
5418 program counter register) and the memory of the inferior are still
5419 changed as they normally would. Their contents are taken from the
5423 If the record for the next instruction is not in the execution log,
5424 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5425 inferior executes normally, and @value{GDBN} records the execution log
5428 The process record and replay target supports reverse execution
5429 (@pxref{Reverse Execution}), even if the platform on which the
5430 inferior runs does not. However, the reverse execution is limited in
5431 this case by the range of the instructions recorded in the execution
5432 log. In other words, reverse execution on platforms that don't
5433 support it directly can only be done in the replay mode.
5435 When debugging in the reverse direction, @value{GDBN} will work in
5436 replay mode as long as the execution log includes the record for the
5437 previous instruction; otherwise, it will work in record mode, if the
5438 platform supports reverse execution, or stop if not.
5440 For architecture environments that support process record and replay,
5441 @value{GDBN} provides the following commands:
5444 @kindex target record
5448 This command starts the process record and replay target. The process
5449 record and replay target can only debug a process that is already
5450 running. Therefore, you need first to start the process with the
5451 @kbd{run} or @kbd{start} commands, and then start the recording with
5452 the @kbd{target record} command.
5454 Both @code{record} and @code{rec} are aliases of @code{target record}.
5456 @cindex displaced stepping, and process record and replay
5457 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5458 will be automatically disabled when process record and replay target
5459 is started. That's because the process record and replay target
5460 doesn't support displaced stepping.
5462 @cindex non-stop mode, and process record and replay
5463 @cindex asynchronous execution, and process record and replay
5464 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5465 the asynchronous execution mode (@pxref{Background Execution}), the
5466 process record and replay target cannot be started because it doesn't
5467 support these two modes.
5472 Stop the process record and replay target. When process record and
5473 replay target stops, the entire execution log will be deleted and the
5474 inferior will either be terminated, or will remain in its final state.
5476 When you stop the process record and replay target in record mode (at
5477 the end of the execution log), the inferior will be stopped at the
5478 next instruction that would have been recorded. In other words, if
5479 you record for a while and then stop recording, the inferior process
5480 will be left in the same state as if the recording never happened.
5482 On the other hand, if the process record and replay target is stopped
5483 while in replay mode (that is, not at the end of the execution log,
5484 but at some earlier point), the inferior process will become ``live''
5485 at that earlier state, and it will then be possible to continue the
5486 usual ``live'' debugging of the process from that state.
5488 When the inferior process exits, or @value{GDBN} detaches from it,
5489 process record and replay target will automatically stop itself.
5491 @kindex set record insn-number-max
5492 @item set record insn-number-max @var{limit}
5493 Set the limit of instructions to be recorded. Default value is 200000.
5495 If @var{limit} is a positive number, then @value{GDBN} will start
5496 deleting instructions from the log once the number of the record
5497 instructions becomes greater than @var{limit}. For every new recorded
5498 instruction, @value{GDBN} will delete the earliest recorded
5499 instruction to keep the number of recorded instructions at the limit.
5500 (Since deleting recorded instructions loses information, @value{GDBN}
5501 lets you control what happens when the limit is reached, by means of
5502 the @code{stop-at-limit} option, described below.)
5504 If @var{limit} is zero, @value{GDBN} will never delete recorded
5505 instructions from the execution log. The number of recorded
5506 instructions is unlimited in this case.
5508 @kindex show record insn-number-max
5509 @item show record insn-number-max
5510 Show the limit of instructions to be recorded.
5512 @kindex set record stop-at-limit
5513 @item set record stop-at-limit
5514 Control the behavior when the number of recorded instructions reaches
5515 the limit. If ON (the default), @value{GDBN} will stop when the limit
5516 is reached for the first time and ask you whether you want to stop the
5517 inferior or continue running it and recording the execution log. If
5518 you decide to continue recording, each new recorded instruction will
5519 cause the oldest one to be deleted.
5521 If this option is OFF, @value{GDBN} will automatically delete the
5522 oldest record to make room for each new one, without asking.
5524 @kindex show record stop-at-limit
5525 @item show record stop-at-limit
5526 Show the current setting of @code{stop-at-limit}.
5530 Show various statistics about the state of process record and its
5531 in-memory execution log buffer, including:
5535 Whether in record mode or replay mode.
5537 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
5539 Highest recorded instruction number.
5541 Current instruction about to be replayed (if in replay mode).
5543 Number of instructions contained in the execution log.
5545 Maximum number of instructions that may be contained in the execution log.
5548 @kindex record delete
5551 When record target runs in replay mode (``in the past''), delete the
5552 subsequent execution log and begin to record a new execution log starting
5553 from the current address. This means you will abandon the previously
5554 recorded ``future'' and begin recording a new ``future''.
5559 @chapter Examining the Stack
5561 When your program has stopped, the first thing you need to know is where it
5562 stopped and how it got there.
5565 Each time your program performs a function call, information about the call
5567 That information includes the location of the call in your program,
5568 the arguments of the call,
5569 and the local variables of the function being called.
5570 The information is saved in a block of data called a @dfn{stack frame}.
5571 The stack frames are allocated in a region of memory called the @dfn{call
5574 When your program stops, the @value{GDBN} commands for examining the
5575 stack allow you to see all of this information.
5577 @cindex selected frame
5578 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5579 @value{GDBN} commands refer implicitly to the selected frame. In
5580 particular, whenever you ask @value{GDBN} for the value of a variable in
5581 your program, the value is found in the selected frame. There are
5582 special @value{GDBN} commands to select whichever frame you are
5583 interested in. @xref{Selection, ,Selecting a Frame}.
5585 When your program stops, @value{GDBN} automatically selects the
5586 currently executing frame and describes it briefly, similar to the
5587 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5590 * Frames:: Stack frames
5591 * Backtrace:: Backtraces
5592 * Selection:: Selecting a frame
5593 * Frame Info:: Information on a frame
5598 @section Stack Frames
5600 @cindex frame, definition
5602 The call stack is divided up into contiguous pieces called @dfn{stack
5603 frames}, or @dfn{frames} for short; each frame is the data associated
5604 with one call to one function. The frame contains the arguments given
5605 to the function, the function's local variables, and the address at
5606 which the function is executing.
5608 @cindex initial frame
5609 @cindex outermost frame
5610 @cindex innermost frame
5611 When your program is started, the stack has only one frame, that of the
5612 function @code{main}. This is called the @dfn{initial} frame or the
5613 @dfn{outermost} frame. Each time a function is called, a new frame is
5614 made. Each time a function returns, the frame for that function invocation
5615 is eliminated. If a function is recursive, there can be many frames for
5616 the same function. The frame for the function in which execution is
5617 actually occurring is called the @dfn{innermost} frame. This is the most
5618 recently created of all the stack frames that still exist.
5620 @cindex frame pointer
5621 Inside your program, stack frames are identified by their addresses. A
5622 stack frame consists of many bytes, each of which has its own address; each
5623 kind of computer has a convention for choosing one byte whose
5624 address serves as the address of the frame. Usually this address is kept
5625 in a register called the @dfn{frame pointer register}
5626 (@pxref{Registers, $fp}) while execution is going on in that frame.
5628 @cindex frame number
5629 @value{GDBN} assigns numbers to all existing stack frames, starting with
5630 zero for the innermost frame, one for the frame that called it,
5631 and so on upward. These numbers do not really exist in your program;
5632 they are assigned by @value{GDBN} to give you a way of designating stack
5633 frames in @value{GDBN} commands.
5635 @c The -fomit-frame-pointer below perennially causes hbox overflow
5636 @c underflow problems.
5637 @cindex frameless execution
5638 Some compilers provide a way to compile functions so that they operate
5639 without stack frames. (For example, the @value{NGCC} option
5641 @samp{-fomit-frame-pointer}
5643 generates functions without a frame.)
5644 This is occasionally done with heavily used library functions to save
5645 the frame setup time. @value{GDBN} has limited facilities for dealing
5646 with these function invocations. If the innermost function invocation
5647 has no stack frame, @value{GDBN} nevertheless regards it as though
5648 it had a separate frame, which is numbered zero as usual, allowing
5649 correct tracing of the function call chain. However, @value{GDBN} has
5650 no provision for frameless functions elsewhere in the stack.
5653 @kindex frame@r{, command}
5654 @cindex current stack frame
5655 @item frame @var{args}
5656 The @code{frame} command allows you to move from one stack frame to another,
5657 and to print the stack frame you select. @var{args} may be either the
5658 address of the frame or the stack frame number. Without an argument,
5659 @code{frame} prints the current stack frame.
5661 @kindex select-frame
5662 @cindex selecting frame silently
5664 The @code{select-frame} command allows you to move from one stack frame
5665 to another without printing the frame. This is the silent version of
5673 @cindex call stack traces
5674 A backtrace is a summary of how your program got where it is. It shows one
5675 line per frame, for many frames, starting with the currently executing
5676 frame (frame zero), followed by its caller (frame one), and on up the
5681 @kindex bt @r{(@code{backtrace})}
5684 Print a backtrace of the entire stack: one line per frame for all
5685 frames in the stack.
5687 You can stop the backtrace at any time by typing the system interrupt
5688 character, normally @kbd{Ctrl-c}.
5690 @item backtrace @var{n}
5692 Similar, but print only the innermost @var{n} frames.
5694 @item backtrace -@var{n}
5696 Similar, but print only the outermost @var{n} frames.
5698 @item backtrace full
5700 @itemx bt full @var{n}
5701 @itemx bt full -@var{n}
5702 Print the values of the local variables also. @var{n} specifies the
5703 number of frames to print, as described above.
5708 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5709 are additional aliases for @code{backtrace}.
5711 @cindex multiple threads, backtrace
5712 In a multi-threaded program, @value{GDBN} by default shows the
5713 backtrace only for the current thread. To display the backtrace for
5714 several or all of the threads, use the command @code{thread apply}
5715 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5716 apply all backtrace}, @value{GDBN} will display the backtrace for all
5717 the threads; this is handy when you debug a core dump of a
5718 multi-threaded program.
5720 Each line in the backtrace shows the frame number and the function name.
5721 The program counter value is also shown---unless you use @code{set
5722 print address off}. The backtrace also shows the source file name and
5723 line number, as well as the arguments to the function. The program
5724 counter value is omitted if it is at the beginning of the code for that
5727 Here is an example of a backtrace. It was made with the command
5728 @samp{bt 3}, so it shows the innermost three frames.
5732 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5734 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
5735 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5737 (More stack frames follow...)
5742 The display for frame zero does not begin with a program counter
5743 value, indicating that your program has stopped at the beginning of the
5744 code for line @code{993} of @code{builtin.c}.
5747 The value of parameter @code{data} in frame 1 has been replaced by
5748 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
5749 only if it is a scalar (integer, pointer, enumeration, etc). See command
5750 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
5751 on how to configure the way function parameter values are printed.
5753 @cindex value optimized out, in backtrace
5754 @cindex function call arguments, optimized out
5755 If your program was compiled with optimizations, some compilers will
5756 optimize away arguments passed to functions if those arguments are
5757 never used after the call. Such optimizations generate code that
5758 passes arguments through registers, but doesn't store those arguments
5759 in the stack frame. @value{GDBN} has no way of displaying such
5760 arguments in stack frames other than the innermost one. Here's what
5761 such a backtrace might look like:
5765 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5767 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
5768 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
5770 (More stack frames follow...)
5775 The values of arguments that were not saved in their stack frames are
5776 shown as @samp{<value optimized out>}.
5778 If you need to display the values of such optimized-out arguments,
5779 either deduce that from other variables whose values depend on the one
5780 you are interested in, or recompile without optimizations.
5782 @cindex backtrace beyond @code{main} function
5783 @cindex program entry point
5784 @cindex startup code, and backtrace
5785 Most programs have a standard user entry point---a place where system
5786 libraries and startup code transition into user code. For C this is
5787 @code{main}@footnote{
5788 Note that embedded programs (the so-called ``free-standing''
5789 environment) are not required to have a @code{main} function as the
5790 entry point. They could even have multiple entry points.}.
5791 When @value{GDBN} finds the entry function in a backtrace
5792 it will terminate the backtrace, to avoid tracing into highly
5793 system-specific (and generally uninteresting) code.
5795 If you need to examine the startup code, or limit the number of levels
5796 in a backtrace, you can change this behavior:
5799 @item set backtrace past-main
5800 @itemx set backtrace past-main on
5801 @kindex set backtrace
5802 Backtraces will continue past the user entry point.
5804 @item set backtrace past-main off
5805 Backtraces will stop when they encounter the user entry point. This is the
5808 @item show backtrace past-main
5809 @kindex show backtrace
5810 Display the current user entry point backtrace policy.
5812 @item set backtrace past-entry
5813 @itemx set backtrace past-entry on
5814 Backtraces will continue past the internal entry point of an application.
5815 This entry point is encoded by the linker when the application is built,
5816 and is likely before the user entry point @code{main} (or equivalent) is called.
5818 @item set backtrace past-entry off
5819 Backtraces will stop when they encounter the internal entry point of an
5820 application. This is the default.
5822 @item show backtrace past-entry
5823 Display the current internal entry point backtrace policy.
5825 @item set backtrace limit @var{n}
5826 @itemx set backtrace limit 0
5827 @cindex backtrace limit
5828 Limit the backtrace to @var{n} levels. A value of zero means
5831 @item show backtrace limit
5832 Display the current limit on backtrace levels.
5836 @section Selecting a Frame
5838 Most commands for examining the stack and other data in your program work on
5839 whichever stack frame is selected at the moment. Here are the commands for
5840 selecting a stack frame; all of them finish by printing a brief description
5841 of the stack frame just selected.
5844 @kindex frame@r{, selecting}
5845 @kindex f @r{(@code{frame})}
5848 Select frame number @var{n}. Recall that frame zero is the innermost
5849 (currently executing) frame, frame one is the frame that called the
5850 innermost one, and so on. The highest-numbered frame is the one for
5853 @item frame @var{addr}
5855 Select the frame at address @var{addr}. This is useful mainly if the
5856 chaining of stack frames has been damaged by a bug, making it
5857 impossible for @value{GDBN} to assign numbers properly to all frames. In
5858 addition, this can be useful when your program has multiple stacks and
5859 switches between them.
5861 On the SPARC architecture, @code{frame} needs two addresses to
5862 select an arbitrary frame: a frame pointer and a stack pointer.
5864 On the MIPS and Alpha architecture, it needs two addresses: a stack
5865 pointer and a program counter.
5867 On the 29k architecture, it needs three addresses: a register stack
5868 pointer, a program counter, and a memory stack pointer.
5872 Move @var{n} frames up the stack. For positive numbers @var{n}, this
5873 advances toward the outermost frame, to higher frame numbers, to frames
5874 that have existed longer. @var{n} defaults to one.
5877 @kindex do @r{(@code{down})}
5879 Move @var{n} frames down the stack. For positive numbers @var{n}, this
5880 advances toward the innermost frame, to lower frame numbers, to frames
5881 that were created more recently. @var{n} defaults to one. You may
5882 abbreviate @code{down} as @code{do}.
5885 All of these commands end by printing two lines of output describing the
5886 frame. The first line shows the frame number, the function name, the
5887 arguments, and the source file and line number of execution in that
5888 frame. The second line shows the text of that source line.
5896 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
5898 10 read_input_file (argv[i]);
5902 After such a printout, the @code{list} command with no arguments
5903 prints ten lines centered on the point of execution in the frame.
5904 You can also edit the program at the point of execution with your favorite
5905 editing program by typing @code{edit}.
5906 @xref{List, ,Printing Source Lines},
5910 @kindex down-silently
5912 @item up-silently @var{n}
5913 @itemx down-silently @var{n}
5914 These two commands are variants of @code{up} and @code{down},
5915 respectively; they differ in that they do their work silently, without
5916 causing display of the new frame. They are intended primarily for use
5917 in @value{GDBN} command scripts, where the output might be unnecessary and
5922 @section Information About a Frame
5924 There are several other commands to print information about the selected
5930 When used without any argument, this command does not change which
5931 frame is selected, but prints a brief description of the currently
5932 selected stack frame. It can be abbreviated @code{f}. With an
5933 argument, this command is used to select a stack frame.
5934 @xref{Selection, ,Selecting a Frame}.
5937 @kindex info f @r{(@code{info frame})}
5940 This command prints a verbose description of the selected stack frame,
5945 the address of the frame
5947 the address of the next frame down (called by this frame)
5949 the address of the next frame up (caller of this frame)
5951 the language in which the source code corresponding to this frame is written
5953 the address of the frame's arguments
5955 the address of the frame's local variables
5957 the program counter saved in it (the address of execution in the caller frame)
5959 which registers were saved in the frame
5962 @noindent The verbose description is useful when
5963 something has gone wrong that has made the stack format fail to fit
5964 the usual conventions.
5966 @item info frame @var{addr}
5967 @itemx info f @var{addr}
5968 Print a verbose description of the frame at address @var{addr}, without
5969 selecting that frame. The selected frame remains unchanged by this
5970 command. This requires the same kind of address (more than one for some
5971 architectures) that you specify in the @code{frame} command.
5972 @xref{Selection, ,Selecting a Frame}.
5976 Print the arguments of the selected frame, each on a separate line.
5980 Print the local variables of the selected frame, each on a separate
5981 line. These are all variables (declared either static or automatic)
5982 accessible at the point of execution of the selected frame.
5985 @cindex catch exceptions, list active handlers
5986 @cindex exception handlers, how to list
5988 Print a list of all the exception handlers that are active in the
5989 current stack frame at the current point of execution. To see other
5990 exception handlers, visit the associated frame (using the @code{up},
5991 @code{down}, or @code{frame} commands); then type @code{info catch}.
5992 @xref{Set Catchpoints, , Setting Catchpoints}.
5998 @chapter Examining Source Files
6000 @value{GDBN} can print parts of your program's source, since the debugging
6001 information recorded in the program tells @value{GDBN} what source files were
6002 used to build it. When your program stops, @value{GDBN} spontaneously prints
6003 the line where it stopped. Likewise, when you select a stack frame
6004 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6005 execution in that frame has stopped. You can print other portions of
6006 source files by explicit command.
6008 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6009 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6010 @value{GDBN} under @sc{gnu} Emacs}.
6013 * List:: Printing source lines
6014 * Specify Location:: How to specify code locations
6015 * Edit:: Editing source files
6016 * Search:: Searching source files
6017 * Source Path:: Specifying source directories
6018 * Machine Code:: Source and machine code
6022 @section Printing Source Lines
6025 @kindex l @r{(@code{list})}
6026 To print lines from a source file, use the @code{list} command
6027 (abbreviated @code{l}). By default, ten lines are printed.
6028 There are several ways to specify what part of the file you want to
6029 print; see @ref{Specify Location}, for the full list.
6031 Here are the forms of the @code{list} command most commonly used:
6034 @item list @var{linenum}
6035 Print lines centered around line number @var{linenum} in the
6036 current source file.
6038 @item list @var{function}
6039 Print lines centered around the beginning of function
6043 Print more lines. If the last lines printed were printed with a
6044 @code{list} command, this prints lines following the last lines
6045 printed; however, if the last line printed was a solitary line printed
6046 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6047 Stack}), this prints lines centered around that line.
6050 Print lines just before the lines last printed.
6053 @cindex @code{list}, how many lines to display
6054 By default, @value{GDBN} prints ten source lines with any of these forms of
6055 the @code{list} command. You can change this using @code{set listsize}:
6058 @kindex set listsize
6059 @item set listsize @var{count}
6060 Make the @code{list} command display @var{count} source lines (unless
6061 the @code{list} argument explicitly specifies some other number).
6063 @kindex show listsize
6065 Display the number of lines that @code{list} prints.
6068 Repeating a @code{list} command with @key{RET} discards the argument,
6069 so it is equivalent to typing just @code{list}. This is more useful
6070 than listing the same lines again. An exception is made for an
6071 argument of @samp{-}; that argument is preserved in repetition so that
6072 each repetition moves up in the source file.
6074 In general, the @code{list} command expects you to supply zero, one or two
6075 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6076 of writing them (@pxref{Specify Location}), but the effect is always
6077 to specify some source line.
6079 Here is a complete description of the possible arguments for @code{list}:
6082 @item list @var{linespec}
6083 Print lines centered around the line specified by @var{linespec}.
6085 @item list @var{first},@var{last}
6086 Print lines from @var{first} to @var{last}. Both arguments are
6087 linespecs. When a @code{list} command has two linespecs, and the
6088 source file of the second linespec is omitted, this refers to
6089 the same source file as the first linespec.
6091 @item list ,@var{last}
6092 Print lines ending with @var{last}.
6094 @item list @var{first},
6095 Print lines starting with @var{first}.
6098 Print lines just after the lines last printed.
6101 Print lines just before the lines last printed.
6104 As described in the preceding table.
6107 @node Specify Location
6108 @section Specifying a Location
6109 @cindex specifying location
6112 Several @value{GDBN} commands accept arguments that specify a location
6113 of your program's code. Since @value{GDBN} is a source-level
6114 debugger, a location usually specifies some line in the source code;
6115 for that reason, locations are also known as @dfn{linespecs}.
6117 Here are all the different ways of specifying a code location that
6118 @value{GDBN} understands:
6122 Specifies the line number @var{linenum} of the current source file.
6125 @itemx +@var{offset}
6126 Specifies the line @var{offset} lines before or after the @dfn{current
6127 line}. For the @code{list} command, the current line is the last one
6128 printed; for the breakpoint commands, this is the line at which
6129 execution stopped in the currently selected @dfn{stack frame}
6130 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6131 used as the second of the two linespecs in a @code{list} command,
6132 this specifies the line @var{offset} lines up or down from the first
6135 @item @var{filename}:@var{linenum}
6136 Specifies the line @var{linenum} in the source file @var{filename}.
6138 @item @var{function}
6139 Specifies the line that begins the body of the function @var{function}.
6140 For example, in C, this is the line with the open brace.
6142 @item @var{filename}:@var{function}
6143 Specifies the line that begins the body of the function @var{function}
6144 in the file @var{filename}. You only need the file name with a
6145 function name to avoid ambiguity when there are identically named
6146 functions in different source files.
6148 @item *@var{address}
6149 Specifies the program address @var{address}. For line-oriented
6150 commands, such as @code{list} and @code{edit}, this specifies a source
6151 line that contains @var{address}. For @code{break} and other
6152 breakpoint oriented commands, this can be used to set breakpoints in
6153 parts of your program which do not have debugging information or
6156 Here @var{address} may be any expression valid in the current working
6157 language (@pxref{Languages, working language}) that specifies a code
6158 address. In addition, as a convenience, @value{GDBN} extends the
6159 semantics of expressions used in locations to cover the situations
6160 that frequently happen during debugging. Here are the various forms
6164 @item @var{expression}
6165 Any expression valid in the current working language.
6167 @item @var{funcaddr}
6168 An address of a function or procedure derived from its name. In C,
6169 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6170 simply the function's name @var{function} (and actually a special case
6171 of a valid expression). In Pascal and Modula-2, this is
6172 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6173 (although the Pascal form also works).
6175 This form specifies the address of the function's first instruction,
6176 before the stack frame and arguments have been set up.
6178 @item '@var{filename}'::@var{funcaddr}
6179 Like @var{funcaddr} above, but also specifies the name of the source
6180 file explicitly. This is useful if the name of the function does not
6181 specify the function unambiguously, e.g., if there are several
6182 functions with identical names in different source files.
6189 @section Editing Source Files
6190 @cindex editing source files
6193 @kindex e @r{(@code{edit})}
6194 To edit the lines in a source file, use the @code{edit} command.
6195 The editing program of your choice
6196 is invoked with the current line set to
6197 the active line in the program.
6198 Alternatively, there are several ways to specify what part of the file you
6199 want to print if you want to see other parts of the program:
6202 @item edit @var{location}
6203 Edit the source file specified by @code{location}. Editing starts at
6204 that @var{location}, e.g., at the specified source line of the
6205 specified file. @xref{Specify Location}, for all the possible forms
6206 of the @var{location} argument; here are the forms of the @code{edit}
6207 command most commonly used:
6210 @item edit @var{number}
6211 Edit the current source file with @var{number} as the active line number.
6213 @item edit @var{function}
6214 Edit the file containing @var{function} at the beginning of its definition.
6219 @subsection Choosing your Editor
6220 You can customize @value{GDBN} to use any editor you want
6222 The only restriction is that your editor (say @code{ex}), recognizes the
6223 following command-line syntax:
6225 ex +@var{number} file
6227 The optional numeric value +@var{number} specifies the number of the line in
6228 the file where to start editing.}.
6229 By default, it is @file{@value{EDITOR}}, but you can change this
6230 by setting the environment variable @code{EDITOR} before using
6231 @value{GDBN}. For example, to configure @value{GDBN} to use the
6232 @code{vi} editor, you could use these commands with the @code{sh} shell:
6238 or in the @code{csh} shell,
6240 setenv EDITOR /usr/bin/vi
6245 @section Searching Source Files
6246 @cindex searching source files
6248 There are two commands for searching through the current source file for a
6253 @kindex forward-search
6254 @item forward-search @var{regexp}
6255 @itemx search @var{regexp}
6256 The command @samp{forward-search @var{regexp}} checks each line,
6257 starting with the one following the last line listed, for a match for
6258 @var{regexp}. It lists the line that is found. You can use the
6259 synonym @samp{search @var{regexp}} or abbreviate the command name as
6262 @kindex reverse-search
6263 @item reverse-search @var{regexp}
6264 The command @samp{reverse-search @var{regexp}} checks each line, starting
6265 with the one before the last line listed and going backward, for a match
6266 for @var{regexp}. It lists the line that is found. You can abbreviate
6267 this command as @code{rev}.
6271 @section Specifying Source Directories
6274 @cindex directories for source files
6275 Executable programs sometimes do not record the directories of the source
6276 files from which they were compiled, just the names. Even when they do,
6277 the directories could be moved between the compilation and your debugging
6278 session. @value{GDBN} has a list of directories to search for source files;
6279 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6280 it tries all the directories in the list, in the order they are present
6281 in the list, until it finds a file with the desired name.
6283 For example, suppose an executable references the file
6284 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6285 @file{/mnt/cross}. The file is first looked up literally; if this
6286 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6287 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6288 message is printed. @value{GDBN} does not look up the parts of the
6289 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6290 Likewise, the subdirectories of the source path are not searched: if
6291 the source path is @file{/mnt/cross}, and the binary refers to
6292 @file{foo.c}, @value{GDBN} would not find it under
6293 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6295 Plain file names, relative file names with leading directories, file
6296 names containing dots, etc.@: are all treated as described above; for
6297 instance, if the source path is @file{/mnt/cross}, and the source file
6298 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6299 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6300 that---@file{/mnt/cross/foo.c}.
6302 Note that the executable search path is @emph{not} used to locate the
6305 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6306 any information it has cached about where source files are found and where
6307 each line is in the file.
6311 When you start @value{GDBN}, its source path includes only @samp{cdir}
6312 and @samp{cwd}, in that order.
6313 To add other directories, use the @code{directory} command.
6315 The search path is used to find both program source files and @value{GDBN}
6316 script files (read using the @samp{-command} option and @samp{source} command).
6318 In addition to the source path, @value{GDBN} provides a set of commands
6319 that manage a list of source path substitution rules. A @dfn{substitution
6320 rule} specifies how to rewrite source directories stored in the program's
6321 debug information in case the sources were moved to a different
6322 directory between compilation and debugging. A rule is made of
6323 two strings, the first specifying what needs to be rewritten in
6324 the path, and the second specifying how it should be rewritten.
6325 In @ref{set substitute-path}, we name these two parts @var{from} and
6326 @var{to} respectively. @value{GDBN} does a simple string replacement
6327 of @var{from} with @var{to} at the start of the directory part of the
6328 source file name, and uses that result instead of the original file
6329 name to look up the sources.
6331 Using the previous example, suppose the @file{foo-1.0} tree has been
6332 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6333 @value{GDBN} to replace @file{/usr/src} in all source path names with
6334 @file{/mnt/cross}. The first lookup will then be
6335 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6336 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6337 substitution rule, use the @code{set substitute-path} command
6338 (@pxref{set substitute-path}).
6340 To avoid unexpected substitution results, a rule is applied only if the
6341 @var{from} part of the directory name ends at a directory separator.
6342 For instance, a rule substituting @file{/usr/source} into
6343 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6344 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6345 is applied only at the beginning of the directory name, this rule will
6346 not be applied to @file{/root/usr/source/baz.c} either.
6348 In many cases, you can achieve the same result using the @code{directory}
6349 command. However, @code{set substitute-path} can be more efficient in
6350 the case where the sources are organized in a complex tree with multiple
6351 subdirectories. With the @code{directory} command, you need to add each
6352 subdirectory of your project. If you moved the entire tree while
6353 preserving its internal organization, then @code{set substitute-path}
6354 allows you to direct the debugger to all the sources with one single
6357 @code{set substitute-path} is also more than just a shortcut command.
6358 The source path is only used if the file at the original location no
6359 longer exists. On the other hand, @code{set substitute-path} modifies
6360 the debugger behavior to look at the rewritten location instead. So, if
6361 for any reason a source file that is not relevant to your executable is
6362 located at the original location, a substitution rule is the only
6363 method available to point @value{GDBN} at the new location.
6365 @cindex @samp{--with-relocated-sources}
6366 @cindex default source path substitution
6367 You can configure a default source path substitution rule by
6368 configuring @value{GDBN} with the
6369 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6370 should be the name of a directory under @value{GDBN}'s configured
6371 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6372 directory names in debug information under @var{dir} will be adjusted
6373 automatically if the installed @value{GDBN} is moved to a new
6374 location. This is useful if @value{GDBN}, libraries or executables
6375 with debug information and corresponding source code are being moved
6379 @item directory @var{dirname} @dots{}
6380 @item dir @var{dirname} @dots{}
6381 Add directory @var{dirname} to the front of the source path. Several
6382 directory names may be given to this command, separated by @samp{:}
6383 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6384 part of absolute file names) or
6385 whitespace. You may specify a directory that is already in the source
6386 path; this moves it forward, so @value{GDBN} searches it sooner.
6390 @vindex $cdir@r{, convenience variable}
6391 @vindex $cwd@r{, convenience variable}
6392 @cindex compilation directory
6393 @cindex current directory
6394 @cindex working directory
6395 @cindex directory, current
6396 @cindex directory, compilation
6397 You can use the string @samp{$cdir} to refer to the compilation
6398 directory (if one is recorded), and @samp{$cwd} to refer to the current
6399 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6400 tracks the current working directory as it changes during your @value{GDBN}
6401 session, while the latter is immediately expanded to the current
6402 directory at the time you add an entry to the source path.
6405 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6407 @c RET-repeat for @code{directory} is explicitly disabled, but since
6408 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6410 @item show directories
6411 @kindex show directories
6412 Print the source path: show which directories it contains.
6414 @anchor{set substitute-path}
6415 @item set substitute-path @var{from} @var{to}
6416 @kindex set substitute-path
6417 Define a source path substitution rule, and add it at the end of the
6418 current list of existing substitution rules. If a rule with the same
6419 @var{from} was already defined, then the old rule is also deleted.
6421 For example, if the file @file{/foo/bar/baz.c} was moved to
6422 @file{/mnt/cross/baz.c}, then the command
6425 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6429 will tell @value{GDBN} to replace @samp{/usr/src} with
6430 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6431 @file{baz.c} even though it was moved.
6433 In the case when more than one substitution rule have been defined,
6434 the rules are evaluated one by one in the order where they have been
6435 defined. The first one matching, if any, is selected to perform
6438 For instance, if we had entered the following commands:
6441 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6442 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6446 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6447 @file{/mnt/include/defs.h} by using the first rule. However, it would
6448 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6449 @file{/mnt/src/lib/foo.c}.
6452 @item unset substitute-path [path]
6453 @kindex unset substitute-path
6454 If a path is specified, search the current list of substitution rules
6455 for a rule that would rewrite that path. Delete that rule if found.
6456 A warning is emitted by the debugger if no rule could be found.
6458 If no path is specified, then all substitution rules are deleted.
6460 @item show substitute-path [path]
6461 @kindex show substitute-path
6462 If a path is specified, then print the source path substitution rule
6463 which would rewrite that path, if any.
6465 If no path is specified, then print all existing source path substitution
6470 If your source path is cluttered with directories that are no longer of
6471 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6472 versions of source. You can correct the situation as follows:
6476 Use @code{directory} with no argument to reset the source path to its default value.
6479 Use @code{directory} with suitable arguments to reinstall the
6480 directories you want in the source path. You can add all the
6481 directories in one command.
6485 @section Source and Machine Code
6486 @cindex source line and its code address
6488 You can use the command @code{info line} to map source lines to program
6489 addresses (and vice versa), and the command @code{disassemble} to display
6490 a range of addresses as machine instructions. You can use the command
6491 @code{set disassemble-next-line} to set whether to disassemble next
6492 source line when execution stops. When run under @sc{gnu} Emacs
6493 mode, the @code{info line} command causes the arrow to point to the
6494 line specified. Also, @code{info line} prints addresses in symbolic form as
6499 @item info line @var{linespec}
6500 Print the starting and ending addresses of the compiled code for
6501 source line @var{linespec}. You can specify source lines in any of
6502 the ways documented in @ref{Specify Location}.
6505 For example, we can use @code{info line} to discover the location of
6506 the object code for the first line of function
6507 @code{m4_changequote}:
6509 @c FIXME: I think this example should also show the addresses in
6510 @c symbolic form, as they usually would be displayed.
6512 (@value{GDBP}) info line m4_changequote
6513 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6517 @cindex code address and its source line
6518 We can also inquire (using @code{*@var{addr}} as the form for
6519 @var{linespec}) what source line covers a particular address:
6521 (@value{GDBP}) info line *0x63ff
6522 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6525 @cindex @code{$_} and @code{info line}
6526 @cindex @code{x} command, default address
6527 @kindex x@r{(examine), and} info line
6528 After @code{info line}, the default address for the @code{x} command
6529 is changed to the starting address of the line, so that @samp{x/i} is
6530 sufficient to begin examining the machine code (@pxref{Memory,
6531 ,Examining Memory}). Also, this address is saved as the value of the
6532 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6537 @cindex assembly instructions
6538 @cindex instructions, assembly
6539 @cindex machine instructions
6540 @cindex listing machine instructions
6542 @itemx disassemble /m
6543 @itemx disassemble /r
6544 This specialized command dumps a range of memory as machine
6545 instructions. It can also print mixed source+disassembly by specifying
6546 the @code{/m} modifier and print the raw instructions in hex as well as
6547 in symbolic form by specifying the @code{/r}.
6548 The default memory range is the function surrounding the
6549 program counter of the selected frame. A single argument to this
6550 command is a program counter value; @value{GDBN} dumps the function
6551 surrounding this value. When two arguments are given, they should
6552 be separated by a comma, possibly surrounded by whitespace. The
6553 arguments specify a range of addresses (first inclusive, second exclusive)
6554 to dump. In that case, the name of the function is also printed (since
6555 there could be several functions in the given range).
6557 The argument(s) can be any expression yielding a numeric value, such as
6558 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
6560 If the range of memory being disassembled contains current program counter,
6561 the instruction at that location is shown with a @code{=>} marker.
6564 The following example shows the disassembly of a range of addresses of
6565 HP PA-RISC 2.0 code:
6568 (@value{GDBP}) disas 0x32c4, 0x32e4
6569 Dump of assembler code from 0x32c4 to 0x32e4:
6570 0x32c4 <main+204>: addil 0,dp
6571 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6572 0x32cc <main+212>: ldil 0x3000,r31
6573 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6574 0x32d4 <main+220>: ldo 0(r31),rp
6575 0x32d8 <main+224>: addil -0x800,dp
6576 0x32dc <main+228>: ldo 0x588(r1),r26
6577 0x32e0 <main+232>: ldil 0x3000,r31
6578 End of assembler dump.
6581 Here is an example showing mixed source+assembly for Intel x86, when the
6582 program is stopped just after function prologue:
6585 (@value{GDBP}) disas /m main
6586 Dump of assembler code for function main:
6588 0x08048330 <+0>: push %ebp
6589 0x08048331 <+1>: mov %esp,%ebp
6590 0x08048333 <+3>: sub $0x8,%esp
6591 0x08048336 <+6>: and $0xfffffff0,%esp
6592 0x08048339 <+9>: sub $0x10,%esp
6594 6 printf ("Hello.\n");
6595 => 0x0804833c <+12>: movl $0x8048440,(%esp)
6596 0x08048343 <+19>: call 0x8048284 <puts@@plt>
6600 0x08048348 <+24>: mov $0x0,%eax
6601 0x0804834d <+29>: leave
6602 0x0804834e <+30>: ret
6604 End of assembler dump.
6607 Some architectures have more than one commonly-used set of instruction
6608 mnemonics or other syntax.
6610 For programs that were dynamically linked and use shared libraries,
6611 instructions that call functions or branch to locations in the shared
6612 libraries might show a seemingly bogus location---it's actually a
6613 location of the relocation table. On some architectures, @value{GDBN}
6614 might be able to resolve these to actual function names.
6617 @kindex set disassembly-flavor
6618 @cindex Intel disassembly flavor
6619 @cindex AT&T disassembly flavor
6620 @item set disassembly-flavor @var{instruction-set}
6621 Select the instruction set to use when disassembling the
6622 program via the @code{disassemble} or @code{x/i} commands.
6624 Currently this command is only defined for the Intel x86 family. You
6625 can set @var{instruction-set} to either @code{intel} or @code{att}.
6626 The default is @code{att}, the AT&T flavor used by default by Unix
6627 assemblers for x86-based targets.
6629 @kindex show disassembly-flavor
6630 @item show disassembly-flavor
6631 Show the current setting of the disassembly flavor.
6635 @kindex set disassemble-next-line
6636 @kindex show disassemble-next-line
6637 @item set disassemble-next-line
6638 @itemx show disassemble-next-line
6639 Control whether or not @value{GDBN} will disassemble the next source
6640 line or instruction when execution stops. If ON, @value{GDBN} will
6641 display disassembly of the next source line when execution of the
6642 program being debugged stops. This is @emph{in addition} to
6643 displaying the source line itself, which @value{GDBN} always does if
6644 possible. If the next source line cannot be displayed for some reason
6645 (e.g., if @value{GDBN} cannot find the source file, or there's no line
6646 info in the debug info), @value{GDBN} will display disassembly of the
6647 next @emph{instruction} instead of showing the next source line. If
6648 AUTO, @value{GDBN} will display disassembly of next instruction only
6649 if the source line cannot be displayed. This setting causes
6650 @value{GDBN} to display some feedback when you step through a function
6651 with no line info or whose source file is unavailable. The default is
6652 OFF, which means never display the disassembly of the next line or
6658 @chapter Examining Data
6660 @cindex printing data
6661 @cindex examining data
6664 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6665 @c document because it is nonstandard... Under Epoch it displays in a
6666 @c different window or something like that.
6667 The usual way to examine data in your program is with the @code{print}
6668 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6669 evaluates and prints the value of an expression of the language your
6670 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6671 Different Languages}). It may also print the expression using a
6672 Python-based pretty-printer (@pxref{Pretty Printing}).
6675 @item print @var{expr}
6676 @itemx print /@var{f} @var{expr}
6677 @var{expr} is an expression (in the source language). By default the
6678 value of @var{expr} is printed in a format appropriate to its data type;
6679 you can choose a different format by specifying @samp{/@var{f}}, where
6680 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6684 @itemx print /@var{f}
6685 @cindex reprint the last value
6686 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6687 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6688 conveniently inspect the same value in an alternative format.
6691 A more low-level way of examining data is with the @code{x} command.
6692 It examines data in memory at a specified address and prints it in a
6693 specified format. @xref{Memory, ,Examining Memory}.
6695 If you are interested in information about types, or about how the
6696 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6697 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6701 * Expressions:: Expressions
6702 * Ambiguous Expressions:: Ambiguous Expressions
6703 * Variables:: Program variables
6704 * Arrays:: Artificial arrays
6705 * Output Formats:: Output formats
6706 * Memory:: Examining memory
6707 * Auto Display:: Automatic display
6708 * Print Settings:: Print settings
6709 * Value History:: Value history
6710 * Convenience Vars:: Convenience variables
6711 * Registers:: Registers
6712 * Floating Point Hardware:: Floating point hardware
6713 * Vector Unit:: Vector Unit
6714 * OS Information:: Auxiliary data provided by operating system
6715 * Memory Region Attributes:: Memory region attributes
6716 * Dump/Restore Files:: Copy between memory and a file
6717 * Core File Generation:: Cause a program dump its core
6718 * Character Sets:: Debugging programs that use a different
6719 character set than GDB does
6720 * Caching Remote Data:: Data caching for remote targets
6721 * Searching Memory:: Searching memory for a sequence of bytes
6725 @section Expressions
6728 @code{print} and many other @value{GDBN} commands accept an expression and
6729 compute its value. Any kind of constant, variable or operator defined
6730 by the programming language you are using is valid in an expression in
6731 @value{GDBN}. This includes conditional expressions, function calls,
6732 casts, and string constants. It also includes preprocessor macros, if
6733 you compiled your program to include this information; see
6736 @cindex arrays in expressions
6737 @value{GDBN} supports array constants in expressions input by
6738 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
6739 you can use the command @code{print @{1, 2, 3@}} to create an array
6740 of three integers. If you pass an array to a function or assign it
6741 to a program variable, @value{GDBN} copies the array to memory that
6742 is @code{malloc}ed in the target program.
6744 Because C is so widespread, most of the expressions shown in examples in
6745 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
6746 Languages}, for information on how to use expressions in other
6749 In this section, we discuss operators that you can use in @value{GDBN}
6750 expressions regardless of your programming language.
6752 @cindex casts, in expressions
6753 Casts are supported in all languages, not just in C, because it is so
6754 useful to cast a number into a pointer in order to examine a structure
6755 at that address in memory.
6756 @c FIXME: casts supported---Mod2 true?
6758 @value{GDBN} supports these operators, in addition to those common
6759 to programming languages:
6763 @samp{@@} is a binary operator for treating parts of memory as arrays.
6764 @xref{Arrays, ,Artificial Arrays}, for more information.
6767 @samp{::} allows you to specify a variable in terms of the file or
6768 function where it is defined. @xref{Variables, ,Program Variables}.
6770 @cindex @{@var{type}@}
6771 @cindex type casting memory
6772 @cindex memory, viewing as typed object
6773 @cindex casts, to view memory
6774 @item @{@var{type}@} @var{addr}
6775 Refers to an object of type @var{type} stored at address @var{addr} in
6776 memory. @var{addr} may be any expression whose value is an integer or
6777 pointer (but parentheses are required around binary operators, just as in
6778 a cast). This construct is allowed regardless of what kind of data is
6779 normally supposed to reside at @var{addr}.
6782 @node Ambiguous Expressions
6783 @section Ambiguous Expressions
6784 @cindex ambiguous expressions
6786 Expressions can sometimes contain some ambiguous elements. For instance,
6787 some programming languages (notably Ada, C@t{++} and Objective-C) permit
6788 a single function name to be defined several times, for application in
6789 different contexts. This is called @dfn{overloading}. Another example
6790 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
6791 templates and is typically instantiated several times, resulting in
6792 the same function name being defined in different contexts.
6794 In some cases and depending on the language, it is possible to adjust
6795 the expression to remove the ambiguity. For instance in C@t{++}, you
6796 can specify the signature of the function you want to break on, as in
6797 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
6798 qualified name of your function often makes the expression unambiguous
6801 When an ambiguity that needs to be resolved is detected, the debugger
6802 has the capability to display a menu of numbered choices for each
6803 possibility, and then waits for the selection with the prompt @samp{>}.
6804 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
6805 aborts the current command. If the command in which the expression was
6806 used allows more than one choice to be selected, the next option in the
6807 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
6810 For example, the following session excerpt shows an attempt to set a
6811 breakpoint at the overloaded symbol @code{String::after}.
6812 We choose three particular definitions of that function name:
6814 @c FIXME! This is likely to change to show arg type lists, at least
6817 (@value{GDBP}) b String::after
6820 [2] file:String.cc; line number:867
6821 [3] file:String.cc; line number:860
6822 [4] file:String.cc; line number:875
6823 [5] file:String.cc; line number:853
6824 [6] file:String.cc; line number:846
6825 [7] file:String.cc; line number:735
6827 Breakpoint 1 at 0xb26c: file String.cc, line 867.
6828 Breakpoint 2 at 0xb344: file String.cc, line 875.
6829 Breakpoint 3 at 0xafcc: file String.cc, line 846.
6830 Multiple breakpoints were set.
6831 Use the "delete" command to delete unwanted
6838 @kindex set multiple-symbols
6839 @item set multiple-symbols @var{mode}
6840 @cindex multiple-symbols menu
6842 This option allows you to adjust the debugger behavior when an expression
6845 By default, @var{mode} is set to @code{all}. If the command with which
6846 the expression is used allows more than one choice, then @value{GDBN}
6847 automatically selects all possible choices. For instance, inserting
6848 a breakpoint on a function using an ambiguous name results in a breakpoint
6849 inserted on each possible match. However, if a unique choice must be made,
6850 then @value{GDBN} uses the menu to help you disambiguate the expression.
6851 For instance, printing the address of an overloaded function will result
6852 in the use of the menu.
6854 When @var{mode} is set to @code{ask}, the debugger always uses the menu
6855 when an ambiguity is detected.
6857 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
6858 an error due to the ambiguity and the command is aborted.
6860 @kindex show multiple-symbols
6861 @item show multiple-symbols
6862 Show the current value of the @code{multiple-symbols} setting.
6866 @section Program Variables
6868 The most common kind of expression to use is the name of a variable
6871 Variables in expressions are understood in the selected stack frame
6872 (@pxref{Selection, ,Selecting a Frame}); they must be either:
6876 global (or file-static)
6883 visible according to the scope rules of the
6884 programming language from the point of execution in that frame
6887 @noindent This means that in the function
6902 you can examine and use the variable @code{a} whenever your program is
6903 executing within the function @code{foo}, but you can only use or
6904 examine the variable @code{b} while your program is executing inside
6905 the block where @code{b} is declared.
6907 @cindex variable name conflict
6908 There is an exception: you can refer to a variable or function whose
6909 scope is a single source file even if the current execution point is not
6910 in this file. But it is possible to have more than one such variable or
6911 function with the same name (in different source files). If that
6912 happens, referring to that name has unpredictable effects. If you wish,
6913 you can specify a static variable in a particular function or file,
6914 using the colon-colon (@code{::}) notation:
6916 @cindex colon-colon, context for variables/functions
6918 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
6919 @cindex @code{::}, context for variables/functions
6922 @var{file}::@var{variable}
6923 @var{function}::@var{variable}
6927 Here @var{file} or @var{function} is the name of the context for the
6928 static @var{variable}. In the case of file names, you can use quotes to
6929 make sure @value{GDBN} parses the file name as a single word---for example,
6930 to print a global value of @code{x} defined in @file{f2.c}:
6933 (@value{GDBP}) p 'f2.c'::x
6936 @cindex C@t{++} scope resolution
6937 This use of @samp{::} is very rarely in conflict with the very similar
6938 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
6939 scope resolution operator in @value{GDBN} expressions.
6940 @c FIXME: Um, so what happens in one of those rare cases where it's in
6943 @cindex wrong values
6944 @cindex variable values, wrong
6945 @cindex function entry/exit, wrong values of variables
6946 @cindex optimized code, wrong values of variables
6948 @emph{Warning:} Occasionally, a local variable may appear to have the
6949 wrong value at certain points in a function---just after entry to a new
6950 scope, and just before exit.
6952 You may see this problem when you are stepping by machine instructions.
6953 This is because, on most machines, it takes more than one instruction to
6954 set up a stack frame (including local variable definitions); if you are
6955 stepping by machine instructions, variables may appear to have the wrong
6956 values until the stack frame is completely built. On exit, it usually
6957 also takes more than one machine instruction to destroy a stack frame;
6958 after you begin stepping through that group of instructions, local
6959 variable definitions may be gone.
6961 This may also happen when the compiler does significant optimizations.
6962 To be sure of always seeing accurate values, turn off all optimization
6965 @cindex ``No symbol "foo" in current context''
6966 Another possible effect of compiler optimizations is to optimize
6967 unused variables out of existence, or assign variables to registers (as
6968 opposed to memory addresses). Depending on the support for such cases
6969 offered by the debug info format used by the compiler, @value{GDBN}
6970 might not be able to display values for such local variables. If that
6971 happens, @value{GDBN} will print a message like this:
6974 No symbol "foo" in current context.
6977 To solve such problems, either recompile without optimizations, or use a
6978 different debug info format, if the compiler supports several such
6979 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
6980 usually supports the @option{-gstabs+} option. @option{-gstabs+}
6981 produces debug info in a format that is superior to formats such as
6982 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
6983 an effective form for debug info. @xref{Debugging Options,,Options
6984 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
6985 Compiler Collection (GCC)}.
6986 @xref{C, ,C and C@t{++}}, for more information about debug info formats
6987 that are best suited to C@t{++} programs.
6989 If you ask to print an object whose contents are unknown to
6990 @value{GDBN}, e.g., because its data type is not completely specified
6991 by the debug information, @value{GDBN} will say @samp{<incomplete
6992 type>}. @xref{Symbols, incomplete type}, for more about this.
6994 Strings are identified as arrays of @code{char} values without specified
6995 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
6996 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
6997 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
6998 defines literal string type @code{"char"} as @code{char} without a sign.
7003 signed char var1[] = "A";
7006 You get during debugging
7011 $2 = @{65 'A', 0 '\0'@}
7015 @section Artificial Arrays
7017 @cindex artificial array
7019 @kindex @@@r{, referencing memory as an array}
7020 It is often useful to print out several successive objects of the
7021 same type in memory; a section of an array, or an array of
7022 dynamically determined size for which only a pointer exists in the
7025 You can do this by referring to a contiguous span of memory as an
7026 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7027 operand of @samp{@@} should be the first element of the desired array
7028 and be an individual object. The right operand should be the desired length
7029 of the array. The result is an array value whose elements are all of
7030 the type of the left argument. The first element is actually the left
7031 argument; the second element comes from bytes of memory immediately
7032 following those that hold the first element, and so on. Here is an
7033 example. If a program says
7036 int *array = (int *) malloc (len * sizeof (int));
7040 you can print the contents of @code{array} with
7046 The left operand of @samp{@@} must reside in memory. Array values made
7047 with @samp{@@} in this way behave just like other arrays in terms of
7048 subscripting, and are coerced to pointers when used in expressions.
7049 Artificial arrays most often appear in expressions via the value history
7050 (@pxref{Value History, ,Value History}), after printing one out.
7052 Another way to create an artificial array is to use a cast.
7053 This re-interprets a value as if it were an array.
7054 The value need not be in memory:
7056 (@value{GDBP}) p/x (short[2])0x12345678
7057 $1 = @{0x1234, 0x5678@}
7060 As a convenience, if you leave the array length out (as in
7061 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7062 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7064 (@value{GDBP}) p/x (short[])0x12345678
7065 $2 = @{0x1234, 0x5678@}
7068 Sometimes the artificial array mechanism is not quite enough; in
7069 moderately complex data structures, the elements of interest may not
7070 actually be adjacent---for example, if you are interested in the values
7071 of pointers in an array. One useful work-around in this situation is
7072 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7073 Variables}) as a counter in an expression that prints the first
7074 interesting value, and then repeat that expression via @key{RET}. For
7075 instance, suppose you have an array @code{dtab} of pointers to
7076 structures, and you are interested in the values of a field @code{fv}
7077 in each structure. Here is an example of what you might type:
7087 @node Output Formats
7088 @section Output Formats
7090 @cindex formatted output
7091 @cindex output formats
7092 By default, @value{GDBN} prints a value according to its data type. Sometimes
7093 this is not what you want. For example, you might want to print a number
7094 in hex, or a pointer in decimal. Or you might want to view data in memory
7095 at a certain address as a character string or as an instruction. To do
7096 these things, specify an @dfn{output format} when you print a value.
7098 The simplest use of output formats is to say how to print a value
7099 already computed. This is done by starting the arguments of the
7100 @code{print} command with a slash and a format letter. The format
7101 letters supported are:
7105 Regard the bits of the value as an integer, and print the integer in
7109 Print as integer in signed decimal.
7112 Print as integer in unsigned decimal.
7115 Print as integer in octal.
7118 Print as integer in binary. The letter @samp{t} stands for ``two''.
7119 @footnote{@samp{b} cannot be used because these format letters are also
7120 used with the @code{x} command, where @samp{b} stands for ``byte'';
7121 see @ref{Memory,,Examining Memory}.}
7124 @cindex unknown address, locating
7125 @cindex locate address
7126 Print as an address, both absolute in hexadecimal and as an offset from
7127 the nearest preceding symbol. You can use this format used to discover
7128 where (in what function) an unknown address is located:
7131 (@value{GDBP}) p/a 0x54320
7132 $3 = 0x54320 <_initialize_vx+396>
7136 The command @code{info symbol 0x54320} yields similar results.
7137 @xref{Symbols, info symbol}.
7140 Regard as an integer and print it as a character constant. This
7141 prints both the numerical value and its character representation. The
7142 character representation is replaced with the octal escape @samp{\nnn}
7143 for characters outside the 7-bit @sc{ascii} range.
7145 Without this format, @value{GDBN} displays @code{char},
7146 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7147 constants. Single-byte members of vectors are displayed as integer
7151 Regard the bits of the value as a floating point number and print
7152 using typical floating point syntax.
7155 @cindex printing strings
7156 @cindex printing byte arrays
7157 Regard as a string, if possible. With this format, pointers to single-byte
7158 data are displayed as null-terminated strings and arrays of single-byte data
7159 are displayed as fixed-length strings. Other values are displayed in their
7162 Without this format, @value{GDBN} displays pointers to and arrays of
7163 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7164 strings. Single-byte members of a vector are displayed as an integer
7168 @cindex raw printing
7169 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7170 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7171 Printing}). This typically results in a higher-level display of the
7172 value's contents. The @samp{r} format bypasses any Python
7173 pretty-printer which might exist.
7176 For example, to print the program counter in hex (@pxref{Registers}), type
7183 Note that no space is required before the slash; this is because command
7184 names in @value{GDBN} cannot contain a slash.
7186 To reprint the last value in the value history with a different format,
7187 you can use the @code{print} command with just a format and no
7188 expression. For example, @samp{p/x} reprints the last value in hex.
7191 @section Examining Memory
7193 You can use the command @code{x} (for ``examine'') to examine memory in
7194 any of several formats, independently of your program's data types.
7196 @cindex examining memory
7198 @kindex x @r{(examine memory)}
7199 @item x/@var{nfu} @var{addr}
7202 Use the @code{x} command to examine memory.
7205 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7206 much memory to display and how to format it; @var{addr} is an
7207 expression giving the address where you want to start displaying memory.
7208 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7209 Several commands set convenient defaults for @var{addr}.
7212 @item @var{n}, the repeat count
7213 The repeat count is a decimal integer; the default is 1. It specifies
7214 how much memory (counting by units @var{u}) to display.
7215 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7218 @item @var{f}, the display format
7219 The display format is one of the formats used by @code{print}
7220 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7221 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7222 The default is @samp{x} (hexadecimal) initially. The default changes
7223 each time you use either @code{x} or @code{print}.
7225 @item @var{u}, the unit size
7226 The unit size is any of
7232 Halfwords (two bytes).
7234 Words (four bytes). This is the initial default.
7236 Giant words (eight bytes).
7239 Each time you specify a unit size with @code{x}, that size becomes the
7240 default unit the next time you use @code{x}. (For the @samp{s} and
7241 @samp{i} formats, the unit size is ignored and is normally not written.)
7243 @item @var{addr}, starting display address
7244 @var{addr} is the address where you want @value{GDBN} to begin displaying
7245 memory. The expression need not have a pointer value (though it may);
7246 it is always interpreted as an integer address of a byte of memory.
7247 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7248 @var{addr} is usually just after the last address examined---but several
7249 other commands also set the default address: @code{info breakpoints} (to
7250 the address of the last breakpoint listed), @code{info line} (to the
7251 starting address of a line), and @code{print} (if you use it to display
7252 a value from memory).
7255 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7256 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7257 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7258 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7259 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7261 Since the letters indicating unit sizes are all distinct from the
7262 letters specifying output formats, you do not have to remember whether
7263 unit size or format comes first; either order works. The output
7264 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7265 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7267 Even though the unit size @var{u} is ignored for the formats @samp{s}
7268 and @samp{i}, you might still want to use a count @var{n}; for example,
7269 @samp{3i} specifies that you want to see three machine instructions,
7270 including any operands. For convenience, especially when used with
7271 the @code{display} command, the @samp{i} format also prints branch delay
7272 slot instructions, if any, beyond the count specified, which immediately
7273 follow the last instruction that is within the count. The command
7274 @code{disassemble} gives an alternative way of inspecting machine
7275 instructions; see @ref{Machine Code,,Source and Machine Code}.
7277 All the defaults for the arguments to @code{x} are designed to make it
7278 easy to continue scanning memory with minimal specifications each time
7279 you use @code{x}. For example, after you have inspected three machine
7280 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7281 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7282 the repeat count @var{n} is used again; the other arguments default as
7283 for successive uses of @code{x}.
7285 When examining machine instructions, the instruction at current program
7286 counter is shown with a @code{=>} marker. For example:
7289 (@value{GDBP}) x/5i $pc-6
7290 0x804837f <main+11>: mov %esp,%ebp
7291 0x8048381 <main+13>: push %ecx
7292 0x8048382 <main+14>: sub $0x4,%esp
7293 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7294 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7297 @cindex @code{$_}, @code{$__}, and value history
7298 The addresses and contents printed by the @code{x} command are not saved
7299 in the value history because there is often too much of them and they
7300 would get in the way. Instead, @value{GDBN} makes these values available for
7301 subsequent use in expressions as values of the convenience variables
7302 @code{$_} and @code{$__}. After an @code{x} command, the last address
7303 examined is available for use in expressions in the convenience variable
7304 @code{$_}. The contents of that address, as examined, are available in
7305 the convenience variable @code{$__}.
7307 If the @code{x} command has a repeat count, the address and contents saved
7308 are from the last memory unit printed; this is not the same as the last
7309 address printed if several units were printed on the last line of output.
7311 @cindex remote memory comparison
7312 @cindex verify remote memory image
7313 When you are debugging a program running on a remote target machine
7314 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7315 remote machine's memory against the executable file you downloaded to
7316 the target. The @code{compare-sections} command is provided for such
7320 @kindex compare-sections
7321 @item compare-sections @r{[}@var{section-name}@r{]}
7322 Compare the data of a loadable section @var{section-name} in the
7323 executable file of the program being debugged with the same section in
7324 the remote machine's memory, and report any mismatches. With no
7325 arguments, compares all loadable sections. This command's
7326 availability depends on the target's support for the @code{"qCRC"}
7331 @section Automatic Display
7332 @cindex automatic display
7333 @cindex display of expressions
7335 If you find that you want to print the value of an expression frequently
7336 (to see how it changes), you might want to add it to the @dfn{automatic
7337 display list} so that @value{GDBN} prints its value each time your program stops.
7338 Each expression added to the list is given a number to identify it;
7339 to remove an expression from the list, you specify that number.
7340 The automatic display looks like this:
7344 3: bar[5] = (struct hack *) 0x3804
7348 This display shows item numbers, expressions and their current values. As with
7349 displays you request manually using @code{x} or @code{print}, you can
7350 specify the output format you prefer; in fact, @code{display} decides
7351 whether to use @code{print} or @code{x} depending your format
7352 specification---it uses @code{x} if you specify either the @samp{i}
7353 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7357 @item display @var{expr}
7358 Add the expression @var{expr} to the list of expressions to display
7359 each time your program stops. @xref{Expressions, ,Expressions}.
7361 @code{display} does not repeat if you press @key{RET} again after using it.
7363 @item display/@var{fmt} @var{expr}
7364 For @var{fmt} specifying only a display format and not a size or
7365 count, add the expression @var{expr} to the auto-display list but
7366 arrange to display it each time in the specified format @var{fmt}.
7367 @xref{Output Formats,,Output Formats}.
7369 @item display/@var{fmt} @var{addr}
7370 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7371 number of units, add the expression @var{addr} as a memory address to
7372 be examined each time your program stops. Examining means in effect
7373 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7376 For example, @samp{display/i $pc} can be helpful, to see the machine
7377 instruction about to be executed each time execution stops (@samp{$pc}
7378 is a common name for the program counter; @pxref{Registers, ,Registers}).
7381 @kindex delete display
7383 @item undisplay @var{dnums}@dots{}
7384 @itemx delete display @var{dnums}@dots{}
7385 Remove item numbers @var{dnums} from the list of expressions to display.
7387 @code{undisplay} does not repeat if you press @key{RET} after using it.
7388 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7390 @kindex disable display
7391 @item disable display @var{dnums}@dots{}
7392 Disable the display of item numbers @var{dnums}. A disabled display
7393 item is not printed automatically, but is not forgotten. It may be
7394 enabled again later.
7396 @kindex enable display
7397 @item enable display @var{dnums}@dots{}
7398 Enable display of item numbers @var{dnums}. It becomes effective once
7399 again in auto display of its expression, until you specify otherwise.
7402 Display the current values of the expressions on the list, just as is
7403 done when your program stops.
7405 @kindex info display
7407 Print the list of expressions previously set up to display
7408 automatically, each one with its item number, but without showing the
7409 values. This includes disabled expressions, which are marked as such.
7410 It also includes expressions which would not be displayed right now
7411 because they refer to automatic variables not currently available.
7414 @cindex display disabled out of scope
7415 If a display expression refers to local variables, then it does not make
7416 sense outside the lexical context for which it was set up. Such an
7417 expression is disabled when execution enters a context where one of its
7418 variables is not defined. For example, if you give the command
7419 @code{display last_char} while inside a function with an argument
7420 @code{last_char}, @value{GDBN} displays this argument while your program
7421 continues to stop inside that function. When it stops elsewhere---where
7422 there is no variable @code{last_char}---the display is disabled
7423 automatically. The next time your program stops where @code{last_char}
7424 is meaningful, you can enable the display expression once again.
7426 @node Print Settings
7427 @section Print Settings
7429 @cindex format options
7430 @cindex print settings
7431 @value{GDBN} provides the following ways to control how arrays, structures,
7432 and symbols are printed.
7435 These settings are useful for debugging programs in any language:
7439 @item set print address
7440 @itemx set print address on
7441 @cindex print/don't print memory addresses
7442 @value{GDBN} prints memory addresses showing the location of stack
7443 traces, structure values, pointer values, breakpoints, and so forth,
7444 even when it also displays the contents of those addresses. The default
7445 is @code{on}. For example, this is what a stack frame display looks like with
7446 @code{set print address on}:
7451 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7453 530 if (lquote != def_lquote)
7457 @item set print address off
7458 Do not print addresses when displaying their contents. For example,
7459 this is the same stack frame displayed with @code{set print address off}:
7463 (@value{GDBP}) set print addr off
7465 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7466 530 if (lquote != def_lquote)
7470 You can use @samp{set print address off} to eliminate all machine
7471 dependent displays from the @value{GDBN} interface. For example, with
7472 @code{print address off}, you should get the same text for backtraces on
7473 all machines---whether or not they involve pointer arguments.
7476 @item show print address
7477 Show whether or not addresses are to be printed.
7480 When @value{GDBN} prints a symbolic address, it normally prints the
7481 closest earlier symbol plus an offset. If that symbol does not uniquely
7482 identify the address (for example, it is a name whose scope is a single
7483 source file), you may need to clarify. One way to do this is with
7484 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7485 you can set @value{GDBN} to print the source file and line number when
7486 it prints a symbolic address:
7489 @item set print symbol-filename on
7490 @cindex source file and line of a symbol
7491 @cindex symbol, source file and line
7492 Tell @value{GDBN} to print the source file name and line number of a
7493 symbol in the symbolic form of an address.
7495 @item set print symbol-filename off
7496 Do not print source file name and line number of a symbol. This is the
7499 @item show print symbol-filename
7500 Show whether or not @value{GDBN} will print the source file name and
7501 line number of a symbol in the symbolic form of an address.
7504 Another situation where it is helpful to show symbol filenames and line
7505 numbers is when disassembling code; @value{GDBN} shows you the line
7506 number and source file that corresponds to each instruction.
7508 Also, you may wish to see the symbolic form only if the address being
7509 printed is reasonably close to the closest earlier symbol:
7512 @item set print max-symbolic-offset @var{max-offset}
7513 @cindex maximum value for offset of closest symbol
7514 Tell @value{GDBN} to only display the symbolic form of an address if the
7515 offset between the closest earlier symbol and the address is less than
7516 @var{max-offset}. The default is 0, which tells @value{GDBN}
7517 to always print the symbolic form of an address if any symbol precedes it.
7519 @item show print max-symbolic-offset
7520 Ask how large the maximum offset is that @value{GDBN} prints in a
7524 @cindex wild pointer, interpreting
7525 @cindex pointer, finding referent
7526 If you have a pointer and you are not sure where it points, try
7527 @samp{set print symbol-filename on}. Then you can determine the name
7528 and source file location of the variable where it points, using
7529 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7530 For example, here @value{GDBN} shows that a variable @code{ptt} points
7531 at another variable @code{t}, defined in @file{hi2.c}:
7534 (@value{GDBP}) set print symbol-filename on
7535 (@value{GDBP}) p/a ptt
7536 $4 = 0xe008 <t in hi2.c>
7540 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
7541 does not show the symbol name and filename of the referent, even with
7542 the appropriate @code{set print} options turned on.
7545 Other settings control how different kinds of objects are printed:
7548 @item set print array
7549 @itemx set print array on
7550 @cindex pretty print arrays
7551 Pretty print arrays. This format is more convenient to read,
7552 but uses more space. The default is off.
7554 @item set print array off
7555 Return to compressed format for arrays.
7557 @item show print array
7558 Show whether compressed or pretty format is selected for displaying
7561 @cindex print array indexes
7562 @item set print array-indexes
7563 @itemx set print array-indexes on
7564 Print the index of each element when displaying arrays. May be more
7565 convenient to locate a given element in the array or quickly find the
7566 index of a given element in that printed array. The default is off.
7568 @item set print array-indexes off
7569 Stop printing element indexes when displaying arrays.
7571 @item show print array-indexes
7572 Show whether the index of each element is printed when displaying
7575 @item set print elements @var{number-of-elements}
7576 @cindex number of array elements to print
7577 @cindex limit on number of printed array elements
7578 Set a limit on how many elements of an array @value{GDBN} will print.
7579 If @value{GDBN} is printing a large array, it stops printing after it has
7580 printed the number of elements set by the @code{set print elements} command.
7581 This limit also applies to the display of strings.
7582 When @value{GDBN} starts, this limit is set to 200.
7583 Setting @var{number-of-elements} to zero means that the printing is unlimited.
7585 @item show print elements
7586 Display the number of elements of a large array that @value{GDBN} will print.
7587 If the number is 0, then the printing is unlimited.
7589 @item set print frame-arguments @var{value}
7590 @kindex set print frame-arguments
7591 @cindex printing frame argument values
7592 @cindex print all frame argument values
7593 @cindex print frame argument values for scalars only
7594 @cindex do not print frame argument values
7595 This command allows to control how the values of arguments are printed
7596 when the debugger prints a frame (@pxref{Frames}). The possible
7601 The values of all arguments are printed.
7604 Print the value of an argument only if it is a scalar. The value of more
7605 complex arguments such as arrays, structures, unions, etc, is replaced
7606 by @code{@dots{}}. This is the default. Here is an example where
7607 only scalar arguments are shown:
7610 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
7615 None of the argument values are printed. Instead, the value of each argument
7616 is replaced by @code{@dots{}}. In this case, the example above now becomes:
7619 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
7624 By default, only scalar arguments are printed. This command can be used
7625 to configure the debugger to print the value of all arguments, regardless
7626 of their type. However, it is often advantageous to not print the value
7627 of more complex parameters. For instance, it reduces the amount of
7628 information printed in each frame, making the backtrace more readable.
7629 Also, it improves performance when displaying Ada frames, because
7630 the computation of large arguments can sometimes be CPU-intensive,
7631 especially in large applications. Setting @code{print frame-arguments}
7632 to @code{scalars} (the default) or @code{none} avoids this computation,
7633 thus speeding up the display of each Ada frame.
7635 @item show print frame-arguments
7636 Show how the value of arguments should be displayed when printing a frame.
7638 @item set print repeats
7639 @cindex repeated array elements
7640 Set the threshold for suppressing display of repeated array
7641 elements. When the number of consecutive identical elements of an
7642 array exceeds the threshold, @value{GDBN} prints the string
7643 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
7644 identical repetitions, instead of displaying the identical elements
7645 themselves. Setting the threshold to zero will cause all elements to
7646 be individually printed. The default threshold is 10.
7648 @item show print repeats
7649 Display the current threshold for printing repeated identical
7652 @item set print null-stop
7653 @cindex @sc{null} elements in arrays
7654 Cause @value{GDBN} to stop printing the characters of an array when the first
7655 @sc{null} is encountered. This is useful when large arrays actually
7656 contain only short strings.
7659 @item show print null-stop
7660 Show whether @value{GDBN} stops printing an array on the first
7661 @sc{null} character.
7663 @item set print pretty on
7664 @cindex print structures in indented form
7665 @cindex indentation in structure display
7666 Cause @value{GDBN} to print structures in an indented format with one member
7667 per line, like this:
7682 @item set print pretty off
7683 Cause @value{GDBN} to print structures in a compact format, like this:
7687 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
7688 meat = 0x54 "Pork"@}
7693 This is the default format.
7695 @item show print pretty
7696 Show which format @value{GDBN} is using to print structures.
7698 @item set print sevenbit-strings on
7699 @cindex eight-bit characters in strings
7700 @cindex octal escapes in strings
7701 Print using only seven-bit characters; if this option is set,
7702 @value{GDBN} displays any eight-bit characters (in strings or
7703 character values) using the notation @code{\}@var{nnn}. This setting is
7704 best if you are working in English (@sc{ascii}) and you use the
7705 high-order bit of characters as a marker or ``meta'' bit.
7707 @item set print sevenbit-strings off
7708 Print full eight-bit characters. This allows the use of more
7709 international character sets, and is the default.
7711 @item show print sevenbit-strings
7712 Show whether or not @value{GDBN} is printing only seven-bit characters.
7714 @item set print union on
7715 @cindex unions in structures, printing
7716 Tell @value{GDBN} to print unions which are contained in structures
7717 and other unions. This is the default setting.
7719 @item set print union off
7720 Tell @value{GDBN} not to print unions which are contained in
7721 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
7724 @item show print union
7725 Ask @value{GDBN} whether or not it will print unions which are contained in
7726 structures and other unions.
7728 For example, given the declarations
7731 typedef enum @{Tree, Bug@} Species;
7732 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
7733 typedef enum @{Caterpillar, Cocoon, Butterfly@}
7744 struct thing foo = @{Tree, @{Acorn@}@};
7748 with @code{set print union on} in effect @samp{p foo} would print
7751 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
7755 and with @code{set print union off} in effect it would print
7758 $1 = @{it = Tree, form = @{...@}@}
7762 @code{set print union} affects programs written in C-like languages
7768 These settings are of interest when debugging C@t{++} programs:
7771 @cindex demangling C@t{++} names
7772 @item set print demangle
7773 @itemx set print demangle on
7774 Print C@t{++} names in their source form rather than in the encoded
7775 (``mangled'') form passed to the assembler and linker for type-safe
7776 linkage. The default is on.
7778 @item show print demangle
7779 Show whether C@t{++} names are printed in mangled or demangled form.
7781 @item set print asm-demangle
7782 @itemx set print asm-demangle on
7783 Print C@t{++} names in their source form rather than their mangled form, even
7784 in assembler code printouts such as instruction disassemblies.
7787 @item show print asm-demangle
7788 Show whether C@t{++} names in assembly listings are printed in mangled
7791 @cindex C@t{++} symbol decoding style
7792 @cindex symbol decoding style, C@t{++}
7793 @kindex set demangle-style
7794 @item set demangle-style @var{style}
7795 Choose among several encoding schemes used by different compilers to
7796 represent C@t{++} names. The choices for @var{style} are currently:
7800 Allow @value{GDBN} to choose a decoding style by inspecting your program.
7803 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
7804 This is the default.
7807 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
7810 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
7813 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
7814 @strong{Warning:} this setting alone is not sufficient to allow
7815 debugging @code{cfront}-generated executables. @value{GDBN} would
7816 require further enhancement to permit that.
7819 If you omit @var{style}, you will see a list of possible formats.
7821 @item show demangle-style
7822 Display the encoding style currently in use for decoding C@t{++} symbols.
7824 @item set print object
7825 @itemx set print object on
7826 @cindex derived type of an object, printing
7827 @cindex display derived types
7828 When displaying a pointer to an object, identify the @emph{actual}
7829 (derived) type of the object rather than the @emph{declared} type, using
7830 the virtual function table.
7832 @item set print object off
7833 Display only the declared type of objects, without reference to the
7834 virtual function table. This is the default setting.
7836 @item show print object
7837 Show whether actual, or declared, object types are displayed.
7839 @item set print static-members
7840 @itemx set print static-members on
7841 @cindex static members of C@t{++} objects
7842 Print static members when displaying a C@t{++} object. The default is on.
7844 @item set print static-members off
7845 Do not print static members when displaying a C@t{++} object.
7847 @item show print static-members
7848 Show whether C@t{++} static members are printed or not.
7850 @item set print pascal_static-members
7851 @itemx set print pascal_static-members on
7852 @cindex static members of Pascal objects
7853 @cindex Pascal objects, static members display
7854 Print static members when displaying a Pascal object. The default is on.
7856 @item set print pascal_static-members off
7857 Do not print static members when displaying a Pascal object.
7859 @item show print pascal_static-members
7860 Show whether Pascal static members are printed or not.
7862 @c These don't work with HP ANSI C++ yet.
7863 @item set print vtbl
7864 @itemx set print vtbl on
7865 @cindex pretty print C@t{++} virtual function tables
7866 @cindex virtual functions (C@t{++}) display
7867 @cindex VTBL display
7868 Pretty print C@t{++} virtual function tables. The default is off.
7869 (The @code{vtbl} commands do not work on programs compiled with the HP
7870 ANSI C@t{++} compiler (@code{aCC}).)
7872 @item set print vtbl off
7873 Do not pretty print C@t{++} virtual function tables.
7875 @item show print vtbl
7876 Show whether C@t{++} virtual function tables are pretty printed, or not.
7880 @section Value History
7882 @cindex value history
7883 @cindex history of values printed by @value{GDBN}
7884 Values printed by the @code{print} command are saved in the @value{GDBN}
7885 @dfn{value history}. This allows you to refer to them in other expressions.
7886 Values are kept until the symbol table is re-read or discarded
7887 (for example with the @code{file} or @code{symbol-file} commands).
7888 When the symbol table changes, the value history is discarded,
7889 since the values may contain pointers back to the types defined in the
7894 @cindex history number
7895 The values printed are given @dfn{history numbers} by which you can
7896 refer to them. These are successive integers starting with one.
7897 @code{print} shows you the history number assigned to a value by
7898 printing @samp{$@var{num} = } before the value; here @var{num} is the
7901 To refer to any previous value, use @samp{$} followed by the value's
7902 history number. The way @code{print} labels its output is designed to
7903 remind you of this. Just @code{$} refers to the most recent value in
7904 the history, and @code{$$} refers to the value before that.
7905 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
7906 is the value just prior to @code{$$}, @code{$$1} is equivalent to
7907 @code{$$}, and @code{$$0} is equivalent to @code{$}.
7909 For example, suppose you have just printed a pointer to a structure and
7910 want to see the contents of the structure. It suffices to type
7916 If you have a chain of structures where the component @code{next} points
7917 to the next one, you can print the contents of the next one with this:
7924 You can print successive links in the chain by repeating this
7925 command---which you can do by just typing @key{RET}.
7927 Note that the history records values, not expressions. If the value of
7928 @code{x} is 4 and you type these commands:
7936 then the value recorded in the value history by the @code{print} command
7937 remains 4 even though the value of @code{x} has changed.
7942 Print the last ten values in the value history, with their item numbers.
7943 This is like @samp{p@ $$9} repeated ten times, except that @code{show
7944 values} does not change the history.
7946 @item show values @var{n}
7947 Print ten history values centered on history item number @var{n}.
7950 Print ten history values just after the values last printed. If no more
7951 values are available, @code{show values +} produces no display.
7954 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
7955 same effect as @samp{show values +}.
7957 @node Convenience Vars
7958 @section Convenience Variables
7960 @cindex convenience variables
7961 @cindex user-defined variables
7962 @value{GDBN} provides @dfn{convenience variables} that you can use within
7963 @value{GDBN} to hold on to a value and refer to it later. These variables
7964 exist entirely within @value{GDBN}; they are not part of your program, and
7965 setting a convenience variable has no direct effect on further execution
7966 of your program. That is why you can use them freely.
7968 Convenience variables are prefixed with @samp{$}. Any name preceded by
7969 @samp{$} can be used for a convenience variable, unless it is one of
7970 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
7971 (Value history references, in contrast, are @emph{numbers} preceded
7972 by @samp{$}. @xref{Value History, ,Value History}.)
7974 You can save a value in a convenience variable with an assignment
7975 expression, just as you would set a variable in your program.
7979 set $foo = *object_ptr
7983 would save in @code{$foo} the value contained in the object pointed to by
7986 Using a convenience variable for the first time creates it, but its
7987 value is @code{void} until you assign a new value. You can alter the
7988 value with another assignment at any time.
7990 Convenience variables have no fixed types. You can assign a convenience
7991 variable any type of value, including structures and arrays, even if
7992 that variable already has a value of a different type. The convenience
7993 variable, when used as an expression, has the type of its current value.
7996 @kindex show convenience
7997 @cindex show all user variables
7998 @item show convenience
7999 Print a list of convenience variables used so far, and their values.
8000 Abbreviated @code{show conv}.
8002 @kindex init-if-undefined
8003 @cindex convenience variables, initializing
8004 @item init-if-undefined $@var{variable} = @var{expression}
8005 Set a convenience variable if it has not already been set. This is useful
8006 for user-defined commands that keep some state. It is similar, in concept,
8007 to using local static variables with initializers in C (except that
8008 convenience variables are global). It can also be used to allow users to
8009 override default values used in a command script.
8011 If the variable is already defined then the expression is not evaluated so
8012 any side-effects do not occur.
8015 One of the ways to use a convenience variable is as a counter to be
8016 incremented or a pointer to be advanced. For example, to print
8017 a field from successive elements of an array of structures:
8021 print bar[$i++]->contents
8025 Repeat that command by typing @key{RET}.
8027 Some convenience variables are created automatically by @value{GDBN} and given
8028 values likely to be useful.
8031 @vindex $_@r{, convenience variable}
8033 The variable @code{$_} is automatically set by the @code{x} command to
8034 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8035 commands which provide a default address for @code{x} to examine also
8036 set @code{$_} to that address; these commands include @code{info line}
8037 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8038 except when set by the @code{x} command, in which case it is a pointer
8039 to the type of @code{$__}.
8041 @vindex $__@r{, convenience variable}
8043 The variable @code{$__} is automatically set by the @code{x} command
8044 to the value found in the last address examined. Its type is chosen
8045 to match the format in which the data was printed.
8048 @vindex $_exitcode@r{, convenience variable}
8049 The variable @code{$_exitcode} is automatically set to the exit code when
8050 the program being debugged terminates.
8053 @vindex $_siginfo@r{, convenience variable}
8054 The variable @code{$_siginfo} contains extra signal information
8055 (@pxref{extra signal information}). Note that @code{$_siginfo}
8056 could be empty, if the application has not yet received any signals.
8057 For example, it will be empty before you execute the @code{run} command.
8060 On HP-UX systems, if you refer to a function or variable name that
8061 begins with a dollar sign, @value{GDBN} searches for a user or system
8062 name first, before it searches for a convenience variable.
8064 @cindex convenience functions
8065 @value{GDBN} also supplies some @dfn{convenience functions}. These
8066 have a syntax similar to convenience variables. A convenience
8067 function can be used in an expression just like an ordinary function;
8068 however, a convenience function is implemented internally to
8073 @kindex help function
8074 @cindex show all convenience functions
8075 Print a list of all convenience functions.
8082 You can refer to machine register contents, in expressions, as variables
8083 with names starting with @samp{$}. The names of registers are different
8084 for each machine; use @code{info registers} to see the names used on
8088 @kindex info registers
8089 @item info registers
8090 Print the names and values of all registers except floating-point
8091 and vector registers (in the selected stack frame).
8093 @kindex info all-registers
8094 @cindex floating point registers
8095 @item info all-registers
8096 Print the names and values of all registers, including floating-point
8097 and vector registers (in the selected stack frame).
8099 @item info registers @var{regname} @dots{}
8100 Print the @dfn{relativized} value of each specified register @var{regname}.
8101 As discussed in detail below, register values are normally relative to
8102 the selected stack frame. @var{regname} may be any register name valid on
8103 the machine you are using, with or without the initial @samp{$}.
8106 @cindex stack pointer register
8107 @cindex program counter register
8108 @cindex process status register
8109 @cindex frame pointer register
8110 @cindex standard registers
8111 @value{GDBN} has four ``standard'' register names that are available (in
8112 expressions) on most machines---whenever they do not conflict with an
8113 architecture's canonical mnemonics for registers. The register names
8114 @code{$pc} and @code{$sp} are used for the program counter register and
8115 the stack pointer. @code{$fp} is used for a register that contains a
8116 pointer to the current stack frame, and @code{$ps} is used for a
8117 register that contains the processor status. For example,
8118 you could print the program counter in hex with
8125 or print the instruction to be executed next with
8132 or add four to the stack pointer@footnote{This is a way of removing
8133 one word from the stack, on machines where stacks grow downward in
8134 memory (most machines, nowadays). This assumes that the innermost
8135 stack frame is selected; setting @code{$sp} is not allowed when other
8136 stack frames are selected. To pop entire frames off the stack,
8137 regardless of machine architecture, use @code{return};
8138 see @ref{Returning, ,Returning from a Function}.} with
8144 Whenever possible, these four standard register names are available on
8145 your machine even though the machine has different canonical mnemonics,
8146 so long as there is no conflict. The @code{info registers} command
8147 shows the canonical names. For example, on the SPARC, @code{info
8148 registers} displays the processor status register as @code{$psr} but you
8149 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
8150 is an alias for the @sc{eflags} register.
8152 @value{GDBN} always considers the contents of an ordinary register as an
8153 integer when the register is examined in this way. Some machines have
8154 special registers which can hold nothing but floating point; these
8155 registers are considered to have floating point values. There is no way
8156 to refer to the contents of an ordinary register as floating point value
8157 (although you can @emph{print} it as a floating point value with
8158 @samp{print/f $@var{regname}}).
8160 Some registers have distinct ``raw'' and ``virtual'' data formats. This
8161 means that the data format in which the register contents are saved by
8162 the operating system is not the same one that your program normally
8163 sees. For example, the registers of the 68881 floating point
8164 coprocessor are always saved in ``extended'' (raw) format, but all C
8165 programs expect to work with ``double'' (virtual) format. In such
8166 cases, @value{GDBN} normally works with the virtual format only (the format
8167 that makes sense for your program), but the @code{info registers} command
8168 prints the data in both formats.
8170 @cindex SSE registers (x86)
8171 @cindex MMX registers (x86)
8172 Some machines have special registers whose contents can be interpreted
8173 in several different ways. For example, modern x86-based machines
8174 have SSE and MMX registers that can hold several values packed
8175 together in several different formats. @value{GDBN} refers to such
8176 registers in @code{struct} notation:
8179 (@value{GDBP}) print $xmm1
8181 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
8182 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
8183 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
8184 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
8185 v4_int32 = @{0, 20657912, 11, 13@},
8186 v2_int64 = @{88725056443645952, 55834574859@},
8187 uint128 = 0x0000000d0000000b013b36f800000000
8192 To set values of such registers, you need to tell @value{GDBN} which
8193 view of the register you wish to change, as if you were assigning
8194 value to a @code{struct} member:
8197 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
8200 Normally, register values are relative to the selected stack frame
8201 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
8202 value that the register would contain if all stack frames farther in
8203 were exited and their saved registers restored. In order to see the
8204 true contents of hardware registers, you must select the innermost
8205 frame (with @samp{frame 0}).
8207 However, @value{GDBN} must deduce where registers are saved, from the machine
8208 code generated by your compiler. If some registers are not saved, or if
8209 @value{GDBN} is unable to locate the saved registers, the selected stack
8210 frame makes no difference.
8212 @node Floating Point Hardware
8213 @section Floating Point Hardware
8214 @cindex floating point
8216 Depending on the configuration, @value{GDBN} may be able to give
8217 you more information about the status of the floating point hardware.
8222 Display hardware-dependent information about the floating
8223 point unit. The exact contents and layout vary depending on the
8224 floating point chip. Currently, @samp{info float} is supported on
8225 the ARM and x86 machines.
8229 @section Vector Unit
8232 Depending on the configuration, @value{GDBN} may be able to give you
8233 more information about the status of the vector unit.
8238 Display information about the vector unit. The exact contents and
8239 layout vary depending on the hardware.
8242 @node OS Information
8243 @section Operating System Auxiliary Information
8244 @cindex OS information
8246 @value{GDBN} provides interfaces to useful OS facilities that can help
8247 you debug your program.
8249 @cindex @code{ptrace} system call
8250 @cindex @code{struct user} contents
8251 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
8252 machines), it interfaces with the inferior via the @code{ptrace}
8253 system call. The operating system creates a special sata structure,
8254 called @code{struct user}, for this interface. You can use the
8255 command @code{info udot} to display the contents of this data
8261 Display the contents of the @code{struct user} maintained by the OS
8262 kernel for the program being debugged. @value{GDBN} displays the
8263 contents of @code{struct user} as a list of hex numbers, similar to
8264 the @code{examine} command.
8267 @cindex auxiliary vector
8268 @cindex vector, auxiliary
8269 Some operating systems supply an @dfn{auxiliary vector} to programs at
8270 startup. This is akin to the arguments and environment that you
8271 specify for a program, but contains a system-dependent variety of
8272 binary values that tell system libraries important details about the
8273 hardware, operating system, and process. Each value's purpose is
8274 identified by an integer tag; the meanings are well-known but system-specific.
8275 Depending on the configuration and operating system facilities,
8276 @value{GDBN} may be able to show you this information. For remote
8277 targets, this functionality may further depend on the remote stub's
8278 support of the @samp{qXfer:auxv:read} packet, see
8279 @ref{qXfer auxiliary vector read}.
8284 Display the auxiliary vector of the inferior, which can be either a
8285 live process or a core dump file. @value{GDBN} prints each tag value
8286 numerically, and also shows names and text descriptions for recognized
8287 tags. Some values in the vector are numbers, some bit masks, and some
8288 pointers to strings or other data. @value{GDBN} displays each value in the
8289 most appropriate form for a recognized tag, and in hexadecimal for
8290 an unrecognized tag.
8293 On some targets, @value{GDBN} can access operating-system-specific information
8294 and display it to user, without interpretation. For remote targets,
8295 this functionality depends on the remote stub's support of the
8296 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
8299 @kindex info os processes
8300 @item info os processes
8301 Display the list of processes on the target. For each process,
8302 @value{GDBN} prints the process identifier, the name of the user, and
8303 the command corresponding to the process.
8306 @node Memory Region Attributes
8307 @section Memory Region Attributes
8308 @cindex memory region attributes
8310 @dfn{Memory region attributes} allow you to describe special handling
8311 required by regions of your target's memory. @value{GDBN} uses
8312 attributes to determine whether to allow certain types of memory
8313 accesses; whether to use specific width accesses; and whether to cache
8314 target memory. By default the description of memory regions is
8315 fetched from the target (if the current target supports this), but the
8316 user can override the fetched regions.
8318 Defined memory regions can be individually enabled and disabled. When a
8319 memory region is disabled, @value{GDBN} uses the default attributes when
8320 accessing memory in that region. Similarly, if no memory regions have
8321 been defined, @value{GDBN} uses the default attributes when accessing
8324 When a memory region is defined, it is given a number to identify it;
8325 to enable, disable, or remove a memory region, you specify that number.
8329 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
8330 Define a memory region bounded by @var{lower} and @var{upper} with
8331 attributes @var{attributes}@dots{}, and add it to the list of regions
8332 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
8333 case: it is treated as the target's maximum memory address.
8334 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
8337 Discard any user changes to the memory regions and use target-supplied
8338 regions, if available, or no regions if the target does not support.
8341 @item delete mem @var{nums}@dots{}
8342 Remove memory regions @var{nums}@dots{} from the list of regions
8343 monitored by @value{GDBN}.
8346 @item disable mem @var{nums}@dots{}
8347 Disable monitoring of memory regions @var{nums}@dots{}.
8348 A disabled memory region is not forgotten.
8349 It may be enabled again later.
8352 @item enable mem @var{nums}@dots{}
8353 Enable monitoring of memory regions @var{nums}@dots{}.
8357 Print a table of all defined memory regions, with the following columns
8361 @item Memory Region Number
8362 @item Enabled or Disabled.
8363 Enabled memory regions are marked with @samp{y}.
8364 Disabled memory regions are marked with @samp{n}.
8367 The address defining the inclusive lower bound of the memory region.
8370 The address defining the exclusive upper bound of the memory region.
8373 The list of attributes set for this memory region.
8378 @subsection Attributes
8380 @subsubsection Memory Access Mode
8381 The access mode attributes set whether @value{GDBN} may make read or
8382 write accesses to a memory region.
8384 While these attributes prevent @value{GDBN} from performing invalid
8385 memory accesses, they do nothing to prevent the target system, I/O DMA,
8386 etc.@: from accessing memory.
8390 Memory is read only.
8392 Memory is write only.
8394 Memory is read/write. This is the default.
8397 @subsubsection Memory Access Size
8398 The access size attribute tells @value{GDBN} to use specific sized
8399 accesses in the memory region. Often memory mapped device registers
8400 require specific sized accesses. If no access size attribute is
8401 specified, @value{GDBN} may use accesses of any size.
8405 Use 8 bit memory accesses.
8407 Use 16 bit memory accesses.
8409 Use 32 bit memory accesses.
8411 Use 64 bit memory accesses.
8414 @c @subsubsection Hardware/Software Breakpoints
8415 @c The hardware/software breakpoint attributes set whether @value{GDBN}
8416 @c will use hardware or software breakpoints for the internal breakpoints
8417 @c used by the step, next, finish, until, etc. commands.
8421 @c Always use hardware breakpoints
8422 @c @item swbreak (default)
8425 @subsubsection Data Cache
8426 The data cache attributes set whether @value{GDBN} will cache target
8427 memory. While this generally improves performance by reducing debug
8428 protocol overhead, it can lead to incorrect results because @value{GDBN}
8429 does not know about volatile variables or memory mapped device
8434 Enable @value{GDBN} to cache target memory.
8436 Disable @value{GDBN} from caching target memory. This is the default.
8439 @subsection Memory Access Checking
8440 @value{GDBN} can be instructed to refuse accesses to memory that is
8441 not explicitly described. This can be useful if accessing such
8442 regions has undesired effects for a specific target, or to provide
8443 better error checking. The following commands control this behaviour.
8446 @kindex set mem inaccessible-by-default
8447 @item set mem inaccessible-by-default [on|off]
8448 If @code{on} is specified, make @value{GDBN} treat memory not
8449 explicitly described by the memory ranges as non-existent and refuse accesses
8450 to such memory. The checks are only performed if there's at least one
8451 memory range defined. If @code{off} is specified, make @value{GDBN}
8452 treat the memory not explicitly described by the memory ranges as RAM.
8453 The default value is @code{on}.
8454 @kindex show mem inaccessible-by-default
8455 @item show mem inaccessible-by-default
8456 Show the current handling of accesses to unknown memory.
8460 @c @subsubsection Memory Write Verification
8461 @c The memory write verification attributes set whether @value{GDBN}
8462 @c will re-reads data after each write to verify the write was successful.
8466 @c @item noverify (default)
8469 @node Dump/Restore Files
8470 @section Copy Between Memory and a File
8471 @cindex dump/restore files
8472 @cindex append data to a file
8473 @cindex dump data to a file
8474 @cindex restore data from a file
8476 You can use the commands @code{dump}, @code{append}, and
8477 @code{restore} to copy data between target memory and a file. The
8478 @code{dump} and @code{append} commands write data to a file, and the
8479 @code{restore} command reads data from a file back into the inferior's
8480 memory. Files may be in binary, Motorola S-record, Intel hex, or
8481 Tektronix Hex format; however, @value{GDBN} can only append to binary
8487 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8488 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
8489 Dump the contents of memory from @var{start_addr} to @var{end_addr},
8490 or the value of @var{expr}, to @var{filename} in the given format.
8492 The @var{format} parameter may be any one of:
8499 Motorola S-record format.
8501 Tektronix Hex format.
8504 @value{GDBN} uses the same definitions of these formats as the
8505 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
8506 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
8510 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8511 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
8512 Append the contents of memory from @var{start_addr} to @var{end_addr},
8513 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
8514 (@value{GDBN} can only append data to files in raw binary form.)
8517 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
8518 Restore the contents of file @var{filename} into memory. The
8519 @code{restore} command can automatically recognize any known @sc{bfd}
8520 file format, except for raw binary. To restore a raw binary file you
8521 must specify the optional keyword @code{binary} after the filename.
8523 If @var{bias} is non-zero, its value will be added to the addresses
8524 contained in the file. Binary files always start at address zero, so
8525 they will be restored at address @var{bias}. Other bfd files have
8526 a built-in location; they will be restored at offset @var{bias}
8529 If @var{start} and/or @var{end} are non-zero, then only data between
8530 file offset @var{start} and file offset @var{end} will be restored.
8531 These offsets are relative to the addresses in the file, before
8532 the @var{bias} argument is applied.
8536 @node Core File Generation
8537 @section How to Produce a Core File from Your Program
8538 @cindex dump core from inferior
8540 A @dfn{core file} or @dfn{core dump} is a file that records the memory
8541 image of a running process and its process status (register values
8542 etc.). Its primary use is post-mortem debugging of a program that
8543 crashed while it ran outside a debugger. A program that crashes
8544 automatically produces a core file, unless this feature is disabled by
8545 the user. @xref{Files}, for information on invoking @value{GDBN} in
8546 the post-mortem debugging mode.
8548 Occasionally, you may wish to produce a core file of the program you
8549 are debugging in order to preserve a snapshot of its state.
8550 @value{GDBN} has a special command for that.
8554 @kindex generate-core-file
8555 @item generate-core-file [@var{file}]
8556 @itemx gcore [@var{file}]
8557 Produce a core dump of the inferior process. The optional argument
8558 @var{file} specifies the file name where to put the core dump. If not
8559 specified, the file name defaults to @file{core.@var{pid}}, where
8560 @var{pid} is the inferior process ID.
8562 Note that this command is implemented only for some systems (as of
8563 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
8566 @node Character Sets
8567 @section Character Sets
8568 @cindex character sets
8570 @cindex translating between character sets
8571 @cindex host character set
8572 @cindex target character set
8574 If the program you are debugging uses a different character set to
8575 represent characters and strings than the one @value{GDBN} uses itself,
8576 @value{GDBN} can automatically translate between the character sets for
8577 you. The character set @value{GDBN} uses we call the @dfn{host
8578 character set}; the one the inferior program uses we call the
8579 @dfn{target character set}.
8581 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
8582 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
8583 remote protocol (@pxref{Remote Debugging}) to debug a program
8584 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
8585 then the host character set is Latin-1, and the target character set is
8586 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
8587 target-charset EBCDIC-US}, then @value{GDBN} translates between
8588 @sc{ebcdic} and Latin 1 as you print character or string values, or use
8589 character and string literals in expressions.
8591 @value{GDBN} has no way to automatically recognize which character set
8592 the inferior program uses; you must tell it, using the @code{set
8593 target-charset} command, described below.
8595 Here are the commands for controlling @value{GDBN}'s character set
8599 @item set target-charset @var{charset}
8600 @kindex set target-charset
8601 Set the current target character set to @var{charset}. To display the
8602 list of supported target character sets, type
8603 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
8605 @item set host-charset @var{charset}
8606 @kindex set host-charset
8607 Set the current host character set to @var{charset}.
8609 By default, @value{GDBN} uses a host character set appropriate to the
8610 system it is running on; you can override that default using the
8611 @code{set host-charset} command. On some systems, @value{GDBN} cannot
8612 automatically determine the appropriate host character set. In this
8613 case, @value{GDBN} uses @samp{UTF-8}.
8615 @value{GDBN} can only use certain character sets as its host character
8616 set. If you type @kbd{@w{set target-charset @key{TAB}@key{TAB}}},
8617 @value{GDBN} will list the host character sets it supports.
8619 @item set charset @var{charset}
8621 Set the current host and target character sets to @var{charset}. As
8622 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
8623 @value{GDBN} will list the names of the character sets that can be used
8624 for both host and target.
8627 @kindex show charset
8628 Show the names of the current host and target character sets.
8630 @item show host-charset
8631 @kindex show host-charset
8632 Show the name of the current host character set.
8634 @item show target-charset
8635 @kindex show target-charset
8636 Show the name of the current target character set.
8638 @item set target-wide-charset @var{charset}
8639 @kindex set target-wide-charset
8640 Set the current target's wide character set to @var{charset}. This is
8641 the character set used by the target's @code{wchar_t} type. To
8642 display the list of supported wide character sets, type
8643 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
8645 @item show target-wide-charset
8646 @kindex show target-wide-charset
8647 Show the name of the current target's wide character set.
8650 Here is an example of @value{GDBN}'s character set support in action.
8651 Assume that the following source code has been placed in the file
8652 @file{charset-test.c}:
8658 = @{72, 101, 108, 108, 111, 44, 32, 119,
8659 111, 114, 108, 100, 33, 10, 0@};
8660 char ibm1047_hello[]
8661 = @{200, 133, 147, 147, 150, 107, 64, 166,
8662 150, 153, 147, 132, 90, 37, 0@};
8666 printf ("Hello, world!\n");
8670 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
8671 containing the string @samp{Hello, world!} followed by a newline,
8672 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
8674 We compile the program, and invoke the debugger on it:
8677 $ gcc -g charset-test.c -o charset-test
8678 $ gdb -nw charset-test
8679 GNU gdb 2001-12-19-cvs
8680 Copyright 2001 Free Software Foundation, Inc.
8685 We can use the @code{show charset} command to see what character sets
8686 @value{GDBN} is currently using to interpret and display characters and
8690 (@value{GDBP}) show charset
8691 The current host and target character set is `ISO-8859-1'.
8695 For the sake of printing this manual, let's use @sc{ascii} as our
8696 initial character set:
8698 (@value{GDBP}) set charset ASCII
8699 (@value{GDBP}) show charset
8700 The current host and target character set is `ASCII'.
8704 Let's assume that @sc{ascii} is indeed the correct character set for our
8705 host system --- in other words, let's assume that if @value{GDBN} prints
8706 characters using the @sc{ascii} character set, our terminal will display
8707 them properly. Since our current target character set is also
8708 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
8711 (@value{GDBP}) print ascii_hello
8712 $1 = 0x401698 "Hello, world!\n"
8713 (@value{GDBP}) print ascii_hello[0]
8718 @value{GDBN} uses the target character set for character and string
8719 literals you use in expressions:
8722 (@value{GDBP}) print '+'
8727 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
8730 @value{GDBN} relies on the user to tell it which character set the
8731 target program uses. If we print @code{ibm1047_hello} while our target
8732 character set is still @sc{ascii}, we get jibberish:
8735 (@value{GDBP}) print ibm1047_hello
8736 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
8737 (@value{GDBP}) print ibm1047_hello[0]
8742 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
8743 @value{GDBN} tells us the character sets it supports:
8746 (@value{GDBP}) set target-charset
8747 ASCII EBCDIC-US IBM1047 ISO-8859-1
8748 (@value{GDBP}) set target-charset
8751 We can select @sc{ibm1047} as our target character set, and examine the
8752 program's strings again. Now the @sc{ascii} string is wrong, but
8753 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
8754 target character set, @sc{ibm1047}, to the host character set,
8755 @sc{ascii}, and they display correctly:
8758 (@value{GDBP}) set target-charset IBM1047
8759 (@value{GDBP}) show charset
8760 The current host character set is `ASCII'.
8761 The current target character set is `IBM1047'.
8762 (@value{GDBP}) print ascii_hello
8763 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
8764 (@value{GDBP}) print ascii_hello[0]
8766 (@value{GDBP}) print ibm1047_hello
8767 $8 = 0x4016a8 "Hello, world!\n"
8768 (@value{GDBP}) print ibm1047_hello[0]
8773 As above, @value{GDBN} uses the target character set for character and
8774 string literals you use in expressions:
8777 (@value{GDBP}) print '+'
8782 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
8785 @node Caching Remote Data
8786 @section Caching Data of Remote Targets
8787 @cindex caching data of remote targets
8789 @value{GDBN} caches data exchanged between the debugger and a
8790 remote target (@pxref{Remote Debugging}). Such caching generally improves
8791 performance, because it reduces the overhead of the remote protocol by
8792 bundling memory reads and writes into large chunks. Unfortunately, simply
8793 caching everything would lead to incorrect results, since @value{GDBN}
8794 does not necessarily know anything about volatile values, memory-mapped I/O
8795 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
8796 memory can be changed @emph{while} a gdb command is executing.
8797 Therefore, by default, @value{GDBN} only caches data
8798 known to be on the stack@footnote{In non-stop mode, it is moderately
8799 rare for a running thread to modify the stack of a stopped thread
8800 in a way that would interfere with a backtrace, and caching of
8801 stack reads provides a significant speed up of remote backtraces.}.
8802 Other regions of memory can be explicitly marked as
8803 cacheable; see @pxref{Memory Region Attributes}.
8806 @kindex set remotecache
8807 @item set remotecache on
8808 @itemx set remotecache off
8809 This option no longer does anything; it exists for compatibility
8812 @kindex show remotecache
8813 @item show remotecache
8814 Show the current state of the obsolete remotecache flag.
8816 @kindex set stack-cache
8817 @item set stack-cache on
8818 @itemx set stack-cache off
8819 Enable or disable caching of stack accesses. When @code{ON}, use
8820 caching. By default, this option is @code{ON}.
8822 @kindex show stack-cache
8823 @item show stack-cache
8824 Show the current state of data caching for memory accesses.
8827 @item info dcache @r{[}line@r{]}
8828 Print the information about the data cache performance. The
8829 information displayed includes the dcache width and depth, and for
8830 each cache line, its number, address, and how many times it was
8831 referenced. This command is useful for debugging the data cache
8834 If a line number is specified, the contents of that line will be
8838 @node Searching Memory
8839 @section Search Memory
8840 @cindex searching memory
8842 Memory can be searched for a particular sequence of bytes with the
8843 @code{find} command.
8847 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8848 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
8849 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
8850 etc. The search begins at address @var{start_addr} and continues for either
8851 @var{len} bytes or through to @var{end_addr} inclusive.
8854 @var{s} and @var{n} are optional parameters.
8855 They may be specified in either order, apart or together.
8858 @item @var{s}, search query size
8859 The size of each search query value.
8865 halfwords (two bytes)
8869 giant words (eight bytes)
8872 All values are interpreted in the current language.
8873 This means, for example, that if the current source language is C/C@t{++}
8874 then searching for the string ``hello'' includes the trailing '\0'.
8876 If the value size is not specified, it is taken from the
8877 value's type in the current language.
8878 This is useful when one wants to specify the search
8879 pattern as a mixture of types.
8880 Note that this means, for example, that in the case of C-like languages
8881 a search for an untyped 0x42 will search for @samp{(int) 0x42}
8882 which is typically four bytes.
8884 @item @var{n}, maximum number of finds
8885 The maximum number of matches to print. The default is to print all finds.
8888 You can use strings as search values. Quote them with double-quotes
8890 The string value is copied into the search pattern byte by byte,
8891 regardless of the endianness of the target and the size specification.
8893 The address of each match found is printed as well as a count of the
8894 number of matches found.
8896 The address of the last value found is stored in convenience variable
8898 A count of the number of matches is stored in @samp{$numfound}.
8900 For example, if stopped at the @code{printf} in this function:
8906 static char hello[] = "hello-hello";
8907 static struct @{ char c; short s; int i; @}
8908 __attribute__ ((packed)) mixed
8909 = @{ 'c', 0x1234, 0x87654321 @};
8910 printf ("%s\n", hello);
8915 you get during debugging:
8918 (gdb) find &hello[0], +sizeof(hello), "hello"
8919 0x804956d <hello.1620+6>
8921 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
8922 0x8049567 <hello.1620>
8923 0x804956d <hello.1620+6>
8925 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
8926 0x8049567 <hello.1620>
8928 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
8929 0x8049560 <mixed.1625>
8931 (gdb) print $numfound
8934 $2 = (void *) 0x8049560
8937 @node Optimized Code
8938 @chapter Debugging Optimized Code
8939 @cindex optimized code, debugging
8940 @cindex debugging optimized code
8942 Almost all compilers support optimization. With optimization
8943 disabled, the compiler generates assembly code that corresponds
8944 directly to your source code, in a simplistic way. As the compiler
8945 applies more powerful optimizations, the generated assembly code
8946 diverges from your original source code. With help from debugging
8947 information generated by the compiler, @value{GDBN} can map from
8948 the running program back to constructs from your original source.
8950 @value{GDBN} is more accurate with optimization disabled. If you
8951 can recompile without optimization, it is easier to follow the
8952 progress of your program during debugging. But, there are many cases
8953 where you may need to debug an optimized version.
8955 When you debug a program compiled with @samp{-g -O}, remember that the
8956 optimizer has rearranged your code; the debugger shows you what is
8957 really there. Do not be too surprised when the execution path does not
8958 exactly match your source file! An extreme example: if you define a
8959 variable, but never use it, @value{GDBN} never sees that
8960 variable---because the compiler optimizes it out of existence.
8962 Some things do not work as well with @samp{-g -O} as with just
8963 @samp{-g}, particularly on machines with instruction scheduling. If in
8964 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
8965 please report it to us as a bug (including a test case!).
8966 @xref{Variables}, for more information about debugging optimized code.
8969 * Inline Functions:: How @value{GDBN} presents inlining
8972 @node Inline Functions
8973 @section Inline Functions
8974 @cindex inline functions, debugging
8976 @dfn{Inlining} is an optimization that inserts a copy of the function
8977 body directly at each call site, instead of jumping to a shared
8978 routine. @value{GDBN} displays inlined functions just like
8979 non-inlined functions. They appear in backtraces. You can view their
8980 arguments and local variables, step into them with @code{step}, skip
8981 them with @code{next}, and escape from them with @code{finish}.
8982 You can check whether a function was inlined by using the
8983 @code{info frame} command.
8985 For @value{GDBN} to support inlined functions, the compiler must
8986 record information about inlining in the debug information ---
8987 @value{NGCC} using the @sc{dwarf 2} format does this, and several
8988 other compilers do also. @value{GDBN} only supports inlined functions
8989 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
8990 do not emit two required attributes (@samp{DW_AT_call_file} and
8991 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
8992 function calls with earlier versions of @value{NGCC}. It instead
8993 displays the arguments and local variables of inlined functions as
8994 local variables in the caller.
8996 The body of an inlined function is directly included at its call site;
8997 unlike a non-inlined function, there are no instructions devoted to
8998 the call. @value{GDBN} still pretends that the call site and the
8999 start of the inlined function are different instructions. Stepping to
9000 the call site shows the call site, and then stepping again shows
9001 the first line of the inlined function, even though no additional
9002 instructions are executed.
9004 This makes source-level debugging much clearer; you can see both the
9005 context of the call and then the effect of the call. Only stepping by
9006 a single instruction using @code{stepi} or @code{nexti} does not do
9007 this; single instruction steps always show the inlined body.
9009 There are some ways that @value{GDBN} does not pretend that inlined
9010 function calls are the same as normal calls:
9014 You cannot set breakpoints on inlined functions. @value{GDBN}
9015 either reports that there is no symbol with that name, or else sets the
9016 breakpoint only on non-inlined copies of the function. This limitation
9017 will be removed in a future version of @value{GDBN}; until then,
9018 set a breakpoint by line number on the first line of the inlined
9022 Setting breakpoints at the call site of an inlined function may not
9023 work, because the call site does not contain any code. @value{GDBN}
9024 may incorrectly move the breakpoint to the next line of the enclosing
9025 function, after the call. This limitation will be removed in a future
9026 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9027 or inside the inlined function instead.
9030 @value{GDBN} cannot locate the return value of inlined calls after
9031 using the @code{finish} command. This is a limitation of compiler-generated
9032 debugging information; after @code{finish}, you can step to the next line
9033 and print a variable where your program stored the return value.
9039 @chapter C Preprocessor Macros
9041 Some languages, such as C and C@t{++}, provide a way to define and invoke
9042 ``preprocessor macros'' which expand into strings of tokens.
9043 @value{GDBN} can evaluate expressions containing macro invocations, show
9044 the result of macro expansion, and show a macro's definition, including
9045 where it was defined.
9047 You may need to compile your program specially to provide @value{GDBN}
9048 with information about preprocessor macros. Most compilers do not
9049 include macros in their debugging information, even when you compile
9050 with the @option{-g} flag. @xref{Compilation}.
9052 A program may define a macro at one point, remove that definition later,
9053 and then provide a different definition after that. Thus, at different
9054 points in the program, a macro may have different definitions, or have
9055 no definition at all. If there is a current stack frame, @value{GDBN}
9056 uses the macros in scope at that frame's source code line. Otherwise,
9057 @value{GDBN} uses the macros in scope at the current listing location;
9060 Whenever @value{GDBN} evaluates an expression, it always expands any
9061 macro invocations present in the expression. @value{GDBN} also provides
9062 the following commands for working with macros explicitly.
9066 @kindex macro expand
9067 @cindex macro expansion, showing the results of preprocessor
9068 @cindex preprocessor macro expansion, showing the results of
9069 @cindex expanding preprocessor macros
9070 @item macro expand @var{expression}
9071 @itemx macro exp @var{expression}
9072 Show the results of expanding all preprocessor macro invocations in
9073 @var{expression}. Since @value{GDBN} simply expands macros, but does
9074 not parse the result, @var{expression} need not be a valid expression;
9075 it can be any string of tokens.
9078 @item macro expand-once @var{expression}
9079 @itemx macro exp1 @var{expression}
9080 @cindex expand macro once
9081 @i{(This command is not yet implemented.)} Show the results of
9082 expanding those preprocessor macro invocations that appear explicitly in
9083 @var{expression}. Macro invocations appearing in that expansion are
9084 left unchanged. This command allows you to see the effect of a
9085 particular macro more clearly, without being confused by further
9086 expansions. Since @value{GDBN} simply expands macros, but does not
9087 parse the result, @var{expression} need not be a valid expression; it
9088 can be any string of tokens.
9091 @cindex macro definition, showing
9092 @cindex definition, showing a macro's
9093 @item info macro @var{macro}
9094 Show the definition of the macro named @var{macro}, and describe the
9095 source location or compiler command-line where that definition was established.
9097 @kindex macro define
9098 @cindex user-defined macros
9099 @cindex defining macros interactively
9100 @cindex macros, user-defined
9101 @item macro define @var{macro} @var{replacement-list}
9102 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
9103 Introduce a definition for a preprocessor macro named @var{macro},
9104 invocations of which are replaced by the tokens given in
9105 @var{replacement-list}. The first form of this command defines an
9106 ``object-like'' macro, which takes no arguments; the second form
9107 defines a ``function-like'' macro, which takes the arguments given in
9110 A definition introduced by this command is in scope in every
9111 expression evaluated in @value{GDBN}, until it is removed with the
9112 @code{macro undef} command, described below. The definition overrides
9113 all definitions for @var{macro} present in the program being debugged,
9114 as well as any previous user-supplied definition.
9117 @item macro undef @var{macro}
9118 Remove any user-supplied definition for the macro named @var{macro}.
9119 This command only affects definitions provided with the @code{macro
9120 define} command, described above; it cannot remove definitions present
9121 in the program being debugged.
9125 List all the macros defined using the @code{macro define} command.
9128 @cindex macros, example of debugging with
9129 Here is a transcript showing the above commands in action. First, we
9130 show our source files:
9138 #define ADD(x) (M + x)
9143 printf ("Hello, world!\n");
9145 printf ("We're so creative.\n");
9147 printf ("Goodbye, world!\n");
9154 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
9155 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
9156 compiler includes information about preprocessor macros in the debugging
9160 $ gcc -gdwarf-2 -g3 sample.c -o sample
9164 Now, we start @value{GDBN} on our sample program:
9168 GNU gdb 2002-05-06-cvs
9169 Copyright 2002 Free Software Foundation, Inc.
9170 GDB is free software, @dots{}
9174 We can expand macros and examine their definitions, even when the
9175 program is not running. @value{GDBN} uses the current listing position
9176 to decide which macro definitions are in scope:
9179 (@value{GDBP}) list main
9182 5 #define ADD(x) (M + x)
9187 10 printf ("Hello, world!\n");
9189 12 printf ("We're so creative.\n");
9190 (@value{GDBP}) info macro ADD
9191 Defined at /home/jimb/gdb/macros/play/sample.c:5
9192 #define ADD(x) (M + x)
9193 (@value{GDBP}) info macro Q
9194 Defined at /home/jimb/gdb/macros/play/sample.h:1
9195 included at /home/jimb/gdb/macros/play/sample.c:2
9197 (@value{GDBP}) macro expand ADD(1)
9198 expands to: (42 + 1)
9199 (@value{GDBP}) macro expand-once ADD(1)
9200 expands to: once (M + 1)
9204 In the example above, note that @code{macro expand-once} expands only
9205 the macro invocation explicit in the original text --- the invocation of
9206 @code{ADD} --- but does not expand the invocation of the macro @code{M},
9207 which was introduced by @code{ADD}.
9209 Once the program is running, @value{GDBN} uses the macro definitions in
9210 force at the source line of the current stack frame:
9213 (@value{GDBP}) break main
9214 Breakpoint 1 at 0x8048370: file sample.c, line 10.
9216 Starting program: /home/jimb/gdb/macros/play/sample
9218 Breakpoint 1, main () at sample.c:10
9219 10 printf ("Hello, world!\n");
9223 At line 10, the definition of the macro @code{N} at line 9 is in force:
9226 (@value{GDBP}) info macro N
9227 Defined at /home/jimb/gdb/macros/play/sample.c:9
9229 (@value{GDBP}) macro expand N Q M
9231 (@value{GDBP}) print N Q M
9236 As we step over directives that remove @code{N}'s definition, and then
9237 give it a new definition, @value{GDBN} finds the definition (or lack
9238 thereof) in force at each point:
9243 12 printf ("We're so creative.\n");
9244 (@value{GDBP}) info macro N
9245 The symbol `N' has no definition as a C/C++ preprocessor macro
9246 at /home/jimb/gdb/macros/play/sample.c:12
9249 14 printf ("Goodbye, world!\n");
9250 (@value{GDBP}) info macro N
9251 Defined at /home/jimb/gdb/macros/play/sample.c:13
9253 (@value{GDBP}) macro expand N Q M
9254 expands to: 1729 < 42
9255 (@value{GDBP}) print N Q M
9260 In addition to source files, macros can be defined on the compilation command
9261 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
9262 such a way, @value{GDBN} displays the location of their definition as line zero
9263 of the source file submitted to the compiler.
9266 (@value{GDBP}) info macro __STDC__
9267 Defined at /home/jimb/gdb/macros/play/sample.c:0
9274 @chapter Tracepoints
9275 @c This chapter is based on the documentation written by Michael
9276 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
9279 In some applications, it is not feasible for the debugger to interrupt
9280 the program's execution long enough for the developer to learn
9281 anything helpful about its behavior. If the program's correctness
9282 depends on its real-time behavior, delays introduced by a debugger
9283 might cause the program to change its behavior drastically, or perhaps
9284 fail, even when the code itself is correct. It is useful to be able
9285 to observe the program's behavior without interrupting it.
9287 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
9288 specify locations in the program, called @dfn{tracepoints}, and
9289 arbitrary expressions to evaluate when those tracepoints are reached.
9290 Later, using the @code{tfind} command, you can examine the values
9291 those expressions had when the program hit the tracepoints. The
9292 expressions may also denote objects in memory---structures or arrays,
9293 for example---whose values @value{GDBN} should record; while visiting
9294 a particular tracepoint, you may inspect those objects as if they were
9295 in memory at that moment. However, because @value{GDBN} records these
9296 values without interacting with you, it can do so quickly and
9297 unobtrusively, hopefully not disturbing the program's behavior.
9299 The tracepoint facility is currently available only for remote
9300 targets. @xref{Targets}. In addition, your remote target must know
9301 how to collect trace data. This functionality is implemented in the
9302 remote stub; however, none of the stubs distributed with @value{GDBN}
9303 support tracepoints as of this writing. The format of the remote
9304 packets used to implement tracepoints are described in @ref{Tracepoint
9307 It is also possible to get trace data from a file, in a manner reminiscent
9308 of corefiles; you specify the filename, and use @code{tfind} to search
9309 through the file. @xref{Trace Files}, for more details.
9311 This chapter describes the tracepoint commands and features.
9315 * Analyze Collected Data::
9316 * Tracepoint Variables::
9320 @node Set Tracepoints
9321 @section Commands to Set Tracepoints
9323 Before running such a @dfn{trace experiment}, an arbitrary number of
9324 tracepoints can be set. A tracepoint is actually a special type of
9325 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
9326 standard breakpoint commands. For instance, as with breakpoints,
9327 tracepoint numbers are successive integers starting from one, and many
9328 of the commands associated with tracepoints take the tracepoint number
9329 as their argument, to identify which tracepoint to work on.
9331 For each tracepoint, you can specify, in advance, some arbitrary set
9332 of data that you want the target to collect in the trace buffer when
9333 it hits that tracepoint. The collected data can include registers,
9334 local variables, or global data. Later, you can use @value{GDBN}
9335 commands to examine the values these data had at the time the
9338 Tracepoints do not support every breakpoint feature. Ignore counts on
9339 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
9340 commands when they are hit. Tracepoints may not be thread-specific
9343 @cindex fast tracepoints
9344 Some targets may support @dfn{fast tracepoints}, which are inserted in
9345 a different way (such as with a jump instead of a trap), that is
9346 faster but possibly restricted in where they may be installed.
9348 This section describes commands to set tracepoints and associated
9349 conditions and actions.
9352 * Create and Delete Tracepoints::
9353 * Enable and Disable Tracepoints::
9354 * Tracepoint Passcounts::
9355 * Tracepoint Conditions::
9356 * Trace State Variables::
9357 * Tracepoint Actions::
9358 * Listing Tracepoints::
9359 * Starting and Stopping Trace Experiments::
9360 * Tracepoint Restrictions::
9363 @node Create and Delete Tracepoints
9364 @subsection Create and Delete Tracepoints
9367 @cindex set tracepoint
9369 @item trace @var{location}
9370 The @code{trace} command is very similar to the @code{break} command.
9371 Its argument @var{location} can be a source line, a function name, or
9372 an address in the target program. @xref{Specify Location}. The
9373 @code{trace} command defines a tracepoint, which is a point in the
9374 target program where the debugger will briefly stop, collect some
9375 data, and then allow the program to continue. Setting a tracepoint or
9376 changing its actions doesn't take effect until the next @code{tstart}
9377 command, and once a trace experiment is running, further changes will
9378 not have any effect until the next trace experiment starts.
9380 Here are some examples of using the @code{trace} command:
9383 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
9385 (@value{GDBP}) @b{trace +2} // 2 lines forward
9387 (@value{GDBP}) @b{trace my_function} // first source line of function
9389 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
9391 (@value{GDBP}) @b{trace *0x2117c4} // an address
9395 You can abbreviate @code{trace} as @code{tr}.
9397 @item trace @var{location} if @var{cond}
9398 Set a tracepoint with condition @var{cond}; evaluate the expression
9399 @var{cond} each time the tracepoint is reached, and collect data only
9400 if the value is nonzero---that is, if @var{cond} evaluates as true.
9401 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
9402 information on tracepoint conditions.
9404 @item ftrace @var{location} [ if @var{cond} ]
9405 @cindex set fast tracepoint
9407 The @code{ftrace} command sets a fast tracepoint. For targets that
9408 support them, fast tracepoints will use a more efficient but possibly
9409 less general technique to trigger data collection, such as a jump
9410 instruction instead of a trap, or some sort of hardware support. It
9411 may not be possible to create a fast tracepoint at the desired
9412 location, in which case the command will exit with an explanatory
9415 @value{GDBN} handles arguments to @code{ftrace} exactly as for
9419 @cindex last tracepoint number
9420 @cindex recent tracepoint number
9421 @cindex tracepoint number
9422 The convenience variable @code{$tpnum} records the tracepoint number
9423 of the most recently set tracepoint.
9425 @kindex delete tracepoint
9426 @cindex tracepoint deletion
9427 @item delete tracepoint @r{[}@var{num}@r{]}
9428 Permanently delete one or more tracepoints. With no argument, the
9429 default is to delete all tracepoints. Note that the regular
9430 @code{delete} command can remove tracepoints also.
9435 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
9437 (@value{GDBP}) @b{delete trace} // remove all tracepoints
9441 You can abbreviate this command as @code{del tr}.
9444 @node Enable and Disable Tracepoints
9445 @subsection Enable and Disable Tracepoints
9447 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
9450 @kindex disable tracepoint
9451 @item disable tracepoint @r{[}@var{num}@r{]}
9452 Disable tracepoint @var{num}, or all tracepoints if no argument
9453 @var{num} is given. A disabled tracepoint will have no effect during
9454 the next trace experiment, but it is not forgotten. You can re-enable
9455 a disabled tracepoint using the @code{enable tracepoint} command.
9457 @kindex enable tracepoint
9458 @item enable tracepoint @r{[}@var{num}@r{]}
9459 Enable tracepoint @var{num}, or all tracepoints. The enabled
9460 tracepoints will become effective the next time a trace experiment is
9464 @node Tracepoint Passcounts
9465 @subsection Tracepoint Passcounts
9469 @cindex tracepoint pass count
9470 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
9471 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
9472 automatically stop a trace experiment. If a tracepoint's passcount is
9473 @var{n}, then the trace experiment will be automatically stopped on
9474 the @var{n}'th time that tracepoint is hit. If the tracepoint number
9475 @var{num} is not specified, the @code{passcount} command sets the
9476 passcount of the most recently defined tracepoint. If no passcount is
9477 given, the trace experiment will run until stopped explicitly by the
9483 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
9484 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
9486 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
9487 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
9488 (@value{GDBP}) @b{trace foo}
9489 (@value{GDBP}) @b{pass 3}
9490 (@value{GDBP}) @b{trace bar}
9491 (@value{GDBP}) @b{pass 2}
9492 (@value{GDBP}) @b{trace baz}
9493 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
9494 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
9495 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
9496 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
9500 @node Tracepoint Conditions
9501 @subsection Tracepoint Conditions
9502 @cindex conditional tracepoints
9503 @cindex tracepoint conditions
9505 The simplest sort of tracepoint collects data every time your program
9506 reaches a specified place. You can also specify a @dfn{condition} for
9507 a tracepoint. A condition is just a Boolean expression in your
9508 programming language (@pxref{Expressions, ,Expressions}). A
9509 tracepoint with a condition evaluates the expression each time your
9510 program reaches it, and data collection happens only if the condition
9513 Tracepoint conditions can be specified when a tracepoint is set, by
9514 using @samp{if} in the arguments to the @code{trace} command.
9515 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
9516 also be set or changed at any time with the @code{condition} command,
9517 just as with breakpoints.
9519 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
9520 the conditional expression itself. Instead, @value{GDBN} encodes the
9521 expression into an agent expression (@pxref{Agent Expressions}
9522 suitable for execution on the target, independently of @value{GDBN}.
9523 Global variables become raw memory locations, locals become stack
9524 accesses, and so forth.
9526 For instance, suppose you have a function that is usually called
9527 frequently, but should not be called after an error has occurred. You
9528 could use the following tracepoint command to collect data about calls
9529 of that function that happen while the error code is propagating
9530 through the program; an unconditional tracepoint could end up
9531 collecting thousands of useless trace frames that you would have to
9535 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
9538 @node Trace State Variables
9539 @subsection Trace State Variables
9540 @cindex trace state variables
9542 A @dfn{trace state variable} is a special type of variable that is
9543 created and managed by target-side code. The syntax is the same as
9544 that for GDB's convenience variables (a string prefixed with ``$''),
9545 but they are stored on the target. They must be created explicitly,
9546 using a @code{tvariable} command. They are always 64-bit signed
9549 Trace state variables are remembered by @value{GDBN}, and downloaded
9550 to the target along with tracepoint information when the trace
9551 experiment starts. There are no intrinsic limits on the number of
9552 trace state variables, beyond memory limitations of the target.
9554 @cindex convenience variables, and trace state variables
9555 Although trace state variables are managed by the target, you can use
9556 them in print commands and expressions as if they were convenience
9557 variables; @value{GDBN} will get the current value from the target
9558 while the trace experiment is running. Trace state variables share
9559 the same namespace as other ``$'' variables, which means that you
9560 cannot have trace state variables with names like @code{$23} or
9561 @code{$pc}, nor can you have a trace state variable and a convenience
9562 variable with the same name.
9566 @item tvariable $@var{name} [ = @var{expression} ]
9568 The @code{tvariable} command creates a new trace state variable named
9569 @code{$@var{name}}, and optionally gives it an initial value of
9570 @var{expression}. @var{expression} is evaluated when this command is
9571 entered; the result will be converted to an integer if possible,
9572 otherwise @value{GDBN} will report an error. A subsequent
9573 @code{tvariable} command specifying the same name does not create a
9574 variable, but instead assigns the supplied initial value to the
9575 existing variable of that name, overwriting any previous initial
9576 value. The default initial value is 0.
9578 @item info tvariables
9579 @kindex info tvariables
9580 List all the trace state variables along with their initial values.
9581 Their current values may also be displayed, if the trace experiment is
9584 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
9585 @kindex delete tvariable
9586 Delete the given trace state variables, or all of them if no arguments
9591 @node Tracepoint Actions
9592 @subsection Tracepoint Action Lists
9596 @cindex tracepoint actions
9597 @item actions @r{[}@var{num}@r{]}
9598 This command will prompt for a list of actions to be taken when the
9599 tracepoint is hit. If the tracepoint number @var{num} is not
9600 specified, this command sets the actions for the one that was most
9601 recently defined (so that you can define a tracepoint and then say
9602 @code{actions} without bothering about its number). You specify the
9603 actions themselves on the following lines, one action at a time, and
9604 terminate the actions list with a line containing just @code{end}. So
9605 far, the only defined actions are @code{collect}, @code{teval}, and
9606 @code{while-stepping}.
9608 @cindex remove actions from a tracepoint
9609 To remove all actions from a tracepoint, type @samp{actions @var{num}}
9610 and follow it immediately with @samp{end}.
9613 (@value{GDBP}) @b{collect @var{data}} // collect some data
9615 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
9617 (@value{GDBP}) @b{end} // signals the end of actions.
9620 In the following example, the action list begins with @code{collect}
9621 commands indicating the things to be collected when the tracepoint is
9622 hit. Then, in order to single-step and collect additional data
9623 following the tracepoint, a @code{while-stepping} command is used,
9624 followed by the list of things to be collected after each step in a
9625 sequence of single steps. The @code{while-stepping} command is
9626 terminated by its own separate @code{end} command. Lastly, the action
9627 list is terminated by an @code{end} command.
9630 (@value{GDBP}) @b{trace foo}
9631 (@value{GDBP}) @b{actions}
9632 Enter actions for tracepoint 1, one per line:
9641 @kindex collect @r{(tracepoints)}
9642 @item collect @var{expr1}, @var{expr2}, @dots{}
9643 Collect values of the given expressions when the tracepoint is hit.
9644 This command accepts a comma-separated list of any valid expressions.
9645 In addition to global, static, or local variables, the following
9646 special arguments are supported:
9650 collect all registers
9653 collect all function arguments
9656 collect all local variables.
9659 You can give several consecutive @code{collect} commands, each one
9660 with a single argument, or one @code{collect} command with several
9661 arguments separated by commas: the effect is the same.
9663 The command @code{info scope} (@pxref{Symbols, info scope}) is
9664 particularly useful for figuring out what data to collect.
9666 @kindex teval @r{(tracepoints)}
9667 @item teval @var{expr1}, @var{expr2}, @dots{}
9668 Evaluate the given expressions when the tracepoint is hit. This
9669 command accepts a comma-separated list of expressions. The results
9670 are discarded, so this is mainly useful for assigning values to trace
9671 state variables (@pxref{Trace State Variables}) without adding those
9672 values to the trace buffer, as would be the case if the @code{collect}
9675 @kindex while-stepping @r{(tracepoints)}
9676 @item while-stepping @var{n}
9677 Perform @var{n} single-step instruction traces after the tracepoint,
9678 collecting new data after each step. The @code{while-stepping}
9679 command is followed by the list of what to collect while stepping
9680 (followed by its own @code{end} command):
9684 > collect $regs, myglobal
9690 Note that @code{$pc} is not automatically collected by
9691 @code{while-stepping}; you need to explicitly collect that register if
9692 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
9695 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
9696 @kindex set default-collect
9697 @cindex default collection action
9698 This variable is a list of expressions to collect at each tracepoint
9699 hit. It is effectively an additional @code{collect} action prepended
9700 to every tracepoint action list. The expressions are parsed
9701 individually for each tracepoint, so for instance a variable named
9702 @code{xyz} may be interpreted as a global for one tracepoint, and a
9703 local for another, as appropriate to the tracepoint's location.
9705 @item show default-collect
9706 @kindex show default-collect
9707 Show the list of expressions that are collected by default at each
9712 @node Listing Tracepoints
9713 @subsection Listing Tracepoints
9716 @kindex info tracepoints
9718 @cindex information about tracepoints
9719 @item info tracepoints @r{[}@var{num}@r{]}
9720 Display information about the tracepoint @var{num}. If you don't
9721 specify a tracepoint number, displays information about all the
9722 tracepoints defined so far. The format is similar to that used for
9723 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
9724 command, simply restricting itself to tracepoints.
9726 A tracepoint's listing may include additional information specific to
9731 its passcount as given by the @code{passcount @var{n}} command
9733 its step count as given by the @code{while-stepping @var{n}} command
9735 its action list as given by the @code{actions} command. The actions
9736 are prefixed with an @samp{A} so as to distinguish them from commands.
9740 (@value{GDBP}) @b{info trace}
9741 Num Type Disp Enb Address What
9742 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
9746 A collect globfoo, $regs
9754 This command can be abbreviated @code{info tp}.
9757 @node Starting and Stopping Trace Experiments
9758 @subsection Starting and Stopping Trace Experiments
9762 @cindex start a new trace experiment
9763 @cindex collected data discarded
9765 This command takes no arguments. It starts the trace experiment, and
9766 begins collecting data. This has the side effect of discarding all
9767 the data collected in the trace buffer during the previous trace
9771 @cindex stop a running trace experiment
9773 This command takes no arguments. It ends the trace experiment, and
9774 stops collecting data.
9776 @strong{Note}: a trace experiment and data collection may stop
9777 automatically if any tracepoint's passcount is reached
9778 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
9781 @cindex status of trace data collection
9782 @cindex trace experiment, status of
9784 This command displays the status of the current trace data
9788 Here is an example of the commands we described so far:
9791 (@value{GDBP}) @b{trace gdb_c_test}
9792 (@value{GDBP}) @b{actions}
9793 Enter actions for tracepoint #1, one per line.
9794 > collect $regs,$locals,$args
9799 (@value{GDBP}) @b{tstart}
9800 [time passes @dots{}]
9801 (@value{GDBP}) @b{tstop}
9804 @cindex disconnected tracing
9805 You can choose to continue running the trace experiment even if
9806 @value{GDBN} disconnects from the target, voluntarily or
9807 involuntarily. For commands such as @code{detach}, the debugger will
9808 ask what you want to do with the trace. But for unexpected
9809 terminations (@value{GDBN} crash, network outage), it would be
9810 unfortunate to lose hard-won trace data, so the variable
9811 @code{disconnected-tracing} lets you decide whether the trace should
9812 continue running without @value{GDBN}.
9815 @item set disconnected-tracing on
9816 @itemx set disconnected-tracing off
9817 @kindex set disconnected-tracing
9818 Choose whether a tracing run should continue to run if @value{GDBN}
9819 has disconnected from the target. Note that @code{detach} or
9820 @code{quit} will ask you directly what to do about a running trace no
9821 matter what this variable's setting, so the variable is mainly useful
9822 for handling unexpected situations, such as loss of the network.
9824 @item show disconnected-tracing
9825 @kindex show disconnected-tracing
9826 Show the current choice for disconnected tracing.
9830 When you reconnect to the target, the trace experiment may or may not
9831 still be running; it might have filled the trace buffer in the
9832 meantime, or stopped for one of the other reasons. If it is running,
9833 it will continue after reconnection.
9835 Upon reconnection, the target will upload information about the
9836 tracepoints in effect. @value{GDBN} will then compare that
9837 information to the set of tracepoints currently defined, and attempt
9838 to match them up, allowing for the possibility that the numbers may
9839 have changed due to creation and deletion in the meantime. If one of
9840 the target's tracepoints does not match any in @value{GDBN}, the
9841 debugger will create a new tracepoint, so that you have a number with
9842 which to specify that tracepoint. This matching-up process is
9843 necessarily heuristic, and it may result in useless tracepoints being
9844 created; you may simply delete them if they are of no use.
9846 @cindex circular trace buffer
9847 If your target agent supports a @dfn{circular trace buffer}, then you
9848 can run a trace experiment indefinitely without filling the trace
9849 buffer; when space runs out, the agent deletes already-collected trace
9850 frames, oldest first, until there is enough room to continue
9851 collecting. This is especially useful if your tracepoints are being
9852 hit too often, and your trace gets terminated prematurely because the
9853 buffer is full. To ask for a circular trace buffer, simply set
9854 @samp{circular_trace_buffer} to on. You can set this at any time,
9855 including during tracing; if the agent can do it, it will change
9856 buffer handling on the fly, otherwise it will not take effect until
9860 @item set circular-trace-buffer on
9861 @itemx set circular-trace-buffer off
9862 @kindex set circular-trace-buffer
9863 Choose whether a tracing run should use a linear or circular buffer
9864 for trace data. A linear buffer will not lose any trace data, but may
9865 fill up prematurely, while a circular buffer will discard old trace
9866 data, but it will have always room for the latest tracepoint hits.
9868 @item show circular-trace-buffer
9869 @kindex show circular-trace-buffer
9870 Show the current choice for the trace buffer. Note that this may not
9871 match the agent's current buffer handling, nor is it guaranteed to
9872 match the setting that might have been in effect during a past run,
9873 for instance if you are looking at frames from a trace file.
9877 @node Tracepoint Restrictions
9878 @subsection Tracepoint Restrictions
9880 @cindex tracepoint restrictions
9881 There are a number of restrictions on the use of tracepoints. As
9882 described above, tracepoint data gathering occurs on the target
9883 without interaction from @value{GDBN}. Thus the full capabilities of
9884 the debugger are not available during data gathering, and then at data
9885 examination time, you will be limited by only having what was
9886 collected. The following items describe some common problems, but it
9887 is not exhaustive, and you may run into additional difficulties not
9893 Tracepoint expressions are intended to gather objects (lvalues). Thus
9894 the full flexibility of GDB's expression evaluator is not available.
9895 You cannot call functions, cast objects to aggregate types, access
9896 convenience variables or modify values (except by assignment to trace
9897 state variables). Some language features may implicitly call
9898 functions (for instance Objective-C fields with accessors), and therefore
9899 cannot be collected either.
9902 Collection of local variables, either individually or in bulk with
9903 @code{$locals} or @code{$args}, during @code{while-stepping} may
9904 behave erratically. The stepping action may enter a new scope (for
9905 instance by stepping into a function), or the location of the variable
9906 may change (for instance it is loaded into a register). The
9907 tracepoint data recorded uses the location information for the
9908 variables that is correct for the tracepoint location. When the
9909 tracepoint is created, it is not possible, in general, to determine
9910 where the steps of a @code{while-stepping} sequence will advance the
9911 program---particularly if a conditional branch is stepped.
9914 Collection of an incompletely-initialized or partially-destroyed object
9915 may result in something that @value{GDBN} cannot display, or displays
9916 in a misleading way.
9919 When @value{GDBN} displays a pointer to character it automatically
9920 dereferences the pointer to also display characters of the string
9921 being pointed to. However, collecting the pointer during tracing does
9922 not automatically collect the string. You need to explicitly
9923 dereference the pointer and provide size information if you want to
9924 collect not only the pointer, but the memory pointed to. For example,
9925 @code{*ptr@@50} can be used to collect the 50 element array pointed to
9929 It is not possible to collect a complete stack backtrace at a
9930 tracepoint. Instead, you may collect the registers and a few hundred
9931 bytes from the stack pointer with something like @code{*$esp@@300}
9932 (adjust to use the name of the actual stack pointer register on your
9933 target architecture, and the amount of stack you wish to capture).
9934 Then the @code{backtrace} command will show a partial backtrace when
9935 using a trace frame. The number of stack frames that can be examined
9936 depends on the sizes of the frames in the collected stack. Note that
9937 if you ask for a block so large that it goes past the bottom of the
9938 stack, the target agent may report an error trying to read from an
9943 @node Analyze Collected Data
9944 @section Using the Collected Data
9946 After the tracepoint experiment ends, you use @value{GDBN} commands
9947 for examining the trace data. The basic idea is that each tracepoint
9948 collects a trace @dfn{snapshot} every time it is hit and another
9949 snapshot every time it single-steps. All these snapshots are
9950 consecutively numbered from zero and go into a buffer, and you can
9951 examine them later. The way you examine them is to @dfn{focus} on a
9952 specific trace snapshot. When the remote stub is focused on a trace
9953 snapshot, it will respond to all @value{GDBN} requests for memory and
9954 registers by reading from the buffer which belongs to that snapshot,
9955 rather than from @emph{real} memory or registers of the program being
9956 debugged. This means that @strong{all} @value{GDBN} commands
9957 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
9958 behave as if we were currently debugging the program state as it was
9959 when the tracepoint occurred. Any requests for data that are not in
9960 the buffer will fail.
9963 * tfind:: How to select a trace snapshot
9964 * tdump:: How to display all data for a snapshot
9965 * save-tracepoints:: How to save tracepoints for a future run
9969 @subsection @code{tfind @var{n}}
9972 @cindex select trace snapshot
9973 @cindex find trace snapshot
9974 The basic command for selecting a trace snapshot from the buffer is
9975 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
9976 counting from zero. If no argument @var{n} is given, the next
9977 snapshot is selected.
9979 Here are the various forms of using the @code{tfind} command.
9983 Find the first snapshot in the buffer. This is a synonym for
9984 @code{tfind 0} (since 0 is the number of the first snapshot).
9987 Stop debugging trace snapshots, resume @emph{live} debugging.
9990 Same as @samp{tfind none}.
9993 No argument means find the next trace snapshot.
9996 Find the previous trace snapshot before the current one. This permits
9997 retracing earlier steps.
9999 @item tfind tracepoint @var{num}
10000 Find the next snapshot associated with tracepoint @var{num}. Search
10001 proceeds forward from the last examined trace snapshot. If no
10002 argument @var{num} is given, it means find the next snapshot collected
10003 for the same tracepoint as the current snapshot.
10005 @item tfind pc @var{addr}
10006 Find the next snapshot associated with the value @var{addr} of the
10007 program counter. Search proceeds forward from the last examined trace
10008 snapshot. If no argument @var{addr} is given, it means find the next
10009 snapshot with the same value of PC as the current snapshot.
10011 @item tfind outside @var{addr1}, @var{addr2}
10012 Find the next snapshot whose PC is outside the given range of
10013 addresses (exclusive).
10015 @item tfind range @var{addr1}, @var{addr2}
10016 Find the next snapshot whose PC is between @var{addr1} and
10017 @var{addr2} (inclusive).
10019 @item tfind line @r{[}@var{file}:@r{]}@var{n}
10020 Find the next snapshot associated with the source line @var{n}. If
10021 the optional argument @var{file} is given, refer to line @var{n} in
10022 that source file. Search proceeds forward from the last examined
10023 trace snapshot. If no argument @var{n} is given, it means find the
10024 next line other than the one currently being examined; thus saying
10025 @code{tfind line} repeatedly can appear to have the same effect as
10026 stepping from line to line in a @emph{live} debugging session.
10029 The default arguments for the @code{tfind} commands are specifically
10030 designed to make it easy to scan through the trace buffer. For
10031 instance, @code{tfind} with no argument selects the next trace
10032 snapshot, and @code{tfind -} with no argument selects the previous
10033 trace snapshot. So, by giving one @code{tfind} command, and then
10034 simply hitting @key{RET} repeatedly you can examine all the trace
10035 snapshots in order. Or, by saying @code{tfind -} and then hitting
10036 @key{RET} repeatedly you can examine the snapshots in reverse order.
10037 The @code{tfind line} command with no argument selects the snapshot
10038 for the next source line executed. The @code{tfind pc} command with
10039 no argument selects the next snapshot with the same program counter
10040 (PC) as the current frame. The @code{tfind tracepoint} command with
10041 no argument selects the next trace snapshot collected by the same
10042 tracepoint as the current one.
10044 In addition to letting you scan through the trace buffer manually,
10045 these commands make it easy to construct @value{GDBN} scripts that
10046 scan through the trace buffer and print out whatever collected data
10047 you are interested in. Thus, if we want to examine the PC, FP, and SP
10048 registers from each trace frame in the buffer, we can say this:
10051 (@value{GDBP}) @b{tfind start}
10052 (@value{GDBP}) @b{while ($trace_frame != -1)}
10053 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
10054 $trace_frame, $pc, $sp, $fp
10058 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
10059 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
10060 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
10061 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
10062 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
10063 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
10064 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
10065 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
10066 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
10067 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
10068 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
10071 Or, if we want to examine the variable @code{X} at each source line in
10075 (@value{GDBP}) @b{tfind start}
10076 (@value{GDBP}) @b{while ($trace_frame != -1)}
10077 > printf "Frame %d, X == %d\n", $trace_frame, X
10087 @subsection @code{tdump}
10089 @cindex dump all data collected at tracepoint
10090 @cindex tracepoint data, display
10092 This command takes no arguments. It prints all the data collected at
10093 the current trace snapshot.
10096 (@value{GDBP}) @b{trace 444}
10097 (@value{GDBP}) @b{actions}
10098 Enter actions for tracepoint #2, one per line:
10099 > collect $regs, $locals, $args, gdb_long_test
10102 (@value{GDBP}) @b{tstart}
10104 (@value{GDBP}) @b{tfind line 444}
10105 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
10107 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
10109 (@value{GDBP}) @b{tdump}
10110 Data collected at tracepoint 2, trace frame 1:
10111 d0 0xc4aa0085 -995491707
10115 d4 0x71aea3d 119204413
10118 d7 0x380035 3670069
10119 a0 0x19e24a 1696330
10120 a1 0x3000668 50333288
10122 a3 0x322000 3284992
10123 a4 0x3000698 50333336
10124 a5 0x1ad3cc 1758156
10125 fp 0x30bf3c 0x30bf3c
10126 sp 0x30bf34 0x30bf34
10128 pc 0x20b2c8 0x20b2c8
10132 p = 0x20e5b4 "gdb-test"
10139 gdb_long_test = 17 '\021'
10144 @node save-tracepoints
10145 @subsection @code{save-tracepoints @var{filename}}
10146 @kindex save-tracepoints
10147 @cindex save tracepoints for future sessions
10149 This command saves all current tracepoint definitions together with
10150 their actions and passcounts, into a file @file{@var{filename}}
10151 suitable for use in a later debugging session. To read the saved
10152 tracepoint definitions, use the @code{source} command (@pxref{Command
10155 @node Tracepoint Variables
10156 @section Convenience Variables for Tracepoints
10157 @cindex tracepoint variables
10158 @cindex convenience variables for tracepoints
10161 @vindex $trace_frame
10162 @item (int) $trace_frame
10163 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
10164 snapshot is selected.
10166 @vindex $tracepoint
10167 @item (int) $tracepoint
10168 The tracepoint for the current trace snapshot.
10170 @vindex $trace_line
10171 @item (int) $trace_line
10172 The line number for the current trace snapshot.
10174 @vindex $trace_file
10175 @item (char []) $trace_file
10176 The source file for the current trace snapshot.
10178 @vindex $trace_func
10179 @item (char []) $trace_func
10180 The name of the function containing @code{$tracepoint}.
10183 Note: @code{$trace_file} is not suitable for use in @code{printf},
10184 use @code{output} instead.
10186 Here's a simple example of using these convenience variables for
10187 stepping through all the trace snapshots and printing some of their
10188 data. Note that these are not the same as trace state variables,
10189 which are managed by the target.
10192 (@value{GDBP}) @b{tfind start}
10194 (@value{GDBP}) @b{while $trace_frame != -1}
10195 > output $trace_file
10196 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
10202 @section Using Trace Files
10203 @cindex trace files
10205 In some situations, the target running a trace experiment may no
10206 longer be available; perhaps it crashed, or the hardware was needed
10207 for a different activity. To handle these cases, you can arrange to
10208 dump the trace data into a file, and later use that file as a source
10209 of trace data, via the @code{target tfile} command.
10214 @item tsave [ -r ] @var{filename}
10215 Save the trace data to @var{filename}. By default, this command
10216 assumes that @var{filename} refers to the host filesystem, so if
10217 necessary @value{GDBN} will copy raw trace data up from the target and
10218 then save it. If the target supports it, you can also supply the
10219 optional argument @code{-r} (``remote'') to direct the target to save
10220 the data directly into @var{filename} in its own filesystem, which may be
10221 more efficient if the trace buffer is very large. (Note, however, that
10222 @code{target tfile} can only read from files accessible to the host.)
10224 @kindex target tfile
10226 @item target tfile @var{filename}
10227 Use the file named @var{filename} as a source of trace data. Commands
10228 that examine data work as they do with a live target, but it is not
10229 possible to run any new trace experiments. @code{tstatus} will report
10230 the state of the trace run at the moment the data was saved, as well
10231 as the current trace frame you are examining. @var{filename} must be
10232 on a filesystem accessible to the host.
10237 @chapter Debugging Programs That Use Overlays
10240 If your program is too large to fit completely in your target system's
10241 memory, you can sometimes use @dfn{overlays} to work around this
10242 problem. @value{GDBN} provides some support for debugging programs that
10246 * How Overlays Work:: A general explanation of overlays.
10247 * Overlay Commands:: Managing overlays in @value{GDBN}.
10248 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
10249 mapped by asking the inferior.
10250 * Overlay Sample Program:: A sample program using overlays.
10253 @node How Overlays Work
10254 @section How Overlays Work
10255 @cindex mapped overlays
10256 @cindex unmapped overlays
10257 @cindex load address, overlay's
10258 @cindex mapped address
10259 @cindex overlay area
10261 Suppose you have a computer whose instruction address space is only 64
10262 kilobytes long, but which has much more memory which can be accessed by
10263 other means: special instructions, segment registers, or memory
10264 management hardware, for example. Suppose further that you want to
10265 adapt a program which is larger than 64 kilobytes to run on this system.
10267 One solution is to identify modules of your program which are relatively
10268 independent, and need not call each other directly; call these modules
10269 @dfn{overlays}. Separate the overlays from the main program, and place
10270 their machine code in the larger memory. Place your main program in
10271 instruction memory, but leave at least enough space there to hold the
10272 largest overlay as well.
10274 Now, to call a function located in an overlay, you must first copy that
10275 overlay's machine code from the large memory into the space set aside
10276 for it in the instruction memory, and then jump to its entry point
10279 @c NB: In the below the mapped area's size is greater or equal to the
10280 @c size of all overlays. This is intentional to remind the developer
10281 @c that overlays don't necessarily need to be the same size.
10285 Data Instruction Larger
10286 Address Space Address Space Address Space
10287 +-----------+ +-----------+ +-----------+
10289 +-----------+ +-----------+ +-----------+<-- overlay 1
10290 | program | | main | .----| overlay 1 | load address
10291 | variables | | program | | +-----------+
10292 | and heap | | | | | |
10293 +-----------+ | | | +-----------+<-- overlay 2
10294 | | +-----------+ | | | load address
10295 +-----------+ | | | .-| overlay 2 |
10297 mapped --->+-----------+ | | +-----------+
10298 address | | | | | |
10299 | overlay | <-' | | |
10300 | area | <---' +-----------+<-- overlay 3
10301 | | <---. | | load address
10302 +-----------+ `--| overlay 3 |
10309 @anchor{A code overlay}A code overlay
10313 The diagram (@pxref{A code overlay}) shows a system with separate data
10314 and instruction address spaces. To map an overlay, the program copies
10315 its code from the larger address space to the instruction address space.
10316 Since the overlays shown here all use the same mapped address, only one
10317 may be mapped at a time. For a system with a single address space for
10318 data and instructions, the diagram would be similar, except that the
10319 program variables and heap would share an address space with the main
10320 program and the overlay area.
10322 An overlay loaded into instruction memory and ready for use is called a
10323 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
10324 instruction memory. An overlay not present (or only partially present)
10325 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
10326 is its address in the larger memory. The mapped address is also called
10327 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
10328 called the @dfn{load memory address}, or @dfn{LMA}.
10330 Unfortunately, overlays are not a completely transparent way to adapt a
10331 program to limited instruction memory. They introduce a new set of
10332 global constraints you must keep in mind as you design your program:
10337 Before calling or returning to a function in an overlay, your program
10338 must make sure that overlay is actually mapped. Otherwise, the call or
10339 return will transfer control to the right address, but in the wrong
10340 overlay, and your program will probably crash.
10343 If the process of mapping an overlay is expensive on your system, you
10344 will need to choose your overlays carefully to minimize their effect on
10345 your program's performance.
10348 The executable file you load onto your system must contain each
10349 overlay's instructions, appearing at the overlay's load address, not its
10350 mapped address. However, each overlay's instructions must be relocated
10351 and its symbols defined as if the overlay were at its mapped address.
10352 You can use GNU linker scripts to specify different load and relocation
10353 addresses for pieces of your program; see @ref{Overlay Description,,,
10354 ld.info, Using ld: the GNU linker}.
10357 The procedure for loading executable files onto your system must be able
10358 to load their contents into the larger address space as well as the
10359 instruction and data spaces.
10363 The overlay system described above is rather simple, and could be
10364 improved in many ways:
10369 If your system has suitable bank switch registers or memory management
10370 hardware, you could use those facilities to make an overlay's load area
10371 contents simply appear at their mapped address in instruction space.
10372 This would probably be faster than copying the overlay to its mapped
10373 area in the usual way.
10376 If your overlays are small enough, you could set aside more than one
10377 overlay area, and have more than one overlay mapped at a time.
10380 You can use overlays to manage data, as well as instructions. In
10381 general, data overlays are even less transparent to your design than
10382 code overlays: whereas code overlays only require care when you call or
10383 return to functions, data overlays require care every time you access
10384 the data. Also, if you change the contents of a data overlay, you
10385 must copy its contents back out to its load address before you can copy a
10386 different data overlay into the same mapped area.
10391 @node Overlay Commands
10392 @section Overlay Commands
10394 To use @value{GDBN}'s overlay support, each overlay in your program must
10395 correspond to a separate section of the executable file. The section's
10396 virtual memory address and load memory address must be the overlay's
10397 mapped and load addresses. Identifying overlays with sections allows
10398 @value{GDBN} to determine the appropriate address of a function or
10399 variable, depending on whether the overlay is mapped or not.
10401 @value{GDBN}'s overlay commands all start with the word @code{overlay};
10402 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
10407 Disable @value{GDBN}'s overlay support. When overlay support is
10408 disabled, @value{GDBN} assumes that all functions and variables are
10409 always present at their mapped addresses. By default, @value{GDBN}'s
10410 overlay support is disabled.
10412 @item overlay manual
10413 @cindex manual overlay debugging
10414 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
10415 relies on you to tell it which overlays are mapped, and which are not,
10416 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
10417 commands described below.
10419 @item overlay map-overlay @var{overlay}
10420 @itemx overlay map @var{overlay}
10421 @cindex map an overlay
10422 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
10423 be the name of the object file section containing the overlay. When an
10424 overlay is mapped, @value{GDBN} assumes it can find the overlay's
10425 functions and variables at their mapped addresses. @value{GDBN} assumes
10426 that any other overlays whose mapped ranges overlap that of
10427 @var{overlay} are now unmapped.
10429 @item overlay unmap-overlay @var{overlay}
10430 @itemx overlay unmap @var{overlay}
10431 @cindex unmap an overlay
10432 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
10433 must be the name of the object file section containing the overlay.
10434 When an overlay is unmapped, @value{GDBN} assumes it can find the
10435 overlay's functions and variables at their load addresses.
10438 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
10439 consults a data structure the overlay manager maintains in the inferior
10440 to see which overlays are mapped. For details, see @ref{Automatic
10441 Overlay Debugging}.
10443 @item overlay load-target
10444 @itemx overlay load
10445 @cindex reloading the overlay table
10446 Re-read the overlay table from the inferior. Normally, @value{GDBN}
10447 re-reads the table @value{GDBN} automatically each time the inferior
10448 stops, so this command should only be necessary if you have changed the
10449 overlay mapping yourself using @value{GDBN}. This command is only
10450 useful when using automatic overlay debugging.
10452 @item overlay list-overlays
10453 @itemx overlay list
10454 @cindex listing mapped overlays
10455 Display a list of the overlays currently mapped, along with their mapped
10456 addresses, load addresses, and sizes.
10460 Normally, when @value{GDBN} prints a code address, it includes the name
10461 of the function the address falls in:
10464 (@value{GDBP}) print main
10465 $3 = @{int ()@} 0x11a0 <main>
10468 When overlay debugging is enabled, @value{GDBN} recognizes code in
10469 unmapped overlays, and prints the names of unmapped functions with
10470 asterisks around them. For example, if @code{foo} is a function in an
10471 unmapped overlay, @value{GDBN} prints it this way:
10474 (@value{GDBP}) overlay list
10475 No sections are mapped.
10476 (@value{GDBP}) print foo
10477 $5 = @{int (int)@} 0x100000 <*foo*>
10480 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
10484 (@value{GDBP}) overlay list
10485 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
10486 mapped at 0x1016 - 0x104a
10487 (@value{GDBP}) print foo
10488 $6 = @{int (int)@} 0x1016 <foo>
10491 When overlay debugging is enabled, @value{GDBN} can find the correct
10492 address for functions and variables in an overlay, whether or not the
10493 overlay is mapped. This allows most @value{GDBN} commands, like
10494 @code{break} and @code{disassemble}, to work normally, even on unmapped
10495 code. However, @value{GDBN}'s breakpoint support has some limitations:
10499 @cindex breakpoints in overlays
10500 @cindex overlays, setting breakpoints in
10501 You can set breakpoints in functions in unmapped overlays, as long as
10502 @value{GDBN} can write to the overlay at its load address.
10504 @value{GDBN} can not set hardware or simulator-based breakpoints in
10505 unmapped overlays. However, if you set a breakpoint at the end of your
10506 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
10507 you are using manual overlay management), @value{GDBN} will re-set its
10508 breakpoints properly.
10512 @node Automatic Overlay Debugging
10513 @section Automatic Overlay Debugging
10514 @cindex automatic overlay debugging
10516 @value{GDBN} can automatically track which overlays are mapped and which
10517 are not, given some simple co-operation from the overlay manager in the
10518 inferior. If you enable automatic overlay debugging with the
10519 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
10520 looks in the inferior's memory for certain variables describing the
10521 current state of the overlays.
10523 Here are the variables your overlay manager must define to support
10524 @value{GDBN}'s automatic overlay debugging:
10528 @item @code{_ovly_table}:
10529 This variable must be an array of the following structures:
10534 /* The overlay's mapped address. */
10537 /* The size of the overlay, in bytes. */
10538 unsigned long size;
10540 /* The overlay's load address. */
10543 /* Non-zero if the overlay is currently mapped;
10545 unsigned long mapped;
10549 @item @code{_novlys}:
10550 This variable must be a four-byte signed integer, holding the total
10551 number of elements in @code{_ovly_table}.
10555 To decide whether a particular overlay is mapped or not, @value{GDBN}
10556 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
10557 @code{lma} members equal the VMA and LMA of the overlay's section in the
10558 executable file. When @value{GDBN} finds a matching entry, it consults
10559 the entry's @code{mapped} member to determine whether the overlay is
10562 In addition, your overlay manager may define a function called
10563 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
10564 will silently set a breakpoint there. If the overlay manager then
10565 calls this function whenever it has changed the overlay table, this
10566 will enable @value{GDBN} to accurately keep track of which overlays
10567 are in program memory, and update any breakpoints that may be set
10568 in overlays. This will allow breakpoints to work even if the
10569 overlays are kept in ROM or other non-writable memory while they
10570 are not being executed.
10572 @node Overlay Sample Program
10573 @section Overlay Sample Program
10574 @cindex overlay example program
10576 When linking a program which uses overlays, you must place the overlays
10577 at their load addresses, while relocating them to run at their mapped
10578 addresses. To do this, you must write a linker script (@pxref{Overlay
10579 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
10580 since linker scripts are specific to a particular host system, target
10581 architecture, and target memory layout, this manual cannot provide
10582 portable sample code demonstrating @value{GDBN}'s overlay support.
10584 However, the @value{GDBN} source distribution does contain an overlaid
10585 program, with linker scripts for a few systems, as part of its test
10586 suite. The program consists of the following files from
10587 @file{gdb/testsuite/gdb.base}:
10591 The main program file.
10593 A simple overlay manager, used by @file{overlays.c}.
10598 Overlay modules, loaded and used by @file{overlays.c}.
10601 Linker scripts for linking the test program on the @code{d10v-elf}
10602 and @code{m32r-elf} targets.
10605 You can build the test program using the @code{d10v-elf} GCC
10606 cross-compiler like this:
10609 $ d10v-elf-gcc -g -c overlays.c
10610 $ d10v-elf-gcc -g -c ovlymgr.c
10611 $ d10v-elf-gcc -g -c foo.c
10612 $ d10v-elf-gcc -g -c bar.c
10613 $ d10v-elf-gcc -g -c baz.c
10614 $ d10v-elf-gcc -g -c grbx.c
10615 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
10616 baz.o grbx.o -Wl,-Td10v.ld -o overlays
10619 The build process is identical for any other architecture, except that
10620 you must substitute the appropriate compiler and linker script for the
10621 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
10625 @chapter Using @value{GDBN} with Different Languages
10628 Although programming languages generally have common aspects, they are
10629 rarely expressed in the same manner. For instance, in ANSI C,
10630 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
10631 Modula-2, it is accomplished by @code{p^}. Values can also be
10632 represented (and displayed) differently. Hex numbers in C appear as
10633 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
10635 @cindex working language
10636 Language-specific information is built into @value{GDBN} for some languages,
10637 allowing you to express operations like the above in your program's
10638 native language, and allowing @value{GDBN} to output values in a manner
10639 consistent with the syntax of your program's native language. The
10640 language you use to build expressions is called the @dfn{working
10644 * Setting:: Switching between source languages
10645 * Show:: Displaying the language
10646 * Checks:: Type and range checks
10647 * Supported Languages:: Supported languages
10648 * Unsupported Languages:: Unsupported languages
10652 @section Switching Between Source Languages
10654 There are two ways to control the working language---either have @value{GDBN}
10655 set it automatically, or select it manually yourself. You can use the
10656 @code{set language} command for either purpose. On startup, @value{GDBN}
10657 defaults to setting the language automatically. The working language is
10658 used to determine how expressions you type are interpreted, how values
10661 In addition to the working language, every source file that
10662 @value{GDBN} knows about has its own working language. For some object
10663 file formats, the compiler might indicate which language a particular
10664 source file is in. However, most of the time @value{GDBN} infers the
10665 language from the name of the file. The language of a source file
10666 controls whether C@t{++} names are demangled---this way @code{backtrace} can
10667 show each frame appropriately for its own language. There is no way to
10668 set the language of a source file from within @value{GDBN}, but you can
10669 set the language associated with a filename extension. @xref{Show, ,
10670 Displaying the Language}.
10672 This is most commonly a problem when you use a program, such
10673 as @code{cfront} or @code{f2c}, that generates C but is written in
10674 another language. In that case, make the
10675 program use @code{#line} directives in its C output; that way
10676 @value{GDBN} will know the correct language of the source code of the original
10677 program, and will display that source code, not the generated C code.
10680 * Filenames:: Filename extensions and languages.
10681 * Manually:: Setting the working language manually
10682 * Automatically:: Having @value{GDBN} infer the source language
10686 @subsection List of Filename Extensions and Languages
10688 If a source file name ends in one of the following extensions, then
10689 @value{GDBN} infers that its language is the one indicated.
10707 C@t{++} source file
10710 Objective-C source file
10714 Fortran source file
10717 Modula-2 source file
10721 Assembler source file. This actually behaves almost like C, but
10722 @value{GDBN} does not skip over function prologues when stepping.
10725 In addition, you may set the language associated with a filename
10726 extension. @xref{Show, , Displaying the Language}.
10729 @subsection Setting the Working Language
10731 If you allow @value{GDBN} to set the language automatically,
10732 expressions are interpreted the same way in your debugging session and
10735 @kindex set language
10736 If you wish, you may set the language manually. To do this, issue the
10737 command @samp{set language @var{lang}}, where @var{lang} is the name of
10738 a language, such as
10739 @code{c} or @code{modula-2}.
10740 For a list of the supported languages, type @samp{set language}.
10742 Setting the language manually prevents @value{GDBN} from updating the working
10743 language automatically. This can lead to confusion if you try
10744 to debug a program when the working language is not the same as the
10745 source language, when an expression is acceptable to both
10746 languages---but means different things. For instance, if the current
10747 source file were written in C, and @value{GDBN} was parsing Modula-2, a
10755 might not have the effect you intended. In C, this means to add
10756 @code{b} and @code{c} and place the result in @code{a}. The result
10757 printed would be the value of @code{a}. In Modula-2, this means to compare
10758 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
10760 @node Automatically
10761 @subsection Having @value{GDBN} Infer the Source Language
10763 To have @value{GDBN} set the working language automatically, use
10764 @samp{set language local} or @samp{set language auto}. @value{GDBN}
10765 then infers the working language. That is, when your program stops in a
10766 frame (usually by encountering a breakpoint), @value{GDBN} sets the
10767 working language to the language recorded for the function in that
10768 frame. If the language for a frame is unknown (that is, if the function
10769 or block corresponding to the frame was defined in a source file that
10770 does not have a recognized extension), the current working language is
10771 not changed, and @value{GDBN} issues a warning.
10773 This may not seem necessary for most programs, which are written
10774 entirely in one source language. However, program modules and libraries
10775 written in one source language can be used by a main program written in
10776 a different source language. Using @samp{set language auto} in this
10777 case frees you from having to set the working language manually.
10780 @section Displaying the Language
10782 The following commands help you find out which language is the
10783 working language, and also what language source files were written in.
10786 @item show language
10787 @kindex show language
10788 Display the current working language. This is the
10789 language you can use with commands such as @code{print} to
10790 build and compute expressions that may involve variables in your program.
10793 @kindex info frame@r{, show the source language}
10794 Display the source language for this frame. This language becomes the
10795 working language if you use an identifier from this frame.
10796 @xref{Frame Info, ,Information about a Frame}, to identify the other
10797 information listed here.
10800 @kindex info source@r{, show the source language}
10801 Display the source language of this source file.
10802 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
10803 information listed here.
10806 In unusual circumstances, you may have source files with extensions
10807 not in the standard list. You can then set the extension associated
10808 with a language explicitly:
10811 @item set extension-language @var{ext} @var{language}
10812 @kindex set extension-language
10813 Tell @value{GDBN} that source files with extension @var{ext} are to be
10814 assumed as written in the source language @var{language}.
10816 @item info extensions
10817 @kindex info extensions
10818 List all the filename extensions and the associated languages.
10822 @section Type and Range Checking
10825 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
10826 checking are included, but they do not yet have any effect. This
10827 section documents the intended facilities.
10829 @c FIXME remove warning when type/range code added
10831 Some languages are designed to guard you against making seemingly common
10832 errors through a series of compile- and run-time checks. These include
10833 checking the type of arguments to functions and operators, and making
10834 sure mathematical overflows are caught at run time. Checks such as
10835 these help to ensure a program's correctness once it has been compiled
10836 by eliminating type mismatches, and providing active checks for range
10837 errors when your program is running.
10839 @value{GDBN} can check for conditions like the above if you wish.
10840 Although @value{GDBN} does not check the statements in your program,
10841 it can check expressions entered directly into @value{GDBN} for
10842 evaluation via the @code{print} command, for example. As with the
10843 working language, @value{GDBN} can also decide whether or not to check
10844 automatically based on your program's source language.
10845 @xref{Supported Languages, ,Supported Languages}, for the default
10846 settings of supported languages.
10849 * Type Checking:: An overview of type checking
10850 * Range Checking:: An overview of range checking
10853 @cindex type checking
10854 @cindex checks, type
10855 @node Type Checking
10856 @subsection An Overview of Type Checking
10858 Some languages, such as Modula-2, are strongly typed, meaning that the
10859 arguments to operators and functions have to be of the correct type,
10860 otherwise an error occurs. These checks prevent type mismatch
10861 errors from ever causing any run-time problems. For example,
10869 The second example fails because the @code{CARDINAL} 1 is not
10870 type-compatible with the @code{REAL} 2.3.
10872 For the expressions you use in @value{GDBN} commands, you can tell the
10873 @value{GDBN} type checker to skip checking;
10874 to treat any mismatches as errors and abandon the expression;
10875 or to only issue warnings when type mismatches occur,
10876 but evaluate the expression anyway. When you choose the last of
10877 these, @value{GDBN} evaluates expressions like the second example above, but
10878 also issues a warning.
10880 Even if you turn type checking off, there may be other reasons
10881 related to type that prevent @value{GDBN} from evaluating an expression.
10882 For instance, @value{GDBN} does not know how to add an @code{int} and
10883 a @code{struct foo}. These particular type errors have nothing to do
10884 with the language in use, and usually arise from expressions, such as
10885 the one described above, which make little sense to evaluate anyway.
10887 Each language defines to what degree it is strict about type. For
10888 instance, both Modula-2 and C require the arguments to arithmetical
10889 operators to be numbers. In C, enumerated types and pointers can be
10890 represented as numbers, so that they are valid arguments to mathematical
10891 operators. @xref{Supported Languages, ,Supported Languages}, for further
10892 details on specific languages.
10894 @value{GDBN} provides some additional commands for controlling the type checker:
10896 @kindex set check type
10897 @kindex show check type
10899 @item set check type auto
10900 Set type checking on or off based on the current working language.
10901 @xref{Supported Languages, ,Supported Languages}, for the default settings for
10904 @item set check type on
10905 @itemx set check type off
10906 Set type checking on or off, overriding the default setting for the
10907 current working language. Issue a warning if the setting does not
10908 match the language default. If any type mismatches occur in
10909 evaluating an expression while type checking is on, @value{GDBN} prints a
10910 message and aborts evaluation of the expression.
10912 @item set check type warn
10913 Cause the type checker to issue warnings, but to always attempt to
10914 evaluate the expression. Evaluating the expression may still
10915 be impossible for other reasons. For example, @value{GDBN} cannot add
10916 numbers and structures.
10919 Show the current setting of the type checker, and whether or not @value{GDBN}
10920 is setting it automatically.
10923 @cindex range checking
10924 @cindex checks, range
10925 @node Range Checking
10926 @subsection An Overview of Range Checking
10928 In some languages (such as Modula-2), it is an error to exceed the
10929 bounds of a type; this is enforced with run-time checks. Such range
10930 checking is meant to ensure program correctness by making sure
10931 computations do not overflow, or indices on an array element access do
10932 not exceed the bounds of the array.
10934 For expressions you use in @value{GDBN} commands, you can tell
10935 @value{GDBN} to treat range errors in one of three ways: ignore them,
10936 always treat them as errors and abandon the expression, or issue
10937 warnings but evaluate the expression anyway.
10939 A range error can result from numerical overflow, from exceeding an
10940 array index bound, or when you type a constant that is not a member
10941 of any type. Some languages, however, do not treat overflows as an
10942 error. In many implementations of C, mathematical overflow causes the
10943 result to ``wrap around'' to lower values---for example, if @var{m} is
10944 the largest integer value, and @var{s} is the smallest, then
10947 @var{m} + 1 @result{} @var{s}
10950 This, too, is specific to individual languages, and in some cases
10951 specific to individual compilers or machines. @xref{Supported Languages, ,
10952 Supported Languages}, for further details on specific languages.
10954 @value{GDBN} provides some additional commands for controlling the range checker:
10956 @kindex set check range
10957 @kindex show check range
10959 @item set check range auto
10960 Set range checking on or off based on the current working language.
10961 @xref{Supported Languages, ,Supported Languages}, for the default settings for
10964 @item set check range on
10965 @itemx set check range off
10966 Set range checking on or off, overriding the default setting for the
10967 current working language. A warning is issued if the setting does not
10968 match the language default. If a range error occurs and range checking is on,
10969 then a message is printed and evaluation of the expression is aborted.
10971 @item set check range warn
10972 Output messages when the @value{GDBN} range checker detects a range error,
10973 but attempt to evaluate the expression anyway. Evaluating the
10974 expression may still be impossible for other reasons, such as accessing
10975 memory that the process does not own (a typical example from many Unix
10979 Show the current setting of the range checker, and whether or not it is
10980 being set automatically by @value{GDBN}.
10983 @node Supported Languages
10984 @section Supported Languages
10986 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
10987 assembly, Modula-2, and Ada.
10988 @c This is false ...
10989 Some @value{GDBN} features may be used in expressions regardless of the
10990 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
10991 and the @samp{@{type@}addr} construct (@pxref{Expressions,
10992 ,Expressions}) can be used with the constructs of any supported
10995 The following sections detail to what degree each source language is
10996 supported by @value{GDBN}. These sections are not meant to be language
10997 tutorials or references, but serve only as a reference guide to what the
10998 @value{GDBN} expression parser accepts, and what input and output
10999 formats should look like for different languages. There are many good
11000 books written on each of these languages; please look to these for a
11001 language reference or tutorial.
11004 * C:: C and C@t{++}
11005 * Objective-C:: Objective-C
11006 * Fortran:: Fortran
11008 * Modula-2:: Modula-2
11013 @subsection C and C@t{++}
11015 @cindex C and C@t{++}
11016 @cindex expressions in C or C@t{++}
11018 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
11019 to both languages. Whenever this is the case, we discuss those languages
11023 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
11024 @cindex @sc{gnu} C@t{++}
11025 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
11026 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
11027 effectively, you must compile your C@t{++} programs with a supported
11028 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
11029 compiler (@code{aCC}).
11031 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
11032 format; if it doesn't work on your system, try the stabs+ debugging
11033 format. You can select those formats explicitly with the @code{g++}
11034 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
11035 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
11036 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
11039 * C Operators:: C and C@t{++} operators
11040 * C Constants:: C and C@t{++} constants
11041 * C Plus Plus Expressions:: C@t{++} expressions
11042 * C Defaults:: Default settings for C and C@t{++}
11043 * C Checks:: C and C@t{++} type and range checks
11044 * Debugging C:: @value{GDBN} and C
11045 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
11046 * Decimal Floating Point:: Numbers in Decimal Floating Point format
11050 @subsubsection C and C@t{++} Operators
11052 @cindex C and C@t{++} operators
11054 Operators must be defined on values of specific types. For instance,
11055 @code{+} is defined on numbers, but not on structures. Operators are
11056 often defined on groups of types.
11058 For the purposes of C and C@t{++}, the following definitions hold:
11063 @emph{Integral types} include @code{int} with any of its storage-class
11064 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
11067 @emph{Floating-point types} include @code{float}, @code{double}, and
11068 @code{long double} (if supported by the target platform).
11071 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
11074 @emph{Scalar types} include all of the above.
11079 The following operators are supported. They are listed here
11080 in order of increasing precedence:
11084 The comma or sequencing operator. Expressions in a comma-separated list
11085 are evaluated from left to right, with the result of the entire
11086 expression being the last expression evaluated.
11089 Assignment. The value of an assignment expression is the value
11090 assigned. Defined on scalar types.
11093 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
11094 and translated to @w{@code{@var{a} = @var{a op b}}}.
11095 @w{@code{@var{op}=}} and @code{=} have the same precedence.
11096 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
11097 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
11100 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
11101 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
11105 Logical @sc{or}. Defined on integral types.
11108 Logical @sc{and}. Defined on integral types.
11111 Bitwise @sc{or}. Defined on integral types.
11114 Bitwise exclusive-@sc{or}. Defined on integral types.
11117 Bitwise @sc{and}. Defined on integral types.
11120 Equality and inequality. Defined on scalar types. The value of these
11121 expressions is 0 for false and non-zero for true.
11123 @item <@r{, }>@r{, }<=@r{, }>=
11124 Less than, greater than, less than or equal, greater than or equal.
11125 Defined on scalar types. The value of these expressions is 0 for false
11126 and non-zero for true.
11129 left shift, and right shift. Defined on integral types.
11132 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
11135 Addition and subtraction. Defined on integral types, floating-point types and
11138 @item *@r{, }/@r{, }%
11139 Multiplication, division, and modulus. Multiplication and division are
11140 defined on integral and floating-point types. Modulus is defined on
11144 Increment and decrement. When appearing before a variable, the
11145 operation is performed before the variable is used in an expression;
11146 when appearing after it, the variable's value is used before the
11147 operation takes place.
11150 Pointer dereferencing. Defined on pointer types. Same precedence as
11154 Address operator. Defined on variables. Same precedence as @code{++}.
11156 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
11157 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
11158 to examine the address
11159 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
11163 Negative. Defined on integral and floating-point types. Same
11164 precedence as @code{++}.
11167 Logical negation. Defined on integral types. Same precedence as
11171 Bitwise complement operator. Defined on integral types. Same precedence as
11176 Structure member, and pointer-to-structure member. For convenience,
11177 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
11178 pointer based on the stored type information.
11179 Defined on @code{struct} and @code{union} data.
11182 Dereferences of pointers to members.
11185 Array indexing. @code{@var{a}[@var{i}]} is defined as
11186 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
11189 Function parameter list. Same precedence as @code{->}.
11192 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
11193 and @code{class} types.
11196 Doubled colons also represent the @value{GDBN} scope operator
11197 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
11201 If an operator is redefined in the user code, @value{GDBN} usually
11202 attempts to invoke the redefined version instead of using the operator's
11203 predefined meaning.
11206 @subsubsection C and C@t{++} Constants
11208 @cindex C and C@t{++} constants
11210 @value{GDBN} allows you to express the constants of C and C@t{++} in the
11215 Integer constants are a sequence of digits. Octal constants are
11216 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
11217 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
11218 @samp{l}, specifying that the constant should be treated as a
11222 Floating point constants are a sequence of digits, followed by a decimal
11223 point, followed by a sequence of digits, and optionally followed by an
11224 exponent. An exponent is of the form:
11225 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
11226 sequence of digits. The @samp{+} is optional for positive exponents.
11227 A floating-point constant may also end with a letter @samp{f} or
11228 @samp{F}, specifying that the constant should be treated as being of
11229 the @code{float} (as opposed to the default @code{double}) type; or with
11230 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
11234 Enumerated constants consist of enumerated identifiers, or their
11235 integral equivalents.
11238 Character constants are a single character surrounded by single quotes
11239 (@code{'}), or a number---the ordinal value of the corresponding character
11240 (usually its @sc{ascii} value). Within quotes, the single character may
11241 be represented by a letter or by @dfn{escape sequences}, which are of
11242 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
11243 of the character's ordinal value; or of the form @samp{\@var{x}}, where
11244 @samp{@var{x}} is a predefined special character---for example,
11245 @samp{\n} for newline.
11248 String constants are a sequence of character constants surrounded by
11249 double quotes (@code{"}). Any valid character constant (as described
11250 above) may appear. Double quotes within the string must be preceded by
11251 a backslash, so for instance @samp{"a\"b'c"} is a string of five
11255 Pointer constants are an integral value. You can also write pointers
11256 to constants using the C operator @samp{&}.
11259 Array constants are comma-separated lists surrounded by braces @samp{@{}
11260 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
11261 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
11262 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
11265 @node C Plus Plus Expressions
11266 @subsubsection C@t{++} Expressions
11268 @cindex expressions in C@t{++}
11269 @value{GDBN} expression handling can interpret most C@t{++} expressions.
11271 @cindex debugging C@t{++} programs
11272 @cindex C@t{++} compilers
11273 @cindex debug formats and C@t{++}
11274 @cindex @value{NGCC} and C@t{++}
11276 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
11277 proper compiler and the proper debug format. Currently, @value{GDBN}
11278 works best when debugging C@t{++} code that is compiled with
11279 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
11280 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
11281 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
11282 stabs+ as their default debug format, so you usually don't need to
11283 specify a debug format explicitly. Other compilers and/or debug formats
11284 are likely to work badly or not at all when using @value{GDBN} to debug
11290 @cindex member functions
11292 Member function calls are allowed; you can use expressions like
11295 count = aml->GetOriginal(x, y)
11298 @vindex this@r{, inside C@t{++} member functions}
11299 @cindex namespace in C@t{++}
11301 While a member function is active (in the selected stack frame), your
11302 expressions have the same namespace available as the member function;
11303 that is, @value{GDBN} allows implicit references to the class instance
11304 pointer @code{this} following the same rules as C@t{++}.
11306 @cindex call overloaded functions
11307 @cindex overloaded functions, calling
11308 @cindex type conversions in C@t{++}
11310 You can call overloaded functions; @value{GDBN} resolves the function
11311 call to the right definition, with some restrictions. @value{GDBN} does not
11312 perform overload resolution involving user-defined type conversions,
11313 calls to constructors, or instantiations of templates that do not exist
11314 in the program. It also cannot handle ellipsis argument lists or
11317 It does perform integral conversions and promotions, floating-point
11318 promotions, arithmetic conversions, pointer conversions, conversions of
11319 class objects to base classes, and standard conversions such as those of
11320 functions or arrays to pointers; it requires an exact match on the
11321 number of function arguments.
11323 Overload resolution is always performed, unless you have specified
11324 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
11325 ,@value{GDBN} Features for C@t{++}}.
11327 You must specify @code{set overload-resolution off} in order to use an
11328 explicit function signature to call an overloaded function, as in
11330 p 'foo(char,int)'('x', 13)
11333 The @value{GDBN} command-completion facility can simplify this;
11334 see @ref{Completion, ,Command Completion}.
11336 @cindex reference declarations
11338 @value{GDBN} understands variables declared as C@t{++} references; you can use
11339 them in expressions just as you do in C@t{++} source---they are automatically
11342 In the parameter list shown when @value{GDBN} displays a frame, the values of
11343 reference variables are not displayed (unlike other variables); this
11344 avoids clutter, since references are often used for large structures.
11345 The @emph{address} of a reference variable is always shown, unless
11346 you have specified @samp{set print address off}.
11349 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
11350 expressions can use it just as expressions in your program do. Since
11351 one scope may be defined in another, you can use @code{::} repeatedly if
11352 necessary, for example in an expression like
11353 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
11354 resolving name scope by reference to source files, in both C and C@t{++}
11355 debugging (@pxref{Variables, ,Program Variables}).
11358 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
11359 calling virtual functions correctly, printing out virtual bases of
11360 objects, calling functions in a base subobject, casting objects, and
11361 invoking user-defined operators.
11364 @subsubsection C and C@t{++} Defaults
11366 @cindex C and C@t{++} defaults
11368 If you allow @value{GDBN} to set type and range checking automatically, they
11369 both default to @code{off} whenever the working language changes to
11370 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
11371 selects the working language.
11373 If you allow @value{GDBN} to set the language automatically, it
11374 recognizes source files whose names end with @file{.c}, @file{.C}, or
11375 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
11376 these files, it sets the working language to C or C@t{++}.
11377 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
11378 for further details.
11380 @c Type checking is (a) primarily motivated by Modula-2, and (b)
11381 @c unimplemented. If (b) changes, it might make sense to let this node
11382 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
11385 @subsubsection C and C@t{++} Type and Range Checks
11387 @cindex C and C@t{++} checks
11389 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
11390 is not used. However, if you turn type checking on, @value{GDBN}
11391 considers two variables type equivalent if:
11395 The two variables are structured and have the same structure, union, or
11399 The two variables have the same type name, or types that have been
11400 declared equivalent through @code{typedef}.
11403 @c leaving this out because neither J Gilmore nor R Pesch understand it.
11406 The two @code{struct}, @code{union}, or @code{enum} variables are
11407 declared in the same declaration. (Note: this may not be true for all C
11412 Range checking, if turned on, is done on mathematical operations. Array
11413 indices are not checked, since they are often used to index a pointer
11414 that is not itself an array.
11417 @subsubsection @value{GDBN} and C
11419 The @code{set print union} and @code{show print union} commands apply to
11420 the @code{union} type. When set to @samp{on}, any @code{union} that is
11421 inside a @code{struct} or @code{class} is also printed. Otherwise, it
11422 appears as @samp{@{...@}}.
11424 The @code{@@} operator aids in the debugging of dynamic arrays, formed
11425 with pointers and a memory allocation function. @xref{Expressions,
11428 @node Debugging C Plus Plus
11429 @subsubsection @value{GDBN} Features for C@t{++}
11431 @cindex commands for C@t{++}
11433 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
11434 designed specifically for use with C@t{++}. Here is a summary:
11437 @cindex break in overloaded functions
11438 @item @r{breakpoint menus}
11439 When you want a breakpoint in a function whose name is overloaded,
11440 @value{GDBN} has the capability to display a menu of possible breakpoint
11441 locations to help you specify which function definition you want.
11442 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
11444 @cindex overloading in C@t{++}
11445 @item rbreak @var{regex}
11446 Setting breakpoints using regular expressions is helpful for setting
11447 breakpoints on overloaded functions that are not members of any special
11449 @xref{Set Breaks, ,Setting Breakpoints}.
11451 @cindex C@t{++} exception handling
11454 Debug C@t{++} exception handling using these commands. @xref{Set
11455 Catchpoints, , Setting Catchpoints}.
11457 @cindex inheritance
11458 @item ptype @var{typename}
11459 Print inheritance relationships as well as other information for type
11461 @xref{Symbols, ,Examining the Symbol Table}.
11463 @cindex C@t{++} symbol display
11464 @item set print demangle
11465 @itemx show print demangle
11466 @itemx set print asm-demangle
11467 @itemx show print asm-demangle
11468 Control whether C@t{++} symbols display in their source form, both when
11469 displaying code as C@t{++} source and when displaying disassemblies.
11470 @xref{Print Settings, ,Print Settings}.
11472 @item set print object
11473 @itemx show print object
11474 Choose whether to print derived (actual) or declared types of objects.
11475 @xref{Print Settings, ,Print Settings}.
11477 @item set print vtbl
11478 @itemx show print vtbl
11479 Control the format for printing virtual function tables.
11480 @xref{Print Settings, ,Print Settings}.
11481 (The @code{vtbl} commands do not work on programs compiled with the HP
11482 ANSI C@t{++} compiler (@code{aCC}).)
11484 @kindex set overload-resolution
11485 @cindex overloaded functions, overload resolution
11486 @item set overload-resolution on
11487 Enable overload resolution for C@t{++} expression evaluation. The default
11488 is on. For overloaded functions, @value{GDBN} evaluates the arguments
11489 and searches for a function whose signature matches the argument types,
11490 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
11491 Expressions, ,C@t{++} Expressions}, for details).
11492 If it cannot find a match, it emits a message.
11494 @item set overload-resolution off
11495 Disable overload resolution for C@t{++} expression evaluation. For
11496 overloaded functions that are not class member functions, @value{GDBN}
11497 chooses the first function of the specified name that it finds in the
11498 symbol table, whether or not its arguments are of the correct type. For
11499 overloaded functions that are class member functions, @value{GDBN}
11500 searches for a function whose signature @emph{exactly} matches the
11503 @kindex show overload-resolution
11504 @item show overload-resolution
11505 Show the current setting of overload resolution.
11507 @item @r{Overloaded symbol names}
11508 You can specify a particular definition of an overloaded symbol, using
11509 the same notation that is used to declare such symbols in C@t{++}: type
11510 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
11511 also use the @value{GDBN} command-line word completion facilities to list the
11512 available choices, or to finish the type list for you.
11513 @xref{Completion,, Command Completion}, for details on how to do this.
11516 @node Decimal Floating Point
11517 @subsubsection Decimal Floating Point format
11518 @cindex decimal floating point format
11520 @value{GDBN} can examine, set and perform computations with numbers in
11521 decimal floating point format, which in the C language correspond to the
11522 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
11523 specified by the extension to support decimal floating-point arithmetic.
11525 There are two encodings in use, depending on the architecture: BID (Binary
11526 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
11527 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
11530 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
11531 to manipulate decimal floating point numbers, it is not possible to convert
11532 (using a cast, for example) integers wider than 32-bit to decimal float.
11534 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
11535 point computations, error checking in decimal float operations ignores
11536 underflow, overflow and divide by zero exceptions.
11538 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
11539 to inspect @code{_Decimal128} values stored in floating point registers.
11540 See @ref{PowerPC,,PowerPC} for more details.
11543 @subsection Objective-C
11545 @cindex Objective-C
11546 This section provides information about some commands and command
11547 options that are useful for debugging Objective-C code. See also
11548 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
11549 few more commands specific to Objective-C support.
11552 * Method Names in Commands::
11553 * The Print Command with Objective-C::
11556 @node Method Names in Commands
11557 @subsubsection Method Names in Commands
11559 The following commands have been extended to accept Objective-C method
11560 names as line specifications:
11562 @kindex clear@r{, and Objective-C}
11563 @kindex break@r{, and Objective-C}
11564 @kindex info line@r{, and Objective-C}
11565 @kindex jump@r{, and Objective-C}
11566 @kindex list@r{, and Objective-C}
11570 @item @code{info line}
11575 A fully qualified Objective-C method name is specified as
11578 -[@var{Class} @var{methodName}]
11581 where the minus sign is used to indicate an instance method and a
11582 plus sign (not shown) is used to indicate a class method. The class
11583 name @var{Class} and method name @var{methodName} are enclosed in
11584 brackets, similar to the way messages are specified in Objective-C
11585 source code. For example, to set a breakpoint at the @code{create}
11586 instance method of class @code{Fruit} in the program currently being
11590 break -[Fruit create]
11593 To list ten program lines around the @code{initialize} class method,
11597 list +[NSText initialize]
11600 In the current version of @value{GDBN}, the plus or minus sign is
11601 required. In future versions of @value{GDBN}, the plus or minus
11602 sign will be optional, but you can use it to narrow the search. It
11603 is also possible to specify just a method name:
11609 You must specify the complete method name, including any colons. If
11610 your program's source files contain more than one @code{create} method,
11611 you'll be presented with a numbered list of classes that implement that
11612 method. Indicate your choice by number, or type @samp{0} to exit if
11615 As another example, to clear a breakpoint established at the
11616 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
11619 clear -[NSWindow makeKeyAndOrderFront:]
11622 @node The Print Command with Objective-C
11623 @subsubsection The Print Command With Objective-C
11624 @cindex Objective-C, print objects
11625 @kindex print-object
11626 @kindex po @r{(@code{print-object})}
11628 The print command has also been extended to accept methods. For example:
11631 print -[@var{object} hash]
11634 @cindex print an Objective-C object description
11635 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
11637 will tell @value{GDBN} to send the @code{hash} message to @var{object}
11638 and print the result. Also, an additional command has been added,
11639 @code{print-object} or @code{po} for short, which is meant to print
11640 the description of an object. However, this command may only work
11641 with certain Objective-C libraries that have a particular hook
11642 function, @code{_NSPrintForDebugger}, defined.
11645 @subsection Fortran
11646 @cindex Fortran-specific support in @value{GDBN}
11648 @value{GDBN} can be used to debug programs written in Fortran, but it
11649 currently supports only the features of Fortran 77 language.
11651 @cindex trailing underscore, in Fortran symbols
11652 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
11653 among them) append an underscore to the names of variables and
11654 functions. When you debug programs compiled by those compilers, you
11655 will need to refer to variables and functions with a trailing
11659 * Fortran Operators:: Fortran operators and expressions
11660 * Fortran Defaults:: Default settings for Fortran
11661 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
11664 @node Fortran Operators
11665 @subsubsection Fortran Operators and Expressions
11667 @cindex Fortran operators and expressions
11669 Operators must be defined on values of specific types. For instance,
11670 @code{+} is defined on numbers, but not on characters or other non-
11671 arithmetic types. Operators are often defined on groups of types.
11675 The exponentiation operator. It raises the first operand to the power
11679 The range operator. Normally used in the form of array(low:high) to
11680 represent a section of array.
11683 The access component operator. Normally used to access elements in derived
11684 types. Also suitable for unions. As unions aren't part of regular Fortran,
11685 this can only happen when accessing a register that uses a gdbarch-defined
11689 @node Fortran Defaults
11690 @subsubsection Fortran Defaults
11692 @cindex Fortran Defaults
11694 Fortran symbols are usually case-insensitive, so @value{GDBN} by
11695 default uses case-insensitive matches for Fortran symbols. You can
11696 change that with the @samp{set case-insensitive} command, see
11697 @ref{Symbols}, for the details.
11699 @node Special Fortran Commands
11700 @subsubsection Special Fortran Commands
11702 @cindex Special Fortran commands
11704 @value{GDBN} has some commands to support Fortran-specific features,
11705 such as displaying common blocks.
11708 @cindex @code{COMMON} blocks, Fortran
11709 @kindex info common
11710 @item info common @r{[}@var{common-name}@r{]}
11711 This command prints the values contained in the Fortran @code{COMMON}
11712 block whose name is @var{common-name}. With no argument, the names of
11713 all @code{COMMON} blocks visible at the current program location are
11720 @cindex Pascal support in @value{GDBN}, limitations
11721 Debugging Pascal programs which use sets, subranges, file variables, or
11722 nested functions does not currently work. @value{GDBN} does not support
11723 entering expressions, printing values, or similar features using Pascal
11726 The Pascal-specific command @code{set print pascal_static-members}
11727 controls whether static members of Pascal objects are displayed.
11728 @xref{Print Settings, pascal_static-members}.
11731 @subsection Modula-2
11733 @cindex Modula-2, @value{GDBN} support
11735 The extensions made to @value{GDBN} to support Modula-2 only support
11736 output from the @sc{gnu} Modula-2 compiler (which is currently being
11737 developed). Other Modula-2 compilers are not currently supported, and
11738 attempting to debug executables produced by them is most likely
11739 to give an error as @value{GDBN} reads in the executable's symbol
11742 @cindex expressions in Modula-2
11744 * M2 Operators:: Built-in operators
11745 * Built-In Func/Proc:: Built-in functions and procedures
11746 * M2 Constants:: Modula-2 constants
11747 * M2 Types:: Modula-2 types
11748 * M2 Defaults:: Default settings for Modula-2
11749 * Deviations:: Deviations from standard Modula-2
11750 * M2 Checks:: Modula-2 type and range checks
11751 * M2 Scope:: The scope operators @code{::} and @code{.}
11752 * GDB/M2:: @value{GDBN} and Modula-2
11756 @subsubsection Operators
11757 @cindex Modula-2 operators
11759 Operators must be defined on values of specific types. For instance,
11760 @code{+} is defined on numbers, but not on structures. Operators are
11761 often defined on groups of types. For the purposes of Modula-2, the
11762 following definitions hold:
11767 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
11771 @emph{Character types} consist of @code{CHAR} and its subranges.
11774 @emph{Floating-point types} consist of @code{REAL}.
11777 @emph{Pointer types} consist of anything declared as @code{POINTER TO
11781 @emph{Scalar types} consist of all of the above.
11784 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
11787 @emph{Boolean types} consist of @code{BOOLEAN}.
11791 The following operators are supported, and appear in order of
11792 increasing precedence:
11796 Function argument or array index separator.
11799 Assignment. The value of @var{var} @code{:=} @var{value} is
11803 Less than, greater than on integral, floating-point, or enumerated
11807 Less than or equal to, greater than or equal to
11808 on integral, floating-point and enumerated types, or set inclusion on
11809 set types. Same precedence as @code{<}.
11811 @item =@r{, }<>@r{, }#
11812 Equality and two ways of expressing inequality, valid on scalar types.
11813 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
11814 available for inequality, since @code{#} conflicts with the script
11818 Set membership. Defined on set types and the types of their members.
11819 Same precedence as @code{<}.
11822 Boolean disjunction. Defined on boolean types.
11825 Boolean conjunction. Defined on boolean types.
11828 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
11831 Addition and subtraction on integral and floating-point types, or union
11832 and difference on set types.
11835 Multiplication on integral and floating-point types, or set intersection
11839 Division on floating-point types, or symmetric set difference on set
11840 types. Same precedence as @code{*}.
11843 Integer division and remainder. Defined on integral types. Same
11844 precedence as @code{*}.
11847 Negative. Defined on @code{INTEGER} and @code{REAL} data.
11850 Pointer dereferencing. Defined on pointer types.
11853 Boolean negation. Defined on boolean types. Same precedence as
11857 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
11858 precedence as @code{^}.
11861 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
11864 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
11868 @value{GDBN} and Modula-2 scope operators.
11872 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
11873 treats the use of the operator @code{IN}, or the use of operators
11874 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
11875 @code{<=}, and @code{>=} on sets as an error.
11879 @node Built-In Func/Proc
11880 @subsubsection Built-in Functions and Procedures
11881 @cindex Modula-2 built-ins
11883 Modula-2 also makes available several built-in procedures and functions.
11884 In describing these, the following metavariables are used:
11889 represents an @code{ARRAY} variable.
11892 represents a @code{CHAR} constant or variable.
11895 represents a variable or constant of integral type.
11898 represents an identifier that belongs to a set. Generally used in the
11899 same function with the metavariable @var{s}. The type of @var{s} should
11900 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
11903 represents a variable or constant of integral or floating-point type.
11906 represents a variable or constant of floating-point type.
11912 represents a variable.
11915 represents a variable or constant of one of many types. See the
11916 explanation of the function for details.
11919 All Modula-2 built-in procedures also return a result, described below.
11923 Returns the absolute value of @var{n}.
11926 If @var{c} is a lower case letter, it returns its upper case
11927 equivalent, otherwise it returns its argument.
11930 Returns the character whose ordinal value is @var{i}.
11933 Decrements the value in the variable @var{v} by one. Returns the new value.
11935 @item DEC(@var{v},@var{i})
11936 Decrements the value in the variable @var{v} by @var{i}. Returns the
11939 @item EXCL(@var{m},@var{s})
11940 Removes the element @var{m} from the set @var{s}. Returns the new
11943 @item FLOAT(@var{i})
11944 Returns the floating point equivalent of the integer @var{i}.
11946 @item HIGH(@var{a})
11947 Returns the index of the last member of @var{a}.
11950 Increments the value in the variable @var{v} by one. Returns the new value.
11952 @item INC(@var{v},@var{i})
11953 Increments the value in the variable @var{v} by @var{i}. Returns the
11956 @item INCL(@var{m},@var{s})
11957 Adds the element @var{m} to the set @var{s} if it is not already
11958 there. Returns the new set.
11961 Returns the maximum value of the type @var{t}.
11964 Returns the minimum value of the type @var{t}.
11967 Returns boolean TRUE if @var{i} is an odd number.
11970 Returns the ordinal value of its argument. For example, the ordinal
11971 value of a character is its @sc{ascii} value (on machines supporting the
11972 @sc{ascii} character set). @var{x} must be of an ordered type, which include
11973 integral, character and enumerated types.
11975 @item SIZE(@var{x})
11976 Returns the size of its argument. @var{x} can be a variable or a type.
11978 @item TRUNC(@var{r})
11979 Returns the integral part of @var{r}.
11981 @item TSIZE(@var{x})
11982 Returns the size of its argument. @var{x} can be a variable or a type.
11984 @item VAL(@var{t},@var{i})
11985 Returns the member of the type @var{t} whose ordinal value is @var{i}.
11989 @emph{Warning:} Sets and their operations are not yet supported, so
11990 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
11994 @cindex Modula-2 constants
11996 @subsubsection Constants
11998 @value{GDBN} allows you to express the constants of Modula-2 in the following
12004 Integer constants are simply a sequence of digits. When used in an
12005 expression, a constant is interpreted to be type-compatible with the
12006 rest of the expression. Hexadecimal integers are specified by a
12007 trailing @samp{H}, and octal integers by a trailing @samp{B}.
12010 Floating point constants appear as a sequence of digits, followed by a
12011 decimal point and another sequence of digits. An optional exponent can
12012 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
12013 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
12014 digits of the floating point constant must be valid decimal (base 10)
12018 Character constants consist of a single character enclosed by a pair of
12019 like quotes, either single (@code{'}) or double (@code{"}). They may
12020 also be expressed by their ordinal value (their @sc{ascii} value, usually)
12021 followed by a @samp{C}.
12024 String constants consist of a sequence of characters enclosed by a
12025 pair of like quotes, either single (@code{'}) or double (@code{"}).
12026 Escape sequences in the style of C are also allowed. @xref{C
12027 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
12031 Enumerated constants consist of an enumerated identifier.
12034 Boolean constants consist of the identifiers @code{TRUE} and
12038 Pointer constants consist of integral values only.
12041 Set constants are not yet supported.
12045 @subsubsection Modula-2 Types
12046 @cindex Modula-2 types
12048 Currently @value{GDBN} can print the following data types in Modula-2
12049 syntax: array types, record types, set types, pointer types, procedure
12050 types, enumerated types, subrange types and base types. You can also
12051 print the contents of variables declared using these type.
12052 This section gives a number of simple source code examples together with
12053 sample @value{GDBN} sessions.
12055 The first example contains the following section of code:
12064 and you can request @value{GDBN} to interrogate the type and value of
12065 @code{r} and @code{s}.
12068 (@value{GDBP}) print s
12070 (@value{GDBP}) ptype s
12072 (@value{GDBP}) print r
12074 (@value{GDBP}) ptype r
12079 Likewise if your source code declares @code{s} as:
12083 s: SET ['A'..'Z'] ;
12087 then you may query the type of @code{s} by:
12090 (@value{GDBP}) ptype s
12091 type = SET ['A'..'Z']
12095 Note that at present you cannot interactively manipulate set
12096 expressions using the debugger.
12098 The following example shows how you might declare an array in Modula-2
12099 and how you can interact with @value{GDBN} to print its type and contents:
12103 s: ARRAY [-10..10] OF CHAR ;
12107 (@value{GDBP}) ptype s
12108 ARRAY [-10..10] OF CHAR
12111 Note that the array handling is not yet complete and although the type
12112 is printed correctly, expression handling still assumes that all
12113 arrays have a lower bound of zero and not @code{-10} as in the example
12116 Here are some more type related Modula-2 examples:
12120 colour = (blue, red, yellow, green) ;
12121 t = [blue..yellow] ;
12129 The @value{GDBN} interaction shows how you can query the data type
12130 and value of a variable.
12133 (@value{GDBP}) print s
12135 (@value{GDBP}) ptype t
12136 type = [blue..yellow]
12140 In this example a Modula-2 array is declared and its contents
12141 displayed. Observe that the contents are written in the same way as
12142 their @code{C} counterparts.
12146 s: ARRAY [1..5] OF CARDINAL ;
12152 (@value{GDBP}) print s
12153 $1 = @{1, 0, 0, 0, 0@}
12154 (@value{GDBP}) ptype s
12155 type = ARRAY [1..5] OF CARDINAL
12158 The Modula-2 language interface to @value{GDBN} also understands
12159 pointer types as shown in this example:
12163 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
12170 and you can request that @value{GDBN} describes the type of @code{s}.
12173 (@value{GDBP}) ptype s
12174 type = POINTER TO ARRAY [1..5] OF CARDINAL
12177 @value{GDBN} handles compound types as we can see in this example.
12178 Here we combine array types, record types, pointer types and subrange
12189 myarray = ARRAY myrange OF CARDINAL ;
12190 myrange = [-2..2] ;
12192 s: POINTER TO ARRAY myrange OF foo ;
12196 and you can ask @value{GDBN} to describe the type of @code{s} as shown
12200 (@value{GDBP}) ptype s
12201 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
12204 f3 : ARRAY [-2..2] OF CARDINAL;
12209 @subsubsection Modula-2 Defaults
12210 @cindex Modula-2 defaults
12212 If type and range checking are set automatically by @value{GDBN}, they
12213 both default to @code{on} whenever the working language changes to
12214 Modula-2. This happens regardless of whether you or @value{GDBN}
12215 selected the working language.
12217 If you allow @value{GDBN} to set the language automatically, then entering
12218 code compiled from a file whose name ends with @file{.mod} sets the
12219 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
12220 Infer the Source Language}, for further details.
12223 @subsubsection Deviations from Standard Modula-2
12224 @cindex Modula-2, deviations from
12226 A few changes have been made to make Modula-2 programs easier to debug.
12227 This is done primarily via loosening its type strictness:
12231 Unlike in standard Modula-2, pointer constants can be formed by
12232 integers. This allows you to modify pointer variables during
12233 debugging. (In standard Modula-2, the actual address contained in a
12234 pointer variable is hidden from you; it can only be modified
12235 through direct assignment to another pointer variable or expression that
12236 returned a pointer.)
12239 C escape sequences can be used in strings and characters to represent
12240 non-printable characters. @value{GDBN} prints out strings with these
12241 escape sequences embedded. Single non-printable characters are
12242 printed using the @samp{CHR(@var{nnn})} format.
12245 The assignment operator (@code{:=}) returns the value of its right-hand
12249 All built-in procedures both modify @emph{and} return their argument.
12253 @subsubsection Modula-2 Type and Range Checks
12254 @cindex Modula-2 checks
12257 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
12260 @c FIXME remove warning when type/range checks added
12262 @value{GDBN} considers two Modula-2 variables type equivalent if:
12266 They are of types that have been declared equivalent via a @code{TYPE
12267 @var{t1} = @var{t2}} statement
12270 They have been declared on the same line. (Note: This is true of the
12271 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
12274 As long as type checking is enabled, any attempt to combine variables
12275 whose types are not equivalent is an error.
12277 Range checking is done on all mathematical operations, assignment, array
12278 index bounds, and all built-in functions and procedures.
12281 @subsubsection The Scope Operators @code{::} and @code{.}
12283 @cindex @code{.}, Modula-2 scope operator
12284 @cindex colon, doubled as scope operator
12286 @vindex colon-colon@r{, in Modula-2}
12287 @c Info cannot handle :: but TeX can.
12290 @vindex ::@r{, in Modula-2}
12293 There are a few subtle differences between the Modula-2 scope operator
12294 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
12299 @var{module} . @var{id}
12300 @var{scope} :: @var{id}
12304 where @var{scope} is the name of a module or a procedure,
12305 @var{module} the name of a module, and @var{id} is any declared
12306 identifier within your program, except another module.
12308 Using the @code{::} operator makes @value{GDBN} search the scope
12309 specified by @var{scope} for the identifier @var{id}. If it is not
12310 found in the specified scope, then @value{GDBN} searches all scopes
12311 enclosing the one specified by @var{scope}.
12313 Using the @code{.} operator makes @value{GDBN} search the current scope for
12314 the identifier specified by @var{id} that was imported from the
12315 definition module specified by @var{module}. With this operator, it is
12316 an error if the identifier @var{id} was not imported from definition
12317 module @var{module}, or if @var{id} is not an identifier in
12321 @subsubsection @value{GDBN} and Modula-2
12323 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
12324 Five subcommands of @code{set print} and @code{show print} apply
12325 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
12326 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
12327 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
12328 analogue in Modula-2.
12330 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
12331 with any language, is not useful with Modula-2. Its
12332 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
12333 created in Modula-2 as they can in C or C@t{++}. However, because an
12334 address can be specified by an integral constant, the construct
12335 @samp{@{@var{type}@}@var{adrexp}} is still useful.
12337 @cindex @code{#} in Modula-2
12338 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
12339 interpreted as the beginning of a comment. Use @code{<>} instead.
12345 The extensions made to @value{GDBN} for Ada only support
12346 output from the @sc{gnu} Ada (GNAT) compiler.
12347 Other Ada compilers are not currently supported, and
12348 attempting to debug executables produced by them is most likely
12352 @cindex expressions in Ada
12354 * Ada Mode Intro:: General remarks on the Ada syntax
12355 and semantics supported by Ada mode
12357 * Omissions from Ada:: Restrictions on the Ada expression syntax.
12358 * Additions to Ada:: Extensions of the Ada expression syntax.
12359 * Stopping Before Main Program:: Debugging the program during elaboration.
12360 * Ada Tasks:: Listing and setting breakpoints in tasks.
12361 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
12362 * Ada Glitches:: Known peculiarities of Ada mode.
12365 @node Ada Mode Intro
12366 @subsubsection Introduction
12367 @cindex Ada mode, general
12369 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
12370 syntax, with some extensions.
12371 The philosophy behind the design of this subset is
12375 That @value{GDBN} should provide basic literals and access to operations for
12376 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
12377 leaving more sophisticated computations to subprograms written into the
12378 program (which therefore may be called from @value{GDBN}).
12381 That type safety and strict adherence to Ada language restrictions
12382 are not particularly important to the @value{GDBN} user.
12385 That brevity is important to the @value{GDBN} user.
12388 Thus, for brevity, the debugger acts as if all names declared in
12389 user-written packages are directly visible, even if they are not visible
12390 according to Ada rules, thus making it unnecessary to fully qualify most
12391 names with their packages, regardless of context. Where this causes
12392 ambiguity, @value{GDBN} asks the user's intent.
12394 The debugger will start in Ada mode if it detects an Ada main program.
12395 As for other languages, it will enter Ada mode when stopped in a program that
12396 was translated from an Ada source file.
12398 While in Ada mode, you may use `@t{--}' for comments. This is useful
12399 mostly for documenting command files. The standard @value{GDBN} comment
12400 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
12401 middle (to allow based literals).
12403 The debugger supports limited overloading. Given a subprogram call in which
12404 the function symbol has multiple definitions, it will use the number of
12405 actual parameters and some information about their types to attempt to narrow
12406 the set of definitions. It also makes very limited use of context, preferring
12407 procedures to functions in the context of the @code{call} command, and
12408 functions to procedures elsewhere.
12410 @node Omissions from Ada
12411 @subsubsection Omissions from Ada
12412 @cindex Ada, omissions from
12414 Here are the notable omissions from the subset:
12418 Only a subset of the attributes are supported:
12422 @t{'First}, @t{'Last}, and @t{'Length}
12423 on array objects (not on types and subtypes).
12426 @t{'Min} and @t{'Max}.
12429 @t{'Pos} and @t{'Val}.
12435 @t{'Range} on array objects (not subtypes), but only as the right
12436 operand of the membership (@code{in}) operator.
12439 @t{'Access}, @t{'Unchecked_Access}, and
12440 @t{'Unrestricted_Access} (a GNAT extension).
12448 @code{Characters.Latin_1} are not available and
12449 concatenation is not implemented. Thus, escape characters in strings are
12450 not currently available.
12453 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
12454 equality of representations. They will generally work correctly
12455 for strings and arrays whose elements have integer or enumeration types.
12456 They may not work correctly for arrays whose element
12457 types have user-defined equality, for arrays of real values
12458 (in particular, IEEE-conformant floating point, because of negative
12459 zeroes and NaNs), and for arrays whose elements contain unused bits with
12460 indeterminate values.
12463 The other component-by-component array operations (@code{and}, @code{or},
12464 @code{xor}, @code{not}, and relational tests other than equality)
12465 are not implemented.
12468 @cindex array aggregates (Ada)
12469 @cindex record aggregates (Ada)
12470 @cindex aggregates (Ada)
12471 There is limited support for array and record aggregates. They are
12472 permitted only on the right sides of assignments, as in these examples:
12475 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
12476 (@value{GDBP}) set An_Array := (1, others => 0)
12477 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
12478 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
12479 (@value{GDBP}) set A_Record := (1, "Peter", True);
12480 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
12484 discriminant's value by assigning an aggregate has an
12485 undefined effect if that discriminant is used within the record.
12486 However, you can first modify discriminants by directly assigning to
12487 them (which normally would not be allowed in Ada), and then performing an
12488 aggregate assignment. For example, given a variable @code{A_Rec}
12489 declared to have a type such as:
12492 type Rec (Len : Small_Integer := 0) is record
12494 Vals : IntArray (1 .. Len);
12498 you can assign a value with a different size of @code{Vals} with two
12502 (@value{GDBP}) set A_Rec.Len := 4
12503 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
12506 As this example also illustrates, @value{GDBN} is very loose about the usual
12507 rules concerning aggregates. You may leave out some of the
12508 components of an array or record aggregate (such as the @code{Len}
12509 component in the assignment to @code{A_Rec} above); they will retain their
12510 original values upon assignment. You may freely use dynamic values as
12511 indices in component associations. You may even use overlapping or
12512 redundant component associations, although which component values are
12513 assigned in such cases is not defined.
12516 Calls to dispatching subprograms are not implemented.
12519 The overloading algorithm is much more limited (i.e., less selective)
12520 than that of real Ada. It makes only limited use of the context in
12521 which a subexpression appears to resolve its meaning, and it is much
12522 looser in its rules for allowing type matches. As a result, some
12523 function calls will be ambiguous, and the user will be asked to choose
12524 the proper resolution.
12527 The @code{new} operator is not implemented.
12530 Entry calls are not implemented.
12533 Aside from printing, arithmetic operations on the native VAX floating-point
12534 formats are not supported.
12537 It is not possible to slice a packed array.
12540 The names @code{True} and @code{False}, when not part of a qualified name,
12541 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
12543 Should your program
12544 redefine these names in a package or procedure (at best a dubious practice),
12545 you will have to use fully qualified names to access their new definitions.
12548 @node Additions to Ada
12549 @subsubsection Additions to Ada
12550 @cindex Ada, deviations from
12552 As it does for other languages, @value{GDBN} makes certain generic
12553 extensions to Ada (@pxref{Expressions}):
12557 If the expression @var{E} is a variable residing in memory (typically
12558 a local variable or array element) and @var{N} is a positive integer,
12559 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
12560 @var{N}-1 adjacent variables following it in memory as an array. In
12561 Ada, this operator is generally not necessary, since its prime use is
12562 in displaying parts of an array, and slicing will usually do this in
12563 Ada. However, there are occasional uses when debugging programs in
12564 which certain debugging information has been optimized away.
12567 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
12568 appears in function or file @var{B}.'' When @var{B} is a file name,
12569 you must typically surround it in single quotes.
12572 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
12573 @var{type} that appears at address @var{addr}.''
12576 A name starting with @samp{$} is a convenience variable
12577 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
12580 In addition, @value{GDBN} provides a few other shortcuts and outright
12581 additions specific to Ada:
12585 The assignment statement is allowed as an expression, returning
12586 its right-hand operand as its value. Thus, you may enter
12589 (@value{GDBP}) set x := y + 3
12590 (@value{GDBP}) print A(tmp := y + 1)
12594 The semicolon is allowed as an ``operator,'' returning as its value
12595 the value of its right-hand operand.
12596 This allows, for example,
12597 complex conditional breaks:
12600 (@value{GDBP}) break f
12601 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
12605 Rather than use catenation and symbolic character names to introduce special
12606 characters into strings, one may instead use a special bracket notation,
12607 which is also used to print strings. A sequence of characters of the form
12608 @samp{["@var{XX}"]} within a string or character literal denotes the
12609 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
12610 sequence of characters @samp{["""]} also denotes a single quotation mark
12611 in strings. For example,
12613 "One line.["0a"]Next line.["0a"]"
12616 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
12620 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
12621 @t{'Max} is optional (and is ignored in any case). For example, it is valid
12625 (@value{GDBP}) print 'max(x, y)
12629 When printing arrays, @value{GDBN} uses positional notation when the
12630 array has a lower bound of 1, and uses a modified named notation otherwise.
12631 For example, a one-dimensional array of three integers with a lower bound
12632 of 3 might print as
12639 That is, in contrast to valid Ada, only the first component has a @code{=>}
12643 You may abbreviate attributes in expressions with any unique,
12644 multi-character subsequence of
12645 their names (an exact match gets preference).
12646 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
12647 in place of @t{a'length}.
12650 @cindex quoting Ada internal identifiers
12651 Since Ada is case-insensitive, the debugger normally maps identifiers you type
12652 to lower case. The GNAT compiler uses upper-case characters for
12653 some of its internal identifiers, which are normally of no interest to users.
12654 For the rare occasions when you actually have to look at them,
12655 enclose them in angle brackets to avoid the lower-case mapping.
12658 (@value{GDBP}) print <JMPBUF_SAVE>[0]
12662 Printing an object of class-wide type or dereferencing an
12663 access-to-class-wide value will display all the components of the object's
12664 specific type (as indicated by its run-time tag). Likewise, component
12665 selection on such a value will operate on the specific type of the
12670 @node Stopping Before Main Program
12671 @subsubsection Stopping at the Very Beginning
12673 @cindex breakpointing Ada elaboration code
12674 It is sometimes necessary to debug the program during elaboration, and
12675 before reaching the main procedure.
12676 As defined in the Ada Reference
12677 Manual, the elaboration code is invoked from a procedure called
12678 @code{adainit}. To run your program up to the beginning of
12679 elaboration, simply use the following two commands:
12680 @code{tbreak adainit} and @code{run}.
12683 @subsubsection Extensions for Ada Tasks
12684 @cindex Ada, tasking
12686 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
12687 @value{GDBN} provides the following task-related commands:
12692 This command shows a list of current Ada tasks, as in the following example:
12699 (@value{GDBP}) info tasks
12700 ID TID P-ID Pri State Name
12701 1 8088000 0 15 Child Activation Wait main_task
12702 2 80a4000 1 15 Accept Statement b
12703 3 809a800 1 15 Child Activation Wait a
12704 * 4 80ae800 3 15 Runnable c
12709 In this listing, the asterisk before the last task indicates it to be the
12710 task currently being inspected.
12714 Represents @value{GDBN}'s internal task number.
12720 The parent's task ID (@value{GDBN}'s internal task number).
12723 The base priority of the task.
12726 Current state of the task.
12730 The task has been created but has not been activated. It cannot be
12734 The task is not blocked for any reason known to Ada. (It may be waiting
12735 for a mutex, though.) It is conceptually "executing" in normal mode.
12738 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
12739 that were waiting on terminate alternatives have been awakened and have
12740 terminated themselves.
12742 @item Child Activation Wait
12743 The task is waiting for created tasks to complete activation.
12745 @item Accept Statement
12746 The task is waiting on an accept or selective wait statement.
12748 @item Waiting on entry call
12749 The task is waiting on an entry call.
12751 @item Async Select Wait
12752 The task is waiting to start the abortable part of an asynchronous
12756 The task is waiting on a select statement with only a delay
12759 @item Child Termination Wait
12760 The task is sleeping having completed a master within itself, and is
12761 waiting for the tasks dependent on that master to become terminated or
12762 waiting on a terminate Phase.
12764 @item Wait Child in Term Alt
12765 The task is sleeping waiting for tasks on terminate alternatives to
12766 finish terminating.
12768 @item Accepting RV with @var{taskno}
12769 The task is accepting a rendez-vous with the task @var{taskno}.
12773 Name of the task in the program.
12777 @kindex info task @var{taskno}
12778 @item info task @var{taskno}
12779 This command shows detailled informations on the specified task, as in
12780 the following example:
12785 (@value{GDBP}) info tasks
12786 ID TID P-ID Pri State Name
12787 1 8077880 0 15 Child Activation Wait main_task
12788 * 2 807c468 1 15 Runnable task_1
12789 (@value{GDBP}) info task 2
12790 Ada Task: 0x807c468
12793 Parent: 1 (main_task)
12799 @kindex task@r{ (Ada)}
12800 @cindex current Ada task ID
12801 This command prints the ID of the current task.
12807 (@value{GDBP}) info tasks
12808 ID TID P-ID Pri State Name
12809 1 8077870 0 15 Child Activation Wait main_task
12810 * 2 807c458 1 15 Runnable t
12811 (@value{GDBP}) task
12812 [Current task is 2]
12815 @item task @var{taskno}
12816 @cindex Ada task switching
12817 This command is like the @code{thread @var{threadno}}
12818 command (@pxref{Threads}). It switches the context of debugging
12819 from the current task to the given task.
12825 (@value{GDBP}) info tasks
12826 ID TID P-ID Pri State Name
12827 1 8077870 0 15 Child Activation Wait main_task
12828 * 2 807c458 1 15 Runnable t
12829 (@value{GDBP}) task 1
12830 [Switching to task 1]
12831 #0 0x8067726 in pthread_cond_wait ()
12833 #0 0x8067726 in pthread_cond_wait ()
12834 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
12835 #2 0x805cb63 in system.task_primitives.operations.sleep ()
12836 #3 0x806153e in system.tasking.stages.activate_tasks ()
12837 #4 0x804aacc in un () at un.adb:5
12840 @item break @var{linespec} task @var{taskno}
12841 @itemx break @var{linespec} task @var{taskno} if @dots{}
12842 @cindex breakpoints and tasks, in Ada
12843 @cindex task breakpoints, in Ada
12844 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
12845 These commands are like the @code{break @dots{} thread @dots{}}
12846 command (@pxref{Thread Stops}).
12847 @var{linespec} specifies source lines, as described
12848 in @ref{Specify Location}.
12850 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
12851 to specify that you only want @value{GDBN} to stop the program when a
12852 particular Ada task reaches this breakpoint. @var{taskno} is one of the
12853 numeric task identifiers assigned by @value{GDBN}, shown in the first
12854 column of the @samp{info tasks} display.
12856 If you do not specify @samp{task @var{taskno}} when you set a
12857 breakpoint, the breakpoint applies to @emph{all} tasks of your
12860 You can use the @code{task} qualifier on conditional breakpoints as
12861 well; in this case, place @samp{task @var{taskno}} before the
12862 breakpoint condition (before the @code{if}).
12870 (@value{GDBP}) info tasks
12871 ID TID P-ID Pri State Name
12872 1 140022020 0 15 Child Activation Wait main_task
12873 2 140045060 1 15 Accept/Select Wait t2
12874 3 140044840 1 15 Runnable t1
12875 * 4 140056040 1 15 Runnable t3
12876 (@value{GDBP}) b 15 task 2
12877 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
12878 (@value{GDBP}) cont
12883 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
12885 (@value{GDBP}) info tasks
12886 ID TID P-ID Pri State Name
12887 1 140022020 0 15 Child Activation Wait main_task
12888 * 2 140045060 1 15 Runnable t2
12889 3 140044840 1 15 Runnable t1
12890 4 140056040 1 15 Delay Sleep t3
12894 @node Ada Tasks and Core Files
12895 @subsubsection Tasking Support when Debugging Core Files
12896 @cindex Ada tasking and core file debugging
12898 When inspecting a core file, as opposed to debugging a live program,
12899 tasking support may be limited or even unavailable, depending on
12900 the platform being used.
12901 For instance, on x86-linux, the list of tasks is available, but task
12902 switching is not supported. On Tru64, however, task switching will work
12905 On certain platforms, including Tru64, the debugger needs to perform some
12906 memory writes in order to provide Ada tasking support. When inspecting
12907 a core file, this means that the core file must be opened with read-write
12908 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
12909 Under these circumstances, you should make a backup copy of the core
12910 file before inspecting it with @value{GDBN}.
12913 @subsubsection Known Peculiarities of Ada Mode
12914 @cindex Ada, problems
12916 Besides the omissions listed previously (@pxref{Omissions from Ada}),
12917 we know of several problems with and limitations of Ada mode in
12919 some of which will be fixed with planned future releases of the debugger
12920 and the GNU Ada compiler.
12924 Currently, the debugger
12925 has insufficient information to determine whether certain pointers represent
12926 pointers to objects or the objects themselves.
12927 Thus, the user may have to tack an extra @code{.all} after an expression
12928 to get it printed properly.
12931 Static constants that the compiler chooses not to materialize as objects in
12932 storage are invisible to the debugger.
12935 Named parameter associations in function argument lists are ignored (the
12936 argument lists are treated as positional).
12939 Many useful library packages are currently invisible to the debugger.
12942 Fixed-point arithmetic, conversions, input, and output is carried out using
12943 floating-point arithmetic, and may give results that only approximate those on
12947 The GNAT compiler never generates the prefix @code{Standard} for any of
12948 the standard symbols defined by the Ada language. @value{GDBN} knows about
12949 this: it will strip the prefix from names when you use it, and will never
12950 look for a name you have so qualified among local symbols, nor match against
12951 symbols in other packages or subprograms. If you have
12952 defined entities anywhere in your program other than parameters and
12953 local variables whose simple names match names in @code{Standard},
12954 GNAT's lack of qualification here can cause confusion. When this happens,
12955 you can usually resolve the confusion
12956 by qualifying the problematic names with package
12957 @code{Standard} explicitly.
12960 Older versions of the compiler sometimes generate erroneous debugging
12961 information, resulting in the debugger incorrectly printing the value
12962 of affected entities. In some cases, the debugger is able to work
12963 around an issue automatically. In other cases, the debugger is able
12964 to work around the issue, but the work-around has to be specifically
12967 @kindex set ada trust-PAD-over-XVS
12968 @kindex show ada trust-PAD-over-XVS
12971 @item set ada trust-PAD-over-XVS on
12972 Configure GDB to strictly follow the GNAT encoding when computing the
12973 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
12974 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
12975 a complete description of the encoding used by the GNAT compiler).
12976 This is the default.
12978 @item set ada trust-PAD-over-XVS off
12979 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
12980 sometimes prints the wrong value for certain entities, changing @code{ada
12981 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
12982 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
12983 @code{off}, but this incurs a slight performance penalty, so it is
12984 recommended to leave this setting to @code{on} unless necessary.
12988 @node Unsupported Languages
12989 @section Unsupported Languages
12991 @cindex unsupported languages
12992 @cindex minimal language
12993 In addition to the other fully-supported programming languages,
12994 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
12995 It does not represent a real programming language, but provides a set
12996 of capabilities close to what the C or assembly languages provide.
12997 This should allow most simple operations to be performed while debugging
12998 an application that uses a language currently not supported by @value{GDBN}.
13000 If the language is set to @code{auto}, @value{GDBN} will automatically
13001 select this language if the current frame corresponds to an unsupported
13005 @chapter Examining the Symbol Table
13007 The commands described in this chapter allow you to inquire about the
13008 symbols (names of variables, functions and types) defined in your
13009 program. This information is inherent in the text of your program and
13010 does not change as your program executes. @value{GDBN} finds it in your
13011 program's symbol table, in the file indicated when you started @value{GDBN}
13012 (@pxref{File Options, ,Choosing Files}), or by one of the
13013 file-management commands (@pxref{Files, ,Commands to Specify Files}).
13015 @cindex symbol names
13016 @cindex names of symbols
13017 @cindex quoting names
13018 Occasionally, you may need to refer to symbols that contain unusual
13019 characters, which @value{GDBN} ordinarily treats as word delimiters. The
13020 most frequent case is in referring to static variables in other
13021 source files (@pxref{Variables,,Program Variables}). File names
13022 are recorded in object files as debugging symbols, but @value{GDBN} would
13023 ordinarily parse a typical file name, like @file{foo.c}, as the three words
13024 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
13025 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
13032 looks up the value of @code{x} in the scope of the file @file{foo.c}.
13035 @cindex case-insensitive symbol names
13036 @cindex case sensitivity in symbol names
13037 @kindex set case-sensitive
13038 @item set case-sensitive on
13039 @itemx set case-sensitive off
13040 @itemx set case-sensitive auto
13041 Normally, when @value{GDBN} looks up symbols, it matches their names
13042 with case sensitivity determined by the current source language.
13043 Occasionally, you may wish to control that. The command @code{set
13044 case-sensitive} lets you do that by specifying @code{on} for
13045 case-sensitive matches or @code{off} for case-insensitive ones. If
13046 you specify @code{auto}, case sensitivity is reset to the default
13047 suitable for the source language. The default is case-sensitive
13048 matches for all languages except for Fortran, for which the default is
13049 case-insensitive matches.
13051 @kindex show case-sensitive
13052 @item show case-sensitive
13053 This command shows the current setting of case sensitivity for symbols
13056 @kindex info address
13057 @cindex address of a symbol
13058 @item info address @var{symbol}
13059 Describe where the data for @var{symbol} is stored. For a register
13060 variable, this says which register it is kept in. For a non-register
13061 local variable, this prints the stack-frame offset at which the variable
13064 Note the contrast with @samp{print &@var{symbol}}, which does not work
13065 at all for a register variable, and for a stack local variable prints
13066 the exact address of the current instantiation of the variable.
13068 @kindex info symbol
13069 @cindex symbol from address
13070 @cindex closest symbol and offset for an address
13071 @item info symbol @var{addr}
13072 Print the name of a symbol which is stored at the address @var{addr}.
13073 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
13074 nearest symbol and an offset from it:
13077 (@value{GDBP}) info symbol 0x54320
13078 _initialize_vx + 396 in section .text
13082 This is the opposite of the @code{info address} command. You can use
13083 it to find out the name of a variable or a function given its address.
13085 For dynamically linked executables, the name of executable or shared
13086 library containing the symbol is also printed:
13089 (@value{GDBP}) info symbol 0x400225
13090 _start + 5 in section .text of /tmp/a.out
13091 (@value{GDBP}) info symbol 0x2aaaac2811cf
13092 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
13096 @item whatis [@var{arg}]
13097 Print the data type of @var{arg}, which can be either an expression or
13098 a data type. With no argument, print the data type of @code{$}, the
13099 last value in the value history. If @var{arg} is an expression, it is
13100 not actually evaluated, and any side-effecting operations (such as
13101 assignments or function calls) inside it do not take place. If
13102 @var{arg} is a type name, it may be the name of a type or typedef, or
13103 for C code it may have the form @samp{class @var{class-name}},
13104 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
13105 @samp{enum @var{enum-tag}}.
13106 @xref{Expressions, ,Expressions}.
13109 @item ptype [@var{arg}]
13110 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
13111 detailed description of the type, instead of just the name of the type.
13112 @xref{Expressions, ,Expressions}.
13114 For example, for this variable declaration:
13117 struct complex @{double real; double imag;@} v;
13121 the two commands give this output:
13125 (@value{GDBP}) whatis v
13126 type = struct complex
13127 (@value{GDBP}) ptype v
13128 type = struct complex @{
13136 As with @code{whatis}, using @code{ptype} without an argument refers to
13137 the type of @code{$}, the last value in the value history.
13139 @cindex incomplete type
13140 Sometimes, programs use opaque data types or incomplete specifications
13141 of complex data structure. If the debug information included in the
13142 program does not allow @value{GDBN} to display a full declaration of
13143 the data type, it will say @samp{<incomplete type>}. For example,
13144 given these declarations:
13148 struct foo *fooptr;
13152 but no definition for @code{struct foo} itself, @value{GDBN} will say:
13155 (@value{GDBP}) ptype foo
13156 $1 = <incomplete type>
13160 ``Incomplete type'' is C terminology for data types that are not
13161 completely specified.
13164 @item info types @var{regexp}
13166 Print a brief description of all types whose names match the regular
13167 expression @var{regexp} (or all types in your program, if you supply
13168 no argument). Each complete typename is matched as though it were a
13169 complete line; thus, @samp{i type value} gives information on all
13170 types in your program whose names include the string @code{value}, but
13171 @samp{i type ^value$} gives information only on types whose complete
13172 name is @code{value}.
13174 This command differs from @code{ptype} in two ways: first, like
13175 @code{whatis}, it does not print a detailed description; second, it
13176 lists all source files where a type is defined.
13179 @cindex local variables
13180 @item info scope @var{location}
13181 List all the variables local to a particular scope. This command
13182 accepts a @var{location} argument---a function name, a source line, or
13183 an address preceded by a @samp{*}, and prints all the variables local
13184 to the scope defined by that location. (@xref{Specify Location}, for
13185 details about supported forms of @var{location}.) For example:
13188 (@value{GDBP}) @b{info scope command_line_handler}
13189 Scope for command_line_handler:
13190 Symbol rl is an argument at stack/frame offset 8, length 4.
13191 Symbol linebuffer is in static storage at address 0x150a18, length 4.
13192 Symbol linelength is in static storage at address 0x150a1c, length 4.
13193 Symbol p is a local variable in register $esi, length 4.
13194 Symbol p1 is a local variable in register $ebx, length 4.
13195 Symbol nline is a local variable in register $edx, length 4.
13196 Symbol repeat is a local variable at frame offset -8, length 4.
13200 This command is especially useful for determining what data to collect
13201 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
13204 @kindex info source
13206 Show information about the current source file---that is, the source file for
13207 the function containing the current point of execution:
13210 the name of the source file, and the directory containing it,
13212 the directory it was compiled in,
13214 its length, in lines,
13216 which programming language it is written in,
13218 whether the executable includes debugging information for that file, and
13219 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
13221 whether the debugging information includes information about
13222 preprocessor macros.
13226 @kindex info sources
13228 Print the names of all source files in your program for which there is
13229 debugging information, organized into two lists: files whose symbols
13230 have already been read, and files whose symbols will be read when needed.
13232 @kindex info functions
13233 @item info functions
13234 Print the names and data types of all defined functions.
13236 @item info functions @var{regexp}
13237 Print the names and data types of all defined functions
13238 whose names contain a match for regular expression @var{regexp}.
13239 Thus, @samp{info fun step} finds all functions whose names
13240 include @code{step}; @samp{info fun ^step} finds those whose names
13241 start with @code{step}. If a function name contains characters
13242 that conflict with the regular expression language (e.g.@:
13243 @samp{operator*()}), they may be quoted with a backslash.
13245 @kindex info variables
13246 @item info variables
13247 Print the names and data types of all variables that are defined
13248 outside of functions (i.e.@: excluding local variables).
13250 @item info variables @var{regexp}
13251 Print the names and data types of all variables (except for local
13252 variables) whose names contain a match for regular expression
13255 @kindex info classes
13256 @cindex Objective-C, classes and selectors
13258 @itemx info classes @var{regexp}
13259 Display all Objective-C classes in your program, or
13260 (with the @var{regexp} argument) all those matching a particular regular
13263 @kindex info selectors
13264 @item info selectors
13265 @itemx info selectors @var{regexp}
13266 Display all Objective-C selectors in your program, or
13267 (with the @var{regexp} argument) all those matching a particular regular
13271 This was never implemented.
13272 @kindex info methods
13274 @itemx info methods @var{regexp}
13275 The @code{info methods} command permits the user to examine all defined
13276 methods within C@t{++} program, or (with the @var{regexp} argument) a
13277 specific set of methods found in the various C@t{++} classes. Many
13278 C@t{++} classes provide a large number of methods. Thus, the output
13279 from the @code{ptype} command can be overwhelming and hard to use. The
13280 @code{info-methods} command filters the methods, printing only those
13281 which match the regular-expression @var{regexp}.
13284 @cindex reloading symbols
13285 Some systems allow individual object files that make up your program to
13286 be replaced without stopping and restarting your program. For example,
13287 in VxWorks you can simply recompile a defective object file and keep on
13288 running. If you are running on one of these systems, you can allow
13289 @value{GDBN} to reload the symbols for automatically relinked modules:
13292 @kindex set symbol-reloading
13293 @item set symbol-reloading on
13294 Replace symbol definitions for the corresponding source file when an
13295 object file with a particular name is seen again.
13297 @item set symbol-reloading off
13298 Do not replace symbol definitions when encountering object files of the
13299 same name more than once. This is the default state; if you are not
13300 running on a system that permits automatic relinking of modules, you
13301 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
13302 may discard symbols when linking large programs, that may contain
13303 several modules (from different directories or libraries) with the same
13306 @kindex show symbol-reloading
13307 @item show symbol-reloading
13308 Show the current @code{on} or @code{off} setting.
13311 @cindex opaque data types
13312 @kindex set opaque-type-resolution
13313 @item set opaque-type-resolution on
13314 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
13315 declared as a pointer to a @code{struct}, @code{class}, or
13316 @code{union}---for example, @code{struct MyType *}---that is used in one
13317 source file although the full declaration of @code{struct MyType} is in
13318 another source file. The default is on.
13320 A change in the setting of this subcommand will not take effect until
13321 the next time symbols for a file are loaded.
13323 @item set opaque-type-resolution off
13324 Tell @value{GDBN} not to resolve opaque types. In this case, the type
13325 is printed as follows:
13327 @{<no data fields>@}
13330 @kindex show opaque-type-resolution
13331 @item show opaque-type-resolution
13332 Show whether opaque types are resolved or not.
13334 @kindex maint print symbols
13335 @cindex symbol dump
13336 @kindex maint print psymbols
13337 @cindex partial symbol dump
13338 @item maint print symbols @var{filename}
13339 @itemx maint print psymbols @var{filename}
13340 @itemx maint print msymbols @var{filename}
13341 Write a dump of debugging symbol data into the file @var{filename}.
13342 These commands are used to debug the @value{GDBN} symbol-reading code. Only
13343 symbols with debugging data are included. If you use @samp{maint print
13344 symbols}, @value{GDBN} includes all the symbols for which it has already
13345 collected full details: that is, @var{filename} reflects symbols for
13346 only those files whose symbols @value{GDBN} has read. You can use the
13347 command @code{info sources} to find out which files these are. If you
13348 use @samp{maint print psymbols} instead, the dump shows information about
13349 symbols that @value{GDBN} only knows partially---that is, symbols defined in
13350 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
13351 @samp{maint print msymbols} dumps just the minimal symbol information
13352 required for each object file from which @value{GDBN} has read some symbols.
13353 @xref{Files, ,Commands to Specify Files}, for a discussion of how
13354 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
13356 @kindex maint info symtabs
13357 @kindex maint info psymtabs
13358 @cindex listing @value{GDBN}'s internal symbol tables
13359 @cindex symbol tables, listing @value{GDBN}'s internal
13360 @cindex full symbol tables, listing @value{GDBN}'s internal
13361 @cindex partial symbol tables, listing @value{GDBN}'s internal
13362 @item maint info symtabs @r{[} @var{regexp} @r{]}
13363 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
13365 List the @code{struct symtab} or @code{struct partial_symtab}
13366 structures whose names match @var{regexp}. If @var{regexp} is not
13367 given, list them all. The output includes expressions which you can
13368 copy into a @value{GDBN} debugging this one to examine a particular
13369 structure in more detail. For example:
13372 (@value{GDBP}) maint info psymtabs dwarf2read
13373 @{ objfile /home/gnu/build/gdb/gdb
13374 ((struct objfile *) 0x82e69d0)
13375 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
13376 ((struct partial_symtab *) 0x8474b10)
13379 text addresses 0x814d3c8 -- 0x8158074
13380 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
13381 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
13382 dependencies (none)
13385 (@value{GDBP}) maint info symtabs
13389 We see that there is one partial symbol table whose filename contains
13390 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
13391 and we see that @value{GDBN} has not read in any symtabs yet at all.
13392 If we set a breakpoint on a function, that will cause @value{GDBN} to
13393 read the symtab for the compilation unit containing that function:
13396 (@value{GDBP}) break dwarf2_psymtab_to_symtab
13397 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
13399 (@value{GDBP}) maint info symtabs
13400 @{ objfile /home/gnu/build/gdb/gdb
13401 ((struct objfile *) 0x82e69d0)
13402 @{ symtab /home/gnu/src/gdb/dwarf2read.c
13403 ((struct symtab *) 0x86c1f38)
13406 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
13407 linetable ((struct linetable *) 0x8370fa0)
13408 debugformat DWARF 2
13417 @chapter Altering Execution
13419 Once you think you have found an error in your program, you might want to
13420 find out for certain whether correcting the apparent error would lead to
13421 correct results in the rest of the run. You can find the answer by
13422 experiment, using the @value{GDBN} features for altering execution of the
13425 For example, you can store new values into variables or memory
13426 locations, give your program a signal, restart it at a different
13427 address, or even return prematurely from a function.
13430 * Assignment:: Assignment to variables
13431 * Jumping:: Continuing at a different address
13432 * Signaling:: Giving your program a signal
13433 * Returning:: Returning from a function
13434 * Calling:: Calling your program's functions
13435 * Patching:: Patching your program
13439 @section Assignment to Variables
13442 @cindex setting variables
13443 To alter the value of a variable, evaluate an assignment expression.
13444 @xref{Expressions, ,Expressions}. For example,
13451 stores the value 4 into the variable @code{x}, and then prints the
13452 value of the assignment expression (which is 4).
13453 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
13454 information on operators in supported languages.
13456 @kindex set variable
13457 @cindex variables, setting
13458 If you are not interested in seeing the value of the assignment, use the
13459 @code{set} command instead of the @code{print} command. @code{set} is
13460 really the same as @code{print} except that the expression's value is
13461 not printed and is not put in the value history (@pxref{Value History,
13462 ,Value History}). The expression is evaluated only for its effects.
13464 If the beginning of the argument string of the @code{set} command
13465 appears identical to a @code{set} subcommand, use the @code{set
13466 variable} command instead of just @code{set}. This command is identical
13467 to @code{set} except for its lack of subcommands. For example, if your
13468 program has a variable @code{width}, you get an error if you try to set
13469 a new value with just @samp{set width=13}, because @value{GDBN} has the
13470 command @code{set width}:
13473 (@value{GDBP}) whatis width
13475 (@value{GDBP}) p width
13477 (@value{GDBP}) set width=47
13478 Invalid syntax in expression.
13482 The invalid expression, of course, is @samp{=47}. In
13483 order to actually set the program's variable @code{width}, use
13486 (@value{GDBP}) set var width=47
13489 Because the @code{set} command has many subcommands that can conflict
13490 with the names of program variables, it is a good idea to use the
13491 @code{set variable} command instead of just @code{set}. For example, if
13492 your program has a variable @code{g}, you run into problems if you try
13493 to set a new value with just @samp{set g=4}, because @value{GDBN} has
13494 the command @code{set gnutarget}, abbreviated @code{set g}:
13498 (@value{GDBP}) whatis g
13502 (@value{GDBP}) set g=4
13506 The program being debugged has been started already.
13507 Start it from the beginning? (y or n) y
13508 Starting program: /home/smith/cc_progs/a.out
13509 "/home/smith/cc_progs/a.out": can't open to read symbols:
13510 Invalid bfd target.
13511 (@value{GDBP}) show g
13512 The current BFD target is "=4".
13517 The program variable @code{g} did not change, and you silently set the
13518 @code{gnutarget} to an invalid value. In order to set the variable
13522 (@value{GDBP}) set var g=4
13525 @value{GDBN} allows more implicit conversions in assignments than C; you can
13526 freely store an integer value into a pointer variable or vice versa,
13527 and you can convert any structure to any other structure that is the
13528 same length or shorter.
13529 @comment FIXME: how do structs align/pad in these conversions?
13530 @comment /doc@cygnus.com 18dec1990
13532 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
13533 construct to generate a value of specified type at a specified address
13534 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
13535 to memory location @code{0x83040} as an integer (which implies a certain size
13536 and representation in memory), and
13539 set @{int@}0x83040 = 4
13543 stores the value 4 into that memory location.
13546 @section Continuing at a Different Address
13548 Ordinarily, when you continue your program, you do so at the place where
13549 it stopped, with the @code{continue} command. You can instead continue at
13550 an address of your own choosing, with the following commands:
13554 @item jump @var{linespec}
13555 @itemx jump @var{location}
13556 Resume execution at line @var{linespec} or at address given by
13557 @var{location}. Execution stops again immediately if there is a
13558 breakpoint there. @xref{Specify Location}, for a description of the
13559 different forms of @var{linespec} and @var{location}. It is common
13560 practice to use the @code{tbreak} command in conjunction with
13561 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
13563 The @code{jump} command does not change the current stack frame, or
13564 the stack pointer, or the contents of any memory location or any
13565 register other than the program counter. If line @var{linespec} is in
13566 a different function from the one currently executing, the results may
13567 be bizarre if the two functions expect different patterns of arguments or
13568 of local variables. For this reason, the @code{jump} command requests
13569 confirmation if the specified line is not in the function currently
13570 executing. However, even bizarre results are predictable if you are
13571 well acquainted with the machine-language code of your program.
13574 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
13575 On many systems, you can get much the same effect as the @code{jump}
13576 command by storing a new value into the register @code{$pc}. The
13577 difference is that this does not start your program running; it only
13578 changes the address of where it @emph{will} run when you continue. For
13586 makes the next @code{continue} command or stepping command execute at
13587 address @code{0x485}, rather than at the address where your program stopped.
13588 @xref{Continuing and Stepping, ,Continuing and Stepping}.
13590 The most common occasion to use the @code{jump} command is to back
13591 up---perhaps with more breakpoints set---over a portion of a program
13592 that has already executed, in order to examine its execution in more
13597 @section Giving your Program a Signal
13598 @cindex deliver a signal to a program
13602 @item signal @var{signal}
13603 Resume execution where your program stopped, but immediately give it the
13604 signal @var{signal}. @var{signal} can be the name or the number of a
13605 signal. For example, on many systems @code{signal 2} and @code{signal
13606 SIGINT} are both ways of sending an interrupt signal.
13608 Alternatively, if @var{signal} is zero, continue execution without
13609 giving a signal. This is useful when your program stopped on account of
13610 a signal and would ordinary see the signal when resumed with the
13611 @code{continue} command; @samp{signal 0} causes it to resume without a
13614 @code{signal} does not repeat when you press @key{RET} a second time
13615 after executing the command.
13619 Invoking the @code{signal} command is not the same as invoking the
13620 @code{kill} utility from the shell. Sending a signal with @code{kill}
13621 causes @value{GDBN} to decide what to do with the signal depending on
13622 the signal handling tables (@pxref{Signals}). The @code{signal} command
13623 passes the signal directly to your program.
13627 @section Returning from a Function
13630 @cindex returning from a function
13633 @itemx return @var{expression}
13634 You can cancel execution of a function call with the @code{return}
13635 command. If you give an
13636 @var{expression} argument, its value is used as the function's return
13640 When you use @code{return}, @value{GDBN} discards the selected stack frame
13641 (and all frames within it). You can think of this as making the
13642 discarded frame return prematurely. If you wish to specify a value to
13643 be returned, give that value as the argument to @code{return}.
13645 This pops the selected stack frame (@pxref{Selection, ,Selecting a
13646 Frame}), and any other frames inside of it, leaving its caller as the
13647 innermost remaining frame. That frame becomes selected. The
13648 specified value is stored in the registers used for returning values
13651 The @code{return} command does not resume execution; it leaves the
13652 program stopped in the state that would exist if the function had just
13653 returned. In contrast, the @code{finish} command (@pxref{Continuing
13654 and Stepping, ,Continuing and Stepping}) resumes execution until the
13655 selected stack frame returns naturally.
13657 @value{GDBN} needs to know how the @var{expression} argument should be set for
13658 the inferior. The concrete registers assignment depends on the OS ABI and the
13659 type being returned by the selected stack frame. For example it is common for
13660 OS ABI to return floating point values in FPU registers while integer values in
13661 CPU registers. Still some ABIs return even floating point values in CPU
13662 registers. Larger integer widths (such as @code{long long int}) also have
13663 specific placement rules. @value{GDBN} already knows the OS ABI from its
13664 current target so it needs to find out also the type being returned to make the
13665 assignment into the right register(s).
13667 Normally, the selected stack frame has debug info. @value{GDBN} will always
13668 use the debug info instead of the implicit type of @var{expression} when the
13669 debug info is available. For example, if you type @kbd{return -1}, and the
13670 function in the current stack frame is declared to return a @code{long long
13671 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
13672 into a @code{long long int}:
13675 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
13677 (@value{GDBP}) return -1
13678 Make func return now? (y or n) y
13679 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
13680 43 printf ("result=%lld\n", func ());
13684 However, if the selected stack frame does not have a debug info, e.g., if the
13685 function was compiled without debug info, @value{GDBN} has to find out the type
13686 to return from user. Specifying a different type by mistake may set the value
13687 in different inferior registers than the caller code expects. For example,
13688 typing @kbd{return -1} with its implicit type @code{int} would set only a part
13689 of a @code{long long int} result for a debug info less function (on 32-bit
13690 architectures). Therefore the user is required to specify the return type by
13691 an appropriate cast explicitly:
13694 Breakpoint 2, 0x0040050b in func ()
13695 (@value{GDBP}) return -1
13696 Return value type not available for selected stack frame.
13697 Please use an explicit cast of the value to return.
13698 (@value{GDBP}) return (long long int) -1
13699 Make selected stack frame return now? (y or n) y
13700 #0 0x00400526 in main ()
13705 @section Calling Program Functions
13708 @cindex calling functions
13709 @cindex inferior functions, calling
13710 @item print @var{expr}
13711 Evaluate the expression @var{expr} and display the resulting value.
13712 @var{expr} may include calls to functions in the program being
13716 @item call @var{expr}
13717 Evaluate the expression @var{expr} without displaying @code{void}
13720 You can use this variant of the @code{print} command if you want to
13721 execute a function from your program that does not return anything
13722 (a.k.a.@: @dfn{a void function}), but without cluttering the output
13723 with @code{void} returned values that @value{GDBN} will otherwise
13724 print. If the result is not void, it is printed and saved in the
13728 It is possible for the function you call via the @code{print} or
13729 @code{call} command to generate a signal (e.g., if there's a bug in
13730 the function, or if you passed it incorrect arguments). What happens
13731 in that case is controlled by the @code{set unwindonsignal} command.
13733 Similarly, with a C@t{++} program it is possible for the function you
13734 call via the @code{print} or @code{call} command to generate an
13735 exception that is not handled due to the constraints of the dummy
13736 frame. In this case, any exception that is raised in the frame, but has
13737 an out-of-frame exception handler will not be found. GDB builds a
13738 dummy-frame for the inferior function call, and the unwinder cannot
13739 seek for exception handlers outside of this dummy-frame. What happens
13740 in that case is controlled by the
13741 @code{set unwind-on-terminating-exception} command.
13744 @item set unwindonsignal
13745 @kindex set unwindonsignal
13746 @cindex unwind stack in called functions
13747 @cindex call dummy stack unwinding
13748 Set unwinding of the stack if a signal is received while in a function
13749 that @value{GDBN} called in the program being debugged. If set to on,
13750 @value{GDBN} unwinds the stack it created for the call and restores
13751 the context to what it was before the call. If set to off (the
13752 default), @value{GDBN} stops in the frame where the signal was
13755 @item show unwindonsignal
13756 @kindex show unwindonsignal
13757 Show the current setting of stack unwinding in the functions called by
13760 @item set unwind-on-terminating-exception
13761 @kindex set unwind-on-terminating-exception
13762 @cindex unwind stack in called functions with unhandled exceptions
13763 @cindex call dummy stack unwinding on unhandled exception.
13764 Set unwinding of the stack if a C@t{++} exception is raised, but left
13765 unhandled while in a function that @value{GDBN} called in the program being
13766 debugged. If set to on (the default), @value{GDBN} unwinds the stack
13767 it created for the call and restores the context to what it was before
13768 the call. If set to off, @value{GDBN} the exception is delivered to
13769 the default C@t{++} exception handler and the inferior terminated.
13771 @item show unwind-on-terminating-exception
13772 @kindex show unwind-on-terminating-exception
13773 Show the current setting of stack unwinding in the functions called by
13778 @cindex weak alias functions
13779 Sometimes, a function you wish to call is actually a @dfn{weak alias}
13780 for another function. In such case, @value{GDBN} might not pick up
13781 the type information, including the types of the function arguments,
13782 which causes @value{GDBN} to call the inferior function incorrectly.
13783 As a result, the called function will function erroneously and may
13784 even crash. A solution to that is to use the name of the aliased
13788 @section Patching Programs
13790 @cindex patching binaries
13791 @cindex writing into executables
13792 @cindex writing into corefiles
13794 By default, @value{GDBN} opens the file containing your program's
13795 executable code (or the corefile) read-only. This prevents accidental
13796 alterations to machine code; but it also prevents you from intentionally
13797 patching your program's binary.
13799 If you'd like to be able to patch the binary, you can specify that
13800 explicitly with the @code{set write} command. For example, you might
13801 want to turn on internal debugging flags, or even to make emergency
13807 @itemx set write off
13808 If you specify @samp{set write on}, @value{GDBN} opens executable and
13809 core files for both reading and writing; if you specify @kbd{set write
13810 off} (the default), @value{GDBN} opens them read-only.
13812 If you have already loaded a file, you must load it again (using the
13813 @code{exec-file} or @code{core-file} command) after changing @code{set
13814 write}, for your new setting to take effect.
13818 Display whether executable files and core files are opened for writing
13819 as well as reading.
13823 @chapter @value{GDBN} Files
13825 @value{GDBN} needs to know the file name of the program to be debugged,
13826 both in order to read its symbol table and in order to start your
13827 program. To debug a core dump of a previous run, you must also tell
13828 @value{GDBN} the name of the core dump file.
13831 * Files:: Commands to specify files
13832 * Separate Debug Files:: Debugging information in separate files
13833 * Symbol Errors:: Errors reading symbol files
13834 * Data Files:: GDB data files
13838 @section Commands to Specify Files
13840 @cindex symbol table
13841 @cindex core dump file
13843 You may want to specify executable and core dump file names. The usual
13844 way to do this is at start-up time, using the arguments to
13845 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
13846 Out of @value{GDBN}}).
13848 Occasionally it is necessary to change to a different file during a
13849 @value{GDBN} session. Or you may run @value{GDBN} and forget to
13850 specify a file you want to use. Or you are debugging a remote target
13851 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
13852 Program}). In these situations the @value{GDBN} commands to specify
13853 new files are useful.
13856 @cindex executable file
13858 @item file @var{filename}
13859 Use @var{filename} as the program to be debugged. It is read for its
13860 symbols and for the contents of pure memory. It is also the program
13861 executed when you use the @code{run} command. If you do not specify a
13862 directory and the file is not found in the @value{GDBN} working directory,
13863 @value{GDBN} uses the environment variable @code{PATH} as a list of
13864 directories to search, just as the shell does when looking for a program
13865 to run. You can change the value of this variable, for both @value{GDBN}
13866 and your program, using the @code{path} command.
13868 @cindex unlinked object files
13869 @cindex patching object files
13870 You can load unlinked object @file{.o} files into @value{GDBN} using
13871 the @code{file} command. You will not be able to ``run'' an object
13872 file, but you can disassemble functions and inspect variables. Also,
13873 if the underlying BFD functionality supports it, you could use
13874 @kbd{gdb -write} to patch object files using this technique. Note
13875 that @value{GDBN} can neither interpret nor modify relocations in this
13876 case, so branches and some initialized variables will appear to go to
13877 the wrong place. But this feature is still handy from time to time.
13880 @code{file} with no argument makes @value{GDBN} discard any information it
13881 has on both executable file and the symbol table.
13884 @item exec-file @r{[} @var{filename} @r{]}
13885 Specify that the program to be run (but not the symbol table) is found
13886 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
13887 if necessary to locate your program. Omitting @var{filename} means to
13888 discard information on the executable file.
13890 @kindex symbol-file
13891 @item symbol-file @r{[} @var{filename} @r{]}
13892 Read symbol table information from file @var{filename}. @code{PATH} is
13893 searched when necessary. Use the @code{file} command to get both symbol
13894 table and program to run from the same file.
13896 @code{symbol-file} with no argument clears out @value{GDBN} information on your
13897 program's symbol table.
13899 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
13900 some breakpoints and auto-display expressions. This is because they may
13901 contain pointers to the internal data recording symbols and data types,
13902 which are part of the old symbol table data being discarded inside
13905 @code{symbol-file} does not repeat if you press @key{RET} again after
13908 When @value{GDBN} is configured for a particular environment, it
13909 understands debugging information in whatever format is the standard
13910 generated for that environment; you may use either a @sc{gnu} compiler, or
13911 other compilers that adhere to the local conventions.
13912 Best results are usually obtained from @sc{gnu} compilers; for example,
13913 using @code{@value{NGCC}} you can generate debugging information for
13916 For most kinds of object files, with the exception of old SVR3 systems
13917 using COFF, the @code{symbol-file} command does not normally read the
13918 symbol table in full right away. Instead, it scans the symbol table
13919 quickly to find which source files and which symbols are present. The
13920 details are read later, one source file at a time, as they are needed.
13922 The purpose of this two-stage reading strategy is to make @value{GDBN}
13923 start up faster. For the most part, it is invisible except for
13924 occasional pauses while the symbol table details for a particular source
13925 file are being read. (The @code{set verbose} command can turn these
13926 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
13927 Warnings and Messages}.)
13929 We have not implemented the two-stage strategy for COFF yet. When the
13930 symbol table is stored in COFF format, @code{symbol-file} reads the
13931 symbol table data in full right away. Note that ``stabs-in-COFF''
13932 still does the two-stage strategy, since the debug info is actually
13936 @cindex reading symbols immediately
13937 @cindex symbols, reading immediately
13938 @item symbol-file @r{[} -readnow @r{]} @var{filename}
13939 @itemx file @r{[} -readnow @r{]} @var{filename}
13940 You can override the @value{GDBN} two-stage strategy for reading symbol
13941 tables by using the @samp{-readnow} option with any of the commands that
13942 load symbol table information, if you want to be sure @value{GDBN} has the
13943 entire symbol table available.
13945 @c FIXME: for now no mention of directories, since this seems to be in
13946 @c flux. 13mar1992 status is that in theory GDB would look either in
13947 @c current dir or in same dir as myprog; but issues like competing
13948 @c GDB's, or clutter in system dirs, mean that in practice right now
13949 @c only current dir is used. FFish says maybe a special GDB hierarchy
13950 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
13954 @item core-file @r{[}@var{filename}@r{]}
13956 Specify the whereabouts of a core dump file to be used as the ``contents
13957 of memory''. Traditionally, core files contain only some parts of the
13958 address space of the process that generated them; @value{GDBN} can access the
13959 executable file itself for other parts.
13961 @code{core-file} with no argument specifies that no core file is
13964 Note that the core file is ignored when your program is actually running
13965 under @value{GDBN}. So, if you have been running your program and you
13966 wish to debug a core file instead, you must kill the subprocess in which
13967 the program is running. To do this, use the @code{kill} command
13968 (@pxref{Kill Process, ,Killing the Child Process}).
13970 @kindex add-symbol-file
13971 @cindex dynamic linking
13972 @item add-symbol-file @var{filename} @var{address}
13973 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
13974 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
13975 The @code{add-symbol-file} command reads additional symbol table
13976 information from the file @var{filename}. You would use this command
13977 when @var{filename} has been dynamically loaded (by some other means)
13978 into the program that is running. @var{address} should be the memory
13979 address at which the file has been loaded; @value{GDBN} cannot figure
13980 this out for itself. You can additionally specify an arbitrary number
13981 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
13982 section name and base address for that section. You can specify any
13983 @var{address} as an expression.
13985 The symbol table of the file @var{filename} is added to the symbol table
13986 originally read with the @code{symbol-file} command. You can use the
13987 @code{add-symbol-file} command any number of times; the new symbol data
13988 thus read keeps adding to the old. To discard all old symbol data
13989 instead, use the @code{symbol-file} command without any arguments.
13991 @cindex relocatable object files, reading symbols from
13992 @cindex object files, relocatable, reading symbols from
13993 @cindex reading symbols from relocatable object files
13994 @cindex symbols, reading from relocatable object files
13995 @cindex @file{.o} files, reading symbols from
13996 Although @var{filename} is typically a shared library file, an
13997 executable file, or some other object file which has been fully
13998 relocated for loading into a process, you can also load symbolic
13999 information from relocatable @file{.o} files, as long as:
14003 the file's symbolic information refers only to linker symbols defined in
14004 that file, not to symbols defined by other object files,
14006 every section the file's symbolic information refers to has actually
14007 been loaded into the inferior, as it appears in the file, and
14009 you can determine the address at which every section was loaded, and
14010 provide these to the @code{add-symbol-file} command.
14014 Some embedded operating systems, like Sun Chorus and VxWorks, can load
14015 relocatable files into an already running program; such systems
14016 typically make the requirements above easy to meet. However, it's
14017 important to recognize that many native systems use complex link
14018 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
14019 assembly, for example) that make the requirements difficult to meet. In
14020 general, one cannot assume that using @code{add-symbol-file} to read a
14021 relocatable object file's symbolic information will have the same effect
14022 as linking the relocatable object file into the program in the normal
14025 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
14027 @kindex add-symbol-file-from-memory
14028 @cindex @code{syscall DSO}
14029 @cindex load symbols from memory
14030 @item add-symbol-file-from-memory @var{address}
14031 Load symbols from the given @var{address} in a dynamically loaded
14032 object file whose image is mapped directly into the inferior's memory.
14033 For example, the Linux kernel maps a @code{syscall DSO} into each
14034 process's address space; this DSO provides kernel-specific code for
14035 some system calls. The argument can be any expression whose
14036 evaluation yields the address of the file's shared object file header.
14037 For this command to work, you must have used @code{symbol-file} or
14038 @code{exec-file} commands in advance.
14040 @kindex add-shared-symbol-files
14042 @item add-shared-symbol-files @var{library-file}
14043 @itemx assf @var{library-file}
14044 The @code{add-shared-symbol-files} command can currently be used only
14045 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
14046 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
14047 @value{GDBN} automatically looks for shared libraries, however if
14048 @value{GDBN} does not find yours, you can invoke
14049 @code{add-shared-symbol-files}. It takes one argument: the shared
14050 library's file name. @code{assf} is a shorthand alias for
14051 @code{add-shared-symbol-files}.
14054 @item section @var{section} @var{addr}
14055 The @code{section} command changes the base address of the named
14056 @var{section} of the exec file to @var{addr}. This can be used if the
14057 exec file does not contain section addresses, (such as in the
14058 @code{a.out} format), or when the addresses specified in the file
14059 itself are wrong. Each section must be changed separately. The
14060 @code{info files} command, described below, lists all the sections and
14064 @kindex info target
14067 @code{info files} and @code{info target} are synonymous; both print the
14068 current target (@pxref{Targets, ,Specifying a Debugging Target}),
14069 including the names of the executable and core dump files currently in
14070 use by @value{GDBN}, and the files from which symbols were loaded. The
14071 command @code{help target} lists all possible targets rather than
14074 @kindex maint info sections
14075 @item maint info sections
14076 Another command that can give you extra information about program sections
14077 is @code{maint info sections}. In addition to the section information
14078 displayed by @code{info files}, this command displays the flags and file
14079 offset of each section in the executable and core dump files. In addition,
14080 @code{maint info sections} provides the following command options (which
14081 may be arbitrarily combined):
14085 Display sections for all loaded object files, including shared libraries.
14086 @item @var{sections}
14087 Display info only for named @var{sections}.
14088 @item @var{section-flags}
14089 Display info only for sections for which @var{section-flags} are true.
14090 The section flags that @value{GDBN} currently knows about are:
14093 Section will have space allocated in the process when loaded.
14094 Set for all sections except those containing debug information.
14096 Section will be loaded from the file into the child process memory.
14097 Set for pre-initialized code and data, clear for @code{.bss} sections.
14099 Section needs to be relocated before loading.
14101 Section cannot be modified by the child process.
14103 Section contains executable code only.
14105 Section contains data only (no executable code).
14107 Section will reside in ROM.
14109 Section contains data for constructor/destructor lists.
14111 Section is not empty.
14113 An instruction to the linker to not output the section.
14114 @item COFF_SHARED_LIBRARY
14115 A notification to the linker that the section contains
14116 COFF shared library information.
14118 Section contains common symbols.
14121 @kindex set trust-readonly-sections
14122 @cindex read-only sections
14123 @item set trust-readonly-sections on
14124 Tell @value{GDBN} that readonly sections in your object file
14125 really are read-only (i.e.@: that their contents will not change).
14126 In that case, @value{GDBN} can fetch values from these sections
14127 out of the object file, rather than from the target program.
14128 For some targets (notably embedded ones), this can be a significant
14129 enhancement to debugging performance.
14131 The default is off.
14133 @item set trust-readonly-sections off
14134 Tell @value{GDBN} not to trust readonly sections. This means that
14135 the contents of the section might change while the program is running,
14136 and must therefore be fetched from the target when needed.
14138 @item show trust-readonly-sections
14139 Show the current setting of trusting readonly sections.
14142 All file-specifying commands allow both absolute and relative file names
14143 as arguments. @value{GDBN} always converts the file name to an absolute file
14144 name and remembers it that way.
14146 @cindex shared libraries
14147 @anchor{Shared Libraries}
14148 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
14149 and IBM RS/6000 AIX shared libraries.
14151 On MS-Windows @value{GDBN} must be linked with the Expat library to support
14152 shared libraries. @xref{Expat}.
14154 @value{GDBN} automatically loads symbol definitions from shared libraries
14155 when you use the @code{run} command, or when you examine a core file.
14156 (Before you issue the @code{run} command, @value{GDBN} does not understand
14157 references to a function in a shared library, however---unless you are
14158 debugging a core file).
14160 On HP-UX, if the program loads a library explicitly, @value{GDBN}
14161 automatically loads the symbols at the time of the @code{shl_load} call.
14163 @c FIXME: some @value{GDBN} release may permit some refs to undef
14164 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
14165 @c FIXME...lib; check this from time to time when updating manual
14167 There are times, however, when you may wish to not automatically load
14168 symbol definitions from shared libraries, such as when they are
14169 particularly large or there are many of them.
14171 To control the automatic loading of shared library symbols, use the
14175 @kindex set auto-solib-add
14176 @item set auto-solib-add @var{mode}
14177 If @var{mode} is @code{on}, symbols from all shared object libraries
14178 will be loaded automatically when the inferior begins execution, you
14179 attach to an independently started inferior, or when the dynamic linker
14180 informs @value{GDBN} that a new library has been loaded. If @var{mode}
14181 is @code{off}, symbols must be loaded manually, using the
14182 @code{sharedlibrary} command. The default value is @code{on}.
14184 @cindex memory used for symbol tables
14185 If your program uses lots of shared libraries with debug info that
14186 takes large amounts of memory, you can decrease the @value{GDBN}
14187 memory footprint by preventing it from automatically loading the
14188 symbols from shared libraries. To that end, type @kbd{set
14189 auto-solib-add off} before running the inferior, then load each
14190 library whose debug symbols you do need with @kbd{sharedlibrary
14191 @var{regexp}}, where @var{regexp} is a regular expression that matches
14192 the libraries whose symbols you want to be loaded.
14194 @kindex show auto-solib-add
14195 @item show auto-solib-add
14196 Display the current autoloading mode.
14199 @cindex load shared library
14200 To explicitly load shared library symbols, use the @code{sharedlibrary}
14204 @kindex info sharedlibrary
14206 @item info share @var{regex}
14207 @itemx info sharedlibrary @var{regex}
14208 Print the names of the shared libraries which are currently loaded
14209 that match @var{regex}. If @var{regex} is omitted then print
14210 all shared libraries that are loaded.
14212 @kindex sharedlibrary
14214 @item sharedlibrary @var{regex}
14215 @itemx share @var{regex}
14216 Load shared object library symbols for files matching a
14217 Unix regular expression.
14218 As with files loaded automatically, it only loads shared libraries
14219 required by your program for a core file or after typing @code{run}. If
14220 @var{regex} is omitted all shared libraries required by your program are
14223 @item nosharedlibrary
14224 @kindex nosharedlibrary
14225 @cindex unload symbols from shared libraries
14226 Unload all shared object library symbols. This discards all symbols
14227 that have been loaded from all shared libraries. Symbols from shared
14228 libraries that were loaded by explicit user requests are not
14232 Sometimes you may wish that @value{GDBN} stops and gives you control
14233 when any of shared library events happen. Use the @code{set
14234 stop-on-solib-events} command for this:
14237 @item set stop-on-solib-events
14238 @kindex set stop-on-solib-events
14239 This command controls whether @value{GDBN} should give you control
14240 when the dynamic linker notifies it about some shared library event.
14241 The most common event of interest is loading or unloading of a new
14244 @item show stop-on-solib-events
14245 @kindex show stop-on-solib-events
14246 Show whether @value{GDBN} stops and gives you control when shared
14247 library events happen.
14250 Shared libraries are also supported in many cross or remote debugging
14251 configurations. @value{GDBN} needs to have access to the target's libraries;
14252 this can be accomplished either by providing copies of the libraries
14253 on the host system, or by asking @value{GDBN} to automatically retrieve the
14254 libraries from the target. If copies of the target libraries are
14255 provided, they need to be the same as the target libraries, although the
14256 copies on the target can be stripped as long as the copies on the host are
14259 @cindex where to look for shared libraries
14260 For remote debugging, you need to tell @value{GDBN} where the target
14261 libraries are, so that it can load the correct copies---otherwise, it
14262 may try to load the host's libraries. @value{GDBN} has two variables
14263 to specify the search directories for target libraries.
14266 @cindex prefix for shared library file names
14267 @cindex system root, alternate
14268 @kindex set solib-absolute-prefix
14269 @kindex set sysroot
14270 @item set sysroot @var{path}
14271 Use @var{path} as the system root for the program being debugged. Any
14272 absolute shared library paths will be prefixed with @var{path}; many
14273 runtime loaders store the absolute paths to the shared library in the
14274 target program's memory. If you use @code{set sysroot} to find shared
14275 libraries, they need to be laid out in the same way that they are on
14276 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
14279 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
14280 retrieve the target libraries from the remote system. This is only
14281 supported when using a remote target that supports the @code{remote get}
14282 command (@pxref{File Transfer,,Sending files to a remote system}).
14283 The part of @var{path} following the initial @file{remote:}
14284 (if present) is used as system root prefix on the remote file system.
14285 @footnote{If you want to specify a local system root using a directory
14286 that happens to be named @file{remote:}, you need to use some equivalent
14287 variant of the name like @file{./remote:}.}
14289 The @code{set solib-absolute-prefix} command is an alias for @code{set
14292 @cindex default system root
14293 @cindex @samp{--with-sysroot}
14294 You can set the default system root by using the configure-time
14295 @samp{--with-sysroot} option. If the system root is inside
14296 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
14297 @samp{--exec-prefix}), then the default system root will be updated
14298 automatically if the installed @value{GDBN} is moved to a new
14301 @kindex show sysroot
14303 Display the current shared library prefix.
14305 @kindex set solib-search-path
14306 @item set solib-search-path @var{path}
14307 If this variable is set, @var{path} is a colon-separated list of
14308 directories to search for shared libraries. @samp{solib-search-path}
14309 is used after @samp{sysroot} fails to locate the library, or if the
14310 path to the library is relative instead of absolute. If you want to
14311 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
14312 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
14313 finding your host's libraries. @samp{sysroot} is preferred; setting
14314 it to a nonexistent directory may interfere with automatic loading
14315 of shared library symbols.
14317 @kindex show solib-search-path
14318 @item show solib-search-path
14319 Display the current shared library search path.
14323 @node Separate Debug Files
14324 @section Debugging Information in Separate Files
14325 @cindex separate debugging information files
14326 @cindex debugging information in separate files
14327 @cindex @file{.debug} subdirectories
14328 @cindex debugging information directory, global
14329 @cindex global debugging information directory
14330 @cindex build ID, and separate debugging files
14331 @cindex @file{.build-id} directory
14333 @value{GDBN} allows you to put a program's debugging information in a
14334 file separate from the executable itself, in a way that allows
14335 @value{GDBN} to find and load the debugging information automatically.
14336 Since debugging information can be very large---sometimes larger
14337 than the executable code itself---some systems distribute debugging
14338 information for their executables in separate files, which users can
14339 install only when they need to debug a problem.
14341 @value{GDBN} supports two ways of specifying the separate debug info
14346 The executable contains a @dfn{debug link} that specifies the name of
14347 the separate debug info file. The separate debug file's name is
14348 usually @file{@var{executable}.debug}, where @var{executable} is the
14349 name of the corresponding executable file without leading directories
14350 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
14351 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
14352 checksum for the debug file, which @value{GDBN} uses to validate that
14353 the executable and the debug file came from the same build.
14356 The executable contains a @dfn{build ID}, a unique bit string that is
14357 also present in the corresponding debug info file. (This is supported
14358 only on some operating systems, notably those which use the ELF format
14359 for binary files and the @sc{gnu} Binutils.) For more details about
14360 this feature, see the description of the @option{--build-id}
14361 command-line option in @ref{Options, , Command Line Options, ld.info,
14362 The GNU Linker}. The debug info file's name is not specified
14363 explicitly by the build ID, but can be computed from the build ID, see
14367 Depending on the way the debug info file is specified, @value{GDBN}
14368 uses two different methods of looking for the debug file:
14372 For the ``debug link'' method, @value{GDBN} looks up the named file in
14373 the directory of the executable file, then in a subdirectory of that
14374 directory named @file{.debug}, and finally under the global debug
14375 directory, in a subdirectory whose name is identical to the leading
14376 directories of the executable's absolute file name.
14379 For the ``build ID'' method, @value{GDBN} looks in the
14380 @file{.build-id} subdirectory of the global debug directory for a file
14381 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
14382 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
14383 are the rest of the bit string. (Real build ID strings are 32 or more
14384 hex characters, not 10.)
14387 So, for example, suppose you ask @value{GDBN} to debug
14388 @file{/usr/bin/ls}, which has a debug link that specifies the
14389 file @file{ls.debug}, and a build ID whose value in hex is
14390 @code{abcdef1234}. If the global debug directory is
14391 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
14392 debug information files, in the indicated order:
14396 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
14398 @file{/usr/bin/ls.debug}
14400 @file{/usr/bin/.debug/ls.debug}
14402 @file{/usr/lib/debug/usr/bin/ls.debug}.
14405 You can set the global debugging info directory's name, and view the
14406 name @value{GDBN} is currently using.
14410 @kindex set debug-file-directory
14411 @item set debug-file-directory @var{directories}
14412 Set the directories which @value{GDBN} searches for separate debugging
14413 information files to @var{directory}. Multiple directory components can be set
14414 concatenating them by a directory separator.
14416 @kindex show debug-file-directory
14417 @item show debug-file-directory
14418 Show the directories @value{GDBN} searches for separate debugging
14423 @cindex @code{.gnu_debuglink} sections
14424 @cindex debug link sections
14425 A debug link is a special section of the executable file named
14426 @code{.gnu_debuglink}. The section must contain:
14430 A filename, with any leading directory components removed, followed by
14433 zero to three bytes of padding, as needed to reach the next four-byte
14434 boundary within the section, and
14436 a four-byte CRC checksum, stored in the same endianness used for the
14437 executable file itself. The checksum is computed on the debugging
14438 information file's full contents by the function given below, passing
14439 zero as the @var{crc} argument.
14442 Any executable file format can carry a debug link, as long as it can
14443 contain a section named @code{.gnu_debuglink} with the contents
14446 @cindex @code{.note.gnu.build-id} sections
14447 @cindex build ID sections
14448 The build ID is a special section in the executable file (and in other
14449 ELF binary files that @value{GDBN} may consider). This section is
14450 often named @code{.note.gnu.build-id}, but that name is not mandatory.
14451 It contains unique identification for the built files---the ID remains
14452 the same across multiple builds of the same build tree. The default
14453 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
14454 content for the build ID string. The same section with an identical
14455 value is present in the original built binary with symbols, in its
14456 stripped variant, and in the separate debugging information file.
14458 The debugging information file itself should be an ordinary
14459 executable, containing a full set of linker symbols, sections, and
14460 debugging information. The sections of the debugging information file
14461 should have the same names, addresses, and sizes as the original file,
14462 but they need not contain any data---much like a @code{.bss} section
14463 in an ordinary executable.
14465 The @sc{gnu} binary utilities (Binutils) package includes the
14466 @samp{objcopy} utility that can produce
14467 the separated executable / debugging information file pairs using the
14468 following commands:
14471 @kbd{objcopy --only-keep-debug foo foo.debug}
14476 These commands remove the debugging
14477 information from the executable file @file{foo} and place it in the file
14478 @file{foo.debug}. You can use the first, second or both methods to link the
14483 The debug link method needs the following additional command to also leave
14484 behind a debug link in @file{foo}:
14487 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
14490 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
14491 a version of the @code{strip} command such that the command @kbd{strip foo -f
14492 foo.debug} has the same functionality as the two @code{objcopy} commands and
14493 the @code{ln -s} command above, together.
14496 Build ID gets embedded into the main executable using @code{ld --build-id} or
14497 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
14498 compatibility fixes for debug files separation are present in @sc{gnu} binary
14499 utilities (Binutils) package since version 2.18.
14504 @cindex CRC algorithm definition
14505 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
14506 IEEE 802.3 using the polynomial:
14508 @c TexInfo requires naked braces for multi-digit exponents for Tex
14509 @c output, but this causes HTML output to barf. HTML has to be set using
14510 @c raw commands. So we end up having to specify this equation in 2
14515 <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>
14516 + <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
14522 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
14523 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
14527 The function is computed byte at a time, taking the least
14528 significant bit of each byte first. The initial pattern
14529 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
14530 the final result is inverted to ensure trailing zeros also affect the
14533 @emph{Note:} This is the same CRC polynomial as used in handling the
14534 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
14535 , @value{GDBN} Remote Serial Protocol}). However in the
14536 case of the Remote Serial Protocol, the CRC is computed @emph{most}
14537 significant bit first, and the result is not inverted, so trailing
14538 zeros have no effect on the CRC value.
14540 To complete the description, we show below the code of the function
14541 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
14542 initially supplied @code{crc} argument means that an initial call to
14543 this function passing in zero will start computing the CRC using
14546 @kindex gnu_debuglink_crc32
14549 gnu_debuglink_crc32 (unsigned long crc,
14550 unsigned char *buf, size_t len)
14552 static const unsigned long crc32_table[256] =
14554 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
14555 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
14556 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
14557 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
14558 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
14559 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
14560 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
14561 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
14562 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
14563 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
14564 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
14565 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
14566 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
14567 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
14568 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
14569 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
14570 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
14571 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
14572 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
14573 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
14574 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
14575 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
14576 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
14577 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
14578 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
14579 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
14580 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
14581 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
14582 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
14583 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
14584 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
14585 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
14586 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
14587 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
14588 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
14589 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
14590 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
14591 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
14592 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
14593 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
14594 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
14595 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
14596 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
14597 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
14598 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
14599 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
14600 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
14601 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
14602 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
14603 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
14604 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
14607 unsigned char *end;
14609 crc = ~crc & 0xffffffff;
14610 for (end = buf + len; buf < end; ++buf)
14611 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
14612 return ~crc & 0xffffffff;
14617 This computation does not apply to the ``build ID'' method.
14620 @node Symbol Errors
14621 @section Errors Reading Symbol Files
14623 While reading a symbol file, @value{GDBN} occasionally encounters problems,
14624 such as symbol types it does not recognize, or known bugs in compiler
14625 output. By default, @value{GDBN} does not notify you of such problems, since
14626 they are relatively common and primarily of interest to people
14627 debugging compilers. If you are interested in seeing information
14628 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
14629 only one message about each such type of problem, no matter how many
14630 times the problem occurs; or you can ask @value{GDBN} to print more messages,
14631 to see how many times the problems occur, with the @code{set
14632 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
14635 The messages currently printed, and their meanings, include:
14638 @item inner block not inside outer block in @var{symbol}
14640 The symbol information shows where symbol scopes begin and end
14641 (such as at the start of a function or a block of statements). This
14642 error indicates that an inner scope block is not fully contained
14643 in its outer scope blocks.
14645 @value{GDBN} circumvents the problem by treating the inner block as if it had
14646 the same scope as the outer block. In the error message, @var{symbol}
14647 may be shown as ``@code{(don't know)}'' if the outer block is not a
14650 @item block at @var{address} out of order
14652 The symbol information for symbol scope blocks should occur in
14653 order of increasing addresses. This error indicates that it does not
14656 @value{GDBN} does not circumvent this problem, and has trouble
14657 locating symbols in the source file whose symbols it is reading. (You
14658 can often determine what source file is affected by specifying
14659 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
14662 @item bad block start address patched
14664 The symbol information for a symbol scope block has a start address
14665 smaller than the address of the preceding source line. This is known
14666 to occur in the SunOS 4.1.1 (and earlier) C compiler.
14668 @value{GDBN} circumvents the problem by treating the symbol scope block as
14669 starting on the previous source line.
14671 @item bad string table offset in symbol @var{n}
14674 Symbol number @var{n} contains a pointer into the string table which is
14675 larger than the size of the string table.
14677 @value{GDBN} circumvents the problem by considering the symbol to have the
14678 name @code{foo}, which may cause other problems if many symbols end up
14681 @item unknown symbol type @code{0x@var{nn}}
14683 The symbol information contains new data types that @value{GDBN} does
14684 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
14685 uncomprehended information, in hexadecimal.
14687 @value{GDBN} circumvents the error by ignoring this symbol information.
14688 This usually allows you to debug your program, though certain symbols
14689 are not accessible. If you encounter such a problem and feel like
14690 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
14691 on @code{complain}, then go up to the function @code{read_dbx_symtab}
14692 and examine @code{*bufp} to see the symbol.
14694 @item stub type has NULL name
14696 @value{GDBN} could not find the full definition for a struct or class.
14698 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
14699 The symbol information for a C@t{++} member function is missing some
14700 information that recent versions of the compiler should have output for
14703 @item info mismatch between compiler and debugger
14705 @value{GDBN} could not parse a type specification output by the compiler.
14710 @section GDB Data Files
14712 @cindex prefix for data files
14713 @value{GDBN} will sometimes read an auxiliary data file. These files
14714 are kept in a directory known as the @dfn{data directory}.
14716 You can set the data directory's name, and view the name @value{GDBN}
14717 is currently using.
14720 @kindex set data-directory
14721 @item set data-directory @var{directory}
14722 Set the directory which @value{GDBN} searches for auxiliary data files
14723 to @var{directory}.
14725 @kindex show data-directory
14726 @item show data-directory
14727 Show the directory @value{GDBN} searches for auxiliary data files.
14730 @cindex default data directory
14731 @cindex @samp{--with-gdb-datadir}
14732 You can set the default data directory by using the configure-time
14733 @samp{--with-gdb-datadir} option. If the data directory is inside
14734 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
14735 @samp{--exec-prefix}), then the default data directory will be updated
14736 automatically if the installed @value{GDBN} is moved to a new
14740 @chapter Specifying a Debugging Target
14742 @cindex debugging target
14743 A @dfn{target} is the execution environment occupied by your program.
14745 Often, @value{GDBN} runs in the same host environment as your program;
14746 in that case, the debugging target is specified as a side effect when
14747 you use the @code{file} or @code{core} commands. When you need more
14748 flexibility---for example, running @value{GDBN} on a physically separate
14749 host, or controlling a standalone system over a serial port or a
14750 realtime system over a TCP/IP connection---you can use the @code{target}
14751 command to specify one of the target types configured for @value{GDBN}
14752 (@pxref{Target Commands, ,Commands for Managing Targets}).
14754 @cindex target architecture
14755 It is possible to build @value{GDBN} for several different @dfn{target
14756 architectures}. When @value{GDBN} is built like that, you can choose
14757 one of the available architectures with the @kbd{set architecture}
14761 @kindex set architecture
14762 @kindex show architecture
14763 @item set architecture @var{arch}
14764 This command sets the current target architecture to @var{arch}. The
14765 value of @var{arch} can be @code{"auto"}, in addition to one of the
14766 supported architectures.
14768 @item show architecture
14769 Show the current target architecture.
14771 @item set processor
14773 @kindex set processor
14774 @kindex show processor
14775 These are alias commands for, respectively, @code{set architecture}
14776 and @code{show architecture}.
14780 * Active Targets:: Active targets
14781 * Target Commands:: Commands for managing targets
14782 * Byte Order:: Choosing target byte order
14785 @node Active Targets
14786 @section Active Targets
14788 @cindex stacking targets
14789 @cindex active targets
14790 @cindex multiple targets
14792 There are three classes of targets: processes, core files, and
14793 executable files. @value{GDBN} can work concurrently on up to three
14794 active targets, one in each class. This allows you to (for example)
14795 start a process and inspect its activity without abandoning your work on
14798 For example, if you execute @samp{gdb a.out}, then the executable file
14799 @code{a.out} is the only active target. If you designate a core file as
14800 well---presumably from a prior run that crashed and coredumped---then
14801 @value{GDBN} has two active targets and uses them in tandem, looking
14802 first in the corefile target, then in the executable file, to satisfy
14803 requests for memory addresses. (Typically, these two classes of target
14804 are complementary, since core files contain only a program's
14805 read-write memory---variables and so on---plus machine status, while
14806 executable files contain only the program text and initialized data.)
14808 When you type @code{run}, your executable file becomes an active process
14809 target as well. When a process target is active, all @value{GDBN}
14810 commands requesting memory addresses refer to that target; addresses in
14811 an active core file or executable file target are obscured while the
14812 process target is active.
14814 Use the @code{core-file} and @code{exec-file} commands to select a new
14815 core file or executable target (@pxref{Files, ,Commands to Specify
14816 Files}). To specify as a target a process that is already running, use
14817 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
14820 @node Target Commands
14821 @section Commands for Managing Targets
14824 @item target @var{type} @var{parameters}
14825 Connects the @value{GDBN} host environment to a target machine or
14826 process. A target is typically a protocol for talking to debugging
14827 facilities. You use the argument @var{type} to specify the type or
14828 protocol of the target machine.
14830 Further @var{parameters} are interpreted by the target protocol, but
14831 typically include things like device names or host names to connect
14832 with, process numbers, and baud rates.
14834 The @code{target} command does not repeat if you press @key{RET} again
14835 after executing the command.
14837 @kindex help target
14839 Displays the names of all targets available. To display targets
14840 currently selected, use either @code{info target} or @code{info files}
14841 (@pxref{Files, ,Commands to Specify Files}).
14843 @item help target @var{name}
14844 Describe a particular target, including any parameters necessary to
14847 @kindex set gnutarget
14848 @item set gnutarget @var{args}
14849 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
14850 knows whether it is reading an @dfn{executable},
14851 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
14852 with the @code{set gnutarget} command. Unlike most @code{target} commands,
14853 with @code{gnutarget} the @code{target} refers to a program, not a machine.
14856 @emph{Warning:} To specify a file format with @code{set gnutarget},
14857 you must know the actual BFD name.
14861 @xref{Files, , Commands to Specify Files}.
14863 @kindex show gnutarget
14864 @item show gnutarget
14865 Use the @code{show gnutarget} command to display what file format
14866 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
14867 @value{GDBN} will determine the file format for each file automatically,
14868 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
14871 @cindex common targets
14872 Here are some common targets (available, or not, depending on the GDB
14877 @item target exec @var{program}
14878 @cindex executable file target
14879 An executable file. @samp{target exec @var{program}} is the same as
14880 @samp{exec-file @var{program}}.
14882 @item target core @var{filename}
14883 @cindex core dump file target
14884 A core dump file. @samp{target core @var{filename}} is the same as
14885 @samp{core-file @var{filename}}.
14887 @item target remote @var{medium}
14888 @cindex remote target
14889 A remote system connected to @value{GDBN} via a serial line or network
14890 connection. This command tells @value{GDBN} to use its own remote
14891 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
14893 For example, if you have a board connected to @file{/dev/ttya} on the
14894 machine running @value{GDBN}, you could say:
14897 target remote /dev/ttya
14900 @code{target remote} supports the @code{load} command. This is only
14901 useful if you have some other way of getting the stub to the target
14902 system, and you can put it somewhere in memory where it won't get
14903 clobbered by the download.
14905 @item target sim @r{[}@var{simargs}@r{]} @dots{}
14906 @cindex built-in simulator target
14907 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
14915 works; however, you cannot assume that a specific memory map, device
14916 drivers, or even basic I/O is available, although some simulators do
14917 provide these. For info about any processor-specific simulator details,
14918 see the appropriate section in @ref{Embedded Processors, ,Embedded
14923 Some configurations may include these targets as well:
14927 @item target nrom @var{dev}
14928 @cindex NetROM ROM emulator target
14929 NetROM ROM emulator. This target only supports downloading.
14933 Different targets are available on different configurations of @value{GDBN};
14934 your configuration may have more or fewer targets.
14936 Many remote targets require you to download the executable's code once
14937 you've successfully established a connection. You may wish to control
14938 various aspects of this process.
14943 @kindex set hash@r{, for remote monitors}
14944 @cindex hash mark while downloading
14945 This command controls whether a hash mark @samp{#} is displayed while
14946 downloading a file to the remote monitor. If on, a hash mark is
14947 displayed after each S-record is successfully downloaded to the
14951 @kindex show hash@r{, for remote monitors}
14952 Show the current status of displaying the hash mark.
14954 @item set debug monitor
14955 @kindex set debug monitor
14956 @cindex display remote monitor communications
14957 Enable or disable display of communications messages between
14958 @value{GDBN} and the remote monitor.
14960 @item show debug monitor
14961 @kindex show debug monitor
14962 Show the current status of displaying communications between
14963 @value{GDBN} and the remote monitor.
14968 @kindex load @var{filename}
14969 @item load @var{filename}
14971 Depending on what remote debugging facilities are configured into
14972 @value{GDBN}, the @code{load} command may be available. Where it exists, it
14973 is meant to make @var{filename} (an executable) available for debugging
14974 on the remote system---by downloading, or dynamic linking, for example.
14975 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
14976 the @code{add-symbol-file} command.
14978 If your @value{GDBN} does not have a @code{load} command, attempting to
14979 execute it gets the error message ``@code{You can't do that when your
14980 target is @dots{}}''
14982 The file is loaded at whatever address is specified in the executable.
14983 For some object file formats, you can specify the load address when you
14984 link the program; for other formats, like a.out, the object file format
14985 specifies a fixed address.
14986 @c FIXME! This would be a good place for an xref to the GNU linker doc.
14988 Depending on the remote side capabilities, @value{GDBN} may be able to
14989 load programs into flash memory.
14991 @code{load} does not repeat if you press @key{RET} again after using it.
14995 @section Choosing Target Byte Order
14997 @cindex choosing target byte order
14998 @cindex target byte order
15000 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
15001 offer the ability to run either big-endian or little-endian byte
15002 orders. Usually the executable or symbol will include a bit to
15003 designate the endian-ness, and you will not need to worry about
15004 which to use. However, you may still find it useful to adjust
15005 @value{GDBN}'s idea of processor endian-ness manually.
15009 @item set endian big
15010 Instruct @value{GDBN} to assume the target is big-endian.
15012 @item set endian little
15013 Instruct @value{GDBN} to assume the target is little-endian.
15015 @item set endian auto
15016 Instruct @value{GDBN} to use the byte order associated with the
15020 Display @value{GDBN}'s current idea of the target byte order.
15024 Note that these commands merely adjust interpretation of symbolic
15025 data on the host, and that they have absolutely no effect on the
15029 @node Remote Debugging
15030 @chapter Debugging Remote Programs
15031 @cindex remote debugging
15033 If you are trying to debug a program running on a machine that cannot run
15034 @value{GDBN} in the usual way, it is often useful to use remote debugging.
15035 For example, you might use remote debugging on an operating system kernel,
15036 or on a small system which does not have a general purpose operating system
15037 powerful enough to run a full-featured debugger.
15039 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
15040 to make this work with particular debugging targets. In addition,
15041 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
15042 but not specific to any particular target system) which you can use if you
15043 write the remote stubs---the code that runs on the remote system to
15044 communicate with @value{GDBN}.
15046 Other remote targets may be available in your
15047 configuration of @value{GDBN}; use @code{help target} to list them.
15050 * Connecting:: Connecting to a remote target
15051 * File Transfer:: Sending files to a remote system
15052 * Server:: Using the gdbserver program
15053 * Remote Configuration:: Remote configuration
15054 * Remote Stub:: Implementing a remote stub
15058 @section Connecting to a Remote Target
15060 On the @value{GDBN} host machine, you will need an unstripped copy of
15061 your program, since @value{GDBN} needs symbol and debugging information.
15062 Start up @value{GDBN} as usual, using the name of the local copy of your
15063 program as the first argument.
15065 @cindex @code{target remote}
15066 @value{GDBN} can communicate with the target over a serial line, or
15067 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
15068 each case, @value{GDBN} uses the same protocol for debugging your
15069 program; only the medium carrying the debugging packets varies. The
15070 @code{target remote} command establishes a connection to the target.
15071 Its arguments indicate which medium to use:
15075 @item target remote @var{serial-device}
15076 @cindex serial line, @code{target remote}
15077 Use @var{serial-device} to communicate with the target. For example,
15078 to use a serial line connected to the device named @file{/dev/ttyb}:
15081 target remote /dev/ttyb
15084 If you're using a serial line, you may want to give @value{GDBN} the
15085 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
15086 (@pxref{Remote Configuration, set remotebaud}) before the
15087 @code{target} command.
15089 @item target remote @code{@var{host}:@var{port}}
15090 @itemx target remote @code{tcp:@var{host}:@var{port}}
15091 @cindex @acronym{TCP} port, @code{target remote}
15092 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
15093 The @var{host} may be either a host name or a numeric @acronym{IP}
15094 address; @var{port} must be a decimal number. The @var{host} could be
15095 the target machine itself, if it is directly connected to the net, or
15096 it might be a terminal server which in turn has a serial line to the
15099 For example, to connect to port 2828 on a terminal server named
15103 target remote manyfarms:2828
15106 If your remote target is actually running on the same machine as your
15107 debugger session (e.g.@: a simulator for your target running on the
15108 same host), you can omit the hostname. For example, to connect to
15109 port 1234 on your local machine:
15112 target remote :1234
15116 Note that the colon is still required here.
15118 @item target remote @code{udp:@var{host}:@var{port}}
15119 @cindex @acronym{UDP} port, @code{target remote}
15120 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
15121 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
15124 target remote udp:manyfarms:2828
15127 When using a @acronym{UDP} connection for remote debugging, you should
15128 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
15129 can silently drop packets on busy or unreliable networks, which will
15130 cause havoc with your debugging session.
15132 @item target remote | @var{command}
15133 @cindex pipe, @code{target remote} to
15134 Run @var{command} in the background and communicate with it using a
15135 pipe. The @var{command} is a shell command, to be parsed and expanded
15136 by the system's command shell, @code{/bin/sh}; it should expect remote
15137 protocol packets on its standard input, and send replies on its
15138 standard output. You could use this to run a stand-alone simulator
15139 that speaks the remote debugging protocol, to make net connections
15140 using programs like @code{ssh}, or for other similar tricks.
15142 If @var{command} closes its standard output (perhaps by exiting),
15143 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
15144 program has already exited, this will have no effect.)
15148 Once the connection has been established, you can use all the usual
15149 commands to examine and change data. The remote program is already
15150 running; you can use @kbd{step} and @kbd{continue}, and you do not
15151 need to use @kbd{run}.
15153 @cindex interrupting remote programs
15154 @cindex remote programs, interrupting
15155 Whenever @value{GDBN} is waiting for the remote program, if you type the
15156 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
15157 program. This may or may not succeed, depending in part on the hardware
15158 and the serial drivers the remote system uses. If you type the
15159 interrupt character once again, @value{GDBN} displays this prompt:
15162 Interrupted while waiting for the program.
15163 Give up (and stop debugging it)? (y or n)
15166 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
15167 (If you decide you want to try again later, you can use @samp{target
15168 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
15169 goes back to waiting.
15172 @kindex detach (remote)
15174 When you have finished debugging the remote program, you can use the
15175 @code{detach} command to release it from @value{GDBN} control.
15176 Detaching from the target normally resumes its execution, but the results
15177 will depend on your particular remote stub. After the @code{detach}
15178 command, @value{GDBN} is free to connect to another target.
15182 The @code{disconnect} command behaves like @code{detach}, except that
15183 the target is generally not resumed. It will wait for @value{GDBN}
15184 (this instance or another one) to connect and continue debugging. After
15185 the @code{disconnect} command, @value{GDBN} is again free to connect to
15188 @cindex send command to remote monitor
15189 @cindex extend @value{GDBN} for remote targets
15190 @cindex add new commands for external monitor
15192 @item monitor @var{cmd}
15193 This command allows you to send arbitrary commands directly to the
15194 remote monitor. Since @value{GDBN} doesn't care about the commands it
15195 sends like this, this command is the way to extend @value{GDBN}---you
15196 can add new commands that only the external monitor will understand
15200 @node File Transfer
15201 @section Sending files to a remote system
15202 @cindex remote target, file transfer
15203 @cindex file transfer
15204 @cindex sending files to remote systems
15206 Some remote targets offer the ability to transfer files over the same
15207 connection used to communicate with @value{GDBN}. This is convenient
15208 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
15209 running @code{gdbserver} over a network interface. For other targets,
15210 e.g.@: embedded devices with only a single serial port, this may be
15211 the only way to upload or download files.
15213 Not all remote targets support these commands.
15217 @item remote put @var{hostfile} @var{targetfile}
15218 Copy file @var{hostfile} from the host system (the machine running
15219 @value{GDBN}) to @var{targetfile} on the target system.
15222 @item remote get @var{targetfile} @var{hostfile}
15223 Copy file @var{targetfile} from the target system to @var{hostfile}
15224 on the host system.
15226 @kindex remote delete
15227 @item remote delete @var{targetfile}
15228 Delete @var{targetfile} from the target system.
15233 @section Using the @code{gdbserver} Program
15236 @cindex remote connection without stubs
15237 @code{gdbserver} is a control program for Unix-like systems, which
15238 allows you to connect your program with a remote @value{GDBN} via
15239 @code{target remote}---but without linking in the usual debugging stub.
15241 @code{gdbserver} is not a complete replacement for the debugging stubs,
15242 because it requires essentially the same operating-system facilities
15243 that @value{GDBN} itself does. In fact, a system that can run
15244 @code{gdbserver} to connect to a remote @value{GDBN} could also run
15245 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
15246 because it is a much smaller program than @value{GDBN} itself. It is
15247 also easier to port than all of @value{GDBN}, so you may be able to get
15248 started more quickly on a new system by using @code{gdbserver}.
15249 Finally, if you develop code for real-time systems, you may find that
15250 the tradeoffs involved in real-time operation make it more convenient to
15251 do as much development work as possible on another system, for example
15252 by cross-compiling. You can use @code{gdbserver} to make a similar
15253 choice for debugging.
15255 @value{GDBN} and @code{gdbserver} communicate via either a serial line
15256 or a TCP connection, using the standard @value{GDBN} remote serial
15260 @emph{Warning:} @code{gdbserver} does not have any built-in security.
15261 Do not run @code{gdbserver} connected to any public network; a
15262 @value{GDBN} connection to @code{gdbserver} provides access to the
15263 target system with the same privileges as the user running
15267 @subsection Running @code{gdbserver}
15268 @cindex arguments, to @code{gdbserver}
15270 Run @code{gdbserver} on the target system. You need a copy of the
15271 program you want to debug, including any libraries it requires.
15272 @code{gdbserver} does not need your program's symbol table, so you can
15273 strip the program if necessary to save space. @value{GDBN} on the host
15274 system does all the symbol handling.
15276 To use the server, you must tell it how to communicate with @value{GDBN};
15277 the name of your program; and the arguments for your program. The usual
15281 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
15284 @var{comm} is either a device name (to use a serial line) or a TCP
15285 hostname and portnumber. For example, to debug Emacs with the argument
15286 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
15290 target> gdbserver /dev/com1 emacs foo.txt
15293 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
15296 To use a TCP connection instead of a serial line:
15299 target> gdbserver host:2345 emacs foo.txt
15302 The only difference from the previous example is the first argument,
15303 specifying that you are communicating with the host @value{GDBN} via
15304 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
15305 expect a TCP connection from machine @samp{host} to local TCP port 2345.
15306 (Currently, the @samp{host} part is ignored.) You can choose any number
15307 you want for the port number as long as it does not conflict with any
15308 TCP ports already in use on the target system (for example, @code{23} is
15309 reserved for @code{telnet}).@footnote{If you choose a port number that
15310 conflicts with another service, @code{gdbserver} prints an error message
15311 and exits.} You must use the same port number with the host @value{GDBN}
15312 @code{target remote} command.
15314 @subsubsection Attaching to a Running Program
15316 On some targets, @code{gdbserver} can also attach to running programs.
15317 This is accomplished via the @code{--attach} argument. The syntax is:
15320 target> gdbserver --attach @var{comm} @var{pid}
15323 @var{pid} is the process ID of a currently running process. It isn't necessary
15324 to point @code{gdbserver} at a binary for the running process.
15327 @cindex attach to a program by name
15328 You can debug processes by name instead of process ID if your target has the
15329 @code{pidof} utility:
15332 target> gdbserver --attach @var{comm} `pidof @var{program}`
15335 In case more than one copy of @var{program} is running, or @var{program}
15336 has multiple threads, most versions of @code{pidof} support the
15337 @code{-s} option to only return the first process ID.
15339 @subsubsection Multi-Process Mode for @code{gdbserver}
15340 @cindex gdbserver, multiple processes
15341 @cindex multiple processes with gdbserver
15343 When you connect to @code{gdbserver} using @code{target remote},
15344 @code{gdbserver} debugs the specified program only once. When the
15345 program exits, or you detach from it, @value{GDBN} closes the connection
15346 and @code{gdbserver} exits.
15348 If you connect using @kbd{target extended-remote}, @code{gdbserver}
15349 enters multi-process mode. When the debugged program exits, or you
15350 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
15351 though no program is running. The @code{run} and @code{attach}
15352 commands instruct @code{gdbserver} to run or attach to a new program.
15353 The @code{run} command uses @code{set remote exec-file} (@pxref{set
15354 remote exec-file}) to select the program to run. Command line
15355 arguments are supported, except for wildcard expansion and I/O
15356 redirection (@pxref{Arguments}).
15358 To start @code{gdbserver} without supplying an initial command to run
15359 or process ID to attach, use the @option{--multi} command line option.
15360 Then you can connect using @kbd{target extended-remote} and start
15361 the program you want to debug.
15363 @code{gdbserver} does not automatically exit in multi-process mode.
15364 You can terminate it by using @code{monitor exit}
15365 (@pxref{Monitor Commands for gdbserver}).
15367 @subsubsection Other Command-Line Arguments for @code{gdbserver}
15369 The @option{--debug} option tells @code{gdbserver} to display extra
15370 status information about the debugging process. The
15371 @option{--remote-debug} option tells @code{gdbserver} to display
15372 remote protocol debug output. These options are intended for
15373 @code{gdbserver} development and for bug reports to the developers.
15375 The @option{--wrapper} option specifies a wrapper to launch programs
15376 for debugging. The option should be followed by the name of the
15377 wrapper, then any command-line arguments to pass to the wrapper, then
15378 @kbd{--} indicating the end of the wrapper arguments.
15380 @code{gdbserver} runs the specified wrapper program with a combined
15381 command line including the wrapper arguments, then the name of the
15382 program to debug, then any arguments to the program. The wrapper
15383 runs until it executes your program, and then @value{GDBN} gains control.
15385 You can use any program that eventually calls @code{execve} with
15386 its arguments as a wrapper. Several standard Unix utilities do
15387 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
15388 with @code{exec "$@@"} will also work.
15390 For example, you can use @code{env} to pass an environment variable to
15391 the debugged program, without setting the variable in @code{gdbserver}'s
15395 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
15398 @subsection Connecting to @code{gdbserver}
15400 Run @value{GDBN} on the host system.
15402 First make sure you have the necessary symbol files. Load symbols for
15403 your application using the @code{file} command before you connect. Use
15404 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
15405 was compiled with the correct sysroot using @code{--with-sysroot}).
15407 The symbol file and target libraries must exactly match the executable
15408 and libraries on the target, with one exception: the files on the host
15409 system should not be stripped, even if the files on the target system
15410 are. Mismatched or missing files will lead to confusing results
15411 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
15412 files may also prevent @code{gdbserver} from debugging multi-threaded
15415 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
15416 For TCP connections, you must start up @code{gdbserver} prior to using
15417 the @code{target remote} command. Otherwise you may get an error whose
15418 text depends on the host system, but which usually looks something like
15419 @samp{Connection refused}. Don't use the @code{load}
15420 command in @value{GDBN} when using @code{gdbserver}, since the program is
15421 already on the target.
15423 @subsection Monitor Commands for @code{gdbserver}
15424 @cindex monitor commands, for @code{gdbserver}
15425 @anchor{Monitor Commands for gdbserver}
15427 During a @value{GDBN} session using @code{gdbserver}, you can use the
15428 @code{monitor} command to send special requests to @code{gdbserver}.
15429 Here are the available commands.
15433 List the available monitor commands.
15435 @item monitor set debug 0
15436 @itemx monitor set debug 1
15437 Disable or enable general debugging messages.
15439 @item monitor set remote-debug 0
15440 @itemx monitor set remote-debug 1
15441 Disable or enable specific debugging messages associated with the remote
15442 protocol (@pxref{Remote Protocol}).
15444 @item monitor set libthread-db-search-path [PATH]
15445 @cindex gdbserver, search path for @code{libthread_db}
15446 When this command is issued, @var{path} is a colon-separated list of
15447 directories to search for @code{libthread_db} (@pxref{Threads,,set
15448 libthread-db-search-path}). If you omit @var{path},
15449 @samp{libthread-db-search-path} will be reset to an empty list.
15452 Tell gdbserver to exit immediately. This command should be followed by
15453 @code{disconnect} to close the debugging session. @code{gdbserver} will
15454 detach from any attached processes and kill any processes it created.
15455 Use @code{monitor exit} to terminate @code{gdbserver} at the end
15456 of a multi-process mode debug session.
15460 @node Remote Configuration
15461 @section Remote Configuration
15464 @kindex show remote
15465 This section documents the configuration options available when
15466 debugging remote programs. For the options related to the File I/O
15467 extensions of the remote protocol, see @ref{system,
15468 system-call-allowed}.
15471 @item set remoteaddresssize @var{bits}
15472 @cindex address size for remote targets
15473 @cindex bits in remote address
15474 Set the maximum size of address in a memory packet to the specified
15475 number of bits. @value{GDBN} will mask off the address bits above
15476 that number, when it passes addresses to the remote target. The
15477 default value is the number of bits in the target's address.
15479 @item show remoteaddresssize
15480 Show the current value of remote address size in bits.
15482 @item set remotebaud @var{n}
15483 @cindex baud rate for remote targets
15484 Set the baud rate for the remote serial I/O to @var{n} baud. The
15485 value is used to set the speed of the serial port used for debugging
15488 @item show remotebaud
15489 Show the current speed of the remote connection.
15491 @item set remotebreak
15492 @cindex interrupt remote programs
15493 @cindex BREAK signal instead of Ctrl-C
15494 @anchor{set remotebreak}
15495 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
15496 when you type @kbd{Ctrl-c} to interrupt the program running
15497 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
15498 character instead. The default is off, since most remote systems
15499 expect to see @samp{Ctrl-C} as the interrupt signal.
15501 @item show remotebreak
15502 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
15503 interrupt the remote program.
15505 @item set remoteflow on
15506 @itemx set remoteflow off
15507 @kindex set remoteflow
15508 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
15509 on the serial port used to communicate to the remote target.
15511 @item show remoteflow
15512 @kindex show remoteflow
15513 Show the current setting of hardware flow control.
15515 @item set remotelogbase @var{base}
15516 Set the base (a.k.a.@: radix) of logging serial protocol
15517 communications to @var{base}. Supported values of @var{base} are:
15518 @code{ascii}, @code{octal}, and @code{hex}. The default is
15521 @item show remotelogbase
15522 Show the current setting of the radix for logging remote serial
15525 @item set remotelogfile @var{file}
15526 @cindex record serial communications on file
15527 Record remote serial communications on the named @var{file}. The
15528 default is not to record at all.
15530 @item show remotelogfile.
15531 Show the current setting of the file name on which to record the
15532 serial communications.
15534 @item set remotetimeout @var{num}
15535 @cindex timeout for serial communications
15536 @cindex remote timeout
15537 Set the timeout limit to wait for the remote target to respond to
15538 @var{num} seconds. The default is 2 seconds.
15540 @item show remotetimeout
15541 Show the current number of seconds to wait for the remote target
15544 @cindex limit hardware breakpoints and watchpoints
15545 @cindex remote target, limit break- and watchpoints
15546 @anchor{set remote hardware-watchpoint-limit}
15547 @anchor{set remote hardware-breakpoint-limit}
15548 @item set remote hardware-watchpoint-limit @var{limit}
15549 @itemx set remote hardware-breakpoint-limit @var{limit}
15550 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
15551 watchpoints. A limit of -1, the default, is treated as unlimited.
15553 @item set remote exec-file @var{filename}
15554 @itemx show remote exec-file
15555 @anchor{set remote exec-file}
15556 @cindex executable file, for remote target
15557 Select the file used for @code{run} with @code{target
15558 extended-remote}. This should be set to a filename valid on the
15559 target system. If it is not set, the target will use a default
15560 filename (e.g.@: the last program run).
15562 @item set remote interrupt-sequence
15563 @cindex interrupt remote programs
15564 @cindex select Ctrl-C, BREAK or BREAK-g
15565 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
15566 @samp{BREAK-g} as the
15567 sequence to the remote target in order to interrupt the execution.
15568 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
15569 is high level of serial line for some certain time.
15570 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
15571 It is @code{BREAK} signal followed by character @code{g}.
15573 @item show interrupt-sequence
15574 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
15575 is sent by @value{GDBN} to interrupt the remote program.
15576 @code{BREAK-g} is BREAK signal followed by @code{g} and
15577 also known as Magic SysRq g.
15579 @item set remote interrupt-on-connect
15580 @cindex send interrupt-sequence on start
15581 Specify whether interrupt-sequence is sent to remote target when
15582 @value{GDBN} connects to it. This is mostly needed when you debug
15583 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
15584 which is known as Magic SysRq g in order to connect @value{GDBN}.
15586 @item show interrupt-on-connect
15587 Show whether interrupt-sequence is sent
15588 to remote target when @value{GDBN} connects to it.
15592 @item set tcp auto-retry on
15593 @cindex auto-retry, for remote TCP target
15594 Enable auto-retry for remote TCP connections. This is useful if the remote
15595 debugging agent is launched in parallel with @value{GDBN}; there is a race
15596 condition because the agent may not become ready to accept the connection
15597 before @value{GDBN} attempts to connect. When auto-retry is
15598 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
15599 to establish the connection using the timeout specified by
15600 @code{set tcp connect-timeout}.
15602 @item set tcp auto-retry off
15603 Do not auto-retry failed TCP connections.
15605 @item show tcp auto-retry
15606 Show the current auto-retry setting.
15608 @item set tcp connect-timeout @var{seconds}
15609 @cindex connection timeout, for remote TCP target
15610 @cindex timeout, for remote target connection
15611 Set the timeout for establishing a TCP connection to the remote target to
15612 @var{seconds}. The timeout affects both polling to retry failed connections
15613 (enabled by @code{set tcp auto-retry on}) and waiting for connections
15614 that are merely slow to complete, and represents an approximate cumulative
15617 @item show tcp connect-timeout
15618 Show the current connection timeout setting.
15621 @cindex remote packets, enabling and disabling
15622 The @value{GDBN} remote protocol autodetects the packets supported by
15623 your debugging stub. If you need to override the autodetection, you
15624 can use these commands to enable or disable individual packets. Each
15625 packet can be set to @samp{on} (the remote target supports this
15626 packet), @samp{off} (the remote target does not support this packet),
15627 or @samp{auto} (detect remote target support for this packet). They
15628 all default to @samp{auto}. For more information about each packet,
15629 see @ref{Remote Protocol}.
15631 During normal use, you should not have to use any of these commands.
15632 If you do, that may be a bug in your remote debugging stub, or a bug
15633 in @value{GDBN}. You may want to report the problem to the
15634 @value{GDBN} developers.
15636 For each packet @var{name}, the command to enable or disable the
15637 packet is @code{set remote @var{name}-packet}. The available settings
15640 @multitable @columnfractions 0.28 0.32 0.25
15643 @tab Related Features
15645 @item @code{fetch-register}
15647 @tab @code{info registers}
15649 @item @code{set-register}
15653 @item @code{binary-download}
15655 @tab @code{load}, @code{set}
15657 @item @code{read-aux-vector}
15658 @tab @code{qXfer:auxv:read}
15659 @tab @code{info auxv}
15661 @item @code{symbol-lookup}
15662 @tab @code{qSymbol}
15663 @tab Detecting multiple threads
15665 @item @code{attach}
15666 @tab @code{vAttach}
15669 @item @code{verbose-resume}
15671 @tab Stepping or resuming multiple threads
15677 @item @code{software-breakpoint}
15681 @item @code{hardware-breakpoint}
15685 @item @code{write-watchpoint}
15689 @item @code{read-watchpoint}
15693 @item @code{access-watchpoint}
15697 @item @code{target-features}
15698 @tab @code{qXfer:features:read}
15699 @tab @code{set architecture}
15701 @item @code{library-info}
15702 @tab @code{qXfer:libraries:read}
15703 @tab @code{info sharedlibrary}
15705 @item @code{memory-map}
15706 @tab @code{qXfer:memory-map:read}
15707 @tab @code{info mem}
15709 @item @code{read-spu-object}
15710 @tab @code{qXfer:spu:read}
15711 @tab @code{info spu}
15713 @item @code{write-spu-object}
15714 @tab @code{qXfer:spu:write}
15715 @tab @code{info spu}
15717 @item @code{read-siginfo-object}
15718 @tab @code{qXfer:siginfo:read}
15719 @tab @code{print $_siginfo}
15721 @item @code{write-siginfo-object}
15722 @tab @code{qXfer:siginfo:write}
15723 @tab @code{set $_siginfo}
15725 @item @code{threads}
15726 @tab @code{qXfer:threads:read}
15727 @tab @code{info threads}
15729 @item @code{get-thread-local-@*storage-address}
15730 @tab @code{qGetTLSAddr}
15731 @tab Displaying @code{__thread} variables
15733 @item @code{search-memory}
15734 @tab @code{qSearch:memory}
15737 @item @code{supported-packets}
15738 @tab @code{qSupported}
15739 @tab Remote communications parameters
15741 @item @code{pass-signals}
15742 @tab @code{QPassSignals}
15743 @tab @code{handle @var{signal}}
15745 @item @code{hostio-close-packet}
15746 @tab @code{vFile:close}
15747 @tab @code{remote get}, @code{remote put}
15749 @item @code{hostio-open-packet}
15750 @tab @code{vFile:open}
15751 @tab @code{remote get}, @code{remote put}
15753 @item @code{hostio-pread-packet}
15754 @tab @code{vFile:pread}
15755 @tab @code{remote get}, @code{remote put}
15757 @item @code{hostio-pwrite-packet}
15758 @tab @code{vFile:pwrite}
15759 @tab @code{remote get}, @code{remote put}
15761 @item @code{hostio-unlink-packet}
15762 @tab @code{vFile:unlink}
15763 @tab @code{remote delete}
15765 @item @code{noack-packet}
15766 @tab @code{QStartNoAckMode}
15767 @tab Packet acknowledgment
15769 @item @code{osdata}
15770 @tab @code{qXfer:osdata:read}
15771 @tab @code{info os}
15773 @item @code{query-attached}
15774 @tab @code{qAttached}
15775 @tab Querying remote process attach state.
15779 @section Implementing a Remote Stub
15781 @cindex debugging stub, example
15782 @cindex remote stub, example
15783 @cindex stub example, remote debugging
15784 The stub files provided with @value{GDBN} implement the target side of the
15785 communication protocol, and the @value{GDBN} side is implemented in the
15786 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
15787 these subroutines to communicate, and ignore the details. (If you're
15788 implementing your own stub file, you can still ignore the details: start
15789 with one of the existing stub files. @file{sparc-stub.c} is the best
15790 organized, and therefore the easiest to read.)
15792 @cindex remote serial debugging, overview
15793 To debug a program running on another machine (the debugging
15794 @dfn{target} machine), you must first arrange for all the usual
15795 prerequisites for the program to run by itself. For example, for a C
15800 A startup routine to set up the C runtime environment; these usually
15801 have a name like @file{crt0}. The startup routine may be supplied by
15802 your hardware supplier, or you may have to write your own.
15805 A C subroutine library to support your program's
15806 subroutine calls, notably managing input and output.
15809 A way of getting your program to the other machine---for example, a
15810 download program. These are often supplied by the hardware
15811 manufacturer, but you may have to write your own from hardware
15815 The next step is to arrange for your program to use a serial port to
15816 communicate with the machine where @value{GDBN} is running (the @dfn{host}
15817 machine). In general terms, the scheme looks like this:
15821 @value{GDBN} already understands how to use this protocol; when everything
15822 else is set up, you can simply use the @samp{target remote} command
15823 (@pxref{Targets,,Specifying a Debugging Target}).
15825 @item On the target,
15826 you must link with your program a few special-purpose subroutines that
15827 implement the @value{GDBN} remote serial protocol. The file containing these
15828 subroutines is called a @dfn{debugging stub}.
15830 On certain remote targets, you can use an auxiliary program
15831 @code{gdbserver} instead of linking a stub into your program.
15832 @xref{Server,,Using the @code{gdbserver} Program}, for details.
15835 The debugging stub is specific to the architecture of the remote
15836 machine; for example, use @file{sparc-stub.c} to debug programs on
15839 @cindex remote serial stub list
15840 These working remote stubs are distributed with @value{GDBN}:
15845 @cindex @file{i386-stub.c}
15848 For Intel 386 and compatible architectures.
15851 @cindex @file{m68k-stub.c}
15852 @cindex Motorola 680x0
15854 For Motorola 680x0 architectures.
15857 @cindex @file{sh-stub.c}
15860 For Renesas SH architectures.
15863 @cindex @file{sparc-stub.c}
15865 For @sc{sparc} architectures.
15867 @item sparcl-stub.c
15868 @cindex @file{sparcl-stub.c}
15871 For Fujitsu @sc{sparclite} architectures.
15875 The @file{README} file in the @value{GDBN} distribution may list other
15876 recently added stubs.
15879 * Stub Contents:: What the stub can do for you
15880 * Bootstrapping:: What you must do for the stub
15881 * Debug Session:: Putting it all together
15884 @node Stub Contents
15885 @subsection What the Stub Can Do for You
15887 @cindex remote serial stub
15888 The debugging stub for your architecture supplies these three
15892 @item set_debug_traps
15893 @findex set_debug_traps
15894 @cindex remote serial stub, initialization
15895 This routine arranges for @code{handle_exception} to run when your
15896 program stops. You must call this subroutine explicitly near the
15897 beginning of your program.
15899 @item handle_exception
15900 @findex handle_exception
15901 @cindex remote serial stub, main routine
15902 This is the central workhorse, but your program never calls it
15903 explicitly---the setup code arranges for @code{handle_exception} to
15904 run when a trap is triggered.
15906 @code{handle_exception} takes control when your program stops during
15907 execution (for example, on a breakpoint), and mediates communications
15908 with @value{GDBN} on the host machine. This is where the communications
15909 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
15910 representative on the target machine. It begins by sending summary
15911 information on the state of your program, then continues to execute,
15912 retrieving and transmitting any information @value{GDBN} needs, until you
15913 execute a @value{GDBN} command that makes your program resume; at that point,
15914 @code{handle_exception} returns control to your own code on the target
15918 @cindex @code{breakpoint} subroutine, remote
15919 Use this auxiliary subroutine to make your program contain a
15920 breakpoint. Depending on the particular situation, this may be the only
15921 way for @value{GDBN} to get control. For instance, if your target
15922 machine has some sort of interrupt button, you won't need to call this;
15923 pressing the interrupt button transfers control to
15924 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
15925 simply receiving characters on the serial port may also trigger a trap;
15926 again, in that situation, you don't need to call @code{breakpoint} from
15927 your own program---simply running @samp{target remote} from the host
15928 @value{GDBN} session gets control.
15930 Call @code{breakpoint} if none of these is true, or if you simply want
15931 to make certain your program stops at a predetermined point for the
15932 start of your debugging session.
15935 @node Bootstrapping
15936 @subsection What You Must Do for the Stub
15938 @cindex remote stub, support routines
15939 The debugging stubs that come with @value{GDBN} are set up for a particular
15940 chip architecture, but they have no information about the rest of your
15941 debugging target machine.
15943 First of all you need to tell the stub how to communicate with the
15947 @item int getDebugChar()
15948 @findex getDebugChar
15949 Write this subroutine to read a single character from the serial port.
15950 It may be identical to @code{getchar} for your target system; a
15951 different name is used to allow you to distinguish the two if you wish.
15953 @item void putDebugChar(int)
15954 @findex putDebugChar
15955 Write this subroutine to write a single character to the serial port.
15956 It may be identical to @code{putchar} for your target system; a
15957 different name is used to allow you to distinguish the two if you wish.
15960 @cindex control C, and remote debugging
15961 @cindex interrupting remote targets
15962 If you want @value{GDBN} to be able to stop your program while it is
15963 running, you need to use an interrupt-driven serial driver, and arrange
15964 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
15965 character). That is the character which @value{GDBN} uses to tell the
15966 remote system to stop.
15968 Getting the debugging target to return the proper status to @value{GDBN}
15969 probably requires changes to the standard stub; one quick and dirty way
15970 is to just execute a breakpoint instruction (the ``dirty'' part is that
15971 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
15973 Other routines you need to supply are:
15976 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
15977 @findex exceptionHandler
15978 Write this function to install @var{exception_address} in the exception
15979 handling tables. You need to do this because the stub does not have any
15980 way of knowing what the exception handling tables on your target system
15981 are like (for example, the processor's table might be in @sc{rom},
15982 containing entries which point to a table in @sc{ram}).
15983 @var{exception_number} is the exception number which should be changed;
15984 its meaning is architecture-dependent (for example, different numbers
15985 might represent divide by zero, misaligned access, etc). When this
15986 exception occurs, control should be transferred directly to
15987 @var{exception_address}, and the processor state (stack, registers,
15988 and so on) should be just as it is when a processor exception occurs. So if
15989 you want to use a jump instruction to reach @var{exception_address}, it
15990 should be a simple jump, not a jump to subroutine.
15992 For the 386, @var{exception_address} should be installed as an interrupt
15993 gate so that interrupts are masked while the handler runs. The gate
15994 should be at privilege level 0 (the most privileged level). The
15995 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
15996 help from @code{exceptionHandler}.
15998 @item void flush_i_cache()
15999 @findex flush_i_cache
16000 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
16001 instruction cache, if any, on your target machine. If there is no
16002 instruction cache, this subroutine may be a no-op.
16004 On target machines that have instruction caches, @value{GDBN} requires this
16005 function to make certain that the state of your program is stable.
16009 You must also make sure this library routine is available:
16012 @item void *memset(void *, int, int)
16014 This is the standard library function @code{memset} that sets an area of
16015 memory to a known value. If you have one of the free versions of
16016 @code{libc.a}, @code{memset} can be found there; otherwise, you must
16017 either obtain it from your hardware manufacturer, or write your own.
16020 If you do not use the GNU C compiler, you may need other standard
16021 library subroutines as well; this varies from one stub to another,
16022 but in general the stubs are likely to use any of the common library
16023 subroutines which @code{@value{NGCC}} generates as inline code.
16026 @node Debug Session
16027 @subsection Putting it All Together
16029 @cindex remote serial debugging summary
16030 In summary, when your program is ready to debug, you must follow these
16035 Make sure you have defined the supporting low-level routines
16036 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
16038 @code{getDebugChar}, @code{putDebugChar},
16039 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
16043 Insert these lines near the top of your program:
16051 For the 680x0 stub only, you need to provide a variable called
16052 @code{exceptionHook}. Normally you just use:
16055 void (*exceptionHook)() = 0;
16059 but if before calling @code{set_debug_traps}, you set it to point to a
16060 function in your program, that function is called when
16061 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
16062 error). The function indicated by @code{exceptionHook} is called with
16063 one parameter: an @code{int} which is the exception number.
16066 Compile and link together: your program, the @value{GDBN} debugging stub for
16067 your target architecture, and the supporting subroutines.
16070 Make sure you have a serial connection between your target machine and
16071 the @value{GDBN} host, and identify the serial port on the host.
16074 @c The "remote" target now provides a `load' command, so we should
16075 @c document that. FIXME.
16076 Download your program to your target machine (or get it there by
16077 whatever means the manufacturer provides), and start it.
16080 Start @value{GDBN} on the host, and connect to the target
16081 (@pxref{Connecting,,Connecting to a Remote Target}).
16085 @node Configurations
16086 @chapter Configuration-Specific Information
16088 While nearly all @value{GDBN} commands are available for all native and
16089 cross versions of the debugger, there are some exceptions. This chapter
16090 describes things that are only available in certain configurations.
16092 There are three major categories of configurations: native
16093 configurations, where the host and target are the same, embedded
16094 operating system configurations, which are usually the same for several
16095 different processor architectures, and bare embedded processors, which
16096 are quite different from each other.
16101 * Embedded Processors::
16108 This section describes details specific to particular native
16113 * BSD libkvm Interface:: Debugging BSD kernel memory images
16114 * SVR4 Process Information:: SVR4 process information
16115 * DJGPP Native:: Features specific to the DJGPP port
16116 * Cygwin Native:: Features specific to the Cygwin port
16117 * Hurd Native:: Features specific to @sc{gnu} Hurd
16118 * Neutrino:: Features specific to QNX Neutrino
16119 * Darwin:: Features specific to Darwin
16125 On HP-UX systems, if you refer to a function or variable name that
16126 begins with a dollar sign, @value{GDBN} searches for a user or system
16127 name first, before it searches for a convenience variable.
16130 @node BSD libkvm Interface
16131 @subsection BSD libkvm Interface
16134 @cindex kernel memory image
16135 @cindex kernel crash dump
16137 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
16138 interface that provides a uniform interface for accessing kernel virtual
16139 memory images, including live systems and crash dumps. @value{GDBN}
16140 uses this interface to allow you to debug live kernels and kernel crash
16141 dumps on many native BSD configurations. This is implemented as a
16142 special @code{kvm} debugging target. For debugging a live system, load
16143 the currently running kernel into @value{GDBN} and connect to the
16147 (@value{GDBP}) @b{target kvm}
16150 For debugging crash dumps, provide the file name of the crash dump as an
16154 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
16157 Once connected to the @code{kvm} target, the following commands are
16163 Set current context from the @dfn{Process Control Block} (PCB) address.
16166 Set current context from proc address. This command isn't available on
16167 modern FreeBSD systems.
16170 @node SVR4 Process Information
16171 @subsection SVR4 Process Information
16173 @cindex examine process image
16174 @cindex process info via @file{/proc}
16176 Many versions of SVR4 and compatible systems provide a facility called
16177 @samp{/proc} that can be used to examine the image of a running
16178 process using file-system subroutines. If @value{GDBN} is configured
16179 for an operating system with this facility, the command @code{info
16180 proc} is available to report information about the process running
16181 your program, or about any process running on your system. @code{info
16182 proc} works only on SVR4 systems that include the @code{procfs} code.
16183 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
16184 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
16190 @itemx info proc @var{process-id}
16191 Summarize available information about any running process. If a
16192 process ID is specified by @var{process-id}, display information about
16193 that process; otherwise display information about the program being
16194 debugged. The summary includes the debugged process ID, the command
16195 line used to invoke it, its current working directory, and its
16196 executable file's absolute file name.
16198 On some systems, @var{process-id} can be of the form
16199 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
16200 within a process. If the optional @var{pid} part is missing, it means
16201 a thread from the process being debugged (the leading @samp{/} still
16202 needs to be present, or else @value{GDBN} will interpret the number as
16203 a process ID rather than a thread ID).
16205 @item info proc mappings
16206 @cindex memory address space mappings
16207 Report the memory address space ranges accessible in the program, with
16208 information on whether the process has read, write, or execute access
16209 rights to each range. On @sc{gnu}/Linux systems, each memory range
16210 includes the object file which is mapped to that range, instead of the
16211 memory access rights to that range.
16213 @item info proc stat
16214 @itemx info proc status
16215 @cindex process detailed status information
16216 These subcommands are specific to @sc{gnu}/Linux systems. They show
16217 the process-related information, including the user ID and group ID;
16218 how many threads are there in the process; its virtual memory usage;
16219 the signals that are pending, blocked, and ignored; its TTY; its
16220 consumption of system and user time; its stack size; its @samp{nice}
16221 value; etc. For more information, see the @samp{proc} man page
16222 (type @kbd{man 5 proc} from your shell prompt).
16224 @item info proc all
16225 Show all the information about the process described under all of the
16226 above @code{info proc} subcommands.
16229 @comment These sub-options of 'info proc' were not included when
16230 @comment procfs.c was re-written. Keep their descriptions around
16231 @comment against the day when someone finds the time to put them back in.
16232 @kindex info proc times
16233 @item info proc times
16234 Starting time, user CPU time, and system CPU time for your program and
16237 @kindex info proc id
16239 Report on the process IDs related to your program: its own process ID,
16240 the ID of its parent, the process group ID, and the session ID.
16243 @item set procfs-trace
16244 @kindex set procfs-trace
16245 @cindex @code{procfs} API calls
16246 This command enables and disables tracing of @code{procfs} API calls.
16248 @item show procfs-trace
16249 @kindex show procfs-trace
16250 Show the current state of @code{procfs} API call tracing.
16252 @item set procfs-file @var{file}
16253 @kindex set procfs-file
16254 Tell @value{GDBN} to write @code{procfs} API trace to the named
16255 @var{file}. @value{GDBN} appends the trace info to the previous
16256 contents of the file. The default is to display the trace on the
16259 @item show procfs-file
16260 @kindex show procfs-file
16261 Show the file to which @code{procfs} API trace is written.
16263 @item proc-trace-entry
16264 @itemx proc-trace-exit
16265 @itemx proc-untrace-entry
16266 @itemx proc-untrace-exit
16267 @kindex proc-trace-entry
16268 @kindex proc-trace-exit
16269 @kindex proc-untrace-entry
16270 @kindex proc-untrace-exit
16271 These commands enable and disable tracing of entries into and exits
16272 from the @code{syscall} interface.
16275 @kindex info pidlist
16276 @cindex process list, QNX Neutrino
16277 For QNX Neutrino only, this command displays the list of all the
16278 processes and all the threads within each process.
16281 @kindex info meminfo
16282 @cindex mapinfo list, QNX Neutrino
16283 For QNX Neutrino only, this command displays the list of all mapinfos.
16287 @subsection Features for Debugging @sc{djgpp} Programs
16288 @cindex @sc{djgpp} debugging
16289 @cindex native @sc{djgpp} debugging
16290 @cindex MS-DOS-specific commands
16293 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
16294 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
16295 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
16296 top of real-mode DOS systems and their emulations.
16298 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
16299 defines a few commands specific to the @sc{djgpp} port. This
16300 subsection describes those commands.
16305 This is a prefix of @sc{djgpp}-specific commands which print
16306 information about the target system and important OS structures.
16309 @cindex MS-DOS system info
16310 @cindex free memory information (MS-DOS)
16311 @item info dos sysinfo
16312 This command displays assorted information about the underlying
16313 platform: the CPU type and features, the OS version and flavor, the
16314 DPMI version, and the available conventional and DPMI memory.
16319 @cindex segment descriptor tables
16320 @cindex descriptor tables display
16322 @itemx info dos ldt
16323 @itemx info dos idt
16324 These 3 commands display entries from, respectively, Global, Local,
16325 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
16326 tables are data structures which store a descriptor for each segment
16327 that is currently in use. The segment's selector is an index into a
16328 descriptor table; the table entry for that index holds the
16329 descriptor's base address and limit, and its attributes and access
16332 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
16333 segment (used for both data and the stack), and a DOS segment (which
16334 allows access to DOS/BIOS data structures and absolute addresses in
16335 conventional memory). However, the DPMI host will usually define
16336 additional segments in order to support the DPMI environment.
16338 @cindex garbled pointers
16339 These commands allow to display entries from the descriptor tables.
16340 Without an argument, all entries from the specified table are
16341 displayed. An argument, which should be an integer expression, means
16342 display a single entry whose index is given by the argument. For
16343 example, here's a convenient way to display information about the
16344 debugged program's data segment:
16347 @exdent @code{(@value{GDBP}) info dos ldt $ds}
16348 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
16352 This comes in handy when you want to see whether a pointer is outside
16353 the data segment's limit (i.e.@: @dfn{garbled}).
16355 @cindex page tables display (MS-DOS)
16357 @itemx info dos pte
16358 These two commands display entries from, respectively, the Page
16359 Directory and the Page Tables. Page Directories and Page Tables are
16360 data structures which control how virtual memory addresses are mapped
16361 into physical addresses. A Page Table includes an entry for every
16362 page of memory that is mapped into the program's address space; there
16363 may be several Page Tables, each one holding up to 4096 entries. A
16364 Page Directory has up to 4096 entries, one each for every Page Table
16365 that is currently in use.
16367 Without an argument, @kbd{info dos pde} displays the entire Page
16368 Directory, and @kbd{info dos pte} displays all the entries in all of
16369 the Page Tables. An argument, an integer expression, given to the
16370 @kbd{info dos pde} command means display only that entry from the Page
16371 Directory table. An argument given to the @kbd{info dos pte} command
16372 means display entries from a single Page Table, the one pointed to by
16373 the specified entry in the Page Directory.
16375 @cindex direct memory access (DMA) on MS-DOS
16376 These commands are useful when your program uses @dfn{DMA} (Direct
16377 Memory Access), which needs physical addresses to program the DMA
16380 These commands are supported only with some DPMI servers.
16382 @cindex physical address from linear address
16383 @item info dos address-pte @var{addr}
16384 This command displays the Page Table entry for a specified linear
16385 address. The argument @var{addr} is a linear address which should
16386 already have the appropriate segment's base address added to it,
16387 because this command accepts addresses which may belong to @emph{any}
16388 segment. For example, here's how to display the Page Table entry for
16389 the page where a variable @code{i} is stored:
16392 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
16393 @exdent @code{Page Table entry for address 0x11a00d30:}
16394 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
16398 This says that @code{i} is stored at offset @code{0xd30} from the page
16399 whose physical base address is @code{0x02698000}, and shows all the
16400 attributes of that page.
16402 Note that you must cast the addresses of variables to a @code{char *},
16403 since otherwise the value of @code{__djgpp_base_address}, the base
16404 address of all variables and functions in a @sc{djgpp} program, will
16405 be added using the rules of C pointer arithmetics: if @code{i} is
16406 declared an @code{int}, @value{GDBN} will add 4 times the value of
16407 @code{__djgpp_base_address} to the address of @code{i}.
16409 Here's another example, it displays the Page Table entry for the
16413 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
16414 @exdent @code{Page Table entry for address 0x29110:}
16415 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
16419 (The @code{+ 3} offset is because the transfer buffer's address is the
16420 3rd member of the @code{_go32_info_block} structure.) The output
16421 clearly shows that this DPMI server maps the addresses in conventional
16422 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
16423 linear (@code{0x29110}) addresses are identical.
16425 This command is supported only with some DPMI servers.
16428 @cindex DOS serial data link, remote debugging
16429 In addition to native debugging, the DJGPP port supports remote
16430 debugging via a serial data link. The following commands are specific
16431 to remote serial debugging in the DJGPP port of @value{GDBN}.
16434 @kindex set com1base
16435 @kindex set com1irq
16436 @kindex set com2base
16437 @kindex set com2irq
16438 @kindex set com3base
16439 @kindex set com3irq
16440 @kindex set com4base
16441 @kindex set com4irq
16442 @item set com1base @var{addr}
16443 This command sets the base I/O port address of the @file{COM1} serial
16446 @item set com1irq @var{irq}
16447 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
16448 for the @file{COM1} serial port.
16450 There are similar commands @samp{set com2base}, @samp{set com3irq},
16451 etc.@: for setting the port address and the @code{IRQ} lines for the
16454 @kindex show com1base
16455 @kindex show com1irq
16456 @kindex show com2base
16457 @kindex show com2irq
16458 @kindex show com3base
16459 @kindex show com3irq
16460 @kindex show com4base
16461 @kindex show com4irq
16462 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
16463 display the current settings of the base address and the @code{IRQ}
16464 lines used by the COM ports.
16467 @kindex info serial
16468 @cindex DOS serial port status
16469 This command prints the status of the 4 DOS serial ports. For each
16470 port, it prints whether it's active or not, its I/O base address and
16471 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
16472 counts of various errors encountered so far.
16476 @node Cygwin Native
16477 @subsection Features for Debugging MS Windows PE Executables
16478 @cindex MS Windows debugging
16479 @cindex native Cygwin debugging
16480 @cindex Cygwin-specific commands
16482 @value{GDBN} supports native debugging of MS Windows programs, including
16483 DLLs with and without symbolic debugging information.
16485 @cindex Ctrl-BREAK, MS-Windows
16486 @cindex interrupt debuggee on MS-Windows
16487 MS-Windows programs that call @code{SetConsoleMode} to switch off the
16488 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
16489 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
16490 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
16491 sequence, which can be used to interrupt the debuggee even if it
16494 There are various additional Cygwin-specific commands, described in
16495 this section. Working with DLLs that have no debugging symbols is
16496 described in @ref{Non-debug DLL Symbols}.
16501 This is a prefix of MS Windows-specific commands which print
16502 information about the target system and important OS structures.
16504 @item info w32 selector
16505 This command displays information returned by
16506 the Win32 API @code{GetThreadSelectorEntry} function.
16507 It takes an optional argument that is evaluated to
16508 a long value to give the information about this given selector.
16509 Without argument, this command displays information
16510 about the six segment registers.
16514 This is a Cygwin-specific alias of @code{info shared}.
16516 @kindex dll-symbols
16518 This command loads symbols from a dll similarly to
16519 add-sym command but without the need to specify a base address.
16521 @kindex set cygwin-exceptions
16522 @cindex debugging the Cygwin DLL
16523 @cindex Cygwin DLL, debugging
16524 @item set cygwin-exceptions @var{mode}
16525 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
16526 happen inside the Cygwin DLL. If @var{mode} is @code{off},
16527 @value{GDBN} will delay recognition of exceptions, and may ignore some
16528 exceptions which seem to be caused by internal Cygwin DLL
16529 ``bookkeeping''. This option is meant primarily for debugging the
16530 Cygwin DLL itself; the default value is @code{off} to avoid annoying
16531 @value{GDBN} users with false @code{SIGSEGV} signals.
16533 @kindex show cygwin-exceptions
16534 @item show cygwin-exceptions
16535 Displays whether @value{GDBN} will break on exceptions that happen
16536 inside the Cygwin DLL itself.
16538 @kindex set new-console
16539 @item set new-console @var{mode}
16540 If @var{mode} is @code{on} the debuggee will
16541 be started in a new console on next start.
16542 If @var{mode} is @code{off}, the debuggee will
16543 be started in the same console as the debugger.
16545 @kindex show new-console
16546 @item show new-console
16547 Displays whether a new console is used
16548 when the debuggee is started.
16550 @kindex set new-group
16551 @item set new-group @var{mode}
16552 This boolean value controls whether the debuggee should
16553 start a new group or stay in the same group as the debugger.
16554 This affects the way the Windows OS handles
16557 @kindex show new-group
16558 @item show new-group
16559 Displays current value of new-group boolean.
16561 @kindex set debugevents
16562 @item set debugevents
16563 This boolean value adds debug output concerning kernel events related
16564 to the debuggee seen by the debugger. This includes events that
16565 signal thread and process creation and exit, DLL loading and
16566 unloading, console interrupts, and debugging messages produced by the
16567 Windows @code{OutputDebugString} API call.
16569 @kindex set debugexec
16570 @item set debugexec
16571 This boolean value adds debug output concerning execute events
16572 (such as resume thread) seen by the debugger.
16574 @kindex set debugexceptions
16575 @item set debugexceptions
16576 This boolean value adds debug output concerning exceptions in the
16577 debuggee seen by the debugger.
16579 @kindex set debugmemory
16580 @item set debugmemory
16581 This boolean value adds debug output concerning debuggee memory reads
16582 and writes by the debugger.
16586 This boolean values specifies whether the debuggee is called
16587 via a shell or directly (default value is on).
16591 Displays if the debuggee will be started with a shell.
16596 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
16599 @node Non-debug DLL Symbols
16600 @subsubsection Support for DLLs without Debugging Symbols
16601 @cindex DLLs with no debugging symbols
16602 @cindex Minimal symbols and DLLs
16604 Very often on windows, some of the DLLs that your program relies on do
16605 not include symbolic debugging information (for example,
16606 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
16607 symbols in a DLL, it relies on the minimal amount of symbolic
16608 information contained in the DLL's export table. This section
16609 describes working with such symbols, known internally to @value{GDBN} as
16610 ``minimal symbols''.
16612 Note that before the debugged program has started execution, no DLLs
16613 will have been loaded. The easiest way around this problem is simply to
16614 start the program --- either by setting a breakpoint or letting the
16615 program run once to completion. It is also possible to force
16616 @value{GDBN} to load a particular DLL before starting the executable ---
16617 see the shared library information in @ref{Files}, or the
16618 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
16619 explicitly loading symbols from a DLL with no debugging information will
16620 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
16621 which may adversely affect symbol lookup performance.
16623 @subsubsection DLL Name Prefixes
16625 In keeping with the naming conventions used by the Microsoft debugging
16626 tools, DLL export symbols are made available with a prefix based on the
16627 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
16628 also entered into the symbol table, so @code{CreateFileA} is often
16629 sufficient. In some cases there will be name clashes within a program
16630 (particularly if the executable itself includes full debugging symbols)
16631 necessitating the use of the fully qualified name when referring to the
16632 contents of the DLL. Use single-quotes around the name to avoid the
16633 exclamation mark (``!'') being interpreted as a language operator.
16635 Note that the internal name of the DLL may be all upper-case, even
16636 though the file name of the DLL is lower-case, or vice-versa. Since
16637 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
16638 some confusion. If in doubt, try the @code{info functions} and
16639 @code{info variables} commands or even @code{maint print msymbols}
16640 (@pxref{Symbols}). Here's an example:
16643 (@value{GDBP}) info function CreateFileA
16644 All functions matching regular expression "CreateFileA":
16646 Non-debugging symbols:
16647 0x77e885f4 CreateFileA
16648 0x77e885f4 KERNEL32!CreateFileA
16652 (@value{GDBP}) info function !
16653 All functions matching regular expression "!":
16655 Non-debugging symbols:
16656 0x6100114c cygwin1!__assert
16657 0x61004034 cygwin1!_dll_crt0@@0
16658 0x61004240 cygwin1!dll_crt0(per_process *)
16662 @subsubsection Working with Minimal Symbols
16664 Symbols extracted from a DLL's export table do not contain very much
16665 type information. All that @value{GDBN} can do is guess whether a symbol
16666 refers to a function or variable depending on the linker section that
16667 contains the symbol. Also note that the actual contents of the memory
16668 contained in a DLL are not available unless the program is running. This
16669 means that you cannot examine the contents of a variable or disassemble
16670 a function within a DLL without a running program.
16672 Variables are generally treated as pointers and dereferenced
16673 automatically. For this reason, it is often necessary to prefix a
16674 variable name with the address-of operator (``&'') and provide explicit
16675 type information in the command. Here's an example of the type of
16679 (@value{GDBP}) print 'cygwin1!__argv'
16684 (@value{GDBP}) x 'cygwin1!__argv'
16685 0x10021610: "\230y\""
16688 And two possible solutions:
16691 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
16692 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
16696 (@value{GDBP}) x/2x &'cygwin1!__argv'
16697 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
16698 (@value{GDBP}) x/x 0x10021608
16699 0x10021608: 0x0022fd98
16700 (@value{GDBP}) x/s 0x0022fd98
16701 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
16704 Setting a break point within a DLL is possible even before the program
16705 starts execution. However, under these circumstances, @value{GDBN} can't
16706 examine the initial instructions of the function in order to skip the
16707 function's frame set-up code. You can work around this by using ``*&''
16708 to set the breakpoint at a raw memory address:
16711 (@value{GDBP}) break *&'python22!PyOS_Readline'
16712 Breakpoint 1 at 0x1e04eff0
16715 The author of these extensions is not entirely convinced that setting a
16716 break point within a shared DLL like @file{kernel32.dll} is completely
16720 @subsection Commands Specific to @sc{gnu} Hurd Systems
16721 @cindex @sc{gnu} Hurd debugging
16723 This subsection describes @value{GDBN} commands specific to the
16724 @sc{gnu} Hurd native debugging.
16729 @kindex set signals@r{, Hurd command}
16730 @kindex set sigs@r{, Hurd command}
16731 This command toggles the state of inferior signal interception by
16732 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
16733 affected by this command. @code{sigs} is a shorthand alias for
16738 @kindex show signals@r{, Hurd command}
16739 @kindex show sigs@r{, Hurd command}
16740 Show the current state of intercepting inferior's signals.
16742 @item set signal-thread
16743 @itemx set sigthread
16744 @kindex set signal-thread
16745 @kindex set sigthread
16746 This command tells @value{GDBN} which thread is the @code{libc} signal
16747 thread. That thread is run when a signal is delivered to a running
16748 process. @code{set sigthread} is the shorthand alias of @code{set
16751 @item show signal-thread
16752 @itemx show sigthread
16753 @kindex show signal-thread
16754 @kindex show sigthread
16755 These two commands show which thread will run when the inferior is
16756 delivered a signal.
16759 @kindex set stopped@r{, Hurd command}
16760 This commands tells @value{GDBN} that the inferior process is stopped,
16761 as with the @code{SIGSTOP} signal. The stopped process can be
16762 continued by delivering a signal to it.
16765 @kindex show stopped@r{, Hurd command}
16766 This command shows whether @value{GDBN} thinks the debuggee is
16769 @item set exceptions
16770 @kindex set exceptions@r{, Hurd command}
16771 Use this command to turn off trapping of exceptions in the inferior.
16772 When exception trapping is off, neither breakpoints nor
16773 single-stepping will work. To restore the default, set exception
16776 @item show exceptions
16777 @kindex show exceptions@r{, Hurd command}
16778 Show the current state of trapping exceptions in the inferior.
16780 @item set task pause
16781 @kindex set task@r{, Hurd commands}
16782 @cindex task attributes (@sc{gnu} Hurd)
16783 @cindex pause current task (@sc{gnu} Hurd)
16784 This command toggles task suspension when @value{GDBN} has control.
16785 Setting it to on takes effect immediately, and the task is suspended
16786 whenever @value{GDBN} gets control. Setting it to off will take
16787 effect the next time the inferior is continued. If this option is set
16788 to off, you can use @code{set thread default pause on} or @code{set
16789 thread pause on} (see below) to pause individual threads.
16791 @item show task pause
16792 @kindex show task@r{, Hurd commands}
16793 Show the current state of task suspension.
16795 @item set task detach-suspend-count
16796 @cindex task suspend count
16797 @cindex detach from task, @sc{gnu} Hurd
16798 This command sets the suspend count the task will be left with when
16799 @value{GDBN} detaches from it.
16801 @item show task detach-suspend-count
16802 Show the suspend count the task will be left with when detaching.
16804 @item set task exception-port
16805 @itemx set task excp
16806 @cindex task exception port, @sc{gnu} Hurd
16807 This command sets the task exception port to which @value{GDBN} will
16808 forward exceptions. The argument should be the value of the @dfn{send
16809 rights} of the task. @code{set task excp} is a shorthand alias.
16811 @item set noninvasive
16812 @cindex noninvasive task options
16813 This command switches @value{GDBN} to a mode that is the least
16814 invasive as far as interfering with the inferior is concerned. This
16815 is the same as using @code{set task pause}, @code{set exceptions}, and
16816 @code{set signals} to values opposite to the defaults.
16818 @item info send-rights
16819 @itemx info receive-rights
16820 @itemx info port-rights
16821 @itemx info port-sets
16822 @itemx info dead-names
16825 @cindex send rights, @sc{gnu} Hurd
16826 @cindex receive rights, @sc{gnu} Hurd
16827 @cindex port rights, @sc{gnu} Hurd
16828 @cindex port sets, @sc{gnu} Hurd
16829 @cindex dead names, @sc{gnu} Hurd
16830 These commands display information about, respectively, send rights,
16831 receive rights, port rights, port sets, and dead names of a task.
16832 There are also shorthand aliases: @code{info ports} for @code{info
16833 port-rights} and @code{info psets} for @code{info port-sets}.
16835 @item set thread pause
16836 @kindex set thread@r{, Hurd command}
16837 @cindex thread properties, @sc{gnu} Hurd
16838 @cindex pause current thread (@sc{gnu} Hurd)
16839 This command toggles current thread suspension when @value{GDBN} has
16840 control. Setting it to on takes effect immediately, and the current
16841 thread is suspended whenever @value{GDBN} gets control. Setting it to
16842 off will take effect the next time the inferior is continued.
16843 Normally, this command has no effect, since when @value{GDBN} has
16844 control, the whole task is suspended. However, if you used @code{set
16845 task pause off} (see above), this command comes in handy to suspend
16846 only the current thread.
16848 @item show thread pause
16849 @kindex show thread@r{, Hurd command}
16850 This command shows the state of current thread suspension.
16852 @item set thread run
16853 This command sets whether the current thread is allowed to run.
16855 @item show thread run
16856 Show whether the current thread is allowed to run.
16858 @item set thread detach-suspend-count
16859 @cindex thread suspend count, @sc{gnu} Hurd
16860 @cindex detach from thread, @sc{gnu} Hurd
16861 This command sets the suspend count @value{GDBN} will leave on a
16862 thread when detaching. This number is relative to the suspend count
16863 found by @value{GDBN} when it notices the thread; use @code{set thread
16864 takeover-suspend-count} to force it to an absolute value.
16866 @item show thread detach-suspend-count
16867 Show the suspend count @value{GDBN} will leave on the thread when
16870 @item set thread exception-port
16871 @itemx set thread excp
16872 Set the thread exception port to which to forward exceptions. This
16873 overrides the port set by @code{set task exception-port} (see above).
16874 @code{set thread excp} is the shorthand alias.
16876 @item set thread takeover-suspend-count
16877 Normally, @value{GDBN}'s thread suspend counts are relative to the
16878 value @value{GDBN} finds when it notices each thread. This command
16879 changes the suspend counts to be absolute instead.
16881 @item set thread default
16882 @itemx show thread default
16883 @cindex thread default settings, @sc{gnu} Hurd
16884 Each of the above @code{set thread} commands has a @code{set thread
16885 default} counterpart (e.g., @code{set thread default pause}, @code{set
16886 thread default exception-port}, etc.). The @code{thread default}
16887 variety of commands sets the default thread properties for all
16888 threads; you can then change the properties of individual threads with
16889 the non-default commands.
16894 @subsection QNX Neutrino
16895 @cindex QNX Neutrino
16897 @value{GDBN} provides the following commands specific to the QNX
16901 @item set debug nto-debug
16902 @kindex set debug nto-debug
16903 When set to on, enables debugging messages specific to the QNX
16906 @item show debug nto-debug
16907 @kindex show debug nto-debug
16908 Show the current state of QNX Neutrino messages.
16915 @value{GDBN} provides the following commands specific to the Darwin target:
16918 @item set debug darwin @var{num}
16919 @kindex set debug darwin
16920 When set to a non zero value, enables debugging messages specific to
16921 the Darwin support. Higher values produce more verbose output.
16923 @item show debug darwin
16924 @kindex show debug darwin
16925 Show the current state of Darwin messages.
16927 @item set debug mach-o @var{num}
16928 @kindex set debug mach-o
16929 When set to a non zero value, enables debugging messages while
16930 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
16931 file format used on Darwin for object and executable files.) Higher
16932 values produce more verbose output. This is a command to diagnose
16933 problems internal to @value{GDBN} and should not be needed in normal
16936 @item show debug mach-o
16937 @kindex show debug mach-o
16938 Show the current state of Mach-O file messages.
16940 @item set mach-exceptions on
16941 @itemx set mach-exceptions off
16942 @kindex set mach-exceptions
16943 On Darwin, faults are first reported as a Mach exception and are then
16944 mapped to a Posix signal. Use this command to turn on trapping of
16945 Mach exceptions in the inferior. This might be sometimes useful to
16946 better understand the cause of a fault. The default is off.
16948 @item show mach-exceptions
16949 @kindex show mach-exceptions
16950 Show the current state of exceptions trapping.
16955 @section Embedded Operating Systems
16957 This section describes configurations involving the debugging of
16958 embedded operating systems that are available for several different
16962 * VxWorks:: Using @value{GDBN} with VxWorks
16965 @value{GDBN} includes the ability to debug programs running on
16966 various real-time operating systems.
16969 @subsection Using @value{GDBN} with VxWorks
16975 @kindex target vxworks
16976 @item target vxworks @var{machinename}
16977 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
16978 is the target system's machine name or IP address.
16982 On VxWorks, @code{load} links @var{filename} dynamically on the
16983 current target system as well as adding its symbols in @value{GDBN}.
16985 @value{GDBN} enables developers to spawn and debug tasks running on networked
16986 VxWorks targets from a Unix host. Already-running tasks spawned from
16987 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
16988 both the Unix host and on the VxWorks target. The program
16989 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
16990 installed with the name @code{vxgdb}, to distinguish it from a
16991 @value{GDBN} for debugging programs on the host itself.)
16994 @item VxWorks-timeout @var{args}
16995 @kindex vxworks-timeout
16996 All VxWorks-based targets now support the option @code{vxworks-timeout}.
16997 This option is set by the user, and @var{args} represents the number of
16998 seconds @value{GDBN} waits for responses to rpc's. You might use this if
16999 your VxWorks target is a slow software simulator or is on the far side
17000 of a thin network line.
17003 The following information on connecting to VxWorks was current when
17004 this manual was produced; newer releases of VxWorks may use revised
17007 @findex INCLUDE_RDB
17008 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
17009 to include the remote debugging interface routines in the VxWorks
17010 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
17011 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
17012 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
17013 source debugging task @code{tRdbTask} when VxWorks is booted. For more
17014 information on configuring and remaking VxWorks, see the manufacturer's
17016 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
17018 Once you have included @file{rdb.a} in your VxWorks system image and set
17019 your Unix execution search path to find @value{GDBN}, you are ready to
17020 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
17021 @code{vxgdb}, depending on your installation).
17023 @value{GDBN} comes up showing the prompt:
17030 * VxWorks Connection:: Connecting to VxWorks
17031 * VxWorks Download:: VxWorks download
17032 * VxWorks Attach:: Running tasks
17035 @node VxWorks Connection
17036 @subsubsection Connecting to VxWorks
17038 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
17039 network. To connect to a target whose host name is ``@code{tt}'', type:
17042 (vxgdb) target vxworks tt
17046 @value{GDBN} displays messages like these:
17049 Attaching remote machine across net...
17054 @value{GDBN} then attempts to read the symbol tables of any object modules
17055 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
17056 these files by searching the directories listed in the command search
17057 path (@pxref{Environment, ,Your Program's Environment}); if it fails
17058 to find an object file, it displays a message such as:
17061 prog.o: No such file or directory.
17064 When this happens, add the appropriate directory to the search path with
17065 the @value{GDBN} command @code{path}, and execute the @code{target}
17068 @node VxWorks Download
17069 @subsubsection VxWorks Download
17071 @cindex download to VxWorks
17072 If you have connected to the VxWorks target and you want to debug an
17073 object that has not yet been loaded, you can use the @value{GDBN}
17074 @code{load} command to download a file from Unix to VxWorks
17075 incrementally. The object file given as an argument to the @code{load}
17076 command is actually opened twice: first by the VxWorks target in order
17077 to download the code, then by @value{GDBN} in order to read the symbol
17078 table. This can lead to problems if the current working directories on
17079 the two systems differ. If both systems have NFS mounted the same
17080 filesystems, you can avoid these problems by using absolute paths.
17081 Otherwise, it is simplest to set the working directory on both systems
17082 to the directory in which the object file resides, and then to reference
17083 the file by its name, without any path. For instance, a program
17084 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
17085 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
17086 program, type this on VxWorks:
17089 -> cd "@var{vxpath}/vw/demo/rdb"
17093 Then, in @value{GDBN}, type:
17096 (vxgdb) cd @var{hostpath}/vw/demo/rdb
17097 (vxgdb) load prog.o
17100 @value{GDBN} displays a response similar to this:
17103 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
17106 You can also use the @code{load} command to reload an object module
17107 after editing and recompiling the corresponding source file. Note that
17108 this makes @value{GDBN} delete all currently-defined breakpoints,
17109 auto-displays, and convenience variables, and to clear the value
17110 history. (This is necessary in order to preserve the integrity of
17111 debugger's data structures that reference the target system's symbol
17114 @node VxWorks Attach
17115 @subsubsection Running Tasks
17117 @cindex running VxWorks tasks
17118 You can also attach to an existing task using the @code{attach} command as
17122 (vxgdb) attach @var{task}
17126 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
17127 or suspended when you attach to it. Running tasks are suspended at
17128 the time of attachment.
17130 @node Embedded Processors
17131 @section Embedded Processors
17133 This section goes into details specific to particular embedded
17136 @cindex send command to simulator
17137 Whenever a specific embedded processor has a simulator, @value{GDBN}
17138 allows to send an arbitrary command to the simulator.
17141 @item sim @var{command}
17142 @kindex sim@r{, a command}
17143 Send an arbitrary @var{command} string to the simulator. Consult the
17144 documentation for the specific simulator in use for information about
17145 acceptable commands.
17151 * M32R/D:: Renesas M32R/D
17152 * M68K:: Motorola M68K
17153 * MicroBlaze:: Xilinx MicroBlaze
17154 * MIPS Embedded:: MIPS Embedded
17155 * OpenRISC 1000:: OpenRisc 1000
17156 * PA:: HP PA Embedded
17157 * PowerPC Embedded:: PowerPC Embedded
17158 * Sparclet:: Tsqware Sparclet
17159 * Sparclite:: Fujitsu Sparclite
17160 * Z8000:: Zilog Z8000
17163 * Super-H:: Renesas Super-H
17172 @item target rdi @var{dev}
17173 ARM Angel monitor, via RDI library interface to ADP protocol. You may
17174 use this target to communicate with both boards running the Angel
17175 monitor, or with the EmbeddedICE JTAG debug device.
17178 @item target rdp @var{dev}
17183 @value{GDBN} provides the following ARM-specific commands:
17186 @item set arm disassembler
17188 This commands selects from a list of disassembly styles. The
17189 @code{"std"} style is the standard style.
17191 @item show arm disassembler
17193 Show the current disassembly style.
17195 @item set arm apcs32
17196 @cindex ARM 32-bit mode
17197 This command toggles ARM operation mode between 32-bit and 26-bit.
17199 @item show arm apcs32
17200 Display the current usage of the ARM 32-bit mode.
17202 @item set arm fpu @var{fputype}
17203 This command sets the ARM floating-point unit (FPU) type. The
17204 argument @var{fputype} can be one of these:
17208 Determine the FPU type by querying the OS ABI.
17210 Software FPU, with mixed-endian doubles on little-endian ARM
17213 GCC-compiled FPA co-processor.
17215 Software FPU with pure-endian doubles.
17221 Show the current type of the FPU.
17224 This command forces @value{GDBN} to use the specified ABI.
17227 Show the currently used ABI.
17229 @item set arm fallback-mode (arm|thumb|auto)
17230 @value{GDBN} uses the symbol table, when available, to determine
17231 whether instructions are ARM or Thumb. This command controls
17232 @value{GDBN}'s default behavior when the symbol table is not
17233 available. The default is @samp{auto}, which causes @value{GDBN} to
17234 use the current execution mode (from the @code{T} bit in the @code{CPSR}
17237 @item show arm fallback-mode
17238 Show the current fallback instruction mode.
17240 @item set arm force-mode (arm|thumb|auto)
17241 This command overrides use of the symbol table to determine whether
17242 instructions are ARM or Thumb. The default is @samp{auto}, which
17243 causes @value{GDBN} to use the symbol table and then the setting
17244 of @samp{set arm fallback-mode}.
17246 @item show arm force-mode
17247 Show the current forced instruction mode.
17249 @item set debug arm
17250 Toggle whether to display ARM-specific debugging messages from the ARM
17251 target support subsystem.
17253 @item show debug arm
17254 Show whether ARM-specific debugging messages are enabled.
17257 The following commands are available when an ARM target is debugged
17258 using the RDI interface:
17261 @item rdilogfile @r{[}@var{file}@r{]}
17263 @cindex ADP (Angel Debugger Protocol) logging
17264 Set the filename for the ADP (Angel Debugger Protocol) packet log.
17265 With an argument, sets the log file to the specified @var{file}. With
17266 no argument, show the current log file name. The default log file is
17269 @item rdilogenable @r{[}@var{arg}@r{]}
17270 @kindex rdilogenable
17271 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
17272 enables logging, with an argument 0 or @code{"no"} disables it. With
17273 no arguments displays the current setting. When logging is enabled,
17274 ADP packets exchanged between @value{GDBN} and the RDI target device
17275 are logged to a file.
17277 @item set rdiromatzero
17278 @kindex set rdiromatzero
17279 @cindex ROM at zero address, RDI
17280 Tell @value{GDBN} whether the target has ROM at address 0. If on,
17281 vector catching is disabled, so that zero address can be used. If off
17282 (the default), vector catching is enabled. For this command to take
17283 effect, it needs to be invoked prior to the @code{target rdi} command.
17285 @item show rdiromatzero
17286 @kindex show rdiromatzero
17287 Show the current setting of ROM at zero address.
17289 @item set rdiheartbeat
17290 @kindex set rdiheartbeat
17291 @cindex RDI heartbeat
17292 Enable or disable RDI heartbeat packets. It is not recommended to
17293 turn on this option, since it confuses ARM and EPI JTAG interface, as
17294 well as the Angel monitor.
17296 @item show rdiheartbeat
17297 @kindex show rdiheartbeat
17298 Show the setting of RDI heartbeat packets.
17302 @item target sim @r{[}@var{simargs}@r{]} @dots{}
17303 The @value{GDBN} ARM simulator accepts the following optional arguments.
17306 @item --swi-support=@var{type}
17307 Tell the simulator which SWI interfaces to support.
17308 @var{type} may be a comma separated list of the following values.
17309 The default value is @code{all}.
17322 @subsection Renesas M32R/D and M32R/SDI
17325 @kindex target m32r
17326 @item target m32r @var{dev}
17327 Renesas M32R/D ROM monitor.
17329 @kindex target m32rsdi
17330 @item target m32rsdi @var{dev}
17331 Renesas M32R SDI server, connected via parallel port to the board.
17334 The following @value{GDBN} commands are specific to the M32R monitor:
17337 @item set download-path @var{path}
17338 @kindex set download-path
17339 @cindex find downloadable @sc{srec} files (M32R)
17340 Set the default path for finding downloadable @sc{srec} files.
17342 @item show download-path
17343 @kindex show download-path
17344 Show the default path for downloadable @sc{srec} files.
17346 @item set board-address @var{addr}
17347 @kindex set board-address
17348 @cindex M32-EVA target board address
17349 Set the IP address for the M32R-EVA target board.
17351 @item show board-address
17352 @kindex show board-address
17353 Show the current IP address of the target board.
17355 @item set server-address @var{addr}
17356 @kindex set server-address
17357 @cindex download server address (M32R)
17358 Set the IP address for the download server, which is the @value{GDBN}'s
17361 @item show server-address
17362 @kindex show server-address
17363 Display the IP address of the download server.
17365 @item upload @r{[}@var{file}@r{]}
17366 @kindex upload@r{, M32R}
17367 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
17368 upload capability. If no @var{file} argument is given, the current
17369 executable file is uploaded.
17371 @item tload @r{[}@var{file}@r{]}
17372 @kindex tload@r{, M32R}
17373 Test the @code{upload} command.
17376 The following commands are available for M32R/SDI:
17381 @cindex reset SDI connection, M32R
17382 This command resets the SDI connection.
17386 This command shows the SDI connection status.
17389 @kindex debug_chaos
17390 @cindex M32R/Chaos debugging
17391 Instructs the remote that M32R/Chaos debugging is to be used.
17393 @item use_debug_dma
17394 @kindex use_debug_dma
17395 Instructs the remote to use the DEBUG_DMA method of accessing memory.
17398 @kindex use_mon_code
17399 Instructs the remote to use the MON_CODE method of accessing memory.
17402 @kindex use_ib_break
17403 Instructs the remote to set breakpoints by IB break.
17405 @item use_dbt_break
17406 @kindex use_dbt_break
17407 Instructs the remote to set breakpoints by DBT.
17413 The Motorola m68k configuration includes ColdFire support, and a
17414 target command for the following ROM monitor.
17418 @kindex target dbug
17419 @item target dbug @var{dev}
17420 dBUG ROM monitor for Motorola ColdFire.
17425 @subsection MicroBlaze
17426 @cindex Xilinx MicroBlaze
17427 @cindex XMD, Xilinx Microprocessor Debugger
17429 The MicroBlaze is a soft-core processor supported on various Xilinx
17430 FPGAs, such as Spartan or Virtex series. Boards with these processors
17431 usually have JTAG ports which connect to a host system running the Xilinx
17432 Embedded Development Kit (EDK) or Software Development Kit (SDK).
17433 This host system is used to download the configuration bitstream to
17434 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
17435 communicates with the target board using the JTAG interface and
17436 presents a @code{gdbserver} interface to the board. By default
17437 @code{xmd} uses port @code{1234}. (While it is possible to change
17438 this default port, it requires the use of undocumented @code{xmd}
17439 commands. Contact Xilinx support if you need to do this.)
17441 Use these GDB commands to connect to the MicroBlaze target processor.
17444 @item target remote :1234
17445 Use this command to connect to the target if you are running @value{GDBN}
17446 on the same system as @code{xmd}.
17448 @item target remote @var{xmd-host}:1234
17449 Use this command to connect to the target if it is connected to @code{xmd}
17450 running on a different system named @var{xmd-host}.
17453 Use this command to download a program to the MicroBlaze target.
17455 @item set debug microblaze @var{n}
17456 Enable MicroBlaze-specific debugging messages if non-zero.
17458 @item show debug microblaze @var{n}
17459 Show MicroBlaze-specific debugging level.
17462 @node MIPS Embedded
17463 @subsection MIPS Embedded
17465 @cindex MIPS boards
17466 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
17467 MIPS board attached to a serial line. This is available when
17468 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
17471 Use these @value{GDBN} commands to specify the connection to your target board:
17474 @item target mips @var{port}
17475 @kindex target mips @var{port}
17476 To run a program on the board, start up @code{@value{GDBP}} with the
17477 name of your program as the argument. To connect to the board, use the
17478 command @samp{target mips @var{port}}, where @var{port} is the name of
17479 the serial port connected to the board. If the program has not already
17480 been downloaded to the board, you may use the @code{load} command to
17481 download it. You can then use all the usual @value{GDBN} commands.
17483 For example, this sequence connects to the target board through a serial
17484 port, and loads and runs a program called @var{prog} through the
17488 host$ @value{GDBP} @var{prog}
17489 @value{GDBN} is free software and @dots{}
17490 (@value{GDBP}) target mips /dev/ttyb
17491 (@value{GDBP}) load @var{prog}
17495 @item target mips @var{hostname}:@var{portnumber}
17496 On some @value{GDBN} host configurations, you can specify a TCP
17497 connection (for instance, to a serial line managed by a terminal
17498 concentrator) instead of a serial port, using the syntax
17499 @samp{@var{hostname}:@var{portnumber}}.
17501 @item target pmon @var{port}
17502 @kindex target pmon @var{port}
17505 @item target ddb @var{port}
17506 @kindex target ddb @var{port}
17507 NEC's DDB variant of PMON for Vr4300.
17509 @item target lsi @var{port}
17510 @kindex target lsi @var{port}
17511 LSI variant of PMON.
17513 @kindex target r3900
17514 @item target r3900 @var{dev}
17515 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
17517 @kindex target array
17518 @item target array @var{dev}
17519 Array Tech LSI33K RAID controller board.
17525 @value{GDBN} also supports these special commands for MIPS targets:
17528 @item set mipsfpu double
17529 @itemx set mipsfpu single
17530 @itemx set mipsfpu none
17531 @itemx set mipsfpu auto
17532 @itemx show mipsfpu
17533 @kindex set mipsfpu
17534 @kindex show mipsfpu
17535 @cindex MIPS remote floating point
17536 @cindex floating point, MIPS remote
17537 If your target board does not support the MIPS floating point
17538 coprocessor, you should use the command @samp{set mipsfpu none} (if you
17539 need this, you may wish to put the command in your @value{GDBN} init
17540 file). This tells @value{GDBN} how to find the return value of
17541 functions which return floating point values. It also allows
17542 @value{GDBN} to avoid saving the floating point registers when calling
17543 functions on the board. If you are using a floating point coprocessor
17544 with only single precision floating point support, as on the @sc{r4650}
17545 processor, use the command @samp{set mipsfpu single}. The default
17546 double precision floating point coprocessor may be selected using
17547 @samp{set mipsfpu double}.
17549 In previous versions the only choices were double precision or no
17550 floating point, so @samp{set mipsfpu on} will select double precision
17551 and @samp{set mipsfpu off} will select no floating point.
17553 As usual, you can inquire about the @code{mipsfpu} variable with
17554 @samp{show mipsfpu}.
17556 @item set timeout @var{seconds}
17557 @itemx set retransmit-timeout @var{seconds}
17558 @itemx show timeout
17559 @itemx show retransmit-timeout
17560 @cindex @code{timeout}, MIPS protocol
17561 @cindex @code{retransmit-timeout}, MIPS protocol
17562 @kindex set timeout
17563 @kindex show timeout
17564 @kindex set retransmit-timeout
17565 @kindex show retransmit-timeout
17566 You can control the timeout used while waiting for a packet, in the MIPS
17567 remote protocol, with the @code{set timeout @var{seconds}} command. The
17568 default is 5 seconds. Similarly, you can control the timeout used while
17569 waiting for an acknowledgment of a packet with the @code{set
17570 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
17571 You can inspect both values with @code{show timeout} and @code{show
17572 retransmit-timeout}. (These commands are @emph{only} available when
17573 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
17575 The timeout set by @code{set timeout} does not apply when @value{GDBN}
17576 is waiting for your program to stop. In that case, @value{GDBN} waits
17577 forever because it has no way of knowing how long the program is going
17578 to run before stopping.
17580 @item set syn-garbage-limit @var{num}
17581 @kindex set syn-garbage-limit@r{, MIPS remote}
17582 @cindex synchronize with remote MIPS target
17583 Limit the maximum number of characters @value{GDBN} should ignore when
17584 it tries to synchronize with the remote target. The default is 10
17585 characters. Setting the limit to -1 means there's no limit.
17587 @item show syn-garbage-limit
17588 @kindex show syn-garbage-limit@r{, MIPS remote}
17589 Show the current limit on the number of characters to ignore when
17590 trying to synchronize with the remote system.
17592 @item set monitor-prompt @var{prompt}
17593 @kindex set monitor-prompt@r{, MIPS remote}
17594 @cindex remote monitor prompt
17595 Tell @value{GDBN} to expect the specified @var{prompt} string from the
17596 remote monitor. The default depends on the target:
17606 @item show monitor-prompt
17607 @kindex show monitor-prompt@r{, MIPS remote}
17608 Show the current strings @value{GDBN} expects as the prompt from the
17611 @item set monitor-warnings
17612 @kindex set monitor-warnings@r{, MIPS remote}
17613 Enable or disable monitor warnings about hardware breakpoints. This
17614 has effect only for the @code{lsi} target. When on, @value{GDBN} will
17615 display warning messages whose codes are returned by the @code{lsi}
17616 PMON monitor for breakpoint commands.
17618 @item show monitor-warnings
17619 @kindex show monitor-warnings@r{, MIPS remote}
17620 Show the current setting of printing monitor warnings.
17622 @item pmon @var{command}
17623 @kindex pmon@r{, MIPS remote}
17624 @cindex send PMON command
17625 This command allows sending an arbitrary @var{command} string to the
17626 monitor. The monitor must be in debug mode for this to work.
17629 @node OpenRISC 1000
17630 @subsection OpenRISC 1000
17631 @cindex OpenRISC 1000
17633 @cindex or1k boards
17634 See OR1k Architecture document (@uref{www.opencores.org}) for more information
17635 about platform and commands.
17639 @kindex target jtag
17640 @item target jtag jtag://@var{host}:@var{port}
17642 Connects to remote JTAG server.
17643 JTAG remote server can be either an or1ksim or JTAG server,
17644 connected via parallel port to the board.
17646 Example: @code{target jtag jtag://localhost:9999}
17649 @item or1ksim @var{command}
17650 If connected to @code{or1ksim} OpenRISC 1000 Architectural
17651 Simulator, proprietary commands can be executed.
17653 @kindex info or1k spr
17654 @item info or1k spr
17655 Displays spr groups.
17657 @item info or1k spr @var{group}
17658 @itemx info or1k spr @var{groupno}
17659 Displays register names in selected group.
17661 @item info or1k spr @var{group} @var{register}
17662 @itemx info or1k spr @var{register}
17663 @itemx info or1k spr @var{groupno} @var{registerno}
17664 @itemx info or1k spr @var{registerno}
17665 Shows information about specified spr register.
17668 @item spr @var{group} @var{register} @var{value}
17669 @itemx spr @var{register @var{value}}
17670 @itemx spr @var{groupno} @var{registerno @var{value}}
17671 @itemx spr @var{registerno @var{value}}
17672 Writes @var{value} to specified spr register.
17675 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
17676 It is very similar to @value{GDBN} trace, except it does not interfere with normal
17677 program execution and is thus much faster. Hardware breakpoints/watchpoint
17678 triggers can be set using:
17681 Load effective address/data
17683 Store effective address/data
17685 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
17690 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
17691 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
17693 @code{htrace} commands:
17694 @cindex OpenRISC 1000 htrace
17697 @item hwatch @var{conditional}
17698 Set hardware watchpoint on combination of Load/Store Effective Address(es)
17699 or Data. For example:
17701 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
17703 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
17707 Display information about current HW trace configuration.
17709 @item htrace trigger @var{conditional}
17710 Set starting criteria for HW trace.
17712 @item htrace qualifier @var{conditional}
17713 Set acquisition qualifier for HW trace.
17715 @item htrace stop @var{conditional}
17716 Set HW trace stopping criteria.
17718 @item htrace record [@var{data}]*
17719 Selects the data to be recorded, when qualifier is met and HW trace was
17722 @item htrace enable
17723 @itemx htrace disable
17724 Enables/disables the HW trace.
17726 @item htrace rewind [@var{filename}]
17727 Clears currently recorded trace data.
17729 If filename is specified, new trace file is made and any newly collected data
17730 will be written there.
17732 @item htrace print [@var{start} [@var{len}]]
17733 Prints trace buffer, using current record configuration.
17735 @item htrace mode continuous
17736 Set continuous trace mode.
17738 @item htrace mode suspend
17739 Set suspend trace mode.
17743 @node PowerPC Embedded
17744 @subsection PowerPC Embedded
17746 @value{GDBN} provides the following PowerPC-specific commands:
17749 @kindex set powerpc
17750 @item set powerpc soft-float
17751 @itemx show powerpc soft-float
17752 Force @value{GDBN} to use (or not use) a software floating point calling
17753 convention. By default, @value{GDBN} selects the calling convention based
17754 on the selected architecture and the provided executable file.
17756 @item set powerpc vector-abi
17757 @itemx show powerpc vector-abi
17758 Force @value{GDBN} to use the specified calling convention for vector
17759 arguments and return values. The valid options are @samp{auto};
17760 @samp{generic}, to avoid vector registers even if they are present;
17761 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
17762 registers. By default, @value{GDBN} selects the calling convention
17763 based on the selected architecture and the provided executable file.
17765 @kindex target dink32
17766 @item target dink32 @var{dev}
17767 DINK32 ROM monitor.
17769 @kindex target ppcbug
17770 @item target ppcbug @var{dev}
17771 @kindex target ppcbug1
17772 @item target ppcbug1 @var{dev}
17773 PPCBUG ROM monitor for PowerPC.
17776 @item target sds @var{dev}
17777 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
17780 @cindex SDS protocol
17781 The following commands specific to the SDS protocol are supported
17785 @item set sdstimeout @var{nsec}
17786 @kindex set sdstimeout
17787 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
17788 default is 2 seconds.
17790 @item show sdstimeout
17791 @kindex show sdstimeout
17792 Show the current value of the SDS timeout.
17794 @item sds @var{command}
17795 @kindex sds@r{, a command}
17796 Send the specified @var{command} string to the SDS monitor.
17801 @subsection HP PA Embedded
17805 @kindex target op50n
17806 @item target op50n @var{dev}
17807 OP50N monitor, running on an OKI HPPA board.
17809 @kindex target w89k
17810 @item target w89k @var{dev}
17811 W89K monitor, running on a Winbond HPPA board.
17816 @subsection Tsqware Sparclet
17820 @value{GDBN} enables developers to debug tasks running on
17821 Sparclet targets from a Unix host.
17822 @value{GDBN} uses code that runs on
17823 both the Unix host and on the Sparclet target. The program
17824 @code{@value{GDBP}} is installed and executed on the Unix host.
17827 @item remotetimeout @var{args}
17828 @kindex remotetimeout
17829 @value{GDBN} supports the option @code{remotetimeout}.
17830 This option is set by the user, and @var{args} represents the number of
17831 seconds @value{GDBN} waits for responses.
17834 @cindex compiling, on Sparclet
17835 When compiling for debugging, include the options @samp{-g} to get debug
17836 information and @samp{-Ttext} to relocate the program to where you wish to
17837 load it on the target. You may also want to add the options @samp{-n} or
17838 @samp{-N} in order to reduce the size of the sections. Example:
17841 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
17844 You can use @code{objdump} to verify that the addresses are what you intended:
17847 sparclet-aout-objdump --headers --syms prog
17850 @cindex running, on Sparclet
17852 your Unix execution search path to find @value{GDBN}, you are ready to
17853 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
17854 (or @code{sparclet-aout-gdb}, depending on your installation).
17856 @value{GDBN} comes up showing the prompt:
17863 * Sparclet File:: Setting the file to debug
17864 * Sparclet Connection:: Connecting to Sparclet
17865 * Sparclet Download:: Sparclet download
17866 * Sparclet Execution:: Running and debugging
17869 @node Sparclet File
17870 @subsubsection Setting File to Debug
17872 The @value{GDBN} command @code{file} lets you choose with program to debug.
17875 (gdbslet) file prog
17879 @value{GDBN} then attempts to read the symbol table of @file{prog}.
17880 @value{GDBN} locates
17881 the file by searching the directories listed in the command search
17883 If the file was compiled with debug information (option @samp{-g}), source
17884 files will be searched as well.
17885 @value{GDBN} locates
17886 the source files by searching the directories listed in the directory search
17887 path (@pxref{Environment, ,Your Program's Environment}).
17889 to find a file, it displays a message such as:
17892 prog: No such file or directory.
17895 When this happens, add the appropriate directories to the search paths with
17896 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
17897 @code{target} command again.
17899 @node Sparclet Connection
17900 @subsubsection Connecting to Sparclet
17902 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
17903 To connect to a target on serial port ``@code{ttya}'', type:
17906 (gdbslet) target sparclet /dev/ttya
17907 Remote target sparclet connected to /dev/ttya
17908 main () at ../prog.c:3
17912 @value{GDBN} displays messages like these:
17918 @node Sparclet Download
17919 @subsubsection Sparclet Download
17921 @cindex download to Sparclet
17922 Once connected to the Sparclet target,
17923 you can use the @value{GDBN}
17924 @code{load} command to download the file from the host to the target.
17925 The file name and load offset should be given as arguments to the @code{load}
17927 Since the file format is aout, the program must be loaded to the starting
17928 address. You can use @code{objdump} to find out what this value is. The load
17929 offset is an offset which is added to the VMA (virtual memory address)
17930 of each of the file's sections.
17931 For instance, if the program
17932 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
17933 and bss at 0x12010170, in @value{GDBN}, type:
17936 (gdbslet) load prog 0x12010000
17937 Loading section .text, size 0xdb0 vma 0x12010000
17940 If the code is loaded at a different address then what the program was linked
17941 to, you may need to use the @code{section} and @code{add-symbol-file} commands
17942 to tell @value{GDBN} where to map the symbol table.
17944 @node Sparclet Execution
17945 @subsubsection Running and Debugging
17947 @cindex running and debugging Sparclet programs
17948 You can now begin debugging the task using @value{GDBN}'s execution control
17949 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
17950 manual for the list of commands.
17954 Breakpoint 1 at 0x12010000: file prog.c, line 3.
17956 Starting program: prog
17957 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
17958 3 char *symarg = 0;
17960 4 char *execarg = "hello!";
17965 @subsection Fujitsu Sparclite
17969 @kindex target sparclite
17970 @item target sparclite @var{dev}
17971 Fujitsu sparclite boards, used only for the purpose of loading.
17972 You must use an additional command to debug the program.
17973 For example: target remote @var{dev} using @value{GDBN} standard
17979 @subsection Zilog Z8000
17982 @cindex simulator, Z8000
17983 @cindex Zilog Z8000 simulator
17985 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
17988 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
17989 unsegmented variant of the Z8000 architecture) or the Z8001 (the
17990 segmented variant). The simulator recognizes which architecture is
17991 appropriate by inspecting the object code.
17994 @item target sim @var{args}
17996 @kindex target sim@r{, with Z8000}
17997 Debug programs on a simulated CPU. If the simulator supports setup
17998 options, specify them via @var{args}.
18002 After specifying this target, you can debug programs for the simulated
18003 CPU in the same style as programs for your host computer; use the
18004 @code{file} command to load a new program image, the @code{run} command
18005 to run your program, and so on.
18007 As well as making available all the usual machine registers
18008 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
18009 additional items of information as specially named registers:
18014 Counts clock-ticks in the simulator.
18017 Counts instructions run in the simulator.
18020 Execution time in 60ths of a second.
18024 You can refer to these values in @value{GDBN} expressions with the usual
18025 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
18026 conditional breakpoint that suspends only after at least 5000
18027 simulated clock ticks.
18030 @subsection Atmel AVR
18033 When configured for debugging the Atmel AVR, @value{GDBN} supports the
18034 following AVR-specific commands:
18037 @item info io_registers
18038 @kindex info io_registers@r{, AVR}
18039 @cindex I/O registers (Atmel AVR)
18040 This command displays information about the AVR I/O registers. For
18041 each register, @value{GDBN} prints its number and value.
18048 When configured for debugging CRIS, @value{GDBN} provides the
18049 following CRIS-specific commands:
18052 @item set cris-version @var{ver}
18053 @cindex CRIS version
18054 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
18055 The CRIS version affects register names and sizes. This command is useful in
18056 case autodetection of the CRIS version fails.
18058 @item show cris-version
18059 Show the current CRIS version.
18061 @item set cris-dwarf2-cfi
18062 @cindex DWARF-2 CFI and CRIS
18063 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
18064 Change to @samp{off} when using @code{gcc-cris} whose version is below
18067 @item show cris-dwarf2-cfi
18068 Show the current state of using DWARF-2 CFI.
18070 @item set cris-mode @var{mode}
18072 Set the current CRIS mode to @var{mode}. It should only be changed when
18073 debugging in guru mode, in which case it should be set to
18074 @samp{guru} (the default is @samp{normal}).
18076 @item show cris-mode
18077 Show the current CRIS mode.
18081 @subsection Renesas Super-H
18084 For the Renesas Super-H processor, @value{GDBN} provides these
18089 @kindex regs@r{, Super-H}
18090 Show the values of all Super-H registers.
18092 @item set sh calling-convention @var{convention}
18093 @kindex set sh calling-convention
18094 Set the calling-convention used when calling functions from @value{GDBN}.
18095 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
18096 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
18097 convention. If the DWARF-2 information of the called function specifies
18098 that the function follows the Renesas calling convention, the function
18099 is called using the Renesas calling convention. If the calling convention
18100 is set to @samp{renesas}, the Renesas calling convention is always used,
18101 regardless of the DWARF-2 information. This can be used to override the
18102 default of @samp{gcc} if debug information is missing, or the compiler
18103 does not emit the DWARF-2 calling convention entry for a function.
18105 @item show sh calling-convention
18106 @kindex show sh calling-convention
18107 Show the current calling convention setting.
18112 @node Architectures
18113 @section Architectures
18115 This section describes characteristics of architectures that affect
18116 all uses of @value{GDBN} with the architecture, both native and cross.
18123 * HPPA:: HP PA architecture
18124 * SPU:: Cell Broadband Engine SPU architecture
18129 @subsection x86 Architecture-specific Issues
18132 @item set struct-convention @var{mode}
18133 @kindex set struct-convention
18134 @cindex struct return convention
18135 @cindex struct/union returned in registers
18136 Set the convention used by the inferior to return @code{struct}s and
18137 @code{union}s from functions to @var{mode}. Possible values of
18138 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
18139 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
18140 are returned on the stack, while @code{"reg"} means that a
18141 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
18142 be returned in a register.
18144 @item show struct-convention
18145 @kindex show struct-convention
18146 Show the current setting of the convention to return @code{struct}s
18155 @kindex set rstack_high_address
18156 @cindex AMD 29K register stack
18157 @cindex register stack, AMD29K
18158 @item set rstack_high_address @var{address}
18159 On AMD 29000 family processors, registers are saved in a separate
18160 @dfn{register stack}. There is no way for @value{GDBN} to determine the
18161 extent of this stack. Normally, @value{GDBN} just assumes that the
18162 stack is ``large enough''. This may result in @value{GDBN} referencing
18163 memory locations that do not exist. If necessary, you can get around
18164 this problem by specifying the ending address of the register stack with
18165 the @code{set rstack_high_address} command. The argument should be an
18166 address, which you probably want to precede with @samp{0x} to specify in
18169 @kindex show rstack_high_address
18170 @item show rstack_high_address
18171 Display the current limit of the register stack, on AMD 29000 family
18179 See the following section.
18184 @cindex stack on Alpha
18185 @cindex stack on MIPS
18186 @cindex Alpha stack
18188 Alpha- and MIPS-based computers use an unusual stack frame, which
18189 sometimes requires @value{GDBN} to search backward in the object code to
18190 find the beginning of a function.
18192 @cindex response time, MIPS debugging
18193 To improve response time (especially for embedded applications, where
18194 @value{GDBN} may be restricted to a slow serial line for this search)
18195 you may want to limit the size of this search, using one of these
18199 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
18200 @item set heuristic-fence-post @var{limit}
18201 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
18202 search for the beginning of a function. A value of @var{0} (the
18203 default) means there is no limit. However, except for @var{0}, the
18204 larger the limit the more bytes @code{heuristic-fence-post} must search
18205 and therefore the longer it takes to run. You should only need to use
18206 this command when debugging a stripped executable.
18208 @item show heuristic-fence-post
18209 Display the current limit.
18213 These commands are available @emph{only} when @value{GDBN} is configured
18214 for debugging programs on Alpha or MIPS processors.
18216 Several MIPS-specific commands are available when debugging MIPS
18220 @item set mips abi @var{arg}
18221 @kindex set mips abi
18222 @cindex set ABI for MIPS
18223 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
18224 values of @var{arg} are:
18228 The default ABI associated with the current binary (this is the
18239 @item show mips abi
18240 @kindex show mips abi
18241 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
18244 @itemx show mipsfpu
18245 @xref{MIPS Embedded, set mipsfpu}.
18247 @item set mips mask-address @var{arg}
18248 @kindex set mips mask-address
18249 @cindex MIPS addresses, masking
18250 This command determines whether the most-significant 32 bits of 64-bit
18251 MIPS addresses are masked off. The argument @var{arg} can be
18252 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
18253 setting, which lets @value{GDBN} determine the correct value.
18255 @item show mips mask-address
18256 @kindex show mips mask-address
18257 Show whether the upper 32 bits of MIPS addresses are masked off or
18260 @item set remote-mips64-transfers-32bit-regs
18261 @kindex set remote-mips64-transfers-32bit-regs
18262 This command controls compatibility with 64-bit MIPS targets that
18263 transfer data in 32-bit quantities. If you have an old MIPS 64 target
18264 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
18265 and 64 bits for other registers, set this option to @samp{on}.
18267 @item show remote-mips64-transfers-32bit-regs
18268 @kindex show remote-mips64-transfers-32bit-regs
18269 Show the current setting of compatibility with older MIPS 64 targets.
18271 @item set debug mips
18272 @kindex set debug mips
18273 This command turns on and off debugging messages for the MIPS-specific
18274 target code in @value{GDBN}.
18276 @item show debug mips
18277 @kindex show debug mips
18278 Show the current setting of MIPS debugging messages.
18284 @cindex HPPA support
18286 When @value{GDBN} is debugging the HP PA architecture, it provides the
18287 following special commands:
18290 @item set debug hppa
18291 @kindex set debug hppa
18292 This command determines whether HPPA architecture-specific debugging
18293 messages are to be displayed.
18295 @item show debug hppa
18296 Show whether HPPA debugging messages are displayed.
18298 @item maint print unwind @var{address}
18299 @kindex maint print unwind@r{, HPPA}
18300 This command displays the contents of the unwind table entry at the
18301 given @var{address}.
18307 @subsection Cell Broadband Engine SPU architecture
18308 @cindex Cell Broadband Engine
18311 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
18312 it provides the following special commands:
18315 @item info spu event
18317 Display SPU event facility status. Shows current event mask
18318 and pending event status.
18320 @item info spu signal
18321 Display SPU signal notification facility status. Shows pending
18322 signal-control word and signal notification mode of both signal
18323 notification channels.
18325 @item info spu mailbox
18326 Display SPU mailbox facility status. Shows all pending entries,
18327 in order of processing, in each of the SPU Write Outbound,
18328 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
18331 Display MFC DMA status. Shows all pending commands in the MFC
18332 DMA queue. For each entry, opcode, tag, class IDs, effective
18333 and local store addresses and transfer size are shown.
18335 @item info spu proxydma
18336 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
18337 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
18338 and local store addresses and transfer size are shown.
18342 When @value{GDBN} is debugging a combined PowerPC/SPU application
18343 on the Cell Broadband Engine, it provides in addition the following
18347 @item set spu stop-on-load @var{arg}
18349 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
18350 will give control to the user when a new SPE thread enters its @code{main}
18351 function. The default is @code{off}.
18353 @item show spu stop-on-load
18355 Show whether to stop for new SPE threads.
18357 @item set spu auto-flush-cache @var{arg}
18358 Set whether to automatically flush the software-managed cache. When set to
18359 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
18360 cache to be flushed whenever SPE execution stops. This provides a consistent
18361 view of PowerPC memory that is accessed via the cache. If an application
18362 does not use the software-managed cache, this option has no effect.
18364 @item show spu auto-flush-cache
18365 Show whether to automatically flush the software-managed cache.
18370 @subsection PowerPC
18371 @cindex PowerPC architecture
18373 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
18374 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
18375 numbers stored in the floating point registers. These values must be stored
18376 in two consecutive registers, always starting at an even register like
18377 @code{f0} or @code{f2}.
18379 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
18380 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
18381 @code{f2} and @code{f3} for @code{$dl1} and so on.
18383 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
18384 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
18387 @node Controlling GDB
18388 @chapter Controlling @value{GDBN}
18390 You can alter the way @value{GDBN} interacts with you by using the
18391 @code{set} command. For commands controlling how @value{GDBN} displays
18392 data, see @ref{Print Settings, ,Print Settings}. Other settings are
18397 * Editing:: Command editing
18398 * Command History:: Command history
18399 * Screen Size:: Screen size
18400 * Numbers:: Numbers
18401 * ABI:: Configuring the current ABI
18402 * Messages/Warnings:: Optional warnings and messages
18403 * Debugging Output:: Optional messages about internal happenings
18404 * Other Misc Settings:: Other Miscellaneous Settings
18412 @value{GDBN} indicates its readiness to read a command by printing a string
18413 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
18414 can change the prompt string with the @code{set prompt} command. For
18415 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
18416 the prompt in one of the @value{GDBN} sessions so that you can always tell
18417 which one you are talking to.
18419 @emph{Note:} @code{set prompt} does not add a space for you after the
18420 prompt you set. This allows you to set a prompt which ends in a space
18421 or a prompt that does not.
18425 @item set prompt @var{newprompt}
18426 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
18428 @kindex show prompt
18430 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
18434 @section Command Editing
18436 @cindex command line editing
18438 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
18439 @sc{gnu} library provides consistent behavior for programs which provide a
18440 command line interface to the user. Advantages are @sc{gnu} Emacs-style
18441 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
18442 substitution, and a storage and recall of command history across
18443 debugging sessions.
18445 You may control the behavior of command line editing in @value{GDBN} with the
18446 command @code{set}.
18449 @kindex set editing
18452 @itemx set editing on
18453 Enable command line editing (enabled by default).
18455 @item set editing off
18456 Disable command line editing.
18458 @kindex show editing
18460 Show whether command line editing is enabled.
18463 @xref{Command Line Editing}, for more details about the Readline
18464 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
18465 encouraged to read that chapter.
18467 @node Command History
18468 @section Command History
18469 @cindex command history
18471 @value{GDBN} can keep track of the commands you type during your
18472 debugging sessions, so that you can be certain of precisely what
18473 happened. Use these commands to manage the @value{GDBN} command
18476 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
18477 package, to provide the history facility. @xref{Using History
18478 Interactively}, for the detailed description of the History library.
18480 To issue a command to @value{GDBN} without affecting certain aspects of
18481 the state which is seen by users, prefix it with @samp{server }
18482 (@pxref{Server Prefix}). This
18483 means that this command will not affect the command history, nor will it
18484 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
18485 pressed on a line by itself.
18487 @cindex @code{server}, command prefix
18488 The server prefix does not affect the recording of values into the value
18489 history; to print a value without recording it into the value history,
18490 use the @code{output} command instead of the @code{print} command.
18492 Here is the description of @value{GDBN} commands related to command
18496 @cindex history substitution
18497 @cindex history file
18498 @kindex set history filename
18499 @cindex @env{GDBHISTFILE}, environment variable
18500 @item set history filename @var{fname}
18501 Set the name of the @value{GDBN} command history file to @var{fname}.
18502 This is the file where @value{GDBN} reads an initial command history
18503 list, and where it writes the command history from this session when it
18504 exits. You can access this list through history expansion or through
18505 the history command editing characters listed below. This file defaults
18506 to the value of the environment variable @code{GDBHISTFILE}, or to
18507 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
18510 @cindex save command history
18511 @kindex set history save
18512 @item set history save
18513 @itemx set history save on
18514 Record command history in a file, whose name may be specified with the
18515 @code{set history filename} command. By default, this option is disabled.
18517 @item set history save off
18518 Stop recording command history in a file.
18520 @cindex history size
18521 @kindex set history size
18522 @cindex @env{HISTSIZE}, environment variable
18523 @item set history size @var{size}
18524 Set the number of commands which @value{GDBN} keeps in its history list.
18525 This defaults to the value of the environment variable
18526 @code{HISTSIZE}, or to 256 if this variable is not set.
18529 History expansion assigns special meaning to the character @kbd{!}.
18530 @xref{Event Designators}, for more details.
18532 @cindex history expansion, turn on/off
18533 Since @kbd{!} is also the logical not operator in C, history expansion
18534 is off by default. If you decide to enable history expansion with the
18535 @code{set history expansion on} command, you may sometimes need to
18536 follow @kbd{!} (when it is used as logical not, in an expression) with
18537 a space or a tab to prevent it from being expanded. The readline
18538 history facilities do not attempt substitution on the strings
18539 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
18541 The commands to control history expansion are:
18544 @item set history expansion on
18545 @itemx set history expansion
18546 @kindex set history expansion
18547 Enable history expansion. History expansion is off by default.
18549 @item set history expansion off
18550 Disable history expansion.
18553 @kindex show history
18555 @itemx show history filename
18556 @itemx show history save
18557 @itemx show history size
18558 @itemx show history expansion
18559 These commands display the state of the @value{GDBN} history parameters.
18560 @code{show history} by itself displays all four states.
18565 @kindex show commands
18566 @cindex show last commands
18567 @cindex display command history
18568 @item show commands
18569 Display the last ten commands in the command history.
18571 @item show commands @var{n}
18572 Print ten commands centered on command number @var{n}.
18574 @item show commands +
18575 Print ten commands just after the commands last printed.
18579 @section Screen Size
18580 @cindex size of screen
18581 @cindex pauses in output
18583 Certain commands to @value{GDBN} may produce large amounts of
18584 information output to the screen. To help you read all of it,
18585 @value{GDBN} pauses and asks you for input at the end of each page of
18586 output. Type @key{RET} when you want to continue the output, or @kbd{q}
18587 to discard the remaining output. Also, the screen width setting
18588 determines when to wrap lines of output. Depending on what is being
18589 printed, @value{GDBN} tries to break the line at a readable place,
18590 rather than simply letting it overflow onto the following line.
18592 Normally @value{GDBN} knows the size of the screen from the terminal
18593 driver software. For example, on Unix @value{GDBN} uses the termcap data base
18594 together with the value of the @code{TERM} environment variable and the
18595 @code{stty rows} and @code{stty cols} settings. If this is not correct,
18596 you can override it with the @code{set height} and @code{set
18603 @kindex show height
18604 @item set height @var{lpp}
18606 @itemx set width @var{cpl}
18608 These @code{set} commands specify a screen height of @var{lpp} lines and
18609 a screen width of @var{cpl} characters. The associated @code{show}
18610 commands display the current settings.
18612 If you specify a height of zero lines, @value{GDBN} does not pause during
18613 output no matter how long the output is. This is useful if output is to a
18614 file or to an editor buffer.
18616 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
18617 from wrapping its output.
18619 @item set pagination on
18620 @itemx set pagination off
18621 @kindex set pagination
18622 Turn the output pagination on or off; the default is on. Turning
18623 pagination off is the alternative to @code{set height 0}. Note that
18624 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
18625 Options, -batch}) also automatically disables pagination.
18627 @item show pagination
18628 @kindex show pagination
18629 Show the current pagination mode.
18634 @cindex number representation
18635 @cindex entering numbers
18637 You can always enter numbers in octal, decimal, or hexadecimal in
18638 @value{GDBN} by the usual conventions: octal numbers begin with
18639 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
18640 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
18641 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
18642 10; likewise, the default display for numbers---when no particular
18643 format is specified---is base 10. You can change the default base for
18644 both input and output with the commands described below.
18647 @kindex set input-radix
18648 @item set input-radix @var{base}
18649 Set the default base for numeric input. Supported choices
18650 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
18651 specified either unambiguously or using the current input radix; for
18655 set input-radix 012
18656 set input-radix 10.
18657 set input-radix 0xa
18661 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
18662 leaves the input radix unchanged, no matter what it was, since
18663 @samp{10}, being without any leading or trailing signs of its base, is
18664 interpreted in the current radix. Thus, if the current radix is 16,
18665 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
18668 @kindex set output-radix
18669 @item set output-radix @var{base}
18670 Set the default base for numeric display. Supported choices
18671 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
18672 specified either unambiguously or using the current input radix.
18674 @kindex show input-radix
18675 @item show input-radix
18676 Display the current default base for numeric input.
18678 @kindex show output-radix
18679 @item show output-radix
18680 Display the current default base for numeric display.
18682 @item set radix @r{[}@var{base}@r{]}
18686 These commands set and show the default base for both input and output
18687 of numbers. @code{set radix} sets the radix of input and output to
18688 the same base; without an argument, it resets the radix back to its
18689 default value of 10.
18694 @section Configuring the Current ABI
18696 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
18697 application automatically. However, sometimes you need to override its
18698 conclusions. Use these commands to manage @value{GDBN}'s view of the
18705 One @value{GDBN} configuration can debug binaries for multiple operating
18706 system targets, either via remote debugging or native emulation.
18707 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
18708 but you can override its conclusion using the @code{set osabi} command.
18709 One example where this is useful is in debugging of binaries which use
18710 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
18711 not have the same identifying marks that the standard C library for your
18716 Show the OS ABI currently in use.
18719 With no argument, show the list of registered available OS ABI's.
18721 @item set osabi @var{abi}
18722 Set the current OS ABI to @var{abi}.
18725 @cindex float promotion
18727 Generally, the way that an argument of type @code{float} is passed to a
18728 function depends on whether the function is prototyped. For a prototyped
18729 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
18730 according to the architecture's convention for @code{float}. For unprototyped
18731 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
18732 @code{double} and then passed.
18734 Unfortunately, some forms of debug information do not reliably indicate whether
18735 a function is prototyped. If @value{GDBN} calls a function that is not marked
18736 as prototyped, it consults @kbd{set coerce-float-to-double}.
18739 @kindex set coerce-float-to-double
18740 @item set coerce-float-to-double
18741 @itemx set coerce-float-to-double on
18742 Arguments of type @code{float} will be promoted to @code{double} when passed
18743 to an unprototyped function. This is the default setting.
18745 @item set coerce-float-to-double off
18746 Arguments of type @code{float} will be passed directly to unprototyped
18749 @kindex show coerce-float-to-double
18750 @item show coerce-float-to-double
18751 Show the current setting of promoting @code{float} to @code{double}.
18755 @kindex show cp-abi
18756 @value{GDBN} needs to know the ABI used for your program's C@t{++}
18757 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
18758 used to build your application. @value{GDBN} only fully supports
18759 programs with a single C@t{++} ABI; if your program contains code using
18760 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
18761 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
18762 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
18763 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
18764 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
18765 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
18770 Show the C@t{++} ABI currently in use.
18773 With no argument, show the list of supported C@t{++} ABI's.
18775 @item set cp-abi @var{abi}
18776 @itemx set cp-abi auto
18777 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
18780 @node Messages/Warnings
18781 @section Optional Warnings and Messages
18783 @cindex verbose operation
18784 @cindex optional warnings
18785 By default, @value{GDBN} is silent about its inner workings. If you are
18786 running on a slow machine, you may want to use the @code{set verbose}
18787 command. This makes @value{GDBN} tell you when it does a lengthy
18788 internal operation, so you will not think it has crashed.
18790 Currently, the messages controlled by @code{set verbose} are those
18791 which announce that the symbol table for a source file is being read;
18792 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
18795 @kindex set verbose
18796 @item set verbose on
18797 Enables @value{GDBN} output of certain informational messages.
18799 @item set verbose off
18800 Disables @value{GDBN} output of certain informational messages.
18802 @kindex show verbose
18804 Displays whether @code{set verbose} is on or off.
18807 By default, if @value{GDBN} encounters bugs in the symbol table of an
18808 object file, it is silent; but if you are debugging a compiler, you may
18809 find this information useful (@pxref{Symbol Errors, ,Errors Reading
18814 @kindex set complaints
18815 @item set complaints @var{limit}
18816 Permits @value{GDBN} to output @var{limit} complaints about each type of
18817 unusual symbols before becoming silent about the problem. Set
18818 @var{limit} to zero to suppress all complaints; set it to a large number
18819 to prevent complaints from being suppressed.
18821 @kindex show complaints
18822 @item show complaints
18823 Displays how many symbol complaints @value{GDBN} is permitted to produce.
18827 @anchor{confirmation requests}
18828 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
18829 lot of stupid questions to confirm certain commands. For example, if
18830 you try to run a program which is already running:
18834 The program being debugged has been started already.
18835 Start it from the beginning? (y or n)
18838 If you are willing to unflinchingly face the consequences of your own
18839 commands, you can disable this ``feature'':
18843 @kindex set confirm
18845 @cindex confirmation
18846 @cindex stupid questions
18847 @item set confirm off
18848 Disables confirmation requests. Note that running @value{GDBN} with
18849 the @option{--batch} option (@pxref{Mode Options, -batch}) also
18850 automatically disables confirmation requests.
18852 @item set confirm on
18853 Enables confirmation requests (the default).
18855 @kindex show confirm
18857 Displays state of confirmation requests.
18861 @cindex command tracing
18862 If you need to debug user-defined commands or sourced files you may find it
18863 useful to enable @dfn{command tracing}. In this mode each command will be
18864 printed as it is executed, prefixed with one or more @samp{+} symbols, the
18865 quantity denoting the call depth of each command.
18868 @kindex set trace-commands
18869 @cindex command scripts, debugging
18870 @item set trace-commands on
18871 Enable command tracing.
18872 @item set trace-commands off
18873 Disable command tracing.
18874 @item show trace-commands
18875 Display the current state of command tracing.
18878 @node Debugging Output
18879 @section Optional Messages about Internal Happenings
18880 @cindex optional debugging messages
18882 @value{GDBN} has commands that enable optional debugging messages from
18883 various @value{GDBN} subsystems; normally these commands are of
18884 interest to @value{GDBN} maintainers, or when reporting a bug. This
18885 section documents those commands.
18888 @kindex set exec-done-display
18889 @item set exec-done-display
18890 Turns on or off the notification of asynchronous commands'
18891 completion. When on, @value{GDBN} will print a message when an
18892 asynchronous command finishes its execution. The default is off.
18893 @kindex show exec-done-display
18894 @item show exec-done-display
18895 Displays the current setting of asynchronous command completion
18898 @cindex gdbarch debugging info
18899 @cindex architecture debugging info
18900 @item set debug arch
18901 Turns on or off display of gdbarch debugging info. The default is off
18903 @item show debug arch
18904 Displays the current state of displaying gdbarch debugging info.
18905 @item set debug aix-thread
18906 @cindex AIX threads
18907 Display debugging messages about inner workings of the AIX thread
18909 @item show debug aix-thread
18910 Show the current state of AIX thread debugging info display.
18911 @item set debug dwarf2-die
18912 @cindex DWARF2 DIEs
18913 Dump DWARF2 DIEs after they are read in.
18914 The value is the number of nesting levels to print.
18915 A value of zero turns off the display.
18916 @item show debug dwarf2-die
18917 Show the current state of DWARF2 DIE debugging.
18918 @item set debug displaced
18919 @cindex displaced stepping debugging info
18920 Turns on or off display of @value{GDBN} debugging info for the
18921 displaced stepping support. The default is off.
18922 @item show debug displaced
18923 Displays the current state of displaying @value{GDBN} debugging info
18924 related to displaced stepping.
18925 @item set debug event
18926 @cindex event debugging info
18927 Turns on or off display of @value{GDBN} event debugging info. The
18929 @item show debug event
18930 Displays the current state of displaying @value{GDBN} event debugging
18932 @item set debug expression
18933 @cindex expression debugging info
18934 Turns on or off display of debugging info about @value{GDBN}
18935 expression parsing. The default is off.
18936 @item show debug expression
18937 Displays the current state of displaying debugging info about
18938 @value{GDBN} expression parsing.
18939 @item set debug frame
18940 @cindex frame debugging info
18941 Turns on or off display of @value{GDBN} frame debugging info. The
18943 @item show debug frame
18944 Displays the current state of displaying @value{GDBN} frame debugging
18946 @item set debug gnu-nat
18947 @cindex @sc{gnu}/Hurd debug messages
18948 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
18949 @item show debug gnu-nat
18950 Show the current state of @sc{gnu}/Hurd debugging messages.
18951 @item set debug infrun
18952 @cindex inferior debugging info
18953 Turns on or off display of @value{GDBN} debugging info for running the inferior.
18954 The default is off. @file{infrun.c} contains GDB's runtime state machine used
18955 for implementing operations such as single-stepping the inferior.
18956 @item show debug infrun
18957 Displays the current state of @value{GDBN} inferior debugging.
18958 @item set debug lin-lwp
18959 @cindex @sc{gnu}/Linux LWP debug messages
18960 @cindex Linux lightweight processes
18961 Turns on or off debugging messages from the Linux LWP debug support.
18962 @item show debug lin-lwp
18963 Show the current state of Linux LWP debugging messages.
18964 @item set debug lin-lwp-async
18965 @cindex @sc{gnu}/Linux LWP async debug messages
18966 @cindex Linux lightweight processes
18967 Turns on or off debugging messages from the Linux LWP async debug support.
18968 @item show debug lin-lwp-async
18969 Show the current state of Linux LWP async debugging messages.
18970 @item set debug observer
18971 @cindex observer debugging info
18972 Turns on or off display of @value{GDBN} observer debugging. This
18973 includes info such as the notification of observable events.
18974 @item show debug observer
18975 Displays the current state of observer debugging.
18976 @item set debug overload
18977 @cindex C@t{++} overload debugging info
18978 Turns on or off display of @value{GDBN} C@t{++} overload debugging
18979 info. This includes info such as ranking of functions, etc. The default
18981 @item show debug overload
18982 Displays the current state of displaying @value{GDBN} C@t{++} overload
18984 @cindex expression parser, debugging info
18985 @cindex debug expression parser
18986 @item set debug parser
18987 Turns on or off the display of expression parser debugging output.
18988 Internally, this sets the @code{yydebug} variable in the expression
18989 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
18990 details. The default is off.
18991 @item show debug parser
18992 Show the current state of expression parser debugging.
18993 @cindex packets, reporting on stdout
18994 @cindex serial connections, debugging
18995 @cindex debug remote protocol
18996 @cindex remote protocol debugging
18997 @cindex display remote packets
18998 @item set debug remote
18999 Turns on or off display of reports on all packets sent back and forth across
19000 the serial line to the remote machine. The info is printed on the
19001 @value{GDBN} standard output stream. The default is off.
19002 @item show debug remote
19003 Displays the state of display of remote packets.
19004 @item set debug serial
19005 Turns on or off display of @value{GDBN} serial debugging info. The
19007 @item show debug serial
19008 Displays the current state of displaying @value{GDBN} serial debugging
19010 @item set debug solib-frv
19011 @cindex FR-V shared-library debugging
19012 Turns on or off debugging messages for FR-V shared-library code.
19013 @item show debug solib-frv
19014 Display the current state of FR-V shared-library code debugging
19016 @item set debug target
19017 @cindex target debugging info
19018 Turns on or off display of @value{GDBN} target debugging info. This info
19019 includes what is going on at the target level of GDB, as it happens. The
19020 default is 0. Set it to 1 to track events, and to 2 to also track the
19021 value of large memory transfers. Changes to this flag do not take effect
19022 until the next time you connect to a target or use the @code{run} command.
19023 @item show debug target
19024 Displays the current state of displaying @value{GDBN} target debugging
19026 @item set debug timestamp
19027 @cindex timestampping debugging info
19028 Turns on or off display of timestamps with @value{GDBN} debugging info.
19029 When enabled, seconds and microseconds are displayed before each debugging
19031 @item show debug timestamp
19032 Displays the current state of displaying timestamps with @value{GDBN}
19034 @item set debugvarobj
19035 @cindex variable object debugging info
19036 Turns on or off display of @value{GDBN} variable object debugging
19037 info. The default is off.
19038 @item show debugvarobj
19039 Displays the current state of displaying @value{GDBN} variable object
19041 @item set debug xml
19042 @cindex XML parser debugging
19043 Turns on or off debugging messages for built-in XML parsers.
19044 @item show debug xml
19045 Displays the current state of XML debugging messages.
19048 @node Other Misc Settings
19049 @section Other Miscellaneous Settings
19050 @cindex miscellaneous settings
19053 @kindex set interactive-mode
19054 @item set interactive-mode
19055 If @code{on}, forces @value{GDBN} to operate interactively.
19056 If @code{off}, forces @value{GDBN} to operate non-interactively,
19057 If @code{auto} (the default), @value{GDBN} guesses which mode to use,
19058 based on whether the debugger was started in a terminal or not.
19060 In the vast majority of cases, the debugger should be able to guess
19061 correctly which mode should be used. But this setting can be useful
19062 in certain specific cases, such as running a MinGW @value{GDBN}
19063 inside a cygwin window.
19065 @kindex show interactive-mode
19066 @item show interactive-mode
19067 Displays whether the debugger is operating in interactive mode or not.
19070 @node Extending GDB
19071 @chapter Extending @value{GDBN}
19072 @cindex extending GDB
19074 @value{GDBN} provides two mechanisms for extension. The first is based
19075 on composition of @value{GDBN} commands, and the second is based on the
19076 Python scripting language.
19078 To facilitate the use of these extensions, @value{GDBN} is capable
19079 of evaluating the contents of a file. When doing so, @value{GDBN}
19080 can recognize which scripting language is being used by looking at
19081 the filename extension. Files with an unrecognized filename extension
19082 are always treated as a @value{GDBN} Command Files.
19083 @xref{Command Files,, Command files}.
19085 You can control how @value{GDBN} evaluates these files with the following
19089 @kindex set script-extension
19090 @kindex show script-extension
19091 @item set script-extension off
19092 All scripts are always evaluated as @value{GDBN} Command Files.
19094 @item set script-extension soft
19095 The debugger determines the scripting language based on filename
19096 extension. If this scripting language is supported, @value{GDBN}
19097 evaluates the script using that language. Otherwise, it evaluates
19098 the file as a @value{GDBN} Command File.
19100 @item set script-extension strict
19101 The debugger determines the scripting language based on filename
19102 extension, and evaluates the script using that language. If the
19103 language is not supported, then the evaluation fails.
19105 @item show script-extension
19106 Display the current value of the @code{script-extension} option.
19111 * Sequences:: Canned Sequences of Commands
19112 * Python:: Scripting @value{GDBN} using Python
19116 @section Canned Sequences of Commands
19118 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
19119 Command Lists}), @value{GDBN} provides two ways to store sequences of
19120 commands for execution as a unit: user-defined commands and command
19124 * Define:: How to define your own commands
19125 * Hooks:: Hooks for user-defined commands
19126 * Command Files:: How to write scripts of commands to be stored in a file
19127 * Output:: Commands for controlled output
19131 @subsection User-defined Commands
19133 @cindex user-defined command
19134 @cindex arguments, to user-defined commands
19135 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
19136 which you assign a new name as a command. This is done with the
19137 @code{define} command. User commands may accept up to 10 arguments
19138 separated by whitespace. Arguments are accessed within the user command
19139 via @code{$arg0@dots{}$arg9}. A trivial example:
19143 print $arg0 + $arg1 + $arg2
19148 To execute the command use:
19155 This defines the command @code{adder}, which prints the sum of
19156 its three arguments. Note the arguments are text substitutions, so they may
19157 reference variables, use complex expressions, or even perform inferior
19160 @cindex argument count in user-defined commands
19161 @cindex how many arguments (user-defined commands)
19162 In addition, @code{$argc} may be used to find out how many arguments have
19163 been passed. This expands to a number in the range 0@dots{}10.
19168 print $arg0 + $arg1
19171 print $arg0 + $arg1 + $arg2
19179 @item define @var{commandname}
19180 Define a command named @var{commandname}. If there is already a command
19181 by that name, you are asked to confirm that you want to redefine it.
19182 @var{commandname} may be a bare command name consisting of letters,
19183 numbers, dashes, and underscores. It may also start with any predefined
19184 prefix command. For example, @samp{define target my-target} creates
19185 a user-defined @samp{target my-target} command.
19187 The definition of the command is made up of other @value{GDBN} command lines,
19188 which are given following the @code{define} command. The end of these
19189 commands is marked by a line containing @code{end}.
19192 @kindex end@r{ (user-defined commands)}
19193 @item document @var{commandname}
19194 Document the user-defined command @var{commandname}, so that it can be
19195 accessed by @code{help}. The command @var{commandname} must already be
19196 defined. This command reads lines of documentation just as @code{define}
19197 reads the lines of the command definition, ending with @code{end}.
19198 After the @code{document} command is finished, @code{help} on command
19199 @var{commandname} displays the documentation you have written.
19201 You may use the @code{document} command again to change the
19202 documentation of a command. Redefining the command with @code{define}
19203 does not change the documentation.
19205 @kindex dont-repeat
19206 @cindex don't repeat command
19208 Used inside a user-defined command, this tells @value{GDBN} that this
19209 command should not be repeated when the user hits @key{RET}
19210 (@pxref{Command Syntax, repeat last command}).
19212 @kindex help user-defined
19213 @item help user-defined
19214 List all user-defined commands, with the first line of the documentation
19219 @itemx show user @var{commandname}
19220 Display the @value{GDBN} commands used to define @var{commandname} (but
19221 not its documentation). If no @var{commandname} is given, display the
19222 definitions for all user-defined commands.
19224 @cindex infinite recursion in user-defined commands
19225 @kindex show max-user-call-depth
19226 @kindex set max-user-call-depth
19227 @item show max-user-call-depth
19228 @itemx set max-user-call-depth
19229 The value of @code{max-user-call-depth} controls how many recursion
19230 levels are allowed in user-defined commands before @value{GDBN} suspects an
19231 infinite recursion and aborts the command.
19234 In addition to the above commands, user-defined commands frequently
19235 use control flow commands, described in @ref{Command Files}.
19237 When user-defined commands are executed, the
19238 commands of the definition are not printed. An error in any command
19239 stops execution of the user-defined command.
19241 If used interactively, commands that would ask for confirmation proceed
19242 without asking when used inside a user-defined command. Many @value{GDBN}
19243 commands that normally print messages to say what they are doing omit the
19244 messages when used in a user-defined command.
19247 @subsection User-defined Command Hooks
19248 @cindex command hooks
19249 @cindex hooks, for commands
19250 @cindex hooks, pre-command
19253 You may define @dfn{hooks}, which are a special kind of user-defined
19254 command. Whenever you run the command @samp{foo}, if the user-defined
19255 command @samp{hook-foo} exists, it is executed (with no arguments)
19256 before that command.
19258 @cindex hooks, post-command
19260 A hook may also be defined which is run after the command you executed.
19261 Whenever you run the command @samp{foo}, if the user-defined command
19262 @samp{hookpost-foo} exists, it is executed (with no arguments) after
19263 that command. Post-execution hooks may exist simultaneously with
19264 pre-execution hooks, for the same command.
19266 It is valid for a hook to call the command which it hooks. If this
19267 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
19269 @c It would be nice if hookpost could be passed a parameter indicating
19270 @c if the command it hooks executed properly or not. FIXME!
19272 @kindex stop@r{, a pseudo-command}
19273 In addition, a pseudo-command, @samp{stop} exists. Defining
19274 (@samp{hook-stop}) makes the associated commands execute every time
19275 execution stops in your program: before breakpoint commands are run,
19276 displays are printed, or the stack frame is printed.
19278 For example, to ignore @code{SIGALRM} signals while
19279 single-stepping, but treat them normally during normal execution,
19284 handle SIGALRM nopass
19288 handle SIGALRM pass
19291 define hook-continue
19292 handle SIGALRM pass
19296 As a further example, to hook at the beginning and end of the @code{echo}
19297 command, and to add extra text to the beginning and end of the message,
19305 define hookpost-echo
19309 (@value{GDBP}) echo Hello World
19310 <<<---Hello World--->>>
19315 You can define a hook for any single-word command in @value{GDBN}, but
19316 not for command aliases; you should define a hook for the basic command
19317 name, e.g.@: @code{backtrace} rather than @code{bt}.
19318 @c FIXME! So how does Joe User discover whether a command is an alias
19320 You can hook a multi-word command by adding @code{hook-} or
19321 @code{hookpost-} to the last word of the command, e.g.@:
19322 @samp{define target hook-remote} to add a hook to @samp{target remote}.
19324 If an error occurs during the execution of your hook, execution of
19325 @value{GDBN} commands stops and @value{GDBN} issues a prompt
19326 (before the command that you actually typed had a chance to run).
19328 If you try to define a hook which does not match any known command, you
19329 get a warning from the @code{define} command.
19331 @node Command Files
19332 @subsection Command Files
19334 @cindex command files
19335 @cindex scripting commands
19336 A command file for @value{GDBN} is a text file made of lines that are
19337 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
19338 also be included. An empty line in a command file does nothing; it
19339 does not mean to repeat the last command, as it would from the
19342 You can request the execution of a command file with the @code{source}
19343 command. Note that the @code{source} command is also used to evaluate
19344 scripts that are not Command Files. The exact behavior can be configured
19345 using the @code{script-extension} setting.
19346 @xref{Extending GDB,, Extending GDB}.
19350 @cindex execute commands from a file
19351 @item source [@code{-v}] @var{filename}
19352 Execute the command file @var{filename}.
19355 The lines in a command file are generally executed sequentially,
19356 unless the order of execution is changed by one of the
19357 @emph{flow-control commands} described below. The commands are not
19358 printed as they are executed. An error in any command terminates
19359 execution of the command file and control is returned to the console.
19361 @value{GDBN} searches for @var{filename} in the current directory and then
19362 on the search path (specified with the @samp{directory} command).
19364 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
19365 each command as it is executed. The option must be given before
19366 @var{filename}, and is interpreted as part of the filename anywhere else.
19368 Commands that would ask for confirmation if used interactively proceed
19369 without asking when used in a command file. Many @value{GDBN} commands that
19370 normally print messages to say what they are doing omit the messages
19371 when called from command files.
19373 @value{GDBN} also accepts command input from standard input. In this
19374 mode, normal output goes to standard output and error output goes to
19375 standard error. Errors in a command file supplied on standard input do
19376 not terminate execution of the command file---execution continues with
19380 gdb < cmds > log 2>&1
19383 (The syntax above will vary depending on the shell used.) This example
19384 will execute commands from the file @file{cmds}. All output and errors
19385 would be directed to @file{log}.
19387 Since commands stored on command files tend to be more general than
19388 commands typed interactively, they frequently need to deal with
19389 complicated situations, such as different or unexpected values of
19390 variables and symbols, changes in how the program being debugged is
19391 built, etc. @value{GDBN} provides a set of flow-control commands to
19392 deal with these complexities. Using these commands, you can write
19393 complex scripts that loop over data structures, execute commands
19394 conditionally, etc.
19401 This command allows to include in your script conditionally executed
19402 commands. The @code{if} command takes a single argument, which is an
19403 expression to evaluate. It is followed by a series of commands that
19404 are executed only if the expression is true (its value is nonzero).
19405 There can then optionally be an @code{else} line, followed by a series
19406 of commands that are only executed if the expression was false. The
19407 end of the list is marked by a line containing @code{end}.
19411 This command allows to write loops. Its syntax is similar to
19412 @code{if}: the command takes a single argument, which is an expression
19413 to evaluate, and must be followed by the commands to execute, one per
19414 line, terminated by an @code{end}. These commands are called the
19415 @dfn{body} of the loop. The commands in the body of @code{while} are
19416 executed repeatedly as long as the expression evaluates to true.
19420 This command exits the @code{while} loop in whose body it is included.
19421 Execution of the script continues after that @code{while}s @code{end}
19424 @kindex loop_continue
19425 @item loop_continue
19426 This command skips the execution of the rest of the body of commands
19427 in the @code{while} loop in whose body it is included. Execution
19428 branches to the beginning of the @code{while} loop, where it evaluates
19429 the controlling expression.
19431 @kindex end@r{ (if/else/while commands)}
19433 Terminate the block of commands that are the body of @code{if},
19434 @code{else}, or @code{while} flow-control commands.
19439 @subsection Commands for Controlled Output
19441 During the execution of a command file or a user-defined command, normal
19442 @value{GDBN} output is suppressed; the only output that appears is what is
19443 explicitly printed by the commands in the definition. This section
19444 describes three commands useful for generating exactly the output you
19449 @item echo @var{text}
19450 @c I do not consider backslash-space a standard C escape sequence
19451 @c because it is not in ANSI.
19452 Print @var{text}. Nonprinting characters can be included in
19453 @var{text} using C escape sequences, such as @samp{\n} to print a
19454 newline. @strong{No newline is printed unless you specify one.}
19455 In addition to the standard C escape sequences, a backslash followed
19456 by a space stands for a space. This is useful for displaying a
19457 string with spaces at the beginning or the end, since leading and
19458 trailing spaces are otherwise trimmed from all arguments.
19459 To print @samp{@w{ }and foo =@w{ }}, use the command
19460 @samp{echo \@w{ }and foo = \@w{ }}.
19462 A backslash at the end of @var{text} can be used, as in C, to continue
19463 the command onto subsequent lines. For example,
19466 echo This is some text\n\
19467 which is continued\n\
19468 onto several lines.\n
19471 produces the same output as
19474 echo This is some text\n
19475 echo which is continued\n
19476 echo onto several lines.\n
19480 @item output @var{expression}
19481 Print the value of @var{expression} and nothing but that value: no
19482 newlines, no @samp{$@var{nn} = }. The value is not entered in the
19483 value history either. @xref{Expressions, ,Expressions}, for more information
19486 @item output/@var{fmt} @var{expression}
19487 Print the value of @var{expression} in format @var{fmt}. You can use
19488 the same formats as for @code{print}. @xref{Output Formats,,Output
19489 Formats}, for more information.
19492 @item printf @var{template}, @var{expressions}@dots{}
19493 Print the values of one or more @var{expressions} under the control of
19494 the string @var{template}. To print several values, make
19495 @var{expressions} be a comma-separated list of individual expressions,
19496 which may be either numbers or pointers. Their values are printed as
19497 specified by @var{template}, exactly as a C program would do by
19498 executing the code below:
19501 printf (@var{template}, @var{expressions}@dots{});
19504 As in @code{C} @code{printf}, ordinary characters in @var{template}
19505 are printed verbatim, while @dfn{conversion specification} introduced
19506 by the @samp{%} character cause subsequent @var{expressions} to be
19507 evaluated, their values converted and formatted according to type and
19508 style information encoded in the conversion specifications, and then
19511 For example, you can print two values in hex like this:
19514 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
19517 @code{printf} supports all the standard @code{C} conversion
19518 specifications, including the flags and modifiers between the @samp{%}
19519 character and the conversion letter, with the following exceptions:
19523 The argument-ordering modifiers, such as @samp{2$}, are not supported.
19526 The modifier @samp{*} is not supported for specifying precision or
19530 The @samp{'} flag (for separation of digits into groups according to
19531 @code{LC_NUMERIC'}) is not supported.
19534 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
19538 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
19541 The conversion letters @samp{a} and @samp{A} are not supported.
19545 Note that the @samp{ll} type modifier is supported only if the
19546 underlying @code{C} implementation used to build @value{GDBN} supports
19547 the @code{long long int} type, and the @samp{L} type modifier is
19548 supported only if @code{long double} type is available.
19550 As in @code{C}, @code{printf} supports simple backslash-escape
19551 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
19552 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
19553 single character. Octal and hexadecimal escape sequences are not
19556 Additionally, @code{printf} supports conversion specifications for DFP
19557 (@dfn{Decimal Floating Point}) types using the following length modifiers
19558 together with a floating point specifier.
19563 @samp{H} for printing @code{Decimal32} types.
19566 @samp{D} for printing @code{Decimal64} types.
19569 @samp{DD} for printing @code{Decimal128} types.
19572 If the underlying @code{C} implementation used to build @value{GDBN} has
19573 support for the three length modifiers for DFP types, other modifiers
19574 such as width and precision will also be available for @value{GDBN} to use.
19576 In case there is no such @code{C} support, no additional modifiers will be
19577 available and the value will be printed in the standard way.
19579 Here's an example of printing DFP types using the above conversion letters:
19581 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
19587 @section Scripting @value{GDBN} using Python
19588 @cindex python scripting
19589 @cindex scripting with python
19591 You can script @value{GDBN} using the @uref{http://www.python.org/,
19592 Python programming language}. This feature is available only if
19593 @value{GDBN} was configured using @option{--with-python}.
19596 * Python Commands:: Accessing Python from @value{GDBN}.
19597 * Python API:: Accessing @value{GDBN} from Python.
19600 @node Python Commands
19601 @subsection Python Commands
19602 @cindex python commands
19603 @cindex commands to access python
19605 @value{GDBN} provides one command for accessing the Python interpreter,
19606 and one related setting:
19610 @item python @r{[}@var{code}@r{]}
19611 The @code{python} command can be used to evaluate Python code.
19613 If given an argument, the @code{python} command will evaluate the
19614 argument as a Python command. For example:
19617 (@value{GDBP}) python print 23
19621 If you do not provide an argument to @code{python}, it will act as a
19622 multi-line command, like @code{define}. In this case, the Python
19623 script is made up of subsequent command lines, given after the
19624 @code{python} command. This command list is terminated using a line
19625 containing @code{end}. For example:
19628 (@value{GDBP}) python
19630 End with a line saying just "end".
19636 @kindex maint set python print-stack
19637 @item maint set python print-stack
19638 By default, @value{GDBN} will print a stack trace when an error occurs
19639 in a Python script. This can be controlled using @code{maint set
19640 python print-stack}: if @code{on}, the default, then Python stack
19641 printing is enabled; if @code{off}, then Python stack printing is
19645 It is also possible to execute a Python script from the @value{GDBN}
19649 @item source @file{script-name}
19650 The script name must end with @samp{.py} and @value{GDBN} must be configured
19651 to recognize the script language based on filename extension using
19652 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
19654 @item python execfile ("script-name")
19655 This method is based on the @code{execfile} Python built-in function,
19656 and thus is always available.
19660 @subsection Python API
19662 @cindex programming in python
19664 @cindex python stdout
19665 @cindex python pagination
19666 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
19667 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
19668 A Python program which outputs to one of these streams may have its
19669 output interrupted by the user (@pxref{Screen Size}). In this
19670 situation, a Python @code{KeyboardInterrupt} exception is thrown.
19673 * Basic Python:: Basic Python Functions.
19674 * Exception Handling::
19675 * Auto-loading:: Automatically loading Python code.
19676 * Values From Inferior::
19677 * Types In Python:: Python representation of types.
19678 * Pretty Printing:: Pretty-printing values.
19679 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
19680 * Commands In Python:: Implementing new commands in Python.
19681 * Functions In Python:: Writing new convenience functions.
19682 * Objfiles In Python:: Object files.
19683 * Frames In Python:: Accessing inferior stack frames from Python.
19684 * Blocks In Python:: Accessing frame blocks from Python.
19685 * Symbols In Python:: Python representation of symbols.
19686 * Symbol Tables In Python:: Python representation of symbol tables.
19687 * Lazy Strings In Python:: Python representation of lazy strings.
19691 @subsubsection Basic Python
19693 @cindex python functions
19694 @cindex python module
19696 @value{GDBN} introduces a new Python module, named @code{gdb}. All
19697 methods and classes added by @value{GDBN} are placed in this module.
19698 @value{GDBN} automatically @code{import}s the @code{gdb} module for
19699 use in all scripts evaluated by the @code{python} command.
19701 @findex gdb.execute
19702 @defun execute command [from_tty]
19703 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
19704 If a GDB exception happens while @var{command} runs, it is
19705 translated as described in @ref{Exception Handling,,Exception Handling}.
19706 If no exceptions occur, this function returns @code{None}.
19708 @var{from_tty} specifies whether @value{GDBN} ought to consider this
19709 command as having originated from the user invoking it interactively.
19710 It must be a boolean value. If omitted, it defaults to @code{False}.
19713 @findex gdb.parameter
19714 @defun parameter parameter
19715 Return the value of a @value{GDBN} parameter. @var{parameter} is a
19716 string naming the parameter to look up; @var{parameter} may contain
19717 spaces if the parameter has a multi-part name. For example,
19718 @samp{print object} is a valid parameter name.
19720 If the named parameter does not exist, this function throws a
19721 @code{RuntimeError}. Otherwise, the parameter's value is converted to
19722 a Python value of the appropriate type, and returned.
19725 @findex gdb.history
19726 @defun history number
19727 Return a value from @value{GDBN}'s value history (@pxref{Value
19728 History}). @var{number} indicates which history element to return.
19729 If @var{number} is negative, then @value{GDBN} will take its absolute value
19730 and count backward from the last element (i.e., the most recent element) to
19731 find the value to return. If @var{number} is zero, then @value{GDBN} will
19732 return the most recent element. If the element specified by @var{number}
19733 doesn't exist in the value history, a @code{RuntimeError} exception will be
19736 If no exception is raised, the return value is always an instance of
19737 @code{gdb.Value} (@pxref{Values From Inferior}).
19740 @findex gdb.parse_and_eval
19741 @defun parse_and_eval expression
19742 Parse @var{expression} as an expression in the current language,
19743 evaluate it, and return the result as a @code{gdb.Value}.
19744 @var{expression} must be a string.
19746 This function can be useful when implementing a new command
19747 (@pxref{Commands In Python}), as it provides a way to parse the
19748 command's argument as an expression. It is also useful simply to
19749 compute values, for example, it is the only way to get the value of a
19750 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
19754 @defun write string
19755 Print a string to @value{GDBN}'s paginated standard output stream.
19756 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
19757 call this function.
19762 Flush @value{GDBN}'s paginated standard output stream. Flushing
19763 @code{sys.stdout} or @code{sys.stderr} will automatically call this
19767 @findex gdb.target_charset
19768 @defun target_charset
19769 Return the name of the current target character set (@pxref{Character
19770 Sets}). This differs from @code{gdb.parameter('target-charset')} in
19771 that @samp{auto} is never returned.
19774 @findex gdb.target_wide_charset
19775 @defun target_wide_charset
19776 Return the name of the current target wide character set
19777 (@pxref{Character Sets}). This differs from
19778 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
19782 @node Exception Handling
19783 @subsubsection Exception Handling
19784 @cindex python exceptions
19785 @cindex exceptions, python
19787 When executing the @code{python} command, Python exceptions
19788 uncaught within the Python code are translated to calls to
19789 @value{GDBN} error-reporting mechanism. If the command that called
19790 @code{python} does not handle the error, @value{GDBN} will
19791 terminate it and print an error message containing the Python
19792 exception name, the associated value, and the Python call stack
19793 backtrace at the point where the exception was raised. Example:
19796 (@value{GDBP}) python print foo
19797 Traceback (most recent call last):
19798 File "<string>", line 1, in <module>
19799 NameError: name 'foo' is not defined
19802 @value{GDBN} errors that happen in @value{GDBN} commands invoked by Python
19803 code are converted to Python @code{RuntimeError} exceptions. User
19804 interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
19805 prompt) is translated to a Python @code{KeyboardInterrupt}
19806 exception. If you catch these exceptions in your Python code, your
19807 exception handler will see @code{RuntimeError} or
19808 @code{KeyboardInterrupt} as the exception type, the @value{GDBN} error
19809 message as its value, and the Python call stack backtrace at the
19810 Python statement closest to where the @value{GDBN} error occured as the
19814 @subsubsection Auto-loading
19815 @cindex auto-loading, Python
19817 When a new object file is read (for example, due to the @code{file}
19818 command, or because the inferior has loaded a shared library),
19819 @value{GDBN} will look for a file named @file{@var{objfile}-gdb.py},
19820 where @var{objfile} is the object file's real name, formed by ensuring
19821 that the file name is absolute, following all symlinks, and resolving
19822 @code{.} and @code{..} components. If this file exists and is
19823 readable, @value{GDBN} will evaluate it as a Python script.
19825 If this file does not exist, and if the parameter
19826 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
19827 then @value{GDBN} will use for its each separated directory component
19828 @code{component} the file named @file{@code{component}/@var{real-name}}, where
19829 @var{real-name} is the object file's real name, as described above.
19831 Finally, if this file does not exist, then @value{GDBN} will look for
19832 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
19833 @var{data-directory} is @value{GDBN}'s data directory (available via
19834 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
19835 is the object file's real name, as described above.
19837 When reading an auto-loaded file, @value{GDBN} sets the ``current
19838 objfile''. This is available via the @code{gdb.current_objfile}
19839 function (@pxref{Objfiles In Python}). This can be useful for
19840 registering objfile-specific pretty-printers.
19842 The auto-loading feature is useful for supplying application-specific
19843 debugging commands and scripts. You can enable or disable this
19844 feature, and view its current state.
19847 @kindex maint set python auto-load
19848 @item maint set python auto-load [yes|no]
19849 Enable or disable the Python auto-loading feature.
19851 @kindex show python auto-load
19852 @item show python auto-load
19853 Show whether Python auto-loading is enabled or disabled.
19856 @value{GDBN} does not track which files it has already auto-loaded.
19857 So, your @samp{-gdb.py} file should take care to ensure that it may be
19858 evaluated multiple times without error.
19860 @node Values From Inferior
19861 @subsubsection Values From Inferior
19862 @cindex values from inferior, with Python
19863 @cindex python, working with values from inferior
19865 @cindex @code{gdb.Value}
19866 @value{GDBN} provides values it obtains from the inferior program in
19867 an object of type @code{gdb.Value}. @value{GDBN} uses this object
19868 for its internal bookkeeping of the inferior's values, and for
19869 fetching values when necessary.
19871 Inferior values that are simple scalars can be used directly in
19872 Python expressions that are valid for the value's data type. Here's
19873 an example for an integer or floating-point value @code{some_val}:
19880 As result of this, @code{bar} will also be a @code{gdb.Value} object
19881 whose values are of the same type as those of @code{some_val}.
19883 Inferior values that are structures or instances of some class can
19884 be accessed using the Python @dfn{dictionary syntax}. For example, if
19885 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
19886 can access its @code{foo} element with:
19889 bar = some_val['foo']
19892 Again, @code{bar} will also be a @code{gdb.Value} object.
19894 The following attributes are provided:
19897 @defivar Value address
19898 If this object is addressable, this read-only attribute holds a
19899 @code{gdb.Value} object representing the address. Otherwise,
19900 this attribute holds @code{None}.
19903 @cindex optimized out value in Python
19904 @defivar Value is_optimized_out
19905 This read-only boolean attribute is true if the compiler optimized out
19906 this value, thus it is not available for fetching from the inferior.
19909 @defivar Value type
19910 The type of this @code{gdb.Value}. The value of this attribute is a
19911 @code{gdb.Type} object.
19915 The following methods are provided:
19918 @defmethod Value cast type
19919 Return a new instance of @code{gdb.Value} that is the result of
19920 casting this instance to the type described by @var{type}, which must
19921 be a @code{gdb.Type} object. If the cast cannot be performed for some
19922 reason, this method throws an exception.
19925 @defmethod Value dereference
19926 For pointer data types, this method returns a new @code{gdb.Value} object
19927 whose contents is the object pointed to by the pointer. For example, if
19928 @code{foo} is a C pointer to an @code{int}, declared in your C program as
19935 then you can use the corresponding @code{gdb.Value} to access what
19936 @code{foo} points to like this:
19939 bar = foo.dereference ()
19942 The result @code{bar} will be a @code{gdb.Value} object holding the
19943 value pointed to by @code{foo}.
19946 @defmethod Value string @r{[}encoding@r{]} @r{[}errors@r{]} @r{[}length@r{]}
19947 If this @code{gdb.Value} represents a string, then this method
19948 converts the contents to a Python string. Otherwise, this method will
19949 throw an exception.
19951 Strings are recognized in a language-specific way; whether a given
19952 @code{gdb.Value} represents a string is determined by the current
19955 For C-like languages, a value is a string if it is a pointer to or an
19956 array of characters or ints. The string is assumed to be terminated
19957 by a zero of the appropriate width. However if the optional length
19958 argument is given, the string will be converted to that given length,
19959 ignoring any embedded zeros that the string may contain.
19961 If the optional @var{encoding} argument is given, it must be a string
19962 naming the encoding of the string in the @code{gdb.Value}, such as
19963 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
19964 the same encodings as the corresponding argument to Python's
19965 @code{string.decode} method, and the Python codec machinery will be used
19966 to convert the string. If @var{encoding} is not given, or if
19967 @var{encoding} is the empty string, then either the @code{target-charset}
19968 (@pxref{Character Sets}) will be used, or a language-specific encoding
19969 will be used, if the current language is able to supply one.
19971 The optional @var{errors} argument is the same as the corresponding
19972 argument to Python's @code{string.decode} method.
19974 If the optional @var{length} argument is given, the string will be
19975 fetched and converted to the given length.
19978 @defmethod Value lazy_string @r{[}encoding@r{]} @r{[}length@r{]}
19979 If this @code{gdb.Value} represents a string, then this method
19980 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
19981 In Python}). Otherwise, this method will throw an exception.
19983 If the optional @var{encoding} argument is given, it must be a string
19984 naming the encoding of the @code{gdb.LazyString}. Some examples are:
19985 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
19986 @var{encoding} argument is an encoding that @value{GDBN} does
19987 recognize, @value{GDBN} will raise an error.
19989 When a lazy string is printed, the @value{GDBN} encoding machinery is
19990 used to convert the string during printing. If the optional
19991 @var{encoding} argument is not provided, or is an empty string,
19992 @value{GDBN} will automatically select the encoding most suitable for
19993 the string type. For further information on encoding in @value{GDBN}
19994 please see @ref{Character Sets}.
19996 If the optional @var{length} argument is given, the string will be
19997 fetched and encoded to the length of characters specified. If
19998 the @var{length} argument is not provided, the string will be fetched
19999 and encoded until a null of appropriate width is found.
20003 @node Types In Python
20004 @subsubsection Types In Python
20005 @cindex types in Python
20006 @cindex Python, working with types
20009 @value{GDBN} represents types from the inferior using the class
20012 The following type-related functions are available in the @code{gdb}
20015 @findex gdb.lookup_type
20016 @defun lookup_type name [block]
20017 This function looks up a type by name. @var{name} is the name of the
20018 type to look up. It must be a string.
20020 If @var{block} is given, then @var{name} is looked up in that scope.
20021 Otherwise, it is searched for globally.
20023 Ordinarily, this function will return an instance of @code{gdb.Type}.
20024 If the named type cannot be found, it will throw an exception.
20027 An instance of @code{Type} has the following attributes:
20031 The type code for this type. The type code will be one of the
20032 @code{TYPE_CODE_} constants defined below.
20035 @defivar Type sizeof
20036 The size of this type, in target @code{char} units. Usually, a
20037 target's @code{char} type will be an 8-bit byte. However, on some
20038 unusual platforms, this type may have a different size.
20042 The tag name for this type. The tag name is the name after
20043 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
20044 languages have this concept. If this type has no tag name, then
20045 @code{None} is returned.
20049 The following methods are provided:
20052 @defmethod Type fields
20053 For structure and union types, this method returns the fields. Range
20054 types have two fields, the minimum and maximum values. Enum types
20055 have one field per enum constant. Function and method types have one
20056 field per parameter. The base types of C@t{++} classes are also
20057 represented as fields. If the type has no fields, or does not fit
20058 into one of these categories, an empty sequence will be returned.
20060 Each field is an object, with some pre-defined attributes:
20063 This attribute is not available for @code{static} fields (as in
20064 C@t{++} or Java). For non-@code{static} fields, the value is the bit
20065 position of the field.
20068 The name of the field, or @code{None} for anonymous fields.
20071 This is @code{True} if the field is artificial, usually meaning that
20072 it was provided by the compiler and not the user. This attribute is
20073 always provided, and is @code{False} if the field is not artificial.
20075 @item is_base_class
20076 This is @code{True} if the field represents a base class of a C@t{++}
20077 structure. This attribute is always provided, and is @code{False}
20078 if the field is not a base class of the type that is the argument of
20079 @code{fields}, or if that type was not a C@t{++} class.
20082 If the field is packed, or is a bitfield, then this will have a
20083 non-zero value, which is the size of the field in bits. Otherwise,
20084 this will be zero; in this case the field's size is given by its type.
20087 The type of the field. This is usually an instance of @code{Type},
20088 but it can be @code{None} in some situations.
20092 @defmethod Type const
20093 Return a new @code{gdb.Type} object which represents a
20094 @code{const}-qualified variant of this type.
20097 @defmethod Type volatile
20098 Return a new @code{gdb.Type} object which represents a
20099 @code{volatile}-qualified variant of this type.
20102 @defmethod Type unqualified
20103 Return a new @code{gdb.Type} object which represents an unqualified
20104 variant of this type. That is, the result is neither @code{const} nor
20108 @defmethod Type range
20109 Return a Python @code{Tuple} object that contains two elements: the
20110 low bound of the argument type and the high bound of that type. If
20111 the type does not have a range, @value{GDBN} will raise a
20112 @code{RuntimeError} exception.
20115 @defmethod Type reference
20116 Return a new @code{gdb.Type} object which represents a reference to this
20120 @defmethod Type pointer
20121 Return a new @code{gdb.Type} object which represents a pointer to this
20125 @defmethod Type strip_typedefs
20126 Return a new @code{gdb.Type} that represents the real type,
20127 after removing all layers of typedefs.
20130 @defmethod Type target
20131 Return a new @code{gdb.Type} object which represents the target type
20134 For a pointer type, the target type is the type of the pointed-to
20135 object. For an array type (meaning C-like arrays), the target type is
20136 the type of the elements of the array. For a function or method type,
20137 the target type is the type of the return value. For a complex type,
20138 the target type is the type of the elements. For a typedef, the
20139 target type is the aliased type.
20141 If the type does not have a target, this method will throw an
20145 @defmethod Type template_argument n [block]
20146 If this @code{gdb.Type} is an instantiation of a template, this will
20147 return a new @code{gdb.Type} which represents the type of the
20148 @var{n}th template argument.
20150 If this @code{gdb.Type} is not a template type, this will throw an
20151 exception. Ordinarily, only C@t{++} code will have template types.
20153 If @var{block} is given, then @var{name} is looked up in that scope.
20154 Otherwise, it is searched for globally.
20159 Each type has a code, which indicates what category this type falls
20160 into. The available type categories are represented by constants
20161 defined in the @code{gdb} module:
20164 @findex TYPE_CODE_PTR
20165 @findex gdb.TYPE_CODE_PTR
20166 @item TYPE_CODE_PTR
20167 The type is a pointer.
20169 @findex TYPE_CODE_ARRAY
20170 @findex gdb.TYPE_CODE_ARRAY
20171 @item TYPE_CODE_ARRAY
20172 The type is an array.
20174 @findex TYPE_CODE_STRUCT
20175 @findex gdb.TYPE_CODE_STRUCT
20176 @item TYPE_CODE_STRUCT
20177 The type is a structure.
20179 @findex TYPE_CODE_UNION
20180 @findex gdb.TYPE_CODE_UNION
20181 @item TYPE_CODE_UNION
20182 The type is a union.
20184 @findex TYPE_CODE_ENUM
20185 @findex gdb.TYPE_CODE_ENUM
20186 @item TYPE_CODE_ENUM
20187 The type is an enum.
20189 @findex TYPE_CODE_FLAGS
20190 @findex gdb.TYPE_CODE_FLAGS
20191 @item TYPE_CODE_FLAGS
20192 A bit flags type, used for things such as status registers.
20194 @findex TYPE_CODE_FUNC
20195 @findex gdb.TYPE_CODE_FUNC
20196 @item TYPE_CODE_FUNC
20197 The type is a function.
20199 @findex TYPE_CODE_INT
20200 @findex gdb.TYPE_CODE_INT
20201 @item TYPE_CODE_INT
20202 The type is an integer type.
20204 @findex TYPE_CODE_FLT
20205 @findex gdb.TYPE_CODE_FLT
20206 @item TYPE_CODE_FLT
20207 A floating point type.
20209 @findex TYPE_CODE_VOID
20210 @findex gdb.TYPE_CODE_VOID
20211 @item TYPE_CODE_VOID
20212 The special type @code{void}.
20214 @findex TYPE_CODE_SET
20215 @findex gdb.TYPE_CODE_SET
20216 @item TYPE_CODE_SET
20219 @findex TYPE_CODE_RANGE
20220 @findex gdb.TYPE_CODE_RANGE
20221 @item TYPE_CODE_RANGE
20222 A range type, that is, an integer type with bounds.
20224 @findex TYPE_CODE_STRING
20225 @findex gdb.TYPE_CODE_STRING
20226 @item TYPE_CODE_STRING
20227 A string type. Note that this is only used for certain languages with
20228 language-defined string types; C strings are not represented this way.
20230 @findex TYPE_CODE_BITSTRING
20231 @findex gdb.TYPE_CODE_BITSTRING
20232 @item TYPE_CODE_BITSTRING
20235 @findex TYPE_CODE_ERROR
20236 @findex gdb.TYPE_CODE_ERROR
20237 @item TYPE_CODE_ERROR
20238 An unknown or erroneous type.
20240 @findex TYPE_CODE_METHOD
20241 @findex gdb.TYPE_CODE_METHOD
20242 @item TYPE_CODE_METHOD
20243 A method type, as found in C@t{++} or Java.
20245 @findex TYPE_CODE_METHODPTR
20246 @findex gdb.TYPE_CODE_METHODPTR
20247 @item TYPE_CODE_METHODPTR
20248 A pointer-to-member-function.
20250 @findex TYPE_CODE_MEMBERPTR
20251 @findex gdb.TYPE_CODE_MEMBERPTR
20252 @item TYPE_CODE_MEMBERPTR
20253 A pointer-to-member.
20255 @findex TYPE_CODE_REF
20256 @findex gdb.TYPE_CODE_REF
20257 @item TYPE_CODE_REF
20260 @findex TYPE_CODE_CHAR
20261 @findex gdb.TYPE_CODE_CHAR
20262 @item TYPE_CODE_CHAR
20265 @findex TYPE_CODE_BOOL
20266 @findex gdb.TYPE_CODE_BOOL
20267 @item TYPE_CODE_BOOL
20270 @findex TYPE_CODE_COMPLEX
20271 @findex gdb.TYPE_CODE_COMPLEX
20272 @item TYPE_CODE_COMPLEX
20273 A complex float type.
20275 @findex TYPE_CODE_TYPEDEF
20276 @findex gdb.TYPE_CODE_TYPEDEF
20277 @item TYPE_CODE_TYPEDEF
20278 A typedef to some other type.
20280 @findex TYPE_CODE_NAMESPACE
20281 @findex gdb.TYPE_CODE_NAMESPACE
20282 @item TYPE_CODE_NAMESPACE
20283 A C@t{++} namespace.
20285 @findex TYPE_CODE_DECFLOAT
20286 @findex gdb.TYPE_CODE_DECFLOAT
20287 @item TYPE_CODE_DECFLOAT
20288 A decimal floating point type.
20290 @findex TYPE_CODE_INTERNAL_FUNCTION
20291 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
20292 @item TYPE_CODE_INTERNAL_FUNCTION
20293 A function internal to @value{GDBN}. This is the type used to represent
20294 convenience functions.
20297 @node Pretty Printing
20298 @subsubsection Pretty Printing
20300 @value{GDBN} provides a mechanism to allow pretty-printing of values
20301 using Python code. The pretty-printer API allows application-specific
20302 code to greatly simplify the display of complex objects. This
20303 mechanism works for both MI and the CLI.
20305 For example, here is how a C@t{++} @code{std::string} looks without a
20309 (@value{GDBP}) print s
20311 static npos = 4294967295,
20313 <std::allocator<char>> = @{
20314 <__gnu_cxx::new_allocator<char>> = @{<No data fields>@}, <No data fields>@},
20315 members of std::basic_string<char, std::char_traits<char>, std::allocator<char> >::_Alloc_hider:
20316 _M_p = 0x804a014 "abcd"
20321 After a pretty-printer for @code{std::string} has been installed, only
20322 the contents are printed:
20325 (@value{GDBP}) print s
20329 A pretty-printer is just an object that holds a value and implements a
20330 specific interface, defined here.
20332 @defop Operation {pretty printer} children (self)
20333 @value{GDBN} will call this method on a pretty-printer to compute the
20334 children of the pretty-printer's value.
20336 This method must return an object conforming to the Python iterator
20337 protocol. Each item returned by the iterator must be a tuple holding
20338 two elements. The first element is the ``name'' of the child; the
20339 second element is the child's value. The value can be any Python
20340 object which is convertible to a @value{GDBN} value.
20342 This method is optional. If it does not exist, @value{GDBN} will act
20343 as though the value has no children.
20346 @defop Operation {pretty printer} display_hint (self)
20347 The CLI may call this method and use its result to change the
20348 formatting of a value. The result will also be supplied to an MI
20349 consumer as a @samp{displayhint} attribute of the variable being
20352 This method is optional. If it does exist, this method must return a
20355 Some display hints are predefined by @value{GDBN}:
20359 Indicate that the object being printed is ``array-like''. The CLI
20360 uses this to respect parameters such as @code{set print elements} and
20361 @code{set print array}.
20364 Indicate that the object being printed is ``map-like'', and that the
20365 children of this value can be assumed to alternate between keys and
20369 Indicate that the object being printed is ``string-like''. If the
20370 printer's @code{to_string} method returns a Python string of some
20371 kind, then @value{GDBN} will call its internal language-specific
20372 string-printing function to format the string. For the CLI this means
20373 adding quotation marks, possibly escaping some characters, respecting
20374 @code{set print elements}, and the like.
20378 @defop Operation {pretty printer} to_string (self)
20379 @value{GDBN} will call this method to display the string
20380 representation of the value passed to the object's constructor.
20382 When printing from the CLI, if the @code{to_string} method exists,
20383 then @value{GDBN} will prepend its result to the values returned by
20384 @code{children}. Exactly how this formatting is done is dependent on
20385 the display hint, and may change as more hints are added. Also,
20386 depending on the print settings (@pxref{Print Settings}), the CLI may
20387 print just the result of @code{to_string} in a stack trace, omitting
20388 the result of @code{children}.
20390 If this method returns a string, it is printed verbatim.
20392 Otherwise, if this method returns an instance of @code{gdb.Value},
20393 then @value{GDBN} prints this value. This may result in a call to
20394 another pretty-printer.
20396 If instead the method returns a Python value which is convertible to a
20397 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
20398 the resulting value. Again, this may result in a call to another
20399 pretty-printer. Python scalars (integers, floats, and booleans) and
20400 strings are convertible to @code{gdb.Value}; other types are not.
20402 If the result is not one of these types, an exception is raised.
20405 @node Selecting Pretty-Printers
20406 @subsubsection Selecting Pretty-Printers
20408 The Python list @code{gdb.pretty_printers} contains an array of
20409 functions that have been registered via addition as a pretty-printer.
20410 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
20413 A function on one of these lists is passed a single @code{gdb.Value}
20414 argument and should return a pretty-printer object conforming to the
20415 interface definition above (@pxref{Pretty Printing}). If a function
20416 cannot create a pretty-printer for the value, it should return
20419 @value{GDBN} first checks the @code{pretty_printers} attribute of each
20420 @code{gdb.Objfile} and iteratively calls each function in the list for
20421 that @code{gdb.Objfile} until it receives a pretty-printer object.
20422 After these lists have been exhausted, it tries the global
20423 @code{gdb.pretty-printers} list, again calling each function until an
20424 object is returned.
20426 The order in which the objfiles are searched is not specified. For a
20427 given list, functions are always invoked from the head of the list,
20428 and iterated over sequentially until the end of the list, or a printer
20429 object is returned.
20431 Here is an example showing how a @code{std::string} printer might be
20435 class StdStringPrinter:
20436 "Print a std::string"
20438 def __init__ (self, val):
20441 def to_string (self):
20442 return self.val['_M_dataplus']['_M_p']
20444 def display_hint (self):
20448 And here is an example showing how a lookup function for the printer
20449 example above might be written.
20452 def str_lookup_function (val):
20454 lookup_tag = val.type.tag
20455 regex = re.compile ("^std::basic_string<char,.*>$")
20456 if lookup_tag == None:
20458 if regex.match (lookup_tag):
20459 return StdStringPrinter (val)
20464 The example lookup function extracts the value's type, and attempts to
20465 match it to a type that it can pretty-print. If it is a type the
20466 printer can pretty-print, it will return a printer object. If not, it
20467 returns @code{None}.
20469 We recommend that you put your core pretty-printers into a Python
20470 package. If your pretty-printers are for use with a library, we
20471 further recommend embedding a version number into the package name.
20472 This practice will enable @value{GDBN} to load multiple versions of
20473 your pretty-printers at the same time, because they will have
20476 You should write auto-loaded code (@pxref{Auto-loading}) such that it
20477 can be evaluated multiple times without changing its meaning. An
20478 ideal auto-load file will consist solely of @code{import}s of your
20479 printer modules, followed by a call to a register pretty-printers with
20480 the current objfile.
20482 Taken as a whole, this approach will scale nicely to multiple
20483 inferiors, each potentially using a different library version.
20484 Embedding a version number in the Python package name will ensure that
20485 @value{GDBN} is able to load both sets of printers simultaneously.
20486 Then, because the search for pretty-printers is done by objfile, and
20487 because your auto-loaded code took care to register your library's
20488 printers with a specific objfile, @value{GDBN} will find the correct
20489 printers for the specific version of the library used by each
20492 To continue the @code{std::string} example (@pxref{Pretty Printing}),
20493 this code might appear in @code{gdb.libstdcxx.v6}:
20496 def register_printers (objfile):
20497 objfile.pretty_printers.add (str_lookup_function)
20501 And then the corresponding contents of the auto-load file would be:
20504 import gdb.libstdcxx.v6
20505 gdb.libstdcxx.v6.register_printers (gdb.current_objfile ())
20508 @node Commands In Python
20509 @subsubsection Commands In Python
20511 @cindex commands in python
20512 @cindex python commands
20513 You can implement new @value{GDBN} CLI commands in Python. A CLI
20514 command is implemented using an instance of the @code{gdb.Command}
20515 class, most commonly using a subclass.
20517 @defmethod Command __init__ name @var{command_class} @r{[}@var{completer_class}@r{]} @r{[}@var{prefix}@r{]}
20518 The object initializer for @code{Command} registers the new command
20519 with @value{GDBN}. This initializer is normally invoked from the
20520 subclass' own @code{__init__} method.
20522 @var{name} is the name of the command. If @var{name} consists of
20523 multiple words, then the initial words are looked for as prefix
20524 commands. In this case, if one of the prefix commands does not exist,
20525 an exception is raised.
20527 There is no support for multi-line commands.
20529 @var{command_class} should be one of the @samp{COMMAND_} constants
20530 defined below. This argument tells @value{GDBN} how to categorize the
20531 new command in the help system.
20533 @var{completer_class} is an optional argument. If given, it should be
20534 one of the @samp{COMPLETE_} constants defined below. This argument
20535 tells @value{GDBN} how to perform completion for this command. If not
20536 given, @value{GDBN} will attempt to complete using the object's
20537 @code{complete} method (see below); if no such method is found, an
20538 error will occur when completion is attempted.
20540 @var{prefix} is an optional argument. If @code{True}, then the new
20541 command is a prefix command; sub-commands of this command may be
20544 The help text for the new command is taken from the Python
20545 documentation string for the command's class, if there is one. If no
20546 documentation string is provided, the default value ``This command is
20547 not documented.'' is used.
20550 @cindex don't repeat Python command
20551 @defmethod Command dont_repeat
20552 By default, a @value{GDBN} command is repeated when the user enters a
20553 blank line at the command prompt. A command can suppress this
20554 behavior by invoking the @code{dont_repeat} method. This is similar
20555 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
20558 @defmethod Command invoke argument from_tty
20559 This method is called by @value{GDBN} when this command is invoked.
20561 @var{argument} is a string. It is the argument to the command, after
20562 leading and trailing whitespace has been stripped.
20564 @var{from_tty} is a boolean argument. When true, this means that the
20565 command was entered by the user at the terminal; when false it means
20566 that the command came from elsewhere.
20568 If this method throws an exception, it is turned into a @value{GDBN}
20569 @code{error} call. Otherwise, the return value is ignored.
20572 @cindex completion of Python commands
20573 @defmethod Command complete text word
20574 This method is called by @value{GDBN} when the user attempts
20575 completion on this command. All forms of completion are handled by
20576 this method, that is, the @key{TAB} and @key{M-?} key bindings
20577 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
20580 The arguments @var{text} and @var{word} are both strings. @var{text}
20581 holds the complete command line up to the cursor's location.
20582 @var{word} holds the last word of the command line; this is computed
20583 using a word-breaking heuristic.
20585 The @code{complete} method can return several values:
20588 If the return value is a sequence, the contents of the sequence are
20589 used as the completions. It is up to @code{complete} to ensure that the
20590 contents actually do complete the word. A zero-length sequence is
20591 allowed, it means that there were no completions available. Only
20592 string elements of the sequence are used; other elements in the
20593 sequence are ignored.
20596 If the return value is one of the @samp{COMPLETE_} constants defined
20597 below, then the corresponding @value{GDBN}-internal completion
20598 function is invoked, and its result is used.
20601 All other results are treated as though there were no available
20606 When a new command is registered, it must be declared as a member of
20607 some general class of commands. This is used to classify top-level
20608 commands in the on-line help system; note that prefix commands are not
20609 listed under their own category but rather that of their top-level
20610 command. The available classifications are represented by constants
20611 defined in the @code{gdb} module:
20614 @findex COMMAND_NONE
20615 @findex gdb.COMMAND_NONE
20617 The command does not belong to any particular class. A command in
20618 this category will not be displayed in any of the help categories.
20620 @findex COMMAND_RUNNING
20621 @findex gdb.COMMAND_RUNNING
20622 @item COMMAND_RUNNING
20623 The command is related to running the inferior. For example,
20624 @code{start}, @code{step}, and @code{continue} are in this category.
20625 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
20626 commands in this category.
20628 @findex COMMAND_DATA
20629 @findex gdb.COMMAND_DATA
20631 The command is related to data or variables. For example,
20632 @code{call}, @code{find}, and @code{print} are in this category. Type
20633 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
20636 @findex COMMAND_STACK
20637 @findex gdb.COMMAND_STACK
20638 @item COMMAND_STACK
20639 The command has to do with manipulation of the stack. For example,
20640 @code{backtrace}, @code{frame}, and @code{return} are in this
20641 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
20642 list of commands in this category.
20644 @findex COMMAND_FILES
20645 @findex gdb.COMMAND_FILES
20646 @item COMMAND_FILES
20647 This class is used for file-related commands. For example,
20648 @code{file}, @code{list} and @code{section} are in this category.
20649 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
20650 commands in this category.
20652 @findex COMMAND_SUPPORT
20653 @findex gdb.COMMAND_SUPPORT
20654 @item COMMAND_SUPPORT
20655 This should be used for ``support facilities'', generally meaning
20656 things that are useful to the user when interacting with @value{GDBN},
20657 but not related to the state of the inferior. For example,
20658 @code{help}, @code{make}, and @code{shell} are in this category. Type
20659 @kbd{help support} at the @value{GDBN} prompt to see a list of
20660 commands in this category.
20662 @findex COMMAND_STATUS
20663 @findex gdb.COMMAND_STATUS
20664 @item COMMAND_STATUS
20665 The command is an @samp{info}-related command, that is, related to the
20666 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
20667 and @code{show} are in this category. Type @kbd{help status} at the
20668 @value{GDBN} prompt to see a list of commands in this category.
20670 @findex COMMAND_BREAKPOINTS
20671 @findex gdb.COMMAND_BREAKPOINTS
20672 @item COMMAND_BREAKPOINTS
20673 The command has to do with breakpoints. For example, @code{break},
20674 @code{clear}, and @code{delete} are in this category. Type @kbd{help
20675 breakpoints} at the @value{GDBN} prompt to see a list of commands in
20678 @findex COMMAND_TRACEPOINTS
20679 @findex gdb.COMMAND_TRACEPOINTS
20680 @item COMMAND_TRACEPOINTS
20681 The command has to do with tracepoints. For example, @code{trace},
20682 @code{actions}, and @code{tfind} are in this category. Type
20683 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
20684 commands in this category.
20686 @findex COMMAND_OBSCURE
20687 @findex gdb.COMMAND_OBSCURE
20688 @item COMMAND_OBSCURE
20689 The command is only used in unusual circumstances, or is not of
20690 general interest to users. For example, @code{checkpoint},
20691 @code{fork}, and @code{stop} are in this category. Type @kbd{help
20692 obscure} at the @value{GDBN} prompt to see a list of commands in this
20695 @findex COMMAND_MAINTENANCE
20696 @findex gdb.COMMAND_MAINTENANCE
20697 @item COMMAND_MAINTENANCE
20698 The command is only useful to @value{GDBN} maintainers. The
20699 @code{maintenance} and @code{flushregs} commands are in this category.
20700 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
20701 commands in this category.
20704 A new command can use a predefined completion function, either by
20705 specifying it via an argument at initialization, or by returning it
20706 from the @code{complete} method. These predefined completion
20707 constants are all defined in the @code{gdb} module:
20710 @findex COMPLETE_NONE
20711 @findex gdb.COMPLETE_NONE
20712 @item COMPLETE_NONE
20713 This constant means that no completion should be done.
20715 @findex COMPLETE_FILENAME
20716 @findex gdb.COMPLETE_FILENAME
20717 @item COMPLETE_FILENAME
20718 This constant means that filename completion should be performed.
20720 @findex COMPLETE_LOCATION
20721 @findex gdb.COMPLETE_LOCATION
20722 @item COMPLETE_LOCATION
20723 This constant means that location completion should be done.
20724 @xref{Specify Location}.
20726 @findex COMPLETE_COMMAND
20727 @findex gdb.COMPLETE_COMMAND
20728 @item COMPLETE_COMMAND
20729 This constant means that completion should examine @value{GDBN}
20732 @findex COMPLETE_SYMBOL
20733 @findex gdb.COMPLETE_SYMBOL
20734 @item COMPLETE_SYMBOL
20735 This constant means that completion should be done using symbol names
20739 The following code snippet shows how a trivial CLI command can be
20740 implemented in Python:
20743 class HelloWorld (gdb.Command):
20744 """Greet the whole world."""
20746 def __init__ (self):
20747 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
20749 def invoke (self, arg, from_tty):
20750 print "Hello, World!"
20755 The last line instantiates the class, and is necessary to trigger the
20756 registration of the command with @value{GDBN}. Depending on how the
20757 Python code is read into @value{GDBN}, you may need to import the
20758 @code{gdb} module explicitly.
20760 @node Functions In Python
20761 @subsubsection Writing new convenience functions
20763 @cindex writing convenience functions
20764 @cindex convenience functions in python
20765 @cindex python convenience functions
20766 @tindex gdb.Function
20768 You can implement new convenience functions (@pxref{Convenience Vars})
20769 in Python. A convenience function is an instance of a subclass of the
20770 class @code{gdb.Function}.
20772 @defmethod Function __init__ name
20773 The initializer for @code{Function} registers the new function with
20774 @value{GDBN}. The argument @var{name} is the name of the function,
20775 a string. The function will be visible to the user as a convenience
20776 variable of type @code{internal function}, whose name is the same as
20777 the given @var{name}.
20779 The documentation for the new function is taken from the documentation
20780 string for the new class.
20783 @defmethod Function invoke @var{*args}
20784 When a convenience function is evaluated, its arguments are converted
20785 to instances of @code{gdb.Value}, and then the function's
20786 @code{invoke} method is called. Note that @value{GDBN} does not
20787 predetermine the arity of convenience functions. Instead, all
20788 available arguments are passed to @code{invoke}, following the
20789 standard Python calling convention. In particular, a convenience
20790 function can have default values for parameters without ill effect.
20792 The return value of this method is used as its value in the enclosing
20793 expression. If an ordinary Python value is returned, it is converted
20794 to a @code{gdb.Value} following the usual rules.
20797 The following code snippet shows how a trivial convenience function can
20798 be implemented in Python:
20801 class Greet (gdb.Function):
20802 """Return string to greet someone.
20803 Takes a name as argument."""
20805 def __init__ (self):
20806 super (Greet, self).__init__ ("greet")
20808 def invoke (self, name):
20809 return "Hello, %s!" % name.string ()
20814 The last line instantiates the class, and is necessary to trigger the
20815 registration of the function with @value{GDBN}. Depending on how the
20816 Python code is read into @value{GDBN}, you may need to import the
20817 @code{gdb} module explicitly.
20819 @node Objfiles In Python
20820 @subsubsection Objfiles In Python
20822 @cindex objfiles in python
20823 @tindex gdb.Objfile
20825 @value{GDBN} loads symbols for an inferior from various
20826 symbol-containing files (@pxref{Files}). These include the primary
20827 executable file, any shared libraries used by the inferior, and any
20828 separate debug info files (@pxref{Separate Debug Files}).
20829 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
20831 The following objfile-related functions are available in the
20834 @findex gdb.current_objfile
20835 @defun current_objfile
20836 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
20837 sets the ``current objfile'' to the corresponding objfile. This
20838 function returns the current objfile. If there is no current objfile,
20839 this function returns @code{None}.
20842 @findex gdb.objfiles
20844 Return a sequence of all the objfiles current known to @value{GDBN}.
20845 @xref{Objfiles In Python}.
20848 Each objfile is represented by an instance of the @code{gdb.Objfile}
20851 @defivar Objfile filename
20852 The file name of the objfile as a string.
20855 @defivar Objfile pretty_printers
20856 The @code{pretty_printers} attribute is a list of functions. It is
20857 used to look up pretty-printers. A @code{Value} is passed to each
20858 function in order; if the function returns @code{None}, then the
20859 search continues. Otherwise, the return value should be an object
20860 which is used to format the value. @xref{Pretty Printing}, for more
20864 @node Frames In Python
20865 @subsubsection Accessing inferior stack frames from Python.
20867 @cindex frames in python
20868 When the debugged program stops, @value{GDBN} is able to analyze its call
20869 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
20870 represents a frame in the stack. A @code{gdb.Frame} object is only valid
20871 while its corresponding frame exists in the inferior's stack. If you try
20872 to use an invalid frame object, @value{GDBN} will throw a @code{RuntimeError}
20875 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
20879 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
20883 The following frame-related functions are available in the @code{gdb} module:
20885 @findex gdb.selected_frame
20886 @defun selected_frame
20887 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
20890 @defun frame_stop_reason_string reason
20891 Return a string explaining the reason why @value{GDBN} stopped unwinding
20892 frames, as expressed by the given @var{reason} code (an integer, see the
20893 @code{unwind_stop_reason} method further down in this section).
20896 A @code{gdb.Frame} object has the following methods:
20899 @defmethod Frame is_valid
20900 Returns true if the @code{gdb.Frame} object is valid, false if not.
20901 A frame object can become invalid if the frame it refers to doesn't
20902 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
20903 an exception if it is invalid at the time the method is called.
20906 @defmethod Frame name
20907 Returns the function name of the frame, or @code{None} if it can't be
20911 @defmethod Frame type
20912 Returns the type of the frame. The value can be one of
20913 @code{gdb.NORMAL_FRAME}, @code{gdb.DUMMY_FRAME}, @code{gdb.SIGTRAMP_FRAME}
20914 or @code{gdb.SENTINEL_FRAME}.
20917 @defmethod Frame unwind_stop_reason
20918 Return an integer representing the reason why it's not possible to find
20919 more frames toward the outermost frame. Use
20920 @code{gdb.frame_stop_reason_string} to convert the value returned by this
20921 function to a string.
20924 @defmethod Frame pc
20925 Returns the frame's resume address.
20928 @defmethod Frame block
20929 Return the frame's code block. @xref{Blocks In Python}.
20932 @defmethod Frame function
20933 Return the symbol for the function corresponding to this frame.
20934 @xref{Symbols In Python}.
20937 @defmethod Frame older
20938 Return the frame that called this frame.
20941 @defmethod Frame newer
20942 Return the frame called by this frame.
20945 @defmethod Frame find_sal
20946 Return the frame's symtab and line object.
20947 @xref{Symbol Tables In Python}.
20950 @defmethod Frame read_var variable @r{[}block@r{]}
20951 Return the value of @var{variable} in this frame. If the optional
20952 argument @var{block} is provided, search for the variable from that
20953 block; otherwise start at the frame's current block (which is
20954 determined by the frame's current program counter). @var{variable}
20955 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
20956 @code{gdb.Block} object.
20959 @defmethod Frame select
20960 Set this frame to be the selected frame. @xref{Stack, ,Examining the
20965 @node Blocks In Python
20966 @subsubsection Accessing frame blocks from Python.
20968 @cindex blocks in python
20971 Within each frame, @value{GDBN} maintains information on each block
20972 stored in that frame. These blocks are organized hierarchically, and
20973 are represented individually in Python as a @code{gdb.Block}.
20974 Please see @ref{Frames In Python}, for a more in-depth discussion on
20975 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
20976 detailed technical information on @value{GDBN}'s book-keeping of the
20979 The following block-related functions are available in the @code{gdb}
20982 @findex gdb.block_for_pc
20983 @defun block_for_pc pc
20984 Return the @code{gdb.Block} containing the given @var{pc} value. If the
20985 block cannot be found for the @var{pc} value specified, the function
20986 will return @code{None}.
20989 A @code{gdb.Block} object has the following attributes:
20992 @defivar Block start
20993 The start address of the block. This attribute is not writable.
20997 The end address of the block. This attribute is not writable.
21000 @defivar Block function
21001 The name of the block represented as a @code{gdb.Symbol}. If the
21002 block is not named, then this attribute holds @code{None}. This
21003 attribute is not writable.
21006 @defivar Block superblock
21007 The block containing this block. If this parent block does not exist,
21008 this attribute holds @code{None}. This attribute is not writable.
21012 @node Symbols In Python
21013 @subsubsection Python representation of Symbols.
21015 @cindex symbols in python
21018 @value{GDBN} represents every variable, function and type as an
21019 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
21020 Similarly, Python represents these symbols in @value{GDBN} with the
21021 @code{gdb.Symbol} object.
21023 The following symbol-related functions are available in the @code{gdb}
21026 @findex gdb.lookup_symbol
21027 @defun lookup_symbol name [block] [domain]
21028 This function searches for a symbol by name. The search scope can be
21029 restricted to the parameters defined in the optional domain and block
21032 @var{name} is the name of the symbol. It must be a string. The
21033 optional @var{block} argument restricts the search to symbols visible
21034 in that @var{block}. The @var{block} argument must be a
21035 @code{gdb.Block} object. The optional @var{domain} argument restricts
21036 the search to the domain type. The @var{domain} argument must be a
21037 domain constant defined in the @code{gdb} module and described later
21041 A @code{gdb.Symbol} object has the following attributes:
21044 @defivar Symbol symtab
21045 The symbol table in which the symbol appears. This attribute is
21046 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
21047 Python}. This attribute is not writable.
21050 @defivar Symbol name
21051 The name of the symbol as a string. This attribute is not writable.
21054 @defivar Symbol linkage_name
21055 The name of the symbol, as used by the linker (i.e., may be mangled).
21056 This attribute is not writable.
21059 @defivar Symbol print_name
21060 The name of the symbol in a form suitable for output. This is either
21061 @code{name} or @code{linkage_name}, depending on whether the user
21062 asked @value{GDBN} to display demangled or mangled names.
21065 @defivar Symbol addr_class
21066 The address class of the symbol. This classifies how to find the value
21067 of a symbol. Each address class is a constant defined in the
21068 @code{gdb} module and described later in this chapter.
21071 @defivar Symbol is_argument
21072 @code{True} if the symbol is an argument of a function.
21075 @defivar Symbol is_constant
21076 @code{True} if the symbol is a constant.
21079 @defivar Symbol is_function
21080 @code{True} if the symbol is a function or a method.
21083 @defivar Symbol is_variable
21084 @code{True} if the symbol is a variable.
21088 The available domain categories in @code{gdb.Symbol} are represented
21089 as constants in the @code{gdb} module:
21092 @findex SYMBOL_UNDEF_DOMAIN
21093 @findex gdb.SYMBOL_UNDEF_DOMAIN
21094 @item SYMBOL_UNDEF_DOMAIN
21095 This is used when a domain has not been discovered or none of the
21096 following domains apply. This usually indicates an error either
21097 in the symbol information or in @value{GDBN}'s handling of symbols.
21098 @findex SYMBOL_VAR_DOMAIN
21099 @findex gdb.SYMBOL_VAR_DOMAIN
21100 @item SYMBOL_VAR_DOMAIN
21101 This domain contains variables, function names, typedef names and enum
21103 @findex SYMBOL_STRUCT_DOMAIN
21104 @findex gdb.SYMBOL_STRUCT_DOMAIN
21105 @item SYMBOL_STRUCT_DOMAIN
21106 This domain holds struct, union and enum type names.
21107 @findex SYMBOL_LABEL_DOMAIN
21108 @findex gdb.SYMBOL_LABEL_DOMAIN
21109 @item SYMBOL_LABEL_DOMAIN
21110 This domain contains names of labels (for gotos).
21111 @findex SYMBOL_VARIABLES_DOMAIN
21112 @findex gdb.SYMBOL_VARIABLES_DOMAIN
21113 @item SYMBOL_VARIABLES_DOMAIN
21114 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
21115 contains everything minus functions and types.
21116 @findex SYMBOL_FUNCTIONS_DOMAIN
21117 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
21118 @item SYMBOL_FUNCTION_DOMAIN
21119 This domain contains all functions.
21120 @findex SYMBOL_TYPES_DOMAIN
21121 @findex gdb.SYMBOL_TYPES_DOMAIN
21122 @item SYMBOL_TYPES_DOMAIN
21123 This domain contains all types.
21126 The available address class categories in @code{gdb.Symbol} are represented
21127 as constants in the @code{gdb} module:
21130 @findex SYMBOL_LOC_UNDEF
21131 @findex gdb.SYMBOL_LOC_UNDEF
21132 @item SYMBOL_LOC_UNDEF
21133 If this is returned by address class, it indicates an error either in
21134 the symbol information or in @value{GDBN}'s handling of symbols.
21135 @findex SYMBOL_LOC_CONST
21136 @findex gdb.SYMBOL_LOC_CONST
21137 @item SYMBOL_LOC_CONST
21138 Value is constant int.
21139 @findex SYMBOL_LOC_STATIC
21140 @findex gdb.SYMBOL_LOC_STATIC
21141 @item SYMBOL_LOC_STATIC
21142 Value is at a fixed address.
21143 @findex SYMBOL_LOC_REGISTER
21144 @findex gdb.SYMBOL_LOC_REGISTER
21145 @item SYMBOL_LOC_REGISTER
21146 Value is in a register.
21147 @findex SYMBOL_LOC_ARG
21148 @findex gdb.SYMBOL_LOC_ARG
21149 @item SYMBOL_LOC_ARG
21150 Value is an argument. This value is at the offset stored within the
21151 symbol inside the frame's argument list.
21152 @findex SYMBOL_LOC_REF_ARG
21153 @findex gdb.SYMBOL_LOC_REF_ARG
21154 @item SYMBOL_LOC_REF_ARG
21155 Value address is stored in the frame's argument list. Just like
21156 @code{LOC_ARG} except that the value's address is stored at the
21157 offset, not the value itself.
21158 @findex SYMBOL_LOC_REGPARM_ADDR
21159 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
21160 @item SYMBOL_LOC_REGPARM_ADDR
21161 Value is a specified register. Just like @code{LOC_REGISTER} except
21162 the register holds the address of the argument instead of the argument
21164 @findex SYMBOL_LOC_LOCAL
21165 @findex gdb.SYMBOL_LOC_LOCAL
21166 @item SYMBOL_LOC_LOCAL
21167 Value is a local variable.
21168 @findex SYMBOL_LOC_TYPEDEF
21169 @findex gdb.SYMBOL_LOC_TYPEDEF
21170 @item SYMBOL_LOC_TYPEDEF
21171 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
21173 @findex SYMBOL_LOC_BLOCK
21174 @findex gdb.SYMBOL_LOC_BLOCK
21175 @item SYMBOL_LOC_BLOCK
21177 @findex SYMBOL_LOC_CONST_BYTES
21178 @findex gdb.SYMBOL_LOC_CONST_BYTES
21179 @item SYMBOL_LOC_CONST_BYTES
21180 Value is a byte-sequence.
21181 @findex SYMBOL_LOC_UNRESOLVED
21182 @findex gdb.SYMBOL_LOC_UNRESOLVED
21183 @item SYMBOL_LOC_UNRESOLVED
21184 Value is at a fixed address, but the address of the variable has to be
21185 determined from the minimal symbol table whenever the variable is
21187 @findex SYMBOL_LOC_OPTIMIZED_OUT
21188 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
21189 @item SYMBOL_LOC_OPTIMIZED_OUT
21190 The value does not actually exist in the program.
21191 @findex SYMBOL_LOC_COMPUTED
21192 @findex gdb.SYMBOL_LOC_COMPUTED
21193 @item SYMBOL_LOC_COMPUTED
21194 The value's address is a computed location.
21197 @node Symbol Tables In Python
21198 @subsubsection Symbol table representation in Python.
21200 @cindex symbol tables in python
21202 @tindex gdb.Symtab_and_line
21204 Access to symbol table data maintained by @value{GDBN} on the inferior
21205 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
21206 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
21207 from the @code{find_sal} method in @code{gdb.Frame} object.
21208 @xref{Frames In Python}.
21210 For more information on @value{GDBN}'s symbol table management, see
21211 @ref{Symbols, ,Examining the Symbol Table}, for more information.
21213 A @code{gdb.Symtab_and_line} object has the following attributes:
21216 @defivar Symtab_and_line symtab
21217 The symbol table object (@code{gdb.Symtab}) for this frame.
21218 This attribute is not writable.
21221 @defivar Symtab_and_line pc
21222 Indicates the current program counter address. This attribute is not
21226 @defivar Symtab_and_line line
21227 Indicates the current line number for this object. This
21228 attribute is not writable.
21232 A @code{gdb.Symtab} object has the following attributes:
21235 @defivar Symtab filename
21236 The symbol table's source filename. This attribute is not writable.
21239 @defivar Symtab objfile
21240 The symbol table's backing object file. @xref{Objfiles In Python}.
21241 This attribute is not writable.
21245 The following methods are provided:
21248 @defmethod Symtab fullname
21249 Return the symbol table's source absolute file name.
21253 @node Lazy Strings In Python
21254 @subsubsection Python representation of lazy strings.
21256 @cindex lazy strings in python
21257 @tindex gdb.LazyString
21259 A @dfn{lazy string} is a string whose contents is not retrieved or
21260 encoded until it is needed.
21262 A @code{gdb.LazyString} is represented in @value{GDBN} as an
21263 @code{address} that points to a region of memory, an @code{encoding}
21264 that will be used to encode that region of memory, and a @code{length}
21265 to delimit the region of memory that represents the string. The
21266 difference between a @code{gdb.LazyString} and a string wrapped within
21267 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
21268 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
21269 retrieved and encoded during printing, while a @code{gdb.Value}
21270 wrapping a string is immediately retrieved and encoded on creation.
21272 A @code{gdb.LazyString} object has the following functions:
21274 @defmethod LazyString value
21275 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
21276 will point to the string in memory, but will lose all the delayed
21277 retrieval, encoding and handling that @value{GDBN} applies to a
21278 @code{gdb.LazyString}.
21281 @defivar LazyString address
21282 This attribute holds the address of the string. This attribute is not
21286 @defivar LazyString length
21287 This attribute holds the length of the string in characters. If the
21288 length is -1, then the string will be fetched and encoded up to the
21289 first null of appropriate width. This attribute is not writable.
21292 @defivar LazyString encoding
21293 This attribute holds the encoding that will be applied to the string
21294 when the string is printed by @value{GDBN}. If the encoding is not
21295 set, or contains an empty string, then @value{GDBN} will select the
21296 most appropriate encoding when the string is printed. This attribute
21300 @defivar LazyString type
21301 This attribute holds the type that is represented by the lazy string's
21302 type. For a lazy string this will always be a pointer type. To
21303 resolve this to the lazy string's character type, use the type's
21304 @code{target} method. @xref{Types In Python}. This attribute is not
21309 @chapter Command Interpreters
21310 @cindex command interpreters
21312 @value{GDBN} supports multiple command interpreters, and some command
21313 infrastructure to allow users or user interface writers to switch
21314 between interpreters or run commands in other interpreters.
21316 @value{GDBN} currently supports two command interpreters, the console
21317 interpreter (sometimes called the command-line interpreter or @sc{cli})
21318 and the machine interface interpreter (or @sc{gdb/mi}). This manual
21319 describes both of these interfaces in great detail.
21321 By default, @value{GDBN} will start with the console interpreter.
21322 However, the user may choose to start @value{GDBN} with another
21323 interpreter by specifying the @option{-i} or @option{--interpreter}
21324 startup options. Defined interpreters include:
21328 @cindex console interpreter
21329 The traditional console or command-line interpreter. This is the most often
21330 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
21331 @value{GDBN} will use this interpreter.
21334 @cindex mi interpreter
21335 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
21336 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
21337 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
21341 @cindex mi2 interpreter
21342 The current @sc{gdb/mi} interface.
21345 @cindex mi1 interpreter
21346 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
21350 @cindex invoke another interpreter
21351 The interpreter being used by @value{GDBN} may not be dynamically
21352 switched at runtime. Although possible, this could lead to a very
21353 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
21354 enters the command "interpreter-set console" in a console view,
21355 @value{GDBN} would switch to using the console interpreter, rendering
21356 the IDE inoperable!
21358 @kindex interpreter-exec
21359 Although you may only choose a single interpreter at startup, you may execute
21360 commands in any interpreter from the current interpreter using the appropriate
21361 command. If you are running the console interpreter, simply use the
21362 @code{interpreter-exec} command:
21365 interpreter-exec mi "-data-list-register-names"
21368 @sc{gdb/mi} has a similar command, although it is only available in versions of
21369 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
21372 @chapter @value{GDBN} Text User Interface
21374 @cindex Text User Interface
21377 * TUI Overview:: TUI overview
21378 * TUI Keys:: TUI key bindings
21379 * TUI Single Key Mode:: TUI single key mode
21380 * TUI Commands:: TUI-specific commands
21381 * TUI Configuration:: TUI configuration variables
21384 The @value{GDBN} Text User Interface (TUI) is a terminal
21385 interface which uses the @code{curses} library to show the source
21386 file, the assembly output, the program registers and @value{GDBN}
21387 commands in separate text windows. The TUI mode is supported only
21388 on platforms where a suitable version of the @code{curses} library
21391 @pindex @value{GDBTUI}
21392 The TUI mode is enabled by default when you invoke @value{GDBN} as
21393 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
21394 You can also switch in and out of TUI mode while @value{GDBN} runs by
21395 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
21396 @xref{TUI Keys, ,TUI Key Bindings}.
21399 @section TUI Overview
21401 In TUI mode, @value{GDBN} can display several text windows:
21405 This window is the @value{GDBN} command window with the @value{GDBN}
21406 prompt and the @value{GDBN} output. The @value{GDBN} input is still
21407 managed using readline.
21410 The source window shows the source file of the program. The current
21411 line and active breakpoints are displayed in this window.
21414 The assembly window shows the disassembly output of the program.
21417 This window shows the processor registers. Registers are highlighted
21418 when their values change.
21421 The source and assembly windows show the current program position
21422 by highlighting the current line and marking it with a @samp{>} marker.
21423 Breakpoints are indicated with two markers. The first marker
21424 indicates the breakpoint type:
21428 Breakpoint which was hit at least once.
21431 Breakpoint which was never hit.
21434 Hardware breakpoint which was hit at least once.
21437 Hardware breakpoint which was never hit.
21440 The second marker indicates whether the breakpoint is enabled or not:
21444 Breakpoint is enabled.
21447 Breakpoint is disabled.
21450 The source, assembly and register windows are updated when the current
21451 thread changes, when the frame changes, or when the program counter
21454 These windows are not all visible at the same time. The command
21455 window is always visible. The others can be arranged in several
21466 source and assembly,
21469 source and registers, or
21472 assembly and registers.
21475 A status line above the command window shows the following information:
21479 Indicates the current @value{GDBN} target.
21480 (@pxref{Targets, ,Specifying a Debugging Target}).
21483 Gives the current process or thread number.
21484 When no process is being debugged, this field is set to @code{No process}.
21487 Gives the current function name for the selected frame.
21488 The name is demangled if demangling is turned on (@pxref{Print Settings}).
21489 When there is no symbol corresponding to the current program counter,
21490 the string @code{??} is displayed.
21493 Indicates the current line number for the selected frame.
21494 When the current line number is not known, the string @code{??} is displayed.
21497 Indicates the current program counter address.
21501 @section TUI Key Bindings
21502 @cindex TUI key bindings
21504 The TUI installs several key bindings in the readline keymaps
21505 (@pxref{Command Line Editing}). The following key bindings
21506 are installed for both TUI mode and the @value{GDBN} standard mode.
21515 Enter or leave the TUI mode. When leaving the TUI mode,
21516 the curses window management stops and @value{GDBN} operates using
21517 its standard mode, writing on the terminal directly. When reentering
21518 the TUI mode, control is given back to the curses windows.
21519 The screen is then refreshed.
21523 Use a TUI layout with only one window. The layout will
21524 either be @samp{source} or @samp{assembly}. When the TUI mode
21525 is not active, it will switch to the TUI mode.
21527 Think of this key binding as the Emacs @kbd{C-x 1} binding.
21531 Use a TUI layout with at least two windows. When the current
21532 layout already has two windows, the next layout with two windows is used.
21533 When a new layout is chosen, one window will always be common to the
21534 previous layout and the new one.
21536 Think of it as the Emacs @kbd{C-x 2} binding.
21540 Change the active window. The TUI associates several key bindings
21541 (like scrolling and arrow keys) with the active window. This command
21542 gives the focus to the next TUI window.
21544 Think of it as the Emacs @kbd{C-x o} binding.
21548 Switch in and out of the TUI SingleKey mode that binds single
21549 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
21552 The following key bindings only work in the TUI mode:
21557 Scroll the active window one page up.
21561 Scroll the active window one page down.
21565 Scroll the active window one line up.
21569 Scroll the active window one line down.
21573 Scroll the active window one column left.
21577 Scroll the active window one column right.
21581 Refresh the screen.
21584 Because the arrow keys scroll the active window in the TUI mode, they
21585 are not available for their normal use by readline unless the command
21586 window has the focus. When another window is active, you must use
21587 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
21588 and @kbd{C-f} to control the command window.
21590 @node TUI Single Key Mode
21591 @section TUI Single Key Mode
21592 @cindex TUI single key mode
21594 The TUI also provides a @dfn{SingleKey} mode, which binds several
21595 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
21596 switch into this mode, where the following key bindings are used:
21599 @kindex c @r{(SingleKey TUI key)}
21603 @kindex d @r{(SingleKey TUI key)}
21607 @kindex f @r{(SingleKey TUI key)}
21611 @kindex n @r{(SingleKey TUI key)}
21615 @kindex q @r{(SingleKey TUI key)}
21617 exit the SingleKey mode.
21619 @kindex r @r{(SingleKey TUI key)}
21623 @kindex s @r{(SingleKey TUI key)}
21627 @kindex u @r{(SingleKey TUI key)}
21631 @kindex v @r{(SingleKey TUI key)}
21635 @kindex w @r{(SingleKey TUI key)}
21640 Other keys temporarily switch to the @value{GDBN} command prompt.
21641 The key that was pressed is inserted in the editing buffer so that
21642 it is possible to type most @value{GDBN} commands without interaction
21643 with the TUI SingleKey mode. Once the command is entered the TUI
21644 SingleKey mode is restored. The only way to permanently leave
21645 this mode is by typing @kbd{q} or @kbd{C-x s}.
21649 @section TUI-specific Commands
21650 @cindex TUI commands
21652 The TUI has specific commands to control the text windows.
21653 These commands are always available, even when @value{GDBN} is not in
21654 the TUI mode. When @value{GDBN} is in the standard mode, most
21655 of these commands will automatically switch to the TUI mode.
21657 Note that if @value{GDBN}'s @code{stdout} is not connected to a
21658 terminal, or @value{GDBN} has been started with the machine interface
21659 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
21660 these commands will fail with an error, because it would not be
21661 possible or desirable to enable curses window management.
21666 List and give the size of all displayed windows.
21670 Display the next layout.
21673 Display the previous layout.
21676 Display the source window only.
21679 Display the assembly window only.
21682 Display the source and assembly window.
21685 Display the register window together with the source or assembly window.
21689 Make the next window active for scrolling.
21692 Make the previous window active for scrolling.
21695 Make the source window active for scrolling.
21698 Make the assembly window active for scrolling.
21701 Make the register window active for scrolling.
21704 Make the command window active for scrolling.
21708 Refresh the screen. This is similar to typing @kbd{C-L}.
21710 @item tui reg float
21712 Show the floating point registers in the register window.
21714 @item tui reg general
21715 Show the general registers in the register window.
21718 Show the next register group. The list of register groups as well as
21719 their order is target specific. The predefined register groups are the
21720 following: @code{general}, @code{float}, @code{system}, @code{vector},
21721 @code{all}, @code{save}, @code{restore}.
21723 @item tui reg system
21724 Show the system registers in the register window.
21728 Update the source window and the current execution point.
21730 @item winheight @var{name} +@var{count}
21731 @itemx winheight @var{name} -@var{count}
21733 Change the height of the window @var{name} by @var{count}
21734 lines. Positive counts increase the height, while negative counts
21737 @item tabset @var{nchars}
21739 Set the width of tab stops to be @var{nchars} characters.
21742 @node TUI Configuration
21743 @section TUI Configuration Variables
21744 @cindex TUI configuration variables
21746 Several configuration variables control the appearance of TUI windows.
21749 @item set tui border-kind @var{kind}
21750 @kindex set tui border-kind
21751 Select the border appearance for the source, assembly and register windows.
21752 The possible values are the following:
21755 Use a space character to draw the border.
21758 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
21761 Use the Alternate Character Set to draw the border. The border is
21762 drawn using character line graphics if the terminal supports them.
21765 @item set tui border-mode @var{mode}
21766 @kindex set tui border-mode
21767 @itemx set tui active-border-mode @var{mode}
21768 @kindex set tui active-border-mode
21769 Select the display attributes for the borders of the inactive windows
21770 or the active window. The @var{mode} can be one of the following:
21773 Use normal attributes to display the border.
21779 Use reverse video mode.
21782 Use half bright mode.
21784 @item half-standout
21785 Use half bright and standout mode.
21788 Use extra bright or bold mode.
21790 @item bold-standout
21791 Use extra bright or bold and standout mode.
21796 @chapter Using @value{GDBN} under @sc{gnu} Emacs
21799 @cindex @sc{gnu} Emacs
21800 A special interface allows you to use @sc{gnu} Emacs to view (and
21801 edit) the source files for the program you are debugging with
21804 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
21805 executable file you want to debug as an argument. This command starts
21806 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
21807 created Emacs buffer.
21808 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
21810 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
21815 All ``terminal'' input and output goes through an Emacs buffer, called
21818 This applies both to @value{GDBN} commands and their output, and to the input
21819 and output done by the program you are debugging.
21821 This is useful because it means that you can copy the text of previous
21822 commands and input them again; you can even use parts of the output
21825 All the facilities of Emacs' Shell mode are available for interacting
21826 with your program. In particular, you can send signals the usual
21827 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
21831 @value{GDBN} displays source code through Emacs.
21833 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
21834 source file for that frame and puts an arrow (@samp{=>}) at the
21835 left margin of the current line. Emacs uses a separate buffer for
21836 source display, and splits the screen to show both your @value{GDBN} session
21839 Explicit @value{GDBN} @code{list} or search commands still produce output as
21840 usual, but you probably have no reason to use them from Emacs.
21843 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
21844 a graphical mode, enabled by default, which provides further buffers
21845 that can control the execution and describe the state of your program.
21846 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
21848 If you specify an absolute file name when prompted for the @kbd{M-x
21849 gdb} argument, then Emacs sets your current working directory to where
21850 your program resides. If you only specify the file name, then Emacs
21851 sets your current working directory to to the directory associated
21852 with the previous buffer. In this case, @value{GDBN} may find your
21853 program by searching your environment's @code{PATH} variable, but on
21854 some operating systems it might not find the source. So, although the
21855 @value{GDBN} input and output session proceeds normally, the auxiliary
21856 buffer does not display the current source and line of execution.
21858 The initial working directory of @value{GDBN} is printed on the top
21859 line of the GUD buffer and this serves as a default for the commands
21860 that specify files for @value{GDBN} to operate on. @xref{Files,
21861 ,Commands to Specify Files}.
21863 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
21864 need to call @value{GDBN} by a different name (for example, if you
21865 keep several configurations around, with different names) you can
21866 customize the Emacs variable @code{gud-gdb-command-name} to run the
21869 In the GUD buffer, you can use these special Emacs commands in
21870 addition to the standard Shell mode commands:
21874 Describe the features of Emacs' GUD Mode.
21877 Execute to another source line, like the @value{GDBN} @code{step} command; also
21878 update the display window to show the current file and location.
21881 Execute to next source line in this function, skipping all function
21882 calls, like the @value{GDBN} @code{next} command. Then update the display window
21883 to show the current file and location.
21886 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
21887 display window accordingly.
21890 Execute until exit from the selected stack frame, like the @value{GDBN}
21891 @code{finish} command.
21894 Continue execution of your program, like the @value{GDBN} @code{continue}
21898 Go up the number of frames indicated by the numeric argument
21899 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
21900 like the @value{GDBN} @code{up} command.
21903 Go down the number of frames indicated by the numeric argument, like the
21904 @value{GDBN} @code{down} command.
21907 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
21908 tells @value{GDBN} to set a breakpoint on the source line point is on.
21910 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
21911 separate frame which shows a backtrace when the GUD buffer is current.
21912 Move point to any frame in the stack and type @key{RET} to make it
21913 become the current frame and display the associated source in the
21914 source buffer. Alternatively, click @kbd{Mouse-2} to make the
21915 selected frame become the current one. In graphical mode, the
21916 speedbar displays watch expressions.
21918 If you accidentally delete the source-display buffer, an easy way to get
21919 it back is to type the command @code{f} in the @value{GDBN} buffer, to
21920 request a frame display; when you run under Emacs, this recreates
21921 the source buffer if necessary to show you the context of the current
21924 The source files displayed in Emacs are in ordinary Emacs buffers
21925 which are visiting the source files in the usual way. You can edit
21926 the files with these buffers if you wish; but keep in mind that @value{GDBN}
21927 communicates with Emacs in terms of line numbers. If you add or
21928 delete lines from the text, the line numbers that @value{GDBN} knows cease
21929 to correspond properly with the code.
21931 A more detailed description of Emacs' interaction with @value{GDBN} is
21932 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
21935 @c The following dropped because Epoch is nonstandard. Reactivate
21936 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
21938 @kindex Emacs Epoch environment
21942 Version 18 of @sc{gnu} Emacs has a built-in window system
21943 called the @code{epoch}
21944 environment. Users of this environment can use a new command,
21945 @code{inspect} which performs identically to @code{print} except that
21946 each value is printed in its own window.
21951 @chapter The @sc{gdb/mi} Interface
21953 @unnumberedsec Function and Purpose
21955 @cindex @sc{gdb/mi}, its purpose
21956 @sc{gdb/mi} is a line based machine oriented text interface to
21957 @value{GDBN} and is activated by specifying using the
21958 @option{--interpreter} command line option (@pxref{Mode Options}). It
21959 is specifically intended to support the development of systems which
21960 use the debugger as just one small component of a larger system.
21962 This chapter is a specification of the @sc{gdb/mi} interface. It is written
21963 in the form of a reference manual.
21965 Note that @sc{gdb/mi} is still under construction, so some of the
21966 features described below are incomplete and subject to change
21967 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
21969 @unnumberedsec Notation and Terminology
21971 @cindex notational conventions, for @sc{gdb/mi}
21972 This chapter uses the following notation:
21976 @code{|} separates two alternatives.
21979 @code{[ @var{something} ]} indicates that @var{something} is optional:
21980 it may or may not be given.
21983 @code{( @var{group} )*} means that @var{group} inside the parentheses
21984 may repeat zero or more times.
21987 @code{( @var{group} )+} means that @var{group} inside the parentheses
21988 may repeat one or more times.
21991 @code{"@var{string}"} means a literal @var{string}.
21995 @heading Dependencies
21999 * GDB/MI General Design::
22000 * GDB/MI Command Syntax::
22001 * GDB/MI Compatibility with CLI::
22002 * GDB/MI Development and Front Ends::
22003 * GDB/MI Output Records::
22004 * GDB/MI Simple Examples::
22005 * GDB/MI Command Description Format::
22006 * GDB/MI Breakpoint Commands::
22007 * GDB/MI Program Context::
22008 * GDB/MI Thread Commands::
22009 * GDB/MI Program Execution::
22010 * GDB/MI Stack Manipulation::
22011 * GDB/MI Variable Objects::
22012 * GDB/MI Data Manipulation::
22013 * GDB/MI Tracepoint Commands::
22014 * GDB/MI Symbol Query::
22015 * GDB/MI File Commands::
22017 * GDB/MI Kod Commands::
22018 * GDB/MI Memory Overlay Commands::
22019 * GDB/MI Signal Handling Commands::
22021 * GDB/MI Target Manipulation::
22022 * GDB/MI File Transfer Commands::
22023 * GDB/MI Miscellaneous Commands::
22026 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22027 @node GDB/MI General Design
22028 @section @sc{gdb/mi} General Design
22029 @cindex GDB/MI General Design
22031 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
22032 parts---commands sent to @value{GDBN}, responses to those commands
22033 and notifications. Each command results in exactly one response,
22034 indicating either successful completion of the command, or an error.
22035 For the commands that do not resume the target, the response contains the
22036 requested information. For the commands that resume the target, the
22037 response only indicates whether the target was successfully resumed.
22038 Notifications is the mechanism for reporting changes in the state of the
22039 target, or in @value{GDBN} state, that cannot conveniently be associated with
22040 a command and reported as part of that command response.
22042 The important examples of notifications are:
22046 Exec notifications. These are used to report changes in
22047 target state---when a target is resumed, or stopped. It would not
22048 be feasible to include this information in response of resuming
22049 commands, because one resume commands can result in multiple events in
22050 different threads. Also, quite some time may pass before any event
22051 happens in the target, while a frontend needs to know whether the resuming
22052 command itself was successfully executed.
22055 Console output, and status notifications. Console output
22056 notifications are used to report output of CLI commands, as well as
22057 diagnostics for other commands. Status notifications are used to
22058 report the progress of a long-running operation. Naturally, including
22059 this information in command response would mean no output is produced
22060 until the command is finished, which is undesirable.
22063 General notifications. Commands may have various side effects on
22064 the @value{GDBN} or target state beyond their official purpose. For example,
22065 a command may change the selected thread. Although such changes can
22066 be included in command response, using notification allows for more
22067 orthogonal frontend design.
22071 There's no guarantee that whenever an MI command reports an error,
22072 @value{GDBN} or the target are in any specific state, and especially,
22073 the state is not reverted to the state before the MI command was
22074 processed. Therefore, whenever an MI command results in an error,
22075 we recommend that the frontend refreshes all the information shown in
22076 the user interface.
22080 * Context management::
22081 * Asynchronous and non-stop modes::
22085 @node Context management
22086 @subsection Context management
22088 In most cases when @value{GDBN} accesses the target, this access is
22089 done in context of a specific thread and frame (@pxref{Frames}).
22090 Often, even when accessing global data, the target requires that a thread
22091 be specified. The CLI interface maintains the selected thread and frame,
22092 and supplies them to target on each command. This is convenient,
22093 because a command line user would not want to specify that information
22094 explicitly on each command, and because user interacts with
22095 @value{GDBN} via a single terminal, so no confusion is possible as
22096 to what thread and frame are the current ones.
22098 In the case of MI, the concept of selected thread and frame is less
22099 useful. First, a frontend can easily remember this information
22100 itself. Second, a graphical frontend can have more than one window,
22101 each one used for debugging a different thread, and the frontend might
22102 want to access additional threads for internal purposes. This
22103 increases the risk that by relying on implicitly selected thread, the
22104 frontend may be operating on a wrong one. Therefore, each MI command
22105 should explicitly specify which thread and frame to operate on. To
22106 make it possible, each MI command accepts the @samp{--thread} and
22107 @samp{--frame} options, the value to each is @value{GDBN} identifier
22108 for thread and frame to operate on.
22110 Usually, each top-level window in a frontend allows the user to select
22111 a thread and a frame, and remembers the user selection for further
22112 operations. However, in some cases @value{GDBN} may suggest that the
22113 current thread be changed. For example, when stopping on a breakpoint
22114 it is reasonable to switch to the thread where breakpoint is hit. For
22115 another example, if the user issues the CLI @samp{thread} command via
22116 the frontend, it is desirable to change the frontend's selected thread to the
22117 one specified by user. @value{GDBN} communicates the suggestion to
22118 change current thread using the @samp{=thread-selected} notification.
22119 No such notification is available for the selected frame at the moment.
22121 Note that historically, MI shares the selected thread with CLI, so
22122 frontends used the @code{-thread-select} to execute commands in the
22123 right context. However, getting this to work right is cumbersome. The
22124 simplest way is for frontend to emit @code{-thread-select} command
22125 before every command. This doubles the number of commands that need
22126 to be sent. The alternative approach is to suppress @code{-thread-select}
22127 if the selected thread in @value{GDBN} is supposed to be identical to the
22128 thread the frontend wants to operate on. However, getting this
22129 optimization right can be tricky. In particular, if the frontend
22130 sends several commands to @value{GDBN}, and one of the commands changes the
22131 selected thread, then the behaviour of subsequent commands will
22132 change. So, a frontend should either wait for response from such
22133 problematic commands, or explicitly add @code{-thread-select} for
22134 all subsequent commands. No frontend is known to do this exactly
22135 right, so it is suggested to just always pass the @samp{--thread} and
22136 @samp{--frame} options.
22138 @node Asynchronous and non-stop modes
22139 @subsection Asynchronous command execution and non-stop mode
22141 On some targets, @value{GDBN} is capable of processing MI commands
22142 even while the target is running. This is called @dfn{asynchronous
22143 command execution} (@pxref{Background Execution}). The frontend may
22144 specify a preferrence for asynchronous execution using the
22145 @code{-gdb-set target-async 1} command, which should be emitted before
22146 either running the executable or attaching to the target. After the
22147 frontend has started the executable or attached to the target, it can
22148 find if asynchronous execution is enabled using the
22149 @code{-list-target-features} command.
22151 Even if @value{GDBN} can accept a command while target is running,
22152 many commands that access the target do not work when the target is
22153 running. Therefore, asynchronous command execution is most useful
22154 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
22155 it is possible to examine the state of one thread, while other threads
22158 When a given thread is running, MI commands that try to access the
22159 target in the context of that thread may not work, or may work only on
22160 some targets. In particular, commands that try to operate on thread's
22161 stack will not work, on any target. Commands that read memory, or
22162 modify breakpoints, may work or not work, depending on the target. Note
22163 that even commands that operate on global state, such as @code{print},
22164 @code{set}, and breakpoint commands, still access the target in the
22165 context of a specific thread, so frontend should try to find a
22166 stopped thread and perform the operation on that thread (using the
22167 @samp{--thread} option).
22169 Which commands will work in the context of a running thread is
22170 highly target dependent. However, the two commands
22171 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
22172 to find the state of a thread, will always work.
22174 @node Thread groups
22175 @subsection Thread groups
22176 @value{GDBN} may be used to debug several processes at the same time.
22177 On some platfroms, @value{GDBN} may support debugging of several
22178 hardware systems, each one having several cores with several different
22179 processes running on each core. This section describes the MI
22180 mechanism to support such debugging scenarios.
22182 The key observation is that regardless of the structure of the
22183 target, MI can have a global list of threads, because most commands that
22184 accept the @samp{--thread} option do not need to know what process that
22185 thread belongs to. Therefore, it is not necessary to introduce
22186 neither additional @samp{--process} option, nor an notion of the
22187 current process in the MI interface. The only strictly new feature
22188 that is required is the ability to find how the threads are grouped
22191 To allow the user to discover such grouping, and to support arbitrary
22192 hierarchy of machines/cores/processes, MI introduces the concept of a
22193 @dfn{thread group}. Thread group is a collection of threads and other
22194 thread groups. A thread group always has a string identifier, a type,
22195 and may have additional attributes specific to the type. A new
22196 command, @code{-list-thread-groups}, returns the list of top-level
22197 thread groups, which correspond to processes that @value{GDBN} is
22198 debugging at the moment. By passing an identifier of a thread group
22199 to the @code{-list-thread-groups} command, it is possible to obtain
22200 the members of specific thread group.
22202 To allow the user to easily discover processes, and other objects, he
22203 wishes to debug, a concept of @dfn{available thread group} is
22204 introduced. Available thread group is an thread group that
22205 @value{GDBN} is not debugging, but that can be attached to, using the
22206 @code{-target-attach} command. The list of available top-level thread
22207 groups can be obtained using @samp{-list-thread-groups --available}.
22208 In general, the content of a thread group may be only retrieved only
22209 after attaching to that thread group.
22211 Thread groups are related to inferiors (@pxref{Inferiors and
22212 Programs}). Each inferior corresponds to a thread group of a special
22213 type @samp{process}, and some additional operations are permitted on
22214 such thread groups.
22216 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22217 @node GDB/MI Command Syntax
22218 @section @sc{gdb/mi} Command Syntax
22221 * GDB/MI Input Syntax::
22222 * GDB/MI Output Syntax::
22225 @node GDB/MI Input Syntax
22226 @subsection @sc{gdb/mi} Input Syntax
22228 @cindex input syntax for @sc{gdb/mi}
22229 @cindex @sc{gdb/mi}, input syntax
22231 @item @var{command} @expansion{}
22232 @code{@var{cli-command} | @var{mi-command}}
22234 @item @var{cli-command} @expansion{}
22235 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
22236 @var{cli-command} is any existing @value{GDBN} CLI command.
22238 @item @var{mi-command} @expansion{}
22239 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
22240 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
22242 @item @var{token} @expansion{}
22243 "any sequence of digits"
22245 @item @var{option} @expansion{}
22246 @code{"-" @var{parameter} [ " " @var{parameter} ]}
22248 @item @var{parameter} @expansion{}
22249 @code{@var{non-blank-sequence} | @var{c-string}}
22251 @item @var{operation} @expansion{}
22252 @emph{any of the operations described in this chapter}
22254 @item @var{non-blank-sequence} @expansion{}
22255 @emph{anything, provided it doesn't contain special characters such as
22256 "-", @var{nl}, """ and of course " "}
22258 @item @var{c-string} @expansion{}
22259 @code{""" @var{seven-bit-iso-c-string-content} """}
22261 @item @var{nl} @expansion{}
22270 The CLI commands are still handled by the @sc{mi} interpreter; their
22271 output is described below.
22274 The @code{@var{token}}, when present, is passed back when the command
22278 Some @sc{mi} commands accept optional arguments as part of the parameter
22279 list. Each option is identified by a leading @samp{-} (dash) and may be
22280 followed by an optional argument parameter. Options occur first in the
22281 parameter list and can be delimited from normal parameters using
22282 @samp{--} (this is useful when some parameters begin with a dash).
22289 We want easy access to the existing CLI syntax (for debugging).
22292 We want it to be easy to spot a @sc{mi} operation.
22295 @node GDB/MI Output Syntax
22296 @subsection @sc{gdb/mi} Output Syntax
22298 @cindex output syntax of @sc{gdb/mi}
22299 @cindex @sc{gdb/mi}, output syntax
22300 The output from @sc{gdb/mi} consists of zero or more out-of-band records
22301 followed, optionally, by a single result record. This result record
22302 is for the most recent command. The sequence of output records is
22303 terminated by @samp{(gdb)}.
22305 If an input command was prefixed with a @code{@var{token}} then the
22306 corresponding output for that command will also be prefixed by that same
22310 @item @var{output} @expansion{}
22311 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
22313 @item @var{result-record} @expansion{}
22314 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
22316 @item @var{out-of-band-record} @expansion{}
22317 @code{@var{async-record} | @var{stream-record}}
22319 @item @var{async-record} @expansion{}
22320 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
22322 @item @var{exec-async-output} @expansion{}
22323 @code{[ @var{token} ] "*" @var{async-output}}
22325 @item @var{status-async-output} @expansion{}
22326 @code{[ @var{token} ] "+" @var{async-output}}
22328 @item @var{notify-async-output} @expansion{}
22329 @code{[ @var{token} ] "=" @var{async-output}}
22331 @item @var{async-output} @expansion{}
22332 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
22334 @item @var{result-class} @expansion{}
22335 @code{"done" | "running" | "connected" | "error" | "exit"}
22337 @item @var{async-class} @expansion{}
22338 @code{"stopped" | @var{others}} (where @var{others} will be added
22339 depending on the needs---this is still in development).
22341 @item @var{result} @expansion{}
22342 @code{ @var{variable} "=" @var{value}}
22344 @item @var{variable} @expansion{}
22345 @code{ @var{string} }
22347 @item @var{value} @expansion{}
22348 @code{ @var{const} | @var{tuple} | @var{list} }
22350 @item @var{const} @expansion{}
22351 @code{@var{c-string}}
22353 @item @var{tuple} @expansion{}
22354 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
22356 @item @var{list} @expansion{}
22357 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
22358 @var{result} ( "," @var{result} )* "]" }
22360 @item @var{stream-record} @expansion{}
22361 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
22363 @item @var{console-stream-output} @expansion{}
22364 @code{"~" @var{c-string}}
22366 @item @var{target-stream-output} @expansion{}
22367 @code{"@@" @var{c-string}}
22369 @item @var{log-stream-output} @expansion{}
22370 @code{"&" @var{c-string}}
22372 @item @var{nl} @expansion{}
22375 @item @var{token} @expansion{}
22376 @emph{any sequence of digits}.
22384 All output sequences end in a single line containing a period.
22387 The @code{@var{token}} is from the corresponding request. Note that
22388 for all async output, while the token is allowed by the grammar and
22389 may be output by future versions of @value{GDBN} for select async
22390 output messages, it is generally omitted. Frontends should treat
22391 all async output as reporting general changes in the state of the
22392 target and there should be no need to associate async output to any
22396 @cindex status output in @sc{gdb/mi}
22397 @var{status-async-output} contains on-going status information about the
22398 progress of a slow operation. It can be discarded. All status output is
22399 prefixed by @samp{+}.
22402 @cindex async output in @sc{gdb/mi}
22403 @var{exec-async-output} contains asynchronous state change on the target
22404 (stopped, started, disappeared). All async output is prefixed by
22408 @cindex notify output in @sc{gdb/mi}
22409 @var{notify-async-output} contains supplementary information that the
22410 client should handle (e.g., a new breakpoint information). All notify
22411 output is prefixed by @samp{=}.
22414 @cindex console output in @sc{gdb/mi}
22415 @var{console-stream-output} is output that should be displayed as is in the
22416 console. It is the textual response to a CLI command. All the console
22417 output is prefixed by @samp{~}.
22420 @cindex target output in @sc{gdb/mi}
22421 @var{target-stream-output} is the output produced by the target program.
22422 All the target output is prefixed by @samp{@@}.
22425 @cindex log output in @sc{gdb/mi}
22426 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
22427 instance messages that should be displayed as part of an error log. All
22428 the log output is prefixed by @samp{&}.
22431 @cindex list output in @sc{gdb/mi}
22432 New @sc{gdb/mi} commands should only output @var{lists} containing
22438 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
22439 details about the various output records.
22441 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22442 @node GDB/MI Compatibility with CLI
22443 @section @sc{gdb/mi} Compatibility with CLI
22445 @cindex compatibility, @sc{gdb/mi} and CLI
22446 @cindex @sc{gdb/mi}, compatibility with CLI
22448 For the developers convenience CLI commands can be entered directly,
22449 but there may be some unexpected behaviour. For example, commands
22450 that query the user will behave as if the user replied yes, breakpoint
22451 command lists are not executed and some CLI commands, such as
22452 @code{if}, @code{when} and @code{define}, prompt for further input with
22453 @samp{>}, which is not valid MI output.
22455 This feature may be removed at some stage in the future and it is
22456 recommended that front ends use the @code{-interpreter-exec} command
22457 (@pxref{-interpreter-exec}).
22459 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22460 @node GDB/MI Development and Front Ends
22461 @section @sc{gdb/mi} Development and Front Ends
22462 @cindex @sc{gdb/mi} development
22464 The application which takes the MI output and presents the state of the
22465 program being debugged to the user is called a @dfn{front end}.
22467 Although @sc{gdb/mi} is still incomplete, it is currently being used
22468 by a variety of front ends to @value{GDBN}. This makes it difficult
22469 to introduce new functionality without breaking existing usage. This
22470 section tries to minimize the problems by describing how the protocol
22473 Some changes in MI need not break a carefully designed front end, and
22474 for these the MI version will remain unchanged. The following is a
22475 list of changes that may occur within one level, so front ends should
22476 parse MI output in a way that can handle them:
22480 New MI commands may be added.
22483 New fields may be added to the output of any MI command.
22486 The range of values for fields with specified values, e.g.,
22487 @code{in_scope} (@pxref{-var-update}) may be extended.
22489 @c The format of field's content e.g type prefix, may change so parse it
22490 @c at your own risk. Yes, in general?
22492 @c The order of fields may change? Shouldn't really matter but it might
22493 @c resolve inconsistencies.
22496 If the changes are likely to break front ends, the MI version level
22497 will be increased by one. This will allow the front end to parse the
22498 output according to the MI version. Apart from mi0, new versions of
22499 @value{GDBN} will not support old versions of MI and it will be the
22500 responsibility of the front end to work with the new one.
22502 @c Starting with mi3, add a new command -mi-version that prints the MI
22505 The best way to avoid unexpected changes in MI that might break your front
22506 end is to make your project known to @value{GDBN} developers and
22507 follow development on @email{gdb@@sourceware.org} and
22508 @email{gdb-patches@@sourceware.org}.
22509 @cindex mailing lists
22511 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22512 @node GDB/MI Output Records
22513 @section @sc{gdb/mi} Output Records
22516 * GDB/MI Result Records::
22517 * GDB/MI Stream Records::
22518 * GDB/MI Async Records::
22519 * GDB/MI Frame Information::
22520 * GDB/MI Thread Information::
22523 @node GDB/MI Result Records
22524 @subsection @sc{gdb/mi} Result Records
22526 @cindex result records in @sc{gdb/mi}
22527 @cindex @sc{gdb/mi}, result records
22528 In addition to a number of out-of-band notifications, the response to a
22529 @sc{gdb/mi} command includes one of the following result indications:
22533 @item "^done" [ "," @var{results} ]
22534 The synchronous operation was successful, @code{@var{results}} are the return
22539 This result record is equivalent to @samp{^done}. Historically, it
22540 was output instead of @samp{^done} if the command has resumed the
22541 target. This behaviour is maintained for backward compatibility, but
22542 all frontends should treat @samp{^done} and @samp{^running}
22543 identically and rely on the @samp{*running} output record to determine
22544 which threads are resumed.
22548 @value{GDBN} has connected to a remote target.
22550 @item "^error" "," @var{c-string}
22552 The operation failed. The @code{@var{c-string}} contains the corresponding
22557 @value{GDBN} has terminated.
22561 @node GDB/MI Stream Records
22562 @subsection @sc{gdb/mi} Stream Records
22564 @cindex @sc{gdb/mi}, stream records
22565 @cindex stream records in @sc{gdb/mi}
22566 @value{GDBN} internally maintains a number of output streams: the console, the
22567 target, and the log. The output intended for each of these streams is
22568 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
22570 Each stream record begins with a unique @dfn{prefix character} which
22571 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
22572 Syntax}). In addition to the prefix, each stream record contains a
22573 @code{@var{string-output}}. This is either raw text (with an implicit new
22574 line) or a quoted C string (which does not contain an implicit newline).
22577 @item "~" @var{string-output}
22578 The console output stream contains text that should be displayed in the
22579 CLI console window. It contains the textual responses to CLI commands.
22581 @item "@@" @var{string-output}
22582 The target output stream contains any textual output from the running
22583 target. This is only present when GDB's event loop is truly
22584 asynchronous, which is currently only the case for remote targets.
22586 @item "&" @var{string-output}
22587 The log stream contains debugging messages being produced by @value{GDBN}'s
22591 @node GDB/MI Async Records
22592 @subsection @sc{gdb/mi} Async Records
22594 @cindex async records in @sc{gdb/mi}
22595 @cindex @sc{gdb/mi}, async records
22596 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
22597 additional changes that have occurred. Those changes can either be a
22598 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
22599 target activity (e.g., target stopped).
22601 The following is the list of possible async records:
22605 @item *running,thread-id="@var{thread}"
22606 The target is now running. The @var{thread} field tells which
22607 specific thread is now running, and can be @samp{all} if all threads
22608 are running. The frontend should assume that no interaction with a
22609 running thread is possible after this notification is produced.
22610 The frontend should not assume that this notification is output
22611 only once for any command. @value{GDBN} may emit this notification
22612 several times, either for different threads, because it cannot resume
22613 all threads together, or even for a single thread, if the thread must
22614 be stepped though some code before letting it run freely.
22616 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
22617 The target has stopped. The @var{reason} field can have one of the
22621 @item breakpoint-hit
22622 A breakpoint was reached.
22623 @item watchpoint-trigger
22624 A watchpoint was triggered.
22625 @item read-watchpoint-trigger
22626 A read watchpoint was triggered.
22627 @item access-watchpoint-trigger
22628 An access watchpoint was triggered.
22629 @item function-finished
22630 An -exec-finish or similar CLI command was accomplished.
22631 @item location-reached
22632 An -exec-until or similar CLI command was accomplished.
22633 @item watchpoint-scope
22634 A watchpoint has gone out of scope.
22635 @item end-stepping-range
22636 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
22637 similar CLI command was accomplished.
22638 @item exited-signalled
22639 The inferior exited because of a signal.
22641 The inferior exited.
22642 @item exited-normally
22643 The inferior exited normally.
22644 @item signal-received
22645 A signal was received by the inferior.
22648 The @var{id} field identifies the thread that directly caused the stop
22649 -- for example by hitting a breakpoint. Depending on whether all-stop
22650 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
22651 stop all threads, or only the thread that directly triggered the stop.
22652 If all threads are stopped, the @var{stopped} field will have the
22653 value of @code{"all"}. Otherwise, the value of the @var{stopped}
22654 field will be a list of thread identifiers. Presently, this list will
22655 always include a single thread, but frontend should be prepared to see
22656 several threads in the list. The @var{core} field reports the
22657 processor core on which the stop event has happened. This field may be absent
22658 if such information is not available.
22660 @item =thread-group-added,id="@var{id}"
22661 @itemx =thread-group-removed,id="@var{id}"
22662 A thread group was either added or removed. The @var{id} field
22663 contains the @value{GDBN} identifier of the thread group. When a thread
22664 group is added, it generally might not be associated with a running
22665 process. When a thread group is removed, its id becomes invalid and
22666 cannot be used in any way.
22668 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
22669 A thread group became associated with a running program,
22670 either because the program was just started or the thread group
22671 was attached to a program. The @var{id} field contains the
22672 @value{GDBN} identifier of the thread group. The @var{pid} field
22673 contains process identifier, specific to the operating system.
22675 @itemx =thread-group-exited,id="@var{id}"
22676 A thread group is no longer associated with a running program,
22677 either because the program has exited, or because it was detached
22678 from. The @var{id} field contains the @value{GDBN} identifier of the
22681 @item =thread-created,id="@var{id}",group-id="@var{gid}"
22682 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
22683 A thread either was created, or has exited. The @var{id} field
22684 contains the @value{GDBN} identifier of the thread. The @var{gid}
22685 field identifies the thread group this thread belongs to.
22687 @item =thread-selected,id="@var{id}"
22688 Informs that the selected thread was changed as result of the last
22689 command. This notification is not emitted as result of @code{-thread-select}
22690 command but is emitted whenever an MI command that is not documented
22691 to change the selected thread actually changes it. In particular,
22692 invoking, directly or indirectly (via user-defined command), the CLI
22693 @code{thread} command, will generate this notification.
22695 We suggest that in response to this notification, front ends
22696 highlight the selected thread and cause subsequent commands to apply to
22699 @item =library-loaded,...
22700 Reports that a new library file was loaded by the program. This
22701 notification has 4 fields---@var{id}, @var{target-name},
22702 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
22703 opaque identifier of the library. For remote debugging case,
22704 @var{target-name} and @var{host-name} fields give the name of the
22705 library file on the target, and on the host respectively. For native
22706 debugging, both those fields have the same value. The
22707 @var{symbols-loaded} field reports if the debug symbols for this
22708 library are loaded. The @var{thread-group} field, if present,
22709 specifies the id of the thread group in whose context the library was loaded.
22710 If the field is absent, it means the library was loaded in the context
22711 of all present thread groups.
22713 @item =library-unloaded,...
22714 Reports that a library was unloaded by the program. This notification
22715 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
22716 the same meaning as for the @code{=library-loaded} notification.
22717 The @var{thread-group} field, if present, specifies the id of the
22718 thread group in whose context the library was unloaded. If the field is
22719 absent, it means the library was unloaded in the context of all present
22724 @node GDB/MI Frame Information
22725 @subsection @sc{gdb/mi} Frame Information
22727 Response from many MI commands includes an information about stack
22728 frame. This information is a tuple that may have the following
22733 The level of the stack frame. The innermost frame has the level of
22734 zero. This field is always present.
22737 The name of the function corresponding to the frame. This field may
22738 be absent if @value{GDBN} is unable to determine the function name.
22741 The code address for the frame. This field is always present.
22744 The name of the source files that correspond to the frame's code
22745 address. This field may be absent.
22748 The source line corresponding to the frames' code address. This field
22752 The name of the binary file (either executable or shared library) the
22753 corresponds to the frame's code address. This field may be absent.
22757 @node GDB/MI Thread Information
22758 @subsection @sc{gdb/mi} Thread Information
22760 Whenever @value{GDBN} has to report an information about a thread, it
22761 uses a tuple with the following fields:
22765 The numeric id assigned to the thread by @value{GDBN}. This field is
22769 Target-specific string identifying the thread. This field is always present.
22772 Additional information about the thread provided by the target.
22773 It is supposed to be human-readable and not interpreted by the
22774 frontend. This field is optional.
22777 Either @samp{stopped} or @samp{running}, depending on whether the
22778 thread is presently running. This field is always present.
22781 The value of this field is an integer number of the processor core the
22782 thread was last seen on. This field is optional.
22786 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22787 @node GDB/MI Simple Examples
22788 @section Simple Examples of @sc{gdb/mi} Interaction
22789 @cindex @sc{gdb/mi}, simple examples
22791 This subsection presents several simple examples of interaction using
22792 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
22793 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
22794 the output received from @sc{gdb/mi}.
22796 Note the line breaks shown in the examples are here only for
22797 readability, they don't appear in the real output.
22799 @subheading Setting a Breakpoint
22801 Setting a breakpoint generates synchronous output which contains detailed
22802 information of the breakpoint.
22805 -> -break-insert main
22806 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
22807 enabled="y",addr="0x08048564",func="main",file="myprog.c",
22808 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
22812 @subheading Program Execution
22814 Program execution generates asynchronous records and MI gives the
22815 reason that execution stopped.
22821 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
22822 frame=@{addr="0x08048564",func="main",
22823 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
22824 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
22829 <- *stopped,reason="exited-normally"
22833 @subheading Quitting @value{GDBN}
22835 Quitting @value{GDBN} just prints the result class @samp{^exit}.
22843 Please note that @samp{^exit} is printed immediately, but it might
22844 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
22845 performs necessary cleanups, including killing programs being debugged
22846 or disconnecting from debug hardware, so the frontend should wait till
22847 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
22848 fails to exit in reasonable time.
22850 @subheading A Bad Command
22852 Here's what happens if you pass a non-existent command:
22856 <- ^error,msg="Undefined MI command: rubbish"
22861 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22862 @node GDB/MI Command Description Format
22863 @section @sc{gdb/mi} Command Description Format
22865 The remaining sections describe blocks of commands. Each block of
22866 commands is laid out in a fashion similar to this section.
22868 @subheading Motivation
22870 The motivation for this collection of commands.
22872 @subheading Introduction
22874 A brief introduction to this collection of commands as a whole.
22876 @subheading Commands
22878 For each command in the block, the following is described:
22880 @subsubheading Synopsis
22883 -command @var{args}@dots{}
22886 @subsubheading Result
22888 @subsubheading @value{GDBN} Command
22890 The corresponding @value{GDBN} CLI command(s), if any.
22892 @subsubheading Example
22894 Example(s) formatted for readability. Some of the described commands have
22895 not been implemented yet and these are labeled N.A.@: (not available).
22898 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22899 @node GDB/MI Breakpoint Commands
22900 @section @sc{gdb/mi} Breakpoint Commands
22902 @cindex breakpoint commands for @sc{gdb/mi}
22903 @cindex @sc{gdb/mi}, breakpoint commands
22904 This section documents @sc{gdb/mi} commands for manipulating
22907 @subheading The @code{-break-after} Command
22908 @findex -break-after
22910 @subsubheading Synopsis
22913 -break-after @var{number} @var{count}
22916 The breakpoint number @var{number} is not in effect until it has been
22917 hit @var{count} times. To see how this is reflected in the output of
22918 the @samp{-break-list} command, see the description of the
22919 @samp{-break-list} command below.
22921 @subsubheading @value{GDBN} Command
22923 The corresponding @value{GDBN} command is @samp{ignore}.
22925 @subsubheading Example
22930 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
22931 enabled="y",addr="0x000100d0",func="main",file="hello.c",
22932 fullname="/home/foo/hello.c",line="5",times="0"@}
22939 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
22940 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
22941 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
22942 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
22943 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
22944 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
22945 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
22946 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
22947 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
22948 line="5",times="0",ignore="3"@}]@}
22953 @subheading The @code{-break-catch} Command
22954 @findex -break-catch
22957 @subheading The @code{-break-commands} Command
22958 @findex -break-commands
22960 @subsubheading Synopsis
22963 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
22966 Specifies the CLI commands that should be executed when breakpoint
22967 @var{number} is hit. The parameters @var{command1} to @var{commandN}
22968 are the commands. If no command is specified, any previously-set
22969 commands are cleared. @xref{Break Commands}. Typical use of this
22970 functionality is tracing a program, that is, printing of values of
22971 some variables whenever breakpoint is hit and then continuing.
22973 @subsubheading @value{GDBN} Command
22975 The corresponding @value{GDBN} command is @samp{commands}.
22977 @subsubheading Example
22982 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
22983 enabled="y",addr="0x000100d0",func="main",file="hello.c",
22984 fullname="/home/foo/hello.c",line="5",times="0"@}
22986 -break-commands 1 "print v" "continue"
22991 @subheading The @code{-break-condition} Command
22992 @findex -break-condition
22994 @subsubheading Synopsis
22997 -break-condition @var{number} @var{expr}
23000 Breakpoint @var{number} will stop the program only if the condition in
23001 @var{expr} is true. The condition becomes part of the
23002 @samp{-break-list} output (see the description of the @samp{-break-list}
23005 @subsubheading @value{GDBN} Command
23007 The corresponding @value{GDBN} command is @samp{condition}.
23009 @subsubheading Example
23013 -break-condition 1 1
23017 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
23018 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23019 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23020 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23021 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23022 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23023 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23024 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
23025 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
23026 line="5",cond="1",times="0",ignore="3"@}]@}
23030 @subheading The @code{-break-delete} Command
23031 @findex -break-delete
23033 @subsubheading Synopsis
23036 -break-delete ( @var{breakpoint} )+
23039 Delete the breakpoint(s) whose number(s) are specified in the argument
23040 list. This is obviously reflected in the breakpoint list.
23042 @subsubheading @value{GDBN} Command
23044 The corresponding @value{GDBN} command is @samp{delete}.
23046 @subsubheading Example
23054 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
23055 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23056 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23057 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23058 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23059 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23060 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23065 @subheading The @code{-break-disable} Command
23066 @findex -break-disable
23068 @subsubheading Synopsis
23071 -break-disable ( @var{breakpoint} )+
23074 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
23075 break list is now set to @samp{n} for the named @var{breakpoint}(s).
23077 @subsubheading @value{GDBN} Command
23079 The corresponding @value{GDBN} command is @samp{disable}.
23081 @subsubheading Example
23089 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
23090 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23091 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23092 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23093 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23094 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23095 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23096 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
23097 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
23098 line="5",times="0"@}]@}
23102 @subheading The @code{-break-enable} Command
23103 @findex -break-enable
23105 @subsubheading Synopsis
23108 -break-enable ( @var{breakpoint} )+
23111 Enable (previously disabled) @var{breakpoint}(s).
23113 @subsubheading @value{GDBN} Command
23115 The corresponding @value{GDBN} command is @samp{enable}.
23117 @subsubheading Example
23125 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
23126 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23127 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23128 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23129 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23130 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23131 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23132 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
23133 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
23134 line="5",times="0"@}]@}
23138 @subheading The @code{-break-info} Command
23139 @findex -break-info
23141 @subsubheading Synopsis
23144 -break-info @var{breakpoint}
23148 Get information about a single breakpoint.
23150 @subsubheading @value{GDBN} Command
23152 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
23154 @subsubheading Example
23157 @subheading The @code{-break-insert} Command
23158 @findex -break-insert
23160 @subsubheading Synopsis
23163 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
23164 [ -c @var{condition} ] [ -i @var{ignore-count} ]
23165 [ -p @var{thread} ] [ @var{location} ]
23169 If specified, @var{location}, can be one of:
23176 @item filename:linenum
23177 @item filename:function
23181 The possible optional parameters of this command are:
23185 Insert a temporary breakpoint.
23187 Insert a hardware breakpoint.
23188 @item -c @var{condition}
23189 Make the breakpoint conditional on @var{condition}.
23190 @item -i @var{ignore-count}
23191 Initialize the @var{ignore-count}.
23193 If @var{location} cannot be parsed (for example if it
23194 refers to unknown files or functions), create a pending
23195 breakpoint. Without this flag, @value{GDBN} will report
23196 an error, and won't create a breakpoint, if @var{location}
23199 Create a disabled breakpoint.
23201 Create a tracepoint. @xref{Tracepoints}. When this parameter
23202 is used together with @samp{-h}, a fast tracepoint is created.
23205 @subsubheading Result
23207 The result is in the form:
23210 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
23211 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
23212 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
23213 times="@var{times}"@}
23217 where @var{number} is the @value{GDBN} number for this breakpoint,
23218 @var{funcname} is the name of the function where the breakpoint was
23219 inserted, @var{filename} is the name of the source file which contains
23220 this function, @var{lineno} is the source line number within that file
23221 and @var{times} the number of times that the breakpoint has been hit
23222 (always 0 for -break-insert but may be greater for -break-info or -break-list
23223 which use the same output).
23225 Note: this format is open to change.
23226 @c An out-of-band breakpoint instead of part of the result?
23228 @subsubheading @value{GDBN} Command
23230 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
23231 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
23233 @subsubheading Example
23238 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
23239 fullname="/home/foo/recursive2.c,line="4",times="0"@}
23241 -break-insert -t foo
23242 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
23243 fullname="/home/foo/recursive2.c,line="11",times="0"@}
23246 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
23247 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23248 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23249 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23250 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23251 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23252 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23253 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
23254 addr="0x0001072c", func="main",file="recursive2.c",
23255 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
23256 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
23257 addr="0x00010774",func="foo",file="recursive2.c",
23258 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
23260 -break-insert -r foo.*
23261 ~int foo(int, int);
23262 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
23263 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
23267 @subheading The @code{-break-list} Command
23268 @findex -break-list
23270 @subsubheading Synopsis
23276 Displays the list of inserted breakpoints, showing the following fields:
23280 number of the breakpoint
23282 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
23284 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
23287 is the breakpoint enabled or no: @samp{y} or @samp{n}
23289 memory location at which the breakpoint is set
23291 logical location of the breakpoint, expressed by function name, file
23294 number of times the breakpoint has been hit
23297 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
23298 @code{body} field is an empty list.
23300 @subsubheading @value{GDBN} Command
23302 The corresponding @value{GDBN} command is @samp{info break}.
23304 @subsubheading Example
23309 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
23310 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23311 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23312 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23313 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23314 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23315 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23316 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
23317 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
23318 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
23319 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
23320 line="13",times="0"@}]@}
23324 Here's an example of the result when there are no breakpoints:
23329 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
23330 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23331 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23332 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23333 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23334 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23335 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23340 @subheading The @code{-break-passcount} Command
23341 @findex -break-passcount
23343 @subsubheading Synopsis
23346 -break-passcount @var{tracepoint-number} @var{passcount}
23349 Set the passcount for tracepoint @var{tracepoint-number} to
23350 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
23351 is not a tracepoint, error is emitted. This corresponds to CLI
23352 command @samp{passcount}.
23354 @subheading The @code{-break-watch} Command
23355 @findex -break-watch
23357 @subsubheading Synopsis
23360 -break-watch [ -a | -r ]
23363 Create a watchpoint. With the @samp{-a} option it will create an
23364 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
23365 read from or on a write to the memory location. With the @samp{-r}
23366 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
23367 trigger only when the memory location is accessed for reading. Without
23368 either of the options, the watchpoint created is a regular watchpoint,
23369 i.e., it will trigger when the memory location is accessed for writing.
23370 @xref{Set Watchpoints, , Setting Watchpoints}.
23372 Note that @samp{-break-list} will report a single list of watchpoints and
23373 breakpoints inserted.
23375 @subsubheading @value{GDBN} Command
23377 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
23380 @subsubheading Example
23382 Setting a watchpoint on a variable in the @code{main} function:
23387 ^done,wpt=@{number="2",exp="x"@}
23392 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
23393 value=@{old="-268439212",new="55"@},
23394 frame=@{func="main",args=[],file="recursive2.c",
23395 fullname="/home/foo/bar/recursive2.c",line="5"@}
23399 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
23400 the program execution twice: first for the variable changing value, then
23401 for the watchpoint going out of scope.
23406 ^done,wpt=@{number="5",exp="C"@}
23411 *stopped,reason="watchpoint-trigger",
23412 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
23413 frame=@{func="callee4",args=[],
23414 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23415 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
23420 *stopped,reason="watchpoint-scope",wpnum="5",
23421 frame=@{func="callee3",args=[@{name="strarg",
23422 value="0x11940 \"A string argument.\""@}],
23423 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23424 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
23428 Listing breakpoints and watchpoints, at different points in the program
23429 execution. Note that once the watchpoint goes out of scope, it is
23435 ^done,wpt=@{number="2",exp="C"@}
23438 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
23439 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23440 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23441 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23442 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23443 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23444 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23445 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
23446 addr="0x00010734",func="callee4",
23447 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23448 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
23449 bkpt=@{number="2",type="watchpoint",disp="keep",
23450 enabled="y",addr="",what="C",times="0"@}]@}
23455 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
23456 value=@{old="-276895068",new="3"@},
23457 frame=@{func="callee4",args=[],
23458 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23459 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
23462 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
23463 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23464 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23465 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23466 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23467 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23468 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23469 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
23470 addr="0x00010734",func="callee4",
23471 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23472 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
23473 bkpt=@{number="2",type="watchpoint",disp="keep",
23474 enabled="y",addr="",what="C",times="-5"@}]@}
23478 ^done,reason="watchpoint-scope",wpnum="2",
23479 frame=@{func="callee3",args=[@{name="strarg",
23480 value="0x11940 \"A string argument.\""@}],
23481 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23482 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
23485 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
23486 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23487 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23488 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23489 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23490 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23491 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23492 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
23493 addr="0x00010734",func="callee4",
23494 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
23495 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
23500 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23501 @node GDB/MI Program Context
23502 @section @sc{gdb/mi} Program Context
23504 @subheading The @code{-exec-arguments} Command
23505 @findex -exec-arguments
23508 @subsubheading Synopsis
23511 -exec-arguments @var{args}
23514 Set the inferior program arguments, to be used in the next
23517 @subsubheading @value{GDBN} Command
23519 The corresponding @value{GDBN} command is @samp{set args}.
23521 @subsubheading Example
23525 -exec-arguments -v word
23532 @subheading The @code{-exec-show-arguments} Command
23533 @findex -exec-show-arguments
23535 @subsubheading Synopsis
23538 -exec-show-arguments
23541 Print the arguments of the program.
23543 @subsubheading @value{GDBN} Command
23545 The corresponding @value{GDBN} command is @samp{show args}.
23547 @subsubheading Example
23552 @subheading The @code{-environment-cd} Command
23553 @findex -environment-cd
23555 @subsubheading Synopsis
23558 -environment-cd @var{pathdir}
23561 Set @value{GDBN}'s working directory.
23563 @subsubheading @value{GDBN} Command
23565 The corresponding @value{GDBN} command is @samp{cd}.
23567 @subsubheading Example
23571 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
23577 @subheading The @code{-environment-directory} Command
23578 @findex -environment-directory
23580 @subsubheading Synopsis
23583 -environment-directory [ -r ] [ @var{pathdir} ]+
23586 Add directories @var{pathdir} to beginning of search path for source files.
23587 If the @samp{-r} option is used, the search path is reset to the default
23588 search path. If directories @var{pathdir} are supplied in addition to the
23589 @samp{-r} option, the search path is first reset and then addition
23591 Multiple directories may be specified, separated by blanks. Specifying
23592 multiple directories in a single command
23593 results in the directories added to the beginning of the
23594 search path in the same order they were presented in the command.
23595 If blanks are needed as
23596 part of a directory name, double-quotes should be used around
23597 the name. In the command output, the path will show up separated
23598 by the system directory-separator character. The directory-separator
23599 character must not be used
23600 in any directory name.
23601 If no directories are specified, the current search path is displayed.
23603 @subsubheading @value{GDBN} Command
23605 The corresponding @value{GDBN} command is @samp{dir}.
23607 @subsubheading Example
23611 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
23612 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
23614 -environment-directory ""
23615 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
23617 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
23618 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
23620 -environment-directory -r
23621 ^done,source-path="$cdir:$cwd"
23626 @subheading The @code{-environment-path} Command
23627 @findex -environment-path
23629 @subsubheading Synopsis
23632 -environment-path [ -r ] [ @var{pathdir} ]+
23635 Add directories @var{pathdir} to beginning of search path for object files.
23636 If the @samp{-r} option is used, the search path is reset to the original
23637 search path that existed at gdb start-up. If directories @var{pathdir} are
23638 supplied in addition to the
23639 @samp{-r} option, the search path is first reset and then addition
23641 Multiple directories may be specified, separated by blanks. Specifying
23642 multiple directories in a single command
23643 results in the directories added to the beginning of the
23644 search path in the same order they were presented in the command.
23645 If blanks are needed as
23646 part of a directory name, double-quotes should be used around
23647 the name. In the command output, the path will show up separated
23648 by the system directory-separator character. The directory-separator
23649 character must not be used
23650 in any directory name.
23651 If no directories are specified, the current path is displayed.
23654 @subsubheading @value{GDBN} Command
23656 The corresponding @value{GDBN} command is @samp{path}.
23658 @subsubheading Example
23663 ^done,path="/usr/bin"
23665 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
23666 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
23668 -environment-path -r /usr/local/bin
23669 ^done,path="/usr/local/bin:/usr/bin"
23674 @subheading The @code{-environment-pwd} Command
23675 @findex -environment-pwd
23677 @subsubheading Synopsis
23683 Show the current working directory.
23685 @subsubheading @value{GDBN} Command
23687 The corresponding @value{GDBN} command is @samp{pwd}.
23689 @subsubheading Example
23694 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
23698 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23699 @node GDB/MI Thread Commands
23700 @section @sc{gdb/mi} Thread Commands
23703 @subheading The @code{-thread-info} Command
23704 @findex -thread-info
23706 @subsubheading Synopsis
23709 -thread-info [ @var{thread-id} ]
23712 Reports information about either a specific thread, if
23713 the @var{thread-id} parameter is present, or about all
23714 threads. When printing information about all threads,
23715 also reports the current thread.
23717 @subsubheading @value{GDBN} Command
23719 The @samp{info thread} command prints the same information
23722 @subsubheading Example
23727 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
23728 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
23729 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
23730 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
23731 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}],
23732 current-thread-id="1"
23736 The @samp{state} field may have the following values:
23740 The thread is stopped. Frame information is available for stopped
23744 The thread is running. There's no frame information for running
23749 @subheading The @code{-thread-list-ids} Command
23750 @findex -thread-list-ids
23752 @subsubheading Synopsis
23758 Produces a list of the currently known @value{GDBN} thread ids. At the
23759 end of the list it also prints the total number of such threads.
23761 This command is retained for historical reasons, the
23762 @code{-thread-info} command should be used instead.
23764 @subsubheading @value{GDBN} Command
23766 Part of @samp{info threads} supplies the same information.
23768 @subsubheading Example
23773 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
23774 current-thread-id="1",number-of-threads="3"
23779 @subheading The @code{-thread-select} Command
23780 @findex -thread-select
23782 @subsubheading Synopsis
23785 -thread-select @var{threadnum}
23788 Make @var{threadnum} the current thread. It prints the number of the new
23789 current thread, and the topmost frame for that thread.
23791 This command is deprecated in favor of explicitly using the
23792 @samp{--thread} option to each command.
23794 @subsubheading @value{GDBN} Command
23796 The corresponding @value{GDBN} command is @samp{thread}.
23798 @subsubheading Example
23805 *stopped,reason="end-stepping-range",thread-id="2",line="187",
23806 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
23810 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
23811 number-of-threads="3"
23814 ^done,new-thread-id="3",
23815 frame=@{level="0",func="vprintf",
23816 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
23817 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
23821 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23822 @node GDB/MI Program Execution
23823 @section @sc{gdb/mi} Program Execution
23825 These are the asynchronous commands which generate the out-of-band
23826 record @samp{*stopped}. Currently @value{GDBN} only really executes
23827 asynchronously with remote targets and this interaction is mimicked in
23830 @subheading The @code{-exec-continue} Command
23831 @findex -exec-continue
23833 @subsubheading Synopsis
23836 -exec-continue [--reverse] [--all|--thread-group N]
23839 Resumes the execution of the inferior program, which will continue
23840 to execute until it reaches a debugger stop event. If the
23841 @samp{--reverse} option is specified, execution resumes in reverse until
23842 it reaches a stop event. Stop events may include
23845 breakpoints or watchpoints
23847 signals or exceptions
23849 the end of the process (or its beginning under @samp{--reverse})
23851 the end or beginning of a replay log if one is being used.
23853 In all-stop mode (@pxref{All-Stop
23854 Mode}), may resume only one thread, or all threads, depending on the
23855 value of the @samp{scheduler-locking} variable. If @samp{--all} is
23856 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
23857 ignored in all-stop mode. If the @samp{--thread-group} options is
23858 specified, then all threads in that thread group are resumed.
23860 @subsubheading @value{GDBN} Command
23862 The corresponding @value{GDBN} corresponding is @samp{continue}.
23864 @subsubheading Example
23871 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
23872 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
23878 @subheading The @code{-exec-finish} Command
23879 @findex -exec-finish
23881 @subsubheading Synopsis
23884 -exec-finish [--reverse]
23887 Resumes the execution of the inferior program until the current
23888 function is exited. Displays the results returned by the function.
23889 If the @samp{--reverse} option is specified, resumes the reverse
23890 execution of the inferior program until the point where current
23891 function was called.
23893 @subsubheading @value{GDBN} Command
23895 The corresponding @value{GDBN} command is @samp{finish}.
23897 @subsubheading Example
23899 Function returning @code{void}.
23906 *stopped,reason="function-finished",frame=@{func="main",args=[],
23907 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
23911 Function returning other than @code{void}. The name of the internal
23912 @value{GDBN} variable storing the result is printed, together with the
23919 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
23920 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
23921 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
23922 gdb-result-var="$1",return-value="0"
23927 @subheading The @code{-exec-interrupt} Command
23928 @findex -exec-interrupt
23930 @subsubheading Synopsis
23933 -exec-interrupt [--all|--thread-group N]
23936 Interrupts the background execution of the target. Note how the token
23937 associated with the stop message is the one for the execution command
23938 that has been interrupted. The token for the interrupt itself only
23939 appears in the @samp{^done} output. If the user is trying to
23940 interrupt a non-running program, an error message will be printed.
23942 Note that when asynchronous execution is enabled, this command is
23943 asynchronous just like other execution commands. That is, first the
23944 @samp{^done} response will be printed, and the target stop will be
23945 reported after that using the @samp{*stopped} notification.
23947 In non-stop mode, only the context thread is interrupted by default.
23948 All threads (in all inferiors) will be interrupted if the
23949 @samp{--all} option is specified. If the @samp{--thread-group}
23950 option is specified, all threads in that group will be interrupted.
23952 @subsubheading @value{GDBN} Command
23954 The corresponding @value{GDBN} command is @samp{interrupt}.
23956 @subsubheading Example
23967 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
23968 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
23969 fullname="/home/foo/bar/try.c",line="13"@}
23974 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
23978 @subheading The @code{-exec-jump} Command
23981 @subsubheading Synopsis
23984 -exec-jump @var{location}
23987 Resumes execution of the inferior program at the location specified by
23988 parameter. @xref{Specify Location}, for a description of the
23989 different forms of @var{location}.
23991 @subsubheading @value{GDBN} Command
23993 The corresponding @value{GDBN} command is @samp{jump}.
23995 @subsubheading Example
23998 -exec-jump foo.c:10
23999 *running,thread-id="all"
24004 @subheading The @code{-exec-next} Command
24007 @subsubheading Synopsis
24010 -exec-next [--reverse]
24013 Resumes execution of the inferior program, stopping when the beginning
24014 of the next source line is reached.
24016 If the @samp{--reverse} option is specified, resumes reverse execution
24017 of the inferior program, stopping at the beginning of the previous
24018 source line. If you issue this command on the first line of a
24019 function, it will take you back to the caller of that function, to the
24020 source line where the function was called.
24023 @subsubheading @value{GDBN} Command
24025 The corresponding @value{GDBN} command is @samp{next}.
24027 @subsubheading Example
24033 *stopped,reason="end-stepping-range",line="8",file="hello.c"
24038 @subheading The @code{-exec-next-instruction} Command
24039 @findex -exec-next-instruction
24041 @subsubheading Synopsis
24044 -exec-next-instruction [--reverse]
24047 Executes one machine instruction. If the instruction is a function
24048 call, continues until the function returns. If the program stops at an
24049 instruction in the middle of a source line, the address will be
24052 If the @samp{--reverse} option is specified, resumes reverse execution
24053 of the inferior program, stopping at the previous instruction. If the
24054 previously executed instruction was a return from another function,
24055 it will continue to execute in reverse until the call to that function
24056 (from the current stack frame) is reached.
24058 @subsubheading @value{GDBN} Command
24060 The corresponding @value{GDBN} command is @samp{nexti}.
24062 @subsubheading Example
24066 -exec-next-instruction
24070 *stopped,reason="end-stepping-range",
24071 addr="0x000100d4",line="5",file="hello.c"
24076 @subheading The @code{-exec-return} Command
24077 @findex -exec-return
24079 @subsubheading Synopsis
24085 Makes current function return immediately. Doesn't execute the inferior.
24086 Displays the new current frame.
24088 @subsubheading @value{GDBN} Command
24090 The corresponding @value{GDBN} command is @samp{return}.
24092 @subsubheading Example
24096 200-break-insert callee4
24097 200^done,bkpt=@{number="1",addr="0x00010734",
24098 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
24103 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
24104 frame=@{func="callee4",args=[],
24105 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24106 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
24112 111^done,frame=@{level="0",func="callee3",
24113 args=[@{name="strarg",
24114 value="0x11940 \"A string argument.\""@}],
24115 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24116 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
24121 @subheading The @code{-exec-run} Command
24124 @subsubheading Synopsis
24127 -exec-run [--all | --thread-group N]
24130 Starts execution of the inferior from the beginning. The inferior
24131 executes until either a breakpoint is encountered or the program
24132 exits. In the latter case the output will include an exit code, if
24133 the program has exited exceptionally.
24135 When no option is specified, the current inferior is started. If the
24136 @samp{--thread-group} option is specified, it should refer to a thread
24137 group of type @samp{process}, and that thread group will be started.
24138 If the @samp{--all} option is specified, then all inferiors will be started.
24140 @subsubheading @value{GDBN} Command
24142 The corresponding @value{GDBN} command is @samp{run}.
24144 @subsubheading Examples
24149 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
24154 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
24155 frame=@{func="main",args=[],file="recursive2.c",
24156 fullname="/home/foo/bar/recursive2.c",line="4"@}
24161 Program exited normally:
24169 *stopped,reason="exited-normally"
24174 Program exited exceptionally:
24182 *stopped,reason="exited",exit-code="01"
24186 Another way the program can terminate is if it receives a signal such as
24187 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
24191 *stopped,reason="exited-signalled",signal-name="SIGINT",
24192 signal-meaning="Interrupt"
24196 @c @subheading -exec-signal
24199 @subheading The @code{-exec-step} Command
24202 @subsubheading Synopsis
24205 -exec-step [--reverse]
24208 Resumes execution of the inferior program, stopping when the beginning
24209 of the next source line is reached, if the next source line is not a
24210 function call. If it is, stop at the first instruction of the called
24211 function. If the @samp{--reverse} option is specified, resumes reverse
24212 execution of the inferior program, stopping at the beginning of the
24213 previously executed source line.
24215 @subsubheading @value{GDBN} Command
24217 The corresponding @value{GDBN} command is @samp{step}.
24219 @subsubheading Example
24221 Stepping into a function:
24227 *stopped,reason="end-stepping-range",
24228 frame=@{func="foo",args=[@{name="a",value="10"@},
24229 @{name="b",value="0"@}],file="recursive2.c",
24230 fullname="/home/foo/bar/recursive2.c",line="11"@}
24240 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
24245 @subheading The @code{-exec-step-instruction} Command
24246 @findex -exec-step-instruction
24248 @subsubheading Synopsis
24251 -exec-step-instruction [--reverse]
24254 Resumes the inferior which executes one machine instruction. If the
24255 @samp{--reverse} option is specified, resumes reverse execution of the
24256 inferior program, stopping at the previously executed instruction.
24257 The output, once @value{GDBN} has stopped, will vary depending on
24258 whether we have stopped in the middle of a source line or not. In the
24259 former case, the address at which the program stopped will be printed
24262 @subsubheading @value{GDBN} Command
24264 The corresponding @value{GDBN} command is @samp{stepi}.
24266 @subsubheading Example
24270 -exec-step-instruction
24274 *stopped,reason="end-stepping-range",
24275 frame=@{func="foo",args=[],file="try.c",
24276 fullname="/home/foo/bar/try.c",line="10"@}
24278 -exec-step-instruction
24282 *stopped,reason="end-stepping-range",
24283 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
24284 fullname="/home/foo/bar/try.c",line="10"@}
24289 @subheading The @code{-exec-until} Command
24290 @findex -exec-until
24292 @subsubheading Synopsis
24295 -exec-until [ @var{location} ]
24298 Executes the inferior until the @var{location} specified in the
24299 argument is reached. If there is no argument, the inferior executes
24300 until a source line greater than the current one is reached. The
24301 reason for stopping in this case will be @samp{location-reached}.
24303 @subsubheading @value{GDBN} Command
24305 The corresponding @value{GDBN} command is @samp{until}.
24307 @subsubheading Example
24311 -exec-until recursive2.c:6
24315 *stopped,reason="location-reached",frame=@{func="main",args=[],
24316 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
24321 @subheading -file-clear
24322 Is this going away????
24325 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24326 @node GDB/MI Stack Manipulation
24327 @section @sc{gdb/mi} Stack Manipulation Commands
24330 @subheading The @code{-stack-info-frame} Command
24331 @findex -stack-info-frame
24333 @subsubheading Synopsis
24339 Get info on the selected frame.
24341 @subsubheading @value{GDBN} Command
24343 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
24344 (without arguments).
24346 @subsubheading Example
24351 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
24352 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24353 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
24357 @subheading The @code{-stack-info-depth} Command
24358 @findex -stack-info-depth
24360 @subsubheading Synopsis
24363 -stack-info-depth [ @var{max-depth} ]
24366 Return the depth of the stack. If the integer argument @var{max-depth}
24367 is specified, do not count beyond @var{max-depth} frames.
24369 @subsubheading @value{GDBN} Command
24371 There's no equivalent @value{GDBN} command.
24373 @subsubheading Example
24375 For a stack with frame levels 0 through 11:
24382 -stack-info-depth 4
24385 -stack-info-depth 12
24388 -stack-info-depth 11
24391 -stack-info-depth 13
24396 @subheading The @code{-stack-list-arguments} Command
24397 @findex -stack-list-arguments
24399 @subsubheading Synopsis
24402 -stack-list-arguments @var{print-values}
24403 [ @var{low-frame} @var{high-frame} ]
24406 Display a list of the arguments for the frames between @var{low-frame}
24407 and @var{high-frame} (inclusive). If @var{low-frame} and
24408 @var{high-frame} are not provided, list the arguments for the whole
24409 call stack. If the two arguments are equal, show the single frame
24410 at the corresponding level. It is an error if @var{low-frame} is
24411 larger than the actual number of frames. On the other hand,
24412 @var{high-frame} may be larger than the actual number of frames, in
24413 which case only existing frames will be returned.
24415 If @var{print-values} is 0 or @code{--no-values}, print only the names of
24416 the variables; if it is 1 or @code{--all-values}, print also their
24417 values; and if it is 2 or @code{--simple-values}, print the name,
24418 type and value for simple data types, and the name and type for arrays,
24419 structures and unions.
24421 Use of this command to obtain arguments in a single frame is
24422 deprecated in favor of the @samp{-stack-list-variables} command.
24424 @subsubheading @value{GDBN} Command
24426 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
24427 @samp{gdb_get_args} command which partially overlaps with the
24428 functionality of @samp{-stack-list-arguments}.
24430 @subsubheading Example
24437 frame=@{level="0",addr="0x00010734",func="callee4",
24438 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24439 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
24440 frame=@{level="1",addr="0x0001076c",func="callee3",
24441 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24442 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
24443 frame=@{level="2",addr="0x0001078c",func="callee2",
24444 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24445 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
24446 frame=@{level="3",addr="0x000107b4",func="callee1",
24447 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24448 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
24449 frame=@{level="4",addr="0x000107e0",func="main",
24450 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24451 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
24453 -stack-list-arguments 0
24456 frame=@{level="0",args=[]@},
24457 frame=@{level="1",args=[name="strarg"]@},
24458 frame=@{level="2",args=[name="intarg",name="strarg"]@},
24459 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
24460 frame=@{level="4",args=[]@}]
24462 -stack-list-arguments 1
24465 frame=@{level="0",args=[]@},
24467 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
24468 frame=@{level="2",args=[
24469 @{name="intarg",value="2"@},
24470 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
24471 @{frame=@{level="3",args=[
24472 @{name="intarg",value="2"@},
24473 @{name="strarg",value="0x11940 \"A string argument.\""@},
24474 @{name="fltarg",value="3.5"@}]@},
24475 frame=@{level="4",args=[]@}]
24477 -stack-list-arguments 0 2 2
24478 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
24480 -stack-list-arguments 1 2 2
24481 ^done,stack-args=[frame=@{level="2",
24482 args=[@{name="intarg",value="2"@},
24483 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
24487 @c @subheading -stack-list-exception-handlers
24490 @subheading The @code{-stack-list-frames} Command
24491 @findex -stack-list-frames
24493 @subsubheading Synopsis
24496 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
24499 List the frames currently on the stack. For each frame it displays the
24504 The frame number, 0 being the topmost frame, i.e., the innermost function.
24506 The @code{$pc} value for that frame.
24510 File name of the source file where the function lives.
24512 Line number corresponding to the @code{$pc}.
24515 If invoked without arguments, this command prints a backtrace for the
24516 whole stack. If given two integer arguments, it shows the frames whose
24517 levels are between the two arguments (inclusive). If the two arguments
24518 are equal, it shows the single frame at the corresponding level. It is
24519 an error if @var{low-frame} is larger than the actual number of
24520 frames. On the other hand, @var{high-frame} may be larger than the
24521 actual number of frames, in which case only existing frames will be returned.
24523 @subsubheading @value{GDBN} Command
24525 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
24527 @subsubheading Example
24529 Full stack backtrace:
24535 [frame=@{level="0",addr="0x0001076c",func="foo",
24536 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
24537 frame=@{level="1",addr="0x000107a4",func="foo",
24538 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24539 frame=@{level="2",addr="0x000107a4",func="foo",
24540 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24541 frame=@{level="3",addr="0x000107a4",func="foo",
24542 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24543 frame=@{level="4",addr="0x000107a4",func="foo",
24544 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24545 frame=@{level="5",addr="0x000107a4",func="foo",
24546 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24547 frame=@{level="6",addr="0x000107a4",func="foo",
24548 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24549 frame=@{level="7",addr="0x000107a4",func="foo",
24550 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24551 frame=@{level="8",addr="0x000107a4",func="foo",
24552 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24553 frame=@{level="9",addr="0x000107a4",func="foo",
24554 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24555 frame=@{level="10",addr="0x000107a4",func="foo",
24556 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24557 frame=@{level="11",addr="0x00010738",func="main",
24558 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
24562 Show frames between @var{low_frame} and @var{high_frame}:
24566 -stack-list-frames 3 5
24568 [frame=@{level="3",addr="0x000107a4",func="foo",
24569 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24570 frame=@{level="4",addr="0x000107a4",func="foo",
24571 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24572 frame=@{level="5",addr="0x000107a4",func="foo",
24573 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
24577 Show a single frame:
24581 -stack-list-frames 3 3
24583 [frame=@{level="3",addr="0x000107a4",func="foo",
24584 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
24589 @subheading The @code{-stack-list-locals} Command
24590 @findex -stack-list-locals
24592 @subsubheading Synopsis
24595 -stack-list-locals @var{print-values}
24598 Display the local variable names for the selected frame. If
24599 @var{print-values} is 0 or @code{--no-values}, print only the names of
24600 the variables; if it is 1 or @code{--all-values}, print also their
24601 values; and if it is 2 or @code{--simple-values}, print the name,
24602 type and value for simple data types, and the name and type for arrays,
24603 structures and unions. In this last case, a frontend can immediately
24604 display the value of simple data types and create variable objects for
24605 other data types when the user wishes to explore their values in
24608 This command is deprecated in favor of the
24609 @samp{-stack-list-variables} command.
24611 @subsubheading @value{GDBN} Command
24613 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
24615 @subsubheading Example
24619 -stack-list-locals 0
24620 ^done,locals=[name="A",name="B",name="C"]
24622 -stack-list-locals --all-values
24623 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
24624 @{name="C",value="@{1, 2, 3@}"@}]
24625 -stack-list-locals --simple-values
24626 ^done,locals=[@{name="A",type="int",value="1"@},
24627 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
24631 @subheading The @code{-stack-list-variables} Command
24632 @findex -stack-list-variables
24634 @subsubheading Synopsis
24637 -stack-list-variables @var{print-values}
24640 Display the names of local variables and function arguments for the selected frame. If
24641 @var{print-values} is 0 or @code{--no-values}, print only the names of
24642 the variables; if it is 1 or @code{--all-values}, print also their
24643 values; and if it is 2 or @code{--simple-values}, print the name,
24644 type and value for simple data types, and the name and type for arrays,
24645 structures and unions.
24647 @subsubheading Example
24651 -stack-list-variables --thread 1 --frame 0 --all-values
24652 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
24657 @subheading The @code{-stack-select-frame} Command
24658 @findex -stack-select-frame
24660 @subsubheading Synopsis
24663 -stack-select-frame @var{framenum}
24666 Change the selected frame. Select a different frame @var{framenum} on
24669 This command in deprecated in favor of passing the @samp{--frame}
24670 option to every command.
24672 @subsubheading @value{GDBN} Command
24674 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
24675 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
24677 @subsubheading Example
24681 -stack-select-frame 2
24686 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24687 @node GDB/MI Variable Objects
24688 @section @sc{gdb/mi} Variable Objects
24692 @subheading Motivation for Variable Objects in @sc{gdb/mi}
24694 For the implementation of a variable debugger window (locals, watched
24695 expressions, etc.), we are proposing the adaptation of the existing code
24696 used by @code{Insight}.
24698 The two main reasons for that are:
24702 It has been proven in practice (it is already on its second generation).
24705 It will shorten development time (needless to say how important it is
24709 The original interface was designed to be used by Tcl code, so it was
24710 slightly changed so it could be used through @sc{gdb/mi}. This section
24711 describes the @sc{gdb/mi} operations that will be available and gives some
24712 hints about their use.
24714 @emph{Note}: In addition to the set of operations described here, we
24715 expect the @sc{gui} implementation of a variable window to require, at
24716 least, the following operations:
24719 @item @code{-gdb-show} @code{output-radix}
24720 @item @code{-stack-list-arguments}
24721 @item @code{-stack-list-locals}
24722 @item @code{-stack-select-frame}
24727 @subheading Introduction to Variable Objects
24729 @cindex variable objects in @sc{gdb/mi}
24731 Variable objects are "object-oriented" MI interface for examining and
24732 changing values of expressions. Unlike some other MI interfaces that
24733 work with expressions, variable objects are specifically designed for
24734 simple and efficient presentation in the frontend. A variable object
24735 is identified by string name. When a variable object is created, the
24736 frontend specifies the expression for that variable object. The
24737 expression can be a simple variable, or it can be an arbitrary complex
24738 expression, and can even involve CPU registers. After creating a
24739 variable object, the frontend can invoke other variable object
24740 operations---for example to obtain or change the value of a variable
24741 object, or to change display format.
24743 Variable objects have hierarchical tree structure. Any variable object
24744 that corresponds to a composite type, such as structure in C, has
24745 a number of child variable objects, for example corresponding to each
24746 element of a structure. A child variable object can itself have
24747 children, recursively. Recursion ends when we reach
24748 leaf variable objects, which always have built-in types. Child variable
24749 objects are created only by explicit request, so if a frontend
24750 is not interested in the children of a particular variable object, no
24751 child will be created.
24753 For a leaf variable object it is possible to obtain its value as a
24754 string, or set the value from a string. String value can be also
24755 obtained for a non-leaf variable object, but it's generally a string
24756 that only indicates the type of the object, and does not list its
24757 contents. Assignment to a non-leaf variable object is not allowed.
24759 A frontend does not need to read the values of all variable objects each time
24760 the program stops. Instead, MI provides an update command that lists all
24761 variable objects whose values has changed since the last update
24762 operation. This considerably reduces the amount of data that must
24763 be transferred to the frontend. As noted above, children variable
24764 objects are created on demand, and only leaf variable objects have a
24765 real value. As result, gdb will read target memory only for leaf
24766 variables that frontend has created.
24768 The automatic update is not always desirable. For example, a frontend
24769 might want to keep a value of some expression for future reference,
24770 and never update it. For another example, fetching memory is
24771 relatively slow for embedded targets, so a frontend might want
24772 to disable automatic update for the variables that are either not
24773 visible on the screen, or ``closed''. This is possible using so
24774 called ``frozen variable objects''. Such variable objects are never
24775 implicitly updated.
24777 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
24778 fixed variable object, the expression is parsed when the variable
24779 object is created, including associating identifiers to specific
24780 variables. The meaning of expression never changes. For a floating
24781 variable object the values of variables whose names appear in the
24782 expressions are re-evaluated every time in the context of the current
24783 frame. Consider this example:
24788 struct work_state state;
24795 If a fixed variable object for the @code{state} variable is created in
24796 this function, and we enter the recursive call, the the variable
24797 object will report the value of @code{state} in the top-level
24798 @code{do_work} invocation. On the other hand, a floating variable
24799 object will report the value of @code{state} in the current frame.
24801 If an expression specified when creating a fixed variable object
24802 refers to a local variable, the variable object becomes bound to the
24803 thread and frame in which the variable object is created. When such
24804 variable object is updated, @value{GDBN} makes sure that the
24805 thread/frame combination the variable object is bound to still exists,
24806 and re-evaluates the variable object in context of that thread/frame.
24808 The following is the complete set of @sc{gdb/mi} operations defined to
24809 access this functionality:
24811 @multitable @columnfractions .4 .6
24812 @item @strong{Operation}
24813 @tab @strong{Description}
24815 @item @code{-enable-pretty-printing}
24816 @tab enable Python-based pretty-printing
24817 @item @code{-var-create}
24818 @tab create a variable object
24819 @item @code{-var-delete}
24820 @tab delete the variable object and/or its children
24821 @item @code{-var-set-format}
24822 @tab set the display format of this variable
24823 @item @code{-var-show-format}
24824 @tab show the display format of this variable
24825 @item @code{-var-info-num-children}
24826 @tab tells how many children this object has
24827 @item @code{-var-list-children}
24828 @tab return a list of the object's children
24829 @item @code{-var-info-type}
24830 @tab show the type of this variable object
24831 @item @code{-var-info-expression}
24832 @tab print parent-relative expression that this variable object represents
24833 @item @code{-var-info-path-expression}
24834 @tab print full expression that this variable object represents
24835 @item @code{-var-show-attributes}
24836 @tab is this variable editable? does it exist here?
24837 @item @code{-var-evaluate-expression}
24838 @tab get the value of this variable
24839 @item @code{-var-assign}
24840 @tab set the value of this variable
24841 @item @code{-var-update}
24842 @tab update the variable and its children
24843 @item @code{-var-set-frozen}
24844 @tab set frozeness attribute
24845 @item @code{-var-set-update-range}
24846 @tab set range of children to display on update
24849 In the next subsection we describe each operation in detail and suggest
24850 how it can be used.
24852 @subheading Description And Use of Operations on Variable Objects
24854 @subheading The @code{-enable-pretty-printing} Command
24855 @findex -enable-pretty-printing
24858 -enable-pretty-printing
24861 @value{GDBN} allows Python-based visualizers to affect the output of the
24862 MI variable object commands. However, because there was no way to
24863 implement this in a fully backward-compatible way, a front end must
24864 request that this functionality be enabled.
24866 Once enabled, this feature cannot be disabled.
24868 Note that if Python support has not been compiled into @value{GDBN},
24869 this command will still succeed (and do nothing).
24871 This feature is currently (as of @value{GDBN} 7.0) experimental, and
24872 may work differently in future versions of @value{GDBN}.
24874 @subheading The @code{-var-create} Command
24875 @findex -var-create
24877 @subsubheading Synopsis
24880 -var-create @{@var{name} | "-"@}
24881 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
24884 This operation creates a variable object, which allows the monitoring of
24885 a variable, the result of an expression, a memory cell or a CPU
24888 The @var{name} parameter is the string by which the object can be
24889 referenced. It must be unique. If @samp{-} is specified, the varobj
24890 system will generate a string ``varNNNNNN'' automatically. It will be
24891 unique provided that one does not specify @var{name} of that format.
24892 The command fails if a duplicate name is found.
24894 The frame under which the expression should be evaluated can be
24895 specified by @var{frame-addr}. A @samp{*} indicates that the current
24896 frame should be used. A @samp{@@} indicates that a floating variable
24897 object must be created.
24899 @var{expression} is any expression valid on the current language set (must not
24900 begin with a @samp{*}), or one of the following:
24904 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
24907 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
24910 @samp{$@var{regname}} --- a CPU register name
24913 @cindex dynamic varobj
24914 A varobj's contents may be provided by a Python-based pretty-printer. In this
24915 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
24916 have slightly different semantics in some cases. If the
24917 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
24918 will never create a dynamic varobj. This ensures backward
24919 compatibility for existing clients.
24921 @subsubheading Result
24923 This operation returns attributes of the newly-created varobj. These
24928 The name of the varobj.
24931 The number of children of the varobj. This number is not necessarily
24932 reliable for a dynamic varobj. Instead, you must examine the
24933 @samp{has_more} attribute.
24936 The varobj's scalar value. For a varobj whose type is some sort of
24937 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
24938 will not be interesting.
24941 The varobj's type. This is a string representation of the type, as
24942 would be printed by the @value{GDBN} CLI.
24945 If a variable object is bound to a specific thread, then this is the
24946 thread's identifier.
24949 For a dynamic varobj, this indicates whether there appear to be any
24950 children available. For a non-dynamic varobj, this will be 0.
24953 This attribute will be present and have the value @samp{1} if the
24954 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
24955 then this attribute will not be present.
24958 A dynamic varobj can supply a display hint to the front end. The
24959 value comes directly from the Python pretty-printer object's
24960 @code{display_hint} method. @xref{Pretty Printing}.
24963 Typical output will look like this:
24966 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
24967 has_more="@var{has_more}"
24971 @subheading The @code{-var-delete} Command
24972 @findex -var-delete
24974 @subsubheading Synopsis
24977 -var-delete [ -c ] @var{name}
24980 Deletes a previously created variable object and all of its children.
24981 With the @samp{-c} option, just deletes the children.
24983 Returns an error if the object @var{name} is not found.
24986 @subheading The @code{-var-set-format} Command
24987 @findex -var-set-format
24989 @subsubheading Synopsis
24992 -var-set-format @var{name} @var{format-spec}
24995 Sets the output format for the value of the object @var{name} to be
24998 @anchor{-var-set-format}
24999 The syntax for the @var{format-spec} is as follows:
25002 @var{format-spec} @expansion{}
25003 @{binary | decimal | hexadecimal | octal | natural@}
25006 The natural format is the default format choosen automatically
25007 based on the variable type (like decimal for an @code{int}, hex
25008 for pointers, etc.).
25010 For a variable with children, the format is set only on the
25011 variable itself, and the children are not affected.
25013 @subheading The @code{-var-show-format} Command
25014 @findex -var-show-format
25016 @subsubheading Synopsis
25019 -var-show-format @var{name}
25022 Returns the format used to display the value of the object @var{name}.
25025 @var{format} @expansion{}
25030 @subheading The @code{-var-info-num-children} Command
25031 @findex -var-info-num-children
25033 @subsubheading Synopsis
25036 -var-info-num-children @var{name}
25039 Returns the number of children of a variable object @var{name}:
25045 Note that this number is not completely reliable for a dynamic varobj.
25046 It will return the current number of children, but more children may
25050 @subheading The @code{-var-list-children} Command
25051 @findex -var-list-children
25053 @subsubheading Synopsis
25056 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
25058 @anchor{-var-list-children}
25060 Return a list of the children of the specified variable object and
25061 create variable objects for them, if they do not already exist. With
25062 a single argument or if @var{print-values} has a value for of 0 or
25063 @code{--no-values}, print only the names of the variables; if
25064 @var{print-values} is 1 or @code{--all-values}, also print their
25065 values; and if it is 2 or @code{--simple-values} print the name and
25066 value for simple data types and just the name for arrays, structures
25069 @var{from} and @var{to}, if specified, indicate the range of children
25070 to report. If @var{from} or @var{to} is less than zero, the range is
25071 reset and all children will be reported. Otherwise, children starting
25072 at @var{from} (zero-based) and up to and excluding @var{to} will be
25075 If a child range is requested, it will only affect the current call to
25076 @code{-var-list-children}, but not future calls to @code{-var-update}.
25077 For this, you must instead use @code{-var-set-update-range}. The
25078 intent of this approach is to enable a front end to implement any
25079 update approach it likes; for example, scrolling a view may cause the
25080 front end to request more children with @code{-var-list-children}, and
25081 then the front end could call @code{-var-set-update-range} with a
25082 different range to ensure that future updates are restricted to just
25085 For each child the following results are returned:
25090 Name of the variable object created for this child.
25093 The expression to be shown to the user by the front end to designate this child.
25094 For example this may be the name of a structure member.
25096 For a dynamic varobj, this value cannot be used to form an
25097 expression. There is no way to do this at all with a dynamic varobj.
25099 For C/C@t{++} structures there are several pseudo children returned to
25100 designate access qualifiers. For these pseudo children @var{exp} is
25101 @samp{public}, @samp{private}, or @samp{protected}. In this case the
25102 type and value are not present.
25104 A dynamic varobj will not report the access qualifying
25105 pseudo-children, regardless of the language. This information is not
25106 available at all with a dynamic varobj.
25109 Number of children this child has. For a dynamic varobj, this will be
25113 The type of the child.
25116 If values were requested, this is the value.
25119 If this variable object is associated with a thread, this is the thread id.
25120 Otherwise this result is not present.
25123 If the variable object is frozen, this variable will be present with a value of 1.
25126 The result may have its own attributes:
25130 A dynamic varobj can supply a display hint to the front end. The
25131 value comes directly from the Python pretty-printer object's
25132 @code{display_hint} method. @xref{Pretty Printing}.
25135 This is an integer attribute which is nonzero if there are children
25136 remaining after the end of the selected range.
25139 @subsubheading Example
25143 -var-list-children n
25144 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
25145 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
25147 -var-list-children --all-values n
25148 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
25149 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
25153 @subheading The @code{-var-info-type} Command
25154 @findex -var-info-type
25156 @subsubheading Synopsis
25159 -var-info-type @var{name}
25162 Returns the type of the specified variable @var{name}. The type is
25163 returned as a string in the same format as it is output by the
25167 type=@var{typename}
25171 @subheading The @code{-var-info-expression} Command
25172 @findex -var-info-expression
25174 @subsubheading Synopsis
25177 -var-info-expression @var{name}
25180 Returns a string that is suitable for presenting this
25181 variable object in user interface. The string is generally
25182 not valid expression in the current language, and cannot be evaluated.
25184 For example, if @code{a} is an array, and variable object
25185 @code{A} was created for @code{a}, then we'll get this output:
25188 (gdb) -var-info-expression A.1
25189 ^done,lang="C",exp="1"
25193 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
25195 Note that the output of the @code{-var-list-children} command also
25196 includes those expressions, so the @code{-var-info-expression} command
25199 @subheading The @code{-var-info-path-expression} Command
25200 @findex -var-info-path-expression
25202 @subsubheading Synopsis
25205 -var-info-path-expression @var{name}
25208 Returns an expression that can be evaluated in the current
25209 context and will yield the same value that a variable object has.
25210 Compare this with the @code{-var-info-expression} command, which
25211 result can be used only for UI presentation. Typical use of
25212 the @code{-var-info-path-expression} command is creating a
25213 watchpoint from a variable object.
25215 This command is currently not valid for children of a dynamic varobj,
25216 and will give an error when invoked on one.
25218 For example, suppose @code{C} is a C@t{++} class, derived from class
25219 @code{Base}, and that the @code{Base} class has a member called
25220 @code{m_size}. Assume a variable @code{c} is has the type of
25221 @code{C} and a variable object @code{C} was created for variable
25222 @code{c}. Then, we'll get this output:
25224 (gdb) -var-info-path-expression C.Base.public.m_size
25225 ^done,path_expr=((Base)c).m_size)
25228 @subheading The @code{-var-show-attributes} Command
25229 @findex -var-show-attributes
25231 @subsubheading Synopsis
25234 -var-show-attributes @var{name}
25237 List attributes of the specified variable object @var{name}:
25240 status=@var{attr} [ ( ,@var{attr} )* ]
25244 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
25246 @subheading The @code{-var-evaluate-expression} Command
25247 @findex -var-evaluate-expression
25249 @subsubheading Synopsis
25252 -var-evaluate-expression [-f @var{format-spec}] @var{name}
25255 Evaluates the expression that is represented by the specified variable
25256 object and returns its value as a string. The format of the string
25257 can be specified with the @samp{-f} option. The possible values of
25258 this option are the same as for @code{-var-set-format}
25259 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
25260 the current display format will be used. The current display format
25261 can be changed using the @code{-var-set-format} command.
25267 Note that one must invoke @code{-var-list-children} for a variable
25268 before the value of a child variable can be evaluated.
25270 @subheading The @code{-var-assign} Command
25271 @findex -var-assign
25273 @subsubheading Synopsis
25276 -var-assign @var{name} @var{expression}
25279 Assigns the value of @var{expression} to the variable object specified
25280 by @var{name}. The object must be @samp{editable}. If the variable's
25281 value is altered by the assign, the variable will show up in any
25282 subsequent @code{-var-update} list.
25284 @subsubheading Example
25292 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
25296 @subheading The @code{-var-update} Command
25297 @findex -var-update
25299 @subsubheading Synopsis
25302 -var-update [@var{print-values}] @{@var{name} | "*"@}
25305 Reevaluate the expressions corresponding to the variable object
25306 @var{name} and all its direct and indirect children, and return the
25307 list of variable objects whose values have changed; @var{name} must
25308 be a root variable object. Here, ``changed'' means that the result of
25309 @code{-var-evaluate-expression} before and after the
25310 @code{-var-update} is different. If @samp{*} is used as the variable
25311 object names, all existing variable objects are updated, except
25312 for frozen ones (@pxref{-var-set-frozen}). The option
25313 @var{print-values} determines whether both names and values, or just
25314 names are printed. The possible values of this option are the same
25315 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
25316 recommended to use the @samp{--all-values} option, to reduce the
25317 number of MI commands needed on each program stop.
25319 With the @samp{*} parameter, if a variable object is bound to a
25320 currently running thread, it will not be updated, without any
25323 If @code{-var-set-update-range} was previously used on a varobj, then
25324 only the selected range of children will be reported.
25326 @code{-var-update} reports all the changed varobjs in a tuple named
25329 Each item in the change list is itself a tuple holding:
25333 The name of the varobj.
25336 If values were requested for this update, then this field will be
25337 present and will hold the value of the varobj.
25340 @anchor{-var-update}
25341 This field is a string which may take one of three values:
25345 The variable object's current value is valid.
25348 The variable object does not currently hold a valid value but it may
25349 hold one in the future if its associated expression comes back into
25353 The variable object no longer holds a valid value.
25354 This can occur when the executable file being debugged has changed,
25355 either through recompilation or by using the @value{GDBN} @code{file}
25356 command. The front end should normally choose to delete these variable
25360 In the future new values may be added to this list so the front should
25361 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
25364 This is only present if the varobj is still valid. If the type
25365 changed, then this will be the string @samp{true}; otherwise it will
25369 If the varobj's type changed, then this field will be present and will
25372 @item new_num_children
25373 For a dynamic varobj, if the number of children changed, or if the
25374 type changed, this will be the new number of children.
25376 The @samp{numchild} field in other varobj responses is generally not
25377 valid for a dynamic varobj -- it will show the number of children that
25378 @value{GDBN} knows about, but because dynamic varobjs lazily
25379 instantiate their children, this will not reflect the number of
25380 children which may be available.
25382 The @samp{new_num_children} attribute only reports changes to the
25383 number of children known by @value{GDBN}. This is the only way to
25384 detect whether an update has removed children (which necessarily can
25385 only happen at the end of the update range).
25388 The display hint, if any.
25391 This is an integer value, which will be 1 if there are more children
25392 available outside the varobj's update range.
25395 This attribute will be present and have the value @samp{1} if the
25396 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
25397 then this attribute will not be present.
25400 If new children were added to a dynamic varobj within the selected
25401 update range (as set by @code{-var-set-update-range}), then they will
25402 be listed in this attribute.
25405 @subsubheading Example
25412 -var-update --all-values var1
25413 ^done,changelist=[@{name="var1",value="3",in_scope="true",
25414 type_changed="false"@}]
25418 @subheading The @code{-var-set-frozen} Command
25419 @findex -var-set-frozen
25420 @anchor{-var-set-frozen}
25422 @subsubheading Synopsis
25425 -var-set-frozen @var{name} @var{flag}
25428 Set the frozenness flag on the variable object @var{name}. The
25429 @var{flag} parameter should be either @samp{1} to make the variable
25430 frozen or @samp{0} to make it unfrozen. If a variable object is
25431 frozen, then neither itself, nor any of its children, are
25432 implicitly updated by @code{-var-update} of
25433 a parent variable or by @code{-var-update *}. Only
25434 @code{-var-update} of the variable itself will update its value and
25435 values of its children. After a variable object is unfrozen, it is
25436 implicitly updated by all subsequent @code{-var-update} operations.
25437 Unfreezing a variable does not update it, only subsequent
25438 @code{-var-update} does.
25440 @subsubheading Example
25444 -var-set-frozen V 1
25449 @subheading The @code{-var-set-update-range} command
25450 @findex -var-set-update-range
25451 @anchor{-var-set-update-range}
25453 @subsubheading Synopsis
25456 -var-set-update-range @var{name} @var{from} @var{to}
25459 Set the range of children to be returned by future invocations of
25460 @code{-var-update}.
25462 @var{from} and @var{to} indicate the range of children to report. If
25463 @var{from} or @var{to} is less than zero, the range is reset and all
25464 children will be reported. Otherwise, children starting at @var{from}
25465 (zero-based) and up to and excluding @var{to} will be reported.
25467 @subsubheading Example
25471 -var-set-update-range V 1 2
25475 @subheading The @code{-var-set-visualizer} command
25476 @findex -var-set-visualizer
25477 @anchor{-var-set-visualizer}
25479 @subsubheading Synopsis
25482 -var-set-visualizer @var{name} @var{visualizer}
25485 Set a visualizer for the variable object @var{name}.
25487 @var{visualizer} is the visualizer to use. The special value
25488 @samp{None} means to disable any visualizer in use.
25490 If not @samp{None}, @var{visualizer} must be a Python expression.
25491 This expression must evaluate to a callable object which accepts a
25492 single argument. @value{GDBN} will call this object with the value of
25493 the varobj @var{name} as an argument (this is done so that the same
25494 Python pretty-printing code can be used for both the CLI and MI).
25495 When called, this object must return an object which conforms to the
25496 pretty-printing interface (@pxref{Pretty Printing}).
25498 The pre-defined function @code{gdb.default_visualizer} may be used to
25499 select a visualizer by following the built-in process
25500 (@pxref{Selecting Pretty-Printers}). This is done automatically when
25501 a varobj is created, and so ordinarily is not needed.
25503 This feature is only available if Python support is enabled. The MI
25504 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
25505 can be used to check this.
25507 @subsubheading Example
25509 Resetting the visualizer:
25513 -var-set-visualizer V None
25517 Reselecting the default (type-based) visualizer:
25521 -var-set-visualizer V gdb.default_visualizer
25525 Suppose @code{SomeClass} is a visualizer class. A lambda expression
25526 can be used to instantiate this class for a varobj:
25530 -var-set-visualizer V "lambda val: SomeClass()"
25534 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25535 @node GDB/MI Data Manipulation
25536 @section @sc{gdb/mi} Data Manipulation
25538 @cindex data manipulation, in @sc{gdb/mi}
25539 @cindex @sc{gdb/mi}, data manipulation
25540 This section describes the @sc{gdb/mi} commands that manipulate data:
25541 examine memory and registers, evaluate expressions, etc.
25543 @c REMOVED FROM THE INTERFACE.
25544 @c @subheading -data-assign
25545 @c Change the value of a program variable. Plenty of side effects.
25546 @c @subsubheading GDB Command
25548 @c @subsubheading Example
25551 @subheading The @code{-data-disassemble} Command
25552 @findex -data-disassemble
25554 @subsubheading Synopsis
25558 [ -s @var{start-addr} -e @var{end-addr} ]
25559 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
25567 @item @var{start-addr}
25568 is the beginning address (or @code{$pc})
25569 @item @var{end-addr}
25571 @item @var{filename}
25572 is the name of the file to disassemble
25573 @item @var{linenum}
25574 is the line number to disassemble around
25576 is the number of disassembly lines to be produced. If it is -1,
25577 the whole function will be disassembled, in case no @var{end-addr} is
25578 specified. If @var{end-addr} is specified as a non-zero value, and
25579 @var{lines} is lower than the number of disassembly lines between
25580 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
25581 displayed; if @var{lines} is higher than the number of lines between
25582 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
25585 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
25589 @subsubheading Result
25591 The output for each instruction is composed of four fields:
25600 Note that whatever included in the instruction field, is not manipulated
25601 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
25603 @subsubheading @value{GDBN} Command
25605 There's no direct mapping from this command to the CLI.
25607 @subsubheading Example
25609 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
25613 -data-disassemble -s $pc -e "$pc + 20" -- 0
25616 @{address="0x000107c0",func-name="main",offset="4",
25617 inst="mov 2, %o0"@},
25618 @{address="0x000107c4",func-name="main",offset="8",
25619 inst="sethi %hi(0x11800), %o2"@},
25620 @{address="0x000107c8",func-name="main",offset="12",
25621 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
25622 @{address="0x000107cc",func-name="main",offset="16",
25623 inst="sethi %hi(0x11800), %o2"@},
25624 @{address="0x000107d0",func-name="main",offset="20",
25625 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
25629 Disassemble the whole @code{main} function. Line 32 is part of
25633 -data-disassemble -f basics.c -l 32 -- 0
25635 @{address="0x000107bc",func-name="main",offset="0",
25636 inst="save %sp, -112, %sp"@},
25637 @{address="0x000107c0",func-name="main",offset="4",
25638 inst="mov 2, %o0"@},
25639 @{address="0x000107c4",func-name="main",offset="8",
25640 inst="sethi %hi(0x11800), %o2"@},
25642 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
25643 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
25647 Disassemble 3 instructions from the start of @code{main}:
25651 -data-disassemble -f basics.c -l 32 -n 3 -- 0
25653 @{address="0x000107bc",func-name="main",offset="0",
25654 inst="save %sp, -112, %sp"@},
25655 @{address="0x000107c0",func-name="main",offset="4",
25656 inst="mov 2, %o0"@},
25657 @{address="0x000107c4",func-name="main",offset="8",
25658 inst="sethi %hi(0x11800), %o2"@}]
25662 Disassemble 3 instructions from the start of @code{main} in mixed mode:
25666 -data-disassemble -f basics.c -l 32 -n 3 -- 1
25668 src_and_asm_line=@{line="31",
25669 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
25670 testsuite/gdb.mi/basics.c",line_asm_insn=[
25671 @{address="0x000107bc",func-name="main",offset="0",
25672 inst="save %sp, -112, %sp"@}]@},
25673 src_and_asm_line=@{line="32",
25674 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
25675 testsuite/gdb.mi/basics.c",line_asm_insn=[
25676 @{address="0x000107c0",func-name="main",offset="4",
25677 inst="mov 2, %o0"@},
25678 @{address="0x000107c4",func-name="main",offset="8",
25679 inst="sethi %hi(0x11800), %o2"@}]@}]
25684 @subheading The @code{-data-evaluate-expression} Command
25685 @findex -data-evaluate-expression
25687 @subsubheading Synopsis
25690 -data-evaluate-expression @var{expr}
25693 Evaluate @var{expr} as an expression. The expression could contain an
25694 inferior function call. The function call will execute synchronously.
25695 If the expression contains spaces, it must be enclosed in double quotes.
25697 @subsubheading @value{GDBN} Command
25699 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
25700 @samp{call}. In @code{gdbtk} only, there's a corresponding
25701 @samp{gdb_eval} command.
25703 @subsubheading Example
25705 In the following example, the numbers that precede the commands are the
25706 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
25707 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
25711 211-data-evaluate-expression A
25714 311-data-evaluate-expression &A
25715 311^done,value="0xefffeb7c"
25717 411-data-evaluate-expression A+3
25720 511-data-evaluate-expression "A + 3"
25726 @subheading The @code{-data-list-changed-registers} Command
25727 @findex -data-list-changed-registers
25729 @subsubheading Synopsis
25732 -data-list-changed-registers
25735 Display a list of the registers that have changed.
25737 @subsubheading @value{GDBN} Command
25739 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
25740 has the corresponding command @samp{gdb_changed_register_list}.
25742 @subsubheading Example
25744 On a PPC MBX board:
25752 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
25753 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
25756 -data-list-changed-registers
25757 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
25758 "10","11","13","14","15","16","17","18","19","20","21","22","23",
25759 "24","25","26","27","28","30","31","64","65","66","67","69"]
25764 @subheading The @code{-data-list-register-names} Command
25765 @findex -data-list-register-names
25767 @subsubheading Synopsis
25770 -data-list-register-names [ ( @var{regno} )+ ]
25773 Show a list of register names for the current target. If no arguments
25774 are given, it shows a list of the names of all the registers. If
25775 integer numbers are given as arguments, it will print a list of the
25776 names of the registers corresponding to the arguments. To ensure
25777 consistency between a register name and its number, the output list may
25778 include empty register names.
25780 @subsubheading @value{GDBN} Command
25782 @value{GDBN} does not have a command which corresponds to
25783 @samp{-data-list-register-names}. In @code{gdbtk} there is a
25784 corresponding command @samp{gdb_regnames}.
25786 @subsubheading Example
25788 For the PPC MBX board:
25791 -data-list-register-names
25792 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
25793 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
25794 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
25795 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
25796 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
25797 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
25798 "", "pc","ps","cr","lr","ctr","xer"]
25800 -data-list-register-names 1 2 3
25801 ^done,register-names=["r1","r2","r3"]
25805 @subheading The @code{-data-list-register-values} Command
25806 @findex -data-list-register-values
25808 @subsubheading Synopsis
25811 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
25814 Display the registers' contents. @var{fmt} is the format according to
25815 which the registers' contents are to be returned, followed by an optional
25816 list of numbers specifying the registers to display. A missing list of
25817 numbers indicates that the contents of all the registers must be returned.
25819 Allowed formats for @var{fmt} are:
25836 @subsubheading @value{GDBN} Command
25838 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
25839 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
25841 @subsubheading Example
25843 For a PPC MBX board (note: line breaks are for readability only, they
25844 don't appear in the actual output):
25848 -data-list-register-values r 64 65
25849 ^done,register-values=[@{number="64",value="0xfe00a300"@},
25850 @{number="65",value="0x00029002"@}]
25852 -data-list-register-values x
25853 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
25854 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
25855 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
25856 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
25857 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
25858 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
25859 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
25860 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
25861 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
25862 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
25863 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
25864 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
25865 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
25866 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
25867 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
25868 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
25869 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
25870 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
25871 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
25872 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
25873 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
25874 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
25875 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
25876 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
25877 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
25878 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
25879 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
25880 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
25881 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
25882 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
25883 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
25884 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
25885 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
25886 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
25887 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
25888 @{number="69",value="0x20002b03"@}]
25893 @subheading The @code{-data-read-memory} Command
25894 @findex -data-read-memory
25896 @subsubheading Synopsis
25899 -data-read-memory [ -o @var{byte-offset} ]
25900 @var{address} @var{word-format} @var{word-size}
25901 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
25908 @item @var{address}
25909 An expression specifying the address of the first memory word to be
25910 read. Complex expressions containing embedded white space should be
25911 quoted using the C convention.
25913 @item @var{word-format}
25914 The format to be used to print the memory words. The notation is the
25915 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
25918 @item @var{word-size}
25919 The size of each memory word in bytes.
25921 @item @var{nr-rows}
25922 The number of rows in the output table.
25924 @item @var{nr-cols}
25925 The number of columns in the output table.
25928 If present, indicates that each row should include an @sc{ascii} dump. The
25929 value of @var{aschar} is used as a padding character when a byte is not a
25930 member of the printable @sc{ascii} character set (printable @sc{ascii}
25931 characters are those whose code is between 32 and 126, inclusively).
25933 @item @var{byte-offset}
25934 An offset to add to the @var{address} before fetching memory.
25937 This command displays memory contents as a table of @var{nr-rows} by
25938 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
25939 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
25940 (returned as @samp{total-bytes}). Should less than the requested number
25941 of bytes be returned by the target, the missing words are identified
25942 using @samp{N/A}. The number of bytes read from the target is returned
25943 in @samp{nr-bytes} and the starting address used to read memory in
25946 The address of the next/previous row or page is available in
25947 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
25950 @subsubheading @value{GDBN} Command
25952 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
25953 @samp{gdb_get_mem} memory read command.
25955 @subsubheading Example
25957 Read six bytes of memory starting at @code{bytes+6} but then offset by
25958 @code{-6} bytes. Format as three rows of two columns. One byte per
25959 word. Display each word in hex.
25963 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
25964 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
25965 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
25966 prev-page="0x0000138a",memory=[
25967 @{addr="0x00001390",data=["0x00","0x01"]@},
25968 @{addr="0x00001392",data=["0x02","0x03"]@},
25969 @{addr="0x00001394",data=["0x04","0x05"]@}]
25973 Read two bytes of memory starting at address @code{shorts + 64} and
25974 display as a single word formatted in decimal.
25978 5-data-read-memory shorts+64 d 2 1 1
25979 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
25980 next-row="0x00001512",prev-row="0x0000150e",
25981 next-page="0x00001512",prev-page="0x0000150e",memory=[
25982 @{addr="0x00001510",data=["128"]@}]
25986 Read thirty two bytes of memory starting at @code{bytes+16} and format
25987 as eight rows of four columns. Include a string encoding with @samp{x}
25988 used as the non-printable character.
25992 4-data-read-memory bytes+16 x 1 8 4 x
25993 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
25994 next-row="0x000013c0",prev-row="0x0000139c",
25995 next-page="0x000013c0",prev-page="0x00001380",memory=[
25996 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
25997 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
25998 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
25999 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
26000 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
26001 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
26002 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
26003 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
26007 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26008 @node GDB/MI Tracepoint Commands
26009 @section @sc{gdb/mi} Tracepoint Commands
26011 The commands defined in this section implement MI support for
26012 tracepoints. For detailed introduction, see @ref{Tracepoints}.
26014 @subheading The @code{-trace-find} Command
26015 @findex -trace-find
26017 @subsubheading Synopsis
26020 -trace-find @var{mode} [@var{parameters}@dots{}]
26023 Find a trace frame using criteria defined by @var{mode} and
26024 @var{parameters}. The following table lists permissible
26025 modes and their parameters. For details of operation, see @ref{tfind}.
26030 No parameters are required. Stops examining trace frames.
26033 An integer is required as parameter. Selects tracepoint frame with
26036 @item tracepoint-number
26037 An integer is required as parameter. Finds next
26038 trace frame that corresponds to tracepoint with the specified number.
26041 An address is required as parameter. Finds
26042 next trace frame that corresponds to any tracepoint at the specified
26045 @item pc-inside-range
26046 Two addresses are required as parameters. Finds next trace
26047 frame that corresponds to a tracepoint at an address inside the
26048 specified range. Both bounds are considered to be inside the range.
26050 @item pc-outside-range
26051 Two addresses are required as parameters. Finds
26052 next trace frame that corresponds to a tracepoint at an address outside
26053 the specified range. Both bounds are considered to be inside the range.
26056 Line specification is required as parameter. @xref{Specify Location}.
26057 Finds next trace frame that corresponds to a tracepoint at
26058 the specified location.
26062 If @samp{none} was passed as @var{mode}, the response does not
26063 have fields. Otherwise, the response may have the following fields:
26067 This field has either @samp{0} or @samp{1} as the value, depending
26068 on whether a matching tracepoint was found.
26071 The index of the found traceframe. This field is present iff
26072 the @samp{found} field has value of @samp{1}.
26075 The index of the found tracepoint. This field is present iff
26076 the @samp{found} field has value of @samp{1}.
26079 The information about the frame corresponding to the found trace
26080 frame. This field is present only if a trace frame was found.
26081 @xref{GDB/MI Frame Information}, for description of this field.
26085 @subsubheading @value{GDBN} Command
26087 The corresponding @value{GDBN} command is @samp{tfind}.
26089 @subheading -trace-define-variable
26090 @findex -trace-define-variable
26092 @subsubheading Synopsis
26095 -trace-define-variable @var{name} [ @var{value} ]
26098 Create trace variable @var{name} if it does not exist. If
26099 @var{value} is specified, sets the initial value of the specified
26100 trace variable to that value. Note that the @var{name} should start
26101 with the @samp{$} character.
26103 @subsubheading @value{GDBN} Command
26105 The corresponding @value{GDBN} command is @samp{tvariable}.
26107 @subheading -trace-list-variables
26108 @findex -trace-list-variables
26110 @subsubheading Synopsis
26113 -trace-list-variables
26116 Return a table of all defined trace variables. Each element of the
26117 table has the following fields:
26121 The name of the trace variable. This field is always present.
26124 The initial value. This is a 64-bit signed integer. This
26125 field is always present.
26128 The value the trace variable has at the moment. This is a 64-bit
26129 signed integer. This field is absent iff current value is
26130 not defined, for example if the trace was never run, or is
26135 @subsubheading @value{GDBN} Command
26137 The corresponding @value{GDBN} command is @samp{tvariables}.
26139 @subsubheading Example
26143 -trace-list-variables
26144 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
26145 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
26146 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
26147 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
26148 body=[variable=@{name="$trace_timestamp",initial="0"@}
26149 variable=@{name="$foo",initial="10",current="15"@}]@}
26153 @subheading -trace-save
26154 @findex -trace-save
26156 @subsubheading Synopsis
26159 -trace-save [-r ] @var{filename}
26162 Saves the collected trace data to @var{filename}. Without the
26163 @samp{-r} option, the data is downloaded from the target and saved
26164 in a local file. With the @samp{-r} option the target is asked
26165 to perform the save.
26167 @subsubheading @value{GDBN} Command
26169 The corresponding @value{GDBN} command is @samp{tsave}.
26172 @subheading -trace-start
26173 @findex -trace-start
26175 @subsubheading Synopsis
26181 Starts a tracing experiments. The result of this command does not
26184 @subsubheading @value{GDBN} Command
26186 The corresponding @value{GDBN} command is @samp{tstart}.
26188 @subheading -trace-status
26189 @findex -trace-status
26191 @subsubheading Synopsis
26197 Obtains the status of a tracing experiement. The result may include
26198 the following fields:
26203 May have a value of either @samp{0}, when no tracing operations are
26204 supported, @samp{1}, when all tracing operations are supported, or
26205 @samp{file} when examining trace file. In the latter case, examining
26206 of trace frame is possible but new tracing experiement cannot be
26207 started. This field is always present.
26210 May have a value of either @samp{0} or @samp{1} depending on whether
26211 tracing experiement is in progress on target. This field is present
26212 if @samp{supported} field is not @samp{0}.
26215 Report the reason why the tracing was stopped last time. This field
26216 may be absent iff tracing was never stopped on target yet. The
26217 value of @samp{request} means the tracing was stopped as result of
26218 the @code{-trace-stop} command. The value of @samp{overflow} means
26219 the tracing buffer is full. The value of @samp{disconnection} means
26220 tracing was automatically stopped when @value{GDBN} has disconnected.
26221 The value of @samp{passcount} means tracing was stopped when a
26222 tracepoint was passed a maximal number of times for that tracepoint.
26223 This field is present if @samp{supported} field is not @samp{0}.
26225 @item stopping-tracepoint
26226 The number of tracepoint whose passcount as exceeded. This field is
26227 present iff the @samp{stop-reason} field has the value of
26231 This field is an integer number of currently collected frames. This
26236 These fields tell the current size of the tracing buffer and the
26237 remaining space. These field is optional.
26241 @subsubheading @value{GDBN} Command
26243 The corresponding @value{GDBN} command is @samp{tstatus}.
26245 @subheading -trace-stop
26246 @findex -trace-stop
26248 @subsubheading Synopsis
26254 Stops a tracing experiment. The result of this command has the same
26255 fields as @code{-trace-status}, except that the @samp{supported} and
26256 @samp{running} fields are not output.
26258 @subsubheading @value{GDBN} Command
26260 The corresponding @value{GDBN} command is @samp{tstop}.
26263 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26264 @node GDB/MI Symbol Query
26265 @section @sc{gdb/mi} Symbol Query Commands
26269 @subheading The @code{-symbol-info-address} Command
26270 @findex -symbol-info-address
26272 @subsubheading Synopsis
26275 -symbol-info-address @var{symbol}
26278 Describe where @var{symbol} is stored.
26280 @subsubheading @value{GDBN} Command
26282 The corresponding @value{GDBN} command is @samp{info address}.
26284 @subsubheading Example
26288 @subheading The @code{-symbol-info-file} Command
26289 @findex -symbol-info-file
26291 @subsubheading Synopsis
26297 Show the file for the symbol.
26299 @subsubheading @value{GDBN} Command
26301 There's no equivalent @value{GDBN} command. @code{gdbtk} has
26302 @samp{gdb_find_file}.
26304 @subsubheading Example
26308 @subheading The @code{-symbol-info-function} Command
26309 @findex -symbol-info-function
26311 @subsubheading Synopsis
26314 -symbol-info-function
26317 Show which function the symbol lives in.
26319 @subsubheading @value{GDBN} Command
26321 @samp{gdb_get_function} in @code{gdbtk}.
26323 @subsubheading Example
26327 @subheading The @code{-symbol-info-line} Command
26328 @findex -symbol-info-line
26330 @subsubheading Synopsis
26336 Show the core addresses of the code for a source line.
26338 @subsubheading @value{GDBN} Command
26340 The corresponding @value{GDBN} command is @samp{info line}.
26341 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
26343 @subsubheading Example
26347 @subheading The @code{-symbol-info-symbol} Command
26348 @findex -symbol-info-symbol
26350 @subsubheading Synopsis
26353 -symbol-info-symbol @var{addr}
26356 Describe what symbol is at location @var{addr}.
26358 @subsubheading @value{GDBN} Command
26360 The corresponding @value{GDBN} command is @samp{info symbol}.
26362 @subsubheading Example
26366 @subheading The @code{-symbol-list-functions} Command
26367 @findex -symbol-list-functions
26369 @subsubheading Synopsis
26372 -symbol-list-functions
26375 List the functions in the executable.
26377 @subsubheading @value{GDBN} Command
26379 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
26380 @samp{gdb_search} in @code{gdbtk}.
26382 @subsubheading Example
26387 @subheading The @code{-symbol-list-lines} Command
26388 @findex -symbol-list-lines
26390 @subsubheading Synopsis
26393 -symbol-list-lines @var{filename}
26396 Print the list of lines that contain code and their associated program
26397 addresses for the given source filename. The entries are sorted in
26398 ascending PC order.
26400 @subsubheading @value{GDBN} Command
26402 There is no corresponding @value{GDBN} command.
26404 @subsubheading Example
26407 -symbol-list-lines basics.c
26408 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
26414 @subheading The @code{-symbol-list-types} Command
26415 @findex -symbol-list-types
26417 @subsubheading Synopsis
26423 List all the type names.
26425 @subsubheading @value{GDBN} Command
26427 The corresponding commands are @samp{info types} in @value{GDBN},
26428 @samp{gdb_search} in @code{gdbtk}.
26430 @subsubheading Example
26434 @subheading The @code{-symbol-list-variables} Command
26435 @findex -symbol-list-variables
26437 @subsubheading Synopsis
26440 -symbol-list-variables
26443 List all the global and static variable names.
26445 @subsubheading @value{GDBN} Command
26447 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
26449 @subsubheading Example
26453 @subheading The @code{-symbol-locate} Command
26454 @findex -symbol-locate
26456 @subsubheading Synopsis
26462 @subsubheading @value{GDBN} Command
26464 @samp{gdb_loc} in @code{gdbtk}.
26466 @subsubheading Example
26470 @subheading The @code{-symbol-type} Command
26471 @findex -symbol-type
26473 @subsubheading Synopsis
26476 -symbol-type @var{variable}
26479 Show type of @var{variable}.
26481 @subsubheading @value{GDBN} Command
26483 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
26484 @samp{gdb_obj_variable}.
26486 @subsubheading Example
26491 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26492 @node GDB/MI File Commands
26493 @section @sc{gdb/mi} File Commands
26495 This section describes the GDB/MI commands to specify executable file names
26496 and to read in and obtain symbol table information.
26498 @subheading The @code{-file-exec-and-symbols} Command
26499 @findex -file-exec-and-symbols
26501 @subsubheading Synopsis
26504 -file-exec-and-symbols @var{file}
26507 Specify the executable file to be debugged. This file is the one from
26508 which the symbol table is also read. If no file is specified, the
26509 command clears the executable and symbol information. If breakpoints
26510 are set when using this command with no arguments, @value{GDBN} will produce
26511 error messages. Otherwise, no output is produced, except a completion
26514 @subsubheading @value{GDBN} Command
26516 The corresponding @value{GDBN} command is @samp{file}.
26518 @subsubheading Example
26522 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
26528 @subheading The @code{-file-exec-file} Command
26529 @findex -file-exec-file
26531 @subsubheading Synopsis
26534 -file-exec-file @var{file}
26537 Specify the executable file to be debugged. Unlike
26538 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
26539 from this file. If used without argument, @value{GDBN} clears the information
26540 about the executable file. No output is produced, except a completion
26543 @subsubheading @value{GDBN} Command
26545 The corresponding @value{GDBN} command is @samp{exec-file}.
26547 @subsubheading Example
26551 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
26558 @subheading The @code{-file-list-exec-sections} Command
26559 @findex -file-list-exec-sections
26561 @subsubheading Synopsis
26564 -file-list-exec-sections
26567 List the sections of the current executable file.
26569 @subsubheading @value{GDBN} Command
26571 The @value{GDBN} command @samp{info file} shows, among the rest, the same
26572 information as this command. @code{gdbtk} has a corresponding command
26573 @samp{gdb_load_info}.
26575 @subsubheading Example
26580 @subheading The @code{-file-list-exec-source-file} Command
26581 @findex -file-list-exec-source-file
26583 @subsubheading Synopsis
26586 -file-list-exec-source-file
26589 List the line number, the current source file, and the absolute path
26590 to the current source file for the current executable. The macro
26591 information field has a value of @samp{1} or @samp{0} depending on
26592 whether or not the file includes preprocessor macro information.
26594 @subsubheading @value{GDBN} Command
26596 The @value{GDBN} equivalent is @samp{info source}
26598 @subsubheading Example
26602 123-file-list-exec-source-file
26603 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
26608 @subheading The @code{-file-list-exec-source-files} Command
26609 @findex -file-list-exec-source-files
26611 @subsubheading Synopsis
26614 -file-list-exec-source-files
26617 List the source files for the current executable.
26619 It will always output the filename, but only when @value{GDBN} can find
26620 the absolute file name of a source file, will it output the fullname.
26622 @subsubheading @value{GDBN} Command
26624 The @value{GDBN} equivalent is @samp{info sources}.
26625 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
26627 @subsubheading Example
26630 -file-list-exec-source-files
26632 @{file=foo.c,fullname=/home/foo.c@},
26633 @{file=/home/bar.c,fullname=/home/bar.c@},
26634 @{file=gdb_could_not_find_fullpath.c@}]
26639 @subheading The @code{-file-list-shared-libraries} Command
26640 @findex -file-list-shared-libraries
26642 @subsubheading Synopsis
26645 -file-list-shared-libraries
26648 List the shared libraries in the program.
26650 @subsubheading @value{GDBN} Command
26652 The corresponding @value{GDBN} command is @samp{info shared}.
26654 @subsubheading Example
26658 @subheading The @code{-file-list-symbol-files} Command
26659 @findex -file-list-symbol-files
26661 @subsubheading Synopsis
26664 -file-list-symbol-files
26669 @subsubheading @value{GDBN} Command
26671 The corresponding @value{GDBN} command is @samp{info file} (part of it).
26673 @subsubheading Example
26678 @subheading The @code{-file-symbol-file} Command
26679 @findex -file-symbol-file
26681 @subsubheading Synopsis
26684 -file-symbol-file @var{file}
26687 Read symbol table info from the specified @var{file} argument. When
26688 used without arguments, clears @value{GDBN}'s symbol table info. No output is
26689 produced, except for a completion notification.
26691 @subsubheading @value{GDBN} Command
26693 The corresponding @value{GDBN} command is @samp{symbol-file}.
26695 @subsubheading Example
26699 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
26705 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26706 @node GDB/MI Memory Overlay Commands
26707 @section @sc{gdb/mi} Memory Overlay Commands
26709 The memory overlay commands are not implemented.
26711 @c @subheading -overlay-auto
26713 @c @subheading -overlay-list-mapping-state
26715 @c @subheading -overlay-list-overlays
26717 @c @subheading -overlay-map
26719 @c @subheading -overlay-off
26721 @c @subheading -overlay-on
26723 @c @subheading -overlay-unmap
26725 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26726 @node GDB/MI Signal Handling Commands
26727 @section @sc{gdb/mi} Signal Handling Commands
26729 Signal handling commands are not implemented.
26731 @c @subheading -signal-handle
26733 @c @subheading -signal-list-handle-actions
26735 @c @subheading -signal-list-signal-types
26739 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26740 @node GDB/MI Target Manipulation
26741 @section @sc{gdb/mi} Target Manipulation Commands
26744 @subheading The @code{-target-attach} Command
26745 @findex -target-attach
26747 @subsubheading Synopsis
26750 -target-attach @var{pid} | @var{gid} | @var{file}
26753 Attach to a process @var{pid} or a file @var{file} outside of
26754 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
26755 group, the id previously returned by
26756 @samp{-list-thread-groups --available} must be used.
26758 @subsubheading @value{GDBN} Command
26760 The corresponding @value{GDBN} command is @samp{attach}.
26762 @subsubheading Example
26766 =thread-created,id="1"
26767 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
26773 @subheading The @code{-target-compare-sections} Command
26774 @findex -target-compare-sections
26776 @subsubheading Synopsis
26779 -target-compare-sections [ @var{section} ]
26782 Compare data of section @var{section} on target to the exec file.
26783 Without the argument, all sections are compared.
26785 @subsubheading @value{GDBN} Command
26787 The @value{GDBN} equivalent is @samp{compare-sections}.
26789 @subsubheading Example
26794 @subheading The @code{-target-detach} Command
26795 @findex -target-detach
26797 @subsubheading Synopsis
26800 -target-detach [ @var{pid} | @var{gid} ]
26803 Detach from the remote target which normally resumes its execution.
26804 If either @var{pid} or @var{gid} is specified, detaches from either
26805 the specified process, or specified thread group. There's no output.
26807 @subsubheading @value{GDBN} Command
26809 The corresponding @value{GDBN} command is @samp{detach}.
26811 @subsubheading Example
26821 @subheading The @code{-target-disconnect} Command
26822 @findex -target-disconnect
26824 @subsubheading Synopsis
26830 Disconnect from the remote target. There's no output and the target is
26831 generally not resumed.
26833 @subsubheading @value{GDBN} Command
26835 The corresponding @value{GDBN} command is @samp{disconnect}.
26837 @subsubheading Example
26847 @subheading The @code{-target-download} Command
26848 @findex -target-download
26850 @subsubheading Synopsis
26856 Loads the executable onto the remote target.
26857 It prints out an update message every half second, which includes the fields:
26861 The name of the section.
26863 The size of what has been sent so far for that section.
26865 The size of the section.
26867 The total size of what was sent so far (the current and the previous sections).
26869 The size of the overall executable to download.
26873 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
26874 @sc{gdb/mi} Output Syntax}).
26876 In addition, it prints the name and size of the sections, as they are
26877 downloaded. These messages include the following fields:
26881 The name of the section.
26883 The size of the section.
26885 The size of the overall executable to download.
26889 At the end, a summary is printed.
26891 @subsubheading @value{GDBN} Command
26893 The corresponding @value{GDBN} command is @samp{load}.
26895 @subsubheading Example
26897 Note: each status message appears on a single line. Here the messages
26898 have been broken down so that they can fit onto a page.
26903 +download,@{section=".text",section-size="6668",total-size="9880"@}
26904 +download,@{section=".text",section-sent="512",section-size="6668",
26905 total-sent="512",total-size="9880"@}
26906 +download,@{section=".text",section-sent="1024",section-size="6668",
26907 total-sent="1024",total-size="9880"@}
26908 +download,@{section=".text",section-sent="1536",section-size="6668",
26909 total-sent="1536",total-size="9880"@}
26910 +download,@{section=".text",section-sent="2048",section-size="6668",
26911 total-sent="2048",total-size="9880"@}
26912 +download,@{section=".text",section-sent="2560",section-size="6668",
26913 total-sent="2560",total-size="9880"@}
26914 +download,@{section=".text",section-sent="3072",section-size="6668",
26915 total-sent="3072",total-size="9880"@}
26916 +download,@{section=".text",section-sent="3584",section-size="6668",
26917 total-sent="3584",total-size="9880"@}
26918 +download,@{section=".text",section-sent="4096",section-size="6668",
26919 total-sent="4096",total-size="9880"@}
26920 +download,@{section=".text",section-sent="4608",section-size="6668",
26921 total-sent="4608",total-size="9880"@}
26922 +download,@{section=".text",section-sent="5120",section-size="6668",
26923 total-sent="5120",total-size="9880"@}
26924 +download,@{section=".text",section-sent="5632",section-size="6668",
26925 total-sent="5632",total-size="9880"@}
26926 +download,@{section=".text",section-sent="6144",section-size="6668",
26927 total-sent="6144",total-size="9880"@}
26928 +download,@{section=".text",section-sent="6656",section-size="6668",
26929 total-sent="6656",total-size="9880"@}
26930 +download,@{section=".init",section-size="28",total-size="9880"@}
26931 +download,@{section=".fini",section-size="28",total-size="9880"@}
26932 +download,@{section=".data",section-size="3156",total-size="9880"@}
26933 +download,@{section=".data",section-sent="512",section-size="3156",
26934 total-sent="7236",total-size="9880"@}
26935 +download,@{section=".data",section-sent="1024",section-size="3156",
26936 total-sent="7748",total-size="9880"@}
26937 +download,@{section=".data",section-sent="1536",section-size="3156",
26938 total-sent="8260",total-size="9880"@}
26939 +download,@{section=".data",section-sent="2048",section-size="3156",
26940 total-sent="8772",total-size="9880"@}
26941 +download,@{section=".data",section-sent="2560",section-size="3156",
26942 total-sent="9284",total-size="9880"@}
26943 +download,@{section=".data",section-sent="3072",section-size="3156",
26944 total-sent="9796",total-size="9880"@}
26945 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
26952 @subheading The @code{-target-exec-status} Command
26953 @findex -target-exec-status
26955 @subsubheading Synopsis
26958 -target-exec-status
26961 Provide information on the state of the target (whether it is running or
26962 not, for instance).
26964 @subsubheading @value{GDBN} Command
26966 There's no equivalent @value{GDBN} command.
26968 @subsubheading Example
26972 @subheading The @code{-target-list-available-targets} Command
26973 @findex -target-list-available-targets
26975 @subsubheading Synopsis
26978 -target-list-available-targets
26981 List the possible targets to connect to.
26983 @subsubheading @value{GDBN} Command
26985 The corresponding @value{GDBN} command is @samp{help target}.
26987 @subsubheading Example
26991 @subheading The @code{-target-list-current-targets} Command
26992 @findex -target-list-current-targets
26994 @subsubheading Synopsis
26997 -target-list-current-targets
27000 Describe the current target.
27002 @subsubheading @value{GDBN} Command
27004 The corresponding information is printed by @samp{info file} (among
27007 @subsubheading Example
27011 @subheading The @code{-target-list-parameters} Command
27012 @findex -target-list-parameters
27014 @subsubheading Synopsis
27017 -target-list-parameters
27023 @subsubheading @value{GDBN} Command
27027 @subsubheading Example
27031 @subheading The @code{-target-select} Command
27032 @findex -target-select
27034 @subsubheading Synopsis
27037 -target-select @var{type} @var{parameters @dots{}}
27040 Connect @value{GDBN} to the remote target. This command takes two args:
27044 The type of target, for instance @samp{remote}, etc.
27045 @item @var{parameters}
27046 Device names, host names and the like. @xref{Target Commands, ,
27047 Commands for Managing Targets}, for more details.
27050 The output is a connection notification, followed by the address at
27051 which the target program is, in the following form:
27054 ^connected,addr="@var{address}",func="@var{function name}",
27055 args=[@var{arg list}]
27058 @subsubheading @value{GDBN} Command
27060 The corresponding @value{GDBN} command is @samp{target}.
27062 @subsubheading Example
27066 -target-select remote /dev/ttya
27067 ^connected,addr="0xfe00a300",func="??",args=[]
27071 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27072 @node GDB/MI File Transfer Commands
27073 @section @sc{gdb/mi} File Transfer Commands
27076 @subheading The @code{-target-file-put} Command
27077 @findex -target-file-put
27079 @subsubheading Synopsis
27082 -target-file-put @var{hostfile} @var{targetfile}
27085 Copy file @var{hostfile} from the host system (the machine running
27086 @value{GDBN}) to @var{targetfile} on the target system.
27088 @subsubheading @value{GDBN} Command
27090 The corresponding @value{GDBN} command is @samp{remote put}.
27092 @subsubheading Example
27096 -target-file-put localfile remotefile
27102 @subheading The @code{-target-file-get} Command
27103 @findex -target-file-get
27105 @subsubheading Synopsis
27108 -target-file-get @var{targetfile} @var{hostfile}
27111 Copy file @var{targetfile} from the target system to @var{hostfile}
27112 on the host system.
27114 @subsubheading @value{GDBN} Command
27116 The corresponding @value{GDBN} command is @samp{remote get}.
27118 @subsubheading Example
27122 -target-file-get remotefile localfile
27128 @subheading The @code{-target-file-delete} Command
27129 @findex -target-file-delete
27131 @subsubheading Synopsis
27134 -target-file-delete @var{targetfile}
27137 Delete @var{targetfile} from the target system.
27139 @subsubheading @value{GDBN} Command
27141 The corresponding @value{GDBN} command is @samp{remote delete}.
27143 @subsubheading Example
27147 -target-file-delete remotefile
27153 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27154 @node GDB/MI Miscellaneous Commands
27155 @section Miscellaneous @sc{gdb/mi} Commands
27157 @c @subheading -gdb-complete
27159 @subheading The @code{-gdb-exit} Command
27162 @subsubheading Synopsis
27168 Exit @value{GDBN} immediately.
27170 @subsubheading @value{GDBN} Command
27172 Approximately corresponds to @samp{quit}.
27174 @subsubheading Example
27184 @subheading The @code{-exec-abort} Command
27185 @findex -exec-abort
27187 @subsubheading Synopsis
27193 Kill the inferior running program.
27195 @subsubheading @value{GDBN} Command
27197 The corresponding @value{GDBN} command is @samp{kill}.
27199 @subsubheading Example
27204 @subheading The @code{-gdb-set} Command
27207 @subsubheading Synopsis
27213 Set an internal @value{GDBN} variable.
27214 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
27216 @subsubheading @value{GDBN} Command
27218 The corresponding @value{GDBN} command is @samp{set}.
27220 @subsubheading Example
27230 @subheading The @code{-gdb-show} Command
27233 @subsubheading Synopsis
27239 Show the current value of a @value{GDBN} variable.
27241 @subsubheading @value{GDBN} Command
27243 The corresponding @value{GDBN} command is @samp{show}.
27245 @subsubheading Example
27254 @c @subheading -gdb-source
27257 @subheading The @code{-gdb-version} Command
27258 @findex -gdb-version
27260 @subsubheading Synopsis
27266 Show version information for @value{GDBN}. Used mostly in testing.
27268 @subsubheading @value{GDBN} Command
27270 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
27271 default shows this information when you start an interactive session.
27273 @subsubheading Example
27275 @c This example modifies the actual output from GDB to avoid overfull
27281 ~Copyright 2000 Free Software Foundation, Inc.
27282 ~GDB is free software, covered by the GNU General Public License, and
27283 ~you are welcome to change it and/or distribute copies of it under
27284 ~ certain conditions.
27285 ~Type "show copying" to see the conditions.
27286 ~There is absolutely no warranty for GDB. Type "show warranty" for
27288 ~This GDB was configured as
27289 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
27294 @subheading The @code{-list-features} Command
27295 @findex -list-features
27297 Returns a list of particular features of the MI protocol that
27298 this version of gdb implements. A feature can be a command,
27299 or a new field in an output of some command, or even an
27300 important bugfix. While a frontend can sometimes detect presence
27301 of a feature at runtime, it is easier to perform detection at debugger
27304 The command returns a list of strings, with each string naming an
27305 available feature. Each returned string is just a name, it does not
27306 have any internal structure. The list of possible feature names
27312 (gdb) -list-features
27313 ^done,result=["feature1","feature2"]
27316 The current list of features is:
27319 @item frozen-varobjs
27320 Indicates presence of the @code{-var-set-frozen} command, as well
27321 as possible presense of the @code{frozen} field in the output
27322 of @code{-varobj-create}.
27323 @item pending-breakpoints
27324 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
27326 Indicates presence of Python scripting support, Python-based
27327 pretty-printing commands, and possible presence of the
27328 @samp{display_hint} field in the output of @code{-var-list-children}
27330 Indicates presence of the @code{-thread-info} command.
27334 @subheading The @code{-list-target-features} Command
27335 @findex -list-target-features
27337 Returns a list of particular features that are supported by the
27338 target. Those features affect the permitted MI commands, but
27339 unlike the features reported by the @code{-list-features} command, the
27340 features depend on which target GDB is using at the moment. Whenever
27341 a target can change, due to commands such as @code{-target-select},
27342 @code{-target-attach} or @code{-exec-run}, the list of target features
27343 may change, and the frontend should obtain it again.
27347 (gdb) -list-features
27348 ^done,result=["async"]
27351 The current list of features is:
27355 Indicates that the target is capable of asynchronous command
27356 execution, which means that @value{GDBN} will accept further commands
27357 while the target is running.
27361 @subheading The @code{-list-thread-groups} Command
27362 @findex -list-thread-groups
27364 @subheading Synopsis
27367 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
27370 Lists thread groups (@pxref{Thread groups}). When a single thread
27371 group is passed as the argument, lists the children of that group.
27372 When several thread group are passed, lists information about those
27373 thread groups. Without any parameters, lists information about all
27374 top-level thread groups.
27376 Normally, thread groups that are being debugged are reported.
27377 With the @samp{--available} option, @value{GDBN} reports thread groups
27378 available on the target.
27380 The output of this command may have either a @samp{threads} result or
27381 a @samp{groups} result. The @samp{thread} result has a list of tuples
27382 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
27383 Information}). The @samp{groups} result has a list of tuples as value,
27384 each tuple describing a thread group. If top-level groups are
27385 requested (that is, no parameter is passed), or when several groups
27386 are passed, the output always has a @samp{groups} result. The format
27387 of the @samp{group} result is described below.
27389 To reduce the number of roundtrips it's possible to list thread groups
27390 together with their children, by passing the @samp{--recurse} option
27391 and the recursion depth. Presently, only recursion depth of 1 is
27392 permitted. If this option is present, then every reported thread group
27393 will also include its children, either as @samp{group} or
27394 @samp{threads} field.
27396 In general, any combination of option and parameters is permitted, with
27397 the following caveats:
27401 When a single thread group is passed, the output will typically
27402 be the @samp{threads} result. Because threads may not contain
27403 anything, the @samp{recurse} option will be ignored.
27406 When the @samp{--available} option is passed, limited information may
27407 be available. In particular, the list of threads of a process might
27408 be inaccessible. Further, specifying specific thread groups might
27409 not give any performance advantage over listing all thread groups.
27410 The frontend should assume that @samp{-list-thread-groups --available}
27411 is always an expensive operation and cache the results.
27415 The @samp{groups} result is a list of tuples, where each tuple may
27416 have the following fields:
27420 Identifier of the thread group. This field is always present.
27421 The identifier is an opaque string; frontends should not try to
27422 convert it to an integer, even though it might look like one.
27425 The type of the thread group. At present, only @samp{process} is a
27429 The target-specific process identifier. This field is only present
27430 for thread groups of type @samp{process} and only if the process exists.
27433 The number of children this thread group has. This field may be
27434 absent for an available thread group.
27437 This field has a list of tuples as value, each tuple describing a
27438 thread. It may be present if the @samp{--recurse} option is
27439 specified, and it's actually possible to obtain the threads.
27442 This field is a list of integers, each identifying a core that one
27443 thread of the group is running on. This field may be absent if
27444 such information is not available.
27447 The name of the executable file that corresponds to this thread group.
27448 The field is only present for thread groups of type @samp{process},
27449 and only if there is a corresponding executable file.
27453 @subheading Example
27457 -list-thread-groups
27458 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
27459 -list-thread-groups 17
27460 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
27461 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
27462 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
27463 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
27464 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
27465 -list-thread-groups --available
27466 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
27467 -list-thread-groups --available --recurse 1
27468 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
27469 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
27470 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
27471 -list-thread-groups --available --recurse 1 17 18
27472 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
27473 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
27474 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
27478 @subheading The @code{-add-inferior} Command
27479 @findex -add-inferior
27481 @subheading Synopsis
27487 Creates a new inferior (@pxref{Inferiors and Programs}). The created
27488 inferior is not associated with any executable. Such association may
27489 be established with the @samp{-file-exec-and-symbols} command
27490 (@pxref{GDB/MI File Commands}). The command response has a single
27491 field, @samp{thread-group}, whose value is the identifier of the
27492 thread group corresponding to the new inferior.
27494 @subheading Example
27499 ^done,thread-group="i3"
27502 @subheading The @code{-interpreter-exec} Command
27503 @findex -interpreter-exec
27505 @subheading Synopsis
27508 -interpreter-exec @var{interpreter} @var{command}
27510 @anchor{-interpreter-exec}
27512 Execute the specified @var{command} in the given @var{interpreter}.
27514 @subheading @value{GDBN} Command
27516 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
27518 @subheading Example
27522 -interpreter-exec console "break main"
27523 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
27524 &"During symbol reading, bad structure-type format.\n"
27525 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
27530 @subheading The @code{-inferior-tty-set} Command
27531 @findex -inferior-tty-set
27533 @subheading Synopsis
27536 -inferior-tty-set /dev/pts/1
27539 Set terminal for future runs of the program being debugged.
27541 @subheading @value{GDBN} Command
27543 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
27545 @subheading Example
27549 -inferior-tty-set /dev/pts/1
27554 @subheading The @code{-inferior-tty-show} Command
27555 @findex -inferior-tty-show
27557 @subheading Synopsis
27563 Show terminal for future runs of program being debugged.
27565 @subheading @value{GDBN} Command
27567 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
27569 @subheading Example
27573 -inferior-tty-set /dev/pts/1
27577 ^done,inferior_tty_terminal="/dev/pts/1"
27581 @subheading The @code{-enable-timings} Command
27582 @findex -enable-timings
27584 @subheading Synopsis
27587 -enable-timings [yes | no]
27590 Toggle the printing of the wallclock, user and system times for an MI
27591 command as a field in its output. This command is to help frontend
27592 developers optimize the performance of their code. No argument is
27593 equivalent to @samp{yes}.
27595 @subheading @value{GDBN} Command
27599 @subheading Example
27607 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27608 addr="0x080484ed",func="main",file="myprog.c",
27609 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
27610 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
27618 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
27619 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
27620 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
27621 fullname="/home/nickrob/myprog.c",line="73"@}
27626 @chapter @value{GDBN} Annotations
27628 This chapter describes annotations in @value{GDBN}. Annotations were
27629 designed to interface @value{GDBN} to graphical user interfaces or other
27630 similar programs which want to interact with @value{GDBN} at a
27631 relatively high level.
27633 The annotation mechanism has largely been superseded by @sc{gdb/mi}
27637 This is Edition @value{EDITION}, @value{DATE}.
27641 * Annotations Overview:: What annotations are; the general syntax.
27642 * Server Prefix:: Issuing a command without affecting user state.
27643 * Prompting:: Annotations marking @value{GDBN}'s need for input.
27644 * Errors:: Annotations for error messages.
27645 * Invalidation:: Some annotations describe things now invalid.
27646 * Annotations for Running::
27647 Whether the program is running, how it stopped, etc.
27648 * Source Annotations:: Annotations describing source code.
27651 @node Annotations Overview
27652 @section What is an Annotation?
27653 @cindex annotations
27655 Annotations start with a newline character, two @samp{control-z}
27656 characters, and the name of the annotation. If there is no additional
27657 information associated with this annotation, the name of the annotation
27658 is followed immediately by a newline. If there is additional
27659 information, the name of the annotation is followed by a space, the
27660 additional information, and a newline. The additional information
27661 cannot contain newline characters.
27663 Any output not beginning with a newline and two @samp{control-z}
27664 characters denotes literal output from @value{GDBN}. Currently there is
27665 no need for @value{GDBN} to output a newline followed by two
27666 @samp{control-z} characters, but if there was such a need, the
27667 annotations could be extended with an @samp{escape} annotation which
27668 means those three characters as output.
27670 The annotation @var{level}, which is specified using the
27671 @option{--annotate} command line option (@pxref{Mode Options}), controls
27672 how much information @value{GDBN} prints together with its prompt,
27673 values of expressions, source lines, and other types of output. Level 0
27674 is for no annotations, level 1 is for use when @value{GDBN} is run as a
27675 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
27676 for programs that control @value{GDBN}, and level 2 annotations have
27677 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
27678 Interface, annotate, GDB's Obsolete Annotations}).
27681 @kindex set annotate
27682 @item set annotate @var{level}
27683 The @value{GDBN} command @code{set annotate} sets the level of
27684 annotations to the specified @var{level}.
27686 @item show annotate
27687 @kindex show annotate
27688 Show the current annotation level.
27691 This chapter describes level 3 annotations.
27693 A simple example of starting up @value{GDBN} with annotations is:
27696 $ @kbd{gdb --annotate=3}
27698 Copyright 2003 Free Software Foundation, Inc.
27699 GDB is free software, covered by the GNU General Public License,
27700 and you are welcome to change it and/or distribute copies of it
27701 under certain conditions.
27702 Type "show copying" to see the conditions.
27703 There is absolutely no warranty for GDB. Type "show warranty"
27705 This GDB was configured as "i386-pc-linux-gnu"
27716 Here @samp{quit} is input to @value{GDBN}; the rest is output from
27717 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
27718 denotes a @samp{control-z} character) are annotations; the rest is
27719 output from @value{GDBN}.
27721 @node Server Prefix
27722 @section The Server Prefix
27723 @cindex server prefix
27725 If you prefix a command with @samp{server } then it will not affect
27726 the command history, nor will it affect @value{GDBN}'s notion of which
27727 command to repeat if @key{RET} is pressed on a line by itself. This
27728 means that commands can be run behind a user's back by a front-end in
27729 a transparent manner.
27731 The @code{server } prefix does not affect the recording of values into
27732 the value history; to print a value without recording it into the
27733 value history, use the @code{output} command instead of the
27734 @code{print} command.
27736 Using this prefix also disables confirmation requests
27737 (@pxref{confirmation requests}).
27740 @section Annotation for @value{GDBN} Input
27742 @cindex annotations for prompts
27743 When @value{GDBN} prompts for input, it annotates this fact so it is possible
27744 to know when to send output, when the output from a given command is
27747 Different kinds of input each have a different @dfn{input type}. Each
27748 input type has three annotations: a @code{pre-} annotation, which
27749 denotes the beginning of any prompt which is being output, a plain
27750 annotation, which denotes the end of the prompt, and then a @code{post-}
27751 annotation which denotes the end of any echo which may (or may not) be
27752 associated with the input. For example, the @code{prompt} input type
27753 features the following annotations:
27761 The input types are
27764 @findex pre-prompt annotation
27765 @findex prompt annotation
27766 @findex post-prompt annotation
27768 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
27770 @findex pre-commands annotation
27771 @findex commands annotation
27772 @findex post-commands annotation
27774 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
27775 command. The annotations are repeated for each command which is input.
27777 @findex pre-overload-choice annotation
27778 @findex overload-choice annotation
27779 @findex post-overload-choice annotation
27780 @item overload-choice
27781 When @value{GDBN} wants the user to select between various overloaded functions.
27783 @findex pre-query annotation
27784 @findex query annotation
27785 @findex post-query annotation
27787 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
27789 @findex pre-prompt-for-continue annotation
27790 @findex prompt-for-continue annotation
27791 @findex post-prompt-for-continue annotation
27792 @item prompt-for-continue
27793 When @value{GDBN} is asking the user to press return to continue. Note: Don't
27794 expect this to work well; instead use @code{set height 0} to disable
27795 prompting. This is because the counting of lines is buggy in the
27796 presence of annotations.
27801 @cindex annotations for errors, warnings and interrupts
27803 @findex quit annotation
27808 This annotation occurs right before @value{GDBN} responds to an interrupt.
27810 @findex error annotation
27815 This annotation occurs right before @value{GDBN} responds to an error.
27817 Quit and error annotations indicate that any annotations which @value{GDBN} was
27818 in the middle of may end abruptly. For example, if a
27819 @code{value-history-begin} annotation is followed by a @code{error}, one
27820 cannot expect to receive the matching @code{value-history-end}. One
27821 cannot expect not to receive it either, however; an error annotation
27822 does not necessarily mean that @value{GDBN} is immediately returning all the way
27825 @findex error-begin annotation
27826 A quit or error annotation may be preceded by
27832 Any output between that and the quit or error annotation is the error
27835 Warning messages are not yet annotated.
27836 @c If we want to change that, need to fix warning(), type_error(),
27837 @c range_error(), and possibly other places.
27840 @section Invalidation Notices
27842 @cindex annotations for invalidation messages
27843 The following annotations say that certain pieces of state may have
27847 @findex frames-invalid annotation
27848 @item ^Z^Zframes-invalid
27850 The frames (for example, output from the @code{backtrace} command) may
27853 @findex breakpoints-invalid annotation
27854 @item ^Z^Zbreakpoints-invalid
27856 The breakpoints may have changed. For example, the user just added or
27857 deleted a breakpoint.
27860 @node Annotations for Running
27861 @section Running the Program
27862 @cindex annotations for running programs
27864 @findex starting annotation
27865 @findex stopping annotation
27866 When the program starts executing due to a @value{GDBN} command such as
27867 @code{step} or @code{continue},
27873 is output. When the program stops,
27879 is output. Before the @code{stopped} annotation, a variety of
27880 annotations describe how the program stopped.
27883 @findex exited annotation
27884 @item ^Z^Zexited @var{exit-status}
27885 The program exited, and @var{exit-status} is the exit status (zero for
27886 successful exit, otherwise nonzero).
27888 @findex signalled annotation
27889 @findex signal-name annotation
27890 @findex signal-name-end annotation
27891 @findex signal-string annotation
27892 @findex signal-string-end annotation
27893 @item ^Z^Zsignalled
27894 The program exited with a signal. After the @code{^Z^Zsignalled}, the
27895 annotation continues:
27901 ^Z^Zsignal-name-end
27905 ^Z^Zsignal-string-end
27910 where @var{name} is the name of the signal, such as @code{SIGILL} or
27911 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
27912 as @code{Illegal Instruction} or @code{Segmentation fault}.
27913 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
27914 user's benefit and have no particular format.
27916 @findex signal annotation
27918 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
27919 just saying that the program received the signal, not that it was
27920 terminated with it.
27922 @findex breakpoint annotation
27923 @item ^Z^Zbreakpoint @var{number}
27924 The program hit breakpoint number @var{number}.
27926 @findex watchpoint annotation
27927 @item ^Z^Zwatchpoint @var{number}
27928 The program hit watchpoint number @var{number}.
27931 @node Source Annotations
27932 @section Displaying Source
27933 @cindex annotations for source display
27935 @findex source annotation
27936 The following annotation is used instead of displaying source code:
27939 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
27942 where @var{filename} is an absolute file name indicating which source
27943 file, @var{line} is the line number within that file (where 1 is the
27944 first line in the file), @var{character} is the character position
27945 within the file (where 0 is the first character in the file) (for most
27946 debug formats this will necessarily point to the beginning of a line),
27947 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
27948 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
27949 @var{addr} is the address in the target program associated with the
27950 source which is being displayed. @var{addr} is in the form @samp{0x}
27951 followed by one or more lowercase hex digits (note that this does not
27952 depend on the language).
27954 @node JIT Interface
27955 @chapter JIT Compilation Interface
27956 @cindex just-in-time compilation
27957 @cindex JIT compilation interface
27959 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
27960 interface. A JIT compiler is a program or library that generates native
27961 executable code at runtime and executes it, usually in order to achieve good
27962 performance while maintaining platform independence.
27964 Programs that use JIT compilation are normally difficult to debug because
27965 portions of their code are generated at runtime, instead of being loaded from
27966 object files, which is where @value{GDBN} normally finds the program's symbols
27967 and debug information. In order to debug programs that use JIT compilation,
27968 @value{GDBN} has an interface that allows the program to register in-memory
27969 symbol files with @value{GDBN} at runtime.
27971 If you are using @value{GDBN} to debug a program that uses this interface, then
27972 it should work transparently so long as you have not stripped the binary. If
27973 you are developing a JIT compiler, then the interface is documented in the rest
27974 of this chapter. At this time, the only known client of this interface is the
27977 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
27978 JIT compiler communicates with @value{GDBN} by writing data into a global
27979 variable and calling a fuction at a well-known symbol. When @value{GDBN}
27980 attaches, it reads a linked list of symbol files from the global variable to
27981 find existing code, and puts a breakpoint in the function so that it can find
27982 out about additional code.
27985 * Declarations:: Relevant C struct declarations
27986 * Registering Code:: Steps to register code
27987 * Unregistering Code:: Steps to unregister code
27991 @section JIT Declarations
27993 These are the relevant struct declarations that a C program should include to
27994 implement the interface:
28004 struct jit_code_entry
28006 struct jit_code_entry *next_entry;
28007 struct jit_code_entry *prev_entry;
28008 const char *symfile_addr;
28009 uint64_t symfile_size;
28012 struct jit_descriptor
28015 /* This type should be jit_actions_t, but we use uint32_t
28016 to be explicit about the bitwidth. */
28017 uint32_t action_flag;
28018 struct jit_code_entry *relevant_entry;
28019 struct jit_code_entry *first_entry;
28022 /* GDB puts a breakpoint in this function. */
28023 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
28025 /* Make sure to specify the version statically, because the
28026 debugger may check the version before we can set it. */
28027 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
28030 If the JIT is multi-threaded, then it is important that the JIT synchronize any
28031 modifications to this global data properly, which can easily be done by putting
28032 a global mutex around modifications to these structures.
28034 @node Registering Code
28035 @section Registering Code
28037 To register code with @value{GDBN}, the JIT should follow this protocol:
28041 Generate an object file in memory with symbols and other desired debug
28042 information. The file must include the virtual addresses of the sections.
28045 Create a code entry for the file, which gives the start and size of the symbol
28049 Add it to the linked list in the JIT descriptor.
28052 Point the relevant_entry field of the descriptor at the entry.
28055 Set @code{action_flag} to @code{JIT_REGISTER} and call
28056 @code{__jit_debug_register_code}.
28059 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
28060 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
28061 new code. However, the linked list must still be maintained in order to allow
28062 @value{GDBN} to attach to a running process and still find the symbol files.
28064 @node Unregistering Code
28065 @section Unregistering Code
28067 If code is freed, then the JIT should use the following protocol:
28071 Remove the code entry corresponding to the code from the linked list.
28074 Point the @code{relevant_entry} field of the descriptor at the code entry.
28077 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
28078 @code{__jit_debug_register_code}.
28081 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
28082 and the JIT will leak the memory used for the associated symbol files.
28085 @chapter Reporting Bugs in @value{GDBN}
28086 @cindex bugs in @value{GDBN}
28087 @cindex reporting bugs in @value{GDBN}
28089 Your bug reports play an essential role in making @value{GDBN} reliable.
28091 Reporting a bug may help you by bringing a solution to your problem, or it
28092 may not. But in any case the principal function of a bug report is to help
28093 the entire community by making the next version of @value{GDBN} work better. Bug
28094 reports are your contribution to the maintenance of @value{GDBN}.
28096 In order for a bug report to serve its purpose, you must include the
28097 information that enables us to fix the bug.
28100 * Bug Criteria:: Have you found a bug?
28101 * Bug Reporting:: How to report bugs
28105 @section Have You Found a Bug?
28106 @cindex bug criteria
28108 If you are not sure whether you have found a bug, here are some guidelines:
28111 @cindex fatal signal
28112 @cindex debugger crash
28113 @cindex crash of debugger
28115 If the debugger gets a fatal signal, for any input whatever, that is a
28116 @value{GDBN} bug. Reliable debuggers never crash.
28118 @cindex error on valid input
28120 If @value{GDBN} produces an error message for valid input, that is a
28121 bug. (Note that if you're cross debugging, the problem may also be
28122 somewhere in the connection to the target.)
28124 @cindex invalid input
28126 If @value{GDBN} does not produce an error message for invalid input,
28127 that is a bug. However, you should note that your idea of
28128 ``invalid input'' might be our idea of ``an extension'' or ``support
28129 for traditional practice''.
28132 If you are an experienced user of debugging tools, your suggestions
28133 for improvement of @value{GDBN} are welcome in any case.
28136 @node Bug Reporting
28137 @section How to Report Bugs
28138 @cindex bug reports
28139 @cindex @value{GDBN} bugs, reporting
28141 A number of companies and individuals offer support for @sc{gnu} products.
28142 If you obtained @value{GDBN} from a support organization, we recommend you
28143 contact that organization first.
28145 You can find contact information for many support companies and
28146 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
28148 @c should add a web page ref...
28151 @ifset BUGURL_DEFAULT
28152 In any event, we also recommend that you submit bug reports for
28153 @value{GDBN}. The preferred method is to submit them directly using
28154 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
28155 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
28158 @strong{Do not send bug reports to @samp{info-gdb}, or to
28159 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
28160 not want to receive bug reports. Those that do have arranged to receive
28163 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
28164 serves as a repeater. The mailing list and the newsgroup carry exactly
28165 the same messages. Often people think of posting bug reports to the
28166 newsgroup instead of mailing them. This appears to work, but it has one
28167 problem which can be crucial: a newsgroup posting often lacks a mail
28168 path back to the sender. Thus, if we need to ask for more information,
28169 we may be unable to reach you. For this reason, it is better to send
28170 bug reports to the mailing list.
28172 @ifclear BUGURL_DEFAULT
28173 In any event, we also recommend that you submit bug reports for
28174 @value{GDBN} to @value{BUGURL}.
28178 The fundamental principle of reporting bugs usefully is this:
28179 @strong{report all the facts}. If you are not sure whether to state a
28180 fact or leave it out, state it!
28182 Often people omit facts because they think they know what causes the
28183 problem and assume that some details do not matter. Thus, you might
28184 assume that the name of the variable you use in an example does not matter.
28185 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
28186 stray memory reference which happens to fetch from the location where that
28187 name is stored in memory; perhaps, if the name were different, the contents
28188 of that location would fool the debugger into doing the right thing despite
28189 the bug. Play it safe and give a specific, complete example. That is the
28190 easiest thing for you to do, and the most helpful.
28192 Keep in mind that the purpose of a bug report is to enable us to fix the
28193 bug. It may be that the bug has been reported previously, but neither
28194 you nor we can know that unless your bug report is complete and
28197 Sometimes people give a few sketchy facts and ask, ``Does this ring a
28198 bell?'' Those bug reports are useless, and we urge everyone to
28199 @emph{refuse to respond to them} except to chide the sender to report
28202 To enable us to fix the bug, you should include all these things:
28206 The version of @value{GDBN}. @value{GDBN} announces it if you start
28207 with no arguments; you can also print it at any time using @code{show
28210 Without this, we will not know whether there is any point in looking for
28211 the bug in the current version of @value{GDBN}.
28214 The type of machine you are using, and the operating system name and
28218 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
28219 ``@value{GCC}--2.8.1''.
28222 What compiler (and its version) was used to compile the program you are
28223 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
28224 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
28225 to get this information; for other compilers, see the documentation for
28229 The command arguments you gave the compiler to compile your example and
28230 observe the bug. For example, did you use @samp{-O}? To guarantee
28231 you will not omit something important, list them all. A copy of the
28232 Makefile (or the output from make) is sufficient.
28234 If we were to try to guess the arguments, we would probably guess wrong
28235 and then we might not encounter the bug.
28238 A complete input script, and all necessary source files, that will
28242 A description of what behavior you observe that you believe is
28243 incorrect. For example, ``It gets a fatal signal.''
28245 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
28246 will certainly notice it. But if the bug is incorrect output, we might
28247 not notice unless it is glaringly wrong. You might as well not give us
28248 a chance to make a mistake.
28250 Even if the problem you experience is a fatal signal, you should still
28251 say so explicitly. Suppose something strange is going on, such as, your
28252 copy of @value{GDBN} is out of synch, or you have encountered a bug in
28253 the C library on your system. (This has happened!) Your copy might
28254 crash and ours would not. If you told us to expect a crash, then when
28255 ours fails to crash, we would know that the bug was not happening for
28256 us. If you had not told us to expect a crash, then we would not be able
28257 to draw any conclusion from our observations.
28260 @cindex recording a session script
28261 To collect all this information, you can use a session recording program
28262 such as @command{script}, which is available on many Unix systems.
28263 Just run your @value{GDBN} session inside @command{script} and then
28264 include the @file{typescript} file with your bug report.
28266 Another way to record a @value{GDBN} session is to run @value{GDBN}
28267 inside Emacs and then save the entire buffer to a file.
28270 If you wish to suggest changes to the @value{GDBN} source, send us context
28271 diffs. If you even discuss something in the @value{GDBN} source, refer to
28272 it by context, not by line number.
28274 The line numbers in our development sources will not match those in your
28275 sources. Your line numbers would convey no useful information to us.
28279 Here are some things that are not necessary:
28283 A description of the envelope of the bug.
28285 Often people who encounter a bug spend a lot of time investigating
28286 which changes to the input file will make the bug go away and which
28287 changes will not affect it.
28289 This is often time consuming and not very useful, because the way we
28290 will find the bug is by running a single example under the debugger
28291 with breakpoints, not by pure deduction from a series of examples.
28292 We recommend that you save your time for something else.
28294 Of course, if you can find a simpler example to report @emph{instead}
28295 of the original one, that is a convenience for us. Errors in the
28296 output will be easier to spot, running under the debugger will take
28297 less time, and so on.
28299 However, simplification is not vital; if you do not want to do this,
28300 report the bug anyway and send us the entire test case you used.
28303 A patch for the bug.
28305 A patch for the bug does help us if it is a good one. But do not omit
28306 the necessary information, such as the test case, on the assumption that
28307 a patch is all we need. We might see problems with your patch and decide
28308 to fix the problem another way, or we might not understand it at all.
28310 Sometimes with a program as complicated as @value{GDBN} it is very hard to
28311 construct an example that will make the program follow a certain path
28312 through the code. If you do not send us the example, we will not be able
28313 to construct one, so we will not be able to verify that the bug is fixed.
28315 And if we cannot understand what bug you are trying to fix, or why your
28316 patch should be an improvement, we will not install it. A test case will
28317 help us to understand.
28320 A guess about what the bug is or what it depends on.
28322 Such guesses are usually wrong. Even we cannot guess right about such
28323 things without first using the debugger to find the facts.
28326 @c The readline documentation is distributed with the readline code
28327 @c and consists of the two following files:
28329 @c inc-hist.texinfo
28330 @c Use -I with makeinfo to point to the appropriate directory,
28331 @c environment var TEXINPUTS with TeX.
28332 @include rluser.texi
28333 @include inc-hist.texinfo
28336 @node Formatting Documentation
28337 @appendix Formatting Documentation
28339 @cindex @value{GDBN} reference card
28340 @cindex reference card
28341 The @value{GDBN} 4 release includes an already-formatted reference card, ready
28342 for printing with PostScript or Ghostscript, in the @file{gdb}
28343 subdirectory of the main source directory@footnote{In
28344 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
28345 release.}. If you can use PostScript or Ghostscript with your printer,
28346 you can print the reference card immediately with @file{refcard.ps}.
28348 The release also includes the source for the reference card. You
28349 can format it, using @TeX{}, by typing:
28355 The @value{GDBN} reference card is designed to print in @dfn{landscape}
28356 mode on US ``letter'' size paper;
28357 that is, on a sheet 11 inches wide by 8.5 inches
28358 high. You will need to specify this form of printing as an option to
28359 your @sc{dvi} output program.
28361 @cindex documentation
28363 All the documentation for @value{GDBN} comes as part of the machine-readable
28364 distribution. The documentation is written in Texinfo format, which is
28365 a documentation system that uses a single source file to produce both
28366 on-line information and a printed manual. You can use one of the Info
28367 formatting commands to create the on-line version of the documentation
28368 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
28370 @value{GDBN} includes an already formatted copy of the on-line Info
28371 version of this manual in the @file{gdb} subdirectory. The main Info
28372 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
28373 subordinate files matching @samp{gdb.info*} in the same directory. If
28374 necessary, you can print out these files, or read them with any editor;
28375 but they are easier to read using the @code{info} subsystem in @sc{gnu}
28376 Emacs or the standalone @code{info} program, available as part of the
28377 @sc{gnu} Texinfo distribution.
28379 If you want to format these Info files yourself, you need one of the
28380 Info formatting programs, such as @code{texinfo-format-buffer} or
28383 If you have @code{makeinfo} installed, and are in the top level
28384 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
28385 version @value{GDBVN}), you can make the Info file by typing:
28392 If you want to typeset and print copies of this manual, you need @TeX{},
28393 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
28394 Texinfo definitions file.
28396 @TeX{} is a typesetting program; it does not print files directly, but
28397 produces output files called @sc{dvi} files. To print a typeset
28398 document, you need a program to print @sc{dvi} files. If your system
28399 has @TeX{} installed, chances are it has such a program. The precise
28400 command to use depends on your system; @kbd{lpr -d} is common; another
28401 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
28402 require a file name without any extension or a @samp{.dvi} extension.
28404 @TeX{} also requires a macro definitions file called
28405 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
28406 written in Texinfo format. On its own, @TeX{} cannot either read or
28407 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
28408 and is located in the @file{gdb-@var{version-number}/texinfo}
28411 If you have @TeX{} and a @sc{dvi} printer program installed, you can
28412 typeset and print this manual. First switch to the @file{gdb}
28413 subdirectory of the main source directory (for example, to
28414 @file{gdb-@value{GDBVN}/gdb}) and type:
28420 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
28422 @node Installing GDB
28423 @appendix Installing @value{GDBN}
28424 @cindex installation
28427 * Requirements:: Requirements for building @value{GDBN}
28428 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
28429 * Separate Objdir:: Compiling @value{GDBN} in another directory
28430 * Config Names:: Specifying names for hosts and targets
28431 * Configure Options:: Summary of options for configure
28432 * System-wide configuration:: Having a system-wide init file
28436 @section Requirements for Building @value{GDBN}
28437 @cindex building @value{GDBN}, requirements for
28439 Building @value{GDBN} requires various tools and packages to be available.
28440 Other packages will be used only if they are found.
28442 @heading Tools/Packages Necessary for Building @value{GDBN}
28444 @item ISO C90 compiler
28445 @value{GDBN} is written in ISO C90. It should be buildable with any
28446 working C90 compiler, e.g.@: GCC.
28450 @heading Tools/Packages Optional for Building @value{GDBN}
28454 @value{GDBN} can use the Expat XML parsing library. This library may be
28455 included with your operating system distribution; if it is not, you
28456 can get the latest version from @url{http://expat.sourceforge.net}.
28457 The @file{configure} script will search for this library in several
28458 standard locations; if it is installed in an unusual path, you can
28459 use the @option{--with-libexpat-prefix} option to specify its location.
28465 Remote protocol memory maps (@pxref{Memory Map Format})
28467 Target descriptions (@pxref{Target Descriptions})
28469 Remote shared library lists (@pxref{Library List Format})
28471 MS-Windows shared libraries (@pxref{Shared Libraries})
28475 @cindex compressed debug sections
28476 @value{GDBN} will use the @samp{zlib} library, if available, to read
28477 compressed debug sections. Some linkers, such as GNU gold, are capable
28478 of producing binaries with compressed debug sections. If @value{GDBN}
28479 is compiled with @samp{zlib}, it will be able to read the debug
28480 information in such binaries.
28482 The @samp{zlib} library is likely included with your operating system
28483 distribution; if it is not, you can get the latest version from
28484 @url{http://zlib.net}.
28487 @value{GDBN}'s features related to character sets (@pxref{Character
28488 Sets}) require a functioning @code{iconv} implementation. If you are
28489 on a GNU system, then this is provided by the GNU C Library. Some
28490 other systems also provide a working @code{iconv}.
28492 On systems with @code{iconv}, you can install GNU Libiconv. If you
28493 have previously installed Libiconv, you can use the
28494 @option{--with-libiconv-prefix} option to configure.
28496 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
28497 arrange to build Libiconv if a directory named @file{libiconv} appears
28498 in the top-most source directory. If Libiconv is built this way, and
28499 if the operating system does not provide a suitable @code{iconv}
28500 implementation, then the just-built library will automatically be used
28501 by @value{GDBN}. One easy way to set this up is to download GNU
28502 Libiconv, unpack it, and then rename the directory holding the
28503 Libiconv source code to @samp{libiconv}.
28506 @node Running Configure
28507 @section Invoking the @value{GDBN} @file{configure} Script
28508 @cindex configuring @value{GDBN}
28509 @value{GDBN} comes with a @file{configure} script that automates the process
28510 of preparing @value{GDBN} for installation; you can then use @code{make} to
28511 build the @code{gdb} program.
28513 @c irrelevant in info file; it's as current as the code it lives with.
28514 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
28515 look at the @file{README} file in the sources; we may have improved the
28516 installation procedures since publishing this manual.}
28519 The @value{GDBN} distribution includes all the source code you need for
28520 @value{GDBN} in a single directory, whose name is usually composed by
28521 appending the version number to @samp{gdb}.
28523 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
28524 @file{gdb-@value{GDBVN}} directory. That directory contains:
28527 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
28528 script for configuring @value{GDBN} and all its supporting libraries
28530 @item gdb-@value{GDBVN}/gdb
28531 the source specific to @value{GDBN} itself
28533 @item gdb-@value{GDBVN}/bfd
28534 source for the Binary File Descriptor library
28536 @item gdb-@value{GDBVN}/include
28537 @sc{gnu} include files
28539 @item gdb-@value{GDBVN}/libiberty
28540 source for the @samp{-liberty} free software library
28542 @item gdb-@value{GDBVN}/opcodes
28543 source for the library of opcode tables and disassemblers
28545 @item gdb-@value{GDBVN}/readline
28546 source for the @sc{gnu} command-line interface
28548 @item gdb-@value{GDBVN}/glob
28549 source for the @sc{gnu} filename pattern-matching subroutine
28551 @item gdb-@value{GDBVN}/mmalloc
28552 source for the @sc{gnu} memory-mapped malloc package
28555 The simplest way to configure and build @value{GDBN} is to run @file{configure}
28556 from the @file{gdb-@var{version-number}} source directory, which in
28557 this example is the @file{gdb-@value{GDBVN}} directory.
28559 First switch to the @file{gdb-@var{version-number}} source directory
28560 if you are not already in it; then run @file{configure}. Pass the
28561 identifier for the platform on which @value{GDBN} will run as an
28567 cd gdb-@value{GDBVN}
28568 ./configure @var{host}
28573 where @var{host} is an identifier such as @samp{sun4} or
28574 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
28575 (You can often leave off @var{host}; @file{configure} tries to guess the
28576 correct value by examining your system.)
28578 Running @samp{configure @var{host}} and then running @code{make} builds the
28579 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
28580 libraries, then @code{gdb} itself. The configured source files, and the
28581 binaries, are left in the corresponding source directories.
28584 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
28585 system does not recognize this automatically when you run a different
28586 shell, you may need to run @code{sh} on it explicitly:
28589 sh configure @var{host}
28592 If you run @file{configure} from a directory that contains source
28593 directories for multiple libraries or programs, such as the
28594 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
28596 creates configuration files for every directory level underneath (unless
28597 you tell it not to, with the @samp{--norecursion} option).
28599 You should run the @file{configure} script from the top directory in the
28600 source tree, the @file{gdb-@var{version-number}} directory. If you run
28601 @file{configure} from one of the subdirectories, you will configure only
28602 that subdirectory. That is usually not what you want. In particular,
28603 if you run the first @file{configure} from the @file{gdb} subdirectory
28604 of the @file{gdb-@var{version-number}} directory, you will omit the
28605 configuration of @file{bfd}, @file{readline}, and other sibling
28606 directories of the @file{gdb} subdirectory. This leads to build errors
28607 about missing include files such as @file{bfd/bfd.h}.
28609 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
28610 However, you should make sure that the shell on your path (named by
28611 the @samp{SHELL} environment variable) is publicly readable. Remember
28612 that @value{GDBN} uses the shell to start your program---some systems refuse to
28613 let @value{GDBN} debug child processes whose programs are not readable.
28615 @node Separate Objdir
28616 @section Compiling @value{GDBN} in Another Directory
28618 If you want to run @value{GDBN} versions for several host or target machines,
28619 you need a different @code{gdb} compiled for each combination of
28620 host and target. @file{configure} is designed to make this easy by
28621 allowing you to generate each configuration in a separate subdirectory,
28622 rather than in the source directory. If your @code{make} program
28623 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
28624 @code{make} in each of these directories builds the @code{gdb}
28625 program specified there.
28627 To build @code{gdb} in a separate directory, run @file{configure}
28628 with the @samp{--srcdir} option to specify where to find the source.
28629 (You also need to specify a path to find @file{configure}
28630 itself from your working directory. If the path to @file{configure}
28631 would be the same as the argument to @samp{--srcdir}, you can leave out
28632 the @samp{--srcdir} option; it is assumed.)
28634 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
28635 separate directory for a Sun 4 like this:
28639 cd gdb-@value{GDBVN}
28642 ../gdb-@value{GDBVN}/configure sun4
28647 When @file{configure} builds a configuration using a remote source
28648 directory, it creates a tree for the binaries with the same structure
28649 (and using the same names) as the tree under the source directory. In
28650 the example, you'd find the Sun 4 library @file{libiberty.a} in the
28651 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
28652 @file{gdb-sun4/gdb}.
28654 Make sure that your path to the @file{configure} script has just one
28655 instance of @file{gdb} in it. If your path to @file{configure} looks
28656 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
28657 one subdirectory of @value{GDBN}, not the whole package. This leads to
28658 build errors about missing include files such as @file{bfd/bfd.h}.
28660 One popular reason to build several @value{GDBN} configurations in separate
28661 directories is to configure @value{GDBN} for cross-compiling (where
28662 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
28663 programs that run on another machine---the @dfn{target}).
28664 You specify a cross-debugging target by
28665 giving the @samp{--target=@var{target}} option to @file{configure}.
28667 When you run @code{make} to build a program or library, you must run
28668 it in a configured directory---whatever directory you were in when you
28669 called @file{configure} (or one of its subdirectories).
28671 The @code{Makefile} that @file{configure} generates in each source
28672 directory also runs recursively. If you type @code{make} in a source
28673 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
28674 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
28675 will build all the required libraries, and then build GDB.
28677 When you have multiple hosts or targets configured in separate
28678 directories, you can run @code{make} on them in parallel (for example,
28679 if they are NFS-mounted on each of the hosts); they will not interfere
28683 @section Specifying Names for Hosts and Targets
28685 The specifications used for hosts and targets in the @file{configure}
28686 script are based on a three-part naming scheme, but some short predefined
28687 aliases are also supported. The full naming scheme encodes three pieces
28688 of information in the following pattern:
28691 @var{architecture}-@var{vendor}-@var{os}
28694 For example, you can use the alias @code{sun4} as a @var{host} argument,
28695 or as the value for @var{target} in a @code{--target=@var{target}}
28696 option. The equivalent full name is @samp{sparc-sun-sunos4}.
28698 The @file{configure} script accompanying @value{GDBN} does not provide
28699 any query facility to list all supported host and target names or
28700 aliases. @file{configure} calls the Bourne shell script
28701 @code{config.sub} to map abbreviations to full names; you can read the
28702 script, if you wish, or you can use it to test your guesses on
28703 abbreviations---for example:
28706 % sh config.sub i386-linux
28708 % sh config.sub alpha-linux
28709 alpha-unknown-linux-gnu
28710 % sh config.sub hp9k700
28712 % sh config.sub sun4
28713 sparc-sun-sunos4.1.1
28714 % sh config.sub sun3
28715 m68k-sun-sunos4.1.1
28716 % sh config.sub i986v
28717 Invalid configuration `i986v': machine `i986v' not recognized
28721 @code{config.sub} is also distributed in the @value{GDBN} source
28722 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
28724 @node Configure Options
28725 @section @file{configure} Options
28727 Here is a summary of the @file{configure} options and arguments that
28728 are most often useful for building @value{GDBN}. @file{configure} also has
28729 several other options not listed here. @inforef{What Configure
28730 Does,,configure.info}, for a full explanation of @file{configure}.
28733 configure @r{[}--help@r{]}
28734 @r{[}--prefix=@var{dir}@r{]}
28735 @r{[}--exec-prefix=@var{dir}@r{]}
28736 @r{[}--srcdir=@var{dirname}@r{]}
28737 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
28738 @r{[}--target=@var{target}@r{]}
28743 You may introduce options with a single @samp{-} rather than
28744 @samp{--} if you prefer; but you may abbreviate option names if you use
28749 Display a quick summary of how to invoke @file{configure}.
28751 @item --prefix=@var{dir}
28752 Configure the source to install programs and files under directory
28755 @item --exec-prefix=@var{dir}
28756 Configure the source to install programs under directory
28759 @c avoid splitting the warning from the explanation:
28761 @item --srcdir=@var{dirname}
28762 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
28763 @code{make} that implements the @code{VPATH} feature.}@*
28764 Use this option to make configurations in directories separate from the
28765 @value{GDBN} source directories. Among other things, you can use this to
28766 build (or maintain) several configurations simultaneously, in separate
28767 directories. @file{configure} writes configuration-specific files in
28768 the current directory, but arranges for them to use the source in the
28769 directory @var{dirname}. @file{configure} creates directories under
28770 the working directory in parallel to the source directories below
28773 @item --norecursion
28774 Configure only the directory level where @file{configure} is executed; do not
28775 propagate configuration to subdirectories.
28777 @item --target=@var{target}
28778 Configure @value{GDBN} for cross-debugging programs running on the specified
28779 @var{target}. Without this option, @value{GDBN} is configured to debug
28780 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
28782 There is no convenient way to generate a list of all available targets.
28784 @item @var{host} @dots{}
28785 Configure @value{GDBN} to run on the specified @var{host}.
28787 There is no convenient way to generate a list of all available hosts.
28790 There are many other options available as well, but they are generally
28791 needed for special purposes only.
28793 @node System-wide configuration
28794 @section System-wide configuration and settings
28795 @cindex system-wide init file
28797 @value{GDBN} can be configured to have a system-wide init file;
28798 this file will be read and executed at startup (@pxref{Startup, , What
28799 @value{GDBN} does during startup}).
28801 Here is the corresponding configure option:
28804 @item --with-system-gdbinit=@var{file}
28805 Specify that the default location of the system-wide init file is
28809 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
28810 it may be subject to relocation. Two possible cases:
28814 If the default location of this init file contains @file{$prefix},
28815 it will be subject to relocation. Suppose that the configure options
28816 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
28817 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
28818 init file is looked for as @file{$install/etc/gdbinit} instead of
28819 @file{$prefix/etc/gdbinit}.
28822 By contrast, if the default location does not contain the prefix,
28823 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
28824 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
28825 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
28826 wherever @value{GDBN} is installed.
28829 @node Maintenance Commands
28830 @appendix Maintenance Commands
28831 @cindex maintenance commands
28832 @cindex internal commands
28834 In addition to commands intended for @value{GDBN} users, @value{GDBN}
28835 includes a number of commands intended for @value{GDBN} developers,
28836 that are not documented elsewhere in this manual. These commands are
28837 provided here for reference. (For commands that turn on debugging
28838 messages, see @ref{Debugging Output}.)
28841 @kindex maint agent
28842 @kindex maint agent-eval
28843 @item maint agent @var{expression}
28844 @itemx maint agent-eval @var{expression}
28845 Translate the given @var{expression} into remote agent bytecodes.
28846 This command is useful for debugging the Agent Expression mechanism
28847 (@pxref{Agent Expressions}). The @samp{agent} version produces an
28848 expression useful for data collection, such as by tracepoints, while
28849 @samp{maint agent-eval} produces an expression that evaluates directly
28850 to a result. For instance, a collection expression for @code{globa +
28851 globb} will include bytecodes to record four bytes of memory at each
28852 of the addresses of @code{globa} and @code{globb}, while discarding
28853 the result of the addition, while an evaluation expression will do the
28854 addition and return the sum.
28856 @kindex maint info breakpoints
28857 @item @anchor{maint info breakpoints}maint info breakpoints
28858 Using the same format as @samp{info breakpoints}, display both the
28859 breakpoints you've set explicitly, and those @value{GDBN} is using for
28860 internal purposes. Internal breakpoints are shown with negative
28861 breakpoint numbers. The type column identifies what kind of breakpoint
28866 Normal, explicitly set breakpoint.
28869 Normal, explicitly set watchpoint.
28872 Internal breakpoint, used to handle correctly stepping through
28873 @code{longjmp} calls.
28875 @item longjmp resume
28876 Internal breakpoint at the target of a @code{longjmp}.
28879 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
28882 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
28885 Shared library events.
28889 @kindex set displaced-stepping
28890 @kindex show displaced-stepping
28891 @cindex displaced stepping support
28892 @cindex out-of-line single-stepping
28893 @item set displaced-stepping
28894 @itemx show displaced-stepping
28895 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
28896 if the target supports it. Displaced stepping is a way to single-step
28897 over breakpoints without removing them from the inferior, by executing
28898 an out-of-line copy of the instruction that was originally at the
28899 breakpoint location. It is also known as out-of-line single-stepping.
28902 @item set displaced-stepping on
28903 If the target architecture supports it, @value{GDBN} will use
28904 displaced stepping to step over breakpoints.
28906 @item set displaced-stepping off
28907 @value{GDBN} will not use displaced stepping to step over breakpoints,
28908 even if such is supported by the target architecture.
28910 @cindex non-stop mode, and @samp{set displaced-stepping}
28911 @item set displaced-stepping auto
28912 This is the default mode. @value{GDBN} will use displaced stepping
28913 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
28914 architecture supports displaced stepping.
28917 @kindex maint check-symtabs
28918 @item maint check-symtabs
28919 Check the consistency of psymtabs and symtabs.
28921 @kindex maint cplus first_component
28922 @item maint cplus first_component @var{name}
28923 Print the first C@t{++} class/namespace component of @var{name}.
28925 @kindex maint cplus namespace
28926 @item maint cplus namespace
28927 Print the list of possible C@t{++} namespaces.
28929 @kindex maint demangle
28930 @item maint demangle @var{name}
28931 Demangle a C@t{++} or Objective-C mangled @var{name}.
28933 @kindex maint deprecate
28934 @kindex maint undeprecate
28935 @cindex deprecated commands
28936 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
28937 @itemx maint undeprecate @var{command}
28938 Deprecate or undeprecate the named @var{command}. Deprecated commands
28939 cause @value{GDBN} to issue a warning when you use them. The optional
28940 argument @var{replacement} says which newer command should be used in
28941 favor of the deprecated one; if it is given, @value{GDBN} will mention
28942 the replacement as part of the warning.
28944 @kindex maint dump-me
28945 @item maint dump-me
28946 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
28947 Cause a fatal signal in the debugger and force it to dump its core.
28948 This is supported only on systems which support aborting a program
28949 with the @code{SIGQUIT} signal.
28951 @kindex maint internal-error
28952 @kindex maint internal-warning
28953 @item maint internal-error @r{[}@var{message-text}@r{]}
28954 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
28955 Cause @value{GDBN} to call the internal function @code{internal_error}
28956 or @code{internal_warning} and hence behave as though an internal error
28957 or internal warning has been detected. In addition to reporting the
28958 internal problem, these functions give the user the opportunity to
28959 either quit @value{GDBN} or create a core file of the current
28960 @value{GDBN} session.
28962 These commands take an optional parameter @var{message-text} that is
28963 used as the text of the error or warning message.
28965 Here's an example of using @code{internal-error}:
28968 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
28969 @dots{}/maint.c:121: internal-error: testing, 1, 2
28970 A problem internal to GDB has been detected. Further
28971 debugging may prove unreliable.
28972 Quit this debugging session? (y or n) @kbd{n}
28973 Create a core file? (y or n) @kbd{n}
28977 @cindex @value{GDBN} internal error
28978 @cindex internal errors, control of @value{GDBN} behavior
28980 @kindex maint set internal-error
28981 @kindex maint show internal-error
28982 @kindex maint set internal-warning
28983 @kindex maint show internal-warning
28984 @item maint set internal-error @var{action} [ask|yes|no]
28985 @itemx maint show internal-error @var{action}
28986 @itemx maint set internal-warning @var{action} [ask|yes|no]
28987 @itemx maint show internal-warning @var{action}
28988 When @value{GDBN} reports an internal problem (error or warning) it
28989 gives the user the opportunity to both quit @value{GDBN} and create a
28990 core file of the current @value{GDBN} session. These commands let you
28991 override the default behaviour for each particular @var{action},
28992 described in the table below.
28996 You can specify that @value{GDBN} should always (yes) or never (no)
28997 quit. The default is to ask the user what to do.
29000 You can specify that @value{GDBN} should always (yes) or never (no)
29001 create a core file. The default is to ask the user what to do.
29004 @kindex maint packet
29005 @item maint packet @var{text}
29006 If @value{GDBN} is talking to an inferior via the serial protocol,
29007 then this command sends the string @var{text} to the inferior, and
29008 displays the response packet. @value{GDBN} supplies the initial
29009 @samp{$} character, the terminating @samp{#} character, and the
29012 @kindex maint print architecture
29013 @item maint print architecture @r{[}@var{file}@r{]}
29014 Print the entire architecture configuration. The optional argument
29015 @var{file} names the file where the output goes.
29017 @kindex maint print c-tdesc
29018 @item maint print c-tdesc
29019 Print the current target description (@pxref{Target Descriptions}) as
29020 a C source file. The created source file can be used in @value{GDBN}
29021 when an XML parser is not available to parse the description.
29023 @kindex maint print dummy-frames
29024 @item maint print dummy-frames
29025 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
29028 (@value{GDBP}) @kbd{b add}
29030 (@value{GDBP}) @kbd{print add(2,3)}
29031 Breakpoint 2, add (a=2, b=3) at @dots{}
29033 The program being debugged stopped while in a function called from GDB.
29035 (@value{GDBP}) @kbd{maint print dummy-frames}
29036 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
29037 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
29038 call_lo=0x01014000 call_hi=0x01014001
29042 Takes an optional file parameter.
29044 @kindex maint print registers
29045 @kindex maint print raw-registers
29046 @kindex maint print cooked-registers
29047 @kindex maint print register-groups
29048 @item maint print registers @r{[}@var{file}@r{]}
29049 @itemx maint print raw-registers @r{[}@var{file}@r{]}
29050 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
29051 @itemx maint print register-groups @r{[}@var{file}@r{]}
29052 Print @value{GDBN}'s internal register data structures.
29054 The command @code{maint print raw-registers} includes the contents of
29055 the raw register cache; the command @code{maint print cooked-registers}
29056 includes the (cooked) value of all registers; and the command
29057 @code{maint print register-groups} includes the groups that each
29058 register is a member of. @xref{Registers,, Registers, gdbint,
29059 @value{GDBN} Internals}.
29061 These commands take an optional parameter, a file name to which to
29062 write the information.
29064 @kindex maint print reggroups
29065 @item maint print reggroups @r{[}@var{file}@r{]}
29066 Print @value{GDBN}'s internal register group data structures. The
29067 optional argument @var{file} tells to what file to write the
29070 The register groups info looks like this:
29073 (@value{GDBP}) @kbd{maint print reggroups}
29086 This command forces @value{GDBN} to flush its internal register cache.
29088 @kindex maint print objfiles
29089 @cindex info for known object files
29090 @item maint print objfiles
29091 Print a dump of all known object files. For each object file, this
29092 command prints its name, address in memory, and all of its psymtabs
29095 @kindex maint print statistics
29096 @cindex bcache statistics
29097 @item maint print statistics
29098 This command prints, for each object file in the program, various data
29099 about that object file followed by the byte cache (@dfn{bcache})
29100 statistics for the object file. The objfile data includes the number
29101 of minimal, partial, full, and stabs symbols, the number of types
29102 defined by the objfile, the number of as yet unexpanded psym tables,
29103 the number of line tables and string tables, and the amount of memory
29104 used by the various tables. The bcache statistics include the counts,
29105 sizes, and counts of duplicates of all and unique objects, max,
29106 average, and median entry size, total memory used and its overhead and
29107 savings, and various measures of the hash table size and chain
29110 @kindex maint print target-stack
29111 @cindex target stack description
29112 @item maint print target-stack
29113 A @dfn{target} is an interface between the debugger and a particular
29114 kind of file or process. Targets can be stacked in @dfn{strata},
29115 so that more than one target can potentially respond to a request.
29116 In particular, memory accesses will walk down the stack of targets
29117 until they find a target that is interested in handling that particular
29120 This command prints a short description of each layer that was pushed on
29121 the @dfn{target stack}, starting from the top layer down to the bottom one.
29123 @kindex maint print type
29124 @cindex type chain of a data type
29125 @item maint print type @var{expr}
29126 Print the type chain for a type specified by @var{expr}. The argument
29127 can be either a type name or a symbol. If it is a symbol, the type of
29128 that symbol is described. The type chain produced by this command is
29129 a recursive definition of the data type as stored in @value{GDBN}'s
29130 data structures, including its flags and contained types.
29132 @kindex maint set dwarf2 max-cache-age
29133 @kindex maint show dwarf2 max-cache-age
29134 @item maint set dwarf2 max-cache-age
29135 @itemx maint show dwarf2 max-cache-age
29136 Control the DWARF 2 compilation unit cache.
29138 @cindex DWARF 2 compilation units cache
29139 In object files with inter-compilation-unit references, such as those
29140 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
29141 reader needs to frequently refer to previously read compilation units.
29142 This setting controls how long a compilation unit will remain in the
29143 cache if it is not referenced. A higher limit means that cached
29144 compilation units will be stored in memory longer, and more total
29145 memory will be used. Setting it to zero disables caching, which will
29146 slow down @value{GDBN} startup, but reduce memory consumption.
29148 @kindex maint set profile
29149 @kindex maint show profile
29150 @cindex profiling GDB
29151 @item maint set profile
29152 @itemx maint show profile
29153 Control profiling of @value{GDBN}.
29155 Profiling will be disabled until you use the @samp{maint set profile}
29156 command to enable it. When you enable profiling, the system will begin
29157 collecting timing and execution count data; when you disable profiling or
29158 exit @value{GDBN}, the results will be written to a log file. Remember that
29159 if you use profiling, @value{GDBN} will overwrite the profiling log file
29160 (often called @file{gmon.out}). If you have a record of important profiling
29161 data in a @file{gmon.out} file, be sure to move it to a safe location.
29163 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
29164 compiled with the @samp{-pg} compiler option.
29166 @kindex maint set show-debug-regs
29167 @kindex maint show show-debug-regs
29168 @cindex hardware debug registers
29169 @item maint set show-debug-regs
29170 @itemx maint show show-debug-regs
29171 Control whether to show variables that mirror the hardware debug
29172 registers. Use @code{ON} to enable, @code{OFF} to disable. If
29173 enabled, the debug registers values are shown when @value{GDBN} inserts or
29174 removes a hardware breakpoint or watchpoint, and when the inferior
29175 triggers a hardware-assisted breakpoint or watchpoint.
29177 @kindex maint space
29178 @cindex memory used by commands
29180 Control whether to display memory usage for each command. If set to a
29181 nonzero value, @value{GDBN} will display how much memory each command
29182 took, following the command's own output. This can also be requested
29183 by invoking @value{GDBN} with the @option{--statistics} command-line
29184 switch (@pxref{Mode Options}).
29187 @cindex time of command execution
29189 Control whether to display the execution time for each command. If
29190 set to a nonzero value, @value{GDBN} will display how much time it
29191 took to execute each command, following the command's own output.
29192 The time is not printed for the commands that run the target, since
29193 there's no mechanism currently to compute how much time was spend
29194 by @value{GDBN} and how much time was spend by the program been debugged.
29195 it's not possibly currently
29196 This can also be requested by invoking @value{GDBN} with the
29197 @option{--statistics} command-line switch (@pxref{Mode Options}).
29199 @kindex maint translate-address
29200 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
29201 Find the symbol stored at the location specified by the address
29202 @var{addr} and an optional section name @var{section}. If found,
29203 @value{GDBN} prints the name of the closest symbol and an offset from
29204 the symbol's location to the specified address. This is similar to
29205 the @code{info address} command (@pxref{Symbols}), except that this
29206 command also allows to find symbols in other sections.
29208 If section was not specified, the section in which the symbol was found
29209 is also printed. For dynamically linked executables, the name of
29210 executable or shared library containing the symbol is printed as well.
29214 The following command is useful for non-interactive invocations of
29215 @value{GDBN}, such as in the test suite.
29218 @item set watchdog @var{nsec}
29219 @kindex set watchdog
29220 @cindex watchdog timer
29221 @cindex timeout for commands
29222 Set the maximum number of seconds @value{GDBN} will wait for the
29223 target operation to finish. If this time expires, @value{GDBN}
29224 reports and error and the command is aborted.
29226 @item show watchdog
29227 Show the current setting of the target wait timeout.
29230 @node Remote Protocol
29231 @appendix @value{GDBN} Remote Serial Protocol
29236 * Stop Reply Packets::
29237 * General Query Packets::
29238 * Architecture-Specific Protocol Details::
29239 * Tracepoint Packets::
29240 * Host I/O Packets::
29242 * Notification Packets::
29243 * Remote Non-Stop::
29244 * Packet Acknowledgment::
29246 * File-I/O Remote Protocol Extension::
29247 * Library List Format::
29248 * Memory Map Format::
29249 * Thread List Format::
29255 There may be occasions when you need to know something about the
29256 protocol---for example, if there is only one serial port to your target
29257 machine, you might want your program to do something special if it
29258 recognizes a packet meant for @value{GDBN}.
29260 In the examples below, @samp{->} and @samp{<-} are used to indicate
29261 transmitted and received data, respectively.
29263 @cindex protocol, @value{GDBN} remote serial
29264 @cindex serial protocol, @value{GDBN} remote
29265 @cindex remote serial protocol
29266 All @value{GDBN} commands and responses (other than acknowledgments
29267 and notifications, see @ref{Notification Packets}) are sent as a
29268 @var{packet}. A @var{packet} is introduced with the character
29269 @samp{$}, the actual @var{packet-data}, and the terminating character
29270 @samp{#} followed by a two-digit @var{checksum}:
29273 @code{$}@var{packet-data}@code{#}@var{checksum}
29277 @cindex checksum, for @value{GDBN} remote
29279 The two-digit @var{checksum} is computed as the modulo 256 sum of all
29280 characters between the leading @samp{$} and the trailing @samp{#} (an
29281 eight bit unsigned checksum).
29283 Implementors should note that prior to @value{GDBN} 5.0 the protocol
29284 specification also included an optional two-digit @var{sequence-id}:
29287 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
29290 @cindex sequence-id, for @value{GDBN} remote
29292 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
29293 has never output @var{sequence-id}s. Stubs that handle packets added
29294 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
29296 When either the host or the target machine receives a packet, the first
29297 response expected is an acknowledgment: either @samp{+} (to indicate
29298 the package was received correctly) or @samp{-} (to request
29302 -> @code{$}@var{packet-data}@code{#}@var{checksum}
29307 The @samp{+}/@samp{-} acknowledgments can be disabled
29308 once a connection is established.
29309 @xref{Packet Acknowledgment}, for details.
29311 The host (@value{GDBN}) sends @var{command}s, and the target (the
29312 debugging stub incorporated in your program) sends a @var{response}. In
29313 the case of step and continue @var{command}s, the response is only sent
29314 when the operation has completed, and the target has again stopped all
29315 threads in all attached processes. This is the default all-stop mode
29316 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
29317 execution mode; see @ref{Remote Non-Stop}, for details.
29319 @var{packet-data} consists of a sequence of characters with the
29320 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
29323 @cindex remote protocol, field separator
29324 Fields within the packet should be separated using @samp{,} @samp{;} or
29325 @samp{:}. Except where otherwise noted all numbers are represented in
29326 @sc{hex} with leading zeros suppressed.
29328 Implementors should note that prior to @value{GDBN} 5.0, the character
29329 @samp{:} could not appear as the third character in a packet (as it
29330 would potentially conflict with the @var{sequence-id}).
29332 @cindex remote protocol, binary data
29333 @anchor{Binary Data}
29334 Binary data in most packets is encoded either as two hexadecimal
29335 digits per byte of binary data. This allowed the traditional remote
29336 protocol to work over connections which were only seven-bit clean.
29337 Some packets designed more recently assume an eight-bit clean
29338 connection, and use a more efficient encoding to send and receive
29341 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
29342 as an escape character. Any escaped byte is transmitted as the escape
29343 character followed by the original character XORed with @code{0x20}.
29344 For example, the byte @code{0x7d} would be transmitted as the two
29345 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
29346 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
29347 @samp{@}}) must always be escaped. Responses sent by the stub
29348 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
29349 is not interpreted as the start of a run-length encoded sequence
29352 Response @var{data} can be run-length encoded to save space.
29353 Run-length encoding replaces runs of identical characters with one
29354 instance of the repeated character, followed by a @samp{*} and a
29355 repeat count. The repeat count is itself sent encoded, to avoid
29356 binary characters in @var{data}: a value of @var{n} is sent as
29357 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
29358 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
29359 code 32) for a repeat count of 3. (This is because run-length
29360 encoding starts to win for counts 3 or more.) Thus, for example,
29361 @samp{0* } is a run-length encoding of ``0000'': the space character
29362 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
29365 The printable characters @samp{#} and @samp{$} or with a numeric value
29366 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
29367 seven repeats (@samp{$}) can be expanded using a repeat count of only
29368 five (@samp{"}). For example, @samp{00000000} can be encoded as
29371 The error response returned for some packets includes a two character
29372 error number. That number is not well defined.
29374 @cindex empty response, for unsupported packets
29375 For any @var{command} not supported by the stub, an empty response
29376 (@samp{$#00}) should be returned. That way it is possible to extend the
29377 protocol. A newer @value{GDBN} can tell if a packet is supported based
29380 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
29381 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
29387 The following table provides a complete list of all currently defined
29388 @var{command}s and their corresponding response @var{data}.
29389 @xref{File-I/O Remote Protocol Extension}, for details about the File
29390 I/O extension of the remote protocol.
29392 Each packet's description has a template showing the packet's overall
29393 syntax, followed by an explanation of the packet's meaning. We
29394 include spaces in some of the templates for clarity; these are not
29395 part of the packet's syntax. No @value{GDBN} packet uses spaces to
29396 separate its components. For example, a template like @samp{foo
29397 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
29398 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
29399 @var{baz}. @value{GDBN} does not transmit a space character between the
29400 @samp{foo} and the @var{bar}, or between the @var{bar} and the
29403 @cindex @var{thread-id}, in remote protocol
29404 @anchor{thread-id syntax}
29405 Several packets and replies include a @var{thread-id} field to identify
29406 a thread. Normally these are positive numbers with a target-specific
29407 interpretation, formatted as big-endian hex strings. A @var{thread-id}
29408 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
29411 In addition, the remote protocol supports a multiprocess feature in
29412 which the @var{thread-id} syntax is extended to optionally include both
29413 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
29414 The @var{pid} (process) and @var{tid} (thread) components each have the
29415 format described above: a positive number with target-specific
29416 interpretation formatted as a big-endian hex string, literal @samp{-1}
29417 to indicate all processes or threads (respectively), or @samp{0} to
29418 indicate an arbitrary process or thread. Specifying just a process, as
29419 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
29420 error to specify all processes but a specific thread, such as
29421 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
29422 for those packets and replies explicitly documented to include a process
29423 ID, rather than a @var{thread-id}.
29425 The multiprocess @var{thread-id} syntax extensions are only used if both
29426 @value{GDBN} and the stub report support for the @samp{multiprocess}
29427 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
29430 Note that all packet forms beginning with an upper- or lower-case
29431 letter, other than those described here, are reserved for future use.
29433 Here are the packet descriptions.
29438 @cindex @samp{!} packet
29439 @anchor{extended mode}
29440 Enable extended mode. In extended mode, the remote server is made
29441 persistent. The @samp{R} packet is used to restart the program being
29447 The remote target both supports and has enabled extended mode.
29451 @cindex @samp{?} packet
29452 Indicate the reason the target halted. The reply is the same as for
29453 step and continue. This packet has a special interpretation when the
29454 target is in non-stop mode; see @ref{Remote Non-Stop}.
29457 @xref{Stop Reply Packets}, for the reply specifications.
29459 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
29460 @cindex @samp{A} packet
29461 Initialized @code{argv[]} array passed into program. @var{arglen}
29462 specifies the number of bytes in the hex encoded byte stream
29463 @var{arg}. See @code{gdbserver} for more details.
29468 The arguments were set.
29474 @cindex @samp{b} packet
29475 (Don't use this packet; its behavior is not well-defined.)
29476 Change the serial line speed to @var{baud}.
29478 JTC: @emph{When does the transport layer state change? When it's
29479 received, or after the ACK is transmitted. In either case, there are
29480 problems if the command or the acknowledgment packet is dropped.}
29482 Stan: @emph{If people really wanted to add something like this, and get
29483 it working for the first time, they ought to modify ser-unix.c to send
29484 some kind of out-of-band message to a specially-setup stub and have the
29485 switch happen "in between" packets, so that from remote protocol's point
29486 of view, nothing actually happened.}
29488 @item B @var{addr},@var{mode}
29489 @cindex @samp{B} packet
29490 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
29491 breakpoint at @var{addr}.
29493 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
29494 (@pxref{insert breakpoint or watchpoint packet}).
29496 @cindex @samp{bc} packet
29499 Backward continue. Execute the target system in reverse. No parameter.
29500 @xref{Reverse Execution}, for more information.
29503 @xref{Stop Reply Packets}, for the reply specifications.
29505 @cindex @samp{bs} packet
29508 Backward single step. Execute one instruction in reverse. No parameter.
29509 @xref{Reverse Execution}, for more information.
29512 @xref{Stop Reply Packets}, for the reply specifications.
29514 @item c @r{[}@var{addr}@r{]}
29515 @cindex @samp{c} packet
29516 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
29517 resume at current address.
29520 @xref{Stop Reply Packets}, for the reply specifications.
29522 @item C @var{sig}@r{[};@var{addr}@r{]}
29523 @cindex @samp{C} packet
29524 Continue with signal @var{sig} (hex signal number). If
29525 @samp{;@var{addr}} is omitted, resume at same address.
29528 @xref{Stop Reply Packets}, for the reply specifications.
29531 @cindex @samp{d} packet
29534 Don't use this packet; instead, define a general set packet
29535 (@pxref{General Query Packets}).
29539 @cindex @samp{D} packet
29540 The first form of the packet is used to detach @value{GDBN} from the
29541 remote system. It is sent to the remote target
29542 before @value{GDBN} disconnects via the @code{detach} command.
29544 The second form, including a process ID, is used when multiprocess
29545 protocol extensions are enabled (@pxref{multiprocess extensions}), to
29546 detach only a specific process. The @var{pid} is specified as a
29547 big-endian hex string.
29557 @item F @var{RC},@var{EE},@var{CF};@var{XX}
29558 @cindex @samp{F} packet
29559 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
29560 This is part of the File-I/O protocol extension. @xref{File-I/O
29561 Remote Protocol Extension}, for the specification.
29564 @anchor{read registers packet}
29565 @cindex @samp{g} packet
29566 Read general registers.
29570 @item @var{XX@dots{}}
29571 Each byte of register data is described by two hex digits. The bytes
29572 with the register are transmitted in target byte order. The size of
29573 each register and their position within the @samp{g} packet are
29574 determined by the @value{GDBN} internal gdbarch functions
29575 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
29576 specification of several standard @samp{g} packets is specified below.
29581 @item G @var{XX@dots{}}
29582 @cindex @samp{G} packet
29583 Write general registers. @xref{read registers packet}, for a
29584 description of the @var{XX@dots{}} data.
29594 @item H @var{c} @var{thread-id}
29595 @cindex @samp{H} packet
29596 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
29597 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
29598 should be @samp{c} for step and continue operations, @samp{g} for other
29599 operations. The thread designator @var{thread-id} has the format and
29600 interpretation described in @ref{thread-id syntax}.
29611 @c 'H': How restrictive (or permissive) is the thread model. If a
29612 @c thread is selected and stopped, are other threads allowed
29613 @c to continue to execute? As I mentioned above, I think the
29614 @c semantics of each command when a thread is selected must be
29615 @c described. For example:
29617 @c 'g': If the stub supports threads and a specific thread is
29618 @c selected, returns the register block from that thread;
29619 @c otherwise returns current registers.
29621 @c 'G' If the stub supports threads and a specific thread is
29622 @c selected, sets the registers of the register block of
29623 @c that thread; otherwise sets current registers.
29625 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
29626 @anchor{cycle step packet}
29627 @cindex @samp{i} packet
29628 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
29629 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
29630 step starting at that address.
29633 @cindex @samp{I} packet
29634 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
29638 @cindex @samp{k} packet
29641 FIXME: @emph{There is no description of how to operate when a specific
29642 thread context has been selected (i.e.@: does 'k' kill only that
29645 @item m @var{addr},@var{length}
29646 @cindex @samp{m} packet
29647 Read @var{length} bytes of memory starting at address @var{addr}.
29648 Note that @var{addr} may not be aligned to any particular boundary.
29650 The stub need not use any particular size or alignment when gathering
29651 data from memory for the response; even if @var{addr} is word-aligned
29652 and @var{length} is a multiple of the word size, the stub is free to
29653 use byte accesses, or not. For this reason, this packet may not be
29654 suitable for accessing memory-mapped I/O devices.
29655 @cindex alignment of remote memory accesses
29656 @cindex size of remote memory accesses
29657 @cindex memory, alignment and size of remote accesses
29661 @item @var{XX@dots{}}
29662 Memory contents; each byte is transmitted as a two-digit hexadecimal
29663 number. The reply may contain fewer bytes than requested if the
29664 server was able to read only part of the region of memory.
29669 @item M @var{addr},@var{length}:@var{XX@dots{}}
29670 @cindex @samp{M} packet
29671 Write @var{length} bytes of memory starting at address @var{addr}.
29672 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
29673 hexadecimal number.
29680 for an error (this includes the case where only part of the data was
29685 @cindex @samp{p} packet
29686 Read the value of register @var{n}; @var{n} is in hex.
29687 @xref{read registers packet}, for a description of how the returned
29688 register value is encoded.
29692 @item @var{XX@dots{}}
29693 the register's value
29697 Indicating an unrecognized @var{query}.
29700 @item P @var{n@dots{}}=@var{r@dots{}}
29701 @anchor{write register packet}
29702 @cindex @samp{P} packet
29703 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
29704 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
29705 digits for each byte in the register (target byte order).
29715 @item q @var{name} @var{params}@dots{}
29716 @itemx Q @var{name} @var{params}@dots{}
29717 @cindex @samp{q} packet
29718 @cindex @samp{Q} packet
29719 General query (@samp{q}) and set (@samp{Q}). These packets are
29720 described fully in @ref{General Query Packets}.
29723 @cindex @samp{r} packet
29724 Reset the entire system.
29726 Don't use this packet; use the @samp{R} packet instead.
29729 @cindex @samp{R} packet
29730 Restart the program being debugged. @var{XX}, while needed, is ignored.
29731 This packet is only available in extended mode (@pxref{extended mode}).
29733 The @samp{R} packet has no reply.
29735 @item s @r{[}@var{addr}@r{]}
29736 @cindex @samp{s} packet
29737 Single step. @var{addr} is the address at which to resume. If
29738 @var{addr} is omitted, resume at same address.
29741 @xref{Stop Reply Packets}, for the reply specifications.
29743 @item S @var{sig}@r{[};@var{addr}@r{]}
29744 @anchor{step with signal packet}
29745 @cindex @samp{S} packet
29746 Step with signal. This is analogous to the @samp{C} packet, but
29747 requests a single-step, rather than a normal resumption of execution.
29750 @xref{Stop Reply Packets}, for the reply specifications.
29752 @item t @var{addr}:@var{PP},@var{MM}
29753 @cindex @samp{t} packet
29754 Search backwards starting at address @var{addr} for a match with pattern
29755 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
29756 @var{addr} must be at least 3 digits.
29758 @item T @var{thread-id}
29759 @cindex @samp{T} packet
29760 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
29765 thread is still alive
29771 Packets starting with @samp{v} are identified by a multi-letter name,
29772 up to the first @samp{;} or @samp{?} (or the end of the packet).
29774 @item vAttach;@var{pid}
29775 @cindex @samp{vAttach} packet
29776 Attach to a new process with the specified process ID @var{pid}.
29777 The process ID is a
29778 hexadecimal integer identifying the process. In all-stop mode, all
29779 threads in the attached process are stopped; in non-stop mode, it may be
29780 attached without being stopped if that is supported by the target.
29782 @c In non-stop mode, on a successful vAttach, the stub should set the
29783 @c current thread to a thread of the newly-attached process. After
29784 @c attaching, GDB queries for the attached process's thread ID with qC.
29785 @c Also note that, from a user perspective, whether or not the
29786 @c target is stopped on attach in non-stop mode depends on whether you
29787 @c use the foreground or background version of the attach command, not
29788 @c on what vAttach does; GDB does the right thing with respect to either
29789 @c stopping or restarting threads.
29791 This packet is only available in extended mode (@pxref{extended mode}).
29797 @item @r{Any stop packet}
29798 for success in all-stop mode (@pxref{Stop Reply Packets})
29800 for success in non-stop mode (@pxref{Remote Non-Stop})
29803 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
29804 @cindex @samp{vCont} packet
29805 Resume the inferior, specifying different actions for each thread.
29806 If an action is specified with no @var{thread-id}, then it is applied to any
29807 threads that don't have a specific action specified; if no default action is
29808 specified then other threads should remain stopped in all-stop mode and
29809 in their current state in non-stop mode.
29810 Specifying multiple
29811 default actions is an error; specifying no actions is also an error.
29812 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
29814 Currently supported actions are:
29820 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
29824 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
29829 The optional argument @var{addr} normally associated with the
29830 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
29831 not supported in @samp{vCont}.
29833 The @samp{t} action is only relevant in non-stop mode
29834 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
29835 A stop reply should be generated for any affected thread not already stopped.
29836 When a thread is stopped by means of a @samp{t} action,
29837 the corresponding stop reply should indicate that the thread has stopped with
29838 signal @samp{0}, regardless of whether the target uses some other signal
29839 as an implementation detail.
29842 @xref{Stop Reply Packets}, for the reply specifications.
29845 @cindex @samp{vCont?} packet
29846 Request a list of actions supported by the @samp{vCont} packet.
29850 @item vCont@r{[};@var{action}@dots{}@r{]}
29851 The @samp{vCont} packet is supported. Each @var{action} is a supported
29852 command in the @samp{vCont} packet.
29854 The @samp{vCont} packet is not supported.
29857 @item vFile:@var{operation}:@var{parameter}@dots{}
29858 @cindex @samp{vFile} packet
29859 Perform a file operation on the target system. For details,
29860 see @ref{Host I/O Packets}.
29862 @item vFlashErase:@var{addr},@var{length}
29863 @cindex @samp{vFlashErase} packet
29864 Direct the stub to erase @var{length} bytes of flash starting at
29865 @var{addr}. The region may enclose any number of flash blocks, but
29866 its start and end must fall on block boundaries, as indicated by the
29867 flash block size appearing in the memory map (@pxref{Memory Map
29868 Format}). @value{GDBN} groups flash memory programming operations
29869 together, and sends a @samp{vFlashDone} request after each group; the
29870 stub is allowed to delay erase operation until the @samp{vFlashDone}
29871 packet is received.
29873 The stub must support @samp{vCont} if it reports support for
29874 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
29875 this case @samp{vCont} actions can be specified to apply to all threads
29876 in a process by using the @samp{p@var{pid}.-1} form of the
29887 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
29888 @cindex @samp{vFlashWrite} packet
29889 Direct the stub to write data to flash address @var{addr}. The data
29890 is passed in binary form using the same encoding as for the @samp{X}
29891 packet (@pxref{Binary Data}). The memory ranges specified by
29892 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
29893 not overlap, and must appear in order of increasing addresses
29894 (although @samp{vFlashErase} packets for higher addresses may already
29895 have been received; the ordering is guaranteed only between
29896 @samp{vFlashWrite} packets). If a packet writes to an address that was
29897 neither erased by a preceding @samp{vFlashErase} packet nor by some other
29898 target-specific method, the results are unpredictable.
29906 for vFlashWrite addressing non-flash memory
29912 @cindex @samp{vFlashDone} packet
29913 Indicate to the stub that flash programming operation is finished.
29914 The stub is permitted to delay or batch the effects of a group of
29915 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
29916 @samp{vFlashDone} packet is received. The contents of the affected
29917 regions of flash memory are unpredictable until the @samp{vFlashDone}
29918 request is completed.
29920 @item vKill;@var{pid}
29921 @cindex @samp{vKill} packet
29922 Kill the process with the specified process ID. @var{pid} is a
29923 hexadecimal integer identifying the process. This packet is used in
29924 preference to @samp{k} when multiprocess protocol extensions are
29925 supported; see @ref{multiprocess extensions}.
29935 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
29936 @cindex @samp{vRun} packet
29937 Run the program @var{filename}, passing it each @var{argument} on its
29938 command line. The file and arguments are hex-encoded strings. If
29939 @var{filename} is an empty string, the stub may use a default program
29940 (e.g.@: the last program run). The program is created in the stopped
29943 @c FIXME: What about non-stop mode?
29945 This packet is only available in extended mode (@pxref{extended mode}).
29951 @item @r{Any stop packet}
29952 for success (@pxref{Stop Reply Packets})
29956 @anchor{vStopped packet}
29957 @cindex @samp{vStopped} packet
29959 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
29960 reply and prompt for the stub to report another one.
29964 @item @r{Any stop packet}
29965 if there is another unreported stop event (@pxref{Stop Reply Packets})
29967 if there are no unreported stop events
29970 @item X @var{addr},@var{length}:@var{XX@dots{}}
29972 @cindex @samp{X} packet
29973 Write data to memory, where the data is transmitted in binary.
29974 @var{addr} is address, @var{length} is number of bytes,
29975 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
29985 @item z @var{type},@var{addr},@var{kind}
29986 @itemx Z @var{type},@var{addr},@var{kind}
29987 @anchor{insert breakpoint or watchpoint packet}
29988 @cindex @samp{z} packet
29989 @cindex @samp{Z} packets
29990 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
29991 watchpoint starting at address @var{address} of kind @var{kind}.
29993 Each breakpoint and watchpoint packet @var{type} is documented
29996 @emph{Implementation notes: A remote target shall return an empty string
29997 for an unrecognized breakpoint or watchpoint packet @var{type}. A
29998 remote target shall support either both or neither of a given
29999 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
30000 avoid potential problems with duplicate packets, the operations should
30001 be implemented in an idempotent way.}
30003 @item z0,@var{addr},@var{kind}
30004 @itemx Z0,@var{addr},@var{kind}
30005 @cindex @samp{z0} packet
30006 @cindex @samp{Z0} packet
30007 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
30008 @var{addr} of type @var{kind}.
30010 A memory breakpoint is implemented by replacing the instruction at
30011 @var{addr} with a software breakpoint or trap instruction. The
30012 @var{kind} is target-specific and typically indicates the size of
30013 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
30014 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
30015 architectures have additional meanings for @var{kind};
30016 see @ref{Architecture-Specific Protocol Details}.
30018 @emph{Implementation note: It is possible for a target to copy or move
30019 code that contains memory breakpoints (e.g., when implementing
30020 overlays). The behavior of this packet, in the presence of such a
30021 target, is not defined.}
30033 @item z1,@var{addr},@var{kind}
30034 @itemx Z1,@var{addr},@var{kind}
30035 @cindex @samp{z1} packet
30036 @cindex @samp{Z1} packet
30037 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
30038 address @var{addr}.
30040 A hardware breakpoint is implemented using a mechanism that is not
30041 dependant on being able to modify the target's memory. @var{kind}
30042 has the same meaning as in @samp{Z0} packets.
30044 @emph{Implementation note: A hardware breakpoint is not affected by code
30057 @item z2,@var{addr},@var{kind}
30058 @itemx Z2,@var{addr},@var{kind}
30059 @cindex @samp{z2} packet
30060 @cindex @samp{Z2} packet
30061 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
30062 @var{kind} is interpreted as the number of bytes to watch.
30074 @item z3,@var{addr},@var{kind}
30075 @itemx Z3,@var{addr},@var{kind}
30076 @cindex @samp{z3} packet
30077 @cindex @samp{Z3} packet
30078 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
30079 @var{kind} is interpreted as the number of bytes to watch.
30091 @item z4,@var{addr},@var{kind}
30092 @itemx Z4,@var{addr},@var{kind}
30093 @cindex @samp{z4} packet
30094 @cindex @samp{Z4} packet
30095 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
30096 @var{kind} is interpreted as the number of bytes to watch.
30110 @node Stop Reply Packets
30111 @section Stop Reply Packets
30112 @cindex stop reply packets
30114 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
30115 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
30116 receive any of the below as a reply. Except for @samp{?}
30117 and @samp{vStopped}, that reply is only returned
30118 when the target halts. In the below the exact meaning of @dfn{signal
30119 number} is defined by the header @file{include/gdb/signals.h} in the
30120 @value{GDBN} source code.
30122 As in the description of request packets, we include spaces in the
30123 reply templates for clarity; these are not part of the reply packet's
30124 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
30130 The program received signal number @var{AA} (a two-digit hexadecimal
30131 number). This is equivalent to a @samp{T} response with no
30132 @var{n}:@var{r} pairs.
30134 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
30135 @cindex @samp{T} packet reply
30136 The program received signal number @var{AA} (a two-digit hexadecimal
30137 number). This is equivalent to an @samp{S} response, except that the
30138 @samp{@var{n}:@var{r}} pairs can carry values of important registers
30139 and other information directly in the stop reply packet, reducing
30140 round-trip latency. Single-step and breakpoint traps are reported
30141 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
30145 If @var{n} is a hexadecimal number, it is a register number, and the
30146 corresponding @var{r} gives that register's value. @var{r} is a
30147 series of bytes in target byte order, with each byte given by a
30148 two-digit hex number.
30151 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
30152 the stopped thread, as specified in @ref{thread-id syntax}.
30155 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
30156 the core on which the stop event was detected.
30159 If @var{n} is a recognized @dfn{stop reason}, it describes a more
30160 specific event that stopped the target. The currently defined stop
30161 reasons are listed below. @var{aa} should be @samp{05}, the trap
30162 signal. At most one stop reason should be present.
30165 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
30166 and go on to the next; this allows us to extend the protocol in the
30170 The currently defined stop reasons are:
30176 The packet indicates a watchpoint hit, and @var{r} is the data address, in
30179 @cindex shared library events, remote reply
30181 The packet indicates that the loaded libraries have changed.
30182 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
30183 list of loaded libraries. @var{r} is ignored.
30185 @cindex replay log events, remote reply
30187 The packet indicates that the target cannot continue replaying
30188 logged execution events, because it has reached the end (or the
30189 beginning when executing backward) of the log. The value of @var{r}
30190 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
30191 for more information.
30195 @itemx W @var{AA} ; process:@var{pid}
30196 The process exited, and @var{AA} is the exit status. This is only
30197 applicable to certain targets.
30199 The second form of the response, including the process ID of the exited
30200 process, can be used only when @value{GDBN} has reported support for
30201 multiprocess protocol extensions; see @ref{multiprocess extensions}.
30202 The @var{pid} is formatted as a big-endian hex string.
30205 @itemx X @var{AA} ; process:@var{pid}
30206 The process terminated with signal @var{AA}.
30208 The second form of the response, including the process ID of the
30209 terminated process, can be used only when @value{GDBN} has reported
30210 support for multiprocess protocol extensions; see @ref{multiprocess
30211 extensions}. The @var{pid} is formatted as a big-endian hex string.
30213 @item O @var{XX}@dots{}
30214 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
30215 written as the program's console output. This can happen at any time
30216 while the program is running and the debugger should continue to wait
30217 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
30219 @item F @var{call-id},@var{parameter}@dots{}
30220 @var{call-id} is the identifier which says which host system call should
30221 be called. This is just the name of the function. Translation into the
30222 correct system call is only applicable as it's defined in @value{GDBN}.
30223 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
30226 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
30227 this very system call.
30229 The target replies with this packet when it expects @value{GDBN} to
30230 call a host system call on behalf of the target. @value{GDBN} replies
30231 with an appropriate @samp{F} packet and keeps up waiting for the next
30232 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
30233 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
30234 Protocol Extension}, for more details.
30238 @node General Query Packets
30239 @section General Query Packets
30240 @cindex remote query requests
30242 Packets starting with @samp{q} are @dfn{general query packets};
30243 packets starting with @samp{Q} are @dfn{general set packets}. General
30244 query and set packets are a semi-unified form for retrieving and
30245 sending information to and from the stub.
30247 The initial letter of a query or set packet is followed by a name
30248 indicating what sort of thing the packet applies to. For example,
30249 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
30250 definitions with the stub. These packet names follow some
30255 The name must not contain commas, colons or semicolons.
30257 Most @value{GDBN} query and set packets have a leading upper case
30260 The names of custom vendor packets should use a company prefix, in
30261 lower case, followed by a period. For example, packets designed at
30262 the Acme Corporation might begin with @samp{qacme.foo} (for querying
30263 foos) or @samp{Qacme.bar} (for setting bars).
30266 The name of a query or set packet should be separated from any
30267 parameters by a @samp{:}; the parameters themselves should be
30268 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
30269 full packet name, and check for a separator or the end of the packet,
30270 in case two packet names share a common prefix. New packets should not begin
30271 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
30272 packets predate these conventions, and have arguments without any terminator
30273 for the packet name; we suspect they are in widespread use in places that
30274 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
30275 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
30278 Like the descriptions of the other packets, each description here
30279 has a template showing the packet's overall syntax, followed by an
30280 explanation of the packet's meaning. We include spaces in some of the
30281 templates for clarity; these are not part of the packet's syntax. No
30282 @value{GDBN} packet uses spaces to separate its components.
30284 Here are the currently defined query and set packets:
30289 @cindex current thread, remote request
30290 @cindex @samp{qC} packet
30291 Return the current thread ID.
30295 @item QC @var{thread-id}
30296 Where @var{thread-id} is a thread ID as documented in
30297 @ref{thread-id syntax}.
30298 @item @r{(anything else)}
30299 Any other reply implies the old thread ID.
30302 @item qCRC:@var{addr},@var{length}
30303 @cindex CRC of memory block, remote request
30304 @cindex @samp{qCRC} packet
30305 Compute the CRC checksum of a block of memory using CRC-32 defined in
30306 IEEE 802.3. The CRC is computed byte at a time, taking the most
30307 significant bit of each byte first. The initial pattern code
30308 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
30310 @emph{Note:} This is the same CRC used in validating separate debug
30311 files (@pxref{Separate Debug Files, , Debugging Information in Separate
30312 Files}). However the algorithm is slightly different. When validating
30313 separate debug files, the CRC is computed taking the @emph{least}
30314 significant bit of each byte first, and the final result is inverted to
30315 detect trailing zeros.
30320 An error (such as memory fault)
30321 @item C @var{crc32}
30322 The specified memory region's checksum is @var{crc32}.
30326 @itemx qsThreadInfo
30327 @cindex list active threads, remote request
30328 @cindex @samp{qfThreadInfo} packet
30329 @cindex @samp{qsThreadInfo} packet
30330 Obtain a list of all active thread IDs from the target (OS). Since there
30331 may be too many active threads to fit into one reply packet, this query
30332 works iteratively: it may require more than one query/reply sequence to
30333 obtain the entire list of threads. The first query of the sequence will
30334 be the @samp{qfThreadInfo} query; subsequent queries in the
30335 sequence will be the @samp{qsThreadInfo} query.
30337 NOTE: This packet replaces the @samp{qL} query (see below).
30341 @item m @var{thread-id}
30343 @item m @var{thread-id},@var{thread-id}@dots{}
30344 a comma-separated list of thread IDs
30346 (lower case letter @samp{L}) denotes end of list.
30349 In response to each query, the target will reply with a list of one or
30350 more thread IDs, separated by commas.
30351 @value{GDBN} will respond to each reply with a request for more thread
30352 ids (using the @samp{qs} form of the query), until the target responds
30353 with @samp{l} (lower-case el, for @dfn{last}).
30354 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
30357 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
30358 @cindex get thread-local storage address, remote request
30359 @cindex @samp{qGetTLSAddr} packet
30360 Fetch the address associated with thread local storage specified
30361 by @var{thread-id}, @var{offset}, and @var{lm}.
30363 @var{thread-id} is the thread ID associated with the
30364 thread for which to fetch the TLS address. @xref{thread-id syntax}.
30366 @var{offset} is the (big endian, hex encoded) offset associated with the
30367 thread local variable. (This offset is obtained from the debug
30368 information associated with the variable.)
30370 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
30371 the load module associated with the thread local storage. For example,
30372 a @sc{gnu}/Linux system will pass the link map address of the shared
30373 object associated with the thread local storage under consideration.
30374 Other operating environments may choose to represent the load module
30375 differently, so the precise meaning of this parameter will vary.
30379 @item @var{XX}@dots{}
30380 Hex encoded (big endian) bytes representing the address of the thread
30381 local storage requested.
30384 An error occurred. @var{nn} are hex digits.
30387 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
30390 @item qL @var{startflag} @var{threadcount} @var{nextthread}
30391 Obtain thread information from RTOS. Where: @var{startflag} (one hex
30392 digit) is one to indicate the first query and zero to indicate a
30393 subsequent query; @var{threadcount} (two hex digits) is the maximum
30394 number of threads the response packet can contain; and @var{nextthread}
30395 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
30396 returned in the response as @var{argthread}.
30398 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
30402 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
30403 Where: @var{count} (two hex digits) is the number of threads being
30404 returned; @var{done} (one hex digit) is zero to indicate more threads
30405 and one indicates no further threads; @var{argthreadid} (eight hex
30406 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
30407 is a sequence of thread IDs from the target. @var{threadid} (eight hex
30408 digits). See @code{remote.c:parse_threadlist_response()}.
30412 @cindex section offsets, remote request
30413 @cindex @samp{qOffsets} packet
30414 Get section offsets that the target used when relocating the downloaded
30419 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
30420 Relocate the @code{Text} section by @var{xxx} from its original address.
30421 Relocate the @code{Data} section by @var{yyy} from its original address.
30422 If the object file format provides segment information (e.g.@: @sc{elf}
30423 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
30424 segments by the supplied offsets.
30426 @emph{Note: while a @code{Bss} offset may be included in the response,
30427 @value{GDBN} ignores this and instead applies the @code{Data} offset
30428 to the @code{Bss} section.}
30430 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
30431 Relocate the first segment of the object file, which conventionally
30432 contains program code, to a starting address of @var{xxx}. If
30433 @samp{DataSeg} is specified, relocate the second segment, which
30434 conventionally contains modifiable data, to a starting address of
30435 @var{yyy}. @value{GDBN} will report an error if the object file
30436 does not contain segment information, or does not contain at least
30437 as many segments as mentioned in the reply. Extra segments are
30438 kept at fixed offsets relative to the last relocated segment.
30441 @item qP @var{mode} @var{thread-id}
30442 @cindex thread information, remote request
30443 @cindex @samp{qP} packet
30444 Returns information on @var{thread-id}. Where: @var{mode} is a hex
30445 encoded 32 bit mode; @var{thread-id} is a thread ID
30446 (@pxref{thread-id syntax}).
30448 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
30451 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
30455 @cindex non-stop mode, remote request
30456 @cindex @samp{QNonStop} packet
30458 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
30459 @xref{Remote Non-Stop}, for more information.
30464 The request succeeded.
30467 An error occurred. @var{nn} are hex digits.
30470 An empty reply indicates that @samp{QNonStop} is not supported by
30474 This packet is not probed by default; the remote stub must request it,
30475 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
30476 Use of this packet is controlled by the @code{set non-stop} command;
30477 @pxref{Non-Stop Mode}.
30479 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
30480 @cindex pass signals to inferior, remote request
30481 @cindex @samp{QPassSignals} packet
30482 @anchor{QPassSignals}
30483 Each listed @var{signal} should be passed directly to the inferior process.
30484 Signals are numbered identically to continue packets and stop replies
30485 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
30486 strictly greater than the previous item. These signals do not need to stop
30487 the inferior, or be reported to @value{GDBN}. All other signals should be
30488 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
30489 combine; any earlier @samp{QPassSignals} list is completely replaced by the
30490 new list. This packet improves performance when using @samp{handle
30491 @var{signal} nostop noprint pass}.
30496 The request succeeded.
30499 An error occurred. @var{nn} are hex digits.
30502 An empty reply indicates that @samp{QPassSignals} is not supported by
30506 Use of this packet is controlled by the @code{set remote pass-signals}
30507 command (@pxref{Remote Configuration, set remote pass-signals}).
30508 This packet is not probed by default; the remote stub must request it,
30509 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
30511 @item qRcmd,@var{command}
30512 @cindex execute remote command, remote request
30513 @cindex @samp{qRcmd} packet
30514 @var{command} (hex encoded) is passed to the local interpreter for
30515 execution. Invalid commands should be reported using the output
30516 string. Before the final result packet, the target may also respond
30517 with a number of intermediate @samp{O@var{output}} console output
30518 packets. @emph{Implementors should note that providing access to a
30519 stubs's interpreter may have security implications}.
30524 A command response with no output.
30526 A command response with the hex encoded output string @var{OUTPUT}.
30528 Indicate a badly formed request.
30530 An empty reply indicates that @samp{qRcmd} is not recognized.
30533 (Note that the @code{qRcmd} packet's name is separated from the
30534 command by a @samp{,}, not a @samp{:}, contrary to the naming
30535 conventions above. Please don't use this packet as a model for new
30538 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
30539 @cindex searching memory, in remote debugging
30540 @cindex @samp{qSearch:memory} packet
30541 @anchor{qSearch memory}
30542 Search @var{length} bytes at @var{address} for @var{search-pattern}.
30543 @var{address} and @var{length} are encoded in hex.
30544 @var{search-pattern} is a sequence of bytes, hex encoded.
30549 The pattern was not found.
30551 The pattern was found at @var{address}.
30553 A badly formed request or an error was encountered while searching memory.
30555 An empty reply indicates that @samp{qSearch:memory} is not recognized.
30558 @item QStartNoAckMode
30559 @cindex @samp{QStartNoAckMode} packet
30560 @anchor{QStartNoAckMode}
30561 Request that the remote stub disable the normal @samp{+}/@samp{-}
30562 protocol acknowledgments (@pxref{Packet Acknowledgment}).
30567 The stub has switched to no-acknowledgment mode.
30568 @value{GDBN} acknowledges this reponse,
30569 but neither the stub nor @value{GDBN} shall send or expect further
30570 @samp{+}/@samp{-} acknowledgments in the current connection.
30572 An empty reply indicates that the stub does not support no-acknowledgment mode.
30575 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
30576 @cindex supported packets, remote query
30577 @cindex features of the remote protocol
30578 @cindex @samp{qSupported} packet
30579 @anchor{qSupported}
30580 Tell the remote stub about features supported by @value{GDBN}, and
30581 query the stub for features it supports. This packet allows
30582 @value{GDBN} and the remote stub to take advantage of each others'
30583 features. @samp{qSupported} also consolidates multiple feature probes
30584 at startup, to improve @value{GDBN} performance---a single larger
30585 packet performs better than multiple smaller probe packets on
30586 high-latency links. Some features may enable behavior which must not
30587 be on by default, e.g.@: because it would confuse older clients or
30588 stubs. Other features may describe packets which could be
30589 automatically probed for, but are not. These features must be
30590 reported before @value{GDBN} will use them. This ``default
30591 unsupported'' behavior is not appropriate for all packets, but it
30592 helps to keep the initial connection time under control with new
30593 versions of @value{GDBN} which support increasing numbers of packets.
30597 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
30598 The stub supports or does not support each returned @var{stubfeature},
30599 depending on the form of each @var{stubfeature} (see below for the
30602 An empty reply indicates that @samp{qSupported} is not recognized,
30603 or that no features needed to be reported to @value{GDBN}.
30606 The allowed forms for each feature (either a @var{gdbfeature} in the
30607 @samp{qSupported} packet, or a @var{stubfeature} in the response)
30611 @item @var{name}=@var{value}
30612 The remote protocol feature @var{name} is supported, and associated
30613 with the specified @var{value}. The format of @var{value} depends
30614 on the feature, but it must not include a semicolon.
30616 The remote protocol feature @var{name} is supported, and does not
30617 need an associated value.
30619 The remote protocol feature @var{name} is not supported.
30621 The remote protocol feature @var{name} may be supported, and
30622 @value{GDBN} should auto-detect support in some other way when it is
30623 needed. This form will not be used for @var{gdbfeature} notifications,
30624 but may be used for @var{stubfeature} responses.
30627 Whenever the stub receives a @samp{qSupported} request, the
30628 supplied set of @value{GDBN} features should override any previous
30629 request. This allows @value{GDBN} to put the stub in a known
30630 state, even if the stub had previously been communicating with
30631 a different version of @value{GDBN}.
30633 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
30638 This feature indicates whether @value{GDBN} supports multiprocess
30639 extensions to the remote protocol. @value{GDBN} does not use such
30640 extensions unless the stub also reports that it supports them by
30641 including @samp{multiprocess+} in its @samp{qSupported} reply.
30642 @xref{multiprocess extensions}, for details.
30645 This feature indicates that @value{GDBN} supports the XML target
30646 description. If the stub sees @samp{xmlRegisters=} with target
30647 specific strings separated by a comma, it will report register
30651 Stubs should ignore any unknown values for
30652 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
30653 packet supports receiving packets of unlimited length (earlier
30654 versions of @value{GDBN} may reject overly long responses). Additional values
30655 for @var{gdbfeature} may be defined in the future to let the stub take
30656 advantage of new features in @value{GDBN}, e.g.@: incompatible
30657 improvements in the remote protocol---the @samp{multiprocess} feature is
30658 an example of such a feature. The stub's reply should be independent
30659 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
30660 describes all the features it supports, and then the stub replies with
30661 all the features it supports.
30663 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
30664 responses, as long as each response uses one of the standard forms.
30666 Some features are flags. A stub which supports a flag feature
30667 should respond with a @samp{+} form response. Other features
30668 require values, and the stub should respond with an @samp{=}
30671 Each feature has a default value, which @value{GDBN} will use if
30672 @samp{qSupported} is not available or if the feature is not mentioned
30673 in the @samp{qSupported} response. The default values are fixed; a
30674 stub is free to omit any feature responses that match the defaults.
30676 Not all features can be probed, but for those which can, the probing
30677 mechanism is useful: in some cases, a stub's internal
30678 architecture may not allow the protocol layer to know some information
30679 about the underlying target in advance. This is especially common in
30680 stubs which may be configured for multiple targets.
30682 These are the currently defined stub features and their properties:
30684 @multitable @columnfractions 0.35 0.2 0.12 0.2
30685 @c NOTE: The first row should be @headitem, but we do not yet require
30686 @c a new enough version of Texinfo (4.7) to use @headitem.
30688 @tab Value Required
30692 @item @samp{PacketSize}
30697 @item @samp{qXfer:auxv:read}
30702 @item @samp{qXfer:features:read}
30707 @item @samp{qXfer:libraries:read}
30712 @item @samp{qXfer:memory-map:read}
30717 @item @samp{qXfer:spu:read}
30722 @item @samp{qXfer:spu:write}
30727 @item @samp{qXfer:siginfo:read}
30732 @item @samp{qXfer:siginfo:write}
30737 @item @samp{qXfer:threads:read}
30743 @item @samp{QNonStop}
30748 @item @samp{QPassSignals}
30753 @item @samp{QStartNoAckMode}
30758 @item @samp{multiprocess}
30763 @item @samp{ConditionalTracepoints}
30768 @item @samp{ReverseContinue}
30773 @item @samp{ReverseStep}
30778 @item @samp{TracepointSource}
30785 These are the currently defined stub features, in more detail:
30788 @cindex packet size, remote protocol
30789 @item PacketSize=@var{bytes}
30790 The remote stub can accept packets up to at least @var{bytes} in
30791 length. @value{GDBN} will send packets up to this size for bulk
30792 transfers, and will never send larger packets. This is a limit on the
30793 data characters in the packet, including the frame and checksum.
30794 There is no trailing NUL byte in a remote protocol packet; if the stub
30795 stores packets in a NUL-terminated format, it should allow an extra
30796 byte in its buffer for the NUL. If this stub feature is not supported,
30797 @value{GDBN} guesses based on the size of the @samp{g} packet response.
30799 @item qXfer:auxv:read
30800 The remote stub understands the @samp{qXfer:auxv:read} packet
30801 (@pxref{qXfer auxiliary vector read}).
30803 @item qXfer:features:read
30804 The remote stub understands the @samp{qXfer:features:read} packet
30805 (@pxref{qXfer target description read}).
30807 @item qXfer:libraries:read
30808 The remote stub understands the @samp{qXfer:libraries:read} packet
30809 (@pxref{qXfer library list read}).
30811 @item qXfer:memory-map:read
30812 The remote stub understands the @samp{qXfer:memory-map:read} packet
30813 (@pxref{qXfer memory map read}).
30815 @item qXfer:spu:read
30816 The remote stub understands the @samp{qXfer:spu:read} packet
30817 (@pxref{qXfer spu read}).
30819 @item qXfer:spu:write
30820 The remote stub understands the @samp{qXfer:spu:write} packet
30821 (@pxref{qXfer spu write}).
30823 @item qXfer:siginfo:read
30824 The remote stub understands the @samp{qXfer:siginfo:read} packet
30825 (@pxref{qXfer siginfo read}).
30827 @item qXfer:siginfo:write
30828 The remote stub understands the @samp{qXfer:siginfo:write} packet
30829 (@pxref{qXfer siginfo write}).
30831 @item qXfer:threads:read
30832 The remote stub understands the @samp{qXfer:threads:read} packet
30833 (@pxref{qXfer threads read}).
30836 The remote stub understands the @samp{QNonStop} packet
30837 (@pxref{QNonStop}).
30840 The remote stub understands the @samp{QPassSignals} packet
30841 (@pxref{QPassSignals}).
30843 @item QStartNoAckMode
30844 The remote stub understands the @samp{QStartNoAckMode} packet and
30845 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
30848 @anchor{multiprocess extensions}
30849 @cindex multiprocess extensions, in remote protocol
30850 The remote stub understands the multiprocess extensions to the remote
30851 protocol syntax. The multiprocess extensions affect the syntax of
30852 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
30853 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
30854 replies. Note that reporting this feature indicates support for the
30855 syntactic extensions only, not that the stub necessarily supports
30856 debugging of more than one process at a time. The stub must not use
30857 multiprocess extensions in packet replies unless @value{GDBN} has also
30858 indicated it supports them in its @samp{qSupported} request.
30860 @item qXfer:osdata:read
30861 The remote stub understands the @samp{qXfer:osdata:read} packet
30862 ((@pxref{qXfer osdata read}).
30864 @item ConditionalTracepoints
30865 The remote stub accepts and implements conditional expressions defined
30866 for tracepoints (@pxref{Tracepoint Conditions}).
30868 @item ReverseContinue
30869 The remote stub accepts and implements the reverse continue packet
30873 The remote stub accepts and implements the reverse step packet
30876 @item TracepointSource
30877 The remote stub understands the @samp{QTDPsrc} packet that supplies
30878 the source form of tracepoint definitions.
30883 @cindex symbol lookup, remote request
30884 @cindex @samp{qSymbol} packet
30885 Notify the target that @value{GDBN} is prepared to serve symbol lookup
30886 requests. Accept requests from the target for the values of symbols.
30891 The target does not need to look up any (more) symbols.
30892 @item qSymbol:@var{sym_name}
30893 The target requests the value of symbol @var{sym_name} (hex encoded).
30894 @value{GDBN} may provide the value by using the
30895 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
30899 @item qSymbol:@var{sym_value}:@var{sym_name}
30900 Set the value of @var{sym_name} to @var{sym_value}.
30902 @var{sym_name} (hex encoded) is the name of a symbol whose value the
30903 target has previously requested.
30905 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
30906 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
30912 The target does not need to look up any (more) symbols.
30913 @item qSymbol:@var{sym_name}
30914 The target requests the value of a new symbol @var{sym_name} (hex
30915 encoded). @value{GDBN} will continue to supply the values of symbols
30916 (if available), until the target ceases to request them.
30921 @item QTDisconnected
30928 @xref{Tracepoint Packets}.
30930 @item qThreadExtraInfo,@var{thread-id}
30931 @cindex thread attributes info, remote request
30932 @cindex @samp{qThreadExtraInfo} packet
30933 Obtain a printable string description of a thread's attributes from
30934 the target OS. @var{thread-id} is a thread ID;
30935 see @ref{thread-id syntax}. This
30936 string may contain anything that the target OS thinks is interesting
30937 for @value{GDBN} to tell the user about the thread. The string is
30938 displayed in @value{GDBN}'s @code{info threads} display. Some
30939 examples of possible thread extra info strings are @samp{Runnable}, or
30940 @samp{Blocked on Mutex}.
30944 @item @var{XX}@dots{}
30945 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
30946 comprising the printable string containing the extra information about
30947 the thread's attributes.
30950 (Note that the @code{qThreadExtraInfo} packet's name is separated from
30951 the command by a @samp{,}, not a @samp{:}, contrary to the naming
30952 conventions above. Please don't use this packet as a model for new
30964 @xref{Tracepoint Packets}.
30966 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
30967 @cindex read special object, remote request
30968 @cindex @samp{qXfer} packet
30969 @anchor{qXfer read}
30970 Read uninterpreted bytes from the target's special data area
30971 identified by the keyword @var{object}. Request @var{length} bytes
30972 starting at @var{offset} bytes into the data. The content and
30973 encoding of @var{annex} is specific to @var{object}; it can supply
30974 additional details about what data to access.
30976 Here are the specific requests of this form defined so far. All
30977 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
30978 formats, listed below.
30981 @item qXfer:auxv:read::@var{offset},@var{length}
30982 @anchor{qXfer auxiliary vector read}
30983 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
30984 auxiliary vector}. Note @var{annex} must be empty.
30986 This packet is not probed by default; the remote stub must request it,
30987 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
30989 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
30990 @anchor{qXfer target description read}
30991 Access the @dfn{target description}. @xref{Target Descriptions}. The
30992 annex specifies which XML document to access. The main description is
30993 always loaded from the @samp{target.xml} annex.
30995 This packet is not probed by default; the remote stub must request it,
30996 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
30998 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
30999 @anchor{qXfer library list read}
31000 Access the target's list of loaded libraries. @xref{Library List Format}.
31001 The annex part of the generic @samp{qXfer} packet must be empty
31002 (@pxref{qXfer read}).
31004 Targets which maintain a list of libraries in the program's memory do
31005 not need to implement this packet; it is designed for platforms where
31006 the operating system manages the list of loaded libraries.
31008 This packet is not probed by default; the remote stub must request it,
31009 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31011 @item qXfer:memory-map:read::@var{offset},@var{length}
31012 @anchor{qXfer memory map read}
31013 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
31014 annex part of the generic @samp{qXfer} packet must be empty
31015 (@pxref{qXfer read}).
31017 This packet is not probed by default; the remote stub must request it,
31018 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31020 @item qXfer:siginfo:read::@var{offset},@var{length}
31021 @anchor{qXfer siginfo read}
31022 Read contents of the extra signal information on the target
31023 system. The annex part of the generic @samp{qXfer} packet must be
31024 empty (@pxref{qXfer read}).
31026 This packet is not probed by default; the remote stub must request it,
31027 by supplying an appropriate @samp{qSupported} response
31028 (@pxref{qSupported}).
31030 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
31031 @anchor{qXfer spu read}
31032 Read contents of an @code{spufs} file on the target system. The
31033 annex specifies which file to read; it must be of the form
31034 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
31035 in the target process, and @var{name} identifes the @code{spufs} file
31036 in that context to be accessed.
31038 This packet is not probed by default; the remote stub must request it,
31039 by supplying an appropriate @samp{qSupported} response
31040 (@pxref{qSupported}).
31042 @item qXfer:threads:read::@var{offset},@var{length}
31043 @anchor{qXfer threads read}
31044 Access the list of threads on target. @xref{Thread List Format}. The
31045 annex part of the generic @samp{qXfer} packet must be empty
31046 (@pxref{qXfer read}).
31048 This packet is not probed by default; the remote stub must request it,
31049 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31051 @item qXfer:osdata:read::@var{offset},@var{length}
31052 @anchor{qXfer osdata read}
31053 Access the target's @dfn{operating system information}.
31054 @xref{Operating System Information}.
31061 Data @var{data} (@pxref{Binary Data}) has been read from the
31062 target. There may be more data at a higher address (although
31063 it is permitted to return @samp{m} even for the last valid
31064 block of data, as long as at least one byte of data was read).
31065 @var{data} may have fewer bytes than the @var{length} in the
31069 Data @var{data} (@pxref{Binary Data}) has been read from the target.
31070 There is no more data to be read. @var{data} may have fewer bytes
31071 than the @var{length} in the request.
31074 The @var{offset} in the request is at the end of the data.
31075 There is no more data to be read.
31078 The request was malformed, or @var{annex} was invalid.
31081 The offset was invalid, or there was an error encountered reading the data.
31082 @var{nn} is a hex-encoded @code{errno} value.
31085 An empty reply indicates the @var{object} string was not recognized by
31086 the stub, or that the object does not support reading.
31089 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
31090 @cindex write data into object, remote request
31091 @anchor{qXfer write}
31092 Write uninterpreted bytes into the target's special data area
31093 identified by the keyword @var{object}, starting at @var{offset} bytes
31094 into the data. @var{data}@dots{} is the binary-encoded data
31095 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
31096 is specific to @var{object}; it can supply additional details about what data
31099 Here are the specific requests of this form defined so far. All
31100 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
31101 formats, listed below.
31104 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
31105 @anchor{qXfer siginfo write}
31106 Write @var{data} to the extra signal information on the target system.
31107 The annex part of the generic @samp{qXfer} packet must be
31108 empty (@pxref{qXfer write}).
31110 This packet is not probed by default; the remote stub must request it,
31111 by supplying an appropriate @samp{qSupported} response
31112 (@pxref{qSupported}).
31114 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
31115 @anchor{qXfer spu write}
31116 Write @var{data} to an @code{spufs} file on the target system. The
31117 annex specifies which file to write; it must be of the form
31118 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
31119 in the target process, and @var{name} identifes the @code{spufs} file
31120 in that context to be accessed.
31122 This packet is not probed by default; the remote stub must request it,
31123 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31129 @var{nn} (hex encoded) is the number of bytes written.
31130 This may be fewer bytes than supplied in the request.
31133 The request was malformed, or @var{annex} was invalid.
31136 The offset was invalid, or there was an error encountered writing the data.
31137 @var{nn} is a hex-encoded @code{errno} value.
31140 An empty reply indicates the @var{object} string was not
31141 recognized by the stub, or that the object does not support writing.
31144 @item qXfer:@var{object}:@var{operation}:@dots{}
31145 Requests of this form may be added in the future. When a stub does
31146 not recognize the @var{object} keyword, or its support for
31147 @var{object} does not recognize the @var{operation} keyword, the stub
31148 must respond with an empty packet.
31150 @item qAttached:@var{pid}
31151 @cindex query attached, remote request
31152 @cindex @samp{qAttached} packet
31153 Return an indication of whether the remote server attached to an
31154 existing process or created a new process. When the multiprocess
31155 protocol extensions are supported (@pxref{multiprocess extensions}),
31156 @var{pid} is an integer in hexadecimal format identifying the target
31157 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
31158 the query packet will be simplified as @samp{qAttached}.
31160 This query is used, for example, to know whether the remote process
31161 should be detached or killed when a @value{GDBN} session is ended with
31162 the @code{quit} command.
31167 The remote server attached to an existing process.
31169 The remote server created a new process.
31171 A badly formed request or an error was encountered.
31176 @node Architecture-Specific Protocol Details
31177 @section Architecture-Specific Protocol Details
31179 This section describes how the remote protocol is applied to specific
31180 target architectures. Also see @ref{Standard Target Features}, for
31181 details of XML target descriptions for each architecture.
31185 @subsubsection Breakpoint Kinds
31187 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
31192 16-bit Thumb mode breakpoint.
31195 32-bit Thumb mode (Thumb-2) breakpoint.
31198 32-bit ARM mode breakpoint.
31204 @subsubsection Register Packet Format
31206 The following @code{g}/@code{G} packets have previously been defined.
31207 In the below, some thirty-two bit registers are transferred as
31208 sixty-four bits. Those registers should be zero/sign extended (which?)
31209 to fill the space allocated. Register bytes are transferred in target
31210 byte order. The two nibbles within a register byte are transferred
31211 most-significant - least-significant.
31217 All registers are transferred as thirty-two bit quantities in the order:
31218 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
31219 registers; fsr; fir; fp.
31223 All registers are transferred as sixty-four bit quantities (including
31224 thirty-two bit registers such as @code{sr}). The ordering is the same
31229 @node Tracepoint Packets
31230 @section Tracepoint Packets
31231 @cindex tracepoint packets
31232 @cindex packets, tracepoint
31234 Here we describe the packets @value{GDBN} uses to implement
31235 tracepoints (@pxref{Tracepoints}).
31239 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
31240 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
31241 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
31242 the tracepoint is disabled. @var{step} is the tracepoint's step
31243 count, and @var{pass} is its pass count. If an @samp{F} is present,
31244 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
31245 the number of bytes that the target should copy elsewhere to make room
31246 for the tracepoint. If an @samp{X} is present, it introduces a
31247 tracepoint condition, which consists of a hexadecimal length, followed
31248 by a comma and hex-encoded bytes, in a manner similar to action
31249 encodings as described below. If the trailing @samp{-} is present,
31250 further @samp{QTDP} packets will follow to specify this tracepoint's
31256 The packet was understood and carried out.
31258 The packet was not recognized.
31261 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
31262 Define actions to be taken when a tracepoint is hit. @var{n} and
31263 @var{addr} must be the same as in the initial @samp{QTDP} packet for
31264 this tracepoint. This packet may only be sent immediately after
31265 another @samp{QTDP} packet that ended with a @samp{-}. If the
31266 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
31267 specifying more actions for this tracepoint.
31269 In the series of action packets for a given tracepoint, at most one
31270 can have an @samp{S} before its first @var{action}. If such a packet
31271 is sent, it and the following packets define ``while-stepping''
31272 actions. Any prior packets define ordinary actions --- that is, those
31273 taken when the tracepoint is first hit. If no action packet has an
31274 @samp{S}, then all the packets in the series specify ordinary
31275 tracepoint actions.
31277 The @samp{@var{action}@dots{}} portion of the packet is a series of
31278 actions, concatenated without separators. Each action has one of the
31284 Collect the registers whose bits are set in @var{mask}. @var{mask} is
31285 a hexadecimal number whose @var{i}'th bit is set if register number
31286 @var{i} should be collected. (The least significant bit is numbered
31287 zero.) Note that @var{mask} may be any number of digits long; it may
31288 not fit in a 32-bit word.
31290 @item M @var{basereg},@var{offset},@var{len}
31291 Collect @var{len} bytes of memory starting at the address in register
31292 number @var{basereg}, plus @var{offset}. If @var{basereg} is
31293 @samp{-1}, then the range has a fixed address: @var{offset} is the
31294 address of the lowest byte to collect. The @var{basereg},
31295 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
31296 values (the @samp{-1} value for @var{basereg} is a special case).
31298 @item X @var{len},@var{expr}
31299 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
31300 it directs. @var{expr} is an agent expression, as described in
31301 @ref{Agent Expressions}. Each byte of the expression is encoded as a
31302 two-digit hex number in the packet; @var{len} is the number of bytes
31303 in the expression (and thus one-half the number of hex digits in the
31308 Any number of actions may be packed together in a single @samp{QTDP}
31309 packet, as long as the packet does not exceed the maximum packet
31310 length (400 bytes, for many stubs). There may be only one @samp{R}
31311 action per tracepoint, and it must precede any @samp{M} or @samp{X}
31312 actions. Any registers referred to by @samp{M} and @samp{X} actions
31313 must be collected by a preceding @samp{R} action. (The
31314 ``while-stepping'' actions are treated as if they were attached to a
31315 separate tracepoint, as far as these restrictions are concerned.)
31320 The packet was understood and carried out.
31322 The packet was not recognized.
31325 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
31326 @cindex @samp{QTDPsrc} packet
31327 Specify a source string of tracepoint @var{n} at address @var{addr}.
31328 This is useful to get accurate reproduction of the tracepoints
31329 originally downloaded at the beginning of the trace run. @var{type}
31330 is the name of the tracepoint part, such as @samp{cond} for the
31331 tracepoint's conditional expression (see below for a list of types), while
31332 @var{bytes} is the string, encoded in hexadecimal.
31334 @var{start} is the offset of the @var{bytes} within the overall source
31335 string, while @var{slen} is the total length of the source string.
31336 This is intended for handling source strings that are longer than will
31337 fit in a single packet.
31338 @c Add detailed example when this info is moved into a dedicated
31339 @c tracepoint descriptions section.
31341 The available string types are @samp{at} for the location,
31342 @samp{cond} for the conditional, and @samp{cmd} for an action command.
31343 @value{GDBN} sends a separate packet for each command in the action
31344 list, in the same order in which the commands are stored in the list.
31346 The target does not need to do anything with source strings except
31347 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
31350 Although this packet is optional, and @value{GDBN} will only send it
31351 if the target replies with @samp{TracepointSource} @xref{General
31352 Query Packets}, it makes both disconnected tracing and trace files
31353 much easier to use. Otherwise the user must be careful that the
31354 tracepoints in effect while looking at trace frames are identical to
31355 the ones in effect during the trace run; even a small discrepancy
31356 could cause @samp{tdump} not to work, or a particular trace frame not
31359 @item QTDV:@var{n}:@var{value}
31360 @cindex define trace state variable, remote request
31361 @cindex @samp{QTDV} packet
31362 Create a new trace state variable, number @var{n}, with an initial
31363 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
31364 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
31365 the option of not using this packet for initial values of zero; the
31366 target should simply create the trace state variables as they are
31367 mentioned in expressions.
31369 @item QTFrame:@var{n}
31370 Select the @var{n}'th tracepoint frame from the buffer, and use the
31371 register and memory contents recorded there to answer subsequent
31372 request packets from @value{GDBN}.
31374 A successful reply from the stub indicates that the stub has found the
31375 requested frame. The response is a series of parts, concatenated
31376 without separators, describing the frame we selected. Each part has
31377 one of the following forms:
31381 The selected frame is number @var{n} in the trace frame buffer;
31382 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
31383 was no frame matching the criteria in the request packet.
31386 The selected trace frame records a hit of tracepoint number @var{t};
31387 @var{t} is a hexadecimal number.
31391 @item QTFrame:pc:@var{addr}
31392 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
31393 currently selected frame whose PC is @var{addr};
31394 @var{addr} is a hexadecimal number.
31396 @item QTFrame:tdp:@var{t}
31397 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
31398 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
31399 is a hexadecimal number.
31401 @item QTFrame:range:@var{start}:@var{end}
31402 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
31403 currently selected frame whose PC is between @var{start} (inclusive)
31404 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
31407 @item QTFrame:outside:@var{start}:@var{end}
31408 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
31409 frame @emph{outside} the given range of addresses (exclusive).
31412 Begin the tracepoint experiment. Begin collecting data from tracepoint
31413 hits in the trace frame buffer.
31416 End the tracepoint experiment. Stop collecting trace frames.
31419 Clear the table of tracepoints, and empty the trace frame buffer.
31421 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
31422 Establish the given ranges of memory as ``transparent''. The stub
31423 will answer requests for these ranges from memory's current contents,
31424 if they were not collected as part of the tracepoint hit.
31426 @value{GDBN} uses this to mark read-only regions of memory, like those
31427 containing program code. Since these areas never change, they should
31428 still have the same contents they did when the tracepoint was hit, so
31429 there's no reason for the stub to refuse to provide their contents.
31431 @item QTDisconnected:@var{value}
31432 Set the choice to what to do with the tracing run when @value{GDBN}
31433 disconnects from the target. A @var{value} of 1 directs the target to
31434 continue the tracing run, while 0 tells the target to stop tracing if
31435 @value{GDBN} is no longer in the picture.
31438 Ask the stub if there is a trace experiment running right now.
31440 The reply has the form:
31444 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
31445 @var{running} is a single digit @code{1} if the trace is presently
31446 running, or @code{0} if not. It is followed by semicolon-separated
31447 optional fields that an agent may use to report additional status.
31451 If the trace is not running, the agent may report any of several
31452 explanations as one of the optional fields:
31457 No trace has been run yet.
31460 The trace was stopped by a user-originated stop command.
31463 The trace stopped because the trace buffer filled up.
31465 @item tdisconnected:0
31466 The trace stopped because @value{GDBN} disconnected from the target.
31468 @item tpasscount:@var{tpnum}
31469 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
31471 @item terror:@var{text}:@var{tpnum}
31472 The trace stopped because tracepoint @var{tpnum} had an error. The
31473 string @var{text} is available to describe the nature of the error
31474 (for instance, a divide by zero in the condition expression).
31475 @var{text} is hex encoded.
31478 The trace stopped for some other reason.
31482 Additional optional fields supply statistical information. Although
31483 not required, they are extremely useful for users monitoring the
31484 progress of a trace run. If a trace has stopped, and these numbers
31485 are reported, they must reflect the state of the just-stopped trace.
31489 @item tframes:@var{n}
31490 The number of trace frames in the buffer.
31492 @item tcreated:@var{n}
31493 The total number of trace frames created during the run. This may
31494 be larger than the trace frame count, if the buffer is circular.
31496 @item tsize:@var{n}
31497 The total size of the trace buffer, in bytes.
31499 @item tfree:@var{n}
31500 The number of bytes still unused in the buffer.
31504 @item qTV:@var{var}
31505 @cindex trace state variable value, remote request
31506 @cindex @samp{qTV} packet
31507 Ask the stub for the value of the trace state variable number @var{var}.
31512 The value of the variable is @var{value}. This will be the current
31513 value of the variable if the user is examining a running target, or a
31514 saved value if the variable was collected in the trace frame that the
31515 user is looking at. Note that multiple requests may result in
31516 different reply values, such as when requesting values while the
31517 program is running.
31520 The value of the variable is unknown. This would occur, for example,
31521 if the user is examining a trace frame in which the requested variable
31527 These packets request data about tracepoints that are being used by
31528 the target. @value{GDBN} sends @code{qTfP} to get the first piece
31529 of data, and multiple @code{qTsP} to get additional pieces. Replies
31530 to these packets generally take the form of the @code{QTDP} packets
31531 that define tracepoints. (FIXME add detailed syntax)
31535 These packets request data about trace state variables that are on the
31536 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
31537 and multiple @code{qTsV} to get additional variables. Replies to
31538 these packets follow the syntax of the @code{QTDV} packets that define
31539 trace state variables.
31541 @item QTSave:@var{filename}
31542 This packet directs the target to save trace data to the file name
31543 @var{filename} in the target's filesystem. @var{filename} is encoded
31544 as a hex string; the interpretation of the file name (relative vs
31545 absolute, wild cards, etc) is up to the target.
31547 @item qTBuffer:@var{offset},@var{len}
31548 Return up to @var{len} bytes of the current contents of trace buffer,
31549 starting at @var{offset}. The trace buffer is treated as if it were
31550 a contiguous collection of traceframes, as per the trace file format.
31551 The reply consists as many hex-encoded bytes as the target can deliver
31552 in a packet; it is not an error to return fewer than were asked for.
31553 A reply consisting of just @code{l} indicates that no bytes are
31556 @item QTBuffer:circular:@var{value}
31557 This packet directs the target to use a circular trace buffer if
31558 @var{value} is 1, or a linear buffer if the value is 0.
31562 @node Host I/O Packets
31563 @section Host I/O Packets
31564 @cindex Host I/O, remote protocol
31565 @cindex file transfer, remote protocol
31567 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
31568 operations on the far side of a remote link. For example, Host I/O is
31569 used to upload and download files to a remote target with its own
31570 filesystem. Host I/O uses the same constant values and data structure
31571 layout as the target-initiated File-I/O protocol. However, the
31572 Host I/O packets are structured differently. The target-initiated
31573 protocol relies on target memory to store parameters and buffers.
31574 Host I/O requests are initiated by @value{GDBN}, and the
31575 target's memory is not involved. @xref{File-I/O Remote Protocol
31576 Extension}, for more details on the target-initiated protocol.
31578 The Host I/O request packets all encode a single operation along with
31579 its arguments. They have this format:
31583 @item vFile:@var{operation}: @var{parameter}@dots{}
31584 @var{operation} is the name of the particular request; the target
31585 should compare the entire packet name up to the second colon when checking
31586 for a supported operation. The format of @var{parameter} depends on
31587 the operation. Numbers are always passed in hexadecimal. Negative
31588 numbers have an explicit minus sign (i.e.@: two's complement is not
31589 used). Strings (e.g.@: filenames) are encoded as a series of
31590 hexadecimal bytes. The last argument to a system call may be a
31591 buffer of escaped binary data (@pxref{Binary Data}).
31595 The valid responses to Host I/O packets are:
31599 @item F @var{result} [, @var{errno}] [; @var{attachment}]
31600 @var{result} is the integer value returned by this operation, usually
31601 non-negative for success and -1 for errors. If an error has occured,
31602 @var{errno} will be included in the result. @var{errno} will have a
31603 value defined by the File-I/O protocol (@pxref{Errno Values}). For
31604 operations which return data, @var{attachment} supplies the data as a
31605 binary buffer. Binary buffers in response packets are escaped in the
31606 normal way (@pxref{Binary Data}). See the individual packet
31607 documentation for the interpretation of @var{result} and
31611 An empty response indicates that this operation is not recognized.
31615 These are the supported Host I/O operations:
31618 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
31619 Open a file at @var{pathname} and return a file descriptor for it, or
31620 return -1 if an error occurs. @var{pathname} is a string,
31621 @var{flags} is an integer indicating a mask of open flags
31622 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
31623 of mode bits to use if the file is created (@pxref{mode_t Values}).
31624 @xref{open}, for details of the open flags and mode values.
31626 @item vFile:close: @var{fd}
31627 Close the open file corresponding to @var{fd} and return 0, or
31628 -1 if an error occurs.
31630 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
31631 Read data from the open file corresponding to @var{fd}. Up to
31632 @var{count} bytes will be read from the file, starting at @var{offset}
31633 relative to the start of the file. The target may read fewer bytes;
31634 common reasons include packet size limits and an end-of-file
31635 condition. The number of bytes read is returned. Zero should only be
31636 returned for a successful read at the end of the file, or if
31637 @var{count} was zero.
31639 The data read should be returned as a binary attachment on success.
31640 If zero bytes were read, the response should include an empty binary
31641 attachment (i.e.@: a trailing semicolon). The return value is the
31642 number of target bytes read; the binary attachment may be longer if
31643 some characters were escaped.
31645 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
31646 Write @var{data} (a binary buffer) to the open file corresponding
31647 to @var{fd}. Start the write at @var{offset} from the start of the
31648 file. Unlike many @code{write} system calls, there is no
31649 separate @var{count} argument; the length of @var{data} in the
31650 packet is used. @samp{vFile:write} returns the number of bytes written,
31651 which may be shorter than the length of @var{data}, or -1 if an
31654 @item vFile:unlink: @var{pathname}
31655 Delete the file at @var{pathname} on the target. Return 0,
31656 or -1 if an error occurs. @var{pathname} is a string.
31661 @section Interrupts
31662 @cindex interrupts (remote protocol)
31664 When a program on the remote target is running, @value{GDBN} may
31665 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
31666 a @code{BREAK} followed by @code{g},
31667 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
31669 The precise meaning of @code{BREAK} is defined by the transport
31670 mechanism and may, in fact, be undefined. @value{GDBN} does not
31671 currently define a @code{BREAK} mechanism for any of the network
31672 interfaces except for TCP, in which case @value{GDBN} sends the
31673 @code{telnet} BREAK sequence.
31675 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
31676 transport mechanisms. It is represented by sending the single byte
31677 @code{0x03} without any of the usual packet overhead described in
31678 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
31679 transmitted as part of a packet, it is considered to be packet data
31680 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
31681 (@pxref{X packet}), used for binary downloads, may include an unescaped
31682 @code{0x03} as part of its packet.
31684 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
31685 When Linux kernel receives this sequence from serial port,
31686 it stops execution and connects to gdb.
31688 Stubs are not required to recognize these interrupt mechanisms and the
31689 precise meaning associated with receipt of the interrupt is
31690 implementation defined. If the target supports debugging of multiple
31691 threads and/or processes, it should attempt to interrupt all
31692 currently-executing threads and processes.
31693 If the stub is successful at interrupting the
31694 running program, it should send one of the stop
31695 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
31696 of successfully stopping the program in all-stop mode, and a stop reply
31697 for each stopped thread in non-stop mode.
31698 Interrupts received while the
31699 program is stopped are discarded.
31701 @node Notification Packets
31702 @section Notification Packets
31703 @cindex notification packets
31704 @cindex packets, notification
31706 The @value{GDBN} remote serial protocol includes @dfn{notifications},
31707 packets that require no acknowledgment. Both the GDB and the stub
31708 may send notifications (although the only notifications defined at
31709 present are sent by the stub). Notifications carry information
31710 without incurring the round-trip latency of an acknowledgment, and so
31711 are useful for low-impact communications where occasional packet loss
31714 A notification packet has the form @samp{% @var{data} #
31715 @var{checksum}}, where @var{data} is the content of the notification,
31716 and @var{checksum} is a checksum of @var{data}, computed and formatted
31717 as for ordinary @value{GDBN} packets. A notification's @var{data}
31718 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
31719 receiving a notification, the recipient sends no @samp{+} or @samp{-}
31720 to acknowledge the notification's receipt or to report its corruption.
31722 Every notification's @var{data} begins with a name, which contains no
31723 colon characters, followed by a colon character.
31725 Recipients should silently ignore corrupted notifications and
31726 notifications they do not understand. Recipients should restart
31727 timeout periods on receipt of a well-formed notification, whether or
31728 not they understand it.
31730 Senders should only send the notifications described here when this
31731 protocol description specifies that they are permitted. In the
31732 future, we may extend the protocol to permit existing notifications in
31733 new contexts; this rule helps older senders avoid confusing newer
31736 (Older versions of @value{GDBN} ignore bytes received until they see
31737 the @samp{$} byte that begins an ordinary packet, so new stubs may
31738 transmit notifications without fear of confusing older clients. There
31739 are no notifications defined for @value{GDBN} to send at the moment, but we
31740 assume that most older stubs would ignore them, as well.)
31742 The following notification packets from the stub to @value{GDBN} are
31746 @item Stop: @var{reply}
31747 Report an asynchronous stop event in non-stop mode.
31748 The @var{reply} has the form of a stop reply, as
31749 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
31750 for information on how these notifications are acknowledged by
31754 @node Remote Non-Stop
31755 @section Remote Protocol Support for Non-Stop Mode
31757 @value{GDBN}'s remote protocol supports non-stop debugging of
31758 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
31759 supports non-stop mode, it should report that to @value{GDBN} by including
31760 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
31762 @value{GDBN} typically sends a @samp{QNonStop} packet only when
31763 establishing a new connection with the stub. Entering non-stop mode
31764 does not alter the state of any currently-running threads, but targets
31765 must stop all threads in any already-attached processes when entering
31766 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
31767 probe the target state after a mode change.
31769 In non-stop mode, when an attached process encounters an event that
31770 would otherwise be reported with a stop reply, it uses the
31771 asynchronous notification mechanism (@pxref{Notification Packets}) to
31772 inform @value{GDBN}. In contrast to all-stop mode, where all threads
31773 in all processes are stopped when a stop reply is sent, in non-stop
31774 mode only the thread reporting the stop event is stopped. That is,
31775 when reporting a @samp{S} or @samp{T} response to indicate completion
31776 of a step operation, hitting a breakpoint, or a fault, only the
31777 affected thread is stopped; any other still-running threads continue
31778 to run. When reporting a @samp{W} or @samp{X} response, all running
31779 threads belonging to other attached processes continue to run.
31781 Only one stop reply notification at a time may be pending; if
31782 additional stop events occur before @value{GDBN} has acknowledged the
31783 previous notification, they must be queued by the stub for later
31784 synchronous transmission in response to @samp{vStopped} packets from
31785 @value{GDBN}. Because the notification mechanism is unreliable,
31786 the stub is permitted to resend a stop reply notification
31787 if it believes @value{GDBN} may not have received it. @value{GDBN}
31788 ignores additional stop reply notifications received before it has
31789 finished processing a previous notification and the stub has completed
31790 sending any queued stop events.
31792 Otherwise, @value{GDBN} must be prepared to receive a stop reply
31793 notification at any time. Specifically, they may appear when
31794 @value{GDBN} is not otherwise reading input from the stub, or when
31795 @value{GDBN} is expecting to read a normal synchronous response or a
31796 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
31797 Notification packets are distinct from any other communication from
31798 the stub so there is no ambiguity.
31800 After receiving a stop reply notification, @value{GDBN} shall
31801 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
31802 as a regular, synchronous request to the stub. Such acknowledgment
31803 is not required to happen immediately, as @value{GDBN} is permitted to
31804 send other, unrelated packets to the stub first, which the stub should
31807 Upon receiving a @samp{vStopped} packet, if the stub has other queued
31808 stop events to report to @value{GDBN}, it shall respond by sending a
31809 normal stop reply response. @value{GDBN} shall then send another
31810 @samp{vStopped} packet to solicit further responses; again, it is
31811 permitted to send other, unrelated packets as well which the stub
31812 should process normally.
31814 If the stub receives a @samp{vStopped} packet and there are no
31815 additional stop events to report, the stub shall return an @samp{OK}
31816 response. At this point, if further stop events occur, the stub shall
31817 send a new stop reply notification, @value{GDBN} shall accept the
31818 notification, and the process shall be repeated.
31820 In non-stop mode, the target shall respond to the @samp{?} packet as
31821 follows. First, any incomplete stop reply notification/@samp{vStopped}
31822 sequence in progress is abandoned. The target must begin a new
31823 sequence reporting stop events for all stopped threads, whether or not
31824 it has previously reported those events to @value{GDBN}. The first
31825 stop reply is sent as a synchronous reply to the @samp{?} packet, and
31826 subsequent stop replies are sent as responses to @samp{vStopped} packets
31827 using the mechanism described above. The target must not send
31828 asynchronous stop reply notifications until the sequence is complete.
31829 If all threads are running when the target receives the @samp{?} packet,
31830 or if the target is not attached to any process, it shall respond
31833 @node Packet Acknowledgment
31834 @section Packet Acknowledgment
31836 @cindex acknowledgment, for @value{GDBN} remote
31837 @cindex packet acknowledgment, for @value{GDBN} remote
31838 By default, when either the host or the target machine receives a packet,
31839 the first response expected is an acknowledgment: either @samp{+} (to indicate
31840 the package was received correctly) or @samp{-} (to request retransmission).
31841 This mechanism allows the @value{GDBN} remote protocol to operate over
31842 unreliable transport mechanisms, such as a serial line.
31844 In cases where the transport mechanism is itself reliable (such as a pipe or
31845 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
31846 It may be desirable to disable them in that case to reduce communication
31847 overhead, or for other reasons. This can be accomplished by means of the
31848 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
31850 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
31851 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
31852 and response format still includes the normal checksum, as described in
31853 @ref{Overview}, but the checksum may be ignored by the receiver.
31855 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
31856 no-acknowledgment mode, it should report that to @value{GDBN}
31857 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
31858 @pxref{qSupported}.
31859 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
31860 disabled via the @code{set remote noack-packet off} command
31861 (@pxref{Remote Configuration}),
31862 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
31863 Only then may the stub actually turn off packet acknowledgments.
31864 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
31865 response, which can be safely ignored by the stub.
31867 Note that @code{set remote noack-packet} command only affects negotiation
31868 between @value{GDBN} and the stub when subsequent connections are made;
31869 it does not affect the protocol acknowledgment state for any current
31871 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
31872 new connection is established,
31873 there is also no protocol request to re-enable the acknowledgments
31874 for the current connection, once disabled.
31879 Example sequence of a target being re-started. Notice how the restart
31880 does not get any direct output:
31885 @emph{target restarts}
31888 <- @code{T001:1234123412341234}
31892 Example sequence of a target being stepped by a single instruction:
31895 -> @code{G1445@dots{}}
31900 <- @code{T001:1234123412341234}
31904 <- @code{1455@dots{}}
31908 @node File-I/O Remote Protocol Extension
31909 @section File-I/O Remote Protocol Extension
31910 @cindex File-I/O remote protocol extension
31913 * File-I/O Overview::
31914 * Protocol Basics::
31915 * The F Request Packet::
31916 * The F Reply Packet::
31917 * The Ctrl-C Message::
31919 * List of Supported Calls::
31920 * Protocol-specific Representation of Datatypes::
31922 * File-I/O Examples::
31925 @node File-I/O Overview
31926 @subsection File-I/O Overview
31927 @cindex file-i/o overview
31929 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
31930 target to use the host's file system and console I/O to perform various
31931 system calls. System calls on the target system are translated into a
31932 remote protocol packet to the host system, which then performs the needed
31933 actions and returns a response packet to the target system.
31934 This simulates file system operations even on targets that lack file systems.
31936 The protocol is defined to be independent of both the host and target systems.
31937 It uses its own internal representation of datatypes and values. Both
31938 @value{GDBN} and the target's @value{GDBN} stub are responsible for
31939 translating the system-dependent value representations into the internal
31940 protocol representations when data is transmitted.
31942 The communication is synchronous. A system call is possible only when
31943 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
31944 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
31945 the target is stopped to allow deterministic access to the target's
31946 memory. Therefore File-I/O is not interruptible by target signals. On
31947 the other hand, it is possible to interrupt File-I/O by a user interrupt
31948 (@samp{Ctrl-C}) within @value{GDBN}.
31950 The target's request to perform a host system call does not finish
31951 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
31952 after finishing the system call, the target returns to continuing the
31953 previous activity (continue, step). No additional continue or step
31954 request from @value{GDBN} is required.
31957 (@value{GDBP}) continue
31958 <- target requests 'system call X'
31959 target is stopped, @value{GDBN} executes system call
31960 -> @value{GDBN} returns result
31961 ... target continues, @value{GDBN} returns to wait for the target
31962 <- target hits breakpoint and sends a Txx packet
31965 The protocol only supports I/O on the console and to regular files on
31966 the host file system. Character or block special devices, pipes,
31967 named pipes, sockets or any other communication method on the host
31968 system are not supported by this protocol.
31970 File I/O is not supported in non-stop mode.
31972 @node Protocol Basics
31973 @subsection Protocol Basics
31974 @cindex protocol basics, file-i/o
31976 The File-I/O protocol uses the @code{F} packet as the request as well
31977 as reply packet. Since a File-I/O system call can only occur when
31978 @value{GDBN} is waiting for a response from the continuing or stepping target,
31979 the File-I/O request is a reply that @value{GDBN} has to expect as a result
31980 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
31981 This @code{F} packet contains all information needed to allow @value{GDBN}
31982 to call the appropriate host system call:
31986 A unique identifier for the requested system call.
31989 All parameters to the system call. Pointers are given as addresses
31990 in the target memory address space. Pointers to strings are given as
31991 pointer/length pair. Numerical values are given as they are.
31992 Numerical control flags are given in a protocol-specific representation.
31996 At this point, @value{GDBN} has to perform the following actions.
32000 If the parameters include pointer values to data needed as input to a
32001 system call, @value{GDBN} requests this data from the target with a
32002 standard @code{m} packet request. This additional communication has to be
32003 expected by the target implementation and is handled as any other @code{m}
32007 @value{GDBN} translates all value from protocol representation to host
32008 representation as needed. Datatypes are coerced into the host types.
32011 @value{GDBN} calls the system call.
32014 It then coerces datatypes back to protocol representation.
32017 If the system call is expected to return data in buffer space specified
32018 by pointer parameters to the call, the data is transmitted to the
32019 target using a @code{M} or @code{X} packet. This packet has to be expected
32020 by the target implementation and is handled as any other @code{M} or @code{X}
32025 Eventually @value{GDBN} replies with another @code{F} packet which contains all
32026 necessary information for the target to continue. This at least contains
32033 @code{errno}, if has been changed by the system call.
32040 After having done the needed type and value coercion, the target continues
32041 the latest continue or step action.
32043 @node The F Request Packet
32044 @subsection The @code{F} Request Packet
32045 @cindex file-i/o request packet
32046 @cindex @code{F} request packet
32048 The @code{F} request packet has the following format:
32051 @item F@var{call-id},@var{parameter@dots{}}
32053 @var{call-id} is the identifier to indicate the host system call to be called.
32054 This is just the name of the function.
32056 @var{parameter@dots{}} are the parameters to the system call.
32057 Parameters are hexadecimal integer values, either the actual values in case
32058 of scalar datatypes, pointers to target buffer space in case of compound
32059 datatypes and unspecified memory areas, or pointer/length pairs in case
32060 of string parameters. These are appended to the @var{call-id} as a
32061 comma-delimited list. All values are transmitted in ASCII
32062 string representation, pointer/length pairs separated by a slash.
32068 @node The F Reply Packet
32069 @subsection The @code{F} Reply Packet
32070 @cindex file-i/o reply packet
32071 @cindex @code{F} reply packet
32073 The @code{F} reply packet has the following format:
32077 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
32079 @var{retcode} is the return code of the system call as hexadecimal value.
32081 @var{errno} is the @code{errno} set by the call, in protocol-specific
32083 This parameter can be omitted if the call was successful.
32085 @var{Ctrl-C flag} is only sent if the user requested a break. In this
32086 case, @var{errno} must be sent as well, even if the call was successful.
32087 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
32094 or, if the call was interrupted before the host call has been performed:
32101 assuming 4 is the protocol-specific representation of @code{EINTR}.
32106 @node The Ctrl-C Message
32107 @subsection The @samp{Ctrl-C} Message
32108 @cindex ctrl-c message, in file-i/o protocol
32110 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
32111 reply packet (@pxref{The F Reply Packet}),
32112 the target should behave as if it had
32113 gotten a break message. The meaning for the target is ``system call
32114 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
32115 (as with a break message) and return to @value{GDBN} with a @code{T02}
32118 It's important for the target to know in which
32119 state the system call was interrupted. There are two possible cases:
32123 The system call hasn't been performed on the host yet.
32126 The system call on the host has been finished.
32130 These two states can be distinguished by the target by the value of the
32131 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
32132 call hasn't been performed. This is equivalent to the @code{EINTR} handling
32133 on POSIX systems. In any other case, the target may presume that the
32134 system call has been finished --- successfully or not --- and should behave
32135 as if the break message arrived right after the system call.
32137 @value{GDBN} must behave reliably. If the system call has not been called
32138 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
32139 @code{errno} in the packet. If the system call on the host has been finished
32140 before the user requests a break, the full action must be finished by
32141 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
32142 The @code{F} packet may only be sent when either nothing has happened
32143 or the full action has been completed.
32146 @subsection Console I/O
32147 @cindex console i/o as part of file-i/o
32149 By default and if not explicitly closed by the target system, the file
32150 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
32151 on the @value{GDBN} console is handled as any other file output operation
32152 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
32153 by @value{GDBN} so that after the target read request from file descriptor
32154 0 all following typing is buffered until either one of the following
32159 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
32161 system call is treated as finished.
32164 The user presses @key{RET}. This is treated as end of input with a trailing
32168 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
32169 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
32173 If the user has typed more characters than fit in the buffer given to
32174 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
32175 either another @code{read(0, @dots{})} is requested by the target, or debugging
32176 is stopped at the user's request.
32179 @node List of Supported Calls
32180 @subsection List of Supported Calls
32181 @cindex list of supported file-i/o calls
32198 @unnumberedsubsubsec open
32199 @cindex open, file-i/o system call
32204 int open(const char *pathname, int flags);
32205 int open(const char *pathname, int flags, mode_t mode);
32209 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
32212 @var{flags} is the bitwise @code{OR} of the following values:
32216 If the file does not exist it will be created. The host
32217 rules apply as far as file ownership and time stamps
32221 When used with @code{O_CREAT}, if the file already exists it is
32222 an error and open() fails.
32225 If the file already exists and the open mode allows
32226 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
32227 truncated to zero length.
32230 The file is opened in append mode.
32233 The file is opened for reading only.
32236 The file is opened for writing only.
32239 The file is opened for reading and writing.
32243 Other bits are silently ignored.
32247 @var{mode} is the bitwise @code{OR} of the following values:
32251 User has read permission.
32254 User has write permission.
32257 Group has read permission.
32260 Group has write permission.
32263 Others have read permission.
32266 Others have write permission.
32270 Other bits are silently ignored.
32273 @item Return value:
32274 @code{open} returns the new file descriptor or -1 if an error
32281 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
32284 @var{pathname} refers to a directory.
32287 The requested access is not allowed.
32290 @var{pathname} was too long.
32293 A directory component in @var{pathname} does not exist.
32296 @var{pathname} refers to a device, pipe, named pipe or socket.
32299 @var{pathname} refers to a file on a read-only filesystem and
32300 write access was requested.
32303 @var{pathname} is an invalid pointer value.
32306 No space on device to create the file.
32309 The process already has the maximum number of files open.
32312 The limit on the total number of files open on the system
32316 The call was interrupted by the user.
32322 @unnumberedsubsubsec close
32323 @cindex close, file-i/o system call
32332 @samp{Fclose,@var{fd}}
32334 @item Return value:
32335 @code{close} returns zero on success, or -1 if an error occurred.
32341 @var{fd} isn't a valid open file descriptor.
32344 The call was interrupted by the user.
32350 @unnumberedsubsubsec read
32351 @cindex read, file-i/o system call
32356 int read(int fd, void *buf, unsigned int count);
32360 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
32362 @item Return value:
32363 On success, the number of bytes read is returned.
32364 Zero indicates end of file. If count is zero, read
32365 returns zero as well. On error, -1 is returned.
32371 @var{fd} is not a valid file descriptor or is not open for
32375 @var{bufptr} is an invalid pointer value.
32378 The call was interrupted by the user.
32384 @unnumberedsubsubsec write
32385 @cindex write, file-i/o system call
32390 int write(int fd, const void *buf, unsigned int count);
32394 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
32396 @item Return value:
32397 On success, the number of bytes written are returned.
32398 Zero indicates nothing was written. On error, -1
32405 @var{fd} is not a valid file descriptor or is not open for
32409 @var{bufptr} is an invalid pointer value.
32412 An attempt was made to write a file that exceeds the
32413 host-specific maximum file size allowed.
32416 No space on device to write the data.
32419 The call was interrupted by the user.
32425 @unnumberedsubsubsec lseek
32426 @cindex lseek, file-i/o system call
32431 long lseek (int fd, long offset, int flag);
32435 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
32437 @var{flag} is one of:
32441 The offset is set to @var{offset} bytes.
32444 The offset is set to its current location plus @var{offset}
32448 The offset is set to the size of the file plus @var{offset}
32452 @item Return value:
32453 On success, the resulting unsigned offset in bytes from
32454 the beginning of the file is returned. Otherwise, a
32455 value of -1 is returned.
32461 @var{fd} is not a valid open file descriptor.
32464 @var{fd} is associated with the @value{GDBN} console.
32467 @var{flag} is not a proper value.
32470 The call was interrupted by the user.
32476 @unnumberedsubsubsec rename
32477 @cindex rename, file-i/o system call
32482 int rename(const char *oldpath, const char *newpath);
32486 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
32488 @item Return value:
32489 On success, zero is returned. On error, -1 is returned.
32495 @var{newpath} is an existing directory, but @var{oldpath} is not a
32499 @var{newpath} is a non-empty directory.
32502 @var{oldpath} or @var{newpath} is a directory that is in use by some
32506 An attempt was made to make a directory a subdirectory
32510 A component used as a directory in @var{oldpath} or new
32511 path is not a directory. Or @var{oldpath} is a directory
32512 and @var{newpath} exists but is not a directory.
32515 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
32518 No access to the file or the path of the file.
32522 @var{oldpath} or @var{newpath} was too long.
32525 A directory component in @var{oldpath} or @var{newpath} does not exist.
32528 The file is on a read-only filesystem.
32531 The device containing the file has no room for the new
32535 The call was interrupted by the user.
32541 @unnumberedsubsubsec unlink
32542 @cindex unlink, file-i/o system call
32547 int unlink(const char *pathname);
32551 @samp{Funlink,@var{pathnameptr}/@var{len}}
32553 @item Return value:
32554 On success, zero is returned. On error, -1 is returned.
32560 No access to the file or the path of the file.
32563 The system does not allow unlinking of directories.
32566 The file @var{pathname} cannot be unlinked because it's
32567 being used by another process.
32570 @var{pathnameptr} is an invalid pointer value.
32573 @var{pathname} was too long.
32576 A directory component in @var{pathname} does not exist.
32579 A component of the path is not a directory.
32582 The file is on a read-only filesystem.
32585 The call was interrupted by the user.
32591 @unnumberedsubsubsec stat/fstat
32592 @cindex fstat, file-i/o system call
32593 @cindex stat, file-i/o system call
32598 int stat(const char *pathname, struct stat *buf);
32599 int fstat(int fd, struct stat *buf);
32603 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
32604 @samp{Ffstat,@var{fd},@var{bufptr}}
32606 @item Return value:
32607 On success, zero is returned. On error, -1 is returned.
32613 @var{fd} is not a valid open file.
32616 A directory component in @var{pathname} does not exist or the
32617 path is an empty string.
32620 A component of the path is not a directory.
32623 @var{pathnameptr} is an invalid pointer value.
32626 No access to the file or the path of the file.
32629 @var{pathname} was too long.
32632 The call was interrupted by the user.
32638 @unnumberedsubsubsec gettimeofday
32639 @cindex gettimeofday, file-i/o system call
32644 int gettimeofday(struct timeval *tv, void *tz);
32648 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
32650 @item Return value:
32651 On success, 0 is returned, -1 otherwise.
32657 @var{tz} is a non-NULL pointer.
32660 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
32666 @unnumberedsubsubsec isatty
32667 @cindex isatty, file-i/o system call
32672 int isatty(int fd);
32676 @samp{Fisatty,@var{fd}}
32678 @item Return value:
32679 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
32685 The call was interrupted by the user.
32690 Note that the @code{isatty} call is treated as a special case: it returns
32691 1 to the target if the file descriptor is attached
32692 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
32693 would require implementing @code{ioctl} and would be more complex than
32698 @unnumberedsubsubsec system
32699 @cindex system, file-i/o system call
32704 int system(const char *command);
32708 @samp{Fsystem,@var{commandptr}/@var{len}}
32710 @item Return value:
32711 If @var{len} is zero, the return value indicates whether a shell is
32712 available. A zero return value indicates a shell is not available.
32713 For non-zero @var{len}, the value returned is -1 on error and the
32714 return status of the command otherwise. Only the exit status of the
32715 command is returned, which is extracted from the host's @code{system}
32716 return value by calling @code{WEXITSTATUS(retval)}. In case
32717 @file{/bin/sh} could not be executed, 127 is returned.
32723 The call was interrupted by the user.
32728 @value{GDBN} takes over the full task of calling the necessary host calls
32729 to perform the @code{system} call. The return value of @code{system} on
32730 the host is simplified before it's returned
32731 to the target. Any termination signal information from the child process
32732 is discarded, and the return value consists
32733 entirely of the exit status of the called command.
32735 Due to security concerns, the @code{system} call is by default refused
32736 by @value{GDBN}. The user has to allow this call explicitly with the
32737 @code{set remote system-call-allowed 1} command.
32740 @item set remote system-call-allowed
32741 @kindex set remote system-call-allowed
32742 Control whether to allow the @code{system} calls in the File I/O
32743 protocol for the remote target. The default is zero (disabled).
32745 @item show remote system-call-allowed
32746 @kindex show remote system-call-allowed
32747 Show whether the @code{system} calls are allowed in the File I/O
32751 @node Protocol-specific Representation of Datatypes
32752 @subsection Protocol-specific Representation of Datatypes
32753 @cindex protocol-specific representation of datatypes, in file-i/o protocol
32756 * Integral Datatypes::
32758 * Memory Transfer::
32763 @node Integral Datatypes
32764 @unnumberedsubsubsec Integral Datatypes
32765 @cindex integral datatypes, in file-i/o protocol
32767 The integral datatypes used in the system calls are @code{int},
32768 @code{unsigned int}, @code{long}, @code{unsigned long},
32769 @code{mode_t}, and @code{time_t}.
32771 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
32772 implemented as 32 bit values in this protocol.
32774 @code{long} and @code{unsigned long} are implemented as 64 bit types.
32776 @xref{Limits}, for corresponding MIN and MAX values (similar to those
32777 in @file{limits.h}) to allow range checking on host and target.
32779 @code{time_t} datatypes are defined as seconds since the Epoch.
32781 All integral datatypes transferred as part of a memory read or write of a
32782 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
32785 @node Pointer Values
32786 @unnumberedsubsubsec Pointer Values
32787 @cindex pointer values, in file-i/o protocol
32789 Pointers to target data are transmitted as they are. An exception
32790 is made for pointers to buffers for which the length isn't
32791 transmitted as part of the function call, namely strings. Strings
32792 are transmitted as a pointer/length pair, both as hex values, e.g.@:
32799 which is a pointer to data of length 18 bytes at position 0x1aaf.
32800 The length is defined as the full string length in bytes, including
32801 the trailing null byte. For example, the string @code{"hello world"}
32802 at address 0x123456 is transmitted as
32808 @node Memory Transfer
32809 @unnumberedsubsubsec Memory Transfer
32810 @cindex memory transfer, in file-i/o protocol
32812 Structured data which is transferred using a memory read or write (for
32813 example, a @code{struct stat}) is expected to be in a protocol-specific format
32814 with all scalar multibyte datatypes being big endian. Translation to
32815 this representation needs to be done both by the target before the @code{F}
32816 packet is sent, and by @value{GDBN} before
32817 it transfers memory to the target. Transferred pointers to structured
32818 data should point to the already-coerced data at any time.
32822 @unnumberedsubsubsec struct stat
32823 @cindex struct stat, in file-i/o protocol
32825 The buffer of type @code{struct stat} used by the target and @value{GDBN}
32826 is defined as follows:
32830 unsigned int st_dev; /* device */
32831 unsigned int st_ino; /* inode */
32832 mode_t st_mode; /* protection */
32833 unsigned int st_nlink; /* number of hard links */
32834 unsigned int st_uid; /* user ID of owner */
32835 unsigned int st_gid; /* group ID of owner */
32836 unsigned int st_rdev; /* device type (if inode device) */
32837 unsigned long st_size; /* total size, in bytes */
32838 unsigned long st_blksize; /* blocksize for filesystem I/O */
32839 unsigned long st_blocks; /* number of blocks allocated */
32840 time_t st_atime; /* time of last access */
32841 time_t st_mtime; /* time of last modification */
32842 time_t st_ctime; /* time of last change */
32846 The integral datatypes conform to the definitions given in the
32847 appropriate section (see @ref{Integral Datatypes}, for details) so this
32848 structure is of size 64 bytes.
32850 The values of several fields have a restricted meaning and/or
32856 A value of 0 represents a file, 1 the console.
32859 No valid meaning for the target. Transmitted unchanged.
32862 Valid mode bits are described in @ref{Constants}. Any other
32863 bits have currently no meaning for the target.
32868 No valid meaning for the target. Transmitted unchanged.
32873 These values have a host and file system dependent
32874 accuracy. Especially on Windows hosts, the file system may not
32875 support exact timing values.
32878 The target gets a @code{struct stat} of the above representation and is
32879 responsible for coercing it to the target representation before
32882 Note that due to size differences between the host, target, and protocol
32883 representations of @code{struct stat} members, these members could eventually
32884 get truncated on the target.
32886 @node struct timeval
32887 @unnumberedsubsubsec struct timeval
32888 @cindex struct timeval, in file-i/o protocol
32890 The buffer of type @code{struct timeval} used by the File-I/O protocol
32891 is defined as follows:
32895 time_t tv_sec; /* second */
32896 long tv_usec; /* microsecond */
32900 The integral datatypes conform to the definitions given in the
32901 appropriate section (see @ref{Integral Datatypes}, for details) so this
32902 structure is of size 8 bytes.
32905 @subsection Constants
32906 @cindex constants, in file-i/o protocol
32908 The following values are used for the constants inside of the
32909 protocol. @value{GDBN} and target are responsible for translating these
32910 values before and after the call as needed.
32921 @unnumberedsubsubsec Open Flags
32922 @cindex open flags, in file-i/o protocol
32924 All values are given in hexadecimal representation.
32936 @node mode_t Values
32937 @unnumberedsubsubsec mode_t Values
32938 @cindex mode_t values, in file-i/o protocol
32940 All values are given in octal representation.
32957 @unnumberedsubsubsec Errno Values
32958 @cindex errno values, in file-i/o protocol
32960 All values are given in decimal representation.
32985 @code{EUNKNOWN} is used as a fallback error value if a host system returns
32986 any error value not in the list of supported error numbers.
32989 @unnumberedsubsubsec Lseek Flags
32990 @cindex lseek flags, in file-i/o protocol
32999 @unnumberedsubsubsec Limits
33000 @cindex limits, in file-i/o protocol
33002 All values are given in decimal representation.
33005 INT_MIN -2147483648
33007 UINT_MAX 4294967295
33008 LONG_MIN -9223372036854775808
33009 LONG_MAX 9223372036854775807
33010 ULONG_MAX 18446744073709551615
33013 @node File-I/O Examples
33014 @subsection File-I/O Examples
33015 @cindex file-i/o examples
33017 Example sequence of a write call, file descriptor 3, buffer is at target
33018 address 0x1234, 6 bytes should be written:
33021 <- @code{Fwrite,3,1234,6}
33022 @emph{request memory read from target}
33025 @emph{return "6 bytes written"}
33029 Example sequence of a read call, file descriptor 3, buffer is at target
33030 address 0x1234, 6 bytes should be read:
33033 <- @code{Fread,3,1234,6}
33034 @emph{request memory write to target}
33035 -> @code{X1234,6:XXXXXX}
33036 @emph{return "6 bytes read"}
33040 Example sequence of a read call, call fails on the host due to invalid
33041 file descriptor (@code{EBADF}):
33044 <- @code{Fread,3,1234,6}
33048 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
33052 <- @code{Fread,3,1234,6}
33057 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
33061 <- @code{Fread,3,1234,6}
33062 -> @code{X1234,6:XXXXXX}
33066 @node Library List Format
33067 @section Library List Format
33068 @cindex library list format, remote protocol
33070 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
33071 same process as your application to manage libraries. In this case,
33072 @value{GDBN} can use the loader's symbol table and normal memory
33073 operations to maintain a list of shared libraries. On other
33074 platforms, the operating system manages loaded libraries.
33075 @value{GDBN} can not retrieve the list of currently loaded libraries
33076 through memory operations, so it uses the @samp{qXfer:libraries:read}
33077 packet (@pxref{qXfer library list read}) instead. The remote stub
33078 queries the target's operating system and reports which libraries
33081 The @samp{qXfer:libraries:read} packet returns an XML document which
33082 lists loaded libraries and their offsets. Each library has an
33083 associated name and one or more segment or section base addresses,
33084 which report where the library was loaded in memory.
33086 For the common case of libraries that are fully linked binaries, the
33087 library should have a list of segments. If the target supports
33088 dynamic linking of a relocatable object file, its library XML element
33089 should instead include a list of allocated sections. The segment or
33090 section bases are start addresses, not relocation offsets; they do not
33091 depend on the library's link-time base addresses.
33093 @value{GDBN} must be linked with the Expat library to support XML
33094 library lists. @xref{Expat}.
33096 A simple memory map, with one loaded library relocated by a single
33097 offset, looks like this:
33101 <library name="/lib/libc.so.6">
33102 <segment address="0x10000000"/>
33107 Another simple memory map, with one loaded library with three
33108 allocated sections (.text, .data, .bss), looks like this:
33112 <library name="sharedlib.o">
33113 <section address="0x10000000"/>
33114 <section address="0x20000000"/>
33115 <section address="0x30000000"/>
33120 The format of a library list is described by this DTD:
33123 <!-- library-list: Root element with versioning -->
33124 <!ELEMENT library-list (library)*>
33125 <!ATTLIST library-list version CDATA #FIXED "1.0">
33126 <!ELEMENT library (segment*, section*)>
33127 <!ATTLIST library name CDATA #REQUIRED>
33128 <!ELEMENT segment EMPTY>
33129 <!ATTLIST segment address CDATA #REQUIRED>
33130 <!ELEMENT section EMPTY>
33131 <!ATTLIST section address CDATA #REQUIRED>
33134 In addition, segments and section descriptors cannot be mixed within a
33135 single library element, and you must supply at least one segment or
33136 section for each library.
33138 @node Memory Map Format
33139 @section Memory Map Format
33140 @cindex memory map format
33142 To be able to write into flash memory, @value{GDBN} needs to obtain a
33143 memory map from the target. This section describes the format of the
33146 The memory map is obtained using the @samp{qXfer:memory-map:read}
33147 (@pxref{qXfer memory map read}) packet and is an XML document that
33148 lists memory regions.
33150 @value{GDBN} must be linked with the Expat library to support XML
33151 memory maps. @xref{Expat}.
33153 The top-level structure of the document is shown below:
33156 <?xml version="1.0"?>
33157 <!DOCTYPE memory-map
33158 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
33159 "http://sourceware.org/gdb/gdb-memory-map.dtd">
33165 Each region can be either:
33170 A region of RAM starting at @var{addr} and extending for @var{length}
33174 <memory type="ram" start="@var{addr}" length="@var{length}"/>
33179 A region of read-only memory:
33182 <memory type="rom" start="@var{addr}" length="@var{length}"/>
33187 A region of flash memory, with erasure blocks @var{blocksize}
33191 <memory type="flash" start="@var{addr}" length="@var{length}">
33192 <property name="blocksize">@var{blocksize}</property>
33198 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
33199 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
33200 packets to write to addresses in such ranges.
33202 The formal DTD for memory map format is given below:
33205 <!-- ................................................... -->
33206 <!-- Memory Map XML DTD ................................ -->
33207 <!-- File: memory-map.dtd .............................. -->
33208 <!-- .................................... .............. -->
33209 <!-- memory-map.dtd -->
33210 <!-- memory-map: Root element with versioning -->
33211 <!ELEMENT memory-map (memory | property)>
33212 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
33213 <!ELEMENT memory (property)>
33214 <!-- memory: Specifies a memory region,
33215 and its type, or device. -->
33216 <!ATTLIST memory type CDATA #REQUIRED
33217 start CDATA #REQUIRED
33218 length CDATA #REQUIRED
33219 device CDATA #IMPLIED>
33220 <!-- property: Generic attribute tag -->
33221 <!ELEMENT property (#PCDATA | property)*>
33222 <!ATTLIST property name CDATA #REQUIRED>
33225 @node Thread List Format
33226 @section Thread List Format
33227 @cindex thread list format
33229 To efficiently update the list of threads and their attributes,
33230 @value{GDBN} issues the @samp{qXfer:threads:read} packet
33231 (@pxref{qXfer threads read}) and obtains the XML document with
33232 the following structure:
33235 <?xml version="1.0"?>
33237 <thread id="id" core="0">
33238 ... description ...
33243 Each @samp{thread} element must have the @samp{id} attribute that
33244 identifies the thread (@pxref{thread-id syntax}). The
33245 @samp{core} attribute, if present, specifies which processor core
33246 the thread was last executing on. The content of the of @samp{thread}
33247 element is interpreted as human-readable auxilliary information.
33249 @include agentexpr.texi
33251 @node Trace File Format
33252 @appendix Trace File Format
33253 @cindex trace file format
33255 The trace file comes in three parts: a header, a textual description
33256 section, and a trace frame section with binary data.
33258 The header has the form @code{\x7fTRACE0\n}. The first byte is
33259 @code{0x7f} so as to indicate that the file contains binary data,
33260 while the @code{0} is a version number that may have different values
33263 The description section consists of multiple lines of @sc{ascii} text
33264 separated by newline characters (@code{0xa}). The lines may include a
33265 variety of optional descriptive or context-setting information, such
33266 as tracepoint definitions or register set size. @value{GDBN} will
33267 ignore any line that it does not recognize. An empty line marks the end
33270 @c FIXME add some specific types of data
33272 The trace frame section consists of a number of consecutive frames.
33273 Each frame begins with a two-byte tracepoint number, followed by a
33274 four-byte size giving the amount of data in the frame. The data in
33275 the frame consists of a number of blocks, each introduced by a
33276 character indicating its type (at least register, memory, and trace
33277 state variable). The data in this section is raw binary, not a
33278 hexadecimal or other encoding; its endianness matches the target's
33281 @c FIXME bi-arch may require endianness/arch info in description section
33284 @item R @var{bytes}
33285 Register block. The number and ordering of bytes matches that of a
33286 @code{g} packet in the remote protocol. Note that these are the
33287 actual bytes, in target order and @value{GDBN} register order, not a
33288 hexadecimal encoding.
33290 @item M @var{address} @var{length} @var{bytes}...
33291 Memory block. This is a contiguous block of memory, at the 8-byte
33292 address @var{address}, with a 2-byte length @var{length}, followed by
33293 @var{length} bytes.
33295 @item V @var{number} @var{value}
33296 Trace state variable block. This records the 8-byte signed value
33297 @var{value} of trace state variable numbered @var{number}.
33301 Future enhancements of the trace file format may include additional types
33304 @node Target Descriptions
33305 @appendix Target Descriptions
33306 @cindex target descriptions
33308 @strong{Warning:} target descriptions are still under active development,
33309 and the contents and format may change between @value{GDBN} releases.
33310 The format is expected to stabilize in the future.
33312 One of the challenges of using @value{GDBN} to debug embedded systems
33313 is that there are so many minor variants of each processor
33314 architecture in use. It is common practice for vendors to start with
33315 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
33316 and then make changes to adapt it to a particular market niche. Some
33317 architectures have hundreds of variants, available from dozens of
33318 vendors. This leads to a number of problems:
33322 With so many different customized processors, it is difficult for
33323 the @value{GDBN} maintainers to keep up with the changes.
33325 Since individual variants may have short lifetimes or limited
33326 audiences, it may not be worthwhile to carry information about every
33327 variant in the @value{GDBN} source tree.
33329 When @value{GDBN} does support the architecture of the embedded system
33330 at hand, the task of finding the correct architecture name to give the
33331 @command{set architecture} command can be error-prone.
33334 To address these problems, the @value{GDBN} remote protocol allows a
33335 target system to not only identify itself to @value{GDBN}, but to
33336 actually describe its own features. This lets @value{GDBN} support
33337 processor variants it has never seen before --- to the extent that the
33338 descriptions are accurate, and that @value{GDBN} understands them.
33340 @value{GDBN} must be linked with the Expat library to support XML
33341 target descriptions. @xref{Expat}.
33344 * Retrieving Descriptions:: How descriptions are fetched from a target.
33345 * Target Description Format:: The contents of a target description.
33346 * Predefined Target Types:: Standard types available for target
33348 * Standard Target Features:: Features @value{GDBN} knows about.
33351 @node Retrieving Descriptions
33352 @section Retrieving Descriptions
33354 Target descriptions can be read from the target automatically, or
33355 specified by the user manually. The default behavior is to read the
33356 description from the target. @value{GDBN} retrieves it via the remote
33357 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
33358 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
33359 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
33360 XML document, of the form described in @ref{Target Description
33363 Alternatively, you can specify a file to read for the target description.
33364 If a file is set, the target will not be queried. The commands to
33365 specify a file are:
33368 @cindex set tdesc filename
33369 @item set tdesc filename @var{path}
33370 Read the target description from @var{path}.
33372 @cindex unset tdesc filename
33373 @item unset tdesc filename
33374 Do not read the XML target description from a file. @value{GDBN}
33375 will use the description supplied by the current target.
33377 @cindex show tdesc filename
33378 @item show tdesc filename
33379 Show the filename to read for a target description, if any.
33383 @node Target Description Format
33384 @section Target Description Format
33385 @cindex target descriptions, XML format
33387 A target description annex is an @uref{http://www.w3.org/XML/, XML}
33388 document which complies with the Document Type Definition provided in
33389 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
33390 means you can use generally available tools like @command{xmllint} to
33391 check that your feature descriptions are well-formed and valid.
33392 However, to help people unfamiliar with XML write descriptions for
33393 their targets, we also describe the grammar here.
33395 Target descriptions can identify the architecture of the remote target
33396 and (for some architectures) provide information about custom register
33397 sets. They can also identify the OS ABI of the remote target.
33398 @value{GDBN} can use this information to autoconfigure for your
33399 target, or to warn you if you connect to an unsupported target.
33401 Here is a simple target description:
33404 <target version="1.0">
33405 <architecture>i386:x86-64</architecture>
33410 This minimal description only says that the target uses
33411 the x86-64 architecture.
33413 A target description has the following overall form, with [ ] marking
33414 optional elements and @dots{} marking repeatable elements. The elements
33415 are explained further below.
33418 <?xml version="1.0"?>
33419 <!DOCTYPE target SYSTEM "gdb-target.dtd">
33420 <target version="1.0">
33421 @r{[}@var{architecture}@r{]}
33422 @r{[}@var{osabi}@r{]}
33423 @r{[}@var{compatible}@r{]}
33424 @r{[}@var{feature}@dots{}@r{]}
33429 The description is generally insensitive to whitespace and line
33430 breaks, under the usual common-sense rules. The XML version
33431 declaration and document type declaration can generally be omitted
33432 (@value{GDBN} does not require them), but specifying them may be
33433 useful for XML validation tools. The @samp{version} attribute for
33434 @samp{<target>} may also be omitted, but we recommend
33435 including it; if future versions of @value{GDBN} use an incompatible
33436 revision of @file{gdb-target.dtd}, they will detect and report
33437 the version mismatch.
33439 @subsection Inclusion
33440 @cindex target descriptions, inclusion
33443 @cindex <xi:include>
33446 It can sometimes be valuable to split a target description up into
33447 several different annexes, either for organizational purposes, or to
33448 share files between different possible target descriptions. You can
33449 divide a description into multiple files by replacing any element of
33450 the target description with an inclusion directive of the form:
33453 <xi:include href="@var{document}"/>
33457 When @value{GDBN} encounters an element of this form, it will retrieve
33458 the named XML @var{document}, and replace the inclusion directive with
33459 the contents of that document. If the current description was read
33460 using @samp{qXfer}, then so will be the included document;
33461 @var{document} will be interpreted as the name of an annex. If the
33462 current description was read from a file, @value{GDBN} will look for
33463 @var{document} as a file in the same directory where it found the
33464 original description.
33466 @subsection Architecture
33467 @cindex <architecture>
33469 An @samp{<architecture>} element has this form:
33472 <architecture>@var{arch}</architecture>
33475 @var{arch} is one of the architectures from the set accepted by
33476 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
33479 @cindex @code{<osabi>}
33481 This optional field was introduced in @value{GDBN} version 7.0.
33482 Previous versions of @value{GDBN} ignore it.
33484 An @samp{<osabi>} element has this form:
33487 <osabi>@var{abi-name}</osabi>
33490 @var{abi-name} is an OS ABI name from the same selection accepted by
33491 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
33493 @subsection Compatible Architecture
33494 @cindex @code{<compatible>}
33496 This optional field was introduced in @value{GDBN} version 7.0.
33497 Previous versions of @value{GDBN} ignore it.
33499 A @samp{<compatible>} element has this form:
33502 <compatible>@var{arch}</compatible>
33505 @var{arch} is one of the architectures from the set accepted by
33506 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
33508 A @samp{<compatible>} element is used to specify that the target
33509 is able to run binaries in some other than the main target architecture
33510 given by the @samp{<architecture>} element. For example, on the
33511 Cell Broadband Engine, the main architecture is @code{powerpc:common}
33512 or @code{powerpc:common64}, but the system is able to run binaries
33513 in the @code{spu} architecture as well. The way to describe this
33514 capability with @samp{<compatible>} is as follows:
33517 <architecture>powerpc:common</architecture>
33518 <compatible>spu</compatible>
33521 @subsection Features
33524 Each @samp{<feature>} describes some logical portion of the target
33525 system. Features are currently used to describe available CPU
33526 registers and the types of their contents. A @samp{<feature>} element
33530 <feature name="@var{name}">
33531 @r{[}@var{type}@dots{}@r{]}
33537 Each feature's name should be unique within the description. The name
33538 of a feature does not matter unless @value{GDBN} has some special
33539 knowledge of the contents of that feature; if it does, the feature
33540 should have its standard name. @xref{Standard Target Features}.
33544 Any register's value is a collection of bits which @value{GDBN} must
33545 interpret. The default interpretation is a two's complement integer,
33546 but other types can be requested by name in the register description.
33547 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
33548 Target Types}), and the description can define additional composite types.
33550 Each type element must have an @samp{id} attribute, which gives
33551 a unique (within the containing @samp{<feature>}) name to the type.
33552 Types must be defined before they are used.
33555 Some targets offer vector registers, which can be treated as arrays
33556 of scalar elements. These types are written as @samp{<vector>} elements,
33557 specifying the array element type, @var{type}, and the number of elements,
33561 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
33565 If a register's value is usefully viewed in multiple ways, define it
33566 with a union type containing the useful representations. The
33567 @samp{<union>} element contains one or more @samp{<field>} elements,
33568 each of which has a @var{name} and a @var{type}:
33571 <union id="@var{id}">
33572 <field name="@var{name}" type="@var{type}"/>
33578 If a register's value is composed from several separate values, define
33579 it with a structure type. There are two forms of the @samp{<struct>}
33580 element; a @samp{<struct>} element must either contain only bitfields
33581 or contain no bitfields. If the structure contains only bitfields,
33582 its total size in bytes must be specified, each bitfield must have an
33583 explicit start and end, and bitfields are automatically assigned an
33584 integer type. The field's @var{start} should be less than or
33585 equal to its @var{end}, and zero represents the least significant bit.
33588 <struct id="@var{id}" size="@var{size}">
33589 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
33594 If the structure contains no bitfields, then each field has an
33595 explicit type, and no implicit padding is added.
33598 <struct id="@var{id}">
33599 <field name="@var{name}" type="@var{type}"/>
33605 If a register's value is a series of single-bit flags, define it with
33606 a flags type. The @samp{<flags>} element has an explicit @var{size}
33607 and contains one or more @samp{<field>} elements. Each field has a
33608 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
33612 <flags id="@var{id}" size="@var{size}">
33613 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
33618 @subsection Registers
33621 Each register is represented as an element with this form:
33624 <reg name="@var{name}"
33625 bitsize="@var{size}"
33626 @r{[}regnum="@var{num}"@r{]}
33627 @r{[}save-restore="@var{save-restore}"@r{]}
33628 @r{[}type="@var{type}"@r{]}
33629 @r{[}group="@var{group}"@r{]}/>
33633 The components are as follows:
33638 The register's name; it must be unique within the target description.
33641 The register's size, in bits.
33644 The register's number. If omitted, a register's number is one greater
33645 than that of the previous register (either in the current feature or in
33646 a preceeding feature); the first register in the target description
33647 defaults to zero. This register number is used to read or write
33648 the register; e.g.@: it is used in the remote @code{p} and @code{P}
33649 packets, and registers appear in the @code{g} and @code{G} packets
33650 in order of increasing register number.
33653 Whether the register should be preserved across inferior function
33654 calls; this must be either @code{yes} or @code{no}. The default is
33655 @code{yes}, which is appropriate for most registers except for
33656 some system control registers; this is not related to the target's
33660 The type of the register. @var{type} may be a predefined type, a type
33661 defined in the current feature, or one of the special types @code{int}
33662 and @code{float}. @code{int} is an integer type of the correct size
33663 for @var{bitsize}, and @code{float} is a floating point type (in the
33664 architecture's normal floating point format) of the correct size for
33665 @var{bitsize}. The default is @code{int}.
33668 The register group to which this register belongs. @var{group} must
33669 be either @code{general}, @code{float}, or @code{vector}. If no
33670 @var{group} is specified, @value{GDBN} will not display the register
33671 in @code{info registers}.
33675 @node Predefined Target Types
33676 @section Predefined Target Types
33677 @cindex target descriptions, predefined types
33679 Type definitions in the self-description can build up composite types
33680 from basic building blocks, but can not define fundamental types. Instead,
33681 standard identifiers are provided by @value{GDBN} for the fundamental
33682 types. The currently supported types are:
33691 Signed integer types holding the specified number of bits.
33698 Unsigned integer types holding the specified number of bits.
33702 Pointers to unspecified code and data. The program counter and
33703 any dedicated return address register may be marked as code
33704 pointers; printing a code pointer converts it into a symbolic
33705 address. The stack pointer and any dedicated address registers
33706 may be marked as data pointers.
33709 Single precision IEEE floating point.
33712 Double precision IEEE floating point.
33715 The 12-byte extended precision format used by ARM FPA registers.
33718 The 10-byte extended precision format used by x87 registers.
33721 32bit @sc{eflags} register used by x86.
33724 32bit @sc{mxcsr} register used by x86.
33728 @node Standard Target Features
33729 @section Standard Target Features
33730 @cindex target descriptions, standard features
33732 A target description must contain either no registers or all the
33733 target's registers. If the description contains no registers, then
33734 @value{GDBN} will assume a default register layout, selected based on
33735 the architecture. If the description contains any registers, the
33736 default layout will not be used; the standard registers must be
33737 described in the target description, in such a way that @value{GDBN}
33738 can recognize them.
33740 This is accomplished by giving specific names to feature elements
33741 which contain standard registers. @value{GDBN} will look for features
33742 with those names and verify that they contain the expected registers;
33743 if any known feature is missing required registers, or if any required
33744 feature is missing, @value{GDBN} will reject the target
33745 description. You can add additional registers to any of the
33746 standard features --- @value{GDBN} will display them just as if
33747 they were added to an unrecognized feature.
33749 This section lists the known features and their expected contents.
33750 Sample XML documents for these features are included in the
33751 @value{GDBN} source tree, in the directory @file{gdb/features}.
33753 Names recognized by @value{GDBN} should include the name of the
33754 company or organization which selected the name, and the overall
33755 architecture to which the feature applies; so e.g.@: the feature
33756 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
33758 The names of registers are not case sensitive for the purpose
33759 of recognizing standard features, but @value{GDBN} will only display
33760 registers using the capitalization used in the description.
33767 * PowerPC Features::
33772 @subsection ARM Features
33773 @cindex target descriptions, ARM features
33775 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
33776 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
33777 @samp{lr}, @samp{pc}, and @samp{cpsr}.
33779 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
33780 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
33782 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
33783 it should contain at least registers @samp{wR0} through @samp{wR15} and
33784 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
33785 @samp{wCSSF}, and @samp{wCASF} registers are optional.
33787 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
33788 should contain at least registers @samp{d0} through @samp{d15}. If
33789 they are present, @samp{d16} through @samp{d31} should also be included.
33790 @value{GDBN} will synthesize the single-precision registers from
33791 halves of the double-precision registers.
33793 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
33794 need to contain registers; it instructs @value{GDBN} to display the
33795 VFP double-precision registers as vectors and to synthesize the
33796 quad-precision registers from pairs of double-precision registers.
33797 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
33798 be present and include 32 double-precision registers.
33800 @node i386 Features
33801 @subsection i386 Features
33802 @cindex target descriptions, i386 features
33804 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
33805 targets. It should describe the following registers:
33809 @samp{eax} through @samp{edi} plus @samp{eip} for i386
33811 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
33813 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
33814 @samp{fs}, @samp{gs}
33816 @samp{st0} through @samp{st7}
33818 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
33819 @samp{foseg}, @samp{fooff} and @samp{fop}
33822 The register sets may be different, depending on the target.
33824 The @samp{org.gnu.gdb.i386.sse} feature is required. It should
33825 describe registers:
33829 @samp{xmm0} through @samp{xmm7} for i386
33831 @samp{xmm0} through @samp{xmm15} for amd64
33836 The @samp{org.gnu.gdb.i386.avx} feature is optional. It should
33837 describe the upper 128 bits of @sc{ymm} registers:
33841 @samp{ymm0h} through @samp{ymm7h} for i386
33843 @samp{ymm0h} through @samp{ymm15h} for amd64
33847 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
33848 describe a single register, @samp{orig_eax}.
33850 @node MIPS Features
33851 @subsection MIPS Features
33852 @cindex target descriptions, MIPS features
33854 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
33855 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
33856 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
33859 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
33860 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
33861 registers. They may be 32-bit or 64-bit depending on the target.
33863 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
33864 it may be optional in a future version of @value{GDBN}. It should
33865 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
33866 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
33868 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
33869 contain a single register, @samp{restart}, which is used by the
33870 Linux kernel to control restartable syscalls.
33872 @node M68K Features
33873 @subsection M68K Features
33874 @cindex target descriptions, M68K features
33877 @item @samp{org.gnu.gdb.m68k.core}
33878 @itemx @samp{org.gnu.gdb.coldfire.core}
33879 @itemx @samp{org.gnu.gdb.fido.core}
33880 One of those features must be always present.
33881 The feature that is present determines which flavor of m68k is
33882 used. The feature that is present should contain registers
33883 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
33884 @samp{sp}, @samp{ps} and @samp{pc}.
33886 @item @samp{org.gnu.gdb.coldfire.fp}
33887 This feature is optional. If present, it should contain registers
33888 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
33892 @node PowerPC Features
33893 @subsection PowerPC Features
33894 @cindex target descriptions, PowerPC features
33896 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
33897 targets. It should contain registers @samp{r0} through @samp{r31},
33898 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
33899 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
33901 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
33902 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
33904 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
33905 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
33908 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
33909 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
33910 will combine these registers with the floating point registers
33911 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
33912 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
33913 through @samp{vs63}, the set of vector registers for POWER7.
33915 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
33916 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
33917 @samp{spefscr}. SPE targets should provide 32-bit registers in
33918 @samp{org.gnu.gdb.power.core} and provide the upper halves in
33919 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
33920 these to present registers @samp{ev0} through @samp{ev31} to the
33923 @node Operating System Information
33924 @appendix Operating System Information
33925 @cindex operating system information
33931 Users of @value{GDBN} often wish to obtain information about the state of
33932 the operating system running on the target---for example the list of
33933 processes, or the list of open files. This section describes the
33934 mechanism that makes it possible. This mechanism is similar to the
33935 target features mechanism (@pxref{Target Descriptions}), but focuses
33936 on a different aspect of target.
33938 Operating system information is retrived from the target via the
33939 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
33940 read}). The object name in the request should be @samp{osdata}, and
33941 the @var{annex} identifies the data to be fetched.
33944 @appendixsection Process list
33945 @cindex operating system information, process list
33947 When requesting the process list, the @var{annex} field in the
33948 @samp{qXfer} request should be @samp{processes}. The returned data is
33949 an XML document. The formal syntax of this document is defined in
33950 @file{gdb/features/osdata.dtd}.
33952 An example document is:
33955 <?xml version="1.0"?>
33956 <!DOCTYPE target SYSTEM "osdata.dtd">
33957 <osdata type="processes">
33959 <column name="pid">1</column>
33960 <column name="user">root</column>
33961 <column name="command">/sbin/init</column>
33962 <column name="cores">1,2,3</column>
33967 Each item should include a column whose name is @samp{pid}. The value
33968 of that column should identify the process on the target. The
33969 @samp{user} and @samp{command} columns are optional, and will be
33970 displayed by @value{GDBN}. The @samp{cores} column, if present,
33971 should contain a comma-separated list of cores that this process
33972 is running on. Target may provide additional columns,
33973 which @value{GDBN} currently ignores.
33987 % I think something like @colophon should be in texinfo. In the
33989 \long\def\colophon{\hbox to0pt{}\vfill
33990 \centerline{The body of this manual is set in}
33991 \centerline{\fontname\tenrm,}
33992 \centerline{with headings in {\bf\fontname\tenbf}}
33993 \centerline{and examples in {\tt\fontname\tentt}.}
33994 \centerline{{\it\fontname\tenit\/},}
33995 \centerline{{\bf\fontname\tenbf}, and}
33996 \centerline{{\sl\fontname\tensl\/}}
33997 \centerline{are used for emphasis.}\vfill}
33999 % Blame: doc@cygnus.com, 1991.