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++}.
217 Support for D is partial. For information on D, see
221 Support for Modula-2 is partial. For information on Modula-2, see
222 @ref{Modula-2,,Modula-2}.
225 Debugging Pascal programs which use sets, subranges, file variables, or
226 nested functions does not currently work. @value{GDBN} does not support
227 entering expressions, printing values, or similar features using Pascal
231 @value{GDBN} can be used to debug programs written in Fortran, although
232 it may be necessary to refer to some variables with a trailing
235 @value{GDBN} can be used to debug programs written in Objective-C,
236 using either the Apple/NeXT or the GNU Objective-C runtime.
239 * Free Software:: Freely redistributable software
240 * Contributors:: Contributors to GDB
244 @unnumberedsec Free Software
246 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
247 General Public License
248 (GPL). The GPL gives you the freedom to copy or adapt a licensed
249 program---but every person getting a copy also gets with it the
250 freedom to modify that copy (which means that they must get access to
251 the source code), and the freedom to distribute further copies.
252 Typical software companies use copyrights to limit your freedoms; the
253 Free Software Foundation uses the GPL to preserve these freedoms.
255 Fundamentally, the General Public License is a license which says that
256 you have these freedoms and that you cannot take these freedoms away
259 @unnumberedsec Free Software Needs Free Documentation
261 The biggest deficiency in the free software community today is not in
262 the software---it is the lack of good free documentation that we can
263 include with the free software. Many of our most important
264 programs do not come with free reference manuals and free introductory
265 texts. Documentation is an essential part of any software package;
266 when an important free software package does not come with a free
267 manual and a free tutorial, that is a major gap. We have many such
270 Consider Perl, for instance. The tutorial manuals that people
271 normally use are non-free. How did this come about? Because the
272 authors of those manuals published them with restrictive terms---no
273 copying, no modification, source files not available---which exclude
274 them from the free software world.
276 That wasn't the first time this sort of thing happened, and it was far
277 from the last. Many times we have heard a GNU user eagerly describe a
278 manual that he is writing, his intended contribution to the community,
279 only to learn that he had ruined everything by signing a publication
280 contract to make it non-free.
282 Free documentation, like free software, is a matter of freedom, not
283 price. The problem with the non-free manual is not that publishers
284 charge a price for printed copies---that in itself is fine. (The Free
285 Software Foundation sells printed copies of manuals, too.) The
286 problem is the restrictions on the use of the manual. Free manuals
287 are available in source code form, and give you permission to copy and
288 modify. Non-free manuals do not allow this.
290 The criteria of freedom for a free manual are roughly the same as for
291 free software. Redistribution (including the normal kinds of
292 commercial redistribution) must be permitted, so that the manual can
293 accompany every copy of the program, both on-line and on paper.
295 Permission for modification of the technical content is crucial too.
296 When people modify the software, adding or changing features, if they
297 are conscientious they will change the manual too---so they can
298 provide accurate and clear documentation for the modified program. A
299 manual that leaves you no choice but to write a new manual to document
300 a changed version of the program is not really available to our
303 Some kinds of limits on the way modification is handled are
304 acceptable. For example, requirements to preserve the original
305 author's copyright notice, the distribution terms, or the list of
306 authors, are ok. It is also no problem to require modified versions
307 to include notice that they were modified. Even entire sections that
308 may not be deleted or changed are acceptable, as long as they deal
309 with nontechnical topics (like this one). These kinds of restrictions
310 are acceptable because they don't obstruct the community's normal use
313 However, it must be possible to modify all the @emph{technical}
314 content of the manual, and then distribute the result in all the usual
315 media, through all the usual channels. Otherwise, the restrictions
316 obstruct the use of the manual, it is not free, and we need another
317 manual to replace it.
319 Please spread the word about this issue. Our community continues to
320 lose manuals to proprietary publishing. If we spread the word that
321 free software needs free reference manuals and free tutorials, perhaps
322 the next person who wants to contribute by writing documentation will
323 realize, before it is too late, that only free manuals contribute to
324 the free software community.
326 If you are writing documentation, please insist on publishing it under
327 the GNU Free Documentation License or another free documentation
328 license. Remember that this decision requires your approval---you
329 don't have to let the publisher decide. Some commercial publishers
330 will use a free license if you insist, but they will not propose the
331 option; it is up to you to raise the issue and say firmly that this is
332 what you want. If the publisher you are dealing with refuses, please
333 try other publishers. If you're not sure whether a proposed license
334 is free, write to @email{licensing@@gnu.org}.
336 You can encourage commercial publishers to sell more free, copylefted
337 manuals and tutorials by buying them, and particularly by buying
338 copies from the publishers that paid for their writing or for major
339 improvements. Meanwhile, try to avoid buying non-free documentation
340 at all. Check the distribution terms of a manual before you buy it,
341 and insist that whoever seeks your business must respect your freedom.
342 Check the history of the book, and try to reward the publishers that
343 have paid or pay the authors to work on it.
345 The Free Software Foundation maintains a list of free documentation
346 published by other publishers, at
347 @url{http://www.fsf.org/doc/other-free-books.html}.
350 @unnumberedsec Contributors to @value{GDBN}
352 Richard Stallman was the original author of @value{GDBN}, and of many
353 other @sc{gnu} programs. Many others have contributed to its
354 development. This section attempts to credit major contributors. One
355 of the virtues of free software is that everyone is free to contribute
356 to it; with regret, we cannot actually acknowledge everyone here. The
357 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
358 blow-by-blow account.
360 Changes much prior to version 2.0 are lost in the mists of time.
363 @emph{Plea:} Additions to this section are particularly welcome. If you
364 or your friends (or enemies, to be evenhanded) have been unfairly
365 omitted from this list, we would like to add your names!
368 So that they may not regard their many labors as thankless, we
369 particularly thank those who shepherded @value{GDBN} through major
371 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
372 Jim Blandy (release 4.18);
373 Jason Molenda (release 4.17);
374 Stan Shebs (release 4.14);
375 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
376 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
377 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
378 Jim Kingdon (releases 3.5, 3.4, and 3.3);
379 and Randy Smith (releases 3.2, 3.1, and 3.0).
381 Richard Stallman, assisted at various times by Peter TerMaat, Chris
382 Hanson, and Richard Mlynarik, handled releases through 2.8.
384 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
385 in @value{GDBN}, with significant additional contributions from Per
386 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
387 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
388 much general update work leading to release 3.0).
390 @value{GDBN} uses the BFD subroutine library to examine multiple
391 object-file formats; BFD was a joint project of David V.
392 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
394 David Johnson wrote the original COFF support; Pace Willison did
395 the original support for encapsulated COFF.
397 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
399 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
400 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
402 Jean-Daniel Fekete contributed Sun 386i support.
403 Chris Hanson improved the HP9000 support.
404 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
405 David Johnson contributed Encore Umax support.
406 Jyrki Kuoppala contributed Altos 3068 support.
407 Jeff Law contributed HP PA and SOM support.
408 Keith Packard contributed NS32K support.
409 Doug Rabson contributed Acorn Risc Machine support.
410 Bob Rusk contributed Harris Nighthawk CX-UX support.
411 Chris Smith contributed Convex support (and Fortran debugging).
412 Jonathan Stone contributed Pyramid support.
413 Michael Tiemann contributed SPARC support.
414 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
415 Pace Willison contributed Intel 386 support.
416 Jay Vosburgh contributed Symmetry support.
417 Marko Mlinar contributed OpenRISC 1000 support.
419 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
421 Rich Schaefer and Peter Schauer helped with support of SunOS shared
424 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
425 about several machine instruction sets.
427 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
428 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
429 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
430 and RDI targets, respectively.
432 Brian Fox is the author of the readline libraries providing
433 command-line editing and command history.
435 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
436 Modula-2 support, and contributed the Languages chapter of this manual.
438 Fred Fish wrote most of the support for Unix System Vr4.
439 He also enhanced the command-completion support to cover C@t{++} overloaded
442 Hitachi America (now Renesas America), Ltd. sponsored the support for
443 H8/300, H8/500, and Super-H processors.
445 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
447 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
450 Toshiba sponsored the support for the TX39 Mips processor.
452 Matsushita sponsored the support for the MN10200 and MN10300 processors.
454 Fujitsu sponsored the support for SPARClite and FR30 processors.
456 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
459 Michael Snyder added support for tracepoints.
461 Stu Grossman wrote gdbserver.
463 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
464 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
466 The following people at the Hewlett-Packard Company contributed
467 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
468 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
469 compiler, and the Text User Interface (nee Terminal User Interface):
470 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
471 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
472 provided HP-specific information in this manual.
474 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
475 Robert Hoehne made significant contributions to the DJGPP port.
477 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
478 development since 1991. Cygnus engineers who have worked on @value{GDBN}
479 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
480 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
481 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
482 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
483 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
484 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
485 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
486 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
487 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
488 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
489 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
490 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
491 Zuhn have made contributions both large and small.
493 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
494 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
496 Jim Blandy added support for preprocessor macros, while working for Red
499 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
500 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
501 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
502 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
503 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
504 with the migration of old architectures to this new framework.
506 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
507 unwinder framework, this consisting of a fresh new design featuring
508 frame IDs, independent frame sniffers, and the sentinel frame. Mark
509 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
510 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
511 trad unwinders. The architecture-specific changes, each involving a
512 complete rewrite of the architecture's frame code, were carried out by
513 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
514 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
515 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
516 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
519 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
520 Tensilica, Inc.@: contributed support for Xtensa processors. Others
521 who have worked on the Xtensa port of @value{GDBN} in the past include
522 Steve Tjiang, John Newlin, and Scott Foehner.
524 Michael Eager and staff of Xilinx, Inc., contributed support for the
525 Xilinx MicroBlaze architecture.
528 @chapter A Sample @value{GDBN} Session
530 You can use this manual at your leisure to read all about @value{GDBN}.
531 However, a handful of commands are enough to get started using the
532 debugger. This chapter illustrates those commands.
535 In this sample session, we emphasize user input like this: @b{input},
536 to make it easier to pick out from the surrounding output.
539 @c FIXME: this example may not be appropriate for some configs, where
540 @c FIXME...primary interest is in remote use.
542 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
543 processor) exhibits the following bug: sometimes, when we change its
544 quote strings from the default, the commands used to capture one macro
545 definition within another stop working. In the following short @code{m4}
546 session, we define a macro @code{foo} which expands to @code{0000}; we
547 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
548 same thing. However, when we change the open quote string to
549 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
550 procedure fails to define a new synonym @code{baz}:
559 @b{define(bar,defn(`foo'))}
563 @b{changequote(<QUOTE>,<UNQUOTE>)}
565 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
568 m4: End of input: 0: fatal error: EOF in string
572 Let us use @value{GDBN} to try to see what is going on.
575 $ @b{@value{GDBP} m4}
576 @c FIXME: this falsifies the exact text played out, to permit smallbook
577 @c FIXME... format to come out better.
578 @value{GDBN} is free software and you are welcome to distribute copies
579 of it under certain conditions; type "show copying" to see
581 There is absolutely no warranty for @value{GDBN}; type "show warranty"
584 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
589 @value{GDBN} reads only enough symbol data to know where to find the
590 rest when needed; as a result, the first prompt comes up very quickly.
591 We now tell @value{GDBN} to use a narrower display width than usual, so
592 that examples fit in this manual.
595 (@value{GDBP}) @b{set width 70}
599 We need to see how the @code{m4} built-in @code{changequote} works.
600 Having looked at the source, we know the relevant subroutine is
601 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
602 @code{break} command.
605 (@value{GDBP}) @b{break m4_changequote}
606 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
610 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
611 control; as long as control does not reach the @code{m4_changequote}
612 subroutine, the program runs as usual:
615 (@value{GDBP}) @b{run}
616 Starting program: /work/Editorial/gdb/gnu/m4/m4
624 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
625 suspends execution of @code{m4}, displaying information about the
626 context where it stops.
629 @b{changequote(<QUOTE>,<UNQUOTE>)}
631 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
633 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
637 Now we use the command @code{n} (@code{next}) to advance execution to
638 the next line of the current function.
642 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
647 @code{set_quotes} looks like a promising subroutine. We can go into it
648 by using the command @code{s} (@code{step}) instead of @code{next}.
649 @code{step} goes to the next line to be executed in @emph{any}
650 subroutine, so it steps into @code{set_quotes}.
654 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
656 530 if (lquote != def_lquote)
660 The display that shows the subroutine where @code{m4} is now
661 suspended (and its arguments) is called a stack frame display. It
662 shows a summary of the stack. We can use the @code{backtrace}
663 command (which can also be spelled @code{bt}), to see where we are
664 in the stack as a whole: the @code{backtrace} command displays a
665 stack frame for each active subroutine.
668 (@value{GDBP}) @b{bt}
669 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
671 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
673 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
674 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
676 #4 0x79dc in expand_input () at macro.c:40
677 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
681 We step through a few more lines to see what happens. The first two
682 times, we can use @samp{s}; the next two times we use @code{n} to avoid
683 falling into the @code{xstrdup} subroutine.
687 0x3b5c 532 if (rquote != def_rquote)
689 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
690 def_lquote : xstrdup(lq);
692 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
695 538 len_lquote = strlen(rquote);
699 The last line displayed looks a little odd; we can examine the variables
700 @code{lquote} and @code{rquote} to see if they are in fact the new left
701 and right quotes we specified. We use the command @code{p}
702 (@code{print}) to see their values.
705 (@value{GDBP}) @b{p lquote}
706 $1 = 0x35d40 "<QUOTE>"
707 (@value{GDBP}) @b{p rquote}
708 $2 = 0x35d50 "<UNQUOTE>"
712 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
713 To look at some context, we can display ten lines of source
714 surrounding the current line with the @code{l} (@code{list}) command.
720 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
722 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
725 538 len_lquote = strlen(rquote);
726 539 len_rquote = strlen(lquote);
733 Let us step past the two lines that set @code{len_lquote} and
734 @code{len_rquote}, and then examine the values of those variables.
738 539 len_rquote = strlen(lquote);
741 (@value{GDBP}) @b{p len_lquote}
743 (@value{GDBP}) @b{p len_rquote}
748 That certainly looks wrong, assuming @code{len_lquote} and
749 @code{len_rquote} are meant to be the lengths of @code{lquote} and
750 @code{rquote} respectively. We can set them to better values using
751 the @code{p} command, since it can print the value of
752 any expression---and that expression can include subroutine calls and
756 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
758 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
763 Is that enough to fix the problem of using the new quotes with the
764 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
765 executing with the @code{c} (@code{continue}) command, and then try the
766 example that caused trouble initially:
772 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
779 Success! The new quotes now work just as well as the default ones. The
780 problem seems to have been just the two typos defining the wrong
781 lengths. We allow @code{m4} exit by giving it an EOF as input:
785 Program exited normally.
789 The message @samp{Program exited normally.} is from @value{GDBN}; it
790 indicates @code{m4} has finished executing. We can end our @value{GDBN}
791 session with the @value{GDBN} @code{quit} command.
794 (@value{GDBP}) @b{quit}
798 @chapter Getting In and Out of @value{GDBN}
800 This chapter discusses how to start @value{GDBN}, and how to get out of it.
804 type @samp{@value{GDBP}} to start @value{GDBN}.
806 type @kbd{quit} or @kbd{Ctrl-d} to exit.
810 * Invoking GDB:: How to start @value{GDBN}
811 * Quitting GDB:: How to quit @value{GDBN}
812 * Shell Commands:: How to use shell commands inside @value{GDBN}
813 * Logging Output:: How to log @value{GDBN}'s output to a file
817 @section Invoking @value{GDBN}
819 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
820 @value{GDBN} reads commands from the terminal until you tell it to exit.
822 You can also run @code{@value{GDBP}} with a variety of arguments and options,
823 to specify more of your debugging environment at the outset.
825 The command-line options described here are designed
826 to cover a variety of situations; in some environments, some of these
827 options may effectively be unavailable.
829 The most usual way to start @value{GDBN} is with one argument,
830 specifying an executable program:
833 @value{GDBP} @var{program}
837 You can also start with both an executable program and a core file
841 @value{GDBP} @var{program} @var{core}
844 You can, instead, specify a process ID as a second argument, if you want
845 to debug a running process:
848 @value{GDBP} @var{program} 1234
852 would attach @value{GDBN} to process @code{1234} (unless you also have a file
853 named @file{1234}; @value{GDBN} does check for a core file first).
855 Taking advantage of the second command-line argument requires a fairly
856 complete operating system; when you use @value{GDBN} as a remote
857 debugger attached to a bare board, there may not be any notion of
858 ``process'', and there is often no way to get a core dump. @value{GDBN}
859 will warn you if it is unable to attach or to read core dumps.
861 You can optionally have @code{@value{GDBP}} pass any arguments after the
862 executable file to the inferior using @code{--args}. This option stops
865 @value{GDBP} --args gcc -O2 -c foo.c
867 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
868 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
870 You can run @code{@value{GDBP}} without printing the front material, which describes
871 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
878 You can further control how @value{GDBN} starts up by using command-line
879 options. @value{GDBN} itself can remind you of the options available.
889 to display all available options and briefly describe their use
890 (@samp{@value{GDBP} -h} is a shorter equivalent).
892 All options and command line arguments you give are processed
893 in sequential order. The order makes a difference when the
894 @samp{-x} option is used.
898 * File Options:: Choosing files
899 * Mode Options:: Choosing modes
900 * Startup:: What @value{GDBN} does during startup
904 @subsection Choosing Files
906 When @value{GDBN} starts, it reads any arguments other than options as
907 specifying an executable file and core file (or process ID). This is
908 the same as if the arguments were specified by the @samp{-se} and
909 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
910 first argument that does not have an associated option flag as
911 equivalent to the @samp{-se} option followed by that argument; and the
912 second argument that does not have an associated option flag, if any, as
913 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
914 If the second argument begins with a decimal digit, @value{GDBN} will
915 first attempt to attach to it as a process, and if that fails, attempt
916 to open it as a corefile. If you have a corefile whose name begins with
917 a digit, you can prevent @value{GDBN} from treating it as a pid by
918 prefixing it with @file{./}, e.g.@: @file{./12345}.
920 If @value{GDBN} has not been configured to included core file support,
921 such as for most embedded targets, then it will complain about a second
922 argument and ignore it.
924 Many options have both long and short forms; both are shown in the
925 following list. @value{GDBN} also recognizes the long forms if you truncate
926 them, so long as enough of the option is present to be unambiguous.
927 (If you prefer, you can flag option arguments with @samp{--} rather
928 than @samp{-}, though we illustrate the more usual convention.)
930 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
931 @c way, both those who look for -foo and --foo in the index, will find
935 @item -symbols @var{file}
937 @cindex @code{--symbols}
939 Read symbol table from file @var{file}.
941 @item -exec @var{file}
943 @cindex @code{--exec}
945 Use file @var{file} as the executable file to execute when appropriate,
946 and for examining pure data in conjunction with a core dump.
950 Read symbol table from file @var{file} and use it as the executable
953 @item -core @var{file}
955 @cindex @code{--core}
957 Use file @var{file} as a core dump to examine.
959 @item -pid @var{number}
960 @itemx -p @var{number}
963 Connect to process ID @var{number}, as with the @code{attach} command.
965 @item -command @var{file}
967 @cindex @code{--command}
969 Execute commands from file @var{file}. The contents of this file is
970 evaluated exactly as the @code{source} command would.
971 @xref{Command Files,, Command files}.
973 @item -eval-command @var{command}
974 @itemx -ex @var{command}
975 @cindex @code{--eval-command}
977 Execute a single @value{GDBN} command.
979 This option may be used multiple times to call multiple commands. It may
980 also be interleaved with @samp{-command} as required.
983 @value{GDBP} -ex 'target sim' -ex 'load' \
984 -x setbreakpoints -ex 'run' a.out
987 @item -directory @var{directory}
988 @itemx -d @var{directory}
989 @cindex @code{--directory}
991 Add @var{directory} to the path to search for source and script files.
995 @cindex @code{--readnow}
997 Read each symbol file's entire symbol table immediately, rather than
998 the default, which is to read it incrementally as it is needed.
999 This makes startup slower, but makes future operations faster.
1004 @subsection Choosing Modes
1006 You can run @value{GDBN} in various alternative modes---for example, in
1007 batch mode or quiet mode.
1014 Do not execute commands found in any initialization files. Normally,
1015 @value{GDBN} executes the commands in these files after all the command
1016 options and arguments have been processed. @xref{Command Files,,Command
1022 @cindex @code{--quiet}
1023 @cindex @code{--silent}
1025 ``Quiet''. Do not print the introductory and copyright messages. These
1026 messages are also suppressed in batch mode.
1029 @cindex @code{--batch}
1030 Run in batch mode. Exit with status @code{0} after processing all the
1031 command files specified with @samp{-x} (and all commands from
1032 initialization files, if not inhibited with @samp{-n}). Exit with
1033 nonzero status if an error occurs in executing the @value{GDBN} commands
1034 in the command files. Batch mode also disables pagination;
1035 @pxref{Screen Size} and acts as if @kbd{set confirm off} were in
1036 effect (@pxref{Messages/Warnings}).
1038 Batch mode may be useful for running @value{GDBN} as a filter, for
1039 example to download and run a program on another computer; in order to
1040 make this more useful, the message
1043 Program exited normally.
1047 (which is ordinarily issued whenever a program running under
1048 @value{GDBN} control terminates) is not issued when running in batch
1052 @cindex @code{--batch-silent}
1053 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1054 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1055 unaffected). This is much quieter than @samp{-silent} and would be useless
1056 for an interactive session.
1058 This is particularly useful when using targets that give @samp{Loading section}
1059 messages, for example.
1061 Note that targets that give their output via @value{GDBN}, as opposed to
1062 writing directly to @code{stdout}, will also be made silent.
1064 @item -return-child-result
1065 @cindex @code{--return-child-result}
1066 The return code from @value{GDBN} will be the return code from the child
1067 process (the process being debugged), with the following exceptions:
1071 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1072 internal error. In this case the exit code is the same as it would have been
1073 without @samp{-return-child-result}.
1075 The user quits with an explicit value. E.g., @samp{quit 1}.
1077 The child process never runs, or is not allowed to terminate, in which case
1078 the exit code will be -1.
1081 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1082 when @value{GDBN} is being used as a remote program loader or simulator
1087 @cindex @code{--nowindows}
1089 ``No windows''. If @value{GDBN} comes with a graphical user interface
1090 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1091 interface. If no GUI is available, this option has no effect.
1095 @cindex @code{--windows}
1097 If @value{GDBN} includes a GUI, then this option requires it to be
1100 @item -cd @var{directory}
1102 Run @value{GDBN} using @var{directory} as its working directory,
1103 instead of the current directory.
1107 @cindex @code{--fullname}
1109 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1110 subprocess. It tells @value{GDBN} to output the full file name and line
1111 number in a standard, recognizable fashion each time a stack frame is
1112 displayed (which includes each time your program stops). This
1113 recognizable format looks like two @samp{\032} characters, followed by
1114 the file name, line number and character position separated by colons,
1115 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1116 @samp{\032} characters as a signal to display the source code for the
1120 @cindex @code{--epoch}
1121 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1122 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1123 routines so as to allow Epoch to display values of expressions in a
1126 @item -annotate @var{level}
1127 @cindex @code{--annotate}
1128 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1129 effect is identical to using @samp{set annotate @var{level}}
1130 (@pxref{Annotations}). The annotation @var{level} controls how much
1131 information @value{GDBN} prints together with its prompt, values of
1132 expressions, source lines, and other types of output. Level 0 is the
1133 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1134 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1135 that control @value{GDBN}, and level 2 has been deprecated.
1137 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1141 @cindex @code{--args}
1142 Change interpretation of command line so that arguments following the
1143 executable file are passed as command line arguments to the inferior.
1144 This option stops option processing.
1146 @item -baud @var{bps}
1148 @cindex @code{--baud}
1150 Set the line speed (baud rate or bits per second) of any serial
1151 interface used by @value{GDBN} for remote debugging.
1153 @item -l @var{timeout}
1155 Set the timeout (in seconds) of any communication used by @value{GDBN}
1156 for remote debugging.
1158 @item -tty @var{device}
1159 @itemx -t @var{device}
1160 @cindex @code{--tty}
1162 Run using @var{device} for your program's standard input and output.
1163 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1165 @c resolve the situation of these eventually
1167 @cindex @code{--tui}
1168 Activate the @dfn{Text User Interface} when starting. The Text User
1169 Interface manages several text windows on the terminal, showing
1170 source, assembly, registers and @value{GDBN} command outputs
1171 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1172 Text User Interface can be enabled by invoking the program
1173 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1174 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1177 @c @cindex @code{--xdb}
1178 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1179 @c For information, see the file @file{xdb_trans.html}, which is usually
1180 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1183 @item -interpreter @var{interp}
1184 @cindex @code{--interpreter}
1185 Use the interpreter @var{interp} for interface with the controlling
1186 program or device. This option is meant to be set by programs which
1187 communicate with @value{GDBN} using it as a back end.
1188 @xref{Interpreters, , Command Interpreters}.
1190 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1191 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1192 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1193 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1194 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1195 @sc{gdb/mi} interfaces are no longer supported.
1198 @cindex @code{--write}
1199 Open the executable and core files for both reading and writing. This
1200 is equivalent to the @samp{set write on} command inside @value{GDBN}
1204 @cindex @code{--statistics}
1205 This option causes @value{GDBN} to print statistics about time and
1206 memory usage after it completes each command and returns to the prompt.
1209 @cindex @code{--version}
1210 This option causes @value{GDBN} to print its version number and
1211 no-warranty blurb, and exit.
1216 @subsection What @value{GDBN} Does During Startup
1217 @cindex @value{GDBN} startup
1219 Here's the description of what @value{GDBN} does during session startup:
1223 Sets up the command interpreter as specified by the command line
1224 (@pxref{Mode Options, interpreter}).
1228 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1229 used when building @value{GDBN}; @pxref{System-wide configuration,
1230 ,System-wide configuration and settings}) and executes all the commands in
1234 Reads the init file (if any) in your home directory@footnote{On
1235 DOS/Windows systems, the home directory is the one pointed to by the
1236 @code{HOME} environment variable.} and executes all the commands in
1240 Processes command line options and operands.
1243 Reads and executes the commands from init file (if any) in the current
1244 working directory. This is only done if the current directory is
1245 different from your home directory. Thus, you can have more than one
1246 init file, one generic in your home directory, and another, specific
1247 to the program you are debugging, in the directory where you invoke
1251 Reads command files specified by the @samp{-x} option. @xref{Command
1252 Files}, for more details about @value{GDBN} command files.
1255 Reads the command history recorded in the @dfn{history file}.
1256 @xref{Command History}, for more details about the command history and the
1257 files where @value{GDBN} records it.
1260 Init files use the same syntax as @dfn{command files} (@pxref{Command
1261 Files}) and are processed by @value{GDBN} in the same way. The init
1262 file in your home directory can set options (such as @samp{set
1263 complaints}) that affect subsequent processing of command line options
1264 and operands. Init files are not executed if you use the @samp{-nx}
1265 option (@pxref{Mode Options, ,Choosing Modes}).
1267 To display the list of init files loaded by gdb at startup, you
1268 can use @kbd{gdb --help}.
1270 @cindex init file name
1271 @cindex @file{.gdbinit}
1272 @cindex @file{gdb.ini}
1273 The @value{GDBN} init files are normally called @file{.gdbinit}.
1274 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1275 the limitations of file names imposed by DOS filesystems. The Windows
1276 ports of @value{GDBN} use the standard name, but if they find a
1277 @file{gdb.ini} file, they warn you about that and suggest to rename
1278 the file to the standard name.
1282 @section Quitting @value{GDBN}
1283 @cindex exiting @value{GDBN}
1284 @cindex leaving @value{GDBN}
1287 @kindex quit @r{[}@var{expression}@r{]}
1288 @kindex q @r{(@code{quit})}
1289 @item quit @r{[}@var{expression}@r{]}
1291 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1292 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1293 do not supply @var{expression}, @value{GDBN} will terminate normally;
1294 otherwise it will terminate using the result of @var{expression} as the
1299 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1300 terminates the action of any @value{GDBN} command that is in progress and
1301 returns to @value{GDBN} command level. It is safe to type the interrupt
1302 character at any time because @value{GDBN} does not allow it to take effect
1303 until a time when it is safe.
1305 If you have been using @value{GDBN} to control an attached process or
1306 device, you can release it with the @code{detach} command
1307 (@pxref{Attach, ,Debugging an Already-running Process}).
1309 @node Shell Commands
1310 @section Shell Commands
1312 If you need to execute occasional shell commands during your
1313 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1314 just use the @code{shell} command.
1318 @cindex shell escape
1319 @item shell @var{command string}
1320 Invoke a standard shell to execute @var{command string}.
1321 If it exists, the environment variable @code{SHELL} determines which
1322 shell to run. Otherwise @value{GDBN} uses the default shell
1323 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1326 The utility @code{make} is often needed in development environments.
1327 You do not have to use the @code{shell} command for this purpose in
1332 @cindex calling make
1333 @item make @var{make-args}
1334 Execute the @code{make} program with the specified
1335 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1338 @node Logging Output
1339 @section Logging Output
1340 @cindex logging @value{GDBN} output
1341 @cindex save @value{GDBN} output to a file
1343 You may want to save the output of @value{GDBN} commands to a file.
1344 There are several commands to control @value{GDBN}'s logging.
1348 @item set logging on
1350 @item set logging off
1352 @cindex logging file name
1353 @item set logging file @var{file}
1354 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1355 @item set logging overwrite [on|off]
1356 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1357 you want @code{set logging on} to overwrite the logfile instead.
1358 @item set logging redirect [on|off]
1359 By default, @value{GDBN} output will go to both the terminal and the logfile.
1360 Set @code{redirect} if you want output to go only to the log file.
1361 @kindex show logging
1363 Show the current values of the logging settings.
1367 @chapter @value{GDBN} Commands
1369 You can abbreviate a @value{GDBN} command to the first few letters of the command
1370 name, if that abbreviation is unambiguous; and you can repeat certain
1371 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1372 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1373 show you the alternatives available, if there is more than one possibility).
1376 * Command Syntax:: How to give commands to @value{GDBN}
1377 * Completion:: Command completion
1378 * Help:: How to ask @value{GDBN} for help
1381 @node Command Syntax
1382 @section Command Syntax
1384 A @value{GDBN} command is a single line of input. There is no limit on
1385 how long it can be. It starts with a command name, which is followed by
1386 arguments whose meaning depends on the command name. For example, the
1387 command @code{step} accepts an argument which is the number of times to
1388 step, as in @samp{step 5}. You can also use the @code{step} command
1389 with no arguments. Some commands do not allow any arguments.
1391 @cindex abbreviation
1392 @value{GDBN} command names may always be truncated if that abbreviation is
1393 unambiguous. Other possible command abbreviations are listed in the
1394 documentation for individual commands. In some cases, even ambiguous
1395 abbreviations are allowed; for example, @code{s} is specially defined as
1396 equivalent to @code{step} even though there are other commands whose
1397 names start with @code{s}. You can test abbreviations by using them as
1398 arguments to the @code{help} command.
1400 @cindex repeating commands
1401 @kindex RET @r{(repeat last command)}
1402 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1403 repeat the previous command. Certain commands (for example, @code{run})
1404 will not repeat this way; these are commands whose unintentional
1405 repetition might cause trouble and which you are unlikely to want to
1406 repeat. User-defined commands can disable this feature; see
1407 @ref{Define, dont-repeat}.
1409 The @code{list} and @code{x} commands, when you repeat them with
1410 @key{RET}, construct new arguments rather than repeating
1411 exactly as typed. This permits easy scanning of source or memory.
1413 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1414 output, in a way similar to the common utility @code{more}
1415 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1416 @key{RET} too many in this situation, @value{GDBN} disables command
1417 repetition after any command that generates this sort of display.
1419 @kindex # @r{(a comment)}
1421 Any text from a @kbd{#} to the end of the line is a comment; it does
1422 nothing. This is useful mainly in command files (@pxref{Command
1423 Files,,Command Files}).
1425 @cindex repeating command sequences
1426 @kindex Ctrl-o @r{(operate-and-get-next)}
1427 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1428 commands. This command accepts the current line, like @key{RET}, and
1429 then fetches the next line relative to the current line from the history
1433 @section Command Completion
1436 @cindex word completion
1437 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1438 only one possibility; it can also show you what the valid possibilities
1439 are for the next word in a command, at any time. This works for @value{GDBN}
1440 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1442 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1443 of a word. If there is only one possibility, @value{GDBN} fills in the
1444 word, and waits for you to finish the command (or press @key{RET} to
1445 enter it). For example, if you type
1447 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1448 @c complete accuracy in these examples; space introduced for clarity.
1449 @c If texinfo enhancements make it unnecessary, it would be nice to
1450 @c replace " @key" by "@key" in the following...
1452 (@value{GDBP}) info bre @key{TAB}
1456 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1457 the only @code{info} subcommand beginning with @samp{bre}:
1460 (@value{GDBP}) info breakpoints
1464 You can either press @key{RET} at this point, to run the @code{info
1465 breakpoints} command, or backspace and enter something else, if
1466 @samp{breakpoints} does not look like the command you expected. (If you
1467 were sure you wanted @code{info breakpoints} in the first place, you
1468 might as well just type @key{RET} immediately after @samp{info bre},
1469 to exploit command abbreviations rather than command completion).
1471 If there is more than one possibility for the next word when you press
1472 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1473 characters and try again, or just press @key{TAB} a second time;
1474 @value{GDBN} displays all the possible completions for that word. For
1475 example, you might want to set a breakpoint on a subroutine whose name
1476 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1477 just sounds the bell. Typing @key{TAB} again displays all the
1478 function names in your program that begin with those characters, for
1482 (@value{GDBP}) b make_ @key{TAB}
1483 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1484 make_a_section_from_file make_environ
1485 make_abs_section make_function_type
1486 make_blockvector make_pointer_type
1487 make_cleanup make_reference_type
1488 make_command make_symbol_completion_list
1489 (@value{GDBP}) b make_
1493 After displaying the available possibilities, @value{GDBN} copies your
1494 partial input (@samp{b make_} in the example) so you can finish the
1497 If you just want to see the list of alternatives in the first place, you
1498 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1499 means @kbd{@key{META} ?}. You can type this either by holding down a
1500 key designated as the @key{META} shift on your keyboard (if there is
1501 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1503 @cindex quotes in commands
1504 @cindex completion of quoted strings
1505 Sometimes the string you need, while logically a ``word'', may contain
1506 parentheses or other characters that @value{GDBN} normally excludes from
1507 its notion of a word. To permit word completion to work in this
1508 situation, you may enclose words in @code{'} (single quote marks) in
1509 @value{GDBN} commands.
1511 The most likely situation where you might need this is in typing the
1512 name of a C@t{++} function. This is because C@t{++} allows function
1513 overloading (multiple definitions of the same function, distinguished
1514 by argument type). For example, when you want to set a breakpoint you
1515 may need to distinguish whether you mean the version of @code{name}
1516 that takes an @code{int} parameter, @code{name(int)}, or the version
1517 that takes a @code{float} parameter, @code{name(float)}. To use the
1518 word-completion facilities in this situation, type a single quote
1519 @code{'} at the beginning of the function name. This alerts
1520 @value{GDBN} that it may need to consider more information than usual
1521 when you press @key{TAB} or @kbd{M-?} to request word completion:
1524 (@value{GDBP}) b 'bubble( @kbd{M-?}
1525 bubble(double,double) bubble(int,int)
1526 (@value{GDBP}) b 'bubble(
1529 In some cases, @value{GDBN} can tell that completing a name requires using
1530 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1531 completing as much as it can) if you do not type the quote in the first
1535 (@value{GDBP}) b bub @key{TAB}
1536 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1537 (@value{GDBP}) b 'bubble(
1541 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1542 you have not yet started typing the argument list when you ask for
1543 completion on an overloaded symbol.
1545 For more information about overloaded functions, see @ref{C Plus Plus
1546 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1547 overload-resolution off} to disable overload resolution;
1548 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1550 @cindex completion of structure field names
1551 @cindex structure field name completion
1552 @cindex completion of union field names
1553 @cindex union field name completion
1554 When completing in an expression which looks up a field in a
1555 structure, @value{GDBN} also tries@footnote{The completer can be
1556 confused by certain kinds of invalid expressions. Also, it only
1557 examines the static type of the expression, not the dynamic type.} to
1558 limit completions to the field names available in the type of the
1562 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1563 magic to_delete to_fputs to_put to_rewind
1564 to_data to_flush to_isatty to_read to_write
1568 This is because the @code{gdb_stdout} is a variable of the type
1569 @code{struct ui_file} that is defined in @value{GDBN} sources as
1576 ui_file_flush_ftype *to_flush;
1577 ui_file_write_ftype *to_write;
1578 ui_file_fputs_ftype *to_fputs;
1579 ui_file_read_ftype *to_read;
1580 ui_file_delete_ftype *to_delete;
1581 ui_file_isatty_ftype *to_isatty;
1582 ui_file_rewind_ftype *to_rewind;
1583 ui_file_put_ftype *to_put;
1590 @section Getting Help
1591 @cindex online documentation
1594 You can always ask @value{GDBN} itself for information on its commands,
1595 using the command @code{help}.
1598 @kindex h @r{(@code{help})}
1601 You can use @code{help} (abbreviated @code{h}) with no arguments to
1602 display a short list of named classes of commands:
1606 List of classes of commands:
1608 aliases -- Aliases of other commands
1609 breakpoints -- Making program stop at certain points
1610 data -- Examining data
1611 files -- Specifying and examining files
1612 internals -- Maintenance commands
1613 obscure -- Obscure features
1614 running -- Running the program
1615 stack -- Examining the stack
1616 status -- Status inquiries
1617 support -- Support facilities
1618 tracepoints -- Tracing of program execution without
1619 stopping the program
1620 user-defined -- User-defined commands
1622 Type "help" followed by a class name for a list of
1623 commands in that class.
1624 Type "help" followed by command name for full
1626 Command name abbreviations are allowed if unambiguous.
1629 @c the above line break eliminates huge line overfull...
1631 @item help @var{class}
1632 Using one of the general help classes as an argument, you can get a
1633 list of the individual commands in that class. For example, here is the
1634 help display for the class @code{status}:
1637 (@value{GDBP}) help status
1642 @c Line break in "show" line falsifies real output, but needed
1643 @c to fit in smallbook page size.
1644 info -- Generic command for showing things
1645 about the program being debugged
1646 show -- Generic command for showing things
1649 Type "help" followed by command name for full
1651 Command name abbreviations are allowed if unambiguous.
1655 @item help @var{command}
1656 With a command name as @code{help} argument, @value{GDBN} displays a
1657 short paragraph on how to use that command.
1660 @item apropos @var{args}
1661 The @code{apropos} command searches through all of the @value{GDBN}
1662 commands, and their documentation, for the regular expression specified in
1663 @var{args}. It prints out all matches found. For example:
1674 set symbol-reloading -- Set dynamic symbol table reloading
1675 multiple times in one run
1676 show symbol-reloading -- Show dynamic symbol table reloading
1677 multiple times in one run
1682 @item complete @var{args}
1683 The @code{complete @var{args}} command lists all the possible completions
1684 for the beginning of a command. Use @var{args} to specify the beginning of the
1685 command you want completed. For example:
1691 @noindent results in:
1702 @noindent This is intended for use by @sc{gnu} Emacs.
1705 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1706 and @code{show} to inquire about the state of your program, or the state
1707 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1708 manual introduces each of them in the appropriate context. The listings
1709 under @code{info} and under @code{show} in the Index point to
1710 all the sub-commands. @xref{Index}.
1715 @kindex i @r{(@code{info})}
1717 This command (abbreviated @code{i}) is for describing the state of your
1718 program. For example, you can show the arguments passed to a function
1719 with @code{info args}, list the registers currently in use with @code{info
1720 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1721 You can get a complete list of the @code{info} sub-commands with
1722 @w{@code{help info}}.
1726 You can assign the result of an expression to an environment variable with
1727 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1728 @code{set prompt $}.
1732 In contrast to @code{info}, @code{show} is for describing the state of
1733 @value{GDBN} itself.
1734 You can change most of the things you can @code{show}, by using the
1735 related command @code{set}; for example, you can control what number
1736 system is used for displays with @code{set radix}, or simply inquire
1737 which is currently in use with @code{show radix}.
1740 To display all the settable parameters and their current
1741 values, you can use @code{show} with no arguments; you may also use
1742 @code{info set}. Both commands produce the same display.
1743 @c FIXME: "info set" violates the rule that "info" is for state of
1744 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1745 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1749 Here are three miscellaneous @code{show} subcommands, all of which are
1750 exceptional in lacking corresponding @code{set} commands:
1753 @kindex show version
1754 @cindex @value{GDBN} version number
1756 Show what version of @value{GDBN} is running. You should include this
1757 information in @value{GDBN} bug-reports. If multiple versions of
1758 @value{GDBN} are in use at your site, you may need to determine which
1759 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1760 commands are introduced, and old ones may wither away. Also, many
1761 system vendors ship variant versions of @value{GDBN}, and there are
1762 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1763 The version number is the same as the one announced when you start
1766 @kindex show copying
1767 @kindex info copying
1768 @cindex display @value{GDBN} copyright
1771 Display information about permission for copying @value{GDBN}.
1773 @kindex show warranty
1774 @kindex info warranty
1776 @itemx info warranty
1777 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1778 if your version of @value{GDBN} comes with one.
1783 @chapter Running Programs Under @value{GDBN}
1785 When you run a program under @value{GDBN}, you must first generate
1786 debugging information when you compile it.
1788 You may start @value{GDBN} with its arguments, if any, in an environment
1789 of your choice. If you are doing native debugging, you may redirect
1790 your program's input and output, debug an already running process, or
1791 kill a child process.
1794 * Compilation:: Compiling for debugging
1795 * Starting:: Starting your program
1796 * Arguments:: Your program's arguments
1797 * Environment:: Your program's environment
1799 * Working Directory:: Your program's working directory
1800 * Input/Output:: Your program's input and output
1801 * Attach:: Debugging an already-running process
1802 * Kill Process:: Killing the child process
1804 * Inferiors and Programs:: Debugging multiple inferiors and programs
1805 * Threads:: Debugging programs with multiple threads
1806 * Forks:: Debugging forks
1807 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1811 @section Compiling for Debugging
1813 In order to debug a program effectively, you need to generate
1814 debugging information when you compile it. This debugging information
1815 is stored in the object file; it describes the data type of each
1816 variable or function and the correspondence between source line numbers
1817 and addresses in the executable code.
1819 To request debugging information, specify the @samp{-g} option when you run
1822 Programs that are to be shipped to your customers are compiled with
1823 optimizations, using the @samp{-O} compiler option. However, some
1824 compilers are unable to handle the @samp{-g} and @samp{-O} options
1825 together. Using those compilers, you cannot generate optimized
1826 executables containing debugging information.
1828 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1829 without @samp{-O}, making it possible to debug optimized code. We
1830 recommend that you @emph{always} use @samp{-g} whenever you compile a
1831 program. You may think your program is correct, but there is no sense
1832 in pushing your luck. For more information, see @ref{Optimized Code}.
1834 Older versions of the @sc{gnu} C compiler permitted a variant option
1835 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1836 format; if your @sc{gnu} C compiler has this option, do not use it.
1838 @value{GDBN} knows about preprocessor macros and can show you their
1839 expansion (@pxref{Macros}). Most compilers do not include information
1840 about preprocessor macros in the debugging information if you specify
1841 the @option{-g} flag alone, because this information is rather large.
1842 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1843 provides macro information if you specify the options
1844 @option{-gdwarf-2} and @option{-g3}; the former option requests
1845 debugging information in the Dwarf 2 format, and the latter requests
1846 ``extra information''. In the future, we hope to find more compact
1847 ways to represent macro information, so that it can be included with
1852 @section Starting your Program
1858 @kindex r @r{(@code{run})}
1861 Use the @code{run} command to start your program under @value{GDBN}.
1862 You must first specify the program name (except on VxWorks) with an
1863 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1864 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1865 (@pxref{Files, ,Commands to Specify Files}).
1869 If you are running your program in an execution environment that
1870 supports processes, @code{run} creates an inferior process and makes
1871 that process run your program. In some environments without processes,
1872 @code{run} jumps to the start of your program. Other targets,
1873 like @samp{remote}, are always running. If you get an error
1874 message like this one:
1877 The "remote" target does not support "run".
1878 Try "help target" or "continue".
1882 then use @code{continue} to run your program. You may need @code{load}
1883 first (@pxref{load}).
1885 The execution of a program is affected by certain information it
1886 receives from its superior. @value{GDBN} provides ways to specify this
1887 information, which you must do @emph{before} starting your program. (You
1888 can change it after starting your program, but such changes only affect
1889 your program the next time you start it.) This information may be
1890 divided into four categories:
1893 @item The @emph{arguments.}
1894 Specify the arguments to give your program as the arguments of the
1895 @code{run} command. If a shell is available on your target, the shell
1896 is used to pass the arguments, so that you may use normal conventions
1897 (such as wildcard expansion or variable substitution) in describing
1899 In Unix systems, you can control which shell is used with the
1900 @code{SHELL} environment variable.
1901 @xref{Arguments, ,Your Program's Arguments}.
1903 @item The @emph{environment.}
1904 Your program normally inherits its environment from @value{GDBN}, but you can
1905 use the @value{GDBN} commands @code{set environment} and @code{unset
1906 environment} to change parts of the environment that affect
1907 your program. @xref{Environment, ,Your Program's Environment}.
1909 @item The @emph{working directory.}
1910 Your program inherits its working directory from @value{GDBN}. You can set
1911 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1912 @xref{Working Directory, ,Your Program's Working Directory}.
1914 @item The @emph{standard input and output.}
1915 Your program normally uses the same device for standard input and
1916 standard output as @value{GDBN} is using. You can redirect input and output
1917 in the @code{run} command line, or you can use the @code{tty} command to
1918 set a different device for your program.
1919 @xref{Input/Output, ,Your Program's Input and Output}.
1922 @emph{Warning:} While input and output redirection work, you cannot use
1923 pipes to pass the output of the program you are debugging to another
1924 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1928 When you issue the @code{run} command, your program begins to execute
1929 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1930 of how to arrange for your program to stop. Once your program has
1931 stopped, you may call functions in your program, using the @code{print}
1932 or @code{call} commands. @xref{Data, ,Examining Data}.
1934 If the modification time of your symbol file has changed since the last
1935 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1936 table, and reads it again. When it does this, @value{GDBN} tries to retain
1937 your current breakpoints.
1942 @cindex run to main procedure
1943 The name of the main procedure can vary from language to language.
1944 With C or C@t{++}, the main procedure name is always @code{main}, but
1945 other languages such as Ada do not require a specific name for their
1946 main procedure. The debugger provides a convenient way to start the
1947 execution of the program and to stop at the beginning of the main
1948 procedure, depending on the language used.
1950 The @samp{start} command does the equivalent of setting a temporary
1951 breakpoint at the beginning of the main procedure and then invoking
1952 the @samp{run} command.
1954 @cindex elaboration phase
1955 Some programs contain an @dfn{elaboration} phase where some startup code is
1956 executed before the main procedure is called. This depends on the
1957 languages used to write your program. In C@t{++}, for instance,
1958 constructors for static and global objects are executed before
1959 @code{main} is called. It is therefore possible that the debugger stops
1960 before reaching the main procedure. However, the temporary breakpoint
1961 will remain to halt execution.
1963 Specify the arguments to give to your program as arguments to the
1964 @samp{start} command. These arguments will be given verbatim to the
1965 underlying @samp{run} command. Note that the same arguments will be
1966 reused if no argument is provided during subsequent calls to
1967 @samp{start} or @samp{run}.
1969 It is sometimes necessary to debug the program during elaboration. In
1970 these cases, using the @code{start} command would stop the execution of
1971 your program too late, as the program would have already completed the
1972 elaboration phase. Under these circumstances, insert breakpoints in your
1973 elaboration code before running your program.
1975 @kindex set exec-wrapper
1976 @item set exec-wrapper @var{wrapper}
1977 @itemx show exec-wrapper
1978 @itemx unset exec-wrapper
1979 When @samp{exec-wrapper} is set, the specified wrapper is used to
1980 launch programs for debugging. @value{GDBN} starts your program
1981 with a shell command of the form @kbd{exec @var{wrapper}
1982 @var{program}}. Quoting is added to @var{program} and its
1983 arguments, but not to @var{wrapper}, so you should add quotes if
1984 appropriate for your shell. The wrapper runs until it executes
1985 your program, and then @value{GDBN} takes control.
1987 You can use any program that eventually calls @code{execve} with
1988 its arguments as a wrapper. Several standard Unix utilities do
1989 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
1990 with @code{exec "$@@"} will also work.
1992 For example, you can use @code{env} to pass an environment variable to
1993 the debugged program, without setting the variable in your shell's
1997 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2001 This command is available when debugging locally on most targets, excluding
2002 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2004 @kindex set disable-randomization
2005 @item set disable-randomization
2006 @itemx set disable-randomization on
2007 This option (enabled by default in @value{GDBN}) will turn off the native
2008 randomization of the virtual address space of the started program. This option
2009 is useful for multiple debugging sessions to make the execution better
2010 reproducible and memory addresses reusable across debugging sessions.
2012 This feature is implemented only on @sc{gnu}/Linux. You can get the same
2016 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2019 @item set disable-randomization off
2020 Leave the behavior of the started executable unchanged. Some bugs rear their
2021 ugly heads only when the program is loaded at certain addresses. If your bug
2022 disappears when you run the program under @value{GDBN}, that might be because
2023 @value{GDBN} by default disables the address randomization on platforms, such
2024 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2025 disable-randomization off} to try to reproduce such elusive bugs.
2027 The virtual address space randomization is implemented only on @sc{gnu}/Linux.
2028 It protects the programs against some kinds of security attacks. In these
2029 cases the attacker needs to know the exact location of a concrete executable
2030 code. Randomizing its location makes it impossible to inject jumps misusing
2031 a code at its expected addresses.
2033 Prelinking shared libraries provides a startup performance advantage but it
2034 makes addresses in these libraries predictable for privileged processes by
2035 having just unprivileged access at the target system. Reading the shared
2036 library binary gives enough information for assembling the malicious code
2037 misusing it. Still even a prelinked shared library can get loaded at a new
2038 random address just requiring the regular relocation process during the
2039 startup. Shared libraries not already prelinked are always loaded at
2040 a randomly chosen address.
2042 Position independent executables (PIE) contain position independent code
2043 similar to the shared libraries and therefore such executables get loaded at
2044 a randomly chosen address upon startup. PIE executables always load even
2045 already prelinked shared libraries at a random address. You can build such
2046 executable using @command{gcc -fPIE -pie}.
2048 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2049 (as long as the randomization is enabled).
2051 @item show disable-randomization
2052 Show the current setting of the explicit disable of the native randomization of
2053 the virtual address space of the started program.
2058 @section Your Program's Arguments
2060 @cindex arguments (to your program)
2061 The arguments to your program can be specified by the arguments of the
2063 They are passed to a shell, which expands wildcard characters and
2064 performs redirection of I/O, and thence to your program. Your
2065 @code{SHELL} environment variable (if it exists) specifies what shell
2066 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2067 the default shell (@file{/bin/sh} on Unix).
2069 On non-Unix systems, the program is usually invoked directly by
2070 @value{GDBN}, which emulates I/O redirection via the appropriate system
2071 calls, and the wildcard characters are expanded by the startup code of
2072 the program, not by the shell.
2074 @code{run} with no arguments uses the same arguments used by the previous
2075 @code{run}, or those set by the @code{set args} command.
2080 Specify the arguments to be used the next time your program is run. If
2081 @code{set args} has no arguments, @code{run} executes your program
2082 with no arguments. Once you have run your program with arguments,
2083 using @code{set args} before the next @code{run} is the only way to run
2084 it again without arguments.
2088 Show the arguments to give your program when it is started.
2092 @section Your Program's Environment
2094 @cindex environment (of your program)
2095 The @dfn{environment} consists of a set of environment variables and
2096 their values. Environment variables conventionally record such things as
2097 your user name, your home directory, your terminal type, and your search
2098 path for programs to run. Usually you set up environment variables with
2099 the shell and they are inherited by all the other programs you run. When
2100 debugging, it can be useful to try running your program with a modified
2101 environment without having to start @value{GDBN} over again.
2105 @item path @var{directory}
2106 Add @var{directory} to the front of the @code{PATH} environment variable
2107 (the search path for executables) that will be passed to your program.
2108 The value of @code{PATH} used by @value{GDBN} does not change.
2109 You may specify several directory names, separated by whitespace or by a
2110 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2111 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2112 is moved to the front, so it is searched sooner.
2114 You can use the string @samp{$cwd} to refer to whatever is the current
2115 working directory at the time @value{GDBN} searches the path. If you
2116 use @samp{.} instead, it refers to the directory where you executed the
2117 @code{path} command. @value{GDBN} replaces @samp{.} in the
2118 @var{directory} argument (with the current path) before adding
2119 @var{directory} to the search path.
2120 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2121 @c document that, since repeating it would be a no-op.
2125 Display the list of search paths for executables (the @code{PATH}
2126 environment variable).
2128 @kindex show environment
2129 @item show environment @r{[}@var{varname}@r{]}
2130 Print the value of environment variable @var{varname} to be given to
2131 your program when it starts. If you do not supply @var{varname},
2132 print the names and values of all environment variables to be given to
2133 your program. You can abbreviate @code{environment} as @code{env}.
2135 @kindex set environment
2136 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2137 Set environment variable @var{varname} to @var{value}. The value
2138 changes for your program only, not for @value{GDBN} itself. @var{value} may
2139 be any string; the values of environment variables are just strings, and
2140 any interpretation is supplied by your program itself. The @var{value}
2141 parameter is optional; if it is eliminated, the variable is set to a
2143 @c "any string" here does not include leading, trailing
2144 @c blanks. Gnu asks: does anyone care?
2146 For example, this command:
2153 tells the debugged program, when subsequently run, that its user is named
2154 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2155 are not actually required.)
2157 @kindex unset environment
2158 @item unset environment @var{varname}
2159 Remove variable @var{varname} from the environment to be passed to your
2160 program. This is different from @samp{set env @var{varname} =};
2161 @code{unset environment} removes the variable from the environment,
2162 rather than assigning it an empty value.
2165 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2167 by your @code{SHELL} environment variable if it exists (or
2168 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2169 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2170 @file{.bashrc} for BASH---any variables you set in that file affect
2171 your program. You may wish to move setting of environment variables to
2172 files that are only run when you sign on, such as @file{.login} or
2175 @node Working Directory
2176 @section Your Program's Working Directory
2178 @cindex working directory (of your program)
2179 Each time you start your program with @code{run}, it inherits its
2180 working directory from the current working directory of @value{GDBN}.
2181 The @value{GDBN} working directory is initially whatever it inherited
2182 from its parent process (typically the shell), but you can specify a new
2183 working directory in @value{GDBN} with the @code{cd} command.
2185 The @value{GDBN} working directory also serves as a default for the commands
2186 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2191 @cindex change working directory
2192 @item cd @var{directory}
2193 Set the @value{GDBN} working directory to @var{directory}.
2197 Print the @value{GDBN} working directory.
2200 It is generally impossible to find the current working directory of
2201 the process being debugged (since a program can change its directory
2202 during its run). If you work on a system where @value{GDBN} is
2203 configured with the @file{/proc} support, you can use the @code{info
2204 proc} command (@pxref{SVR4 Process Information}) to find out the
2205 current working directory of the debuggee.
2208 @section Your Program's Input and Output
2213 By default, the program you run under @value{GDBN} does input and output to
2214 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2215 to its own terminal modes to interact with you, but it records the terminal
2216 modes your program was using and switches back to them when you continue
2217 running your program.
2220 @kindex info terminal
2222 Displays information recorded by @value{GDBN} about the terminal modes your
2226 You can redirect your program's input and/or output using shell
2227 redirection with the @code{run} command. For example,
2234 starts your program, diverting its output to the file @file{outfile}.
2237 @cindex controlling terminal
2238 Another way to specify where your program should do input and output is
2239 with the @code{tty} command. This command accepts a file name as
2240 argument, and causes this file to be the default for future @code{run}
2241 commands. It also resets the controlling terminal for the child
2242 process, for future @code{run} commands. For example,
2249 directs that processes started with subsequent @code{run} commands
2250 default to do input and output on the terminal @file{/dev/ttyb} and have
2251 that as their controlling terminal.
2253 An explicit redirection in @code{run} overrides the @code{tty} command's
2254 effect on the input/output device, but not its effect on the controlling
2257 When you use the @code{tty} command or redirect input in the @code{run}
2258 command, only the input @emph{for your program} is affected. The input
2259 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2260 for @code{set inferior-tty}.
2262 @cindex inferior tty
2263 @cindex set inferior controlling terminal
2264 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2265 display the name of the terminal that will be used for future runs of your
2269 @item set inferior-tty /dev/ttyb
2270 @kindex set inferior-tty
2271 Set the tty for the program being debugged to /dev/ttyb.
2273 @item show inferior-tty
2274 @kindex show inferior-tty
2275 Show the current tty for the program being debugged.
2279 @section Debugging an Already-running Process
2284 @item attach @var{process-id}
2285 This command attaches to a running process---one that was started
2286 outside @value{GDBN}. (@code{info files} shows your active
2287 targets.) The command takes as argument a process ID. The usual way to
2288 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2289 or with the @samp{jobs -l} shell command.
2291 @code{attach} does not repeat if you press @key{RET} a second time after
2292 executing the command.
2295 To use @code{attach}, your program must be running in an environment
2296 which supports processes; for example, @code{attach} does not work for
2297 programs on bare-board targets that lack an operating system. You must
2298 also have permission to send the process a signal.
2300 When you use @code{attach}, the debugger finds the program running in
2301 the process first by looking in the current working directory, then (if
2302 the program is not found) by using the source file search path
2303 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2304 the @code{file} command to load the program. @xref{Files, ,Commands to
2307 The first thing @value{GDBN} does after arranging to debug the specified
2308 process is to stop it. You can examine and modify an attached process
2309 with all the @value{GDBN} commands that are ordinarily available when
2310 you start processes with @code{run}. You can insert breakpoints; you
2311 can step and continue; you can modify storage. If you would rather the
2312 process continue running, you may use the @code{continue} command after
2313 attaching @value{GDBN} to the process.
2318 When you have finished debugging the attached process, you can use the
2319 @code{detach} command to release it from @value{GDBN} control. Detaching
2320 the process continues its execution. After the @code{detach} command,
2321 that process and @value{GDBN} become completely independent once more, and you
2322 are ready to @code{attach} another process or start one with @code{run}.
2323 @code{detach} does not repeat if you press @key{RET} again after
2324 executing the command.
2327 If you exit @value{GDBN} while you have an attached process, you detach
2328 that process. If you use the @code{run} command, you kill that process.
2329 By default, @value{GDBN} asks for confirmation if you try to do either of these
2330 things; you can control whether or not you need to confirm by using the
2331 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2335 @section Killing the Child Process
2340 Kill the child process in which your program is running under @value{GDBN}.
2343 This command is useful if you wish to debug a core dump instead of a
2344 running process. @value{GDBN} ignores any core dump file while your program
2347 On some operating systems, a program cannot be executed outside @value{GDBN}
2348 while you have breakpoints set on it inside @value{GDBN}. You can use the
2349 @code{kill} command in this situation to permit running your program
2350 outside the debugger.
2352 The @code{kill} command is also useful if you wish to recompile and
2353 relink your program, since on many systems it is impossible to modify an
2354 executable file while it is running in a process. In this case, when you
2355 next type @code{run}, @value{GDBN} notices that the file has changed, and
2356 reads the symbol table again (while trying to preserve your current
2357 breakpoint settings).
2359 @node Inferiors and Programs
2360 @section Debugging Multiple Inferiors and Programs
2362 @value{GDBN} lets you run and debug multiple programs in a single
2363 session. In addition, @value{GDBN} on some systems may let you run
2364 several programs simultaneously (otherwise you have to exit from one
2365 before starting another). In the most general case, you can have
2366 multiple threads of execution in each of multiple processes, launched
2367 from multiple executables.
2370 @value{GDBN} represents the state of each program execution with an
2371 object called an @dfn{inferior}. An inferior typically corresponds to
2372 a process, but is more general and applies also to targets that do not
2373 have processes. Inferiors may be created before a process runs, and
2374 may be retained after a process exits. Inferiors have unique
2375 identifiers that are different from process ids. Usually each
2376 inferior will also have its own distinct address space, although some
2377 embedded targets may have several inferiors running in different parts
2378 of a single address space. Each inferior may in turn have multiple
2379 threads running in it.
2381 To find out what inferiors exist at any moment, use @w{@code{info
2385 @kindex info inferiors
2386 @item info inferiors
2387 Print a list of all inferiors currently being managed by @value{GDBN}.
2389 @value{GDBN} displays for each inferior (in this order):
2393 the inferior number assigned by @value{GDBN}
2396 the target system's inferior identifier
2399 the name of the executable the inferior is running.
2404 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2405 indicates the current inferior.
2409 @c end table here to get a little more width for example
2412 (@value{GDBP}) info inferiors
2413 Num Description Executable
2414 2 process 2307 hello
2415 * 1 process 3401 goodbye
2418 To switch focus between inferiors, use the @code{inferior} command:
2421 @kindex inferior @var{infno}
2422 @item inferior @var{infno}
2423 Make inferior number @var{infno} the current inferior. The argument
2424 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2425 in the first field of the @samp{info inferiors} display.
2429 You can get multiple executables into a debugging session via the
2430 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2431 systems @value{GDBN} can add inferiors to the debug session
2432 automatically by following calls to @code{fork} and @code{exec}. To
2433 remove inferiors from the debugging session use the
2434 @w{@code{remove-inferior}} command.
2437 @kindex add-inferior
2438 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2439 Adds @var{n} inferiors to be run using @var{executable} as the
2440 executable. @var{n} defaults to 1. If no executable is specified,
2441 the inferiors begins empty, with no program. You can still assign or
2442 change the program assigned to the inferior at any time by using the
2443 @code{file} command with the executable name as its argument.
2445 @kindex clone-inferior
2446 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2447 Adds @var{n} inferiors ready to execute the same program as inferior
2448 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2449 number of the current inferior. This is a convenient command when you
2450 want to run another instance of the inferior you are debugging.
2453 (@value{GDBP}) info inferiors
2454 Num Description Executable
2455 * 1 process 29964 helloworld
2456 (@value{GDBP}) clone-inferior
2459 (@value{GDBP}) info inferiors
2460 Num Description Executable
2462 * 1 process 29964 helloworld
2465 You can now simply switch focus to inferior 2 and run it.
2467 @kindex remove-inferior
2468 @item remove-inferior @var{infno}
2469 Removes the inferior @var{infno}. It is not possible to remove an
2470 inferior that is running with this command. For those, use the
2471 @code{kill} or @code{detach} command first.
2475 To quit debugging one of the running inferiors that is not the current
2476 inferior, you can either detach from it by using the @w{@code{detach
2477 inferior}} command (allowing it to run independently), or kill it
2478 using the @w{@code{kill inferior}} command:
2481 @kindex detach inferior @var{infno}
2482 @item detach inferior @var{infno}
2483 Detach from the inferior identified by @value{GDBN} inferior number
2484 @var{infno}, and remove it from the inferior list.
2486 @kindex kill inferior @var{infno}
2487 @item kill inferior @var{infno}
2488 Kill the inferior identified by @value{GDBN} inferior number
2489 @var{infno}, and remove it from the inferior list.
2492 After the successful completion of a command such as @code{detach},
2493 @code{detach inferior}, @code{kill} or @code{kill inferior}, or after
2494 a normal process exit, the inferior is still valid and listed with
2495 @code{info inferiors}, ready to be restarted.
2498 To be notified when inferiors are started or exit under @value{GDBN}'s
2499 control use @w{@code{set print inferior-events}}:
2502 @kindex set print inferior-events
2503 @cindex print messages on inferior start and exit
2504 @item set print inferior-events
2505 @itemx set print inferior-events on
2506 @itemx set print inferior-events off
2507 The @code{set print inferior-events} command allows you to enable or
2508 disable printing of messages when @value{GDBN} notices that new
2509 inferiors have started or that inferiors have exited or have been
2510 detached. By default, these messages will not be printed.
2512 @kindex show print inferior-events
2513 @item show print inferior-events
2514 Show whether messages will be printed when @value{GDBN} detects that
2515 inferiors have started, exited or have been detached.
2518 Many commands will work the same with multiple programs as with a
2519 single program: e.g., @code{print myglobal} will simply display the
2520 value of @code{myglobal} in the current inferior.
2523 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2524 get more info about the relationship of inferiors, programs, address
2525 spaces in a debug session. You can do that with the @w{@code{maint
2526 info program-spaces}} command.
2529 @kindex maint info program-spaces
2530 @item maint info program-spaces
2531 Print a list of all program spaces currently being managed by
2534 @value{GDBN} displays for each program space (in this order):
2538 the program space number assigned by @value{GDBN}
2541 the name of the executable loaded into the program space, with e.g.,
2542 the @code{file} command.
2547 An asterisk @samp{*} preceding the @value{GDBN} program space number
2548 indicates the current program space.
2550 In addition, below each program space line, @value{GDBN} prints extra
2551 information that isn't suitable to display in tabular form. For
2552 example, the list of inferiors bound to the program space.
2555 (@value{GDBP}) maint info program-spaces
2558 Bound inferiors: ID 1 (process 21561)
2562 Here we can see that no inferior is running the program @code{hello},
2563 while @code{process 21561} is running the program @code{goodbye}. On
2564 some targets, it is possible that multiple inferiors are bound to the
2565 same program space. The most common example is that of debugging both
2566 the parent and child processes of a @code{vfork} call. For example,
2569 (@value{GDBP}) maint info program-spaces
2572 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2575 Here, both inferior 2 and inferior 1 are running in the same program
2576 space as a result of inferior 1 having executed a @code{vfork} call.
2580 @section Debugging Programs with Multiple Threads
2582 @cindex threads of execution
2583 @cindex multiple threads
2584 @cindex switching threads
2585 In some operating systems, such as HP-UX and Solaris, a single program
2586 may have more than one @dfn{thread} of execution. The precise semantics
2587 of threads differ from one operating system to another, but in general
2588 the threads of a single program are akin to multiple processes---except
2589 that they share one address space (that is, they can all examine and
2590 modify the same variables). On the other hand, each thread has its own
2591 registers and execution stack, and perhaps private memory.
2593 @value{GDBN} provides these facilities for debugging multi-thread
2597 @item automatic notification of new threads
2598 @item @samp{thread @var{threadno}}, a command to switch among threads
2599 @item @samp{info threads}, a command to inquire about existing threads
2600 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2601 a command to apply a command to a list of threads
2602 @item thread-specific breakpoints
2603 @item @samp{set print thread-events}, which controls printing of
2604 messages on thread start and exit.
2605 @item @samp{set libthread-db-search-path @var{path}}, which lets
2606 the user specify which @code{libthread_db} to use if the default choice
2607 isn't compatible with the program.
2611 @emph{Warning:} These facilities are not yet available on every
2612 @value{GDBN} configuration where the operating system supports threads.
2613 If your @value{GDBN} does not support threads, these commands have no
2614 effect. For example, a system without thread support shows no output
2615 from @samp{info threads}, and always rejects the @code{thread} command,
2619 (@value{GDBP}) info threads
2620 (@value{GDBP}) thread 1
2621 Thread ID 1 not known. Use the "info threads" command to
2622 see the IDs of currently known threads.
2624 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2625 @c doesn't support threads"?
2628 @cindex focus of debugging
2629 @cindex current thread
2630 The @value{GDBN} thread debugging facility allows you to observe all
2631 threads while your program runs---but whenever @value{GDBN} takes
2632 control, one thread in particular is always the focus of debugging.
2633 This thread is called the @dfn{current thread}. Debugging commands show
2634 program information from the perspective of the current thread.
2636 @cindex @code{New} @var{systag} message
2637 @cindex thread identifier (system)
2638 @c FIXME-implementors!! It would be more helpful if the [New...] message
2639 @c included GDB's numeric thread handle, so you could just go to that
2640 @c thread without first checking `info threads'.
2641 Whenever @value{GDBN} detects a new thread in your program, it displays
2642 the target system's identification for the thread with a message in the
2643 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2644 whose form varies depending on the particular system. For example, on
2645 @sc{gnu}/Linux, you might see
2648 [New Thread 46912507313328 (LWP 25582)]
2652 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2653 the @var{systag} is simply something like @samp{process 368}, with no
2656 @c FIXME!! (1) Does the [New...] message appear even for the very first
2657 @c thread of a program, or does it only appear for the
2658 @c second---i.e.@: when it becomes obvious we have a multithread
2660 @c (2) *Is* there necessarily a first thread always? Or do some
2661 @c multithread systems permit starting a program with multiple
2662 @c threads ab initio?
2664 @cindex thread number
2665 @cindex thread identifier (GDB)
2666 For debugging purposes, @value{GDBN} associates its own thread
2667 number---always a single integer---with each thread in your program.
2670 @kindex info threads
2672 Display a summary of all threads currently in your
2673 program. @value{GDBN} displays for each thread (in this order):
2677 the thread number assigned by @value{GDBN}
2680 the target system's thread identifier (@var{systag})
2683 the current stack frame summary for that thread
2687 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2688 indicates the current thread.
2692 @c end table here to get a little more width for example
2695 (@value{GDBP}) info threads
2696 3 process 35 thread 27 0x34e5 in sigpause ()
2697 2 process 35 thread 23 0x34e5 in sigpause ()
2698 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2704 @cindex debugging multithreaded programs (on HP-UX)
2705 @cindex thread identifier (GDB), on HP-UX
2706 For debugging purposes, @value{GDBN} associates its own thread
2707 number---a small integer assigned in thread-creation order---with each
2708 thread in your program.
2710 @cindex @code{New} @var{systag} message, on HP-UX
2711 @cindex thread identifier (system), on HP-UX
2712 @c FIXME-implementors!! It would be more helpful if the [New...] message
2713 @c included GDB's numeric thread handle, so you could just go to that
2714 @c thread without first checking `info threads'.
2715 Whenever @value{GDBN} detects a new thread in your program, it displays
2716 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2717 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2718 whose form varies depending on the particular system. For example, on
2722 [New thread 2 (system thread 26594)]
2726 when @value{GDBN} notices a new thread.
2729 @kindex info threads (HP-UX)
2731 Display a summary of all threads currently in your
2732 program. @value{GDBN} displays for each thread (in this order):
2735 @item the thread number assigned by @value{GDBN}
2737 @item the target system's thread identifier (@var{systag})
2739 @item the current stack frame summary for that thread
2743 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2744 indicates the current thread.
2748 @c end table here to get a little more width for example
2751 (@value{GDBP}) info threads
2752 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2754 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2755 from /usr/lib/libc.2
2756 1 system thread 27905 0x7b003498 in _brk () \@*
2757 from /usr/lib/libc.2
2760 On Solaris, you can display more information about user threads with a
2761 Solaris-specific command:
2764 @item maint info sol-threads
2765 @kindex maint info sol-threads
2766 @cindex thread info (Solaris)
2767 Display info on Solaris user threads.
2771 @kindex thread @var{threadno}
2772 @item thread @var{threadno}
2773 Make thread number @var{threadno} the current thread. The command
2774 argument @var{threadno} is the internal @value{GDBN} thread number, as
2775 shown in the first field of the @samp{info threads} display.
2776 @value{GDBN} responds by displaying the system identifier of the thread
2777 you selected, and its current stack frame summary:
2780 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2781 (@value{GDBP}) thread 2
2782 [Switching to process 35 thread 23]
2783 0x34e5 in sigpause ()
2787 As with the @samp{[New @dots{}]} message, the form of the text after
2788 @samp{Switching to} depends on your system's conventions for identifying
2791 @kindex thread apply
2792 @cindex apply command to several threads
2793 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2794 The @code{thread apply} command allows you to apply the named
2795 @var{command} to one or more threads. Specify the numbers of the
2796 threads that you want affected with the command argument
2797 @var{threadno}. It can be a single thread number, one of the numbers
2798 shown in the first field of the @samp{info threads} display; or it
2799 could be a range of thread numbers, as in @code{2-4}. To apply a
2800 command to all threads, type @kbd{thread apply all @var{command}}.
2802 @kindex set print thread-events
2803 @cindex print messages on thread start and exit
2804 @item set print thread-events
2805 @itemx set print thread-events on
2806 @itemx set print thread-events off
2807 The @code{set print thread-events} command allows you to enable or
2808 disable printing of messages when @value{GDBN} notices that new threads have
2809 started or that threads have exited. By default, these messages will
2810 be printed if detection of these events is supported by the target.
2811 Note that these messages cannot be disabled on all targets.
2813 @kindex show print thread-events
2814 @item show print thread-events
2815 Show whether messages will be printed when @value{GDBN} detects that threads
2816 have started and exited.
2819 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2820 more information about how @value{GDBN} behaves when you stop and start
2821 programs with multiple threads.
2823 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2824 watchpoints in programs with multiple threads.
2827 @kindex set libthread-db-search-path
2828 @cindex search path for @code{libthread_db}
2829 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2830 If this variable is set, @var{path} is a colon-separated list of
2831 directories @value{GDBN} will use to search for @code{libthread_db}.
2832 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2835 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2836 @code{libthread_db} library to obtain information about threads in the
2837 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2838 to find @code{libthread_db}. If that fails, @value{GDBN} will continue
2839 with default system shared library directories, and finally the directory
2840 from which @code{libpthread} was loaded in the inferior process.
2842 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2843 @value{GDBN} attempts to initialize it with the current inferior process.
2844 If this initialization fails (which could happen because of a version
2845 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2846 will unload @code{libthread_db}, and continue with the next directory.
2847 If none of @code{libthread_db} libraries initialize successfully,
2848 @value{GDBN} will issue a warning and thread debugging will be disabled.
2850 Setting @code{libthread-db-search-path} is currently implemented
2851 only on some platforms.
2853 @kindex show libthread-db-search-path
2854 @item show libthread-db-search-path
2855 Display current libthread_db search path.
2859 @section Debugging Forks
2861 @cindex fork, debugging programs which call
2862 @cindex multiple processes
2863 @cindex processes, multiple
2864 On most systems, @value{GDBN} has no special support for debugging
2865 programs which create additional processes using the @code{fork}
2866 function. When a program forks, @value{GDBN} will continue to debug the
2867 parent process and the child process will run unimpeded. If you have
2868 set a breakpoint in any code which the child then executes, the child
2869 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2870 will cause it to terminate.
2872 However, if you want to debug the child process there is a workaround
2873 which isn't too painful. Put a call to @code{sleep} in the code which
2874 the child process executes after the fork. It may be useful to sleep
2875 only if a certain environment variable is set, or a certain file exists,
2876 so that the delay need not occur when you don't want to run @value{GDBN}
2877 on the child. While the child is sleeping, use the @code{ps} program to
2878 get its process ID. Then tell @value{GDBN} (a new invocation of
2879 @value{GDBN} if you are also debugging the parent process) to attach to
2880 the child process (@pxref{Attach}). From that point on you can debug
2881 the child process just like any other process which you attached to.
2883 On some systems, @value{GDBN} provides support for debugging programs that
2884 create additional processes using the @code{fork} or @code{vfork} functions.
2885 Currently, the only platforms with this feature are HP-UX (11.x and later
2886 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2888 By default, when a program forks, @value{GDBN} will continue to debug
2889 the parent process and the child process will run unimpeded.
2891 If you want to follow the child process instead of the parent process,
2892 use the command @w{@code{set follow-fork-mode}}.
2895 @kindex set follow-fork-mode
2896 @item set follow-fork-mode @var{mode}
2897 Set the debugger response to a program call of @code{fork} or
2898 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2899 process. The @var{mode} argument can be:
2903 The original process is debugged after a fork. The child process runs
2904 unimpeded. This is the default.
2907 The new process is debugged after a fork. The parent process runs
2912 @kindex show follow-fork-mode
2913 @item show follow-fork-mode
2914 Display the current debugger response to a @code{fork} or @code{vfork} call.
2917 @cindex debugging multiple processes
2918 On Linux, if you want to debug both the parent and child processes, use the
2919 command @w{@code{set detach-on-fork}}.
2922 @kindex set detach-on-fork
2923 @item set detach-on-fork @var{mode}
2924 Tells gdb whether to detach one of the processes after a fork, or
2925 retain debugger control over them both.
2929 The child process (or parent process, depending on the value of
2930 @code{follow-fork-mode}) will be detached and allowed to run
2931 independently. This is the default.
2934 Both processes will be held under the control of @value{GDBN}.
2935 One process (child or parent, depending on the value of
2936 @code{follow-fork-mode}) is debugged as usual, while the other
2941 @kindex show detach-on-fork
2942 @item show detach-on-fork
2943 Show whether detach-on-fork mode is on/off.
2946 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
2947 will retain control of all forked processes (including nested forks).
2948 You can list the forked processes under the control of @value{GDBN} by
2949 using the @w{@code{info inferiors}} command, and switch from one fork
2950 to another by using the @code{inferior} command (@pxref{Inferiors and
2951 Programs, ,Debugging Multiple Inferiors and Programs}).
2953 To quit debugging one of the forked processes, you can either detach
2954 from it by using the @w{@code{detach inferior}} command (allowing it
2955 to run independently), or kill it using the @w{@code{kill inferior}}
2956 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
2959 If you ask to debug a child process and a @code{vfork} is followed by an
2960 @code{exec}, @value{GDBN} executes the new target up to the first
2961 breakpoint in the new target. If you have a breakpoint set on
2962 @code{main} in your original program, the breakpoint will also be set on
2963 the child process's @code{main}.
2965 On some systems, when a child process is spawned by @code{vfork}, you
2966 cannot debug the child or parent until an @code{exec} call completes.
2968 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2969 call executes, the new target restarts. To restart the parent
2970 process, use the @code{file} command with the parent executable name
2971 as its argument. By default, after an @code{exec} call executes,
2972 @value{GDBN} discards the symbols of the previous executable image.
2973 You can change this behaviour with the @w{@code{set follow-exec-mode}}
2977 @kindex set follow-exec-mode
2978 @item set follow-exec-mode @var{mode}
2980 Set debugger response to a program call of @code{exec}. An
2981 @code{exec} call replaces the program image of a process.
2983 @code{follow-exec-mode} can be:
2987 @value{GDBN} creates a new inferior and rebinds the process to this
2988 new inferior. The program the process was running before the
2989 @code{exec} call can be restarted afterwards by restarting the
2995 (@value{GDBP}) info inferiors
2997 Id Description Executable
3000 process 12020 is executing new program: prog2
3001 Program exited normally.
3002 (@value{GDBP}) info inferiors
3003 Id Description Executable
3009 @value{GDBN} keeps the process bound to the same inferior. The new
3010 executable image replaces the previous executable loaded in the
3011 inferior. Restarting the inferior after the @code{exec} call, with
3012 e.g., the @code{run} command, restarts the executable the process was
3013 running after the @code{exec} call. This is the default mode.
3018 (@value{GDBP}) info inferiors
3019 Id Description Executable
3022 process 12020 is executing new program: prog2
3023 Program exited normally.
3024 (@value{GDBP}) info inferiors
3025 Id Description Executable
3032 You can use the @code{catch} command to make @value{GDBN} stop whenever
3033 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3034 Catchpoints, ,Setting Catchpoints}.
3036 @node Checkpoint/Restart
3037 @section Setting a @emph{Bookmark} to Return to Later
3042 @cindex snapshot of a process
3043 @cindex rewind program state
3045 On certain operating systems@footnote{Currently, only
3046 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3047 program's state, called a @dfn{checkpoint}, and come back to it
3050 Returning to a checkpoint effectively undoes everything that has
3051 happened in the program since the @code{checkpoint} was saved. This
3052 includes changes in memory, registers, and even (within some limits)
3053 system state. Effectively, it is like going back in time to the
3054 moment when the checkpoint was saved.
3056 Thus, if you're stepping thru a program and you think you're
3057 getting close to the point where things go wrong, you can save
3058 a checkpoint. Then, if you accidentally go too far and miss
3059 the critical statement, instead of having to restart your program
3060 from the beginning, you can just go back to the checkpoint and
3061 start again from there.
3063 This can be especially useful if it takes a lot of time or
3064 steps to reach the point where you think the bug occurs.
3066 To use the @code{checkpoint}/@code{restart} method of debugging:
3071 Save a snapshot of the debugged program's current execution state.
3072 The @code{checkpoint} command takes no arguments, but each checkpoint
3073 is assigned a small integer id, similar to a breakpoint id.
3075 @kindex info checkpoints
3076 @item info checkpoints
3077 List the checkpoints that have been saved in the current debugging
3078 session. For each checkpoint, the following information will be
3085 @item Source line, or label
3088 @kindex restart @var{checkpoint-id}
3089 @item restart @var{checkpoint-id}
3090 Restore the program state that was saved as checkpoint number
3091 @var{checkpoint-id}. All program variables, registers, stack frames
3092 etc.@: will be returned to the values that they had when the checkpoint
3093 was saved. In essence, gdb will ``wind back the clock'' to the point
3094 in time when the checkpoint was saved.
3096 Note that breakpoints, @value{GDBN} variables, command history etc.
3097 are not affected by restoring a checkpoint. In general, a checkpoint
3098 only restores things that reside in the program being debugged, not in
3101 @kindex delete checkpoint @var{checkpoint-id}
3102 @item delete checkpoint @var{checkpoint-id}
3103 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3107 Returning to a previously saved checkpoint will restore the user state
3108 of the program being debugged, plus a significant subset of the system
3109 (OS) state, including file pointers. It won't ``un-write'' data from
3110 a file, but it will rewind the file pointer to the previous location,
3111 so that the previously written data can be overwritten. For files
3112 opened in read mode, the pointer will also be restored so that the
3113 previously read data can be read again.
3115 Of course, characters that have been sent to a printer (or other
3116 external device) cannot be ``snatched back'', and characters received
3117 from eg.@: a serial device can be removed from internal program buffers,
3118 but they cannot be ``pushed back'' into the serial pipeline, ready to
3119 be received again. Similarly, the actual contents of files that have
3120 been changed cannot be restored (at this time).
3122 However, within those constraints, you actually can ``rewind'' your
3123 program to a previously saved point in time, and begin debugging it
3124 again --- and you can change the course of events so as to debug a
3125 different execution path this time.
3127 @cindex checkpoints and process id
3128 Finally, there is one bit of internal program state that will be
3129 different when you return to a checkpoint --- the program's process
3130 id. Each checkpoint will have a unique process id (or @var{pid}),
3131 and each will be different from the program's original @var{pid}.
3132 If your program has saved a local copy of its process id, this could
3133 potentially pose a problem.
3135 @subsection A Non-obvious Benefit of Using Checkpoints
3137 On some systems such as @sc{gnu}/Linux, address space randomization
3138 is performed on new processes for security reasons. This makes it
3139 difficult or impossible to set a breakpoint, or watchpoint, on an
3140 absolute address if you have to restart the program, since the
3141 absolute location of a symbol will change from one execution to the
3144 A checkpoint, however, is an @emph{identical} copy of a process.
3145 Therefore if you create a checkpoint at (eg.@:) the start of main,
3146 and simply return to that checkpoint instead of restarting the
3147 process, you can avoid the effects of address randomization and
3148 your symbols will all stay in the same place.
3151 @chapter Stopping and Continuing
3153 The principal purposes of using a debugger are so that you can stop your
3154 program before it terminates; or so that, if your program runs into
3155 trouble, you can investigate and find out why.
3157 Inside @value{GDBN}, your program may stop for any of several reasons,
3158 such as a signal, a breakpoint, or reaching a new line after a
3159 @value{GDBN} command such as @code{step}. You may then examine and
3160 change variables, set new breakpoints or remove old ones, and then
3161 continue execution. Usually, the messages shown by @value{GDBN} provide
3162 ample explanation of the status of your program---but you can also
3163 explicitly request this information at any time.
3166 @kindex info program
3168 Display information about the status of your program: whether it is
3169 running or not, what process it is, and why it stopped.
3173 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3174 * Continuing and Stepping:: Resuming execution
3176 * Thread Stops:: Stopping and starting multi-thread programs
3180 @section Breakpoints, Watchpoints, and Catchpoints
3183 A @dfn{breakpoint} makes your program stop whenever a certain point in
3184 the program is reached. For each breakpoint, you can add conditions to
3185 control in finer detail whether your program stops. You can set
3186 breakpoints with the @code{break} command and its variants (@pxref{Set
3187 Breaks, ,Setting Breakpoints}), to specify the place where your program
3188 should stop by line number, function name or exact address in the
3191 On some systems, you can set breakpoints in shared libraries before
3192 the executable is run. There is a minor limitation on HP-UX systems:
3193 you must wait until the executable is run in order to set breakpoints
3194 in shared library routines that are not called directly by the program
3195 (for example, routines that are arguments in a @code{pthread_create}
3199 @cindex data breakpoints
3200 @cindex memory tracing
3201 @cindex breakpoint on memory address
3202 @cindex breakpoint on variable modification
3203 A @dfn{watchpoint} is a special breakpoint that stops your program
3204 when the value of an expression changes. The expression may be a value
3205 of a variable, or it could involve values of one or more variables
3206 combined by operators, such as @samp{a + b}. This is sometimes called
3207 @dfn{data breakpoints}. You must use a different command to set
3208 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3209 from that, you can manage a watchpoint like any other breakpoint: you
3210 enable, disable, and delete both breakpoints and watchpoints using the
3213 You can arrange to have values from your program displayed automatically
3214 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3218 @cindex breakpoint on events
3219 A @dfn{catchpoint} is another special breakpoint that stops your program
3220 when a certain kind of event occurs, such as the throwing of a C@t{++}
3221 exception or the loading of a library. As with watchpoints, you use a
3222 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3223 Catchpoints}), but aside from that, you can manage a catchpoint like any
3224 other breakpoint. (To stop when your program receives a signal, use the
3225 @code{handle} command; see @ref{Signals, ,Signals}.)
3227 @cindex breakpoint numbers
3228 @cindex numbers for breakpoints
3229 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3230 catchpoint when you create it; these numbers are successive integers
3231 starting with one. In many of the commands for controlling various
3232 features of breakpoints you use the breakpoint number to say which
3233 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3234 @dfn{disabled}; if disabled, it has no effect on your program until you
3237 @cindex breakpoint ranges
3238 @cindex ranges of breakpoints
3239 Some @value{GDBN} commands accept a range of breakpoints on which to
3240 operate. A breakpoint range is either a single breakpoint number, like
3241 @samp{5}, or two such numbers, in increasing order, separated by a
3242 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3243 all breakpoints in that range are operated on.
3246 * Set Breaks:: Setting breakpoints
3247 * Set Watchpoints:: Setting watchpoints
3248 * Set Catchpoints:: Setting catchpoints
3249 * Delete Breaks:: Deleting breakpoints
3250 * Disabling:: Disabling breakpoints
3251 * Conditions:: Break conditions
3252 * Break Commands:: Breakpoint command lists
3253 * Save Breakpoints:: How to save breakpoints in a file
3254 * Error in Breakpoints:: ``Cannot insert breakpoints''
3255 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3259 @subsection Setting Breakpoints
3261 @c FIXME LMB what does GDB do if no code on line of breakpt?
3262 @c consider in particular declaration with/without initialization.
3264 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3267 @kindex b @r{(@code{break})}
3268 @vindex $bpnum@r{, convenience variable}
3269 @cindex latest breakpoint
3270 Breakpoints are set with the @code{break} command (abbreviated
3271 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3272 number of the breakpoint you've set most recently; see @ref{Convenience
3273 Vars,, Convenience Variables}, for a discussion of what you can do with
3274 convenience variables.
3277 @item break @var{location}
3278 Set a breakpoint at the given @var{location}, which can specify a
3279 function name, a line number, or an address of an instruction.
3280 (@xref{Specify Location}, for a list of all the possible ways to
3281 specify a @var{location}.) The breakpoint will stop your program just
3282 before it executes any of the code in the specified @var{location}.
3284 When using source languages that permit overloading of symbols, such as
3285 C@t{++}, a function name may refer to more than one possible place to break.
3286 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3289 It is also possible to insert a breakpoint that will stop the program
3290 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3291 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3294 When called without any arguments, @code{break} sets a breakpoint at
3295 the next instruction to be executed in the selected stack frame
3296 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3297 innermost, this makes your program stop as soon as control
3298 returns to that frame. This is similar to the effect of a
3299 @code{finish} command in the frame inside the selected frame---except
3300 that @code{finish} does not leave an active breakpoint. If you use
3301 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3302 the next time it reaches the current location; this may be useful
3305 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3306 least one instruction has been executed. If it did not do this, you
3307 would be unable to proceed past a breakpoint without first disabling the
3308 breakpoint. This rule applies whether or not the breakpoint already
3309 existed when your program stopped.
3311 @item break @dots{} if @var{cond}
3312 Set a breakpoint with condition @var{cond}; evaluate the expression
3313 @var{cond} each time the breakpoint is reached, and stop only if the
3314 value is nonzero---that is, if @var{cond} evaluates as true.
3315 @samp{@dots{}} stands for one of the possible arguments described
3316 above (or no argument) specifying where to break. @xref{Conditions,
3317 ,Break Conditions}, for more information on breakpoint conditions.
3320 @item tbreak @var{args}
3321 Set a breakpoint enabled only for one stop. @var{args} are the
3322 same as for the @code{break} command, and the breakpoint is set in the same
3323 way, but the breakpoint is automatically deleted after the first time your
3324 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3327 @cindex hardware breakpoints
3328 @item hbreak @var{args}
3329 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3330 @code{break} command and the breakpoint is set in the same way, but the
3331 breakpoint requires hardware support and some target hardware may not
3332 have this support. The main purpose of this is EPROM/ROM code
3333 debugging, so you can set a breakpoint at an instruction without
3334 changing the instruction. This can be used with the new trap-generation
3335 provided by SPARClite DSU and most x86-based targets. These targets
3336 will generate traps when a program accesses some data or instruction
3337 address that is assigned to the debug registers. However the hardware
3338 breakpoint registers can take a limited number of breakpoints. For
3339 example, on the DSU, only two data breakpoints can be set at a time, and
3340 @value{GDBN} will reject this command if more than two are used. Delete
3341 or disable unused hardware breakpoints before setting new ones
3342 (@pxref{Disabling, ,Disabling Breakpoints}).
3343 @xref{Conditions, ,Break Conditions}.
3344 For remote targets, you can restrict the number of hardware
3345 breakpoints @value{GDBN} will use, see @ref{set remote
3346 hardware-breakpoint-limit}.
3349 @item thbreak @var{args}
3350 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3351 are the same as for the @code{hbreak} command and the breakpoint is set in
3352 the same way. However, like the @code{tbreak} command,
3353 the breakpoint is automatically deleted after the
3354 first time your program stops there. Also, like the @code{hbreak}
3355 command, the breakpoint requires hardware support and some target hardware
3356 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3357 See also @ref{Conditions, ,Break Conditions}.
3360 @cindex regular expression
3361 @cindex breakpoints at functions matching a regexp
3362 @cindex set breakpoints in many functions
3363 @item rbreak @var{regex}
3364 Set breakpoints on all functions matching the regular expression
3365 @var{regex}. This command sets an unconditional breakpoint on all
3366 matches, printing a list of all breakpoints it set. Once these
3367 breakpoints are set, they are treated just like the breakpoints set with
3368 the @code{break} command. You can delete them, disable them, or make
3369 them conditional the same way as any other breakpoint.
3371 The syntax of the regular expression is the standard one used with tools
3372 like @file{grep}. Note that this is different from the syntax used by
3373 shells, so for instance @code{foo*} matches all functions that include
3374 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3375 @code{.*} leading and trailing the regular expression you supply, so to
3376 match only functions that begin with @code{foo}, use @code{^foo}.
3378 @cindex non-member C@t{++} functions, set breakpoint in
3379 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3380 breakpoints on overloaded functions that are not members of any special
3383 @cindex set breakpoints on all functions
3384 The @code{rbreak} command can be used to set breakpoints in
3385 @strong{all} the functions in a program, like this:
3388 (@value{GDBP}) rbreak .
3391 @item rbreak @var{file}:@var{regex}
3392 If @code{rbreak} is called with a filename qualification, it limits
3393 the search for functions matching the given regular expression to the
3394 specified @var{file}. This can be used, for example, to set breakpoints on
3395 every function in a given file:
3398 (@value{GDBP}) rbreak file.c:.
3401 The colon separating the filename qualifier from the regex may
3402 optionally be surrounded by spaces.
3404 @kindex info breakpoints
3405 @cindex @code{$_} and @code{info breakpoints}
3406 @item info breakpoints @r{[}@var{n}@r{]}
3407 @itemx info break @r{[}@var{n}@r{]}
3408 Print a table of all breakpoints, watchpoints, and catchpoints set and
3409 not deleted. Optional argument @var{n} means print information only
3410 about the specified breakpoint (or watchpoint or catchpoint). For
3411 each breakpoint, following columns are printed:
3414 @item Breakpoint Numbers
3416 Breakpoint, watchpoint, or catchpoint.
3418 Whether the breakpoint is marked to be disabled or deleted when hit.
3419 @item Enabled or Disabled
3420 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3421 that are not enabled.
3423 Where the breakpoint is in your program, as a memory address. For a
3424 pending breakpoint whose address is not yet known, this field will
3425 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3426 library that has the symbol or line referred by breakpoint is loaded.
3427 See below for details. A breakpoint with several locations will
3428 have @samp{<MULTIPLE>} in this field---see below for details.
3430 Where the breakpoint is in the source for your program, as a file and
3431 line number. For a pending breakpoint, the original string passed to
3432 the breakpoint command will be listed as it cannot be resolved until
3433 the appropriate shared library is loaded in the future.
3437 If a breakpoint is conditional, @code{info break} shows the condition on
3438 the line following the affected breakpoint; breakpoint commands, if any,
3439 are listed after that. A pending breakpoint is allowed to have a condition
3440 specified for it. The condition is not parsed for validity until a shared
3441 library is loaded that allows the pending breakpoint to resolve to a
3445 @code{info break} with a breakpoint
3446 number @var{n} as argument lists only that breakpoint. The
3447 convenience variable @code{$_} and the default examining-address for
3448 the @code{x} command are set to the address of the last breakpoint
3449 listed (@pxref{Memory, ,Examining Memory}).
3452 @code{info break} displays a count of the number of times the breakpoint
3453 has been hit. This is especially useful in conjunction with the
3454 @code{ignore} command. You can ignore a large number of breakpoint
3455 hits, look at the breakpoint info to see how many times the breakpoint
3456 was hit, and then run again, ignoring one less than that number. This
3457 will get you quickly to the last hit of that breakpoint.
3460 @value{GDBN} allows you to set any number of breakpoints at the same place in
3461 your program. There is nothing silly or meaningless about this. When
3462 the breakpoints are conditional, this is even useful
3463 (@pxref{Conditions, ,Break Conditions}).
3465 @cindex multiple locations, breakpoints
3466 @cindex breakpoints, multiple locations
3467 It is possible that a breakpoint corresponds to several locations
3468 in your program. Examples of this situation are:
3472 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3473 instances of the function body, used in different cases.
3476 For a C@t{++} template function, a given line in the function can
3477 correspond to any number of instantiations.
3480 For an inlined function, a given source line can correspond to
3481 several places where that function is inlined.
3484 In all those cases, @value{GDBN} will insert a breakpoint at all
3485 the relevant locations@footnote{
3486 As of this writing, multiple-location breakpoints work only if there's
3487 line number information for all the locations. This means that they
3488 will generally not work in system libraries, unless you have debug
3489 info with line numbers for them.}.
3491 A breakpoint with multiple locations is displayed in the breakpoint
3492 table using several rows---one header row, followed by one row for
3493 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3494 address column. The rows for individual locations contain the actual
3495 addresses for locations, and show the functions to which those
3496 locations belong. The number column for a location is of the form
3497 @var{breakpoint-number}.@var{location-number}.
3502 Num Type Disp Enb Address What
3503 1 breakpoint keep y <MULTIPLE>
3505 breakpoint already hit 1 time
3506 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3507 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3510 Each location can be individually enabled or disabled by passing
3511 @var{breakpoint-number}.@var{location-number} as argument to the
3512 @code{enable} and @code{disable} commands. Note that you cannot
3513 delete the individual locations from the list, you can only delete the
3514 entire list of locations that belong to their parent breakpoint (with
3515 the @kbd{delete @var{num}} command, where @var{num} is the number of
3516 the parent breakpoint, 1 in the above example). Disabling or enabling
3517 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3518 that belong to that breakpoint.
3520 @cindex pending breakpoints
3521 It's quite common to have a breakpoint inside a shared library.
3522 Shared libraries can be loaded and unloaded explicitly,
3523 and possibly repeatedly, as the program is executed. To support
3524 this use case, @value{GDBN} updates breakpoint locations whenever
3525 any shared library is loaded or unloaded. Typically, you would
3526 set a breakpoint in a shared library at the beginning of your
3527 debugging session, when the library is not loaded, and when the
3528 symbols from the library are not available. When you try to set
3529 breakpoint, @value{GDBN} will ask you if you want to set
3530 a so called @dfn{pending breakpoint}---breakpoint whose address
3531 is not yet resolved.
3533 After the program is run, whenever a new shared library is loaded,
3534 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3535 shared library contains the symbol or line referred to by some
3536 pending breakpoint, that breakpoint is resolved and becomes an
3537 ordinary breakpoint. When a library is unloaded, all breakpoints
3538 that refer to its symbols or source lines become pending again.
3540 This logic works for breakpoints with multiple locations, too. For
3541 example, if you have a breakpoint in a C@t{++} template function, and
3542 a newly loaded shared library has an instantiation of that template,
3543 a new location is added to the list of locations for the breakpoint.
3545 Except for having unresolved address, pending breakpoints do not
3546 differ from regular breakpoints. You can set conditions or commands,
3547 enable and disable them and perform other breakpoint operations.
3549 @value{GDBN} provides some additional commands for controlling what
3550 happens when the @samp{break} command cannot resolve breakpoint
3551 address specification to an address:
3553 @kindex set breakpoint pending
3554 @kindex show breakpoint pending
3556 @item set breakpoint pending auto
3557 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3558 location, it queries you whether a pending breakpoint should be created.
3560 @item set breakpoint pending on
3561 This indicates that an unrecognized breakpoint location should automatically
3562 result in a pending breakpoint being created.
3564 @item set breakpoint pending off
3565 This indicates that pending breakpoints are not to be created. Any
3566 unrecognized breakpoint location results in an error. This setting does
3567 not affect any pending breakpoints previously created.
3569 @item show breakpoint pending
3570 Show the current behavior setting for creating pending breakpoints.
3573 The settings above only affect the @code{break} command and its
3574 variants. Once breakpoint is set, it will be automatically updated
3575 as shared libraries are loaded and unloaded.
3577 @cindex automatic hardware breakpoints
3578 For some targets, @value{GDBN} can automatically decide if hardware or
3579 software breakpoints should be used, depending on whether the
3580 breakpoint address is read-only or read-write. This applies to
3581 breakpoints set with the @code{break} command as well as to internal
3582 breakpoints set by commands like @code{next} and @code{finish}. For
3583 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3586 You can control this automatic behaviour with the following commands::
3588 @kindex set breakpoint auto-hw
3589 @kindex show breakpoint auto-hw
3591 @item set breakpoint auto-hw on
3592 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3593 will try to use the target memory map to decide if software or hardware
3594 breakpoint must be used.
3596 @item set breakpoint auto-hw off
3597 This indicates @value{GDBN} should not automatically select breakpoint
3598 type. If the target provides a memory map, @value{GDBN} will warn when
3599 trying to set software breakpoint at a read-only address.
3602 @value{GDBN} normally implements breakpoints by replacing the program code
3603 at the breakpoint address with a special instruction, which, when
3604 executed, given control to the debugger. By default, the program
3605 code is so modified only when the program is resumed. As soon as
3606 the program stops, @value{GDBN} restores the original instructions. This
3607 behaviour guards against leaving breakpoints inserted in the
3608 target should gdb abrubptly disconnect. However, with slow remote
3609 targets, inserting and removing breakpoint can reduce the performance.
3610 This behavior can be controlled with the following commands::
3612 @kindex set breakpoint always-inserted
3613 @kindex show breakpoint always-inserted
3615 @item set breakpoint always-inserted off
3616 All breakpoints, including newly added by the user, are inserted in
3617 the target only when the target is resumed. All breakpoints are
3618 removed from the target when it stops.
3620 @item set breakpoint always-inserted on
3621 Causes all breakpoints to be inserted in the target at all times. If
3622 the user adds a new breakpoint, or changes an existing breakpoint, the
3623 breakpoints in the target are updated immediately. A breakpoint is
3624 removed from the target only when breakpoint itself is removed.
3626 @cindex non-stop mode, and @code{breakpoint always-inserted}
3627 @item set breakpoint always-inserted auto
3628 This is the default mode. If @value{GDBN} is controlling the inferior
3629 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3630 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3631 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3632 @code{breakpoint always-inserted} mode is off.
3635 @cindex negative breakpoint numbers
3636 @cindex internal @value{GDBN} breakpoints
3637 @value{GDBN} itself sometimes sets breakpoints in your program for
3638 special purposes, such as proper handling of @code{longjmp} (in C
3639 programs). These internal breakpoints are assigned negative numbers,
3640 starting with @code{-1}; @samp{info breakpoints} does not display them.
3641 You can see these breakpoints with the @value{GDBN} maintenance command
3642 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3645 @node Set Watchpoints
3646 @subsection Setting Watchpoints
3648 @cindex setting watchpoints
3649 You can use a watchpoint to stop execution whenever the value of an
3650 expression changes, without having to predict a particular place where
3651 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3652 The expression may be as simple as the value of a single variable, or
3653 as complex as many variables combined by operators. Examples include:
3657 A reference to the value of a single variable.
3660 An address cast to an appropriate data type. For example,
3661 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3662 address (assuming an @code{int} occupies 4 bytes).
3665 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3666 expression can use any operators valid in the program's native
3667 language (@pxref{Languages}).
3670 You can set a watchpoint on an expression even if the expression can
3671 not be evaluated yet. For instance, you can set a watchpoint on
3672 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3673 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3674 the expression produces a valid value. If the expression becomes
3675 valid in some other way than changing a variable (e.g.@: if the memory
3676 pointed to by @samp{*global_ptr} becomes readable as the result of a
3677 @code{malloc} call), @value{GDBN} may not stop until the next time
3678 the expression changes.
3680 @cindex software watchpoints
3681 @cindex hardware watchpoints
3682 Depending on your system, watchpoints may be implemented in software or
3683 hardware. @value{GDBN} does software watchpointing by single-stepping your
3684 program and testing the variable's value each time, which is hundreds of
3685 times slower than normal execution. (But this may still be worth it, to
3686 catch errors where you have no clue what part of your program is the
3689 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3690 x86-based targets, @value{GDBN} includes support for hardware
3691 watchpoints, which do not slow down the running of your program.
3695 @item watch @var{expr} @r{[}thread @var{threadnum}@r{]}
3696 Set a watchpoint for an expression. @value{GDBN} will break when the
3697 expression @var{expr} is written into by the program and its value
3698 changes. The simplest (and the most popular) use of this command is
3699 to watch the value of a single variable:
3702 (@value{GDBP}) watch foo
3705 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3706 clause, @value{GDBN} breaks only when the thread identified by
3707 @var{threadnum} changes the value of @var{expr}. If any other threads
3708 change the value of @var{expr}, @value{GDBN} will not break. Note
3709 that watchpoints restricted to a single thread in this way only work
3710 with Hardware Watchpoints.
3713 @item rwatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3714 Set a watchpoint that will break when the value of @var{expr} is read
3718 @item awatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3719 Set a watchpoint that will break when @var{expr} is either read from
3720 or written into by the program.
3722 @kindex info watchpoints @r{[}@var{n}@r{]}
3723 @item info watchpoints
3724 This command prints a list of watchpoints, using the same format as
3725 @code{info break} (@pxref{Set Breaks}).
3728 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3729 watchpoints execute very quickly, and the debugger reports a change in
3730 value at the exact instruction where the change occurs. If @value{GDBN}
3731 cannot set a hardware watchpoint, it sets a software watchpoint, which
3732 executes more slowly and reports the change in value at the next
3733 @emph{statement}, not the instruction, after the change occurs.
3735 @cindex use only software watchpoints
3736 You can force @value{GDBN} to use only software watchpoints with the
3737 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3738 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3739 the underlying system supports them. (Note that hardware-assisted
3740 watchpoints that were set @emph{before} setting
3741 @code{can-use-hw-watchpoints} to zero will still use the hardware
3742 mechanism of watching expression values.)
3745 @item set can-use-hw-watchpoints
3746 @kindex set can-use-hw-watchpoints
3747 Set whether or not to use hardware watchpoints.
3749 @item show can-use-hw-watchpoints
3750 @kindex show can-use-hw-watchpoints
3751 Show the current mode of using hardware watchpoints.
3754 For remote targets, you can restrict the number of hardware
3755 watchpoints @value{GDBN} will use, see @ref{set remote
3756 hardware-breakpoint-limit}.
3758 When you issue the @code{watch} command, @value{GDBN} reports
3761 Hardware watchpoint @var{num}: @var{expr}
3765 if it was able to set a hardware watchpoint.
3767 Currently, the @code{awatch} and @code{rwatch} commands can only set
3768 hardware watchpoints, because accesses to data that don't change the
3769 value of the watched expression cannot be detected without examining
3770 every instruction as it is being executed, and @value{GDBN} does not do
3771 that currently. If @value{GDBN} finds that it is unable to set a
3772 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3773 will print a message like this:
3776 Expression cannot be implemented with read/access watchpoint.
3779 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3780 data type of the watched expression is wider than what a hardware
3781 watchpoint on the target machine can handle. For example, some systems
3782 can only watch regions that are up to 4 bytes wide; on such systems you
3783 cannot set hardware watchpoints for an expression that yields a
3784 double-precision floating-point number (which is typically 8 bytes
3785 wide). As a work-around, it might be possible to break the large region
3786 into a series of smaller ones and watch them with separate watchpoints.
3788 If you set too many hardware watchpoints, @value{GDBN} might be unable
3789 to insert all of them when you resume the execution of your program.
3790 Since the precise number of active watchpoints is unknown until such
3791 time as the program is about to be resumed, @value{GDBN} might not be
3792 able to warn you about this when you set the watchpoints, and the
3793 warning will be printed only when the program is resumed:
3796 Hardware watchpoint @var{num}: Could not insert watchpoint
3800 If this happens, delete or disable some of the watchpoints.
3802 Watching complex expressions that reference many variables can also
3803 exhaust the resources available for hardware-assisted watchpoints.
3804 That's because @value{GDBN} needs to watch every variable in the
3805 expression with separately allocated resources.
3807 If you call a function interactively using @code{print} or @code{call},
3808 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3809 kind of breakpoint or the call completes.
3811 @value{GDBN} automatically deletes watchpoints that watch local
3812 (automatic) variables, or expressions that involve such variables, when
3813 they go out of scope, that is, when the execution leaves the block in
3814 which these variables were defined. In particular, when the program
3815 being debugged terminates, @emph{all} local variables go out of scope,
3816 and so only watchpoints that watch global variables remain set. If you
3817 rerun the program, you will need to set all such watchpoints again. One
3818 way of doing that would be to set a code breakpoint at the entry to the
3819 @code{main} function and when it breaks, set all the watchpoints.
3821 @cindex watchpoints and threads
3822 @cindex threads and watchpoints
3823 In multi-threaded programs, watchpoints will detect changes to the
3824 watched expression from every thread.
3827 @emph{Warning:} In multi-threaded programs, software watchpoints
3828 have only limited usefulness. If @value{GDBN} creates a software
3829 watchpoint, it can only watch the value of an expression @emph{in a
3830 single thread}. If you are confident that the expression can only
3831 change due to the current thread's activity (and if you are also
3832 confident that no other thread can become current), then you can use
3833 software watchpoints as usual. However, @value{GDBN} may not notice
3834 when a non-current thread's activity changes the expression. (Hardware
3835 watchpoints, in contrast, watch an expression in all threads.)
3838 @xref{set remote hardware-watchpoint-limit}.
3840 @node Set Catchpoints
3841 @subsection Setting Catchpoints
3842 @cindex catchpoints, setting
3843 @cindex exception handlers
3844 @cindex event handling
3846 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3847 kinds of program events, such as C@t{++} exceptions or the loading of a
3848 shared library. Use the @code{catch} command to set a catchpoint.
3852 @item catch @var{event}
3853 Stop when @var{event} occurs. @var{event} can be any of the following:
3856 @cindex stop on C@t{++} exceptions
3857 The throwing of a C@t{++} exception.
3860 The catching of a C@t{++} exception.
3863 @cindex Ada exception catching
3864 @cindex catch Ada exceptions
3865 An Ada exception being raised. If an exception name is specified
3866 at the end of the command (eg @code{catch exception Program_Error}),
3867 the debugger will stop only when this specific exception is raised.
3868 Otherwise, the debugger stops execution when any Ada exception is raised.
3870 When inserting an exception catchpoint on a user-defined exception whose
3871 name is identical to one of the exceptions defined by the language, the
3872 fully qualified name must be used as the exception name. Otherwise,
3873 @value{GDBN} will assume that it should stop on the pre-defined exception
3874 rather than the user-defined one. For instance, assuming an exception
3875 called @code{Constraint_Error} is defined in package @code{Pck}, then
3876 the command to use to catch such exceptions is @kbd{catch exception
3877 Pck.Constraint_Error}.
3879 @item exception unhandled
3880 An exception that was raised but is not handled by the program.
3883 A failed Ada assertion.
3886 @cindex break on fork/exec
3887 A call to @code{exec}. This is currently only available for HP-UX
3891 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
3892 @cindex break on a system call.
3893 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
3894 syscall is a mechanism for application programs to request a service
3895 from the operating system (OS) or one of the OS system services.
3896 @value{GDBN} can catch some or all of the syscalls issued by the
3897 debuggee, and show the related information for each syscall. If no
3898 argument is specified, calls to and returns from all system calls
3901 @var{name} can be any system call name that is valid for the
3902 underlying OS. Just what syscalls are valid depends on the OS. On
3903 GNU and Unix systems, you can find the full list of valid syscall
3904 names on @file{/usr/include/asm/unistd.h}.
3906 @c For MS-Windows, the syscall names and the corresponding numbers
3907 @c can be found, e.g., on this URL:
3908 @c http://www.metasploit.com/users/opcode/syscalls.html
3909 @c but we don't support Windows syscalls yet.
3911 Normally, @value{GDBN} knows in advance which syscalls are valid for
3912 each OS, so you can use the @value{GDBN} command-line completion
3913 facilities (@pxref{Completion,, command completion}) to list the
3916 You may also specify the system call numerically. A syscall's
3917 number is the value passed to the OS's syscall dispatcher to
3918 identify the requested service. When you specify the syscall by its
3919 name, @value{GDBN} uses its database of syscalls to convert the name
3920 into the corresponding numeric code, but using the number directly
3921 may be useful if @value{GDBN}'s database does not have the complete
3922 list of syscalls on your system (e.g., because @value{GDBN} lags
3923 behind the OS upgrades).
3925 The example below illustrates how this command works if you don't provide
3929 (@value{GDBP}) catch syscall
3930 Catchpoint 1 (syscall)
3932 Starting program: /tmp/catch-syscall
3934 Catchpoint 1 (call to syscall 'close'), \
3935 0xffffe424 in __kernel_vsyscall ()
3939 Catchpoint 1 (returned from syscall 'close'), \
3940 0xffffe424 in __kernel_vsyscall ()
3944 Here is an example of catching a system call by name:
3947 (@value{GDBP}) catch syscall chroot
3948 Catchpoint 1 (syscall 'chroot' [61])
3950 Starting program: /tmp/catch-syscall
3952 Catchpoint 1 (call to syscall 'chroot'), \
3953 0xffffe424 in __kernel_vsyscall ()
3957 Catchpoint 1 (returned from syscall 'chroot'), \
3958 0xffffe424 in __kernel_vsyscall ()
3962 An example of specifying a system call numerically. In the case
3963 below, the syscall number has a corresponding entry in the XML
3964 file, so @value{GDBN} finds its name and prints it:
3967 (@value{GDBP}) catch syscall 252
3968 Catchpoint 1 (syscall(s) 'exit_group')
3970 Starting program: /tmp/catch-syscall
3972 Catchpoint 1 (call to syscall 'exit_group'), \
3973 0xffffe424 in __kernel_vsyscall ()
3977 Program exited normally.
3981 However, there can be situations when there is no corresponding name
3982 in XML file for that syscall number. In this case, @value{GDBN} prints
3983 a warning message saying that it was not able to find the syscall name,
3984 but the catchpoint will be set anyway. See the example below:
3987 (@value{GDBP}) catch syscall 764
3988 warning: The number '764' does not represent a known syscall.
3989 Catchpoint 2 (syscall 764)
3993 If you configure @value{GDBN} using the @samp{--without-expat} option,
3994 it will not be able to display syscall names. Also, if your
3995 architecture does not have an XML file describing its system calls,
3996 you will not be able to see the syscall names. It is important to
3997 notice that these two features are used for accessing the syscall
3998 name database. In either case, you will see a warning like this:
4001 (@value{GDBP}) catch syscall
4002 warning: Could not open "syscalls/i386-linux.xml"
4003 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4004 GDB will not be able to display syscall names.
4005 Catchpoint 1 (syscall)
4009 Of course, the file name will change depending on your architecture and system.
4011 Still using the example above, you can also try to catch a syscall by its
4012 number. In this case, you would see something like:
4015 (@value{GDBP}) catch syscall 252
4016 Catchpoint 1 (syscall(s) 252)
4019 Again, in this case @value{GDBN} would not be able to display syscall's names.
4022 A call to @code{fork}. This is currently only available for HP-UX
4026 A call to @code{vfork}. This is currently only available for HP-UX
4031 @item tcatch @var{event}
4032 Set a catchpoint that is enabled only for one stop. The catchpoint is
4033 automatically deleted after the first time the event is caught.
4037 Use the @code{info break} command to list the current catchpoints.
4039 There are currently some limitations to C@t{++} exception handling
4040 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4044 If you call a function interactively, @value{GDBN} normally returns
4045 control to you when the function has finished executing. If the call
4046 raises an exception, however, the call may bypass the mechanism that
4047 returns control to you and cause your program either to abort or to
4048 simply continue running until it hits a breakpoint, catches a signal
4049 that @value{GDBN} is listening for, or exits. This is the case even if
4050 you set a catchpoint for the exception; catchpoints on exceptions are
4051 disabled within interactive calls.
4054 You cannot raise an exception interactively.
4057 You cannot install an exception handler interactively.
4060 @cindex raise exceptions
4061 Sometimes @code{catch} is not the best way to debug exception handling:
4062 if you need to know exactly where an exception is raised, it is better to
4063 stop @emph{before} the exception handler is called, since that way you
4064 can see the stack before any unwinding takes place. If you set a
4065 breakpoint in an exception handler instead, it may not be easy to find
4066 out where the exception was raised.
4068 To stop just before an exception handler is called, you need some
4069 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4070 raised by calling a library function named @code{__raise_exception}
4071 which has the following ANSI C interface:
4074 /* @var{addr} is where the exception identifier is stored.
4075 @var{id} is the exception identifier. */
4076 void __raise_exception (void **addr, void *id);
4080 To make the debugger catch all exceptions before any stack
4081 unwinding takes place, set a breakpoint on @code{__raise_exception}
4082 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4084 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4085 that depends on the value of @var{id}, you can stop your program when
4086 a specific exception is raised. You can use multiple conditional
4087 breakpoints to stop your program when any of a number of exceptions are
4092 @subsection Deleting Breakpoints
4094 @cindex clearing breakpoints, watchpoints, catchpoints
4095 @cindex deleting breakpoints, watchpoints, catchpoints
4096 It is often necessary to eliminate a breakpoint, watchpoint, or
4097 catchpoint once it has done its job and you no longer want your program
4098 to stop there. This is called @dfn{deleting} the breakpoint. A
4099 breakpoint that has been deleted no longer exists; it is forgotten.
4101 With the @code{clear} command you can delete breakpoints according to
4102 where they are in your program. With the @code{delete} command you can
4103 delete individual breakpoints, watchpoints, or catchpoints by specifying
4104 their breakpoint numbers.
4106 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4107 automatically ignores breakpoints on the first instruction to be executed
4108 when you continue execution without changing the execution address.
4113 Delete any breakpoints at the next instruction to be executed in the
4114 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4115 the innermost frame is selected, this is a good way to delete a
4116 breakpoint where your program just stopped.
4118 @item clear @var{location}
4119 Delete any breakpoints set at the specified @var{location}.
4120 @xref{Specify Location}, for the various forms of @var{location}; the
4121 most useful ones are listed below:
4124 @item clear @var{function}
4125 @itemx clear @var{filename}:@var{function}
4126 Delete any breakpoints set at entry to the named @var{function}.
4128 @item clear @var{linenum}
4129 @itemx clear @var{filename}:@var{linenum}
4130 Delete any breakpoints set at or within the code of the specified
4131 @var{linenum} of the specified @var{filename}.
4134 @cindex delete breakpoints
4136 @kindex d @r{(@code{delete})}
4137 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4138 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4139 ranges specified as arguments. If no argument is specified, delete all
4140 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4141 confirm off}). You can abbreviate this command as @code{d}.
4145 @subsection Disabling Breakpoints
4147 @cindex enable/disable a breakpoint
4148 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4149 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4150 it had been deleted, but remembers the information on the breakpoint so
4151 that you can @dfn{enable} it again later.
4153 You disable and enable breakpoints, watchpoints, and catchpoints with
4154 the @code{enable} and @code{disable} commands, optionally specifying
4155 one or more breakpoint numbers as arguments. Use @code{info break} to
4156 print a list of all breakpoints, watchpoints, and catchpoints if you
4157 do not know which numbers to use.
4159 Disabling and enabling a breakpoint that has multiple locations
4160 affects all of its locations.
4162 A breakpoint, watchpoint, or catchpoint can have any of four different
4163 states of enablement:
4167 Enabled. The breakpoint stops your program. A breakpoint set
4168 with the @code{break} command starts out in this state.
4170 Disabled. The breakpoint has no effect on your program.
4172 Enabled once. The breakpoint stops your program, but then becomes
4175 Enabled for deletion. The breakpoint stops your program, but
4176 immediately after it does so it is deleted permanently. A breakpoint
4177 set with the @code{tbreak} command starts out in this state.
4180 You can use the following commands to enable or disable breakpoints,
4181 watchpoints, and catchpoints:
4185 @kindex dis @r{(@code{disable})}
4186 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4187 Disable the specified breakpoints---or all breakpoints, if none are
4188 listed. A disabled breakpoint has no effect but is not forgotten. All
4189 options such as ignore-counts, conditions and commands are remembered in
4190 case the breakpoint is enabled again later. You may abbreviate
4191 @code{disable} as @code{dis}.
4194 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4195 Enable the specified breakpoints (or all defined breakpoints). They
4196 become effective once again in stopping your program.
4198 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4199 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4200 of these breakpoints immediately after stopping your program.
4202 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4203 Enable the specified breakpoints to work once, then die. @value{GDBN}
4204 deletes any of these breakpoints as soon as your program stops there.
4205 Breakpoints set by the @code{tbreak} command start out in this state.
4208 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4209 @c confusing: tbreak is also initially enabled.
4210 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4211 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4212 subsequently, they become disabled or enabled only when you use one of
4213 the commands above. (The command @code{until} can set and delete a
4214 breakpoint of its own, but it does not change the state of your other
4215 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4219 @subsection Break Conditions
4220 @cindex conditional breakpoints
4221 @cindex breakpoint conditions
4223 @c FIXME what is scope of break condition expr? Context where wanted?
4224 @c in particular for a watchpoint?
4225 The simplest sort of breakpoint breaks every time your program reaches a
4226 specified place. You can also specify a @dfn{condition} for a
4227 breakpoint. A condition is just a Boolean expression in your
4228 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4229 a condition evaluates the expression each time your program reaches it,
4230 and your program stops only if the condition is @emph{true}.
4232 This is the converse of using assertions for program validation; in that
4233 situation, you want to stop when the assertion is violated---that is,
4234 when the condition is false. In C, if you want to test an assertion expressed
4235 by the condition @var{assert}, you should set the condition
4236 @samp{! @var{assert}} on the appropriate breakpoint.
4238 Conditions are also accepted for watchpoints; you may not need them,
4239 since a watchpoint is inspecting the value of an expression anyhow---but
4240 it might be simpler, say, to just set a watchpoint on a variable name,
4241 and specify a condition that tests whether the new value is an interesting
4244 Break conditions can have side effects, and may even call functions in
4245 your program. This can be useful, for example, to activate functions
4246 that log program progress, or to use your own print functions to
4247 format special data structures. The effects are completely predictable
4248 unless there is another enabled breakpoint at the same address. (In
4249 that case, @value{GDBN} might see the other breakpoint first and stop your
4250 program without checking the condition of this one.) Note that
4251 breakpoint commands are usually more convenient and flexible than break
4253 purpose of performing side effects when a breakpoint is reached
4254 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4256 Break conditions can be specified when a breakpoint is set, by using
4257 @samp{if} in the arguments to the @code{break} command. @xref{Set
4258 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4259 with the @code{condition} command.
4261 You can also use the @code{if} keyword with the @code{watch} command.
4262 The @code{catch} command does not recognize the @code{if} keyword;
4263 @code{condition} is the only way to impose a further condition on a
4268 @item condition @var{bnum} @var{expression}
4269 Specify @var{expression} as the break condition for breakpoint,
4270 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4271 breakpoint @var{bnum} stops your program only if the value of
4272 @var{expression} is true (nonzero, in C). When you use
4273 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4274 syntactic correctness, and to determine whether symbols in it have
4275 referents in the context of your breakpoint. If @var{expression} uses
4276 symbols not referenced in the context of the breakpoint, @value{GDBN}
4277 prints an error message:
4280 No symbol "foo" in current context.
4285 not actually evaluate @var{expression} at the time the @code{condition}
4286 command (or a command that sets a breakpoint with a condition, like
4287 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4289 @item condition @var{bnum}
4290 Remove the condition from breakpoint number @var{bnum}. It becomes
4291 an ordinary unconditional breakpoint.
4294 @cindex ignore count (of breakpoint)
4295 A special case of a breakpoint condition is to stop only when the
4296 breakpoint has been reached a certain number of times. This is so
4297 useful that there is a special way to do it, using the @dfn{ignore
4298 count} of the breakpoint. Every breakpoint has an ignore count, which
4299 is an integer. Most of the time, the ignore count is zero, and
4300 therefore has no effect. But if your program reaches a breakpoint whose
4301 ignore count is positive, then instead of stopping, it just decrements
4302 the ignore count by one and continues. As a result, if the ignore count
4303 value is @var{n}, the breakpoint does not stop the next @var{n} times
4304 your program reaches it.
4308 @item ignore @var{bnum} @var{count}
4309 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4310 The next @var{count} times the breakpoint is reached, your program's
4311 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4314 To make the breakpoint stop the next time it is reached, specify
4317 When you use @code{continue} to resume execution of your program from a
4318 breakpoint, you can specify an ignore count directly as an argument to
4319 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4320 Stepping,,Continuing and Stepping}.
4322 If a breakpoint has a positive ignore count and a condition, the
4323 condition is not checked. Once the ignore count reaches zero,
4324 @value{GDBN} resumes checking the condition.
4326 You could achieve the effect of the ignore count with a condition such
4327 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4328 is decremented each time. @xref{Convenience Vars, ,Convenience
4332 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4335 @node Break Commands
4336 @subsection Breakpoint Command Lists
4338 @cindex breakpoint commands
4339 You can give any breakpoint (or watchpoint or catchpoint) a series of
4340 commands to execute when your program stops due to that breakpoint. For
4341 example, you might want to print the values of certain expressions, or
4342 enable other breakpoints.
4346 @kindex end@r{ (breakpoint commands)}
4347 @item commands @r{[}@var{range}@dots{}@r{]}
4348 @itemx @dots{} @var{command-list} @dots{}
4350 Specify a list of commands for the given breakpoints. The commands
4351 themselves appear on the following lines. Type a line containing just
4352 @code{end} to terminate the commands.
4354 To remove all commands from a breakpoint, type @code{commands} and
4355 follow it immediately with @code{end}; that is, give no commands.
4357 With no argument, @code{commands} refers to the last breakpoint,
4358 watchpoint, or catchpoint set (not to the breakpoint most recently
4359 encountered). If the most recent breakpoints were set with a single
4360 command, then the @code{commands} will apply to all the breakpoints
4361 set by that command. This applies to breakpoints set by
4362 @code{rbreak}, and also applies when a single @code{break} command
4363 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4367 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4368 disabled within a @var{command-list}.
4370 You can use breakpoint commands to start your program up again. Simply
4371 use the @code{continue} command, or @code{step}, or any other command
4372 that resumes execution.
4374 Any other commands in the command list, after a command that resumes
4375 execution, are ignored. This is because any time you resume execution
4376 (even with a simple @code{next} or @code{step}), you may encounter
4377 another breakpoint---which could have its own command list, leading to
4378 ambiguities about which list to execute.
4381 If the first command you specify in a command list is @code{silent}, the
4382 usual message about stopping at a breakpoint is not printed. This may
4383 be desirable for breakpoints that are to print a specific message and
4384 then continue. If none of the remaining commands print anything, you
4385 see no sign that the breakpoint was reached. @code{silent} is
4386 meaningful only at the beginning of a breakpoint command list.
4388 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4389 print precisely controlled output, and are often useful in silent
4390 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4392 For example, here is how you could use breakpoint commands to print the
4393 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4399 printf "x is %d\n",x
4404 One application for breakpoint commands is to compensate for one bug so
4405 you can test for another. Put a breakpoint just after the erroneous line
4406 of code, give it a condition to detect the case in which something
4407 erroneous has been done, and give it commands to assign correct values
4408 to any variables that need them. End with the @code{continue} command
4409 so that your program does not stop, and start with the @code{silent}
4410 command so that no output is produced. Here is an example:
4421 @node Save Breakpoints
4422 @subsection How to save breakpoints to a file
4424 To save breakpoint definitions to a file use the @w{@code{save
4425 breakpoints}} command.
4428 @kindex save breakpoints
4429 @cindex save breakpoints to a file for future sessions
4430 @item save breakpoints [@var{filename}]
4431 This command saves all current breakpoint definitions together with
4432 their commands and ignore counts, into a file @file{@var{filename}}
4433 suitable for use in a later debugging session. This includes all
4434 types of breakpoints (breakpoints, watchpoints, catchpoints,
4435 tracepoints). To read the saved breakpoint definitions, use the
4436 @code{source} command (@pxref{Command Files}). Note that watchpoints
4437 with expressions involving local variables may fail to be recreated
4438 because it may not be possible to access the context where the
4439 watchpoint is valid anymore. Because the saved breakpoint definitions
4440 are simply a sequence of @value{GDBN} commands that recreate the
4441 breakpoints, you can edit the file in your favorite editing program,
4442 and remove the breakpoint definitions you're not interested in, or
4443 that can no longer be recreated.
4446 @c @ifclear BARETARGET
4447 @node Error in Breakpoints
4448 @subsection ``Cannot insert breakpoints''
4450 If you request too many active hardware-assisted breakpoints and
4451 watchpoints, you will see this error message:
4453 @c FIXME: the precise wording of this message may change; the relevant
4454 @c source change is not committed yet (Sep 3, 1999).
4456 Stopped; cannot insert breakpoints.
4457 You may have requested too many hardware breakpoints and watchpoints.
4461 This message is printed when you attempt to resume the program, since
4462 only then @value{GDBN} knows exactly how many hardware breakpoints and
4463 watchpoints it needs to insert.
4465 When this message is printed, you need to disable or remove some of the
4466 hardware-assisted breakpoints and watchpoints, and then continue.
4468 @node Breakpoint-related Warnings
4469 @subsection ``Breakpoint address adjusted...''
4470 @cindex breakpoint address adjusted
4472 Some processor architectures place constraints on the addresses at
4473 which breakpoints may be placed. For architectures thus constrained,
4474 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4475 with the constraints dictated by the architecture.
4477 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4478 a VLIW architecture in which a number of RISC-like instructions may be
4479 bundled together for parallel execution. The FR-V architecture
4480 constrains the location of a breakpoint instruction within such a
4481 bundle to the instruction with the lowest address. @value{GDBN}
4482 honors this constraint by adjusting a breakpoint's address to the
4483 first in the bundle.
4485 It is not uncommon for optimized code to have bundles which contain
4486 instructions from different source statements, thus it may happen that
4487 a breakpoint's address will be adjusted from one source statement to
4488 another. Since this adjustment may significantly alter @value{GDBN}'s
4489 breakpoint related behavior from what the user expects, a warning is
4490 printed when the breakpoint is first set and also when the breakpoint
4493 A warning like the one below is printed when setting a breakpoint
4494 that's been subject to address adjustment:
4497 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4500 Such warnings are printed both for user settable and @value{GDBN}'s
4501 internal breakpoints. If you see one of these warnings, you should
4502 verify that a breakpoint set at the adjusted address will have the
4503 desired affect. If not, the breakpoint in question may be removed and
4504 other breakpoints may be set which will have the desired behavior.
4505 E.g., it may be sufficient to place the breakpoint at a later
4506 instruction. A conditional breakpoint may also be useful in some
4507 cases to prevent the breakpoint from triggering too often.
4509 @value{GDBN} will also issue a warning when stopping at one of these
4510 adjusted breakpoints:
4513 warning: Breakpoint 1 address previously adjusted from 0x00010414
4517 When this warning is encountered, it may be too late to take remedial
4518 action except in cases where the breakpoint is hit earlier or more
4519 frequently than expected.
4521 @node Continuing and Stepping
4522 @section Continuing and Stepping
4526 @cindex resuming execution
4527 @dfn{Continuing} means resuming program execution until your program
4528 completes normally. In contrast, @dfn{stepping} means executing just
4529 one more ``step'' of your program, where ``step'' may mean either one
4530 line of source code, or one machine instruction (depending on what
4531 particular command you use). Either when continuing or when stepping,
4532 your program may stop even sooner, due to a breakpoint or a signal. (If
4533 it stops due to a signal, you may want to use @code{handle}, or use
4534 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4538 @kindex c @r{(@code{continue})}
4539 @kindex fg @r{(resume foreground execution)}
4540 @item continue @r{[}@var{ignore-count}@r{]}
4541 @itemx c @r{[}@var{ignore-count}@r{]}
4542 @itemx fg @r{[}@var{ignore-count}@r{]}
4543 Resume program execution, at the address where your program last stopped;
4544 any breakpoints set at that address are bypassed. The optional argument
4545 @var{ignore-count} allows you to specify a further number of times to
4546 ignore a breakpoint at this location; its effect is like that of
4547 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4549 The argument @var{ignore-count} is meaningful only when your program
4550 stopped due to a breakpoint. At other times, the argument to
4551 @code{continue} is ignored.
4553 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4554 debugged program is deemed to be the foreground program) are provided
4555 purely for convenience, and have exactly the same behavior as
4559 To resume execution at a different place, you can use @code{return}
4560 (@pxref{Returning, ,Returning from a Function}) to go back to the
4561 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4562 Different Address}) to go to an arbitrary location in your program.
4564 A typical technique for using stepping is to set a breakpoint
4565 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4566 beginning of the function or the section of your program where a problem
4567 is believed to lie, run your program until it stops at that breakpoint,
4568 and then step through the suspect area, examining the variables that are
4569 interesting, until you see the problem happen.
4573 @kindex s @r{(@code{step})}
4575 Continue running your program until control reaches a different source
4576 line, then stop it and return control to @value{GDBN}. This command is
4577 abbreviated @code{s}.
4580 @c "without debugging information" is imprecise; actually "without line
4581 @c numbers in the debugging information". (gcc -g1 has debugging info but
4582 @c not line numbers). But it seems complex to try to make that
4583 @c distinction here.
4584 @emph{Warning:} If you use the @code{step} command while control is
4585 within a function that was compiled without debugging information,
4586 execution proceeds until control reaches a function that does have
4587 debugging information. Likewise, it will not step into a function which
4588 is compiled without debugging information. To step through functions
4589 without debugging information, use the @code{stepi} command, described
4593 The @code{step} command only stops at the first instruction of a source
4594 line. This prevents the multiple stops that could otherwise occur in
4595 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4596 to stop if a function that has debugging information is called within
4597 the line. In other words, @code{step} @emph{steps inside} any functions
4598 called within the line.
4600 Also, the @code{step} command only enters a function if there is line
4601 number information for the function. Otherwise it acts like the
4602 @code{next} command. This avoids problems when using @code{cc -gl}
4603 on MIPS machines. Previously, @code{step} entered subroutines if there
4604 was any debugging information about the routine.
4606 @item step @var{count}
4607 Continue running as in @code{step}, but do so @var{count} times. If a
4608 breakpoint is reached, or a signal not related to stepping occurs before
4609 @var{count} steps, stepping stops right away.
4612 @kindex n @r{(@code{next})}
4613 @item next @r{[}@var{count}@r{]}
4614 Continue to the next source line in the current (innermost) stack frame.
4615 This is similar to @code{step}, but function calls that appear within
4616 the line of code are executed without stopping. Execution stops when
4617 control reaches a different line of code at the original stack level
4618 that was executing when you gave the @code{next} command. This command
4619 is abbreviated @code{n}.
4621 An argument @var{count} is a repeat count, as for @code{step}.
4624 @c FIX ME!! Do we delete this, or is there a way it fits in with
4625 @c the following paragraph? --- Vctoria
4627 @c @code{next} within a function that lacks debugging information acts like
4628 @c @code{step}, but any function calls appearing within the code of the
4629 @c function are executed without stopping.
4631 The @code{next} command only stops at the first instruction of a
4632 source line. This prevents multiple stops that could otherwise occur in
4633 @code{switch} statements, @code{for} loops, etc.
4635 @kindex set step-mode
4637 @cindex functions without line info, and stepping
4638 @cindex stepping into functions with no line info
4639 @itemx set step-mode on
4640 The @code{set step-mode on} command causes the @code{step} command to
4641 stop at the first instruction of a function which contains no debug line
4642 information rather than stepping over it.
4644 This is useful in cases where you may be interested in inspecting the
4645 machine instructions of a function which has no symbolic info and do not
4646 want @value{GDBN} to automatically skip over this function.
4648 @item set step-mode off
4649 Causes the @code{step} command to step over any functions which contains no
4650 debug information. This is the default.
4652 @item show step-mode
4653 Show whether @value{GDBN} will stop in or step over functions without
4654 source line debug information.
4657 @kindex fin @r{(@code{finish})}
4659 Continue running until just after function in the selected stack frame
4660 returns. Print the returned value (if any). This command can be
4661 abbreviated as @code{fin}.
4663 Contrast this with the @code{return} command (@pxref{Returning,
4664 ,Returning from a Function}).
4667 @kindex u @r{(@code{until})}
4668 @cindex run until specified location
4671 Continue running until a source line past the current line, in the
4672 current stack frame, is reached. This command is used to avoid single
4673 stepping through a loop more than once. It is like the @code{next}
4674 command, except that when @code{until} encounters a jump, it
4675 automatically continues execution until the program counter is greater
4676 than the address of the jump.
4678 This means that when you reach the end of a loop after single stepping
4679 though it, @code{until} makes your program continue execution until it
4680 exits the loop. In contrast, a @code{next} command at the end of a loop
4681 simply steps back to the beginning of the loop, which forces you to step
4682 through the next iteration.
4684 @code{until} always stops your program if it attempts to exit the current
4687 @code{until} may produce somewhat counterintuitive results if the order
4688 of machine code does not match the order of the source lines. For
4689 example, in the following excerpt from a debugging session, the @code{f}
4690 (@code{frame}) command shows that execution is stopped at line
4691 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4695 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4697 (@value{GDBP}) until
4698 195 for ( ; argc > 0; NEXTARG) @{
4701 This happened because, for execution efficiency, the compiler had
4702 generated code for the loop closure test at the end, rather than the
4703 start, of the loop---even though the test in a C @code{for}-loop is
4704 written before the body of the loop. The @code{until} command appeared
4705 to step back to the beginning of the loop when it advanced to this
4706 expression; however, it has not really gone to an earlier
4707 statement---not in terms of the actual machine code.
4709 @code{until} with no argument works by means of single
4710 instruction stepping, and hence is slower than @code{until} with an
4713 @item until @var{location}
4714 @itemx u @var{location}
4715 Continue running your program until either the specified location is
4716 reached, or the current stack frame returns. @var{location} is any of
4717 the forms described in @ref{Specify Location}.
4718 This form of the command uses temporary breakpoints, and
4719 hence is quicker than @code{until} without an argument. The specified
4720 location is actually reached only if it is in the current frame. This
4721 implies that @code{until} can be used to skip over recursive function
4722 invocations. For instance in the code below, if the current location is
4723 line @code{96}, issuing @code{until 99} will execute the program up to
4724 line @code{99} in the same invocation of factorial, i.e., after the inner
4725 invocations have returned.
4728 94 int factorial (int value)
4730 96 if (value > 1) @{
4731 97 value *= factorial (value - 1);
4738 @kindex advance @var{location}
4739 @itemx advance @var{location}
4740 Continue running the program up to the given @var{location}. An argument is
4741 required, which should be of one of the forms described in
4742 @ref{Specify Location}.
4743 Execution will also stop upon exit from the current stack
4744 frame. This command is similar to @code{until}, but @code{advance} will
4745 not skip over recursive function calls, and the target location doesn't
4746 have to be in the same frame as the current one.
4750 @kindex si @r{(@code{stepi})}
4752 @itemx stepi @var{arg}
4754 Execute one machine instruction, then stop and return to the debugger.
4756 It is often useful to do @samp{display/i $pc} when stepping by machine
4757 instructions. This makes @value{GDBN} automatically display the next
4758 instruction to be executed, each time your program stops. @xref{Auto
4759 Display,, Automatic Display}.
4761 An argument is a repeat count, as in @code{step}.
4765 @kindex ni @r{(@code{nexti})}
4767 @itemx nexti @var{arg}
4769 Execute one machine instruction, but if it is a function call,
4770 proceed until the function returns.
4772 An argument is a repeat count, as in @code{next}.
4779 A signal is an asynchronous event that can happen in a program. The
4780 operating system defines the possible kinds of signals, and gives each
4781 kind a name and a number. For example, in Unix @code{SIGINT} is the
4782 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4783 @code{SIGSEGV} is the signal a program gets from referencing a place in
4784 memory far away from all the areas in use; @code{SIGALRM} occurs when
4785 the alarm clock timer goes off (which happens only if your program has
4786 requested an alarm).
4788 @cindex fatal signals
4789 Some signals, including @code{SIGALRM}, are a normal part of the
4790 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4791 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4792 program has not specified in advance some other way to handle the signal.
4793 @code{SIGINT} does not indicate an error in your program, but it is normally
4794 fatal so it can carry out the purpose of the interrupt: to kill the program.
4796 @value{GDBN} has the ability to detect any occurrence of a signal in your
4797 program. You can tell @value{GDBN} in advance what to do for each kind of
4800 @cindex handling signals
4801 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4802 @code{SIGALRM} be silently passed to your program
4803 (so as not to interfere with their role in the program's functioning)
4804 but to stop your program immediately whenever an error signal happens.
4805 You can change these settings with the @code{handle} command.
4808 @kindex info signals
4812 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4813 handle each one. You can use this to see the signal numbers of all
4814 the defined types of signals.
4816 @item info signals @var{sig}
4817 Similar, but print information only about the specified signal number.
4819 @code{info handle} is an alias for @code{info signals}.
4822 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4823 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4824 can be the number of a signal or its name (with or without the
4825 @samp{SIG} at the beginning); a list of signal numbers of the form
4826 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4827 known signals. Optional arguments @var{keywords}, described below,
4828 say what change to make.
4832 The keywords allowed by the @code{handle} command can be abbreviated.
4833 Their full names are:
4837 @value{GDBN} should not stop your program when this signal happens. It may
4838 still print a message telling you that the signal has come in.
4841 @value{GDBN} should stop your program when this signal happens. This implies
4842 the @code{print} keyword as well.
4845 @value{GDBN} should print a message when this signal happens.
4848 @value{GDBN} should not mention the occurrence of the signal at all. This
4849 implies the @code{nostop} keyword as well.
4853 @value{GDBN} should allow your program to see this signal; your program
4854 can handle the signal, or else it may terminate if the signal is fatal
4855 and not handled. @code{pass} and @code{noignore} are synonyms.
4859 @value{GDBN} should not allow your program to see this signal.
4860 @code{nopass} and @code{ignore} are synonyms.
4864 When a signal stops your program, the signal is not visible to the
4866 continue. Your program sees the signal then, if @code{pass} is in
4867 effect for the signal in question @emph{at that time}. In other words,
4868 after @value{GDBN} reports a signal, you can use the @code{handle}
4869 command with @code{pass} or @code{nopass} to control whether your
4870 program sees that signal when you continue.
4872 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4873 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4874 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4877 You can also use the @code{signal} command to prevent your program from
4878 seeing a signal, or cause it to see a signal it normally would not see,
4879 or to give it any signal at any time. For example, if your program stopped
4880 due to some sort of memory reference error, you might store correct
4881 values into the erroneous variables and continue, hoping to see more
4882 execution; but your program would probably terminate immediately as
4883 a result of the fatal signal once it saw the signal. To prevent this,
4884 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4887 @cindex extra signal information
4888 @anchor{extra signal information}
4890 On some targets, @value{GDBN} can inspect extra signal information
4891 associated with the intercepted signal, before it is actually
4892 delivered to the program being debugged. This information is exported
4893 by the convenience variable @code{$_siginfo}, and consists of data
4894 that is passed by the kernel to the signal handler at the time of the
4895 receipt of a signal. The data type of the information itself is
4896 target dependent. You can see the data type using the @code{ptype
4897 $_siginfo} command. On Unix systems, it typically corresponds to the
4898 standard @code{siginfo_t} type, as defined in the @file{signal.h}
4901 Here's an example, on a @sc{gnu}/Linux system, printing the stray
4902 referenced address that raised a segmentation fault.
4906 (@value{GDBP}) continue
4907 Program received signal SIGSEGV, Segmentation fault.
4908 0x0000000000400766 in main ()
4910 (@value{GDBP}) ptype $_siginfo
4917 struct @{...@} _kill;
4918 struct @{...@} _timer;
4920 struct @{...@} _sigchld;
4921 struct @{...@} _sigfault;
4922 struct @{...@} _sigpoll;
4925 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
4929 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
4930 $1 = (void *) 0x7ffff7ff7000
4934 Depending on target support, @code{$_siginfo} may also be writable.
4937 @section Stopping and Starting Multi-thread Programs
4939 @cindex stopped threads
4940 @cindex threads, stopped
4942 @cindex continuing threads
4943 @cindex threads, continuing
4945 @value{GDBN} supports debugging programs with multiple threads
4946 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
4947 are two modes of controlling execution of your program within the
4948 debugger. In the default mode, referred to as @dfn{all-stop mode},
4949 when any thread in your program stops (for example, at a breakpoint
4950 or while being stepped), all other threads in the program are also stopped by
4951 @value{GDBN}. On some targets, @value{GDBN} also supports
4952 @dfn{non-stop mode}, in which other threads can continue to run freely while
4953 you examine the stopped thread in the debugger.
4956 * All-Stop Mode:: All threads stop when GDB takes control
4957 * Non-Stop Mode:: Other threads continue to execute
4958 * Background Execution:: Running your program asynchronously
4959 * Thread-Specific Breakpoints:: Controlling breakpoints
4960 * Interrupted System Calls:: GDB may interfere with system calls
4961 * Observer Mode:: GDB does not alter program behavior
4965 @subsection All-Stop Mode
4967 @cindex all-stop mode
4969 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
4970 @emph{all} threads of execution stop, not just the current thread. This
4971 allows you to examine the overall state of the program, including
4972 switching between threads, without worrying that things may change
4975 Conversely, whenever you restart the program, @emph{all} threads start
4976 executing. @emph{This is true even when single-stepping} with commands
4977 like @code{step} or @code{next}.
4979 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4980 Since thread scheduling is up to your debugging target's operating
4981 system (not controlled by @value{GDBN}), other threads may
4982 execute more than one statement while the current thread completes a
4983 single step. Moreover, in general other threads stop in the middle of a
4984 statement, rather than at a clean statement boundary, when the program
4987 You might even find your program stopped in another thread after
4988 continuing or even single-stepping. This happens whenever some other
4989 thread runs into a breakpoint, a signal, or an exception before the
4990 first thread completes whatever you requested.
4992 @cindex automatic thread selection
4993 @cindex switching threads automatically
4994 @cindex threads, automatic switching
4995 Whenever @value{GDBN} stops your program, due to a breakpoint or a
4996 signal, it automatically selects the thread where that breakpoint or
4997 signal happened. @value{GDBN} alerts you to the context switch with a
4998 message such as @samp{[Switching to Thread @var{n}]} to identify the
5001 On some OSes, you can modify @value{GDBN}'s default behavior by
5002 locking the OS scheduler to allow only a single thread to run.
5005 @item set scheduler-locking @var{mode}
5006 @cindex scheduler locking mode
5007 @cindex lock scheduler
5008 Set the scheduler locking mode. If it is @code{off}, then there is no
5009 locking and any thread may run at any time. If @code{on}, then only the
5010 current thread may run when the inferior is resumed. The @code{step}
5011 mode optimizes for single-stepping; it prevents other threads
5012 from preempting the current thread while you are stepping, so that
5013 the focus of debugging does not change unexpectedly.
5014 Other threads only rarely (or never) get a chance to run
5015 when you step. They are more likely to run when you @samp{next} over a
5016 function call, and they are completely free to run when you use commands
5017 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5018 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5019 the current thread away from the thread that you are debugging.
5021 @item show scheduler-locking
5022 Display the current scheduler locking mode.
5025 @cindex resume threads of multiple processes simultaneously
5026 By default, when you issue one of the execution commands such as
5027 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5028 threads of the current inferior to run. For example, if @value{GDBN}
5029 is attached to two inferiors, each with two threads, the
5030 @code{continue} command resumes only the two threads of the current
5031 inferior. This is useful, for example, when you debug a program that
5032 forks and you want to hold the parent stopped (so that, for instance,
5033 it doesn't run to exit), while you debug the child. In other
5034 situations, you may not be interested in inspecting the current state
5035 of any of the processes @value{GDBN} is attached to, and you may want
5036 to resume them all until some breakpoint is hit. In the latter case,
5037 you can instruct @value{GDBN} to allow all threads of all the
5038 inferiors to run with the @w{@code{set schedule-multiple}} command.
5041 @kindex set schedule-multiple
5042 @item set schedule-multiple
5043 Set the mode for allowing threads of multiple processes to be resumed
5044 when an execution command is issued. When @code{on}, all threads of
5045 all processes are allowed to run. When @code{off}, only the threads
5046 of the current process are resumed. The default is @code{off}. The
5047 @code{scheduler-locking} mode takes precedence when set to @code{on},
5048 or while you are stepping and set to @code{step}.
5050 @item show schedule-multiple
5051 Display the current mode for resuming the execution of threads of
5056 @subsection Non-Stop Mode
5058 @cindex non-stop mode
5060 @c This section is really only a place-holder, and needs to be expanded
5061 @c with more details.
5063 For some multi-threaded targets, @value{GDBN} supports an optional
5064 mode of operation in which you can examine stopped program threads in
5065 the debugger while other threads continue to execute freely. This
5066 minimizes intrusion when debugging live systems, such as programs
5067 where some threads have real-time constraints or must continue to
5068 respond to external events. This is referred to as @dfn{non-stop} mode.
5070 In non-stop mode, when a thread stops to report a debugging event,
5071 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5072 threads as well, in contrast to the all-stop mode behavior. Additionally,
5073 execution commands such as @code{continue} and @code{step} apply by default
5074 only to the current thread in non-stop mode, rather than all threads as
5075 in all-stop mode. This allows you to control threads explicitly in
5076 ways that are not possible in all-stop mode --- for example, stepping
5077 one thread while allowing others to run freely, stepping
5078 one thread while holding all others stopped, or stepping several threads
5079 independently and simultaneously.
5081 To enter non-stop mode, use this sequence of commands before you run
5082 or attach to your program:
5085 # Enable the async interface.
5088 # If using the CLI, pagination breaks non-stop.
5091 # Finally, turn it on!
5095 You can use these commands to manipulate the non-stop mode setting:
5098 @kindex set non-stop
5099 @item set non-stop on
5100 Enable selection of non-stop mode.
5101 @item set non-stop off
5102 Disable selection of non-stop mode.
5103 @kindex show non-stop
5105 Show the current non-stop enablement setting.
5108 Note these commands only reflect whether non-stop mode is enabled,
5109 not whether the currently-executing program is being run in non-stop mode.
5110 In particular, the @code{set non-stop} preference is only consulted when
5111 @value{GDBN} starts or connects to the target program, and it is generally
5112 not possible to switch modes once debugging has started. Furthermore,
5113 since not all targets support non-stop mode, even when you have enabled
5114 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5117 In non-stop mode, all execution commands apply only to the current thread
5118 by default. That is, @code{continue} only continues one thread.
5119 To continue all threads, issue @code{continue -a} or @code{c -a}.
5121 You can use @value{GDBN}'s background execution commands
5122 (@pxref{Background Execution}) to run some threads in the background
5123 while you continue to examine or step others from @value{GDBN}.
5124 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5125 always executed asynchronously in non-stop mode.
5127 Suspending execution is done with the @code{interrupt} command when
5128 running in the background, or @kbd{Ctrl-c} during foreground execution.
5129 In all-stop mode, this stops the whole process;
5130 but in non-stop mode the interrupt applies only to the current thread.
5131 To stop the whole program, use @code{interrupt -a}.
5133 Other execution commands do not currently support the @code{-a} option.
5135 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5136 that thread current, as it does in all-stop mode. This is because the
5137 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5138 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5139 changed to a different thread just as you entered a command to operate on the
5140 previously current thread.
5142 @node Background Execution
5143 @subsection Background Execution
5145 @cindex foreground execution
5146 @cindex background execution
5147 @cindex asynchronous execution
5148 @cindex execution, foreground, background and asynchronous
5150 @value{GDBN}'s execution commands have two variants: the normal
5151 foreground (synchronous) behavior, and a background
5152 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5153 the program to report that some thread has stopped before prompting for
5154 another command. In background execution, @value{GDBN} immediately gives
5155 a command prompt so that you can issue other commands while your program runs.
5157 You need to explicitly enable asynchronous mode before you can use
5158 background execution commands. You can use these commands to
5159 manipulate the asynchronous mode setting:
5162 @kindex set target-async
5163 @item set target-async on
5164 Enable asynchronous mode.
5165 @item set target-async off
5166 Disable asynchronous mode.
5167 @kindex show target-async
5168 @item show target-async
5169 Show the current target-async setting.
5172 If the target doesn't support async mode, @value{GDBN} issues an error
5173 message if you attempt to use the background execution commands.
5175 To specify background execution, add a @code{&} to the command. For example,
5176 the background form of the @code{continue} command is @code{continue&}, or
5177 just @code{c&}. The execution commands that accept background execution
5183 @xref{Starting, , Starting your Program}.
5187 @xref{Attach, , Debugging an Already-running Process}.
5191 @xref{Continuing and Stepping, step}.
5195 @xref{Continuing and Stepping, stepi}.
5199 @xref{Continuing and Stepping, next}.
5203 @xref{Continuing and Stepping, nexti}.
5207 @xref{Continuing and Stepping, continue}.
5211 @xref{Continuing and Stepping, finish}.
5215 @xref{Continuing and Stepping, until}.
5219 Background execution is especially useful in conjunction with non-stop
5220 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5221 However, you can also use these commands in the normal all-stop mode with
5222 the restriction that you cannot issue another execution command until the
5223 previous one finishes. Examples of commands that are valid in all-stop
5224 mode while the program is running include @code{help} and @code{info break}.
5226 You can interrupt your program while it is running in the background by
5227 using the @code{interrupt} command.
5234 Suspend execution of the running program. In all-stop mode,
5235 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5236 only the current thread. To stop the whole program in non-stop mode,
5237 use @code{interrupt -a}.
5240 @node Thread-Specific Breakpoints
5241 @subsection Thread-Specific Breakpoints
5243 When your program has multiple threads (@pxref{Threads,, Debugging
5244 Programs with Multiple Threads}), you can choose whether to set
5245 breakpoints on all threads, or on a particular thread.
5248 @cindex breakpoints and threads
5249 @cindex thread breakpoints
5250 @kindex break @dots{} thread @var{threadno}
5251 @item break @var{linespec} thread @var{threadno}
5252 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5253 @var{linespec} specifies source lines; there are several ways of
5254 writing them (@pxref{Specify Location}), but the effect is always to
5255 specify some source line.
5257 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5258 to specify that you only want @value{GDBN} to stop the program when a
5259 particular thread reaches this breakpoint. @var{threadno} is one of the
5260 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5261 column of the @samp{info threads} display.
5263 If you do not specify @samp{thread @var{threadno}} when you set a
5264 breakpoint, the breakpoint applies to @emph{all} threads of your
5267 You can use the @code{thread} qualifier on conditional breakpoints as
5268 well; in this case, place @samp{thread @var{threadno}} before or
5269 after the breakpoint condition, like this:
5272 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5277 @node Interrupted System Calls
5278 @subsection Interrupted System Calls
5280 @cindex thread breakpoints and system calls
5281 @cindex system calls and thread breakpoints
5282 @cindex premature return from system calls
5283 There is an unfortunate side effect when using @value{GDBN} to debug
5284 multi-threaded programs. If one thread stops for a
5285 breakpoint, or for some other reason, and another thread is blocked in a
5286 system call, then the system call may return prematurely. This is a
5287 consequence of the interaction between multiple threads and the signals
5288 that @value{GDBN} uses to implement breakpoints and other events that
5291 To handle this problem, your program should check the return value of
5292 each system call and react appropriately. This is good programming
5295 For example, do not write code like this:
5301 The call to @code{sleep} will return early if a different thread stops
5302 at a breakpoint or for some other reason.
5304 Instead, write this:
5309 unslept = sleep (unslept);
5312 A system call is allowed to return early, so the system is still
5313 conforming to its specification. But @value{GDBN} does cause your
5314 multi-threaded program to behave differently than it would without
5317 Also, @value{GDBN} uses internal breakpoints in the thread library to
5318 monitor certain events such as thread creation and thread destruction.
5319 When such an event happens, a system call in another thread may return
5320 prematurely, even though your program does not appear to stop.
5323 @subsection Observer Mode
5325 If you want to build on non-stop mode and observe program behavior
5326 without any chance of disruption by @value{GDBN}, you can set
5327 variables to disable all of the debugger's attempts to modify state,
5328 whether by writing memory, inserting breakpoints, etc. These operate
5329 at a low level, intercepting operations from all commands.
5331 When all of these are set to @code{off}, then @value{GDBN} is said to
5332 be @dfn{observer mode}. As a convenience, the variable
5333 @code{observer} can be set to disable these, plus enable non-stop
5336 Note that @value{GDBN} will not prevent you from making nonsensical
5337 combinations of these settings. For instance, if you have enabled
5338 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5339 then breakpoints that work by writing trap instructions into the code
5340 stream will still not be able to be placed.
5345 @item set observer on
5346 @itemx set observer off
5347 When set to @code{on}, this disables all the permission variables
5348 below (except for @code{insert-fast-tracepoints}), plus enables
5349 non-stop debugging. Setting this to @code{off} switches back to
5350 normal debugging, though remaining in non-stop mode.
5353 Show whether observer mode is on or off.
5355 @kindex may-write-registers
5356 @item set may-write-registers on
5357 @itemx set may-write-registers off
5358 This controls whether @value{GDBN} will attempt to alter the values of
5359 registers, such as with assignment expressions in @code{print}, or the
5360 @code{jump} command. It defaults to @code{on}.
5362 @item show may-write-registers
5363 Show the current permission to write registers.
5365 @kindex may-write-memory
5366 @item set may-write-memory on
5367 @itemx set may-write-memory off
5368 This controls whether @value{GDBN} will attempt to alter the contents
5369 of memory, such as with assignment expressions in @code{print}. It
5370 defaults to @code{on}.
5372 @item show may-write-memory
5373 Show the current permission to write memory.
5375 @kindex may-insert-breakpoints
5376 @item set may-insert-breakpoints on
5377 @itemx set may-insert-breakpoints off
5378 This controls whether @value{GDBN} will attempt to insert breakpoints.
5379 This affects all breakpoints, including internal breakpoints defined
5380 by @value{GDBN}. It defaults to @code{on}.
5382 @item show may-insert-breakpoints
5383 Show the current permission to insert breakpoints.
5385 @kindex may-insert-tracepoints
5386 @item set may-insert-tracepoints on
5387 @itemx set may-insert-tracepoints off
5388 This controls whether @value{GDBN} will attempt to insert (regular)
5389 tracepoints at the beginning of a tracing experiment. It affects only
5390 non-fast tracepoints, fast tracepoints being under the control of
5391 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5393 @item show may-insert-tracepoints
5394 Show the current permission to insert tracepoints.
5396 @kindex may-insert-fast-tracepoints
5397 @item set may-insert-fast-tracepoints on
5398 @itemx set may-insert-fast-tracepoints off
5399 This controls whether @value{GDBN} will attempt to insert fast
5400 tracepoints at the beginning of a tracing experiment. It affects only
5401 fast tracepoints, regular (non-fast) tracepoints being under the
5402 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5404 @item show may-insert-fast-tracepoints
5405 Show the current permission to insert fast tracepoints.
5407 @kindex may-interrupt
5408 @item set may-interrupt on
5409 @itemx set may-interrupt off
5410 This controls whether @value{GDBN} will attempt to interrupt or stop
5411 program execution. When this variable is @code{off}, the
5412 @code{interrupt} command will have no effect, nor will
5413 @kbd{Ctrl-c}. It defaults to @code{on}.
5415 @item show may-interrupt
5416 Show the current permission to interrupt or stop the program.
5420 @node Reverse Execution
5421 @chapter Running programs backward
5422 @cindex reverse execution
5423 @cindex running programs backward
5425 When you are debugging a program, it is not unusual to realize that
5426 you have gone too far, and some event of interest has already happened.
5427 If the target environment supports it, @value{GDBN} can allow you to
5428 ``rewind'' the program by running it backward.
5430 A target environment that supports reverse execution should be able
5431 to ``undo'' the changes in machine state that have taken place as the
5432 program was executing normally. Variables, registers etc.@: should
5433 revert to their previous values. Obviously this requires a great
5434 deal of sophistication on the part of the target environment; not
5435 all target environments can support reverse execution.
5437 When a program is executed in reverse, the instructions that
5438 have most recently been executed are ``un-executed'', in reverse
5439 order. The program counter runs backward, following the previous
5440 thread of execution in reverse. As each instruction is ``un-executed'',
5441 the values of memory and/or registers that were changed by that
5442 instruction are reverted to their previous states. After executing
5443 a piece of source code in reverse, all side effects of that code
5444 should be ``undone'', and all variables should be returned to their
5445 prior values@footnote{
5446 Note that some side effects are easier to undo than others. For instance,
5447 memory and registers are relatively easy, but device I/O is hard. Some
5448 targets may be able undo things like device I/O, and some may not.
5450 The contract between @value{GDBN} and the reverse executing target
5451 requires only that the target do something reasonable when
5452 @value{GDBN} tells it to execute backwards, and then report the
5453 results back to @value{GDBN}. Whatever the target reports back to
5454 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5455 assumes that the memory and registers that the target reports are in a
5456 consistant state, but @value{GDBN} accepts whatever it is given.
5459 If you are debugging in a target environment that supports
5460 reverse execution, @value{GDBN} provides the following commands.
5463 @kindex reverse-continue
5464 @kindex rc @r{(@code{reverse-continue})}
5465 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5466 @itemx rc @r{[}@var{ignore-count}@r{]}
5467 Beginning at the point where your program last stopped, start executing
5468 in reverse. Reverse execution will stop for breakpoints and synchronous
5469 exceptions (signals), just like normal execution. Behavior of
5470 asynchronous signals depends on the target environment.
5472 @kindex reverse-step
5473 @kindex rs @r{(@code{step})}
5474 @item reverse-step @r{[}@var{count}@r{]}
5475 Run the program backward until control reaches the start of a
5476 different source line; then stop it, and return control to @value{GDBN}.
5478 Like the @code{step} command, @code{reverse-step} will only stop
5479 at the beginning of a source line. It ``un-executes'' the previously
5480 executed source line. If the previous source line included calls to
5481 debuggable functions, @code{reverse-step} will step (backward) into
5482 the called function, stopping at the beginning of the @emph{last}
5483 statement in the called function (typically a return statement).
5485 Also, as with the @code{step} command, if non-debuggable functions are
5486 called, @code{reverse-step} will run thru them backward without stopping.
5488 @kindex reverse-stepi
5489 @kindex rsi @r{(@code{reverse-stepi})}
5490 @item reverse-stepi @r{[}@var{count}@r{]}
5491 Reverse-execute one machine instruction. Note that the instruction
5492 to be reverse-executed is @emph{not} the one pointed to by the program
5493 counter, but the instruction executed prior to that one. For instance,
5494 if the last instruction was a jump, @code{reverse-stepi} will take you
5495 back from the destination of the jump to the jump instruction itself.
5497 @kindex reverse-next
5498 @kindex rn @r{(@code{reverse-next})}
5499 @item reverse-next @r{[}@var{count}@r{]}
5500 Run backward to the beginning of the previous line executed in
5501 the current (innermost) stack frame. If the line contains function
5502 calls, they will be ``un-executed'' without stopping. Starting from
5503 the first line of a function, @code{reverse-next} will take you back
5504 to the caller of that function, @emph{before} the function was called,
5505 just as the normal @code{next} command would take you from the last
5506 line of a function back to its return to its caller
5507 @footnote{Unless the code is too heavily optimized.}.
5509 @kindex reverse-nexti
5510 @kindex rni @r{(@code{reverse-nexti})}
5511 @item reverse-nexti @r{[}@var{count}@r{]}
5512 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5513 in reverse, except that called functions are ``un-executed'' atomically.
5514 That is, if the previously executed instruction was a return from
5515 another function, @code{reverse-nexti} will continue to execute
5516 in reverse until the call to that function (from the current stack
5519 @kindex reverse-finish
5520 @item reverse-finish
5521 Just as the @code{finish} command takes you to the point where the
5522 current function returns, @code{reverse-finish} takes you to the point
5523 where it was called. Instead of ending up at the end of the current
5524 function invocation, you end up at the beginning.
5526 @kindex set exec-direction
5527 @item set exec-direction
5528 Set the direction of target execution.
5529 @itemx set exec-direction reverse
5530 @cindex execute forward or backward in time
5531 @value{GDBN} will perform all execution commands in reverse, until the
5532 exec-direction mode is changed to ``forward''. Affected commands include
5533 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5534 command cannot be used in reverse mode.
5535 @item set exec-direction forward
5536 @value{GDBN} will perform all execution commands in the normal fashion.
5537 This is the default.
5541 @node Process Record and Replay
5542 @chapter Recording Inferior's Execution and Replaying It
5543 @cindex process record and replay
5544 @cindex recording inferior's execution and replaying it
5546 On some platforms, @value{GDBN} provides a special @dfn{process record
5547 and replay} target that can record a log of the process execution, and
5548 replay it later with both forward and reverse execution commands.
5551 When this target is in use, if the execution log includes the record
5552 for the next instruction, @value{GDBN} will debug in @dfn{replay
5553 mode}. In the replay mode, the inferior does not really execute code
5554 instructions. Instead, all the events that normally happen during
5555 code execution are taken from the execution log. While code is not
5556 really executed in replay mode, the values of registers (including the
5557 program counter register) and the memory of the inferior are still
5558 changed as they normally would. Their contents are taken from the
5562 If the record for the next instruction is not in the execution log,
5563 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5564 inferior executes normally, and @value{GDBN} records the execution log
5567 The process record and replay target supports reverse execution
5568 (@pxref{Reverse Execution}), even if the platform on which the
5569 inferior runs does not. However, the reverse execution is limited in
5570 this case by the range of the instructions recorded in the execution
5571 log. In other words, reverse execution on platforms that don't
5572 support it directly can only be done in the replay mode.
5574 When debugging in the reverse direction, @value{GDBN} will work in
5575 replay mode as long as the execution log includes the record for the
5576 previous instruction; otherwise, it will work in record mode, if the
5577 platform supports reverse execution, or stop if not.
5579 For architecture environments that support process record and replay,
5580 @value{GDBN} provides the following commands:
5583 @kindex target record
5587 This command starts the process record and replay target. The process
5588 record and replay target can only debug a process that is already
5589 running. Therefore, you need first to start the process with the
5590 @kbd{run} or @kbd{start} commands, and then start the recording with
5591 the @kbd{target record} command.
5593 Both @code{record} and @code{rec} are aliases of @code{target record}.
5595 @cindex displaced stepping, and process record and replay
5596 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5597 will be automatically disabled when process record and replay target
5598 is started. That's because the process record and replay target
5599 doesn't support displaced stepping.
5601 @cindex non-stop mode, and process record and replay
5602 @cindex asynchronous execution, and process record and replay
5603 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5604 the asynchronous execution mode (@pxref{Background Execution}), the
5605 process record and replay target cannot be started because it doesn't
5606 support these two modes.
5611 Stop the process record and replay target. When process record and
5612 replay target stops, the entire execution log will be deleted and the
5613 inferior will either be terminated, or will remain in its final state.
5615 When you stop the process record and replay target in record mode (at
5616 the end of the execution log), the inferior will be stopped at the
5617 next instruction that would have been recorded. In other words, if
5618 you record for a while and then stop recording, the inferior process
5619 will be left in the same state as if the recording never happened.
5621 On the other hand, if the process record and replay target is stopped
5622 while in replay mode (that is, not at the end of the execution log,
5623 but at some earlier point), the inferior process will become ``live''
5624 at that earlier state, and it will then be possible to continue the
5625 usual ``live'' debugging of the process from that state.
5627 When the inferior process exits, or @value{GDBN} detaches from it,
5628 process record and replay target will automatically stop itself.
5630 @kindex set record insn-number-max
5631 @item set record insn-number-max @var{limit}
5632 Set the limit of instructions to be recorded. Default value is 200000.
5634 If @var{limit} is a positive number, then @value{GDBN} will start
5635 deleting instructions from the log once the number of the record
5636 instructions becomes greater than @var{limit}. For every new recorded
5637 instruction, @value{GDBN} will delete the earliest recorded
5638 instruction to keep the number of recorded instructions at the limit.
5639 (Since deleting recorded instructions loses information, @value{GDBN}
5640 lets you control what happens when the limit is reached, by means of
5641 the @code{stop-at-limit} option, described below.)
5643 If @var{limit} is zero, @value{GDBN} will never delete recorded
5644 instructions from the execution log. The number of recorded
5645 instructions is unlimited in this case.
5647 @kindex show record insn-number-max
5648 @item show record insn-number-max
5649 Show the limit of instructions to be recorded.
5651 @kindex set record stop-at-limit
5652 @item set record stop-at-limit
5653 Control the behavior when the number of recorded instructions reaches
5654 the limit. If ON (the default), @value{GDBN} will stop when the limit
5655 is reached for the first time and ask you whether you want to stop the
5656 inferior or continue running it and recording the execution log. If
5657 you decide to continue recording, each new recorded instruction will
5658 cause the oldest one to be deleted.
5660 If this option is OFF, @value{GDBN} will automatically delete the
5661 oldest record to make room for each new one, without asking.
5663 @kindex show record stop-at-limit
5664 @item show record stop-at-limit
5665 Show the current setting of @code{stop-at-limit}.
5669 Show various statistics about the state of process record and its
5670 in-memory execution log buffer, including:
5674 Whether in record mode or replay mode.
5676 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
5678 Highest recorded instruction number.
5680 Current instruction about to be replayed (if in replay mode).
5682 Number of instructions contained in the execution log.
5684 Maximum number of instructions that may be contained in the execution log.
5687 @kindex record delete
5690 When record target runs in replay mode (``in the past''), delete the
5691 subsequent execution log and begin to record a new execution log starting
5692 from the current address. This means you will abandon the previously
5693 recorded ``future'' and begin recording a new ``future''.
5698 @chapter Examining the Stack
5700 When your program has stopped, the first thing you need to know is where it
5701 stopped and how it got there.
5704 Each time your program performs a function call, information about the call
5706 That information includes the location of the call in your program,
5707 the arguments of the call,
5708 and the local variables of the function being called.
5709 The information is saved in a block of data called a @dfn{stack frame}.
5710 The stack frames are allocated in a region of memory called the @dfn{call
5713 When your program stops, the @value{GDBN} commands for examining the
5714 stack allow you to see all of this information.
5716 @cindex selected frame
5717 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5718 @value{GDBN} commands refer implicitly to the selected frame. In
5719 particular, whenever you ask @value{GDBN} for the value of a variable in
5720 your program, the value is found in the selected frame. There are
5721 special @value{GDBN} commands to select whichever frame you are
5722 interested in. @xref{Selection, ,Selecting a Frame}.
5724 When your program stops, @value{GDBN} automatically selects the
5725 currently executing frame and describes it briefly, similar to the
5726 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5729 * Frames:: Stack frames
5730 * Backtrace:: Backtraces
5731 * Selection:: Selecting a frame
5732 * Frame Info:: Information on a frame
5737 @section Stack Frames
5739 @cindex frame, definition
5741 The call stack is divided up into contiguous pieces called @dfn{stack
5742 frames}, or @dfn{frames} for short; each frame is the data associated
5743 with one call to one function. The frame contains the arguments given
5744 to the function, the function's local variables, and the address at
5745 which the function is executing.
5747 @cindex initial frame
5748 @cindex outermost frame
5749 @cindex innermost frame
5750 When your program is started, the stack has only one frame, that of the
5751 function @code{main}. This is called the @dfn{initial} frame or the
5752 @dfn{outermost} frame. Each time a function is called, a new frame is
5753 made. Each time a function returns, the frame for that function invocation
5754 is eliminated. If a function is recursive, there can be many frames for
5755 the same function. The frame for the function in which execution is
5756 actually occurring is called the @dfn{innermost} frame. This is the most
5757 recently created of all the stack frames that still exist.
5759 @cindex frame pointer
5760 Inside your program, stack frames are identified by their addresses. A
5761 stack frame consists of many bytes, each of which has its own address; each
5762 kind of computer has a convention for choosing one byte whose
5763 address serves as the address of the frame. Usually this address is kept
5764 in a register called the @dfn{frame pointer register}
5765 (@pxref{Registers, $fp}) while execution is going on in that frame.
5767 @cindex frame number
5768 @value{GDBN} assigns numbers to all existing stack frames, starting with
5769 zero for the innermost frame, one for the frame that called it,
5770 and so on upward. These numbers do not really exist in your program;
5771 they are assigned by @value{GDBN} to give you a way of designating stack
5772 frames in @value{GDBN} commands.
5774 @c The -fomit-frame-pointer below perennially causes hbox overflow
5775 @c underflow problems.
5776 @cindex frameless execution
5777 Some compilers provide a way to compile functions so that they operate
5778 without stack frames. (For example, the @value{NGCC} option
5780 @samp{-fomit-frame-pointer}
5782 generates functions without a frame.)
5783 This is occasionally done with heavily used library functions to save
5784 the frame setup time. @value{GDBN} has limited facilities for dealing
5785 with these function invocations. If the innermost function invocation
5786 has no stack frame, @value{GDBN} nevertheless regards it as though
5787 it had a separate frame, which is numbered zero as usual, allowing
5788 correct tracing of the function call chain. However, @value{GDBN} has
5789 no provision for frameless functions elsewhere in the stack.
5792 @kindex frame@r{, command}
5793 @cindex current stack frame
5794 @item frame @var{args}
5795 The @code{frame} command allows you to move from one stack frame to another,
5796 and to print the stack frame you select. @var{args} may be either the
5797 address of the frame or the stack frame number. Without an argument,
5798 @code{frame} prints the current stack frame.
5800 @kindex select-frame
5801 @cindex selecting frame silently
5803 The @code{select-frame} command allows you to move from one stack frame
5804 to another without printing the frame. This is the silent version of
5812 @cindex call stack traces
5813 A backtrace is a summary of how your program got where it is. It shows one
5814 line per frame, for many frames, starting with the currently executing
5815 frame (frame zero), followed by its caller (frame one), and on up the
5820 @kindex bt @r{(@code{backtrace})}
5823 Print a backtrace of the entire stack: one line per frame for all
5824 frames in the stack.
5826 You can stop the backtrace at any time by typing the system interrupt
5827 character, normally @kbd{Ctrl-c}.
5829 @item backtrace @var{n}
5831 Similar, but print only the innermost @var{n} frames.
5833 @item backtrace -@var{n}
5835 Similar, but print only the outermost @var{n} frames.
5837 @item backtrace full
5839 @itemx bt full @var{n}
5840 @itemx bt full -@var{n}
5841 Print the values of the local variables also. @var{n} specifies the
5842 number of frames to print, as described above.
5847 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5848 are additional aliases for @code{backtrace}.
5850 @cindex multiple threads, backtrace
5851 In a multi-threaded program, @value{GDBN} by default shows the
5852 backtrace only for the current thread. To display the backtrace for
5853 several or all of the threads, use the command @code{thread apply}
5854 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5855 apply all backtrace}, @value{GDBN} will display the backtrace for all
5856 the threads; this is handy when you debug a core dump of a
5857 multi-threaded program.
5859 Each line in the backtrace shows the frame number and the function name.
5860 The program counter value is also shown---unless you use @code{set
5861 print address off}. The backtrace also shows the source file name and
5862 line number, as well as the arguments to the function. The program
5863 counter value is omitted if it is at the beginning of the code for that
5866 Here is an example of a backtrace. It was made with the command
5867 @samp{bt 3}, so it shows the innermost three frames.
5871 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5873 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
5874 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5876 (More stack frames follow...)
5881 The display for frame zero does not begin with a program counter
5882 value, indicating that your program has stopped at the beginning of the
5883 code for line @code{993} of @code{builtin.c}.
5886 The value of parameter @code{data} in frame 1 has been replaced by
5887 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
5888 only if it is a scalar (integer, pointer, enumeration, etc). See command
5889 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
5890 on how to configure the way function parameter values are printed.
5892 @cindex value optimized out, in backtrace
5893 @cindex function call arguments, optimized out
5894 If your program was compiled with optimizations, some compilers will
5895 optimize away arguments passed to functions if those arguments are
5896 never used after the call. Such optimizations generate code that
5897 passes arguments through registers, but doesn't store those arguments
5898 in the stack frame. @value{GDBN} has no way of displaying such
5899 arguments in stack frames other than the innermost one. Here's what
5900 such a backtrace might look like:
5904 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5906 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
5907 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
5909 (More stack frames follow...)
5914 The values of arguments that were not saved in their stack frames are
5915 shown as @samp{<value optimized out>}.
5917 If you need to display the values of such optimized-out arguments,
5918 either deduce that from other variables whose values depend on the one
5919 you are interested in, or recompile without optimizations.
5921 @cindex backtrace beyond @code{main} function
5922 @cindex program entry point
5923 @cindex startup code, and backtrace
5924 Most programs have a standard user entry point---a place where system
5925 libraries and startup code transition into user code. For C this is
5926 @code{main}@footnote{
5927 Note that embedded programs (the so-called ``free-standing''
5928 environment) are not required to have a @code{main} function as the
5929 entry point. They could even have multiple entry points.}.
5930 When @value{GDBN} finds the entry function in a backtrace
5931 it will terminate the backtrace, to avoid tracing into highly
5932 system-specific (and generally uninteresting) code.
5934 If you need to examine the startup code, or limit the number of levels
5935 in a backtrace, you can change this behavior:
5938 @item set backtrace past-main
5939 @itemx set backtrace past-main on
5940 @kindex set backtrace
5941 Backtraces will continue past the user entry point.
5943 @item set backtrace past-main off
5944 Backtraces will stop when they encounter the user entry point. This is the
5947 @item show backtrace past-main
5948 @kindex show backtrace
5949 Display the current user entry point backtrace policy.
5951 @item set backtrace past-entry
5952 @itemx set backtrace past-entry on
5953 Backtraces will continue past the internal entry point of an application.
5954 This entry point is encoded by the linker when the application is built,
5955 and is likely before the user entry point @code{main} (or equivalent) is called.
5957 @item set backtrace past-entry off
5958 Backtraces will stop when they encounter the internal entry point of an
5959 application. This is the default.
5961 @item show backtrace past-entry
5962 Display the current internal entry point backtrace policy.
5964 @item set backtrace limit @var{n}
5965 @itemx set backtrace limit 0
5966 @cindex backtrace limit
5967 Limit the backtrace to @var{n} levels. A value of zero means
5970 @item show backtrace limit
5971 Display the current limit on backtrace levels.
5975 @section Selecting a Frame
5977 Most commands for examining the stack and other data in your program work on
5978 whichever stack frame is selected at the moment. Here are the commands for
5979 selecting a stack frame; all of them finish by printing a brief description
5980 of the stack frame just selected.
5983 @kindex frame@r{, selecting}
5984 @kindex f @r{(@code{frame})}
5987 Select frame number @var{n}. Recall that frame zero is the innermost
5988 (currently executing) frame, frame one is the frame that called the
5989 innermost one, and so on. The highest-numbered frame is the one for
5992 @item frame @var{addr}
5994 Select the frame at address @var{addr}. This is useful mainly if the
5995 chaining of stack frames has been damaged by a bug, making it
5996 impossible for @value{GDBN} to assign numbers properly to all frames. In
5997 addition, this can be useful when your program has multiple stacks and
5998 switches between them.
6000 On the SPARC architecture, @code{frame} needs two addresses to
6001 select an arbitrary frame: a frame pointer and a stack pointer.
6003 On the MIPS and Alpha architecture, it needs two addresses: a stack
6004 pointer and a program counter.
6006 On the 29k architecture, it needs three addresses: a register stack
6007 pointer, a program counter, and a memory stack pointer.
6011 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6012 advances toward the outermost frame, to higher frame numbers, to frames
6013 that have existed longer. @var{n} defaults to one.
6016 @kindex do @r{(@code{down})}
6018 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6019 advances toward the innermost frame, to lower frame numbers, to frames
6020 that were created more recently. @var{n} defaults to one. You may
6021 abbreviate @code{down} as @code{do}.
6024 All of these commands end by printing two lines of output describing the
6025 frame. The first line shows the frame number, the function name, the
6026 arguments, and the source file and line number of execution in that
6027 frame. The second line shows the text of that source line.
6035 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6037 10 read_input_file (argv[i]);
6041 After such a printout, the @code{list} command with no arguments
6042 prints ten lines centered on the point of execution in the frame.
6043 You can also edit the program at the point of execution with your favorite
6044 editing program by typing @code{edit}.
6045 @xref{List, ,Printing Source Lines},
6049 @kindex down-silently
6051 @item up-silently @var{n}
6052 @itemx down-silently @var{n}
6053 These two commands are variants of @code{up} and @code{down},
6054 respectively; they differ in that they do their work silently, without
6055 causing display of the new frame. They are intended primarily for use
6056 in @value{GDBN} command scripts, where the output might be unnecessary and
6061 @section Information About a Frame
6063 There are several other commands to print information about the selected
6069 When used without any argument, this command does not change which
6070 frame is selected, but prints a brief description of the currently
6071 selected stack frame. It can be abbreviated @code{f}. With an
6072 argument, this command is used to select a stack frame.
6073 @xref{Selection, ,Selecting a Frame}.
6076 @kindex info f @r{(@code{info frame})}
6079 This command prints a verbose description of the selected stack frame,
6084 the address of the frame
6086 the address of the next frame down (called by this frame)
6088 the address of the next frame up (caller of this frame)
6090 the language in which the source code corresponding to this frame is written
6092 the address of the frame's arguments
6094 the address of the frame's local variables
6096 the program counter saved in it (the address of execution in the caller frame)
6098 which registers were saved in the frame
6101 @noindent The verbose description is useful when
6102 something has gone wrong that has made the stack format fail to fit
6103 the usual conventions.
6105 @item info frame @var{addr}
6106 @itemx info f @var{addr}
6107 Print a verbose description of the frame at address @var{addr}, without
6108 selecting that frame. The selected frame remains unchanged by this
6109 command. This requires the same kind of address (more than one for some
6110 architectures) that you specify in the @code{frame} command.
6111 @xref{Selection, ,Selecting a Frame}.
6115 Print the arguments of the selected frame, each on a separate line.
6119 Print the local variables of the selected frame, each on a separate
6120 line. These are all variables (declared either static or automatic)
6121 accessible at the point of execution of the selected frame.
6124 @cindex catch exceptions, list active handlers
6125 @cindex exception handlers, how to list
6127 Print a list of all the exception handlers that are active in the
6128 current stack frame at the current point of execution. To see other
6129 exception handlers, visit the associated frame (using the @code{up},
6130 @code{down}, or @code{frame} commands); then type @code{info catch}.
6131 @xref{Set Catchpoints, , Setting Catchpoints}.
6137 @chapter Examining Source Files
6139 @value{GDBN} can print parts of your program's source, since the debugging
6140 information recorded in the program tells @value{GDBN} what source files were
6141 used to build it. When your program stops, @value{GDBN} spontaneously prints
6142 the line where it stopped. Likewise, when you select a stack frame
6143 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6144 execution in that frame has stopped. You can print other portions of
6145 source files by explicit command.
6147 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6148 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6149 @value{GDBN} under @sc{gnu} Emacs}.
6152 * List:: Printing source lines
6153 * Specify Location:: How to specify code locations
6154 * Edit:: Editing source files
6155 * Search:: Searching source files
6156 * Source Path:: Specifying source directories
6157 * Machine Code:: Source and machine code
6161 @section Printing Source Lines
6164 @kindex l @r{(@code{list})}
6165 To print lines from a source file, use the @code{list} command
6166 (abbreviated @code{l}). By default, ten lines are printed.
6167 There are several ways to specify what part of the file you want to
6168 print; see @ref{Specify Location}, for the full list.
6170 Here are the forms of the @code{list} command most commonly used:
6173 @item list @var{linenum}
6174 Print lines centered around line number @var{linenum} in the
6175 current source file.
6177 @item list @var{function}
6178 Print lines centered around the beginning of function
6182 Print more lines. If the last lines printed were printed with a
6183 @code{list} command, this prints lines following the last lines
6184 printed; however, if the last line printed was a solitary line printed
6185 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6186 Stack}), this prints lines centered around that line.
6189 Print lines just before the lines last printed.
6192 @cindex @code{list}, how many lines to display
6193 By default, @value{GDBN} prints ten source lines with any of these forms of
6194 the @code{list} command. You can change this using @code{set listsize}:
6197 @kindex set listsize
6198 @item set listsize @var{count}
6199 Make the @code{list} command display @var{count} source lines (unless
6200 the @code{list} argument explicitly specifies some other number).
6202 @kindex show listsize
6204 Display the number of lines that @code{list} prints.
6207 Repeating a @code{list} command with @key{RET} discards the argument,
6208 so it is equivalent to typing just @code{list}. This is more useful
6209 than listing the same lines again. An exception is made for an
6210 argument of @samp{-}; that argument is preserved in repetition so that
6211 each repetition moves up in the source file.
6213 In general, the @code{list} command expects you to supply zero, one or two
6214 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6215 of writing them (@pxref{Specify Location}), but the effect is always
6216 to specify some source line.
6218 Here is a complete description of the possible arguments for @code{list}:
6221 @item list @var{linespec}
6222 Print lines centered around the line specified by @var{linespec}.
6224 @item list @var{first},@var{last}
6225 Print lines from @var{first} to @var{last}. Both arguments are
6226 linespecs. When a @code{list} command has two linespecs, and the
6227 source file of the second linespec is omitted, this refers to
6228 the same source file as the first linespec.
6230 @item list ,@var{last}
6231 Print lines ending with @var{last}.
6233 @item list @var{first},
6234 Print lines starting with @var{first}.
6237 Print lines just after the lines last printed.
6240 Print lines just before the lines last printed.
6243 As described in the preceding table.
6246 @node Specify Location
6247 @section Specifying a Location
6248 @cindex specifying location
6251 Several @value{GDBN} commands accept arguments that specify a location
6252 of your program's code. Since @value{GDBN} is a source-level
6253 debugger, a location usually specifies some line in the source code;
6254 for that reason, locations are also known as @dfn{linespecs}.
6256 Here are all the different ways of specifying a code location that
6257 @value{GDBN} understands:
6261 Specifies the line number @var{linenum} of the current source file.
6264 @itemx +@var{offset}
6265 Specifies the line @var{offset} lines before or after the @dfn{current
6266 line}. For the @code{list} command, the current line is the last one
6267 printed; for the breakpoint commands, this is the line at which
6268 execution stopped in the currently selected @dfn{stack frame}
6269 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6270 used as the second of the two linespecs in a @code{list} command,
6271 this specifies the line @var{offset} lines up or down from the first
6274 @item @var{filename}:@var{linenum}
6275 Specifies the line @var{linenum} in the source file @var{filename}.
6277 @item @var{function}
6278 Specifies the line that begins the body of the function @var{function}.
6279 For example, in C, this is the line with the open brace.
6281 @item @var{filename}:@var{function}
6282 Specifies the line that begins the body of the function @var{function}
6283 in the file @var{filename}. You only need the file name with a
6284 function name to avoid ambiguity when there are identically named
6285 functions in different source files.
6287 @item *@var{address}
6288 Specifies the program address @var{address}. For line-oriented
6289 commands, such as @code{list} and @code{edit}, this specifies a source
6290 line that contains @var{address}. For @code{break} and other
6291 breakpoint oriented commands, this can be used to set breakpoints in
6292 parts of your program which do not have debugging information or
6295 Here @var{address} may be any expression valid in the current working
6296 language (@pxref{Languages, working language}) that specifies a code
6297 address. In addition, as a convenience, @value{GDBN} extends the
6298 semantics of expressions used in locations to cover the situations
6299 that frequently happen during debugging. Here are the various forms
6303 @item @var{expression}
6304 Any expression valid in the current working language.
6306 @item @var{funcaddr}
6307 An address of a function or procedure derived from its name. In C,
6308 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6309 simply the function's name @var{function} (and actually a special case
6310 of a valid expression). In Pascal and Modula-2, this is
6311 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6312 (although the Pascal form also works).
6314 This form specifies the address of the function's first instruction,
6315 before the stack frame and arguments have been set up.
6317 @item '@var{filename}'::@var{funcaddr}
6318 Like @var{funcaddr} above, but also specifies the name of the source
6319 file explicitly. This is useful if the name of the function does not
6320 specify the function unambiguously, e.g., if there are several
6321 functions with identical names in different source files.
6328 @section Editing Source Files
6329 @cindex editing source files
6332 @kindex e @r{(@code{edit})}
6333 To edit the lines in a source file, use the @code{edit} command.
6334 The editing program of your choice
6335 is invoked with the current line set to
6336 the active line in the program.
6337 Alternatively, there are several ways to specify what part of the file you
6338 want to print if you want to see other parts of the program:
6341 @item edit @var{location}
6342 Edit the source file specified by @code{location}. Editing starts at
6343 that @var{location}, e.g., at the specified source line of the
6344 specified file. @xref{Specify Location}, for all the possible forms
6345 of the @var{location} argument; here are the forms of the @code{edit}
6346 command most commonly used:
6349 @item edit @var{number}
6350 Edit the current source file with @var{number} as the active line number.
6352 @item edit @var{function}
6353 Edit the file containing @var{function} at the beginning of its definition.
6358 @subsection Choosing your Editor
6359 You can customize @value{GDBN} to use any editor you want
6361 The only restriction is that your editor (say @code{ex}), recognizes the
6362 following command-line syntax:
6364 ex +@var{number} file
6366 The optional numeric value +@var{number} specifies the number of the line in
6367 the file where to start editing.}.
6368 By default, it is @file{@value{EDITOR}}, but you can change this
6369 by setting the environment variable @code{EDITOR} before using
6370 @value{GDBN}. For example, to configure @value{GDBN} to use the
6371 @code{vi} editor, you could use these commands with the @code{sh} shell:
6377 or in the @code{csh} shell,
6379 setenv EDITOR /usr/bin/vi
6384 @section Searching Source Files
6385 @cindex searching source files
6387 There are two commands for searching through the current source file for a
6392 @kindex forward-search
6393 @item forward-search @var{regexp}
6394 @itemx search @var{regexp}
6395 The command @samp{forward-search @var{regexp}} checks each line,
6396 starting with the one following the last line listed, for a match for
6397 @var{regexp}. It lists the line that is found. You can use the
6398 synonym @samp{search @var{regexp}} or abbreviate the command name as
6401 @kindex reverse-search
6402 @item reverse-search @var{regexp}
6403 The command @samp{reverse-search @var{regexp}} checks each line, starting
6404 with the one before the last line listed and going backward, for a match
6405 for @var{regexp}. It lists the line that is found. You can abbreviate
6406 this command as @code{rev}.
6410 @section Specifying Source Directories
6413 @cindex directories for source files
6414 Executable programs sometimes do not record the directories of the source
6415 files from which they were compiled, just the names. Even when they do,
6416 the directories could be moved between the compilation and your debugging
6417 session. @value{GDBN} has a list of directories to search for source files;
6418 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6419 it tries all the directories in the list, in the order they are present
6420 in the list, until it finds a file with the desired name.
6422 For example, suppose an executable references the file
6423 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6424 @file{/mnt/cross}. The file is first looked up literally; if this
6425 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6426 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6427 message is printed. @value{GDBN} does not look up the parts of the
6428 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6429 Likewise, the subdirectories of the source path are not searched: if
6430 the source path is @file{/mnt/cross}, and the binary refers to
6431 @file{foo.c}, @value{GDBN} would not find it under
6432 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6434 Plain file names, relative file names with leading directories, file
6435 names containing dots, etc.@: are all treated as described above; for
6436 instance, if the source path is @file{/mnt/cross}, and the source file
6437 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6438 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6439 that---@file{/mnt/cross/foo.c}.
6441 Note that the executable search path is @emph{not} used to locate the
6444 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6445 any information it has cached about where source files are found and where
6446 each line is in the file.
6450 When you start @value{GDBN}, its source path includes only @samp{cdir}
6451 and @samp{cwd}, in that order.
6452 To add other directories, use the @code{directory} command.
6454 The search path is used to find both program source files and @value{GDBN}
6455 script files (read using the @samp{-command} option and @samp{source} command).
6457 In addition to the source path, @value{GDBN} provides a set of commands
6458 that manage a list of source path substitution rules. A @dfn{substitution
6459 rule} specifies how to rewrite source directories stored in the program's
6460 debug information in case the sources were moved to a different
6461 directory between compilation and debugging. A rule is made of
6462 two strings, the first specifying what needs to be rewritten in
6463 the path, and the second specifying how it should be rewritten.
6464 In @ref{set substitute-path}, we name these two parts @var{from} and
6465 @var{to} respectively. @value{GDBN} does a simple string replacement
6466 of @var{from} with @var{to} at the start of the directory part of the
6467 source file name, and uses that result instead of the original file
6468 name to look up the sources.
6470 Using the previous example, suppose the @file{foo-1.0} tree has been
6471 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6472 @value{GDBN} to replace @file{/usr/src} in all source path names with
6473 @file{/mnt/cross}. The first lookup will then be
6474 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6475 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6476 substitution rule, use the @code{set substitute-path} command
6477 (@pxref{set substitute-path}).
6479 To avoid unexpected substitution results, a rule is applied only if the
6480 @var{from} part of the directory name ends at a directory separator.
6481 For instance, a rule substituting @file{/usr/source} into
6482 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6483 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6484 is applied only at the beginning of the directory name, this rule will
6485 not be applied to @file{/root/usr/source/baz.c} either.
6487 In many cases, you can achieve the same result using the @code{directory}
6488 command. However, @code{set substitute-path} can be more efficient in
6489 the case where the sources are organized in a complex tree with multiple
6490 subdirectories. With the @code{directory} command, you need to add each
6491 subdirectory of your project. If you moved the entire tree while
6492 preserving its internal organization, then @code{set substitute-path}
6493 allows you to direct the debugger to all the sources with one single
6496 @code{set substitute-path} is also more than just a shortcut command.
6497 The source path is only used if the file at the original location no
6498 longer exists. On the other hand, @code{set substitute-path} modifies
6499 the debugger behavior to look at the rewritten location instead. So, if
6500 for any reason a source file that is not relevant to your executable is
6501 located at the original location, a substitution rule is the only
6502 method available to point @value{GDBN} at the new location.
6504 @cindex @samp{--with-relocated-sources}
6505 @cindex default source path substitution
6506 You can configure a default source path substitution rule by
6507 configuring @value{GDBN} with the
6508 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6509 should be the name of a directory under @value{GDBN}'s configured
6510 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6511 directory names in debug information under @var{dir} will be adjusted
6512 automatically if the installed @value{GDBN} is moved to a new
6513 location. This is useful if @value{GDBN}, libraries or executables
6514 with debug information and corresponding source code are being moved
6518 @item directory @var{dirname} @dots{}
6519 @item dir @var{dirname} @dots{}
6520 Add directory @var{dirname} to the front of the source path. Several
6521 directory names may be given to this command, separated by @samp{:}
6522 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6523 part of absolute file names) or
6524 whitespace. You may specify a directory that is already in the source
6525 path; this moves it forward, so @value{GDBN} searches it sooner.
6529 @vindex $cdir@r{, convenience variable}
6530 @vindex $cwd@r{, convenience variable}
6531 @cindex compilation directory
6532 @cindex current directory
6533 @cindex working directory
6534 @cindex directory, current
6535 @cindex directory, compilation
6536 You can use the string @samp{$cdir} to refer to the compilation
6537 directory (if one is recorded), and @samp{$cwd} to refer to the current
6538 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6539 tracks the current working directory as it changes during your @value{GDBN}
6540 session, while the latter is immediately expanded to the current
6541 directory at the time you add an entry to the source path.
6544 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6546 @c RET-repeat for @code{directory} is explicitly disabled, but since
6547 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6549 @item show directories
6550 @kindex show directories
6551 Print the source path: show which directories it contains.
6553 @anchor{set substitute-path}
6554 @item set substitute-path @var{from} @var{to}
6555 @kindex set substitute-path
6556 Define a source path substitution rule, and add it at the end of the
6557 current list of existing substitution rules. If a rule with the same
6558 @var{from} was already defined, then the old rule is also deleted.
6560 For example, if the file @file{/foo/bar/baz.c} was moved to
6561 @file{/mnt/cross/baz.c}, then the command
6564 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6568 will tell @value{GDBN} to replace @samp{/usr/src} with
6569 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6570 @file{baz.c} even though it was moved.
6572 In the case when more than one substitution rule have been defined,
6573 the rules are evaluated one by one in the order where they have been
6574 defined. The first one matching, if any, is selected to perform
6577 For instance, if we had entered the following commands:
6580 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6581 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6585 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6586 @file{/mnt/include/defs.h} by using the first rule. However, it would
6587 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6588 @file{/mnt/src/lib/foo.c}.
6591 @item unset substitute-path [path]
6592 @kindex unset substitute-path
6593 If a path is specified, search the current list of substitution rules
6594 for a rule that would rewrite that path. Delete that rule if found.
6595 A warning is emitted by the debugger if no rule could be found.
6597 If no path is specified, then all substitution rules are deleted.
6599 @item show substitute-path [path]
6600 @kindex show substitute-path
6601 If a path is specified, then print the source path substitution rule
6602 which would rewrite that path, if any.
6604 If no path is specified, then print all existing source path substitution
6609 If your source path is cluttered with directories that are no longer of
6610 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6611 versions of source. You can correct the situation as follows:
6615 Use @code{directory} with no argument to reset the source path to its default value.
6618 Use @code{directory} with suitable arguments to reinstall the
6619 directories you want in the source path. You can add all the
6620 directories in one command.
6624 @section Source and Machine Code
6625 @cindex source line and its code address
6627 You can use the command @code{info line} to map source lines to program
6628 addresses (and vice versa), and the command @code{disassemble} to display
6629 a range of addresses as machine instructions. You can use the command
6630 @code{set disassemble-next-line} to set whether to disassemble next
6631 source line when execution stops. When run under @sc{gnu} Emacs
6632 mode, the @code{info line} command causes the arrow to point to the
6633 line specified. Also, @code{info line} prints addresses in symbolic form as
6638 @item info line @var{linespec}
6639 Print the starting and ending addresses of the compiled code for
6640 source line @var{linespec}. You can specify source lines in any of
6641 the ways documented in @ref{Specify Location}.
6644 For example, we can use @code{info line} to discover the location of
6645 the object code for the first line of function
6646 @code{m4_changequote}:
6648 @c FIXME: I think this example should also show the addresses in
6649 @c symbolic form, as they usually would be displayed.
6651 (@value{GDBP}) info line m4_changequote
6652 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6656 @cindex code address and its source line
6657 We can also inquire (using @code{*@var{addr}} as the form for
6658 @var{linespec}) what source line covers a particular address:
6660 (@value{GDBP}) info line *0x63ff
6661 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6664 @cindex @code{$_} and @code{info line}
6665 @cindex @code{x} command, default address
6666 @kindex x@r{(examine), and} info line
6667 After @code{info line}, the default address for the @code{x} command
6668 is changed to the starting address of the line, so that @samp{x/i} is
6669 sufficient to begin examining the machine code (@pxref{Memory,
6670 ,Examining Memory}). Also, this address is saved as the value of the
6671 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6676 @cindex assembly instructions
6677 @cindex instructions, assembly
6678 @cindex machine instructions
6679 @cindex listing machine instructions
6681 @itemx disassemble /m
6682 @itemx disassemble /r
6683 This specialized command dumps a range of memory as machine
6684 instructions. It can also print mixed source+disassembly by specifying
6685 the @code{/m} modifier and print the raw instructions in hex as well as
6686 in symbolic form by specifying the @code{/r}.
6687 The default memory range is the function surrounding the
6688 program counter of the selected frame. A single argument to this
6689 command is a program counter value; @value{GDBN} dumps the function
6690 surrounding this value. When two arguments are given, they should
6691 be separated by a comma, possibly surrounded by whitespace. The
6692 arguments specify a range of addresses (first inclusive, second exclusive)
6693 to dump. In that case, the name of the function is also printed (since
6694 there could be several functions in the given range).
6696 The argument(s) can be any expression yielding a numeric value, such as
6697 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
6699 If the range of memory being disassembled contains current program counter,
6700 the instruction at that location is shown with a @code{=>} marker.
6703 The following example shows the disassembly of a range of addresses of
6704 HP PA-RISC 2.0 code:
6707 (@value{GDBP}) disas 0x32c4, 0x32e4
6708 Dump of assembler code from 0x32c4 to 0x32e4:
6709 0x32c4 <main+204>: addil 0,dp
6710 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6711 0x32cc <main+212>: ldil 0x3000,r31
6712 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6713 0x32d4 <main+220>: ldo 0(r31),rp
6714 0x32d8 <main+224>: addil -0x800,dp
6715 0x32dc <main+228>: ldo 0x588(r1),r26
6716 0x32e0 <main+232>: ldil 0x3000,r31
6717 End of assembler dump.
6720 Here is an example showing mixed source+assembly for Intel x86, when the
6721 program is stopped just after function prologue:
6724 (@value{GDBP}) disas /m main
6725 Dump of assembler code for function main:
6727 0x08048330 <+0>: push %ebp
6728 0x08048331 <+1>: mov %esp,%ebp
6729 0x08048333 <+3>: sub $0x8,%esp
6730 0x08048336 <+6>: and $0xfffffff0,%esp
6731 0x08048339 <+9>: sub $0x10,%esp
6733 6 printf ("Hello.\n");
6734 => 0x0804833c <+12>: movl $0x8048440,(%esp)
6735 0x08048343 <+19>: call 0x8048284 <puts@@plt>
6739 0x08048348 <+24>: mov $0x0,%eax
6740 0x0804834d <+29>: leave
6741 0x0804834e <+30>: ret
6743 End of assembler dump.
6746 Some architectures have more than one commonly-used set of instruction
6747 mnemonics or other syntax.
6749 For programs that were dynamically linked and use shared libraries,
6750 instructions that call functions or branch to locations in the shared
6751 libraries might show a seemingly bogus location---it's actually a
6752 location of the relocation table. On some architectures, @value{GDBN}
6753 might be able to resolve these to actual function names.
6756 @kindex set disassembly-flavor
6757 @cindex Intel disassembly flavor
6758 @cindex AT&T disassembly flavor
6759 @item set disassembly-flavor @var{instruction-set}
6760 Select the instruction set to use when disassembling the
6761 program via the @code{disassemble} or @code{x/i} commands.
6763 Currently this command is only defined for the Intel x86 family. You
6764 can set @var{instruction-set} to either @code{intel} or @code{att}.
6765 The default is @code{att}, the AT&T flavor used by default by Unix
6766 assemblers for x86-based targets.
6768 @kindex show disassembly-flavor
6769 @item show disassembly-flavor
6770 Show the current setting of the disassembly flavor.
6774 @kindex set disassemble-next-line
6775 @kindex show disassemble-next-line
6776 @item set disassemble-next-line
6777 @itemx show disassemble-next-line
6778 Control whether or not @value{GDBN} will disassemble the next source
6779 line or instruction when execution stops. If ON, @value{GDBN} will
6780 display disassembly of the next source line when execution of the
6781 program being debugged stops. This is @emph{in addition} to
6782 displaying the source line itself, which @value{GDBN} always does if
6783 possible. If the next source line cannot be displayed for some reason
6784 (e.g., if @value{GDBN} cannot find the source file, or there's no line
6785 info in the debug info), @value{GDBN} will display disassembly of the
6786 next @emph{instruction} instead of showing the next source line. If
6787 AUTO, @value{GDBN} will display disassembly of next instruction only
6788 if the source line cannot be displayed. This setting causes
6789 @value{GDBN} to display some feedback when you step through a function
6790 with no line info or whose source file is unavailable. The default is
6791 OFF, which means never display the disassembly of the next line or
6797 @chapter Examining Data
6799 @cindex printing data
6800 @cindex examining data
6803 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6804 @c document because it is nonstandard... Under Epoch it displays in a
6805 @c different window or something like that.
6806 The usual way to examine data in your program is with the @code{print}
6807 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6808 evaluates and prints the value of an expression of the language your
6809 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6810 Different Languages}). It may also print the expression using a
6811 Python-based pretty-printer (@pxref{Pretty Printing}).
6814 @item print @var{expr}
6815 @itemx print /@var{f} @var{expr}
6816 @var{expr} is an expression (in the source language). By default the
6817 value of @var{expr} is printed in a format appropriate to its data type;
6818 you can choose a different format by specifying @samp{/@var{f}}, where
6819 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6823 @itemx print /@var{f}
6824 @cindex reprint the last value
6825 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6826 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6827 conveniently inspect the same value in an alternative format.
6830 A more low-level way of examining data is with the @code{x} command.
6831 It examines data in memory at a specified address and prints it in a
6832 specified format. @xref{Memory, ,Examining Memory}.
6834 If you are interested in information about types, or about how the
6835 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6836 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6840 * Expressions:: Expressions
6841 * Ambiguous Expressions:: Ambiguous Expressions
6842 * Variables:: Program variables
6843 * Arrays:: Artificial arrays
6844 * Output Formats:: Output formats
6845 * Memory:: Examining memory
6846 * Auto Display:: Automatic display
6847 * Print Settings:: Print settings
6848 * Pretty Printing:: Python pretty printing
6849 * Value History:: Value history
6850 * Convenience Vars:: Convenience variables
6851 * Registers:: Registers
6852 * Floating Point Hardware:: Floating point hardware
6853 * Vector Unit:: Vector Unit
6854 * OS Information:: Auxiliary data provided by operating system
6855 * Memory Region Attributes:: Memory region attributes
6856 * Dump/Restore Files:: Copy between memory and a file
6857 * Core File Generation:: Cause a program dump its core
6858 * Character Sets:: Debugging programs that use a different
6859 character set than GDB does
6860 * Caching Remote Data:: Data caching for remote targets
6861 * Searching Memory:: Searching memory for a sequence of bytes
6865 @section Expressions
6868 @code{print} and many other @value{GDBN} commands accept an expression and
6869 compute its value. Any kind of constant, variable or operator defined
6870 by the programming language you are using is valid in an expression in
6871 @value{GDBN}. This includes conditional expressions, function calls,
6872 casts, and string constants. It also includes preprocessor macros, if
6873 you compiled your program to include this information; see
6876 @cindex arrays in expressions
6877 @value{GDBN} supports array constants in expressions input by
6878 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
6879 you can use the command @code{print @{1, 2, 3@}} to create an array
6880 of three integers. If you pass an array to a function or assign it
6881 to a program variable, @value{GDBN} copies the array to memory that
6882 is @code{malloc}ed in the target program.
6884 Because C is so widespread, most of the expressions shown in examples in
6885 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
6886 Languages}, for information on how to use expressions in other
6889 In this section, we discuss operators that you can use in @value{GDBN}
6890 expressions regardless of your programming language.
6892 @cindex casts, in expressions
6893 Casts are supported in all languages, not just in C, because it is so
6894 useful to cast a number into a pointer in order to examine a structure
6895 at that address in memory.
6896 @c FIXME: casts supported---Mod2 true?
6898 @value{GDBN} supports these operators, in addition to those common
6899 to programming languages:
6903 @samp{@@} is a binary operator for treating parts of memory as arrays.
6904 @xref{Arrays, ,Artificial Arrays}, for more information.
6907 @samp{::} allows you to specify a variable in terms of the file or
6908 function where it is defined. @xref{Variables, ,Program Variables}.
6910 @cindex @{@var{type}@}
6911 @cindex type casting memory
6912 @cindex memory, viewing as typed object
6913 @cindex casts, to view memory
6914 @item @{@var{type}@} @var{addr}
6915 Refers to an object of type @var{type} stored at address @var{addr} in
6916 memory. @var{addr} may be any expression whose value is an integer or
6917 pointer (but parentheses are required around binary operators, just as in
6918 a cast). This construct is allowed regardless of what kind of data is
6919 normally supposed to reside at @var{addr}.
6922 @node Ambiguous Expressions
6923 @section Ambiguous Expressions
6924 @cindex ambiguous expressions
6926 Expressions can sometimes contain some ambiguous elements. For instance,
6927 some programming languages (notably Ada, C@t{++} and Objective-C) permit
6928 a single function name to be defined several times, for application in
6929 different contexts. This is called @dfn{overloading}. Another example
6930 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
6931 templates and is typically instantiated several times, resulting in
6932 the same function name being defined in different contexts.
6934 In some cases and depending on the language, it is possible to adjust
6935 the expression to remove the ambiguity. For instance in C@t{++}, you
6936 can specify the signature of the function you want to break on, as in
6937 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
6938 qualified name of your function often makes the expression unambiguous
6941 When an ambiguity that needs to be resolved is detected, the debugger
6942 has the capability to display a menu of numbered choices for each
6943 possibility, and then waits for the selection with the prompt @samp{>}.
6944 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
6945 aborts the current command. If the command in which the expression was
6946 used allows more than one choice to be selected, the next option in the
6947 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
6950 For example, the following session excerpt shows an attempt to set a
6951 breakpoint at the overloaded symbol @code{String::after}.
6952 We choose three particular definitions of that function name:
6954 @c FIXME! This is likely to change to show arg type lists, at least
6957 (@value{GDBP}) b String::after
6960 [2] file:String.cc; line number:867
6961 [3] file:String.cc; line number:860
6962 [4] file:String.cc; line number:875
6963 [5] file:String.cc; line number:853
6964 [6] file:String.cc; line number:846
6965 [7] file:String.cc; line number:735
6967 Breakpoint 1 at 0xb26c: file String.cc, line 867.
6968 Breakpoint 2 at 0xb344: file String.cc, line 875.
6969 Breakpoint 3 at 0xafcc: file String.cc, line 846.
6970 Multiple breakpoints were set.
6971 Use the "delete" command to delete unwanted
6978 @kindex set multiple-symbols
6979 @item set multiple-symbols @var{mode}
6980 @cindex multiple-symbols menu
6982 This option allows you to adjust the debugger behavior when an expression
6985 By default, @var{mode} is set to @code{all}. If the command with which
6986 the expression is used allows more than one choice, then @value{GDBN}
6987 automatically selects all possible choices. For instance, inserting
6988 a breakpoint on a function using an ambiguous name results in a breakpoint
6989 inserted on each possible match. However, if a unique choice must be made,
6990 then @value{GDBN} uses the menu to help you disambiguate the expression.
6991 For instance, printing the address of an overloaded function will result
6992 in the use of the menu.
6994 When @var{mode} is set to @code{ask}, the debugger always uses the menu
6995 when an ambiguity is detected.
6997 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
6998 an error due to the ambiguity and the command is aborted.
7000 @kindex show multiple-symbols
7001 @item show multiple-symbols
7002 Show the current value of the @code{multiple-symbols} setting.
7006 @section Program Variables
7008 The most common kind of expression to use is the name of a variable
7011 Variables in expressions are understood in the selected stack frame
7012 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7016 global (or file-static)
7023 visible according to the scope rules of the
7024 programming language from the point of execution in that frame
7027 @noindent This means that in the function
7042 you can examine and use the variable @code{a} whenever your program is
7043 executing within the function @code{foo}, but you can only use or
7044 examine the variable @code{b} while your program is executing inside
7045 the block where @code{b} is declared.
7047 @cindex variable name conflict
7048 There is an exception: you can refer to a variable or function whose
7049 scope is a single source file even if the current execution point is not
7050 in this file. But it is possible to have more than one such variable or
7051 function with the same name (in different source files). If that
7052 happens, referring to that name has unpredictable effects. If you wish,
7053 you can specify a static variable in a particular function or file,
7054 using the colon-colon (@code{::}) notation:
7056 @cindex colon-colon, context for variables/functions
7058 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7059 @cindex @code{::}, context for variables/functions
7062 @var{file}::@var{variable}
7063 @var{function}::@var{variable}
7067 Here @var{file} or @var{function} is the name of the context for the
7068 static @var{variable}. In the case of file names, you can use quotes to
7069 make sure @value{GDBN} parses the file name as a single word---for example,
7070 to print a global value of @code{x} defined in @file{f2.c}:
7073 (@value{GDBP}) p 'f2.c'::x
7076 @cindex C@t{++} scope resolution
7077 This use of @samp{::} is very rarely in conflict with the very similar
7078 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7079 scope resolution operator in @value{GDBN} expressions.
7080 @c FIXME: Um, so what happens in one of those rare cases where it's in
7083 @cindex wrong values
7084 @cindex variable values, wrong
7085 @cindex function entry/exit, wrong values of variables
7086 @cindex optimized code, wrong values of variables
7088 @emph{Warning:} Occasionally, a local variable may appear to have the
7089 wrong value at certain points in a function---just after entry to a new
7090 scope, and just before exit.
7092 You may see this problem when you are stepping by machine instructions.
7093 This is because, on most machines, it takes more than one instruction to
7094 set up a stack frame (including local variable definitions); if you are
7095 stepping by machine instructions, variables may appear to have the wrong
7096 values until the stack frame is completely built. On exit, it usually
7097 also takes more than one machine instruction to destroy a stack frame;
7098 after you begin stepping through that group of instructions, local
7099 variable definitions may be gone.
7101 This may also happen when the compiler does significant optimizations.
7102 To be sure of always seeing accurate values, turn off all optimization
7105 @cindex ``No symbol "foo" in current context''
7106 Another possible effect of compiler optimizations is to optimize
7107 unused variables out of existence, or assign variables to registers (as
7108 opposed to memory addresses). Depending on the support for such cases
7109 offered by the debug info format used by the compiler, @value{GDBN}
7110 might not be able to display values for such local variables. If that
7111 happens, @value{GDBN} will print a message like this:
7114 No symbol "foo" in current context.
7117 To solve such problems, either recompile without optimizations, or use a
7118 different debug info format, if the compiler supports several such
7119 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
7120 usually supports the @option{-gstabs+} option. @option{-gstabs+}
7121 produces debug info in a format that is superior to formats such as
7122 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
7123 an effective form for debug info. @xref{Debugging Options,,Options
7124 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
7125 Compiler Collection (GCC)}.
7126 @xref{C, ,C and C@t{++}}, for more information about debug info formats
7127 that are best suited to C@t{++} programs.
7129 If you ask to print an object whose contents are unknown to
7130 @value{GDBN}, e.g., because its data type is not completely specified
7131 by the debug information, @value{GDBN} will say @samp{<incomplete
7132 type>}. @xref{Symbols, incomplete type}, for more about this.
7134 Strings are identified as arrays of @code{char} values without specified
7135 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7136 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7137 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7138 defines literal string type @code{"char"} as @code{char} without a sign.
7143 signed char var1[] = "A";
7146 You get during debugging
7151 $2 = @{65 'A', 0 '\0'@}
7155 @section Artificial Arrays
7157 @cindex artificial array
7159 @kindex @@@r{, referencing memory as an array}
7160 It is often useful to print out several successive objects of the
7161 same type in memory; a section of an array, or an array of
7162 dynamically determined size for which only a pointer exists in the
7165 You can do this by referring to a contiguous span of memory as an
7166 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7167 operand of @samp{@@} should be the first element of the desired array
7168 and be an individual object. The right operand should be the desired length
7169 of the array. The result is an array value whose elements are all of
7170 the type of the left argument. The first element is actually the left
7171 argument; the second element comes from bytes of memory immediately
7172 following those that hold the first element, and so on. Here is an
7173 example. If a program says
7176 int *array = (int *) malloc (len * sizeof (int));
7180 you can print the contents of @code{array} with
7186 The left operand of @samp{@@} must reside in memory. Array values made
7187 with @samp{@@} in this way behave just like other arrays in terms of
7188 subscripting, and are coerced to pointers when used in expressions.
7189 Artificial arrays most often appear in expressions via the value history
7190 (@pxref{Value History, ,Value History}), after printing one out.
7192 Another way to create an artificial array is to use a cast.
7193 This re-interprets a value as if it were an array.
7194 The value need not be in memory:
7196 (@value{GDBP}) p/x (short[2])0x12345678
7197 $1 = @{0x1234, 0x5678@}
7200 As a convenience, if you leave the array length out (as in
7201 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7202 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7204 (@value{GDBP}) p/x (short[])0x12345678
7205 $2 = @{0x1234, 0x5678@}
7208 Sometimes the artificial array mechanism is not quite enough; in
7209 moderately complex data structures, the elements of interest may not
7210 actually be adjacent---for example, if you are interested in the values
7211 of pointers in an array. One useful work-around in this situation is
7212 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7213 Variables}) as a counter in an expression that prints the first
7214 interesting value, and then repeat that expression via @key{RET}. For
7215 instance, suppose you have an array @code{dtab} of pointers to
7216 structures, and you are interested in the values of a field @code{fv}
7217 in each structure. Here is an example of what you might type:
7227 @node Output Formats
7228 @section Output Formats
7230 @cindex formatted output
7231 @cindex output formats
7232 By default, @value{GDBN} prints a value according to its data type. Sometimes
7233 this is not what you want. For example, you might want to print a number
7234 in hex, or a pointer in decimal. Or you might want to view data in memory
7235 at a certain address as a character string or as an instruction. To do
7236 these things, specify an @dfn{output format} when you print a value.
7238 The simplest use of output formats is to say how to print a value
7239 already computed. This is done by starting the arguments of the
7240 @code{print} command with a slash and a format letter. The format
7241 letters supported are:
7245 Regard the bits of the value as an integer, and print the integer in
7249 Print as integer in signed decimal.
7252 Print as integer in unsigned decimal.
7255 Print as integer in octal.
7258 Print as integer in binary. The letter @samp{t} stands for ``two''.
7259 @footnote{@samp{b} cannot be used because these format letters are also
7260 used with the @code{x} command, where @samp{b} stands for ``byte'';
7261 see @ref{Memory,,Examining Memory}.}
7264 @cindex unknown address, locating
7265 @cindex locate address
7266 Print as an address, both absolute in hexadecimal and as an offset from
7267 the nearest preceding symbol. You can use this format used to discover
7268 where (in what function) an unknown address is located:
7271 (@value{GDBP}) p/a 0x54320
7272 $3 = 0x54320 <_initialize_vx+396>
7276 The command @code{info symbol 0x54320} yields similar results.
7277 @xref{Symbols, info symbol}.
7280 Regard as an integer and print it as a character constant. This
7281 prints both the numerical value and its character representation. The
7282 character representation is replaced with the octal escape @samp{\nnn}
7283 for characters outside the 7-bit @sc{ascii} range.
7285 Without this format, @value{GDBN} displays @code{char},
7286 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7287 constants. Single-byte members of vectors are displayed as integer
7291 Regard the bits of the value as a floating point number and print
7292 using typical floating point syntax.
7295 @cindex printing strings
7296 @cindex printing byte arrays
7297 Regard as a string, if possible. With this format, pointers to single-byte
7298 data are displayed as null-terminated strings and arrays of single-byte data
7299 are displayed as fixed-length strings. Other values are displayed in their
7302 Without this format, @value{GDBN} displays pointers to and arrays of
7303 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7304 strings. Single-byte members of a vector are displayed as an integer
7308 @cindex raw printing
7309 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7310 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7311 Printing}). This typically results in a higher-level display of the
7312 value's contents. The @samp{r} format bypasses any Python
7313 pretty-printer which might exist.
7316 For example, to print the program counter in hex (@pxref{Registers}), type
7323 Note that no space is required before the slash; this is because command
7324 names in @value{GDBN} cannot contain a slash.
7326 To reprint the last value in the value history with a different format,
7327 you can use the @code{print} command with just a format and no
7328 expression. For example, @samp{p/x} reprints the last value in hex.
7331 @section Examining Memory
7333 You can use the command @code{x} (for ``examine'') to examine memory in
7334 any of several formats, independently of your program's data types.
7336 @cindex examining memory
7338 @kindex x @r{(examine memory)}
7339 @item x/@var{nfu} @var{addr}
7342 Use the @code{x} command to examine memory.
7345 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7346 much memory to display and how to format it; @var{addr} is an
7347 expression giving the address where you want to start displaying memory.
7348 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7349 Several commands set convenient defaults for @var{addr}.
7352 @item @var{n}, the repeat count
7353 The repeat count is a decimal integer; the default is 1. It specifies
7354 how much memory (counting by units @var{u}) to display.
7355 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7358 @item @var{f}, the display format
7359 The display format is one of the formats used by @code{print}
7360 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7361 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7362 The default is @samp{x} (hexadecimal) initially. The default changes
7363 each time you use either @code{x} or @code{print}.
7365 @item @var{u}, the unit size
7366 The unit size is any of
7372 Halfwords (two bytes).
7374 Words (four bytes). This is the initial default.
7376 Giant words (eight bytes).
7379 Each time you specify a unit size with @code{x}, that size becomes the
7380 default unit the next time you use @code{x}. For the @samp{i} format,
7381 the unit size is ignored and is normally not written. For the @samp{s} format,
7382 the unit size defaults to @samp{b}, unless it is explicitly given.
7383 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
7384 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
7385 Note that the results depend on the programming language of the
7386 current compilation unit. If the language is C, the @samp{s}
7387 modifier will use the UTF-16 encoding while @samp{w} will use
7388 UTF-32. The encoding is set by the programming language and cannot
7391 @item @var{addr}, starting display address
7392 @var{addr} is the address where you want @value{GDBN} to begin displaying
7393 memory. The expression need not have a pointer value (though it may);
7394 it is always interpreted as an integer address of a byte of memory.
7395 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7396 @var{addr} is usually just after the last address examined---but several
7397 other commands also set the default address: @code{info breakpoints} (to
7398 the address of the last breakpoint listed), @code{info line} (to the
7399 starting address of a line), and @code{print} (if you use it to display
7400 a value from memory).
7403 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7404 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7405 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7406 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7407 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7409 Since the letters indicating unit sizes are all distinct from the
7410 letters specifying output formats, you do not have to remember whether
7411 unit size or format comes first; either order works. The output
7412 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7413 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7415 Even though the unit size @var{u} is ignored for the formats @samp{s}
7416 and @samp{i}, you might still want to use a count @var{n}; for example,
7417 @samp{3i} specifies that you want to see three machine instructions,
7418 including any operands. For convenience, especially when used with
7419 the @code{display} command, the @samp{i} format also prints branch delay
7420 slot instructions, if any, beyond the count specified, which immediately
7421 follow the last instruction that is within the count. The command
7422 @code{disassemble} gives an alternative way of inspecting machine
7423 instructions; see @ref{Machine Code,,Source and Machine Code}.
7425 All the defaults for the arguments to @code{x} are designed to make it
7426 easy to continue scanning memory with minimal specifications each time
7427 you use @code{x}. For example, after you have inspected three machine
7428 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7429 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7430 the repeat count @var{n} is used again; the other arguments default as
7431 for successive uses of @code{x}.
7433 When examining machine instructions, the instruction at current program
7434 counter is shown with a @code{=>} marker. For example:
7437 (@value{GDBP}) x/5i $pc-6
7438 0x804837f <main+11>: mov %esp,%ebp
7439 0x8048381 <main+13>: push %ecx
7440 0x8048382 <main+14>: sub $0x4,%esp
7441 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7442 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7445 @cindex @code{$_}, @code{$__}, and value history
7446 The addresses and contents printed by the @code{x} command are not saved
7447 in the value history because there is often too much of them and they
7448 would get in the way. Instead, @value{GDBN} makes these values available for
7449 subsequent use in expressions as values of the convenience variables
7450 @code{$_} and @code{$__}. After an @code{x} command, the last address
7451 examined is available for use in expressions in the convenience variable
7452 @code{$_}. The contents of that address, as examined, are available in
7453 the convenience variable @code{$__}.
7455 If the @code{x} command has a repeat count, the address and contents saved
7456 are from the last memory unit printed; this is not the same as the last
7457 address printed if several units were printed on the last line of output.
7459 @cindex remote memory comparison
7460 @cindex verify remote memory image
7461 When you are debugging a program running on a remote target machine
7462 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7463 remote machine's memory against the executable file you downloaded to
7464 the target. The @code{compare-sections} command is provided for such
7468 @kindex compare-sections
7469 @item compare-sections @r{[}@var{section-name}@r{]}
7470 Compare the data of a loadable section @var{section-name} in the
7471 executable file of the program being debugged with the same section in
7472 the remote machine's memory, and report any mismatches. With no
7473 arguments, compares all loadable sections. This command's
7474 availability depends on the target's support for the @code{"qCRC"}
7479 @section Automatic Display
7480 @cindex automatic display
7481 @cindex display of expressions
7483 If you find that you want to print the value of an expression frequently
7484 (to see how it changes), you might want to add it to the @dfn{automatic
7485 display list} so that @value{GDBN} prints its value each time your program stops.
7486 Each expression added to the list is given a number to identify it;
7487 to remove an expression from the list, you specify that number.
7488 The automatic display looks like this:
7492 3: bar[5] = (struct hack *) 0x3804
7496 This display shows item numbers, expressions and their current values. As with
7497 displays you request manually using @code{x} or @code{print}, you can
7498 specify the output format you prefer; in fact, @code{display} decides
7499 whether to use @code{print} or @code{x} depending your format
7500 specification---it uses @code{x} if you specify either the @samp{i}
7501 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7505 @item display @var{expr}
7506 Add the expression @var{expr} to the list of expressions to display
7507 each time your program stops. @xref{Expressions, ,Expressions}.
7509 @code{display} does not repeat if you press @key{RET} again after using it.
7511 @item display/@var{fmt} @var{expr}
7512 For @var{fmt} specifying only a display format and not a size or
7513 count, add the expression @var{expr} to the auto-display list but
7514 arrange to display it each time in the specified format @var{fmt}.
7515 @xref{Output Formats,,Output Formats}.
7517 @item display/@var{fmt} @var{addr}
7518 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7519 number of units, add the expression @var{addr} as a memory address to
7520 be examined each time your program stops. Examining means in effect
7521 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7524 For example, @samp{display/i $pc} can be helpful, to see the machine
7525 instruction about to be executed each time execution stops (@samp{$pc}
7526 is a common name for the program counter; @pxref{Registers, ,Registers}).
7529 @kindex delete display
7531 @item undisplay @var{dnums}@dots{}
7532 @itemx delete display @var{dnums}@dots{}
7533 Remove item numbers @var{dnums} from the list of expressions to display.
7535 @code{undisplay} does not repeat if you press @key{RET} after using it.
7536 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7538 @kindex disable display
7539 @item disable display @var{dnums}@dots{}
7540 Disable the display of item numbers @var{dnums}. A disabled display
7541 item is not printed automatically, but is not forgotten. It may be
7542 enabled again later.
7544 @kindex enable display
7545 @item enable display @var{dnums}@dots{}
7546 Enable display of item numbers @var{dnums}. It becomes effective once
7547 again in auto display of its expression, until you specify otherwise.
7550 Display the current values of the expressions on the list, just as is
7551 done when your program stops.
7553 @kindex info display
7555 Print the list of expressions previously set up to display
7556 automatically, each one with its item number, but without showing the
7557 values. This includes disabled expressions, which are marked as such.
7558 It also includes expressions which would not be displayed right now
7559 because they refer to automatic variables not currently available.
7562 @cindex display disabled out of scope
7563 If a display expression refers to local variables, then it does not make
7564 sense outside the lexical context for which it was set up. Such an
7565 expression is disabled when execution enters a context where one of its
7566 variables is not defined. For example, if you give the command
7567 @code{display last_char} while inside a function with an argument
7568 @code{last_char}, @value{GDBN} displays this argument while your program
7569 continues to stop inside that function. When it stops elsewhere---where
7570 there is no variable @code{last_char}---the display is disabled
7571 automatically. The next time your program stops where @code{last_char}
7572 is meaningful, you can enable the display expression once again.
7574 @node Print Settings
7575 @section Print Settings
7577 @cindex format options
7578 @cindex print settings
7579 @value{GDBN} provides the following ways to control how arrays, structures,
7580 and symbols are printed.
7583 These settings are useful for debugging programs in any language:
7587 @item set print address
7588 @itemx set print address on
7589 @cindex print/don't print memory addresses
7590 @value{GDBN} prints memory addresses showing the location of stack
7591 traces, structure values, pointer values, breakpoints, and so forth,
7592 even when it also displays the contents of those addresses. The default
7593 is @code{on}. For example, this is what a stack frame display looks like with
7594 @code{set print address on}:
7599 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7601 530 if (lquote != def_lquote)
7605 @item set print address off
7606 Do not print addresses when displaying their contents. For example,
7607 this is the same stack frame displayed with @code{set print address off}:
7611 (@value{GDBP}) set print addr off
7613 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7614 530 if (lquote != def_lquote)
7618 You can use @samp{set print address off} to eliminate all machine
7619 dependent displays from the @value{GDBN} interface. For example, with
7620 @code{print address off}, you should get the same text for backtraces on
7621 all machines---whether or not they involve pointer arguments.
7624 @item show print address
7625 Show whether or not addresses are to be printed.
7628 When @value{GDBN} prints a symbolic address, it normally prints the
7629 closest earlier symbol plus an offset. If that symbol does not uniquely
7630 identify the address (for example, it is a name whose scope is a single
7631 source file), you may need to clarify. One way to do this is with
7632 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7633 you can set @value{GDBN} to print the source file and line number when
7634 it prints a symbolic address:
7637 @item set print symbol-filename on
7638 @cindex source file and line of a symbol
7639 @cindex symbol, source file and line
7640 Tell @value{GDBN} to print the source file name and line number of a
7641 symbol in the symbolic form of an address.
7643 @item set print symbol-filename off
7644 Do not print source file name and line number of a symbol. This is the
7647 @item show print symbol-filename
7648 Show whether or not @value{GDBN} will print the source file name and
7649 line number of a symbol in the symbolic form of an address.
7652 Another situation where it is helpful to show symbol filenames and line
7653 numbers is when disassembling code; @value{GDBN} shows you the line
7654 number and source file that corresponds to each instruction.
7656 Also, you may wish to see the symbolic form only if the address being
7657 printed is reasonably close to the closest earlier symbol:
7660 @item set print max-symbolic-offset @var{max-offset}
7661 @cindex maximum value for offset of closest symbol
7662 Tell @value{GDBN} to only display the symbolic form of an address if the
7663 offset between the closest earlier symbol and the address is less than
7664 @var{max-offset}. The default is 0, which tells @value{GDBN}
7665 to always print the symbolic form of an address if any symbol precedes it.
7667 @item show print max-symbolic-offset
7668 Ask how large the maximum offset is that @value{GDBN} prints in a
7672 @cindex wild pointer, interpreting
7673 @cindex pointer, finding referent
7674 If you have a pointer and you are not sure where it points, try
7675 @samp{set print symbol-filename on}. Then you can determine the name
7676 and source file location of the variable where it points, using
7677 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7678 For example, here @value{GDBN} shows that a variable @code{ptt} points
7679 at another variable @code{t}, defined in @file{hi2.c}:
7682 (@value{GDBP}) set print symbol-filename on
7683 (@value{GDBP}) p/a ptt
7684 $4 = 0xe008 <t in hi2.c>
7688 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
7689 does not show the symbol name and filename of the referent, even with
7690 the appropriate @code{set print} options turned on.
7693 Other settings control how different kinds of objects are printed:
7696 @item set print array
7697 @itemx set print array on
7698 @cindex pretty print arrays
7699 Pretty print arrays. This format is more convenient to read,
7700 but uses more space. The default is off.
7702 @item set print array off
7703 Return to compressed format for arrays.
7705 @item show print array
7706 Show whether compressed or pretty format is selected for displaying
7709 @cindex print array indexes
7710 @item set print array-indexes
7711 @itemx set print array-indexes on
7712 Print the index of each element when displaying arrays. May be more
7713 convenient to locate a given element in the array or quickly find the
7714 index of a given element in that printed array. The default is off.
7716 @item set print array-indexes off
7717 Stop printing element indexes when displaying arrays.
7719 @item show print array-indexes
7720 Show whether the index of each element is printed when displaying
7723 @item set print elements @var{number-of-elements}
7724 @cindex number of array elements to print
7725 @cindex limit on number of printed array elements
7726 Set a limit on how many elements of an array @value{GDBN} will print.
7727 If @value{GDBN} is printing a large array, it stops printing after it has
7728 printed the number of elements set by the @code{set print elements} command.
7729 This limit also applies to the display of strings.
7730 When @value{GDBN} starts, this limit is set to 200.
7731 Setting @var{number-of-elements} to zero means that the printing is unlimited.
7733 @item show print elements
7734 Display the number of elements of a large array that @value{GDBN} will print.
7735 If the number is 0, then the printing is unlimited.
7737 @item set print frame-arguments @var{value}
7738 @kindex set print frame-arguments
7739 @cindex printing frame argument values
7740 @cindex print all frame argument values
7741 @cindex print frame argument values for scalars only
7742 @cindex do not print frame argument values
7743 This command allows to control how the values of arguments are printed
7744 when the debugger prints a frame (@pxref{Frames}). The possible
7749 The values of all arguments are printed.
7752 Print the value of an argument only if it is a scalar. The value of more
7753 complex arguments such as arrays, structures, unions, etc, is replaced
7754 by @code{@dots{}}. This is the default. Here is an example where
7755 only scalar arguments are shown:
7758 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
7763 None of the argument values are printed. Instead, the value of each argument
7764 is replaced by @code{@dots{}}. In this case, the example above now becomes:
7767 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
7772 By default, only scalar arguments are printed. This command can be used
7773 to configure the debugger to print the value of all arguments, regardless
7774 of their type. However, it is often advantageous to not print the value
7775 of more complex parameters. For instance, it reduces the amount of
7776 information printed in each frame, making the backtrace more readable.
7777 Also, it improves performance when displaying Ada frames, because
7778 the computation of large arguments can sometimes be CPU-intensive,
7779 especially in large applications. Setting @code{print frame-arguments}
7780 to @code{scalars} (the default) or @code{none} avoids this computation,
7781 thus speeding up the display of each Ada frame.
7783 @item show print frame-arguments
7784 Show how the value of arguments should be displayed when printing a frame.
7786 @item set print repeats
7787 @cindex repeated array elements
7788 Set the threshold for suppressing display of repeated array
7789 elements. When the number of consecutive identical elements of an
7790 array exceeds the threshold, @value{GDBN} prints the string
7791 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
7792 identical repetitions, instead of displaying the identical elements
7793 themselves. Setting the threshold to zero will cause all elements to
7794 be individually printed. The default threshold is 10.
7796 @item show print repeats
7797 Display the current threshold for printing repeated identical
7800 @item set print null-stop
7801 @cindex @sc{null} elements in arrays
7802 Cause @value{GDBN} to stop printing the characters of an array when the first
7803 @sc{null} is encountered. This is useful when large arrays actually
7804 contain only short strings.
7807 @item show print null-stop
7808 Show whether @value{GDBN} stops printing an array on the first
7809 @sc{null} character.
7811 @item set print pretty on
7812 @cindex print structures in indented form
7813 @cindex indentation in structure display
7814 Cause @value{GDBN} to print structures in an indented format with one member
7815 per line, like this:
7830 @item set print pretty off
7831 Cause @value{GDBN} to print structures in a compact format, like this:
7835 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
7836 meat = 0x54 "Pork"@}
7841 This is the default format.
7843 @item show print pretty
7844 Show which format @value{GDBN} is using to print structures.
7846 @item set print sevenbit-strings on
7847 @cindex eight-bit characters in strings
7848 @cindex octal escapes in strings
7849 Print using only seven-bit characters; if this option is set,
7850 @value{GDBN} displays any eight-bit characters (in strings or
7851 character values) using the notation @code{\}@var{nnn}. This setting is
7852 best if you are working in English (@sc{ascii}) and you use the
7853 high-order bit of characters as a marker or ``meta'' bit.
7855 @item set print sevenbit-strings off
7856 Print full eight-bit characters. This allows the use of more
7857 international character sets, and is the default.
7859 @item show print sevenbit-strings
7860 Show whether or not @value{GDBN} is printing only seven-bit characters.
7862 @item set print union on
7863 @cindex unions in structures, printing
7864 Tell @value{GDBN} to print unions which are contained in structures
7865 and other unions. This is the default setting.
7867 @item set print union off
7868 Tell @value{GDBN} not to print unions which are contained in
7869 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
7872 @item show print union
7873 Ask @value{GDBN} whether or not it will print unions which are contained in
7874 structures and other unions.
7876 For example, given the declarations
7879 typedef enum @{Tree, Bug@} Species;
7880 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
7881 typedef enum @{Caterpillar, Cocoon, Butterfly@}
7892 struct thing foo = @{Tree, @{Acorn@}@};
7896 with @code{set print union on} in effect @samp{p foo} would print
7899 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
7903 and with @code{set print union off} in effect it would print
7906 $1 = @{it = Tree, form = @{...@}@}
7910 @code{set print union} affects programs written in C-like languages
7916 These settings are of interest when debugging C@t{++} programs:
7919 @cindex demangling C@t{++} names
7920 @item set print demangle
7921 @itemx set print demangle on
7922 Print C@t{++} names in their source form rather than in the encoded
7923 (``mangled'') form passed to the assembler and linker for type-safe
7924 linkage. The default is on.
7926 @item show print demangle
7927 Show whether C@t{++} names are printed in mangled or demangled form.
7929 @item set print asm-demangle
7930 @itemx set print asm-demangle on
7931 Print C@t{++} names in their source form rather than their mangled form, even
7932 in assembler code printouts such as instruction disassemblies.
7935 @item show print asm-demangle
7936 Show whether C@t{++} names in assembly listings are printed in mangled
7939 @cindex C@t{++} symbol decoding style
7940 @cindex symbol decoding style, C@t{++}
7941 @kindex set demangle-style
7942 @item set demangle-style @var{style}
7943 Choose among several encoding schemes used by different compilers to
7944 represent C@t{++} names. The choices for @var{style} are currently:
7948 Allow @value{GDBN} to choose a decoding style by inspecting your program.
7951 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
7952 This is the default.
7955 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
7958 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
7961 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
7962 @strong{Warning:} this setting alone is not sufficient to allow
7963 debugging @code{cfront}-generated executables. @value{GDBN} would
7964 require further enhancement to permit that.
7967 If you omit @var{style}, you will see a list of possible formats.
7969 @item show demangle-style
7970 Display the encoding style currently in use for decoding C@t{++} symbols.
7972 @item set print object
7973 @itemx set print object on
7974 @cindex derived type of an object, printing
7975 @cindex display derived types
7976 When displaying a pointer to an object, identify the @emph{actual}
7977 (derived) type of the object rather than the @emph{declared} type, using
7978 the virtual function table.
7980 @item set print object off
7981 Display only the declared type of objects, without reference to the
7982 virtual function table. This is the default setting.
7984 @item show print object
7985 Show whether actual, or declared, object types are displayed.
7987 @item set print static-members
7988 @itemx set print static-members on
7989 @cindex static members of C@t{++} objects
7990 Print static members when displaying a C@t{++} object. The default is on.
7992 @item set print static-members off
7993 Do not print static members when displaying a C@t{++} object.
7995 @item show print static-members
7996 Show whether C@t{++} static members are printed or not.
7998 @item set print pascal_static-members
7999 @itemx set print pascal_static-members on
8000 @cindex static members of Pascal objects
8001 @cindex Pascal objects, static members display
8002 Print static members when displaying a Pascal object. The default is on.
8004 @item set print pascal_static-members off
8005 Do not print static members when displaying a Pascal object.
8007 @item show print pascal_static-members
8008 Show whether Pascal static members are printed or not.
8010 @c These don't work with HP ANSI C++ yet.
8011 @item set print vtbl
8012 @itemx set print vtbl on
8013 @cindex pretty print C@t{++} virtual function tables
8014 @cindex virtual functions (C@t{++}) display
8015 @cindex VTBL display
8016 Pretty print C@t{++} virtual function tables. The default is off.
8017 (The @code{vtbl} commands do not work on programs compiled with the HP
8018 ANSI C@t{++} compiler (@code{aCC}).)
8020 @item set print vtbl off
8021 Do not pretty print C@t{++} virtual function tables.
8023 @item show print vtbl
8024 Show whether C@t{++} virtual function tables are pretty printed, or not.
8027 @node Pretty Printing
8028 @section Pretty Printing
8030 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8031 Python code. It greatly simplifies the display of complex objects. This
8032 mechanism works for both MI and the CLI.
8034 For example, here is how a C@t{++} @code{std::string} looks without a
8038 (@value{GDBP}) print s
8040 static npos = 4294967295,
8042 <std::allocator<char>> = @{
8043 <__gnu_cxx::new_allocator<char>> = @{
8044 <No data fields>@}, <No data fields>
8046 members of std::basic_string<char, std::char_traits<char>,
8047 std::allocator<char> >::_Alloc_hider:
8048 _M_p = 0x804a014 "abcd"
8053 With a pretty-printer for @code{std::string} only the contents are printed:
8056 (@value{GDBP}) print s
8060 For implementing pretty printers for new types you should read the Python API
8061 details (@pxref{Pretty Printing API}).
8064 @section Value History
8066 @cindex value history
8067 @cindex history of values printed by @value{GDBN}
8068 Values printed by the @code{print} command are saved in the @value{GDBN}
8069 @dfn{value history}. This allows you to refer to them in other expressions.
8070 Values are kept until the symbol table is re-read or discarded
8071 (for example with the @code{file} or @code{symbol-file} commands).
8072 When the symbol table changes, the value history is discarded,
8073 since the values may contain pointers back to the types defined in the
8078 @cindex history number
8079 The values printed are given @dfn{history numbers} by which you can
8080 refer to them. These are successive integers starting with one.
8081 @code{print} shows you the history number assigned to a value by
8082 printing @samp{$@var{num} = } before the value; here @var{num} is the
8085 To refer to any previous value, use @samp{$} followed by the value's
8086 history number. The way @code{print} labels its output is designed to
8087 remind you of this. Just @code{$} refers to the most recent value in
8088 the history, and @code{$$} refers to the value before that.
8089 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
8090 is the value just prior to @code{$$}, @code{$$1} is equivalent to
8091 @code{$$}, and @code{$$0} is equivalent to @code{$}.
8093 For example, suppose you have just printed a pointer to a structure and
8094 want to see the contents of the structure. It suffices to type
8100 If you have a chain of structures where the component @code{next} points
8101 to the next one, you can print the contents of the next one with this:
8108 You can print successive links in the chain by repeating this
8109 command---which you can do by just typing @key{RET}.
8111 Note that the history records values, not expressions. If the value of
8112 @code{x} is 4 and you type these commands:
8120 then the value recorded in the value history by the @code{print} command
8121 remains 4 even though the value of @code{x} has changed.
8126 Print the last ten values in the value history, with their item numbers.
8127 This is like @samp{p@ $$9} repeated ten times, except that @code{show
8128 values} does not change the history.
8130 @item show values @var{n}
8131 Print ten history values centered on history item number @var{n}.
8134 Print ten history values just after the values last printed. If no more
8135 values are available, @code{show values +} produces no display.
8138 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
8139 same effect as @samp{show values +}.
8141 @node Convenience Vars
8142 @section Convenience Variables
8144 @cindex convenience variables
8145 @cindex user-defined variables
8146 @value{GDBN} provides @dfn{convenience variables} that you can use within
8147 @value{GDBN} to hold on to a value and refer to it later. These variables
8148 exist entirely within @value{GDBN}; they are not part of your program, and
8149 setting a convenience variable has no direct effect on further execution
8150 of your program. That is why you can use them freely.
8152 Convenience variables are prefixed with @samp{$}. Any name preceded by
8153 @samp{$} can be used for a convenience variable, unless it is one of
8154 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
8155 (Value history references, in contrast, are @emph{numbers} preceded
8156 by @samp{$}. @xref{Value History, ,Value History}.)
8158 You can save a value in a convenience variable with an assignment
8159 expression, just as you would set a variable in your program.
8163 set $foo = *object_ptr
8167 would save in @code{$foo} the value contained in the object pointed to by
8170 Using a convenience variable for the first time creates it, but its
8171 value is @code{void} until you assign a new value. You can alter the
8172 value with another assignment at any time.
8174 Convenience variables have no fixed types. You can assign a convenience
8175 variable any type of value, including structures and arrays, even if
8176 that variable already has a value of a different type. The convenience
8177 variable, when used as an expression, has the type of its current value.
8180 @kindex show convenience
8181 @cindex show all user variables
8182 @item show convenience
8183 Print a list of convenience variables used so far, and their values.
8184 Abbreviated @code{show conv}.
8186 @kindex init-if-undefined
8187 @cindex convenience variables, initializing
8188 @item init-if-undefined $@var{variable} = @var{expression}
8189 Set a convenience variable if it has not already been set. This is useful
8190 for user-defined commands that keep some state. It is similar, in concept,
8191 to using local static variables with initializers in C (except that
8192 convenience variables are global). It can also be used to allow users to
8193 override default values used in a command script.
8195 If the variable is already defined then the expression is not evaluated so
8196 any side-effects do not occur.
8199 One of the ways to use a convenience variable is as a counter to be
8200 incremented or a pointer to be advanced. For example, to print
8201 a field from successive elements of an array of structures:
8205 print bar[$i++]->contents
8209 Repeat that command by typing @key{RET}.
8211 Some convenience variables are created automatically by @value{GDBN} and given
8212 values likely to be useful.
8215 @vindex $_@r{, convenience variable}
8217 The variable @code{$_} is automatically set by the @code{x} command to
8218 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8219 commands which provide a default address for @code{x} to examine also
8220 set @code{$_} to that address; these commands include @code{info line}
8221 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8222 except when set by the @code{x} command, in which case it is a pointer
8223 to the type of @code{$__}.
8225 @vindex $__@r{, convenience variable}
8227 The variable @code{$__} is automatically set by the @code{x} command
8228 to the value found in the last address examined. Its type is chosen
8229 to match the format in which the data was printed.
8232 @vindex $_exitcode@r{, convenience variable}
8233 The variable @code{$_exitcode} is automatically set to the exit code when
8234 the program being debugged terminates.
8237 @vindex $_siginfo@r{, convenience variable}
8238 The variable @code{$_siginfo} contains extra signal information
8239 (@pxref{extra signal information}). Note that @code{$_siginfo}
8240 could be empty, if the application has not yet received any signals.
8241 For example, it will be empty before you execute the @code{run} command.
8244 @vindex $_tlb@r{, convenience variable}
8245 The variable @code{$_tlb} is automatically set when debugging
8246 applications running on MS-Windows in native mode or connected to
8247 gdbserver that supports the @code{qGetTIBAddr} request.
8248 @xref{General Query Packets}.
8249 This variable contains the address of the thread information block.
8253 On HP-UX systems, if you refer to a function or variable name that
8254 begins with a dollar sign, @value{GDBN} searches for a user or system
8255 name first, before it searches for a convenience variable.
8257 @cindex convenience functions
8258 @value{GDBN} also supplies some @dfn{convenience functions}. These
8259 have a syntax similar to convenience variables. A convenience
8260 function can be used in an expression just like an ordinary function;
8261 however, a convenience function is implemented internally to
8266 @kindex help function
8267 @cindex show all convenience functions
8268 Print a list of all convenience functions.
8275 You can refer to machine register contents, in expressions, as variables
8276 with names starting with @samp{$}. The names of registers are different
8277 for each machine; use @code{info registers} to see the names used on
8281 @kindex info registers
8282 @item info registers
8283 Print the names and values of all registers except floating-point
8284 and vector registers (in the selected stack frame).
8286 @kindex info all-registers
8287 @cindex floating point registers
8288 @item info all-registers
8289 Print the names and values of all registers, including floating-point
8290 and vector registers (in the selected stack frame).
8292 @item info registers @var{regname} @dots{}
8293 Print the @dfn{relativized} value of each specified register @var{regname}.
8294 As discussed in detail below, register values are normally relative to
8295 the selected stack frame. @var{regname} may be any register name valid on
8296 the machine you are using, with or without the initial @samp{$}.
8299 @cindex stack pointer register
8300 @cindex program counter register
8301 @cindex process status register
8302 @cindex frame pointer register
8303 @cindex standard registers
8304 @value{GDBN} has four ``standard'' register names that are available (in
8305 expressions) on most machines---whenever they do not conflict with an
8306 architecture's canonical mnemonics for registers. The register names
8307 @code{$pc} and @code{$sp} are used for the program counter register and
8308 the stack pointer. @code{$fp} is used for a register that contains a
8309 pointer to the current stack frame, and @code{$ps} is used for a
8310 register that contains the processor status. For example,
8311 you could print the program counter in hex with
8318 or print the instruction to be executed next with
8325 or add four to the stack pointer@footnote{This is a way of removing
8326 one word from the stack, on machines where stacks grow downward in
8327 memory (most machines, nowadays). This assumes that the innermost
8328 stack frame is selected; setting @code{$sp} is not allowed when other
8329 stack frames are selected. To pop entire frames off the stack,
8330 regardless of machine architecture, use @code{return};
8331 see @ref{Returning, ,Returning from a Function}.} with
8337 Whenever possible, these four standard register names are available on
8338 your machine even though the machine has different canonical mnemonics,
8339 so long as there is no conflict. The @code{info registers} command
8340 shows the canonical names. For example, on the SPARC, @code{info
8341 registers} displays the processor status register as @code{$psr} but you
8342 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
8343 is an alias for the @sc{eflags} register.
8345 @value{GDBN} always considers the contents of an ordinary register as an
8346 integer when the register is examined in this way. Some machines have
8347 special registers which can hold nothing but floating point; these
8348 registers are considered to have floating point values. There is no way
8349 to refer to the contents of an ordinary register as floating point value
8350 (although you can @emph{print} it as a floating point value with
8351 @samp{print/f $@var{regname}}).
8353 Some registers have distinct ``raw'' and ``virtual'' data formats. This
8354 means that the data format in which the register contents are saved by
8355 the operating system is not the same one that your program normally
8356 sees. For example, the registers of the 68881 floating point
8357 coprocessor are always saved in ``extended'' (raw) format, but all C
8358 programs expect to work with ``double'' (virtual) format. In such
8359 cases, @value{GDBN} normally works with the virtual format only (the format
8360 that makes sense for your program), but the @code{info registers} command
8361 prints the data in both formats.
8363 @cindex SSE registers (x86)
8364 @cindex MMX registers (x86)
8365 Some machines have special registers whose contents can be interpreted
8366 in several different ways. For example, modern x86-based machines
8367 have SSE and MMX registers that can hold several values packed
8368 together in several different formats. @value{GDBN} refers to such
8369 registers in @code{struct} notation:
8372 (@value{GDBP}) print $xmm1
8374 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
8375 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
8376 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
8377 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
8378 v4_int32 = @{0, 20657912, 11, 13@},
8379 v2_int64 = @{88725056443645952, 55834574859@},
8380 uint128 = 0x0000000d0000000b013b36f800000000
8385 To set values of such registers, you need to tell @value{GDBN} which
8386 view of the register you wish to change, as if you were assigning
8387 value to a @code{struct} member:
8390 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
8393 Normally, register values are relative to the selected stack frame
8394 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
8395 value that the register would contain if all stack frames farther in
8396 were exited and their saved registers restored. In order to see the
8397 true contents of hardware registers, you must select the innermost
8398 frame (with @samp{frame 0}).
8400 However, @value{GDBN} must deduce where registers are saved, from the machine
8401 code generated by your compiler. If some registers are not saved, or if
8402 @value{GDBN} is unable to locate the saved registers, the selected stack
8403 frame makes no difference.
8405 @node Floating Point Hardware
8406 @section Floating Point Hardware
8407 @cindex floating point
8409 Depending on the configuration, @value{GDBN} may be able to give
8410 you more information about the status of the floating point hardware.
8415 Display hardware-dependent information about the floating
8416 point unit. The exact contents and layout vary depending on the
8417 floating point chip. Currently, @samp{info float} is supported on
8418 the ARM and x86 machines.
8422 @section Vector Unit
8425 Depending on the configuration, @value{GDBN} may be able to give you
8426 more information about the status of the vector unit.
8431 Display information about the vector unit. The exact contents and
8432 layout vary depending on the hardware.
8435 @node OS Information
8436 @section Operating System Auxiliary Information
8437 @cindex OS information
8439 @value{GDBN} provides interfaces to useful OS facilities that can help
8440 you debug your program.
8442 @cindex @code{ptrace} system call
8443 @cindex @code{struct user} contents
8444 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
8445 machines), it interfaces with the inferior via the @code{ptrace}
8446 system call. The operating system creates a special sata structure,
8447 called @code{struct user}, for this interface. You can use the
8448 command @code{info udot} to display the contents of this data
8454 Display the contents of the @code{struct user} maintained by the OS
8455 kernel for the program being debugged. @value{GDBN} displays the
8456 contents of @code{struct user} as a list of hex numbers, similar to
8457 the @code{examine} command.
8460 @cindex auxiliary vector
8461 @cindex vector, auxiliary
8462 Some operating systems supply an @dfn{auxiliary vector} to programs at
8463 startup. This is akin to the arguments and environment that you
8464 specify for a program, but contains a system-dependent variety of
8465 binary values that tell system libraries important details about the
8466 hardware, operating system, and process. Each value's purpose is
8467 identified by an integer tag; the meanings are well-known but system-specific.
8468 Depending on the configuration and operating system facilities,
8469 @value{GDBN} may be able to show you this information. For remote
8470 targets, this functionality may further depend on the remote stub's
8471 support of the @samp{qXfer:auxv:read} packet, see
8472 @ref{qXfer auxiliary vector read}.
8477 Display the auxiliary vector of the inferior, which can be either a
8478 live process or a core dump file. @value{GDBN} prints each tag value
8479 numerically, and also shows names and text descriptions for recognized
8480 tags. Some values in the vector are numbers, some bit masks, and some
8481 pointers to strings or other data. @value{GDBN} displays each value in the
8482 most appropriate form for a recognized tag, and in hexadecimal for
8483 an unrecognized tag.
8486 On some targets, @value{GDBN} can access operating-system-specific information
8487 and display it to user, without interpretation. For remote targets,
8488 this functionality depends on the remote stub's support of the
8489 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
8492 @kindex info os processes
8493 @item info os processes
8494 Display the list of processes on the target. For each process,
8495 @value{GDBN} prints the process identifier, the name of the user, and
8496 the command corresponding to the process.
8499 @node Memory Region Attributes
8500 @section Memory Region Attributes
8501 @cindex memory region attributes
8503 @dfn{Memory region attributes} allow you to describe special handling
8504 required by regions of your target's memory. @value{GDBN} uses
8505 attributes to determine whether to allow certain types of memory
8506 accesses; whether to use specific width accesses; and whether to cache
8507 target memory. By default the description of memory regions is
8508 fetched from the target (if the current target supports this), but the
8509 user can override the fetched regions.
8511 Defined memory regions can be individually enabled and disabled. When a
8512 memory region is disabled, @value{GDBN} uses the default attributes when
8513 accessing memory in that region. Similarly, if no memory regions have
8514 been defined, @value{GDBN} uses the default attributes when accessing
8517 When a memory region is defined, it is given a number to identify it;
8518 to enable, disable, or remove a memory region, you specify that number.
8522 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
8523 Define a memory region bounded by @var{lower} and @var{upper} with
8524 attributes @var{attributes}@dots{}, and add it to the list of regions
8525 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
8526 case: it is treated as the target's maximum memory address.
8527 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
8530 Discard any user changes to the memory regions and use target-supplied
8531 regions, if available, or no regions if the target does not support.
8534 @item delete mem @var{nums}@dots{}
8535 Remove memory regions @var{nums}@dots{} from the list of regions
8536 monitored by @value{GDBN}.
8539 @item disable mem @var{nums}@dots{}
8540 Disable monitoring of memory regions @var{nums}@dots{}.
8541 A disabled memory region is not forgotten.
8542 It may be enabled again later.
8545 @item enable mem @var{nums}@dots{}
8546 Enable monitoring of memory regions @var{nums}@dots{}.
8550 Print a table of all defined memory regions, with the following columns
8554 @item Memory Region Number
8555 @item Enabled or Disabled.
8556 Enabled memory regions are marked with @samp{y}.
8557 Disabled memory regions are marked with @samp{n}.
8560 The address defining the inclusive lower bound of the memory region.
8563 The address defining the exclusive upper bound of the memory region.
8566 The list of attributes set for this memory region.
8571 @subsection Attributes
8573 @subsubsection Memory Access Mode
8574 The access mode attributes set whether @value{GDBN} may make read or
8575 write accesses to a memory region.
8577 While these attributes prevent @value{GDBN} from performing invalid
8578 memory accesses, they do nothing to prevent the target system, I/O DMA,
8579 etc.@: from accessing memory.
8583 Memory is read only.
8585 Memory is write only.
8587 Memory is read/write. This is the default.
8590 @subsubsection Memory Access Size
8591 The access size attribute tells @value{GDBN} to use specific sized
8592 accesses in the memory region. Often memory mapped device registers
8593 require specific sized accesses. If no access size attribute is
8594 specified, @value{GDBN} may use accesses of any size.
8598 Use 8 bit memory accesses.
8600 Use 16 bit memory accesses.
8602 Use 32 bit memory accesses.
8604 Use 64 bit memory accesses.
8607 @c @subsubsection Hardware/Software Breakpoints
8608 @c The hardware/software breakpoint attributes set whether @value{GDBN}
8609 @c will use hardware or software breakpoints for the internal breakpoints
8610 @c used by the step, next, finish, until, etc. commands.
8614 @c Always use hardware breakpoints
8615 @c @item swbreak (default)
8618 @subsubsection Data Cache
8619 The data cache attributes set whether @value{GDBN} will cache target
8620 memory. While this generally improves performance by reducing debug
8621 protocol overhead, it can lead to incorrect results because @value{GDBN}
8622 does not know about volatile variables or memory mapped device
8627 Enable @value{GDBN} to cache target memory.
8629 Disable @value{GDBN} from caching target memory. This is the default.
8632 @subsection Memory Access Checking
8633 @value{GDBN} can be instructed to refuse accesses to memory that is
8634 not explicitly described. This can be useful if accessing such
8635 regions has undesired effects for a specific target, or to provide
8636 better error checking. The following commands control this behaviour.
8639 @kindex set mem inaccessible-by-default
8640 @item set mem inaccessible-by-default [on|off]
8641 If @code{on} is specified, make @value{GDBN} treat memory not
8642 explicitly described by the memory ranges as non-existent and refuse accesses
8643 to such memory. The checks are only performed if there's at least one
8644 memory range defined. If @code{off} is specified, make @value{GDBN}
8645 treat the memory not explicitly described by the memory ranges as RAM.
8646 The default value is @code{on}.
8647 @kindex show mem inaccessible-by-default
8648 @item show mem inaccessible-by-default
8649 Show the current handling of accesses to unknown memory.
8653 @c @subsubsection Memory Write Verification
8654 @c The memory write verification attributes set whether @value{GDBN}
8655 @c will re-reads data after each write to verify the write was successful.
8659 @c @item noverify (default)
8662 @node Dump/Restore Files
8663 @section Copy Between Memory and a File
8664 @cindex dump/restore files
8665 @cindex append data to a file
8666 @cindex dump data to a file
8667 @cindex restore data from a file
8669 You can use the commands @code{dump}, @code{append}, and
8670 @code{restore} to copy data between target memory and a file. The
8671 @code{dump} and @code{append} commands write data to a file, and the
8672 @code{restore} command reads data from a file back into the inferior's
8673 memory. Files may be in binary, Motorola S-record, Intel hex, or
8674 Tektronix Hex format; however, @value{GDBN} can only append to binary
8680 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8681 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
8682 Dump the contents of memory from @var{start_addr} to @var{end_addr},
8683 or the value of @var{expr}, to @var{filename} in the given format.
8685 The @var{format} parameter may be any one of:
8692 Motorola S-record format.
8694 Tektronix Hex format.
8697 @value{GDBN} uses the same definitions of these formats as the
8698 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
8699 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
8703 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8704 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
8705 Append the contents of memory from @var{start_addr} to @var{end_addr},
8706 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
8707 (@value{GDBN} can only append data to files in raw binary form.)
8710 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
8711 Restore the contents of file @var{filename} into memory. The
8712 @code{restore} command can automatically recognize any known @sc{bfd}
8713 file format, except for raw binary. To restore a raw binary file you
8714 must specify the optional keyword @code{binary} after the filename.
8716 If @var{bias} is non-zero, its value will be added to the addresses
8717 contained in the file. Binary files always start at address zero, so
8718 they will be restored at address @var{bias}. Other bfd files have
8719 a built-in location; they will be restored at offset @var{bias}
8722 If @var{start} and/or @var{end} are non-zero, then only data between
8723 file offset @var{start} and file offset @var{end} will be restored.
8724 These offsets are relative to the addresses in the file, before
8725 the @var{bias} argument is applied.
8729 @node Core File Generation
8730 @section How to Produce a Core File from Your Program
8731 @cindex dump core from inferior
8733 A @dfn{core file} or @dfn{core dump} is a file that records the memory
8734 image of a running process and its process status (register values
8735 etc.). Its primary use is post-mortem debugging of a program that
8736 crashed while it ran outside a debugger. A program that crashes
8737 automatically produces a core file, unless this feature is disabled by
8738 the user. @xref{Files}, for information on invoking @value{GDBN} in
8739 the post-mortem debugging mode.
8741 Occasionally, you may wish to produce a core file of the program you
8742 are debugging in order to preserve a snapshot of its state.
8743 @value{GDBN} has a special command for that.
8747 @kindex generate-core-file
8748 @item generate-core-file [@var{file}]
8749 @itemx gcore [@var{file}]
8750 Produce a core dump of the inferior process. The optional argument
8751 @var{file} specifies the file name where to put the core dump. If not
8752 specified, the file name defaults to @file{core.@var{pid}}, where
8753 @var{pid} is the inferior process ID.
8755 Note that this command is implemented only for some systems (as of
8756 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
8759 @node Character Sets
8760 @section Character Sets
8761 @cindex character sets
8763 @cindex translating between character sets
8764 @cindex host character set
8765 @cindex target character set
8767 If the program you are debugging uses a different character set to
8768 represent characters and strings than the one @value{GDBN} uses itself,
8769 @value{GDBN} can automatically translate between the character sets for
8770 you. The character set @value{GDBN} uses we call the @dfn{host
8771 character set}; the one the inferior program uses we call the
8772 @dfn{target character set}.
8774 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
8775 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
8776 remote protocol (@pxref{Remote Debugging}) to debug a program
8777 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
8778 then the host character set is Latin-1, and the target character set is
8779 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
8780 target-charset EBCDIC-US}, then @value{GDBN} translates between
8781 @sc{ebcdic} and Latin 1 as you print character or string values, or use
8782 character and string literals in expressions.
8784 @value{GDBN} has no way to automatically recognize which character set
8785 the inferior program uses; you must tell it, using the @code{set
8786 target-charset} command, described below.
8788 Here are the commands for controlling @value{GDBN}'s character set
8792 @item set target-charset @var{charset}
8793 @kindex set target-charset
8794 Set the current target character set to @var{charset}. To display the
8795 list of supported target character sets, type
8796 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
8798 @item set host-charset @var{charset}
8799 @kindex set host-charset
8800 Set the current host character set to @var{charset}.
8802 By default, @value{GDBN} uses a host character set appropriate to the
8803 system it is running on; you can override that default using the
8804 @code{set host-charset} command. On some systems, @value{GDBN} cannot
8805 automatically determine the appropriate host character set. In this
8806 case, @value{GDBN} uses @samp{UTF-8}.
8808 @value{GDBN} can only use certain character sets as its host character
8809 set. If you type @kbd{@w{set target-charset @key{TAB}@key{TAB}}},
8810 @value{GDBN} will list the host character sets it supports.
8812 @item set charset @var{charset}
8814 Set the current host and target character sets to @var{charset}. As
8815 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
8816 @value{GDBN} will list the names of the character sets that can be used
8817 for both host and target.
8820 @kindex show charset
8821 Show the names of the current host and target character sets.
8823 @item show host-charset
8824 @kindex show host-charset
8825 Show the name of the current host character set.
8827 @item show target-charset
8828 @kindex show target-charset
8829 Show the name of the current target character set.
8831 @item set target-wide-charset @var{charset}
8832 @kindex set target-wide-charset
8833 Set the current target's wide character set to @var{charset}. This is
8834 the character set used by the target's @code{wchar_t} type. To
8835 display the list of supported wide character sets, type
8836 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
8838 @item show target-wide-charset
8839 @kindex show target-wide-charset
8840 Show the name of the current target's wide character set.
8843 Here is an example of @value{GDBN}'s character set support in action.
8844 Assume that the following source code has been placed in the file
8845 @file{charset-test.c}:
8851 = @{72, 101, 108, 108, 111, 44, 32, 119,
8852 111, 114, 108, 100, 33, 10, 0@};
8853 char ibm1047_hello[]
8854 = @{200, 133, 147, 147, 150, 107, 64, 166,
8855 150, 153, 147, 132, 90, 37, 0@};
8859 printf ("Hello, world!\n");
8863 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
8864 containing the string @samp{Hello, world!} followed by a newline,
8865 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
8867 We compile the program, and invoke the debugger on it:
8870 $ gcc -g charset-test.c -o charset-test
8871 $ gdb -nw charset-test
8872 GNU gdb 2001-12-19-cvs
8873 Copyright 2001 Free Software Foundation, Inc.
8878 We can use the @code{show charset} command to see what character sets
8879 @value{GDBN} is currently using to interpret and display characters and
8883 (@value{GDBP}) show charset
8884 The current host and target character set is `ISO-8859-1'.
8888 For the sake of printing this manual, let's use @sc{ascii} as our
8889 initial character set:
8891 (@value{GDBP}) set charset ASCII
8892 (@value{GDBP}) show charset
8893 The current host and target character set is `ASCII'.
8897 Let's assume that @sc{ascii} is indeed the correct character set for our
8898 host system --- in other words, let's assume that if @value{GDBN} prints
8899 characters using the @sc{ascii} character set, our terminal will display
8900 them properly. Since our current target character set is also
8901 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
8904 (@value{GDBP}) print ascii_hello
8905 $1 = 0x401698 "Hello, world!\n"
8906 (@value{GDBP}) print ascii_hello[0]
8911 @value{GDBN} uses the target character set for character and string
8912 literals you use in expressions:
8915 (@value{GDBP}) print '+'
8920 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
8923 @value{GDBN} relies on the user to tell it which character set the
8924 target program uses. If we print @code{ibm1047_hello} while our target
8925 character set is still @sc{ascii}, we get jibberish:
8928 (@value{GDBP}) print ibm1047_hello
8929 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
8930 (@value{GDBP}) print ibm1047_hello[0]
8935 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
8936 @value{GDBN} tells us the character sets it supports:
8939 (@value{GDBP}) set target-charset
8940 ASCII EBCDIC-US IBM1047 ISO-8859-1
8941 (@value{GDBP}) set target-charset
8944 We can select @sc{ibm1047} as our target character set, and examine the
8945 program's strings again. Now the @sc{ascii} string is wrong, but
8946 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
8947 target character set, @sc{ibm1047}, to the host character set,
8948 @sc{ascii}, and they display correctly:
8951 (@value{GDBP}) set target-charset IBM1047
8952 (@value{GDBP}) show charset
8953 The current host character set is `ASCII'.
8954 The current target character set is `IBM1047'.
8955 (@value{GDBP}) print ascii_hello
8956 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
8957 (@value{GDBP}) print ascii_hello[0]
8959 (@value{GDBP}) print ibm1047_hello
8960 $8 = 0x4016a8 "Hello, world!\n"
8961 (@value{GDBP}) print ibm1047_hello[0]
8966 As above, @value{GDBN} uses the target character set for character and
8967 string literals you use in expressions:
8970 (@value{GDBP}) print '+'
8975 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
8978 @node Caching Remote Data
8979 @section Caching Data of Remote Targets
8980 @cindex caching data of remote targets
8982 @value{GDBN} caches data exchanged between the debugger and a
8983 remote target (@pxref{Remote Debugging}). Such caching generally improves
8984 performance, because it reduces the overhead of the remote protocol by
8985 bundling memory reads and writes into large chunks. Unfortunately, simply
8986 caching everything would lead to incorrect results, since @value{GDBN}
8987 does not necessarily know anything about volatile values, memory-mapped I/O
8988 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
8989 memory can be changed @emph{while} a gdb command is executing.
8990 Therefore, by default, @value{GDBN} only caches data
8991 known to be on the stack@footnote{In non-stop mode, it is moderately
8992 rare for a running thread to modify the stack of a stopped thread
8993 in a way that would interfere with a backtrace, and caching of
8994 stack reads provides a significant speed up of remote backtraces.}.
8995 Other regions of memory can be explicitly marked as
8996 cacheable; see @pxref{Memory Region Attributes}.
8999 @kindex set remotecache
9000 @item set remotecache on
9001 @itemx set remotecache off
9002 This option no longer does anything; it exists for compatibility
9005 @kindex show remotecache
9006 @item show remotecache
9007 Show the current state of the obsolete remotecache flag.
9009 @kindex set stack-cache
9010 @item set stack-cache on
9011 @itemx set stack-cache off
9012 Enable or disable caching of stack accesses. When @code{ON}, use
9013 caching. By default, this option is @code{ON}.
9015 @kindex show stack-cache
9016 @item show stack-cache
9017 Show the current state of data caching for memory accesses.
9020 @item info dcache @r{[}line@r{]}
9021 Print the information about the data cache performance. The
9022 information displayed includes the dcache width and depth, and for
9023 each cache line, its number, address, and how many times it was
9024 referenced. This command is useful for debugging the data cache
9027 If a line number is specified, the contents of that line will be
9031 @node Searching Memory
9032 @section Search Memory
9033 @cindex searching memory
9035 Memory can be searched for a particular sequence of bytes with the
9036 @code{find} command.
9040 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9041 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9042 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
9043 etc. The search begins at address @var{start_addr} and continues for either
9044 @var{len} bytes or through to @var{end_addr} inclusive.
9047 @var{s} and @var{n} are optional parameters.
9048 They may be specified in either order, apart or together.
9051 @item @var{s}, search query size
9052 The size of each search query value.
9058 halfwords (two bytes)
9062 giant words (eight bytes)
9065 All values are interpreted in the current language.
9066 This means, for example, that if the current source language is C/C@t{++}
9067 then searching for the string ``hello'' includes the trailing '\0'.
9069 If the value size is not specified, it is taken from the
9070 value's type in the current language.
9071 This is useful when one wants to specify the search
9072 pattern as a mixture of types.
9073 Note that this means, for example, that in the case of C-like languages
9074 a search for an untyped 0x42 will search for @samp{(int) 0x42}
9075 which is typically four bytes.
9077 @item @var{n}, maximum number of finds
9078 The maximum number of matches to print. The default is to print all finds.
9081 You can use strings as search values. Quote them with double-quotes
9083 The string value is copied into the search pattern byte by byte,
9084 regardless of the endianness of the target and the size specification.
9086 The address of each match found is printed as well as a count of the
9087 number of matches found.
9089 The address of the last value found is stored in convenience variable
9091 A count of the number of matches is stored in @samp{$numfound}.
9093 For example, if stopped at the @code{printf} in this function:
9099 static char hello[] = "hello-hello";
9100 static struct @{ char c; short s; int i; @}
9101 __attribute__ ((packed)) mixed
9102 = @{ 'c', 0x1234, 0x87654321 @};
9103 printf ("%s\n", hello);
9108 you get during debugging:
9111 (gdb) find &hello[0], +sizeof(hello), "hello"
9112 0x804956d <hello.1620+6>
9114 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
9115 0x8049567 <hello.1620>
9116 0x804956d <hello.1620+6>
9118 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
9119 0x8049567 <hello.1620>
9121 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
9122 0x8049560 <mixed.1625>
9124 (gdb) print $numfound
9127 $2 = (void *) 0x8049560
9130 @node Optimized Code
9131 @chapter Debugging Optimized Code
9132 @cindex optimized code, debugging
9133 @cindex debugging optimized code
9135 Almost all compilers support optimization. With optimization
9136 disabled, the compiler generates assembly code that corresponds
9137 directly to your source code, in a simplistic way. As the compiler
9138 applies more powerful optimizations, the generated assembly code
9139 diverges from your original source code. With help from debugging
9140 information generated by the compiler, @value{GDBN} can map from
9141 the running program back to constructs from your original source.
9143 @value{GDBN} is more accurate with optimization disabled. If you
9144 can recompile without optimization, it is easier to follow the
9145 progress of your program during debugging. But, there are many cases
9146 where you may need to debug an optimized version.
9148 When you debug a program compiled with @samp{-g -O}, remember that the
9149 optimizer has rearranged your code; the debugger shows you what is
9150 really there. Do not be too surprised when the execution path does not
9151 exactly match your source file! An extreme example: if you define a
9152 variable, but never use it, @value{GDBN} never sees that
9153 variable---because the compiler optimizes it out of existence.
9155 Some things do not work as well with @samp{-g -O} as with just
9156 @samp{-g}, particularly on machines with instruction scheduling. If in
9157 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
9158 please report it to us as a bug (including a test case!).
9159 @xref{Variables}, for more information about debugging optimized code.
9162 * Inline Functions:: How @value{GDBN} presents inlining
9165 @node Inline Functions
9166 @section Inline Functions
9167 @cindex inline functions, debugging
9169 @dfn{Inlining} is an optimization that inserts a copy of the function
9170 body directly at each call site, instead of jumping to a shared
9171 routine. @value{GDBN} displays inlined functions just like
9172 non-inlined functions. They appear in backtraces. You can view their
9173 arguments and local variables, step into them with @code{step}, skip
9174 them with @code{next}, and escape from them with @code{finish}.
9175 You can check whether a function was inlined by using the
9176 @code{info frame} command.
9178 For @value{GDBN} to support inlined functions, the compiler must
9179 record information about inlining in the debug information ---
9180 @value{NGCC} using the @sc{dwarf 2} format does this, and several
9181 other compilers do also. @value{GDBN} only supports inlined functions
9182 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
9183 do not emit two required attributes (@samp{DW_AT_call_file} and
9184 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
9185 function calls with earlier versions of @value{NGCC}. It instead
9186 displays the arguments and local variables of inlined functions as
9187 local variables in the caller.
9189 The body of an inlined function is directly included at its call site;
9190 unlike a non-inlined function, there are no instructions devoted to
9191 the call. @value{GDBN} still pretends that the call site and the
9192 start of the inlined function are different instructions. Stepping to
9193 the call site shows the call site, and then stepping again shows
9194 the first line of the inlined function, even though no additional
9195 instructions are executed.
9197 This makes source-level debugging much clearer; you can see both the
9198 context of the call and then the effect of the call. Only stepping by
9199 a single instruction using @code{stepi} or @code{nexti} does not do
9200 this; single instruction steps always show the inlined body.
9202 There are some ways that @value{GDBN} does not pretend that inlined
9203 function calls are the same as normal calls:
9207 You cannot set breakpoints on inlined functions. @value{GDBN}
9208 either reports that there is no symbol with that name, or else sets the
9209 breakpoint only on non-inlined copies of the function. This limitation
9210 will be removed in a future version of @value{GDBN}; until then,
9211 set a breakpoint by line number on the first line of the inlined
9215 Setting breakpoints at the call site of an inlined function may not
9216 work, because the call site does not contain any code. @value{GDBN}
9217 may incorrectly move the breakpoint to the next line of the enclosing
9218 function, after the call. This limitation will be removed in a future
9219 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9220 or inside the inlined function instead.
9223 @value{GDBN} cannot locate the return value of inlined calls after
9224 using the @code{finish} command. This is a limitation of compiler-generated
9225 debugging information; after @code{finish}, you can step to the next line
9226 and print a variable where your program stored the return value.
9232 @chapter C Preprocessor Macros
9234 Some languages, such as C and C@t{++}, provide a way to define and invoke
9235 ``preprocessor macros'' which expand into strings of tokens.
9236 @value{GDBN} can evaluate expressions containing macro invocations, show
9237 the result of macro expansion, and show a macro's definition, including
9238 where it was defined.
9240 You may need to compile your program specially to provide @value{GDBN}
9241 with information about preprocessor macros. Most compilers do not
9242 include macros in their debugging information, even when you compile
9243 with the @option{-g} flag. @xref{Compilation}.
9245 A program may define a macro at one point, remove that definition later,
9246 and then provide a different definition after that. Thus, at different
9247 points in the program, a macro may have different definitions, or have
9248 no definition at all. If there is a current stack frame, @value{GDBN}
9249 uses the macros in scope at that frame's source code line. Otherwise,
9250 @value{GDBN} uses the macros in scope at the current listing location;
9253 Whenever @value{GDBN} evaluates an expression, it always expands any
9254 macro invocations present in the expression. @value{GDBN} also provides
9255 the following commands for working with macros explicitly.
9259 @kindex macro expand
9260 @cindex macro expansion, showing the results of preprocessor
9261 @cindex preprocessor macro expansion, showing the results of
9262 @cindex expanding preprocessor macros
9263 @item macro expand @var{expression}
9264 @itemx macro exp @var{expression}
9265 Show the results of expanding all preprocessor macro invocations in
9266 @var{expression}. Since @value{GDBN} simply expands macros, but does
9267 not parse the result, @var{expression} need not be a valid expression;
9268 it can be any string of tokens.
9271 @item macro expand-once @var{expression}
9272 @itemx macro exp1 @var{expression}
9273 @cindex expand macro once
9274 @i{(This command is not yet implemented.)} Show the results of
9275 expanding those preprocessor macro invocations that appear explicitly in
9276 @var{expression}. Macro invocations appearing in that expansion are
9277 left unchanged. This command allows you to see the effect of a
9278 particular macro more clearly, without being confused by further
9279 expansions. Since @value{GDBN} simply expands macros, but does not
9280 parse the result, @var{expression} need not be a valid expression; it
9281 can be any string of tokens.
9284 @cindex macro definition, showing
9285 @cindex definition, showing a macro's
9286 @item info macro @var{macro}
9287 Show the definition of the macro named @var{macro}, and describe the
9288 source location or compiler command-line where that definition was established.
9290 @kindex macro define
9291 @cindex user-defined macros
9292 @cindex defining macros interactively
9293 @cindex macros, user-defined
9294 @item macro define @var{macro} @var{replacement-list}
9295 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
9296 Introduce a definition for a preprocessor macro named @var{macro},
9297 invocations of which are replaced by the tokens given in
9298 @var{replacement-list}. The first form of this command defines an
9299 ``object-like'' macro, which takes no arguments; the second form
9300 defines a ``function-like'' macro, which takes the arguments given in
9303 A definition introduced by this command is in scope in every
9304 expression evaluated in @value{GDBN}, until it is removed with the
9305 @code{macro undef} command, described below. The definition overrides
9306 all definitions for @var{macro} present in the program being debugged,
9307 as well as any previous user-supplied definition.
9310 @item macro undef @var{macro}
9311 Remove any user-supplied definition for the macro named @var{macro}.
9312 This command only affects definitions provided with the @code{macro
9313 define} command, described above; it cannot remove definitions present
9314 in the program being debugged.
9318 List all the macros defined using the @code{macro define} command.
9321 @cindex macros, example of debugging with
9322 Here is a transcript showing the above commands in action. First, we
9323 show our source files:
9331 #define ADD(x) (M + x)
9336 printf ("Hello, world!\n");
9338 printf ("We're so creative.\n");
9340 printf ("Goodbye, world!\n");
9347 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
9348 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
9349 compiler includes information about preprocessor macros in the debugging
9353 $ gcc -gdwarf-2 -g3 sample.c -o sample
9357 Now, we start @value{GDBN} on our sample program:
9361 GNU gdb 2002-05-06-cvs
9362 Copyright 2002 Free Software Foundation, Inc.
9363 GDB is free software, @dots{}
9367 We can expand macros and examine their definitions, even when the
9368 program is not running. @value{GDBN} uses the current listing position
9369 to decide which macro definitions are in scope:
9372 (@value{GDBP}) list main
9375 5 #define ADD(x) (M + x)
9380 10 printf ("Hello, world!\n");
9382 12 printf ("We're so creative.\n");
9383 (@value{GDBP}) info macro ADD
9384 Defined at /home/jimb/gdb/macros/play/sample.c:5
9385 #define ADD(x) (M + x)
9386 (@value{GDBP}) info macro Q
9387 Defined at /home/jimb/gdb/macros/play/sample.h:1
9388 included at /home/jimb/gdb/macros/play/sample.c:2
9390 (@value{GDBP}) macro expand ADD(1)
9391 expands to: (42 + 1)
9392 (@value{GDBP}) macro expand-once ADD(1)
9393 expands to: once (M + 1)
9397 In the example above, note that @code{macro expand-once} expands only
9398 the macro invocation explicit in the original text --- the invocation of
9399 @code{ADD} --- but does not expand the invocation of the macro @code{M},
9400 which was introduced by @code{ADD}.
9402 Once the program is running, @value{GDBN} uses the macro definitions in
9403 force at the source line of the current stack frame:
9406 (@value{GDBP}) break main
9407 Breakpoint 1 at 0x8048370: file sample.c, line 10.
9409 Starting program: /home/jimb/gdb/macros/play/sample
9411 Breakpoint 1, main () at sample.c:10
9412 10 printf ("Hello, world!\n");
9416 At line 10, the definition of the macro @code{N} at line 9 is in force:
9419 (@value{GDBP}) info macro N
9420 Defined at /home/jimb/gdb/macros/play/sample.c:9
9422 (@value{GDBP}) macro expand N Q M
9424 (@value{GDBP}) print N Q M
9429 As we step over directives that remove @code{N}'s definition, and then
9430 give it a new definition, @value{GDBN} finds the definition (or lack
9431 thereof) in force at each point:
9436 12 printf ("We're so creative.\n");
9437 (@value{GDBP}) info macro N
9438 The symbol `N' has no definition as a C/C++ preprocessor macro
9439 at /home/jimb/gdb/macros/play/sample.c:12
9442 14 printf ("Goodbye, world!\n");
9443 (@value{GDBP}) info macro N
9444 Defined at /home/jimb/gdb/macros/play/sample.c:13
9446 (@value{GDBP}) macro expand N Q M
9447 expands to: 1729 < 42
9448 (@value{GDBP}) print N Q M
9453 In addition to source files, macros can be defined on the compilation command
9454 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
9455 such a way, @value{GDBN} displays the location of their definition as line zero
9456 of the source file submitted to the compiler.
9459 (@value{GDBP}) info macro __STDC__
9460 Defined at /home/jimb/gdb/macros/play/sample.c:0
9467 @chapter Tracepoints
9468 @c This chapter is based on the documentation written by Michael
9469 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
9472 In some applications, it is not feasible for the debugger to interrupt
9473 the program's execution long enough for the developer to learn
9474 anything helpful about its behavior. If the program's correctness
9475 depends on its real-time behavior, delays introduced by a debugger
9476 might cause the program to change its behavior drastically, or perhaps
9477 fail, even when the code itself is correct. It is useful to be able
9478 to observe the program's behavior without interrupting it.
9480 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
9481 specify locations in the program, called @dfn{tracepoints}, and
9482 arbitrary expressions to evaluate when those tracepoints are reached.
9483 Later, using the @code{tfind} command, you can examine the values
9484 those expressions had when the program hit the tracepoints. The
9485 expressions may also denote objects in memory---structures or arrays,
9486 for example---whose values @value{GDBN} should record; while visiting
9487 a particular tracepoint, you may inspect those objects as if they were
9488 in memory at that moment. However, because @value{GDBN} records these
9489 values without interacting with you, it can do so quickly and
9490 unobtrusively, hopefully not disturbing the program's behavior.
9492 The tracepoint facility is currently available only for remote
9493 targets. @xref{Targets}. In addition, your remote target must know
9494 how to collect trace data. This functionality is implemented in the
9495 remote stub; however, none of the stubs distributed with @value{GDBN}
9496 support tracepoints as of this writing. The format of the remote
9497 packets used to implement tracepoints are described in @ref{Tracepoint
9500 It is also possible to get trace data from a file, in a manner reminiscent
9501 of corefiles; you specify the filename, and use @code{tfind} to search
9502 through the file. @xref{Trace Files}, for more details.
9504 This chapter describes the tracepoint commands and features.
9508 * Analyze Collected Data::
9509 * Tracepoint Variables::
9513 @node Set Tracepoints
9514 @section Commands to Set Tracepoints
9516 Before running such a @dfn{trace experiment}, an arbitrary number of
9517 tracepoints can be set. A tracepoint is actually a special type of
9518 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
9519 standard breakpoint commands. For instance, as with breakpoints,
9520 tracepoint numbers are successive integers starting from one, and many
9521 of the commands associated with tracepoints take the tracepoint number
9522 as their argument, to identify which tracepoint to work on.
9524 For each tracepoint, you can specify, in advance, some arbitrary set
9525 of data that you want the target to collect in the trace buffer when
9526 it hits that tracepoint. The collected data can include registers,
9527 local variables, or global data. Later, you can use @value{GDBN}
9528 commands to examine the values these data had at the time the
9531 Tracepoints do not support every breakpoint feature. Ignore counts on
9532 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
9533 commands when they are hit. Tracepoints may not be thread-specific
9536 @cindex fast tracepoints
9537 Some targets may support @dfn{fast tracepoints}, which are inserted in
9538 a different way (such as with a jump instead of a trap), that is
9539 faster but possibly restricted in where they may be installed.
9541 @code{gdbserver} supports tracepoints on some target systems.
9542 @xref{Server,,Tracepoints support in @code{gdbserver}}.
9544 This section describes commands to set tracepoints and associated
9545 conditions and actions.
9548 * Create and Delete Tracepoints::
9549 * Enable and Disable Tracepoints::
9550 * Tracepoint Passcounts::
9551 * Tracepoint Conditions::
9552 * Trace State Variables::
9553 * Tracepoint Actions::
9554 * Listing Tracepoints::
9555 * Starting and Stopping Trace Experiments::
9556 * Tracepoint Restrictions::
9559 @node Create and Delete Tracepoints
9560 @subsection Create and Delete Tracepoints
9563 @cindex set tracepoint
9565 @item trace @var{location}
9566 The @code{trace} command is very similar to the @code{break} command.
9567 Its argument @var{location} can be a source line, a function name, or
9568 an address in the target program. @xref{Specify Location}. The
9569 @code{trace} command defines a tracepoint, which is a point in the
9570 target program where the debugger will briefly stop, collect some
9571 data, and then allow the program to continue. Setting a tracepoint or
9572 changing its actions doesn't take effect until the next @code{tstart}
9573 command, and once a trace experiment is running, further changes will
9574 not have any effect until the next trace experiment starts.
9576 Here are some examples of using the @code{trace} command:
9579 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
9581 (@value{GDBP}) @b{trace +2} // 2 lines forward
9583 (@value{GDBP}) @b{trace my_function} // first source line of function
9585 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
9587 (@value{GDBP}) @b{trace *0x2117c4} // an address
9591 You can abbreviate @code{trace} as @code{tr}.
9593 @item trace @var{location} if @var{cond}
9594 Set a tracepoint with condition @var{cond}; evaluate the expression
9595 @var{cond} each time the tracepoint is reached, and collect data only
9596 if the value is nonzero---that is, if @var{cond} evaluates as true.
9597 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
9598 information on tracepoint conditions.
9600 @item ftrace @var{location} [ if @var{cond} ]
9601 @cindex set fast tracepoint
9603 The @code{ftrace} command sets a fast tracepoint. For targets that
9604 support them, fast tracepoints will use a more efficient but possibly
9605 less general technique to trigger data collection, such as a jump
9606 instruction instead of a trap, or some sort of hardware support. It
9607 may not be possible to create a fast tracepoint at the desired
9608 location, in which case the command will exit with an explanatory
9611 @value{GDBN} handles arguments to @code{ftrace} exactly as for
9615 @cindex last tracepoint number
9616 @cindex recent tracepoint number
9617 @cindex tracepoint number
9618 The convenience variable @code{$tpnum} records the tracepoint number
9619 of the most recently set tracepoint.
9621 @kindex delete tracepoint
9622 @cindex tracepoint deletion
9623 @item delete tracepoint @r{[}@var{num}@r{]}
9624 Permanently delete one or more tracepoints. With no argument, the
9625 default is to delete all tracepoints. Note that the regular
9626 @code{delete} command can remove tracepoints also.
9631 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
9633 (@value{GDBP}) @b{delete trace} // remove all tracepoints
9637 You can abbreviate this command as @code{del tr}.
9640 @node Enable and Disable Tracepoints
9641 @subsection Enable and Disable Tracepoints
9643 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
9646 @kindex disable tracepoint
9647 @item disable tracepoint @r{[}@var{num}@r{]}
9648 Disable tracepoint @var{num}, or all tracepoints if no argument
9649 @var{num} is given. A disabled tracepoint will have no effect during
9650 the next trace experiment, but it is not forgotten. You can re-enable
9651 a disabled tracepoint using the @code{enable tracepoint} command.
9653 @kindex enable tracepoint
9654 @item enable tracepoint @r{[}@var{num}@r{]}
9655 Enable tracepoint @var{num}, or all tracepoints. The enabled
9656 tracepoints will become effective the next time a trace experiment is
9660 @node Tracepoint Passcounts
9661 @subsection Tracepoint Passcounts
9665 @cindex tracepoint pass count
9666 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
9667 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
9668 automatically stop a trace experiment. If a tracepoint's passcount is
9669 @var{n}, then the trace experiment will be automatically stopped on
9670 the @var{n}'th time that tracepoint is hit. If the tracepoint number
9671 @var{num} is not specified, the @code{passcount} command sets the
9672 passcount of the most recently defined tracepoint. If no passcount is
9673 given, the trace experiment will run until stopped explicitly by the
9679 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
9680 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
9682 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
9683 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
9684 (@value{GDBP}) @b{trace foo}
9685 (@value{GDBP}) @b{pass 3}
9686 (@value{GDBP}) @b{trace bar}
9687 (@value{GDBP}) @b{pass 2}
9688 (@value{GDBP}) @b{trace baz}
9689 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
9690 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
9691 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
9692 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
9696 @node Tracepoint Conditions
9697 @subsection Tracepoint Conditions
9698 @cindex conditional tracepoints
9699 @cindex tracepoint conditions
9701 The simplest sort of tracepoint collects data every time your program
9702 reaches a specified place. You can also specify a @dfn{condition} for
9703 a tracepoint. A condition is just a Boolean expression in your
9704 programming language (@pxref{Expressions, ,Expressions}). A
9705 tracepoint with a condition evaluates the expression each time your
9706 program reaches it, and data collection happens only if the condition
9709 Tracepoint conditions can be specified when a tracepoint is set, by
9710 using @samp{if} in the arguments to the @code{trace} command.
9711 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
9712 also be set or changed at any time with the @code{condition} command,
9713 just as with breakpoints.
9715 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
9716 the conditional expression itself. Instead, @value{GDBN} encodes the
9717 expression into an agent expression (@pxref{Agent Expressions}
9718 suitable for execution on the target, independently of @value{GDBN}.
9719 Global variables become raw memory locations, locals become stack
9720 accesses, and so forth.
9722 For instance, suppose you have a function that is usually called
9723 frequently, but should not be called after an error has occurred. You
9724 could use the following tracepoint command to collect data about calls
9725 of that function that happen while the error code is propagating
9726 through the program; an unconditional tracepoint could end up
9727 collecting thousands of useless trace frames that you would have to
9731 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
9734 @node Trace State Variables
9735 @subsection Trace State Variables
9736 @cindex trace state variables
9738 A @dfn{trace state variable} is a special type of variable that is
9739 created and managed by target-side code. The syntax is the same as
9740 that for GDB's convenience variables (a string prefixed with ``$''),
9741 but they are stored on the target. They must be created explicitly,
9742 using a @code{tvariable} command. They are always 64-bit signed
9745 Trace state variables are remembered by @value{GDBN}, and downloaded
9746 to the target along with tracepoint information when the trace
9747 experiment starts. There are no intrinsic limits on the number of
9748 trace state variables, beyond memory limitations of the target.
9750 @cindex convenience variables, and trace state variables
9751 Although trace state variables are managed by the target, you can use
9752 them in print commands and expressions as if they were convenience
9753 variables; @value{GDBN} will get the current value from the target
9754 while the trace experiment is running. Trace state variables share
9755 the same namespace as other ``$'' variables, which means that you
9756 cannot have trace state variables with names like @code{$23} or
9757 @code{$pc}, nor can you have a trace state variable and a convenience
9758 variable with the same name.
9762 @item tvariable $@var{name} [ = @var{expression} ]
9764 The @code{tvariable} command creates a new trace state variable named
9765 @code{$@var{name}}, and optionally gives it an initial value of
9766 @var{expression}. @var{expression} is evaluated when this command is
9767 entered; the result will be converted to an integer if possible,
9768 otherwise @value{GDBN} will report an error. A subsequent
9769 @code{tvariable} command specifying the same name does not create a
9770 variable, but instead assigns the supplied initial value to the
9771 existing variable of that name, overwriting any previous initial
9772 value. The default initial value is 0.
9774 @item info tvariables
9775 @kindex info tvariables
9776 List all the trace state variables along with their initial values.
9777 Their current values may also be displayed, if the trace experiment is
9780 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
9781 @kindex delete tvariable
9782 Delete the given trace state variables, or all of them if no arguments
9787 @node Tracepoint Actions
9788 @subsection Tracepoint Action Lists
9792 @cindex tracepoint actions
9793 @item actions @r{[}@var{num}@r{]}
9794 This command will prompt for a list of actions to be taken when the
9795 tracepoint is hit. If the tracepoint number @var{num} is not
9796 specified, this command sets the actions for the one that was most
9797 recently defined (so that you can define a tracepoint and then say
9798 @code{actions} without bothering about its number). You specify the
9799 actions themselves on the following lines, one action at a time, and
9800 terminate the actions list with a line containing just @code{end}. So
9801 far, the only defined actions are @code{collect}, @code{teval}, and
9802 @code{while-stepping}.
9804 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
9805 Commands, ,Breakpoint Command Lists}), except that only the defined
9806 actions are allowed; any other @value{GDBN} command is rejected.
9808 @cindex remove actions from a tracepoint
9809 To remove all actions from a tracepoint, type @samp{actions @var{num}}
9810 and follow it immediately with @samp{end}.
9813 (@value{GDBP}) @b{collect @var{data}} // collect some data
9815 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
9817 (@value{GDBP}) @b{end} // signals the end of actions.
9820 In the following example, the action list begins with @code{collect}
9821 commands indicating the things to be collected when the tracepoint is
9822 hit. Then, in order to single-step and collect additional data
9823 following the tracepoint, a @code{while-stepping} command is used,
9824 followed by the list of things to be collected after each step in a
9825 sequence of single steps. The @code{while-stepping} command is
9826 terminated by its own separate @code{end} command. Lastly, the action
9827 list is terminated by an @code{end} command.
9830 (@value{GDBP}) @b{trace foo}
9831 (@value{GDBP}) @b{actions}
9832 Enter actions for tracepoint 1, one per line:
9836 > collect $pc, arr[i]
9841 @kindex collect @r{(tracepoints)}
9842 @item collect @var{expr1}, @var{expr2}, @dots{}
9843 Collect values of the given expressions when the tracepoint is hit.
9844 This command accepts a comma-separated list of any valid expressions.
9845 In addition to global, static, or local variables, the following
9846 special arguments are supported:
9850 collect all registers
9853 collect all function arguments
9856 collect all local variables.
9859 You can give several consecutive @code{collect} commands, each one
9860 with a single argument, or one @code{collect} command with several
9861 arguments separated by commas; the effect is the same.
9863 The command @code{info scope} (@pxref{Symbols, info scope}) is
9864 particularly useful for figuring out what data to collect.
9866 @kindex teval @r{(tracepoints)}
9867 @item teval @var{expr1}, @var{expr2}, @dots{}
9868 Evaluate the given expressions when the tracepoint is hit. This
9869 command accepts a comma-separated list of expressions. The results
9870 are discarded, so this is mainly useful for assigning values to trace
9871 state variables (@pxref{Trace State Variables}) without adding those
9872 values to the trace buffer, as would be the case if the @code{collect}
9875 @kindex while-stepping @r{(tracepoints)}
9876 @item while-stepping @var{n}
9877 Perform @var{n} single-step instruction traces after the tracepoint,
9878 collecting new data after each step. The @code{while-stepping}
9879 command is followed by the list of what to collect while stepping
9880 (followed by its own @code{end} command):
9884 > collect $regs, myglobal
9890 Note that @code{$pc} is not automatically collected by
9891 @code{while-stepping}; you need to explicitly collect that register if
9892 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
9895 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
9896 @kindex set default-collect
9897 @cindex default collection action
9898 This variable is a list of expressions to collect at each tracepoint
9899 hit. It is effectively an additional @code{collect} action prepended
9900 to every tracepoint action list. The expressions are parsed
9901 individually for each tracepoint, so for instance a variable named
9902 @code{xyz} may be interpreted as a global for one tracepoint, and a
9903 local for another, as appropriate to the tracepoint's location.
9905 @item show default-collect
9906 @kindex show default-collect
9907 Show the list of expressions that are collected by default at each
9912 @node Listing Tracepoints
9913 @subsection Listing Tracepoints
9916 @kindex info tracepoints
9918 @cindex information about tracepoints
9919 @item info tracepoints @r{[}@var{num}@r{]}
9920 Display information about the tracepoint @var{num}. If you don't
9921 specify a tracepoint number, displays information about all the
9922 tracepoints defined so far. The format is similar to that used for
9923 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
9924 command, simply restricting itself to tracepoints.
9926 A tracepoint's listing may include additional information specific to
9931 its passcount as given by the @code{passcount @var{n}} command
9935 (@value{GDBP}) @b{info trace}
9936 Num Type Disp Enb Address What
9937 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
9939 collect globfoo, $regs
9948 This command can be abbreviated @code{info tp}.
9951 @node Starting and Stopping Trace Experiments
9952 @subsection Starting and Stopping Trace Experiments
9956 @cindex start a new trace experiment
9957 @cindex collected data discarded
9959 This command takes no arguments. It starts the trace experiment, and
9960 begins collecting data. This has the side effect of discarding all
9961 the data collected in the trace buffer during the previous trace
9965 @cindex stop a running trace experiment
9967 This command takes no arguments. It ends the trace experiment, and
9968 stops collecting data.
9970 @strong{Note}: a trace experiment and data collection may stop
9971 automatically if any tracepoint's passcount is reached
9972 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
9975 @cindex status of trace data collection
9976 @cindex trace experiment, status of
9978 This command displays the status of the current trace data
9982 Here is an example of the commands we described so far:
9985 (@value{GDBP}) @b{trace gdb_c_test}
9986 (@value{GDBP}) @b{actions}
9987 Enter actions for tracepoint #1, one per line.
9988 > collect $regs,$locals,$args
9993 (@value{GDBP}) @b{tstart}
9994 [time passes @dots{}]
9995 (@value{GDBP}) @b{tstop}
9998 @cindex disconnected tracing
9999 You can choose to continue running the trace experiment even if
10000 @value{GDBN} disconnects from the target, voluntarily or
10001 involuntarily. For commands such as @code{detach}, the debugger will
10002 ask what you want to do with the trace. But for unexpected
10003 terminations (@value{GDBN} crash, network outage), it would be
10004 unfortunate to lose hard-won trace data, so the variable
10005 @code{disconnected-tracing} lets you decide whether the trace should
10006 continue running without @value{GDBN}.
10009 @item set disconnected-tracing on
10010 @itemx set disconnected-tracing off
10011 @kindex set disconnected-tracing
10012 Choose whether a tracing run should continue to run if @value{GDBN}
10013 has disconnected from the target. Note that @code{detach} or
10014 @code{quit} will ask you directly what to do about a running trace no
10015 matter what this variable's setting, so the variable is mainly useful
10016 for handling unexpected situations, such as loss of the network.
10018 @item show disconnected-tracing
10019 @kindex show disconnected-tracing
10020 Show the current choice for disconnected tracing.
10024 When you reconnect to the target, the trace experiment may or may not
10025 still be running; it might have filled the trace buffer in the
10026 meantime, or stopped for one of the other reasons. If it is running,
10027 it will continue after reconnection.
10029 Upon reconnection, the target will upload information about the
10030 tracepoints in effect. @value{GDBN} will then compare that
10031 information to the set of tracepoints currently defined, and attempt
10032 to match them up, allowing for the possibility that the numbers may
10033 have changed due to creation and deletion in the meantime. If one of
10034 the target's tracepoints does not match any in @value{GDBN}, the
10035 debugger will create a new tracepoint, so that you have a number with
10036 which to specify that tracepoint. This matching-up process is
10037 necessarily heuristic, and it may result in useless tracepoints being
10038 created; you may simply delete them if they are of no use.
10040 @cindex circular trace buffer
10041 If your target agent supports a @dfn{circular trace buffer}, then you
10042 can run a trace experiment indefinitely without filling the trace
10043 buffer; when space runs out, the agent deletes already-collected trace
10044 frames, oldest first, until there is enough room to continue
10045 collecting. This is especially useful if your tracepoints are being
10046 hit too often, and your trace gets terminated prematurely because the
10047 buffer is full. To ask for a circular trace buffer, simply set
10048 @samp{circular_trace_buffer} to on. You can set this at any time,
10049 including during tracing; if the agent can do it, it will change
10050 buffer handling on the fly, otherwise it will not take effect until
10054 @item set circular-trace-buffer on
10055 @itemx set circular-trace-buffer off
10056 @kindex set circular-trace-buffer
10057 Choose whether a tracing run should use a linear or circular buffer
10058 for trace data. A linear buffer will not lose any trace data, but may
10059 fill up prematurely, while a circular buffer will discard old trace
10060 data, but it will have always room for the latest tracepoint hits.
10062 @item show circular-trace-buffer
10063 @kindex show circular-trace-buffer
10064 Show the current choice for the trace buffer. Note that this may not
10065 match the agent's current buffer handling, nor is it guaranteed to
10066 match the setting that might have been in effect during a past run,
10067 for instance if you are looking at frames from a trace file.
10071 @node Tracepoint Restrictions
10072 @subsection Tracepoint Restrictions
10074 @cindex tracepoint restrictions
10075 There are a number of restrictions on the use of tracepoints. As
10076 described above, tracepoint data gathering occurs on the target
10077 without interaction from @value{GDBN}. Thus the full capabilities of
10078 the debugger are not available during data gathering, and then at data
10079 examination time, you will be limited by only having what was
10080 collected. The following items describe some common problems, but it
10081 is not exhaustive, and you may run into additional difficulties not
10087 Tracepoint expressions are intended to gather objects (lvalues). Thus
10088 the full flexibility of GDB's expression evaluator is not available.
10089 You cannot call functions, cast objects to aggregate types, access
10090 convenience variables or modify values (except by assignment to trace
10091 state variables). Some language features may implicitly call
10092 functions (for instance Objective-C fields with accessors), and therefore
10093 cannot be collected either.
10096 Collection of local variables, either individually or in bulk with
10097 @code{$locals} or @code{$args}, during @code{while-stepping} may
10098 behave erratically. The stepping action may enter a new scope (for
10099 instance by stepping into a function), or the location of the variable
10100 may change (for instance it is loaded into a register). The
10101 tracepoint data recorded uses the location information for the
10102 variables that is correct for the tracepoint location. When the
10103 tracepoint is created, it is not possible, in general, to determine
10104 where the steps of a @code{while-stepping} sequence will advance the
10105 program---particularly if a conditional branch is stepped.
10108 Collection of an incompletely-initialized or partially-destroyed object
10109 may result in something that @value{GDBN} cannot display, or displays
10110 in a misleading way.
10113 When @value{GDBN} displays a pointer to character it automatically
10114 dereferences the pointer to also display characters of the string
10115 being pointed to. However, collecting the pointer during tracing does
10116 not automatically collect the string. You need to explicitly
10117 dereference the pointer and provide size information if you want to
10118 collect not only the pointer, but the memory pointed to. For example,
10119 @code{*ptr@@50} can be used to collect the 50 element array pointed to
10123 It is not possible to collect a complete stack backtrace at a
10124 tracepoint. Instead, you may collect the registers and a few hundred
10125 bytes from the stack pointer with something like @code{*$esp@@300}
10126 (adjust to use the name of the actual stack pointer register on your
10127 target architecture, and the amount of stack you wish to capture).
10128 Then the @code{backtrace} command will show a partial backtrace when
10129 using a trace frame. The number of stack frames that can be examined
10130 depends on the sizes of the frames in the collected stack. Note that
10131 if you ask for a block so large that it goes past the bottom of the
10132 stack, the target agent may report an error trying to read from an
10136 If you do not collect registers at a tracepoint, @value{GDBN} can
10137 infer that the value of @code{$pc} must be the same as the address of
10138 the tracepoint and use that when you are looking at a trace frame
10139 for that tracepoint. However, this cannot work if the tracepoint has
10140 multiple locations (for instance if it was set in a function that was
10141 inlined), or if it has a @code{while-stepping} loop. In those cases
10142 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
10147 @node Analyze Collected Data
10148 @section Using the Collected Data
10150 After the tracepoint experiment ends, you use @value{GDBN} commands
10151 for examining the trace data. The basic idea is that each tracepoint
10152 collects a trace @dfn{snapshot} every time it is hit and another
10153 snapshot every time it single-steps. All these snapshots are
10154 consecutively numbered from zero and go into a buffer, and you can
10155 examine them later. The way you examine them is to @dfn{focus} on a
10156 specific trace snapshot. When the remote stub is focused on a trace
10157 snapshot, it will respond to all @value{GDBN} requests for memory and
10158 registers by reading from the buffer which belongs to that snapshot,
10159 rather than from @emph{real} memory or registers of the program being
10160 debugged. This means that @strong{all} @value{GDBN} commands
10161 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
10162 behave as if we were currently debugging the program state as it was
10163 when the tracepoint occurred. Any requests for data that are not in
10164 the buffer will fail.
10167 * tfind:: How to select a trace snapshot
10168 * tdump:: How to display all data for a snapshot
10169 * save tracepoints:: How to save tracepoints for a future run
10173 @subsection @code{tfind @var{n}}
10176 @cindex select trace snapshot
10177 @cindex find trace snapshot
10178 The basic command for selecting a trace snapshot from the buffer is
10179 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
10180 counting from zero. If no argument @var{n} is given, the next
10181 snapshot is selected.
10183 Here are the various forms of using the @code{tfind} command.
10187 Find the first snapshot in the buffer. This is a synonym for
10188 @code{tfind 0} (since 0 is the number of the first snapshot).
10191 Stop debugging trace snapshots, resume @emph{live} debugging.
10194 Same as @samp{tfind none}.
10197 No argument means find the next trace snapshot.
10200 Find the previous trace snapshot before the current one. This permits
10201 retracing earlier steps.
10203 @item tfind tracepoint @var{num}
10204 Find the next snapshot associated with tracepoint @var{num}. Search
10205 proceeds forward from the last examined trace snapshot. If no
10206 argument @var{num} is given, it means find the next snapshot collected
10207 for the same tracepoint as the current snapshot.
10209 @item tfind pc @var{addr}
10210 Find the next snapshot associated with the value @var{addr} of the
10211 program counter. Search proceeds forward from the last examined trace
10212 snapshot. If no argument @var{addr} is given, it means find the next
10213 snapshot with the same value of PC as the current snapshot.
10215 @item tfind outside @var{addr1}, @var{addr2}
10216 Find the next snapshot whose PC is outside the given range of
10217 addresses (exclusive).
10219 @item tfind range @var{addr1}, @var{addr2}
10220 Find the next snapshot whose PC is between @var{addr1} and
10221 @var{addr2} (inclusive).
10223 @item tfind line @r{[}@var{file}:@r{]}@var{n}
10224 Find the next snapshot associated with the source line @var{n}. If
10225 the optional argument @var{file} is given, refer to line @var{n} in
10226 that source file. Search proceeds forward from the last examined
10227 trace snapshot. If no argument @var{n} is given, it means find the
10228 next line other than the one currently being examined; thus saying
10229 @code{tfind line} repeatedly can appear to have the same effect as
10230 stepping from line to line in a @emph{live} debugging session.
10233 The default arguments for the @code{tfind} commands are specifically
10234 designed to make it easy to scan through the trace buffer. For
10235 instance, @code{tfind} with no argument selects the next trace
10236 snapshot, and @code{tfind -} with no argument selects the previous
10237 trace snapshot. So, by giving one @code{tfind} command, and then
10238 simply hitting @key{RET} repeatedly you can examine all the trace
10239 snapshots in order. Or, by saying @code{tfind -} and then hitting
10240 @key{RET} repeatedly you can examine the snapshots in reverse order.
10241 The @code{tfind line} command with no argument selects the snapshot
10242 for the next source line executed. The @code{tfind pc} command with
10243 no argument selects the next snapshot with the same program counter
10244 (PC) as the current frame. The @code{tfind tracepoint} command with
10245 no argument selects the next trace snapshot collected by the same
10246 tracepoint as the current one.
10248 In addition to letting you scan through the trace buffer manually,
10249 these commands make it easy to construct @value{GDBN} scripts that
10250 scan through the trace buffer and print out whatever collected data
10251 you are interested in. Thus, if we want to examine the PC, FP, and SP
10252 registers from each trace frame in the buffer, we can say this:
10255 (@value{GDBP}) @b{tfind start}
10256 (@value{GDBP}) @b{while ($trace_frame != -1)}
10257 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
10258 $trace_frame, $pc, $sp, $fp
10262 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
10263 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
10264 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
10265 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
10266 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
10267 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
10268 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
10269 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
10270 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
10271 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
10272 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
10275 Or, if we want to examine the variable @code{X} at each source line in
10279 (@value{GDBP}) @b{tfind start}
10280 (@value{GDBP}) @b{while ($trace_frame != -1)}
10281 > printf "Frame %d, X == %d\n", $trace_frame, X
10291 @subsection @code{tdump}
10293 @cindex dump all data collected at tracepoint
10294 @cindex tracepoint data, display
10296 This command takes no arguments. It prints all the data collected at
10297 the current trace snapshot.
10300 (@value{GDBP}) @b{trace 444}
10301 (@value{GDBP}) @b{actions}
10302 Enter actions for tracepoint #2, one per line:
10303 > collect $regs, $locals, $args, gdb_long_test
10306 (@value{GDBP}) @b{tstart}
10308 (@value{GDBP}) @b{tfind line 444}
10309 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
10311 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
10313 (@value{GDBP}) @b{tdump}
10314 Data collected at tracepoint 2, trace frame 1:
10315 d0 0xc4aa0085 -995491707
10319 d4 0x71aea3d 119204413
10322 d7 0x380035 3670069
10323 a0 0x19e24a 1696330
10324 a1 0x3000668 50333288
10326 a3 0x322000 3284992
10327 a4 0x3000698 50333336
10328 a5 0x1ad3cc 1758156
10329 fp 0x30bf3c 0x30bf3c
10330 sp 0x30bf34 0x30bf34
10332 pc 0x20b2c8 0x20b2c8
10336 p = 0x20e5b4 "gdb-test"
10343 gdb_long_test = 17 '\021'
10348 @code{tdump} works by scanning the tracepoint's current collection
10349 actions and printing the value of each expression listed. So
10350 @code{tdump} can fail, if after a run, you change the tracepoint's
10351 actions to mention variables that were not collected during the run.
10353 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
10354 uses the collected value of @code{$pc} to distinguish between trace
10355 frames that were collected at the tracepoint hit, and frames that were
10356 collected while stepping. This allows it to correctly choose whether
10357 to display the basic list of collections, or the collections from the
10358 body of the while-stepping loop. However, if @code{$pc} was not collected,
10359 then @code{tdump} will always attempt to dump using the basic collection
10360 list, and may fail if a while-stepping frame does not include all the
10361 same data that is collected at the tracepoint hit.
10362 @c This is getting pretty arcane, example would be good.
10364 @node save tracepoints
10365 @subsection @code{save tracepoints @var{filename}}
10366 @kindex save tracepoints
10367 @kindex save-tracepoints
10368 @cindex save tracepoints for future sessions
10370 This command saves all current tracepoint definitions together with
10371 their actions and passcounts, into a file @file{@var{filename}}
10372 suitable for use in a later debugging session. To read the saved
10373 tracepoint definitions, use the @code{source} command (@pxref{Command
10374 Files}). The @w{@code{save-tracepoints}} command is a deprecated
10375 alias for @w{@code{save tracepoints}}
10377 @node Tracepoint Variables
10378 @section Convenience Variables for Tracepoints
10379 @cindex tracepoint variables
10380 @cindex convenience variables for tracepoints
10383 @vindex $trace_frame
10384 @item (int) $trace_frame
10385 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
10386 snapshot is selected.
10388 @vindex $tracepoint
10389 @item (int) $tracepoint
10390 The tracepoint for the current trace snapshot.
10392 @vindex $trace_line
10393 @item (int) $trace_line
10394 The line number for the current trace snapshot.
10396 @vindex $trace_file
10397 @item (char []) $trace_file
10398 The source file for the current trace snapshot.
10400 @vindex $trace_func
10401 @item (char []) $trace_func
10402 The name of the function containing @code{$tracepoint}.
10405 Note: @code{$trace_file} is not suitable for use in @code{printf},
10406 use @code{output} instead.
10408 Here's a simple example of using these convenience variables for
10409 stepping through all the trace snapshots and printing some of their
10410 data. Note that these are not the same as trace state variables,
10411 which are managed by the target.
10414 (@value{GDBP}) @b{tfind start}
10416 (@value{GDBP}) @b{while $trace_frame != -1}
10417 > output $trace_file
10418 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
10424 @section Using Trace Files
10425 @cindex trace files
10427 In some situations, the target running a trace experiment may no
10428 longer be available; perhaps it crashed, or the hardware was needed
10429 for a different activity. To handle these cases, you can arrange to
10430 dump the trace data into a file, and later use that file as a source
10431 of trace data, via the @code{target tfile} command.
10436 @item tsave [ -r ] @var{filename}
10437 Save the trace data to @var{filename}. By default, this command
10438 assumes that @var{filename} refers to the host filesystem, so if
10439 necessary @value{GDBN} will copy raw trace data up from the target and
10440 then save it. If the target supports it, you can also supply the
10441 optional argument @code{-r} (``remote'') to direct the target to save
10442 the data directly into @var{filename} in its own filesystem, which may be
10443 more efficient if the trace buffer is very large. (Note, however, that
10444 @code{target tfile} can only read from files accessible to the host.)
10446 @kindex target tfile
10448 @item target tfile @var{filename}
10449 Use the file named @var{filename} as a source of trace data. Commands
10450 that examine data work as they do with a live target, but it is not
10451 possible to run any new trace experiments. @code{tstatus} will report
10452 the state of the trace run at the moment the data was saved, as well
10453 as the current trace frame you are examining. @var{filename} must be
10454 on a filesystem accessible to the host.
10459 @chapter Debugging Programs That Use Overlays
10462 If your program is too large to fit completely in your target system's
10463 memory, you can sometimes use @dfn{overlays} to work around this
10464 problem. @value{GDBN} provides some support for debugging programs that
10468 * How Overlays Work:: A general explanation of overlays.
10469 * Overlay Commands:: Managing overlays in @value{GDBN}.
10470 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
10471 mapped by asking the inferior.
10472 * Overlay Sample Program:: A sample program using overlays.
10475 @node How Overlays Work
10476 @section How Overlays Work
10477 @cindex mapped overlays
10478 @cindex unmapped overlays
10479 @cindex load address, overlay's
10480 @cindex mapped address
10481 @cindex overlay area
10483 Suppose you have a computer whose instruction address space is only 64
10484 kilobytes long, but which has much more memory which can be accessed by
10485 other means: special instructions, segment registers, or memory
10486 management hardware, for example. Suppose further that you want to
10487 adapt a program which is larger than 64 kilobytes to run on this system.
10489 One solution is to identify modules of your program which are relatively
10490 independent, and need not call each other directly; call these modules
10491 @dfn{overlays}. Separate the overlays from the main program, and place
10492 their machine code in the larger memory. Place your main program in
10493 instruction memory, but leave at least enough space there to hold the
10494 largest overlay as well.
10496 Now, to call a function located in an overlay, you must first copy that
10497 overlay's machine code from the large memory into the space set aside
10498 for it in the instruction memory, and then jump to its entry point
10501 @c NB: In the below the mapped area's size is greater or equal to the
10502 @c size of all overlays. This is intentional to remind the developer
10503 @c that overlays don't necessarily need to be the same size.
10507 Data Instruction Larger
10508 Address Space Address Space Address Space
10509 +-----------+ +-----------+ +-----------+
10511 +-----------+ +-----------+ +-----------+<-- overlay 1
10512 | program | | main | .----| overlay 1 | load address
10513 | variables | | program | | +-----------+
10514 | and heap | | | | | |
10515 +-----------+ | | | +-----------+<-- overlay 2
10516 | | +-----------+ | | | load address
10517 +-----------+ | | | .-| overlay 2 |
10519 mapped --->+-----------+ | | +-----------+
10520 address | | | | | |
10521 | overlay | <-' | | |
10522 | area | <---' +-----------+<-- overlay 3
10523 | | <---. | | load address
10524 +-----------+ `--| overlay 3 |
10531 @anchor{A code overlay}A code overlay
10535 The diagram (@pxref{A code overlay}) shows a system with separate data
10536 and instruction address spaces. To map an overlay, the program copies
10537 its code from the larger address space to the instruction address space.
10538 Since the overlays shown here all use the same mapped address, only one
10539 may be mapped at a time. For a system with a single address space for
10540 data and instructions, the diagram would be similar, except that the
10541 program variables and heap would share an address space with the main
10542 program and the overlay area.
10544 An overlay loaded into instruction memory and ready for use is called a
10545 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
10546 instruction memory. An overlay not present (or only partially present)
10547 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
10548 is its address in the larger memory. The mapped address is also called
10549 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
10550 called the @dfn{load memory address}, or @dfn{LMA}.
10552 Unfortunately, overlays are not a completely transparent way to adapt a
10553 program to limited instruction memory. They introduce a new set of
10554 global constraints you must keep in mind as you design your program:
10559 Before calling or returning to a function in an overlay, your program
10560 must make sure that overlay is actually mapped. Otherwise, the call or
10561 return will transfer control to the right address, but in the wrong
10562 overlay, and your program will probably crash.
10565 If the process of mapping an overlay is expensive on your system, you
10566 will need to choose your overlays carefully to minimize their effect on
10567 your program's performance.
10570 The executable file you load onto your system must contain each
10571 overlay's instructions, appearing at the overlay's load address, not its
10572 mapped address. However, each overlay's instructions must be relocated
10573 and its symbols defined as if the overlay were at its mapped address.
10574 You can use GNU linker scripts to specify different load and relocation
10575 addresses for pieces of your program; see @ref{Overlay Description,,,
10576 ld.info, Using ld: the GNU linker}.
10579 The procedure for loading executable files onto your system must be able
10580 to load their contents into the larger address space as well as the
10581 instruction and data spaces.
10585 The overlay system described above is rather simple, and could be
10586 improved in many ways:
10591 If your system has suitable bank switch registers or memory management
10592 hardware, you could use those facilities to make an overlay's load area
10593 contents simply appear at their mapped address in instruction space.
10594 This would probably be faster than copying the overlay to its mapped
10595 area in the usual way.
10598 If your overlays are small enough, you could set aside more than one
10599 overlay area, and have more than one overlay mapped at a time.
10602 You can use overlays to manage data, as well as instructions. In
10603 general, data overlays are even less transparent to your design than
10604 code overlays: whereas code overlays only require care when you call or
10605 return to functions, data overlays require care every time you access
10606 the data. Also, if you change the contents of a data overlay, you
10607 must copy its contents back out to its load address before you can copy a
10608 different data overlay into the same mapped area.
10613 @node Overlay Commands
10614 @section Overlay Commands
10616 To use @value{GDBN}'s overlay support, each overlay in your program must
10617 correspond to a separate section of the executable file. The section's
10618 virtual memory address and load memory address must be the overlay's
10619 mapped and load addresses. Identifying overlays with sections allows
10620 @value{GDBN} to determine the appropriate address of a function or
10621 variable, depending on whether the overlay is mapped or not.
10623 @value{GDBN}'s overlay commands all start with the word @code{overlay};
10624 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
10629 Disable @value{GDBN}'s overlay support. When overlay support is
10630 disabled, @value{GDBN} assumes that all functions and variables are
10631 always present at their mapped addresses. By default, @value{GDBN}'s
10632 overlay support is disabled.
10634 @item overlay manual
10635 @cindex manual overlay debugging
10636 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
10637 relies on you to tell it which overlays are mapped, and which are not,
10638 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
10639 commands described below.
10641 @item overlay map-overlay @var{overlay}
10642 @itemx overlay map @var{overlay}
10643 @cindex map an overlay
10644 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
10645 be the name of the object file section containing the overlay. When an
10646 overlay is mapped, @value{GDBN} assumes it can find the overlay's
10647 functions and variables at their mapped addresses. @value{GDBN} assumes
10648 that any other overlays whose mapped ranges overlap that of
10649 @var{overlay} are now unmapped.
10651 @item overlay unmap-overlay @var{overlay}
10652 @itemx overlay unmap @var{overlay}
10653 @cindex unmap an overlay
10654 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
10655 must be the name of the object file section containing the overlay.
10656 When an overlay is unmapped, @value{GDBN} assumes it can find the
10657 overlay's functions and variables at their load addresses.
10660 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
10661 consults a data structure the overlay manager maintains in the inferior
10662 to see which overlays are mapped. For details, see @ref{Automatic
10663 Overlay Debugging}.
10665 @item overlay load-target
10666 @itemx overlay load
10667 @cindex reloading the overlay table
10668 Re-read the overlay table from the inferior. Normally, @value{GDBN}
10669 re-reads the table @value{GDBN} automatically each time the inferior
10670 stops, so this command should only be necessary if you have changed the
10671 overlay mapping yourself using @value{GDBN}. This command is only
10672 useful when using automatic overlay debugging.
10674 @item overlay list-overlays
10675 @itemx overlay list
10676 @cindex listing mapped overlays
10677 Display a list of the overlays currently mapped, along with their mapped
10678 addresses, load addresses, and sizes.
10682 Normally, when @value{GDBN} prints a code address, it includes the name
10683 of the function the address falls in:
10686 (@value{GDBP}) print main
10687 $3 = @{int ()@} 0x11a0 <main>
10690 When overlay debugging is enabled, @value{GDBN} recognizes code in
10691 unmapped overlays, and prints the names of unmapped functions with
10692 asterisks around them. For example, if @code{foo} is a function in an
10693 unmapped overlay, @value{GDBN} prints it this way:
10696 (@value{GDBP}) overlay list
10697 No sections are mapped.
10698 (@value{GDBP}) print foo
10699 $5 = @{int (int)@} 0x100000 <*foo*>
10702 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
10706 (@value{GDBP}) overlay list
10707 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
10708 mapped at 0x1016 - 0x104a
10709 (@value{GDBP}) print foo
10710 $6 = @{int (int)@} 0x1016 <foo>
10713 When overlay debugging is enabled, @value{GDBN} can find the correct
10714 address for functions and variables in an overlay, whether or not the
10715 overlay is mapped. This allows most @value{GDBN} commands, like
10716 @code{break} and @code{disassemble}, to work normally, even on unmapped
10717 code. However, @value{GDBN}'s breakpoint support has some limitations:
10721 @cindex breakpoints in overlays
10722 @cindex overlays, setting breakpoints in
10723 You can set breakpoints in functions in unmapped overlays, as long as
10724 @value{GDBN} can write to the overlay at its load address.
10726 @value{GDBN} can not set hardware or simulator-based breakpoints in
10727 unmapped overlays. However, if you set a breakpoint at the end of your
10728 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
10729 you are using manual overlay management), @value{GDBN} will re-set its
10730 breakpoints properly.
10734 @node Automatic Overlay Debugging
10735 @section Automatic Overlay Debugging
10736 @cindex automatic overlay debugging
10738 @value{GDBN} can automatically track which overlays are mapped and which
10739 are not, given some simple co-operation from the overlay manager in the
10740 inferior. If you enable automatic overlay debugging with the
10741 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
10742 looks in the inferior's memory for certain variables describing the
10743 current state of the overlays.
10745 Here are the variables your overlay manager must define to support
10746 @value{GDBN}'s automatic overlay debugging:
10750 @item @code{_ovly_table}:
10751 This variable must be an array of the following structures:
10756 /* The overlay's mapped address. */
10759 /* The size of the overlay, in bytes. */
10760 unsigned long size;
10762 /* The overlay's load address. */
10765 /* Non-zero if the overlay is currently mapped;
10767 unsigned long mapped;
10771 @item @code{_novlys}:
10772 This variable must be a four-byte signed integer, holding the total
10773 number of elements in @code{_ovly_table}.
10777 To decide whether a particular overlay is mapped or not, @value{GDBN}
10778 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
10779 @code{lma} members equal the VMA and LMA of the overlay's section in the
10780 executable file. When @value{GDBN} finds a matching entry, it consults
10781 the entry's @code{mapped} member to determine whether the overlay is
10784 In addition, your overlay manager may define a function called
10785 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
10786 will silently set a breakpoint there. If the overlay manager then
10787 calls this function whenever it has changed the overlay table, this
10788 will enable @value{GDBN} to accurately keep track of which overlays
10789 are in program memory, and update any breakpoints that may be set
10790 in overlays. This will allow breakpoints to work even if the
10791 overlays are kept in ROM or other non-writable memory while they
10792 are not being executed.
10794 @node Overlay Sample Program
10795 @section Overlay Sample Program
10796 @cindex overlay example program
10798 When linking a program which uses overlays, you must place the overlays
10799 at their load addresses, while relocating them to run at their mapped
10800 addresses. To do this, you must write a linker script (@pxref{Overlay
10801 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
10802 since linker scripts are specific to a particular host system, target
10803 architecture, and target memory layout, this manual cannot provide
10804 portable sample code demonstrating @value{GDBN}'s overlay support.
10806 However, the @value{GDBN} source distribution does contain an overlaid
10807 program, with linker scripts for a few systems, as part of its test
10808 suite. The program consists of the following files from
10809 @file{gdb/testsuite/gdb.base}:
10813 The main program file.
10815 A simple overlay manager, used by @file{overlays.c}.
10820 Overlay modules, loaded and used by @file{overlays.c}.
10823 Linker scripts for linking the test program on the @code{d10v-elf}
10824 and @code{m32r-elf} targets.
10827 You can build the test program using the @code{d10v-elf} GCC
10828 cross-compiler like this:
10831 $ d10v-elf-gcc -g -c overlays.c
10832 $ d10v-elf-gcc -g -c ovlymgr.c
10833 $ d10v-elf-gcc -g -c foo.c
10834 $ d10v-elf-gcc -g -c bar.c
10835 $ d10v-elf-gcc -g -c baz.c
10836 $ d10v-elf-gcc -g -c grbx.c
10837 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
10838 baz.o grbx.o -Wl,-Td10v.ld -o overlays
10841 The build process is identical for any other architecture, except that
10842 you must substitute the appropriate compiler and linker script for the
10843 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
10847 @chapter Using @value{GDBN} with Different Languages
10850 Although programming languages generally have common aspects, they are
10851 rarely expressed in the same manner. For instance, in ANSI C,
10852 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
10853 Modula-2, it is accomplished by @code{p^}. Values can also be
10854 represented (and displayed) differently. Hex numbers in C appear as
10855 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
10857 @cindex working language
10858 Language-specific information is built into @value{GDBN} for some languages,
10859 allowing you to express operations like the above in your program's
10860 native language, and allowing @value{GDBN} to output values in a manner
10861 consistent with the syntax of your program's native language. The
10862 language you use to build expressions is called the @dfn{working
10866 * Setting:: Switching between source languages
10867 * Show:: Displaying the language
10868 * Checks:: Type and range checks
10869 * Supported Languages:: Supported languages
10870 * Unsupported Languages:: Unsupported languages
10874 @section Switching Between Source Languages
10876 There are two ways to control the working language---either have @value{GDBN}
10877 set it automatically, or select it manually yourself. You can use the
10878 @code{set language} command for either purpose. On startup, @value{GDBN}
10879 defaults to setting the language automatically. The working language is
10880 used to determine how expressions you type are interpreted, how values
10883 In addition to the working language, every source file that
10884 @value{GDBN} knows about has its own working language. For some object
10885 file formats, the compiler might indicate which language a particular
10886 source file is in. However, most of the time @value{GDBN} infers the
10887 language from the name of the file. The language of a source file
10888 controls whether C@t{++} names are demangled---this way @code{backtrace} can
10889 show each frame appropriately for its own language. There is no way to
10890 set the language of a source file from within @value{GDBN}, but you can
10891 set the language associated with a filename extension. @xref{Show, ,
10892 Displaying the Language}.
10894 This is most commonly a problem when you use a program, such
10895 as @code{cfront} or @code{f2c}, that generates C but is written in
10896 another language. In that case, make the
10897 program use @code{#line} directives in its C output; that way
10898 @value{GDBN} will know the correct language of the source code of the original
10899 program, and will display that source code, not the generated C code.
10902 * Filenames:: Filename extensions and languages.
10903 * Manually:: Setting the working language manually
10904 * Automatically:: Having @value{GDBN} infer the source language
10908 @subsection List of Filename Extensions and Languages
10910 If a source file name ends in one of the following extensions, then
10911 @value{GDBN} infers that its language is the one indicated.
10929 C@t{++} source file
10935 Objective-C source file
10939 Fortran source file
10942 Modula-2 source file
10946 Assembler source file. This actually behaves almost like C, but
10947 @value{GDBN} does not skip over function prologues when stepping.
10950 In addition, you may set the language associated with a filename
10951 extension. @xref{Show, , Displaying the Language}.
10954 @subsection Setting the Working Language
10956 If you allow @value{GDBN} to set the language automatically,
10957 expressions are interpreted the same way in your debugging session and
10960 @kindex set language
10961 If you wish, you may set the language manually. To do this, issue the
10962 command @samp{set language @var{lang}}, where @var{lang} is the name of
10963 a language, such as
10964 @code{c} or @code{modula-2}.
10965 For a list of the supported languages, type @samp{set language}.
10967 Setting the language manually prevents @value{GDBN} from updating the working
10968 language automatically. This can lead to confusion if you try
10969 to debug a program when the working language is not the same as the
10970 source language, when an expression is acceptable to both
10971 languages---but means different things. For instance, if the current
10972 source file were written in C, and @value{GDBN} was parsing Modula-2, a
10980 might not have the effect you intended. In C, this means to add
10981 @code{b} and @code{c} and place the result in @code{a}. The result
10982 printed would be the value of @code{a}. In Modula-2, this means to compare
10983 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
10985 @node Automatically
10986 @subsection Having @value{GDBN} Infer the Source Language
10988 To have @value{GDBN} set the working language automatically, use
10989 @samp{set language local} or @samp{set language auto}. @value{GDBN}
10990 then infers the working language. That is, when your program stops in a
10991 frame (usually by encountering a breakpoint), @value{GDBN} sets the
10992 working language to the language recorded for the function in that
10993 frame. If the language for a frame is unknown (that is, if the function
10994 or block corresponding to the frame was defined in a source file that
10995 does not have a recognized extension), the current working language is
10996 not changed, and @value{GDBN} issues a warning.
10998 This may not seem necessary for most programs, which are written
10999 entirely in one source language. However, program modules and libraries
11000 written in one source language can be used by a main program written in
11001 a different source language. Using @samp{set language auto} in this
11002 case frees you from having to set the working language manually.
11005 @section Displaying the Language
11007 The following commands help you find out which language is the
11008 working language, and also what language source files were written in.
11011 @item show language
11012 @kindex show language
11013 Display the current working language. This is the
11014 language you can use with commands such as @code{print} to
11015 build and compute expressions that may involve variables in your program.
11018 @kindex info frame@r{, show the source language}
11019 Display the source language for this frame. This language becomes the
11020 working language if you use an identifier from this frame.
11021 @xref{Frame Info, ,Information about a Frame}, to identify the other
11022 information listed here.
11025 @kindex info source@r{, show the source language}
11026 Display the source language of this source file.
11027 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
11028 information listed here.
11031 In unusual circumstances, you may have source files with extensions
11032 not in the standard list. You can then set the extension associated
11033 with a language explicitly:
11036 @item set extension-language @var{ext} @var{language}
11037 @kindex set extension-language
11038 Tell @value{GDBN} that source files with extension @var{ext} are to be
11039 assumed as written in the source language @var{language}.
11041 @item info extensions
11042 @kindex info extensions
11043 List all the filename extensions and the associated languages.
11047 @section Type and Range Checking
11050 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
11051 checking are included, but they do not yet have any effect. This
11052 section documents the intended facilities.
11054 @c FIXME remove warning when type/range code added
11056 Some languages are designed to guard you against making seemingly common
11057 errors through a series of compile- and run-time checks. These include
11058 checking the type of arguments to functions and operators, and making
11059 sure mathematical overflows are caught at run time. Checks such as
11060 these help to ensure a program's correctness once it has been compiled
11061 by eliminating type mismatches, and providing active checks for range
11062 errors when your program is running.
11064 @value{GDBN} can check for conditions like the above if you wish.
11065 Although @value{GDBN} does not check the statements in your program,
11066 it can check expressions entered directly into @value{GDBN} for
11067 evaluation via the @code{print} command, for example. As with the
11068 working language, @value{GDBN} can also decide whether or not to check
11069 automatically based on your program's source language.
11070 @xref{Supported Languages, ,Supported Languages}, for the default
11071 settings of supported languages.
11074 * Type Checking:: An overview of type checking
11075 * Range Checking:: An overview of range checking
11078 @cindex type checking
11079 @cindex checks, type
11080 @node Type Checking
11081 @subsection An Overview of Type Checking
11083 Some languages, such as Modula-2, are strongly typed, meaning that the
11084 arguments to operators and functions have to be of the correct type,
11085 otherwise an error occurs. These checks prevent type mismatch
11086 errors from ever causing any run-time problems. For example,
11094 The second example fails because the @code{CARDINAL} 1 is not
11095 type-compatible with the @code{REAL} 2.3.
11097 For the expressions you use in @value{GDBN} commands, you can tell the
11098 @value{GDBN} type checker to skip checking;
11099 to treat any mismatches as errors and abandon the expression;
11100 or to only issue warnings when type mismatches occur,
11101 but evaluate the expression anyway. When you choose the last of
11102 these, @value{GDBN} evaluates expressions like the second example above, but
11103 also issues a warning.
11105 Even if you turn type checking off, there may be other reasons
11106 related to type that prevent @value{GDBN} from evaluating an expression.
11107 For instance, @value{GDBN} does not know how to add an @code{int} and
11108 a @code{struct foo}. These particular type errors have nothing to do
11109 with the language in use, and usually arise from expressions, such as
11110 the one described above, which make little sense to evaluate anyway.
11112 Each language defines to what degree it is strict about type. For
11113 instance, both Modula-2 and C require the arguments to arithmetical
11114 operators to be numbers. In C, enumerated types and pointers can be
11115 represented as numbers, so that they are valid arguments to mathematical
11116 operators. @xref{Supported Languages, ,Supported Languages}, for further
11117 details on specific languages.
11119 @value{GDBN} provides some additional commands for controlling the type checker:
11121 @kindex set check type
11122 @kindex show check type
11124 @item set check type auto
11125 Set type checking on or off based on the current working language.
11126 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11129 @item set check type on
11130 @itemx set check type off
11131 Set type checking on or off, overriding the default setting for the
11132 current working language. Issue a warning if the setting does not
11133 match the language default. If any type mismatches occur in
11134 evaluating an expression while type checking is on, @value{GDBN} prints a
11135 message and aborts evaluation of the expression.
11137 @item set check type warn
11138 Cause the type checker to issue warnings, but to always attempt to
11139 evaluate the expression. Evaluating the expression may still
11140 be impossible for other reasons. For example, @value{GDBN} cannot add
11141 numbers and structures.
11144 Show the current setting of the type checker, and whether or not @value{GDBN}
11145 is setting it automatically.
11148 @cindex range checking
11149 @cindex checks, range
11150 @node Range Checking
11151 @subsection An Overview of Range Checking
11153 In some languages (such as Modula-2), it is an error to exceed the
11154 bounds of a type; this is enforced with run-time checks. Such range
11155 checking is meant to ensure program correctness by making sure
11156 computations do not overflow, or indices on an array element access do
11157 not exceed the bounds of the array.
11159 For expressions you use in @value{GDBN} commands, you can tell
11160 @value{GDBN} to treat range errors in one of three ways: ignore them,
11161 always treat them as errors and abandon the expression, or issue
11162 warnings but evaluate the expression anyway.
11164 A range error can result from numerical overflow, from exceeding an
11165 array index bound, or when you type a constant that is not a member
11166 of any type. Some languages, however, do not treat overflows as an
11167 error. In many implementations of C, mathematical overflow causes the
11168 result to ``wrap around'' to lower values---for example, if @var{m} is
11169 the largest integer value, and @var{s} is the smallest, then
11172 @var{m} + 1 @result{} @var{s}
11175 This, too, is specific to individual languages, and in some cases
11176 specific to individual compilers or machines. @xref{Supported Languages, ,
11177 Supported Languages}, for further details on specific languages.
11179 @value{GDBN} provides some additional commands for controlling the range checker:
11181 @kindex set check range
11182 @kindex show check range
11184 @item set check range auto
11185 Set range checking on or off based on the current working language.
11186 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11189 @item set check range on
11190 @itemx set check range off
11191 Set range checking on or off, overriding the default setting for the
11192 current working language. A warning is issued if the setting does not
11193 match the language default. If a range error occurs and range checking is on,
11194 then a message is printed and evaluation of the expression is aborted.
11196 @item set check range warn
11197 Output messages when the @value{GDBN} range checker detects a range error,
11198 but attempt to evaluate the expression anyway. Evaluating the
11199 expression may still be impossible for other reasons, such as accessing
11200 memory that the process does not own (a typical example from many Unix
11204 Show the current setting of the range checker, and whether or not it is
11205 being set automatically by @value{GDBN}.
11208 @node Supported Languages
11209 @section Supported Languages
11211 @value{GDBN} supports C, C@t{++}, D, Objective-C, Fortran, Java, Pascal,
11212 assembly, Modula-2, and Ada.
11213 @c This is false ...
11214 Some @value{GDBN} features may be used in expressions regardless of the
11215 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
11216 and the @samp{@{type@}addr} construct (@pxref{Expressions,
11217 ,Expressions}) can be used with the constructs of any supported
11220 The following sections detail to what degree each source language is
11221 supported by @value{GDBN}. These sections are not meant to be language
11222 tutorials or references, but serve only as a reference guide to what the
11223 @value{GDBN} expression parser accepts, and what input and output
11224 formats should look like for different languages. There are many good
11225 books written on each of these languages; please look to these for a
11226 language reference or tutorial.
11229 * C:: C and C@t{++}
11231 * Objective-C:: Objective-C
11232 * Fortran:: Fortran
11234 * Modula-2:: Modula-2
11239 @subsection C and C@t{++}
11241 @cindex C and C@t{++}
11242 @cindex expressions in C or C@t{++}
11244 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
11245 to both languages. Whenever this is the case, we discuss those languages
11249 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
11250 @cindex @sc{gnu} C@t{++}
11251 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
11252 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
11253 effectively, you must compile your C@t{++} programs with a supported
11254 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
11255 compiler (@code{aCC}).
11257 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
11258 format; if it doesn't work on your system, try the stabs+ debugging
11259 format. You can select those formats explicitly with the @code{g++}
11260 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
11261 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
11262 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
11265 * C Operators:: C and C@t{++} operators
11266 * C Constants:: C and C@t{++} constants
11267 * C Plus Plus Expressions:: C@t{++} expressions
11268 * C Defaults:: Default settings for C and C@t{++}
11269 * C Checks:: C and C@t{++} type and range checks
11270 * Debugging C:: @value{GDBN} and C
11271 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
11272 * Decimal Floating Point:: Numbers in Decimal Floating Point format
11276 @subsubsection C and C@t{++} Operators
11278 @cindex C and C@t{++} operators
11280 Operators must be defined on values of specific types. For instance,
11281 @code{+} is defined on numbers, but not on structures. Operators are
11282 often defined on groups of types.
11284 For the purposes of C and C@t{++}, the following definitions hold:
11289 @emph{Integral types} include @code{int} with any of its storage-class
11290 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
11293 @emph{Floating-point types} include @code{float}, @code{double}, and
11294 @code{long double} (if supported by the target platform).
11297 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
11300 @emph{Scalar types} include all of the above.
11305 The following operators are supported. They are listed here
11306 in order of increasing precedence:
11310 The comma or sequencing operator. Expressions in a comma-separated list
11311 are evaluated from left to right, with the result of the entire
11312 expression being the last expression evaluated.
11315 Assignment. The value of an assignment expression is the value
11316 assigned. Defined on scalar types.
11319 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
11320 and translated to @w{@code{@var{a} = @var{a op b}}}.
11321 @w{@code{@var{op}=}} and @code{=} have the same precedence.
11322 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
11323 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
11326 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
11327 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
11331 Logical @sc{or}. Defined on integral types.
11334 Logical @sc{and}. Defined on integral types.
11337 Bitwise @sc{or}. Defined on integral types.
11340 Bitwise exclusive-@sc{or}. Defined on integral types.
11343 Bitwise @sc{and}. Defined on integral types.
11346 Equality and inequality. Defined on scalar types. The value of these
11347 expressions is 0 for false and non-zero for true.
11349 @item <@r{, }>@r{, }<=@r{, }>=
11350 Less than, greater than, less than or equal, greater than or equal.
11351 Defined on scalar types. The value of these expressions is 0 for false
11352 and non-zero for true.
11355 left shift, and right shift. Defined on integral types.
11358 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
11361 Addition and subtraction. Defined on integral types, floating-point types and
11364 @item *@r{, }/@r{, }%
11365 Multiplication, division, and modulus. Multiplication and division are
11366 defined on integral and floating-point types. Modulus is defined on
11370 Increment and decrement. When appearing before a variable, the
11371 operation is performed before the variable is used in an expression;
11372 when appearing after it, the variable's value is used before the
11373 operation takes place.
11376 Pointer dereferencing. Defined on pointer types. Same precedence as
11380 Address operator. Defined on variables. Same precedence as @code{++}.
11382 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
11383 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
11384 to examine the address
11385 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
11389 Negative. Defined on integral and floating-point types. Same
11390 precedence as @code{++}.
11393 Logical negation. Defined on integral types. Same precedence as
11397 Bitwise complement operator. Defined on integral types. Same precedence as
11402 Structure member, and pointer-to-structure member. For convenience,
11403 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
11404 pointer based on the stored type information.
11405 Defined on @code{struct} and @code{union} data.
11408 Dereferences of pointers to members.
11411 Array indexing. @code{@var{a}[@var{i}]} is defined as
11412 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
11415 Function parameter list. Same precedence as @code{->}.
11418 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
11419 and @code{class} types.
11422 Doubled colons also represent the @value{GDBN} scope operator
11423 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
11427 If an operator is redefined in the user code, @value{GDBN} usually
11428 attempts to invoke the redefined version instead of using the operator's
11429 predefined meaning.
11432 @subsubsection C and C@t{++} Constants
11434 @cindex C and C@t{++} constants
11436 @value{GDBN} allows you to express the constants of C and C@t{++} in the
11441 Integer constants are a sequence of digits. Octal constants are
11442 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
11443 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
11444 @samp{l}, specifying that the constant should be treated as a
11448 Floating point constants are a sequence of digits, followed by a decimal
11449 point, followed by a sequence of digits, and optionally followed by an
11450 exponent. An exponent is of the form:
11451 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
11452 sequence of digits. The @samp{+} is optional for positive exponents.
11453 A floating-point constant may also end with a letter @samp{f} or
11454 @samp{F}, specifying that the constant should be treated as being of
11455 the @code{float} (as opposed to the default @code{double}) type; or with
11456 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
11460 Enumerated constants consist of enumerated identifiers, or their
11461 integral equivalents.
11464 Character constants are a single character surrounded by single quotes
11465 (@code{'}), or a number---the ordinal value of the corresponding character
11466 (usually its @sc{ascii} value). Within quotes, the single character may
11467 be represented by a letter or by @dfn{escape sequences}, which are of
11468 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
11469 of the character's ordinal value; or of the form @samp{\@var{x}}, where
11470 @samp{@var{x}} is a predefined special character---for example,
11471 @samp{\n} for newline.
11474 String constants are a sequence of character constants surrounded by
11475 double quotes (@code{"}). Any valid character constant (as described
11476 above) may appear. Double quotes within the string must be preceded by
11477 a backslash, so for instance @samp{"a\"b'c"} is a string of five
11481 Pointer constants are an integral value. You can also write pointers
11482 to constants using the C operator @samp{&}.
11485 Array constants are comma-separated lists surrounded by braces @samp{@{}
11486 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
11487 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
11488 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
11491 @node C Plus Plus Expressions
11492 @subsubsection C@t{++} Expressions
11494 @cindex expressions in C@t{++}
11495 @value{GDBN} expression handling can interpret most C@t{++} expressions.
11497 @cindex debugging C@t{++} programs
11498 @cindex C@t{++} compilers
11499 @cindex debug formats and C@t{++}
11500 @cindex @value{NGCC} and C@t{++}
11502 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
11503 proper compiler and the proper debug format. Currently, @value{GDBN}
11504 works best when debugging C@t{++} code that is compiled with
11505 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
11506 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
11507 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
11508 stabs+ as their default debug format, so you usually don't need to
11509 specify a debug format explicitly. Other compilers and/or debug formats
11510 are likely to work badly or not at all when using @value{GDBN} to debug
11516 @cindex member functions
11518 Member function calls are allowed; you can use expressions like
11521 count = aml->GetOriginal(x, y)
11524 @vindex this@r{, inside C@t{++} member functions}
11525 @cindex namespace in C@t{++}
11527 While a member function is active (in the selected stack frame), your
11528 expressions have the same namespace available as the member function;
11529 that is, @value{GDBN} allows implicit references to the class instance
11530 pointer @code{this} following the same rules as C@t{++}.
11532 @cindex call overloaded functions
11533 @cindex overloaded functions, calling
11534 @cindex type conversions in C@t{++}
11536 You can call overloaded functions; @value{GDBN} resolves the function
11537 call to the right definition, with some restrictions. @value{GDBN} does not
11538 perform overload resolution involving user-defined type conversions,
11539 calls to constructors, or instantiations of templates that do not exist
11540 in the program. It also cannot handle ellipsis argument lists or
11543 It does perform integral conversions and promotions, floating-point
11544 promotions, arithmetic conversions, pointer conversions, conversions of
11545 class objects to base classes, and standard conversions such as those of
11546 functions or arrays to pointers; it requires an exact match on the
11547 number of function arguments.
11549 Overload resolution is always performed, unless you have specified
11550 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
11551 ,@value{GDBN} Features for C@t{++}}.
11553 You must specify @code{set overload-resolution off} in order to use an
11554 explicit function signature to call an overloaded function, as in
11556 p 'foo(char,int)'('x', 13)
11559 The @value{GDBN} command-completion facility can simplify this;
11560 see @ref{Completion, ,Command Completion}.
11562 @cindex reference declarations
11564 @value{GDBN} understands variables declared as C@t{++} references; you can use
11565 them in expressions just as you do in C@t{++} source---they are automatically
11568 In the parameter list shown when @value{GDBN} displays a frame, the values of
11569 reference variables are not displayed (unlike other variables); this
11570 avoids clutter, since references are often used for large structures.
11571 The @emph{address} of a reference variable is always shown, unless
11572 you have specified @samp{set print address off}.
11575 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
11576 expressions can use it just as expressions in your program do. Since
11577 one scope may be defined in another, you can use @code{::} repeatedly if
11578 necessary, for example in an expression like
11579 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
11580 resolving name scope by reference to source files, in both C and C@t{++}
11581 debugging (@pxref{Variables, ,Program Variables}).
11584 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
11585 calling virtual functions correctly, printing out virtual bases of
11586 objects, calling functions in a base subobject, casting objects, and
11587 invoking user-defined operators.
11590 @subsubsection C and C@t{++} Defaults
11592 @cindex C and C@t{++} defaults
11594 If you allow @value{GDBN} to set type and range checking automatically, they
11595 both default to @code{off} whenever the working language changes to
11596 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
11597 selects the working language.
11599 If you allow @value{GDBN} to set the language automatically, it
11600 recognizes source files whose names end with @file{.c}, @file{.C}, or
11601 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
11602 these files, it sets the working language to C or C@t{++}.
11603 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
11604 for further details.
11606 @c Type checking is (a) primarily motivated by Modula-2, and (b)
11607 @c unimplemented. If (b) changes, it might make sense to let this node
11608 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
11611 @subsubsection C and C@t{++} Type and Range Checks
11613 @cindex C and C@t{++} checks
11615 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
11616 is not used. However, if you turn type checking on, @value{GDBN}
11617 considers two variables type equivalent if:
11621 The two variables are structured and have the same structure, union, or
11625 The two variables have the same type name, or types that have been
11626 declared equivalent through @code{typedef}.
11629 @c leaving this out because neither J Gilmore nor R Pesch understand it.
11632 The two @code{struct}, @code{union}, or @code{enum} variables are
11633 declared in the same declaration. (Note: this may not be true for all C
11638 Range checking, if turned on, is done on mathematical operations. Array
11639 indices are not checked, since they are often used to index a pointer
11640 that is not itself an array.
11643 @subsubsection @value{GDBN} and C
11645 The @code{set print union} and @code{show print union} commands apply to
11646 the @code{union} type. When set to @samp{on}, any @code{union} that is
11647 inside a @code{struct} or @code{class} is also printed. Otherwise, it
11648 appears as @samp{@{...@}}.
11650 The @code{@@} operator aids in the debugging of dynamic arrays, formed
11651 with pointers and a memory allocation function. @xref{Expressions,
11654 @node Debugging C Plus Plus
11655 @subsubsection @value{GDBN} Features for C@t{++}
11657 @cindex commands for C@t{++}
11659 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
11660 designed specifically for use with C@t{++}. Here is a summary:
11663 @cindex break in overloaded functions
11664 @item @r{breakpoint menus}
11665 When you want a breakpoint in a function whose name is overloaded,
11666 @value{GDBN} has the capability to display a menu of possible breakpoint
11667 locations to help you specify which function definition you want.
11668 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
11670 @cindex overloading in C@t{++}
11671 @item rbreak @var{regex}
11672 Setting breakpoints using regular expressions is helpful for setting
11673 breakpoints on overloaded functions that are not members of any special
11675 @xref{Set Breaks, ,Setting Breakpoints}.
11677 @cindex C@t{++} exception handling
11680 Debug C@t{++} exception handling using these commands. @xref{Set
11681 Catchpoints, , Setting Catchpoints}.
11683 @cindex inheritance
11684 @item ptype @var{typename}
11685 Print inheritance relationships as well as other information for type
11687 @xref{Symbols, ,Examining the Symbol Table}.
11689 @cindex C@t{++} symbol display
11690 @item set print demangle
11691 @itemx show print demangle
11692 @itemx set print asm-demangle
11693 @itemx show print asm-demangle
11694 Control whether C@t{++} symbols display in their source form, both when
11695 displaying code as C@t{++} source and when displaying disassemblies.
11696 @xref{Print Settings, ,Print Settings}.
11698 @item set print object
11699 @itemx show print object
11700 Choose whether to print derived (actual) or declared types of objects.
11701 @xref{Print Settings, ,Print Settings}.
11703 @item set print vtbl
11704 @itemx show print vtbl
11705 Control the format for printing virtual function tables.
11706 @xref{Print Settings, ,Print Settings}.
11707 (The @code{vtbl} commands do not work on programs compiled with the HP
11708 ANSI C@t{++} compiler (@code{aCC}).)
11710 @kindex set overload-resolution
11711 @cindex overloaded functions, overload resolution
11712 @item set overload-resolution on
11713 Enable overload resolution for C@t{++} expression evaluation. The default
11714 is on. For overloaded functions, @value{GDBN} evaluates the arguments
11715 and searches for a function whose signature matches the argument types,
11716 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
11717 Expressions, ,C@t{++} Expressions}, for details).
11718 If it cannot find a match, it emits a message.
11720 @item set overload-resolution off
11721 Disable overload resolution for C@t{++} expression evaluation. For
11722 overloaded functions that are not class member functions, @value{GDBN}
11723 chooses the first function of the specified name that it finds in the
11724 symbol table, whether or not its arguments are of the correct type. For
11725 overloaded functions that are class member functions, @value{GDBN}
11726 searches for a function whose signature @emph{exactly} matches the
11729 @kindex show overload-resolution
11730 @item show overload-resolution
11731 Show the current setting of overload resolution.
11733 @item @r{Overloaded symbol names}
11734 You can specify a particular definition of an overloaded symbol, using
11735 the same notation that is used to declare such symbols in C@t{++}: type
11736 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
11737 also use the @value{GDBN} command-line word completion facilities to list the
11738 available choices, or to finish the type list for you.
11739 @xref{Completion,, Command Completion}, for details on how to do this.
11742 @node Decimal Floating Point
11743 @subsubsection Decimal Floating Point format
11744 @cindex decimal floating point format
11746 @value{GDBN} can examine, set and perform computations with numbers in
11747 decimal floating point format, which in the C language correspond to the
11748 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
11749 specified by the extension to support decimal floating-point arithmetic.
11751 There are two encodings in use, depending on the architecture: BID (Binary
11752 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
11753 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
11756 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
11757 to manipulate decimal floating point numbers, it is not possible to convert
11758 (using a cast, for example) integers wider than 32-bit to decimal float.
11760 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
11761 point computations, error checking in decimal float operations ignores
11762 underflow, overflow and divide by zero exceptions.
11764 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
11765 to inspect @code{_Decimal128} values stored in floating point registers.
11766 See @ref{PowerPC,,PowerPC} for more details.
11772 @value{GDBN} can be used to debug programs written in D and compiled with
11773 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
11774 specific feature --- dynamic arrays.
11777 @subsection Objective-C
11779 @cindex Objective-C
11780 This section provides information about some commands and command
11781 options that are useful for debugging Objective-C code. See also
11782 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
11783 few more commands specific to Objective-C support.
11786 * Method Names in Commands::
11787 * The Print Command with Objective-C::
11790 @node Method Names in Commands
11791 @subsubsection Method Names in Commands
11793 The following commands have been extended to accept Objective-C method
11794 names as line specifications:
11796 @kindex clear@r{, and Objective-C}
11797 @kindex break@r{, and Objective-C}
11798 @kindex info line@r{, and Objective-C}
11799 @kindex jump@r{, and Objective-C}
11800 @kindex list@r{, and Objective-C}
11804 @item @code{info line}
11809 A fully qualified Objective-C method name is specified as
11812 -[@var{Class} @var{methodName}]
11815 where the minus sign is used to indicate an instance method and a
11816 plus sign (not shown) is used to indicate a class method. The class
11817 name @var{Class} and method name @var{methodName} are enclosed in
11818 brackets, similar to the way messages are specified in Objective-C
11819 source code. For example, to set a breakpoint at the @code{create}
11820 instance method of class @code{Fruit} in the program currently being
11824 break -[Fruit create]
11827 To list ten program lines around the @code{initialize} class method,
11831 list +[NSText initialize]
11834 In the current version of @value{GDBN}, the plus or minus sign is
11835 required. In future versions of @value{GDBN}, the plus or minus
11836 sign will be optional, but you can use it to narrow the search. It
11837 is also possible to specify just a method name:
11843 You must specify the complete method name, including any colons. If
11844 your program's source files contain more than one @code{create} method,
11845 you'll be presented with a numbered list of classes that implement that
11846 method. Indicate your choice by number, or type @samp{0} to exit if
11849 As another example, to clear a breakpoint established at the
11850 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
11853 clear -[NSWindow makeKeyAndOrderFront:]
11856 @node The Print Command with Objective-C
11857 @subsubsection The Print Command With Objective-C
11858 @cindex Objective-C, print objects
11859 @kindex print-object
11860 @kindex po @r{(@code{print-object})}
11862 The print command has also been extended to accept methods. For example:
11865 print -[@var{object} hash]
11868 @cindex print an Objective-C object description
11869 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
11871 will tell @value{GDBN} to send the @code{hash} message to @var{object}
11872 and print the result. Also, an additional command has been added,
11873 @code{print-object} or @code{po} for short, which is meant to print
11874 the description of an object. However, this command may only work
11875 with certain Objective-C libraries that have a particular hook
11876 function, @code{_NSPrintForDebugger}, defined.
11879 @subsection Fortran
11880 @cindex Fortran-specific support in @value{GDBN}
11882 @value{GDBN} can be used to debug programs written in Fortran, but it
11883 currently supports only the features of Fortran 77 language.
11885 @cindex trailing underscore, in Fortran symbols
11886 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
11887 among them) append an underscore to the names of variables and
11888 functions. When you debug programs compiled by those compilers, you
11889 will need to refer to variables and functions with a trailing
11893 * Fortran Operators:: Fortran operators and expressions
11894 * Fortran Defaults:: Default settings for Fortran
11895 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
11898 @node Fortran Operators
11899 @subsubsection Fortran Operators and Expressions
11901 @cindex Fortran operators and expressions
11903 Operators must be defined on values of specific types. For instance,
11904 @code{+} is defined on numbers, but not on characters or other non-
11905 arithmetic types. Operators are often defined on groups of types.
11909 The exponentiation operator. It raises the first operand to the power
11913 The range operator. Normally used in the form of array(low:high) to
11914 represent a section of array.
11917 The access component operator. Normally used to access elements in derived
11918 types. Also suitable for unions. As unions aren't part of regular Fortran,
11919 this can only happen when accessing a register that uses a gdbarch-defined
11923 @node Fortran Defaults
11924 @subsubsection Fortran Defaults
11926 @cindex Fortran Defaults
11928 Fortran symbols are usually case-insensitive, so @value{GDBN} by
11929 default uses case-insensitive matches for Fortran symbols. You can
11930 change that with the @samp{set case-insensitive} command, see
11931 @ref{Symbols}, for the details.
11933 @node Special Fortran Commands
11934 @subsubsection Special Fortran Commands
11936 @cindex Special Fortran commands
11938 @value{GDBN} has some commands to support Fortran-specific features,
11939 such as displaying common blocks.
11942 @cindex @code{COMMON} blocks, Fortran
11943 @kindex info common
11944 @item info common @r{[}@var{common-name}@r{]}
11945 This command prints the values contained in the Fortran @code{COMMON}
11946 block whose name is @var{common-name}. With no argument, the names of
11947 all @code{COMMON} blocks visible at the current program location are
11954 @cindex Pascal support in @value{GDBN}, limitations
11955 Debugging Pascal programs which use sets, subranges, file variables, or
11956 nested functions does not currently work. @value{GDBN} does not support
11957 entering expressions, printing values, or similar features using Pascal
11960 The Pascal-specific command @code{set print pascal_static-members}
11961 controls whether static members of Pascal objects are displayed.
11962 @xref{Print Settings, pascal_static-members}.
11965 @subsection Modula-2
11967 @cindex Modula-2, @value{GDBN} support
11969 The extensions made to @value{GDBN} to support Modula-2 only support
11970 output from the @sc{gnu} Modula-2 compiler (which is currently being
11971 developed). Other Modula-2 compilers are not currently supported, and
11972 attempting to debug executables produced by them is most likely
11973 to give an error as @value{GDBN} reads in the executable's symbol
11976 @cindex expressions in Modula-2
11978 * M2 Operators:: Built-in operators
11979 * Built-In Func/Proc:: Built-in functions and procedures
11980 * M2 Constants:: Modula-2 constants
11981 * M2 Types:: Modula-2 types
11982 * M2 Defaults:: Default settings for Modula-2
11983 * Deviations:: Deviations from standard Modula-2
11984 * M2 Checks:: Modula-2 type and range checks
11985 * M2 Scope:: The scope operators @code{::} and @code{.}
11986 * GDB/M2:: @value{GDBN} and Modula-2
11990 @subsubsection Operators
11991 @cindex Modula-2 operators
11993 Operators must be defined on values of specific types. For instance,
11994 @code{+} is defined on numbers, but not on structures. Operators are
11995 often defined on groups of types. For the purposes of Modula-2, the
11996 following definitions hold:
12001 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
12005 @emph{Character types} consist of @code{CHAR} and its subranges.
12008 @emph{Floating-point types} consist of @code{REAL}.
12011 @emph{Pointer types} consist of anything declared as @code{POINTER TO
12015 @emph{Scalar types} consist of all of the above.
12018 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
12021 @emph{Boolean types} consist of @code{BOOLEAN}.
12025 The following operators are supported, and appear in order of
12026 increasing precedence:
12030 Function argument or array index separator.
12033 Assignment. The value of @var{var} @code{:=} @var{value} is
12037 Less than, greater than on integral, floating-point, or enumerated
12041 Less than or equal to, greater than or equal to
12042 on integral, floating-point and enumerated types, or set inclusion on
12043 set types. Same precedence as @code{<}.
12045 @item =@r{, }<>@r{, }#
12046 Equality and two ways of expressing inequality, valid on scalar types.
12047 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
12048 available for inequality, since @code{#} conflicts with the script
12052 Set membership. Defined on set types and the types of their members.
12053 Same precedence as @code{<}.
12056 Boolean disjunction. Defined on boolean types.
12059 Boolean conjunction. Defined on boolean types.
12062 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12065 Addition and subtraction on integral and floating-point types, or union
12066 and difference on set types.
12069 Multiplication on integral and floating-point types, or set intersection
12073 Division on floating-point types, or symmetric set difference on set
12074 types. Same precedence as @code{*}.
12077 Integer division and remainder. Defined on integral types. Same
12078 precedence as @code{*}.
12081 Negative. Defined on @code{INTEGER} and @code{REAL} data.
12084 Pointer dereferencing. Defined on pointer types.
12087 Boolean negation. Defined on boolean types. Same precedence as
12091 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
12092 precedence as @code{^}.
12095 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
12098 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
12102 @value{GDBN} and Modula-2 scope operators.
12106 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
12107 treats the use of the operator @code{IN}, or the use of operators
12108 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
12109 @code{<=}, and @code{>=} on sets as an error.
12113 @node Built-In Func/Proc
12114 @subsubsection Built-in Functions and Procedures
12115 @cindex Modula-2 built-ins
12117 Modula-2 also makes available several built-in procedures and functions.
12118 In describing these, the following metavariables are used:
12123 represents an @code{ARRAY} variable.
12126 represents a @code{CHAR} constant or variable.
12129 represents a variable or constant of integral type.
12132 represents an identifier that belongs to a set. Generally used in the
12133 same function with the metavariable @var{s}. The type of @var{s} should
12134 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
12137 represents a variable or constant of integral or floating-point type.
12140 represents a variable or constant of floating-point type.
12146 represents a variable.
12149 represents a variable or constant of one of many types. See the
12150 explanation of the function for details.
12153 All Modula-2 built-in procedures also return a result, described below.
12157 Returns the absolute value of @var{n}.
12160 If @var{c} is a lower case letter, it returns its upper case
12161 equivalent, otherwise it returns its argument.
12164 Returns the character whose ordinal value is @var{i}.
12167 Decrements the value in the variable @var{v} by one. Returns the new value.
12169 @item DEC(@var{v},@var{i})
12170 Decrements the value in the variable @var{v} by @var{i}. Returns the
12173 @item EXCL(@var{m},@var{s})
12174 Removes the element @var{m} from the set @var{s}. Returns the new
12177 @item FLOAT(@var{i})
12178 Returns the floating point equivalent of the integer @var{i}.
12180 @item HIGH(@var{a})
12181 Returns the index of the last member of @var{a}.
12184 Increments the value in the variable @var{v} by one. Returns the new value.
12186 @item INC(@var{v},@var{i})
12187 Increments the value in the variable @var{v} by @var{i}. Returns the
12190 @item INCL(@var{m},@var{s})
12191 Adds the element @var{m} to the set @var{s} if it is not already
12192 there. Returns the new set.
12195 Returns the maximum value of the type @var{t}.
12198 Returns the minimum value of the type @var{t}.
12201 Returns boolean TRUE if @var{i} is an odd number.
12204 Returns the ordinal value of its argument. For example, the ordinal
12205 value of a character is its @sc{ascii} value (on machines supporting the
12206 @sc{ascii} character set). @var{x} must be of an ordered type, which include
12207 integral, character and enumerated types.
12209 @item SIZE(@var{x})
12210 Returns the size of its argument. @var{x} can be a variable or a type.
12212 @item TRUNC(@var{r})
12213 Returns the integral part of @var{r}.
12215 @item TSIZE(@var{x})
12216 Returns the size of its argument. @var{x} can be a variable or a type.
12218 @item VAL(@var{t},@var{i})
12219 Returns the member of the type @var{t} whose ordinal value is @var{i}.
12223 @emph{Warning:} Sets and their operations are not yet supported, so
12224 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
12228 @cindex Modula-2 constants
12230 @subsubsection Constants
12232 @value{GDBN} allows you to express the constants of Modula-2 in the following
12238 Integer constants are simply a sequence of digits. When used in an
12239 expression, a constant is interpreted to be type-compatible with the
12240 rest of the expression. Hexadecimal integers are specified by a
12241 trailing @samp{H}, and octal integers by a trailing @samp{B}.
12244 Floating point constants appear as a sequence of digits, followed by a
12245 decimal point and another sequence of digits. An optional exponent can
12246 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
12247 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
12248 digits of the floating point constant must be valid decimal (base 10)
12252 Character constants consist of a single character enclosed by a pair of
12253 like quotes, either single (@code{'}) or double (@code{"}). They may
12254 also be expressed by their ordinal value (their @sc{ascii} value, usually)
12255 followed by a @samp{C}.
12258 String constants consist of a sequence of characters enclosed by a
12259 pair of like quotes, either single (@code{'}) or double (@code{"}).
12260 Escape sequences in the style of C are also allowed. @xref{C
12261 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
12265 Enumerated constants consist of an enumerated identifier.
12268 Boolean constants consist of the identifiers @code{TRUE} and
12272 Pointer constants consist of integral values only.
12275 Set constants are not yet supported.
12279 @subsubsection Modula-2 Types
12280 @cindex Modula-2 types
12282 Currently @value{GDBN} can print the following data types in Modula-2
12283 syntax: array types, record types, set types, pointer types, procedure
12284 types, enumerated types, subrange types and base types. You can also
12285 print the contents of variables declared using these type.
12286 This section gives a number of simple source code examples together with
12287 sample @value{GDBN} sessions.
12289 The first example contains the following section of code:
12298 and you can request @value{GDBN} to interrogate the type and value of
12299 @code{r} and @code{s}.
12302 (@value{GDBP}) print s
12304 (@value{GDBP}) ptype s
12306 (@value{GDBP}) print r
12308 (@value{GDBP}) ptype r
12313 Likewise if your source code declares @code{s} as:
12317 s: SET ['A'..'Z'] ;
12321 then you may query the type of @code{s} by:
12324 (@value{GDBP}) ptype s
12325 type = SET ['A'..'Z']
12329 Note that at present you cannot interactively manipulate set
12330 expressions using the debugger.
12332 The following example shows how you might declare an array in Modula-2
12333 and how you can interact with @value{GDBN} to print its type and contents:
12337 s: ARRAY [-10..10] OF CHAR ;
12341 (@value{GDBP}) ptype s
12342 ARRAY [-10..10] OF CHAR
12345 Note that the array handling is not yet complete and although the type
12346 is printed correctly, expression handling still assumes that all
12347 arrays have a lower bound of zero and not @code{-10} as in the example
12350 Here are some more type related Modula-2 examples:
12354 colour = (blue, red, yellow, green) ;
12355 t = [blue..yellow] ;
12363 The @value{GDBN} interaction shows how you can query the data type
12364 and value of a variable.
12367 (@value{GDBP}) print s
12369 (@value{GDBP}) ptype t
12370 type = [blue..yellow]
12374 In this example a Modula-2 array is declared and its contents
12375 displayed. Observe that the contents are written in the same way as
12376 their @code{C} counterparts.
12380 s: ARRAY [1..5] OF CARDINAL ;
12386 (@value{GDBP}) print s
12387 $1 = @{1, 0, 0, 0, 0@}
12388 (@value{GDBP}) ptype s
12389 type = ARRAY [1..5] OF CARDINAL
12392 The Modula-2 language interface to @value{GDBN} also understands
12393 pointer types as shown in this example:
12397 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
12404 and you can request that @value{GDBN} describes the type of @code{s}.
12407 (@value{GDBP}) ptype s
12408 type = POINTER TO ARRAY [1..5] OF CARDINAL
12411 @value{GDBN} handles compound types as we can see in this example.
12412 Here we combine array types, record types, pointer types and subrange
12423 myarray = ARRAY myrange OF CARDINAL ;
12424 myrange = [-2..2] ;
12426 s: POINTER TO ARRAY myrange OF foo ;
12430 and you can ask @value{GDBN} to describe the type of @code{s} as shown
12434 (@value{GDBP}) ptype s
12435 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
12438 f3 : ARRAY [-2..2] OF CARDINAL;
12443 @subsubsection Modula-2 Defaults
12444 @cindex Modula-2 defaults
12446 If type and range checking are set automatically by @value{GDBN}, they
12447 both default to @code{on} whenever the working language changes to
12448 Modula-2. This happens regardless of whether you or @value{GDBN}
12449 selected the working language.
12451 If you allow @value{GDBN} to set the language automatically, then entering
12452 code compiled from a file whose name ends with @file{.mod} sets the
12453 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
12454 Infer the Source Language}, for further details.
12457 @subsubsection Deviations from Standard Modula-2
12458 @cindex Modula-2, deviations from
12460 A few changes have been made to make Modula-2 programs easier to debug.
12461 This is done primarily via loosening its type strictness:
12465 Unlike in standard Modula-2, pointer constants can be formed by
12466 integers. This allows you to modify pointer variables during
12467 debugging. (In standard Modula-2, the actual address contained in a
12468 pointer variable is hidden from you; it can only be modified
12469 through direct assignment to another pointer variable or expression that
12470 returned a pointer.)
12473 C escape sequences can be used in strings and characters to represent
12474 non-printable characters. @value{GDBN} prints out strings with these
12475 escape sequences embedded. Single non-printable characters are
12476 printed using the @samp{CHR(@var{nnn})} format.
12479 The assignment operator (@code{:=}) returns the value of its right-hand
12483 All built-in procedures both modify @emph{and} return their argument.
12487 @subsubsection Modula-2 Type and Range Checks
12488 @cindex Modula-2 checks
12491 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
12494 @c FIXME remove warning when type/range checks added
12496 @value{GDBN} considers two Modula-2 variables type equivalent if:
12500 They are of types that have been declared equivalent via a @code{TYPE
12501 @var{t1} = @var{t2}} statement
12504 They have been declared on the same line. (Note: This is true of the
12505 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
12508 As long as type checking is enabled, any attempt to combine variables
12509 whose types are not equivalent is an error.
12511 Range checking is done on all mathematical operations, assignment, array
12512 index bounds, and all built-in functions and procedures.
12515 @subsubsection The Scope Operators @code{::} and @code{.}
12517 @cindex @code{.}, Modula-2 scope operator
12518 @cindex colon, doubled as scope operator
12520 @vindex colon-colon@r{, in Modula-2}
12521 @c Info cannot handle :: but TeX can.
12524 @vindex ::@r{, in Modula-2}
12527 There are a few subtle differences between the Modula-2 scope operator
12528 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
12533 @var{module} . @var{id}
12534 @var{scope} :: @var{id}
12538 where @var{scope} is the name of a module or a procedure,
12539 @var{module} the name of a module, and @var{id} is any declared
12540 identifier within your program, except another module.
12542 Using the @code{::} operator makes @value{GDBN} search the scope
12543 specified by @var{scope} for the identifier @var{id}. If it is not
12544 found in the specified scope, then @value{GDBN} searches all scopes
12545 enclosing the one specified by @var{scope}.
12547 Using the @code{.} operator makes @value{GDBN} search the current scope for
12548 the identifier specified by @var{id} that was imported from the
12549 definition module specified by @var{module}. With this operator, it is
12550 an error if the identifier @var{id} was not imported from definition
12551 module @var{module}, or if @var{id} is not an identifier in
12555 @subsubsection @value{GDBN} and Modula-2
12557 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
12558 Five subcommands of @code{set print} and @code{show print} apply
12559 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
12560 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
12561 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
12562 analogue in Modula-2.
12564 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
12565 with any language, is not useful with Modula-2. Its
12566 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
12567 created in Modula-2 as they can in C or C@t{++}. However, because an
12568 address can be specified by an integral constant, the construct
12569 @samp{@{@var{type}@}@var{adrexp}} is still useful.
12571 @cindex @code{#} in Modula-2
12572 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
12573 interpreted as the beginning of a comment. Use @code{<>} instead.
12579 The extensions made to @value{GDBN} for Ada only support
12580 output from the @sc{gnu} Ada (GNAT) compiler.
12581 Other Ada compilers are not currently supported, and
12582 attempting to debug executables produced by them is most likely
12586 @cindex expressions in Ada
12588 * Ada Mode Intro:: General remarks on the Ada syntax
12589 and semantics supported by Ada mode
12591 * Omissions from Ada:: Restrictions on the Ada expression syntax.
12592 * Additions to Ada:: Extensions of the Ada expression syntax.
12593 * Stopping Before Main Program:: Debugging the program during elaboration.
12594 * Ada Tasks:: Listing and setting breakpoints in tasks.
12595 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
12596 * Ada Glitches:: Known peculiarities of Ada mode.
12599 @node Ada Mode Intro
12600 @subsubsection Introduction
12601 @cindex Ada mode, general
12603 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
12604 syntax, with some extensions.
12605 The philosophy behind the design of this subset is
12609 That @value{GDBN} should provide basic literals and access to operations for
12610 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
12611 leaving more sophisticated computations to subprograms written into the
12612 program (which therefore may be called from @value{GDBN}).
12615 That type safety and strict adherence to Ada language restrictions
12616 are not particularly important to the @value{GDBN} user.
12619 That brevity is important to the @value{GDBN} user.
12622 Thus, for brevity, the debugger acts as if all names declared in
12623 user-written packages are directly visible, even if they are not visible
12624 according to Ada rules, thus making it unnecessary to fully qualify most
12625 names with their packages, regardless of context. Where this causes
12626 ambiguity, @value{GDBN} asks the user's intent.
12628 The debugger will start in Ada mode if it detects an Ada main program.
12629 As for other languages, it will enter Ada mode when stopped in a program that
12630 was translated from an Ada source file.
12632 While in Ada mode, you may use `@t{--}' for comments. This is useful
12633 mostly for documenting command files. The standard @value{GDBN} comment
12634 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
12635 middle (to allow based literals).
12637 The debugger supports limited overloading. Given a subprogram call in which
12638 the function symbol has multiple definitions, it will use the number of
12639 actual parameters and some information about their types to attempt to narrow
12640 the set of definitions. It also makes very limited use of context, preferring
12641 procedures to functions in the context of the @code{call} command, and
12642 functions to procedures elsewhere.
12644 @node Omissions from Ada
12645 @subsubsection Omissions from Ada
12646 @cindex Ada, omissions from
12648 Here are the notable omissions from the subset:
12652 Only a subset of the attributes are supported:
12656 @t{'First}, @t{'Last}, and @t{'Length}
12657 on array objects (not on types and subtypes).
12660 @t{'Min} and @t{'Max}.
12663 @t{'Pos} and @t{'Val}.
12669 @t{'Range} on array objects (not subtypes), but only as the right
12670 operand of the membership (@code{in}) operator.
12673 @t{'Access}, @t{'Unchecked_Access}, and
12674 @t{'Unrestricted_Access} (a GNAT extension).
12682 @code{Characters.Latin_1} are not available and
12683 concatenation is not implemented. Thus, escape characters in strings are
12684 not currently available.
12687 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
12688 equality of representations. They will generally work correctly
12689 for strings and arrays whose elements have integer or enumeration types.
12690 They may not work correctly for arrays whose element
12691 types have user-defined equality, for arrays of real values
12692 (in particular, IEEE-conformant floating point, because of negative
12693 zeroes and NaNs), and for arrays whose elements contain unused bits with
12694 indeterminate values.
12697 The other component-by-component array operations (@code{and}, @code{or},
12698 @code{xor}, @code{not}, and relational tests other than equality)
12699 are not implemented.
12702 @cindex array aggregates (Ada)
12703 @cindex record aggregates (Ada)
12704 @cindex aggregates (Ada)
12705 There is limited support for array and record aggregates. They are
12706 permitted only on the right sides of assignments, as in these examples:
12709 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
12710 (@value{GDBP}) set An_Array := (1, others => 0)
12711 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
12712 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
12713 (@value{GDBP}) set A_Record := (1, "Peter", True);
12714 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
12718 discriminant's value by assigning an aggregate has an
12719 undefined effect if that discriminant is used within the record.
12720 However, you can first modify discriminants by directly assigning to
12721 them (which normally would not be allowed in Ada), and then performing an
12722 aggregate assignment. For example, given a variable @code{A_Rec}
12723 declared to have a type such as:
12726 type Rec (Len : Small_Integer := 0) is record
12728 Vals : IntArray (1 .. Len);
12732 you can assign a value with a different size of @code{Vals} with two
12736 (@value{GDBP}) set A_Rec.Len := 4
12737 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
12740 As this example also illustrates, @value{GDBN} is very loose about the usual
12741 rules concerning aggregates. You may leave out some of the
12742 components of an array or record aggregate (such as the @code{Len}
12743 component in the assignment to @code{A_Rec} above); they will retain their
12744 original values upon assignment. You may freely use dynamic values as
12745 indices in component associations. You may even use overlapping or
12746 redundant component associations, although which component values are
12747 assigned in such cases is not defined.
12750 Calls to dispatching subprograms are not implemented.
12753 The overloading algorithm is much more limited (i.e., less selective)
12754 than that of real Ada. It makes only limited use of the context in
12755 which a subexpression appears to resolve its meaning, and it is much
12756 looser in its rules for allowing type matches. As a result, some
12757 function calls will be ambiguous, and the user will be asked to choose
12758 the proper resolution.
12761 The @code{new} operator is not implemented.
12764 Entry calls are not implemented.
12767 Aside from printing, arithmetic operations on the native VAX floating-point
12768 formats are not supported.
12771 It is not possible to slice a packed array.
12774 The names @code{True} and @code{False}, when not part of a qualified name,
12775 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
12777 Should your program
12778 redefine these names in a package or procedure (at best a dubious practice),
12779 you will have to use fully qualified names to access their new definitions.
12782 @node Additions to Ada
12783 @subsubsection Additions to Ada
12784 @cindex Ada, deviations from
12786 As it does for other languages, @value{GDBN} makes certain generic
12787 extensions to Ada (@pxref{Expressions}):
12791 If the expression @var{E} is a variable residing in memory (typically
12792 a local variable or array element) and @var{N} is a positive integer,
12793 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
12794 @var{N}-1 adjacent variables following it in memory as an array. In
12795 Ada, this operator is generally not necessary, since its prime use is
12796 in displaying parts of an array, and slicing will usually do this in
12797 Ada. However, there are occasional uses when debugging programs in
12798 which certain debugging information has been optimized away.
12801 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
12802 appears in function or file @var{B}.'' When @var{B} is a file name,
12803 you must typically surround it in single quotes.
12806 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
12807 @var{type} that appears at address @var{addr}.''
12810 A name starting with @samp{$} is a convenience variable
12811 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
12814 In addition, @value{GDBN} provides a few other shortcuts and outright
12815 additions specific to Ada:
12819 The assignment statement is allowed as an expression, returning
12820 its right-hand operand as its value. Thus, you may enter
12823 (@value{GDBP}) set x := y + 3
12824 (@value{GDBP}) print A(tmp := y + 1)
12828 The semicolon is allowed as an ``operator,'' returning as its value
12829 the value of its right-hand operand.
12830 This allows, for example,
12831 complex conditional breaks:
12834 (@value{GDBP}) break f
12835 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
12839 Rather than use catenation and symbolic character names to introduce special
12840 characters into strings, one may instead use a special bracket notation,
12841 which is also used to print strings. A sequence of characters of the form
12842 @samp{["@var{XX}"]} within a string or character literal denotes the
12843 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
12844 sequence of characters @samp{["""]} also denotes a single quotation mark
12845 in strings. For example,
12847 "One line.["0a"]Next line.["0a"]"
12850 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
12854 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
12855 @t{'Max} is optional (and is ignored in any case). For example, it is valid
12859 (@value{GDBP}) print 'max(x, y)
12863 When printing arrays, @value{GDBN} uses positional notation when the
12864 array has a lower bound of 1, and uses a modified named notation otherwise.
12865 For example, a one-dimensional array of three integers with a lower bound
12866 of 3 might print as
12873 That is, in contrast to valid Ada, only the first component has a @code{=>}
12877 You may abbreviate attributes in expressions with any unique,
12878 multi-character subsequence of
12879 their names (an exact match gets preference).
12880 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
12881 in place of @t{a'length}.
12884 @cindex quoting Ada internal identifiers
12885 Since Ada is case-insensitive, the debugger normally maps identifiers you type
12886 to lower case. The GNAT compiler uses upper-case characters for
12887 some of its internal identifiers, which are normally of no interest to users.
12888 For the rare occasions when you actually have to look at them,
12889 enclose them in angle brackets to avoid the lower-case mapping.
12892 (@value{GDBP}) print <JMPBUF_SAVE>[0]
12896 Printing an object of class-wide type or dereferencing an
12897 access-to-class-wide value will display all the components of the object's
12898 specific type (as indicated by its run-time tag). Likewise, component
12899 selection on such a value will operate on the specific type of the
12904 @node Stopping Before Main Program
12905 @subsubsection Stopping at the Very Beginning
12907 @cindex breakpointing Ada elaboration code
12908 It is sometimes necessary to debug the program during elaboration, and
12909 before reaching the main procedure.
12910 As defined in the Ada Reference
12911 Manual, the elaboration code is invoked from a procedure called
12912 @code{adainit}. To run your program up to the beginning of
12913 elaboration, simply use the following two commands:
12914 @code{tbreak adainit} and @code{run}.
12917 @subsubsection Extensions for Ada Tasks
12918 @cindex Ada, tasking
12920 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
12921 @value{GDBN} provides the following task-related commands:
12926 This command shows a list of current Ada tasks, as in the following example:
12933 (@value{GDBP}) info tasks
12934 ID TID P-ID Pri State Name
12935 1 8088000 0 15 Child Activation Wait main_task
12936 2 80a4000 1 15 Accept Statement b
12937 3 809a800 1 15 Child Activation Wait a
12938 * 4 80ae800 3 15 Runnable c
12943 In this listing, the asterisk before the last task indicates it to be the
12944 task currently being inspected.
12948 Represents @value{GDBN}'s internal task number.
12954 The parent's task ID (@value{GDBN}'s internal task number).
12957 The base priority of the task.
12960 Current state of the task.
12964 The task has been created but has not been activated. It cannot be
12968 The task is not blocked for any reason known to Ada. (It may be waiting
12969 for a mutex, though.) It is conceptually "executing" in normal mode.
12972 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
12973 that were waiting on terminate alternatives have been awakened and have
12974 terminated themselves.
12976 @item Child Activation Wait
12977 The task is waiting for created tasks to complete activation.
12979 @item Accept Statement
12980 The task is waiting on an accept or selective wait statement.
12982 @item Waiting on entry call
12983 The task is waiting on an entry call.
12985 @item Async Select Wait
12986 The task is waiting to start the abortable part of an asynchronous
12990 The task is waiting on a select statement with only a delay
12993 @item Child Termination Wait
12994 The task is sleeping having completed a master within itself, and is
12995 waiting for the tasks dependent on that master to become terminated or
12996 waiting on a terminate Phase.
12998 @item Wait Child in Term Alt
12999 The task is sleeping waiting for tasks on terminate alternatives to
13000 finish terminating.
13002 @item Accepting RV with @var{taskno}
13003 The task is accepting a rendez-vous with the task @var{taskno}.
13007 Name of the task in the program.
13011 @kindex info task @var{taskno}
13012 @item info task @var{taskno}
13013 This command shows detailled informations on the specified task, as in
13014 the following example:
13019 (@value{GDBP}) info tasks
13020 ID TID P-ID Pri State Name
13021 1 8077880 0 15 Child Activation Wait main_task
13022 * 2 807c468 1 15 Runnable task_1
13023 (@value{GDBP}) info task 2
13024 Ada Task: 0x807c468
13027 Parent: 1 (main_task)
13033 @kindex task@r{ (Ada)}
13034 @cindex current Ada task ID
13035 This command prints the ID of the current task.
13041 (@value{GDBP}) info tasks
13042 ID TID P-ID Pri State Name
13043 1 8077870 0 15 Child Activation Wait main_task
13044 * 2 807c458 1 15 Runnable t
13045 (@value{GDBP}) task
13046 [Current task is 2]
13049 @item task @var{taskno}
13050 @cindex Ada task switching
13051 This command is like the @code{thread @var{threadno}}
13052 command (@pxref{Threads}). It switches the context of debugging
13053 from the current task to the given task.
13059 (@value{GDBP}) info tasks
13060 ID TID P-ID Pri State Name
13061 1 8077870 0 15 Child Activation Wait main_task
13062 * 2 807c458 1 15 Runnable t
13063 (@value{GDBP}) task 1
13064 [Switching to task 1]
13065 #0 0x8067726 in pthread_cond_wait ()
13067 #0 0x8067726 in pthread_cond_wait ()
13068 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
13069 #2 0x805cb63 in system.task_primitives.operations.sleep ()
13070 #3 0x806153e in system.tasking.stages.activate_tasks ()
13071 #4 0x804aacc in un () at un.adb:5
13074 @item break @var{linespec} task @var{taskno}
13075 @itemx break @var{linespec} task @var{taskno} if @dots{}
13076 @cindex breakpoints and tasks, in Ada
13077 @cindex task breakpoints, in Ada
13078 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
13079 These commands are like the @code{break @dots{} thread @dots{}}
13080 command (@pxref{Thread Stops}).
13081 @var{linespec} specifies source lines, as described
13082 in @ref{Specify Location}.
13084 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
13085 to specify that you only want @value{GDBN} to stop the program when a
13086 particular Ada task reaches this breakpoint. @var{taskno} is one of the
13087 numeric task identifiers assigned by @value{GDBN}, shown in the first
13088 column of the @samp{info tasks} display.
13090 If you do not specify @samp{task @var{taskno}} when you set a
13091 breakpoint, the breakpoint applies to @emph{all} tasks of your
13094 You can use the @code{task} qualifier on conditional breakpoints as
13095 well; in this case, place @samp{task @var{taskno}} before the
13096 breakpoint condition (before the @code{if}).
13104 (@value{GDBP}) info tasks
13105 ID TID P-ID Pri State Name
13106 1 140022020 0 15 Child Activation Wait main_task
13107 2 140045060 1 15 Accept/Select Wait t2
13108 3 140044840 1 15 Runnable t1
13109 * 4 140056040 1 15 Runnable t3
13110 (@value{GDBP}) b 15 task 2
13111 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
13112 (@value{GDBP}) cont
13117 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
13119 (@value{GDBP}) info tasks
13120 ID TID P-ID Pri State Name
13121 1 140022020 0 15 Child Activation Wait main_task
13122 * 2 140045060 1 15 Runnable t2
13123 3 140044840 1 15 Runnable t1
13124 4 140056040 1 15 Delay Sleep t3
13128 @node Ada Tasks and Core Files
13129 @subsubsection Tasking Support when Debugging Core Files
13130 @cindex Ada tasking and core file debugging
13132 When inspecting a core file, as opposed to debugging a live program,
13133 tasking support may be limited or even unavailable, depending on
13134 the platform being used.
13135 For instance, on x86-linux, the list of tasks is available, but task
13136 switching is not supported. On Tru64, however, task switching will work
13139 On certain platforms, including Tru64, the debugger needs to perform some
13140 memory writes in order to provide Ada tasking support. When inspecting
13141 a core file, this means that the core file must be opened with read-write
13142 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
13143 Under these circumstances, you should make a backup copy of the core
13144 file before inspecting it with @value{GDBN}.
13147 @subsubsection Known Peculiarities of Ada Mode
13148 @cindex Ada, problems
13150 Besides the omissions listed previously (@pxref{Omissions from Ada}),
13151 we know of several problems with and limitations of Ada mode in
13153 some of which will be fixed with planned future releases of the debugger
13154 and the GNU Ada compiler.
13158 Currently, the debugger
13159 has insufficient information to determine whether certain pointers represent
13160 pointers to objects or the objects themselves.
13161 Thus, the user may have to tack an extra @code{.all} after an expression
13162 to get it printed properly.
13165 Static constants that the compiler chooses not to materialize as objects in
13166 storage are invisible to the debugger.
13169 Named parameter associations in function argument lists are ignored (the
13170 argument lists are treated as positional).
13173 Many useful library packages are currently invisible to the debugger.
13176 Fixed-point arithmetic, conversions, input, and output is carried out using
13177 floating-point arithmetic, and may give results that only approximate those on
13181 The GNAT compiler never generates the prefix @code{Standard} for any of
13182 the standard symbols defined by the Ada language. @value{GDBN} knows about
13183 this: it will strip the prefix from names when you use it, and will never
13184 look for a name you have so qualified among local symbols, nor match against
13185 symbols in other packages or subprograms. If you have
13186 defined entities anywhere in your program other than parameters and
13187 local variables whose simple names match names in @code{Standard},
13188 GNAT's lack of qualification here can cause confusion. When this happens,
13189 you can usually resolve the confusion
13190 by qualifying the problematic names with package
13191 @code{Standard} explicitly.
13194 Older versions of the compiler sometimes generate erroneous debugging
13195 information, resulting in the debugger incorrectly printing the value
13196 of affected entities. In some cases, the debugger is able to work
13197 around an issue automatically. In other cases, the debugger is able
13198 to work around the issue, but the work-around has to be specifically
13201 @kindex set ada trust-PAD-over-XVS
13202 @kindex show ada trust-PAD-over-XVS
13205 @item set ada trust-PAD-over-XVS on
13206 Configure GDB to strictly follow the GNAT encoding when computing the
13207 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
13208 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
13209 a complete description of the encoding used by the GNAT compiler).
13210 This is the default.
13212 @item set ada trust-PAD-over-XVS off
13213 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
13214 sometimes prints the wrong value for certain entities, changing @code{ada
13215 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
13216 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
13217 @code{off}, but this incurs a slight performance penalty, so it is
13218 recommended to leave this setting to @code{on} unless necessary.
13222 @node Unsupported Languages
13223 @section Unsupported Languages
13225 @cindex unsupported languages
13226 @cindex minimal language
13227 In addition to the other fully-supported programming languages,
13228 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
13229 It does not represent a real programming language, but provides a set
13230 of capabilities close to what the C or assembly languages provide.
13231 This should allow most simple operations to be performed while debugging
13232 an application that uses a language currently not supported by @value{GDBN}.
13234 If the language is set to @code{auto}, @value{GDBN} will automatically
13235 select this language if the current frame corresponds to an unsupported
13239 @chapter Examining the Symbol Table
13241 The commands described in this chapter allow you to inquire about the
13242 symbols (names of variables, functions and types) defined in your
13243 program. This information is inherent in the text of your program and
13244 does not change as your program executes. @value{GDBN} finds it in your
13245 program's symbol table, in the file indicated when you started @value{GDBN}
13246 (@pxref{File Options, ,Choosing Files}), or by one of the
13247 file-management commands (@pxref{Files, ,Commands to Specify Files}).
13249 @cindex symbol names
13250 @cindex names of symbols
13251 @cindex quoting names
13252 Occasionally, you may need to refer to symbols that contain unusual
13253 characters, which @value{GDBN} ordinarily treats as word delimiters. The
13254 most frequent case is in referring to static variables in other
13255 source files (@pxref{Variables,,Program Variables}). File names
13256 are recorded in object files as debugging symbols, but @value{GDBN} would
13257 ordinarily parse a typical file name, like @file{foo.c}, as the three words
13258 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
13259 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
13266 looks up the value of @code{x} in the scope of the file @file{foo.c}.
13269 @cindex case-insensitive symbol names
13270 @cindex case sensitivity in symbol names
13271 @kindex set case-sensitive
13272 @item set case-sensitive on
13273 @itemx set case-sensitive off
13274 @itemx set case-sensitive auto
13275 Normally, when @value{GDBN} looks up symbols, it matches their names
13276 with case sensitivity determined by the current source language.
13277 Occasionally, you may wish to control that. The command @code{set
13278 case-sensitive} lets you do that by specifying @code{on} for
13279 case-sensitive matches or @code{off} for case-insensitive ones. If
13280 you specify @code{auto}, case sensitivity is reset to the default
13281 suitable for the source language. The default is case-sensitive
13282 matches for all languages except for Fortran, for which the default is
13283 case-insensitive matches.
13285 @kindex show case-sensitive
13286 @item show case-sensitive
13287 This command shows the current setting of case sensitivity for symbols
13290 @kindex info address
13291 @cindex address of a symbol
13292 @item info address @var{symbol}
13293 Describe where the data for @var{symbol} is stored. For a register
13294 variable, this says which register it is kept in. For a non-register
13295 local variable, this prints the stack-frame offset at which the variable
13298 Note the contrast with @samp{print &@var{symbol}}, which does not work
13299 at all for a register variable, and for a stack local variable prints
13300 the exact address of the current instantiation of the variable.
13302 @kindex info symbol
13303 @cindex symbol from address
13304 @cindex closest symbol and offset for an address
13305 @item info symbol @var{addr}
13306 Print the name of a symbol which is stored at the address @var{addr}.
13307 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
13308 nearest symbol and an offset from it:
13311 (@value{GDBP}) info symbol 0x54320
13312 _initialize_vx + 396 in section .text
13316 This is the opposite of the @code{info address} command. You can use
13317 it to find out the name of a variable or a function given its address.
13319 For dynamically linked executables, the name of executable or shared
13320 library containing the symbol is also printed:
13323 (@value{GDBP}) info symbol 0x400225
13324 _start + 5 in section .text of /tmp/a.out
13325 (@value{GDBP}) info symbol 0x2aaaac2811cf
13326 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
13330 @item whatis [@var{arg}]
13331 Print the data type of @var{arg}, which can be either an expression or
13332 a data type. With no argument, print the data type of @code{$}, the
13333 last value in the value history. If @var{arg} is an expression, it is
13334 not actually evaluated, and any side-effecting operations (such as
13335 assignments or function calls) inside it do not take place. If
13336 @var{arg} is a type name, it may be the name of a type or typedef, or
13337 for C code it may have the form @samp{class @var{class-name}},
13338 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
13339 @samp{enum @var{enum-tag}}.
13340 @xref{Expressions, ,Expressions}.
13343 @item ptype [@var{arg}]
13344 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
13345 detailed description of the type, instead of just the name of the type.
13346 @xref{Expressions, ,Expressions}.
13348 For example, for this variable declaration:
13351 struct complex @{double real; double imag;@} v;
13355 the two commands give this output:
13359 (@value{GDBP}) whatis v
13360 type = struct complex
13361 (@value{GDBP}) ptype v
13362 type = struct complex @{
13370 As with @code{whatis}, using @code{ptype} without an argument refers to
13371 the type of @code{$}, the last value in the value history.
13373 @cindex incomplete type
13374 Sometimes, programs use opaque data types or incomplete specifications
13375 of complex data structure. If the debug information included in the
13376 program does not allow @value{GDBN} to display a full declaration of
13377 the data type, it will say @samp{<incomplete type>}. For example,
13378 given these declarations:
13382 struct foo *fooptr;
13386 but no definition for @code{struct foo} itself, @value{GDBN} will say:
13389 (@value{GDBP}) ptype foo
13390 $1 = <incomplete type>
13394 ``Incomplete type'' is C terminology for data types that are not
13395 completely specified.
13398 @item info types @var{regexp}
13400 Print a brief description of all types whose names match the regular
13401 expression @var{regexp} (or all types in your program, if you supply
13402 no argument). Each complete typename is matched as though it were a
13403 complete line; thus, @samp{i type value} gives information on all
13404 types in your program whose names include the string @code{value}, but
13405 @samp{i type ^value$} gives information only on types whose complete
13406 name is @code{value}.
13408 This command differs from @code{ptype} in two ways: first, like
13409 @code{whatis}, it does not print a detailed description; second, it
13410 lists all source files where a type is defined.
13413 @cindex local variables
13414 @item info scope @var{location}
13415 List all the variables local to a particular scope. This command
13416 accepts a @var{location} argument---a function name, a source line, or
13417 an address preceded by a @samp{*}, and prints all the variables local
13418 to the scope defined by that location. (@xref{Specify Location}, for
13419 details about supported forms of @var{location}.) For example:
13422 (@value{GDBP}) @b{info scope command_line_handler}
13423 Scope for command_line_handler:
13424 Symbol rl is an argument at stack/frame offset 8, length 4.
13425 Symbol linebuffer is in static storage at address 0x150a18, length 4.
13426 Symbol linelength is in static storage at address 0x150a1c, length 4.
13427 Symbol p is a local variable in register $esi, length 4.
13428 Symbol p1 is a local variable in register $ebx, length 4.
13429 Symbol nline is a local variable in register $edx, length 4.
13430 Symbol repeat is a local variable at frame offset -8, length 4.
13434 This command is especially useful for determining what data to collect
13435 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
13438 @kindex info source
13440 Show information about the current source file---that is, the source file for
13441 the function containing the current point of execution:
13444 the name of the source file, and the directory containing it,
13446 the directory it was compiled in,
13448 its length, in lines,
13450 which programming language it is written in,
13452 whether the executable includes debugging information for that file, and
13453 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
13455 whether the debugging information includes information about
13456 preprocessor macros.
13460 @kindex info sources
13462 Print the names of all source files in your program for which there is
13463 debugging information, organized into two lists: files whose symbols
13464 have already been read, and files whose symbols will be read when needed.
13466 @kindex info functions
13467 @item info functions
13468 Print the names and data types of all defined functions.
13470 @item info functions @var{regexp}
13471 Print the names and data types of all defined functions
13472 whose names contain a match for regular expression @var{regexp}.
13473 Thus, @samp{info fun step} finds all functions whose names
13474 include @code{step}; @samp{info fun ^step} finds those whose names
13475 start with @code{step}. If a function name contains characters
13476 that conflict with the regular expression language (e.g.@:
13477 @samp{operator*()}), they may be quoted with a backslash.
13479 @kindex info variables
13480 @item info variables
13481 Print the names and data types of all variables that are defined
13482 outside of functions (i.e.@: excluding local variables).
13484 @item info variables @var{regexp}
13485 Print the names and data types of all variables (except for local
13486 variables) whose names contain a match for regular expression
13489 @kindex info classes
13490 @cindex Objective-C, classes and selectors
13492 @itemx info classes @var{regexp}
13493 Display all Objective-C classes in your program, or
13494 (with the @var{regexp} argument) all those matching a particular regular
13497 @kindex info selectors
13498 @item info selectors
13499 @itemx info selectors @var{regexp}
13500 Display all Objective-C selectors in your program, or
13501 (with the @var{regexp} argument) all those matching a particular regular
13505 This was never implemented.
13506 @kindex info methods
13508 @itemx info methods @var{regexp}
13509 The @code{info methods} command permits the user to examine all defined
13510 methods within C@t{++} program, or (with the @var{regexp} argument) a
13511 specific set of methods found in the various C@t{++} classes. Many
13512 C@t{++} classes provide a large number of methods. Thus, the output
13513 from the @code{ptype} command can be overwhelming and hard to use. The
13514 @code{info-methods} command filters the methods, printing only those
13515 which match the regular-expression @var{regexp}.
13518 @cindex reloading symbols
13519 Some systems allow individual object files that make up your program to
13520 be replaced without stopping and restarting your program. For example,
13521 in VxWorks you can simply recompile a defective object file and keep on
13522 running. If you are running on one of these systems, you can allow
13523 @value{GDBN} to reload the symbols for automatically relinked modules:
13526 @kindex set symbol-reloading
13527 @item set symbol-reloading on
13528 Replace symbol definitions for the corresponding source file when an
13529 object file with a particular name is seen again.
13531 @item set symbol-reloading off
13532 Do not replace symbol definitions when encountering object files of the
13533 same name more than once. This is the default state; if you are not
13534 running on a system that permits automatic relinking of modules, you
13535 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
13536 may discard symbols when linking large programs, that may contain
13537 several modules (from different directories or libraries) with the same
13540 @kindex show symbol-reloading
13541 @item show symbol-reloading
13542 Show the current @code{on} or @code{off} setting.
13545 @cindex opaque data types
13546 @kindex set opaque-type-resolution
13547 @item set opaque-type-resolution on
13548 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
13549 declared as a pointer to a @code{struct}, @code{class}, or
13550 @code{union}---for example, @code{struct MyType *}---that is used in one
13551 source file although the full declaration of @code{struct MyType} is in
13552 another source file. The default is on.
13554 A change in the setting of this subcommand will not take effect until
13555 the next time symbols for a file are loaded.
13557 @item set opaque-type-resolution off
13558 Tell @value{GDBN} not to resolve opaque types. In this case, the type
13559 is printed as follows:
13561 @{<no data fields>@}
13564 @kindex show opaque-type-resolution
13565 @item show opaque-type-resolution
13566 Show whether opaque types are resolved or not.
13568 @kindex maint print symbols
13569 @cindex symbol dump
13570 @kindex maint print psymbols
13571 @cindex partial symbol dump
13572 @item maint print symbols @var{filename}
13573 @itemx maint print psymbols @var{filename}
13574 @itemx maint print msymbols @var{filename}
13575 Write a dump of debugging symbol data into the file @var{filename}.
13576 These commands are used to debug the @value{GDBN} symbol-reading code. Only
13577 symbols with debugging data are included. If you use @samp{maint print
13578 symbols}, @value{GDBN} includes all the symbols for which it has already
13579 collected full details: that is, @var{filename} reflects symbols for
13580 only those files whose symbols @value{GDBN} has read. You can use the
13581 command @code{info sources} to find out which files these are. If you
13582 use @samp{maint print psymbols} instead, the dump shows information about
13583 symbols that @value{GDBN} only knows partially---that is, symbols defined in
13584 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
13585 @samp{maint print msymbols} dumps just the minimal symbol information
13586 required for each object file from which @value{GDBN} has read some symbols.
13587 @xref{Files, ,Commands to Specify Files}, for a discussion of how
13588 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
13590 @kindex maint info symtabs
13591 @kindex maint info psymtabs
13592 @cindex listing @value{GDBN}'s internal symbol tables
13593 @cindex symbol tables, listing @value{GDBN}'s internal
13594 @cindex full symbol tables, listing @value{GDBN}'s internal
13595 @cindex partial symbol tables, listing @value{GDBN}'s internal
13596 @item maint info symtabs @r{[} @var{regexp} @r{]}
13597 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
13599 List the @code{struct symtab} or @code{struct partial_symtab}
13600 structures whose names match @var{regexp}. If @var{regexp} is not
13601 given, list them all. The output includes expressions which you can
13602 copy into a @value{GDBN} debugging this one to examine a particular
13603 structure in more detail. For example:
13606 (@value{GDBP}) maint info psymtabs dwarf2read
13607 @{ objfile /home/gnu/build/gdb/gdb
13608 ((struct objfile *) 0x82e69d0)
13609 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
13610 ((struct partial_symtab *) 0x8474b10)
13613 text addresses 0x814d3c8 -- 0x8158074
13614 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
13615 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
13616 dependencies (none)
13619 (@value{GDBP}) maint info symtabs
13623 We see that there is one partial symbol table whose filename contains
13624 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
13625 and we see that @value{GDBN} has not read in any symtabs yet at all.
13626 If we set a breakpoint on a function, that will cause @value{GDBN} to
13627 read the symtab for the compilation unit containing that function:
13630 (@value{GDBP}) break dwarf2_psymtab_to_symtab
13631 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
13633 (@value{GDBP}) maint info symtabs
13634 @{ objfile /home/gnu/build/gdb/gdb
13635 ((struct objfile *) 0x82e69d0)
13636 @{ symtab /home/gnu/src/gdb/dwarf2read.c
13637 ((struct symtab *) 0x86c1f38)
13640 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
13641 linetable ((struct linetable *) 0x8370fa0)
13642 debugformat DWARF 2
13651 @chapter Altering Execution
13653 Once you think you have found an error in your program, you might want to
13654 find out for certain whether correcting the apparent error would lead to
13655 correct results in the rest of the run. You can find the answer by
13656 experiment, using the @value{GDBN} features for altering execution of the
13659 For example, you can store new values into variables or memory
13660 locations, give your program a signal, restart it at a different
13661 address, or even return prematurely from a function.
13664 * Assignment:: Assignment to variables
13665 * Jumping:: Continuing at a different address
13666 * Signaling:: Giving your program a signal
13667 * Returning:: Returning from a function
13668 * Calling:: Calling your program's functions
13669 * Patching:: Patching your program
13673 @section Assignment to Variables
13676 @cindex setting variables
13677 To alter the value of a variable, evaluate an assignment expression.
13678 @xref{Expressions, ,Expressions}. For example,
13685 stores the value 4 into the variable @code{x}, and then prints the
13686 value of the assignment expression (which is 4).
13687 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
13688 information on operators in supported languages.
13690 @kindex set variable
13691 @cindex variables, setting
13692 If you are not interested in seeing the value of the assignment, use the
13693 @code{set} command instead of the @code{print} command. @code{set} is
13694 really the same as @code{print} except that the expression's value is
13695 not printed and is not put in the value history (@pxref{Value History,
13696 ,Value History}). The expression is evaluated only for its effects.
13698 If the beginning of the argument string of the @code{set} command
13699 appears identical to a @code{set} subcommand, use the @code{set
13700 variable} command instead of just @code{set}. This command is identical
13701 to @code{set} except for its lack of subcommands. For example, if your
13702 program has a variable @code{width}, you get an error if you try to set
13703 a new value with just @samp{set width=13}, because @value{GDBN} has the
13704 command @code{set width}:
13707 (@value{GDBP}) whatis width
13709 (@value{GDBP}) p width
13711 (@value{GDBP}) set width=47
13712 Invalid syntax in expression.
13716 The invalid expression, of course, is @samp{=47}. In
13717 order to actually set the program's variable @code{width}, use
13720 (@value{GDBP}) set var width=47
13723 Because the @code{set} command has many subcommands that can conflict
13724 with the names of program variables, it is a good idea to use the
13725 @code{set variable} command instead of just @code{set}. For example, if
13726 your program has a variable @code{g}, you run into problems if you try
13727 to set a new value with just @samp{set g=4}, because @value{GDBN} has
13728 the command @code{set gnutarget}, abbreviated @code{set g}:
13732 (@value{GDBP}) whatis g
13736 (@value{GDBP}) set g=4
13740 The program being debugged has been started already.
13741 Start it from the beginning? (y or n) y
13742 Starting program: /home/smith/cc_progs/a.out
13743 "/home/smith/cc_progs/a.out": can't open to read symbols:
13744 Invalid bfd target.
13745 (@value{GDBP}) show g
13746 The current BFD target is "=4".
13751 The program variable @code{g} did not change, and you silently set the
13752 @code{gnutarget} to an invalid value. In order to set the variable
13756 (@value{GDBP}) set var g=4
13759 @value{GDBN} allows more implicit conversions in assignments than C; you can
13760 freely store an integer value into a pointer variable or vice versa,
13761 and you can convert any structure to any other structure that is the
13762 same length or shorter.
13763 @comment FIXME: how do structs align/pad in these conversions?
13764 @comment /doc@cygnus.com 18dec1990
13766 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
13767 construct to generate a value of specified type at a specified address
13768 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
13769 to memory location @code{0x83040} as an integer (which implies a certain size
13770 and representation in memory), and
13773 set @{int@}0x83040 = 4
13777 stores the value 4 into that memory location.
13780 @section Continuing at a Different Address
13782 Ordinarily, when you continue your program, you do so at the place where
13783 it stopped, with the @code{continue} command. You can instead continue at
13784 an address of your own choosing, with the following commands:
13788 @item jump @var{linespec}
13789 @itemx jump @var{location}
13790 Resume execution at line @var{linespec} or at address given by
13791 @var{location}. Execution stops again immediately if there is a
13792 breakpoint there. @xref{Specify Location}, for a description of the
13793 different forms of @var{linespec} and @var{location}. It is common
13794 practice to use the @code{tbreak} command in conjunction with
13795 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
13797 The @code{jump} command does not change the current stack frame, or
13798 the stack pointer, or the contents of any memory location or any
13799 register other than the program counter. If line @var{linespec} is in
13800 a different function from the one currently executing, the results may
13801 be bizarre if the two functions expect different patterns of arguments or
13802 of local variables. For this reason, the @code{jump} command requests
13803 confirmation if the specified line is not in the function currently
13804 executing. However, even bizarre results are predictable if you are
13805 well acquainted with the machine-language code of your program.
13808 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
13809 On many systems, you can get much the same effect as the @code{jump}
13810 command by storing a new value into the register @code{$pc}. The
13811 difference is that this does not start your program running; it only
13812 changes the address of where it @emph{will} run when you continue. For
13820 makes the next @code{continue} command or stepping command execute at
13821 address @code{0x485}, rather than at the address where your program stopped.
13822 @xref{Continuing and Stepping, ,Continuing and Stepping}.
13824 The most common occasion to use the @code{jump} command is to back
13825 up---perhaps with more breakpoints set---over a portion of a program
13826 that has already executed, in order to examine its execution in more
13831 @section Giving your Program a Signal
13832 @cindex deliver a signal to a program
13836 @item signal @var{signal}
13837 Resume execution where your program stopped, but immediately give it the
13838 signal @var{signal}. @var{signal} can be the name or the number of a
13839 signal. For example, on many systems @code{signal 2} and @code{signal
13840 SIGINT} are both ways of sending an interrupt signal.
13842 Alternatively, if @var{signal} is zero, continue execution without
13843 giving a signal. This is useful when your program stopped on account of
13844 a signal and would ordinary see the signal when resumed with the
13845 @code{continue} command; @samp{signal 0} causes it to resume without a
13848 @code{signal} does not repeat when you press @key{RET} a second time
13849 after executing the command.
13853 Invoking the @code{signal} command is not the same as invoking the
13854 @code{kill} utility from the shell. Sending a signal with @code{kill}
13855 causes @value{GDBN} to decide what to do with the signal depending on
13856 the signal handling tables (@pxref{Signals}). The @code{signal} command
13857 passes the signal directly to your program.
13861 @section Returning from a Function
13864 @cindex returning from a function
13867 @itemx return @var{expression}
13868 You can cancel execution of a function call with the @code{return}
13869 command. If you give an
13870 @var{expression} argument, its value is used as the function's return
13874 When you use @code{return}, @value{GDBN} discards the selected stack frame
13875 (and all frames within it). You can think of this as making the
13876 discarded frame return prematurely. If you wish to specify a value to
13877 be returned, give that value as the argument to @code{return}.
13879 This pops the selected stack frame (@pxref{Selection, ,Selecting a
13880 Frame}), and any other frames inside of it, leaving its caller as the
13881 innermost remaining frame. That frame becomes selected. The
13882 specified value is stored in the registers used for returning values
13885 The @code{return} command does not resume execution; it leaves the
13886 program stopped in the state that would exist if the function had just
13887 returned. In contrast, the @code{finish} command (@pxref{Continuing
13888 and Stepping, ,Continuing and Stepping}) resumes execution until the
13889 selected stack frame returns naturally.
13891 @value{GDBN} needs to know how the @var{expression} argument should be set for
13892 the inferior. The concrete registers assignment depends on the OS ABI and the
13893 type being returned by the selected stack frame. For example it is common for
13894 OS ABI to return floating point values in FPU registers while integer values in
13895 CPU registers. Still some ABIs return even floating point values in CPU
13896 registers. Larger integer widths (such as @code{long long int}) also have
13897 specific placement rules. @value{GDBN} already knows the OS ABI from its
13898 current target so it needs to find out also the type being returned to make the
13899 assignment into the right register(s).
13901 Normally, the selected stack frame has debug info. @value{GDBN} will always
13902 use the debug info instead of the implicit type of @var{expression} when the
13903 debug info is available. For example, if you type @kbd{return -1}, and the
13904 function in the current stack frame is declared to return a @code{long long
13905 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
13906 into a @code{long long int}:
13909 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
13911 (@value{GDBP}) return -1
13912 Make func return now? (y or n) y
13913 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
13914 43 printf ("result=%lld\n", func ());
13918 However, if the selected stack frame does not have a debug info, e.g., if the
13919 function was compiled without debug info, @value{GDBN} has to find out the type
13920 to return from user. Specifying a different type by mistake may set the value
13921 in different inferior registers than the caller code expects. For example,
13922 typing @kbd{return -1} with its implicit type @code{int} would set only a part
13923 of a @code{long long int} result for a debug info less function (on 32-bit
13924 architectures). Therefore the user is required to specify the return type by
13925 an appropriate cast explicitly:
13928 Breakpoint 2, 0x0040050b in func ()
13929 (@value{GDBP}) return -1
13930 Return value type not available for selected stack frame.
13931 Please use an explicit cast of the value to return.
13932 (@value{GDBP}) return (long long int) -1
13933 Make selected stack frame return now? (y or n) y
13934 #0 0x00400526 in main ()
13939 @section Calling Program Functions
13942 @cindex calling functions
13943 @cindex inferior functions, calling
13944 @item print @var{expr}
13945 Evaluate the expression @var{expr} and display the resulting value.
13946 @var{expr} may include calls to functions in the program being
13950 @item call @var{expr}
13951 Evaluate the expression @var{expr} without displaying @code{void}
13954 You can use this variant of the @code{print} command if you want to
13955 execute a function from your program that does not return anything
13956 (a.k.a.@: @dfn{a void function}), but without cluttering the output
13957 with @code{void} returned values that @value{GDBN} will otherwise
13958 print. If the result is not void, it is printed and saved in the
13962 It is possible for the function you call via the @code{print} or
13963 @code{call} command to generate a signal (e.g., if there's a bug in
13964 the function, or if you passed it incorrect arguments). What happens
13965 in that case is controlled by the @code{set unwindonsignal} command.
13967 Similarly, with a C@t{++} program it is possible for the function you
13968 call via the @code{print} or @code{call} command to generate an
13969 exception that is not handled due to the constraints of the dummy
13970 frame. In this case, any exception that is raised in the frame, but has
13971 an out-of-frame exception handler will not be found. GDB builds a
13972 dummy-frame for the inferior function call, and the unwinder cannot
13973 seek for exception handlers outside of this dummy-frame. What happens
13974 in that case is controlled by the
13975 @code{set unwind-on-terminating-exception} command.
13978 @item set unwindonsignal
13979 @kindex set unwindonsignal
13980 @cindex unwind stack in called functions
13981 @cindex call dummy stack unwinding
13982 Set unwinding of the stack if a signal is received while in a function
13983 that @value{GDBN} called in the program being debugged. If set to on,
13984 @value{GDBN} unwinds the stack it created for the call and restores
13985 the context to what it was before the call. If set to off (the
13986 default), @value{GDBN} stops in the frame where the signal was
13989 @item show unwindonsignal
13990 @kindex show unwindonsignal
13991 Show the current setting of stack unwinding in the functions called by
13994 @item set unwind-on-terminating-exception
13995 @kindex set unwind-on-terminating-exception
13996 @cindex unwind stack in called functions with unhandled exceptions
13997 @cindex call dummy stack unwinding on unhandled exception.
13998 Set unwinding of the stack if a C@t{++} exception is raised, but left
13999 unhandled while in a function that @value{GDBN} called in the program being
14000 debugged. If set to on (the default), @value{GDBN} unwinds the stack
14001 it created for the call and restores the context to what it was before
14002 the call. If set to off, @value{GDBN} the exception is delivered to
14003 the default C@t{++} exception handler and the inferior terminated.
14005 @item show unwind-on-terminating-exception
14006 @kindex show unwind-on-terminating-exception
14007 Show the current setting of stack unwinding in the functions called by
14012 @cindex weak alias functions
14013 Sometimes, a function you wish to call is actually a @dfn{weak alias}
14014 for another function. In such case, @value{GDBN} might not pick up
14015 the type information, including the types of the function arguments,
14016 which causes @value{GDBN} to call the inferior function incorrectly.
14017 As a result, the called function will function erroneously and may
14018 even crash. A solution to that is to use the name of the aliased
14022 @section Patching Programs
14024 @cindex patching binaries
14025 @cindex writing into executables
14026 @cindex writing into corefiles
14028 By default, @value{GDBN} opens the file containing your program's
14029 executable code (or the corefile) read-only. This prevents accidental
14030 alterations to machine code; but it also prevents you from intentionally
14031 patching your program's binary.
14033 If you'd like to be able to patch the binary, you can specify that
14034 explicitly with the @code{set write} command. For example, you might
14035 want to turn on internal debugging flags, or even to make emergency
14041 @itemx set write off
14042 If you specify @samp{set write on}, @value{GDBN} opens executable and
14043 core files for both reading and writing; if you specify @kbd{set write
14044 off} (the default), @value{GDBN} opens them read-only.
14046 If you have already loaded a file, you must load it again (using the
14047 @code{exec-file} or @code{core-file} command) after changing @code{set
14048 write}, for your new setting to take effect.
14052 Display whether executable files and core files are opened for writing
14053 as well as reading.
14057 @chapter @value{GDBN} Files
14059 @value{GDBN} needs to know the file name of the program to be debugged,
14060 both in order to read its symbol table and in order to start your
14061 program. To debug a core dump of a previous run, you must also tell
14062 @value{GDBN} the name of the core dump file.
14065 * Files:: Commands to specify files
14066 * Separate Debug Files:: Debugging information in separate files
14067 * Symbol Errors:: Errors reading symbol files
14068 * Data Files:: GDB data files
14072 @section Commands to Specify Files
14074 @cindex symbol table
14075 @cindex core dump file
14077 You may want to specify executable and core dump file names. The usual
14078 way to do this is at start-up time, using the arguments to
14079 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
14080 Out of @value{GDBN}}).
14082 Occasionally it is necessary to change to a different file during a
14083 @value{GDBN} session. Or you may run @value{GDBN} and forget to
14084 specify a file you want to use. Or you are debugging a remote target
14085 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
14086 Program}). In these situations the @value{GDBN} commands to specify
14087 new files are useful.
14090 @cindex executable file
14092 @item file @var{filename}
14093 Use @var{filename} as the program to be debugged. It is read for its
14094 symbols and for the contents of pure memory. It is also the program
14095 executed when you use the @code{run} command. If you do not specify a
14096 directory and the file is not found in the @value{GDBN} working directory,
14097 @value{GDBN} uses the environment variable @code{PATH} as a list of
14098 directories to search, just as the shell does when looking for a program
14099 to run. You can change the value of this variable, for both @value{GDBN}
14100 and your program, using the @code{path} command.
14102 @cindex unlinked object files
14103 @cindex patching object files
14104 You can load unlinked object @file{.o} files into @value{GDBN} using
14105 the @code{file} command. You will not be able to ``run'' an object
14106 file, but you can disassemble functions and inspect variables. Also,
14107 if the underlying BFD functionality supports it, you could use
14108 @kbd{gdb -write} to patch object files using this technique. Note
14109 that @value{GDBN} can neither interpret nor modify relocations in this
14110 case, so branches and some initialized variables will appear to go to
14111 the wrong place. But this feature is still handy from time to time.
14114 @code{file} with no argument makes @value{GDBN} discard any information it
14115 has on both executable file and the symbol table.
14118 @item exec-file @r{[} @var{filename} @r{]}
14119 Specify that the program to be run (but not the symbol table) is found
14120 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
14121 if necessary to locate your program. Omitting @var{filename} means to
14122 discard information on the executable file.
14124 @kindex symbol-file
14125 @item symbol-file @r{[} @var{filename} @r{]}
14126 Read symbol table information from file @var{filename}. @code{PATH} is
14127 searched when necessary. Use the @code{file} command to get both symbol
14128 table and program to run from the same file.
14130 @code{symbol-file} with no argument clears out @value{GDBN} information on your
14131 program's symbol table.
14133 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
14134 some breakpoints and auto-display expressions. This is because they may
14135 contain pointers to the internal data recording symbols and data types,
14136 which are part of the old symbol table data being discarded inside
14139 @code{symbol-file} does not repeat if you press @key{RET} again after
14142 When @value{GDBN} is configured for a particular environment, it
14143 understands debugging information in whatever format is the standard
14144 generated for that environment; you may use either a @sc{gnu} compiler, or
14145 other compilers that adhere to the local conventions.
14146 Best results are usually obtained from @sc{gnu} compilers; for example,
14147 using @code{@value{NGCC}} you can generate debugging information for
14150 For most kinds of object files, with the exception of old SVR3 systems
14151 using COFF, the @code{symbol-file} command does not normally read the
14152 symbol table in full right away. Instead, it scans the symbol table
14153 quickly to find which source files and which symbols are present. The
14154 details are read later, one source file at a time, as they are needed.
14156 The purpose of this two-stage reading strategy is to make @value{GDBN}
14157 start up faster. For the most part, it is invisible except for
14158 occasional pauses while the symbol table details for a particular source
14159 file are being read. (The @code{set verbose} command can turn these
14160 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
14161 Warnings and Messages}.)
14163 We have not implemented the two-stage strategy for COFF yet. When the
14164 symbol table is stored in COFF format, @code{symbol-file} reads the
14165 symbol table data in full right away. Note that ``stabs-in-COFF''
14166 still does the two-stage strategy, since the debug info is actually
14170 @cindex reading symbols immediately
14171 @cindex symbols, reading immediately
14172 @item symbol-file @r{[} -readnow @r{]} @var{filename}
14173 @itemx file @r{[} -readnow @r{]} @var{filename}
14174 You can override the @value{GDBN} two-stage strategy for reading symbol
14175 tables by using the @samp{-readnow} option with any of the commands that
14176 load symbol table information, if you want to be sure @value{GDBN} has the
14177 entire symbol table available.
14179 @c FIXME: for now no mention of directories, since this seems to be in
14180 @c flux. 13mar1992 status is that in theory GDB would look either in
14181 @c current dir or in same dir as myprog; but issues like competing
14182 @c GDB's, or clutter in system dirs, mean that in practice right now
14183 @c only current dir is used. FFish says maybe a special GDB hierarchy
14184 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
14188 @item core-file @r{[}@var{filename}@r{]}
14190 Specify the whereabouts of a core dump file to be used as the ``contents
14191 of memory''. Traditionally, core files contain only some parts of the
14192 address space of the process that generated them; @value{GDBN} can access the
14193 executable file itself for other parts.
14195 @code{core-file} with no argument specifies that no core file is
14198 Note that the core file is ignored when your program is actually running
14199 under @value{GDBN}. So, if you have been running your program and you
14200 wish to debug a core file instead, you must kill the subprocess in which
14201 the program is running. To do this, use the @code{kill} command
14202 (@pxref{Kill Process, ,Killing the Child Process}).
14204 @kindex add-symbol-file
14205 @cindex dynamic linking
14206 @item add-symbol-file @var{filename} @var{address}
14207 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
14208 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
14209 The @code{add-symbol-file} command reads additional symbol table
14210 information from the file @var{filename}. You would use this command
14211 when @var{filename} has been dynamically loaded (by some other means)
14212 into the program that is running. @var{address} should be the memory
14213 address at which the file has been loaded; @value{GDBN} cannot figure
14214 this out for itself. You can additionally specify an arbitrary number
14215 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
14216 section name and base address for that section. You can specify any
14217 @var{address} as an expression.
14219 The symbol table of the file @var{filename} is added to the symbol table
14220 originally read with the @code{symbol-file} command. You can use the
14221 @code{add-symbol-file} command any number of times; the new symbol data
14222 thus read keeps adding to the old. To discard all old symbol data
14223 instead, use the @code{symbol-file} command without any arguments.
14225 @cindex relocatable object files, reading symbols from
14226 @cindex object files, relocatable, reading symbols from
14227 @cindex reading symbols from relocatable object files
14228 @cindex symbols, reading from relocatable object files
14229 @cindex @file{.o} files, reading symbols from
14230 Although @var{filename} is typically a shared library file, an
14231 executable file, or some other object file which has been fully
14232 relocated for loading into a process, you can also load symbolic
14233 information from relocatable @file{.o} files, as long as:
14237 the file's symbolic information refers only to linker symbols defined in
14238 that file, not to symbols defined by other object files,
14240 every section the file's symbolic information refers to has actually
14241 been loaded into the inferior, as it appears in the file, and
14243 you can determine the address at which every section was loaded, and
14244 provide these to the @code{add-symbol-file} command.
14248 Some embedded operating systems, like Sun Chorus and VxWorks, can load
14249 relocatable files into an already running program; such systems
14250 typically make the requirements above easy to meet. However, it's
14251 important to recognize that many native systems use complex link
14252 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
14253 assembly, for example) that make the requirements difficult to meet. In
14254 general, one cannot assume that using @code{add-symbol-file} to read a
14255 relocatable object file's symbolic information will have the same effect
14256 as linking the relocatable object file into the program in the normal
14259 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
14261 @kindex add-symbol-file-from-memory
14262 @cindex @code{syscall DSO}
14263 @cindex load symbols from memory
14264 @item add-symbol-file-from-memory @var{address}
14265 Load symbols from the given @var{address} in a dynamically loaded
14266 object file whose image is mapped directly into the inferior's memory.
14267 For example, the Linux kernel maps a @code{syscall DSO} into each
14268 process's address space; this DSO provides kernel-specific code for
14269 some system calls. The argument can be any expression whose
14270 evaluation yields the address of the file's shared object file header.
14271 For this command to work, you must have used @code{symbol-file} or
14272 @code{exec-file} commands in advance.
14274 @kindex add-shared-symbol-files
14276 @item add-shared-symbol-files @var{library-file}
14277 @itemx assf @var{library-file}
14278 The @code{add-shared-symbol-files} command can currently be used only
14279 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
14280 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
14281 @value{GDBN} automatically looks for shared libraries, however if
14282 @value{GDBN} does not find yours, you can invoke
14283 @code{add-shared-symbol-files}. It takes one argument: the shared
14284 library's file name. @code{assf} is a shorthand alias for
14285 @code{add-shared-symbol-files}.
14288 @item section @var{section} @var{addr}
14289 The @code{section} command changes the base address of the named
14290 @var{section} of the exec file to @var{addr}. This can be used if the
14291 exec file does not contain section addresses, (such as in the
14292 @code{a.out} format), or when the addresses specified in the file
14293 itself are wrong. Each section must be changed separately. The
14294 @code{info files} command, described below, lists all the sections and
14298 @kindex info target
14301 @code{info files} and @code{info target} are synonymous; both print the
14302 current target (@pxref{Targets, ,Specifying a Debugging Target}),
14303 including the names of the executable and core dump files currently in
14304 use by @value{GDBN}, and the files from which symbols were loaded. The
14305 command @code{help target} lists all possible targets rather than
14308 @kindex maint info sections
14309 @item maint info sections
14310 Another command that can give you extra information about program sections
14311 is @code{maint info sections}. In addition to the section information
14312 displayed by @code{info files}, this command displays the flags and file
14313 offset of each section in the executable and core dump files. In addition,
14314 @code{maint info sections} provides the following command options (which
14315 may be arbitrarily combined):
14319 Display sections for all loaded object files, including shared libraries.
14320 @item @var{sections}
14321 Display info only for named @var{sections}.
14322 @item @var{section-flags}
14323 Display info only for sections for which @var{section-flags} are true.
14324 The section flags that @value{GDBN} currently knows about are:
14327 Section will have space allocated in the process when loaded.
14328 Set for all sections except those containing debug information.
14330 Section will be loaded from the file into the child process memory.
14331 Set for pre-initialized code and data, clear for @code{.bss} sections.
14333 Section needs to be relocated before loading.
14335 Section cannot be modified by the child process.
14337 Section contains executable code only.
14339 Section contains data only (no executable code).
14341 Section will reside in ROM.
14343 Section contains data for constructor/destructor lists.
14345 Section is not empty.
14347 An instruction to the linker to not output the section.
14348 @item COFF_SHARED_LIBRARY
14349 A notification to the linker that the section contains
14350 COFF shared library information.
14352 Section contains common symbols.
14355 @kindex set trust-readonly-sections
14356 @cindex read-only sections
14357 @item set trust-readonly-sections on
14358 Tell @value{GDBN} that readonly sections in your object file
14359 really are read-only (i.e.@: that their contents will not change).
14360 In that case, @value{GDBN} can fetch values from these sections
14361 out of the object file, rather than from the target program.
14362 For some targets (notably embedded ones), this can be a significant
14363 enhancement to debugging performance.
14365 The default is off.
14367 @item set trust-readonly-sections off
14368 Tell @value{GDBN} not to trust readonly sections. This means that
14369 the contents of the section might change while the program is running,
14370 and must therefore be fetched from the target when needed.
14372 @item show trust-readonly-sections
14373 Show the current setting of trusting readonly sections.
14376 All file-specifying commands allow both absolute and relative file names
14377 as arguments. @value{GDBN} always converts the file name to an absolute file
14378 name and remembers it that way.
14380 @cindex shared libraries
14381 @anchor{Shared Libraries}
14382 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
14383 and IBM RS/6000 AIX shared libraries.
14385 On MS-Windows @value{GDBN} must be linked with the Expat library to support
14386 shared libraries. @xref{Expat}.
14388 @value{GDBN} automatically loads symbol definitions from shared libraries
14389 when you use the @code{run} command, or when you examine a core file.
14390 (Before you issue the @code{run} command, @value{GDBN} does not understand
14391 references to a function in a shared library, however---unless you are
14392 debugging a core file).
14394 On HP-UX, if the program loads a library explicitly, @value{GDBN}
14395 automatically loads the symbols at the time of the @code{shl_load} call.
14397 @c FIXME: some @value{GDBN} release may permit some refs to undef
14398 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
14399 @c FIXME...lib; check this from time to time when updating manual
14401 There are times, however, when you may wish to not automatically load
14402 symbol definitions from shared libraries, such as when they are
14403 particularly large or there are many of them.
14405 To control the automatic loading of shared library symbols, use the
14409 @kindex set auto-solib-add
14410 @item set auto-solib-add @var{mode}
14411 If @var{mode} is @code{on}, symbols from all shared object libraries
14412 will be loaded automatically when the inferior begins execution, you
14413 attach to an independently started inferior, or when the dynamic linker
14414 informs @value{GDBN} that a new library has been loaded. If @var{mode}
14415 is @code{off}, symbols must be loaded manually, using the
14416 @code{sharedlibrary} command. The default value is @code{on}.
14418 @cindex memory used for symbol tables
14419 If your program uses lots of shared libraries with debug info that
14420 takes large amounts of memory, you can decrease the @value{GDBN}
14421 memory footprint by preventing it from automatically loading the
14422 symbols from shared libraries. To that end, type @kbd{set
14423 auto-solib-add off} before running the inferior, then load each
14424 library whose debug symbols you do need with @kbd{sharedlibrary
14425 @var{regexp}}, where @var{regexp} is a regular expression that matches
14426 the libraries whose symbols you want to be loaded.
14428 @kindex show auto-solib-add
14429 @item show auto-solib-add
14430 Display the current autoloading mode.
14433 @cindex load shared library
14434 To explicitly load shared library symbols, use the @code{sharedlibrary}
14438 @kindex info sharedlibrary
14440 @item info share @var{regex}
14441 @itemx info sharedlibrary @var{regex}
14442 Print the names of the shared libraries which are currently loaded
14443 that match @var{regex}. If @var{regex} is omitted then print
14444 all shared libraries that are loaded.
14446 @kindex sharedlibrary
14448 @item sharedlibrary @var{regex}
14449 @itemx share @var{regex}
14450 Load shared object library symbols for files matching a
14451 Unix regular expression.
14452 As with files loaded automatically, it only loads shared libraries
14453 required by your program for a core file or after typing @code{run}. If
14454 @var{regex} is omitted all shared libraries required by your program are
14457 @item nosharedlibrary
14458 @kindex nosharedlibrary
14459 @cindex unload symbols from shared libraries
14460 Unload all shared object library symbols. This discards all symbols
14461 that have been loaded from all shared libraries. Symbols from shared
14462 libraries that were loaded by explicit user requests are not
14466 Sometimes you may wish that @value{GDBN} stops and gives you control
14467 when any of shared library events happen. Use the @code{set
14468 stop-on-solib-events} command for this:
14471 @item set stop-on-solib-events
14472 @kindex set stop-on-solib-events
14473 This command controls whether @value{GDBN} should give you control
14474 when the dynamic linker notifies it about some shared library event.
14475 The most common event of interest is loading or unloading of a new
14478 @item show stop-on-solib-events
14479 @kindex show stop-on-solib-events
14480 Show whether @value{GDBN} stops and gives you control when shared
14481 library events happen.
14484 Shared libraries are also supported in many cross or remote debugging
14485 configurations. @value{GDBN} needs to have access to the target's libraries;
14486 this can be accomplished either by providing copies of the libraries
14487 on the host system, or by asking @value{GDBN} to automatically retrieve the
14488 libraries from the target. If copies of the target libraries are
14489 provided, they need to be the same as the target libraries, although the
14490 copies on the target can be stripped as long as the copies on the host are
14493 @cindex where to look for shared libraries
14494 For remote debugging, you need to tell @value{GDBN} where the target
14495 libraries are, so that it can load the correct copies---otherwise, it
14496 may try to load the host's libraries. @value{GDBN} has two variables
14497 to specify the search directories for target libraries.
14500 @cindex prefix for shared library file names
14501 @cindex system root, alternate
14502 @kindex set solib-absolute-prefix
14503 @kindex set sysroot
14504 @item set sysroot @var{path}
14505 Use @var{path} as the system root for the program being debugged. Any
14506 absolute shared library paths will be prefixed with @var{path}; many
14507 runtime loaders store the absolute paths to the shared library in the
14508 target program's memory. If you use @code{set sysroot} to find shared
14509 libraries, they need to be laid out in the same way that they are on
14510 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
14513 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
14514 retrieve the target libraries from the remote system. This is only
14515 supported when using a remote target that supports the @code{remote get}
14516 command (@pxref{File Transfer,,Sending files to a remote system}).
14517 The part of @var{path} following the initial @file{remote:}
14518 (if present) is used as system root prefix on the remote file system.
14519 @footnote{If you want to specify a local system root using a directory
14520 that happens to be named @file{remote:}, you need to use some equivalent
14521 variant of the name like @file{./remote:}.}
14523 For targets with an MS-DOS based filesystem, such as MS-Windows and
14524 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
14525 absolute file name with @var{path}. But first, on Unix hosts,
14526 @value{GDBN} converts all backslash directory separators into forward
14527 slashes, because the backslash is not a directory separator on Unix:
14530 c:\foo\bar.dll @result{} c:/foo/bar.dll
14533 Then, @value{GDBN} attempts prefixing the target file name with
14534 @var{path}, and looks for the resulting file name in the host file
14538 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
14541 If that does not find the shared library, @value{GDBN} tries removing
14542 the @samp{:} character from the drive spec, both for convenience, and,
14543 for the case of the host file system not supporting file names with
14547 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
14550 This makes it possible to have a system root that mirrors a target
14551 with more than one drive. E.g., you may want to setup your local
14552 copies of the target system shared libraries like so (note @samp{c} vs
14556 @file{/path/to/sysroot/c/sys/bin/foo.dll}
14557 @file{/path/to/sysroot/c/sys/bin/bar.dll}
14558 @file{/path/to/sysroot/z/sys/bin/bar.dll}
14562 and point the system root at @file{/path/to/sysroot}, so that
14563 @value{GDBN} can find the correct copies of both
14564 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
14566 If that still does not find the shared library, @value{GDBN} tries
14567 removing the whole drive spec from the target file name:
14570 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
14573 This last lookup makes it possible to not care about the drive name,
14574 if you don't want or need to.
14576 The @code{set solib-absolute-prefix} command is an alias for @code{set
14579 @cindex default system root
14580 @cindex @samp{--with-sysroot}
14581 You can set the default system root by using the configure-time
14582 @samp{--with-sysroot} option. If the system root is inside
14583 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
14584 @samp{--exec-prefix}), then the default system root will be updated
14585 automatically if the installed @value{GDBN} is moved to a new
14588 @kindex show sysroot
14590 Display the current shared library prefix.
14592 @kindex set solib-search-path
14593 @item set solib-search-path @var{path}
14594 If this variable is set, @var{path} is a colon-separated list of
14595 directories to search for shared libraries. @samp{solib-search-path}
14596 is used after @samp{sysroot} fails to locate the library, or if the
14597 path to the library is relative instead of absolute. If you want to
14598 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
14599 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
14600 finding your host's libraries. @samp{sysroot} is preferred; setting
14601 it to a nonexistent directory may interfere with automatic loading
14602 of shared library symbols.
14604 @kindex show solib-search-path
14605 @item show solib-search-path
14606 Display the current shared library search path.
14608 @cindex DOS file-name semantics of file names.
14609 @kindex set target-file-system-kind (unix|dos-based|auto)
14610 @kindex show target-file-system-kind
14611 @item set target-file-system-kind @var{kind}
14612 Set assumed file system kind for target reported file names.
14614 Shared library file names as reported by the target system may not
14615 make sense as is on the system @value{GDBN} is running on. For
14616 example, when remote debugging a target that has MS-DOS based file
14617 system semantics, from a Unix host, the target may be reporting to
14618 @value{GDBN} a list of loaded shared libraries with file names such as
14619 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
14620 drive letters, so the @samp{c:\} prefix is not normally understood as
14621 indicating an absolute file name, and neither is the backslash
14622 normally considered a directory separator character. In that case,
14623 the native file system would interpret this whole absolute file name
14624 as a relative file name with no directory components. This would make
14625 it impossible to point @value{GDBN} at a copy of the remote target's
14626 shared libraries on the host using @code{set sysroot}, and impractical
14627 with @code{set solib-search-path}. Setting
14628 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
14629 to interpret such file names similarly to how the target would, and to
14630 map them to file names valid on @value{GDBN}'s native file system
14631 semantics. The value of @var{kind} can be @code{"auto"}, in addition
14632 to one of the supported file system kinds. In that case, @value{GDBN}
14633 tries to determine the appropriate file system variant based on the
14634 current target's operating system (@pxref{ABI, ,Configuring the
14635 Current ABI}). The supported file system settings are:
14639 Instruct @value{GDBN} to assume the target file system is of Unix
14640 kind. Only file names starting the forward slash (@samp{/}) character
14641 are considered absolute, and the directory separator character is also
14645 Instruct @value{GDBN} to assume the target file system is DOS based.
14646 File names starting with either a forward slash, or a drive letter
14647 followed by a colon (e.g., @samp{c:}), are considered absolute, and
14648 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
14649 considered directory separators.
14652 Instruct @value{GDBN} to use the file system kind associated with the
14653 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
14654 This is the default.
14659 @node Separate Debug Files
14660 @section Debugging Information in Separate Files
14661 @cindex separate debugging information files
14662 @cindex debugging information in separate files
14663 @cindex @file{.debug} subdirectories
14664 @cindex debugging information directory, global
14665 @cindex global debugging information directory
14666 @cindex build ID, and separate debugging files
14667 @cindex @file{.build-id} directory
14669 @value{GDBN} allows you to put a program's debugging information in a
14670 file separate from the executable itself, in a way that allows
14671 @value{GDBN} to find and load the debugging information automatically.
14672 Since debugging information can be very large---sometimes larger
14673 than the executable code itself---some systems distribute debugging
14674 information for their executables in separate files, which users can
14675 install only when they need to debug a problem.
14677 @value{GDBN} supports two ways of specifying the separate debug info
14682 The executable contains a @dfn{debug link} that specifies the name of
14683 the separate debug info file. The separate debug file's name is
14684 usually @file{@var{executable}.debug}, where @var{executable} is the
14685 name of the corresponding executable file without leading directories
14686 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
14687 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
14688 checksum for the debug file, which @value{GDBN} uses to validate that
14689 the executable and the debug file came from the same build.
14692 The executable contains a @dfn{build ID}, a unique bit string that is
14693 also present in the corresponding debug info file. (This is supported
14694 only on some operating systems, notably those which use the ELF format
14695 for binary files and the @sc{gnu} Binutils.) For more details about
14696 this feature, see the description of the @option{--build-id}
14697 command-line option in @ref{Options, , Command Line Options, ld.info,
14698 The GNU Linker}. The debug info file's name is not specified
14699 explicitly by the build ID, but can be computed from the build ID, see
14703 Depending on the way the debug info file is specified, @value{GDBN}
14704 uses two different methods of looking for the debug file:
14708 For the ``debug link'' method, @value{GDBN} looks up the named file in
14709 the directory of the executable file, then in a subdirectory of that
14710 directory named @file{.debug}, and finally under the global debug
14711 directory, in a subdirectory whose name is identical to the leading
14712 directories of the executable's absolute file name.
14715 For the ``build ID'' method, @value{GDBN} looks in the
14716 @file{.build-id} subdirectory of the global debug directory for a file
14717 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
14718 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
14719 are the rest of the bit string. (Real build ID strings are 32 or more
14720 hex characters, not 10.)
14723 So, for example, suppose you ask @value{GDBN} to debug
14724 @file{/usr/bin/ls}, which has a debug link that specifies the
14725 file @file{ls.debug}, and a build ID whose value in hex is
14726 @code{abcdef1234}. If the global debug directory is
14727 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
14728 debug information files, in the indicated order:
14732 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
14734 @file{/usr/bin/ls.debug}
14736 @file{/usr/bin/.debug/ls.debug}
14738 @file{/usr/lib/debug/usr/bin/ls.debug}.
14741 You can set the global debugging info directory's name, and view the
14742 name @value{GDBN} is currently using.
14746 @kindex set debug-file-directory
14747 @item set debug-file-directory @var{directories}
14748 Set the directories which @value{GDBN} searches for separate debugging
14749 information files to @var{directory}. Multiple directory components can be set
14750 concatenating them by a directory separator.
14752 @kindex show debug-file-directory
14753 @item show debug-file-directory
14754 Show the directories @value{GDBN} searches for separate debugging
14759 @cindex @code{.gnu_debuglink} sections
14760 @cindex debug link sections
14761 A debug link is a special section of the executable file named
14762 @code{.gnu_debuglink}. The section must contain:
14766 A filename, with any leading directory components removed, followed by
14769 zero to three bytes of padding, as needed to reach the next four-byte
14770 boundary within the section, and
14772 a four-byte CRC checksum, stored in the same endianness used for the
14773 executable file itself. The checksum is computed on the debugging
14774 information file's full contents by the function given below, passing
14775 zero as the @var{crc} argument.
14778 Any executable file format can carry a debug link, as long as it can
14779 contain a section named @code{.gnu_debuglink} with the contents
14782 @cindex @code{.note.gnu.build-id} sections
14783 @cindex build ID sections
14784 The build ID is a special section in the executable file (and in other
14785 ELF binary files that @value{GDBN} may consider). This section is
14786 often named @code{.note.gnu.build-id}, but that name is not mandatory.
14787 It contains unique identification for the built files---the ID remains
14788 the same across multiple builds of the same build tree. The default
14789 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
14790 content for the build ID string. The same section with an identical
14791 value is present in the original built binary with symbols, in its
14792 stripped variant, and in the separate debugging information file.
14794 The debugging information file itself should be an ordinary
14795 executable, containing a full set of linker symbols, sections, and
14796 debugging information. The sections of the debugging information file
14797 should have the same names, addresses, and sizes as the original file,
14798 but they need not contain any data---much like a @code{.bss} section
14799 in an ordinary executable.
14801 The @sc{gnu} binary utilities (Binutils) package includes the
14802 @samp{objcopy} utility that can produce
14803 the separated executable / debugging information file pairs using the
14804 following commands:
14807 @kbd{objcopy --only-keep-debug foo foo.debug}
14812 These commands remove the debugging
14813 information from the executable file @file{foo} and place it in the file
14814 @file{foo.debug}. You can use the first, second or both methods to link the
14819 The debug link method needs the following additional command to also leave
14820 behind a debug link in @file{foo}:
14823 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
14826 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
14827 a version of the @code{strip} command such that the command @kbd{strip foo -f
14828 foo.debug} has the same functionality as the two @code{objcopy} commands and
14829 the @code{ln -s} command above, together.
14832 Build ID gets embedded into the main executable using @code{ld --build-id} or
14833 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
14834 compatibility fixes for debug files separation are present in @sc{gnu} binary
14835 utilities (Binutils) package since version 2.18.
14840 @cindex CRC algorithm definition
14841 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
14842 IEEE 802.3 using the polynomial:
14844 @c TexInfo requires naked braces for multi-digit exponents for Tex
14845 @c output, but this causes HTML output to barf. HTML has to be set using
14846 @c raw commands. So we end up having to specify this equation in 2
14851 <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>
14852 + <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
14858 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
14859 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
14863 The function is computed byte at a time, taking the least
14864 significant bit of each byte first. The initial pattern
14865 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
14866 the final result is inverted to ensure trailing zeros also affect the
14869 @emph{Note:} This is the same CRC polynomial as used in handling the
14870 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
14871 , @value{GDBN} Remote Serial Protocol}). However in the
14872 case of the Remote Serial Protocol, the CRC is computed @emph{most}
14873 significant bit first, and the result is not inverted, so trailing
14874 zeros have no effect on the CRC value.
14876 To complete the description, we show below the code of the function
14877 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
14878 initially supplied @code{crc} argument means that an initial call to
14879 this function passing in zero will start computing the CRC using
14882 @kindex gnu_debuglink_crc32
14885 gnu_debuglink_crc32 (unsigned long crc,
14886 unsigned char *buf, size_t len)
14888 static const unsigned long crc32_table[256] =
14890 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
14891 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
14892 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
14893 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
14894 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
14895 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
14896 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
14897 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
14898 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
14899 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
14900 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
14901 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
14902 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
14903 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
14904 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
14905 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
14906 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
14907 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
14908 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
14909 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
14910 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
14911 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
14912 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
14913 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
14914 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
14915 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
14916 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
14917 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
14918 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
14919 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
14920 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
14921 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
14922 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
14923 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
14924 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
14925 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
14926 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
14927 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
14928 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
14929 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
14930 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
14931 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
14932 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
14933 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
14934 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
14935 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
14936 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
14937 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
14938 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
14939 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
14940 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
14943 unsigned char *end;
14945 crc = ~crc & 0xffffffff;
14946 for (end = buf + len; buf < end; ++buf)
14947 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
14948 return ~crc & 0xffffffff;
14953 This computation does not apply to the ``build ID'' method.
14956 @node Symbol Errors
14957 @section Errors Reading Symbol Files
14959 While reading a symbol file, @value{GDBN} occasionally encounters problems,
14960 such as symbol types it does not recognize, or known bugs in compiler
14961 output. By default, @value{GDBN} does not notify you of such problems, since
14962 they are relatively common and primarily of interest to people
14963 debugging compilers. If you are interested in seeing information
14964 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
14965 only one message about each such type of problem, no matter how many
14966 times the problem occurs; or you can ask @value{GDBN} to print more messages,
14967 to see how many times the problems occur, with the @code{set
14968 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
14971 The messages currently printed, and their meanings, include:
14974 @item inner block not inside outer block in @var{symbol}
14976 The symbol information shows where symbol scopes begin and end
14977 (such as at the start of a function or a block of statements). This
14978 error indicates that an inner scope block is not fully contained
14979 in its outer scope blocks.
14981 @value{GDBN} circumvents the problem by treating the inner block as if it had
14982 the same scope as the outer block. In the error message, @var{symbol}
14983 may be shown as ``@code{(don't know)}'' if the outer block is not a
14986 @item block at @var{address} out of order
14988 The symbol information for symbol scope blocks should occur in
14989 order of increasing addresses. This error indicates that it does not
14992 @value{GDBN} does not circumvent this problem, and has trouble
14993 locating symbols in the source file whose symbols it is reading. (You
14994 can often determine what source file is affected by specifying
14995 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
14998 @item bad block start address patched
15000 The symbol information for a symbol scope block has a start address
15001 smaller than the address of the preceding source line. This is known
15002 to occur in the SunOS 4.1.1 (and earlier) C compiler.
15004 @value{GDBN} circumvents the problem by treating the symbol scope block as
15005 starting on the previous source line.
15007 @item bad string table offset in symbol @var{n}
15010 Symbol number @var{n} contains a pointer into the string table which is
15011 larger than the size of the string table.
15013 @value{GDBN} circumvents the problem by considering the symbol to have the
15014 name @code{foo}, which may cause other problems if many symbols end up
15017 @item unknown symbol type @code{0x@var{nn}}
15019 The symbol information contains new data types that @value{GDBN} does
15020 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
15021 uncomprehended information, in hexadecimal.
15023 @value{GDBN} circumvents the error by ignoring this symbol information.
15024 This usually allows you to debug your program, though certain symbols
15025 are not accessible. If you encounter such a problem and feel like
15026 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
15027 on @code{complain}, then go up to the function @code{read_dbx_symtab}
15028 and examine @code{*bufp} to see the symbol.
15030 @item stub type has NULL name
15032 @value{GDBN} could not find the full definition for a struct or class.
15034 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
15035 The symbol information for a C@t{++} member function is missing some
15036 information that recent versions of the compiler should have output for
15039 @item info mismatch between compiler and debugger
15041 @value{GDBN} could not parse a type specification output by the compiler.
15046 @section GDB Data Files
15048 @cindex prefix for data files
15049 @value{GDBN} will sometimes read an auxiliary data file. These files
15050 are kept in a directory known as the @dfn{data directory}.
15052 You can set the data directory's name, and view the name @value{GDBN}
15053 is currently using.
15056 @kindex set data-directory
15057 @item set data-directory @var{directory}
15058 Set the directory which @value{GDBN} searches for auxiliary data files
15059 to @var{directory}.
15061 @kindex show data-directory
15062 @item show data-directory
15063 Show the directory @value{GDBN} searches for auxiliary data files.
15066 @cindex default data directory
15067 @cindex @samp{--with-gdb-datadir}
15068 You can set the default data directory by using the configure-time
15069 @samp{--with-gdb-datadir} option. If the data directory is inside
15070 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15071 @samp{--exec-prefix}), then the default data directory will be updated
15072 automatically if the installed @value{GDBN} is moved to a new
15076 @chapter Specifying a Debugging Target
15078 @cindex debugging target
15079 A @dfn{target} is the execution environment occupied by your program.
15081 Often, @value{GDBN} runs in the same host environment as your program;
15082 in that case, the debugging target is specified as a side effect when
15083 you use the @code{file} or @code{core} commands. When you need more
15084 flexibility---for example, running @value{GDBN} on a physically separate
15085 host, or controlling a standalone system over a serial port or a
15086 realtime system over a TCP/IP connection---you can use the @code{target}
15087 command to specify one of the target types configured for @value{GDBN}
15088 (@pxref{Target Commands, ,Commands for Managing Targets}).
15090 @cindex target architecture
15091 It is possible to build @value{GDBN} for several different @dfn{target
15092 architectures}. When @value{GDBN} is built like that, you can choose
15093 one of the available architectures with the @kbd{set architecture}
15097 @kindex set architecture
15098 @kindex show architecture
15099 @item set architecture @var{arch}
15100 This command sets the current target architecture to @var{arch}. The
15101 value of @var{arch} can be @code{"auto"}, in addition to one of the
15102 supported architectures.
15104 @item show architecture
15105 Show the current target architecture.
15107 @item set processor
15109 @kindex set processor
15110 @kindex show processor
15111 These are alias commands for, respectively, @code{set architecture}
15112 and @code{show architecture}.
15116 * Active Targets:: Active targets
15117 * Target Commands:: Commands for managing targets
15118 * Byte Order:: Choosing target byte order
15121 @node Active Targets
15122 @section Active Targets
15124 @cindex stacking targets
15125 @cindex active targets
15126 @cindex multiple targets
15128 There are three classes of targets: processes, core files, and
15129 executable files. @value{GDBN} can work concurrently on up to three
15130 active targets, one in each class. This allows you to (for example)
15131 start a process and inspect its activity without abandoning your work on
15134 For example, if you execute @samp{gdb a.out}, then the executable file
15135 @code{a.out} is the only active target. If you designate a core file as
15136 well---presumably from a prior run that crashed and coredumped---then
15137 @value{GDBN} has two active targets and uses them in tandem, looking
15138 first in the corefile target, then in the executable file, to satisfy
15139 requests for memory addresses. (Typically, these two classes of target
15140 are complementary, since core files contain only a program's
15141 read-write memory---variables and so on---plus machine status, while
15142 executable files contain only the program text and initialized data.)
15144 When you type @code{run}, your executable file becomes an active process
15145 target as well. When a process target is active, all @value{GDBN}
15146 commands requesting memory addresses refer to that target; addresses in
15147 an active core file or executable file target are obscured while the
15148 process target is active.
15150 Use the @code{core-file} and @code{exec-file} commands to select a new
15151 core file or executable target (@pxref{Files, ,Commands to Specify
15152 Files}). To specify as a target a process that is already running, use
15153 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
15156 @node Target Commands
15157 @section Commands for Managing Targets
15160 @item target @var{type} @var{parameters}
15161 Connects the @value{GDBN} host environment to a target machine or
15162 process. A target is typically a protocol for talking to debugging
15163 facilities. You use the argument @var{type} to specify the type or
15164 protocol of the target machine.
15166 Further @var{parameters} are interpreted by the target protocol, but
15167 typically include things like device names or host names to connect
15168 with, process numbers, and baud rates.
15170 The @code{target} command does not repeat if you press @key{RET} again
15171 after executing the command.
15173 @kindex help target
15175 Displays the names of all targets available. To display targets
15176 currently selected, use either @code{info target} or @code{info files}
15177 (@pxref{Files, ,Commands to Specify Files}).
15179 @item help target @var{name}
15180 Describe a particular target, including any parameters necessary to
15183 @kindex set gnutarget
15184 @item set gnutarget @var{args}
15185 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
15186 knows whether it is reading an @dfn{executable},
15187 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
15188 with the @code{set gnutarget} command. Unlike most @code{target} commands,
15189 with @code{gnutarget} the @code{target} refers to a program, not a machine.
15192 @emph{Warning:} To specify a file format with @code{set gnutarget},
15193 you must know the actual BFD name.
15197 @xref{Files, , Commands to Specify Files}.
15199 @kindex show gnutarget
15200 @item show gnutarget
15201 Use the @code{show gnutarget} command to display what file format
15202 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
15203 @value{GDBN} will determine the file format for each file automatically,
15204 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
15207 @cindex common targets
15208 Here are some common targets (available, or not, depending on the GDB
15213 @item target exec @var{program}
15214 @cindex executable file target
15215 An executable file. @samp{target exec @var{program}} is the same as
15216 @samp{exec-file @var{program}}.
15218 @item target core @var{filename}
15219 @cindex core dump file target
15220 A core dump file. @samp{target core @var{filename}} is the same as
15221 @samp{core-file @var{filename}}.
15223 @item target remote @var{medium}
15224 @cindex remote target
15225 A remote system connected to @value{GDBN} via a serial line or network
15226 connection. This command tells @value{GDBN} to use its own remote
15227 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
15229 For example, if you have a board connected to @file{/dev/ttya} on the
15230 machine running @value{GDBN}, you could say:
15233 target remote /dev/ttya
15236 @code{target remote} supports the @code{load} command. This is only
15237 useful if you have some other way of getting the stub to the target
15238 system, and you can put it somewhere in memory where it won't get
15239 clobbered by the download.
15241 @item target sim @r{[}@var{simargs}@r{]} @dots{}
15242 @cindex built-in simulator target
15243 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
15251 works; however, you cannot assume that a specific memory map, device
15252 drivers, or even basic I/O is available, although some simulators do
15253 provide these. For info about any processor-specific simulator details,
15254 see the appropriate section in @ref{Embedded Processors, ,Embedded
15259 Some configurations may include these targets as well:
15263 @item target nrom @var{dev}
15264 @cindex NetROM ROM emulator target
15265 NetROM ROM emulator. This target only supports downloading.
15269 Different targets are available on different configurations of @value{GDBN};
15270 your configuration may have more or fewer targets.
15272 Many remote targets require you to download the executable's code once
15273 you've successfully established a connection. You may wish to control
15274 various aspects of this process.
15279 @kindex set hash@r{, for remote monitors}
15280 @cindex hash mark while downloading
15281 This command controls whether a hash mark @samp{#} is displayed while
15282 downloading a file to the remote monitor. If on, a hash mark is
15283 displayed after each S-record is successfully downloaded to the
15287 @kindex show hash@r{, for remote monitors}
15288 Show the current status of displaying the hash mark.
15290 @item set debug monitor
15291 @kindex set debug monitor
15292 @cindex display remote monitor communications
15293 Enable or disable display of communications messages between
15294 @value{GDBN} and the remote monitor.
15296 @item show debug monitor
15297 @kindex show debug monitor
15298 Show the current status of displaying communications between
15299 @value{GDBN} and the remote monitor.
15304 @kindex load @var{filename}
15305 @item load @var{filename}
15307 Depending on what remote debugging facilities are configured into
15308 @value{GDBN}, the @code{load} command may be available. Where it exists, it
15309 is meant to make @var{filename} (an executable) available for debugging
15310 on the remote system---by downloading, or dynamic linking, for example.
15311 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
15312 the @code{add-symbol-file} command.
15314 If your @value{GDBN} does not have a @code{load} command, attempting to
15315 execute it gets the error message ``@code{You can't do that when your
15316 target is @dots{}}''
15318 The file is loaded at whatever address is specified in the executable.
15319 For some object file formats, you can specify the load address when you
15320 link the program; for other formats, like a.out, the object file format
15321 specifies a fixed address.
15322 @c FIXME! This would be a good place for an xref to the GNU linker doc.
15324 Depending on the remote side capabilities, @value{GDBN} may be able to
15325 load programs into flash memory.
15327 @code{load} does not repeat if you press @key{RET} again after using it.
15331 @section Choosing Target Byte Order
15333 @cindex choosing target byte order
15334 @cindex target byte order
15336 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
15337 offer the ability to run either big-endian or little-endian byte
15338 orders. Usually the executable or symbol will include a bit to
15339 designate the endian-ness, and you will not need to worry about
15340 which to use. However, you may still find it useful to adjust
15341 @value{GDBN}'s idea of processor endian-ness manually.
15345 @item set endian big
15346 Instruct @value{GDBN} to assume the target is big-endian.
15348 @item set endian little
15349 Instruct @value{GDBN} to assume the target is little-endian.
15351 @item set endian auto
15352 Instruct @value{GDBN} to use the byte order associated with the
15356 Display @value{GDBN}'s current idea of the target byte order.
15360 Note that these commands merely adjust interpretation of symbolic
15361 data on the host, and that they have absolutely no effect on the
15365 @node Remote Debugging
15366 @chapter Debugging Remote Programs
15367 @cindex remote debugging
15369 If you are trying to debug a program running on a machine that cannot run
15370 @value{GDBN} in the usual way, it is often useful to use remote debugging.
15371 For example, you might use remote debugging on an operating system kernel,
15372 or on a small system which does not have a general purpose operating system
15373 powerful enough to run a full-featured debugger.
15375 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
15376 to make this work with particular debugging targets. In addition,
15377 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
15378 but not specific to any particular target system) which you can use if you
15379 write the remote stubs---the code that runs on the remote system to
15380 communicate with @value{GDBN}.
15382 Other remote targets may be available in your
15383 configuration of @value{GDBN}; use @code{help target} to list them.
15386 * Connecting:: Connecting to a remote target
15387 * File Transfer:: Sending files to a remote system
15388 * Server:: Using the gdbserver program
15389 * Remote Configuration:: Remote configuration
15390 * Remote Stub:: Implementing a remote stub
15394 @section Connecting to a Remote Target
15396 On the @value{GDBN} host machine, you will need an unstripped copy of
15397 your program, since @value{GDBN} needs symbol and debugging information.
15398 Start up @value{GDBN} as usual, using the name of the local copy of your
15399 program as the first argument.
15401 @cindex @code{target remote}
15402 @value{GDBN} can communicate with the target over a serial line, or
15403 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
15404 each case, @value{GDBN} uses the same protocol for debugging your
15405 program; only the medium carrying the debugging packets varies. The
15406 @code{target remote} command establishes a connection to the target.
15407 Its arguments indicate which medium to use:
15411 @item target remote @var{serial-device}
15412 @cindex serial line, @code{target remote}
15413 Use @var{serial-device} to communicate with the target. For example,
15414 to use a serial line connected to the device named @file{/dev/ttyb}:
15417 target remote /dev/ttyb
15420 If you're using a serial line, you may want to give @value{GDBN} the
15421 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
15422 (@pxref{Remote Configuration, set remotebaud}) before the
15423 @code{target} command.
15425 @item target remote @code{@var{host}:@var{port}}
15426 @itemx target remote @code{tcp:@var{host}:@var{port}}
15427 @cindex @acronym{TCP} port, @code{target remote}
15428 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
15429 The @var{host} may be either a host name or a numeric @acronym{IP}
15430 address; @var{port} must be a decimal number. The @var{host} could be
15431 the target machine itself, if it is directly connected to the net, or
15432 it might be a terminal server which in turn has a serial line to the
15435 For example, to connect to port 2828 on a terminal server named
15439 target remote manyfarms:2828
15442 If your remote target is actually running on the same machine as your
15443 debugger session (e.g.@: a simulator for your target running on the
15444 same host), you can omit the hostname. For example, to connect to
15445 port 1234 on your local machine:
15448 target remote :1234
15452 Note that the colon is still required here.
15454 @item target remote @code{udp:@var{host}:@var{port}}
15455 @cindex @acronym{UDP} port, @code{target remote}
15456 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
15457 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
15460 target remote udp:manyfarms:2828
15463 When using a @acronym{UDP} connection for remote debugging, you should
15464 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
15465 can silently drop packets on busy or unreliable networks, which will
15466 cause havoc with your debugging session.
15468 @item target remote | @var{command}
15469 @cindex pipe, @code{target remote} to
15470 Run @var{command} in the background and communicate with it using a
15471 pipe. The @var{command} is a shell command, to be parsed and expanded
15472 by the system's command shell, @code{/bin/sh}; it should expect remote
15473 protocol packets on its standard input, and send replies on its
15474 standard output. You could use this to run a stand-alone simulator
15475 that speaks the remote debugging protocol, to make net connections
15476 using programs like @code{ssh}, or for other similar tricks.
15478 If @var{command} closes its standard output (perhaps by exiting),
15479 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
15480 program has already exited, this will have no effect.)
15484 Once the connection has been established, you can use all the usual
15485 commands to examine and change data. The remote program is already
15486 running; you can use @kbd{step} and @kbd{continue}, and you do not
15487 need to use @kbd{run}.
15489 @cindex interrupting remote programs
15490 @cindex remote programs, interrupting
15491 Whenever @value{GDBN} is waiting for the remote program, if you type the
15492 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
15493 program. This may or may not succeed, depending in part on the hardware
15494 and the serial drivers the remote system uses. If you type the
15495 interrupt character once again, @value{GDBN} displays this prompt:
15498 Interrupted while waiting for the program.
15499 Give up (and stop debugging it)? (y or n)
15502 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
15503 (If you decide you want to try again later, you can use @samp{target
15504 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
15505 goes back to waiting.
15508 @kindex detach (remote)
15510 When you have finished debugging the remote program, you can use the
15511 @code{detach} command to release it from @value{GDBN} control.
15512 Detaching from the target normally resumes its execution, but the results
15513 will depend on your particular remote stub. After the @code{detach}
15514 command, @value{GDBN} is free to connect to another target.
15518 The @code{disconnect} command behaves like @code{detach}, except that
15519 the target is generally not resumed. It will wait for @value{GDBN}
15520 (this instance or another one) to connect and continue debugging. After
15521 the @code{disconnect} command, @value{GDBN} is again free to connect to
15524 @cindex send command to remote monitor
15525 @cindex extend @value{GDBN} for remote targets
15526 @cindex add new commands for external monitor
15528 @item monitor @var{cmd}
15529 This command allows you to send arbitrary commands directly to the
15530 remote monitor. Since @value{GDBN} doesn't care about the commands it
15531 sends like this, this command is the way to extend @value{GDBN}---you
15532 can add new commands that only the external monitor will understand
15536 @node File Transfer
15537 @section Sending files to a remote system
15538 @cindex remote target, file transfer
15539 @cindex file transfer
15540 @cindex sending files to remote systems
15542 Some remote targets offer the ability to transfer files over the same
15543 connection used to communicate with @value{GDBN}. This is convenient
15544 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
15545 running @code{gdbserver} over a network interface. For other targets,
15546 e.g.@: embedded devices with only a single serial port, this may be
15547 the only way to upload or download files.
15549 Not all remote targets support these commands.
15553 @item remote put @var{hostfile} @var{targetfile}
15554 Copy file @var{hostfile} from the host system (the machine running
15555 @value{GDBN}) to @var{targetfile} on the target system.
15558 @item remote get @var{targetfile} @var{hostfile}
15559 Copy file @var{targetfile} from the target system to @var{hostfile}
15560 on the host system.
15562 @kindex remote delete
15563 @item remote delete @var{targetfile}
15564 Delete @var{targetfile} from the target system.
15569 @section Using the @code{gdbserver} Program
15572 @cindex remote connection without stubs
15573 @code{gdbserver} is a control program for Unix-like systems, which
15574 allows you to connect your program with a remote @value{GDBN} via
15575 @code{target remote}---but without linking in the usual debugging stub.
15577 @code{gdbserver} is not a complete replacement for the debugging stubs,
15578 because it requires essentially the same operating-system facilities
15579 that @value{GDBN} itself does. In fact, a system that can run
15580 @code{gdbserver} to connect to a remote @value{GDBN} could also run
15581 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
15582 because it is a much smaller program than @value{GDBN} itself. It is
15583 also easier to port than all of @value{GDBN}, so you may be able to get
15584 started more quickly on a new system by using @code{gdbserver}.
15585 Finally, if you develop code for real-time systems, you may find that
15586 the tradeoffs involved in real-time operation make it more convenient to
15587 do as much development work as possible on another system, for example
15588 by cross-compiling. You can use @code{gdbserver} to make a similar
15589 choice for debugging.
15591 @value{GDBN} and @code{gdbserver} communicate via either a serial line
15592 or a TCP connection, using the standard @value{GDBN} remote serial
15596 @emph{Warning:} @code{gdbserver} does not have any built-in security.
15597 Do not run @code{gdbserver} connected to any public network; a
15598 @value{GDBN} connection to @code{gdbserver} provides access to the
15599 target system with the same privileges as the user running
15603 @subsection Running @code{gdbserver}
15604 @cindex arguments, to @code{gdbserver}
15606 Run @code{gdbserver} on the target system. You need a copy of the
15607 program you want to debug, including any libraries it requires.
15608 @code{gdbserver} does not need your program's symbol table, so you can
15609 strip the program if necessary to save space. @value{GDBN} on the host
15610 system does all the symbol handling.
15612 To use the server, you must tell it how to communicate with @value{GDBN};
15613 the name of your program; and the arguments for your program. The usual
15617 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
15620 @var{comm} is either a device name (to use a serial line) or a TCP
15621 hostname and portnumber. For example, to debug Emacs with the argument
15622 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
15626 target> gdbserver /dev/com1 emacs foo.txt
15629 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
15632 To use a TCP connection instead of a serial line:
15635 target> gdbserver host:2345 emacs foo.txt
15638 The only difference from the previous example is the first argument,
15639 specifying that you are communicating with the host @value{GDBN} via
15640 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
15641 expect a TCP connection from machine @samp{host} to local TCP port 2345.
15642 (Currently, the @samp{host} part is ignored.) You can choose any number
15643 you want for the port number as long as it does not conflict with any
15644 TCP ports already in use on the target system (for example, @code{23} is
15645 reserved for @code{telnet}).@footnote{If you choose a port number that
15646 conflicts with another service, @code{gdbserver} prints an error message
15647 and exits.} You must use the same port number with the host @value{GDBN}
15648 @code{target remote} command.
15650 @subsubsection Attaching to a Running Program
15652 On some targets, @code{gdbserver} can also attach to running programs.
15653 This is accomplished via the @code{--attach} argument. The syntax is:
15656 target> gdbserver --attach @var{comm} @var{pid}
15659 @var{pid} is the process ID of a currently running process. It isn't necessary
15660 to point @code{gdbserver} at a binary for the running process.
15663 @cindex attach to a program by name
15664 You can debug processes by name instead of process ID if your target has the
15665 @code{pidof} utility:
15668 target> gdbserver --attach @var{comm} `pidof @var{program}`
15671 In case more than one copy of @var{program} is running, or @var{program}
15672 has multiple threads, most versions of @code{pidof} support the
15673 @code{-s} option to only return the first process ID.
15675 @subsubsection Multi-Process Mode for @code{gdbserver}
15676 @cindex gdbserver, multiple processes
15677 @cindex multiple processes with gdbserver
15679 When you connect to @code{gdbserver} using @code{target remote},
15680 @code{gdbserver} debugs the specified program only once. When the
15681 program exits, or you detach from it, @value{GDBN} closes the connection
15682 and @code{gdbserver} exits.
15684 If you connect using @kbd{target extended-remote}, @code{gdbserver}
15685 enters multi-process mode. When the debugged program exits, or you
15686 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
15687 though no program is running. The @code{run} and @code{attach}
15688 commands instruct @code{gdbserver} to run or attach to a new program.
15689 The @code{run} command uses @code{set remote exec-file} (@pxref{set
15690 remote exec-file}) to select the program to run. Command line
15691 arguments are supported, except for wildcard expansion and I/O
15692 redirection (@pxref{Arguments}).
15694 To start @code{gdbserver} without supplying an initial command to run
15695 or process ID to attach, use the @option{--multi} command line option.
15696 Then you can connect using @kbd{target extended-remote} and start
15697 the program you want to debug.
15699 @code{gdbserver} does not automatically exit in multi-process mode.
15700 You can terminate it by using @code{monitor exit}
15701 (@pxref{Monitor Commands for gdbserver}).
15703 @subsubsection Other Command-Line Arguments for @code{gdbserver}
15705 The @option{--debug} option tells @code{gdbserver} to display extra
15706 status information about the debugging process. The
15707 @option{--remote-debug} option tells @code{gdbserver} to display
15708 remote protocol debug output. These options are intended for
15709 @code{gdbserver} development and for bug reports to the developers.
15711 The @option{--wrapper} option specifies a wrapper to launch programs
15712 for debugging. The option should be followed by the name of the
15713 wrapper, then any command-line arguments to pass to the wrapper, then
15714 @kbd{--} indicating the end of the wrapper arguments.
15716 @code{gdbserver} runs the specified wrapper program with a combined
15717 command line including the wrapper arguments, then the name of the
15718 program to debug, then any arguments to the program. The wrapper
15719 runs until it executes your program, and then @value{GDBN} gains control.
15721 You can use any program that eventually calls @code{execve} with
15722 its arguments as a wrapper. Several standard Unix utilities do
15723 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
15724 with @code{exec "$@@"} will also work.
15726 For example, you can use @code{env} to pass an environment variable to
15727 the debugged program, without setting the variable in @code{gdbserver}'s
15731 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
15734 @subsection Connecting to @code{gdbserver}
15736 Run @value{GDBN} on the host system.
15738 First make sure you have the necessary symbol files. Load symbols for
15739 your application using the @code{file} command before you connect. Use
15740 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
15741 was compiled with the correct sysroot using @code{--with-sysroot}).
15743 The symbol file and target libraries must exactly match the executable
15744 and libraries on the target, with one exception: the files on the host
15745 system should not be stripped, even if the files on the target system
15746 are. Mismatched or missing files will lead to confusing results
15747 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
15748 files may also prevent @code{gdbserver} from debugging multi-threaded
15751 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
15752 For TCP connections, you must start up @code{gdbserver} prior to using
15753 the @code{target remote} command. Otherwise you may get an error whose
15754 text depends on the host system, but which usually looks something like
15755 @samp{Connection refused}. Don't use the @code{load}
15756 command in @value{GDBN} when using @code{gdbserver}, since the program is
15757 already on the target.
15759 @subsection Monitor Commands for @code{gdbserver}
15760 @cindex monitor commands, for @code{gdbserver}
15761 @anchor{Monitor Commands for gdbserver}
15763 During a @value{GDBN} session using @code{gdbserver}, you can use the
15764 @code{monitor} command to send special requests to @code{gdbserver}.
15765 Here are the available commands.
15769 List the available monitor commands.
15771 @item monitor set debug 0
15772 @itemx monitor set debug 1
15773 Disable or enable general debugging messages.
15775 @item monitor set remote-debug 0
15776 @itemx monitor set remote-debug 1
15777 Disable or enable specific debugging messages associated with the remote
15778 protocol (@pxref{Remote Protocol}).
15780 @item monitor set libthread-db-search-path [PATH]
15781 @cindex gdbserver, search path for @code{libthread_db}
15782 When this command is issued, @var{path} is a colon-separated list of
15783 directories to search for @code{libthread_db} (@pxref{Threads,,set
15784 libthread-db-search-path}). If you omit @var{path},
15785 @samp{libthread-db-search-path} will be reset to an empty list.
15788 Tell gdbserver to exit immediately. This command should be followed by
15789 @code{disconnect} to close the debugging session. @code{gdbserver} will
15790 detach from any attached processes and kill any processes it created.
15791 Use @code{monitor exit} to terminate @code{gdbserver} at the end
15792 of a multi-process mode debug session.
15796 @subsection Tracepoints support in @code{gdbserver}
15797 @cindex tracepoints support in @code{gdbserver}
15799 On some targets, @code{gdbserver} supports tracepoints and fast
15802 For fast tracepoints to work, a special library called the
15803 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
15804 This library is built and distributed as an integral part of
15807 There are several ways to load the in-process agent in your program:
15810 @item Specifying it as dependency at link time
15812 You can link your program dynamically with the in-process agent
15813 library. On most systems, this is accomplished by adding
15814 @code{-linproctrace} to the link command.
15816 @item Using the system's preloading mechanisms
15818 You can force loading the in-process agent at startup time by using
15819 your system's support for preloading shared libraries. Many Unixes
15820 support the concept of preloading user defined libraries. In most
15821 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
15822 in the environment. See also the description of @code{gdbserver}'s
15823 @option{--wrapper} command line option.
15825 @item Using @value{GDBN} to force loading the agent at run time
15827 On some systems, you can force the inferior to load a shared library,
15828 by calling a dynamic loader function in the inferior that takes care
15829 of dynamically looking up and loading a shared library. On most Unix
15830 systems, the function is @code{dlopen}. You'll use the @code{call}
15831 command for that. For example:
15834 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
15837 Note that on most Unix systems, for the @code{dlopen} function to be
15838 available, the program needs to be linked with @code{-ldl}.
15841 On systems that have a userspace dynamic loader, like most Unix
15842 systems, when you connect to @code{gdbserver} using @code{target
15843 remote}, you'll find that the program is stopped at the dynamic
15844 loader's entry point, and no shared library has been loaded in the
15845 program's address space yet, including the in-process agent. In that
15846 case, before being able to use any of the fast tracepoints features,
15847 you need to let the loader run and load the shared libraries. The
15848 most simple way to do that is to run the program to the main
15849 procedure. E.g., if debugging a C or C@t{++} program, start
15850 @code{gdbserver} like so:
15853 $ gdbserver :9999 myprogram
15856 Start GDB and connect to @code{gdbserver} like so, and run to main:
15860 (@value{GDBP}) target remote myhost:9999
15861 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
15862 (@value{GDBP}) b main
15863 (@value{GDBP}) continue
15866 The in-process tracing agent library should now be loaded into the
15867 process; you can confirm it with the @code{info sharedlibrary}
15868 command, which will list @file{libinproctrace.so} as loaded in the
15869 process. You are now ready to install fast tracepoints and start
15872 @node Remote Configuration
15873 @section Remote Configuration
15876 @kindex show remote
15877 This section documents the configuration options available when
15878 debugging remote programs. For the options related to the File I/O
15879 extensions of the remote protocol, see @ref{system,
15880 system-call-allowed}.
15883 @item set remoteaddresssize @var{bits}
15884 @cindex address size for remote targets
15885 @cindex bits in remote address
15886 Set the maximum size of address in a memory packet to the specified
15887 number of bits. @value{GDBN} will mask off the address bits above
15888 that number, when it passes addresses to the remote target. The
15889 default value is the number of bits in the target's address.
15891 @item show remoteaddresssize
15892 Show the current value of remote address size in bits.
15894 @item set remotebaud @var{n}
15895 @cindex baud rate for remote targets
15896 Set the baud rate for the remote serial I/O to @var{n} baud. The
15897 value is used to set the speed of the serial port used for debugging
15900 @item show remotebaud
15901 Show the current speed of the remote connection.
15903 @item set remotebreak
15904 @cindex interrupt remote programs
15905 @cindex BREAK signal instead of Ctrl-C
15906 @anchor{set remotebreak}
15907 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
15908 when you type @kbd{Ctrl-c} to interrupt the program running
15909 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
15910 character instead. The default is off, since most remote systems
15911 expect to see @samp{Ctrl-C} as the interrupt signal.
15913 @item show remotebreak
15914 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
15915 interrupt the remote program.
15917 @item set remoteflow on
15918 @itemx set remoteflow off
15919 @kindex set remoteflow
15920 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
15921 on the serial port used to communicate to the remote target.
15923 @item show remoteflow
15924 @kindex show remoteflow
15925 Show the current setting of hardware flow control.
15927 @item set remotelogbase @var{base}
15928 Set the base (a.k.a.@: radix) of logging serial protocol
15929 communications to @var{base}. Supported values of @var{base} are:
15930 @code{ascii}, @code{octal}, and @code{hex}. The default is
15933 @item show remotelogbase
15934 Show the current setting of the radix for logging remote serial
15937 @item set remotelogfile @var{file}
15938 @cindex record serial communications on file
15939 Record remote serial communications on the named @var{file}. The
15940 default is not to record at all.
15942 @item show remotelogfile.
15943 Show the current setting of the file name on which to record the
15944 serial communications.
15946 @item set remotetimeout @var{num}
15947 @cindex timeout for serial communications
15948 @cindex remote timeout
15949 Set the timeout limit to wait for the remote target to respond to
15950 @var{num} seconds. The default is 2 seconds.
15952 @item show remotetimeout
15953 Show the current number of seconds to wait for the remote target
15956 @cindex limit hardware breakpoints and watchpoints
15957 @cindex remote target, limit break- and watchpoints
15958 @anchor{set remote hardware-watchpoint-limit}
15959 @anchor{set remote hardware-breakpoint-limit}
15960 @item set remote hardware-watchpoint-limit @var{limit}
15961 @itemx set remote hardware-breakpoint-limit @var{limit}
15962 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
15963 watchpoints. A limit of -1, the default, is treated as unlimited.
15965 @item set remote exec-file @var{filename}
15966 @itemx show remote exec-file
15967 @anchor{set remote exec-file}
15968 @cindex executable file, for remote target
15969 Select the file used for @code{run} with @code{target
15970 extended-remote}. This should be set to a filename valid on the
15971 target system. If it is not set, the target will use a default
15972 filename (e.g.@: the last program run).
15974 @item set remote interrupt-sequence
15975 @cindex interrupt remote programs
15976 @cindex select Ctrl-C, BREAK or BREAK-g
15977 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
15978 @samp{BREAK-g} as the
15979 sequence to the remote target in order to interrupt the execution.
15980 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
15981 is high level of serial line for some certain time.
15982 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
15983 It is @code{BREAK} signal followed by character @code{g}.
15985 @item show interrupt-sequence
15986 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
15987 is sent by @value{GDBN} to interrupt the remote program.
15988 @code{BREAK-g} is BREAK signal followed by @code{g} and
15989 also known as Magic SysRq g.
15991 @item set remote interrupt-on-connect
15992 @cindex send interrupt-sequence on start
15993 Specify whether interrupt-sequence is sent to remote target when
15994 @value{GDBN} connects to it. This is mostly needed when you debug
15995 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
15996 which is known as Magic SysRq g in order to connect @value{GDBN}.
15998 @item show interrupt-on-connect
15999 Show whether interrupt-sequence is sent
16000 to remote target when @value{GDBN} connects to it.
16004 @item set tcp auto-retry on
16005 @cindex auto-retry, for remote TCP target
16006 Enable auto-retry for remote TCP connections. This is useful if the remote
16007 debugging agent is launched in parallel with @value{GDBN}; there is a race
16008 condition because the agent may not become ready to accept the connection
16009 before @value{GDBN} attempts to connect. When auto-retry is
16010 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
16011 to establish the connection using the timeout specified by
16012 @code{set tcp connect-timeout}.
16014 @item set tcp auto-retry off
16015 Do not auto-retry failed TCP connections.
16017 @item show tcp auto-retry
16018 Show the current auto-retry setting.
16020 @item set tcp connect-timeout @var{seconds}
16021 @cindex connection timeout, for remote TCP target
16022 @cindex timeout, for remote target connection
16023 Set the timeout for establishing a TCP connection to the remote target to
16024 @var{seconds}. The timeout affects both polling to retry failed connections
16025 (enabled by @code{set tcp auto-retry on}) and waiting for connections
16026 that are merely slow to complete, and represents an approximate cumulative
16029 @item show tcp connect-timeout
16030 Show the current connection timeout setting.
16033 @cindex remote packets, enabling and disabling
16034 The @value{GDBN} remote protocol autodetects the packets supported by
16035 your debugging stub. If you need to override the autodetection, you
16036 can use these commands to enable or disable individual packets. Each
16037 packet can be set to @samp{on} (the remote target supports this
16038 packet), @samp{off} (the remote target does not support this packet),
16039 or @samp{auto} (detect remote target support for this packet). They
16040 all default to @samp{auto}. For more information about each packet,
16041 see @ref{Remote Protocol}.
16043 During normal use, you should not have to use any of these commands.
16044 If you do, that may be a bug in your remote debugging stub, or a bug
16045 in @value{GDBN}. You may want to report the problem to the
16046 @value{GDBN} developers.
16048 For each packet @var{name}, the command to enable or disable the
16049 packet is @code{set remote @var{name}-packet}. The available settings
16052 @multitable @columnfractions 0.28 0.32 0.25
16055 @tab Related Features
16057 @item @code{fetch-register}
16059 @tab @code{info registers}
16061 @item @code{set-register}
16065 @item @code{binary-download}
16067 @tab @code{load}, @code{set}
16069 @item @code{read-aux-vector}
16070 @tab @code{qXfer:auxv:read}
16071 @tab @code{info auxv}
16073 @item @code{symbol-lookup}
16074 @tab @code{qSymbol}
16075 @tab Detecting multiple threads
16077 @item @code{attach}
16078 @tab @code{vAttach}
16081 @item @code{verbose-resume}
16083 @tab Stepping or resuming multiple threads
16089 @item @code{software-breakpoint}
16093 @item @code{hardware-breakpoint}
16097 @item @code{write-watchpoint}
16101 @item @code{read-watchpoint}
16105 @item @code{access-watchpoint}
16109 @item @code{target-features}
16110 @tab @code{qXfer:features:read}
16111 @tab @code{set architecture}
16113 @item @code{library-info}
16114 @tab @code{qXfer:libraries:read}
16115 @tab @code{info sharedlibrary}
16117 @item @code{memory-map}
16118 @tab @code{qXfer:memory-map:read}
16119 @tab @code{info mem}
16121 @item @code{read-spu-object}
16122 @tab @code{qXfer:spu:read}
16123 @tab @code{info spu}
16125 @item @code{write-spu-object}
16126 @tab @code{qXfer:spu:write}
16127 @tab @code{info spu}
16129 @item @code{read-siginfo-object}
16130 @tab @code{qXfer:siginfo:read}
16131 @tab @code{print $_siginfo}
16133 @item @code{write-siginfo-object}
16134 @tab @code{qXfer:siginfo:write}
16135 @tab @code{set $_siginfo}
16137 @item @code{threads}
16138 @tab @code{qXfer:threads:read}
16139 @tab @code{info threads}
16141 @item @code{get-thread-local-@*storage-address}
16142 @tab @code{qGetTLSAddr}
16143 @tab Displaying @code{__thread} variables
16145 @item @code{get-thread-information-block-address}
16146 @tab @code{qGetTIBAddr}
16147 @tab Display MS-Windows Thread Information Block.
16149 @item @code{search-memory}
16150 @tab @code{qSearch:memory}
16153 @item @code{supported-packets}
16154 @tab @code{qSupported}
16155 @tab Remote communications parameters
16157 @item @code{pass-signals}
16158 @tab @code{QPassSignals}
16159 @tab @code{handle @var{signal}}
16161 @item @code{hostio-close-packet}
16162 @tab @code{vFile:close}
16163 @tab @code{remote get}, @code{remote put}
16165 @item @code{hostio-open-packet}
16166 @tab @code{vFile:open}
16167 @tab @code{remote get}, @code{remote put}
16169 @item @code{hostio-pread-packet}
16170 @tab @code{vFile:pread}
16171 @tab @code{remote get}, @code{remote put}
16173 @item @code{hostio-pwrite-packet}
16174 @tab @code{vFile:pwrite}
16175 @tab @code{remote get}, @code{remote put}
16177 @item @code{hostio-unlink-packet}
16178 @tab @code{vFile:unlink}
16179 @tab @code{remote delete}
16181 @item @code{noack-packet}
16182 @tab @code{QStartNoAckMode}
16183 @tab Packet acknowledgment
16185 @item @code{osdata}
16186 @tab @code{qXfer:osdata:read}
16187 @tab @code{info os}
16189 @item @code{query-attached}
16190 @tab @code{qAttached}
16191 @tab Querying remote process attach state.
16195 @section Implementing a Remote Stub
16197 @cindex debugging stub, example
16198 @cindex remote stub, example
16199 @cindex stub example, remote debugging
16200 The stub files provided with @value{GDBN} implement the target side of the
16201 communication protocol, and the @value{GDBN} side is implemented in the
16202 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
16203 these subroutines to communicate, and ignore the details. (If you're
16204 implementing your own stub file, you can still ignore the details: start
16205 with one of the existing stub files. @file{sparc-stub.c} is the best
16206 organized, and therefore the easiest to read.)
16208 @cindex remote serial debugging, overview
16209 To debug a program running on another machine (the debugging
16210 @dfn{target} machine), you must first arrange for all the usual
16211 prerequisites for the program to run by itself. For example, for a C
16216 A startup routine to set up the C runtime environment; these usually
16217 have a name like @file{crt0}. The startup routine may be supplied by
16218 your hardware supplier, or you may have to write your own.
16221 A C subroutine library to support your program's
16222 subroutine calls, notably managing input and output.
16225 A way of getting your program to the other machine---for example, a
16226 download program. These are often supplied by the hardware
16227 manufacturer, but you may have to write your own from hardware
16231 The next step is to arrange for your program to use a serial port to
16232 communicate with the machine where @value{GDBN} is running (the @dfn{host}
16233 machine). In general terms, the scheme looks like this:
16237 @value{GDBN} already understands how to use this protocol; when everything
16238 else is set up, you can simply use the @samp{target remote} command
16239 (@pxref{Targets,,Specifying a Debugging Target}).
16241 @item On the target,
16242 you must link with your program a few special-purpose subroutines that
16243 implement the @value{GDBN} remote serial protocol. The file containing these
16244 subroutines is called a @dfn{debugging stub}.
16246 On certain remote targets, you can use an auxiliary program
16247 @code{gdbserver} instead of linking a stub into your program.
16248 @xref{Server,,Using the @code{gdbserver} Program}, for details.
16251 The debugging stub is specific to the architecture of the remote
16252 machine; for example, use @file{sparc-stub.c} to debug programs on
16255 @cindex remote serial stub list
16256 These working remote stubs are distributed with @value{GDBN}:
16261 @cindex @file{i386-stub.c}
16264 For Intel 386 and compatible architectures.
16267 @cindex @file{m68k-stub.c}
16268 @cindex Motorola 680x0
16270 For Motorola 680x0 architectures.
16273 @cindex @file{sh-stub.c}
16276 For Renesas SH architectures.
16279 @cindex @file{sparc-stub.c}
16281 For @sc{sparc} architectures.
16283 @item sparcl-stub.c
16284 @cindex @file{sparcl-stub.c}
16287 For Fujitsu @sc{sparclite} architectures.
16291 The @file{README} file in the @value{GDBN} distribution may list other
16292 recently added stubs.
16295 * Stub Contents:: What the stub can do for you
16296 * Bootstrapping:: What you must do for the stub
16297 * Debug Session:: Putting it all together
16300 @node Stub Contents
16301 @subsection What the Stub Can Do for You
16303 @cindex remote serial stub
16304 The debugging stub for your architecture supplies these three
16308 @item set_debug_traps
16309 @findex set_debug_traps
16310 @cindex remote serial stub, initialization
16311 This routine arranges for @code{handle_exception} to run when your
16312 program stops. You must call this subroutine explicitly near the
16313 beginning of your program.
16315 @item handle_exception
16316 @findex handle_exception
16317 @cindex remote serial stub, main routine
16318 This is the central workhorse, but your program never calls it
16319 explicitly---the setup code arranges for @code{handle_exception} to
16320 run when a trap is triggered.
16322 @code{handle_exception} takes control when your program stops during
16323 execution (for example, on a breakpoint), and mediates communications
16324 with @value{GDBN} on the host machine. This is where the communications
16325 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
16326 representative on the target machine. It begins by sending summary
16327 information on the state of your program, then continues to execute,
16328 retrieving and transmitting any information @value{GDBN} needs, until you
16329 execute a @value{GDBN} command that makes your program resume; at that point,
16330 @code{handle_exception} returns control to your own code on the target
16334 @cindex @code{breakpoint} subroutine, remote
16335 Use this auxiliary subroutine to make your program contain a
16336 breakpoint. Depending on the particular situation, this may be the only
16337 way for @value{GDBN} to get control. For instance, if your target
16338 machine has some sort of interrupt button, you won't need to call this;
16339 pressing the interrupt button transfers control to
16340 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
16341 simply receiving characters on the serial port may also trigger a trap;
16342 again, in that situation, you don't need to call @code{breakpoint} from
16343 your own program---simply running @samp{target remote} from the host
16344 @value{GDBN} session gets control.
16346 Call @code{breakpoint} if none of these is true, or if you simply want
16347 to make certain your program stops at a predetermined point for the
16348 start of your debugging session.
16351 @node Bootstrapping
16352 @subsection What You Must Do for the Stub
16354 @cindex remote stub, support routines
16355 The debugging stubs that come with @value{GDBN} are set up for a particular
16356 chip architecture, but they have no information about the rest of your
16357 debugging target machine.
16359 First of all you need to tell the stub how to communicate with the
16363 @item int getDebugChar()
16364 @findex getDebugChar
16365 Write this subroutine to read a single character from the serial port.
16366 It may be identical to @code{getchar} for your target system; a
16367 different name is used to allow you to distinguish the two if you wish.
16369 @item void putDebugChar(int)
16370 @findex putDebugChar
16371 Write this subroutine to write a single character to the serial port.
16372 It may be identical to @code{putchar} for your target system; a
16373 different name is used to allow you to distinguish the two if you wish.
16376 @cindex control C, and remote debugging
16377 @cindex interrupting remote targets
16378 If you want @value{GDBN} to be able to stop your program while it is
16379 running, you need to use an interrupt-driven serial driver, and arrange
16380 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
16381 character). That is the character which @value{GDBN} uses to tell the
16382 remote system to stop.
16384 Getting the debugging target to return the proper status to @value{GDBN}
16385 probably requires changes to the standard stub; one quick and dirty way
16386 is to just execute a breakpoint instruction (the ``dirty'' part is that
16387 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
16389 Other routines you need to supply are:
16392 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
16393 @findex exceptionHandler
16394 Write this function to install @var{exception_address} in the exception
16395 handling tables. You need to do this because the stub does not have any
16396 way of knowing what the exception handling tables on your target system
16397 are like (for example, the processor's table might be in @sc{rom},
16398 containing entries which point to a table in @sc{ram}).
16399 @var{exception_number} is the exception number which should be changed;
16400 its meaning is architecture-dependent (for example, different numbers
16401 might represent divide by zero, misaligned access, etc). When this
16402 exception occurs, control should be transferred directly to
16403 @var{exception_address}, and the processor state (stack, registers,
16404 and so on) should be just as it is when a processor exception occurs. So if
16405 you want to use a jump instruction to reach @var{exception_address}, it
16406 should be a simple jump, not a jump to subroutine.
16408 For the 386, @var{exception_address} should be installed as an interrupt
16409 gate so that interrupts are masked while the handler runs. The gate
16410 should be at privilege level 0 (the most privileged level). The
16411 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
16412 help from @code{exceptionHandler}.
16414 @item void flush_i_cache()
16415 @findex flush_i_cache
16416 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
16417 instruction cache, if any, on your target machine. If there is no
16418 instruction cache, this subroutine may be a no-op.
16420 On target machines that have instruction caches, @value{GDBN} requires this
16421 function to make certain that the state of your program is stable.
16425 You must also make sure this library routine is available:
16428 @item void *memset(void *, int, int)
16430 This is the standard library function @code{memset} that sets an area of
16431 memory to a known value. If you have one of the free versions of
16432 @code{libc.a}, @code{memset} can be found there; otherwise, you must
16433 either obtain it from your hardware manufacturer, or write your own.
16436 If you do not use the GNU C compiler, you may need other standard
16437 library subroutines as well; this varies from one stub to another,
16438 but in general the stubs are likely to use any of the common library
16439 subroutines which @code{@value{NGCC}} generates as inline code.
16442 @node Debug Session
16443 @subsection Putting it All Together
16445 @cindex remote serial debugging summary
16446 In summary, when your program is ready to debug, you must follow these
16451 Make sure you have defined the supporting low-level routines
16452 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
16454 @code{getDebugChar}, @code{putDebugChar},
16455 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
16459 Insert these lines near the top of your program:
16467 For the 680x0 stub only, you need to provide a variable called
16468 @code{exceptionHook}. Normally you just use:
16471 void (*exceptionHook)() = 0;
16475 but if before calling @code{set_debug_traps}, you set it to point to a
16476 function in your program, that function is called when
16477 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
16478 error). The function indicated by @code{exceptionHook} is called with
16479 one parameter: an @code{int} which is the exception number.
16482 Compile and link together: your program, the @value{GDBN} debugging stub for
16483 your target architecture, and the supporting subroutines.
16486 Make sure you have a serial connection between your target machine and
16487 the @value{GDBN} host, and identify the serial port on the host.
16490 @c The "remote" target now provides a `load' command, so we should
16491 @c document that. FIXME.
16492 Download your program to your target machine (or get it there by
16493 whatever means the manufacturer provides), and start it.
16496 Start @value{GDBN} on the host, and connect to the target
16497 (@pxref{Connecting,,Connecting to a Remote Target}).
16501 @node Configurations
16502 @chapter Configuration-Specific Information
16504 While nearly all @value{GDBN} commands are available for all native and
16505 cross versions of the debugger, there are some exceptions. This chapter
16506 describes things that are only available in certain configurations.
16508 There are three major categories of configurations: native
16509 configurations, where the host and target are the same, embedded
16510 operating system configurations, which are usually the same for several
16511 different processor architectures, and bare embedded processors, which
16512 are quite different from each other.
16517 * Embedded Processors::
16524 This section describes details specific to particular native
16529 * BSD libkvm Interface:: Debugging BSD kernel memory images
16530 * SVR4 Process Information:: SVR4 process information
16531 * DJGPP Native:: Features specific to the DJGPP port
16532 * Cygwin Native:: Features specific to the Cygwin port
16533 * Hurd Native:: Features specific to @sc{gnu} Hurd
16534 * Neutrino:: Features specific to QNX Neutrino
16535 * Darwin:: Features specific to Darwin
16541 On HP-UX systems, if you refer to a function or variable name that
16542 begins with a dollar sign, @value{GDBN} searches for a user or system
16543 name first, before it searches for a convenience variable.
16546 @node BSD libkvm Interface
16547 @subsection BSD libkvm Interface
16550 @cindex kernel memory image
16551 @cindex kernel crash dump
16553 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
16554 interface that provides a uniform interface for accessing kernel virtual
16555 memory images, including live systems and crash dumps. @value{GDBN}
16556 uses this interface to allow you to debug live kernels and kernel crash
16557 dumps on many native BSD configurations. This is implemented as a
16558 special @code{kvm} debugging target. For debugging a live system, load
16559 the currently running kernel into @value{GDBN} and connect to the
16563 (@value{GDBP}) @b{target kvm}
16566 For debugging crash dumps, provide the file name of the crash dump as an
16570 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
16573 Once connected to the @code{kvm} target, the following commands are
16579 Set current context from the @dfn{Process Control Block} (PCB) address.
16582 Set current context from proc address. This command isn't available on
16583 modern FreeBSD systems.
16586 @node SVR4 Process Information
16587 @subsection SVR4 Process Information
16589 @cindex examine process image
16590 @cindex process info via @file{/proc}
16592 Many versions of SVR4 and compatible systems provide a facility called
16593 @samp{/proc} that can be used to examine the image of a running
16594 process using file-system subroutines. If @value{GDBN} is configured
16595 for an operating system with this facility, the command @code{info
16596 proc} is available to report information about the process running
16597 your program, or about any process running on your system. @code{info
16598 proc} works only on SVR4 systems that include the @code{procfs} code.
16599 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
16600 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
16606 @itemx info proc @var{process-id}
16607 Summarize available information about any running process. If a
16608 process ID is specified by @var{process-id}, display information about
16609 that process; otherwise display information about the program being
16610 debugged. The summary includes the debugged process ID, the command
16611 line used to invoke it, its current working directory, and its
16612 executable file's absolute file name.
16614 On some systems, @var{process-id} can be of the form
16615 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
16616 within a process. If the optional @var{pid} part is missing, it means
16617 a thread from the process being debugged (the leading @samp{/} still
16618 needs to be present, or else @value{GDBN} will interpret the number as
16619 a process ID rather than a thread ID).
16621 @item info proc mappings
16622 @cindex memory address space mappings
16623 Report the memory address space ranges accessible in the program, with
16624 information on whether the process has read, write, or execute access
16625 rights to each range. On @sc{gnu}/Linux systems, each memory range
16626 includes the object file which is mapped to that range, instead of the
16627 memory access rights to that range.
16629 @item info proc stat
16630 @itemx info proc status
16631 @cindex process detailed status information
16632 These subcommands are specific to @sc{gnu}/Linux systems. They show
16633 the process-related information, including the user ID and group ID;
16634 how many threads are there in the process; its virtual memory usage;
16635 the signals that are pending, blocked, and ignored; its TTY; its
16636 consumption of system and user time; its stack size; its @samp{nice}
16637 value; etc. For more information, see the @samp{proc} man page
16638 (type @kbd{man 5 proc} from your shell prompt).
16640 @item info proc all
16641 Show all the information about the process described under all of the
16642 above @code{info proc} subcommands.
16645 @comment These sub-options of 'info proc' were not included when
16646 @comment procfs.c was re-written. Keep their descriptions around
16647 @comment against the day when someone finds the time to put them back in.
16648 @kindex info proc times
16649 @item info proc times
16650 Starting time, user CPU time, and system CPU time for your program and
16653 @kindex info proc id
16655 Report on the process IDs related to your program: its own process ID,
16656 the ID of its parent, the process group ID, and the session ID.
16659 @item set procfs-trace
16660 @kindex set procfs-trace
16661 @cindex @code{procfs} API calls
16662 This command enables and disables tracing of @code{procfs} API calls.
16664 @item show procfs-trace
16665 @kindex show procfs-trace
16666 Show the current state of @code{procfs} API call tracing.
16668 @item set procfs-file @var{file}
16669 @kindex set procfs-file
16670 Tell @value{GDBN} to write @code{procfs} API trace to the named
16671 @var{file}. @value{GDBN} appends the trace info to the previous
16672 contents of the file. The default is to display the trace on the
16675 @item show procfs-file
16676 @kindex show procfs-file
16677 Show the file to which @code{procfs} API trace is written.
16679 @item proc-trace-entry
16680 @itemx proc-trace-exit
16681 @itemx proc-untrace-entry
16682 @itemx proc-untrace-exit
16683 @kindex proc-trace-entry
16684 @kindex proc-trace-exit
16685 @kindex proc-untrace-entry
16686 @kindex proc-untrace-exit
16687 These commands enable and disable tracing of entries into and exits
16688 from the @code{syscall} interface.
16691 @kindex info pidlist
16692 @cindex process list, QNX Neutrino
16693 For QNX Neutrino only, this command displays the list of all the
16694 processes and all the threads within each process.
16697 @kindex info meminfo
16698 @cindex mapinfo list, QNX Neutrino
16699 For QNX Neutrino only, this command displays the list of all mapinfos.
16703 @subsection Features for Debugging @sc{djgpp} Programs
16704 @cindex @sc{djgpp} debugging
16705 @cindex native @sc{djgpp} debugging
16706 @cindex MS-DOS-specific commands
16709 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
16710 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
16711 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
16712 top of real-mode DOS systems and their emulations.
16714 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
16715 defines a few commands specific to the @sc{djgpp} port. This
16716 subsection describes those commands.
16721 This is a prefix of @sc{djgpp}-specific commands which print
16722 information about the target system and important OS structures.
16725 @cindex MS-DOS system info
16726 @cindex free memory information (MS-DOS)
16727 @item info dos sysinfo
16728 This command displays assorted information about the underlying
16729 platform: the CPU type and features, the OS version and flavor, the
16730 DPMI version, and the available conventional and DPMI memory.
16735 @cindex segment descriptor tables
16736 @cindex descriptor tables display
16738 @itemx info dos ldt
16739 @itemx info dos idt
16740 These 3 commands display entries from, respectively, Global, Local,
16741 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
16742 tables are data structures which store a descriptor for each segment
16743 that is currently in use. The segment's selector is an index into a
16744 descriptor table; the table entry for that index holds the
16745 descriptor's base address and limit, and its attributes and access
16748 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
16749 segment (used for both data and the stack), and a DOS segment (which
16750 allows access to DOS/BIOS data structures and absolute addresses in
16751 conventional memory). However, the DPMI host will usually define
16752 additional segments in order to support the DPMI environment.
16754 @cindex garbled pointers
16755 These commands allow to display entries from the descriptor tables.
16756 Without an argument, all entries from the specified table are
16757 displayed. An argument, which should be an integer expression, means
16758 display a single entry whose index is given by the argument. For
16759 example, here's a convenient way to display information about the
16760 debugged program's data segment:
16763 @exdent @code{(@value{GDBP}) info dos ldt $ds}
16764 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
16768 This comes in handy when you want to see whether a pointer is outside
16769 the data segment's limit (i.e.@: @dfn{garbled}).
16771 @cindex page tables display (MS-DOS)
16773 @itemx info dos pte
16774 These two commands display entries from, respectively, the Page
16775 Directory and the Page Tables. Page Directories and Page Tables are
16776 data structures which control how virtual memory addresses are mapped
16777 into physical addresses. A Page Table includes an entry for every
16778 page of memory that is mapped into the program's address space; there
16779 may be several Page Tables, each one holding up to 4096 entries. A
16780 Page Directory has up to 4096 entries, one each for every Page Table
16781 that is currently in use.
16783 Without an argument, @kbd{info dos pde} displays the entire Page
16784 Directory, and @kbd{info dos pte} displays all the entries in all of
16785 the Page Tables. An argument, an integer expression, given to the
16786 @kbd{info dos pde} command means display only that entry from the Page
16787 Directory table. An argument given to the @kbd{info dos pte} command
16788 means display entries from a single Page Table, the one pointed to by
16789 the specified entry in the Page Directory.
16791 @cindex direct memory access (DMA) on MS-DOS
16792 These commands are useful when your program uses @dfn{DMA} (Direct
16793 Memory Access), which needs physical addresses to program the DMA
16796 These commands are supported only with some DPMI servers.
16798 @cindex physical address from linear address
16799 @item info dos address-pte @var{addr}
16800 This command displays the Page Table entry for a specified linear
16801 address. The argument @var{addr} is a linear address which should
16802 already have the appropriate segment's base address added to it,
16803 because this command accepts addresses which may belong to @emph{any}
16804 segment. For example, here's how to display the Page Table entry for
16805 the page where a variable @code{i} is stored:
16808 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
16809 @exdent @code{Page Table entry for address 0x11a00d30:}
16810 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
16814 This says that @code{i} is stored at offset @code{0xd30} from the page
16815 whose physical base address is @code{0x02698000}, and shows all the
16816 attributes of that page.
16818 Note that you must cast the addresses of variables to a @code{char *},
16819 since otherwise the value of @code{__djgpp_base_address}, the base
16820 address of all variables and functions in a @sc{djgpp} program, will
16821 be added using the rules of C pointer arithmetics: if @code{i} is
16822 declared an @code{int}, @value{GDBN} will add 4 times the value of
16823 @code{__djgpp_base_address} to the address of @code{i}.
16825 Here's another example, it displays the Page Table entry for the
16829 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
16830 @exdent @code{Page Table entry for address 0x29110:}
16831 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
16835 (The @code{+ 3} offset is because the transfer buffer's address is the
16836 3rd member of the @code{_go32_info_block} structure.) The output
16837 clearly shows that this DPMI server maps the addresses in conventional
16838 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
16839 linear (@code{0x29110}) addresses are identical.
16841 This command is supported only with some DPMI servers.
16844 @cindex DOS serial data link, remote debugging
16845 In addition to native debugging, the DJGPP port supports remote
16846 debugging via a serial data link. The following commands are specific
16847 to remote serial debugging in the DJGPP port of @value{GDBN}.
16850 @kindex set com1base
16851 @kindex set com1irq
16852 @kindex set com2base
16853 @kindex set com2irq
16854 @kindex set com3base
16855 @kindex set com3irq
16856 @kindex set com4base
16857 @kindex set com4irq
16858 @item set com1base @var{addr}
16859 This command sets the base I/O port address of the @file{COM1} serial
16862 @item set com1irq @var{irq}
16863 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
16864 for the @file{COM1} serial port.
16866 There are similar commands @samp{set com2base}, @samp{set com3irq},
16867 etc.@: for setting the port address and the @code{IRQ} lines for the
16870 @kindex show com1base
16871 @kindex show com1irq
16872 @kindex show com2base
16873 @kindex show com2irq
16874 @kindex show com3base
16875 @kindex show com3irq
16876 @kindex show com4base
16877 @kindex show com4irq
16878 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
16879 display the current settings of the base address and the @code{IRQ}
16880 lines used by the COM ports.
16883 @kindex info serial
16884 @cindex DOS serial port status
16885 This command prints the status of the 4 DOS serial ports. For each
16886 port, it prints whether it's active or not, its I/O base address and
16887 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
16888 counts of various errors encountered so far.
16892 @node Cygwin Native
16893 @subsection Features for Debugging MS Windows PE Executables
16894 @cindex MS Windows debugging
16895 @cindex native Cygwin debugging
16896 @cindex Cygwin-specific commands
16898 @value{GDBN} supports native debugging of MS Windows programs, including
16899 DLLs with and without symbolic debugging information.
16901 @cindex Ctrl-BREAK, MS-Windows
16902 @cindex interrupt debuggee on MS-Windows
16903 MS-Windows programs that call @code{SetConsoleMode} to switch off the
16904 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
16905 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
16906 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
16907 sequence, which can be used to interrupt the debuggee even if it
16910 There are various additional Cygwin-specific commands, described in
16911 this section. Working with DLLs that have no debugging symbols is
16912 described in @ref{Non-debug DLL Symbols}.
16917 This is a prefix of MS Windows-specific commands which print
16918 information about the target system and important OS structures.
16920 @item info w32 selector
16921 This command displays information returned by
16922 the Win32 API @code{GetThreadSelectorEntry} function.
16923 It takes an optional argument that is evaluated to
16924 a long value to give the information about this given selector.
16925 Without argument, this command displays information
16926 about the six segment registers.
16928 @item info w32 thread-information-block
16929 This command displays thread specific information stored in the
16930 Thread Information Block (readable on the X86 CPU family using @code{$fs}
16931 selector for 32-bit programs and @code{$gs} for 64-bit programs).
16935 This is a Cygwin-specific alias of @code{info shared}.
16937 @kindex dll-symbols
16939 This command loads symbols from a dll similarly to
16940 add-sym command but without the need to specify a base address.
16942 @kindex set cygwin-exceptions
16943 @cindex debugging the Cygwin DLL
16944 @cindex Cygwin DLL, debugging
16945 @item set cygwin-exceptions @var{mode}
16946 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
16947 happen inside the Cygwin DLL. If @var{mode} is @code{off},
16948 @value{GDBN} will delay recognition of exceptions, and may ignore some
16949 exceptions which seem to be caused by internal Cygwin DLL
16950 ``bookkeeping''. This option is meant primarily for debugging the
16951 Cygwin DLL itself; the default value is @code{off} to avoid annoying
16952 @value{GDBN} users with false @code{SIGSEGV} signals.
16954 @kindex show cygwin-exceptions
16955 @item show cygwin-exceptions
16956 Displays whether @value{GDBN} will break on exceptions that happen
16957 inside the Cygwin DLL itself.
16959 @kindex set new-console
16960 @item set new-console @var{mode}
16961 If @var{mode} is @code{on} the debuggee will
16962 be started in a new console on next start.
16963 If @var{mode} is @code{off}, the debuggee will
16964 be started in the same console as the debugger.
16966 @kindex show new-console
16967 @item show new-console
16968 Displays whether a new console is used
16969 when the debuggee is started.
16971 @kindex set new-group
16972 @item set new-group @var{mode}
16973 This boolean value controls whether the debuggee should
16974 start a new group or stay in the same group as the debugger.
16975 This affects the way the Windows OS handles
16978 @kindex show new-group
16979 @item show new-group
16980 Displays current value of new-group boolean.
16982 @kindex set debugevents
16983 @item set debugevents
16984 This boolean value adds debug output concerning kernel events related
16985 to the debuggee seen by the debugger. This includes events that
16986 signal thread and process creation and exit, DLL loading and
16987 unloading, console interrupts, and debugging messages produced by the
16988 Windows @code{OutputDebugString} API call.
16990 @kindex set debugexec
16991 @item set debugexec
16992 This boolean value adds debug output concerning execute events
16993 (such as resume thread) seen by the debugger.
16995 @kindex set debugexceptions
16996 @item set debugexceptions
16997 This boolean value adds debug output concerning exceptions in the
16998 debuggee seen by the debugger.
17000 @kindex set debugmemory
17001 @item set debugmemory
17002 This boolean value adds debug output concerning debuggee memory reads
17003 and writes by the debugger.
17007 This boolean values specifies whether the debuggee is called
17008 via a shell or directly (default value is on).
17012 Displays if the debuggee will be started with a shell.
17017 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
17020 @node Non-debug DLL Symbols
17021 @subsubsection Support for DLLs without Debugging Symbols
17022 @cindex DLLs with no debugging symbols
17023 @cindex Minimal symbols and DLLs
17025 Very often on windows, some of the DLLs that your program relies on do
17026 not include symbolic debugging information (for example,
17027 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
17028 symbols in a DLL, it relies on the minimal amount of symbolic
17029 information contained in the DLL's export table. This section
17030 describes working with such symbols, known internally to @value{GDBN} as
17031 ``minimal symbols''.
17033 Note that before the debugged program has started execution, no DLLs
17034 will have been loaded. The easiest way around this problem is simply to
17035 start the program --- either by setting a breakpoint or letting the
17036 program run once to completion. It is also possible to force
17037 @value{GDBN} to load a particular DLL before starting the executable ---
17038 see the shared library information in @ref{Files}, or the
17039 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
17040 explicitly loading symbols from a DLL with no debugging information will
17041 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
17042 which may adversely affect symbol lookup performance.
17044 @subsubsection DLL Name Prefixes
17046 In keeping with the naming conventions used by the Microsoft debugging
17047 tools, DLL export symbols are made available with a prefix based on the
17048 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
17049 also entered into the symbol table, so @code{CreateFileA} is often
17050 sufficient. In some cases there will be name clashes within a program
17051 (particularly if the executable itself includes full debugging symbols)
17052 necessitating the use of the fully qualified name when referring to the
17053 contents of the DLL. Use single-quotes around the name to avoid the
17054 exclamation mark (``!'') being interpreted as a language operator.
17056 Note that the internal name of the DLL may be all upper-case, even
17057 though the file name of the DLL is lower-case, or vice-versa. Since
17058 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
17059 some confusion. If in doubt, try the @code{info functions} and
17060 @code{info variables} commands or even @code{maint print msymbols}
17061 (@pxref{Symbols}). Here's an example:
17064 (@value{GDBP}) info function CreateFileA
17065 All functions matching regular expression "CreateFileA":
17067 Non-debugging symbols:
17068 0x77e885f4 CreateFileA
17069 0x77e885f4 KERNEL32!CreateFileA
17073 (@value{GDBP}) info function !
17074 All functions matching regular expression "!":
17076 Non-debugging symbols:
17077 0x6100114c cygwin1!__assert
17078 0x61004034 cygwin1!_dll_crt0@@0
17079 0x61004240 cygwin1!dll_crt0(per_process *)
17083 @subsubsection Working with Minimal Symbols
17085 Symbols extracted from a DLL's export table do not contain very much
17086 type information. All that @value{GDBN} can do is guess whether a symbol
17087 refers to a function or variable depending on the linker section that
17088 contains the symbol. Also note that the actual contents of the memory
17089 contained in a DLL are not available unless the program is running. This
17090 means that you cannot examine the contents of a variable or disassemble
17091 a function within a DLL without a running program.
17093 Variables are generally treated as pointers and dereferenced
17094 automatically. For this reason, it is often necessary to prefix a
17095 variable name with the address-of operator (``&'') and provide explicit
17096 type information in the command. Here's an example of the type of
17100 (@value{GDBP}) print 'cygwin1!__argv'
17105 (@value{GDBP}) x 'cygwin1!__argv'
17106 0x10021610: "\230y\""
17109 And two possible solutions:
17112 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
17113 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
17117 (@value{GDBP}) x/2x &'cygwin1!__argv'
17118 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
17119 (@value{GDBP}) x/x 0x10021608
17120 0x10021608: 0x0022fd98
17121 (@value{GDBP}) x/s 0x0022fd98
17122 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
17125 Setting a break point within a DLL is possible even before the program
17126 starts execution. However, under these circumstances, @value{GDBN} can't
17127 examine the initial instructions of the function in order to skip the
17128 function's frame set-up code. You can work around this by using ``*&''
17129 to set the breakpoint at a raw memory address:
17132 (@value{GDBP}) break *&'python22!PyOS_Readline'
17133 Breakpoint 1 at 0x1e04eff0
17136 The author of these extensions is not entirely convinced that setting a
17137 break point within a shared DLL like @file{kernel32.dll} is completely
17141 @subsection Commands Specific to @sc{gnu} Hurd Systems
17142 @cindex @sc{gnu} Hurd debugging
17144 This subsection describes @value{GDBN} commands specific to the
17145 @sc{gnu} Hurd native debugging.
17150 @kindex set signals@r{, Hurd command}
17151 @kindex set sigs@r{, Hurd command}
17152 This command toggles the state of inferior signal interception by
17153 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
17154 affected by this command. @code{sigs} is a shorthand alias for
17159 @kindex show signals@r{, Hurd command}
17160 @kindex show sigs@r{, Hurd command}
17161 Show the current state of intercepting inferior's signals.
17163 @item set signal-thread
17164 @itemx set sigthread
17165 @kindex set signal-thread
17166 @kindex set sigthread
17167 This command tells @value{GDBN} which thread is the @code{libc} signal
17168 thread. That thread is run when a signal is delivered to a running
17169 process. @code{set sigthread} is the shorthand alias of @code{set
17172 @item show signal-thread
17173 @itemx show sigthread
17174 @kindex show signal-thread
17175 @kindex show sigthread
17176 These two commands show which thread will run when the inferior is
17177 delivered a signal.
17180 @kindex set stopped@r{, Hurd command}
17181 This commands tells @value{GDBN} that the inferior process is stopped,
17182 as with the @code{SIGSTOP} signal. The stopped process can be
17183 continued by delivering a signal to it.
17186 @kindex show stopped@r{, Hurd command}
17187 This command shows whether @value{GDBN} thinks the debuggee is
17190 @item set exceptions
17191 @kindex set exceptions@r{, Hurd command}
17192 Use this command to turn off trapping of exceptions in the inferior.
17193 When exception trapping is off, neither breakpoints nor
17194 single-stepping will work. To restore the default, set exception
17197 @item show exceptions
17198 @kindex show exceptions@r{, Hurd command}
17199 Show the current state of trapping exceptions in the inferior.
17201 @item set task pause
17202 @kindex set task@r{, Hurd commands}
17203 @cindex task attributes (@sc{gnu} Hurd)
17204 @cindex pause current task (@sc{gnu} Hurd)
17205 This command toggles task suspension when @value{GDBN} has control.
17206 Setting it to on takes effect immediately, and the task is suspended
17207 whenever @value{GDBN} gets control. Setting it to off will take
17208 effect the next time the inferior is continued. If this option is set
17209 to off, you can use @code{set thread default pause on} or @code{set
17210 thread pause on} (see below) to pause individual threads.
17212 @item show task pause
17213 @kindex show task@r{, Hurd commands}
17214 Show the current state of task suspension.
17216 @item set task detach-suspend-count
17217 @cindex task suspend count
17218 @cindex detach from task, @sc{gnu} Hurd
17219 This command sets the suspend count the task will be left with when
17220 @value{GDBN} detaches from it.
17222 @item show task detach-suspend-count
17223 Show the suspend count the task will be left with when detaching.
17225 @item set task exception-port
17226 @itemx set task excp
17227 @cindex task exception port, @sc{gnu} Hurd
17228 This command sets the task exception port to which @value{GDBN} will
17229 forward exceptions. The argument should be the value of the @dfn{send
17230 rights} of the task. @code{set task excp} is a shorthand alias.
17232 @item set noninvasive
17233 @cindex noninvasive task options
17234 This command switches @value{GDBN} to a mode that is the least
17235 invasive as far as interfering with the inferior is concerned. This
17236 is the same as using @code{set task pause}, @code{set exceptions}, and
17237 @code{set signals} to values opposite to the defaults.
17239 @item info send-rights
17240 @itemx info receive-rights
17241 @itemx info port-rights
17242 @itemx info port-sets
17243 @itemx info dead-names
17246 @cindex send rights, @sc{gnu} Hurd
17247 @cindex receive rights, @sc{gnu} Hurd
17248 @cindex port rights, @sc{gnu} Hurd
17249 @cindex port sets, @sc{gnu} Hurd
17250 @cindex dead names, @sc{gnu} Hurd
17251 These commands display information about, respectively, send rights,
17252 receive rights, port rights, port sets, and dead names of a task.
17253 There are also shorthand aliases: @code{info ports} for @code{info
17254 port-rights} and @code{info psets} for @code{info port-sets}.
17256 @item set thread pause
17257 @kindex set thread@r{, Hurd command}
17258 @cindex thread properties, @sc{gnu} Hurd
17259 @cindex pause current thread (@sc{gnu} Hurd)
17260 This command toggles current thread suspension when @value{GDBN} has
17261 control. Setting it to on takes effect immediately, and the current
17262 thread is suspended whenever @value{GDBN} gets control. Setting it to
17263 off will take effect the next time the inferior is continued.
17264 Normally, this command has no effect, since when @value{GDBN} has
17265 control, the whole task is suspended. However, if you used @code{set
17266 task pause off} (see above), this command comes in handy to suspend
17267 only the current thread.
17269 @item show thread pause
17270 @kindex show thread@r{, Hurd command}
17271 This command shows the state of current thread suspension.
17273 @item set thread run
17274 This command sets whether the current thread is allowed to run.
17276 @item show thread run
17277 Show whether the current thread is allowed to run.
17279 @item set thread detach-suspend-count
17280 @cindex thread suspend count, @sc{gnu} Hurd
17281 @cindex detach from thread, @sc{gnu} Hurd
17282 This command sets the suspend count @value{GDBN} will leave on a
17283 thread when detaching. This number is relative to the suspend count
17284 found by @value{GDBN} when it notices the thread; use @code{set thread
17285 takeover-suspend-count} to force it to an absolute value.
17287 @item show thread detach-suspend-count
17288 Show the suspend count @value{GDBN} will leave on the thread when
17291 @item set thread exception-port
17292 @itemx set thread excp
17293 Set the thread exception port to which to forward exceptions. This
17294 overrides the port set by @code{set task exception-port} (see above).
17295 @code{set thread excp} is the shorthand alias.
17297 @item set thread takeover-suspend-count
17298 Normally, @value{GDBN}'s thread suspend counts are relative to the
17299 value @value{GDBN} finds when it notices each thread. This command
17300 changes the suspend counts to be absolute instead.
17302 @item set thread default
17303 @itemx show thread default
17304 @cindex thread default settings, @sc{gnu} Hurd
17305 Each of the above @code{set thread} commands has a @code{set thread
17306 default} counterpart (e.g., @code{set thread default pause}, @code{set
17307 thread default exception-port}, etc.). The @code{thread default}
17308 variety of commands sets the default thread properties for all
17309 threads; you can then change the properties of individual threads with
17310 the non-default commands.
17315 @subsection QNX Neutrino
17316 @cindex QNX Neutrino
17318 @value{GDBN} provides the following commands specific to the QNX
17322 @item set debug nto-debug
17323 @kindex set debug nto-debug
17324 When set to on, enables debugging messages specific to the QNX
17327 @item show debug nto-debug
17328 @kindex show debug nto-debug
17329 Show the current state of QNX Neutrino messages.
17336 @value{GDBN} provides the following commands specific to the Darwin target:
17339 @item set debug darwin @var{num}
17340 @kindex set debug darwin
17341 When set to a non zero value, enables debugging messages specific to
17342 the Darwin support. Higher values produce more verbose output.
17344 @item show debug darwin
17345 @kindex show debug darwin
17346 Show the current state of Darwin messages.
17348 @item set debug mach-o @var{num}
17349 @kindex set debug mach-o
17350 When set to a non zero value, enables debugging messages while
17351 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
17352 file format used on Darwin for object and executable files.) Higher
17353 values produce more verbose output. This is a command to diagnose
17354 problems internal to @value{GDBN} and should not be needed in normal
17357 @item show debug mach-o
17358 @kindex show debug mach-o
17359 Show the current state of Mach-O file messages.
17361 @item set mach-exceptions on
17362 @itemx set mach-exceptions off
17363 @kindex set mach-exceptions
17364 On Darwin, faults are first reported as a Mach exception and are then
17365 mapped to a Posix signal. Use this command to turn on trapping of
17366 Mach exceptions in the inferior. This might be sometimes useful to
17367 better understand the cause of a fault. The default is off.
17369 @item show mach-exceptions
17370 @kindex show mach-exceptions
17371 Show the current state of exceptions trapping.
17376 @section Embedded Operating Systems
17378 This section describes configurations involving the debugging of
17379 embedded operating systems that are available for several different
17383 * VxWorks:: Using @value{GDBN} with VxWorks
17386 @value{GDBN} includes the ability to debug programs running on
17387 various real-time operating systems.
17390 @subsection Using @value{GDBN} with VxWorks
17396 @kindex target vxworks
17397 @item target vxworks @var{machinename}
17398 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
17399 is the target system's machine name or IP address.
17403 On VxWorks, @code{load} links @var{filename} dynamically on the
17404 current target system as well as adding its symbols in @value{GDBN}.
17406 @value{GDBN} enables developers to spawn and debug tasks running on networked
17407 VxWorks targets from a Unix host. Already-running tasks spawned from
17408 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
17409 both the Unix host and on the VxWorks target. The program
17410 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
17411 installed with the name @code{vxgdb}, to distinguish it from a
17412 @value{GDBN} for debugging programs on the host itself.)
17415 @item VxWorks-timeout @var{args}
17416 @kindex vxworks-timeout
17417 All VxWorks-based targets now support the option @code{vxworks-timeout}.
17418 This option is set by the user, and @var{args} represents the number of
17419 seconds @value{GDBN} waits for responses to rpc's. You might use this if
17420 your VxWorks target is a slow software simulator or is on the far side
17421 of a thin network line.
17424 The following information on connecting to VxWorks was current when
17425 this manual was produced; newer releases of VxWorks may use revised
17428 @findex INCLUDE_RDB
17429 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
17430 to include the remote debugging interface routines in the VxWorks
17431 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
17432 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
17433 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
17434 source debugging task @code{tRdbTask} when VxWorks is booted. For more
17435 information on configuring and remaking VxWorks, see the manufacturer's
17437 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
17439 Once you have included @file{rdb.a} in your VxWorks system image and set
17440 your Unix execution search path to find @value{GDBN}, you are ready to
17441 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
17442 @code{vxgdb}, depending on your installation).
17444 @value{GDBN} comes up showing the prompt:
17451 * VxWorks Connection:: Connecting to VxWorks
17452 * VxWorks Download:: VxWorks download
17453 * VxWorks Attach:: Running tasks
17456 @node VxWorks Connection
17457 @subsubsection Connecting to VxWorks
17459 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
17460 network. To connect to a target whose host name is ``@code{tt}'', type:
17463 (vxgdb) target vxworks tt
17467 @value{GDBN} displays messages like these:
17470 Attaching remote machine across net...
17475 @value{GDBN} then attempts to read the symbol tables of any object modules
17476 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
17477 these files by searching the directories listed in the command search
17478 path (@pxref{Environment, ,Your Program's Environment}); if it fails
17479 to find an object file, it displays a message such as:
17482 prog.o: No such file or directory.
17485 When this happens, add the appropriate directory to the search path with
17486 the @value{GDBN} command @code{path}, and execute the @code{target}
17489 @node VxWorks Download
17490 @subsubsection VxWorks Download
17492 @cindex download to VxWorks
17493 If you have connected to the VxWorks target and you want to debug an
17494 object that has not yet been loaded, you can use the @value{GDBN}
17495 @code{load} command to download a file from Unix to VxWorks
17496 incrementally. The object file given as an argument to the @code{load}
17497 command is actually opened twice: first by the VxWorks target in order
17498 to download the code, then by @value{GDBN} in order to read the symbol
17499 table. This can lead to problems if the current working directories on
17500 the two systems differ. If both systems have NFS mounted the same
17501 filesystems, you can avoid these problems by using absolute paths.
17502 Otherwise, it is simplest to set the working directory on both systems
17503 to the directory in which the object file resides, and then to reference
17504 the file by its name, without any path. For instance, a program
17505 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
17506 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
17507 program, type this on VxWorks:
17510 -> cd "@var{vxpath}/vw/demo/rdb"
17514 Then, in @value{GDBN}, type:
17517 (vxgdb) cd @var{hostpath}/vw/demo/rdb
17518 (vxgdb) load prog.o
17521 @value{GDBN} displays a response similar to this:
17524 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
17527 You can also use the @code{load} command to reload an object module
17528 after editing and recompiling the corresponding source file. Note that
17529 this makes @value{GDBN} delete all currently-defined breakpoints,
17530 auto-displays, and convenience variables, and to clear the value
17531 history. (This is necessary in order to preserve the integrity of
17532 debugger's data structures that reference the target system's symbol
17535 @node VxWorks Attach
17536 @subsubsection Running Tasks
17538 @cindex running VxWorks tasks
17539 You can also attach to an existing task using the @code{attach} command as
17543 (vxgdb) attach @var{task}
17547 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
17548 or suspended when you attach to it. Running tasks are suspended at
17549 the time of attachment.
17551 @node Embedded Processors
17552 @section Embedded Processors
17554 This section goes into details specific to particular embedded
17557 @cindex send command to simulator
17558 Whenever a specific embedded processor has a simulator, @value{GDBN}
17559 allows to send an arbitrary command to the simulator.
17562 @item sim @var{command}
17563 @kindex sim@r{, a command}
17564 Send an arbitrary @var{command} string to the simulator. Consult the
17565 documentation for the specific simulator in use for information about
17566 acceptable commands.
17572 * M32R/D:: Renesas M32R/D
17573 * M68K:: Motorola M68K
17574 * MicroBlaze:: Xilinx MicroBlaze
17575 * MIPS Embedded:: MIPS Embedded
17576 * OpenRISC 1000:: OpenRisc 1000
17577 * PA:: HP PA Embedded
17578 * PowerPC Embedded:: PowerPC Embedded
17579 * Sparclet:: Tsqware Sparclet
17580 * Sparclite:: Fujitsu Sparclite
17581 * Z8000:: Zilog Z8000
17584 * Super-H:: Renesas Super-H
17593 @item target rdi @var{dev}
17594 ARM Angel monitor, via RDI library interface to ADP protocol. You may
17595 use this target to communicate with both boards running the Angel
17596 monitor, or with the EmbeddedICE JTAG debug device.
17599 @item target rdp @var{dev}
17604 @value{GDBN} provides the following ARM-specific commands:
17607 @item set arm disassembler
17609 This commands selects from a list of disassembly styles. The
17610 @code{"std"} style is the standard style.
17612 @item show arm disassembler
17614 Show the current disassembly style.
17616 @item set arm apcs32
17617 @cindex ARM 32-bit mode
17618 This command toggles ARM operation mode between 32-bit and 26-bit.
17620 @item show arm apcs32
17621 Display the current usage of the ARM 32-bit mode.
17623 @item set arm fpu @var{fputype}
17624 This command sets the ARM floating-point unit (FPU) type. The
17625 argument @var{fputype} can be one of these:
17629 Determine the FPU type by querying the OS ABI.
17631 Software FPU, with mixed-endian doubles on little-endian ARM
17634 GCC-compiled FPA co-processor.
17636 Software FPU with pure-endian doubles.
17642 Show the current type of the FPU.
17645 This command forces @value{GDBN} to use the specified ABI.
17648 Show the currently used ABI.
17650 @item set arm fallback-mode (arm|thumb|auto)
17651 @value{GDBN} uses the symbol table, when available, to determine
17652 whether instructions are ARM or Thumb. This command controls
17653 @value{GDBN}'s default behavior when the symbol table is not
17654 available. The default is @samp{auto}, which causes @value{GDBN} to
17655 use the current execution mode (from the @code{T} bit in the @code{CPSR}
17658 @item show arm fallback-mode
17659 Show the current fallback instruction mode.
17661 @item set arm force-mode (arm|thumb|auto)
17662 This command overrides use of the symbol table to determine whether
17663 instructions are ARM or Thumb. The default is @samp{auto}, which
17664 causes @value{GDBN} to use the symbol table and then the setting
17665 of @samp{set arm fallback-mode}.
17667 @item show arm force-mode
17668 Show the current forced instruction mode.
17670 @item set debug arm
17671 Toggle whether to display ARM-specific debugging messages from the ARM
17672 target support subsystem.
17674 @item show debug arm
17675 Show whether ARM-specific debugging messages are enabled.
17678 The following commands are available when an ARM target is debugged
17679 using the RDI interface:
17682 @item rdilogfile @r{[}@var{file}@r{]}
17684 @cindex ADP (Angel Debugger Protocol) logging
17685 Set the filename for the ADP (Angel Debugger Protocol) packet log.
17686 With an argument, sets the log file to the specified @var{file}. With
17687 no argument, show the current log file name. The default log file is
17690 @item rdilogenable @r{[}@var{arg}@r{]}
17691 @kindex rdilogenable
17692 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
17693 enables logging, with an argument 0 or @code{"no"} disables it. With
17694 no arguments displays the current setting. When logging is enabled,
17695 ADP packets exchanged between @value{GDBN} and the RDI target device
17696 are logged to a file.
17698 @item set rdiromatzero
17699 @kindex set rdiromatzero
17700 @cindex ROM at zero address, RDI
17701 Tell @value{GDBN} whether the target has ROM at address 0. If on,
17702 vector catching is disabled, so that zero address can be used. If off
17703 (the default), vector catching is enabled. For this command to take
17704 effect, it needs to be invoked prior to the @code{target rdi} command.
17706 @item show rdiromatzero
17707 @kindex show rdiromatzero
17708 Show the current setting of ROM at zero address.
17710 @item set rdiheartbeat
17711 @kindex set rdiheartbeat
17712 @cindex RDI heartbeat
17713 Enable or disable RDI heartbeat packets. It is not recommended to
17714 turn on this option, since it confuses ARM and EPI JTAG interface, as
17715 well as the Angel monitor.
17717 @item show rdiheartbeat
17718 @kindex show rdiheartbeat
17719 Show the setting of RDI heartbeat packets.
17723 @item target sim @r{[}@var{simargs}@r{]} @dots{}
17724 The @value{GDBN} ARM simulator accepts the following optional arguments.
17727 @item --swi-support=@var{type}
17728 Tell the simulator which SWI interfaces to support.
17729 @var{type} may be a comma separated list of the following values.
17730 The default value is @code{all}.
17743 @subsection Renesas M32R/D and M32R/SDI
17746 @kindex target m32r
17747 @item target m32r @var{dev}
17748 Renesas M32R/D ROM monitor.
17750 @kindex target m32rsdi
17751 @item target m32rsdi @var{dev}
17752 Renesas M32R SDI server, connected via parallel port to the board.
17755 The following @value{GDBN} commands are specific to the M32R monitor:
17758 @item set download-path @var{path}
17759 @kindex set download-path
17760 @cindex find downloadable @sc{srec} files (M32R)
17761 Set the default path for finding downloadable @sc{srec} files.
17763 @item show download-path
17764 @kindex show download-path
17765 Show the default path for downloadable @sc{srec} files.
17767 @item set board-address @var{addr}
17768 @kindex set board-address
17769 @cindex M32-EVA target board address
17770 Set the IP address for the M32R-EVA target board.
17772 @item show board-address
17773 @kindex show board-address
17774 Show the current IP address of the target board.
17776 @item set server-address @var{addr}
17777 @kindex set server-address
17778 @cindex download server address (M32R)
17779 Set the IP address for the download server, which is the @value{GDBN}'s
17782 @item show server-address
17783 @kindex show server-address
17784 Display the IP address of the download server.
17786 @item upload @r{[}@var{file}@r{]}
17787 @kindex upload@r{, M32R}
17788 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
17789 upload capability. If no @var{file} argument is given, the current
17790 executable file is uploaded.
17792 @item tload @r{[}@var{file}@r{]}
17793 @kindex tload@r{, M32R}
17794 Test the @code{upload} command.
17797 The following commands are available for M32R/SDI:
17802 @cindex reset SDI connection, M32R
17803 This command resets the SDI connection.
17807 This command shows the SDI connection status.
17810 @kindex debug_chaos
17811 @cindex M32R/Chaos debugging
17812 Instructs the remote that M32R/Chaos debugging is to be used.
17814 @item use_debug_dma
17815 @kindex use_debug_dma
17816 Instructs the remote to use the DEBUG_DMA method of accessing memory.
17819 @kindex use_mon_code
17820 Instructs the remote to use the MON_CODE method of accessing memory.
17823 @kindex use_ib_break
17824 Instructs the remote to set breakpoints by IB break.
17826 @item use_dbt_break
17827 @kindex use_dbt_break
17828 Instructs the remote to set breakpoints by DBT.
17834 The Motorola m68k configuration includes ColdFire support, and a
17835 target command for the following ROM monitor.
17839 @kindex target dbug
17840 @item target dbug @var{dev}
17841 dBUG ROM monitor for Motorola ColdFire.
17846 @subsection MicroBlaze
17847 @cindex Xilinx MicroBlaze
17848 @cindex XMD, Xilinx Microprocessor Debugger
17850 The MicroBlaze is a soft-core processor supported on various Xilinx
17851 FPGAs, such as Spartan or Virtex series. Boards with these processors
17852 usually have JTAG ports which connect to a host system running the Xilinx
17853 Embedded Development Kit (EDK) or Software Development Kit (SDK).
17854 This host system is used to download the configuration bitstream to
17855 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
17856 communicates with the target board using the JTAG interface and
17857 presents a @code{gdbserver} interface to the board. By default
17858 @code{xmd} uses port @code{1234}. (While it is possible to change
17859 this default port, it requires the use of undocumented @code{xmd}
17860 commands. Contact Xilinx support if you need to do this.)
17862 Use these GDB commands to connect to the MicroBlaze target processor.
17865 @item target remote :1234
17866 Use this command to connect to the target if you are running @value{GDBN}
17867 on the same system as @code{xmd}.
17869 @item target remote @var{xmd-host}:1234
17870 Use this command to connect to the target if it is connected to @code{xmd}
17871 running on a different system named @var{xmd-host}.
17874 Use this command to download a program to the MicroBlaze target.
17876 @item set debug microblaze @var{n}
17877 Enable MicroBlaze-specific debugging messages if non-zero.
17879 @item show debug microblaze @var{n}
17880 Show MicroBlaze-specific debugging level.
17883 @node MIPS Embedded
17884 @subsection MIPS Embedded
17886 @cindex MIPS boards
17887 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
17888 MIPS board attached to a serial line. This is available when
17889 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
17892 Use these @value{GDBN} commands to specify the connection to your target board:
17895 @item target mips @var{port}
17896 @kindex target mips @var{port}
17897 To run a program on the board, start up @code{@value{GDBP}} with the
17898 name of your program as the argument. To connect to the board, use the
17899 command @samp{target mips @var{port}}, where @var{port} is the name of
17900 the serial port connected to the board. If the program has not already
17901 been downloaded to the board, you may use the @code{load} command to
17902 download it. You can then use all the usual @value{GDBN} commands.
17904 For example, this sequence connects to the target board through a serial
17905 port, and loads and runs a program called @var{prog} through the
17909 host$ @value{GDBP} @var{prog}
17910 @value{GDBN} is free software and @dots{}
17911 (@value{GDBP}) target mips /dev/ttyb
17912 (@value{GDBP}) load @var{prog}
17916 @item target mips @var{hostname}:@var{portnumber}
17917 On some @value{GDBN} host configurations, you can specify a TCP
17918 connection (for instance, to a serial line managed by a terminal
17919 concentrator) instead of a serial port, using the syntax
17920 @samp{@var{hostname}:@var{portnumber}}.
17922 @item target pmon @var{port}
17923 @kindex target pmon @var{port}
17926 @item target ddb @var{port}
17927 @kindex target ddb @var{port}
17928 NEC's DDB variant of PMON for Vr4300.
17930 @item target lsi @var{port}
17931 @kindex target lsi @var{port}
17932 LSI variant of PMON.
17934 @kindex target r3900
17935 @item target r3900 @var{dev}
17936 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
17938 @kindex target array
17939 @item target array @var{dev}
17940 Array Tech LSI33K RAID controller board.
17946 @value{GDBN} also supports these special commands for MIPS targets:
17949 @item set mipsfpu double
17950 @itemx set mipsfpu single
17951 @itemx set mipsfpu none
17952 @itemx set mipsfpu auto
17953 @itemx show mipsfpu
17954 @kindex set mipsfpu
17955 @kindex show mipsfpu
17956 @cindex MIPS remote floating point
17957 @cindex floating point, MIPS remote
17958 If your target board does not support the MIPS floating point
17959 coprocessor, you should use the command @samp{set mipsfpu none} (if you
17960 need this, you may wish to put the command in your @value{GDBN} init
17961 file). This tells @value{GDBN} how to find the return value of
17962 functions which return floating point values. It also allows
17963 @value{GDBN} to avoid saving the floating point registers when calling
17964 functions on the board. If you are using a floating point coprocessor
17965 with only single precision floating point support, as on the @sc{r4650}
17966 processor, use the command @samp{set mipsfpu single}. The default
17967 double precision floating point coprocessor may be selected using
17968 @samp{set mipsfpu double}.
17970 In previous versions the only choices were double precision or no
17971 floating point, so @samp{set mipsfpu on} will select double precision
17972 and @samp{set mipsfpu off} will select no floating point.
17974 As usual, you can inquire about the @code{mipsfpu} variable with
17975 @samp{show mipsfpu}.
17977 @item set timeout @var{seconds}
17978 @itemx set retransmit-timeout @var{seconds}
17979 @itemx show timeout
17980 @itemx show retransmit-timeout
17981 @cindex @code{timeout}, MIPS protocol
17982 @cindex @code{retransmit-timeout}, MIPS protocol
17983 @kindex set timeout
17984 @kindex show timeout
17985 @kindex set retransmit-timeout
17986 @kindex show retransmit-timeout
17987 You can control the timeout used while waiting for a packet, in the MIPS
17988 remote protocol, with the @code{set timeout @var{seconds}} command. The
17989 default is 5 seconds. Similarly, you can control the timeout used while
17990 waiting for an acknowledgment of a packet with the @code{set
17991 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
17992 You can inspect both values with @code{show timeout} and @code{show
17993 retransmit-timeout}. (These commands are @emph{only} available when
17994 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
17996 The timeout set by @code{set timeout} does not apply when @value{GDBN}
17997 is waiting for your program to stop. In that case, @value{GDBN} waits
17998 forever because it has no way of knowing how long the program is going
17999 to run before stopping.
18001 @item set syn-garbage-limit @var{num}
18002 @kindex set syn-garbage-limit@r{, MIPS remote}
18003 @cindex synchronize with remote MIPS target
18004 Limit the maximum number of characters @value{GDBN} should ignore when
18005 it tries to synchronize with the remote target. The default is 10
18006 characters. Setting the limit to -1 means there's no limit.
18008 @item show syn-garbage-limit
18009 @kindex show syn-garbage-limit@r{, MIPS remote}
18010 Show the current limit on the number of characters to ignore when
18011 trying to synchronize with the remote system.
18013 @item set monitor-prompt @var{prompt}
18014 @kindex set monitor-prompt@r{, MIPS remote}
18015 @cindex remote monitor prompt
18016 Tell @value{GDBN} to expect the specified @var{prompt} string from the
18017 remote monitor. The default depends on the target:
18027 @item show monitor-prompt
18028 @kindex show monitor-prompt@r{, MIPS remote}
18029 Show the current strings @value{GDBN} expects as the prompt from the
18032 @item set monitor-warnings
18033 @kindex set monitor-warnings@r{, MIPS remote}
18034 Enable or disable monitor warnings about hardware breakpoints. This
18035 has effect only for the @code{lsi} target. When on, @value{GDBN} will
18036 display warning messages whose codes are returned by the @code{lsi}
18037 PMON monitor for breakpoint commands.
18039 @item show monitor-warnings
18040 @kindex show monitor-warnings@r{, MIPS remote}
18041 Show the current setting of printing monitor warnings.
18043 @item pmon @var{command}
18044 @kindex pmon@r{, MIPS remote}
18045 @cindex send PMON command
18046 This command allows sending an arbitrary @var{command} string to the
18047 monitor. The monitor must be in debug mode for this to work.
18050 @node OpenRISC 1000
18051 @subsection OpenRISC 1000
18052 @cindex OpenRISC 1000
18054 @cindex or1k boards
18055 See OR1k Architecture document (@uref{www.opencores.org}) for more information
18056 about platform and commands.
18060 @kindex target jtag
18061 @item target jtag jtag://@var{host}:@var{port}
18063 Connects to remote JTAG server.
18064 JTAG remote server can be either an or1ksim or JTAG server,
18065 connected via parallel port to the board.
18067 Example: @code{target jtag jtag://localhost:9999}
18070 @item or1ksim @var{command}
18071 If connected to @code{or1ksim} OpenRISC 1000 Architectural
18072 Simulator, proprietary commands can be executed.
18074 @kindex info or1k spr
18075 @item info or1k spr
18076 Displays spr groups.
18078 @item info or1k spr @var{group}
18079 @itemx info or1k spr @var{groupno}
18080 Displays register names in selected group.
18082 @item info or1k spr @var{group} @var{register}
18083 @itemx info or1k spr @var{register}
18084 @itemx info or1k spr @var{groupno} @var{registerno}
18085 @itemx info or1k spr @var{registerno}
18086 Shows information about specified spr register.
18089 @item spr @var{group} @var{register} @var{value}
18090 @itemx spr @var{register @var{value}}
18091 @itemx spr @var{groupno} @var{registerno @var{value}}
18092 @itemx spr @var{registerno @var{value}}
18093 Writes @var{value} to specified spr register.
18096 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
18097 It is very similar to @value{GDBN} trace, except it does not interfere with normal
18098 program execution and is thus much faster. Hardware breakpoints/watchpoint
18099 triggers can be set using:
18102 Load effective address/data
18104 Store effective address/data
18106 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
18111 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
18112 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
18114 @code{htrace} commands:
18115 @cindex OpenRISC 1000 htrace
18118 @item hwatch @var{conditional}
18119 Set hardware watchpoint on combination of Load/Store Effective Address(es)
18120 or Data. For example:
18122 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
18124 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
18128 Display information about current HW trace configuration.
18130 @item htrace trigger @var{conditional}
18131 Set starting criteria for HW trace.
18133 @item htrace qualifier @var{conditional}
18134 Set acquisition qualifier for HW trace.
18136 @item htrace stop @var{conditional}
18137 Set HW trace stopping criteria.
18139 @item htrace record [@var{data}]*
18140 Selects the data to be recorded, when qualifier is met and HW trace was
18143 @item htrace enable
18144 @itemx htrace disable
18145 Enables/disables the HW trace.
18147 @item htrace rewind [@var{filename}]
18148 Clears currently recorded trace data.
18150 If filename is specified, new trace file is made and any newly collected data
18151 will be written there.
18153 @item htrace print [@var{start} [@var{len}]]
18154 Prints trace buffer, using current record configuration.
18156 @item htrace mode continuous
18157 Set continuous trace mode.
18159 @item htrace mode suspend
18160 Set suspend trace mode.
18164 @node PowerPC Embedded
18165 @subsection PowerPC Embedded
18167 @value{GDBN} provides the following PowerPC-specific commands:
18170 @kindex set powerpc
18171 @item set powerpc soft-float
18172 @itemx show powerpc soft-float
18173 Force @value{GDBN} to use (or not use) a software floating point calling
18174 convention. By default, @value{GDBN} selects the calling convention based
18175 on the selected architecture and the provided executable file.
18177 @item set powerpc vector-abi
18178 @itemx show powerpc vector-abi
18179 Force @value{GDBN} to use the specified calling convention for vector
18180 arguments and return values. The valid options are @samp{auto};
18181 @samp{generic}, to avoid vector registers even if they are present;
18182 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
18183 registers. By default, @value{GDBN} selects the calling convention
18184 based on the selected architecture and the provided executable file.
18186 @kindex target dink32
18187 @item target dink32 @var{dev}
18188 DINK32 ROM monitor.
18190 @kindex target ppcbug
18191 @item target ppcbug @var{dev}
18192 @kindex target ppcbug1
18193 @item target ppcbug1 @var{dev}
18194 PPCBUG ROM monitor for PowerPC.
18197 @item target sds @var{dev}
18198 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
18201 @cindex SDS protocol
18202 The following commands specific to the SDS protocol are supported
18206 @item set sdstimeout @var{nsec}
18207 @kindex set sdstimeout
18208 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
18209 default is 2 seconds.
18211 @item show sdstimeout
18212 @kindex show sdstimeout
18213 Show the current value of the SDS timeout.
18215 @item sds @var{command}
18216 @kindex sds@r{, a command}
18217 Send the specified @var{command} string to the SDS monitor.
18222 @subsection HP PA Embedded
18226 @kindex target op50n
18227 @item target op50n @var{dev}
18228 OP50N monitor, running on an OKI HPPA board.
18230 @kindex target w89k
18231 @item target w89k @var{dev}
18232 W89K monitor, running on a Winbond HPPA board.
18237 @subsection Tsqware Sparclet
18241 @value{GDBN} enables developers to debug tasks running on
18242 Sparclet targets from a Unix host.
18243 @value{GDBN} uses code that runs on
18244 both the Unix host and on the Sparclet target. The program
18245 @code{@value{GDBP}} is installed and executed on the Unix host.
18248 @item remotetimeout @var{args}
18249 @kindex remotetimeout
18250 @value{GDBN} supports the option @code{remotetimeout}.
18251 This option is set by the user, and @var{args} represents the number of
18252 seconds @value{GDBN} waits for responses.
18255 @cindex compiling, on Sparclet
18256 When compiling for debugging, include the options @samp{-g} to get debug
18257 information and @samp{-Ttext} to relocate the program to where you wish to
18258 load it on the target. You may also want to add the options @samp{-n} or
18259 @samp{-N} in order to reduce the size of the sections. Example:
18262 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
18265 You can use @code{objdump} to verify that the addresses are what you intended:
18268 sparclet-aout-objdump --headers --syms prog
18271 @cindex running, on Sparclet
18273 your Unix execution search path to find @value{GDBN}, you are ready to
18274 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
18275 (or @code{sparclet-aout-gdb}, depending on your installation).
18277 @value{GDBN} comes up showing the prompt:
18284 * Sparclet File:: Setting the file to debug
18285 * Sparclet Connection:: Connecting to Sparclet
18286 * Sparclet Download:: Sparclet download
18287 * Sparclet Execution:: Running and debugging
18290 @node Sparclet File
18291 @subsubsection Setting File to Debug
18293 The @value{GDBN} command @code{file} lets you choose with program to debug.
18296 (gdbslet) file prog
18300 @value{GDBN} then attempts to read the symbol table of @file{prog}.
18301 @value{GDBN} locates
18302 the file by searching the directories listed in the command search
18304 If the file was compiled with debug information (option @samp{-g}), source
18305 files will be searched as well.
18306 @value{GDBN} locates
18307 the source files by searching the directories listed in the directory search
18308 path (@pxref{Environment, ,Your Program's Environment}).
18310 to find a file, it displays a message such as:
18313 prog: No such file or directory.
18316 When this happens, add the appropriate directories to the search paths with
18317 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
18318 @code{target} command again.
18320 @node Sparclet Connection
18321 @subsubsection Connecting to Sparclet
18323 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
18324 To connect to a target on serial port ``@code{ttya}'', type:
18327 (gdbslet) target sparclet /dev/ttya
18328 Remote target sparclet connected to /dev/ttya
18329 main () at ../prog.c:3
18333 @value{GDBN} displays messages like these:
18339 @node Sparclet Download
18340 @subsubsection Sparclet Download
18342 @cindex download to Sparclet
18343 Once connected to the Sparclet target,
18344 you can use the @value{GDBN}
18345 @code{load} command to download the file from the host to the target.
18346 The file name and load offset should be given as arguments to the @code{load}
18348 Since the file format is aout, the program must be loaded to the starting
18349 address. You can use @code{objdump} to find out what this value is. The load
18350 offset is an offset which is added to the VMA (virtual memory address)
18351 of each of the file's sections.
18352 For instance, if the program
18353 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
18354 and bss at 0x12010170, in @value{GDBN}, type:
18357 (gdbslet) load prog 0x12010000
18358 Loading section .text, size 0xdb0 vma 0x12010000
18361 If the code is loaded at a different address then what the program was linked
18362 to, you may need to use the @code{section} and @code{add-symbol-file} commands
18363 to tell @value{GDBN} where to map the symbol table.
18365 @node Sparclet Execution
18366 @subsubsection Running and Debugging
18368 @cindex running and debugging Sparclet programs
18369 You can now begin debugging the task using @value{GDBN}'s execution control
18370 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
18371 manual for the list of commands.
18375 Breakpoint 1 at 0x12010000: file prog.c, line 3.
18377 Starting program: prog
18378 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
18379 3 char *symarg = 0;
18381 4 char *execarg = "hello!";
18386 @subsection Fujitsu Sparclite
18390 @kindex target sparclite
18391 @item target sparclite @var{dev}
18392 Fujitsu sparclite boards, used only for the purpose of loading.
18393 You must use an additional command to debug the program.
18394 For example: target remote @var{dev} using @value{GDBN} standard
18400 @subsection Zilog Z8000
18403 @cindex simulator, Z8000
18404 @cindex Zilog Z8000 simulator
18406 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
18409 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
18410 unsegmented variant of the Z8000 architecture) or the Z8001 (the
18411 segmented variant). The simulator recognizes which architecture is
18412 appropriate by inspecting the object code.
18415 @item target sim @var{args}
18417 @kindex target sim@r{, with Z8000}
18418 Debug programs on a simulated CPU. If the simulator supports setup
18419 options, specify them via @var{args}.
18423 After specifying this target, you can debug programs for the simulated
18424 CPU in the same style as programs for your host computer; use the
18425 @code{file} command to load a new program image, the @code{run} command
18426 to run your program, and so on.
18428 As well as making available all the usual machine registers
18429 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
18430 additional items of information as specially named registers:
18435 Counts clock-ticks in the simulator.
18438 Counts instructions run in the simulator.
18441 Execution time in 60ths of a second.
18445 You can refer to these values in @value{GDBN} expressions with the usual
18446 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
18447 conditional breakpoint that suspends only after at least 5000
18448 simulated clock ticks.
18451 @subsection Atmel AVR
18454 When configured for debugging the Atmel AVR, @value{GDBN} supports the
18455 following AVR-specific commands:
18458 @item info io_registers
18459 @kindex info io_registers@r{, AVR}
18460 @cindex I/O registers (Atmel AVR)
18461 This command displays information about the AVR I/O registers. For
18462 each register, @value{GDBN} prints its number and value.
18469 When configured for debugging CRIS, @value{GDBN} provides the
18470 following CRIS-specific commands:
18473 @item set cris-version @var{ver}
18474 @cindex CRIS version
18475 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
18476 The CRIS version affects register names and sizes. This command is useful in
18477 case autodetection of the CRIS version fails.
18479 @item show cris-version
18480 Show the current CRIS version.
18482 @item set cris-dwarf2-cfi
18483 @cindex DWARF-2 CFI and CRIS
18484 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
18485 Change to @samp{off} when using @code{gcc-cris} whose version is below
18488 @item show cris-dwarf2-cfi
18489 Show the current state of using DWARF-2 CFI.
18491 @item set cris-mode @var{mode}
18493 Set the current CRIS mode to @var{mode}. It should only be changed when
18494 debugging in guru mode, in which case it should be set to
18495 @samp{guru} (the default is @samp{normal}).
18497 @item show cris-mode
18498 Show the current CRIS mode.
18502 @subsection Renesas Super-H
18505 For the Renesas Super-H processor, @value{GDBN} provides these
18510 @kindex regs@r{, Super-H}
18511 Show the values of all Super-H registers.
18513 @item set sh calling-convention @var{convention}
18514 @kindex set sh calling-convention
18515 Set the calling-convention used when calling functions from @value{GDBN}.
18516 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
18517 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
18518 convention. If the DWARF-2 information of the called function specifies
18519 that the function follows the Renesas calling convention, the function
18520 is called using the Renesas calling convention. If the calling convention
18521 is set to @samp{renesas}, the Renesas calling convention is always used,
18522 regardless of the DWARF-2 information. This can be used to override the
18523 default of @samp{gcc} if debug information is missing, or the compiler
18524 does not emit the DWARF-2 calling convention entry for a function.
18526 @item show sh calling-convention
18527 @kindex show sh calling-convention
18528 Show the current calling convention setting.
18533 @node Architectures
18534 @section Architectures
18536 This section describes characteristics of architectures that affect
18537 all uses of @value{GDBN} with the architecture, both native and cross.
18544 * HPPA:: HP PA architecture
18545 * SPU:: Cell Broadband Engine SPU architecture
18550 @subsection x86 Architecture-specific Issues
18553 @item set struct-convention @var{mode}
18554 @kindex set struct-convention
18555 @cindex struct return convention
18556 @cindex struct/union returned in registers
18557 Set the convention used by the inferior to return @code{struct}s and
18558 @code{union}s from functions to @var{mode}. Possible values of
18559 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
18560 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
18561 are returned on the stack, while @code{"reg"} means that a
18562 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
18563 be returned in a register.
18565 @item show struct-convention
18566 @kindex show struct-convention
18567 Show the current setting of the convention to return @code{struct}s
18576 @kindex set rstack_high_address
18577 @cindex AMD 29K register stack
18578 @cindex register stack, AMD29K
18579 @item set rstack_high_address @var{address}
18580 On AMD 29000 family processors, registers are saved in a separate
18581 @dfn{register stack}. There is no way for @value{GDBN} to determine the
18582 extent of this stack. Normally, @value{GDBN} just assumes that the
18583 stack is ``large enough''. This may result in @value{GDBN} referencing
18584 memory locations that do not exist. If necessary, you can get around
18585 this problem by specifying the ending address of the register stack with
18586 the @code{set rstack_high_address} command. The argument should be an
18587 address, which you probably want to precede with @samp{0x} to specify in
18590 @kindex show rstack_high_address
18591 @item show rstack_high_address
18592 Display the current limit of the register stack, on AMD 29000 family
18600 See the following section.
18605 @cindex stack on Alpha
18606 @cindex stack on MIPS
18607 @cindex Alpha stack
18609 Alpha- and MIPS-based computers use an unusual stack frame, which
18610 sometimes requires @value{GDBN} to search backward in the object code to
18611 find the beginning of a function.
18613 @cindex response time, MIPS debugging
18614 To improve response time (especially for embedded applications, where
18615 @value{GDBN} may be restricted to a slow serial line for this search)
18616 you may want to limit the size of this search, using one of these
18620 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
18621 @item set heuristic-fence-post @var{limit}
18622 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
18623 search for the beginning of a function. A value of @var{0} (the
18624 default) means there is no limit. However, except for @var{0}, the
18625 larger the limit the more bytes @code{heuristic-fence-post} must search
18626 and therefore the longer it takes to run. You should only need to use
18627 this command when debugging a stripped executable.
18629 @item show heuristic-fence-post
18630 Display the current limit.
18634 These commands are available @emph{only} when @value{GDBN} is configured
18635 for debugging programs on Alpha or MIPS processors.
18637 Several MIPS-specific commands are available when debugging MIPS
18641 @item set mips abi @var{arg}
18642 @kindex set mips abi
18643 @cindex set ABI for MIPS
18644 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
18645 values of @var{arg} are:
18649 The default ABI associated with the current binary (this is the
18660 @item show mips abi
18661 @kindex show mips abi
18662 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
18665 @itemx show mipsfpu
18666 @xref{MIPS Embedded, set mipsfpu}.
18668 @item set mips mask-address @var{arg}
18669 @kindex set mips mask-address
18670 @cindex MIPS addresses, masking
18671 This command determines whether the most-significant 32 bits of 64-bit
18672 MIPS addresses are masked off. The argument @var{arg} can be
18673 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
18674 setting, which lets @value{GDBN} determine the correct value.
18676 @item show mips mask-address
18677 @kindex show mips mask-address
18678 Show whether the upper 32 bits of MIPS addresses are masked off or
18681 @item set remote-mips64-transfers-32bit-regs
18682 @kindex set remote-mips64-transfers-32bit-regs
18683 This command controls compatibility with 64-bit MIPS targets that
18684 transfer data in 32-bit quantities. If you have an old MIPS 64 target
18685 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
18686 and 64 bits for other registers, set this option to @samp{on}.
18688 @item show remote-mips64-transfers-32bit-regs
18689 @kindex show remote-mips64-transfers-32bit-regs
18690 Show the current setting of compatibility with older MIPS 64 targets.
18692 @item set debug mips
18693 @kindex set debug mips
18694 This command turns on and off debugging messages for the MIPS-specific
18695 target code in @value{GDBN}.
18697 @item show debug mips
18698 @kindex show debug mips
18699 Show the current setting of MIPS debugging messages.
18705 @cindex HPPA support
18707 When @value{GDBN} is debugging the HP PA architecture, it provides the
18708 following special commands:
18711 @item set debug hppa
18712 @kindex set debug hppa
18713 This command determines whether HPPA architecture-specific debugging
18714 messages are to be displayed.
18716 @item show debug hppa
18717 Show whether HPPA debugging messages are displayed.
18719 @item maint print unwind @var{address}
18720 @kindex maint print unwind@r{, HPPA}
18721 This command displays the contents of the unwind table entry at the
18722 given @var{address}.
18728 @subsection Cell Broadband Engine SPU architecture
18729 @cindex Cell Broadband Engine
18732 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
18733 it provides the following special commands:
18736 @item info spu event
18738 Display SPU event facility status. Shows current event mask
18739 and pending event status.
18741 @item info spu signal
18742 Display SPU signal notification facility status. Shows pending
18743 signal-control word and signal notification mode of both signal
18744 notification channels.
18746 @item info spu mailbox
18747 Display SPU mailbox facility status. Shows all pending entries,
18748 in order of processing, in each of the SPU Write Outbound,
18749 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
18752 Display MFC DMA status. Shows all pending commands in the MFC
18753 DMA queue. For each entry, opcode, tag, class IDs, effective
18754 and local store addresses and transfer size are shown.
18756 @item info spu proxydma
18757 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
18758 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
18759 and local store addresses and transfer size are shown.
18763 When @value{GDBN} is debugging a combined PowerPC/SPU application
18764 on the Cell Broadband Engine, it provides in addition the following
18768 @item set spu stop-on-load @var{arg}
18770 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
18771 will give control to the user when a new SPE thread enters its @code{main}
18772 function. The default is @code{off}.
18774 @item show spu stop-on-load
18776 Show whether to stop for new SPE threads.
18778 @item set spu auto-flush-cache @var{arg}
18779 Set whether to automatically flush the software-managed cache. When set to
18780 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
18781 cache to be flushed whenever SPE execution stops. This provides a consistent
18782 view of PowerPC memory that is accessed via the cache. If an application
18783 does not use the software-managed cache, this option has no effect.
18785 @item show spu auto-flush-cache
18786 Show whether to automatically flush the software-managed cache.
18791 @subsection PowerPC
18792 @cindex PowerPC architecture
18794 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
18795 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
18796 numbers stored in the floating point registers. These values must be stored
18797 in two consecutive registers, always starting at an even register like
18798 @code{f0} or @code{f2}.
18800 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
18801 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
18802 @code{f2} and @code{f3} for @code{$dl1} and so on.
18804 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
18805 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
18808 @node Controlling GDB
18809 @chapter Controlling @value{GDBN}
18811 You can alter the way @value{GDBN} interacts with you by using the
18812 @code{set} command. For commands controlling how @value{GDBN} displays
18813 data, see @ref{Print Settings, ,Print Settings}. Other settings are
18818 * Editing:: Command editing
18819 * Command History:: Command history
18820 * Screen Size:: Screen size
18821 * Numbers:: Numbers
18822 * ABI:: Configuring the current ABI
18823 * Messages/Warnings:: Optional warnings and messages
18824 * Debugging Output:: Optional messages about internal happenings
18825 * Other Misc Settings:: Other Miscellaneous Settings
18833 @value{GDBN} indicates its readiness to read a command by printing a string
18834 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
18835 can change the prompt string with the @code{set prompt} command. For
18836 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
18837 the prompt in one of the @value{GDBN} sessions so that you can always tell
18838 which one you are talking to.
18840 @emph{Note:} @code{set prompt} does not add a space for you after the
18841 prompt you set. This allows you to set a prompt which ends in a space
18842 or a prompt that does not.
18846 @item set prompt @var{newprompt}
18847 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
18849 @kindex show prompt
18851 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
18855 @section Command Editing
18857 @cindex command line editing
18859 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
18860 @sc{gnu} library provides consistent behavior for programs which provide a
18861 command line interface to the user. Advantages are @sc{gnu} Emacs-style
18862 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
18863 substitution, and a storage and recall of command history across
18864 debugging sessions.
18866 You may control the behavior of command line editing in @value{GDBN} with the
18867 command @code{set}.
18870 @kindex set editing
18873 @itemx set editing on
18874 Enable command line editing (enabled by default).
18876 @item set editing off
18877 Disable command line editing.
18879 @kindex show editing
18881 Show whether command line editing is enabled.
18884 @xref{Command Line Editing}, for more details about the Readline
18885 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
18886 encouraged to read that chapter.
18888 @node Command History
18889 @section Command History
18890 @cindex command history
18892 @value{GDBN} can keep track of the commands you type during your
18893 debugging sessions, so that you can be certain of precisely what
18894 happened. Use these commands to manage the @value{GDBN} command
18897 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
18898 package, to provide the history facility. @xref{Using History
18899 Interactively}, for the detailed description of the History library.
18901 To issue a command to @value{GDBN} without affecting certain aspects of
18902 the state which is seen by users, prefix it with @samp{server }
18903 (@pxref{Server Prefix}). This
18904 means that this command will not affect the command history, nor will it
18905 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
18906 pressed on a line by itself.
18908 @cindex @code{server}, command prefix
18909 The server prefix does not affect the recording of values into the value
18910 history; to print a value without recording it into the value history,
18911 use the @code{output} command instead of the @code{print} command.
18913 Here is the description of @value{GDBN} commands related to command
18917 @cindex history substitution
18918 @cindex history file
18919 @kindex set history filename
18920 @cindex @env{GDBHISTFILE}, environment variable
18921 @item set history filename @var{fname}
18922 Set the name of the @value{GDBN} command history file to @var{fname}.
18923 This is the file where @value{GDBN} reads an initial command history
18924 list, and where it writes the command history from this session when it
18925 exits. You can access this list through history expansion or through
18926 the history command editing characters listed below. This file defaults
18927 to the value of the environment variable @code{GDBHISTFILE}, or to
18928 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
18931 @cindex save command history
18932 @kindex set history save
18933 @item set history save
18934 @itemx set history save on
18935 Record command history in a file, whose name may be specified with the
18936 @code{set history filename} command. By default, this option is disabled.
18938 @item set history save off
18939 Stop recording command history in a file.
18941 @cindex history size
18942 @kindex set history size
18943 @cindex @env{HISTSIZE}, environment variable
18944 @item set history size @var{size}
18945 Set the number of commands which @value{GDBN} keeps in its history list.
18946 This defaults to the value of the environment variable
18947 @code{HISTSIZE}, or to 256 if this variable is not set.
18950 History expansion assigns special meaning to the character @kbd{!}.
18951 @xref{Event Designators}, for more details.
18953 @cindex history expansion, turn on/off
18954 Since @kbd{!} is also the logical not operator in C, history expansion
18955 is off by default. If you decide to enable history expansion with the
18956 @code{set history expansion on} command, you may sometimes need to
18957 follow @kbd{!} (when it is used as logical not, in an expression) with
18958 a space or a tab to prevent it from being expanded. The readline
18959 history facilities do not attempt substitution on the strings
18960 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
18962 The commands to control history expansion are:
18965 @item set history expansion on
18966 @itemx set history expansion
18967 @kindex set history expansion
18968 Enable history expansion. History expansion is off by default.
18970 @item set history expansion off
18971 Disable history expansion.
18974 @kindex show history
18976 @itemx show history filename
18977 @itemx show history save
18978 @itemx show history size
18979 @itemx show history expansion
18980 These commands display the state of the @value{GDBN} history parameters.
18981 @code{show history} by itself displays all four states.
18986 @kindex show commands
18987 @cindex show last commands
18988 @cindex display command history
18989 @item show commands
18990 Display the last ten commands in the command history.
18992 @item show commands @var{n}
18993 Print ten commands centered on command number @var{n}.
18995 @item show commands +
18996 Print ten commands just after the commands last printed.
19000 @section Screen Size
19001 @cindex size of screen
19002 @cindex pauses in output
19004 Certain commands to @value{GDBN} may produce large amounts of
19005 information output to the screen. To help you read all of it,
19006 @value{GDBN} pauses and asks you for input at the end of each page of
19007 output. Type @key{RET} when you want to continue the output, or @kbd{q}
19008 to discard the remaining output. Also, the screen width setting
19009 determines when to wrap lines of output. Depending on what is being
19010 printed, @value{GDBN} tries to break the line at a readable place,
19011 rather than simply letting it overflow onto the following line.
19013 Normally @value{GDBN} knows the size of the screen from the terminal
19014 driver software. For example, on Unix @value{GDBN} uses the termcap data base
19015 together with the value of the @code{TERM} environment variable and the
19016 @code{stty rows} and @code{stty cols} settings. If this is not correct,
19017 you can override it with the @code{set height} and @code{set
19024 @kindex show height
19025 @item set height @var{lpp}
19027 @itemx set width @var{cpl}
19029 These @code{set} commands specify a screen height of @var{lpp} lines and
19030 a screen width of @var{cpl} characters. The associated @code{show}
19031 commands display the current settings.
19033 If you specify a height of zero lines, @value{GDBN} does not pause during
19034 output no matter how long the output is. This is useful if output is to a
19035 file or to an editor buffer.
19037 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
19038 from wrapping its output.
19040 @item set pagination on
19041 @itemx set pagination off
19042 @kindex set pagination
19043 Turn the output pagination on or off; the default is on. Turning
19044 pagination off is the alternative to @code{set height 0}. Note that
19045 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
19046 Options, -batch}) also automatically disables pagination.
19048 @item show pagination
19049 @kindex show pagination
19050 Show the current pagination mode.
19055 @cindex number representation
19056 @cindex entering numbers
19058 You can always enter numbers in octal, decimal, or hexadecimal in
19059 @value{GDBN} by the usual conventions: octal numbers begin with
19060 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
19061 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
19062 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
19063 10; likewise, the default display for numbers---when no particular
19064 format is specified---is base 10. You can change the default base for
19065 both input and output with the commands described below.
19068 @kindex set input-radix
19069 @item set input-radix @var{base}
19070 Set the default base for numeric input. Supported choices
19071 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
19072 specified either unambiguously or using the current input radix; for
19076 set input-radix 012
19077 set input-radix 10.
19078 set input-radix 0xa
19082 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
19083 leaves the input radix unchanged, no matter what it was, since
19084 @samp{10}, being without any leading or trailing signs of its base, is
19085 interpreted in the current radix. Thus, if the current radix is 16,
19086 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
19089 @kindex set output-radix
19090 @item set output-radix @var{base}
19091 Set the default base for numeric display. Supported choices
19092 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
19093 specified either unambiguously or using the current input radix.
19095 @kindex show input-radix
19096 @item show input-radix
19097 Display the current default base for numeric input.
19099 @kindex show output-radix
19100 @item show output-radix
19101 Display the current default base for numeric display.
19103 @item set radix @r{[}@var{base}@r{]}
19107 These commands set and show the default base for both input and output
19108 of numbers. @code{set radix} sets the radix of input and output to
19109 the same base; without an argument, it resets the radix back to its
19110 default value of 10.
19115 @section Configuring the Current ABI
19117 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
19118 application automatically. However, sometimes you need to override its
19119 conclusions. Use these commands to manage @value{GDBN}'s view of the
19126 One @value{GDBN} configuration can debug binaries for multiple operating
19127 system targets, either via remote debugging or native emulation.
19128 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
19129 but you can override its conclusion using the @code{set osabi} command.
19130 One example where this is useful is in debugging of binaries which use
19131 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
19132 not have the same identifying marks that the standard C library for your
19137 Show the OS ABI currently in use.
19140 With no argument, show the list of registered available OS ABI's.
19142 @item set osabi @var{abi}
19143 Set the current OS ABI to @var{abi}.
19146 @cindex float promotion
19148 Generally, the way that an argument of type @code{float} is passed to a
19149 function depends on whether the function is prototyped. For a prototyped
19150 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
19151 according to the architecture's convention for @code{float}. For unprototyped
19152 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
19153 @code{double} and then passed.
19155 Unfortunately, some forms of debug information do not reliably indicate whether
19156 a function is prototyped. If @value{GDBN} calls a function that is not marked
19157 as prototyped, it consults @kbd{set coerce-float-to-double}.
19160 @kindex set coerce-float-to-double
19161 @item set coerce-float-to-double
19162 @itemx set coerce-float-to-double on
19163 Arguments of type @code{float} will be promoted to @code{double} when passed
19164 to an unprototyped function. This is the default setting.
19166 @item set coerce-float-to-double off
19167 Arguments of type @code{float} will be passed directly to unprototyped
19170 @kindex show coerce-float-to-double
19171 @item show coerce-float-to-double
19172 Show the current setting of promoting @code{float} to @code{double}.
19176 @kindex show cp-abi
19177 @value{GDBN} needs to know the ABI used for your program's C@t{++}
19178 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
19179 used to build your application. @value{GDBN} only fully supports
19180 programs with a single C@t{++} ABI; if your program contains code using
19181 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
19182 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
19183 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
19184 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
19185 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
19186 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
19191 Show the C@t{++} ABI currently in use.
19194 With no argument, show the list of supported C@t{++} ABI's.
19196 @item set cp-abi @var{abi}
19197 @itemx set cp-abi auto
19198 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
19201 @node Messages/Warnings
19202 @section Optional Warnings and Messages
19204 @cindex verbose operation
19205 @cindex optional warnings
19206 By default, @value{GDBN} is silent about its inner workings. If you are
19207 running on a slow machine, you may want to use the @code{set verbose}
19208 command. This makes @value{GDBN} tell you when it does a lengthy
19209 internal operation, so you will not think it has crashed.
19211 Currently, the messages controlled by @code{set verbose} are those
19212 which announce that the symbol table for a source file is being read;
19213 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
19216 @kindex set verbose
19217 @item set verbose on
19218 Enables @value{GDBN} output of certain informational messages.
19220 @item set verbose off
19221 Disables @value{GDBN} output of certain informational messages.
19223 @kindex show verbose
19225 Displays whether @code{set verbose} is on or off.
19228 By default, if @value{GDBN} encounters bugs in the symbol table of an
19229 object file, it is silent; but if you are debugging a compiler, you may
19230 find this information useful (@pxref{Symbol Errors, ,Errors Reading
19235 @kindex set complaints
19236 @item set complaints @var{limit}
19237 Permits @value{GDBN} to output @var{limit} complaints about each type of
19238 unusual symbols before becoming silent about the problem. Set
19239 @var{limit} to zero to suppress all complaints; set it to a large number
19240 to prevent complaints from being suppressed.
19242 @kindex show complaints
19243 @item show complaints
19244 Displays how many symbol complaints @value{GDBN} is permitted to produce.
19248 @anchor{confirmation requests}
19249 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
19250 lot of stupid questions to confirm certain commands. For example, if
19251 you try to run a program which is already running:
19255 The program being debugged has been started already.
19256 Start it from the beginning? (y or n)
19259 If you are willing to unflinchingly face the consequences of your own
19260 commands, you can disable this ``feature'':
19264 @kindex set confirm
19266 @cindex confirmation
19267 @cindex stupid questions
19268 @item set confirm off
19269 Disables confirmation requests. Note that running @value{GDBN} with
19270 the @option{--batch} option (@pxref{Mode Options, -batch}) also
19271 automatically disables confirmation requests.
19273 @item set confirm on
19274 Enables confirmation requests (the default).
19276 @kindex show confirm
19278 Displays state of confirmation requests.
19282 @cindex command tracing
19283 If you need to debug user-defined commands or sourced files you may find it
19284 useful to enable @dfn{command tracing}. In this mode each command will be
19285 printed as it is executed, prefixed with one or more @samp{+} symbols, the
19286 quantity denoting the call depth of each command.
19289 @kindex set trace-commands
19290 @cindex command scripts, debugging
19291 @item set trace-commands on
19292 Enable command tracing.
19293 @item set trace-commands off
19294 Disable command tracing.
19295 @item show trace-commands
19296 Display the current state of command tracing.
19299 @node Debugging Output
19300 @section Optional Messages about Internal Happenings
19301 @cindex optional debugging messages
19303 @value{GDBN} has commands that enable optional debugging messages from
19304 various @value{GDBN} subsystems; normally these commands are of
19305 interest to @value{GDBN} maintainers, or when reporting a bug. This
19306 section documents those commands.
19309 @kindex set exec-done-display
19310 @item set exec-done-display
19311 Turns on or off the notification of asynchronous commands'
19312 completion. When on, @value{GDBN} will print a message when an
19313 asynchronous command finishes its execution. The default is off.
19314 @kindex show exec-done-display
19315 @item show exec-done-display
19316 Displays the current setting of asynchronous command completion
19319 @cindex gdbarch debugging info
19320 @cindex architecture debugging info
19321 @item set debug arch
19322 Turns on or off display of gdbarch debugging info. The default is off
19324 @item show debug arch
19325 Displays the current state of displaying gdbarch debugging info.
19326 @item set debug aix-thread
19327 @cindex AIX threads
19328 Display debugging messages about inner workings of the AIX thread
19330 @item show debug aix-thread
19331 Show the current state of AIX thread debugging info display.
19332 @item set debug dwarf2-die
19333 @cindex DWARF2 DIEs
19334 Dump DWARF2 DIEs after they are read in.
19335 The value is the number of nesting levels to print.
19336 A value of zero turns off the display.
19337 @item show debug dwarf2-die
19338 Show the current state of DWARF2 DIE debugging.
19339 @item set debug displaced
19340 @cindex displaced stepping debugging info
19341 Turns on or off display of @value{GDBN} debugging info for the
19342 displaced stepping support. The default is off.
19343 @item show debug displaced
19344 Displays the current state of displaying @value{GDBN} debugging info
19345 related to displaced stepping.
19346 @item set debug event
19347 @cindex event debugging info
19348 Turns on or off display of @value{GDBN} event debugging info. The
19350 @item show debug event
19351 Displays the current state of displaying @value{GDBN} event debugging
19353 @item set debug expression
19354 @cindex expression debugging info
19355 Turns on or off display of debugging info about @value{GDBN}
19356 expression parsing. The default is off.
19357 @item show debug expression
19358 Displays the current state of displaying debugging info about
19359 @value{GDBN} expression parsing.
19360 @item set debug frame
19361 @cindex frame debugging info
19362 Turns on or off display of @value{GDBN} frame debugging info. The
19364 @item show debug frame
19365 Displays the current state of displaying @value{GDBN} frame debugging
19367 @item set debug gnu-nat
19368 @cindex @sc{gnu}/Hurd debug messages
19369 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
19370 @item show debug gnu-nat
19371 Show the current state of @sc{gnu}/Hurd debugging messages.
19372 @item set debug infrun
19373 @cindex inferior debugging info
19374 Turns on or off display of @value{GDBN} debugging info for running the inferior.
19375 The default is off. @file{infrun.c} contains GDB's runtime state machine used
19376 for implementing operations such as single-stepping the inferior.
19377 @item show debug infrun
19378 Displays the current state of @value{GDBN} inferior debugging.
19379 @item set debug lin-lwp
19380 @cindex @sc{gnu}/Linux LWP debug messages
19381 @cindex Linux lightweight processes
19382 Turns on or off debugging messages from the Linux LWP debug support.
19383 @item show debug lin-lwp
19384 Show the current state of Linux LWP debugging messages.
19385 @item set debug lin-lwp-async
19386 @cindex @sc{gnu}/Linux LWP async debug messages
19387 @cindex Linux lightweight processes
19388 Turns on or off debugging messages from the Linux LWP async debug support.
19389 @item show debug lin-lwp-async
19390 Show the current state of Linux LWP async debugging messages.
19391 @item set debug observer
19392 @cindex observer debugging info
19393 Turns on or off display of @value{GDBN} observer debugging. This
19394 includes info such as the notification of observable events.
19395 @item show debug observer
19396 Displays the current state of observer debugging.
19397 @item set debug overload
19398 @cindex C@t{++} overload debugging info
19399 Turns on or off display of @value{GDBN} C@t{++} overload debugging
19400 info. This includes info such as ranking of functions, etc. The default
19402 @item show debug overload
19403 Displays the current state of displaying @value{GDBN} C@t{++} overload
19405 @cindex expression parser, debugging info
19406 @cindex debug expression parser
19407 @item set debug parser
19408 Turns on or off the display of expression parser debugging output.
19409 Internally, this sets the @code{yydebug} variable in the expression
19410 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
19411 details. The default is off.
19412 @item show debug parser
19413 Show the current state of expression parser debugging.
19414 @cindex packets, reporting on stdout
19415 @cindex serial connections, debugging
19416 @cindex debug remote protocol
19417 @cindex remote protocol debugging
19418 @cindex display remote packets
19419 @item set debug remote
19420 Turns on or off display of reports on all packets sent back and forth across
19421 the serial line to the remote machine. The info is printed on the
19422 @value{GDBN} standard output stream. The default is off.
19423 @item show debug remote
19424 Displays the state of display of remote packets.
19425 @item set debug serial
19426 Turns on or off display of @value{GDBN} serial debugging info. The
19428 @item show debug serial
19429 Displays the current state of displaying @value{GDBN} serial debugging
19431 @item set debug solib-frv
19432 @cindex FR-V shared-library debugging
19433 Turns on or off debugging messages for FR-V shared-library code.
19434 @item show debug solib-frv
19435 Display the current state of FR-V shared-library code debugging
19437 @item set debug target
19438 @cindex target debugging info
19439 Turns on or off display of @value{GDBN} target debugging info. This info
19440 includes what is going on at the target level of GDB, as it happens. The
19441 default is 0. Set it to 1 to track events, and to 2 to also track the
19442 value of large memory transfers. Changes to this flag do not take effect
19443 until the next time you connect to a target or use the @code{run} command.
19444 @item show debug target
19445 Displays the current state of displaying @value{GDBN} target debugging
19447 @item set debug timestamp
19448 @cindex timestampping debugging info
19449 Turns on or off display of timestamps with @value{GDBN} debugging info.
19450 When enabled, seconds and microseconds are displayed before each debugging
19452 @item show debug timestamp
19453 Displays the current state of displaying timestamps with @value{GDBN}
19455 @item set debugvarobj
19456 @cindex variable object debugging info
19457 Turns on or off display of @value{GDBN} variable object debugging
19458 info. The default is off.
19459 @item show debugvarobj
19460 Displays the current state of displaying @value{GDBN} variable object
19462 @item set debug xml
19463 @cindex XML parser debugging
19464 Turns on or off debugging messages for built-in XML parsers.
19465 @item show debug xml
19466 Displays the current state of XML debugging messages.
19469 @node Other Misc Settings
19470 @section Other Miscellaneous Settings
19471 @cindex miscellaneous settings
19474 @kindex set interactive-mode
19475 @item set interactive-mode
19476 If @code{on}, forces @value{GDBN} to operate interactively.
19477 If @code{off}, forces @value{GDBN} to operate non-interactively,
19478 If @code{auto} (the default), @value{GDBN} guesses which mode to use,
19479 based on whether the debugger was started in a terminal or not.
19481 In the vast majority of cases, the debugger should be able to guess
19482 correctly which mode should be used. But this setting can be useful
19483 in certain specific cases, such as running a MinGW @value{GDBN}
19484 inside a cygwin window.
19486 @kindex show interactive-mode
19487 @item show interactive-mode
19488 Displays whether the debugger is operating in interactive mode or not.
19491 @node Extending GDB
19492 @chapter Extending @value{GDBN}
19493 @cindex extending GDB
19495 @value{GDBN} provides two mechanisms for extension. The first is based
19496 on composition of @value{GDBN} commands, and the second is based on the
19497 Python scripting language.
19499 To facilitate the use of these extensions, @value{GDBN} is capable
19500 of evaluating the contents of a file. When doing so, @value{GDBN}
19501 can recognize which scripting language is being used by looking at
19502 the filename extension. Files with an unrecognized filename extension
19503 are always treated as a @value{GDBN} Command Files.
19504 @xref{Command Files,, Command files}.
19506 You can control how @value{GDBN} evaluates these files with the following
19510 @kindex set script-extension
19511 @kindex show script-extension
19512 @item set script-extension off
19513 All scripts are always evaluated as @value{GDBN} Command Files.
19515 @item set script-extension soft
19516 The debugger determines the scripting language based on filename
19517 extension. If this scripting language is supported, @value{GDBN}
19518 evaluates the script using that language. Otherwise, it evaluates
19519 the file as a @value{GDBN} Command File.
19521 @item set script-extension strict
19522 The debugger determines the scripting language based on filename
19523 extension, and evaluates the script using that language. If the
19524 language is not supported, then the evaluation fails.
19526 @item show script-extension
19527 Display the current value of the @code{script-extension} option.
19532 * Sequences:: Canned Sequences of Commands
19533 * Python:: Scripting @value{GDBN} using Python
19537 @section Canned Sequences of Commands
19539 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
19540 Command Lists}), @value{GDBN} provides two ways to store sequences of
19541 commands for execution as a unit: user-defined commands and command
19545 * Define:: How to define your own commands
19546 * Hooks:: Hooks for user-defined commands
19547 * Command Files:: How to write scripts of commands to be stored in a file
19548 * Output:: Commands for controlled output
19552 @subsection User-defined Commands
19554 @cindex user-defined command
19555 @cindex arguments, to user-defined commands
19556 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
19557 which you assign a new name as a command. This is done with the
19558 @code{define} command. User commands may accept up to 10 arguments
19559 separated by whitespace. Arguments are accessed within the user command
19560 via @code{$arg0@dots{}$arg9}. A trivial example:
19564 print $arg0 + $arg1 + $arg2
19569 To execute the command use:
19576 This defines the command @code{adder}, which prints the sum of
19577 its three arguments. Note the arguments are text substitutions, so they may
19578 reference variables, use complex expressions, or even perform inferior
19581 @cindex argument count in user-defined commands
19582 @cindex how many arguments (user-defined commands)
19583 In addition, @code{$argc} may be used to find out how many arguments have
19584 been passed. This expands to a number in the range 0@dots{}10.
19589 print $arg0 + $arg1
19592 print $arg0 + $arg1 + $arg2
19600 @item define @var{commandname}
19601 Define a command named @var{commandname}. If there is already a command
19602 by that name, you are asked to confirm that you want to redefine it.
19603 @var{commandname} may be a bare command name consisting of letters,
19604 numbers, dashes, and underscores. It may also start with any predefined
19605 prefix command. For example, @samp{define target my-target} creates
19606 a user-defined @samp{target my-target} command.
19608 The definition of the command is made up of other @value{GDBN} command lines,
19609 which are given following the @code{define} command. The end of these
19610 commands is marked by a line containing @code{end}.
19613 @kindex end@r{ (user-defined commands)}
19614 @item document @var{commandname}
19615 Document the user-defined command @var{commandname}, so that it can be
19616 accessed by @code{help}. The command @var{commandname} must already be
19617 defined. This command reads lines of documentation just as @code{define}
19618 reads the lines of the command definition, ending with @code{end}.
19619 After the @code{document} command is finished, @code{help} on command
19620 @var{commandname} displays the documentation you have written.
19622 You may use the @code{document} command again to change the
19623 documentation of a command. Redefining the command with @code{define}
19624 does not change the documentation.
19626 @kindex dont-repeat
19627 @cindex don't repeat command
19629 Used inside a user-defined command, this tells @value{GDBN} that this
19630 command should not be repeated when the user hits @key{RET}
19631 (@pxref{Command Syntax, repeat last command}).
19633 @kindex help user-defined
19634 @item help user-defined
19635 List all user-defined commands, with the first line of the documentation
19640 @itemx show user @var{commandname}
19641 Display the @value{GDBN} commands used to define @var{commandname} (but
19642 not its documentation). If no @var{commandname} is given, display the
19643 definitions for all user-defined commands.
19645 @cindex infinite recursion in user-defined commands
19646 @kindex show max-user-call-depth
19647 @kindex set max-user-call-depth
19648 @item show max-user-call-depth
19649 @itemx set max-user-call-depth
19650 The value of @code{max-user-call-depth} controls how many recursion
19651 levels are allowed in user-defined commands before @value{GDBN} suspects an
19652 infinite recursion and aborts the command.
19655 In addition to the above commands, user-defined commands frequently
19656 use control flow commands, described in @ref{Command Files}.
19658 When user-defined commands are executed, the
19659 commands of the definition are not printed. An error in any command
19660 stops execution of the user-defined command.
19662 If used interactively, commands that would ask for confirmation proceed
19663 without asking when used inside a user-defined command. Many @value{GDBN}
19664 commands that normally print messages to say what they are doing omit the
19665 messages when used in a user-defined command.
19668 @subsection User-defined Command Hooks
19669 @cindex command hooks
19670 @cindex hooks, for commands
19671 @cindex hooks, pre-command
19674 You may define @dfn{hooks}, which are a special kind of user-defined
19675 command. Whenever you run the command @samp{foo}, if the user-defined
19676 command @samp{hook-foo} exists, it is executed (with no arguments)
19677 before that command.
19679 @cindex hooks, post-command
19681 A hook may also be defined which is run after the command you executed.
19682 Whenever you run the command @samp{foo}, if the user-defined command
19683 @samp{hookpost-foo} exists, it is executed (with no arguments) after
19684 that command. Post-execution hooks may exist simultaneously with
19685 pre-execution hooks, for the same command.
19687 It is valid for a hook to call the command which it hooks. If this
19688 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
19690 @c It would be nice if hookpost could be passed a parameter indicating
19691 @c if the command it hooks executed properly or not. FIXME!
19693 @kindex stop@r{, a pseudo-command}
19694 In addition, a pseudo-command, @samp{stop} exists. Defining
19695 (@samp{hook-stop}) makes the associated commands execute every time
19696 execution stops in your program: before breakpoint commands are run,
19697 displays are printed, or the stack frame is printed.
19699 For example, to ignore @code{SIGALRM} signals while
19700 single-stepping, but treat them normally during normal execution,
19705 handle SIGALRM nopass
19709 handle SIGALRM pass
19712 define hook-continue
19713 handle SIGALRM pass
19717 As a further example, to hook at the beginning and end of the @code{echo}
19718 command, and to add extra text to the beginning and end of the message,
19726 define hookpost-echo
19730 (@value{GDBP}) echo Hello World
19731 <<<---Hello World--->>>
19736 You can define a hook for any single-word command in @value{GDBN}, but
19737 not for command aliases; you should define a hook for the basic command
19738 name, e.g.@: @code{backtrace} rather than @code{bt}.
19739 @c FIXME! So how does Joe User discover whether a command is an alias
19741 You can hook a multi-word command by adding @code{hook-} or
19742 @code{hookpost-} to the last word of the command, e.g.@:
19743 @samp{define target hook-remote} to add a hook to @samp{target remote}.
19745 If an error occurs during the execution of your hook, execution of
19746 @value{GDBN} commands stops and @value{GDBN} issues a prompt
19747 (before the command that you actually typed had a chance to run).
19749 If you try to define a hook which does not match any known command, you
19750 get a warning from the @code{define} command.
19752 @node Command Files
19753 @subsection Command Files
19755 @cindex command files
19756 @cindex scripting commands
19757 A command file for @value{GDBN} is a text file made of lines that are
19758 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
19759 also be included. An empty line in a command file does nothing; it
19760 does not mean to repeat the last command, as it would from the
19763 You can request the execution of a command file with the @code{source}
19764 command. Note that the @code{source} command is also used to evaluate
19765 scripts that are not Command Files. The exact behavior can be configured
19766 using the @code{script-extension} setting.
19767 @xref{Extending GDB,, Extending GDB}.
19771 @cindex execute commands from a file
19772 @item source [-s] [-v] @var{filename}
19773 Execute the command file @var{filename}.
19776 The lines in a command file are generally executed sequentially,
19777 unless the order of execution is changed by one of the
19778 @emph{flow-control commands} described below. The commands are not
19779 printed as they are executed. An error in any command terminates
19780 execution of the command file and control is returned to the console.
19782 @value{GDBN} first searches for @var{filename} in the current directory.
19783 If the file is not found there, and @var{filename} does not specify a
19784 directory, then @value{GDBN} also looks for the file on the source search path
19785 (specified with the @samp{directory} command);
19786 except that @file{$cdir} is not searched because the compilation directory
19787 is not relevant to scripts.
19789 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
19790 on the search path even if @var{filename} specifies a directory.
19791 The search is done by appending @var{filename} to each element of the
19792 search path. So, for example, if @var{filename} is @file{mylib/myscript}
19793 and the search path contains @file{/home/user} then @value{GDBN} will
19794 look for the script @file{/home/user/mylib/myscript}.
19795 The search is also done if @var{filename} is an absolute path.
19796 For example, if @var{filename} is @file{/tmp/myscript} and
19797 the search path contains @file{/home/user} then @value{GDBN} will
19798 look for the script @file{/home/user/tmp/myscript}.
19799 For DOS-like systems, if @var{filename} contains a drive specification,
19800 it is stripped before concatenation. For example, if @var{filename} is
19801 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
19802 will look for the script @file{c:/tmp/myscript}.
19804 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
19805 each command as it is executed. The option must be given before
19806 @var{filename}, and is interpreted as part of the filename anywhere else.
19808 Commands that would ask for confirmation if used interactively proceed
19809 without asking when used in a command file. Many @value{GDBN} commands that
19810 normally print messages to say what they are doing omit the messages
19811 when called from command files.
19813 @value{GDBN} also accepts command input from standard input. In this
19814 mode, normal output goes to standard output and error output goes to
19815 standard error. Errors in a command file supplied on standard input do
19816 not terminate execution of the command file---execution continues with
19820 gdb < cmds > log 2>&1
19823 (The syntax above will vary depending on the shell used.) This example
19824 will execute commands from the file @file{cmds}. All output and errors
19825 would be directed to @file{log}.
19827 Since commands stored on command files tend to be more general than
19828 commands typed interactively, they frequently need to deal with
19829 complicated situations, such as different or unexpected values of
19830 variables and symbols, changes in how the program being debugged is
19831 built, etc. @value{GDBN} provides a set of flow-control commands to
19832 deal with these complexities. Using these commands, you can write
19833 complex scripts that loop over data structures, execute commands
19834 conditionally, etc.
19841 This command allows to include in your script conditionally executed
19842 commands. The @code{if} command takes a single argument, which is an
19843 expression to evaluate. It is followed by a series of commands that
19844 are executed only if the expression is true (its value is nonzero).
19845 There can then optionally be an @code{else} line, followed by a series
19846 of commands that are only executed if the expression was false. The
19847 end of the list is marked by a line containing @code{end}.
19851 This command allows to write loops. Its syntax is similar to
19852 @code{if}: the command takes a single argument, which is an expression
19853 to evaluate, and must be followed by the commands to execute, one per
19854 line, terminated by an @code{end}. These commands are called the
19855 @dfn{body} of the loop. The commands in the body of @code{while} are
19856 executed repeatedly as long as the expression evaluates to true.
19860 This command exits the @code{while} loop in whose body it is included.
19861 Execution of the script continues after that @code{while}s @code{end}
19864 @kindex loop_continue
19865 @item loop_continue
19866 This command skips the execution of the rest of the body of commands
19867 in the @code{while} loop in whose body it is included. Execution
19868 branches to the beginning of the @code{while} loop, where it evaluates
19869 the controlling expression.
19871 @kindex end@r{ (if/else/while commands)}
19873 Terminate the block of commands that are the body of @code{if},
19874 @code{else}, or @code{while} flow-control commands.
19879 @subsection Commands for Controlled Output
19881 During the execution of a command file or a user-defined command, normal
19882 @value{GDBN} output is suppressed; the only output that appears is what is
19883 explicitly printed by the commands in the definition. This section
19884 describes three commands useful for generating exactly the output you
19889 @item echo @var{text}
19890 @c I do not consider backslash-space a standard C escape sequence
19891 @c because it is not in ANSI.
19892 Print @var{text}. Nonprinting characters can be included in
19893 @var{text} using C escape sequences, such as @samp{\n} to print a
19894 newline. @strong{No newline is printed unless you specify one.}
19895 In addition to the standard C escape sequences, a backslash followed
19896 by a space stands for a space. This is useful for displaying a
19897 string with spaces at the beginning or the end, since leading and
19898 trailing spaces are otherwise trimmed from all arguments.
19899 To print @samp{@w{ }and foo =@w{ }}, use the command
19900 @samp{echo \@w{ }and foo = \@w{ }}.
19902 A backslash at the end of @var{text} can be used, as in C, to continue
19903 the command onto subsequent lines. For example,
19906 echo This is some text\n\
19907 which is continued\n\
19908 onto several lines.\n
19911 produces the same output as
19914 echo This is some text\n
19915 echo which is continued\n
19916 echo onto several lines.\n
19920 @item output @var{expression}
19921 Print the value of @var{expression} and nothing but that value: no
19922 newlines, no @samp{$@var{nn} = }. The value is not entered in the
19923 value history either. @xref{Expressions, ,Expressions}, for more information
19926 @item output/@var{fmt} @var{expression}
19927 Print the value of @var{expression} in format @var{fmt}. You can use
19928 the same formats as for @code{print}. @xref{Output Formats,,Output
19929 Formats}, for more information.
19932 @item printf @var{template}, @var{expressions}@dots{}
19933 Print the values of one or more @var{expressions} under the control of
19934 the string @var{template}. To print several values, make
19935 @var{expressions} be a comma-separated list of individual expressions,
19936 which may be either numbers or pointers. Their values are printed as
19937 specified by @var{template}, exactly as a C program would do by
19938 executing the code below:
19941 printf (@var{template}, @var{expressions}@dots{});
19944 As in @code{C} @code{printf}, ordinary characters in @var{template}
19945 are printed verbatim, while @dfn{conversion specification} introduced
19946 by the @samp{%} character cause subsequent @var{expressions} to be
19947 evaluated, their values converted and formatted according to type and
19948 style information encoded in the conversion specifications, and then
19951 For example, you can print two values in hex like this:
19954 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
19957 @code{printf} supports all the standard @code{C} conversion
19958 specifications, including the flags and modifiers between the @samp{%}
19959 character and the conversion letter, with the following exceptions:
19963 The argument-ordering modifiers, such as @samp{2$}, are not supported.
19966 The modifier @samp{*} is not supported for specifying precision or
19970 The @samp{'} flag (for separation of digits into groups according to
19971 @code{LC_NUMERIC'}) is not supported.
19974 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
19978 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
19981 The conversion letters @samp{a} and @samp{A} are not supported.
19985 Note that the @samp{ll} type modifier is supported only if the
19986 underlying @code{C} implementation used to build @value{GDBN} supports
19987 the @code{long long int} type, and the @samp{L} type modifier is
19988 supported only if @code{long double} type is available.
19990 As in @code{C}, @code{printf} supports simple backslash-escape
19991 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
19992 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
19993 single character. Octal and hexadecimal escape sequences are not
19996 Additionally, @code{printf} supports conversion specifications for DFP
19997 (@dfn{Decimal Floating Point}) types using the following length modifiers
19998 together with a floating point specifier.
20003 @samp{H} for printing @code{Decimal32} types.
20006 @samp{D} for printing @code{Decimal64} types.
20009 @samp{DD} for printing @code{Decimal128} types.
20012 If the underlying @code{C} implementation used to build @value{GDBN} has
20013 support for the three length modifiers for DFP types, other modifiers
20014 such as width and precision will also be available for @value{GDBN} to use.
20016 In case there is no such @code{C} support, no additional modifiers will be
20017 available and the value will be printed in the standard way.
20019 Here's an example of printing DFP types using the above conversion letters:
20021 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
20027 @section Scripting @value{GDBN} using Python
20028 @cindex python scripting
20029 @cindex scripting with python
20031 You can script @value{GDBN} using the @uref{http://www.python.org/,
20032 Python programming language}. This feature is available only if
20033 @value{GDBN} was configured using @option{--with-python}.
20036 * Python Commands:: Accessing Python from @value{GDBN}.
20037 * Python API:: Accessing @value{GDBN} from Python.
20038 * Auto-loading:: Automatically loading Python code.
20041 @node Python Commands
20042 @subsection Python Commands
20043 @cindex python commands
20044 @cindex commands to access python
20046 @value{GDBN} provides one command for accessing the Python interpreter,
20047 and one related setting:
20051 @item python @r{[}@var{code}@r{]}
20052 The @code{python} command can be used to evaluate Python code.
20054 If given an argument, the @code{python} command will evaluate the
20055 argument as a Python command. For example:
20058 (@value{GDBP}) python print 23
20062 If you do not provide an argument to @code{python}, it will act as a
20063 multi-line command, like @code{define}. In this case, the Python
20064 script is made up of subsequent command lines, given after the
20065 @code{python} command. This command list is terminated using a line
20066 containing @code{end}. For example:
20069 (@value{GDBP}) python
20071 End with a line saying just "end".
20077 @kindex maint set python print-stack
20078 @item maint set python print-stack
20079 By default, @value{GDBN} will print a stack trace when an error occurs
20080 in a Python script. This can be controlled using @code{maint set
20081 python print-stack}: if @code{on}, the default, then Python stack
20082 printing is enabled; if @code{off}, then Python stack printing is
20086 It is also possible to execute a Python script from the @value{GDBN}
20090 @item source @file{script-name}
20091 The script name must end with @samp{.py} and @value{GDBN} must be configured
20092 to recognize the script language based on filename extension using
20093 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
20095 @item python execfile ("script-name")
20096 This method is based on the @code{execfile} Python built-in function,
20097 and thus is always available.
20101 @subsection Python API
20103 @cindex programming in python
20105 @cindex python stdout
20106 @cindex python pagination
20107 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
20108 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
20109 A Python program which outputs to one of these streams may have its
20110 output interrupted by the user (@pxref{Screen Size}). In this
20111 situation, a Python @code{KeyboardInterrupt} exception is thrown.
20114 * Basic Python:: Basic Python Functions.
20115 * Exception Handling::
20116 * Values From Inferior::
20117 * Types In Python:: Python representation of types.
20118 * Pretty Printing API:: Pretty-printing values.
20119 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
20120 * Disabling Pretty-Printers:: Disabling broken printers.
20121 * Commands In Python:: Implementing new commands in Python.
20122 * Parameters In Python:: Adding new @value{GDBN} parameters.
20123 * Functions In Python:: Writing new convenience functions.
20124 * Progspaces In Python:: Program spaces.
20125 * Objfiles In Python:: Object files.
20126 * Frames In Python:: Accessing inferior stack frames from Python.
20127 * Blocks In Python:: Accessing frame blocks from Python.
20128 * Symbols In Python:: Python representation of symbols.
20129 * Symbol Tables In Python:: Python representation of symbol tables.
20130 * Lazy Strings In Python:: Python representation of lazy strings.
20131 * Breakpoints In Python:: Manipulating breakpoints using Python.
20135 @subsubsection Basic Python
20137 @cindex python functions
20138 @cindex python module
20140 @value{GDBN} introduces a new Python module, named @code{gdb}. All
20141 methods and classes added by @value{GDBN} are placed in this module.
20142 @value{GDBN} automatically @code{import}s the @code{gdb} module for
20143 use in all scripts evaluated by the @code{python} command.
20145 @findex gdb.execute
20146 @defun execute command [from_tty]
20147 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
20148 If a GDB exception happens while @var{command} runs, it is
20149 translated as described in @ref{Exception Handling,,Exception Handling}.
20150 If no exceptions occur, this function returns @code{None}.
20152 @var{from_tty} specifies whether @value{GDBN} ought to consider this
20153 command as having originated from the user invoking it interactively.
20154 It must be a boolean value. If omitted, it defaults to @code{False}.
20157 @findex gdb.breakpoints
20159 Return a sequence holding all of @value{GDBN}'s breakpoints.
20160 @xref{Breakpoints In Python}, for more information.
20163 @findex gdb.parameter
20164 @defun parameter parameter
20165 Return the value of a @value{GDBN} parameter. @var{parameter} is a
20166 string naming the parameter to look up; @var{parameter} may contain
20167 spaces if the parameter has a multi-part name. For example,
20168 @samp{print object} is a valid parameter name.
20170 If the named parameter does not exist, this function throws a
20171 @code{RuntimeError}. Otherwise, the parameter's value is converted to
20172 a Python value of the appropriate type, and returned.
20175 @findex gdb.history
20176 @defun history number
20177 Return a value from @value{GDBN}'s value history (@pxref{Value
20178 History}). @var{number} indicates which history element to return.
20179 If @var{number} is negative, then @value{GDBN} will take its absolute value
20180 and count backward from the last element (i.e., the most recent element) to
20181 find the value to return. If @var{number} is zero, then @value{GDBN} will
20182 return the most recent element. If the element specified by @var{number}
20183 doesn't exist in the value history, a @code{RuntimeError} exception will be
20186 If no exception is raised, the return value is always an instance of
20187 @code{gdb.Value} (@pxref{Values From Inferior}).
20190 @findex gdb.parse_and_eval
20191 @defun parse_and_eval expression
20192 Parse @var{expression} as an expression in the current language,
20193 evaluate it, and return the result as a @code{gdb.Value}.
20194 @var{expression} must be a string.
20196 This function can be useful when implementing a new command
20197 (@pxref{Commands In Python}), as it provides a way to parse the
20198 command's argument as an expression. It is also useful simply to
20199 compute values, for example, it is the only way to get the value of a
20200 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
20204 @defun write string
20205 Print a string to @value{GDBN}'s paginated standard output stream.
20206 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
20207 call this function.
20212 Flush @value{GDBN}'s paginated standard output stream. Flushing
20213 @code{sys.stdout} or @code{sys.stderr} will automatically call this
20217 @findex gdb.target_charset
20218 @defun target_charset
20219 Return the name of the current target character set (@pxref{Character
20220 Sets}). This differs from @code{gdb.parameter('target-charset')} in
20221 that @samp{auto} is never returned.
20224 @findex gdb.target_wide_charset
20225 @defun target_wide_charset
20226 Return the name of the current target wide character set
20227 (@pxref{Character Sets}). This differs from
20228 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
20232 @node Exception Handling
20233 @subsubsection Exception Handling
20234 @cindex python exceptions
20235 @cindex exceptions, python
20237 When executing the @code{python} command, Python exceptions
20238 uncaught within the Python code are translated to calls to
20239 @value{GDBN} error-reporting mechanism. If the command that called
20240 @code{python} does not handle the error, @value{GDBN} will
20241 terminate it and print an error message containing the Python
20242 exception name, the associated value, and the Python call stack
20243 backtrace at the point where the exception was raised. Example:
20246 (@value{GDBP}) python print foo
20247 Traceback (most recent call last):
20248 File "<string>", line 1, in <module>
20249 NameError: name 'foo' is not defined
20252 @value{GDBN} errors that happen in @value{GDBN} commands invoked by Python
20253 code are converted to Python @code{RuntimeError} exceptions. User
20254 interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
20255 prompt) is translated to a Python @code{KeyboardInterrupt}
20256 exception. If you catch these exceptions in your Python code, your
20257 exception handler will see @code{RuntimeError} or
20258 @code{KeyboardInterrupt} as the exception type, the @value{GDBN} error
20259 message as its value, and the Python call stack backtrace at the
20260 Python statement closest to where the @value{GDBN} error occured as the
20263 @findex gdb.GdbError
20264 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
20265 it is useful to be able to throw an exception that doesn't cause a
20266 traceback to be printed. For example, the user may have invoked the
20267 command incorrectly. Use the @code{gdb.GdbError} exception
20268 to handle this case. Example:
20272 >class HelloWorld (gdb.Command):
20273 > """Greet the whole world."""
20274 > def __init__ (self):
20275 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
20276 > def invoke (self, args, from_tty):
20277 > argv = gdb.string_to_argv (args)
20278 > if len (argv) != 0:
20279 > raise gdb.GdbError ("hello-world takes no arguments")
20280 > print "Hello, World!"
20283 (gdb) hello-world 42
20284 hello-world takes no arguments
20287 @node Values From Inferior
20288 @subsubsection Values From Inferior
20289 @cindex values from inferior, with Python
20290 @cindex python, working with values from inferior
20292 @cindex @code{gdb.Value}
20293 @value{GDBN} provides values it obtains from the inferior program in
20294 an object of type @code{gdb.Value}. @value{GDBN} uses this object
20295 for its internal bookkeeping of the inferior's values, and for
20296 fetching values when necessary.
20298 Inferior values that are simple scalars can be used directly in
20299 Python expressions that are valid for the value's data type. Here's
20300 an example for an integer or floating-point value @code{some_val}:
20307 As result of this, @code{bar} will also be a @code{gdb.Value} object
20308 whose values are of the same type as those of @code{some_val}.
20310 Inferior values that are structures or instances of some class can
20311 be accessed using the Python @dfn{dictionary syntax}. For example, if
20312 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
20313 can access its @code{foo} element with:
20316 bar = some_val['foo']
20319 Again, @code{bar} will also be a @code{gdb.Value} object.
20321 The following attributes are provided:
20324 @defivar Value address
20325 If this object is addressable, this read-only attribute holds a
20326 @code{gdb.Value} object representing the address. Otherwise,
20327 this attribute holds @code{None}.
20330 @cindex optimized out value in Python
20331 @defivar Value is_optimized_out
20332 This read-only boolean attribute is true if the compiler optimized out
20333 this value, thus it is not available for fetching from the inferior.
20336 @defivar Value type
20337 The type of this @code{gdb.Value}. The value of this attribute is a
20338 @code{gdb.Type} object.
20342 The following methods are provided:
20345 @defmethod Value cast type
20346 Return a new instance of @code{gdb.Value} that is the result of
20347 casting this instance to the type described by @var{type}, which must
20348 be a @code{gdb.Type} object. If the cast cannot be performed for some
20349 reason, this method throws an exception.
20352 @defmethod Value dereference
20353 For pointer data types, this method returns a new @code{gdb.Value} object
20354 whose contents is the object pointed to by the pointer. For example, if
20355 @code{foo} is a C pointer to an @code{int}, declared in your C program as
20362 then you can use the corresponding @code{gdb.Value} to access what
20363 @code{foo} points to like this:
20366 bar = foo.dereference ()
20369 The result @code{bar} will be a @code{gdb.Value} object holding the
20370 value pointed to by @code{foo}.
20373 @defmethod Value string @r{[}encoding@r{]} @r{[}errors@r{]} @r{[}length@r{]}
20374 If this @code{gdb.Value} represents a string, then this method
20375 converts the contents to a Python string. Otherwise, this method will
20376 throw an exception.
20378 Strings are recognized in a language-specific way; whether a given
20379 @code{gdb.Value} represents a string is determined by the current
20382 For C-like languages, a value is a string if it is a pointer to or an
20383 array of characters or ints. The string is assumed to be terminated
20384 by a zero of the appropriate width. However if the optional length
20385 argument is given, the string will be converted to that given length,
20386 ignoring any embedded zeros that the string may contain.
20388 If the optional @var{encoding} argument is given, it must be a string
20389 naming the encoding of the string in the @code{gdb.Value}, such as
20390 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
20391 the same encodings as the corresponding argument to Python's
20392 @code{string.decode} method, and the Python codec machinery will be used
20393 to convert the string. If @var{encoding} is not given, or if
20394 @var{encoding} is the empty string, then either the @code{target-charset}
20395 (@pxref{Character Sets}) will be used, or a language-specific encoding
20396 will be used, if the current language is able to supply one.
20398 The optional @var{errors} argument is the same as the corresponding
20399 argument to Python's @code{string.decode} method.
20401 If the optional @var{length} argument is given, the string will be
20402 fetched and converted to the given length.
20405 @defmethod Value lazy_string @r{[}encoding@r{]} @r{[}length@r{]}
20406 If this @code{gdb.Value} represents a string, then this method
20407 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
20408 In Python}). Otherwise, this method will throw an exception.
20410 If the optional @var{encoding} argument is given, it must be a string
20411 naming the encoding of the @code{gdb.LazyString}. Some examples are:
20412 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
20413 @var{encoding} argument is an encoding that @value{GDBN} does
20414 recognize, @value{GDBN} will raise an error.
20416 When a lazy string is printed, the @value{GDBN} encoding machinery is
20417 used to convert the string during printing. If the optional
20418 @var{encoding} argument is not provided, or is an empty string,
20419 @value{GDBN} will automatically select the encoding most suitable for
20420 the string type. For further information on encoding in @value{GDBN}
20421 please see @ref{Character Sets}.
20423 If the optional @var{length} argument is given, the string will be
20424 fetched and encoded to the length of characters specified. If
20425 the @var{length} argument is not provided, the string will be fetched
20426 and encoded until a null of appropriate width is found.
20430 @node Types In Python
20431 @subsubsection Types In Python
20432 @cindex types in Python
20433 @cindex Python, working with types
20436 @value{GDBN} represents types from the inferior using the class
20439 The following type-related functions are available in the @code{gdb}
20442 @findex gdb.lookup_type
20443 @defun lookup_type name [block]
20444 This function looks up a type by name. @var{name} is the name of the
20445 type to look up. It must be a string.
20447 If @var{block} is given, then @var{name} is looked up in that scope.
20448 Otherwise, it is searched for globally.
20450 Ordinarily, this function will return an instance of @code{gdb.Type}.
20451 If the named type cannot be found, it will throw an exception.
20454 An instance of @code{Type} has the following attributes:
20458 The type code for this type. The type code will be one of the
20459 @code{TYPE_CODE_} constants defined below.
20462 @defivar Type sizeof
20463 The size of this type, in target @code{char} units. Usually, a
20464 target's @code{char} type will be an 8-bit byte. However, on some
20465 unusual platforms, this type may have a different size.
20469 The tag name for this type. The tag name is the name after
20470 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
20471 languages have this concept. If this type has no tag name, then
20472 @code{None} is returned.
20476 The following methods are provided:
20479 @defmethod Type fields
20480 For structure and union types, this method returns the fields. Range
20481 types have two fields, the minimum and maximum values. Enum types
20482 have one field per enum constant. Function and method types have one
20483 field per parameter. The base types of C@t{++} classes are also
20484 represented as fields. If the type has no fields, or does not fit
20485 into one of these categories, an empty sequence will be returned.
20487 Each field is an object, with some pre-defined attributes:
20490 This attribute is not available for @code{static} fields (as in
20491 C@t{++} or Java). For non-@code{static} fields, the value is the bit
20492 position of the field.
20495 The name of the field, or @code{None} for anonymous fields.
20498 This is @code{True} if the field is artificial, usually meaning that
20499 it was provided by the compiler and not the user. This attribute is
20500 always provided, and is @code{False} if the field is not artificial.
20502 @item is_base_class
20503 This is @code{True} if the field represents a base class of a C@t{++}
20504 structure. This attribute is always provided, and is @code{False}
20505 if the field is not a base class of the type that is the argument of
20506 @code{fields}, or if that type was not a C@t{++} class.
20509 If the field is packed, or is a bitfield, then this will have a
20510 non-zero value, which is the size of the field in bits. Otherwise,
20511 this will be zero; in this case the field's size is given by its type.
20514 The type of the field. This is usually an instance of @code{Type},
20515 but it can be @code{None} in some situations.
20519 @defmethod Type const
20520 Return a new @code{gdb.Type} object which represents a
20521 @code{const}-qualified variant of this type.
20524 @defmethod Type volatile
20525 Return a new @code{gdb.Type} object which represents a
20526 @code{volatile}-qualified variant of this type.
20529 @defmethod Type unqualified
20530 Return a new @code{gdb.Type} object which represents an unqualified
20531 variant of this type. That is, the result is neither @code{const} nor
20535 @defmethod Type range
20536 Return a Python @code{Tuple} object that contains two elements: the
20537 low bound of the argument type and the high bound of that type. If
20538 the type does not have a range, @value{GDBN} will raise a
20539 @code{RuntimeError} exception.
20542 @defmethod Type reference
20543 Return a new @code{gdb.Type} object which represents a reference to this
20547 @defmethod Type pointer
20548 Return a new @code{gdb.Type} object which represents a pointer to this
20552 @defmethod Type strip_typedefs
20553 Return a new @code{gdb.Type} that represents the real type,
20554 after removing all layers of typedefs.
20557 @defmethod Type target
20558 Return a new @code{gdb.Type} object which represents the target type
20561 For a pointer type, the target type is the type of the pointed-to
20562 object. For an array type (meaning C-like arrays), the target type is
20563 the type of the elements of the array. For a function or method type,
20564 the target type is the type of the return value. For a complex type,
20565 the target type is the type of the elements. For a typedef, the
20566 target type is the aliased type.
20568 If the type does not have a target, this method will throw an
20572 @defmethod Type template_argument n [block]
20573 If this @code{gdb.Type} is an instantiation of a template, this will
20574 return a new @code{gdb.Type} which represents the type of the
20575 @var{n}th template argument.
20577 If this @code{gdb.Type} is not a template type, this will throw an
20578 exception. Ordinarily, only C@t{++} code will have template types.
20580 If @var{block} is given, then @var{name} is looked up in that scope.
20581 Otherwise, it is searched for globally.
20586 Each type has a code, which indicates what category this type falls
20587 into. The available type categories are represented by constants
20588 defined in the @code{gdb} module:
20591 @findex TYPE_CODE_PTR
20592 @findex gdb.TYPE_CODE_PTR
20593 @item TYPE_CODE_PTR
20594 The type is a pointer.
20596 @findex TYPE_CODE_ARRAY
20597 @findex gdb.TYPE_CODE_ARRAY
20598 @item TYPE_CODE_ARRAY
20599 The type is an array.
20601 @findex TYPE_CODE_STRUCT
20602 @findex gdb.TYPE_CODE_STRUCT
20603 @item TYPE_CODE_STRUCT
20604 The type is a structure.
20606 @findex TYPE_CODE_UNION
20607 @findex gdb.TYPE_CODE_UNION
20608 @item TYPE_CODE_UNION
20609 The type is a union.
20611 @findex TYPE_CODE_ENUM
20612 @findex gdb.TYPE_CODE_ENUM
20613 @item TYPE_CODE_ENUM
20614 The type is an enum.
20616 @findex TYPE_CODE_FLAGS
20617 @findex gdb.TYPE_CODE_FLAGS
20618 @item TYPE_CODE_FLAGS
20619 A bit flags type, used for things such as status registers.
20621 @findex TYPE_CODE_FUNC
20622 @findex gdb.TYPE_CODE_FUNC
20623 @item TYPE_CODE_FUNC
20624 The type is a function.
20626 @findex TYPE_CODE_INT
20627 @findex gdb.TYPE_CODE_INT
20628 @item TYPE_CODE_INT
20629 The type is an integer type.
20631 @findex TYPE_CODE_FLT
20632 @findex gdb.TYPE_CODE_FLT
20633 @item TYPE_CODE_FLT
20634 A floating point type.
20636 @findex TYPE_CODE_VOID
20637 @findex gdb.TYPE_CODE_VOID
20638 @item TYPE_CODE_VOID
20639 The special type @code{void}.
20641 @findex TYPE_CODE_SET
20642 @findex gdb.TYPE_CODE_SET
20643 @item TYPE_CODE_SET
20646 @findex TYPE_CODE_RANGE
20647 @findex gdb.TYPE_CODE_RANGE
20648 @item TYPE_CODE_RANGE
20649 A range type, that is, an integer type with bounds.
20651 @findex TYPE_CODE_STRING
20652 @findex gdb.TYPE_CODE_STRING
20653 @item TYPE_CODE_STRING
20654 A string type. Note that this is only used for certain languages with
20655 language-defined string types; C strings are not represented this way.
20657 @findex TYPE_CODE_BITSTRING
20658 @findex gdb.TYPE_CODE_BITSTRING
20659 @item TYPE_CODE_BITSTRING
20662 @findex TYPE_CODE_ERROR
20663 @findex gdb.TYPE_CODE_ERROR
20664 @item TYPE_CODE_ERROR
20665 An unknown or erroneous type.
20667 @findex TYPE_CODE_METHOD
20668 @findex gdb.TYPE_CODE_METHOD
20669 @item TYPE_CODE_METHOD
20670 A method type, as found in C@t{++} or Java.
20672 @findex TYPE_CODE_METHODPTR
20673 @findex gdb.TYPE_CODE_METHODPTR
20674 @item TYPE_CODE_METHODPTR
20675 A pointer-to-member-function.
20677 @findex TYPE_CODE_MEMBERPTR
20678 @findex gdb.TYPE_CODE_MEMBERPTR
20679 @item TYPE_CODE_MEMBERPTR
20680 A pointer-to-member.
20682 @findex TYPE_CODE_REF
20683 @findex gdb.TYPE_CODE_REF
20684 @item TYPE_CODE_REF
20687 @findex TYPE_CODE_CHAR
20688 @findex gdb.TYPE_CODE_CHAR
20689 @item TYPE_CODE_CHAR
20692 @findex TYPE_CODE_BOOL
20693 @findex gdb.TYPE_CODE_BOOL
20694 @item TYPE_CODE_BOOL
20697 @findex TYPE_CODE_COMPLEX
20698 @findex gdb.TYPE_CODE_COMPLEX
20699 @item TYPE_CODE_COMPLEX
20700 A complex float type.
20702 @findex TYPE_CODE_TYPEDEF
20703 @findex gdb.TYPE_CODE_TYPEDEF
20704 @item TYPE_CODE_TYPEDEF
20705 A typedef to some other type.
20707 @findex TYPE_CODE_NAMESPACE
20708 @findex gdb.TYPE_CODE_NAMESPACE
20709 @item TYPE_CODE_NAMESPACE
20710 A C@t{++} namespace.
20712 @findex TYPE_CODE_DECFLOAT
20713 @findex gdb.TYPE_CODE_DECFLOAT
20714 @item TYPE_CODE_DECFLOAT
20715 A decimal floating point type.
20717 @findex TYPE_CODE_INTERNAL_FUNCTION
20718 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
20719 @item TYPE_CODE_INTERNAL_FUNCTION
20720 A function internal to @value{GDBN}. This is the type used to represent
20721 convenience functions.
20724 @node Pretty Printing API
20725 @subsubsection Pretty Printing API
20727 An example output is provided (@pxref{Pretty Printing}).
20729 A pretty-printer is just an object that holds a value and implements a
20730 specific interface, defined here.
20732 @defop Operation {pretty printer} children (self)
20733 @value{GDBN} will call this method on a pretty-printer to compute the
20734 children of the pretty-printer's value.
20736 This method must return an object conforming to the Python iterator
20737 protocol. Each item returned by the iterator must be a tuple holding
20738 two elements. The first element is the ``name'' of the child; the
20739 second element is the child's value. The value can be any Python
20740 object which is convertible to a @value{GDBN} value.
20742 This method is optional. If it does not exist, @value{GDBN} will act
20743 as though the value has no children.
20746 @defop Operation {pretty printer} display_hint (self)
20747 The CLI may call this method and use its result to change the
20748 formatting of a value. The result will also be supplied to an MI
20749 consumer as a @samp{displayhint} attribute of the variable being
20752 This method is optional. If it does exist, this method must return a
20755 Some display hints are predefined by @value{GDBN}:
20759 Indicate that the object being printed is ``array-like''. The CLI
20760 uses this to respect parameters such as @code{set print elements} and
20761 @code{set print array}.
20764 Indicate that the object being printed is ``map-like'', and that the
20765 children of this value can be assumed to alternate between keys and
20769 Indicate that the object being printed is ``string-like''. If the
20770 printer's @code{to_string} method returns a Python string of some
20771 kind, then @value{GDBN} will call its internal language-specific
20772 string-printing function to format the string. For the CLI this means
20773 adding quotation marks, possibly escaping some characters, respecting
20774 @code{set print elements}, and the like.
20778 @defop Operation {pretty printer} to_string (self)
20779 @value{GDBN} will call this method to display the string
20780 representation of the value passed to the object's constructor.
20782 When printing from the CLI, if the @code{to_string} method exists,
20783 then @value{GDBN} will prepend its result to the values returned by
20784 @code{children}. Exactly how this formatting is done is dependent on
20785 the display hint, and may change as more hints are added. Also,
20786 depending on the print settings (@pxref{Print Settings}), the CLI may
20787 print just the result of @code{to_string} in a stack trace, omitting
20788 the result of @code{children}.
20790 If this method returns a string, it is printed verbatim.
20792 Otherwise, if this method returns an instance of @code{gdb.Value},
20793 then @value{GDBN} prints this value. This may result in a call to
20794 another pretty-printer.
20796 If instead the method returns a Python value which is convertible to a
20797 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
20798 the resulting value. Again, this may result in a call to another
20799 pretty-printer. Python scalars (integers, floats, and booleans) and
20800 strings are convertible to @code{gdb.Value}; other types are not.
20802 Finally, if this method returns @code{None} then no further operations
20803 are peformed in this method and nothing is printed.
20805 If the result is not one of these types, an exception is raised.
20808 @node Selecting Pretty-Printers
20809 @subsubsection Selecting Pretty-Printers
20811 The Python list @code{gdb.pretty_printers} contains an array of
20812 functions or callable objects that have been registered via addition
20813 as a pretty-printer.
20814 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
20815 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
20818 A function on one of these lists is passed a single @code{gdb.Value}
20819 argument and should return a pretty-printer object conforming to the
20820 interface definition above (@pxref{Pretty Printing API}). If a function
20821 cannot create a pretty-printer for the value, it should return
20824 @value{GDBN} first checks the @code{pretty_printers} attribute of each
20825 @code{gdb.Objfile} in the current program space and iteratively calls
20826 each enabled function (@pxref{Disabling Pretty-Printers})
20827 in the list for that @code{gdb.Objfile} until it receives
20828 a pretty-printer object.
20829 If no pretty-printer is found in the objfile lists, @value{GDBN} then
20830 searches the pretty-printer list of the current program space,
20831 calling each enabled function until an object is returned.
20832 After these lists have been exhausted, it tries the global
20833 @code{gdb.pretty_printers} list, again calling each enabled function until an
20834 object is returned.
20836 The order in which the objfiles are searched is not specified. For a
20837 given list, functions are always invoked from the head of the list,
20838 and iterated over sequentially until the end of the list, or a printer
20839 object is returned.
20841 Here is an example showing how a @code{std::string} printer might be
20845 class StdStringPrinter:
20846 "Print a std::string"
20848 def __init__ (self, val):
20851 def to_string (self):
20852 return self.val['_M_dataplus']['_M_p']
20854 def display_hint (self):
20858 And here is an example showing how a lookup function for the printer
20859 example above might be written.
20862 def str_lookup_function (val):
20864 lookup_tag = val.type.tag
20865 regex = re.compile ("^std::basic_string<char,.*>$")
20866 if lookup_tag == None:
20868 if regex.match (lookup_tag):
20869 return StdStringPrinter (val)
20874 The example lookup function extracts the value's type, and attempts to
20875 match it to a type that it can pretty-print. If it is a type the
20876 printer can pretty-print, it will return a printer object. If not, it
20877 returns @code{None}.
20879 We recommend that you put your core pretty-printers into a Python
20880 package. If your pretty-printers are for use with a library, we
20881 further recommend embedding a version number into the package name.
20882 This practice will enable @value{GDBN} to load multiple versions of
20883 your pretty-printers at the same time, because they will have
20886 You should write auto-loaded code (@pxref{Auto-loading}) such that it
20887 can be evaluated multiple times without changing its meaning. An
20888 ideal auto-load file will consist solely of @code{import}s of your
20889 printer modules, followed by a call to a register pretty-printers with
20890 the current objfile.
20892 Taken as a whole, this approach will scale nicely to multiple
20893 inferiors, each potentially using a different library version.
20894 Embedding a version number in the Python package name will ensure that
20895 @value{GDBN} is able to load both sets of printers simultaneously.
20896 Then, because the search for pretty-printers is done by objfile, and
20897 because your auto-loaded code took care to register your library's
20898 printers with a specific objfile, @value{GDBN} will find the correct
20899 printers for the specific version of the library used by each
20902 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
20903 this code might appear in @code{gdb.libstdcxx.v6}:
20906 def register_printers (objfile):
20907 objfile.pretty_printers.add (str_lookup_function)
20911 And then the corresponding contents of the auto-load file would be:
20914 import gdb.libstdcxx.v6
20915 gdb.libstdcxx.v6.register_printers (gdb.current_objfile ())
20918 @node Disabling Pretty-Printers
20919 @subsubsection Disabling Pretty-Printers
20920 @cindex disabling pretty-printers
20922 For various reasons a pretty-printer may not work.
20923 For example, the underlying data structure may have changed and
20924 the pretty-printer is out of date.
20926 The consequences of a broken pretty-printer are severe enough that
20927 @value{GDBN} provides support for enabling and disabling individual
20928 printers. For example, if @code{print frame-arguments} is on,
20929 a backtrace can become highly illegible if any argument is printed
20930 with a broken printer.
20932 Pretty-printers are enabled and disabled by attaching an @code{enabled}
20933 attribute to the registered function or callable object. If this attribute
20934 is present and its value is @code{False}, the printer is disabled, otherwise
20935 the printer is enabled.
20937 @node Commands In Python
20938 @subsubsection Commands In Python
20940 @cindex commands in python
20941 @cindex python commands
20942 You can implement new @value{GDBN} CLI commands in Python. A CLI
20943 command is implemented using an instance of the @code{gdb.Command}
20944 class, most commonly using a subclass.
20946 @defmethod Command __init__ name @var{command_class} @r{[}@var{completer_class}@r{]} @r{[}@var{prefix}@r{]}
20947 The object initializer for @code{Command} registers the new command
20948 with @value{GDBN}. This initializer is normally invoked from the
20949 subclass' own @code{__init__} method.
20951 @var{name} is the name of the command. If @var{name} consists of
20952 multiple words, then the initial words are looked for as prefix
20953 commands. In this case, if one of the prefix commands does not exist,
20954 an exception is raised.
20956 There is no support for multi-line commands.
20958 @var{command_class} should be one of the @samp{COMMAND_} constants
20959 defined below. This argument tells @value{GDBN} how to categorize the
20960 new command in the help system.
20962 @var{completer_class} is an optional argument. If given, it should be
20963 one of the @samp{COMPLETE_} constants defined below. This argument
20964 tells @value{GDBN} how to perform completion for this command. If not
20965 given, @value{GDBN} will attempt to complete using the object's
20966 @code{complete} method (see below); if no such method is found, an
20967 error will occur when completion is attempted.
20969 @var{prefix} is an optional argument. If @code{True}, then the new
20970 command is a prefix command; sub-commands of this command may be
20973 The help text for the new command is taken from the Python
20974 documentation string for the command's class, if there is one. If no
20975 documentation string is provided, the default value ``This command is
20976 not documented.'' is used.
20979 @cindex don't repeat Python command
20980 @defmethod Command dont_repeat
20981 By default, a @value{GDBN} command is repeated when the user enters a
20982 blank line at the command prompt. A command can suppress this
20983 behavior by invoking the @code{dont_repeat} method. This is similar
20984 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
20987 @defmethod Command invoke argument from_tty
20988 This method is called by @value{GDBN} when this command is invoked.
20990 @var{argument} is a string. It is the argument to the command, after
20991 leading and trailing whitespace has been stripped.
20993 @var{from_tty} is a boolean argument. When true, this means that the
20994 command was entered by the user at the terminal; when false it means
20995 that the command came from elsewhere.
20997 If this method throws an exception, it is turned into a @value{GDBN}
20998 @code{error} call. Otherwise, the return value is ignored.
21000 @findex gdb.string_to_argv
21001 To break @var{argument} up into an argv-like string use
21002 @code{gdb.string_to_argv}. This function behaves identically to
21003 @value{GDBN}'s internal argument lexer @code{buildargv}.
21004 It is recommended to use this for consistency.
21005 Arguments are separated by spaces and may be quoted.
21009 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
21010 ['1', '2 "3', '4 "5', "6 '7"]
21015 @cindex completion of Python commands
21016 @defmethod Command complete text word
21017 This method is called by @value{GDBN} when the user attempts
21018 completion on this command. All forms of completion are handled by
21019 this method, that is, the @key{TAB} and @key{M-?} key bindings
21020 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
21023 The arguments @var{text} and @var{word} are both strings. @var{text}
21024 holds the complete command line up to the cursor's location.
21025 @var{word} holds the last word of the command line; this is computed
21026 using a word-breaking heuristic.
21028 The @code{complete} method can return several values:
21031 If the return value is a sequence, the contents of the sequence are
21032 used as the completions. It is up to @code{complete} to ensure that the
21033 contents actually do complete the word. A zero-length sequence is
21034 allowed, it means that there were no completions available. Only
21035 string elements of the sequence are used; other elements in the
21036 sequence are ignored.
21039 If the return value is one of the @samp{COMPLETE_} constants defined
21040 below, then the corresponding @value{GDBN}-internal completion
21041 function is invoked, and its result is used.
21044 All other results are treated as though there were no available
21049 When a new command is registered, it must be declared as a member of
21050 some general class of commands. This is used to classify top-level
21051 commands in the on-line help system; note that prefix commands are not
21052 listed under their own category but rather that of their top-level
21053 command. The available classifications are represented by constants
21054 defined in the @code{gdb} module:
21057 @findex COMMAND_NONE
21058 @findex gdb.COMMAND_NONE
21060 The command does not belong to any particular class. A command in
21061 this category will not be displayed in any of the help categories.
21063 @findex COMMAND_RUNNING
21064 @findex gdb.COMMAND_RUNNING
21065 @item COMMAND_RUNNING
21066 The command is related to running the inferior. For example,
21067 @code{start}, @code{step}, and @code{continue} are in this category.
21068 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
21069 commands in this category.
21071 @findex COMMAND_DATA
21072 @findex gdb.COMMAND_DATA
21074 The command is related to data or variables. For example,
21075 @code{call}, @code{find}, and @code{print} are in this category. Type
21076 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
21079 @findex COMMAND_STACK
21080 @findex gdb.COMMAND_STACK
21081 @item COMMAND_STACK
21082 The command has to do with manipulation of the stack. For example,
21083 @code{backtrace}, @code{frame}, and @code{return} are in this
21084 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
21085 list of commands in this category.
21087 @findex COMMAND_FILES
21088 @findex gdb.COMMAND_FILES
21089 @item COMMAND_FILES
21090 This class is used for file-related commands. For example,
21091 @code{file}, @code{list} and @code{section} are in this category.
21092 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
21093 commands in this category.
21095 @findex COMMAND_SUPPORT
21096 @findex gdb.COMMAND_SUPPORT
21097 @item COMMAND_SUPPORT
21098 This should be used for ``support facilities'', generally meaning
21099 things that are useful to the user when interacting with @value{GDBN},
21100 but not related to the state of the inferior. For example,
21101 @code{help}, @code{make}, and @code{shell} are in this category. Type
21102 @kbd{help support} at the @value{GDBN} prompt to see a list of
21103 commands in this category.
21105 @findex COMMAND_STATUS
21106 @findex gdb.COMMAND_STATUS
21107 @item COMMAND_STATUS
21108 The command is an @samp{info}-related command, that is, related to the
21109 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
21110 and @code{show} are in this category. Type @kbd{help status} at the
21111 @value{GDBN} prompt to see a list of commands in this category.
21113 @findex COMMAND_BREAKPOINTS
21114 @findex gdb.COMMAND_BREAKPOINTS
21115 @item COMMAND_BREAKPOINTS
21116 The command has to do with breakpoints. For example, @code{break},
21117 @code{clear}, and @code{delete} are in this category. Type @kbd{help
21118 breakpoints} at the @value{GDBN} prompt to see a list of commands in
21121 @findex COMMAND_TRACEPOINTS
21122 @findex gdb.COMMAND_TRACEPOINTS
21123 @item COMMAND_TRACEPOINTS
21124 The command has to do with tracepoints. For example, @code{trace},
21125 @code{actions}, and @code{tfind} are in this category. Type
21126 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
21127 commands in this category.
21129 @findex COMMAND_OBSCURE
21130 @findex gdb.COMMAND_OBSCURE
21131 @item COMMAND_OBSCURE
21132 The command is only used in unusual circumstances, or is not of
21133 general interest to users. For example, @code{checkpoint},
21134 @code{fork}, and @code{stop} are in this category. Type @kbd{help
21135 obscure} at the @value{GDBN} prompt to see a list of commands in this
21138 @findex COMMAND_MAINTENANCE
21139 @findex gdb.COMMAND_MAINTENANCE
21140 @item COMMAND_MAINTENANCE
21141 The command is only useful to @value{GDBN} maintainers. The
21142 @code{maintenance} and @code{flushregs} commands are in this category.
21143 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
21144 commands in this category.
21147 A new command can use a predefined completion function, either by
21148 specifying it via an argument at initialization, or by returning it
21149 from the @code{complete} method. These predefined completion
21150 constants are all defined in the @code{gdb} module:
21153 @findex COMPLETE_NONE
21154 @findex gdb.COMPLETE_NONE
21155 @item COMPLETE_NONE
21156 This constant means that no completion should be done.
21158 @findex COMPLETE_FILENAME
21159 @findex gdb.COMPLETE_FILENAME
21160 @item COMPLETE_FILENAME
21161 This constant means that filename completion should be performed.
21163 @findex COMPLETE_LOCATION
21164 @findex gdb.COMPLETE_LOCATION
21165 @item COMPLETE_LOCATION
21166 This constant means that location completion should be done.
21167 @xref{Specify Location}.
21169 @findex COMPLETE_COMMAND
21170 @findex gdb.COMPLETE_COMMAND
21171 @item COMPLETE_COMMAND
21172 This constant means that completion should examine @value{GDBN}
21175 @findex COMPLETE_SYMBOL
21176 @findex gdb.COMPLETE_SYMBOL
21177 @item COMPLETE_SYMBOL
21178 This constant means that completion should be done using symbol names
21182 The following code snippet shows how a trivial CLI command can be
21183 implemented in Python:
21186 class HelloWorld (gdb.Command):
21187 """Greet the whole world."""
21189 def __init__ (self):
21190 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
21192 def invoke (self, arg, from_tty):
21193 print "Hello, World!"
21198 The last line instantiates the class, and is necessary to trigger the
21199 registration of the command with @value{GDBN}. Depending on how the
21200 Python code is read into @value{GDBN}, you may need to import the
21201 @code{gdb} module explicitly.
21203 @node Parameters In Python
21204 @subsubsection Parameters In Python
21206 @cindex parameters in python
21207 @cindex python parameters
21208 @tindex gdb.Parameter
21210 You can implement new @value{GDBN} parameters using Python. A new
21211 parameter is implemented as an instance of the @code{gdb.Parameter}
21214 Parameters are exposed to the user via the @code{set} and
21215 @code{show} commands. @xref{Help}.
21217 There are many parameters that already exist and can be set in
21218 @value{GDBN}. Two examples are: @code{set follow fork} and
21219 @code{set charset}. Setting these parameters influences certain
21220 behavior in @value{GDBN}. Similarly, you can define parameters that
21221 can be used to influence behavior in custom Python scripts and commands.
21223 @defmethod Parameter __init__ name @var{command-class} @var{parameter-class} @r{[}@var{enum-sequence}@r{]}
21224 The object initializer for @code{Parameter} registers the new
21225 parameter with @value{GDBN}. This initializer is normally invoked
21226 from the subclass' own @code{__init__} method.
21228 @var{name} is the name of the new parameter. If @var{name} consists
21229 of multiple words, then the initial words are looked for as prefix
21230 parameters. An example of this can be illustrated with the
21231 @code{set print} set of parameters. If @var{name} is
21232 @code{print foo}, then @code{print} will be searched as the prefix
21233 parameter. In this case the parameter can subsequently be accessed in
21234 @value{GDBN} as @code{set print foo}.
21236 If @var{name} consists of multiple words, and no prefix parameter group
21237 can be found, an exception is raised.
21239 @var{command-class} should be one of the @samp{COMMAND_} constants
21240 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
21241 categorize the new parameter in the help system.
21243 @var{parameter-class} should be one of the @samp{PARAM_} constants
21244 defined below. This argument tells @value{GDBN} the type of the new
21245 parameter; this information is used for input validation and
21248 If @var{parameter-class} is @code{PARAM_ENUM}, then
21249 @var{enum-sequence} must be a sequence of strings. These strings
21250 represent the possible values for the parameter.
21252 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
21253 of a fourth argument will cause an exception to be thrown.
21255 The help text for the new parameter is taken from the Python
21256 documentation string for the parameter's class, if there is one. If
21257 there is no documentation string, a default value is used.
21260 @defivar Parameter set_doc
21261 If this attribute exists, and is a string, then its value is used as
21262 the help text for this parameter's @code{set} command. The value is
21263 examined when @code{Parameter.__init__} is invoked; subsequent changes
21267 @defivar Parameter show_doc
21268 If this attribute exists, and is a string, then its value is used as
21269 the help text for this parameter's @code{show} command. The value is
21270 examined when @code{Parameter.__init__} is invoked; subsequent changes
21274 @defivar Parameter value
21275 The @code{value} attribute holds the underlying value of the
21276 parameter. It can be read and assigned to just as any other
21277 attribute. @value{GDBN} does validation when assignments are made.
21281 When a new parameter is defined, its type must be specified. The
21282 available types are represented by constants defined in the @code{gdb}
21286 @findex PARAM_BOOLEAN
21287 @findex gdb.PARAM_BOOLEAN
21288 @item PARAM_BOOLEAN
21289 The value is a plain boolean. The Python boolean values, @code{True}
21290 and @code{False} are the only valid values.
21292 @findex PARAM_AUTO_BOOLEAN
21293 @findex gdb.PARAM_AUTO_BOOLEAN
21294 @item PARAM_AUTO_BOOLEAN
21295 The value has three possible states: true, false, and @samp{auto}. In
21296 Python, true and false are represented using boolean constants, and
21297 @samp{auto} is represented using @code{None}.
21299 @findex PARAM_UINTEGER
21300 @findex gdb.PARAM_UINTEGER
21301 @item PARAM_UINTEGER
21302 The value is an unsigned integer. The value of 0 should be
21303 interpreted to mean ``unlimited''.
21305 @findex PARAM_INTEGER
21306 @findex gdb.PARAM_INTEGER
21307 @item PARAM_INTEGER
21308 The value is a signed integer. The value of 0 should be interpreted
21309 to mean ``unlimited''.
21311 @findex PARAM_STRING
21312 @findex gdb.PARAM_STRING
21314 The value is a string. When the user modifies the string, any escape
21315 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
21316 translated into corresponding characters and encoded into the current
21319 @findex PARAM_STRING_NOESCAPE
21320 @findex gdb.PARAM_STRING_NOESCAPE
21321 @item PARAM_STRING_NOESCAPE
21322 The value is a string. When the user modifies the string, escapes are
21323 passed through untranslated.
21325 @findex PARAM_OPTIONAL_FILENAME
21326 @findex gdb.PARAM_OPTIONAL_FILENAME
21327 @item PARAM_OPTIONAL_FILENAME
21328 The value is a either a filename (a string), or @code{None}.
21330 @findex PARAM_FILENAME
21331 @findex gdb.PARAM_FILENAME
21332 @item PARAM_FILENAME
21333 The value is a filename. This is just like
21334 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
21336 @findex PARAM_ZINTEGER
21337 @findex gdb.PARAM_ZINTEGER
21338 @item PARAM_ZINTEGER
21339 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
21340 is interpreted as itself.
21343 @findex gdb.PARAM_ENUM
21345 The value is a string, which must be one of a collection string
21346 constants provided when the parameter is created.
21349 @node Functions In Python
21350 @subsubsection Writing new convenience functions
21352 @cindex writing convenience functions
21353 @cindex convenience functions in python
21354 @cindex python convenience functions
21355 @tindex gdb.Function
21357 You can implement new convenience functions (@pxref{Convenience Vars})
21358 in Python. A convenience function is an instance of a subclass of the
21359 class @code{gdb.Function}.
21361 @defmethod Function __init__ name
21362 The initializer for @code{Function} registers the new function with
21363 @value{GDBN}. The argument @var{name} is the name of the function,
21364 a string. The function will be visible to the user as a convenience
21365 variable of type @code{internal function}, whose name is the same as
21366 the given @var{name}.
21368 The documentation for the new function is taken from the documentation
21369 string for the new class.
21372 @defmethod Function invoke @var{*args}
21373 When a convenience function is evaluated, its arguments are converted
21374 to instances of @code{gdb.Value}, and then the function's
21375 @code{invoke} method is called. Note that @value{GDBN} does not
21376 predetermine the arity of convenience functions. Instead, all
21377 available arguments are passed to @code{invoke}, following the
21378 standard Python calling convention. In particular, a convenience
21379 function can have default values for parameters without ill effect.
21381 The return value of this method is used as its value in the enclosing
21382 expression. If an ordinary Python value is returned, it is converted
21383 to a @code{gdb.Value} following the usual rules.
21386 The following code snippet shows how a trivial convenience function can
21387 be implemented in Python:
21390 class Greet (gdb.Function):
21391 """Return string to greet someone.
21392 Takes a name as argument."""
21394 def __init__ (self):
21395 super (Greet, self).__init__ ("greet")
21397 def invoke (self, name):
21398 return "Hello, %s!" % name.string ()
21403 The last line instantiates the class, and is necessary to trigger the
21404 registration of the function with @value{GDBN}. Depending on how the
21405 Python code is read into @value{GDBN}, you may need to import the
21406 @code{gdb} module explicitly.
21408 @node Progspaces In Python
21409 @subsubsection Program Spaces In Python
21411 @cindex progspaces in python
21412 @tindex gdb.Progspace
21414 A program space, or @dfn{progspace}, represents a symbolic view
21415 of an address space.
21416 It consists of all of the objfiles of the program.
21417 @xref{Objfiles In Python}.
21418 @xref{Inferiors and Programs, program spaces}, for more details
21419 about program spaces.
21421 The following progspace-related functions are available in the
21424 @findex gdb.current_progspace
21425 @defun current_progspace
21426 This function returns the program space of the currently selected inferior.
21427 @xref{Inferiors and Programs}.
21430 @findex gdb.progspaces
21432 Return a sequence of all the progspaces currently known to @value{GDBN}.
21435 Each progspace is represented by an instance of the @code{gdb.Progspace}
21438 @defivar Progspace filename
21439 The file name of the progspace as a string.
21442 @defivar Progspace pretty_printers
21443 The @code{pretty_printers} attribute is a list of functions. It is
21444 used to look up pretty-printers. A @code{Value} is passed to each
21445 function in order; if the function returns @code{None}, then the
21446 search continues. Otherwise, the return value should be an object
21447 which is used to format the value. @xref{Pretty Printing API}, for more
21451 @node Objfiles In Python
21452 @subsubsection Objfiles In Python
21454 @cindex objfiles in python
21455 @tindex gdb.Objfile
21457 @value{GDBN} loads symbols for an inferior from various
21458 symbol-containing files (@pxref{Files}). These include the primary
21459 executable file, any shared libraries used by the inferior, and any
21460 separate debug info files (@pxref{Separate Debug Files}).
21461 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
21463 The following objfile-related functions are available in the
21466 @findex gdb.current_objfile
21467 @defun current_objfile
21468 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
21469 sets the ``current objfile'' to the corresponding objfile. This
21470 function returns the current objfile. If there is no current objfile,
21471 this function returns @code{None}.
21474 @findex gdb.objfiles
21476 Return a sequence of all the objfiles current known to @value{GDBN}.
21477 @xref{Objfiles In Python}.
21480 Each objfile is represented by an instance of the @code{gdb.Objfile}
21483 @defivar Objfile filename
21484 The file name of the objfile as a string.
21487 @defivar Objfile pretty_printers
21488 The @code{pretty_printers} attribute is a list of functions. It is
21489 used to look up pretty-printers. A @code{Value} is passed to each
21490 function in order; if the function returns @code{None}, then the
21491 search continues. Otherwise, the return value should be an object
21492 which is used to format the value. @xref{Pretty Printing API}, for more
21496 @node Frames In Python
21497 @subsubsection Accessing inferior stack frames from Python.
21499 @cindex frames in python
21500 When the debugged program stops, @value{GDBN} is able to analyze its call
21501 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
21502 represents a frame in the stack. A @code{gdb.Frame} object is only valid
21503 while its corresponding frame exists in the inferior's stack. If you try
21504 to use an invalid frame object, @value{GDBN} will throw a @code{RuntimeError}
21507 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
21511 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
21515 The following frame-related functions are available in the @code{gdb} module:
21517 @findex gdb.selected_frame
21518 @defun selected_frame
21519 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
21522 @defun frame_stop_reason_string reason
21523 Return a string explaining the reason why @value{GDBN} stopped unwinding
21524 frames, as expressed by the given @var{reason} code (an integer, see the
21525 @code{unwind_stop_reason} method further down in this section).
21528 A @code{gdb.Frame} object has the following methods:
21531 @defmethod Frame is_valid
21532 Returns true if the @code{gdb.Frame} object is valid, false if not.
21533 A frame object can become invalid if the frame it refers to doesn't
21534 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
21535 an exception if it is invalid at the time the method is called.
21538 @defmethod Frame name
21539 Returns the function name of the frame, or @code{None} if it can't be
21543 @defmethod Frame type
21544 Returns the type of the frame. The value can be one of
21545 @code{gdb.NORMAL_FRAME}, @code{gdb.DUMMY_FRAME}, @code{gdb.SIGTRAMP_FRAME}
21546 or @code{gdb.SENTINEL_FRAME}.
21549 @defmethod Frame unwind_stop_reason
21550 Return an integer representing the reason why it's not possible to find
21551 more frames toward the outermost frame. Use
21552 @code{gdb.frame_stop_reason_string} to convert the value returned by this
21553 function to a string.
21556 @defmethod Frame pc
21557 Returns the frame's resume address.
21560 @defmethod Frame block
21561 Return the frame's code block. @xref{Blocks In Python}.
21564 @defmethod Frame function
21565 Return the symbol for the function corresponding to this frame.
21566 @xref{Symbols In Python}.
21569 @defmethod Frame older
21570 Return the frame that called this frame.
21573 @defmethod Frame newer
21574 Return the frame called by this frame.
21577 @defmethod Frame find_sal
21578 Return the frame's symtab and line object.
21579 @xref{Symbol Tables In Python}.
21582 @defmethod Frame read_var variable @r{[}block@r{]}
21583 Return the value of @var{variable} in this frame. If the optional
21584 argument @var{block} is provided, search for the variable from that
21585 block; otherwise start at the frame's current block (which is
21586 determined by the frame's current program counter). @var{variable}
21587 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
21588 @code{gdb.Block} object.
21591 @defmethod Frame select
21592 Set this frame to be the selected frame. @xref{Stack, ,Examining the
21597 @node Blocks In Python
21598 @subsubsection Accessing frame blocks from Python.
21600 @cindex blocks in python
21603 Within each frame, @value{GDBN} maintains information on each block
21604 stored in that frame. These blocks are organized hierarchically, and
21605 are represented individually in Python as a @code{gdb.Block}.
21606 Please see @ref{Frames In Python}, for a more in-depth discussion on
21607 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
21608 detailed technical information on @value{GDBN}'s book-keeping of the
21611 The following block-related functions are available in the @code{gdb}
21614 @findex gdb.block_for_pc
21615 @defun block_for_pc pc
21616 Return the @code{gdb.Block} containing the given @var{pc} value. If the
21617 block cannot be found for the @var{pc} value specified, the function
21618 will return @code{None}.
21621 A @code{gdb.Block} object has the following attributes:
21624 @defivar Block start
21625 The start address of the block. This attribute is not writable.
21629 The end address of the block. This attribute is not writable.
21632 @defivar Block function
21633 The name of the block represented as a @code{gdb.Symbol}. If the
21634 block is not named, then this attribute holds @code{None}. This
21635 attribute is not writable.
21638 @defivar Block superblock
21639 The block containing this block. If this parent block does not exist,
21640 this attribute holds @code{None}. This attribute is not writable.
21644 @node Symbols In Python
21645 @subsubsection Python representation of Symbols.
21647 @cindex symbols in python
21650 @value{GDBN} represents every variable, function and type as an
21651 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
21652 Similarly, Python represents these symbols in @value{GDBN} with the
21653 @code{gdb.Symbol} object.
21655 The following symbol-related functions are available in the @code{gdb}
21658 @findex gdb.lookup_symbol
21659 @defun lookup_symbol name [block] [domain]
21660 This function searches for a symbol by name. The search scope can be
21661 restricted to the parameters defined in the optional domain and block
21664 @var{name} is the name of the symbol. It must be a string. The
21665 optional @var{block} argument restricts the search to symbols visible
21666 in that @var{block}. The @var{block} argument must be a
21667 @code{gdb.Block} object. The optional @var{domain} argument restricts
21668 the search to the domain type. The @var{domain} argument must be a
21669 domain constant defined in the @code{gdb} module and described later
21673 A @code{gdb.Symbol} object has the following attributes:
21676 @defivar Symbol symtab
21677 The symbol table in which the symbol appears. This attribute is
21678 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
21679 Python}. This attribute is not writable.
21682 @defivar Symbol name
21683 The name of the symbol as a string. This attribute is not writable.
21686 @defivar Symbol linkage_name
21687 The name of the symbol, as used by the linker (i.e., may be mangled).
21688 This attribute is not writable.
21691 @defivar Symbol print_name
21692 The name of the symbol in a form suitable for output. This is either
21693 @code{name} or @code{linkage_name}, depending on whether the user
21694 asked @value{GDBN} to display demangled or mangled names.
21697 @defivar Symbol addr_class
21698 The address class of the symbol. This classifies how to find the value
21699 of a symbol. Each address class is a constant defined in the
21700 @code{gdb} module and described later in this chapter.
21703 @defivar Symbol is_argument
21704 @code{True} if the symbol is an argument of a function.
21707 @defivar Symbol is_constant
21708 @code{True} if the symbol is a constant.
21711 @defivar Symbol is_function
21712 @code{True} if the symbol is a function or a method.
21715 @defivar Symbol is_variable
21716 @code{True} if the symbol is a variable.
21720 The available domain categories in @code{gdb.Symbol} are represented
21721 as constants in the @code{gdb} module:
21724 @findex SYMBOL_UNDEF_DOMAIN
21725 @findex gdb.SYMBOL_UNDEF_DOMAIN
21726 @item SYMBOL_UNDEF_DOMAIN
21727 This is used when a domain has not been discovered or none of the
21728 following domains apply. This usually indicates an error either
21729 in the symbol information or in @value{GDBN}'s handling of symbols.
21730 @findex SYMBOL_VAR_DOMAIN
21731 @findex gdb.SYMBOL_VAR_DOMAIN
21732 @item SYMBOL_VAR_DOMAIN
21733 This domain contains variables, function names, typedef names and enum
21735 @findex SYMBOL_STRUCT_DOMAIN
21736 @findex gdb.SYMBOL_STRUCT_DOMAIN
21737 @item SYMBOL_STRUCT_DOMAIN
21738 This domain holds struct, union and enum type names.
21739 @findex SYMBOL_LABEL_DOMAIN
21740 @findex gdb.SYMBOL_LABEL_DOMAIN
21741 @item SYMBOL_LABEL_DOMAIN
21742 This domain contains names of labels (for gotos).
21743 @findex SYMBOL_VARIABLES_DOMAIN
21744 @findex gdb.SYMBOL_VARIABLES_DOMAIN
21745 @item SYMBOL_VARIABLES_DOMAIN
21746 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
21747 contains everything minus functions and types.
21748 @findex SYMBOL_FUNCTIONS_DOMAIN
21749 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
21750 @item SYMBOL_FUNCTION_DOMAIN
21751 This domain contains all functions.
21752 @findex SYMBOL_TYPES_DOMAIN
21753 @findex gdb.SYMBOL_TYPES_DOMAIN
21754 @item SYMBOL_TYPES_DOMAIN
21755 This domain contains all types.
21758 The available address class categories in @code{gdb.Symbol} are represented
21759 as constants in the @code{gdb} module:
21762 @findex SYMBOL_LOC_UNDEF
21763 @findex gdb.SYMBOL_LOC_UNDEF
21764 @item SYMBOL_LOC_UNDEF
21765 If this is returned by address class, it indicates an error either in
21766 the symbol information or in @value{GDBN}'s handling of symbols.
21767 @findex SYMBOL_LOC_CONST
21768 @findex gdb.SYMBOL_LOC_CONST
21769 @item SYMBOL_LOC_CONST
21770 Value is constant int.
21771 @findex SYMBOL_LOC_STATIC
21772 @findex gdb.SYMBOL_LOC_STATIC
21773 @item SYMBOL_LOC_STATIC
21774 Value is at a fixed address.
21775 @findex SYMBOL_LOC_REGISTER
21776 @findex gdb.SYMBOL_LOC_REGISTER
21777 @item SYMBOL_LOC_REGISTER
21778 Value is in a register.
21779 @findex SYMBOL_LOC_ARG
21780 @findex gdb.SYMBOL_LOC_ARG
21781 @item SYMBOL_LOC_ARG
21782 Value is an argument. This value is at the offset stored within the
21783 symbol inside the frame's argument list.
21784 @findex SYMBOL_LOC_REF_ARG
21785 @findex gdb.SYMBOL_LOC_REF_ARG
21786 @item SYMBOL_LOC_REF_ARG
21787 Value address is stored in the frame's argument list. Just like
21788 @code{LOC_ARG} except that the value's address is stored at the
21789 offset, not the value itself.
21790 @findex SYMBOL_LOC_REGPARM_ADDR
21791 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
21792 @item SYMBOL_LOC_REGPARM_ADDR
21793 Value is a specified register. Just like @code{LOC_REGISTER} except
21794 the register holds the address of the argument instead of the argument
21796 @findex SYMBOL_LOC_LOCAL
21797 @findex gdb.SYMBOL_LOC_LOCAL
21798 @item SYMBOL_LOC_LOCAL
21799 Value is a local variable.
21800 @findex SYMBOL_LOC_TYPEDEF
21801 @findex gdb.SYMBOL_LOC_TYPEDEF
21802 @item SYMBOL_LOC_TYPEDEF
21803 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
21805 @findex SYMBOL_LOC_BLOCK
21806 @findex gdb.SYMBOL_LOC_BLOCK
21807 @item SYMBOL_LOC_BLOCK
21809 @findex SYMBOL_LOC_CONST_BYTES
21810 @findex gdb.SYMBOL_LOC_CONST_BYTES
21811 @item SYMBOL_LOC_CONST_BYTES
21812 Value is a byte-sequence.
21813 @findex SYMBOL_LOC_UNRESOLVED
21814 @findex gdb.SYMBOL_LOC_UNRESOLVED
21815 @item SYMBOL_LOC_UNRESOLVED
21816 Value is at a fixed address, but the address of the variable has to be
21817 determined from the minimal symbol table whenever the variable is
21819 @findex SYMBOL_LOC_OPTIMIZED_OUT
21820 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
21821 @item SYMBOL_LOC_OPTIMIZED_OUT
21822 The value does not actually exist in the program.
21823 @findex SYMBOL_LOC_COMPUTED
21824 @findex gdb.SYMBOL_LOC_COMPUTED
21825 @item SYMBOL_LOC_COMPUTED
21826 The value's address is a computed location.
21829 @node Symbol Tables In Python
21830 @subsubsection Symbol table representation in Python.
21832 @cindex symbol tables in python
21834 @tindex gdb.Symtab_and_line
21836 Access to symbol table data maintained by @value{GDBN} on the inferior
21837 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
21838 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
21839 from the @code{find_sal} method in @code{gdb.Frame} object.
21840 @xref{Frames In Python}.
21842 For more information on @value{GDBN}'s symbol table management, see
21843 @ref{Symbols, ,Examining the Symbol Table}, for more information.
21845 A @code{gdb.Symtab_and_line} object has the following attributes:
21848 @defivar Symtab_and_line symtab
21849 The symbol table object (@code{gdb.Symtab}) for this frame.
21850 This attribute is not writable.
21853 @defivar Symtab_and_line pc
21854 Indicates the current program counter address. This attribute is not
21858 @defivar Symtab_and_line line
21859 Indicates the current line number for this object. This
21860 attribute is not writable.
21864 A @code{gdb.Symtab} object has the following attributes:
21867 @defivar Symtab filename
21868 The symbol table's source filename. This attribute is not writable.
21871 @defivar Symtab objfile
21872 The symbol table's backing object file. @xref{Objfiles In Python}.
21873 This attribute is not writable.
21877 The following methods are provided:
21880 @defmethod Symtab fullname
21881 Return the symbol table's source absolute file name.
21885 @node Breakpoints In Python
21886 @subsubsection Manipulating breakpoints using Python
21888 @cindex breakpoints in python
21889 @tindex gdb.Breakpoint
21891 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
21894 @defmethod Breakpoint __init__ spec @r{[}type@r{]} @r{[}wp_class@r{]}
21895 Create a new breakpoint. @var{spec} is a string naming the
21896 location of the breakpoint, or an expression that defines a
21897 watchpoint. The contents can be any location recognized by the
21898 @code{break} command, or in the case of a watchpoint, by the @code{watch}
21899 command. The optional @var{type} denotes the breakpoint to create
21900 from the types defined later in this chapter. This argument can be
21901 either: @code{BP_BREAKPOINT} or @code{BP_WATCHPOINT}. @var{type}
21902 defaults to @code{BP_BREAKPOINT}. The optional @var{wp_class}
21903 argument defines the class of watchpoint to create, if @var{type} is
21904 defined as @code{BP_WATCHPOINT}. If a watchpoint class is not
21905 provided, it is assumed to be a @var{WP_WRITE} class.
21908 The available watchpoint types represented by constants are defined in the
21913 @findex gdb.WP_READ
21915 Read only watchpoint.
21918 @findex gdb.WP_WRITE
21920 Write only watchpoint.
21923 @findex gdb.WP_ACCESS
21925 Read/Write watchpoint.
21928 @defmethod Breakpoint is_valid
21929 Return @code{True} if this @code{Breakpoint} object is valid,
21930 @code{False} otherwise. A @code{Breakpoint} object can become invalid
21931 if the user deletes the breakpoint. In this case, the object still
21932 exists, but the underlying breakpoint does not. In the cases of
21933 watchpoint scope, the watchpoint remains valid even if execution of the
21934 inferior leaves the scope of that watchpoint.
21937 @defivar Breakpoint enabled
21938 This attribute is @code{True} if the breakpoint is enabled, and
21939 @code{False} otherwise. This attribute is writable.
21942 @defivar Breakpoint silent
21943 This attribute is @code{True} if the breakpoint is silent, and
21944 @code{False} otherwise. This attribute is writable.
21946 Note that a breakpoint can also be silent if it has commands and the
21947 first command is @code{silent}. This is not reported by the
21948 @code{silent} attribute.
21951 @defivar Breakpoint thread
21952 If the breakpoint is thread-specific, this attribute holds the thread
21953 id. If the breakpoint is not thread-specific, this attribute is
21954 @code{None}. This attribute is writable.
21957 @defivar Breakpoint task
21958 If the breakpoint is Ada task-specific, this attribute holds the Ada task
21959 id. If the breakpoint is not task-specific (or the underlying
21960 language is not Ada), this attribute is @code{None}. This attribute
21964 @defivar Breakpoint ignore_count
21965 This attribute holds the ignore count for the breakpoint, an integer.
21966 This attribute is writable.
21969 @defivar Breakpoint number
21970 This attribute holds the breakpoint's number --- the identifier used by
21971 the user to manipulate the breakpoint. This attribute is not writable.
21974 @defivar Breakpoint type
21975 This attribute holds the breakpoint's type --- the identifier used to
21976 determine the actual breakpoint type or use-case. This attribute is not
21980 The available types are represented by constants defined in the @code{gdb}
21984 @findex BP_BREAKPOINT
21985 @findex gdb.BP_BREAKPOINT
21986 @item BP_BREAKPOINT
21987 Normal code breakpoint.
21989 @findex BP_WATCHPOINT
21990 @findex gdb.BP_WATCHPOINT
21991 @item BP_WATCHPOINT
21992 Watchpoint breakpoint.
21994 @findex BP_HARDWARE_WATCHPOINT
21995 @findex gdb.BP_HARDWARE_WATCHPOINT
21996 @item BP_HARDWARE_WATCHPOINT
21997 Hardware assisted watchpoint.
21999 @findex BP_READ_WATCHPOINT
22000 @findex gdb.BP_READ_WATCHPOINT
22001 @item BP_READ_WATCHPOINT
22002 Hardware assisted read watchpoint.
22004 @findex BP_ACCESS_WATCHPOINT
22005 @findex gdb.BP_ACCESS_WATCHPOINT
22006 @item BP_ACCESS_WATCHPOINT
22007 Hardware assisted access watchpoint.
22010 @defivar Breakpoint hit_count
22011 This attribute holds the hit count for the breakpoint, an integer.
22012 This attribute is writable, but currently it can only be set to zero.
22015 @defivar Breakpoint location
22016 This attribute holds the location of the breakpoint, as specified by
22017 the user. It is a string. If the breakpoint does not have a location
22018 (that is, it is a watchpoint) the attribute's value is @code{None}. This
22019 attribute is not writable.
22022 @defivar Breakpoint expression
22023 This attribute holds a breakpoint expression, as specified by
22024 the user. It is a string. If the breakpoint does not have an
22025 expression (the breakpoint is not a watchpoint) the attribute's value
22026 is @code{None}. This attribute is not writable.
22029 @defivar Breakpoint condition
22030 This attribute holds the condition of the breakpoint, as specified by
22031 the user. It is a string. If there is no condition, this attribute's
22032 value is @code{None}. This attribute is writable.
22035 @defivar Breakpoint commands
22036 This attribute holds the commands attached to the breakpoint. If
22037 there are commands, this attribute's value is a string holding all the
22038 commands, separated by newlines. If there are no commands, this
22039 attribute is @code{None}. This attribute is not writable.
22042 @node Lazy Strings In Python
22043 @subsubsection Python representation of lazy strings.
22045 @cindex lazy strings in python
22046 @tindex gdb.LazyString
22048 A @dfn{lazy string} is a string whose contents is not retrieved or
22049 encoded until it is needed.
22051 A @code{gdb.LazyString} is represented in @value{GDBN} as an
22052 @code{address} that points to a region of memory, an @code{encoding}
22053 that will be used to encode that region of memory, and a @code{length}
22054 to delimit the region of memory that represents the string. The
22055 difference between a @code{gdb.LazyString} and a string wrapped within
22056 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
22057 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
22058 retrieved and encoded during printing, while a @code{gdb.Value}
22059 wrapping a string is immediately retrieved and encoded on creation.
22061 A @code{gdb.LazyString} object has the following functions:
22063 @defmethod LazyString value
22064 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
22065 will point to the string in memory, but will lose all the delayed
22066 retrieval, encoding and handling that @value{GDBN} applies to a
22067 @code{gdb.LazyString}.
22070 @defivar LazyString address
22071 This attribute holds the address of the string. This attribute is not
22075 @defivar LazyString length
22076 This attribute holds the length of the string in characters. If the
22077 length is -1, then the string will be fetched and encoded up to the
22078 first null of appropriate width. This attribute is not writable.
22081 @defivar LazyString encoding
22082 This attribute holds the encoding that will be applied to the string
22083 when the string is printed by @value{GDBN}. If the encoding is not
22084 set, or contains an empty string, then @value{GDBN} will select the
22085 most appropriate encoding when the string is printed. This attribute
22089 @defivar LazyString type
22090 This attribute holds the type that is represented by the lazy string's
22091 type. For a lazy string this will always be a pointer type. To
22092 resolve this to the lazy string's character type, use the type's
22093 @code{target} method. @xref{Types In Python}. This attribute is not
22098 @subsection Auto-loading
22099 @cindex auto-loading, Python
22101 When a new object file is read (for example, due to the @code{file}
22102 command, or because the inferior has loaded a shared library),
22103 @value{GDBN} will look for Python support scripts in several ways:
22104 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
22107 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
22108 * .debug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
22109 * Which flavor to choose?::
22112 The auto-loading feature is useful for supplying application-specific
22113 debugging commands and scripts.
22115 Auto-loading can be enabled or disabled.
22118 @kindex maint set python auto-load
22119 @item maint set python auto-load [yes|no]
22120 Enable or disable the Python auto-loading feature.
22122 @kindex maint show python auto-load
22123 @item maint show python auto-load
22124 Show whether Python auto-loading is enabled or disabled.
22127 When reading an auto-loaded file, @value{GDBN} sets the
22128 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
22129 function (@pxref{Objfiles In Python}). This can be useful for
22130 registering objfile-specific pretty-printers.
22132 @node objfile-gdb.py file
22133 @subsubsection The @file{@var{objfile}-gdb.py} file
22134 @cindex @file{@var{objfile}-gdb.py}
22136 When a new object file is read, @value{GDBN} looks for
22137 a file named @file{@var{objfile}-gdb.py},
22138 where @var{objfile} is the object file's real name, formed by ensuring
22139 that the file name is absolute, following all symlinks, and resolving
22140 @code{.} and @code{..} components. If this file exists and is
22141 readable, @value{GDBN} will evaluate it as a Python script.
22143 If this file does not exist, and if the parameter
22144 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
22145 then @value{GDBN} will look for @var{real-name} in all of the
22146 directories mentioned in the value of @code{debug-file-directory}.
22148 Finally, if this file does not exist, then @value{GDBN} will look for
22149 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
22150 @var{data-directory} is @value{GDBN}'s data directory (available via
22151 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
22152 is the object file's real name, as described above.
22154 @value{GDBN} does not track which files it has already auto-loaded this way.
22155 @value{GDBN} will load the associated script every time the corresponding
22156 @var{objfile} is opened.
22157 So your @file{-gdb.py} file should be careful to avoid errors if it
22158 is evaluated more than once.
22160 @node .debug_gdb_scripts section
22161 @subsubsection The @code{.debug_gdb_scripts} section
22162 @cindex @code{.debug_gdb_scripts} section
22164 For systems using file formats like ELF and COFF,
22165 when @value{GDBN} loads a new object file
22166 it will look for a special section named @samp{.debug_gdb_scripts}.
22167 If this section exists, its contents is a list of names of scripts to load.
22169 @value{GDBN} will look for each specified script file first in the
22170 current directory and then along the source search path
22171 (@pxref{Source Path, ,Specifying Source Directories}),
22172 except that @file{$cdir} is not searched, since the compilation
22173 directory is not relevant to scripts.
22175 Entries can be placed in section @code{.debug_gdb_scripts} with,
22176 for example, this GCC macro:
22179 /* Note: The "MS" section flags are to remote duplicates. */
22180 #define DEFINE_GDB_SCRIPT(script_name) \
22182 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
22184 .asciz \"" script_name "\"\n\
22190 Then one can reference the macro in a header or source file like this:
22193 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
22196 The script name may include directories if desired.
22198 If the macro is put in a header, any application or library
22199 using this header will get a reference to the specified script.
22201 @node Which flavor to choose?
22202 @subsubsection Which flavor to choose?
22204 Given the multiple ways of auto-loading Python scripts, it might not always
22205 be clear which one to choose. This section provides some guidance.
22207 Benefits of the @file{-gdb.py} way:
22211 Can be used with file formats that don't support multiple sections.
22214 Ease of finding scripts for public libraries.
22216 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
22217 in the source search path.
22218 For publicly installed libraries, e.g., @file{libstdc++}, there typically
22219 isn't a source directory in which to find the script.
22222 Doesn't require source code additions.
22225 Benefits of the @code{.debug_gdb_scripts} way:
22229 Works with static linking.
22231 Scripts for libraries done the @file{-gdb.py} way require an objfile to
22232 trigger their loading. When an application is statically linked the only
22233 objfile available is the executable, and it is cumbersome to attach all the
22234 scripts from all the input libraries to the executable's @file{-gdb.py} script.
22237 Works with classes that are entirely inlined.
22239 Some classes can be entirely inlined, and thus there may not be an associated
22240 shared library to attach a @file{-gdb.py} script to.
22243 Scripts needn't be copied out of the source tree.
22245 In some circumstances, apps can be built out of large collections of internal
22246 libraries, and the build infrastructure necessary to install the
22247 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
22248 cumbersome. It may be easier to specify the scripts in the
22249 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
22250 top of the source tree to the source search path.
22254 @chapter Command Interpreters
22255 @cindex command interpreters
22257 @value{GDBN} supports multiple command interpreters, and some command
22258 infrastructure to allow users or user interface writers to switch
22259 between interpreters or run commands in other interpreters.
22261 @value{GDBN} currently supports two command interpreters, the console
22262 interpreter (sometimes called the command-line interpreter or @sc{cli})
22263 and the machine interface interpreter (or @sc{gdb/mi}). This manual
22264 describes both of these interfaces in great detail.
22266 By default, @value{GDBN} will start with the console interpreter.
22267 However, the user may choose to start @value{GDBN} with another
22268 interpreter by specifying the @option{-i} or @option{--interpreter}
22269 startup options. Defined interpreters include:
22273 @cindex console interpreter
22274 The traditional console or command-line interpreter. This is the most often
22275 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
22276 @value{GDBN} will use this interpreter.
22279 @cindex mi interpreter
22280 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
22281 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
22282 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
22286 @cindex mi2 interpreter
22287 The current @sc{gdb/mi} interface.
22290 @cindex mi1 interpreter
22291 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
22295 @cindex invoke another interpreter
22296 The interpreter being used by @value{GDBN} may not be dynamically
22297 switched at runtime. Although possible, this could lead to a very
22298 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
22299 enters the command "interpreter-set console" in a console view,
22300 @value{GDBN} would switch to using the console interpreter, rendering
22301 the IDE inoperable!
22303 @kindex interpreter-exec
22304 Although you may only choose a single interpreter at startup, you may execute
22305 commands in any interpreter from the current interpreter using the appropriate
22306 command. If you are running the console interpreter, simply use the
22307 @code{interpreter-exec} command:
22310 interpreter-exec mi "-data-list-register-names"
22313 @sc{gdb/mi} has a similar command, although it is only available in versions of
22314 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
22317 @chapter @value{GDBN} Text User Interface
22319 @cindex Text User Interface
22322 * TUI Overview:: TUI overview
22323 * TUI Keys:: TUI key bindings
22324 * TUI Single Key Mode:: TUI single key mode
22325 * TUI Commands:: TUI-specific commands
22326 * TUI Configuration:: TUI configuration variables
22329 The @value{GDBN} Text User Interface (TUI) is a terminal
22330 interface which uses the @code{curses} library to show the source
22331 file, the assembly output, the program registers and @value{GDBN}
22332 commands in separate text windows. The TUI mode is supported only
22333 on platforms where a suitable version of the @code{curses} library
22336 @pindex @value{GDBTUI}
22337 The TUI mode is enabled by default when you invoke @value{GDBN} as
22338 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
22339 You can also switch in and out of TUI mode while @value{GDBN} runs by
22340 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
22341 @xref{TUI Keys, ,TUI Key Bindings}.
22344 @section TUI Overview
22346 In TUI mode, @value{GDBN} can display several text windows:
22350 This window is the @value{GDBN} command window with the @value{GDBN}
22351 prompt and the @value{GDBN} output. The @value{GDBN} input is still
22352 managed using readline.
22355 The source window shows the source file of the program. The current
22356 line and active breakpoints are displayed in this window.
22359 The assembly window shows the disassembly output of the program.
22362 This window shows the processor registers. Registers are highlighted
22363 when their values change.
22366 The source and assembly windows show the current program position
22367 by highlighting the current line and marking it with a @samp{>} marker.
22368 Breakpoints are indicated with two markers. The first marker
22369 indicates the breakpoint type:
22373 Breakpoint which was hit at least once.
22376 Breakpoint which was never hit.
22379 Hardware breakpoint which was hit at least once.
22382 Hardware breakpoint which was never hit.
22385 The second marker indicates whether the breakpoint is enabled or not:
22389 Breakpoint is enabled.
22392 Breakpoint is disabled.
22395 The source, assembly and register windows are updated when the current
22396 thread changes, when the frame changes, or when the program counter
22399 These windows are not all visible at the same time. The command
22400 window is always visible. The others can be arranged in several
22411 source and assembly,
22414 source and registers, or
22417 assembly and registers.
22420 A status line above the command window shows the following information:
22424 Indicates the current @value{GDBN} target.
22425 (@pxref{Targets, ,Specifying a Debugging Target}).
22428 Gives the current process or thread number.
22429 When no process is being debugged, this field is set to @code{No process}.
22432 Gives the current function name for the selected frame.
22433 The name is demangled if demangling is turned on (@pxref{Print Settings}).
22434 When there is no symbol corresponding to the current program counter,
22435 the string @code{??} is displayed.
22438 Indicates the current line number for the selected frame.
22439 When the current line number is not known, the string @code{??} is displayed.
22442 Indicates the current program counter address.
22446 @section TUI Key Bindings
22447 @cindex TUI key bindings
22449 The TUI installs several key bindings in the readline keymaps
22450 (@pxref{Command Line Editing}). The following key bindings
22451 are installed for both TUI mode and the @value{GDBN} standard mode.
22460 Enter or leave the TUI mode. When leaving the TUI mode,
22461 the curses window management stops and @value{GDBN} operates using
22462 its standard mode, writing on the terminal directly. When reentering
22463 the TUI mode, control is given back to the curses windows.
22464 The screen is then refreshed.
22468 Use a TUI layout with only one window. The layout will
22469 either be @samp{source} or @samp{assembly}. When the TUI mode
22470 is not active, it will switch to the TUI mode.
22472 Think of this key binding as the Emacs @kbd{C-x 1} binding.
22476 Use a TUI layout with at least two windows. When the current
22477 layout already has two windows, the next layout with two windows is used.
22478 When a new layout is chosen, one window will always be common to the
22479 previous layout and the new one.
22481 Think of it as the Emacs @kbd{C-x 2} binding.
22485 Change the active window. The TUI associates several key bindings
22486 (like scrolling and arrow keys) with the active window. This command
22487 gives the focus to the next TUI window.
22489 Think of it as the Emacs @kbd{C-x o} binding.
22493 Switch in and out of the TUI SingleKey mode that binds single
22494 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
22497 The following key bindings only work in the TUI mode:
22502 Scroll the active window one page up.
22506 Scroll the active window one page down.
22510 Scroll the active window one line up.
22514 Scroll the active window one line down.
22518 Scroll the active window one column left.
22522 Scroll the active window one column right.
22526 Refresh the screen.
22529 Because the arrow keys scroll the active window in the TUI mode, they
22530 are not available for their normal use by readline unless the command
22531 window has the focus. When another window is active, you must use
22532 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
22533 and @kbd{C-f} to control the command window.
22535 @node TUI Single Key Mode
22536 @section TUI Single Key Mode
22537 @cindex TUI single key mode
22539 The TUI also provides a @dfn{SingleKey} mode, which binds several
22540 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
22541 switch into this mode, where the following key bindings are used:
22544 @kindex c @r{(SingleKey TUI key)}
22548 @kindex d @r{(SingleKey TUI key)}
22552 @kindex f @r{(SingleKey TUI key)}
22556 @kindex n @r{(SingleKey TUI key)}
22560 @kindex q @r{(SingleKey TUI key)}
22562 exit the SingleKey mode.
22564 @kindex r @r{(SingleKey TUI key)}
22568 @kindex s @r{(SingleKey TUI key)}
22572 @kindex u @r{(SingleKey TUI key)}
22576 @kindex v @r{(SingleKey TUI key)}
22580 @kindex w @r{(SingleKey TUI key)}
22585 Other keys temporarily switch to the @value{GDBN} command prompt.
22586 The key that was pressed is inserted in the editing buffer so that
22587 it is possible to type most @value{GDBN} commands without interaction
22588 with the TUI SingleKey mode. Once the command is entered the TUI
22589 SingleKey mode is restored. The only way to permanently leave
22590 this mode is by typing @kbd{q} or @kbd{C-x s}.
22594 @section TUI-specific Commands
22595 @cindex TUI commands
22597 The TUI has specific commands to control the text windows.
22598 These commands are always available, even when @value{GDBN} is not in
22599 the TUI mode. When @value{GDBN} is in the standard mode, most
22600 of these commands will automatically switch to the TUI mode.
22602 Note that if @value{GDBN}'s @code{stdout} is not connected to a
22603 terminal, or @value{GDBN} has been started with the machine interface
22604 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
22605 these commands will fail with an error, because it would not be
22606 possible or desirable to enable curses window management.
22611 List and give the size of all displayed windows.
22615 Display the next layout.
22618 Display the previous layout.
22621 Display the source window only.
22624 Display the assembly window only.
22627 Display the source and assembly window.
22630 Display the register window together with the source or assembly window.
22634 Make the next window active for scrolling.
22637 Make the previous window active for scrolling.
22640 Make the source window active for scrolling.
22643 Make the assembly window active for scrolling.
22646 Make the register window active for scrolling.
22649 Make the command window active for scrolling.
22653 Refresh the screen. This is similar to typing @kbd{C-L}.
22655 @item tui reg float
22657 Show the floating point registers in the register window.
22659 @item tui reg general
22660 Show the general registers in the register window.
22663 Show the next register group. The list of register groups as well as
22664 their order is target specific. The predefined register groups are the
22665 following: @code{general}, @code{float}, @code{system}, @code{vector},
22666 @code{all}, @code{save}, @code{restore}.
22668 @item tui reg system
22669 Show the system registers in the register window.
22673 Update the source window and the current execution point.
22675 @item winheight @var{name} +@var{count}
22676 @itemx winheight @var{name} -@var{count}
22678 Change the height of the window @var{name} by @var{count}
22679 lines. Positive counts increase the height, while negative counts
22682 @item tabset @var{nchars}
22684 Set the width of tab stops to be @var{nchars} characters.
22687 @node TUI Configuration
22688 @section TUI Configuration Variables
22689 @cindex TUI configuration variables
22691 Several configuration variables control the appearance of TUI windows.
22694 @item set tui border-kind @var{kind}
22695 @kindex set tui border-kind
22696 Select the border appearance for the source, assembly and register windows.
22697 The possible values are the following:
22700 Use a space character to draw the border.
22703 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
22706 Use the Alternate Character Set to draw the border. The border is
22707 drawn using character line graphics if the terminal supports them.
22710 @item set tui border-mode @var{mode}
22711 @kindex set tui border-mode
22712 @itemx set tui active-border-mode @var{mode}
22713 @kindex set tui active-border-mode
22714 Select the display attributes for the borders of the inactive windows
22715 or the active window. The @var{mode} can be one of the following:
22718 Use normal attributes to display the border.
22724 Use reverse video mode.
22727 Use half bright mode.
22729 @item half-standout
22730 Use half bright and standout mode.
22733 Use extra bright or bold mode.
22735 @item bold-standout
22736 Use extra bright or bold and standout mode.
22741 @chapter Using @value{GDBN} under @sc{gnu} Emacs
22744 @cindex @sc{gnu} Emacs
22745 A special interface allows you to use @sc{gnu} Emacs to view (and
22746 edit) the source files for the program you are debugging with
22749 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
22750 executable file you want to debug as an argument. This command starts
22751 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
22752 created Emacs buffer.
22753 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
22755 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
22760 All ``terminal'' input and output goes through an Emacs buffer, called
22763 This applies both to @value{GDBN} commands and their output, and to the input
22764 and output done by the program you are debugging.
22766 This is useful because it means that you can copy the text of previous
22767 commands and input them again; you can even use parts of the output
22770 All the facilities of Emacs' Shell mode are available for interacting
22771 with your program. In particular, you can send signals the usual
22772 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
22776 @value{GDBN} displays source code through Emacs.
22778 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
22779 source file for that frame and puts an arrow (@samp{=>}) at the
22780 left margin of the current line. Emacs uses a separate buffer for
22781 source display, and splits the screen to show both your @value{GDBN} session
22784 Explicit @value{GDBN} @code{list} or search commands still produce output as
22785 usual, but you probably have no reason to use them from Emacs.
22788 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
22789 a graphical mode, enabled by default, which provides further buffers
22790 that can control the execution and describe the state of your program.
22791 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
22793 If you specify an absolute file name when prompted for the @kbd{M-x
22794 gdb} argument, then Emacs sets your current working directory to where
22795 your program resides. If you only specify the file name, then Emacs
22796 sets your current working directory to to the directory associated
22797 with the previous buffer. In this case, @value{GDBN} may find your
22798 program by searching your environment's @code{PATH} variable, but on
22799 some operating systems it might not find the source. So, although the
22800 @value{GDBN} input and output session proceeds normally, the auxiliary
22801 buffer does not display the current source and line of execution.
22803 The initial working directory of @value{GDBN} is printed on the top
22804 line of the GUD buffer and this serves as a default for the commands
22805 that specify files for @value{GDBN} to operate on. @xref{Files,
22806 ,Commands to Specify Files}.
22808 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
22809 need to call @value{GDBN} by a different name (for example, if you
22810 keep several configurations around, with different names) you can
22811 customize the Emacs variable @code{gud-gdb-command-name} to run the
22814 In the GUD buffer, you can use these special Emacs commands in
22815 addition to the standard Shell mode commands:
22819 Describe the features of Emacs' GUD Mode.
22822 Execute to another source line, like the @value{GDBN} @code{step} command; also
22823 update the display window to show the current file and location.
22826 Execute to next source line in this function, skipping all function
22827 calls, like the @value{GDBN} @code{next} command. Then update the display window
22828 to show the current file and location.
22831 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
22832 display window accordingly.
22835 Execute until exit from the selected stack frame, like the @value{GDBN}
22836 @code{finish} command.
22839 Continue execution of your program, like the @value{GDBN} @code{continue}
22843 Go up the number of frames indicated by the numeric argument
22844 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
22845 like the @value{GDBN} @code{up} command.
22848 Go down the number of frames indicated by the numeric argument, like the
22849 @value{GDBN} @code{down} command.
22852 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
22853 tells @value{GDBN} to set a breakpoint on the source line point is on.
22855 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
22856 separate frame which shows a backtrace when the GUD buffer is current.
22857 Move point to any frame in the stack and type @key{RET} to make it
22858 become the current frame and display the associated source in the
22859 source buffer. Alternatively, click @kbd{Mouse-2} to make the
22860 selected frame become the current one. In graphical mode, the
22861 speedbar displays watch expressions.
22863 If you accidentally delete the source-display buffer, an easy way to get
22864 it back is to type the command @code{f} in the @value{GDBN} buffer, to
22865 request a frame display; when you run under Emacs, this recreates
22866 the source buffer if necessary to show you the context of the current
22869 The source files displayed in Emacs are in ordinary Emacs buffers
22870 which are visiting the source files in the usual way. You can edit
22871 the files with these buffers if you wish; but keep in mind that @value{GDBN}
22872 communicates with Emacs in terms of line numbers. If you add or
22873 delete lines from the text, the line numbers that @value{GDBN} knows cease
22874 to correspond properly with the code.
22876 A more detailed description of Emacs' interaction with @value{GDBN} is
22877 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
22880 @c The following dropped because Epoch is nonstandard. Reactivate
22881 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
22883 @kindex Emacs Epoch environment
22887 Version 18 of @sc{gnu} Emacs has a built-in window system
22888 called the @code{epoch}
22889 environment. Users of this environment can use a new command,
22890 @code{inspect} which performs identically to @code{print} except that
22891 each value is printed in its own window.
22896 @chapter The @sc{gdb/mi} Interface
22898 @unnumberedsec Function and Purpose
22900 @cindex @sc{gdb/mi}, its purpose
22901 @sc{gdb/mi} is a line based machine oriented text interface to
22902 @value{GDBN} and is activated by specifying using the
22903 @option{--interpreter} command line option (@pxref{Mode Options}). It
22904 is specifically intended to support the development of systems which
22905 use the debugger as just one small component of a larger system.
22907 This chapter is a specification of the @sc{gdb/mi} interface. It is written
22908 in the form of a reference manual.
22910 Note that @sc{gdb/mi} is still under construction, so some of the
22911 features described below are incomplete and subject to change
22912 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
22914 @unnumberedsec Notation and Terminology
22916 @cindex notational conventions, for @sc{gdb/mi}
22917 This chapter uses the following notation:
22921 @code{|} separates two alternatives.
22924 @code{[ @var{something} ]} indicates that @var{something} is optional:
22925 it may or may not be given.
22928 @code{( @var{group} )*} means that @var{group} inside the parentheses
22929 may repeat zero or more times.
22932 @code{( @var{group} )+} means that @var{group} inside the parentheses
22933 may repeat one or more times.
22936 @code{"@var{string}"} means a literal @var{string}.
22940 @heading Dependencies
22944 * GDB/MI General Design::
22945 * GDB/MI Command Syntax::
22946 * GDB/MI Compatibility with CLI::
22947 * GDB/MI Development and Front Ends::
22948 * GDB/MI Output Records::
22949 * GDB/MI Simple Examples::
22950 * GDB/MI Command Description Format::
22951 * GDB/MI Breakpoint Commands::
22952 * GDB/MI Program Context::
22953 * GDB/MI Thread Commands::
22954 * GDB/MI Program Execution::
22955 * GDB/MI Stack Manipulation::
22956 * GDB/MI Variable Objects::
22957 * GDB/MI Data Manipulation::
22958 * GDB/MI Tracepoint Commands::
22959 * GDB/MI Symbol Query::
22960 * GDB/MI File Commands::
22962 * GDB/MI Kod Commands::
22963 * GDB/MI Memory Overlay Commands::
22964 * GDB/MI Signal Handling Commands::
22966 * GDB/MI Target Manipulation::
22967 * GDB/MI File Transfer Commands::
22968 * GDB/MI Miscellaneous Commands::
22971 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
22972 @node GDB/MI General Design
22973 @section @sc{gdb/mi} General Design
22974 @cindex GDB/MI General Design
22976 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
22977 parts---commands sent to @value{GDBN}, responses to those commands
22978 and notifications. Each command results in exactly one response,
22979 indicating either successful completion of the command, or an error.
22980 For the commands that do not resume the target, the response contains the
22981 requested information. For the commands that resume the target, the
22982 response only indicates whether the target was successfully resumed.
22983 Notifications is the mechanism for reporting changes in the state of the
22984 target, or in @value{GDBN} state, that cannot conveniently be associated with
22985 a command and reported as part of that command response.
22987 The important examples of notifications are:
22991 Exec notifications. These are used to report changes in
22992 target state---when a target is resumed, or stopped. It would not
22993 be feasible to include this information in response of resuming
22994 commands, because one resume commands can result in multiple events in
22995 different threads. Also, quite some time may pass before any event
22996 happens in the target, while a frontend needs to know whether the resuming
22997 command itself was successfully executed.
23000 Console output, and status notifications. Console output
23001 notifications are used to report output of CLI commands, as well as
23002 diagnostics for other commands. Status notifications are used to
23003 report the progress of a long-running operation. Naturally, including
23004 this information in command response would mean no output is produced
23005 until the command is finished, which is undesirable.
23008 General notifications. Commands may have various side effects on
23009 the @value{GDBN} or target state beyond their official purpose. For example,
23010 a command may change the selected thread. Although such changes can
23011 be included in command response, using notification allows for more
23012 orthogonal frontend design.
23016 There's no guarantee that whenever an MI command reports an error,
23017 @value{GDBN} or the target are in any specific state, and especially,
23018 the state is not reverted to the state before the MI command was
23019 processed. Therefore, whenever an MI command results in an error,
23020 we recommend that the frontend refreshes all the information shown in
23021 the user interface.
23025 * Context management::
23026 * Asynchronous and non-stop modes::
23030 @node Context management
23031 @subsection Context management
23033 In most cases when @value{GDBN} accesses the target, this access is
23034 done in context of a specific thread and frame (@pxref{Frames}).
23035 Often, even when accessing global data, the target requires that a thread
23036 be specified. The CLI interface maintains the selected thread and frame,
23037 and supplies them to target on each command. This is convenient,
23038 because a command line user would not want to specify that information
23039 explicitly on each command, and because user interacts with
23040 @value{GDBN} via a single terminal, so no confusion is possible as
23041 to what thread and frame are the current ones.
23043 In the case of MI, the concept of selected thread and frame is less
23044 useful. First, a frontend can easily remember this information
23045 itself. Second, a graphical frontend can have more than one window,
23046 each one used for debugging a different thread, and the frontend might
23047 want to access additional threads for internal purposes. This
23048 increases the risk that by relying on implicitly selected thread, the
23049 frontend may be operating on a wrong one. Therefore, each MI command
23050 should explicitly specify which thread and frame to operate on. To
23051 make it possible, each MI command accepts the @samp{--thread} and
23052 @samp{--frame} options, the value to each is @value{GDBN} identifier
23053 for thread and frame to operate on.
23055 Usually, each top-level window in a frontend allows the user to select
23056 a thread and a frame, and remembers the user selection for further
23057 operations. However, in some cases @value{GDBN} may suggest that the
23058 current thread be changed. For example, when stopping on a breakpoint
23059 it is reasonable to switch to the thread where breakpoint is hit. For
23060 another example, if the user issues the CLI @samp{thread} command via
23061 the frontend, it is desirable to change the frontend's selected thread to the
23062 one specified by user. @value{GDBN} communicates the suggestion to
23063 change current thread using the @samp{=thread-selected} notification.
23064 No such notification is available for the selected frame at the moment.
23066 Note that historically, MI shares the selected thread with CLI, so
23067 frontends used the @code{-thread-select} to execute commands in the
23068 right context. However, getting this to work right is cumbersome. The
23069 simplest way is for frontend to emit @code{-thread-select} command
23070 before every command. This doubles the number of commands that need
23071 to be sent. The alternative approach is to suppress @code{-thread-select}
23072 if the selected thread in @value{GDBN} is supposed to be identical to the
23073 thread the frontend wants to operate on. However, getting this
23074 optimization right can be tricky. In particular, if the frontend
23075 sends several commands to @value{GDBN}, and one of the commands changes the
23076 selected thread, then the behaviour of subsequent commands will
23077 change. So, a frontend should either wait for response from such
23078 problematic commands, or explicitly add @code{-thread-select} for
23079 all subsequent commands. No frontend is known to do this exactly
23080 right, so it is suggested to just always pass the @samp{--thread} and
23081 @samp{--frame} options.
23083 @node Asynchronous and non-stop modes
23084 @subsection Asynchronous command execution and non-stop mode
23086 On some targets, @value{GDBN} is capable of processing MI commands
23087 even while the target is running. This is called @dfn{asynchronous
23088 command execution} (@pxref{Background Execution}). The frontend may
23089 specify a preferrence for asynchronous execution using the
23090 @code{-gdb-set target-async 1} command, which should be emitted before
23091 either running the executable or attaching to the target. After the
23092 frontend has started the executable or attached to the target, it can
23093 find if asynchronous execution is enabled using the
23094 @code{-list-target-features} command.
23096 Even if @value{GDBN} can accept a command while target is running,
23097 many commands that access the target do not work when the target is
23098 running. Therefore, asynchronous command execution is most useful
23099 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
23100 it is possible to examine the state of one thread, while other threads
23103 When a given thread is running, MI commands that try to access the
23104 target in the context of that thread may not work, or may work only on
23105 some targets. In particular, commands that try to operate on thread's
23106 stack will not work, on any target. Commands that read memory, or
23107 modify breakpoints, may work or not work, depending on the target. Note
23108 that even commands that operate on global state, such as @code{print},
23109 @code{set}, and breakpoint commands, still access the target in the
23110 context of a specific thread, so frontend should try to find a
23111 stopped thread and perform the operation on that thread (using the
23112 @samp{--thread} option).
23114 Which commands will work in the context of a running thread is
23115 highly target dependent. However, the two commands
23116 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
23117 to find the state of a thread, will always work.
23119 @node Thread groups
23120 @subsection Thread groups
23121 @value{GDBN} may be used to debug several processes at the same time.
23122 On some platfroms, @value{GDBN} may support debugging of several
23123 hardware systems, each one having several cores with several different
23124 processes running on each core. This section describes the MI
23125 mechanism to support such debugging scenarios.
23127 The key observation is that regardless of the structure of the
23128 target, MI can have a global list of threads, because most commands that
23129 accept the @samp{--thread} option do not need to know what process that
23130 thread belongs to. Therefore, it is not necessary to introduce
23131 neither additional @samp{--process} option, nor an notion of the
23132 current process in the MI interface. The only strictly new feature
23133 that is required is the ability to find how the threads are grouped
23136 To allow the user to discover such grouping, and to support arbitrary
23137 hierarchy of machines/cores/processes, MI introduces the concept of a
23138 @dfn{thread group}. Thread group is a collection of threads and other
23139 thread groups. A thread group always has a string identifier, a type,
23140 and may have additional attributes specific to the type. A new
23141 command, @code{-list-thread-groups}, returns the list of top-level
23142 thread groups, which correspond to processes that @value{GDBN} is
23143 debugging at the moment. By passing an identifier of a thread group
23144 to the @code{-list-thread-groups} command, it is possible to obtain
23145 the members of specific thread group.
23147 To allow the user to easily discover processes, and other objects, he
23148 wishes to debug, a concept of @dfn{available thread group} is
23149 introduced. Available thread group is an thread group that
23150 @value{GDBN} is not debugging, but that can be attached to, using the
23151 @code{-target-attach} command. The list of available top-level thread
23152 groups can be obtained using @samp{-list-thread-groups --available}.
23153 In general, the content of a thread group may be only retrieved only
23154 after attaching to that thread group.
23156 Thread groups are related to inferiors (@pxref{Inferiors and
23157 Programs}). Each inferior corresponds to a thread group of a special
23158 type @samp{process}, and some additional operations are permitted on
23159 such thread groups.
23161 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23162 @node GDB/MI Command Syntax
23163 @section @sc{gdb/mi} Command Syntax
23166 * GDB/MI Input Syntax::
23167 * GDB/MI Output Syntax::
23170 @node GDB/MI Input Syntax
23171 @subsection @sc{gdb/mi} Input Syntax
23173 @cindex input syntax for @sc{gdb/mi}
23174 @cindex @sc{gdb/mi}, input syntax
23176 @item @var{command} @expansion{}
23177 @code{@var{cli-command} | @var{mi-command}}
23179 @item @var{cli-command} @expansion{}
23180 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
23181 @var{cli-command} is any existing @value{GDBN} CLI command.
23183 @item @var{mi-command} @expansion{}
23184 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
23185 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
23187 @item @var{token} @expansion{}
23188 "any sequence of digits"
23190 @item @var{option} @expansion{}
23191 @code{"-" @var{parameter} [ " " @var{parameter} ]}
23193 @item @var{parameter} @expansion{}
23194 @code{@var{non-blank-sequence} | @var{c-string}}
23196 @item @var{operation} @expansion{}
23197 @emph{any of the operations described in this chapter}
23199 @item @var{non-blank-sequence} @expansion{}
23200 @emph{anything, provided it doesn't contain special characters such as
23201 "-", @var{nl}, """ and of course " "}
23203 @item @var{c-string} @expansion{}
23204 @code{""" @var{seven-bit-iso-c-string-content} """}
23206 @item @var{nl} @expansion{}
23215 The CLI commands are still handled by the @sc{mi} interpreter; their
23216 output is described below.
23219 The @code{@var{token}}, when present, is passed back when the command
23223 Some @sc{mi} commands accept optional arguments as part of the parameter
23224 list. Each option is identified by a leading @samp{-} (dash) and may be
23225 followed by an optional argument parameter. Options occur first in the
23226 parameter list and can be delimited from normal parameters using
23227 @samp{--} (this is useful when some parameters begin with a dash).
23234 We want easy access to the existing CLI syntax (for debugging).
23237 We want it to be easy to spot a @sc{mi} operation.
23240 @node GDB/MI Output Syntax
23241 @subsection @sc{gdb/mi} Output Syntax
23243 @cindex output syntax of @sc{gdb/mi}
23244 @cindex @sc{gdb/mi}, output syntax
23245 The output from @sc{gdb/mi} consists of zero or more out-of-band records
23246 followed, optionally, by a single result record. This result record
23247 is for the most recent command. The sequence of output records is
23248 terminated by @samp{(gdb)}.
23250 If an input command was prefixed with a @code{@var{token}} then the
23251 corresponding output for that command will also be prefixed by that same
23255 @item @var{output} @expansion{}
23256 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
23258 @item @var{result-record} @expansion{}
23259 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
23261 @item @var{out-of-band-record} @expansion{}
23262 @code{@var{async-record} | @var{stream-record}}
23264 @item @var{async-record} @expansion{}
23265 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
23267 @item @var{exec-async-output} @expansion{}
23268 @code{[ @var{token} ] "*" @var{async-output}}
23270 @item @var{status-async-output} @expansion{}
23271 @code{[ @var{token} ] "+" @var{async-output}}
23273 @item @var{notify-async-output} @expansion{}
23274 @code{[ @var{token} ] "=" @var{async-output}}
23276 @item @var{async-output} @expansion{}
23277 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
23279 @item @var{result-class} @expansion{}
23280 @code{"done" | "running" | "connected" | "error" | "exit"}
23282 @item @var{async-class} @expansion{}
23283 @code{"stopped" | @var{others}} (where @var{others} will be added
23284 depending on the needs---this is still in development).
23286 @item @var{result} @expansion{}
23287 @code{ @var{variable} "=" @var{value}}
23289 @item @var{variable} @expansion{}
23290 @code{ @var{string} }
23292 @item @var{value} @expansion{}
23293 @code{ @var{const} | @var{tuple} | @var{list} }
23295 @item @var{const} @expansion{}
23296 @code{@var{c-string}}
23298 @item @var{tuple} @expansion{}
23299 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
23301 @item @var{list} @expansion{}
23302 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
23303 @var{result} ( "," @var{result} )* "]" }
23305 @item @var{stream-record} @expansion{}
23306 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
23308 @item @var{console-stream-output} @expansion{}
23309 @code{"~" @var{c-string}}
23311 @item @var{target-stream-output} @expansion{}
23312 @code{"@@" @var{c-string}}
23314 @item @var{log-stream-output} @expansion{}
23315 @code{"&" @var{c-string}}
23317 @item @var{nl} @expansion{}
23320 @item @var{token} @expansion{}
23321 @emph{any sequence of digits}.
23329 All output sequences end in a single line containing a period.
23332 The @code{@var{token}} is from the corresponding request. Note that
23333 for all async output, while the token is allowed by the grammar and
23334 may be output by future versions of @value{GDBN} for select async
23335 output messages, it is generally omitted. Frontends should treat
23336 all async output as reporting general changes in the state of the
23337 target and there should be no need to associate async output to any
23341 @cindex status output in @sc{gdb/mi}
23342 @var{status-async-output} contains on-going status information about the
23343 progress of a slow operation. It can be discarded. All status output is
23344 prefixed by @samp{+}.
23347 @cindex async output in @sc{gdb/mi}
23348 @var{exec-async-output} contains asynchronous state change on the target
23349 (stopped, started, disappeared). All async output is prefixed by
23353 @cindex notify output in @sc{gdb/mi}
23354 @var{notify-async-output} contains supplementary information that the
23355 client should handle (e.g., a new breakpoint information). All notify
23356 output is prefixed by @samp{=}.
23359 @cindex console output in @sc{gdb/mi}
23360 @var{console-stream-output} is output that should be displayed as is in the
23361 console. It is the textual response to a CLI command. All the console
23362 output is prefixed by @samp{~}.
23365 @cindex target output in @sc{gdb/mi}
23366 @var{target-stream-output} is the output produced by the target program.
23367 All the target output is prefixed by @samp{@@}.
23370 @cindex log output in @sc{gdb/mi}
23371 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
23372 instance messages that should be displayed as part of an error log. All
23373 the log output is prefixed by @samp{&}.
23376 @cindex list output in @sc{gdb/mi}
23377 New @sc{gdb/mi} commands should only output @var{lists} containing
23383 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
23384 details about the various output records.
23386 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23387 @node GDB/MI Compatibility with CLI
23388 @section @sc{gdb/mi} Compatibility with CLI
23390 @cindex compatibility, @sc{gdb/mi} and CLI
23391 @cindex @sc{gdb/mi}, compatibility with CLI
23393 For the developers convenience CLI commands can be entered directly,
23394 but there may be some unexpected behaviour. For example, commands
23395 that query the user will behave as if the user replied yes, breakpoint
23396 command lists are not executed and some CLI commands, such as
23397 @code{if}, @code{when} and @code{define}, prompt for further input with
23398 @samp{>}, which is not valid MI output.
23400 This feature may be removed at some stage in the future and it is
23401 recommended that front ends use the @code{-interpreter-exec} command
23402 (@pxref{-interpreter-exec}).
23404 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23405 @node GDB/MI Development and Front Ends
23406 @section @sc{gdb/mi} Development and Front Ends
23407 @cindex @sc{gdb/mi} development
23409 The application which takes the MI output and presents the state of the
23410 program being debugged to the user is called a @dfn{front end}.
23412 Although @sc{gdb/mi} is still incomplete, it is currently being used
23413 by a variety of front ends to @value{GDBN}. This makes it difficult
23414 to introduce new functionality without breaking existing usage. This
23415 section tries to minimize the problems by describing how the protocol
23418 Some changes in MI need not break a carefully designed front end, and
23419 for these the MI version will remain unchanged. The following is a
23420 list of changes that may occur within one level, so front ends should
23421 parse MI output in a way that can handle them:
23425 New MI commands may be added.
23428 New fields may be added to the output of any MI command.
23431 The range of values for fields with specified values, e.g.,
23432 @code{in_scope} (@pxref{-var-update}) may be extended.
23434 @c The format of field's content e.g type prefix, may change so parse it
23435 @c at your own risk. Yes, in general?
23437 @c The order of fields may change? Shouldn't really matter but it might
23438 @c resolve inconsistencies.
23441 If the changes are likely to break front ends, the MI version level
23442 will be increased by one. This will allow the front end to parse the
23443 output according to the MI version. Apart from mi0, new versions of
23444 @value{GDBN} will not support old versions of MI and it will be the
23445 responsibility of the front end to work with the new one.
23447 @c Starting with mi3, add a new command -mi-version that prints the MI
23450 The best way to avoid unexpected changes in MI that might break your front
23451 end is to make your project known to @value{GDBN} developers and
23452 follow development on @email{gdb@@sourceware.org} and
23453 @email{gdb-patches@@sourceware.org}.
23454 @cindex mailing lists
23456 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23457 @node GDB/MI Output Records
23458 @section @sc{gdb/mi} Output Records
23461 * GDB/MI Result Records::
23462 * GDB/MI Stream Records::
23463 * GDB/MI Async Records::
23464 * GDB/MI Frame Information::
23465 * GDB/MI Thread Information::
23468 @node GDB/MI Result Records
23469 @subsection @sc{gdb/mi} Result Records
23471 @cindex result records in @sc{gdb/mi}
23472 @cindex @sc{gdb/mi}, result records
23473 In addition to a number of out-of-band notifications, the response to a
23474 @sc{gdb/mi} command includes one of the following result indications:
23478 @item "^done" [ "," @var{results} ]
23479 The synchronous operation was successful, @code{@var{results}} are the return
23484 This result record is equivalent to @samp{^done}. Historically, it
23485 was output instead of @samp{^done} if the command has resumed the
23486 target. This behaviour is maintained for backward compatibility, but
23487 all frontends should treat @samp{^done} and @samp{^running}
23488 identically and rely on the @samp{*running} output record to determine
23489 which threads are resumed.
23493 @value{GDBN} has connected to a remote target.
23495 @item "^error" "," @var{c-string}
23497 The operation failed. The @code{@var{c-string}} contains the corresponding
23502 @value{GDBN} has terminated.
23506 @node GDB/MI Stream Records
23507 @subsection @sc{gdb/mi} Stream Records
23509 @cindex @sc{gdb/mi}, stream records
23510 @cindex stream records in @sc{gdb/mi}
23511 @value{GDBN} internally maintains a number of output streams: the console, the
23512 target, and the log. The output intended for each of these streams is
23513 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
23515 Each stream record begins with a unique @dfn{prefix character} which
23516 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
23517 Syntax}). In addition to the prefix, each stream record contains a
23518 @code{@var{string-output}}. This is either raw text (with an implicit new
23519 line) or a quoted C string (which does not contain an implicit newline).
23522 @item "~" @var{string-output}
23523 The console output stream contains text that should be displayed in the
23524 CLI console window. It contains the textual responses to CLI commands.
23526 @item "@@" @var{string-output}
23527 The target output stream contains any textual output from the running
23528 target. This is only present when GDB's event loop is truly
23529 asynchronous, which is currently only the case for remote targets.
23531 @item "&" @var{string-output}
23532 The log stream contains debugging messages being produced by @value{GDBN}'s
23536 @node GDB/MI Async Records
23537 @subsection @sc{gdb/mi} Async Records
23539 @cindex async records in @sc{gdb/mi}
23540 @cindex @sc{gdb/mi}, async records
23541 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
23542 additional changes that have occurred. Those changes can either be a
23543 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
23544 target activity (e.g., target stopped).
23546 The following is the list of possible async records:
23550 @item *running,thread-id="@var{thread}"
23551 The target is now running. The @var{thread} field tells which
23552 specific thread is now running, and can be @samp{all} if all threads
23553 are running. The frontend should assume that no interaction with a
23554 running thread is possible after this notification is produced.
23555 The frontend should not assume that this notification is output
23556 only once for any command. @value{GDBN} may emit this notification
23557 several times, either for different threads, because it cannot resume
23558 all threads together, or even for a single thread, if the thread must
23559 be stepped though some code before letting it run freely.
23561 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
23562 The target has stopped. The @var{reason} field can have one of the
23566 @item breakpoint-hit
23567 A breakpoint was reached.
23568 @item watchpoint-trigger
23569 A watchpoint was triggered.
23570 @item read-watchpoint-trigger
23571 A read watchpoint was triggered.
23572 @item access-watchpoint-trigger
23573 An access watchpoint was triggered.
23574 @item function-finished
23575 An -exec-finish or similar CLI command was accomplished.
23576 @item location-reached
23577 An -exec-until or similar CLI command was accomplished.
23578 @item watchpoint-scope
23579 A watchpoint has gone out of scope.
23580 @item end-stepping-range
23581 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
23582 similar CLI command was accomplished.
23583 @item exited-signalled
23584 The inferior exited because of a signal.
23586 The inferior exited.
23587 @item exited-normally
23588 The inferior exited normally.
23589 @item signal-received
23590 A signal was received by the inferior.
23593 The @var{id} field identifies the thread that directly caused the stop
23594 -- for example by hitting a breakpoint. Depending on whether all-stop
23595 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
23596 stop all threads, or only the thread that directly triggered the stop.
23597 If all threads are stopped, the @var{stopped} field will have the
23598 value of @code{"all"}. Otherwise, the value of the @var{stopped}
23599 field will be a list of thread identifiers. Presently, this list will
23600 always include a single thread, but frontend should be prepared to see
23601 several threads in the list. The @var{core} field reports the
23602 processor core on which the stop event has happened. This field may be absent
23603 if such information is not available.
23605 @item =thread-group-added,id="@var{id}"
23606 @itemx =thread-group-removed,id="@var{id}"
23607 A thread group was either added or removed. The @var{id} field
23608 contains the @value{GDBN} identifier of the thread group. When a thread
23609 group is added, it generally might not be associated with a running
23610 process. When a thread group is removed, its id becomes invalid and
23611 cannot be used in any way.
23613 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
23614 A thread group became associated with a running program,
23615 either because the program was just started or the thread group
23616 was attached to a program. The @var{id} field contains the
23617 @value{GDBN} identifier of the thread group. The @var{pid} field
23618 contains process identifier, specific to the operating system.
23620 @itemx =thread-group-exited,id="@var{id}"
23621 A thread group is no longer associated with a running program,
23622 either because the program has exited, or because it was detached
23623 from. The @var{id} field contains the @value{GDBN} identifier of the
23626 @item =thread-created,id="@var{id}",group-id="@var{gid}"
23627 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
23628 A thread either was created, or has exited. The @var{id} field
23629 contains the @value{GDBN} identifier of the thread. The @var{gid}
23630 field identifies the thread group this thread belongs to.
23632 @item =thread-selected,id="@var{id}"
23633 Informs that the selected thread was changed as result of the last
23634 command. This notification is not emitted as result of @code{-thread-select}
23635 command but is emitted whenever an MI command that is not documented
23636 to change the selected thread actually changes it. In particular,
23637 invoking, directly or indirectly (via user-defined command), the CLI
23638 @code{thread} command, will generate this notification.
23640 We suggest that in response to this notification, front ends
23641 highlight the selected thread and cause subsequent commands to apply to
23644 @item =library-loaded,...
23645 Reports that a new library file was loaded by the program. This
23646 notification has 4 fields---@var{id}, @var{target-name},
23647 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
23648 opaque identifier of the library. For remote debugging case,
23649 @var{target-name} and @var{host-name} fields give the name of the
23650 library file on the target, and on the host respectively. For native
23651 debugging, both those fields have the same value. The
23652 @var{symbols-loaded} field reports if the debug symbols for this
23653 library are loaded. The @var{thread-group} field, if present,
23654 specifies the id of the thread group in whose context the library was loaded.
23655 If the field is absent, it means the library was loaded in the context
23656 of all present thread groups.
23658 @item =library-unloaded,...
23659 Reports that a library was unloaded by the program. This notification
23660 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
23661 the same meaning as for the @code{=library-loaded} notification.
23662 The @var{thread-group} field, if present, specifies the id of the
23663 thread group in whose context the library was unloaded. If the field is
23664 absent, it means the library was unloaded in the context of all present
23669 @node GDB/MI Frame Information
23670 @subsection @sc{gdb/mi} Frame Information
23672 Response from many MI commands includes an information about stack
23673 frame. This information is a tuple that may have the following
23678 The level of the stack frame. The innermost frame has the level of
23679 zero. This field is always present.
23682 The name of the function corresponding to the frame. This field may
23683 be absent if @value{GDBN} is unable to determine the function name.
23686 The code address for the frame. This field is always present.
23689 The name of the source files that correspond to the frame's code
23690 address. This field may be absent.
23693 The source line corresponding to the frames' code address. This field
23697 The name of the binary file (either executable or shared library) the
23698 corresponds to the frame's code address. This field may be absent.
23702 @node GDB/MI Thread Information
23703 @subsection @sc{gdb/mi} Thread Information
23705 Whenever @value{GDBN} has to report an information about a thread, it
23706 uses a tuple with the following fields:
23710 The numeric id assigned to the thread by @value{GDBN}. This field is
23714 Target-specific string identifying the thread. This field is always present.
23717 Additional information about the thread provided by the target.
23718 It is supposed to be human-readable and not interpreted by the
23719 frontend. This field is optional.
23722 Either @samp{stopped} or @samp{running}, depending on whether the
23723 thread is presently running. This field is always present.
23726 The value of this field is an integer number of the processor core the
23727 thread was last seen on. This field is optional.
23731 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23732 @node GDB/MI Simple Examples
23733 @section Simple Examples of @sc{gdb/mi} Interaction
23734 @cindex @sc{gdb/mi}, simple examples
23736 This subsection presents several simple examples of interaction using
23737 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
23738 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
23739 the output received from @sc{gdb/mi}.
23741 Note the line breaks shown in the examples are here only for
23742 readability, they don't appear in the real output.
23744 @subheading Setting a Breakpoint
23746 Setting a breakpoint generates synchronous output which contains detailed
23747 information of the breakpoint.
23750 -> -break-insert main
23751 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
23752 enabled="y",addr="0x08048564",func="main",file="myprog.c",
23753 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
23757 @subheading Program Execution
23759 Program execution generates asynchronous records and MI gives the
23760 reason that execution stopped.
23766 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
23767 frame=@{addr="0x08048564",func="main",
23768 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
23769 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
23774 <- *stopped,reason="exited-normally"
23778 @subheading Quitting @value{GDBN}
23780 Quitting @value{GDBN} just prints the result class @samp{^exit}.
23788 Please note that @samp{^exit} is printed immediately, but it might
23789 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
23790 performs necessary cleanups, including killing programs being debugged
23791 or disconnecting from debug hardware, so the frontend should wait till
23792 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
23793 fails to exit in reasonable time.
23795 @subheading A Bad Command
23797 Here's what happens if you pass a non-existent command:
23801 <- ^error,msg="Undefined MI command: rubbish"
23806 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23807 @node GDB/MI Command Description Format
23808 @section @sc{gdb/mi} Command Description Format
23810 The remaining sections describe blocks of commands. Each block of
23811 commands is laid out in a fashion similar to this section.
23813 @subheading Motivation
23815 The motivation for this collection of commands.
23817 @subheading Introduction
23819 A brief introduction to this collection of commands as a whole.
23821 @subheading Commands
23823 For each command in the block, the following is described:
23825 @subsubheading Synopsis
23828 -command @var{args}@dots{}
23831 @subsubheading Result
23833 @subsubheading @value{GDBN} Command
23835 The corresponding @value{GDBN} CLI command(s), if any.
23837 @subsubheading Example
23839 Example(s) formatted for readability. Some of the described commands have
23840 not been implemented yet and these are labeled N.A.@: (not available).
23843 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23844 @node GDB/MI Breakpoint Commands
23845 @section @sc{gdb/mi} Breakpoint Commands
23847 @cindex breakpoint commands for @sc{gdb/mi}
23848 @cindex @sc{gdb/mi}, breakpoint commands
23849 This section documents @sc{gdb/mi} commands for manipulating
23852 @subheading The @code{-break-after} Command
23853 @findex -break-after
23855 @subsubheading Synopsis
23858 -break-after @var{number} @var{count}
23861 The breakpoint number @var{number} is not in effect until it has been
23862 hit @var{count} times. To see how this is reflected in the output of
23863 the @samp{-break-list} command, see the description of the
23864 @samp{-break-list} command below.
23866 @subsubheading @value{GDBN} Command
23868 The corresponding @value{GDBN} command is @samp{ignore}.
23870 @subsubheading Example
23875 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
23876 enabled="y",addr="0x000100d0",func="main",file="hello.c",
23877 fullname="/home/foo/hello.c",line="5",times="0"@}
23884 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
23885 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23886 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23887 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23888 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23889 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23890 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23891 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
23892 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
23893 line="5",times="0",ignore="3"@}]@}
23898 @subheading The @code{-break-catch} Command
23899 @findex -break-catch
23902 @subheading The @code{-break-commands} Command
23903 @findex -break-commands
23905 @subsubheading Synopsis
23908 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
23911 Specifies the CLI commands that should be executed when breakpoint
23912 @var{number} is hit. The parameters @var{command1} to @var{commandN}
23913 are the commands. If no command is specified, any previously-set
23914 commands are cleared. @xref{Break Commands}. Typical use of this
23915 functionality is tracing a program, that is, printing of values of
23916 some variables whenever breakpoint is hit and then continuing.
23918 @subsubheading @value{GDBN} Command
23920 The corresponding @value{GDBN} command is @samp{commands}.
23922 @subsubheading Example
23927 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
23928 enabled="y",addr="0x000100d0",func="main",file="hello.c",
23929 fullname="/home/foo/hello.c",line="5",times="0"@}
23931 -break-commands 1 "print v" "continue"
23936 @subheading The @code{-break-condition} Command
23937 @findex -break-condition
23939 @subsubheading Synopsis
23942 -break-condition @var{number} @var{expr}
23945 Breakpoint @var{number} will stop the program only if the condition in
23946 @var{expr} is true. The condition becomes part of the
23947 @samp{-break-list} output (see the description of the @samp{-break-list}
23950 @subsubheading @value{GDBN} Command
23952 The corresponding @value{GDBN} command is @samp{condition}.
23954 @subsubheading Example
23958 -break-condition 1 1
23962 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
23963 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
23964 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
23965 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
23966 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
23967 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
23968 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
23969 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
23970 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
23971 line="5",cond="1",times="0",ignore="3"@}]@}
23975 @subheading The @code{-break-delete} Command
23976 @findex -break-delete
23978 @subsubheading Synopsis
23981 -break-delete ( @var{breakpoint} )+
23984 Delete the breakpoint(s) whose number(s) are specified in the argument
23985 list. This is obviously reflected in the breakpoint list.
23987 @subsubheading @value{GDBN} Command
23989 The corresponding @value{GDBN} command is @samp{delete}.
23991 @subsubheading Example
23999 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
24000 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24001 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24002 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24003 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24004 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24005 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24010 @subheading The @code{-break-disable} Command
24011 @findex -break-disable
24013 @subsubheading Synopsis
24016 -break-disable ( @var{breakpoint} )+
24019 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
24020 break list is now set to @samp{n} for the named @var{breakpoint}(s).
24022 @subsubheading @value{GDBN} Command
24024 The corresponding @value{GDBN} command is @samp{disable}.
24026 @subsubheading Example
24034 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24035 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24036 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24037 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24038 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24039 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24040 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24041 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
24042 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
24043 line="5",times="0"@}]@}
24047 @subheading The @code{-break-enable} Command
24048 @findex -break-enable
24050 @subsubheading Synopsis
24053 -break-enable ( @var{breakpoint} )+
24056 Enable (previously disabled) @var{breakpoint}(s).
24058 @subsubheading @value{GDBN} Command
24060 The corresponding @value{GDBN} command is @samp{enable}.
24062 @subsubheading Example
24070 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24071 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24072 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24073 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24074 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24075 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24076 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24077 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
24078 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
24079 line="5",times="0"@}]@}
24083 @subheading The @code{-break-info} Command
24084 @findex -break-info
24086 @subsubheading Synopsis
24089 -break-info @var{breakpoint}
24093 Get information about a single breakpoint.
24095 @subsubheading @value{GDBN} Command
24097 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
24099 @subsubheading Example
24102 @subheading The @code{-break-insert} Command
24103 @findex -break-insert
24105 @subsubheading Synopsis
24108 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
24109 [ -c @var{condition} ] [ -i @var{ignore-count} ]
24110 [ -p @var{thread} ] [ @var{location} ]
24114 If specified, @var{location}, can be one of:
24121 @item filename:linenum
24122 @item filename:function
24126 The possible optional parameters of this command are:
24130 Insert a temporary breakpoint.
24132 Insert a hardware breakpoint.
24133 @item -c @var{condition}
24134 Make the breakpoint conditional on @var{condition}.
24135 @item -i @var{ignore-count}
24136 Initialize the @var{ignore-count}.
24138 If @var{location} cannot be parsed (for example if it
24139 refers to unknown files or functions), create a pending
24140 breakpoint. Without this flag, @value{GDBN} will report
24141 an error, and won't create a breakpoint, if @var{location}
24144 Create a disabled breakpoint.
24146 Create a tracepoint. @xref{Tracepoints}. When this parameter
24147 is used together with @samp{-h}, a fast tracepoint is created.
24150 @subsubheading Result
24152 The result is in the form:
24155 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
24156 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
24157 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
24158 times="@var{times}"@}
24162 where @var{number} is the @value{GDBN} number for this breakpoint,
24163 @var{funcname} is the name of the function where the breakpoint was
24164 inserted, @var{filename} is the name of the source file which contains
24165 this function, @var{lineno} is the source line number within that file
24166 and @var{times} the number of times that the breakpoint has been hit
24167 (always 0 for -break-insert but may be greater for -break-info or -break-list
24168 which use the same output).
24170 Note: this format is open to change.
24171 @c An out-of-band breakpoint instead of part of the result?
24173 @subsubheading @value{GDBN} Command
24175 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
24176 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
24178 @subsubheading Example
24183 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
24184 fullname="/home/foo/recursive2.c,line="4",times="0"@}
24186 -break-insert -t foo
24187 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
24188 fullname="/home/foo/recursive2.c,line="11",times="0"@}
24191 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
24192 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24193 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24194 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24195 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24196 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24197 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24198 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24199 addr="0x0001072c", func="main",file="recursive2.c",
24200 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
24201 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
24202 addr="0x00010774",func="foo",file="recursive2.c",
24203 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
24205 -break-insert -r foo.*
24206 ~int foo(int, int);
24207 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
24208 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
24212 @subheading The @code{-break-list} Command
24213 @findex -break-list
24215 @subsubheading Synopsis
24221 Displays the list of inserted breakpoints, showing the following fields:
24225 number of the breakpoint
24227 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
24229 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
24232 is the breakpoint enabled or no: @samp{y} or @samp{n}
24234 memory location at which the breakpoint is set
24236 logical location of the breakpoint, expressed by function name, file
24239 number of times the breakpoint has been hit
24242 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
24243 @code{body} field is an empty list.
24245 @subsubheading @value{GDBN} Command
24247 The corresponding @value{GDBN} command is @samp{info break}.
24249 @subsubheading Example
24254 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
24255 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24256 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24257 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24258 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24259 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24260 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24261 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24262 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
24263 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
24264 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
24265 line="13",times="0"@}]@}
24269 Here's an example of the result when there are no breakpoints:
24274 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
24275 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24276 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24277 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24278 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24279 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24280 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24285 @subheading The @code{-break-passcount} Command
24286 @findex -break-passcount
24288 @subsubheading Synopsis
24291 -break-passcount @var{tracepoint-number} @var{passcount}
24294 Set the passcount for tracepoint @var{tracepoint-number} to
24295 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
24296 is not a tracepoint, error is emitted. This corresponds to CLI
24297 command @samp{passcount}.
24299 @subheading The @code{-break-watch} Command
24300 @findex -break-watch
24302 @subsubheading Synopsis
24305 -break-watch [ -a | -r ]
24308 Create a watchpoint. With the @samp{-a} option it will create an
24309 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
24310 read from or on a write to the memory location. With the @samp{-r}
24311 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
24312 trigger only when the memory location is accessed for reading. Without
24313 either of the options, the watchpoint created is a regular watchpoint,
24314 i.e., it will trigger when the memory location is accessed for writing.
24315 @xref{Set Watchpoints, , Setting Watchpoints}.
24317 Note that @samp{-break-list} will report a single list of watchpoints and
24318 breakpoints inserted.
24320 @subsubheading @value{GDBN} Command
24322 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
24325 @subsubheading Example
24327 Setting a watchpoint on a variable in the @code{main} function:
24332 ^done,wpt=@{number="2",exp="x"@}
24337 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
24338 value=@{old="-268439212",new="55"@},
24339 frame=@{func="main",args=[],file="recursive2.c",
24340 fullname="/home/foo/bar/recursive2.c",line="5"@}
24344 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
24345 the program execution twice: first for the variable changing value, then
24346 for the watchpoint going out of scope.
24351 ^done,wpt=@{number="5",exp="C"@}
24356 *stopped,reason="watchpoint-trigger",
24357 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
24358 frame=@{func="callee4",args=[],
24359 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24360 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
24365 *stopped,reason="watchpoint-scope",wpnum="5",
24366 frame=@{func="callee3",args=[@{name="strarg",
24367 value="0x11940 \"A string argument.\""@}],
24368 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24369 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
24373 Listing breakpoints and watchpoints, at different points in the program
24374 execution. Note that once the watchpoint goes out of scope, it is
24380 ^done,wpt=@{number="2",exp="C"@}
24383 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
24384 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24385 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24386 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24387 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24388 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24389 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24390 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24391 addr="0x00010734",func="callee4",
24392 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24393 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
24394 bkpt=@{number="2",type="watchpoint",disp="keep",
24395 enabled="y",addr="",what="C",times="0"@}]@}
24400 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
24401 value=@{old="-276895068",new="3"@},
24402 frame=@{func="callee4",args=[],
24403 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24404 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
24407 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
24408 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24409 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24410 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24411 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24412 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24413 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24414 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24415 addr="0x00010734",func="callee4",
24416 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24417 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
24418 bkpt=@{number="2",type="watchpoint",disp="keep",
24419 enabled="y",addr="",what="C",times="-5"@}]@}
24423 ^done,reason="watchpoint-scope",wpnum="2",
24424 frame=@{func="callee3",args=[@{name="strarg",
24425 value="0x11940 \"A string argument.\""@}],
24426 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24427 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
24430 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24431 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24432 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24433 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24434 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24435 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24436 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24437 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24438 addr="0x00010734",func="callee4",
24439 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24440 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
24445 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24446 @node GDB/MI Program Context
24447 @section @sc{gdb/mi} Program Context
24449 @subheading The @code{-exec-arguments} Command
24450 @findex -exec-arguments
24453 @subsubheading Synopsis
24456 -exec-arguments @var{args}
24459 Set the inferior program arguments, to be used in the next
24462 @subsubheading @value{GDBN} Command
24464 The corresponding @value{GDBN} command is @samp{set args}.
24466 @subsubheading Example
24470 -exec-arguments -v word
24477 @subheading The @code{-exec-show-arguments} Command
24478 @findex -exec-show-arguments
24480 @subsubheading Synopsis
24483 -exec-show-arguments
24486 Print the arguments of the program.
24488 @subsubheading @value{GDBN} Command
24490 The corresponding @value{GDBN} command is @samp{show args}.
24492 @subsubheading Example
24497 @subheading The @code{-environment-cd} Command
24498 @findex -environment-cd
24500 @subsubheading Synopsis
24503 -environment-cd @var{pathdir}
24506 Set @value{GDBN}'s working directory.
24508 @subsubheading @value{GDBN} Command
24510 The corresponding @value{GDBN} command is @samp{cd}.
24512 @subsubheading Example
24516 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
24522 @subheading The @code{-environment-directory} Command
24523 @findex -environment-directory
24525 @subsubheading Synopsis
24528 -environment-directory [ -r ] [ @var{pathdir} ]+
24531 Add directories @var{pathdir} to beginning of search path for source files.
24532 If the @samp{-r} option is used, the search path is reset to the default
24533 search path. If directories @var{pathdir} are supplied in addition to the
24534 @samp{-r} option, the search path is first reset and then addition
24536 Multiple directories may be specified, separated by blanks. Specifying
24537 multiple directories in a single command
24538 results in the directories added to the beginning of the
24539 search path in the same order they were presented in the command.
24540 If blanks are needed as
24541 part of a directory name, double-quotes should be used around
24542 the name. In the command output, the path will show up separated
24543 by the system directory-separator character. The directory-separator
24544 character must not be used
24545 in any directory name.
24546 If no directories are specified, the current search path is displayed.
24548 @subsubheading @value{GDBN} Command
24550 The corresponding @value{GDBN} command is @samp{dir}.
24552 @subsubheading Example
24556 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
24557 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
24559 -environment-directory ""
24560 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
24562 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
24563 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
24565 -environment-directory -r
24566 ^done,source-path="$cdir:$cwd"
24571 @subheading The @code{-environment-path} Command
24572 @findex -environment-path
24574 @subsubheading Synopsis
24577 -environment-path [ -r ] [ @var{pathdir} ]+
24580 Add directories @var{pathdir} to beginning of search path for object files.
24581 If the @samp{-r} option is used, the search path is reset to the original
24582 search path that existed at gdb start-up. If directories @var{pathdir} are
24583 supplied in addition to the
24584 @samp{-r} option, the search path is first reset and then addition
24586 Multiple directories may be specified, separated by blanks. Specifying
24587 multiple directories in a single command
24588 results in the directories added to the beginning of the
24589 search path in the same order they were presented in the command.
24590 If blanks are needed as
24591 part of a directory name, double-quotes should be used around
24592 the name. In the command output, the path will show up separated
24593 by the system directory-separator character. The directory-separator
24594 character must not be used
24595 in any directory name.
24596 If no directories are specified, the current path is displayed.
24599 @subsubheading @value{GDBN} Command
24601 The corresponding @value{GDBN} command is @samp{path}.
24603 @subsubheading Example
24608 ^done,path="/usr/bin"
24610 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
24611 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
24613 -environment-path -r /usr/local/bin
24614 ^done,path="/usr/local/bin:/usr/bin"
24619 @subheading The @code{-environment-pwd} Command
24620 @findex -environment-pwd
24622 @subsubheading Synopsis
24628 Show the current working directory.
24630 @subsubheading @value{GDBN} Command
24632 The corresponding @value{GDBN} command is @samp{pwd}.
24634 @subsubheading Example
24639 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
24643 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24644 @node GDB/MI Thread Commands
24645 @section @sc{gdb/mi} Thread Commands
24648 @subheading The @code{-thread-info} Command
24649 @findex -thread-info
24651 @subsubheading Synopsis
24654 -thread-info [ @var{thread-id} ]
24657 Reports information about either a specific thread, if
24658 the @var{thread-id} parameter is present, or about all
24659 threads. When printing information about all threads,
24660 also reports the current thread.
24662 @subsubheading @value{GDBN} Command
24664 The @samp{info thread} command prints the same information
24667 @subsubheading Example
24672 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
24673 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
24674 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
24675 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
24676 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}],
24677 current-thread-id="1"
24681 The @samp{state} field may have the following values:
24685 The thread is stopped. Frame information is available for stopped
24689 The thread is running. There's no frame information for running
24694 @subheading The @code{-thread-list-ids} Command
24695 @findex -thread-list-ids
24697 @subsubheading Synopsis
24703 Produces a list of the currently known @value{GDBN} thread ids. At the
24704 end of the list it also prints the total number of such threads.
24706 This command is retained for historical reasons, the
24707 @code{-thread-info} command should be used instead.
24709 @subsubheading @value{GDBN} Command
24711 Part of @samp{info threads} supplies the same information.
24713 @subsubheading Example
24718 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
24719 current-thread-id="1",number-of-threads="3"
24724 @subheading The @code{-thread-select} Command
24725 @findex -thread-select
24727 @subsubheading Synopsis
24730 -thread-select @var{threadnum}
24733 Make @var{threadnum} the current thread. It prints the number of the new
24734 current thread, and the topmost frame for that thread.
24736 This command is deprecated in favor of explicitly using the
24737 @samp{--thread} option to each command.
24739 @subsubheading @value{GDBN} Command
24741 The corresponding @value{GDBN} command is @samp{thread}.
24743 @subsubheading Example
24750 *stopped,reason="end-stepping-range",thread-id="2",line="187",
24751 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
24755 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
24756 number-of-threads="3"
24759 ^done,new-thread-id="3",
24760 frame=@{level="0",func="vprintf",
24761 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
24762 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
24766 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24767 @node GDB/MI Program Execution
24768 @section @sc{gdb/mi} Program Execution
24770 These are the asynchronous commands which generate the out-of-band
24771 record @samp{*stopped}. Currently @value{GDBN} only really executes
24772 asynchronously with remote targets and this interaction is mimicked in
24775 @subheading The @code{-exec-continue} Command
24776 @findex -exec-continue
24778 @subsubheading Synopsis
24781 -exec-continue [--reverse] [--all|--thread-group N]
24784 Resumes the execution of the inferior program, which will continue
24785 to execute until it reaches a debugger stop event. If the
24786 @samp{--reverse} option is specified, execution resumes in reverse until
24787 it reaches a stop event. Stop events may include
24790 breakpoints or watchpoints
24792 signals or exceptions
24794 the end of the process (or its beginning under @samp{--reverse})
24796 the end or beginning of a replay log if one is being used.
24798 In all-stop mode (@pxref{All-Stop
24799 Mode}), may resume only one thread, or all threads, depending on the
24800 value of the @samp{scheduler-locking} variable. If @samp{--all} is
24801 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
24802 ignored in all-stop mode. If the @samp{--thread-group} options is
24803 specified, then all threads in that thread group are resumed.
24805 @subsubheading @value{GDBN} Command
24807 The corresponding @value{GDBN} corresponding is @samp{continue}.
24809 @subsubheading Example
24816 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
24817 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
24823 @subheading The @code{-exec-finish} Command
24824 @findex -exec-finish
24826 @subsubheading Synopsis
24829 -exec-finish [--reverse]
24832 Resumes the execution of the inferior program until the current
24833 function is exited. Displays the results returned by the function.
24834 If the @samp{--reverse} option is specified, resumes the reverse
24835 execution of the inferior program until the point where current
24836 function was called.
24838 @subsubheading @value{GDBN} Command
24840 The corresponding @value{GDBN} command is @samp{finish}.
24842 @subsubheading Example
24844 Function returning @code{void}.
24851 *stopped,reason="function-finished",frame=@{func="main",args=[],
24852 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
24856 Function returning other than @code{void}. The name of the internal
24857 @value{GDBN} variable storing the result is printed, together with the
24864 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
24865 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
24866 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
24867 gdb-result-var="$1",return-value="0"
24872 @subheading The @code{-exec-interrupt} Command
24873 @findex -exec-interrupt
24875 @subsubheading Synopsis
24878 -exec-interrupt [--all|--thread-group N]
24881 Interrupts the background execution of the target. Note how the token
24882 associated with the stop message is the one for the execution command
24883 that has been interrupted. The token for the interrupt itself only
24884 appears in the @samp{^done} output. If the user is trying to
24885 interrupt a non-running program, an error message will be printed.
24887 Note that when asynchronous execution is enabled, this command is
24888 asynchronous just like other execution commands. That is, first the
24889 @samp{^done} response will be printed, and the target stop will be
24890 reported after that using the @samp{*stopped} notification.
24892 In non-stop mode, only the context thread is interrupted by default.
24893 All threads (in all inferiors) will be interrupted if the
24894 @samp{--all} option is specified. If the @samp{--thread-group}
24895 option is specified, all threads in that group will be interrupted.
24897 @subsubheading @value{GDBN} Command
24899 The corresponding @value{GDBN} command is @samp{interrupt}.
24901 @subsubheading Example
24912 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
24913 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
24914 fullname="/home/foo/bar/try.c",line="13"@}
24919 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
24923 @subheading The @code{-exec-jump} Command
24926 @subsubheading Synopsis
24929 -exec-jump @var{location}
24932 Resumes execution of the inferior program at the location specified by
24933 parameter. @xref{Specify Location}, for a description of the
24934 different forms of @var{location}.
24936 @subsubheading @value{GDBN} Command
24938 The corresponding @value{GDBN} command is @samp{jump}.
24940 @subsubheading Example
24943 -exec-jump foo.c:10
24944 *running,thread-id="all"
24949 @subheading The @code{-exec-next} Command
24952 @subsubheading Synopsis
24955 -exec-next [--reverse]
24958 Resumes execution of the inferior program, stopping when the beginning
24959 of the next source line is reached.
24961 If the @samp{--reverse} option is specified, resumes reverse execution
24962 of the inferior program, stopping at the beginning of the previous
24963 source line. If you issue this command on the first line of a
24964 function, it will take you back to the caller of that function, to the
24965 source line where the function was called.
24968 @subsubheading @value{GDBN} Command
24970 The corresponding @value{GDBN} command is @samp{next}.
24972 @subsubheading Example
24978 *stopped,reason="end-stepping-range",line="8",file="hello.c"
24983 @subheading The @code{-exec-next-instruction} Command
24984 @findex -exec-next-instruction
24986 @subsubheading Synopsis
24989 -exec-next-instruction [--reverse]
24992 Executes one machine instruction. If the instruction is a function
24993 call, continues until the function returns. If the program stops at an
24994 instruction in the middle of a source line, the address will be
24997 If the @samp{--reverse} option is specified, resumes reverse execution
24998 of the inferior program, stopping at the previous instruction. If the
24999 previously executed instruction was a return from another function,
25000 it will continue to execute in reverse until the call to that function
25001 (from the current stack frame) is reached.
25003 @subsubheading @value{GDBN} Command
25005 The corresponding @value{GDBN} command is @samp{nexti}.
25007 @subsubheading Example
25011 -exec-next-instruction
25015 *stopped,reason="end-stepping-range",
25016 addr="0x000100d4",line="5",file="hello.c"
25021 @subheading The @code{-exec-return} Command
25022 @findex -exec-return
25024 @subsubheading Synopsis
25030 Makes current function return immediately. Doesn't execute the inferior.
25031 Displays the new current frame.
25033 @subsubheading @value{GDBN} Command
25035 The corresponding @value{GDBN} command is @samp{return}.
25037 @subsubheading Example
25041 200-break-insert callee4
25042 200^done,bkpt=@{number="1",addr="0x00010734",
25043 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
25048 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
25049 frame=@{func="callee4",args=[],
25050 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25051 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
25057 111^done,frame=@{level="0",func="callee3",
25058 args=[@{name="strarg",
25059 value="0x11940 \"A string argument.\""@}],
25060 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25061 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
25066 @subheading The @code{-exec-run} Command
25069 @subsubheading Synopsis
25072 -exec-run [--all | --thread-group N]
25075 Starts execution of the inferior from the beginning. The inferior
25076 executes until either a breakpoint is encountered or the program
25077 exits. In the latter case the output will include an exit code, if
25078 the program has exited exceptionally.
25080 When no option is specified, the current inferior is started. If the
25081 @samp{--thread-group} option is specified, it should refer to a thread
25082 group of type @samp{process}, and that thread group will be started.
25083 If the @samp{--all} option is specified, then all inferiors will be started.
25085 @subsubheading @value{GDBN} Command
25087 The corresponding @value{GDBN} command is @samp{run}.
25089 @subsubheading Examples
25094 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
25099 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
25100 frame=@{func="main",args=[],file="recursive2.c",
25101 fullname="/home/foo/bar/recursive2.c",line="4"@}
25106 Program exited normally:
25114 *stopped,reason="exited-normally"
25119 Program exited exceptionally:
25127 *stopped,reason="exited",exit-code="01"
25131 Another way the program can terminate is if it receives a signal such as
25132 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
25136 *stopped,reason="exited-signalled",signal-name="SIGINT",
25137 signal-meaning="Interrupt"
25141 @c @subheading -exec-signal
25144 @subheading The @code{-exec-step} Command
25147 @subsubheading Synopsis
25150 -exec-step [--reverse]
25153 Resumes execution of the inferior program, stopping when the beginning
25154 of the next source line is reached, if the next source line is not a
25155 function call. If it is, stop at the first instruction of the called
25156 function. If the @samp{--reverse} option is specified, resumes reverse
25157 execution of the inferior program, stopping at the beginning of the
25158 previously executed source line.
25160 @subsubheading @value{GDBN} Command
25162 The corresponding @value{GDBN} command is @samp{step}.
25164 @subsubheading Example
25166 Stepping into a function:
25172 *stopped,reason="end-stepping-range",
25173 frame=@{func="foo",args=[@{name="a",value="10"@},
25174 @{name="b",value="0"@}],file="recursive2.c",
25175 fullname="/home/foo/bar/recursive2.c",line="11"@}
25185 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
25190 @subheading The @code{-exec-step-instruction} Command
25191 @findex -exec-step-instruction
25193 @subsubheading Synopsis
25196 -exec-step-instruction [--reverse]
25199 Resumes the inferior which executes one machine instruction. If the
25200 @samp{--reverse} option is specified, resumes reverse execution of the
25201 inferior program, stopping at the previously executed instruction.
25202 The output, once @value{GDBN} has stopped, will vary depending on
25203 whether we have stopped in the middle of a source line or not. In the
25204 former case, the address at which the program stopped will be printed
25207 @subsubheading @value{GDBN} Command
25209 The corresponding @value{GDBN} command is @samp{stepi}.
25211 @subsubheading Example
25215 -exec-step-instruction
25219 *stopped,reason="end-stepping-range",
25220 frame=@{func="foo",args=[],file="try.c",
25221 fullname="/home/foo/bar/try.c",line="10"@}
25223 -exec-step-instruction
25227 *stopped,reason="end-stepping-range",
25228 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
25229 fullname="/home/foo/bar/try.c",line="10"@}
25234 @subheading The @code{-exec-until} Command
25235 @findex -exec-until
25237 @subsubheading Synopsis
25240 -exec-until [ @var{location} ]
25243 Executes the inferior until the @var{location} specified in the
25244 argument is reached. If there is no argument, the inferior executes
25245 until a source line greater than the current one is reached. The
25246 reason for stopping in this case will be @samp{location-reached}.
25248 @subsubheading @value{GDBN} Command
25250 The corresponding @value{GDBN} command is @samp{until}.
25252 @subsubheading Example
25256 -exec-until recursive2.c:6
25260 *stopped,reason="location-reached",frame=@{func="main",args=[],
25261 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
25266 @subheading -file-clear
25267 Is this going away????
25270 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25271 @node GDB/MI Stack Manipulation
25272 @section @sc{gdb/mi} Stack Manipulation Commands
25275 @subheading The @code{-stack-info-frame} Command
25276 @findex -stack-info-frame
25278 @subsubheading Synopsis
25284 Get info on the selected frame.
25286 @subsubheading @value{GDBN} Command
25288 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
25289 (without arguments).
25291 @subsubheading Example
25296 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
25297 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25298 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
25302 @subheading The @code{-stack-info-depth} Command
25303 @findex -stack-info-depth
25305 @subsubheading Synopsis
25308 -stack-info-depth [ @var{max-depth} ]
25311 Return the depth of the stack. If the integer argument @var{max-depth}
25312 is specified, do not count beyond @var{max-depth} frames.
25314 @subsubheading @value{GDBN} Command
25316 There's no equivalent @value{GDBN} command.
25318 @subsubheading Example
25320 For a stack with frame levels 0 through 11:
25327 -stack-info-depth 4
25330 -stack-info-depth 12
25333 -stack-info-depth 11
25336 -stack-info-depth 13
25341 @subheading The @code{-stack-list-arguments} Command
25342 @findex -stack-list-arguments
25344 @subsubheading Synopsis
25347 -stack-list-arguments @var{print-values}
25348 [ @var{low-frame} @var{high-frame} ]
25351 Display a list of the arguments for the frames between @var{low-frame}
25352 and @var{high-frame} (inclusive). If @var{low-frame} and
25353 @var{high-frame} are not provided, list the arguments for the whole
25354 call stack. If the two arguments are equal, show the single frame
25355 at the corresponding level. It is an error if @var{low-frame} is
25356 larger than the actual number of frames. On the other hand,
25357 @var{high-frame} may be larger than the actual number of frames, in
25358 which case only existing frames will be returned.
25360 If @var{print-values} is 0 or @code{--no-values}, print only the names of
25361 the variables; if it is 1 or @code{--all-values}, print also their
25362 values; and if it is 2 or @code{--simple-values}, print the name,
25363 type and value for simple data types, and the name and type for arrays,
25364 structures and unions.
25366 Use of this command to obtain arguments in a single frame is
25367 deprecated in favor of the @samp{-stack-list-variables} command.
25369 @subsubheading @value{GDBN} Command
25371 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
25372 @samp{gdb_get_args} command which partially overlaps with the
25373 functionality of @samp{-stack-list-arguments}.
25375 @subsubheading Example
25382 frame=@{level="0",addr="0x00010734",func="callee4",
25383 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25384 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
25385 frame=@{level="1",addr="0x0001076c",func="callee3",
25386 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25387 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
25388 frame=@{level="2",addr="0x0001078c",func="callee2",
25389 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25390 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
25391 frame=@{level="3",addr="0x000107b4",func="callee1",
25392 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25393 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
25394 frame=@{level="4",addr="0x000107e0",func="main",
25395 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25396 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
25398 -stack-list-arguments 0
25401 frame=@{level="0",args=[]@},
25402 frame=@{level="1",args=[name="strarg"]@},
25403 frame=@{level="2",args=[name="intarg",name="strarg"]@},
25404 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
25405 frame=@{level="4",args=[]@}]
25407 -stack-list-arguments 1
25410 frame=@{level="0",args=[]@},
25412 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
25413 frame=@{level="2",args=[
25414 @{name="intarg",value="2"@},
25415 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
25416 @{frame=@{level="3",args=[
25417 @{name="intarg",value="2"@},
25418 @{name="strarg",value="0x11940 \"A string argument.\""@},
25419 @{name="fltarg",value="3.5"@}]@},
25420 frame=@{level="4",args=[]@}]
25422 -stack-list-arguments 0 2 2
25423 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
25425 -stack-list-arguments 1 2 2
25426 ^done,stack-args=[frame=@{level="2",
25427 args=[@{name="intarg",value="2"@},
25428 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
25432 @c @subheading -stack-list-exception-handlers
25435 @subheading The @code{-stack-list-frames} Command
25436 @findex -stack-list-frames
25438 @subsubheading Synopsis
25441 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
25444 List the frames currently on the stack. For each frame it displays the
25449 The frame number, 0 being the topmost frame, i.e., the innermost function.
25451 The @code{$pc} value for that frame.
25455 File name of the source file where the function lives.
25457 Line number corresponding to the @code{$pc}.
25460 If invoked without arguments, this command prints a backtrace for the
25461 whole stack. If given two integer arguments, it shows the frames whose
25462 levels are between the two arguments (inclusive). If the two arguments
25463 are equal, it shows the single frame at the corresponding level. It is
25464 an error if @var{low-frame} is larger than the actual number of
25465 frames. On the other hand, @var{high-frame} may be larger than the
25466 actual number of frames, in which case only existing frames will be returned.
25468 @subsubheading @value{GDBN} Command
25470 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
25472 @subsubheading Example
25474 Full stack backtrace:
25480 [frame=@{level="0",addr="0x0001076c",func="foo",
25481 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
25482 frame=@{level="1",addr="0x000107a4",func="foo",
25483 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25484 frame=@{level="2",addr="0x000107a4",func="foo",
25485 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25486 frame=@{level="3",addr="0x000107a4",func="foo",
25487 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25488 frame=@{level="4",addr="0x000107a4",func="foo",
25489 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25490 frame=@{level="5",addr="0x000107a4",func="foo",
25491 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25492 frame=@{level="6",addr="0x000107a4",func="foo",
25493 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25494 frame=@{level="7",addr="0x000107a4",func="foo",
25495 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25496 frame=@{level="8",addr="0x000107a4",func="foo",
25497 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25498 frame=@{level="9",addr="0x000107a4",func="foo",
25499 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25500 frame=@{level="10",addr="0x000107a4",func="foo",
25501 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25502 frame=@{level="11",addr="0x00010738",func="main",
25503 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
25507 Show frames between @var{low_frame} and @var{high_frame}:
25511 -stack-list-frames 3 5
25513 [frame=@{level="3",addr="0x000107a4",func="foo",
25514 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25515 frame=@{level="4",addr="0x000107a4",func="foo",
25516 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25517 frame=@{level="5",addr="0x000107a4",func="foo",
25518 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
25522 Show a single frame:
25526 -stack-list-frames 3 3
25528 [frame=@{level="3",addr="0x000107a4",func="foo",
25529 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
25534 @subheading The @code{-stack-list-locals} Command
25535 @findex -stack-list-locals
25537 @subsubheading Synopsis
25540 -stack-list-locals @var{print-values}
25543 Display the local variable names for the selected frame. If
25544 @var{print-values} is 0 or @code{--no-values}, print only the names of
25545 the variables; if it is 1 or @code{--all-values}, print also their
25546 values; and if it is 2 or @code{--simple-values}, print the name,
25547 type and value for simple data types, and the name and type for arrays,
25548 structures and unions. In this last case, a frontend can immediately
25549 display the value of simple data types and create variable objects for
25550 other data types when the user wishes to explore their values in
25553 This command is deprecated in favor of the
25554 @samp{-stack-list-variables} command.
25556 @subsubheading @value{GDBN} Command
25558 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
25560 @subsubheading Example
25564 -stack-list-locals 0
25565 ^done,locals=[name="A",name="B",name="C"]
25567 -stack-list-locals --all-values
25568 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
25569 @{name="C",value="@{1, 2, 3@}"@}]
25570 -stack-list-locals --simple-values
25571 ^done,locals=[@{name="A",type="int",value="1"@},
25572 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
25576 @subheading The @code{-stack-list-variables} Command
25577 @findex -stack-list-variables
25579 @subsubheading Synopsis
25582 -stack-list-variables @var{print-values}
25585 Display the names of local variables and function arguments for the selected frame. If
25586 @var{print-values} is 0 or @code{--no-values}, print only the names of
25587 the variables; if it is 1 or @code{--all-values}, print also their
25588 values; and if it is 2 or @code{--simple-values}, print the name,
25589 type and value for simple data types, and the name and type for arrays,
25590 structures and unions.
25592 @subsubheading Example
25596 -stack-list-variables --thread 1 --frame 0 --all-values
25597 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
25602 @subheading The @code{-stack-select-frame} Command
25603 @findex -stack-select-frame
25605 @subsubheading Synopsis
25608 -stack-select-frame @var{framenum}
25611 Change the selected frame. Select a different frame @var{framenum} on
25614 This command in deprecated in favor of passing the @samp{--frame}
25615 option to every command.
25617 @subsubheading @value{GDBN} Command
25619 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
25620 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
25622 @subsubheading Example
25626 -stack-select-frame 2
25631 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25632 @node GDB/MI Variable Objects
25633 @section @sc{gdb/mi} Variable Objects
25637 @subheading Motivation for Variable Objects in @sc{gdb/mi}
25639 For the implementation of a variable debugger window (locals, watched
25640 expressions, etc.), we are proposing the adaptation of the existing code
25641 used by @code{Insight}.
25643 The two main reasons for that are:
25647 It has been proven in practice (it is already on its second generation).
25650 It will shorten development time (needless to say how important it is
25654 The original interface was designed to be used by Tcl code, so it was
25655 slightly changed so it could be used through @sc{gdb/mi}. This section
25656 describes the @sc{gdb/mi} operations that will be available and gives some
25657 hints about their use.
25659 @emph{Note}: In addition to the set of operations described here, we
25660 expect the @sc{gui} implementation of a variable window to require, at
25661 least, the following operations:
25664 @item @code{-gdb-show} @code{output-radix}
25665 @item @code{-stack-list-arguments}
25666 @item @code{-stack-list-locals}
25667 @item @code{-stack-select-frame}
25672 @subheading Introduction to Variable Objects
25674 @cindex variable objects in @sc{gdb/mi}
25676 Variable objects are "object-oriented" MI interface for examining and
25677 changing values of expressions. Unlike some other MI interfaces that
25678 work with expressions, variable objects are specifically designed for
25679 simple and efficient presentation in the frontend. A variable object
25680 is identified by string name. When a variable object is created, the
25681 frontend specifies the expression for that variable object. The
25682 expression can be a simple variable, or it can be an arbitrary complex
25683 expression, and can even involve CPU registers. After creating a
25684 variable object, the frontend can invoke other variable object
25685 operations---for example to obtain or change the value of a variable
25686 object, or to change display format.
25688 Variable objects have hierarchical tree structure. Any variable object
25689 that corresponds to a composite type, such as structure in C, has
25690 a number of child variable objects, for example corresponding to each
25691 element of a structure. A child variable object can itself have
25692 children, recursively. Recursion ends when we reach
25693 leaf variable objects, which always have built-in types. Child variable
25694 objects are created only by explicit request, so if a frontend
25695 is not interested in the children of a particular variable object, no
25696 child will be created.
25698 For a leaf variable object it is possible to obtain its value as a
25699 string, or set the value from a string. String value can be also
25700 obtained for a non-leaf variable object, but it's generally a string
25701 that only indicates the type of the object, and does not list its
25702 contents. Assignment to a non-leaf variable object is not allowed.
25704 A frontend does not need to read the values of all variable objects each time
25705 the program stops. Instead, MI provides an update command that lists all
25706 variable objects whose values has changed since the last update
25707 operation. This considerably reduces the amount of data that must
25708 be transferred to the frontend. As noted above, children variable
25709 objects are created on demand, and only leaf variable objects have a
25710 real value. As result, gdb will read target memory only for leaf
25711 variables that frontend has created.
25713 The automatic update is not always desirable. For example, a frontend
25714 might want to keep a value of some expression for future reference,
25715 and never update it. For another example, fetching memory is
25716 relatively slow for embedded targets, so a frontend might want
25717 to disable automatic update for the variables that are either not
25718 visible on the screen, or ``closed''. This is possible using so
25719 called ``frozen variable objects''. Such variable objects are never
25720 implicitly updated.
25722 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
25723 fixed variable object, the expression is parsed when the variable
25724 object is created, including associating identifiers to specific
25725 variables. The meaning of expression never changes. For a floating
25726 variable object the values of variables whose names appear in the
25727 expressions are re-evaluated every time in the context of the current
25728 frame. Consider this example:
25733 struct work_state state;
25740 If a fixed variable object for the @code{state} variable is created in
25741 this function, and we enter the recursive call, the the variable
25742 object will report the value of @code{state} in the top-level
25743 @code{do_work} invocation. On the other hand, a floating variable
25744 object will report the value of @code{state} in the current frame.
25746 If an expression specified when creating a fixed variable object
25747 refers to a local variable, the variable object becomes bound to the
25748 thread and frame in which the variable object is created. When such
25749 variable object is updated, @value{GDBN} makes sure that the
25750 thread/frame combination the variable object is bound to still exists,
25751 and re-evaluates the variable object in context of that thread/frame.
25753 The following is the complete set of @sc{gdb/mi} operations defined to
25754 access this functionality:
25756 @multitable @columnfractions .4 .6
25757 @item @strong{Operation}
25758 @tab @strong{Description}
25760 @item @code{-enable-pretty-printing}
25761 @tab enable Python-based pretty-printing
25762 @item @code{-var-create}
25763 @tab create a variable object
25764 @item @code{-var-delete}
25765 @tab delete the variable object and/or its children
25766 @item @code{-var-set-format}
25767 @tab set the display format of this variable
25768 @item @code{-var-show-format}
25769 @tab show the display format of this variable
25770 @item @code{-var-info-num-children}
25771 @tab tells how many children this object has
25772 @item @code{-var-list-children}
25773 @tab return a list of the object's children
25774 @item @code{-var-info-type}
25775 @tab show the type of this variable object
25776 @item @code{-var-info-expression}
25777 @tab print parent-relative expression that this variable object represents
25778 @item @code{-var-info-path-expression}
25779 @tab print full expression that this variable object represents
25780 @item @code{-var-show-attributes}
25781 @tab is this variable editable? does it exist here?
25782 @item @code{-var-evaluate-expression}
25783 @tab get the value of this variable
25784 @item @code{-var-assign}
25785 @tab set the value of this variable
25786 @item @code{-var-update}
25787 @tab update the variable and its children
25788 @item @code{-var-set-frozen}
25789 @tab set frozeness attribute
25790 @item @code{-var-set-update-range}
25791 @tab set range of children to display on update
25794 In the next subsection we describe each operation in detail and suggest
25795 how it can be used.
25797 @subheading Description And Use of Operations on Variable Objects
25799 @subheading The @code{-enable-pretty-printing} Command
25800 @findex -enable-pretty-printing
25803 -enable-pretty-printing
25806 @value{GDBN} allows Python-based visualizers to affect the output of the
25807 MI variable object commands. However, because there was no way to
25808 implement this in a fully backward-compatible way, a front end must
25809 request that this functionality be enabled.
25811 Once enabled, this feature cannot be disabled.
25813 Note that if Python support has not been compiled into @value{GDBN},
25814 this command will still succeed (and do nothing).
25816 This feature is currently (as of @value{GDBN} 7.0) experimental, and
25817 may work differently in future versions of @value{GDBN}.
25819 @subheading The @code{-var-create} Command
25820 @findex -var-create
25822 @subsubheading Synopsis
25825 -var-create @{@var{name} | "-"@}
25826 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
25829 This operation creates a variable object, which allows the monitoring of
25830 a variable, the result of an expression, a memory cell or a CPU
25833 The @var{name} parameter is the string by which the object can be
25834 referenced. It must be unique. If @samp{-} is specified, the varobj
25835 system will generate a string ``varNNNNNN'' automatically. It will be
25836 unique provided that one does not specify @var{name} of that format.
25837 The command fails if a duplicate name is found.
25839 The frame under which the expression should be evaluated can be
25840 specified by @var{frame-addr}. A @samp{*} indicates that the current
25841 frame should be used. A @samp{@@} indicates that a floating variable
25842 object must be created.
25844 @var{expression} is any expression valid on the current language set (must not
25845 begin with a @samp{*}), or one of the following:
25849 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
25852 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
25855 @samp{$@var{regname}} --- a CPU register name
25858 @cindex dynamic varobj
25859 A varobj's contents may be provided by a Python-based pretty-printer. In this
25860 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
25861 have slightly different semantics in some cases. If the
25862 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
25863 will never create a dynamic varobj. This ensures backward
25864 compatibility for existing clients.
25866 @subsubheading Result
25868 This operation returns attributes of the newly-created varobj. These
25873 The name of the varobj.
25876 The number of children of the varobj. This number is not necessarily
25877 reliable for a dynamic varobj. Instead, you must examine the
25878 @samp{has_more} attribute.
25881 The varobj's scalar value. For a varobj whose type is some sort of
25882 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
25883 will not be interesting.
25886 The varobj's type. This is a string representation of the type, as
25887 would be printed by the @value{GDBN} CLI.
25890 If a variable object is bound to a specific thread, then this is the
25891 thread's identifier.
25894 For a dynamic varobj, this indicates whether there appear to be any
25895 children available. For a non-dynamic varobj, this will be 0.
25898 This attribute will be present and have the value @samp{1} if the
25899 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
25900 then this attribute will not be present.
25903 A dynamic varobj can supply a display hint to the front end. The
25904 value comes directly from the Python pretty-printer object's
25905 @code{display_hint} method. @xref{Pretty Printing API}.
25908 Typical output will look like this:
25911 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
25912 has_more="@var{has_more}"
25916 @subheading The @code{-var-delete} Command
25917 @findex -var-delete
25919 @subsubheading Synopsis
25922 -var-delete [ -c ] @var{name}
25925 Deletes a previously created variable object and all of its children.
25926 With the @samp{-c} option, just deletes the children.
25928 Returns an error if the object @var{name} is not found.
25931 @subheading The @code{-var-set-format} Command
25932 @findex -var-set-format
25934 @subsubheading Synopsis
25937 -var-set-format @var{name} @var{format-spec}
25940 Sets the output format for the value of the object @var{name} to be
25943 @anchor{-var-set-format}
25944 The syntax for the @var{format-spec} is as follows:
25947 @var{format-spec} @expansion{}
25948 @{binary | decimal | hexadecimal | octal | natural@}
25951 The natural format is the default format choosen automatically
25952 based on the variable type (like decimal for an @code{int}, hex
25953 for pointers, etc.).
25955 For a variable with children, the format is set only on the
25956 variable itself, and the children are not affected.
25958 @subheading The @code{-var-show-format} Command
25959 @findex -var-show-format
25961 @subsubheading Synopsis
25964 -var-show-format @var{name}
25967 Returns the format used to display the value of the object @var{name}.
25970 @var{format} @expansion{}
25975 @subheading The @code{-var-info-num-children} Command
25976 @findex -var-info-num-children
25978 @subsubheading Synopsis
25981 -var-info-num-children @var{name}
25984 Returns the number of children of a variable object @var{name}:
25990 Note that this number is not completely reliable for a dynamic varobj.
25991 It will return the current number of children, but more children may
25995 @subheading The @code{-var-list-children} Command
25996 @findex -var-list-children
25998 @subsubheading Synopsis
26001 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
26003 @anchor{-var-list-children}
26005 Return a list of the children of the specified variable object and
26006 create variable objects for them, if they do not already exist. With
26007 a single argument or if @var{print-values} has a value for of 0 or
26008 @code{--no-values}, print only the names of the variables; if
26009 @var{print-values} is 1 or @code{--all-values}, also print their
26010 values; and if it is 2 or @code{--simple-values} print the name and
26011 value for simple data types and just the name for arrays, structures
26014 @var{from} and @var{to}, if specified, indicate the range of children
26015 to report. If @var{from} or @var{to} is less than zero, the range is
26016 reset and all children will be reported. Otherwise, children starting
26017 at @var{from} (zero-based) and up to and excluding @var{to} will be
26020 If a child range is requested, it will only affect the current call to
26021 @code{-var-list-children}, but not future calls to @code{-var-update}.
26022 For this, you must instead use @code{-var-set-update-range}. The
26023 intent of this approach is to enable a front end to implement any
26024 update approach it likes; for example, scrolling a view may cause the
26025 front end to request more children with @code{-var-list-children}, and
26026 then the front end could call @code{-var-set-update-range} with a
26027 different range to ensure that future updates are restricted to just
26030 For each child the following results are returned:
26035 Name of the variable object created for this child.
26038 The expression to be shown to the user by the front end to designate this child.
26039 For example this may be the name of a structure member.
26041 For a dynamic varobj, this value cannot be used to form an
26042 expression. There is no way to do this at all with a dynamic varobj.
26044 For C/C@t{++} structures there are several pseudo children returned to
26045 designate access qualifiers. For these pseudo children @var{exp} is
26046 @samp{public}, @samp{private}, or @samp{protected}. In this case the
26047 type and value are not present.
26049 A dynamic varobj will not report the access qualifying
26050 pseudo-children, regardless of the language. This information is not
26051 available at all with a dynamic varobj.
26054 Number of children this child has. For a dynamic varobj, this will be
26058 The type of the child.
26061 If values were requested, this is the value.
26064 If this variable object is associated with a thread, this is the thread id.
26065 Otherwise this result is not present.
26068 If the variable object is frozen, this variable will be present with a value of 1.
26071 The result may have its own attributes:
26075 A dynamic varobj can supply a display hint to the front end. The
26076 value comes directly from the Python pretty-printer object's
26077 @code{display_hint} method. @xref{Pretty Printing API}.
26080 This is an integer attribute which is nonzero if there are children
26081 remaining after the end of the selected range.
26084 @subsubheading Example
26088 -var-list-children n
26089 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
26090 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
26092 -var-list-children --all-values n
26093 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
26094 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
26098 @subheading The @code{-var-info-type} Command
26099 @findex -var-info-type
26101 @subsubheading Synopsis
26104 -var-info-type @var{name}
26107 Returns the type of the specified variable @var{name}. The type is
26108 returned as a string in the same format as it is output by the
26112 type=@var{typename}
26116 @subheading The @code{-var-info-expression} Command
26117 @findex -var-info-expression
26119 @subsubheading Synopsis
26122 -var-info-expression @var{name}
26125 Returns a string that is suitable for presenting this
26126 variable object in user interface. The string is generally
26127 not valid expression in the current language, and cannot be evaluated.
26129 For example, if @code{a} is an array, and variable object
26130 @code{A} was created for @code{a}, then we'll get this output:
26133 (gdb) -var-info-expression A.1
26134 ^done,lang="C",exp="1"
26138 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
26140 Note that the output of the @code{-var-list-children} command also
26141 includes those expressions, so the @code{-var-info-expression} command
26144 @subheading The @code{-var-info-path-expression} Command
26145 @findex -var-info-path-expression
26147 @subsubheading Synopsis
26150 -var-info-path-expression @var{name}
26153 Returns an expression that can be evaluated in the current
26154 context and will yield the same value that a variable object has.
26155 Compare this with the @code{-var-info-expression} command, which
26156 result can be used only for UI presentation. Typical use of
26157 the @code{-var-info-path-expression} command is creating a
26158 watchpoint from a variable object.
26160 This command is currently not valid for children of a dynamic varobj,
26161 and will give an error when invoked on one.
26163 For example, suppose @code{C} is a C@t{++} class, derived from class
26164 @code{Base}, and that the @code{Base} class has a member called
26165 @code{m_size}. Assume a variable @code{c} is has the type of
26166 @code{C} and a variable object @code{C} was created for variable
26167 @code{c}. Then, we'll get this output:
26169 (gdb) -var-info-path-expression C.Base.public.m_size
26170 ^done,path_expr=((Base)c).m_size)
26173 @subheading The @code{-var-show-attributes} Command
26174 @findex -var-show-attributes
26176 @subsubheading Synopsis
26179 -var-show-attributes @var{name}
26182 List attributes of the specified variable object @var{name}:
26185 status=@var{attr} [ ( ,@var{attr} )* ]
26189 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
26191 @subheading The @code{-var-evaluate-expression} Command
26192 @findex -var-evaluate-expression
26194 @subsubheading Synopsis
26197 -var-evaluate-expression [-f @var{format-spec}] @var{name}
26200 Evaluates the expression that is represented by the specified variable
26201 object and returns its value as a string. The format of the string
26202 can be specified with the @samp{-f} option. The possible values of
26203 this option are the same as for @code{-var-set-format}
26204 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
26205 the current display format will be used. The current display format
26206 can be changed using the @code{-var-set-format} command.
26212 Note that one must invoke @code{-var-list-children} for a variable
26213 before the value of a child variable can be evaluated.
26215 @subheading The @code{-var-assign} Command
26216 @findex -var-assign
26218 @subsubheading Synopsis
26221 -var-assign @var{name} @var{expression}
26224 Assigns the value of @var{expression} to the variable object specified
26225 by @var{name}. The object must be @samp{editable}. If the variable's
26226 value is altered by the assign, the variable will show up in any
26227 subsequent @code{-var-update} list.
26229 @subsubheading Example
26237 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
26241 @subheading The @code{-var-update} Command
26242 @findex -var-update
26244 @subsubheading Synopsis
26247 -var-update [@var{print-values}] @{@var{name} | "*"@}
26250 Reevaluate the expressions corresponding to the variable object
26251 @var{name} and all its direct and indirect children, and return the
26252 list of variable objects whose values have changed; @var{name} must
26253 be a root variable object. Here, ``changed'' means that the result of
26254 @code{-var-evaluate-expression} before and after the
26255 @code{-var-update} is different. If @samp{*} is used as the variable
26256 object names, all existing variable objects are updated, except
26257 for frozen ones (@pxref{-var-set-frozen}). The option
26258 @var{print-values} determines whether both names and values, or just
26259 names are printed. The possible values of this option are the same
26260 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
26261 recommended to use the @samp{--all-values} option, to reduce the
26262 number of MI commands needed on each program stop.
26264 With the @samp{*} parameter, if a variable object is bound to a
26265 currently running thread, it will not be updated, without any
26268 If @code{-var-set-update-range} was previously used on a varobj, then
26269 only the selected range of children will be reported.
26271 @code{-var-update} reports all the changed varobjs in a tuple named
26274 Each item in the change list is itself a tuple holding:
26278 The name of the varobj.
26281 If values were requested for this update, then this field will be
26282 present and will hold the value of the varobj.
26285 @anchor{-var-update}
26286 This field is a string which may take one of three values:
26290 The variable object's current value is valid.
26293 The variable object does not currently hold a valid value but it may
26294 hold one in the future if its associated expression comes back into
26298 The variable object no longer holds a valid value.
26299 This can occur when the executable file being debugged has changed,
26300 either through recompilation or by using the @value{GDBN} @code{file}
26301 command. The front end should normally choose to delete these variable
26305 In the future new values may be added to this list so the front should
26306 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
26309 This is only present if the varobj is still valid. If the type
26310 changed, then this will be the string @samp{true}; otherwise it will
26314 If the varobj's type changed, then this field will be present and will
26317 @item new_num_children
26318 For a dynamic varobj, if the number of children changed, or if the
26319 type changed, this will be the new number of children.
26321 The @samp{numchild} field in other varobj responses is generally not
26322 valid for a dynamic varobj -- it will show the number of children that
26323 @value{GDBN} knows about, but because dynamic varobjs lazily
26324 instantiate their children, this will not reflect the number of
26325 children which may be available.
26327 The @samp{new_num_children} attribute only reports changes to the
26328 number of children known by @value{GDBN}. This is the only way to
26329 detect whether an update has removed children (which necessarily can
26330 only happen at the end of the update range).
26333 The display hint, if any.
26336 This is an integer value, which will be 1 if there are more children
26337 available outside the varobj's update range.
26340 This attribute will be present and have the value @samp{1} if the
26341 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
26342 then this attribute will not be present.
26345 If new children were added to a dynamic varobj within the selected
26346 update range (as set by @code{-var-set-update-range}), then they will
26347 be listed in this attribute.
26350 @subsubheading Example
26357 -var-update --all-values var1
26358 ^done,changelist=[@{name="var1",value="3",in_scope="true",
26359 type_changed="false"@}]
26363 @subheading The @code{-var-set-frozen} Command
26364 @findex -var-set-frozen
26365 @anchor{-var-set-frozen}
26367 @subsubheading Synopsis
26370 -var-set-frozen @var{name} @var{flag}
26373 Set the frozenness flag on the variable object @var{name}. The
26374 @var{flag} parameter should be either @samp{1} to make the variable
26375 frozen or @samp{0} to make it unfrozen. If a variable object is
26376 frozen, then neither itself, nor any of its children, are
26377 implicitly updated by @code{-var-update} of
26378 a parent variable or by @code{-var-update *}. Only
26379 @code{-var-update} of the variable itself will update its value and
26380 values of its children. After a variable object is unfrozen, it is
26381 implicitly updated by all subsequent @code{-var-update} operations.
26382 Unfreezing a variable does not update it, only subsequent
26383 @code{-var-update} does.
26385 @subsubheading Example
26389 -var-set-frozen V 1
26394 @subheading The @code{-var-set-update-range} command
26395 @findex -var-set-update-range
26396 @anchor{-var-set-update-range}
26398 @subsubheading Synopsis
26401 -var-set-update-range @var{name} @var{from} @var{to}
26404 Set the range of children to be returned by future invocations of
26405 @code{-var-update}.
26407 @var{from} and @var{to} indicate the range of children to report. If
26408 @var{from} or @var{to} is less than zero, the range is reset and all
26409 children will be reported. Otherwise, children starting at @var{from}
26410 (zero-based) and up to and excluding @var{to} will be reported.
26412 @subsubheading Example
26416 -var-set-update-range V 1 2
26420 @subheading The @code{-var-set-visualizer} command
26421 @findex -var-set-visualizer
26422 @anchor{-var-set-visualizer}
26424 @subsubheading Synopsis
26427 -var-set-visualizer @var{name} @var{visualizer}
26430 Set a visualizer for the variable object @var{name}.
26432 @var{visualizer} is the visualizer to use. The special value
26433 @samp{None} means to disable any visualizer in use.
26435 If not @samp{None}, @var{visualizer} must be a Python expression.
26436 This expression must evaluate to a callable object which accepts a
26437 single argument. @value{GDBN} will call this object with the value of
26438 the varobj @var{name} as an argument (this is done so that the same
26439 Python pretty-printing code can be used for both the CLI and MI).
26440 When called, this object must return an object which conforms to the
26441 pretty-printing interface (@pxref{Pretty Printing API}).
26443 The pre-defined function @code{gdb.default_visualizer} may be used to
26444 select a visualizer by following the built-in process
26445 (@pxref{Selecting Pretty-Printers}). This is done automatically when
26446 a varobj is created, and so ordinarily is not needed.
26448 This feature is only available if Python support is enabled. The MI
26449 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
26450 can be used to check this.
26452 @subsubheading Example
26454 Resetting the visualizer:
26458 -var-set-visualizer V None
26462 Reselecting the default (type-based) visualizer:
26466 -var-set-visualizer V gdb.default_visualizer
26470 Suppose @code{SomeClass} is a visualizer class. A lambda expression
26471 can be used to instantiate this class for a varobj:
26475 -var-set-visualizer V "lambda val: SomeClass()"
26479 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26480 @node GDB/MI Data Manipulation
26481 @section @sc{gdb/mi} Data Manipulation
26483 @cindex data manipulation, in @sc{gdb/mi}
26484 @cindex @sc{gdb/mi}, data manipulation
26485 This section describes the @sc{gdb/mi} commands that manipulate data:
26486 examine memory and registers, evaluate expressions, etc.
26488 @c REMOVED FROM THE INTERFACE.
26489 @c @subheading -data-assign
26490 @c Change the value of a program variable. Plenty of side effects.
26491 @c @subsubheading GDB Command
26493 @c @subsubheading Example
26496 @subheading The @code{-data-disassemble} Command
26497 @findex -data-disassemble
26499 @subsubheading Synopsis
26503 [ -s @var{start-addr} -e @var{end-addr} ]
26504 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
26512 @item @var{start-addr}
26513 is the beginning address (or @code{$pc})
26514 @item @var{end-addr}
26516 @item @var{filename}
26517 is the name of the file to disassemble
26518 @item @var{linenum}
26519 is the line number to disassemble around
26521 is the number of disassembly lines to be produced. If it is -1,
26522 the whole function will be disassembled, in case no @var{end-addr} is
26523 specified. If @var{end-addr} is specified as a non-zero value, and
26524 @var{lines} is lower than the number of disassembly lines between
26525 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
26526 displayed; if @var{lines} is higher than the number of lines between
26527 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
26530 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
26534 @subsubheading Result
26536 The output for each instruction is composed of four fields:
26545 Note that whatever included in the instruction field, is not manipulated
26546 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
26548 @subsubheading @value{GDBN} Command
26550 There's no direct mapping from this command to the CLI.
26552 @subsubheading Example
26554 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
26558 -data-disassemble -s $pc -e "$pc + 20" -- 0
26561 @{address="0x000107c0",func-name="main",offset="4",
26562 inst="mov 2, %o0"@},
26563 @{address="0x000107c4",func-name="main",offset="8",
26564 inst="sethi %hi(0x11800), %o2"@},
26565 @{address="0x000107c8",func-name="main",offset="12",
26566 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
26567 @{address="0x000107cc",func-name="main",offset="16",
26568 inst="sethi %hi(0x11800), %o2"@},
26569 @{address="0x000107d0",func-name="main",offset="20",
26570 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
26574 Disassemble the whole @code{main} function. Line 32 is part of
26578 -data-disassemble -f basics.c -l 32 -- 0
26580 @{address="0x000107bc",func-name="main",offset="0",
26581 inst="save %sp, -112, %sp"@},
26582 @{address="0x000107c0",func-name="main",offset="4",
26583 inst="mov 2, %o0"@},
26584 @{address="0x000107c4",func-name="main",offset="8",
26585 inst="sethi %hi(0x11800), %o2"@},
26587 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
26588 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
26592 Disassemble 3 instructions from the start of @code{main}:
26596 -data-disassemble -f basics.c -l 32 -n 3 -- 0
26598 @{address="0x000107bc",func-name="main",offset="0",
26599 inst="save %sp, -112, %sp"@},
26600 @{address="0x000107c0",func-name="main",offset="4",
26601 inst="mov 2, %o0"@},
26602 @{address="0x000107c4",func-name="main",offset="8",
26603 inst="sethi %hi(0x11800), %o2"@}]
26607 Disassemble 3 instructions from the start of @code{main} in mixed mode:
26611 -data-disassemble -f basics.c -l 32 -n 3 -- 1
26613 src_and_asm_line=@{line="31",
26614 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
26615 testsuite/gdb.mi/basics.c",line_asm_insn=[
26616 @{address="0x000107bc",func-name="main",offset="0",
26617 inst="save %sp, -112, %sp"@}]@},
26618 src_and_asm_line=@{line="32",
26619 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
26620 testsuite/gdb.mi/basics.c",line_asm_insn=[
26621 @{address="0x000107c0",func-name="main",offset="4",
26622 inst="mov 2, %o0"@},
26623 @{address="0x000107c4",func-name="main",offset="8",
26624 inst="sethi %hi(0x11800), %o2"@}]@}]
26629 @subheading The @code{-data-evaluate-expression} Command
26630 @findex -data-evaluate-expression
26632 @subsubheading Synopsis
26635 -data-evaluate-expression @var{expr}
26638 Evaluate @var{expr} as an expression. The expression could contain an
26639 inferior function call. The function call will execute synchronously.
26640 If the expression contains spaces, it must be enclosed in double quotes.
26642 @subsubheading @value{GDBN} Command
26644 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
26645 @samp{call}. In @code{gdbtk} only, there's a corresponding
26646 @samp{gdb_eval} command.
26648 @subsubheading Example
26650 In the following example, the numbers that precede the commands are the
26651 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
26652 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
26656 211-data-evaluate-expression A
26659 311-data-evaluate-expression &A
26660 311^done,value="0xefffeb7c"
26662 411-data-evaluate-expression A+3
26665 511-data-evaluate-expression "A + 3"
26671 @subheading The @code{-data-list-changed-registers} Command
26672 @findex -data-list-changed-registers
26674 @subsubheading Synopsis
26677 -data-list-changed-registers
26680 Display a list of the registers that have changed.
26682 @subsubheading @value{GDBN} Command
26684 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
26685 has the corresponding command @samp{gdb_changed_register_list}.
26687 @subsubheading Example
26689 On a PPC MBX board:
26697 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
26698 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
26701 -data-list-changed-registers
26702 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
26703 "10","11","13","14","15","16","17","18","19","20","21","22","23",
26704 "24","25","26","27","28","30","31","64","65","66","67","69"]
26709 @subheading The @code{-data-list-register-names} Command
26710 @findex -data-list-register-names
26712 @subsubheading Synopsis
26715 -data-list-register-names [ ( @var{regno} )+ ]
26718 Show a list of register names for the current target. If no arguments
26719 are given, it shows a list of the names of all the registers. If
26720 integer numbers are given as arguments, it will print a list of the
26721 names of the registers corresponding to the arguments. To ensure
26722 consistency between a register name and its number, the output list may
26723 include empty register names.
26725 @subsubheading @value{GDBN} Command
26727 @value{GDBN} does not have a command which corresponds to
26728 @samp{-data-list-register-names}. In @code{gdbtk} there is a
26729 corresponding command @samp{gdb_regnames}.
26731 @subsubheading Example
26733 For the PPC MBX board:
26736 -data-list-register-names
26737 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
26738 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
26739 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
26740 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
26741 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
26742 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
26743 "", "pc","ps","cr","lr","ctr","xer"]
26745 -data-list-register-names 1 2 3
26746 ^done,register-names=["r1","r2","r3"]
26750 @subheading The @code{-data-list-register-values} Command
26751 @findex -data-list-register-values
26753 @subsubheading Synopsis
26756 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
26759 Display the registers' contents. @var{fmt} is the format according to
26760 which the registers' contents are to be returned, followed by an optional
26761 list of numbers specifying the registers to display. A missing list of
26762 numbers indicates that the contents of all the registers must be returned.
26764 Allowed formats for @var{fmt} are:
26781 @subsubheading @value{GDBN} Command
26783 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
26784 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
26786 @subsubheading Example
26788 For a PPC MBX board (note: line breaks are for readability only, they
26789 don't appear in the actual output):
26793 -data-list-register-values r 64 65
26794 ^done,register-values=[@{number="64",value="0xfe00a300"@},
26795 @{number="65",value="0x00029002"@}]
26797 -data-list-register-values x
26798 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
26799 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
26800 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
26801 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
26802 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
26803 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
26804 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
26805 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
26806 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
26807 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
26808 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
26809 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
26810 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
26811 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
26812 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
26813 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
26814 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
26815 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
26816 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
26817 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
26818 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
26819 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
26820 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
26821 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
26822 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
26823 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
26824 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
26825 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
26826 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
26827 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
26828 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
26829 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
26830 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
26831 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
26832 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
26833 @{number="69",value="0x20002b03"@}]
26838 @subheading The @code{-data-read-memory} Command
26839 @findex -data-read-memory
26841 @subsubheading Synopsis
26844 -data-read-memory [ -o @var{byte-offset} ]
26845 @var{address} @var{word-format} @var{word-size}
26846 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
26853 @item @var{address}
26854 An expression specifying the address of the first memory word to be
26855 read. Complex expressions containing embedded white space should be
26856 quoted using the C convention.
26858 @item @var{word-format}
26859 The format to be used to print the memory words. The notation is the
26860 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
26863 @item @var{word-size}
26864 The size of each memory word in bytes.
26866 @item @var{nr-rows}
26867 The number of rows in the output table.
26869 @item @var{nr-cols}
26870 The number of columns in the output table.
26873 If present, indicates that each row should include an @sc{ascii} dump. The
26874 value of @var{aschar} is used as a padding character when a byte is not a
26875 member of the printable @sc{ascii} character set (printable @sc{ascii}
26876 characters are those whose code is between 32 and 126, inclusively).
26878 @item @var{byte-offset}
26879 An offset to add to the @var{address} before fetching memory.
26882 This command displays memory contents as a table of @var{nr-rows} by
26883 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
26884 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
26885 (returned as @samp{total-bytes}). Should less than the requested number
26886 of bytes be returned by the target, the missing words are identified
26887 using @samp{N/A}. The number of bytes read from the target is returned
26888 in @samp{nr-bytes} and the starting address used to read memory in
26891 The address of the next/previous row or page is available in
26892 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
26895 @subsubheading @value{GDBN} Command
26897 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
26898 @samp{gdb_get_mem} memory read command.
26900 @subsubheading Example
26902 Read six bytes of memory starting at @code{bytes+6} but then offset by
26903 @code{-6} bytes. Format as three rows of two columns. One byte per
26904 word. Display each word in hex.
26908 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
26909 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
26910 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
26911 prev-page="0x0000138a",memory=[
26912 @{addr="0x00001390",data=["0x00","0x01"]@},
26913 @{addr="0x00001392",data=["0x02","0x03"]@},
26914 @{addr="0x00001394",data=["0x04","0x05"]@}]
26918 Read two bytes of memory starting at address @code{shorts + 64} and
26919 display as a single word formatted in decimal.
26923 5-data-read-memory shorts+64 d 2 1 1
26924 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
26925 next-row="0x00001512",prev-row="0x0000150e",
26926 next-page="0x00001512",prev-page="0x0000150e",memory=[
26927 @{addr="0x00001510",data=["128"]@}]
26931 Read thirty two bytes of memory starting at @code{bytes+16} and format
26932 as eight rows of four columns. Include a string encoding with @samp{x}
26933 used as the non-printable character.
26937 4-data-read-memory bytes+16 x 1 8 4 x
26938 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
26939 next-row="0x000013c0",prev-row="0x0000139c",
26940 next-page="0x000013c0",prev-page="0x00001380",memory=[
26941 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
26942 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
26943 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
26944 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
26945 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
26946 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
26947 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
26948 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
26952 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26953 @node GDB/MI Tracepoint Commands
26954 @section @sc{gdb/mi} Tracepoint Commands
26956 The commands defined in this section implement MI support for
26957 tracepoints. For detailed introduction, see @ref{Tracepoints}.
26959 @subheading The @code{-trace-find} Command
26960 @findex -trace-find
26962 @subsubheading Synopsis
26965 -trace-find @var{mode} [@var{parameters}@dots{}]
26968 Find a trace frame using criteria defined by @var{mode} and
26969 @var{parameters}. The following table lists permissible
26970 modes and their parameters. For details of operation, see @ref{tfind}.
26975 No parameters are required. Stops examining trace frames.
26978 An integer is required as parameter. Selects tracepoint frame with
26981 @item tracepoint-number
26982 An integer is required as parameter. Finds next
26983 trace frame that corresponds to tracepoint with the specified number.
26986 An address is required as parameter. Finds
26987 next trace frame that corresponds to any tracepoint at the specified
26990 @item pc-inside-range
26991 Two addresses are required as parameters. Finds next trace
26992 frame that corresponds to a tracepoint at an address inside the
26993 specified range. Both bounds are considered to be inside the range.
26995 @item pc-outside-range
26996 Two addresses are required as parameters. Finds
26997 next trace frame that corresponds to a tracepoint at an address outside
26998 the specified range. Both bounds are considered to be inside the range.
27001 Line specification is required as parameter. @xref{Specify Location}.
27002 Finds next trace frame that corresponds to a tracepoint at
27003 the specified location.
27007 If @samp{none} was passed as @var{mode}, the response does not
27008 have fields. Otherwise, the response may have the following fields:
27012 This field has either @samp{0} or @samp{1} as the value, depending
27013 on whether a matching tracepoint was found.
27016 The index of the found traceframe. This field is present iff
27017 the @samp{found} field has value of @samp{1}.
27020 The index of the found tracepoint. This field is present iff
27021 the @samp{found} field has value of @samp{1}.
27024 The information about the frame corresponding to the found trace
27025 frame. This field is present only if a trace frame was found.
27026 @xref{GDB/MI Frame Information}, for description of this field.
27030 @subsubheading @value{GDBN} Command
27032 The corresponding @value{GDBN} command is @samp{tfind}.
27034 @subheading -trace-define-variable
27035 @findex -trace-define-variable
27037 @subsubheading Synopsis
27040 -trace-define-variable @var{name} [ @var{value} ]
27043 Create trace variable @var{name} if it does not exist. If
27044 @var{value} is specified, sets the initial value of the specified
27045 trace variable to that value. Note that the @var{name} should start
27046 with the @samp{$} character.
27048 @subsubheading @value{GDBN} Command
27050 The corresponding @value{GDBN} command is @samp{tvariable}.
27052 @subheading -trace-list-variables
27053 @findex -trace-list-variables
27055 @subsubheading Synopsis
27058 -trace-list-variables
27061 Return a table of all defined trace variables. Each element of the
27062 table has the following fields:
27066 The name of the trace variable. This field is always present.
27069 The initial value. This is a 64-bit signed integer. This
27070 field is always present.
27073 The value the trace variable has at the moment. This is a 64-bit
27074 signed integer. This field is absent iff current value is
27075 not defined, for example if the trace was never run, or is
27080 @subsubheading @value{GDBN} Command
27082 The corresponding @value{GDBN} command is @samp{tvariables}.
27084 @subsubheading Example
27088 -trace-list-variables
27089 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
27090 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
27091 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
27092 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
27093 body=[variable=@{name="$trace_timestamp",initial="0"@}
27094 variable=@{name="$foo",initial="10",current="15"@}]@}
27098 @subheading -trace-save
27099 @findex -trace-save
27101 @subsubheading Synopsis
27104 -trace-save [-r ] @var{filename}
27107 Saves the collected trace data to @var{filename}. Without the
27108 @samp{-r} option, the data is downloaded from the target and saved
27109 in a local file. With the @samp{-r} option the target is asked
27110 to perform the save.
27112 @subsubheading @value{GDBN} Command
27114 The corresponding @value{GDBN} command is @samp{tsave}.
27117 @subheading -trace-start
27118 @findex -trace-start
27120 @subsubheading Synopsis
27126 Starts a tracing experiments. The result of this command does not
27129 @subsubheading @value{GDBN} Command
27131 The corresponding @value{GDBN} command is @samp{tstart}.
27133 @subheading -trace-status
27134 @findex -trace-status
27136 @subsubheading Synopsis
27142 Obtains the status of a tracing experiment. The result may include
27143 the following fields:
27148 May have a value of either @samp{0}, when no tracing operations are
27149 supported, @samp{1}, when all tracing operations are supported, or
27150 @samp{file} when examining trace file. In the latter case, examining
27151 of trace frame is possible but new tracing experiement cannot be
27152 started. This field is always present.
27155 May have a value of either @samp{0} or @samp{1} depending on whether
27156 tracing experiement is in progress on target. This field is present
27157 if @samp{supported} field is not @samp{0}.
27160 Report the reason why the tracing was stopped last time. This field
27161 may be absent iff tracing was never stopped on target yet. The
27162 value of @samp{request} means the tracing was stopped as result of
27163 the @code{-trace-stop} command. The value of @samp{overflow} means
27164 the tracing buffer is full. The value of @samp{disconnection} means
27165 tracing was automatically stopped when @value{GDBN} has disconnected.
27166 The value of @samp{passcount} means tracing was stopped when a
27167 tracepoint was passed a maximal number of times for that tracepoint.
27168 This field is present if @samp{supported} field is not @samp{0}.
27170 @item stopping-tracepoint
27171 The number of tracepoint whose passcount as exceeded. This field is
27172 present iff the @samp{stop-reason} field has the value of
27176 @itemx frames-created
27177 The @samp{frames} field is a count of the total number of trace frames
27178 in the trace buffer, while @samp{frames-created} is the total created
27179 during the run, including ones that were discarded, such as when a
27180 circular trace buffer filled up. Both fields are optional.
27184 These fields tell the current size of the tracing buffer and the
27185 remaining space. These fields are optional.
27188 The value of the circular trace buffer flag. @code{1} means that the
27189 trace buffer is circular and old trace frames will be discarded if
27190 necessary to make room, @code{0} means that the trace buffer is linear
27194 The value of the disconnected tracing flag. @code{1} means that
27195 tracing will continue after @value{GDBN} disconnects, @code{0} means
27196 that the trace run will stop.
27200 @subsubheading @value{GDBN} Command
27202 The corresponding @value{GDBN} command is @samp{tstatus}.
27204 @subheading -trace-stop
27205 @findex -trace-stop
27207 @subsubheading Synopsis
27213 Stops a tracing experiment. The result of this command has the same
27214 fields as @code{-trace-status}, except that the @samp{supported} and
27215 @samp{running} fields are not output.
27217 @subsubheading @value{GDBN} Command
27219 The corresponding @value{GDBN} command is @samp{tstop}.
27222 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27223 @node GDB/MI Symbol Query
27224 @section @sc{gdb/mi} Symbol Query Commands
27228 @subheading The @code{-symbol-info-address} Command
27229 @findex -symbol-info-address
27231 @subsubheading Synopsis
27234 -symbol-info-address @var{symbol}
27237 Describe where @var{symbol} is stored.
27239 @subsubheading @value{GDBN} Command
27241 The corresponding @value{GDBN} command is @samp{info address}.
27243 @subsubheading Example
27247 @subheading The @code{-symbol-info-file} Command
27248 @findex -symbol-info-file
27250 @subsubheading Synopsis
27256 Show the file for the symbol.
27258 @subsubheading @value{GDBN} Command
27260 There's no equivalent @value{GDBN} command. @code{gdbtk} has
27261 @samp{gdb_find_file}.
27263 @subsubheading Example
27267 @subheading The @code{-symbol-info-function} Command
27268 @findex -symbol-info-function
27270 @subsubheading Synopsis
27273 -symbol-info-function
27276 Show which function the symbol lives in.
27278 @subsubheading @value{GDBN} Command
27280 @samp{gdb_get_function} in @code{gdbtk}.
27282 @subsubheading Example
27286 @subheading The @code{-symbol-info-line} Command
27287 @findex -symbol-info-line
27289 @subsubheading Synopsis
27295 Show the core addresses of the code for a source line.
27297 @subsubheading @value{GDBN} Command
27299 The corresponding @value{GDBN} command is @samp{info line}.
27300 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
27302 @subsubheading Example
27306 @subheading The @code{-symbol-info-symbol} Command
27307 @findex -symbol-info-symbol
27309 @subsubheading Synopsis
27312 -symbol-info-symbol @var{addr}
27315 Describe what symbol is at location @var{addr}.
27317 @subsubheading @value{GDBN} Command
27319 The corresponding @value{GDBN} command is @samp{info symbol}.
27321 @subsubheading Example
27325 @subheading The @code{-symbol-list-functions} Command
27326 @findex -symbol-list-functions
27328 @subsubheading Synopsis
27331 -symbol-list-functions
27334 List the functions in the executable.
27336 @subsubheading @value{GDBN} Command
27338 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
27339 @samp{gdb_search} in @code{gdbtk}.
27341 @subsubheading Example
27346 @subheading The @code{-symbol-list-lines} Command
27347 @findex -symbol-list-lines
27349 @subsubheading Synopsis
27352 -symbol-list-lines @var{filename}
27355 Print the list of lines that contain code and their associated program
27356 addresses for the given source filename. The entries are sorted in
27357 ascending PC order.
27359 @subsubheading @value{GDBN} Command
27361 There is no corresponding @value{GDBN} command.
27363 @subsubheading Example
27366 -symbol-list-lines basics.c
27367 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
27373 @subheading The @code{-symbol-list-types} Command
27374 @findex -symbol-list-types
27376 @subsubheading Synopsis
27382 List all the type names.
27384 @subsubheading @value{GDBN} Command
27386 The corresponding commands are @samp{info types} in @value{GDBN},
27387 @samp{gdb_search} in @code{gdbtk}.
27389 @subsubheading Example
27393 @subheading The @code{-symbol-list-variables} Command
27394 @findex -symbol-list-variables
27396 @subsubheading Synopsis
27399 -symbol-list-variables
27402 List all the global and static variable names.
27404 @subsubheading @value{GDBN} Command
27406 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
27408 @subsubheading Example
27412 @subheading The @code{-symbol-locate} Command
27413 @findex -symbol-locate
27415 @subsubheading Synopsis
27421 @subsubheading @value{GDBN} Command
27423 @samp{gdb_loc} in @code{gdbtk}.
27425 @subsubheading Example
27429 @subheading The @code{-symbol-type} Command
27430 @findex -symbol-type
27432 @subsubheading Synopsis
27435 -symbol-type @var{variable}
27438 Show type of @var{variable}.
27440 @subsubheading @value{GDBN} Command
27442 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
27443 @samp{gdb_obj_variable}.
27445 @subsubheading Example
27450 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27451 @node GDB/MI File Commands
27452 @section @sc{gdb/mi} File Commands
27454 This section describes the GDB/MI commands to specify executable file names
27455 and to read in and obtain symbol table information.
27457 @subheading The @code{-file-exec-and-symbols} Command
27458 @findex -file-exec-and-symbols
27460 @subsubheading Synopsis
27463 -file-exec-and-symbols @var{file}
27466 Specify the executable file to be debugged. This file is the one from
27467 which the symbol table is also read. If no file is specified, the
27468 command clears the executable and symbol information. If breakpoints
27469 are set when using this command with no arguments, @value{GDBN} will produce
27470 error messages. Otherwise, no output is produced, except a completion
27473 @subsubheading @value{GDBN} Command
27475 The corresponding @value{GDBN} command is @samp{file}.
27477 @subsubheading Example
27481 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
27487 @subheading The @code{-file-exec-file} Command
27488 @findex -file-exec-file
27490 @subsubheading Synopsis
27493 -file-exec-file @var{file}
27496 Specify the executable file to be debugged. Unlike
27497 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
27498 from this file. If used without argument, @value{GDBN} clears the information
27499 about the executable file. No output is produced, except a completion
27502 @subsubheading @value{GDBN} Command
27504 The corresponding @value{GDBN} command is @samp{exec-file}.
27506 @subsubheading Example
27510 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
27517 @subheading The @code{-file-list-exec-sections} Command
27518 @findex -file-list-exec-sections
27520 @subsubheading Synopsis
27523 -file-list-exec-sections
27526 List the sections of the current executable file.
27528 @subsubheading @value{GDBN} Command
27530 The @value{GDBN} command @samp{info file} shows, among the rest, the same
27531 information as this command. @code{gdbtk} has a corresponding command
27532 @samp{gdb_load_info}.
27534 @subsubheading Example
27539 @subheading The @code{-file-list-exec-source-file} Command
27540 @findex -file-list-exec-source-file
27542 @subsubheading Synopsis
27545 -file-list-exec-source-file
27548 List the line number, the current source file, and the absolute path
27549 to the current source file for the current executable. The macro
27550 information field has a value of @samp{1} or @samp{0} depending on
27551 whether or not the file includes preprocessor macro information.
27553 @subsubheading @value{GDBN} Command
27555 The @value{GDBN} equivalent is @samp{info source}
27557 @subsubheading Example
27561 123-file-list-exec-source-file
27562 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
27567 @subheading The @code{-file-list-exec-source-files} Command
27568 @findex -file-list-exec-source-files
27570 @subsubheading Synopsis
27573 -file-list-exec-source-files
27576 List the source files for the current executable.
27578 It will always output the filename, but only when @value{GDBN} can find
27579 the absolute file name of a source file, will it output the fullname.
27581 @subsubheading @value{GDBN} Command
27583 The @value{GDBN} equivalent is @samp{info sources}.
27584 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
27586 @subsubheading Example
27589 -file-list-exec-source-files
27591 @{file=foo.c,fullname=/home/foo.c@},
27592 @{file=/home/bar.c,fullname=/home/bar.c@},
27593 @{file=gdb_could_not_find_fullpath.c@}]
27598 @subheading The @code{-file-list-shared-libraries} Command
27599 @findex -file-list-shared-libraries
27601 @subsubheading Synopsis
27604 -file-list-shared-libraries
27607 List the shared libraries in the program.
27609 @subsubheading @value{GDBN} Command
27611 The corresponding @value{GDBN} command is @samp{info shared}.
27613 @subsubheading Example
27617 @subheading The @code{-file-list-symbol-files} Command
27618 @findex -file-list-symbol-files
27620 @subsubheading Synopsis
27623 -file-list-symbol-files
27628 @subsubheading @value{GDBN} Command
27630 The corresponding @value{GDBN} command is @samp{info file} (part of it).
27632 @subsubheading Example
27637 @subheading The @code{-file-symbol-file} Command
27638 @findex -file-symbol-file
27640 @subsubheading Synopsis
27643 -file-symbol-file @var{file}
27646 Read symbol table info from the specified @var{file} argument. When
27647 used without arguments, clears @value{GDBN}'s symbol table info. No output is
27648 produced, except for a completion notification.
27650 @subsubheading @value{GDBN} Command
27652 The corresponding @value{GDBN} command is @samp{symbol-file}.
27654 @subsubheading Example
27658 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
27664 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27665 @node GDB/MI Memory Overlay Commands
27666 @section @sc{gdb/mi} Memory Overlay Commands
27668 The memory overlay commands are not implemented.
27670 @c @subheading -overlay-auto
27672 @c @subheading -overlay-list-mapping-state
27674 @c @subheading -overlay-list-overlays
27676 @c @subheading -overlay-map
27678 @c @subheading -overlay-off
27680 @c @subheading -overlay-on
27682 @c @subheading -overlay-unmap
27684 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27685 @node GDB/MI Signal Handling Commands
27686 @section @sc{gdb/mi} Signal Handling Commands
27688 Signal handling commands are not implemented.
27690 @c @subheading -signal-handle
27692 @c @subheading -signal-list-handle-actions
27694 @c @subheading -signal-list-signal-types
27698 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27699 @node GDB/MI Target Manipulation
27700 @section @sc{gdb/mi} Target Manipulation Commands
27703 @subheading The @code{-target-attach} Command
27704 @findex -target-attach
27706 @subsubheading Synopsis
27709 -target-attach @var{pid} | @var{gid} | @var{file}
27712 Attach to a process @var{pid} or a file @var{file} outside of
27713 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
27714 group, the id previously returned by
27715 @samp{-list-thread-groups --available} must be used.
27717 @subsubheading @value{GDBN} Command
27719 The corresponding @value{GDBN} command is @samp{attach}.
27721 @subsubheading Example
27725 =thread-created,id="1"
27726 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
27732 @subheading The @code{-target-compare-sections} Command
27733 @findex -target-compare-sections
27735 @subsubheading Synopsis
27738 -target-compare-sections [ @var{section} ]
27741 Compare data of section @var{section} on target to the exec file.
27742 Without the argument, all sections are compared.
27744 @subsubheading @value{GDBN} Command
27746 The @value{GDBN} equivalent is @samp{compare-sections}.
27748 @subsubheading Example
27753 @subheading The @code{-target-detach} Command
27754 @findex -target-detach
27756 @subsubheading Synopsis
27759 -target-detach [ @var{pid} | @var{gid} ]
27762 Detach from the remote target which normally resumes its execution.
27763 If either @var{pid} or @var{gid} is specified, detaches from either
27764 the specified process, or specified thread group. There's no output.
27766 @subsubheading @value{GDBN} Command
27768 The corresponding @value{GDBN} command is @samp{detach}.
27770 @subsubheading Example
27780 @subheading The @code{-target-disconnect} Command
27781 @findex -target-disconnect
27783 @subsubheading Synopsis
27789 Disconnect from the remote target. There's no output and the target is
27790 generally not resumed.
27792 @subsubheading @value{GDBN} Command
27794 The corresponding @value{GDBN} command is @samp{disconnect}.
27796 @subsubheading Example
27806 @subheading The @code{-target-download} Command
27807 @findex -target-download
27809 @subsubheading Synopsis
27815 Loads the executable onto the remote target.
27816 It prints out an update message every half second, which includes the fields:
27820 The name of the section.
27822 The size of what has been sent so far for that section.
27824 The size of the section.
27826 The total size of what was sent so far (the current and the previous sections).
27828 The size of the overall executable to download.
27832 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
27833 @sc{gdb/mi} Output Syntax}).
27835 In addition, it prints the name and size of the sections, as they are
27836 downloaded. These messages include the following fields:
27840 The name of the section.
27842 The size of the section.
27844 The size of the overall executable to download.
27848 At the end, a summary is printed.
27850 @subsubheading @value{GDBN} Command
27852 The corresponding @value{GDBN} command is @samp{load}.
27854 @subsubheading Example
27856 Note: each status message appears on a single line. Here the messages
27857 have been broken down so that they can fit onto a page.
27862 +download,@{section=".text",section-size="6668",total-size="9880"@}
27863 +download,@{section=".text",section-sent="512",section-size="6668",
27864 total-sent="512",total-size="9880"@}
27865 +download,@{section=".text",section-sent="1024",section-size="6668",
27866 total-sent="1024",total-size="9880"@}
27867 +download,@{section=".text",section-sent="1536",section-size="6668",
27868 total-sent="1536",total-size="9880"@}
27869 +download,@{section=".text",section-sent="2048",section-size="6668",
27870 total-sent="2048",total-size="9880"@}
27871 +download,@{section=".text",section-sent="2560",section-size="6668",
27872 total-sent="2560",total-size="9880"@}
27873 +download,@{section=".text",section-sent="3072",section-size="6668",
27874 total-sent="3072",total-size="9880"@}
27875 +download,@{section=".text",section-sent="3584",section-size="6668",
27876 total-sent="3584",total-size="9880"@}
27877 +download,@{section=".text",section-sent="4096",section-size="6668",
27878 total-sent="4096",total-size="9880"@}
27879 +download,@{section=".text",section-sent="4608",section-size="6668",
27880 total-sent="4608",total-size="9880"@}
27881 +download,@{section=".text",section-sent="5120",section-size="6668",
27882 total-sent="5120",total-size="9880"@}
27883 +download,@{section=".text",section-sent="5632",section-size="6668",
27884 total-sent="5632",total-size="9880"@}
27885 +download,@{section=".text",section-sent="6144",section-size="6668",
27886 total-sent="6144",total-size="9880"@}
27887 +download,@{section=".text",section-sent="6656",section-size="6668",
27888 total-sent="6656",total-size="9880"@}
27889 +download,@{section=".init",section-size="28",total-size="9880"@}
27890 +download,@{section=".fini",section-size="28",total-size="9880"@}
27891 +download,@{section=".data",section-size="3156",total-size="9880"@}
27892 +download,@{section=".data",section-sent="512",section-size="3156",
27893 total-sent="7236",total-size="9880"@}
27894 +download,@{section=".data",section-sent="1024",section-size="3156",
27895 total-sent="7748",total-size="9880"@}
27896 +download,@{section=".data",section-sent="1536",section-size="3156",
27897 total-sent="8260",total-size="9880"@}
27898 +download,@{section=".data",section-sent="2048",section-size="3156",
27899 total-sent="8772",total-size="9880"@}
27900 +download,@{section=".data",section-sent="2560",section-size="3156",
27901 total-sent="9284",total-size="9880"@}
27902 +download,@{section=".data",section-sent="3072",section-size="3156",
27903 total-sent="9796",total-size="9880"@}
27904 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
27911 @subheading The @code{-target-exec-status} Command
27912 @findex -target-exec-status
27914 @subsubheading Synopsis
27917 -target-exec-status
27920 Provide information on the state of the target (whether it is running or
27921 not, for instance).
27923 @subsubheading @value{GDBN} Command
27925 There's no equivalent @value{GDBN} command.
27927 @subsubheading Example
27931 @subheading The @code{-target-list-available-targets} Command
27932 @findex -target-list-available-targets
27934 @subsubheading Synopsis
27937 -target-list-available-targets
27940 List the possible targets to connect to.
27942 @subsubheading @value{GDBN} Command
27944 The corresponding @value{GDBN} command is @samp{help target}.
27946 @subsubheading Example
27950 @subheading The @code{-target-list-current-targets} Command
27951 @findex -target-list-current-targets
27953 @subsubheading Synopsis
27956 -target-list-current-targets
27959 Describe the current target.
27961 @subsubheading @value{GDBN} Command
27963 The corresponding information is printed by @samp{info file} (among
27966 @subsubheading Example
27970 @subheading The @code{-target-list-parameters} Command
27971 @findex -target-list-parameters
27973 @subsubheading Synopsis
27976 -target-list-parameters
27982 @subsubheading @value{GDBN} Command
27986 @subsubheading Example
27990 @subheading The @code{-target-select} Command
27991 @findex -target-select
27993 @subsubheading Synopsis
27996 -target-select @var{type} @var{parameters @dots{}}
27999 Connect @value{GDBN} to the remote target. This command takes two args:
28003 The type of target, for instance @samp{remote}, etc.
28004 @item @var{parameters}
28005 Device names, host names and the like. @xref{Target Commands, ,
28006 Commands for Managing Targets}, for more details.
28009 The output is a connection notification, followed by the address at
28010 which the target program is, in the following form:
28013 ^connected,addr="@var{address}",func="@var{function name}",
28014 args=[@var{arg list}]
28017 @subsubheading @value{GDBN} Command
28019 The corresponding @value{GDBN} command is @samp{target}.
28021 @subsubheading Example
28025 -target-select remote /dev/ttya
28026 ^connected,addr="0xfe00a300",func="??",args=[]
28030 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28031 @node GDB/MI File Transfer Commands
28032 @section @sc{gdb/mi} File Transfer Commands
28035 @subheading The @code{-target-file-put} Command
28036 @findex -target-file-put
28038 @subsubheading Synopsis
28041 -target-file-put @var{hostfile} @var{targetfile}
28044 Copy file @var{hostfile} from the host system (the machine running
28045 @value{GDBN}) to @var{targetfile} on the target system.
28047 @subsubheading @value{GDBN} Command
28049 The corresponding @value{GDBN} command is @samp{remote put}.
28051 @subsubheading Example
28055 -target-file-put localfile remotefile
28061 @subheading The @code{-target-file-get} Command
28062 @findex -target-file-get
28064 @subsubheading Synopsis
28067 -target-file-get @var{targetfile} @var{hostfile}
28070 Copy file @var{targetfile} from the target system to @var{hostfile}
28071 on the host system.
28073 @subsubheading @value{GDBN} Command
28075 The corresponding @value{GDBN} command is @samp{remote get}.
28077 @subsubheading Example
28081 -target-file-get remotefile localfile
28087 @subheading The @code{-target-file-delete} Command
28088 @findex -target-file-delete
28090 @subsubheading Synopsis
28093 -target-file-delete @var{targetfile}
28096 Delete @var{targetfile} from the target system.
28098 @subsubheading @value{GDBN} Command
28100 The corresponding @value{GDBN} command is @samp{remote delete}.
28102 @subsubheading Example
28106 -target-file-delete remotefile
28112 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28113 @node GDB/MI Miscellaneous Commands
28114 @section Miscellaneous @sc{gdb/mi} Commands
28116 @c @subheading -gdb-complete
28118 @subheading The @code{-gdb-exit} Command
28121 @subsubheading Synopsis
28127 Exit @value{GDBN} immediately.
28129 @subsubheading @value{GDBN} Command
28131 Approximately corresponds to @samp{quit}.
28133 @subsubheading Example
28143 @subheading The @code{-exec-abort} Command
28144 @findex -exec-abort
28146 @subsubheading Synopsis
28152 Kill the inferior running program.
28154 @subsubheading @value{GDBN} Command
28156 The corresponding @value{GDBN} command is @samp{kill}.
28158 @subsubheading Example
28163 @subheading The @code{-gdb-set} Command
28166 @subsubheading Synopsis
28172 Set an internal @value{GDBN} variable.
28173 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
28175 @subsubheading @value{GDBN} Command
28177 The corresponding @value{GDBN} command is @samp{set}.
28179 @subsubheading Example
28189 @subheading The @code{-gdb-show} Command
28192 @subsubheading Synopsis
28198 Show the current value of a @value{GDBN} variable.
28200 @subsubheading @value{GDBN} Command
28202 The corresponding @value{GDBN} command is @samp{show}.
28204 @subsubheading Example
28213 @c @subheading -gdb-source
28216 @subheading The @code{-gdb-version} Command
28217 @findex -gdb-version
28219 @subsubheading Synopsis
28225 Show version information for @value{GDBN}. Used mostly in testing.
28227 @subsubheading @value{GDBN} Command
28229 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
28230 default shows this information when you start an interactive session.
28232 @subsubheading Example
28234 @c This example modifies the actual output from GDB to avoid overfull
28240 ~Copyright 2000 Free Software Foundation, Inc.
28241 ~GDB is free software, covered by the GNU General Public License, and
28242 ~you are welcome to change it and/or distribute copies of it under
28243 ~ certain conditions.
28244 ~Type "show copying" to see the conditions.
28245 ~There is absolutely no warranty for GDB. Type "show warranty" for
28247 ~This GDB was configured as
28248 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
28253 @subheading The @code{-list-features} Command
28254 @findex -list-features
28256 Returns a list of particular features of the MI protocol that
28257 this version of gdb implements. A feature can be a command,
28258 or a new field in an output of some command, or even an
28259 important bugfix. While a frontend can sometimes detect presence
28260 of a feature at runtime, it is easier to perform detection at debugger
28263 The command returns a list of strings, with each string naming an
28264 available feature. Each returned string is just a name, it does not
28265 have any internal structure. The list of possible feature names
28271 (gdb) -list-features
28272 ^done,result=["feature1","feature2"]
28275 The current list of features is:
28278 @item frozen-varobjs
28279 Indicates presence of the @code{-var-set-frozen} command, as well
28280 as possible presense of the @code{frozen} field in the output
28281 of @code{-varobj-create}.
28282 @item pending-breakpoints
28283 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
28285 Indicates presence of Python scripting support, Python-based
28286 pretty-printing commands, and possible presence of the
28287 @samp{display_hint} field in the output of @code{-var-list-children}
28289 Indicates presence of the @code{-thread-info} command.
28293 @subheading The @code{-list-target-features} Command
28294 @findex -list-target-features
28296 Returns a list of particular features that are supported by the
28297 target. Those features affect the permitted MI commands, but
28298 unlike the features reported by the @code{-list-features} command, the
28299 features depend on which target GDB is using at the moment. Whenever
28300 a target can change, due to commands such as @code{-target-select},
28301 @code{-target-attach} or @code{-exec-run}, the list of target features
28302 may change, and the frontend should obtain it again.
28306 (gdb) -list-features
28307 ^done,result=["async"]
28310 The current list of features is:
28314 Indicates that the target is capable of asynchronous command
28315 execution, which means that @value{GDBN} will accept further commands
28316 while the target is running.
28320 @subheading The @code{-list-thread-groups} Command
28321 @findex -list-thread-groups
28323 @subheading Synopsis
28326 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
28329 Lists thread groups (@pxref{Thread groups}). When a single thread
28330 group is passed as the argument, lists the children of that group.
28331 When several thread group are passed, lists information about those
28332 thread groups. Without any parameters, lists information about all
28333 top-level thread groups.
28335 Normally, thread groups that are being debugged are reported.
28336 With the @samp{--available} option, @value{GDBN} reports thread groups
28337 available on the target.
28339 The output of this command may have either a @samp{threads} result or
28340 a @samp{groups} result. The @samp{thread} result has a list of tuples
28341 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
28342 Information}). The @samp{groups} result has a list of tuples as value,
28343 each tuple describing a thread group. If top-level groups are
28344 requested (that is, no parameter is passed), or when several groups
28345 are passed, the output always has a @samp{groups} result. The format
28346 of the @samp{group} result is described below.
28348 To reduce the number of roundtrips it's possible to list thread groups
28349 together with their children, by passing the @samp{--recurse} option
28350 and the recursion depth. Presently, only recursion depth of 1 is
28351 permitted. If this option is present, then every reported thread group
28352 will also include its children, either as @samp{group} or
28353 @samp{threads} field.
28355 In general, any combination of option and parameters is permitted, with
28356 the following caveats:
28360 When a single thread group is passed, the output will typically
28361 be the @samp{threads} result. Because threads may not contain
28362 anything, the @samp{recurse} option will be ignored.
28365 When the @samp{--available} option is passed, limited information may
28366 be available. In particular, the list of threads of a process might
28367 be inaccessible. Further, specifying specific thread groups might
28368 not give any performance advantage over listing all thread groups.
28369 The frontend should assume that @samp{-list-thread-groups --available}
28370 is always an expensive operation and cache the results.
28374 The @samp{groups} result is a list of tuples, where each tuple may
28375 have the following fields:
28379 Identifier of the thread group. This field is always present.
28380 The identifier is an opaque string; frontends should not try to
28381 convert it to an integer, even though it might look like one.
28384 The type of the thread group. At present, only @samp{process} is a
28388 The target-specific process identifier. This field is only present
28389 for thread groups of type @samp{process} and only if the process exists.
28392 The number of children this thread group has. This field may be
28393 absent for an available thread group.
28396 This field has a list of tuples as value, each tuple describing a
28397 thread. It may be present if the @samp{--recurse} option is
28398 specified, and it's actually possible to obtain the threads.
28401 This field is a list of integers, each identifying a core that one
28402 thread of the group is running on. This field may be absent if
28403 such information is not available.
28406 The name of the executable file that corresponds to this thread group.
28407 The field is only present for thread groups of type @samp{process},
28408 and only if there is a corresponding executable file.
28412 @subheading Example
28416 -list-thread-groups
28417 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
28418 -list-thread-groups 17
28419 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
28420 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
28421 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
28422 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
28423 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
28424 -list-thread-groups --available
28425 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
28426 -list-thread-groups --available --recurse 1
28427 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
28428 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
28429 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
28430 -list-thread-groups --available --recurse 1 17 18
28431 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
28432 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
28433 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
28437 @subheading The @code{-add-inferior} Command
28438 @findex -add-inferior
28440 @subheading Synopsis
28446 Creates a new inferior (@pxref{Inferiors and Programs}). The created
28447 inferior is not associated with any executable. Such association may
28448 be established with the @samp{-file-exec-and-symbols} command
28449 (@pxref{GDB/MI File Commands}). The command response has a single
28450 field, @samp{thread-group}, whose value is the identifier of the
28451 thread group corresponding to the new inferior.
28453 @subheading Example
28458 ^done,thread-group="i3"
28461 @subheading The @code{-interpreter-exec} Command
28462 @findex -interpreter-exec
28464 @subheading Synopsis
28467 -interpreter-exec @var{interpreter} @var{command}
28469 @anchor{-interpreter-exec}
28471 Execute the specified @var{command} in the given @var{interpreter}.
28473 @subheading @value{GDBN} Command
28475 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
28477 @subheading Example
28481 -interpreter-exec console "break main"
28482 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
28483 &"During symbol reading, bad structure-type format.\n"
28484 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
28489 @subheading The @code{-inferior-tty-set} Command
28490 @findex -inferior-tty-set
28492 @subheading Synopsis
28495 -inferior-tty-set /dev/pts/1
28498 Set terminal for future runs of the program being debugged.
28500 @subheading @value{GDBN} Command
28502 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
28504 @subheading Example
28508 -inferior-tty-set /dev/pts/1
28513 @subheading The @code{-inferior-tty-show} Command
28514 @findex -inferior-tty-show
28516 @subheading Synopsis
28522 Show terminal for future runs of program being debugged.
28524 @subheading @value{GDBN} Command
28526 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
28528 @subheading Example
28532 -inferior-tty-set /dev/pts/1
28536 ^done,inferior_tty_terminal="/dev/pts/1"
28540 @subheading The @code{-enable-timings} Command
28541 @findex -enable-timings
28543 @subheading Synopsis
28546 -enable-timings [yes | no]
28549 Toggle the printing of the wallclock, user and system times for an MI
28550 command as a field in its output. This command is to help frontend
28551 developers optimize the performance of their code. No argument is
28552 equivalent to @samp{yes}.
28554 @subheading @value{GDBN} Command
28558 @subheading Example
28566 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28567 addr="0x080484ed",func="main",file="myprog.c",
28568 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
28569 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
28577 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
28578 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
28579 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
28580 fullname="/home/nickrob/myprog.c",line="73"@}
28585 @chapter @value{GDBN} Annotations
28587 This chapter describes annotations in @value{GDBN}. Annotations were
28588 designed to interface @value{GDBN} to graphical user interfaces or other
28589 similar programs which want to interact with @value{GDBN} at a
28590 relatively high level.
28592 The annotation mechanism has largely been superseded by @sc{gdb/mi}
28596 This is Edition @value{EDITION}, @value{DATE}.
28600 * Annotations Overview:: What annotations are; the general syntax.
28601 * Server Prefix:: Issuing a command without affecting user state.
28602 * Prompting:: Annotations marking @value{GDBN}'s need for input.
28603 * Errors:: Annotations for error messages.
28604 * Invalidation:: Some annotations describe things now invalid.
28605 * Annotations for Running::
28606 Whether the program is running, how it stopped, etc.
28607 * Source Annotations:: Annotations describing source code.
28610 @node Annotations Overview
28611 @section What is an Annotation?
28612 @cindex annotations
28614 Annotations start with a newline character, two @samp{control-z}
28615 characters, and the name of the annotation. If there is no additional
28616 information associated with this annotation, the name of the annotation
28617 is followed immediately by a newline. If there is additional
28618 information, the name of the annotation is followed by a space, the
28619 additional information, and a newline. The additional information
28620 cannot contain newline characters.
28622 Any output not beginning with a newline and two @samp{control-z}
28623 characters denotes literal output from @value{GDBN}. Currently there is
28624 no need for @value{GDBN} to output a newline followed by two
28625 @samp{control-z} characters, but if there was such a need, the
28626 annotations could be extended with an @samp{escape} annotation which
28627 means those three characters as output.
28629 The annotation @var{level}, which is specified using the
28630 @option{--annotate} command line option (@pxref{Mode Options}), controls
28631 how much information @value{GDBN} prints together with its prompt,
28632 values of expressions, source lines, and other types of output. Level 0
28633 is for no annotations, level 1 is for use when @value{GDBN} is run as a
28634 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
28635 for programs that control @value{GDBN}, and level 2 annotations have
28636 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
28637 Interface, annotate, GDB's Obsolete Annotations}).
28640 @kindex set annotate
28641 @item set annotate @var{level}
28642 The @value{GDBN} command @code{set annotate} sets the level of
28643 annotations to the specified @var{level}.
28645 @item show annotate
28646 @kindex show annotate
28647 Show the current annotation level.
28650 This chapter describes level 3 annotations.
28652 A simple example of starting up @value{GDBN} with annotations is:
28655 $ @kbd{gdb --annotate=3}
28657 Copyright 2003 Free Software Foundation, Inc.
28658 GDB is free software, covered by the GNU General Public License,
28659 and you are welcome to change it and/or distribute copies of it
28660 under certain conditions.
28661 Type "show copying" to see the conditions.
28662 There is absolutely no warranty for GDB. Type "show warranty"
28664 This GDB was configured as "i386-pc-linux-gnu"
28675 Here @samp{quit} is input to @value{GDBN}; the rest is output from
28676 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
28677 denotes a @samp{control-z} character) are annotations; the rest is
28678 output from @value{GDBN}.
28680 @node Server Prefix
28681 @section The Server Prefix
28682 @cindex server prefix
28684 If you prefix a command with @samp{server } then it will not affect
28685 the command history, nor will it affect @value{GDBN}'s notion of which
28686 command to repeat if @key{RET} is pressed on a line by itself. This
28687 means that commands can be run behind a user's back by a front-end in
28688 a transparent manner.
28690 The @code{server } prefix does not affect the recording of values into
28691 the value history; to print a value without recording it into the
28692 value history, use the @code{output} command instead of the
28693 @code{print} command.
28695 Using this prefix also disables confirmation requests
28696 (@pxref{confirmation requests}).
28699 @section Annotation for @value{GDBN} Input
28701 @cindex annotations for prompts
28702 When @value{GDBN} prompts for input, it annotates this fact so it is possible
28703 to know when to send output, when the output from a given command is
28706 Different kinds of input each have a different @dfn{input type}. Each
28707 input type has three annotations: a @code{pre-} annotation, which
28708 denotes the beginning of any prompt which is being output, a plain
28709 annotation, which denotes the end of the prompt, and then a @code{post-}
28710 annotation which denotes the end of any echo which may (or may not) be
28711 associated with the input. For example, the @code{prompt} input type
28712 features the following annotations:
28720 The input types are
28723 @findex pre-prompt annotation
28724 @findex prompt annotation
28725 @findex post-prompt annotation
28727 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
28729 @findex pre-commands annotation
28730 @findex commands annotation
28731 @findex post-commands annotation
28733 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
28734 command. The annotations are repeated for each command which is input.
28736 @findex pre-overload-choice annotation
28737 @findex overload-choice annotation
28738 @findex post-overload-choice annotation
28739 @item overload-choice
28740 When @value{GDBN} wants the user to select between various overloaded functions.
28742 @findex pre-query annotation
28743 @findex query annotation
28744 @findex post-query annotation
28746 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
28748 @findex pre-prompt-for-continue annotation
28749 @findex prompt-for-continue annotation
28750 @findex post-prompt-for-continue annotation
28751 @item prompt-for-continue
28752 When @value{GDBN} is asking the user to press return to continue. Note: Don't
28753 expect this to work well; instead use @code{set height 0} to disable
28754 prompting. This is because the counting of lines is buggy in the
28755 presence of annotations.
28760 @cindex annotations for errors, warnings and interrupts
28762 @findex quit annotation
28767 This annotation occurs right before @value{GDBN} responds to an interrupt.
28769 @findex error annotation
28774 This annotation occurs right before @value{GDBN} responds to an error.
28776 Quit and error annotations indicate that any annotations which @value{GDBN} was
28777 in the middle of may end abruptly. For example, if a
28778 @code{value-history-begin} annotation is followed by a @code{error}, one
28779 cannot expect to receive the matching @code{value-history-end}. One
28780 cannot expect not to receive it either, however; an error annotation
28781 does not necessarily mean that @value{GDBN} is immediately returning all the way
28784 @findex error-begin annotation
28785 A quit or error annotation may be preceded by
28791 Any output between that and the quit or error annotation is the error
28794 Warning messages are not yet annotated.
28795 @c If we want to change that, need to fix warning(), type_error(),
28796 @c range_error(), and possibly other places.
28799 @section Invalidation Notices
28801 @cindex annotations for invalidation messages
28802 The following annotations say that certain pieces of state may have
28806 @findex frames-invalid annotation
28807 @item ^Z^Zframes-invalid
28809 The frames (for example, output from the @code{backtrace} command) may
28812 @findex breakpoints-invalid annotation
28813 @item ^Z^Zbreakpoints-invalid
28815 The breakpoints may have changed. For example, the user just added or
28816 deleted a breakpoint.
28819 @node Annotations for Running
28820 @section Running the Program
28821 @cindex annotations for running programs
28823 @findex starting annotation
28824 @findex stopping annotation
28825 When the program starts executing due to a @value{GDBN} command such as
28826 @code{step} or @code{continue},
28832 is output. When the program stops,
28838 is output. Before the @code{stopped} annotation, a variety of
28839 annotations describe how the program stopped.
28842 @findex exited annotation
28843 @item ^Z^Zexited @var{exit-status}
28844 The program exited, and @var{exit-status} is the exit status (zero for
28845 successful exit, otherwise nonzero).
28847 @findex signalled annotation
28848 @findex signal-name annotation
28849 @findex signal-name-end annotation
28850 @findex signal-string annotation
28851 @findex signal-string-end annotation
28852 @item ^Z^Zsignalled
28853 The program exited with a signal. After the @code{^Z^Zsignalled}, the
28854 annotation continues:
28860 ^Z^Zsignal-name-end
28864 ^Z^Zsignal-string-end
28869 where @var{name} is the name of the signal, such as @code{SIGILL} or
28870 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
28871 as @code{Illegal Instruction} or @code{Segmentation fault}.
28872 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
28873 user's benefit and have no particular format.
28875 @findex signal annotation
28877 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
28878 just saying that the program received the signal, not that it was
28879 terminated with it.
28881 @findex breakpoint annotation
28882 @item ^Z^Zbreakpoint @var{number}
28883 The program hit breakpoint number @var{number}.
28885 @findex watchpoint annotation
28886 @item ^Z^Zwatchpoint @var{number}
28887 The program hit watchpoint number @var{number}.
28890 @node Source Annotations
28891 @section Displaying Source
28892 @cindex annotations for source display
28894 @findex source annotation
28895 The following annotation is used instead of displaying source code:
28898 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
28901 where @var{filename} is an absolute file name indicating which source
28902 file, @var{line} is the line number within that file (where 1 is the
28903 first line in the file), @var{character} is the character position
28904 within the file (where 0 is the first character in the file) (for most
28905 debug formats this will necessarily point to the beginning of a line),
28906 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
28907 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
28908 @var{addr} is the address in the target program associated with the
28909 source which is being displayed. @var{addr} is in the form @samp{0x}
28910 followed by one or more lowercase hex digits (note that this does not
28911 depend on the language).
28913 @node JIT Interface
28914 @chapter JIT Compilation Interface
28915 @cindex just-in-time compilation
28916 @cindex JIT compilation interface
28918 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
28919 interface. A JIT compiler is a program or library that generates native
28920 executable code at runtime and executes it, usually in order to achieve good
28921 performance while maintaining platform independence.
28923 Programs that use JIT compilation are normally difficult to debug because
28924 portions of their code are generated at runtime, instead of being loaded from
28925 object files, which is where @value{GDBN} normally finds the program's symbols
28926 and debug information. In order to debug programs that use JIT compilation,
28927 @value{GDBN} has an interface that allows the program to register in-memory
28928 symbol files with @value{GDBN} at runtime.
28930 If you are using @value{GDBN} to debug a program that uses this interface, then
28931 it should work transparently so long as you have not stripped the binary. If
28932 you are developing a JIT compiler, then the interface is documented in the rest
28933 of this chapter. At this time, the only known client of this interface is the
28936 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
28937 JIT compiler communicates with @value{GDBN} by writing data into a global
28938 variable and calling a fuction at a well-known symbol. When @value{GDBN}
28939 attaches, it reads a linked list of symbol files from the global variable to
28940 find existing code, and puts a breakpoint in the function so that it can find
28941 out about additional code.
28944 * Declarations:: Relevant C struct declarations
28945 * Registering Code:: Steps to register code
28946 * Unregistering Code:: Steps to unregister code
28950 @section JIT Declarations
28952 These are the relevant struct declarations that a C program should include to
28953 implement the interface:
28963 struct jit_code_entry
28965 struct jit_code_entry *next_entry;
28966 struct jit_code_entry *prev_entry;
28967 const char *symfile_addr;
28968 uint64_t symfile_size;
28971 struct jit_descriptor
28974 /* This type should be jit_actions_t, but we use uint32_t
28975 to be explicit about the bitwidth. */
28976 uint32_t action_flag;
28977 struct jit_code_entry *relevant_entry;
28978 struct jit_code_entry *first_entry;
28981 /* GDB puts a breakpoint in this function. */
28982 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
28984 /* Make sure to specify the version statically, because the
28985 debugger may check the version before we can set it. */
28986 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
28989 If the JIT is multi-threaded, then it is important that the JIT synchronize any
28990 modifications to this global data properly, which can easily be done by putting
28991 a global mutex around modifications to these structures.
28993 @node Registering Code
28994 @section Registering Code
28996 To register code with @value{GDBN}, the JIT should follow this protocol:
29000 Generate an object file in memory with symbols and other desired debug
29001 information. The file must include the virtual addresses of the sections.
29004 Create a code entry for the file, which gives the start and size of the symbol
29008 Add it to the linked list in the JIT descriptor.
29011 Point the relevant_entry field of the descriptor at the entry.
29014 Set @code{action_flag} to @code{JIT_REGISTER} and call
29015 @code{__jit_debug_register_code}.
29018 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
29019 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
29020 new code. However, the linked list must still be maintained in order to allow
29021 @value{GDBN} to attach to a running process and still find the symbol files.
29023 @node Unregistering Code
29024 @section Unregistering Code
29026 If code is freed, then the JIT should use the following protocol:
29030 Remove the code entry corresponding to the code from the linked list.
29033 Point the @code{relevant_entry} field of the descriptor at the code entry.
29036 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
29037 @code{__jit_debug_register_code}.
29040 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
29041 and the JIT will leak the memory used for the associated symbol files.
29044 @chapter Reporting Bugs in @value{GDBN}
29045 @cindex bugs in @value{GDBN}
29046 @cindex reporting bugs in @value{GDBN}
29048 Your bug reports play an essential role in making @value{GDBN} reliable.
29050 Reporting a bug may help you by bringing a solution to your problem, or it
29051 may not. But in any case the principal function of a bug report is to help
29052 the entire community by making the next version of @value{GDBN} work better. Bug
29053 reports are your contribution to the maintenance of @value{GDBN}.
29055 In order for a bug report to serve its purpose, you must include the
29056 information that enables us to fix the bug.
29059 * Bug Criteria:: Have you found a bug?
29060 * Bug Reporting:: How to report bugs
29064 @section Have You Found a Bug?
29065 @cindex bug criteria
29067 If you are not sure whether you have found a bug, here are some guidelines:
29070 @cindex fatal signal
29071 @cindex debugger crash
29072 @cindex crash of debugger
29074 If the debugger gets a fatal signal, for any input whatever, that is a
29075 @value{GDBN} bug. Reliable debuggers never crash.
29077 @cindex error on valid input
29079 If @value{GDBN} produces an error message for valid input, that is a
29080 bug. (Note that if you're cross debugging, the problem may also be
29081 somewhere in the connection to the target.)
29083 @cindex invalid input
29085 If @value{GDBN} does not produce an error message for invalid input,
29086 that is a bug. However, you should note that your idea of
29087 ``invalid input'' might be our idea of ``an extension'' or ``support
29088 for traditional practice''.
29091 If you are an experienced user of debugging tools, your suggestions
29092 for improvement of @value{GDBN} are welcome in any case.
29095 @node Bug Reporting
29096 @section How to Report Bugs
29097 @cindex bug reports
29098 @cindex @value{GDBN} bugs, reporting
29100 A number of companies and individuals offer support for @sc{gnu} products.
29101 If you obtained @value{GDBN} from a support organization, we recommend you
29102 contact that organization first.
29104 You can find contact information for many support companies and
29105 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
29107 @c should add a web page ref...
29110 @ifset BUGURL_DEFAULT
29111 In any event, we also recommend that you submit bug reports for
29112 @value{GDBN}. The preferred method is to submit them directly using
29113 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
29114 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
29117 @strong{Do not send bug reports to @samp{info-gdb}, or to
29118 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
29119 not want to receive bug reports. Those that do have arranged to receive
29122 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
29123 serves as a repeater. The mailing list and the newsgroup carry exactly
29124 the same messages. Often people think of posting bug reports to the
29125 newsgroup instead of mailing them. This appears to work, but it has one
29126 problem which can be crucial: a newsgroup posting often lacks a mail
29127 path back to the sender. Thus, if we need to ask for more information,
29128 we may be unable to reach you. For this reason, it is better to send
29129 bug reports to the mailing list.
29131 @ifclear BUGURL_DEFAULT
29132 In any event, we also recommend that you submit bug reports for
29133 @value{GDBN} to @value{BUGURL}.
29137 The fundamental principle of reporting bugs usefully is this:
29138 @strong{report all the facts}. If you are not sure whether to state a
29139 fact or leave it out, state it!
29141 Often people omit facts because they think they know what causes the
29142 problem and assume that some details do not matter. Thus, you might
29143 assume that the name of the variable you use in an example does not matter.
29144 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
29145 stray memory reference which happens to fetch from the location where that
29146 name is stored in memory; perhaps, if the name were different, the contents
29147 of that location would fool the debugger into doing the right thing despite
29148 the bug. Play it safe and give a specific, complete example. That is the
29149 easiest thing for you to do, and the most helpful.
29151 Keep in mind that the purpose of a bug report is to enable us to fix the
29152 bug. It may be that the bug has been reported previously, but neither
29153 you nor we can know that unless your bug report is complete and
29156 Sometimes people give a few sketchy facts and ask, ``Does this ring a
29157 bell?'' Those bug reports are useless, and we urge everyone to
29158 @emph{refuse to respond to them} except to chide the sender to report
29161 To enable us to fix the bug, you should include all these things:
29165 The version of @value{GDBN}. @value{GDBN} announces it if you start
29166 with no arguments; you can also print it at any time using @code{show
29169 Without this, we will not know whether there is any point in looking for
29170 the bug in the current version of @value{GDBN}.
29173 The type of machine you are using, and the operating system name and
29177 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
29178 ``@value{GCC}--2.8.1''.
29181 What compiler (and its version) was used to compile the program you are
29182 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
29183 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
29184 to get this information; for other compilers, see the documentation for
29188 The command arguments you gave the compiler to compile your example and
29189 observe the bug. For example, did you use @samp{-O}? To guarantee
29190 you will not omit something important, list them all. A copy of the
29191 Makefile (or the output from make) is sufficient.
29193 If we were to try to guess the arguments, we would probably guess wrong
29194 and then we might not encounter the bug.
29197 A complete input script, and all necessary source files, that will
29201 A description of what behavior you observe that you believe is
29202 incorrect. For example, ``It gets a fatal signal.''
29204 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
29205 will certainly notice it. But if the bug is incorrect output, we might
29206 not notice unless it is glaringly wrong. You might as well not give us
29207 a chance to make a mistake.
29209 Even if the problem you experience is a fatal signal, you should still
29210 say so explicitly. Suppose something strange is going on, such as, your
29211 copy of @value{GDBN} is out of synch, or you have encountered a bug in
29212 the C library on your system. (This has happened!) Your copy might
29213 crash and ours would not. If you told us to expect a crash, then when
29214 ours fails to crash, we would know that the bug was not happening for
29215 us. If you had not told us to expect a crash, then we would not be able
29216 to draw any conclusion from our observations.
29219 @cindex recording a session script
29220 To collect all this information, you can use a session recording program
29221 such as @command{script}, which is available on many Unix systems.
29222 Just run your @value{GDBN} session inside @command{script} and then
29223 include the @file{typescript} file with your bug report.
29225 Another way to record a @value{GDBN} session is to run @value{GDBN}
29226 inside Emacs and then save the entire buffer to a file.
29229 If you wish to suggest changes to the @value{GDBN} source, send us context
29230 diffs. If you even discuss something in the @value{GDBN} source, refer to
29231 it by context, not by line number.
29233 The line numbers in our development sources will not match those in your
29234 sources. Your line numbers would convey no useful information to us.
29238 Here are some things that are not necessary:
29242 A description of the envelope of the bug.
29244 Often people who encounter a bug spend a lot of time investigating
29245 which changes to the input file will make the bug go away and which
29246 changes will not affect it.
29248 This is often time consuming and not very useful, because the way we
29249 will find the bug is by running a single example under the debugger
29250 with breakpoints, not by pure deduction from a series of examples.
29251 We recommend that you save your time for something else.
29253 Of course, if you can find a simpler example to report @emph{instead}
29254 of the original one, that is a convenience for us. Errors in the
29255 output will be easier to spot, running under the debugger will take
29256 less time, and so on.
29258 However, simplification is not vital; if you do not want to do this,
29259 report the bug anyway and send us the entire test case you used.
29262 A patch for the bug.
29264 A patch for the bug does help us if it is a good one. But do not omit
29265 the necessary information, such as the test case, on the assumption that
29266 a patch is all we need. We might see problems with your patch and decide
29267 to fix the problem another way, or we might not understand it at all.
29269 Sometimes with a program as complicated as @value{GDBN} it is very hard to
29270 construct an example that will make the program follow a certain path
29271 through the code. If you do not send us the example, we will not be able
29272 to construct one, so we will not be able to verify that the bug is fixed.
29274 And if we cannot understand what bug you are trying to fix, or why your
29275 patch should be an improvement, we will not install it. A test case will
29276 help us to understand.
29279 A guess about what the bug is or what it depends on.
29281 Such guesses are usually wrong. Even we cannot guess right about such
29282 things without first using the debugger to find the facts.
29285 @c The readline documentation is distributed with the readline code
29286 @c and consists of the two following files:
29288 @c inc-hist.texinfo
29289 @c Use -I with makeinfo to point to the appropriate directory,
29290 @c environment var TEXINPUTS with TeX.
29291 @include rluser.texi
29292 @include inc-hist.texinfo
29295 @node Formatting Documentation
29296 @appendix Formatting Documentation
29298 @cindex @value{GDBN} reference card
29299 @cindex reference card
29300 The @value{GDBN} 4 release includes an already-formatted reference card, ready
29301 for printing with PostScript or Ghostscript, in the @file{gdb}
29302 subdirectory of the main source directory@footnote{In
29303 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
29304 release.}. If you can use PostScript or Ghostscript with your printer,
29305 you can print the reference card immediately with @file{refcard.ps}.
29307 The release also includes the source for the reference card. You
29308 can format it, using @TeX{}, by typing:
29314 The @value{GDBN} reference card is designed to print in @dfn{landscape}
29315 mode on US ``letter'' size paper;
29316 that is, on a sheet 11 inches wide by 8.5 inches
29317 high. You will need to specify this form of printing as an option to
29318 your @sc{dvi} output program.
29320 @cindex documentation
29322 All the documentation for @value{GDBN} comes as part of the machine-readable
29323 distribution. The documentation is written in Texinfo format, which is
29324 a documentation system that uses a single source file to produce both
29325 on-line information and a printed manual. You can use one of the Info
29326 formatting commands to create the on-line version of the documentation
29327 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
29329 @value{GDBN} includes an already formatted copy of the on-line Info
29330 version of this manual in the @file{gdb} subdirectory. The main Info
29331 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
29332 subordinate files matching @samp{gdb.info*} in the same directory. If
29333 necessary, you can print out these files, or read them with any editor;
29334 but they are easier to read using the @code{info} subsystem in @sc{gnu}
29335 Emacs or the standalone @code{info} program, available as part of the
29336 @sc{gnu} Texinfo distribution.
29338 If you want to format these Info files yourself, you need one of the
29339 Info formatting programs, such as @code{texinfo-format-buffer} or
29342 If you have @code{makeinfo} installed, and are in the top level
29343 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
29344 version @value{GDBVN}), you can make the Info file by typing:
29351 If you want to typeset and print copies of this manual, you need @TeX{},
29352 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
29353 Texinfo definitions file.
29355 @TeX{} is a typesetting program; it does not print files directly, but
29356 produces output files called @sc{dvi} files. To print a typeset
29357 document, you need a program to print @sc{dvi} files. If your system
29358 has @TeX{} installed, chances are it has such a program. The precise
29359 command to use depends on your system; @kbd{lpr -d} is common; another
29360 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
29361 require a file name without any extension or a @samp{.dvi} extension.
29363 @TeX{} also requires a macro definitions file called
29364 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
29365 written in Texinfo format. On its own, @TeX{} cannot either read or
29366 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
29367 and is located in the @file{gdb-@var{version-number}/texinfo}
29370 If you have @TeX{} and a @sc{dvi} printer program installed, you can
29371 typeset and print this manual. First switch to the @file{gdb}
29372 subdirectory of the main source directory (for example, to
29373 @file{gdb-@value{GDBVN}/gdb}) and type:
29379 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
29381 @node Installing GDB
29382 @appendix Installing @value{GDBN}
29383 @cindex installation
29386 * Requirements:: Requirements for building @value{GDBN}
29387 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
29388 * Separate Objdir:: Compiling @value{GDBN} in another directory
29389 * Config Names:: Specifying names for hosts and targets
29390 * Configure Options:: Summary of options for configure
29391 * System-wide configuration:: Having a system-wide init file
29395 @section Requirements for Building @value{GDBN}
29396 @cindex building @value{GDBN}, requirements for
29398 Building @value{GDBN} requires various tools and packages to be available.
29399 Other packages will be used only if they are found.
29401 @heading Tools/Packages Necessary for Building @value{GDBN}
29403 @item ISO C90 compiler
29404 @value{GDBN} is written in ISO C90. It should be buildable with any
29405 working C90 compiler, e.g.@: GCC.
29409 @heading Tools/Packages Optional for Building @value{GDBN}
29413 @value{GDBN} can use the Expat XML parsing library. This library may be
29414 included with your operating system distribution; if it is not, you
29415 can get the latest version from @url{http://expat.sourceforge.net}.
29416 The @file{configure} script will search for this library in several
29417 standard locations; if it is installed in an unusual path, you can
29418 use the @option{--with-libexpat-prefix} option to specify its location.
29424 Remote protocol memory maps (@pxref{Memory Map Format})
29426 Target descriptions (@pxref{Target Descriptions})
29428 Remote shared library lists (@pxref{Library List Format})
29430 MS-Windows shared libraries (@pxref{Shared Libraries})
29434 @cindex compressed debug sections
29435 @value{GDBN} will use the @samp{zlib} library, if available, to read
29436 compressed debug sections. Some linkers, such as GNU gold, are capable
29437 of producing binaries with compressed debug sections. If @value{GDBN}
29438 is compiled with @samp{zlib}, it will be able to read the debug
29439 information in such binaries.
29441 The @samp{zlib} library is likely included with your operating system
29442 distribution; if it is not, you can get the latest version from
29443 @url{http://zlib.net}.
29446 @value{GDBN}'s features related to character sets (@pxref{Character
29447 Sets}) require a functioning @code{iconv} implementation. If you are
29448 on a GNU system, then this is provided by the GNU C Library. Some
29449 other systems also provide a working @code{iconv}.
29451 On systems with @code{iconv}, you can install GNU Libiconv. If you
29452 have previously installed Libiconv, you can use the
29453 @option{--with-libiconv-prefix} option to configure.
29455 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
29456 arrange to build Libiconv if a directory named @file{libiconv} appears
29457 in the top-most source directory. If Libiconv is built this way, and
29458 if the operating system does not provide a suitable @code{iconv}
29459 implementation, then the just-built library will automatically be used
29460 by @value{GDBN}. One easy way to set this up is to download GNU
29461 Libiconv, unpack it, and then rename the directory holding the
29462 Libiconv source code to @samp{libiconv}.
29465 @node Running Configure
29466 @section Invoking the @value{GDBN} @file{configure} Script
29467 @cindex configuring @value{GDBN}
29468 @value{GDBN} comes with a @file{configure} script that automates the process
29469 of preparing @value{GDBN} for installation; you can then use @code{make} to
29470 build the @code{gdb} program.
29472 @c irrelevant in info file; it's as current as the code it lives with.
29473 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
29474 look at the @file{README} file in the sources; we may have improved the
29475 installation procedures since publishing this manual.}
29478 The @value{GDBN} distribution includes all the source code you need for
29479 @value{GDBN} in a single directory, whose name is usually composed by
29480 appending the version number to @samp{gdb}.
29482 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
29483 @file{gdb-@value{GDBVN}} directory. That directory contains:
29486 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
29487 script for configuring @value{GDBN} and all its supporting libraries
29489 @item gdb-@value{GDBVN}/gdb
29490 the source specific to @value{GDBN} itself
29492 @item gdb-@value{GDBVN}/bfd
29493 source for the Binary File Descriptor library
29495 @item gdb-@value{GDBVN}/include
29496 @sc{gnu} include files
29498 @item gdb-@value{GDBVN}/libiberty
29499 source for the @samp{-liberty} free software library
29501 @item gdb-@value{GDBVN}/opcodes
29502 source for the library of opcode tables and disassemblers
29504 @item gdb-@value{GDBVN}/readline
29505 source for the @sc{gnu} command-line interface
29507 @item gdb-@value{GDBVN}/glob
29508 source for the @sc{gnu} filename pattern-matching subroutine
29510 @item gdb-@value{GDBVN}/mmalloc
29511 source for the @sc{gnu} memory-mapped malloc package
29514 The simplest way to configure and build @value{GDBN} is to run @file{configure}
29515 from the @file{gdb-@var{version-number}} source directory, which in
29516 this example is the @file{gdb-@value{GDBVN}} directory.
29518 First switch to the @file{gdb-@var{version-number}} source directory
29519 if you are not already in it; then run @file{configure}. Pass the
29520 identifier for the platform on which @value{GDBN} will run as an
29526 cd gdb-@value{GDBVN}
29527 ./configure @var{host}
29532 where @var{host} is an identifier such as @samp{sun4} or
29533 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
29534 (You can often leave off @var{host}; @file{configure} tries to guess the
29535 correct value by examining your system.)
29537 Running @samp{configure @var{host}} and then running @code{make} builds the
29538 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
29539 libraries, then @code{gdb} itself. The configured source files, and the
29540 binaries, are left in the corresponding source directories.
29543 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
29544 system does not recognize this automatically when you run a different
29545 shell, you may need to run @code{sh} on it explicitly:
29548 sh configure @var{host}
29551 If you run @file{configure} from a directory that contains source
29552 directories for multiple libraries or programs, such as the
29553 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
29555 creates configuration files for every directory level underneath (unless
29556 you tell it not to, with the @samp{--norecursion} option).
29558 You should run the @file{configure} script from the top directory in the
29559 source tree, the @file{gdb-@var{version-number}} directory. If you run
29560 @file{configure} from one of the subdirectories, you will configure only
29561 that subdirectory. That is usually not what you want. In particular,
29562 if you run the first @file{configure} from the @file{gdb} subdirectory
29563 of the @file{gdb-@var{version-number}} directory, you will omit the
29564 configuration of @file{bfd}, @file{readline}, and other sibling
29565 directories of the @file{gdb} subdirectory. This leads to build errors
29566 about missing include files such as @file{bfd/bfd.h}.
29568 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
29569 However, you should make sure that the shell on your path (named by
29570 the @samp{SHELL} environment variable) is publicly readable. Remember
29571 that @value{GDBN} uses the shell to start your program---some systems refuse to
29572 let @value{GDBN} debug child processes whose programs are not readable.
29574 @node Separate Objdir
29575 @section Compiling @value{GDBN} in Another Directory
29577 If you want to run @value{GDBN} versions for several host or target machines,
29578 you need a different @code{gdb} compiled for each combination of
29579 host and target. @file{configure} is designed to make this easy by
29580 allowing you to generate each configuration in a separate subdirectory,
29581 rather than in the source directory. If your @code{make} program
29582 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
29583 @code{make} in each of these directories builds the @code{gdb}
29584 program specified there.
29586 To build @code{gdb} in a separate directory, run @file{configure}
29587 with the @samp{--srcdir} option to specify where to find the source.
29588 (You also need to specify a path to find @file{configure}
29589 itself from your working directory. If the path to @file{configure}
29590 would be the same as the argument to @samp{--srcdir}, you can leave out
29591 the @samp{--srcdir} option; it is assumed.)
29593 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
29594 separate directory for a Sun 4 like this:
29598 cd gdb-@value{GDBVN}
29601 ../gdb-@value{GDBVN}/configure sun4
29606 When @file{configure} builds a configuration using a remote source
29607 directory, it creates a tree for the binaries with the same structure
29608 (and using the same names) as the tree under the source directory. In
29609 the example, you'd find the Sun 4 library @file{libiberty.a} in the
29610 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
29611 @file{gdb-sun4/gdb}.
29613 Make sure that your path to the @file{configure} script has just one
29614 instance of @file{gdb} in it. If your path to @file{configure} looks
29615 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
29616 one subdirectory of @value{GDBN}, not the whole package. This leads to
29617 build errors about missing include files such as @file{bfd/bfd.h}.
29619 One popular reason to build several @value{GDBN} configurations in separate
29620 directories is to configure @value{GDBN} for cross-compiling (where
29621 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
29622 programs that run on another machine---the @dfn{target}).
29623 You specify a cross-debugging target by
29624 giving the @samp{--target=@var{target}} option to @file{configure}.
29626 When you run @code{make} to build a program or library, you must run
29627 it in a configured directory---whatever directory you were in when you
29628 called @file{configure} (or one of its subdirectories).
29630 The @code{Makefile} that @file{configure} generates in each source
29631 directory also runs recursively. If you type @code{make} in a source
29632 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
29633 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
29634 will build all the required libraries, and then build GDB.
29636 When you have multiple hosts or targets configured in separate
29637 directories, you can run @code{make} on them in parallel (for example,
29638 if they are NFS-mounted on each of the hosts); they will not interfere
29642 @section Specifying Names for Hosts and Targets
29644 The specifications used for hosts and targets in the @file{configure}
29645 script are based on a three-part naming scheme, but some short predefined
29646 aliases are also supported. The full naming scheme encodes three pieces
29647 of information in the following pattern:
29650 @var{architecture}-@var{vendor}-@var{os}
29653 For example, you can use the alias @code{sun4} as a @var{host} argument,
29654 or as the value for @var{target} in a @code{--target=@var{target}}
29655 option. The equivalent full name is @samp{sparc-sun-sunos4}.
29657 The @file{configure} script accompanying @value{GDBN} does not provide
29658 any query facility to list all supported host and target names or
29659 aliases. @file{configure} calls the Bourne shell script
29660 @code{config.sub} to map abbreviations to full names; you can read the
29661 script, if you wish, or you can use it to test your guesses on
29662 abbreviations---for example:
29665 % sh config.sub i386-linux
29667 % sh config.sub alpha-linux
29668 alpha-unknown-linux-gnu
29669 % sh config.sub hp9k700
29671 % sh config.sub sun4
29672 sparc-sun-sunos4.1.1
29673 % sh config.sub sun3
29674 m68k-sun-sunos4.1.1
29675 % sh config.sub i986v
29676 Invalid configuration `i986v': machine `i986v' not recognized
29680 @code{config.sub} is also distributed in the @value{GDBN} source
29681 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
29683 @node Configure Options
29684 @section @file{configure} Options
29686 Here is a summary of the @file{configure} options and arguments that
29687 are most often useful for building @value{GDBN}. @file{configure} also has
29688 several other options not listed here. @inforef{What Configure
29689 Does,,configure.info}, for a full explanation of @file{configure}.
29692 configure @r{[}--help@r{]}
29693 @r{[}--prefix=@var{dir}@r{]}
29694 @r{[}--exec-prefix=@var{dir}@r{]}
29695 @r{[}--srcdir=@var{dirname}@r{]}
29696 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
29697 @r{[}--target=@var{target}@r{]}
29702 You may introduce options with a single @samp{-} rather than
29703 @samp{--} if you prefer; but you may abbreviate option names if you use
29708 Display a quick summary of how to invoke @file{configure}.
29710 @item --prefix=@var{dir}
29711 Configure the source to install programs and files under directory
29714 @item --exec-prefix=@var{dir}
29715 Configure the source to install programs under directory
29718 @c avoid splitting the warning from the explanation:
29720 @item --srcdir=@var{dirname}
29721 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
29722 @code{make} that implements the @code{VPATH} feature.}@*
29723 Use this option to make configurations in directories separate from the
29724 @value{GDBN} source directories. Among other things, you can use this to
29725 build (or maintain) several configurations simultaneously, in separate
29726 directories. @file{configure} writes configuration-specific files in
29727 the current directory, but arranges for them to use the source in the
29728 directory @var{dirname}. @file{configure} creates directories under
29729 the working directory in parallel to the source directories below
29732 @item --norecursion
29733 Configure only the directory level where @file{configure} is executed; do not
29734 propagate configuration to subdirectories.
29736 @item --target=@var{target}
29737 Configure @value{GDBN} for cross-debugging programs running on the specified
29738 @var{target}. Without this option, @value{GDBN} is configured to debug
29739 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
29741 There is no convenient way to generate a list of all available targets.
29743 @item @var{host} @dots{}
29744 Configure @value{GDBN} to run on the specified @var{host}.
29746 There is no convenient way to generate a list of all available hosts.
29749 There are many other options available as well, but they are generally
29750 needed for special purposes only.
29752 @node System-wide configuration
29753 @section System-wide configuration and settings
29754 @cindex system-wide init file
29756 @value{GDBN} can be configured to have a system-wide init file;
29757 this file will be read and executed at startup (@pxref{Startup, , What
29758 @value{GDBN} does during startup}).
29760 Here is the corresponding configure option:
29763 @item --with-system-gdbinit=@var{file}
29764 Specify that the default location of the system-wide init file is
29768 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
29769 it may be subject to relocation. Two possible cases:
29773 If the default location of this init file contains @file{$prefix},
29774 it will be subject to relocation. Suppose that the configure options
29775 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
29776 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
29777 init file is looked for as @file{$install/etc/gdbinit} instead of
29778 @file{$prefix/etc/gdbinit}.
29781 By contrast, if the default location does not contain the prefix,
29782 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
29783 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
29784 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
29785 wherever @value{GDBN} is installed.
29788 @node Maintenance Commands
29789 @appendix Maintenance Commands
29790 @cindex maintenance commands
29791 @cindex internal commands
29793 In addition to commands intended for @value{GDBN} users, @value{GDBN}
29794 includes a number of commands intended for @value{GDBN} developers,
29795 that are not documented elsewhere in this manual. These commands are
29796 provided here for reference. (For commands that turn on debugging
29797 messages, see @ref{Debugging Output}.)
29800 @kindex maint agent
29801 @kindex maint agent-eval
29802 @item maint agent @var{expression}
29803 @itemx maint agent-eval @var{expression}
29804 Translate the given @var{expression} into remote agent bytecodes.
29805 This command is useful for debugging the Agent Expression mechanism
29806 (@pxref{Agent Expressions}). The @samp{agent} version produces an
29807 expression useful for data collection, such as by tracepoints, while
29808 @samp{maint agent-eval} produces an expression that evaluates directly
29809 to a result. For instance, a collection expression for @code{globa +
29810 globb} will include bytecodes to record four bytes of memory at each
29811 of the addresses of @code{globa} and @code{globb}, while discarding
29812 the result of the addition, while an evaluation expression will do the
29813 addition and return the sum.
29815 @kindex maint info breakpoints
29816 @item @anchor{maint info breakpoints}maint info breakpoints
29817 Using the same format as @samp{info breakpoints}, display both the
29818 breakpoints you've set explicitly, and those @value{GDBN} is using for
29819 internal purposes. Internal breakpoints are shown with negative
29820 breakpoint numbers. The type column identifies what kind of breakpoint
29825 Normal, explicitly set breakpoint.
29828 Normal, explicitly set watchpoint.
29831 Internal breakpoint, used to handle correctly stepping through
29832 @code{longjmp} calls.
29834 @item longjmp resume
29835 Internal breakpoint at the target of a @code{longjmp}.
29838 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
29841 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
29844 Shared library events.
29848 @kindex set displaced-stepping
29849 @kindex show displaced-stepping
29850 @cindex displaced stepping support
29851 @cindex out-of-line single-stepping
29852 @item set displaced-stepping
29853 @itemx show displaced-stepping
29854 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
29855 if the target supports it. Displaced stepping is a way to single-step
29856 over breakpoints without removing them from the inferior, by executing
29857 an out-of-line copy of the instruction that was originally at the
29858 breakpoint location. It is also known as out-of-line single-stepping.
29861 @item set displaced-stepping on
29862 If the target architecture supports it, @value{GDBN} will use
29863 displaced stepping to step over breakpoints.
29865 @item set displaced-stepping off
29866 @value{GDBN} will not use displaced stepping to step over breakpoints,
29867 even if such is supported by the target architecture.
29869 @cindex non-stop mode, and @samp{set displaced-stepping}
29870 @item set displaced-stepping auto
29871 This is the default mode. @value{GDBN} will use displaced stepping
29872 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
29873 architecture supports displaced stepping.
29876 @kindex maint check-symtabs
29877 @item maint check-symtabs
29878 Check the consistency of psymtabs and symtabs.
29880 @kindex maint cplus first_component
29881 @item maint cplus first_component @var{name}
29882 Print the first C@t{++} class/namespace component of @var{name}.
29884 @kindex maint cplus namespace
29885 @item maint cplus namespace
29886 Print the list of possible C@t{++} namespaces.
29888 @kindex maint demangle
29889 @item maint demangle @var{name}
29890 Demangle a C@t{++} or Objective-C mangled @var{name}.
29892 @kindex maint deprecate
29893 @kindex maint undeprecate
29894 @cindex deprecated commands
29895 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
29896 @itemx maint undeprecate @var{command}
29897 Deprecate or undeprecate the named @var{command}. Deprecated commands
29898 cause @value{GDBN} to issue a warning when you use them. The optional
29899 argument @var{replacement} says which newer command should be used in
29900 favor of the deprecated one; if it is given, @value{GDBN} will mention
29901 the replacement as part of the warning.
29903 @kindex maint dump-me
29904 @item maint dump-me
29905 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
29906 Cause a fatal signal in the debugger and force it to dump its core.
29907 This is supported only on systems which support aborting a program
29908 with the @code{SIGQUIT} signal.
29910 @kindex maint internal-error
29911 @kindex maint internal-warning
29912 @item maint internal-error @r{[}@var{message-text}@r{]}
29913 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
29914 Cause @value{GDBN} to call the internal function @code{internal_error}
29915 or @code{internal_warning} and hence behave as though an internal error
29916 or internal warning has been detected. In addition to reporting the
29917 internal problem, these functions give the user the opportunity to
29918 either quit @value{GDBN} or create a core file of the current
29919 @value{GDBN} session.
29921 These commands take an optional parameter @var{message-text} that is
29922 used as the text of the error or warning message.
29924 Here's an example of using @code{internal-error}:
29927 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
29928 @dots{}/maint.c:121: internal-error: testing, 1, 2
29929 A problem internal to GDB has been detected. Further
29930 debugging may prove unreliable.
29931 Quit this debugging session? (y or n) @kbd{n}
29932 Create a core file? (y or n) @kbd{n}
29936 @cindex @value{GDBN} internal error
29937 @cindex internal errors, control of @value{GDBN} behavior
29939 @kindex maint set internal-error
29940 @kindex maint show internal-error
29941 @kindex maint set internal-warning
29942 @kindex maint show internal-warning
29943 @item maint set internal-error @var{action} [ask|yes|no]
29944 @itemx maint show internal-error @var{action}
29945 @itemx maint set internal-warning @var{action} [ask|yes|no]
29946 @itemx maint show internal-warning @var{action}
29947 When @value{GDBN} reports an internal problem (error or warning) it
29948 gives the user the opportunity to both quit @value{GDBN} and create a
29949 core file of the current @value{GDBN} session. These commands let you
29950 override the default behaviour for each particular @var{action},
29951 described in the table below.
29955 You can specify that @value{GDBN} should always (yes) or never (no)
29956 quit. The default is to ask the user what to do.
29959 You can specify that @value{GDBN} should always (yes) or never (no)
29960 create a core file. The default is to ask the user what to do.
29963 @kindex maint packet
29964 @item maint packet @var{text}
29965 If @value{GDBN} is talking to an inferior via the serial protocol,
29966 then this command sends the string @var{text} to the inferior, and
29967 displays the response packet. @value{GDBN} supplies the initial
29968 @samp{$} character, the terminating @samp{#} character, and the
29971 @kindex maint print architecture
29972 @item maint print architecture @r{[}@var{file}@r{]}
29973 Print the entire architecture configuration. The optional argument
29974 @var{file} names the file where the output goes.
29976 @kindex maint print c-tdesc
29977 @item maint print c-tdesc
29978 Print the current target description (@pxref{Target Descriptions}) as
29979 a C source file. The created source file can be used in @value{GDBN}
29980 when an XML parser is not available to parse the description.
29982 @kindex maint print dummy-frames
29983 @item maint print dummy-frames
29984 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
29987 (@value{GDBP}) @kbd{b add}
29989 (@value{GDBP}) @kbd{print add(2,3)}
29990 Breakpoint 2, add (a=2, b=3) at @dots{}
29992 The program being debugged stopped while in a function called from GDB.
29994 (@value{GDBP}) @kbd{maint print dummy-frames}
29995 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
29996 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
29997 call_lo=0x01014000 call_hi=0x01014001
30001 Takes an optional file parameter.
30003 @kindex maint print registers
30004 @kindex maint print raw-registers
30005 @kindex maint print cooked-registers
30006 @kindex maint print register-groups
30007 @item maint print registers @r{[}@var{file}@r{]}
30008 @itemx maint print raw-registers @r{[}@var{file}@r{]}
30009 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
30010 @itemx maint print register-groups @r{[}@var{file}@r{]}
30011 Print @value{GDBN}'s internal register data structures.
30013 The command @code{maint print raw-registers} includes the contents of
30014 the raw register cache; the command @code{maint print cooked-registers}
30015 includes the (cooked) value of all registers, including registers which
30016 aren't available on the target nor visible to user; and the
30017 command @code{maint print register-groups} includes the groups that each
30018 register is a member of. @xref{Registers,, Registers, gdbint,
30019 @value{GDBN} Internals}.
30021 These commands take an optional parameter, a file name to which to
30022 write the information.
30024 @kindex maint print reggroups
30025 @item maint print reggroups @r{[}@var{file}@r{]}
30026 Print @value{GDBN}'s internal register group data structures. The
30027 optional argument @var{file} tells to what file to write the
30030 The register groups info looks like this:
30033 (@value{GDBP}) @kbd{maint print reggroups}
30046 This command forces @value{GDBN} to flush its internal register cache.
30048 @kindex maint print objfiles
30049 @cindex info for known object files
30050 @item maint print objfiles
30051 Print a dump of all known object files. For each object file, this
30052 command prints its name, address in memory, and all of its psymtabs
30055 @kindex maint print section-scripts
30056 @cindex info for known .debug_gdb_scripts-loaded scripts
30057 @item maint print section-scripts [@var{regexp}]
30058 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
30059 If @var{regexp} is specified, only print scripts loaded by object files
30060 matching @var{regexp}.
30061 For each script, this command prints its name as specified in the objfile,
30062 and the full path if known.
30063 @xref{.debug_gdb_scripts section}.
30065 @kindex maint print statistics
30066 @cindex bcache statistics
30067 @item maint print statistics
30068 This command prints, for each object file in the program, various data
30069 about that object file followed by the byte cache (@dfn{bcache})
30070 statistics for the object file. The objfile data includes the number
30071 of minimal, partial, full, and stabs symbols, the number of types
30072 defined by the objfile, the number of as yet unexpanded psym tables,
30073 the number of line tables and string tables, and the amount of memory
30074 used by the various tables. The bcache statistics include the counts,
30075 sizes, and counts of duplicates of all and unique objects, max,
30076 average, and median entry size, total memory used and its overhead and
30077 savings, and various measures of the hash table size and chain
30080 @kindex maint print target-stack
30081 @cindex target stack description
30082 @item maint print target-stack
30083 A @dfn{target} is an interface between the debugger and a particular
30084 kind of file or process. Targets can be stacked in @dfn{strata},
30085 so that more than one target can potentially respond to a request.
30086 In particular, memory accesses will walk down the stack of targets
30087 until they find a target that is interested in handling that particular
30090 This command prints a short description of each layer that was pushed on
30091 the @dfn{target stack}, starting from the top layer down to the bottom one.
30093 @kindex maint print type
30094 @cindex type chain of a data type
30095 @item maint print type @var{expr}
30096 Print the type chain for a type specified by @var{expr}. The argument
30097 can be either a type name or a symbol. If it is a symbol, the type of
30098 that symbol is described. The type chain produced by this command is
30099 a recursive definition of the data type as stored in @value{GDBN}'s
30100 data structures, including its flags and contained types.
30102 @kindex maint set dwarf2 always-disassemble
30103 @kindex maint show dwarf2 always-disassemble
30104 @item maint set dwarf2 always-disassemble
30105 @item maint show dwarf2 always-disassemble
30106 Control the behavior of @code{info address} when using DWARF debugging
30109 The default is @code{off}, which means that @value{GDBN} should try to
30110 describe a variable's location in an easily readable format. When
30111 @code{on}, @value{GDBN} will instead display the DWARF location
30112 expression in an assembly-like format. Note that some locations are
30113 too complex for @value{GDBN} to describe simply; in this case you will
30114 always see the disassembly form.
30116 Here is an example of the resulting disassembly:
30119 (gdb) info addr argc
30120 Symbol "argc" is a complex DWARF expression:
30124 For more information on these expressions, see
30125 @uref{http://www.dwarfstd.org/, the DWARF standard}.
30127 @kindex maint set dwarf2 max-cache-age
30128 @kindex maint show dwarf2 max-cache-age
30129 @item maint set dwarf2 max-cache-age
30130 @itemx maint show dwarf2 max-cache-age
30131 Control the DWARF 2 compilation unit cache.
30133 @cindex DWARF 2 compilation units cache
30134 In object files with inter-compilation-unit references, such as those
30135 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
30136 reader needs to frequently refer to previously read compilation units.
30137 This setting controls how long a compilation unit will remain in the
30138 cache if it is not referenced. A higher limit means that cached
30139 compilation units will be stored in memory longer, and more total
30140 memory will be used. Setting it to zero disables caching, which will
30141 slow down @value{GDBN} startup, but reduce memory consumption.
30143 @kindex maint set profile
30144 @kindex maint show profile
30145 @cindex profiling GDB
30146 @item maint set profile
30147 @itemx maint show profile
30148 Control profiling of @value{GDBN}.
30150 Profiling will be disabled until you use the @samp{maint set profile}
30151 command to enable it. When you enable profiling, the system will begin
30152 collecting timing and execution count data; when you disable profiling or
30153 exit @value{GDBN}, the results will be written to a log file. Remember that
30154 if you use profiling, @value{GDBN} will overwrite the profiling log file
30155 (often called @file{gmon.out}). If you have a record of important profiling
30156 data in a @file{gmon.out} file, be sure to move it to a safe location.
30158 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
30159 compiled with the @samp{-pg} compiler option.
30161 @kindex maint set show-debug-regs
30162 @kindex maint show show-debug-regs
30163 @cindex hardware debug registers
30164 @item maint set show-debug-regs
30165 @itemx maint show show-debug-regs
30166 Control whether to show variables that mirror the hardware debug
30167 registers. Use @code{ON} to enable, @code{OFF} to disable. If
30168 enabled, the debug registers values are shown when @value{GDBN} inserts or
30169 removes a hardware breakpoint or watchpoint, and when the inferior
30170 triggers a hardware-assisted breakpoint or watchpoint.
30172 @kindex maint set show-all-tib
30173 @kindex maint show show-all-tib
30174 @item maint set show-all-tib
30175 @itemx maint show show-all-tib
30176 Control whether to show all non zero areas within a 1k block starting
30177 at thread local base, when using the @samp{info w32 thread-information-block}
30180 @kindex maint space
30181 @cindex memory used by commands
30183 Control whether to display memory usage for each command. If set to a
30184 nonzero value, @value{GDBN} will display how much memory each command
30185 took, following the command's own output. This can also be requested
30186 by invoking @value{GDBN} with the @option{--statistics} command-line
30187 switch (@pxref{Mode Options}).
30190 @cindex time of command execution
30192 Control whether to display the execution time for each command. If
30193 set to a nonzero value, @value{GDBN} will display how much time it
30194 took to execute each command, following the command's own output.
30195 The time is not printed for the commands that run the target, since
30196 there's no mechanism currently to compute how much time was spend
30197 by @value{GDBN} and how much time was spend by the program been debugged.
30198 it's not possibly currently
30199 This can also be requested by invoking @value{GDBN} with the
30200 @option{--statistics} command-line switch (@pxref{Mode Options}).
30202 @kindex maint translate-address
30203 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
30204 Find the symbol stored at the location specified by the address
30205 @var{addr} and an optional section name @var{section}. If found,
30206 @value{GDBN} prints the name of the closest symbol and an offset from
30207 the symbol's location to the specified address. This is similar to
30208 the @code{info address} command (@pxref{Symbols}), except that this
30209 command also allows to find symbols in other sections.
30211 If section was not specified, the section in which the symbol was found
30212 is also printed. For dynamically linked executables, the name of
30213 executable or shared library containing the symbol is printed as well.
30217 The following command is useful for non-interactive invocations of
30218 @value{GDBN}, such as in the test suite.
30221 @item set watchdog @var{nsec}
30222 @kindex set watchdog
30223 @cindex watchdog timer
30224 @cindex timeout for commands
30225 Set the maximum number of seconds @value{GDBN} will wait for the
30226 target operation to finish. If this time expires, @value{GDBN}
30227 reports and error and the command is aborted.
30229 @item show watchdog
30230 Show the current setting of the target wait timeout.
30233 @node Remote Protocol
30234 @appendix @value{GDBN} Remote Serial Protocol
30239 * Stop Reply Packets::
30240 * General Query Packets::
30241 * Architecture-Specific Protocol Details::
30242 * Tracepoint Packets::
30243 * Host I/O Packets::
30245 * Notification Packets::
30246 * Remote Non-Stop::
30247 * Packet Acknowledgment::
30249 * File-I/O Remote Protocol Extension::
30250 * Library List Format::
30251 * Memory Map Format::
30252 * Thread List Format::
30258 There may be occasions when you need to know something about the
30259 protocol---for example, if there is only one serial port to your target
30260 machine, you might want your program to do something special if it
30261 recognizes a packet meant for @value{GDBN}.
30263 In the examples below, @samp{->} and @samp{<-} are used to indicate
30264 transmitted and received data, respectively.
30266 @cindex protocol, @value{GDBN} remote serial
30267 @cindex serial protocol, @value{GDBN} remote
30268 @cindex remote serial protocol
30269 All @value{GDBN} commands and responses (other than acknowledgments
30270 and notifications, see @ref{Notification Packets}) are sent as a
30271 @var{packet}. A @var{packet} is introduced with the character
30272 @samp{$}, the actual @var{packet-data}, and the terminating character
30273 @samp{#} followed by a two-digit @var{checksum}:
30276 @code{$}@var{packet-data}@code{#}@var{checksum}
30280 @cindex checksum, for @value{GDBN} remote
30282 The two-digit @var{checksum} is computed as the modulo 256 sum of all
30283 characters between the leading @samp{$} and the trailing @samp{#} (an
30284 eight bit unsigned checksum).
30286 Implementors should note that prior to @value{GDBN} 5.0 the protocol
30287 specification also included an optional two-digit @var{sequence-id}:
30290 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
30293 @cindex sequence-id, for @value{GDBN} remote
30295 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
30296 has never output @var{sequence-id}s. Stubs that handle packets added
30297 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
30299 When either the host or the target machine receives a packet, the first
30300 response expected is an acknowledgment: either @samp{+} (to indicate
30301 the package was received correctly) or @samp{-} (to request
30305 -> @code{$}@var{packet-data}@code{#}@var{checksum}
30310 The @samp{+}/@samp{-} acknowledgments can be disabled
30311 once a connection is established.
30312 @xref{Packet Acknowledgment}, for details.
30314 The host (@value{GDBN}) sends @var{command}s, and the target (the
30315 debugging stub incorporated in your program) sends a @var{response}. In
30316 the case of step and continue @var{command}s, the response is only sent
30317 when the operation has completed, and the target has again stopped all
30318 threads in all attached processes. This is the default all-stop mode
30319 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
30320 execution mode; see @ref{Remote Non-Stop}, for details.
30322 @var{packet-data} consists of a sequence of characters with the
30323 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
30326 @cindex remote protocol, field separator
30327 Fields within the packet should be separated using @samp{,} @samp{;} or
30328 @samp{:}. Except where otherwise noted all numbers are represented in
30329 @sc{hex} with leading zeros suppressed.
30331 Implementors should note that prior to @value{GDBN} 5.0, the character
30332 @samp{:} could not appear as the third character in a packet (as it
30333 would potentially conflict with the @var{sequence-id}).
30335 @cindex remote protocol, binary data
30336 @anchor{Binary Data}
30337 Binary data in most packets is encoded either as two hexadecimal
30338 digits per byte of binary data. This allowed the traditional remote
30339 protocol to work over connections which were only seven-bit clean.
30340 Some packets designed more recently assume an eight-bit clean
30341 connection, and use a more efficient encoding to send and receive
30344 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
30345 as an escape character. Any escaped byte is transmitted as the escape
30346 character followed by the original character XORed with @code{0x20}.
30347 For example, the byte @code{0x7d} would be transmitted as the two
30348 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
30349 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
30350 @samp{@}}) must always be escaped. Responses sent by the stub
30351 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
30352 is not interpreted as the start of a run-length encoded sequence
30355 Response @var{data} can be run-length encoded to save space.
30356 Run-length encoding replaces runs of identical characters with one
30357 instance of the repeated character, followed by a @samp{*} and a
30358 repeat count. The repeat count is itself sent encoded, to avoid
30359 binary characters in @var{data}: a value of @var{n} is sent as
30360 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
30361 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
30362 code 32) for a repeat count of 3. (This is because run-length
30363 encoding starts to win for counts 3 or more.) Thus, for example,
30364 @samp{0* } is a run-length encoding of ``0000'': the space character
30365 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
30368 The printable characters @samp{#} and @samp{$} or with a numeric value
30369 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
30370 seven repeats (@samp{$}) can be expanded using a repeat count of only
30371 five (@samp{"}). For example, @samp{00000000} can be encoded as
30374 The error response returned for some packets includes a two character
30375 error number. That number is not well defined.
30377 @cindex empty response, for unsupported packets
30378 For any @var{command} not supported by the stub, an empty response
30379 (@samp{$#00}) should be returned. That way it is possible to extend the
30380 protocol. A newer @value{GDBN} can tell if a packet is supported based
30383 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
30384 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
30390 The following table provides a complete list of all currently defined
30391 @var{command}s and their corresponding response @var{data}.
30392 @xref{File-I/O Remote Protocol Extension}, for details about the File
30393 I/O extension of the remote protocol.
30395 Each packet's description has a template showing the packet's overall
30396 syntax, followed by an explanation of the packet's meaning. We
30397 include spaces in some of the templates for clarity; these are not
30398 part of the packet's syntax. No @value{GDBN} packet uses spaces to
30399 separate its components. For example, a template like @samp{foo
30400 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
30401 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
30402 @var{baz}. @value{GDBN} does not transmit a space character between the
30403 @samp{foo} and the @var{bar}, or between the @var{bar} and the
30406 @cindex @var{thread-id}, in remote protocol
30407 @anchor{thread-id syntax}
30408 Several packets and replies include a @var{thread-id} field to identify
30409 a thread. Normally these are positive numbers with a target-specific
30410 interpretation, formatted as big-endian hex strings. A @var{thread-id}
30411 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
30414 In addition, the remote protocol supports a multiprocess feature in
30415 which the @var{thread-id} syntax is extended to optionally include both
30416 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
30417 The @var{pid} (process) and @var{tid} (thread) components each have the
30418 format described above: a positive number with target-specific
30419 interpretation formatted as a big-endian hex string, literal @samp{-1}
30420 to indicate all processes or threads (respectively), or @samp{0} to
30421 indicate an arbitrary process or thread. Specifying just a process, as
30422 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
30423 error to specify all processes but a specific thread, such as
30424 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
30425 for those packets and replies explicitly documented to include a process
30426 ID, rather than a @var{thread-id}.
30428 The multiprocess @var{thread-id} syntax extensions are only used if both
30429 @value{GDBN} and the stub report support for the @samp{multiprocess}
30430 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
30433 Note that all packet forms beginning with an upper- or lower-case
30434 letter, other than those described here, are reserved for future use.
30436 Here are the packet descriptions.
30441 @cindex @samp{!} packet
30442 @anchor{extended mode}
30443 Enable extended mode. In extended mode, the remote server is made
30444 persistent. The @samp{R} packet is used to restart the program being
30450 The remote target both supports and has enabled extended mode.
30454 @cindex @samp{?} packet
30455 Indicate the reason the target halted. The reply is the same as for
30456 step and continue. This packet has a special interpretation when the
30457 target is in non-stop mode; see @ref{Remote Non-Stop}.
30460 @xref{Stop Reply Packets}, for the reply specifications.
30462 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
30463 @cindex @samp{A} packet
30464 Initialized @code{argv[]} array passed into program. @var{arglen}
30465 specifies the number of bytes in the hex encoded byte stream
30466 @var{arg}. See @code{gdbserver} for more details.
30471 The arguments were set.
30477 @cindex @samp{b} packet
30478 (Don't use this packet; its behavior is not well-defined.)
30479 Change the serial line speed to @var{baud}.
30481 JTC: @emph{When does the transport layer state change? When it's
30482 received, or after the ACK is transmitted. In either case, there are
30483 problems if the command or the acknowledgment packet is dropped.}
30485 Stan: @emph{If people really wanted to add something like this, and get
30486 it working for the first time, they ought to modify ser-unix.c to send
30487 some kind of out-of-band message to a specially-setup stub and have the
30488 switch happen "in between" packets, so that from remote protocol's point
30489 of view, nothing actually happened.}
30491 @item B @var{addr},@var{mode}
30492 @cindex @samp{B} packet
30493 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
30494 breakpoint at @var{addr}.
30496 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
30497 (@pxref{insert breakpoint or watchpoint packet}).
30499 @cindex @samp{bc} packet
30502 Backward continue. Execute the target system in reverse. No parameter.
30503 @xref{Reverse Execution}, for more information.
30506 @xref{Stop Reply Packets}, for the reply specifications.
30508 @cindex @samp{bs} packet
30511 Backward single step. Execute one instruction in reverse. No parameter.
30512 @xref{Reverse Execution}, for more information.
30515 @xref{Stop Reply Packets}, for the reply specifications.
30517 @item c @r{[}@var{addr}@r{]}
30518 @cindex @samp{c} packet
30519 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
30520 resume at current address.
30523 @xref{Stop Reply Packets}, for the reply specifications.
30525 @item C @var{sig}@r{[};@var{addr}@r{]}
30526 @cindex @samp{C} packet
30527 Continue with signal @var{sig} (hex signal number). If
30528 @samp{;@var{addr}} is omitted, resume at same address.
30531 @xref{Stop Reply Packets}, for the reply specifications.
30534 @cindex @samp{d} packet
30537 Don't use this packet; instead, define a general set packet
30538 (@pxref{General Query Packets}).
30542 @cindex @samp{D} packet
30543 The first form of the packet is used to detach @value{GDBN} from the
30544 remote system. It is sent to the remote target
30545 before @value{GDBN} disconnects via the @code{detach} command.
30547 The second form, including a process ID, is used when multiprocess
30548 protocol extensions are enabled (@pxref{multiprocess extensions}), to
30549 detach only a specific process. The @var{pid} is specified as a
30550 big-endian hex string.
30560 @item F @var{RC},@var{EE},@var{CF};@var{XX}
30561 @cindex @samp{F} packet
30562 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
30563 This is part of the File-I/O protocol extension. @xref{File-I/O
30564 Remote Protocol Extension}, for the specification.
30567 @anchor{read registers packet}
30568 @cindex @samp{g} packet
30569 Read general registers.
30573 @item @var{XX@dots{}}
30574 Each byte of register data is described by two hex digits. The bytes
30575 with the register are transmitted in target byte order. The size of
30576 each register and their position within the @samp{g} packet are
30577 determined by the @value{GDBN} internal gdbarch functions
30578 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
30579 specification of several standard @samp{g} packets is specified below.
30584 @item G @var{XX@dots{}}
30585 @cindex @samp{G} packet
30586 Write general registers. @xref{read registers packet}, for a
30587 description of the @var{XX@dots{}} data.
30597 @item H @var{c} @var{thread-id}
30598 @cindex @samp{H} packet
30599 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
30600 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
30601 should be @samp{c} for step and continue operations, @samp{g} for other
30602 operations. The thread designator @var{thread-id} has the format and
30603 interpretation described in @ref{thread-id syntax}.
30614 @c 'H': How restrictive (or permissive) is the thread model. If a
30615 @c thread is selected and stopped, are other threads allowed
30616 @c to continue to execute? As I mentioned above, I think the
30617 @c semantics of each command when a thread is selected must be
30618 @c described. For example:
30620 @c 'g': If the stub supports threads and a specific thread is
30621 @c selected, returns the register block from that thread;
30622 @c otherwise returns current registers.
30624 @c 'G' If the stub supports threads and a specific thread is
30625 @c selected, sets the registers of the register block of
30626 @c that thread; otherwise sets current registers.
30628 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
30629 @anchor{cycle step packet}
30630 @cindex @samp{i} packet
30631 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
30632 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
30633 step starting at that address.
30636 @cindex @samp{I} packet
30637 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
30641 @cindex @samp{k} packet
30644 FIXME: @emph{There is no description of how to operate when a specific
30645 thread context has been selected (i.e.@: does 'k' kill only that
30648 @item m @var{addr},@var{length}
30649 @cindex @samp{m} packet
30650 Read @var{length} bytes of memory starting at address @var{addr}.
30651 Note that @var{addr} may not be aligned to any particular boundary.
30653 The stub need not use any particular size or alignment when gathering
30654 data from memory for the response; even if @var{addr} is word-aligned
30655 and @var{length} is a multiple of the word size, the stub is free to
30656 use byte accesses, or not. For this reason, this packet may not be
30657 suitable for accessing memory-mapped I/O devices.
30658 @cindex alignment of remote memory accesses
30659 @cindex size of remote memory accesses
30660 @cindex memory, alignment and size of remote accesses
30664 @item @var{XX@dots{}}
30665 Memory contents; each byte is transmitted as a two-digit hexadecimal
30666 number. The reply may contain fewer bytes than requested if the
30667 server was able to read only part of the region of memory.
30672 @item M @var{addr},@var{length}:@var{XX@dots{}}
30673 @cindex @samp{M} packet
30674 Write @var{length} bytes of memory starting at address @var{addr}.
30675 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
30676 hexadecimal number.
30683 for an error (this includes the case where only part of the data was
30688 @cindex @samp{p} packet
30689 Read the value of register @var{n}; @var{n} is in hex.
30690 @xref{read registers packet}, for a description of how the returned
30691 register value is encoded.
30695 @item @var{XX@dots{}}
30696 the register's value
30700 Indicating an unrecognized @var{query}.
30703 @item P @var{n@dots{}}=@var{r@dots{}}
30704 @anchor{write register packet}
30705 @cindex @samp{P} packet
30706 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
30707 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
30708 digits for each byte in the register (target byte order).
30718 @item q @var{name} @var{params}@dots{}
30719 @itemx Q @var{name} @var{params}@dots{}
30720 @cindex @samp{q} packet
30721 @cindex @samp{Q} packet
30722 General query (@samp{q}) and set (@samp{Q}). These packets are
30723 described fully in @ref{General Query Packets}.
30726 @cindex @samp{r} packet
30727 Reset the entire system.
30729 Don't use this packet; use the @samp{R} packet instead.
30732 @cindex @samp{R} packet
30733 Restart the program being debugged. @var{XX}, while needed, is ignored.
30734 This packet is only available in extended mode (@pxref{extended mode}).
30736 The @samp{R} packet has no reply.
30738 @item s @r{[}@var{addr}@r{]}
30739 @cindex @samp{s} packet
30740 Single step. @var{addr} is the address at which to resume. If
30741 @var{addr} is omitted, resume at same address.
30744 @xref{Stop Reply Packets}, for the reply specifications.
30746 @item S @var{sig}@r{[};@var{addr}@r{]}
30747 @anchor{step with signal packet}
30748 @cindex @samp{S} packet
30749 Step with signal. This is analogous to the @samp{C} packet, but
30750 requests a single-step, rather than a normal resumption of execution.
30753 @xref{Stop Reply Packets}, for the reply specifications.
30755 @item t @var{addr}:@var{PP},@var{MM}
30756 @cindex @samp{t} packet
30757 Search backwards starting at address @var{addr} for a match with pattern
30758 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
30759 @var{addr} must be at least 3 digits.
30761 @item T @var{thread-id}
30762 @cindex @samp{T} packet
30763 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
30768 thread is still alive
30774 Packets starting with @samp{v} are identified by a multi-letter name,
30775 up to the first @samp{;} or @samp{?} (or the end of the packet).
30777 @item vAttach;@var{pid}
30778 @cindex @samp{vAttach} packet
30779 Attach to a new process with the specified process ID @var{pid}.
30780 The process ID is a
30781 hexadecimal integer identifying the process. In all-stop mode, all
30782 threads in the attached process are stopped; in non-stop mode, it may be
30783 attached without being stopped if that is supported by the target.
30785 @c In non-stop mode, on a successful vAttach, the stub should set the
30786 @c current thread to a thread of the newly-attached process. After
30787 @c attaching, GDB queries for the attached process's thread ID with qC.
30788 @c Also note that, from a user perspective, whether or not the
30789 @c target is stopped on attach in non-stop mode depends on whether you
30790 @c use the foreground or background version of the attach command, not
30791 @c on what vAttach does; GDB does the right thing with respect to either
30792 @c stopping or restarting threads.
30794 This packet is only available in extended mode (@pxref{extended mode}).
30800 @item @r{Any stop packet}
30801 for success in all-stop mode (@pxref{Stop Reply Packets})
30803 for success in non-stop mode (@pxref{Remote Non-Stop})
30806 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
30807 @cindex @samp{vCont} packet
30808 Resume the inferior, specifying different actions for each thread.
30809 If an action is specified with no @var{thread-id}, then it is applied to any
30810 threads that don't have a specific action specified; if no default action is
30811 specified then other threads should remain stopped in all-stop mode and
30812 in their current state in non-stop mode.
30813 Specifying multiple
30814 default actions is an error; specifying no actions is also an error.
30815 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
30817 Currently supported actions are:
30823 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
30827 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
30832 The optional argument @var{addr} normally associated with the
30833 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
30834 not supported in @samp{vCont}.
30836 The @samp{t} action is only relevant in non-stop mode
30837 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
30838 A stop reply should be generated for any affected thread not already stopped.
30839 When a thread is stopped by means of a @samp{t} action,
30840 the corresponding stop reply should indicate that the thread has stopped with
30841 signal @samp{0}, regardless of whether the target uses some other signal
30842 as an implementation detail.
30845 @xref{Stop Reply Packets}, for the reply specifications.
30848 @cindex @samp{vCont?} packet
30849 Request a list of actions supported by the @samp{vCont} packet.
30853 @item vCont@r{[};@var{action}@dots{}@r{]}
30854 The @samp{vCont} packet is supported. Each @var{action} is a supported
30855 command in the @samp{vCont} packet.
30857 The @samp{vCont} packet is not supported.
30860 @item vFile:@var{operation}:@var{parameter}@dots{}
30861 @cindex @samp{vFile} packet
30862 Perform a file operation on the target system. For details,
30863 see @ref{Host I/O Packets}.
30865 @item vFlashErase:@var{addr},@var{length}
30866 @cindex @samp{vFlashErase} packet
30867 Direct the stub to erase @var{length} bytes of flash starting at
30868 @var{addr}. The region may enclose any number of flash blocks, but
30869 its start and end must fall on block boundaries, as indicated by the
30870 flash block size appearing in the memory map (@pxref{Memory Map
30871 Format}). @value{GDBN} groups flash memory programming operations
30872 together, and sends a @samp{vFlashDone} request after each group; the
30873 stub is allowed to delay erase operation until the @samp{vFlashDone}
30874 packet is received.
30876 The stub must support @samp{vCont} if it reports support for
30877 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
30878 this case @samp{vCont} actions can be specified to apply to all threads
30879 in a process by using the @samp{p@var{pid}.-1} form of the
30890 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
30891 @cindex @samp{vFlashWrite} packet
30892 Direct the stub to write data to flash address @var{addr}. The data
30893 is passed in binary form using the same encoding as for the @samp{X}
30894 packet (@pxref{Binary Data}). The memory ranges specified by
30895 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
30896 not overlap, and must appear in order of increasing addresses
30897 (although @samp{vFlashErase} packets for higher addresses may already
30898 have been received; the ordering is guaranteed only between
30899 @samp{vFlashWrite} packets). If a packet writes to an address that was
30900 neither erased by a preceding @samp{vFlashErase} packet nor by some other
30901 target-specific method, the results are unpredictable.
30909 for vFlashWrite addressing non-flash memory
30915 @cindex @samp{vFlashDone} packet
30916 Indicate to the stub that flash programming operation is finished.
30917 The stub is permitted to delay or batch the effects of a group of
30918 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
30919 @samp{vFlashDone} packet is received. The contents of the affected
30920 regions of flash memory are unpredictable until the @samp{vFlashDone}
30921 request is completed.
30923 @item vKill;@var{pid}
30924 @cindex @samp{vKill} packet
30925 Kill the process with the specified process ID. @var{pid} is a
30926 hexadecimal integer identifying the process. This packet is used in
30927 preference to @samp{k} when multiprocess protocol extensions are
30928 supported; see @ref{multiprocess extensions}.
30938 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
30939 @cindex @samp{vRun} packet
30940 Run the program @var{filename}, passing it each @var{argument} on its
30941 command line. The file and arguments are hex-encoded strings. If
30942 @var{filename} is an empty string, the stub may use a default program
30943 (e.g.@: the last program run). The program is created in the stopped
30946 @c FIXME: What about non-stop mode?
30948 This packet is only available in extended mode (@pxref{extended mode}).
30954 @item @r{Any stop packet}
30955 for success (@pxref{Stop Reply Packets})
30959 @anchor{vStopped packet}
30960 @cindex @samp{vStopped} packet
30962 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
30963 reply and prompt for the stub to report another one.
30967 @item @r{Any stop packet}
30968 if there is another unreported stop event (@pxref{Stop Reply Packets})
30970 if there are no unreported stop events
30973 @item X @var{addr},@var{length}:@var{XX@dots{}}
30975 @cindex @samp{X} packet
30976 Write data to memory, where the data is transmitted in binary.
30977 @var{addr} is address, @var{length} is number of bytes,
30978 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
30988 @item z @var{type},@var{addr},@var{kind}
30989 @itemx Z @var{type},@var{addr},@var{kind}
30990 @anchor{insert breakpoint or watchpoint packet}
30991 @cindex @samp{z} packet
30992 @cindex @samp{Z} packets
30993 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
30994 watchpoint starting at address @var{address} of kind @var{kind}.
30996 Each breakpoint and watchpoint packet @var{type} is documented
30999 @emph{Implementation notes: A remote target shall return an empty string
31000 for an unrecognized breakpoint or watchpoint packet @var{type}. A
31001 remote target shall support either both or neither of a given
31002 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
31003 avoid potential problems with duplicate packets, the operations should
31004 be implemented in an idempotent way.}
31006 @item z0,@var{addr},@var{kind}
31007 @itemx Z0,@var{addr},@var{kind}
31008 @cindex @samp{z0} packet
31009 @cindex @samp{Z0} packet
31010 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
31011 @var{addr} of type @var{kind}.
31013 A memory breakpoint is implemented by replacing the instruction at
31014 @var{addr} with a software breakpoint or trap instruction. The
31015 @var{kind} is target-specific and typically indicates the size of
31016 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
31017 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
31018 architectures have additional meanings for @var{kind};
31019 see @ref{Architecture-Specific Protocol Details}.
31021 @emph{Implementation note: It is possible for a target to copy or move
31022 code that contains memory breakpoints (e.g., when implementing
31023 overlays). The behavior of this packet, in the presence of such a
31024 target, is not defined.}
31036 @item z1,@var{addr},@var{kind}
31037 @itemx Z1,@var{addr},@var{kind}
31038 @cindex @samp{z1} packet
31039 @cindex @samp{Z1} packet
31040 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
31041 address @var{addr}.
31043 A hardware breakpoint is implemented using a mechanism that is not
31044 dependant on being able to modify the target's memory. @var{kind}
31045 has the same meaning as in @samp{Z0} packets.
31047 @emph{Implementation note: A hardware breakpoint is not affected by code
31060 @item z2,@var{addr},@var{kind}
31061 @itemx Z2,@var{addr},@var{kind}
31062 @cindex @samp{z2} packet
31063 @cindex @samp{Z2} packet
31064 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
31065 @var{kind} is interpreted as the number of bytes to watch.
31077 @item z3,@var{addr},@var{kind}
31078 @itemx Z3,@var{addr},@var{kind}
31079 @cindex @samp{z3} packet
31080 @cindex @samp{Z3} packet
31081 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
31082 @var{kind} is interpreted as the number of bytes to watch.
31094 @item z4,@var{addr},@var{kind}
31095 @itemx Z4,@var{addr},@var{kind}
31096 @cindex @samp{z4} packet
31097 @cindex @samp{Z4} packet
31098 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
31099 @var{kind} is interpreted as the number of bytes to watch.
31113 @node Stop Reply Packets
31114 @section Stop Reply Packets
31115 @cindex stop reply packets
31117 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
31118 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
31119 receive any of the below as a reply. Except for @samp{?}
31120 and @samp{vStopped}, that reply is only returned
31121 when the target halts. In the below the exact meaning of @dfn{signal
31122 number} is defined by the header @file{include/gdb/signals.h} in the
31123 @value{GDBN} source code.
31125 As in the description of request packets, we include spaces in the
31126 reply templates for clarity; these are not part of the reply packet's
31127 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
31133 The program received signal number @var{AA} (a two-digit hexadecimal
31134 number). This is equivalent to a @samp{T} response with no
31135 @var{n}:@var{r} pairs.
31137 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
31138 @cindex @samp{T} packet reply
31139 The program received signal number @var{AA} (a two-digit hexadecimal
31140 number). This is equivalent to an @samp{S} response, except that the
31141 @samp{@var{n}:@var{r}} pairs can carry values of important registers
31142 and other information directly in the stop reply packet, reducing
31143 round-trip latency. Single-step and breakpoint traps are reported
31144 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
31148 If @var{n} is a hexadecimal number, it is a register number, and the
31149 corresponding @var{r} gives that register's value. @var{r} is a
31150 series of bytes in target byte order, with each byte given by a
31151 two-digit hex number.
31154 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
31155 the stopped thread, as specified in @ref{thread-id syntax}.
31158 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
31159 the core on which the stop event was detected.
31162 If @var{n} is a recognized @dfn{stop reason}, it describes a more
31163 specific event that stopped the target. The currently defined stop
31164 reasons are listed below. @var{aa} should be @samp{05}, the trap
31165 signal. At most one stop reason should be present.
31168 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
31169 and go on to the next; this allows us to extend the protocol in the
31173 The currently defined stop reasons are:
31179 The packet indicates a watchpoint hit, and @var{r} is the data address, in
31182 @cindex shared library events, remote reply
31184 The packet indicates that the loaded libraries have changed.
31185 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
31186 list of loaded libraries. @var{r} is ignored.
31188 @cindex replay log events, remote reply
31190 The packet indicates that the target cannot continue replaying
31191 logged execution events, because it has reached the end (or the
31192 beginning when executing backward) of the log. The value of @var{r}
31193 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
31194 for more information.
31198 @itemx W @var{AA} ; process:@var{pid}
31199 The process exited, and @var{AA} is the exit status. This is only
31200 applicable to certain targets.
31202 The second form of the response, including the process ID of the exited
31203 process, can be used only when @value{GDBN} has reported support for
31204 multiprocess protocol extensions; see @ref{multiprocess extensions}.
31205 The @var{pid} is formatted as a big-endian hex string.
31208 @itemx X @var{AA} ; process:@var{pid}
31209 The process terminated with signal @var{AA}.
31211 The second form of the response, including the process ID of the
31212 terminated process, can be used only when @value{GDBN} has reported
31213 support for multiprocess protocol extensions; see @ref{multiprocess
31214 extensions}. The @var{pid} is formatted as a big-endian hex string.
31216 @item O @var{XX}@dots{}
31217 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
31218 written as the program's console output. This can happen at any time
31219 while the program is running and the debugger should continue to wait
31220 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
31222 @item F @var{call-id},@var{parameter}@dots{}
31223 @var{call-id} is the identifier which says which host system call should
31224 be called. This is just the name of the function. Translation into the
31225 correct system call is only applicable as it's defined in @value{GDBN}.
31226 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
31229 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
31230 this very system call.
31232 The target replies with this packet when it expects @value{GDBN} to
31233 call a host system call on behalf of the target. @value{GDBN} replies
31234 with an appropriate @samp{F} packet and keeps up waiting for the next
31235 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
31236 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
31237 Protocol Extension}, for more details.
31241 @node General Query Packets
31242 @section General Query Packets
31243 @cindex remote query requests
31245 Packets starting with @samp{q} are @dfn{general query packets};
31246 packets starting with @samp{Q} are @dfn{general set packets}. General
31247 query and set packets are a semi-unified form for retrieving and
31248 sending information to and from the stub.
31250 The initial letter of a query or set packet is followed by a name
31251 indicating what sort of thing the packet applies to. For example,
31252 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
31253 definitions with the stub. These packet names follow some
31258 The name must not contain commas, colons or semicolons.
31260 Most @value{GDBN} query and set packets have a leading upper case
31263 The names of custom vendor packets should use a company prefix, in
31264 lower case, followed by a period. For example, packets designed at
31265 the Acme Corporation might begin with @samp{qacme.foo} (for querying
31266 foos) or @samp{Qacme.bar} (for setting bars).
31269 The name of a query or set packet should be separated from any
31270 parameters by a @samp{:}; the parameters themselves should be
31271 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
31272 full packet name, and check for a separator or the end of the packet,
31273 in case two packet names share a common prefix. New packets should not begin
31274 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
31275 packets predate these conventions, and have arguments without any terminator
31276 for the packet name; we suspect they are in widespread use in places that
31277 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
31278 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
31281 Like the descriptions of the other packets, each description here
31282 has a template showing the packet's overall syntax, followed by an
31283 explanation of the packet's meaning. We include spaces in some of the
31284 templates for clarity; these are not part of the packet's syntax. No
31285 @value{GDBN} packet uses spaces to separate its components.
31287 Here are the currently defined query and set packets:
31291 @item QAllow:@var{op}:@var{val}@dots{}
31292 @cindex @samp{QAllow} packet
31293 Specify which operations @value{GDBN} expects to request of the
31294 target, as a semicolon-separated list of operation name and value
31295 pairs. Possible values for @var{op} include @samp{WriteReg},
31296 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
31297 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
31298 indicating that @value{GDBN} will not request the operation, or 1,
31299 indicating that it may. (The target can then use this to set up its
31300 own internals optimally, for instance if the debugger never expects to
31301 insert breakpoints, it may not need to install its own trap handler.)
31304 @cindex current thread, remote request
31305 @cindex @samp{qC} packet
31306 Return the current thread ID.
31310 @item QC @var{thread-id}
31311 Where @var{thread-id} is a thread ID as documented in
31312 @ref{thread-id syntax}.
31313 @item @r{(anything else)}
31314 Any other reply implies the old thread ID.
31317 @item qCRC:@var{addr},@var{length}
31318 @cindex CRC of memory block, remote request
31319 @cindex @samp{qCRC} packet
31320 Compute the CRC checksum of a block of memory using CRC-32 defined in
31321 IEEE 802.3. The CRC is computed byte at a time, taking the most
31322 significant bit of each byte first. The initial pattern code
31323 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
31325 @emph{Note:} This is the same CRC used in validating separate debug
31326 files (@pxref{Separate Debug Files, , Debugging Information in Separate
31327 Files}). However the algorithm is slightly different. When validating
31328 separate debug files, the CRC is computed taking the @emph{least}
31329 significant bit of each byte first, and the final result is inverted to
31330 detect trailing zeros.
31335 An error (such as memory fault)
31336 @item C @var{crc32}
31337 The specified memory region's checksum is @var{crc32}.
31341 @itemx qsThreadInfo
31342 @cindex list active threads, remote request
31343 @cindex @samp{qfThreadInfo} packet
31344 @cindex @samp{qsThreadInfo} packet
31345 Obtain a list of all active thread IDs from the target (OS). Since there
31346 may be too many active threads to fit into one reply packet, this query
31347 works iteratively: it may require more than one query/reply sequence to
31348 obtain the entire list of threads. The first query of the sequence will
31349 be the @samp{qfThreadInfo} query; subsequent queries in the
31350 sequence will be the @samp{qsThreadInfo} query.
31352 NOTE: This packet replaces the @samp{qL} query (see below).
31356 @item m @var{thread-id}
31358 @item m @var{thread-id},@var{thread-id}@dots{}
31359 a comma-separated list of thread IDs
31361 (lower case letter @samp{L}) denotes end of list.
31364 In response to each query, the target will reply with a list of one or
31365 more thread IDs, separated by commas.
31366 @value{GDBN} will respond to each reply with a request for more thread
31367 ids (using the @samp{qs} form of the query), until the target responds
31368 with @samp{l} (lower-case el, for @dfn{last}).
31369 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
31372 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
31373 @cindex get thread-local storage address, remote request
31374 @cindex @samp{qGetTLSAddr} packet
31375 Fetch the address associated with thread local storage specified
31376 by @var{thread-id}, @var{offset}, and @var{lm}.
31378 @var{thread-id} is the thread ID associated with the
31379 thread for which to fetch the TLS address. @xref{thread-id syntax}.
31381 @var{offset} is the (big endian, hex encoded) offset associated with the
31382 thread local variable. (This offset is obtained from the debug
31383 information associated with the variable.)
31385 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
31386 the load module associated with the thread local storage. For example,
31387 a @sc{gnu}/Linux system will pass the link map address of the shared
31388 object associated with the thread local storage under consideration.
31389 Other operating environments may choose to represent the load module
31390 differently, so the precise meaning of this parameter will vary.
31394 @item @var{XX}@dots{}
31395 Hex encoded (big endian) bytes representing the address of the thread
31396 local storage requested.
31399 An error occurred. @var{nn} are hex digits.
31402 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
31405 @item qGetTIBAddr:@var{thread-id}
31406 @cindex get thread information block address
31407 @cindex @samp{qGetTIBAddr} packet
31408 Fetch address of the Windows OS specific Thread Information Block.
31410 @var{thread-id} is the thread ID associated with the thread.
31414 @item @var{XX}@dots{}
31415 Hex encoded (big endian) bytes representing the linear address of the
31416 thread information block.
31419 An error occured. This means that either the thread was not found, or the
31420 address could not be retrieved.
31423 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
31426 @item qL @var{startflag} @var{threadcount} @var{nextthread}
31427 Obtain thread information from RTOS. Where: @var{startflag} (one hex
31428 digit) is one to indicate the first query and zero to indicate a
31429 subsequent query; @var{threadcount} (two hex digits) is the maximum
31430 number of threads the response packet can contain; and @var{nextthread}
31431 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
31432 returned in the response as @var{argthread}.
31434 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
31438 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
31439 Where: @var{count} (two hex digits) is the number of threads being
31440 returned; @var{done} (one hex digit) is zero to indicate more threads
31441 and one indicates no further threads; @var{argthreadid} (eight hex
31442 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
31443 is a sequence of thread IDs from the target. @var{threadid} (eight hex
31444 digits). See @code{remote.c:parse_threadlist_response()}.
31448 @cindex section offsets, remote request
31449 @cindex @samp{qOffsets} packet
31450 Get section offsets that the target used when relocating the downloaded
31455 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
31456 Relocate the @code{Text} section by @var{xxx} from its original address.
31457 Relocate the @code{Data} section by @var{yyy} from its original address.
31458 If the object file format provides segment information (e.g.@: @sc{elf}
31459 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
31460 segments by the supplied offsets.
31462 @emph{Note: while a @code{Bss} offset may be included in the response,
31463 @value{GDBN} ignores this and instead applies the @code{Data} offset
31464 to the @code{Bss} section.}
31466 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
31467 Relocate the first segment of the object file, which conventionally
31468 contains program code, to a starting address of @var{xxx}. If
31469 @samp{DataSeg} is specified, relocate the second segment, which
31470 conventionally contains modifiable data, to a starting address of
31471 @var{yyy}. @value{GDBN} will report an error if the object file
31472 does not contain segment information, or does not contain at least
31473 as many segments as mentioned in the reply. Extra segments are
31474 kept at fixed offsets relative to the last relocated segment.
31477 @item qP @var{mode} @var{thread-id}
31478 @cindex thread information, remote request
31479 @cindex @samp{qP} packet
31480 Returns information on @var{thread-id}. Where: @var{mode} is a hex
31481 encoded 32 bit mode; @var{thread-id} is a thread ID
31482 (@pxref{thread-id syntax}).
31484 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
31487 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
31491 @cindex non-stop mode, remote request
31492 @cindex @samp{QNonStop} packet
31494 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
31495 @xref{Remote Non-Stop}, for more information.
31500 The request succeeded.
31503 An error occurred. @var{nn} are hex digits.
31506 An empty reply indicates that @samp{QNonStop} is not supported by
31510 This packet is not probed by default; the remote stub must request it,
31511 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31512 Use of this packet is controlled by the @code{set non-stop} command;
31513 @pxref{Non-Stop Mode}.
31515 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
31516 @cindex pass signals to inferior, remote request
31517 @cindex @samp{QPassSignals} packet
31518 @anchor{QPassSignals}
31519 Each listed @var{signal} should be passed directly to the inferior process.
31520 Signals are numbered identically to continue packets and stop replies
31521 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
31522 strictly greater than the previous item. These signals do not need to stop
31523 the inferior, or be reported to @value{GDBN}. All other signals should be
31524 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
31525 combine; any earlier @samp{QPassSignals} list is completely replaced by the
31526 new list. This packet improves performance when using @samp{handle
31527 @var{signal} nostop noprint pass}.
31532 The request succeeded.
31535 An error occurred. @var{nn} are hex digits.
31538 An empty reply indicates that @samp{QPassSignals} is not supported by
31542 Use of this packet is controlled by the @code{set remote pass-signals}
31543 command (@pxref{Remote Configuration, set remote pass-signals}).
31544 This packet is not probed by default; the remote stub must request it,
31545 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31547 @item qRcmd,@var{command}
31548 @cindex execute remote command, remote request
31549 @cindex @samp{qRcmd} packet
31550 @var{command} (hex encoded) is passed to the local interpreter for
31551 execution. Invalid commands should be reported using the output
31552 string. Before the final result packet, the target may also respond
31553 with a number of intermediate @samp{O@var{output}} console output
31554 packets. @emph{Implementors should note that providing access to a
31555 stubs's interpreter may have security implications}.
31560 A command response with no output.
31562 A command response with the hex encoded output string @var{OUTPUT}.
31564 Indicate a badly formed request.
31566 An empty reply indicates that @samp{qRcmd} is not recognized.
31569 (Note that the @code{qRcmd} packet's name is separated from the
31570 command by a @samp{,}, not a @samp{:}, contrary to the naming
31571 conventions above. Please don't use this packet as a model for new
31574 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
31575 @cindex searching memory, in remote debugging
31576 @cindex @samp{qSearch:memory} packet
31577 @anchor{qSearch memory}
31578 Search @var{length} bytes at @var{address} for @var{search-pattern}.
31579 @var{address} and @var{length} are encoded in hex.
31580 @var{search-pattern} is a sequence of bytes, hex encoded.
31585 The pattern was not found.
31587 The pattern was found at @var{address}.
31589 A badly formed request or an error was encountered while searching memory.
31591 An empty reply indicates that @samp{qSearch:memory} is not recognized.
31594 @item QStartNoAckMode
31595 @cindex @samp{QStartNoAckMode} packet
31596 @anchor{QStartNoAckMode}
31597 Request that the remote stub disable the normal @samp{+}/@samp{-}
31598 protocol acknowledgments (@pxref{Packet Acknowledgment}).
31603 The stub has switched to no-acknowledgment mode.
31604 @value{GDBN} acknowledges this reponse,
31605 but neither the stub nor @value{GDBN} shall send or expect further
31606 @samp{+}/@samp{-} acknowledgments in the current connection.
31608 An empty reply indicates that the stub does not support no-acknowledgment mode.
31611 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
31612 @cindex supported packets, remote query
31613 @cindex features of the remote protocol
31614 @cindex @samp{qSupported} packet
31615 @anchor{qSupported}
31616 Tell the remote stub about features supported by @value{GDBN}, and
31617 query the stub for features it supports. This packet allows
31618 @value{GDBN} and the remote stub to take advantage of each others'
31619 features. @samp{qSupported} also consolidates multiple feature probes
31620 at startup, to improve @value{GDBN} performance---a single larger
31621 packet performs better than multiple smaller probe packets on
31622 high-latency links. Some features may enable behavior which must not
31623 be on by default, e.g.@: because it would confuse older clients or
31624 stubs. Other features may describe packets which could be
31625 automatically probed for, but are not. These features must be
31626 reported before @value{GDBN} will use them. This ``default
31627 unsupported'' behavior is not appropriate for all packets, but it
31628 helps to keep the initial connection time under control with new
31629 versions of @value{GDBN} which support increasing numbers of packets.
31633 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
31634 The stub supports or does not support each returned @var{stubfeature},
31635 depending on the form of each @var{stubfeature} (see below for the
31638 An empty reply indicates that @samp{qSupported} is not recognized,
31639 or that no features needed to be reported to @value{GDBN}.
31642 The allowed forms for each feature (either a @var{gdbfeature} in the
31643 @samp{qSupported} packet, or a @var{stubfeature} in the response)
31647 @item @var{name}=@var{value}
31648 The remote protocol feature @var{name} is supported, and associated
31649 with the specified @var{value}. The format of @var{value} depends
31650 on the feature, but it must not include a semicolon.
31652 The remote protocol feature @var{name} is supported, and does not
31653 need an associated value.
31655 The remote protocol feature @var{name} is not supported.
31657 The remote protocol feature @var{name} may be supported, and
31658 @value{GDBN} should auto-detect support in some other way when it is
31659 needed. This form will not be used for @var{gdbfeature} notifications,
31660 but may be used for @var{stubfeature} responses.
31663 Whenever the stub receives a @samp{qSupported} request, the
31664 supplied set of @value{GDBN} features should override any previous
31665 request. This allows @value{GDBN} to put the stub in a known
31666 state, even if the stub had previously been communicating with
31667 a different version of @value{GDBN}.
31669 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
31674 This feature indicates whether @value{GDBN} supports multiprocess
31675 extensions to the remote protocol. @value{GDBN} does not use such
31676 extensions unless the stub also reports that it supports them by
31677 including @samp{multiprocess+} in its @samp{qSupported} reply.
31678 @xref{multiprocess extensions}, for details.
31681 This feature indicates that @value{GDBN} supports the XML target
31682 description. If the stub sees @samp{xmlRegisters=} with target
31683 specific strings separated by a comma, it will report register
31687 This feature indicates whether @value{GDBN} supports the
31688 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
31689 instruction reply packet}).
31692 Stubs should ignore any unknown values for
31693 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
31694 packet supports receiving packets of unlimited length (earlier
31695 versions of @value{GDBN} may reject overly long responses). Additional values
31696 for @var{gdbfeature} may be defined in the future to let the stub take
31697 advantage of new features in @value{GDBN}, e.g.@: incompatible
31698 improvements in the remote protocol---the @samp{multiprocess} feature is
31699 an example of such a feature. The stub's reply should be independent
31700 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
31701 describes all the features it supports, and then the stub replies with
31702 all the features it supports.
31704 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
31705 responses, as long as each response uses one of the standard forms.
31707 Some features are flags. A stub which supports a flag feature
31708 should respond with a @samp{+} form response. Other features
31709 require values, and the stub should respond with an @samp{=}
31712 Each feature has a default value, which @value{GDBN} will use if
31713 @samp{qSupported} is not available or if the feature is not mentioned
31714 in the @samp{qSupported} response. The default values are fixed; a
31715 stub is free to omit any feature responses that match the defaults.
31717 Not all features can be probed, but for those which can, the probing
31718 mechanism is useful: in some cases, a stub's internal
31719 architecture may not allow the protocol layer to know some information
31720 about the underlying target in advance. This is especially common in
31721 stubs which may be configured for multiple targets.
31723 These are the currently defined stub features and their properties:
31725 @multitable @columnfractions 0.35 0.2 0.12 0.2
31726 @c NOTE: The first row should be @headitem, but we do not yet require
31727 @c a new enough version of Texinfo (4.7) to use @headitem.
31729 @tab Value Required
31733 @item @samp{PacketSize}
31738 @item @samp{qXfer:auxv:read}
31743 @item @samp{qXfer:features:read}
31748 @item @samp{qXfer:libraries:read}
31753 @item @samp{qXfer:memory-map:read}
31758 @item @samp{qXfer:spu:read}
31763 @item @samp{qXfer:spu:write}
31768 @item @samp{qXfer:siginfo:read}
31773 @item @samp{qXfer:siginfo:write}
31778 @item @samp{qXfer:threads:read}
31784 @item @samp{QNonStop}
31789 @item @samp{QPassSignals}
31794 @item @samp{QStartNoAckMode}
31799 @item @samp{multiprocess}
31804 @item @samp{ConditionalTracepoints}
31809 @item @samp{ReverseContinue}
31814 @item @samp{ReverseStep}
31819 @item @samp{TracepointSource}
31824 @item @samp{QAllow}
31831 These are the currently defined stub features, in more detail:
31834 @cindex packet size, remote protocol
31835 @item PacketSize=@var{bytes}
31836 The remote stub can accept packets up to at least @var{bytes} in
31837 length. @value{GDBN} will send packets up to this size for bulk
31838 transfers, and will never send larger packets. This is a limit on the
31839 data characters in the packet, including the frame and checksum.
31840 There is no trailing NUL byte in a remote protocol packet; if the stub
31841 stores packets in a NUL-terminated format, it should allow an extra
31842 byte in its buffer for the NUL. If this stub feature is not supported,
31843 @value{GDBN} guesses based on the size of the @samp{g} packet response.
31845 @item qXfer:auxv:read
31846 The remote stub understands the @samp{qXfer:auxv:read} packet
31847 (@pxref{qXfer auxiliary vector read}).
31849 @item qXfer:features:read
31850 The remote stub understands the @samp{qXfer:features:read} packet
31851 (@pxref{qXfer target description read}).
31853 @item qXfer:libraries:read
31854 The remote stub understands the @samp{qXfer:libraries:read} packet
31855 (@pxref{qXfer library list read}).
31857 @item qXfer:memory-map:read
31858 The remote stub understands the @samp{qXfer:memory-map:read} packet
31859 (@pxref{qXfer memory map read}).
31861 @item qXfer:spu:read
31862 The remote stub understands the @samp{qXfer:spu:read} packet
31863 (@pxref{qXfer spu read}).
31865 @item qXfer:spu:write
31866 The remote stub understands the @samp{qXfer:spu:write} packet
31867 (@pxref{qXfer spu write}).
31869 @item qXfer:siginfo:read
31870 The remote stub understands the @samp{qXfer:siginfo:read} packet
31871 (@pxref{qXfer siginfo read}).
31873 @item qXfer:siginfo:write
31874 The remote stub understands the @samp{qXfer:siginfo:write} packet
31875 (@pxref{qXfer siginfo write}).
31877 @item qXfer:threads:read
31878 The remote stub understands the @samp{qXfer:threads:read} packet
31879 (@pxref{qXfer threads read}).
31882 The remote stub understands the @samp{QNonStop} packet
31883 (@pxref{QNonStop}).
31886 The remote stub understands the @samp{QPassSignals} packet
31887 (@pxref{QPassSignals}).
31889 @item QStartNoAckMode
31890 The remote stub understands the @samp{QStartNoAckMode} packet and
31891 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
31894 @anchor{multiprocess extensions}
31895 @cindex multiprocess extensions, in remote protocol
31896 The remote stub understands the multiprocess extensions to the remote
31897 protocol syntax. The multiprocess extensions affect the syntax of
31898 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
31899 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
31900 replies. Note that reporting this feature indicates support for the
31901 syntactic extensions only, not that the stub necessarily supports
31902 debugging of more than one process at a time. The stub must not use
31903 multiprocess extensions in packet replies unless @value{GDBN} has also
31904 indicated it supports them in its @samp{qSupported} request.
31906 @item qXfer:osdata:read
31907 The remote stub understands the @samp{qXfer:osdata:read} packet
31908 ((@pxref{qXfer osdata read}).
31910 @item ConditionalTracepoints
31911 The remote stub accepts and implements conditional expressions defined
31912 for tracepoints (@pxref{Tracepoint Conditions}).
31914 @item ReverseContinue
31915 The remote stub accepts and implements the reverse continue packet
31919 The remote stub accepts and implements the reverse step packet
31922 @item TracepointSource
31923 The remote stub understands the @samp{QTDPsrc} packet that supplies
31924 the source form of tracepoint definitions.
31927 The remote stub understands the @samp{QAllow} packet.
31932 @cindex symbol lookup, remote request
31933 @cindex @samp{qSymbol} packet
31934 Notify the target that @value{GDBN} is prepared to serve symbol lookup
31935 requests. Accept requests from the target for the values of symbols.
31940 The target does not need to look up any (more) symbols.
31941 @item qSymbol:@var{sym_name}
31942 The target requests the value of symbol @var{sym_name} (hex encoded).
31943 @value{GDBN} may provide the value by using the
31944 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
31948 @item qSymbol:@var{sym_value}:@var{sym_name}
31949 Set the value of @var{sym_name} to @var{sym_value}.
31951 @var{sym_name} (hex encoded) is the name of a symbol whose value the
31952 target has previously requested.
31954 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
31955 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
31961 The target does not need to look up any (more) symbols.
31962 @item qSymbol:@var{sym_name}
31963 The target requests the value of a new symbol @var{sym_name} (hex
31964 encoded). @value{GDBN} will continue to supply the values of symbols
31965 (if available), until the target ceases to request them.
31970 @item QTDisconnected
31977 @xref{Tracepoint Packets}.
31979 @item qThreadExtraInfo,@var{thread-id}
31980 @cindex thread attributes info, remote request
31981 @cindex @samp{qThreadExtraInfo} packet
31982 Obtain a printable string description of a thread's attributes from
31983 the target OS. @var{thread-id} is a thread ID;
31984 see @ref{thread-id syntax}. This
31985 string may contain anything that the target OS thinks is interesting
31986 for @value{GDBN} to tell the user about the thread. The string is
31987 displayed in @value{GDBN}'s @code{info threads} display. Some
31988 examples of possible thread extra info strings are @samp{Runnable}, or
31989 @samp{Blocked on Mutex}.
31993 @item @var{XX}@dots{}
31994 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
31995 comprising the printable string containing the extra information about
31996 the thread's attributes.
31999 (Note that the @code{qThreadExtraInfo} packet's name is separated from
32000 the command by a @samp{,}, not a @samp{:}, contrary to the naming
32001 conventions above. Please don't use this packet as a model for new
32013 @xref{Tracepoint Packets}.
32015 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
32016 @cindex read special object, remote request
32017 @cindex @samp{qXfer} packet
32018 @anchor{qXfer read}
32019 Read uninterpreted bytes from the target's special data area
32020 identified by the keyword @var{object}. Request @var{length} bytes
32021 starting at @var{offset} bytes into the data. The content and
32022 encoding of @var{annex} is specific to @var{object}; it can supply
32023 additional details about what data to access.
32025 Here are the specific requests of this form defined so far. All
32026 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
32027 formats, listed below.
32030 @item qXfer:auxv:read::@var{offset},@var{length}
32031 @anchor{qXfer auxiliary vector read}
32032 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
32033 auxiliary vector}. Note @var{annex} must be empty.
32035 This packet is not probed by default; the remote stub must request it,
32036 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32038 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
32039 @anchor{qXfer target description read}
32040 Access the @dfn{target description}. @xref{Target Descriptions}. The
32041 annex specifies which XML document to access. The main description is
32042 always loaded from the @samp{target.xml} annex.
32044 This packet is not probed by default; the remote stub must request it,
32045 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32047 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
32048 @anchor{qXfer library list read}
32049 Access the target's list of loaded libraries. @xref{Library List Format}.
32050 The annex part of the generic @samp{qXfer} packet must be empty
32051 (@pxref{qXfer read}).
32053 Targets which maintain a list of libraries in the program's memory do
32054 not need to implement this packet; it is designed for platforms where
32055 the operating system manages the list of loaded libraries.
32057 This packet is not probed by default; the remote stub must request it,
32058 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32060 @item qXfer:memory-map:read::@var{offset},@var{length}
32061 @anchor{qXfer memory map read}
32062 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
32063 annex part of the generic @samp{qXfer} packet must be empty
32064 (@pxref{qXfer read}).
32066 This packet is not probed by default; the remote stub must request it,
32067 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32069 @item qXfer:siginfo:read::@var{offset},@var{length}
32070 @anchor{qXfer siginfo read}
32071 Read contents of the extra signal information on the target
32072 system. The annex part of the generic @samp{qXfer} packet must be
32073 empty (@pxref{qXfer read}).
32075 This packet is not probed by default; the remote stub must request it,
32076 by supplying an appropriate @samp{qSupported} response
32077 (@pxref{qSupported}).
32079 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
32080 @anchor{qXfer spu read}
32081 Read contents of an @code{spufs} file on the target system. The
32082 annex specifies which file to read; it must be of the form
32083 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
32084 in the target process, and @var{name} identifes the @code{spufs} file
32085 in that context to be accessed.
32087 This packet is not probed by default; the remote stub must request it,
32088 by supplying an appropriate @samp{qSupported} response
32089 (@pxref{qSupported}).
32091 @item qXfer:threads:read::@var{offset},@var{length}
32092 @anchor{qXfer threads read}
32093 Access the list of threads on target. @xref{Thread List Format}. The
32094 annex part of the generic @samp{qXfer} packet must be empty
32095 (@pxref{qXfer read}).
32097 This packet is not probed by default; the remote stub must request it,
32098 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32100 @item qXfer:osdata:read::@var{offset},@var{length}
32101 @anchor{qXfer osdata read}
32102 Access the target's @dfn{operating system information}.
32103 @xref{Operating System Information}.
32110 Data @var{data} (@pxref{Binary Data}) has been read from the
32111 target. There may be more data at a higher address (although
32112 it is permitted to return @samp{m} even for the last valid
32113 block of data, as long as at least one byte of data was read).
32114 @var{data} may have fewer bytes than the @var{length} in the
32118 Data @var{data} (@pxref{Binary Data}) has been read from the target.
32119 There is no more data to be read. @var{data} may have fewer bytes
32120 than the @var{length} in the request.
32123 The @var{offset} in the request is at the end of the data.
32124 There is no more data to be read.
32127 The request was malformed, or @var{annex} was invalid.
32130 The offset was invalid, or there was an error encountered reading the data.
32131 @var{nn} is a hex-encoded @code{errno} value.
32134 An empty reply indicates the @var{object} string was not recognized by
32135 the stub, or that the object does not support reading.
32138 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
32139 @cindex write data into object, remote request
32140 @anchor{qXfer write}
32141 Write uninterpreted bytes into the target's special data area
32142 identified by the keyword @var{object}, starting at @var{offset} bytes
32143 into the data. @var{data}@dots{} is the binary-encoded data
32144 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
32145 is specific to @var{object}; it can supply additional details about what data
32148 Here are the specific requests of this form defined so far. All
32149 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
32150 formats, listed below.
32153 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
32154 @anchor{qXfer siginfo write}
32155 Write @var{data} to the extra signal information on the target system.
32156 The annex part of the generic @samp{qXfer} packet must be
32157 empty (@pxref{qXfer write}).
32159 This packet is not probed by default; the remote stub must request it,
32160 by supplying an appropriate @samp{qSupported} response
32161 (@pxref{qSupported}).
32163 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
32164 @anchor{qXfer spu write}
32165 Write @var{data} to an @code{spufs} file on the target system. The
32166 annex specifies which file to write; it must be of the form
32167 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
32168 in the target process, and @var{name} identifes the @code{spufs} file
32169 in that context to be accessed.
32171 This packet is not probed by default; the remote stub must request it,
32172 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32178 @var{nn} (hex encoded) is the number of bytes written.
32179 This may be fewer bytes than supplied in the request.
32182 The request was malformed, or @var{annex} was invalid.
32185 The offset was invalid, or there was an error encountered writing the data.
32186 @var{nn} is a hex-encoded @code{errno} value.
32189 An empty reply indicates the @var{object} string was not
32190 recognized by the stub, or that the object does not support writing.
32193 @item qXfer:@var{object}:@var{operation}:@dots{}
32194 Requests of this form may be added in the future. When a stub does
32195 not recognize the @var{object} keyword, or its support for
32196 @var{object} does not recognize the @var{operation} keyword, the stub
32197 must respond with an empty packet.
32199 @item qAttached:@var{pid}
32200 @cindex query attached, remote request
32201 @cindex @samp{qAttached} packet
32202 Return an indication of whether the remote server attached to an
32203 existing process or created a new process. When the multiprocess
32204 protocol extensions are supported (@pxref{multiprocess extensions}),
32205 @var{pid} is an integer in hexadecimal format identifying the target
32206 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
32207 the query packet will be simplified as @samp{qAttached}.
32209 This query is used, for example, to know whether the remote process
32210 should be detached or killed when a @value{GDBN} session is ended with
32211 the @code{quit} command.
32216 The remote server attached to an existing process.
32218 The remote server created a new process.
32220 A badly formed request or an error was encountered.
32225 @node Architecture-Specific Protocol Details
32226 @section Architecture-Specific Protocol Details
32228 This section describes how the remote protocol is applied to specific
32229 target architectures. Also see @ref{Standard Target Features}, for
32230 details of XML target descriptions for each architecture.
32234 @subsubsection Breakpoint Kinds
32236 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
32241 16-bit Thumb mode breakpoint.
32244 32-bit Thumb mode (Thumb-2) breakpoint.
32247 32-bit ARM mode breakpoint.
32253 @subsubsection Register Packet Format
32255 The following @code{g}/@code{G} packets have previously been defined.
32256 In the below, some thirty-two bit registers are transferred as
32257 sixty-four bits. Those registers should be zero/sign extended (which?)
32258 to fill the space allocated. Register bytes are transferred in target
32259 byte order. The two nibbles within a register byte are transferred
32260 most-significant - least-significant.
32266 All registers are transferred as thirty-two bit quantities in the order:
32267 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
32268 registers; fsr; fir; fp.
32272 All registers are transferred as sixty-four bit quantities (including
32273 thirty-two bit registers such as @code{sr}). The ordering is the same
32278 @node Tracepoint Packets
32279 @section Tracepoint Packets
32280 @cindex tracepoint packets
32281 @cindex packets, tracepoint
32283 Here we describe the packets @value{GDBN} uses to implement
32284 tracepoints (@pxref{Tracepoints}).
32288 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
32289 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
32290 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
32291 the tracepoint is disabled. @var{step} is the tracepoint's step
32292 count, and @var{pass} is its pass count. If an @samp{F} is present,
32293 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
32294 the number of bytes that the target should copy elsewhere to make room
32295 for the tracepoint. If an @samp{X} is present, it introduces a
32296 tracepoint condition, which consists of a hexadecimal length, followed
32297 by a comma and hex-encoded bytes, in a manner similar to action
32298 encodings as described below. If the trailing @samp{-} is present,
32299 further @samp{QTDP} packets will follow to specify this tracepoint's
32305 The packet was understood and carried out.
32307 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
32309 The packet was not recognized.
32312 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
32313 Define actions to be taken when a tracepoint is hit. @var{n} and
32314 @var{addr} must be the same as in the initial @samp{QTDP} packet for
32315 this tracepoint. This packet may only be sent immediately after
32316 another @samp{QTDP} packet that ended with a @samp{-}. If the
32317 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
32318 specifying more actions for this tracepoint.
32320 In the series of action packets for a given tracepoint, at most one
32321 can have an @samp{S} before its first @var{action}. If such a packet
32322 is sent, it and the following packets define ``while-stepping''
32323 actions. Any prior packets define ordinary actions --- that is, those
32324 taken when the tracepoint is first hit. If no action packet has an
32325 @samp{S}, then all the packets in the series specify ordinary
32326 tracepoint actions.
32328 The @samp{@var{action}@dots{}} portion of the packet is a series of
32329 actions, concatenated without separators. Each action has one of the
32335 Collect the registers whose bits are set in @var{mask}. @var{mask} is
32336 a hexadecimal number whose @var{i}'th bit is set if register number
32337 @var{i} should be collected. (The least significant bit is numbered
32338 zero.) Note that @var{mask} may be any number of digits long; it may
32339 not fit in a 32-bit word.
32341 @item M @var{basereg},@var{offset},@var{len}
32342 Collect @var{len} bytes of memory starting at the address in register
32343 number @var{basereg}, plus @var{offset}. If @var{basereg} is
32344 @samp{-1}, then the range has a fixed address: @var{offset} is the
32345 address of the lowest byte to collect. The @var{basereg},
32346 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
32347 values (the @samp{-1} value for @var{basereg} is a special case).
32349 @item X @var{len},@var{expr}
32350 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
32351 it directs. @var{expr} is an agent expression, as described in
32352 @ref{Agent Expressions}. Each byte of the expression is encoded as a
32353 two-digit hex number in the packet; @var{len} is the number of bytes
32354 in the expression (and thus one-half the number of hex digits in the
32359 Any number of actions may be packed together in a single @samp{QTDP}
32360 packet, as long as the packet does not exceed the maximum packet
32361 length (400 bytes, for many stubs). There may be only one @samp{R}
32362 action per tracepoint, and it must precede any @samp{M} or @samp{X}
32363 actions. Any registers referred to by @samp{M} and @samp{X} actions
32364 must be collected by a preceding @samp{R} action. (The
32365 ``while-stepping'' actions are treated as if they were attached to a
32366 separate tracepoint, as far as these restrictions are concerned.)
32371 The packet was understood and carried out.
32373 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
32375 The packet was not recognized.
32378 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
32379 @cindex @samp{QTDPsrc} packet
32380 Specify a source string of tracepoint @var{n} at address @var{addr}.
32381 This is useful to get accurate reproduction of the tracepoints
32382 originally downloaded at the beginning of the trace run. @var{type}
32383 is the name of the tracepoint part, such as @samp{cond} for the
32384 tracepoint's conditional expression (see below for a list of types), while
32385 @var{bytes} is the string, encoded in hexadecimal.
32387 @var{start} is the offset of the @var{bytes} within the overall source
32388 string, while @var{slen} is the total length of the source string.
32389 This is intended for handling source strings that are longer than will
32390 fit in a single packet.
32391 @c Add detailed example when this info is moved into a dedicated
32392 @c tracepoint descriptions section.
32394 The available string types are @samp{at} for the location,
32395 @samp{cond} for the conditional, and @samp{cmd} for an action command.
32396 @value{GDBN} sends a separate packet for each command in the action
32397 list, in the same order in which the commands are stored in the list.
32399 The target does not need to do anything with source strings except
32400 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
32403 Although this packet is optional, and @value{GDBN} will only send it
32404 if the target replies with @samp{TracepointSource} @xref{General
32405 Query Packets}, it makes both disconnected tracing and trace files
32406 much easier to use. Otherwise the user must be careful that the
32407 tracepoints in effect while looking at trace frames are identical to
32408 the ones in effect during the trace run; even a small discrepancy
32409 could cause @samp{tdump} not to work, or a particular trace frame not
32412 @item QTDV:@var{n}:@var{value}
32413 @cindex define trace state variable, remote request
32414 @cindex @samp{QTDV} packet
32415 Create a new trace state variable, number @var{n}, with an initial
32416 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
32417 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
32418 the option of not using this packet for initial values of zero; the
32419 target should simply create the trace state variables as they are
32420 mentioned in expressions.
32422 @item QTFrame:@var{n}
32423 Select the @var{n}'th tracepoint frame from the buffer, and use the
32424 register and memory contents recorded there to answer subsequent
32425 request packets from @value{GDBN}.
32427 A successful reply from the stub indicates that the stub has found the
32428 requested frame. The response is a series of parts, concatenated
32429 without separators, describing the frame we selected. Each part has
32430 one of the following forms:
32434 The selected frame is number @var{n} in the trace frame buffer;
32435 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
32436 was no frame matching the criteria in the request packet.
32439 The selected trace frame records a hit of tracepoint number @var{t};
32440 @var{t} is a hexadecimal number.
32444 @item QTFrame:pc:@var{addr}
32445 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
32446 currently selected frame whose PC is @var{addr};
32447 @var{addr} is a hexadecimal number.
32449 @item QTFrame:tdp:@var{t}
32450 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
32451 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
32452 is a hexadecimal number.
32454 @item QTFrame:range:@var{start}:@var{end}
32455 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
32456 currently selected frame whose PC is between @var{start} (inclusive)
32457 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
32460 @item QTFrame:outside:@var{start}:@var{end}
32461 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
32462 frame @emph{outside} the given range of addresses (exclusive).
32465 Begin the tracepoint experiment. Begin collecting data from
32466 tracepoint hits in the trace frame buffer. This packet supports the
32467 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
32468 instruction reply packet}).
32471 End the tracepoint experiment. Stop collecting trace frames.
32474 Clear the table of tracepoints, and empty the trace frame buffer.
32476 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
32477 Establish the given ranges of memory as ``transparent''. The stub
32478 will answer requests for these ranges from memory's current contents,
32479 if they were not collected as part of the tracepoint hit.
32481 @value{GDBN} uses this to mark read-only regions of memory, like those
32482 containing program code. Since these areas never change, they should
32483 still have the same contents they did when the tracepoint was hit, so
32484 there's no reason for the stub to refuse to provide their contents.
32486 @item QTDisconnected:@var{value}
32487 Set the choice to what to do with the tracing run when @value{GDBN}
32488 disconnects from the target. A @var{value} of 1 directs the target to
32489 continue the tracing run, while 0 tells the target to stop tracing if
32490 @value{GDBN} is no longer in the picture.
32493 Ask the stub if there is a trace experiment running right now.
32495 The reply has the form:
32499 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
32500 @var{running} is a single digit @code{1} if the trace is presently
32501 running, or @code{0} if not. It is followed by semicolon-separated
32502 optional fields that an agent may use to report additional status.
32506 If the trace is not running, the agent may report any of several
32507 explanations as one of the optional fields:
32512 No trace has been run yet.
32515 The trace was stopped by a user-originated stop command.
32518 The trace stopped because the trace buffer filled up.
32520 @item tdisconnected:0
32521 The trace stopped because @value{GDBN} disconnected from the target.
32523 @item tpasscount:@var{tpnum}
32524 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
32526 @item terror:@var{text}:@var{tpnum}
32527 The trace stopped because tracepoint @var{tpnum} had an error. The
32528 string @var{text} is available to describe the nature of the error
32529 (for instance, a divide by zero in the condition expression).
32530 @var{text} is hex encoded.
32533 The trace stopped for some other reason.
32537 Additional optional fields supply statistical and other information.
32538 Although not required, they are extremely useful for users monitoring
32539 the progress of a trace run. If a trace has stopped, and these
32540 numbers are reported, they must reflect the state of the just-stopped
32545 @item tframes:@var{n}
32546 The number of trace frames in the buffer.
32548 @item tcreated:@var{n}
32549 The total number of trace frames created during the run. This may
32550 be larger than the trace frame count, if the buffer is circular.
32552 @item tsize:@var{n}
32553 The total size of the trace buffer, in bytes.
32555 @item tfree:@var{n}
32556 The number of bytes still unused in the buffer.
32558 @item circular:@var{n}
32559 The value of the circular trace buffer flag. @code{1} means that the
32560 trace buffer is circular and old trace frames will be discarded if
32561 necessary to make room, @code{0} means that the trace buffer is linear
32564 @item disconn:@var{n}
32565 The value of the disconnected tracing flag. @code{1} means that
32566 tracing will continue after @value{GDBN} disconnects, @code{0} means
32567 that the trace run will stop.
32571 @item qTV:@var{var}
32572 @cindex trace state variable value, remote request
32573 @cindex @samp{qTV} packet
32574 Ask the stub for the value of the trace state variable number @var{var}.
32579 The value of the variable is @var{value}. This will be the current
32580 value of the variable if the user is examining a running target, or a
32581 saved value if the variable was collected in the trace frame that the
32582 user is looking at. Note that multiple requests may result in
32583 different reply values, such as when requesting values while the
32584 program is running.
32587 The value of the variable is unknown. This would occur, for example,
32588 if the user is examining a trace frame in which the requested variable
32594 These packets request data about tracepoints that are being used by
32595 the target. @value{GDBN} sends @code{qTfP} to get the first piece
32596 of data, and multiple @code{qTsP} to get additional pieces. Replies
32597 to these packets generally take the form of the @code{QTDP} packets
32598 that define tracepoints. (FIXME add detailed syntax)
32602 These packets request data about trace state variables that are on the
32603 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
32604 and multiple @code{qTsV} to get additional variables. Replies to
32605 these packets follow the syntax of the @code{QTDV} packets that define
32606 trace state variables.
32608 @item QTSave:@var{filename}
32609 This packet directs the target to save trace data to the file name
32610 @var{filename} in the target's filesystem. @var{filename} is encoded
32611 as a hex string; the interpretation of the file name (relative vs
32612 absolute, wild cards, etc) is up to the target.
32614 @item qTBuffer:@var{offset},@var{len}
32615 Return up to @var{len} bytes of the current contents of trace buffer,
32616 starting at @var{offset}. The trace buffer is treated as if it were
32617 a contiguous collection of traceframes, as per the trace file format.
32618 The reply consists as many hex-encoded bytes as the target can deliver
32619 in a packet; it is not an error to return fewer than were asked for.
32620 A reply consisting of just @code{l} indicates that no bytes are
32623 @item QTBuffer:circular:@var{value}
32624 This packet directs the target to use a circular trace buffer if
32625 @var{value} is 1, or a linear buffer if the value is 0.
32629 @subsection Relocate instruction reply packet
32630 When installing fast tracepoints in memory, the target may need to
32631 relocate the instruction currently at the tracepoint address to a
32632 different address in memory. For most instructions, a simple copy is
32633 enough, but, for example, call instructions that implicitly push the
32634 return address on the stack, and relative branches or other
32635 PC-relative instructions require offset adjustment, so that the effect
32636 of executing the instruction at a different address is the same as if
32637 it had executed in the original location.
32639 In response to several of the tracepoint packets, the target may also
32640 respond with a number of intermediate @samp{qRelocInsn} request
32641 packets before the final result packet, to have @value{GDBN} handle
32642 this relocation operation. If a packet supports this mechanism, its
32643 documentation will explicitly say so. See for example the above
32644 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
32645 format of the request is:
32648 @item qRelocInsn:@var{from};@var{to}
32650 This requests @value{GDBN} to copy instruction at address @var{from}
32651 to address @var{to}, possibly adjusted so that executing the
32652 instruction at @var{to} has the same effect as executing it at
32653 @var{from}. @value{GDBN} writes the adjusted instruction to target
32654 memory starting at @var{to}.
32659 @item qRelocInsn:@var{adjusted_size}
32660 Informs the stub the relocation is complete. @var{adjusted_size} is
32661 the length in bytes of resulting relocated instruction sequence.
32663 A badly formed request was detected, or an error was encountered while
32664 relocating the instruction.
32667 @node Host I/O Packets
32668 @section Host I/O Packets
32669 @cindex Host I/O, remote protocol
32670 @cindex file transfer, remote protocol
32672 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
32673 operations on the far side of a remote link. For example, Host I/O is
32674 used to upload and download files to a remote target with its own
32675 filesystem. Host I/O uses the same constant values and data structure
32676 layout as the target-initiated File-I/O protocol. However, the
32677 Host I/O packets are structured differently. The target-initiated
32678 protocol relies on target memory to store parameters and buffers.
32679 Host I/O requests are initiated by @value{GDBN}, and the
32680 target's memory is not involved. @xref{File-I/O Remote Protocol
32681 Extension}, for more details on the target-initiated protocol.
32683 The Host I/O request packets all encode a single operation along with
32684 its arguments. They have this format:
32688 @item vFile:@var{operation}: @var{parameter}@dots{}
32689 @var{operation} is the name of the particular request; the target
32690 should compare the entire packet name up to the second colon when checking
32691 for a supported operation. The format of @var{parameter} depends on
32692 the operation. Numbers are always passed in hexadecimal. Negative
32693 numbers have an explicit minus sign (i.e.@: two's complement is not
32694 used). Strings (e.g.@: filenames) are encoded as a series of
32695 hexadecimal bytes. The last argument to a system call may be a
32696 buffer of escaped binary data (@pxref{Binary Data}).
32700 The valid responses to Host I/O packets are:
32704 @item F @var{result} [, @var{errno}] [; @var{attachment}]
32705 @var{result} is the integer value returned by this operation, usually
32706 non-negative for success and -1 for errors. If an error has occured,
32707 @var{errno} will be included in the result. @var{errno} will have a
32708 value defined by the File-I/O protocol (@pxref{Errno Values}). For
32709 operations which return data, @var{attachment} supplies the data as a
32710 binary buffer. Binary buffers in response packets are escaped in the
32711 normal way (@pxref{Binary Data}). See the individual packet
32712 documentation for the interpretation of @var{result} and
32716 An empty response indicates that this operation is not recognized.
32720 These are the supported Host I/O operations:
32723 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
32724 Open a file at @var{pathname} and return a file descriptor for it, or
32725 return -1 if an error occurs. @var{pathname} is a string,
32726 @var{flags} is an integer indicating a mask of open flags
32727 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
32728 of mode bits to use if the file is created (@pxref{mode_t Values}).
32729 @xref{open}, for details of the open flags and mode values.
32731 @item vFile:close: @var{fd}
32732 Close the open file corresponding to @var{fd} and return 0, or
32733 -1 if an error occurs.
32735 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
32736 Read data from the open file corresponding to @var{fd}. Up to
32737 @var{count} bytes will be read from the file, starting at @var{offset}
32738 relative to the start of the file. The target may read fewer bytes;
32739 common reasons include packet size limits and an end-of-file
32740 condition. The number of bytes read is returned. Zero should only be
32741 returned for a successful read at the end of the file, or if
32742 @var{count} was zero.
32744 The data read should be returned as a binary attachment on success.
32745 If zero bytes were read, the response should include an empty binary
32746 attachment (i.e.@: a trailing semicolon). The return value is the
32747 number of target bytes read; the binary attachment may be longer if
32748 some characters were escaped.
32750 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
32751 Write @var{data} (a binary buffer) to the open file corresponding
32752 to @var{fd}. Start the write at @var{offset} from the start of the
32753 file. Unlike many @code{write} system calls, there is no
32754 separate @var{count} argument; the length of @var{data} in the
32755 packet is used. @samp{vFile:write} returns the number of bytes written,
32756 which may be shorter than the length of @var{data}, or -1 if an
32759 @item vFile:unlink: @var{pathname}
32760 Delete the file at @var{pathname} on the target. Return 0,
32761 or -1 if an error occurs. @var{pathname} is a string.
32766 @section Interrupts
32767 @cindex interrupts (remote protocol)
32769 When a program on the remote target is running, @value{GDBN} may
32770 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
32771 a @code{BREAK} followed by @code{g},
32772 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
32774 The precise meaning of @code{BREAK} is defined by the transport
32775 mechanism and may, in fact, be undefined. @value{GDBN} does not
32776 currently define a @code{BREAK} mechanism for any of the network
32777 interfaces except for TCP, in which case @value{GDBN} sends the
32778 @code{telnet} BREAK sequence.
32780 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
32781 transport mechanisms. It is represented by sending the single byte
32782 @code{0x03} without any of the usual packet overhead described in
32783 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
32784 transmitted as part of a packet, it is considered to be packet data
32785 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
32786 (@pxref{X packet}), used for binary downloads, may include an unescaped
32787 @code{0x03} as part of its packet.
32789 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
32790 When Linux kernel receives this sequence from serial port,
32791 it stops execution and connects to gdb.
32793 Stubs are not required to recognize these interrupt mechanisms and the
32794 precise meaning associated with receipt of the interrupt is
32795 implementation defined. If the target supports debugging of multiple
32796 threads and/or processes, it should attempt to interrupt all
32797 currently-executing threads and processes.
32798 If the stub is successful at interrupting the
32799 running program, it should send one of the stop
32800 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
32801 of successfully stopping the program in all-stop mode, and a stop reply
32802 for each stopped thread in non-stop mode.
32803 Interrupts received while the
32804 program is stopped are discarded.
32806 @node Notification Packets
32807 @section Notification Packets
32808 @cindex notification packets
32809 @cindex packets, notification
32811 The @value{GDBN} remote serial protocol includes @dfn{notifications},
32812 packets that require no acknowledgment. Both the GDB and the stub
32813 may send notifications (although the only notifications defined at
32814 present are sent by the stub). Notifications carry information
32815 without incurring the round-trip latency of an acknowledgment, and so
32816 are useful for low-impact communications where occasional packet loss
32819 A notification packet has the form @samp{% @var{data} #
32820 @var{checksum}}, where @var{data} is the content of the notification,
32821 and @var{checksum} is a checksum of @var{data}, computed and formatted
32822 as for ordinary @value{GDBN} packets. A notification's @var{data}
32823 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
32824 receiving a notification, the recipient sends no @samp{+} or @samp{-}
32825 to acknowledge the notification's receipt or to report its corruption.
32827 Every notification's @var{data} begins with a name, which contains no
32828 colon characters, followed by a colon character.
32830 Recipients should silently ignore corrupted notifications and
32831 notifications they do not understand. Recipients should restart
32832 timeout periods on receipt of a well-formed notification, whether or
32833 not they understand it.
32835 Senders should only send the notifications described here when this
32836 protocol description specifies that they are permitted. In the
32837 future, we may extend the protocol to permit existing notifications in
32838 new contexts; this rule helps older senders avoid confusing newer
32841 (Older versions of @value{GDBN} ignore bytes received until they see
32842 the @samp{$} byte that begins an ordinary packet, so new stubs may
32843 transmit notifications without fear of confusing older clients. There
32844 are no notifications defined for @value{GDBN} to send at the moment, but we
32845 assume that most older stubs would ignore them, as well.)
32847 The following notification packets from the stub to @value{GDBN} are
32851 @item Stop: @var{reply}
32852 Report an asynchronous stop event in non-stop mode.
32853 The @var{reply} has the form of a stop reply, as
32854 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
32855 for information on how these notifications are acknowledged by
32859 @node Remote Non-Stop
32860 @section Remote Protocol Support for Non-Stop Mode
32862 @value{GDBN}'s remote protocol supports non-stop debugging of
32863 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
32864 supports non-stop mode, it should report that to @value{GDBN} by including
32865 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
32867 @value{GDBN} typically sends a @samp{QNonStop} packet only when
32868 establishing a new connection with the stub. Entering non-stop mode
32869 does not alter the state of any currently-running threads, but targets
32870 must stop all threads in any already-attached processes when entering
32871 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
32872 probe the target state after a mode change.
32874 In non-stop mode, when an attached process encounters an event that
32875 would otherwise be reported with a stop reply, it uses the
32876 asynchronous notification mechanism (@pxref{Notification Packets}) to
32877 inform @value{GDBN}. In contrast to all-stop mode, where all threads
32878 in all processes are stopped when a stop reply is sent, in non-stop
32879 mode only the thread reporting the stop event is stopped. That is,
32880 when reporting a @samp{S} or @samp{T} response to indicate completion
32881 of a step operation, hitting a breakpoint, or a fault, only the
32882 affected thread is stopped; any other still-running threads continue
32883 to run. When reporting a @samp{W} or @samp{X} response, all running
32884 threads belonging to other attached processes continue to run.
32886 Only one stop reply notification at a time may be pending; if
32887 additional stop events occur before @value{GDBN} has acknowledged the
32888 previous notification, they must be queued by the stub for later
32889 synchronous transmission in response to @samp{vStopped} packets from
32890 @value{GDBN}. Because the notification mechanism is unreliable,
32891 the stub is permitted to resend a stop reply notification
32892 if it believes @value{GDBN} may not have received it. @value{GDBN}
32893 ignores additional stop reply notifications received before it has
32894 finished processing a previous notification and the stub has completed
32895 sending any queued stop events.
32897 Otherwise, @value{GDBN} must be prepared to receive a stop reply
32898 notification at any time. Specifically, they may appear when
32899 @value{GDBN} is not otherwise reading input from the stub, or when
32900 @value{GDBN} is expecting to read a normal synchronous response or a
32901 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
32902 Notification packets are distinct from any other communication from
32903 the stub so there is no ambiguity.
32905 After receiving a stop reply notification, @value{GDBN} shall
32906 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
32907 as a regular, synchronous request to the stub. Such acknowledgment
32908 is not required to happen immediately, as @value{GDBN} is permitted to
32909 send other, unrelated packets to the stub first, which the stub should
32912 Upon receiving a @samp{vStopped} packet, if the stub has other queued
32913 stop events to report to @value{GDBN}, it shall respond by sending a
32914 normal stop reply response. @value{GDBN} shall then send another
32915 @samp{vStopped} packet to solicit further responses; again, it is
32916 permitted to send other, unrelated packets as well which the stub
32917 should process normally.
32919 If the stub receives a @samp{vStopped} packet and there are no
32920 additional stop events to report, the stub shall return an @samp{OK}
32921 response. At this point, if further stop events occur, the stub shall
32922 send a new stop reply notification, @value{GDBN} shall accept the
32923 notification, and the process shall be repeated.
32925 In non-stop mode, the target shall respond to the @samp{?} packet as
32926 follows. First, any incomplete stop reply notification/@samp{vStopped}
32927 sequence in progress is abandoned. The target must begin a new
32928 sequence reporting stop events for all stopped threads, whether or not
32929 it has previously reported those events to @value{GDBN}. The first
32930 stop reply is sent as a synchronous reply to the @samp{?} packet, and
32931 subsequent stop replies are sent as responses to @samp{vStopped} packets
32932 using the mechanism described above. The target must not send
32933 asynchronous stop reply notifications until the sequence is complete.
32934 If all threads are running when the target receives the @samp{?} packet,
32935 or if the target is not attached to any process, it shall respond
32938 @node Packet Acknowledgment
32939 @section Packet Acknowledgment
32941 @cindex acknowledgment, for @value{GDBN} remote
32942 @cindex packet acknowledgment, for @value{GDBN} remote
32943 By default, when either the host or the target machine receives a packet,
32944 the first response expected is an acknowledgment: either @samp{+} (to indicate
32945 the package was received correctly) or @samp{-} (to request retransmission).
32946 This mechanism allows the @value{GDBN} remote protocol to operate over
32947 unreliable transport mechanisms, such as a serial line.
32949 In cases where the transport mechanism is itself reliable (such as a pipe or
32950 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
32951 It may be desirable to disable them in that case to reduce communication
32952 overhead, or for other reasons. This can be accomplished by means of the
32953 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
32955 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
32956 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
32957 and response format still includes the normal checksum, as described in
32958 @ref{Overview}, but the checksum may be ignored by the receiver.
32960 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
32961 no-acknowledgment mode, it should report that to @value{GDBN}
32962 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
32963 @pxref{qSupported}.
32964 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
32965 disabled via the @code{set remote noack-packet off} command
32966 (@pxref{Remote Configuration}),
32967 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
32968 Only then may the stub actually turn off packet acknowledgments.
32969 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
32970 response, which can be safely ignored by the stub.
32972 Note that @code{set remote noack-packet} command only affects negotiation
32973 between @value{GDBN} and the stub when subsequent connections are made;
32974 it does not affect the protocol acknowledgment state for any current
32976 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
32977 new connection is established,
32978 there is also no protocol request to re-enable the acknowledgments
32979 for the current connection, once disabled.
32984 Example sequence of a target being re-started. Notice how the restart
32985 does not get any direct output:
32990 @emph{target restarts}
32993 <- @code{T001:1234123412341234}
32997 Example sequence of a target being stepped by a single instruction:
33000 -> @code{G1445@dots{}}
33005 <- @code{T001:1234123412341234}
33009 <- @code{1455@dots{}}
33013 @node File-I/O Remote Protocol Extension
33014 @section File-I/O Remote Protocol Extension
33015 @cindex File-I/O remote protocol extension
33018 * File-I/O Overview::
33019 * Protocol Basics::
33020 * The F Request Packet::
33021 * The F Reply Packet::
33022 * The Ctrl-C Message::
33024 * List of Supported Calls::
33025 * Protocol-specific Representation of Datatypes::
33027 * File-I/O Examples::
33030 @node File-I/O Overview
33031 @subsection File-I/O Overview
33032 @cindex file-i/o overview
33034 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
33035 target to use the host's file system and console I/O to perform various
33036 system calls. System calls on the target system are translated into a
33037 remote protocol packet to the host system, which then performs the needed
33038 actions and returns a response packet to the target system.
33039 This simulates file system operations even on targets that lack file systems.
33041 The protocol is defined to be independent of both the host and target systems.
33042 It uses its own internal representation of datatypes and values. Both
33043 @value{GDBN} and the target's @value{GDBN} stub are responsible for
33044 translating the system-dependent value representations into the internal
33045 protocol representations when data is transmitted.
33047 The communication is synchronous. A system call is possible only when
33048 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
33049 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
33050 the target is stopped to allow deterministic access to the target's
33051 memory. Therefore File-I/O is not interruptible by target signals. On
33052 the other hand, it is possible to interrupt File-I/O by a user interrupt
33053 (@samp{Ctrl-C}) within @value{GDBN}.
33055 The target's request to perform a host system call does not finish
33056 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
33057 after finishing the system call, the target returns to continuing the
33058 previous activity (continue, step). No additional continue or step
33059 request from @value{GDBN} is required.
33062 (@value{GDBP}) continue
33063 <- target requests 'system call X'
33064 target is stopped, @value{GDBN} executes system call
33065 -> @value{GDBN} returns result
33066 ... target continues, @value{GDBN} returns to wait for the target
33067 <- target hits breakpoint and sends a Txx packet
33070 The protocol only supports I/O on the console and to regular files on
33071 the host file system. Character or block special devices, pipes,
33072 named pipes, sockets or any other communication method on the host
33073 system are not supported by this protocol.
33075 File I/O is not supported in non-stop mode.
33077 @node Protocol Basics
33078 @subsection Protocol Basics
33079 @cindex protocol basics, file-i/o
33081 The File-I/O protocol uses the @code{F} packet as the request as well
33082 as reply packet. Since a File-I/O system call can only occur when
33083 @value{GDBN} is waiting for a response from the continuing or stepping target,
33084 the File-I/O request is a reply that @value{GDBN} has to expect as a result
33085 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
33086 This @code{F} packet contains all information needed to allow @value{GDBN}
33087 to call the appropriate host system call:
33091 A unique identifier for the requested system call.
33094 All parameters to the system call. Pointers are given as addresses
33095 in the target memory address space. Pointers to strings are given as
33096 pointer/length pair. Numerical values are given as they are.
33097 Numerical control flags are given in a protocol-specific representation.
33101 At this point, @value{GDBN} has to perform the following actions.
33105 If the parameters include pointer values to data needed as input to a
33106 system call, @value{GDBN} requests this data from the target with a
33107 standard @code{m} packet request. This additional communication has to be
33108 expected by the target implementation and is handled as any other @code{m}
33112 @value{GDBN} translates all value from protocol representation to host
33113 representation as needed. Datatypes are coerced into the host types.
33116 @value{GDBN} calls the system call.
33119 It then coerces datatypes back to protocol representation.
33122 If the system call is expected to return data in buffer space specified
33123 by pointer parameters to the call, the data is transmitted to the
33124 target using a @code{M} or @code{X} packet. This packet has to be expected
33125 by the target implementation and is handled as any other @code{M} or @code{X}
33130 Eventually @value{GDBN} replies with another @code{F} packet which contains all
33131 necessary information for the target to continue. This at least contains
33138 @code{errno}, if has been changed by the system call.
33145 After having done the needed type and value coercion, the target continues
33146 the latest continue or step action.
33148 @node The F Request Packet
33149 @subsection The @code{F} Request Packet
33150 @cindex file-i/o request packet
33151 @cindex @code{F} request packet
33153 The @code{F} request packet has the following format:
33156 @item F@var{call-id},@var{parameter@dots{}}
33158 @var{call-id} is the identifier to indicate the host system call to be called.
33159 This is just the name of the function.
33161 @var{parameter@dots{}} are the parameters to the system call.
33162 Parameters are hexadecimal integer values, either the actual values in case
33163 of scalar datatypes, pointers to target buffer space in case of compound
33164 datatypes and unspecified memory areas, or pointer/length pairs in case
33165 of string parameters. These are appended to the @var{call-id} as a
33166 comma-delimited list. All values are transmitted in ASCII
33167 string representation, pointer/length pairs separated by a slash.
33173 @node The F Reply Packet
33174 @subsection The @code{F} Reply Packet
33175 @cindex file-i/o reply packet
33176 @cindex @code{F} reply packet
33178 The @code{F} reply packet has the following format:
33182 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
33184 @var{retcode} is the return code of the system call as hexadecimal value.
33186 @var{errno} is the @code{errno} set by the call, in protocol-specific
33188 This parameter can be omitted if the call was successful.
33190 @var{Ctrl-C flag} is only sent if the user requested a break. In this
33191 case, @var{errno} must be sent as well, even if the call was successful.
33192 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
33199 or, if the call was interrupted before the host call has been performed:
33206 assuming 4 is the protocol-specific representation of @code{EINTR}.
33211 @node The Ctrl-C Message
33212 @subsection The @samp{Ctrl-C} Message
33213 @cindex ctrl-c message, in file-i/o protocol
33215 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
33216 reply packet (@pxref{The F Reply Packet}),
33217 the target should behave as if it had
33218 gotten a break message. The meaning for the target is ``system call
33219 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
33220 (as with a break message) and return to @value{GDBN} with a @code{T02}
33223 It's important for the target to know in which
33224 state the system call was interrupted. There are two possible cases:
33228 The system call hasn't been performed on the host yet.
33231 The system call on the host has been finished.
33235 These two states can be distinguished by the target by the value of the
33236 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
33237 call hasn't been performed. This is equivalent to the @code{EINTR} handling
33238 on POSIX systems. In any other case, the target may presume that the
33239 system call has been finished --- successfully or not --- and should behave
33240 as if the break message arrived right after the system call.
33242 @value{GDBN} must behave reliably. If the system call has not been called
33243 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
33244 @code{errno} in the packet. If the system call on the host has been finished
33245 before the user requests a break, the full action must be finished by
33246 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
33247 The @code{F} packet may only be sent when either nothing has happened
33248 or the full action has been completed.
33251 @subsection Console I/O
33252 @cindex console i/o as part of file-i/o
33254 By default and if not explicitly closed by the target system, the file
33255 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
33256 on the @value{GDBN} console is handled as any other file output operation
33257 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
33258 by @value{GDBN} so that after the target read request from file descriptor
33259 0 all following typing is buffered until either one of the following
33264 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
33266 system call is treated as finished.
33269 The user presses @key{RET}. This is treated as end of input with a trailing
33273 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
33274 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
33278 If the user has typed more characters than fit in the buffer given to
33279 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
33280 either another @code{read(0, @dots{})} is requested by the target, or debugging
33281 is stopped at the user's request.
33284 @node List of Supported Calls
33285 @subsection List of Supported Calls
33286 @cindex list of supported file-i/o calls
33303 @unnumberedsubsubsec open
33304 @cindex open, file-i/o system call
33309 int open(const char *pathname, int flags);
33310 int open(const char *pathname, int flags, mode_t mode);
33314 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
33317 @var{flags} is the bitwise @code{OR} of the following values:
33321 If the file does not exist it will be created. The host
33322 rules apply as far as file ownership and time stamps
33326 When used with @code{O_CREAT}, if the file already exists it is
33327 an error and open() fails.
33330 If the file already exists and the open mode allows
33331 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
33332 truncated to zero length.
33335 The file is opened in append mode.
33338 The file is opened for reading only.
33341 The file is opened for writing only.
33344 The file is opened for reading and writing.
33348 Other bits are silently ignored.
33352 @var{mode} is the bitwise @code{OR} of the following values:
33356 User has read permission.
33359 User has write permission.
33362 Group has read permission.
33365 Group has write permission.
33368 Others have read permission.
33371 Others have write permission.
33375 Other bits are silently ignored.
33378 @item Return value:
33379 @code{open} returns the new file descriptor or -1 if an error
33386 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
33389 @var{pathname} refers to a directory.
33392 The requested access is not allowed.
33395 @var{pathname} was too long.
33398 A directory component in @var{pathname} does not exist.
33401 @var{pathname} refers to a device, pipe, named pipe or socket.
33404 @var{pathname} refers to a file on a read-only filesystem and
33405 write access was requested.
33408 @var{pathname} is an invalid pointer value.
33411 No space on device to create the file.
33414 The process already has the maximum number of files open.
33417 The limit on the total number of files open on the system
33421 The call was interrupted by the user.
33427 @unnumberedsubsubsec close
33428 @cindex close, file-i/o system call
33437 @samp{Fclose,@var{fd}}
33439 @item Return value:
33440 @code{close} returns zero on success, or -1 if an error occurred.
33446 @var{fd} isn't a valid open file descriptor.
33449 The call was interrupted by the user.
33455 @unnumberedsubsubsec read
33456 @cindex read, file-i/o system call
33461 int read(int fd, void *buf, unsigned int count);
33465 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
33467 @item Return value:
33468 On success, the number of bytes read is returned.
33469 Zero indicates end of file. If count is zero, read
33470 returns zero as well. On error, -1 is returned.
33476 @var{fd} is not a valid file descriptor or is not open for
33480 @var{bufptr} is an invalid pointer value.
33483 The call was interrupted by the user.
33489 @unnumberedsubsubsec write
33490 @cindex write, file-i/o system call
33495 int write(int fd, const void *buf, unsigned int count);
33499 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
33501 @item Return value:
33502 On success, the number of bytes written are returned.
33503 Zero indicates nothing was written. On error, -1
33510 @var{fd} is not a valid file descriptor or is not open for
33514 @var{bufptr} is an invalid pointer value.
33517 An attempt was made to write a file that exceeds the
33518 host-specific maximum file size allowed.
33521 No space on device to write the data.
33524 The call was interrupted by the user.
33530 @unnumberedsubsubsec lseek
33531 @cindex lseek, file-i/o system call
33536 long lseek (int fd, long offset, int flag);
33540 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
33542 @var{flag} is one of:
33546 The offset is set to @var{offset} bytes.
33549 The offset is set to its current location plus @var{offset}
33553 The offset is set to the size of the file plus @var{offset}
33557 @item Return value:
33558 On success, the resulting unsigned offset in bytes from
33559 the beginning of the file is returned. Otherwise, a
33560 value of -1 is returned.
33566 @var{fd} is not a valid open file descriptor.
33569 @var{fd} is associated with the @value{GDBN} console.
33572 @var{flag} is not a proper value.
33575 The call was interrupted by the user.
33581 @unnumberedsubsubsec rename
33582 @cindex rename, file-i/o system call
33587 int rename(const char *oldpath, const char *newpath);
33591 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
33593 @item Return value:
33594 On success, zero is returned. On error, -1 is returned.
33600 @var{newpath} is an existing directory, but @var{oldpath} is not a
33604 @var{newpath} is a non-empty directory.
33607 @var{oldpath} or @var{newpath} is a directory that is in use by some
33611 An attempt was made to make a directory a subdirectory
33615 A component used as a directory in @var{oldpath} or new
33616 path is not a directory. Or @var{oldpath} is a directory
33617 and @var{newpath} exists but is not a directory.
33620 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
33623 No access to the file or the path of the file.
33627 @var{oldpath} or @var{newpath} was too long.
33630 A directory component in @var{oldpath} or @var{newpath} does not exist.
33633 The file is on a read-only filesystem.
33636 The device containing the file has no room for the new
33640 The call was interrupted by the user.
33646 @unnumberedsubsubsec unlink
33647 @cindex unlink, file-i/o system call
33652 int unlink(const char *pathname);
33656 @samp{Funlink,@var{pathnameptr}/@var{len}}
33658 @item Return value:
33659 On success, zero is returned. On error, -1 is returned.
33665 No access to the file or the path of the file.
33668 The system does not allow unlinking of directories.
33671 The file @var{pathname} cannot be unlinked because it's
33672 being used by another process.
33675 @var{pathnameptr} is an invalid pointer value.
33678 @var{pathname} was too long.
33681 A directory component in @var{pathname} does not exist.
33684 A component of the path is not a directory.
33687 The file is on a read-only filesystem.
33690 The call was interrupted by the user.
33696 @unnumberedsubsubsec stat/fstat
33697 @cindex fstat, file-i/o system call
33698 @cindex stat, file-i/o system call
33703 int stat(const char *pathname, struct stat *buf);
33704 int fstat(int fd, struct stat *buf);
33708 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
33709 @samp{Ffstat,@var{fd},@var{bufptr}}
33711 @item Return value:
33712 On success, zero is returned. On error, -1 is returned.
33718 @var{fd} is not a valid open file.
33721 A directory component in @var{pathname} does not exist or the
33722 path is an empty string.
33725 A component of the path is not a directory.
33728 @var{pathnameptr} is an invalid pointer value.
33731 No access to the file or the path of the file.
33734 @var{pathname} was too long.
33737 The call was interrupted by the user.
33743 @unnumberedsubsubsec gettimeofday
33744 @cindex gettimeofday, file-i/o system call
33749 int gettimeofday(struct timeval *tv, void *tz);
33753 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
33755 @item Return value:
33756 On success, 0 is returned, -1 otherwise.
33762 @var{tz} is a non-NULL pointer.
33765 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
33771 @unnumberedsubsubsec isatty
33772 @cindex isatty, file-i/o system call
33777 int isatty(int fd);
33781 @samp{Fisatty,@var{fd}}
33783 @item Return value:
33784 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
33790 The call was interrupted by the user.
33795 Note that the @code{isatty} call is treated as a special case: it returns
33796 1 to the target if the file descriptor is attached
33797 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
33798 would require implementing @code{ioctl} and would be more complex than
33803 @unnumberedsubsubsec system
33804 @cindex system, file-i/o system call
33809 int system(const char *command);
33813 @samp{Fsystem,@var{commandptr}/@var{len}}
33815 @item Return value:
33816 If @var{len} is zero, the return value indicates whether a shell is
33817 available. A zero return value indicates a shell is not available.
33818 For non-zero @var{len}, the value returned is -1 on error and the
33819 return status of the command otherwise. Only the exit status of the
33820 command is returned, which is extracted from the host's @code{system}
33821 return value by calling @code{WEXITSTATUS(retval)}. In case
33822 @file{/bin/sh} could not be executed, 127 is returned.
33828 The call was interrupted by the user.
33833 @value{GDBN} takes over the full task of calling the necessary host calls
33834 to perform the @code{system} call. The return value of @code{system} on
33835 the host is simplified before it's returned
33836 to the target. Any termination signal information from the child process
33837 is discarded, and the return value consists
33838 entirely of the exit status of the called command.
33840 Due to security concerns, the @code{system} call is by default refused
33841 by @value{GDBN}. The user has to allow this call explicitly with the
33842 @code{set remote system-call-allowed 1} command.
33845 @item set remote system-call-allowed
33846 @kindex set remote system-call-allowed
33847 Control whether to allow the @code{system} calls in the File I/O
33848 protocol for the remote target. The default is zero (disabled).
33850 @item show remote system-call-allowed
33851 @kindex show remote system-call-allowed
33852 Show whether the @code{system} calls are allowed in the File I/O
33856 @node Protocol-specific Representation of Datatypes
33857 @subsection Protocol-specific Representation of Datatypes
33858 @cindex protocol-specific representation of datatypes, in file-i/o protocol
33861 * Integral Datatypes::
33863 * Memory Transfer::
33868 @node Integral Datatypes
33869 @unnumberedsubsubsec Integral Datatypes
33870 @cindex integral datatypes, in file-i/o protocol
33872 The integral datatypes used in the system calls are @code{int},
33873 @code{unsigned int}, @code{long}, @code{unsigned long},
33874 @code{mode_t}, and @code{time_t}.
33876 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
33877 implemented as 32 bit values in this protocol.
33879 @code{long} and @code{unsigned long} are implemented as 64 bit types.
33881 @xref{Limits}, for corresponding MIN and MAX values (similar to those
33882 in @file{limits.h}) to allow range checking on host and target.
33884 @code{time_t} datatypes are defined as seconds since the Epoch.
33886 All integral datatypes transferred as part of a memory read or write of a
33887 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
33890 @node Pointer Values
33891 @unnumberedsubsubsec Pointer Values
33892 @cindex pointer values, in file-i/o protocol
33894 Pointers to target data are transmitted as they are. An exception
33895 is made for pointers to buffers for which the length isn't
33896 transmitted as part of the function call, namely strings. Strings
33897 are transmitted as a pointer/length pair, both as hex values, e.g.@:
33904 which is a pointer to data of length 18 bytes at position 0x1aaf.
33905 The length is defined as the full string length in bytes, including
33906 the trailing null byte. For example, the string @code{"hello world"}
33907 at address 0x123456 is transmitted as
33913 @node Memory Transfer
33914 @unnumberedsubsubsec Memory Transfer
33915 @cindex memory transfer, in file-i/o protocol
33917 Structured data which is transferred using a memory read or write (for
33918 example, a @code{struct stat}) is expected to be in a protocol-specific format
33919 with all scalar multibyte datatypes being big endian. Translation to
33920 this representation needs to be done both by the target before the @code{F}
33921 packet is sent, and by @value{GDBN} before
33922 it transfers memory to the target. Transferred pointers to structured
33923 data should point to the already-coerced data at any time.
33927 @unnumberedsubsubsec struct stat
33928 @cindex struct stat, in file-i/o protocol
33930 The buffer of type @code{struct stat} used by the target and @value{GDBN}
33931 is defined as follows:
33935 unsigned int st_dev; /* device */
33936 unsigned int st_ino; /* inode */
33937 mode_t st_mode; /* protection */
33938 unsigned int st_nlink; /* number of hard links */
33939 unsigned int st_uid; /* user ID of owner */
33940 unsigned int st_gid; /* group ID of owner */
33941 unsigned int st_rdev; /* device type (if inode device) */
33942 unsigned long st_size; /* total size, in bytes */
33943 unsigned long st_blksize; /* blocksize for filesystem I/O */
33944 unsigned long st_blocks; /* number of blocks allocated */
33945 time_t st_atime; /* time of last access */
33946 time_t st_mtime; /* time of last modification */
33947 time_t st_ctime; /* time of last change */
33951 The integral datatypes conform to the definitions given in the
33952 appropriate section (see @ref{Integral Datatypes}, for details) so this
33953 structure is of size 64 bytes.
33955 The values of several fields have a restricted meaning and/or
33961 A value of 0 represents a file, 1 the console.
33964 No valid meaning for the target. Transmitted unchanged.
33967 Valid mode bits are described in @ref{Constants}. Any other
33968 bits have currently no meaning for the target.
33973 No valid meaning for the target. Transmitted unchanged.
33978 These values have a host and file system dependent
33979 accuracy. Especially on Windows hosts, the file system may not
33980 support exact timing values.
33983 The target gets a @code{struct stat} of the above representation and is
33984 responsible for coercing it to the target representation before
33987 Note that due to size differences between the host, target, and protocol
33988 representations of @code{struct stat} members, these members could eventually
33989 get truncated on the target.
33991 @node struct timeval
33992 @unnumberedsubsubsec struct timeval
33993 @cindex struct timeval, in file-i/o protocol
33995 The buffer of type @code{struct timeval} used by the File-I/O protocol
33996 is defined as follows:
34000 time_t tv_sec; /* second */
34001 long tv_usec; /* microsecond */
34005 The integral datatypes conform to the definitions given in the
34006 appropriate section (see @ref{Integral Datatypes}, for details) so this
34007 structure is of size 8 bytes.
34010 @subsection Constants
34011 @cindex constants, in file-i/o protocol
34013 The following values are used for the constants inside of the
34014 protocol. @value{GDBN} and target are responsible for translating these
34015 values before and after the call as needed.
34026 @unnumberedsubsubsec Open Flags
34027 @cindex open flags, in file-i/o protocol
34029 All values are given in hexadecimal representation.
34041 @node mode_t Values
34042 @unnumberedsubsubsec mode_t Values
34043 @cindex mode_t values, in file-i/o protocol
34045 All values are given in octal representation.
34062 @unnumberedsubsubsec Errno Values
34063 @cindex errno values, in file-i/o protocol
34065 All values are given in decimal representation.
34090 @code{EUNKNOWN} is used as a fallback error value if a host system returns
34091 any error value not in the list of supported error numbers.
34094 @unnumberedsubsubsec Lseek Flags
34095 @cindex lseek flags, in file-i/o protocol
34104 @unnumberedsubsubsec Limits
34105 @cindex limits, in file-i/o protocol
34107 All values are given in decimal representation.
34110 INT_MIN -2147483648
34112 UINT_MAX 4294967295
34113 LONG_MIN -9223372036854775808
34114 LONG_MAX 9223372036854775807
34115 ULONG_MAX 18446744073709551615
34118 @node File-I/O Examples
34119 @subsection File-I/O Examples
34120 @cindex file-i/o examples
34122 Example sequence of a write call, file descriptor 3, buffer is at target
34123 address 0x1234, 6 bytes should be written:
34126 <- @code{Fwrite,3,1234,6}
34127 @emph{request memory read from target}
34130 @emph{return "6 bytes written"}
34134 Example sequence of a read call, file descriptor 3, buffer is at target
34135 address 0x1234, 6 bytes should be read:
34138 <- @code{Fread,3,1234,6}
34139 @emph{request memory write to target}
34140 -> @code{X1234,6:XXXXXX}
34141 @emph{return "6 bytes read"}
34145 Example sequence of a read call, call fails on the host due to invalid
34146 file descriptor (@code{EBADF}):
34149 <- @code{Fread,3,1234,6}
34153 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
34157 <- @code{Fread,3,1234,6}
34162 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
34166 <- @code{Fread,3,1234,6}
34167 -> @code{X1234,6:XXXXXX}
34171 @node Library List Format
34172 @section Library List Format
34173 @cindex library list format, remote protocol
34175 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
34176 same process as your application to manage libraries. In this case,
34177 @value{GDBN} can use the loader's symbol table and normal memory
34178 operations to maintain a list of shared libraries. On other
34179 platforms, the operating system manages loaded libraries.
34180 @value{GDBN} can not retrieve the list of currently loaded libraries
34181 through memory operations, so it uses the @samp{qXfer:libraries:read}
34182 packet (@pxref{qXfer library list read}) instead. The remote stub
34183 queries the target's operating system and reports which libraries
34186 The @samp{qXfer:libraries:read} packet returns an XML document which
34187 lists loaded libraries and their offsets. Each library has an
34188 associated name and one or more segment or section base addresses,
34189 which report where the library was loaded in memory.
34191 For the common case of libraries that are fully linked binaries, the
34192 library should have a list of segments. If the target supports
34193 dynamic linking of a relocatable object file, its library XML element
34194 should instead include a list of allocated sections. The segment or
34195 section bases are start addresses, not relocation offsets; they do not
34196 depend on the library's link-time base addresses.
34198 @value{GDBN} must be linked with the Expat library to support XML
34199 library lists. @xref{Expat}.
34201 A simple memory map, with one loaded library relocated by a single
34202 offset, looks like this:
34206 <library name="/lib/libc.so.6">
34207 <segment address="0x10000000"/>
34212 Another simple memory map, with one loaded library with three
34213 allocated sections (.text, .data, .bss), looks like this:
34217 <library name="sharedlib.o">
34218 <section address="0x10000000"/>
34219 <section address="0x20000000"/>
34220 <section address="0x30000000"/>
34225 The format of a library list is described by this DTD:
34228 <!-- library-list: Root element with versioning -->
34229 <!ELEMENT library-list (library)*>
34230 <!ATTLIST library-list version CDATA #FIXED "1.0">
34231 <!ELEMENT library (segment*, section*)>
34232 <!ATTLIST library name CDATA #REQUIRED>
34233 <!ELEMENT segment EMPTY>
34234 <!ATTLIST segment address CDATA #REQUIRED>
34235 <!ELEMENT section EMPTY>
34236 <!ATTLIST section address CDATA #REQUIRED>
34239 In addition, segments and section descriptors cannot be mixed within a
34240 single library element, and you must supply at least one segment or
34241 section for each library.
34243 @node Memory Map Format
34244 @section Memory Map Format
34245 @cindex memory map format
34247 To be able to write into flash memory, @value{GDBN} needs to obtain a
34248 memory map from the target. This section describes the format of the
34251 The memory map is obtained using the @samp{qXfer:memory-map:read}
34252 (@pxref{qXfer memory map read}) packet and is an XML document that
34253 lists memory regions.
34255 @value{GDBN} must be linked with the Expat library to support XML
34256 memory maps. @xref{Expat}.
34258 The top-level structure of the document is shown below:
34261 <?xml version="1.0"?>
34262 <!DOCTYPE memory-map
34263 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
34264 "http://sourceware.org/gdb/gdb-memory-map.dtd">
34270 Each region can be either:
34275 A region of RAM starting at @var{addr} and extending for @var{length}
34279 <memory type="ram" start="@var{addr}" length="@var{length}"/>
34284 A region of read-only memory:
34287 <memory type="rom" start="@var{addr}" length="@var{length}"/>
34292 A region of flash memory, with erasure blocks @var{blocksize}
34296 <memory type="flash" start="@var{addr}" length="@var{length}">
34297 <property name="blocksize">@var{blocksize}</property>
34303 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
34304 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
34305 packets to write to addresses in such ranges.
34307 The formal DTD for memory map format is given below:
34310 <!-- ................................................... -->
34311 <!-- Memory Map XML DTD ................................ -->
34312 <!-- File: memory-map.dtd .............................. -->
34313 <!-- .................................... .............. -->
34314 <!-- memory-map.dtd -->
34315 <!-- memory-map: Root element with versioning -->
34316 <!ELEMENT memory-map (memory | property)>
34317 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
34318 <!ELEMENT memory (property)>
34319 <!-- memory: Specifies a memory region,
34320 and its type, or device. -->
34321 <!ATTLIST memory type CDATA #REQUIRED
34322 start CDATA #REQUIRED
34323 length CDATA #REQUIRED
34324 device CDATA #IMPLIED>
34325 <!-- property: Generic attribute tag -->
34326 <!ELEMENT property (#PCDATA | property)*>
34327 <!ATTLIST property name CDATA #REQUIRED>
34330 @node Thread List Format
34331 @section Thread List Format
34332 @cindex thread list format
34334 To efficiently update the list of threads and their attributes,
34335 @value{GDBN} issues the @samp{qXfer:threads:read} packet
34336 (@pxref{qXfer threads read}) and obtains the XML document with
34337 the following structure:
34340 <?xml version="1.0"?>
34342 <thread id="id" core="0">
34343 ... description ...
34348 Each @samp{thread} element must have the @samp{id} attribute that
34349 identifies the thread (@pxref{thread-id syntax}). The
34350 @samp{core} attribute, if present, specifies which processor core
34351 the thread was last executing on. The content of the of @samp{thread}
34352 element is interpreted as human-readable auxilliary information.
34354 @include agentexpr.texi
34356 @node Trace File Format
34357 @appendix Trace File Format
34358 @cindex trace file format
34360 The trace file comes in three parts: a header, a textual description
34361 section, and a trace frame section with binary data.
34363 The header has the form @code{\x7fTRACE0\n}. The first byte is
34364 @code{0x7f} so as to indicate that the file contains binary data,
34365 while the @code{0} is a version number that may have different values
34368 The description section consists of multiple lines of @sc{ascii} text
34369 separated by newline characters (@code{0xa}). The lines may include a
34370 variety of optional descriptive or context-setting information, such
34371 as tracepoint definitions or register set size. @value{GDBN} will
34372 ignore any line that it does not recognize. An empty line marks the end
34375 @c FIXME add some specific types of data
34377 The trace frame section consists of a number of consecutive frames.
34378 Each frame begins with a two-byte tracepoint number, followed by a
34379 four-byte size giving the amount of data in the frame. The data in
34380 the frame consists of a number of blocks, each introduced by a
34381 character indicating its type (at least register, memory, and trace
34382 state variable). The data in this section is raw binary, not a
34383 hexadecimal or other encoding; its endianness matches the target's
34386 @c FIXME bi-arch may require endianness/arch info in description section
34389 @item R @var{bytes}
34390 Register block. The number and ordering of bytes matches that of a
34391 @code{g} packet in the remote protocol. Note that these are the
34392 actual bytes, in target order and @value{GDBN} register order, not a
34393 hexadecimal encoding.
34395 @item M @var{address} @var{length} @var{bytes}...
34396 Memory block. This is a contiguous block of memory, at the 8-byte
34397 address @var{address}, with a 2-byte length @var{length}, followed by
34398 @var{length} bytes.
34400 @item V @var{number} @var{value}
34401 Trace state variable block. This records the 8-byte signed value
34402 @var{value} of trace state variable numbered @var{number}.
34406 Future enhancements of the trace file format may include additional types
34409 @node Target Descriptions
34410 @appendix Target Descriptions
34411 @cindex target descriptions
34413 @strong{Warning:} target descriptions are still under active development,
34414 and the contents and format may change between @value{GDBN} releases.
34415 The format is expected to stabilize in the future.
34417 One of the challenges of using @value{GDBN} to debug embedded systems
34418 is that there are so many minor variants of each processor
34419 architecture in use. It is common practice for vendors to start with
34420 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
34421 and then make changes to adapt it to a particular market niche. Some
34422 architectures have hundreds of variants, available from dozens of
34423 vendors. This leads to a number of problems:
34427 With so many different customized processors, it is difficult for
34428 the @value{GDBN} maintainers to keep up with the changes.
34430 Since individual variants may have short lifetimes or limited
34431 audiences, it may not be worthwhile to carry information about every
34432 variant in the @value{GDBN} source tree.
34434 When @value{GDBN} does support the architecture of the embedded system
34435 at hand, the task of finding the correct architecture name to give the
34436 @command{set architecture} command can be error-prone.
34439 To address these problems, the @value{GDBN} remote protocol allows a
34440 target system to not only identify itself to @value{GDBN}, but to
34441 actually describe its own features. This lets @value{GDBN} support
34442 processor variants it has never seen before --- to the extent that the
34443 descriptions are accurate, and that @value{GDBN} understands them.
34445 @value{GDBN} must be linked with the Expat library to support XML
34446 target descriptions. @xref{Expat}.
34449 * Retrieving Descriptions:: How descriptions are fetched from a target.
34450 * Target Description Format:: The contents of a target description.
34451 * Predefined Target Types:: Standard types available for target
34453 * Standard Target Features:: Features @value{GDBN} knows about.
34456 @node Retrieving Descriptions
34457 @section Retrieving Descriptions
34459 Target descriptions can be read from the target automatically, or
34460 specified by the user manually. The default behavior is to read the
34461 description from the target. @value{GDBN} retrieves it via the remote
34462 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
34463 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
34464 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
34465 XML document, of the form described in @ref{Target Description
34468 Alternatively, you can specify a file to read for the target description.
34469 If a file is set, the target will not be queried. The commands to
34470 specify a file are:
34473 @cindex set tdesc filename
34474 @item set tdesc filename @var{path}
34475 Read the target description from @var{path}.
34477 @cindex unset tdesc filename
34478 @item unset tdesc filename
34479 Do not read the XML target description from a file. @value{GDBN}
34480 will use the description supplied by the current target.
34482 @cindex show tdesc filename
34483 @item show tdesc filename
34484 Show the filename to read for a target description, if any.
34488 @node Target Description Format
34489 @section Target Description Format
34490 @cindex target descriptions, XML format
34492 A target description annex is an @uref{http://www.w3.org/XML/, XML}
34493 document which complies with the Document Type Definition provided in
34494 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
34495 means you can use generally available tools like @command{xmllint} to
34496 check that your feature descriptions are well-formed and valid.
34497 However, to help people unfamiliar with XML write descriptions for
34498 their targets, we also describe the grammar here.
34500 Target descriptions can identify the architecture of the remote target
34501 and (for some architectures) provide information about custom register
34502 sets. They can also identify the OS ABI of the remote target.
34503 @value{GDBN} can use this information to autoconfigure for your
34504 target, or to warn you if you connect to an unsupported target.
34506 Here is a simple target description:
34509 <target version="1.0">
34510 <architecture>i386:x86-64</architecture>
34515 This minimal description only says that the target uses
34516 the x86-64 architecture.
34518 A target description has the following overall form, with [ ] marking
34519 optional elements and @dots{} marking repeatable elements. The elements
34520 are explained further below.
34523 <?xml version="1.0"?>
34524 <!DOCTYPE target SYSTEM "gdb-target.dtd">
34525 <target version="1.0">
34526 @r{[}@var{architecture}@r{]}
34527 @r{[}@var{osabi}@r{]}
34528 @r{[}@var{compatible}@r{]}
34529 @r{[}@var{feature}@dots{}@r{]}
34534 The description is generally insensitive to whitespace and line
34535 breaks, under the usual common-sense rules. The XML version
34536 declaration and document type declaration can generally be omitted
34537 (@value{GDBN} does not require them), but specifying them may be
34538 useful for XML validation tools. The @samp{version} attribute for
34539 @samp{<target>} may also be omitted, but we recommend
34540 including it; if future versions of @value{GDBN} use an incompatible
34541 revision of @file{gdb-target.dtd}, they will detect and report
34542 the version mismatch.
34544 @subsection Inclusion
34545 @cindex target descriptions, inclusion
34548 @cindex <xi:include>
34551 It can sometimes be valuable to split a target description up into
34552 several different annexes, either for organizational purposes, or to
34553 share files between different possible target descriptions. You can
34554 divide a description into multiple files by replacing any element of
34555 the target description with an inclusion directive of the form:
34558 <xi:include href="@var{document}"/>
34562 When @value{GDBN} encounters an element of this form, it will retrieve
34563 the named XML @var{document}, and replace the inclusion directive with
34564 the contents of that document. If the current description was read
34565 using @samp{qXfer}, then so will be the included document;
34566 @var{document} will be interpreted as the name of an annex. If the
34567 current description was read from a file, @value{GDBN} will look for
34568 @var{document} as a file in the same directory where it found the
34569 original description.
34571 @subsection Architecture
34572 @cindex <architecture>
34574 An @samp{<architecture>} element has this form:
34577 <architecture>@var{arch}</architecture>
34580 @var{arch} is one of the architectures from the set accepted by
34581 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
34584 @cindex @code{<osabi>}
34586 This optional field was introduced in @value{GDBN} version 7.0.
34587 Previous versions of @value{GDBN} ignore it.
34589 An @samp{<osabi>} element has this form:
34592 <osabi>@var{abi-name}</osabi>
34595 @var{abi-name} is an OS ABI name from the same selection accepted by
34596 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
34598 @subsection Compatible Architecture
34599 @cindex @code{<compatible>}
34601 This optional field was introduced in @value{GDBN} version 7.0.
34602 Previous versions of @value{GDBN} ignore it.
34604 A @samp{<compatible>} element has this form:
34607 <compatible>@var{arch}</compatible>
34610 @var{arch} is one of the architectures from the set accepted by
34611 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
34613 A @samp{<compatible>} element is used to specify that the target
34614 is able to run binaries in some other than the main target architecture
34615 given by the @samp{<architecture>} element. For example, on the
34616 Cell Broadband Engine, the main architecture is @code{powerpc:common}
34617 or @code{powerpc:common64}, but the system is able to run binaries
34618 in the @code{spu} architecture as well. The way to describe this
34619 capability with @samp{<compatible>} is as follows:
34622 <architecture>powerpc:common</architecture>
34623 <compatible>spu</compatible>
34626 @subsection Features
34629 Each @samp{<feature>} describes some logical portion of the target
34630 system. Features are currently used to describe available CPU
34631 registers and the types of their contents. A @samp{<feature>} element
34635 <feature name="@var{name}">
34636 @r{[}@var{type}@dots{}@r{]}
34642 Each feature's name should be unique within the description. The name
34643 of a feature does not matter unless @value{GDBN} has some special
34644 knowledge of the contents of that feature; if it does, the feature
34645 should have its standard name. @xref{Standard Target Features}.
34649 Any register's value is a collection of bits which @value{GDBN} must
34650 interpret. The default interpretation is a two's complement integer,
34651 but other types can be requested by name in the register description.
34652 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
34653 Target Types}), and the description can define additional composite types.
34655 Each type element must have an @samp{id} attribute, which gives
34656 a unique (within the containing @samp{<feature>}) name to the type.
34657 Types must be defined before they are used.
34660 Some targets offer vector registers, which can be treated as arrays
34661 of scalar elements. These types are written as @samp{<vector>} elements,
34662 specifying the array element type, @var{type}, and the number of elements,
34666 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
34670 If a register's value is usefully viewed in multiple ways, define it
34671 with a union type containing the useful representations. The
34672 @samp{<union>} element contains one or more @samp{<field>} elements,
34673 each of which has a @var{name} and a @var{type}:
34676 <union id="@var{id}">
34677 <field name="@var{name}" type="@var{type}"/>
34683 If a register's value is composed from several separate values, define
34684 it with a structure type. There are two forms of the @samp{<struct>}
34685 element; a @samp{<struct>} element must either contain only bitfields
34686 or contain no bitfields. If the structure contains only bitfields,
34687 its total size in bytes must be specified, each bitfield must have an
34688 explicit start and end, and bitfields are automatically assigned an
34689 integer type. The field's @var{start} should be less than or
34690 equal to its @var{end}, and zero represents the least significant bit.
34693 <struct id="@var{id}" size="@var{size}">
34694 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
34699 If the structure contains no bitfields, then each field has an
34700 explicit type, and no implicit padding is added.
34703 <struct id="@var{id}">
34704 <field name="@var{name}" type="@var{type}"/>
34710 If a register's value is a series of single-bit flags, define it with
34711 a flags type. The @samp{<flags>} element has an explicit @var{size}
34712 and contains one or more @samp{<field>} elements. Each field has a
34713 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
34717 <flags id="@var{id}" size="@var{size}">
34718 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
34723 @subsection Registers
34726 Each register is represented as an element with this form:
34729 <reg name="@var{name}"
34730 bitsize="@var{size}"
34731 @r{[}regnum="@var{num}"@r{]}
34732 @r{[}save-restore="@var{save-restore}"@r{]}
34733 @r{[}type="@var{type}"@r{]}
34734 @r{[}group="@var{group}"@r{]}/>
34738 The components are as follows:
34743 The register's name; it must be unique within the target description.
34746 The register's size, in bits.
34749 The register's number. If omitted, a register's number is one greater
34750 than that of the previous register (either in the current feature or in
34751 a preceeding feature); the first register in the target description
34752 defaults to zero. This register number is used to read or write
34753 the register; e.g.@: it is used in the remote @code{p} and @code{P}
34754 packets, and registers appear in the @code{g} and @code{G} packets
34755 in order of increasing register number.
34758 Whether the register should be preserved across inferior function
34759 calls; this must be either @code{yes} or @code{no}. The default is
34760 @code{yes}, which is appropriate for most registers except for
34761 some system control registers; this is not related to the target's
34765 The type of the register. @var{type} may be a predefined type, a type
34766 defined in the current feature, or one of the special types @code{int}
34767 and @code{float}. @code{int} is an integer type of the correct size
34768 for @var{bitsize}, and @code{float} is a floating point type (in the
34769 architecture's normal floating point format) of the correct size for
34770 @var{bitsize}. The default is @code{int}.
34773 The register group to which this register belongs. @var{group} must
34774 be either @code{general}, @code{float}, or @code{vector}. If no
34775 @var{group} is specified, @value{GDBN} will not display the register
34776 in @code{info registers}.
34780 @node Predefined Target Types
34781 @section Predefined Target Types
34782 @cindex target descriptions, predefined types
34784 Type definitions in the self-description can build up composite types
34785 from basic building blocks, but can not define fundamental types. Instead,
34786 standard identifiers are provided by @value{GDBN} for the fundamental
34787 types. The currently supported types are:
34796 Signed integer types holding the specified number of bits.
34803 Unsigned integer types holding the specified number of bits.
34807 Pointers to unspecified code and data. The program counter and
34808 any dedicated return address register may be marked as code
34809 pointers; printing a code pointer converts it into a symbolic
34810 address. The stack pointer and any dedicated address registers
34811 may be marked as data pointers.
34814 Single precision IEEE floating point.
34817 Double precision IEEE floating point.
34820 The 12-byte extended precision format used by ARM FPA registers.
34823 The 10-byte extended precision format used by x87 registers.
34826 32bit @sc{eflags} register used by x86.
34829 32bit @sc{mxcsr} register used by x86.
34833 @node Standard Target Features
34834 @section Standard Target Features
34835 @cindex target descriptions, standard features
34837 A target description must contain either no registers or all the
34838 target's registers. If the description contains no registers, then
34839 @value{GDBN} will assume a default register layout, selected based on
34840 the architecture. If the description contains any registers, the
34841 default layout will not be used; the standard registers must be
34842 described in the target description, in such a way that @value{GDBN}
34843 can recognize them.
34845 This is accomplished by giving specific names to feature elements
34846 which contain standard registers. @value{GDBN} will look for features
34847 with those names and verify that they contain the expected registers;
34848 if any known feature is missing required registers, or if any required
34849 feature is missing, @value{GDBN} will reject the target
34850 description. You can add additional registers to any of the
34851 standard features --- @value{GDBN} will display them just as if
34852 they were added to an unrecognized feature.
34854 This section lists the known features and their expected contents.
34855 Sample XML documents for these features are included in the
34856 @value{GDBN} source tree, in the directory @file{gdb/features}.
34858 Names recognized by @value{GDBN} should include the name of the
34859 company or organization which selected the name, and the overall
34860 architecture to which the feature applies; so e.g.@: the feature
34861 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
34863 The names of registers are not case sensitive for the purpose
34864 of recognizing standard features, but @value{GDBN} will only display
34865 registers using the capitalization used in the description.
34872 * PowerPC Features::
34877 @subsection ARM Features
34878 @cindex target descriptions, ARM features
34880 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
34881 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
34882 @samp{lr}, @samp{pc}, and @samp{cpsr}.
34884 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
34885 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
34887 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
34888 it should contain at least registers @samp{wR0} through @samp{wR15} and
34889 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
34890 @samp{wCSSF}, and @samp{wCASF} registers are optional.
34892 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
34893 should contain at least registers @samp{d0} through @samp{d15}. If
34894 they are present, @samp{d16} through @samp{d31} should also be included.
34895 @value{GDBN} will synthesize the single-precision registers from
34896 halves of the double-precision registers.
34898 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
34899 need to contain registers; it instructs @value{GDBN} to display the
34900 VFP double-precision registers as vectors and to synthesize the
34901 quad-precision registers from pairs of double-precision registers.
34902 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
34903 be present and include 32 double-precision registers.
34905 @node i386 Features
34906 @subsection i386 Features
34907 @cindex target descriptions, i386 features
34909 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
34910 targets. It should describe the following registers:
34914 @samp{eax} through @samp{edi} plus @samp{eip} for i386
34916 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
34918 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
34919 @samp{fs}, @samp{gs}
34921 @samp{st0} through @samp{st7}
34923 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
34924 @samp{foseg}, @samp{fooff} and @samp{fop}
34927 The register sets may be different, depending on the target.
34929 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
34930 describe registers:
34934 @samp{xmm0} through @samp{xmm7} for i386
34936 @samp{xmm0} through @samp{xmm15} for amd64
34941 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
34942 @samp{org.gnu.gdb.i386.sse} feature. It should
34943 describe the upper 128 bits of @sc{ymm} registers:
34947 @samp{ymm0h} through @samp{ymm7h} for i386
34949 @samp{ymm0h} through @samp{ymm15h} for amd64
34953 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
34954 describe a single register, @samp{orig_eax}.
34956 @node MIPS Features
34957 @subsection MIPS Features
34958 @cindex target descriptions, MIPS features
34960 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
34961 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
34962 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
34965 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
34966 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
34967 registers. They may be 32-bit or 64-bit depending on the target.
34969 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
34970 it may be optional in a future version of @value{GDBN}. It should
34971 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
34972 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
34974 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
34975 contain a single register, @samp{restart}, which is used by the
34976 Linux kernel to control restartable syscalls.
34978 @node M68K Features
34979 @subsection M68K Features
34980 @cindex target descriptions, M68K features
34983 @item @samp{org.gnu.gdb.m68k.core}
34984 @itemx @samp{org.gnu.gdb.coldfire.core}
34985 @itemx @samp{org.gnu.gdb.fido.core}
34986 One of those features must be always present.
34987 The feature that is present determines which flavor of m68k is
34988 used. The feature that is present should contain registers
34989 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
34990 @samp{sp}, @samp{ps} and @samp{pc}.
34992 @item @samp{org.gnu.gdb.coldfire.fp}
34993 This feature is optional. If present, it should contain registers
34994 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
34998 @node PowerPC Features
34999 @subsection PowerPC Features
35000 @cindex target descriptions, PowerPC features
35002 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
35003 targets. It should contain registers @samp{r0} through @samp{r31},
35004 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
35005 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
35007 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
35008 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
35010 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
35011 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
35014 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
35015 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
35016 will combine these registers with the floating point registers
35017 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
35018 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
35019 through @samp{vs63}, the set of vector registers for POWER7.
35021 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
35022 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
35023 @samp{spefscr}. SPE targets should provide 32-bit registers in
35024 @samp{org.gnu.gdb.power.core} and provide the upper halves in
35025 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
35026 these to present registers @samp{ev0} through @samp{ev31} to the
35029 @node Operating System Information
35030 @appendix Operating System Information
35031 @cindex operating system information
35037 Users of @value{GDBN} often wish to obtain information about the state of
35038 the operating system running on the target---for example the list of
35039 processes, or the list of open files. This section describes the
35040 mechanism that makes it possible. This mechanism is similar to the
35041 target features mechanism (@pxref{Target Descriptions}), but focuses
35042 on a different aspect of target.
35044 Operating system information is retrived from the target via the
35045 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
35046 read}). The object name in the request should be @samp{osdata}, and
35047 the @var{annex} identifies the data to be fetched.
35050 @appendixsection Process list
35051 @cindex operating system information, process list
35053 When requesting the process list, the @var{annex} field in the
35054 @samp{qXfer} request should be @samp{processes}. The returned data is
35055 an XML document. The formal syntax of this document is defined in
35056 @file{gdb/features/osdata.dtd}.
35058 An example document is:
35061 <?xml version="1.0"?>
35062 <!DOCTYPE target SYSTEM "osdata.dtd">
35063 <osdata type="processes">
35065 <column name="pid">1</column>
35066 <column name="user">root</column>
35067 <column name="command">/sbin/init</column>
35068 <column name="cores">1,2,3</column>
35073 Each item should include a column whose name is @samp{pid}. The value
35074 of that column should identify the process on the target. The
35075 @samp{user} and @samp{command} columns are optional, and will be
35076 displayed by @value{GDBN}. The @samp{cores} column, if present,
35077 should contain a comma-separated list of cores that this process
35078 is running on. Target may provide additional columns,
35079 which @value{GDBN} currently ignores.
35093 % I think something like @colophon should be in texinfo. In the
35095 \long\def\colophon{\hbox to0pt{}\vfill
35096 \centerline{The body of this manual is set in}
35097 \centerline{\fontname\tenrm,}
35098 \centerline{with headings in {\bf\fontname\tenbf}}
35099 \centerline{and examples in {\tt\fontname\tentt}.}
35100 \centerline{{\it\fontname\tenit\/},}
35101 \centerline{{\bf\fontname\tenbf}, and}
35102 \centerline{{\sl\fontname\tensl\/}}
35103 \centerline{are used for emphasis.}\vfill}
35105 % Blame: doc@cygnus.com, 1991.