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 1.3 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 @vindex $_thread@r{, convenience variable}
2792 The debugger convenience variable @samp{$_thread} contains the number
2793 of the current thread. You may find this useful in writing breakpoint
2794 conditional expressions, command scripts, and so forth. See
2795 @xref{Convenience Vars,, Convenience Variables}, for general
2796 information on convenience variables.
2798 @kindex thread apply
2799 @cindex apply command to several threads
2800 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2801 The @code{thread apply} command allows you to apply the named
2802 @var{command} to one or more threads. Specify the numbers of the
2803 threads that you want affected with the command argument
2804 @var{threadno}. It can be a single thread number, one of the numbers
2805 shown in the first field of the @samp{info threads} display; or it
2806 could be a range of thread numbers, as in @code{2-4}. To apply a
2807 command to all threads, type @kbd{thread apply all @var{command}}.
2809 @kindex set print thread-events
2810 @cindex print messages on thread start and exit
2811 @item set print thread-events
2812 @itemx set print thread-events on
2813 @itemx set print thread-events off
2814 The @code{set print thread-events} command allows you to enable or
2815 disable printing of messages when @value{GDBN} notices that new threads have
2816 started or that threads have exited. By default, these messages will
2817 be printed if detection of these events is supported by the target.
2818 Note that these messages cannot be disabled on all targets.
2820 @kindex show print thread-events
2821 @item show print thread-events
2822 Show whether messages will be printed when @value{GDBN} detects that threads
2823 have started and exited.
2826 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2827 more information about how @value{GDBN} behaves when you stop and start
2828 programs with multiple threads.
2830 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2831 watchpoints in programs with multiple threads.
2834 @kindex set libthread-db-search-path
2835 @cindex search path for @code{libthread_db}
2836 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2837 If this variable is set, @var{path} is a colon-separated list of
2838 directories @value{GDBN} will use to search for @code{libthread_db}.
2839 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2842 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2843 @code{libthread_db} library to obtain information about threads in the
2844 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2845 to find @code{libthread_db}. If that fails, @value{GDBN} will continue
2846 with default system shared library directories, and finally the directory
2847 from which @code{libpthread} was loaded in the inferior process.
2849 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2850 @value{GDBN} attempts to initialize it with the current inferior process.
2851 If this initialization fails (which could happen because of a version
2852 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2853 will unload @code{libthread_db}, and continue with the next directory.
2854 If none of @code{libthread_db} libraries initialize successfully,
2855 @value{GDBN} will issue a warning and thread debugging will be disabled.
2857 Setting @code{libthread-db-search-path} is currently implemented
2858 only on some platforms.
2860 @kindex show libthread-db-search-path
2861 @item show libthread-db-search-path
2862 Display current libthread_db search path.
2866 @section Debugging Forks
2868 @cindex fork, debugging programs which call
2869 @cindex multiple processes
2870 @cindex processes, multiple
2871 On most systems, @value{GDBN} has no special support for debugging
2872 programs which create additional processes using the @code{fork}
2873 function. When a program forks, @value{GDBN} will continue to debug the
2874 parent process and the child process will run unimpeded. If you have
2875 set a breakpoint in any code which the child then executes, the child
2876 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2877 will cause it to terminate.
2879 However, if you want to debug the child process there is a workaround
2880 which isn't too painful. Put a call to @code{sleep} in the code which
2881 the child process executes after the fork. It may be useful to sleep
2882 only if a certain environment variable is set, or a certain file exists,
2883 so that the delay need not occur when you don't want to run @value{GDBN}
2884 on the child. While the child is sleeping, use the @code{ps} program to
2885 get its process ID. Then tell @value{GDBN} (a new invocation of
2886 @value{GDBN} if you are also debugging the parent process) to attach to
2887 the child process (@pxref{Attach}). From that point on you can debug
2888 the child process just like any other process which you attached to.
2890 On some systems, @value{GDBN} provides support for debugging programs that
2891 create additional processes using the @code{fork} or @code{vfork} functions.
2892 Currently, the only platforms with this feature are HP-UX (11.x and later
2893 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2895 By default, when a program forks, @value{GDBN} will continue to debug
2896 the parent process and the child process will run unimpeded.
2898 If you want to follow the child process instead of the parent process,
2899 use the command @w{@code{set follow-fork-mode}}.
2902 @kindex set follow-fork-mode
2903 @item set follow-fork-mode @var{mode}
2904 Set the debugger response to a program call of @code{fork} or
2905 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2906 process. The @var{mode} argument can be:
2910 The original process is debugged after a fork. The child process runs
2911 unimpeded. This is the default.
2914 The new process is debugged after a fork. The parent process runs
2919 @kindex show follow-fork-mode
2920 @item show follow-fork-mode
2921 Display the current debugger response to a @code{fork} or @code{vfork} call.
2924 @cindex debugging multiple processes
2925 On Linux, if you want to debug both the parent and child processes, use the
2926 command @w{@code{set detach-on-fork}}.
2929 @kindex set detach-on-fork
2930 @item set detach-on-fork @var{mode}
2931 Tells gdb whether to detach one of the processes after a fork, or
2932 retain debugger control over them both.
2936 The child process (or parent process, depending on the value of
2937 @code{follow-fork-mode}) will be detached and allowed to run
2938 independently. This is the default.
2941 Both processes will be held under the control of @value{GDBN}.
2942 One process (child or parent, depending on the value of
2943 @code{follow-fork-mode}) is debugged as usual, while the other
2948 @kindex show detach-on-fork
2949 @item show detach-on-fork
2950 Show whether detach-on-fork mode is on/off.
2953 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
2954 will retain control of all forked processes (including nested forks).
2955 You can list the forked processes under the control of @value{GDBN} by
2956 using the @w{@code{info inferiors}} command, and switch from one fork
2957 to another by using the @code{inferior} command (@pxref{Inferiors and
2958 Programs, ,Debugging Multiple Inferiors and Programs}).
2960 To quit debugging one of the forked processes, you can either detach
2961 from it by using the @w{@code{detach inferior}} command (allowing it
2962 to run independently), or kill it using the @w{@code{kill inferior}}
2963 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
2966 If you ask to debug a child process and a @code{vfork} is followed by an
2967 @code{exec}, @value{GDBN} executes the new target up to the first
2968 breakpoint in the new target. If you have a breakpoint set on
2969 @code{main} in your original program, the breakpoint will also be set on
2970 the child process's @code{main}.
2972 On some systems, when a child process is spawned by @code{vfork}, you
2973 cannot debug the child or parent until an @code{exec} call completes.
2975 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2976 call executes, the new target restarts. To restart the parent
2977 process, use the @code{file} command with the parent executable name
2978 as its argument. By default, after an @code{exec} call executes,
2979 @value{GDBN} discards the symbols of the previous executable image.
2980 You can change this behaviour with the @w{@code{set follow-exec-mode}}
2984 @kindex set follow-exec-mode
2985 @item set follow-exec-mode @var{mode}
2987 Set debugger response to a program call of @code{exec}. An
2988 @code{exec} call replaces the program image of a process.
2990 @code{follow-exec-mode} can be:
2994 @value{GDBN} creates a new inferior and rebinds the process to this
2995 new inferior. The program the process was running before the
2996 @code{exec} call can be restarted afterwards by restarting the
3002 (@value{GDBP}) info inferiors
3004 Id Description Executable
3007 process 12020 is executing new program: prog2
3008 Program exited normally.
3009 (@value{GDBP}) info inferiors
3010 Id Description Executable
3016 @value{GDBN} keeps the process bound to the same inferior. The new
3017 executable image replaces the previous executable loaded in the
3018 inferior. Restarting the inferior after the @code{exec} call, with
3019 e.g., the @code{run} command, restarts the executable the process was
3020 running after the @code{exec} call. This is the default mode.
3025 (@value{GDBP}) info inferiors
3026 Id Description Executable
3029 process 12020 is executing new program: prog2
3030 Program exited normally.
3031 (@value{GDBP}) info inferiors
3032 Id Description Executable
3039 You can use the @code{catch} command to make @value{GDBN} stop whenever
3040 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3041 Catchpoints, ,Setting Catchpoints}.
3043 @node Checkpoint/Restart
3044 @section Setting a @emph{Bookmark} to Return to Later
3049 @cindex snapshot of a process
3050 @cindex rewind program state
3052 On certain operating systems@footnote{Currently, only
3053 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3054 program's state, called a @dfn{checkpoint}, and come back to it
3057 Returning to a checkpoint effectively undoes everything that has
3058 happened in the program since the @code{checkpoint} was saved. This
3059 includes changes in memory, registers, and even (within some limits)
3060 system state. Effectively, it is like going back in time to the
3061 moment when the checkpoint was saved.
3063 Thus, if you're stepping thru a program and you think you're
3064 getting close to the point where things go wrong, you can save
3065 a checkpoint. Then, if you accidentally go too far and miss
3066 the critical statement, instead of having to restart your program
3067 from the beginning, you can just go back to the checkpoint and
3068 start again from there.
3070 This can be especially useful if it takes a lot of time or
3071 steps to reach the point where you think the bug occurs.
3073 To use the @code{checkpoint}/@code{restart} method of debugging:
3078 Save a snapshot of the debugged program's current execution state.
3079 The @code{checkpoint} command takes no arguments, but each checkpoint
3080 is assigned a small integer id, similar to a breakpoint id.
3082 @kindex info checkpoints
3083 @item info checkpoints
3084 List the checkpoints that have been saved in the current debugging
3085 session. For each checkpoint, the following information will be
3092 @item Source line, or label
3095 @kindex restart @var{checkpoint-id}
3096 @item restart @var{checkpoint-id}
3097 Restore the program state that was saved as checkpoint number
3098 @var{checkpoint-id}. All program variables, registers, stack frames
3099 etc.@: will be returned to the values that they had when the checkpoint
3100 was saved. In essence, gdb will ``wind back the clock'' to the point
3101 in time when the checkpoint was saved.
3103 Note that breakpoints, @value{GDBN} variables, command history etc.
3104 are not affected by restoring a checkpoint. In general, a checkpoint
3105 only restores things that reside in the program being debugged, not in
3108 @kindex delete checkpoint @var{checkpoint-id}
3109 @item delete checkpoint @var{checkpoint-id}
3110 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3114 Returning to a previously saved checkpoint will restore the user state
3115 of the program being debugged, plus a significant subset of the system
3116 (OS) state, including file pointers. It won't ``un-write'' data from
3117 a file, but it will rewind the file pointer to the previous location,
3118 so that the previously written data can be overwritten. For files
3119 opened in read mode, the pointer will also be restored so that the
3120 previously read data can be read again.
3122 Of course, characters that have been sent to a printer (or other
3123 external device) cannot be ``snatched back'', and characters received
3124 from eg.@: a serial device can be removed from internal program buffers,
3125 but they cannot be ``pushed back'' into the serial pipeline, ready to
3126 be received again. Similarly, the actual contents of files that have
3127 been changed cannot be restored (at this time).
3129 However, within those constraints, you actually can ``rewind'' your
3130 program to a previously saved point in time, and begin debugging it
3131 again --- and you can change the course of events so as to debug a
3132 different execution path this time.
3134 @cindex checkpoints and process id
3135 Finally, there is one bit of internal program state that will be
3136 different when you return to a checkpoint --- the program's process
3137 id. Each checkpoint will have a unique process id (or @var{pid}),
3138 and each will be different from the program's original @var{pid}.
3139 If your program has saved a local copy of its process id, this could
3140 potentially pose a problem.
3142 @subsection A Non-obvious Benefit of Using Checkpoints
3144 On some systems such as @sc{gnu}/Linux, address space randomization
3145 is performed on new processes for security reasons. This makes it
3146 difficult or impossible to set a breakpoint, or watchpoint, on an
3147 absolute address if you have to restart the program, since the
3148 absolute location of a symbol will change from one execution to the
3151 A checkpoint, however, is an @emph{identical} copy of a process.
3152 Therefore if you create a checkpoint at (eg.@:) the start of main,
3153 and simply return to that checkpoint instead of restarting the
3154 process, you can avoid the effects of address randomization and
3155 your symbols will all stay in the same place.
3158 @chapter Stopping and Continuing
3160 The principal purposes of using a debugger are so that you can stop your
3161 program before it terminates; or so that, if your program runs into
3162 trouble, you can investigate and find out why.
3164 Inside @value{GDBN}, your program may stop for any of several reasons,
3165 such as a signal, a breakpoint, or reaching a new line after a
3166 @value{GDBN} command such as @code{step}. You may then examine and
3167 change variables, set new breakpoints or remove old ones, and then
3168 continue execution. Usually, the messages shown by @value{GDBN} provide
3169 ample explanation of the status of your program---but you can also
3170 explicitly request this information at any time.
3173 @kindex info program
3175 Display information about the status of your program: whether it is
3176 running or not, what process it is, and why it stopped.
3180 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3181 * Continuing and Stepping:: Resuming execution
3183 * Thread Stops:: Stopping and starting multi-thread programs
3187 @section Breakpoints, Watchpoints, and Catchpoints
3190 A @dfn{breakpoint} makes your program stop whenever a certain point in
3191 the program is reached. For each breakpoint, you can add conditions to
3192 control in finer detail whether your program stops. You can set
3193 breakpoints with the @code{break} command and its variants (@pxref{Set
3194 Breaks, ,Setting Breakpoints}), to specify the place where your program
3195 should stop by line number, function name or exact address in the
3198 On some systems, you can set breakpoints in shared libraries before
3199 the executable is run. There is a minor limitation on HP-UX systems:
3200 you must wait until the executable is run in order to set breakpoints
3201 in shared library routines that are not called directly by the program
3202 (for example, routines that are arguments in a @code{pthread_create}
3206 @cindex data breakpoints
3207 @cindex memory tracing
3208 @cindex breakpoint on memory address
3209 @cindex breakpoint on variable modification
3210 A @dfn{watchpoint} is a special breakpoint that stops your program
3211 when the value of an expression changes. The expression may be a value
3212 of a variable, or it could involve values of one or more variables
3213 combined by operators, such as @samp{a + b}. This is sometimes called
3214 @dfn{data breakpoints}. You must use a different command to set
3215 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3216 from that, you can manage a watchpoint like any other breakpoint: you
3217 enable, disable, and delete both breakpoints and watchpoints using the
3220 You can arrange to have values from your program displayed automatically
3221 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3225 @cindex breakpoint on events
3226 A @dfn{catchpoint} is another special breakpoint that stops your program
3227 when a certain kind of event occurs, such as the throwing of a C@t{++}
3228 exception or the loading of a library. As with watchpoints, you use a
3229 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3230 Catchpoints}), but aside from that, you can manage a catchpoint like any
3231 other breakpoint. (To stop when your program receives a signal, use the
3232 @code{handle} command; see @ref{Signals, ,Signals}.)
3234 @cindex breakpoint numbers
3235 @cindex numbers for breakpoints
3236 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3237 catchpoint when you create it; these numbers are successive integers
3238 starting with one. In many of the commands for controlling various
3239 features of breakpoints you use the breakpoint number to say which
3240 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3241 @dfn{disabled}; if disabled, it has no effect on your program until you
3244 @cindex breakpoint ranges
3245 @cindex ranges of breakpoints
3246 Some @value{GDBN} commands accept a range of breakpoints on which to
3247 operate. A breakpoint range is either a single breakpoint number, like
3248 @samp{5}, or two such numbers, in increasing order, separated by a
3249 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3250 all breakpoints in that range are operated on.
3253 * Set Breaks:: Setting breakpoints
3254 * Set Watchpoints:: Setting watchpoints
3255 * Set Catchpoints:: Setting catchpoints
3256 * Delete Breaks:: Deleting breakpoints
3257 * Disabling:: Disabling breakpoints
3258 * Conditions:: Break conditions
3259 * Break Commands:: Breakpoint command lists
3260 * Save Breakpoints:: How to save breakpoints in a file
3261 * Error in Breakpoints:: ``Cannot insert breakpoints''
3262 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3266 @subsection Setting Breakpoints
3268 @c FIXME LMB what does GDB do if no code on line of breakpt?
3269 @c consider in particular declaration with/without initialization.
3271 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3274 @kindex b @r{(@code{break})}
3275 @vindex $bpnum@r{, convenience variable}
3276 @cindex latest breakpoint
3277 Breakpoints are set with the @code{break} command (abbreviated
3278 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3279 number of the breakpoint you've set most recently; see @ref{Convenience
3280 Vars,, Convenience Variables}, for a discussion of what you can do with
3281 convenience variables.
3284 @item break @var{location}
3285 Set a breakpoint at the given @var{location}, which can specify a
3286 function name, a line number, or an address of an instruction.
3287 (@xref{Specify Location}, for a list of all the possible ways to
3288 specify a @var{location}.) The breakpoint will stop your program just
3289 before it executes any of the code in the specified @var{location}.
3291 When using source languages that permit overloading of symbols, such as
3292 C@t{++}, a function name may refer to more than one possible place to break.
3293 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3296 It is also possible to insert a breakpoint that will stop the program
3297 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3298 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3301 When called without any arguments, @code{break} sets a breakpoint at
3302 the next instruction to be executed in the selected stack frame
3303 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3304 innermost, this makes your program stop as soon as control
3305 returns to that frame. This is similar to the effect of a
3306 @code{finish} command in the frame inside the selected frame---except
3307 that @code{finish} does not leave an active breakpoint. If you use
3308 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3309 the next time it reaches the current location; this may be useful
3312 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3313 least one instruction has been executed. If it did not do this, you
3314 would be unable to proceed past a breakpoint without first disabling the
3315 breakpoint. This rule applies whether or not the breakpoint already
3316 existed when your program stopped.
3318 @item break @dots{} if @var{cond}
3319 Set a breakpoint with condition @var{cond}; evaluate the expression
3320 @var{cond} each time the breakpoint is reached, and stop only if the
3321 value is nonzero---that is, if @var{cond} evaluates as true.
3322 @samp{@dots{}} stands for one of the possible arguments described
3323 above (or no argument) specifying where to break. @xref{Conditions,
3324 ,Break Conditions}, for more information on breakpoint conditions.
3327 @item tbreak @var{args}
3328 Set a breakpoint enabled only for one stop. @var{args} are the
3329 same as for the @code{break} command, and the breakpoint is set in the same
3330 way, but the breakpoint is automatically deleted after the first time your
3331 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3334 @cindex hardware breakpoints
3335 @item hbreak @var{args}
3336 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3337 @code{break} command and the breakpoint is set in the same way, but the
3338 breakpoint requires hardware support and some target hardware may not
3339 have this support. The main purpose of this is EPROM/ROM code
3340 debugging, so you can set a breakpoint at an instruction without
3341 changing the instruction. This can be used with the new trap-generation
3342 provided by SPARClite DSU and most x86-based targets. These targets
3343 will generate traps when a program accesses some data or instruction
3344 address that is assigned to the debug registers. However the hardware
3345 breakpoint registers can take a limited number of breakpoints. For
3346 example, on the DSU, only two data breakpoints can be set at a time, and
3347 @value{GDBN} will reject this command if more than two are used. Delete
3348 or disable unused hardware breakpoints before setting new ones
3349 (@pxref{Disabling, ,Disabling Breakpoints}).
3350 @xref{Conditions, ,Break Conditions}.
3351 For remote targets, you can restrict the number of hardware
3352 breakpoints @value{GDBN} will use, see @ref{set remote
3353 hardware-breakpoint-limit}.
3356 @item thbreak @var{args}
3357 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3358 are the same as for the @code{hbreak} command and the breakpoint is set in
3359 the same way. However, like the @code{tbreak} command,
3360 the breakpoint is automatically deleted after the
3361 first time your program stops there. Also, like the @code{hbreak}
3362 command, the breakpoint requires hardware support and some target hardware
3363 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3364 See also @ref{Conditions, ,Break Conditions}.
3367 @cindex regular expression
3368 @cindex breakpoints at functions matching a regexp
3369 @cindex set breakpoints in many functions
3370 @item rbreak @var{regex}
3371 Set breakpoints on all functions matching the regular expression
3372 @var{regex}. This command sets an unconditional breakpoint on all
3373 matches, printing a list of all breakpoints it set. Once these
3374 breakpoints are set, they are treated just like the breakpoints set with
3375 the @code{break} command. You can delete them, disable them, or make
3376 them conditional the same way as any other breakpoint.
3378 The syntax of the regular expression is the standard one used with tools
3379 like @file{grep}. Note that this is different from the syntax used by
3380 shells, so for instance @code{foo*} matches all functions that include
3381 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3382 @code{.*} leading and trailing the regular expression you supply, so to
3383 match only functions that begin with @code{foo}, use @code{^foo}.
3385 @cindex non-member C@t{++} functions, set breakpoint in
3386 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3387 breakpoints on overloaded functions that are not members of any special
3390 @cindex set breakpoints on all functions
3391 The @code{rbreak} command can be used to set breakpoints in
3392 @strong{all} the functions in a program, like this:
3395 (@value{GDBP}) rbreak .
3398 @item rbreak @var{file}:@var{regex}
3399 If @code{rbreak} is called with a filename qualification, it limits
3400 the search for functions matching the given regular expression to the
3401 specified @var{file}. This can be used, for example, to set breakpoints on
3402 every function in a given file:
3405 (@value{GDBP}) rbreak file.c:.
3408 The colon separating the filename qualifier from the regex may
3409 optionally be surrounded by spaces.
3411 @kindex info breakpoints
3412 @cindex @code{$_} and @code{info breakpoints}
3413 @item info breakpoints @r{[}@var{n}@r{]}
3414 @itemx info break @r{[}@var{n}@r{]}
3415 Print a table of all breakpoints, watchpoints, and catchpoints set and
3416 not deleted. Optional argument @var{n} means print information only
3417 about the specified breakpoint (or watchpoint or catchpoint). For
3418 each breakpoint, following columns are printed:
3421 @item Breakpoint Numbers
3423 Breakpoint, watchpoint, or catchpoint.
3425 Whether the breakpoint is marked to be disabled or deleted when hit.
3426 @item Enabled or Disabled
3427 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3428 that are not enabled.
3430 Where the breakpoint is in your program, as a memory address. For a
3431 pending breakpoint whose address is not yet known, this field will
3432 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3433 library that has the symbol or line referred by breakpoint is loaded.
3434 See below for details. A breakpoint with several locations will
3435 have @samp{<MULTIPLE>} in this field---see below for details.
3437 Where the breakpoint is in the source for your program, as a file and
3438 line number. For a pending breakpoint, the original string passed to
3439 the breakpoint command will be listed as it cannot be resolved until
3440 the appropriate shared library is loaded in the future.
3444 If a breakpoint is conditional, @code{info break} shows the condition on
3445 the line following the affected breakpoint; breakpoint commands, if any,
3446 are listed after that. A pending breakpoint is allowed to have a condition
3447 specified for it. The condition is not parsed for validity until a shared
3448 library is loaded that allows the pending breakpoint to resolve to a
3452 @code{info break} with a breakpoint
3453 number @var{n} as argument lists only that breakpoint. The
3454 convenience variable @code{$_} and the default examining-address for
3455 the @code{x} command are set to the address of the last breakpoint
3456 listed (@pxref{Memory, ,Examining Memory}).
3459 @code{info break} displays a count of the number of times the breakpoint
3460 has been hit. This is especially useful in conjunction with the
3461 @code{ignore} command. You can ignore a large number of breakpoint
3462 hits, look at the breakpoint info to see how many times the breakpoint
3463 was hit, and then run again, ignoring one less than that number. This
3464 will get you quickly to the last hit of that breakpoint.
3467 @value{GDBN} allows you to set any number of breakpoints at the same place in
3468 your program. There is nothing silly or meaningless about this. When
3469 the breakpoints are conditional, this is even useful
3470 (@pxref{Conditions, ,Break Conditions}).
3472 @cindex multiple locations, breakpoints
3473 @cindex breakpoints, multiple locations
3474 It is possible that a breakpoint corresponds to several locations
3475 in your program. Examples of this situation are:
3479 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3480 instances of the function body, used in different cases.
3483 For a C@t{++} template function, a given line in the function can
3484 correspond to any number of instantiations.
3487 For an inlined function, a given source line can correspond to
3488 several places where that function is inlined.
3491 In all those cases, @value{GDBN} will insert a breakpoint at all
3492 the relevant locations@footnote{
3493 As of this writing, multiple-location breakpoints work only if there's
3494 line number information for all the locations. This means that they
3495 will generally not work in system libraries, unless you have debug
3496 info with line numbers for them.}.
3498 A breakpoint with multiple locations is displayed in the breakpoint
3499 table using several rows---one header row, followed by one row for
3500 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3501 address column. The rows for individual locations contain the actual
3502 addresses for locations, and show the functions to which those
3503 locations belong. The number column for a location is of the form
3504 @var{breakpoint-number}.@var{location-number}.
3509 Num Type Disp Enb Address What
3510 1 breakpoint keep y <MULTIPLE>
3512 breakpoint already hit 1 time
3513 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3514 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3517 Each location can be individually enabled or disabled by passing
3518 @var{breakpoint-number}.@var{location-number} as argument to the
3519 @code{enable} and @code{disable} commands. Note that you cannot
3520 delete the individual locations from the list, you can only delete the
3521 entire list of locations that belong to their parent breakpoint (with
3522 the @kbd{delete @var{num}} command, where @var{num} is the number of
3523 the parent breakpoint, 1 in the above example). Disabling or enabling
3524 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3525 that belong to that breakpoint.
3527 @cindex pending breakpoints
3528 It's quite common to have a breakpoint inside a shared library.
3529 Shared libraries can be loaded and unloaded explicitly,
3530 and possibly repeatedly, as the program is executed. To support
3531 this use case, @value{GDBN} updates breakpoint locations whenever
3532 any shared library is loaded or unloaded. Typically, you would
3533 set a breakpoint in a shared library at the beginning of your
3534 debugging session, when the library is not loaded, and when the
3535 symbols from the library are not available. When you try to set
3536 breakpoint, @value{GDBN} will ask you if you want to set
3537 a so called @dfn{pending breakpoint}---breakpoint whose address
3538 is not yet resolved.
3540 After the program is run, whenever a new shared library is loaded,
3541 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3542 shared library contains the symbol or line referred to by some
3543 pending breakpoint, that breakpoint is resolved and becomes an
3544 ordinary breakpoint. When a library is unloaded, all breakpoints
3545 that refer to its symbols or source lines become pending again.
3547 This logic works for breakpoints with multiple locations, too. For
3548 example, if you have a breakpoint in a C@t{++} template function, and
3549 a newly loaded shared library has an instantiation of that template,
3550 a new location is added to the list of locations for the breakpoint.
3552 Except for having unresolved address, pending breakpoints do not
3553 differ from regular breakpoints. You can set conditions or commands,
3554 enable and disable them and perform other breakpoint operations.
3556 @value{GDBN} provides some additional commands for controlling what
3557 happens when the @samp{break} command cannot resolve breakpoint
3558 address specification to an address:
3560 @kindex set breakpoint pending
3561 @kindex show breakpoint pending
3563 @item set breakpoint pending auto
3564 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3565 location, it queries you whether a pending breakpoint should be created.
3567 @item set breakpoint pending on
3568 This indicates that an unrecognized breakpoint location should automatically
3569 result in a pending breakpoint being created.
3571 @item set breakpoint pending off
3572 This indicates that pending breakpoints are not to be created. Any
3573 unrecognized breakpoint location results in an error. This setting does
3574 not affect any pending breakpoints previously created.
3576 @item show breakpoint pending
3577 Show the current behavior setting for creating pending breakpoints.
3580 The settings above only affect the @code{break} command and its
3581 variants. Once breakpoint is set, it will be automatically updated
3582 as shared libraries are loaded and unloaded.
3584 @cindex automatic hardware breakpoints
3585 For some targets, @value{GDBN} can automatically decide if hardware or
3586 software breakpoints should be used, depending on whether the
3587 breakpoint address is read-only or read-write. This applies to
3588 breakpoints set with the @code{break} command as well as to internal
3589 breakpoints set by commands like @code{next} and @code{finish}. For
3590 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3593 You can control this automatic behaviour with the following commands::
3595 @kindex set breakpoint auto-hw
3596 @kindex show breakpoint auto-hw
3598 @item set breakpoint auto-hw on
3599 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3600 will try to use the target memory map to decide if software or hardware
3601 breakpoint must be used.
3603 @item set breakpoint auto-hw off
3604 This indicates @value{GDBN} should not automatically select breakpoint
3605 type. If the target provides a memory map, @value{GDBN} will warn when
3606 trying to set software breakpoint at a read-only address.
3609 @value{GDBN} normally implements breakpoints by replacing the program code
3610 at the breakpoint address with a special instruction, which, when
3611 executed, given control to the debugger. By default, the program
3612 code is so modified only when the program is resumed. As soon as
3613 the program stops, @value{GDBN} restores the original instructions. This
3614 behaviour guards against leaving breakpoints inserted in the
3615 target should gdb abrubptly disconnect. However, with slow remote
3616 targets, inserting and removing breakpoint can reduce the performance.
3617 This behavior can be controlled with the following commands::
3619 @kindex set breakpoint always-inserted
3620 @kindex show breakpoint always-inserted
3622 @item set breakpoint always-inserted off
3623 All breakpoints, including newly added by the user, are inserted in
3624 the target only when the target is resumed. All breakpoints are
3625 removed from the target when it stops.
3627 @item set breakpoint always-inserted on
3628 Causes all breakpoints to be inserted in the target at all times. If
3629 the user adds a new breakpoint, or changes an existing breakpoint, the
3630 breakpoints in the target are updated immediately. A breakpoint is
3631 removed from the target only when breakpoint itself is removed.
3633 @cindex non-stop mode, and @code{breakpoint always-inserted}
3634 @item set breakpoint always-inserted auto
3635 This is the default mode. If @value{GDBN} is controlling the inferior
3636 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3637 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3638 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3639 @code{breakpoint always-inserted} mode is off.
3642 @cindex negative breakpoint numbers
3643 @cindex internal @value{GDBN} breakpoints
3644 @value{GDBN} itself sometimes sets breakpoints in your program for
3645 special purposes, such as proper handling of @code{longjmp} (in C
3646 programs). These internal breakpoints are assigned negative numbers,
3647 starting with @code{-1}; @samp{info breakpoints} does not display them.
3648 You can see these breakpoints with the @value{GDBN} maintenance command
3649 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3652 @node Set Watchpoints
3653 @subsection Setting Watchpoints
3655 @cindex setting watchpoints
3656 You can use a watchpoint to stop execution whenever the value of an
3657 expression changes, without having to predict a particular place where
3658 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3659 The expression may be as simple as the value of a single variable, or
3660 as complex as many variables combined by operators. Examples include:
3664 A reference to the value of a single variable.
3667 An address cast to an appropriate data type. For example,
3668 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3669 address (assuming an @code{int} occupies 4 bytes).
3672 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3673 expression can use any operators valid in the program's native
3674 language (@pxref{Languages}).
3677 You can set a watchpoint on an expression even if the expression can
3678 not be evaluated yet. For instance, you can set a watchpoint on
3679 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3680 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3681 the expression produces a valid value. If the expression becomes
3682 valid in some other way than changing a variable (e.g.@: if the memory
3683 pointed to by @samp{*global_ptr} becomes readable as the result of a
3684 @code{malloc} call), @value{GDBN} may not stop until the next time
3685 the expression changes.
3687 @cindex software watchpoints
3688 @cindex hardware watchpoints
3689 Depending on your system, watchpoints may be implemented in software or
3690 hardware. @value{GDBN} does software watchpointing by single-stepping your
3691 program and testing the variable's value each time, which is hundreds of
3692 times slower than normal execution. (But this may still be worth it, to
3693 catch errors where you have no clue what part of your program is the
3696 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3697 x86-based targets, @value{GDBN} includes support for hardware
3698 watchpoints, which do not slow down the running of your program.
3702 @item watch @var{expr} @r{[}thread @var{threadnum}@r{]}
3703 Set a watchpoint for an expression. @value{GDBN} will break when the
3704 expression @var{expr} is written into by the program and its value
3705 changes. The simplest (and the most popular) use of this command is
3706 to watch the value of a single variable:
3709 (@value{GDBP}) watch foo
3712 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3713 clause, @value{GDBN} breaks only when the thread identified by
3714 @var{threadnum} changes the value of @var{expr}. If any other threads
3715 change the value of @var{expr}, @value{GDBN} will not break. Note
3716 that watchpoints restricted to a single thread in this way only work
3717 with Hardware Watchpoints.
3720 @item rwatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3721 Set a watchpoint that will break when the value of @var{expr} is read
3725 @item awatch @var{expr} @r{[}thread @var{threadnum}@r{]}
3726 Set a watchpoint that will break when @var{expr} is either read from
3727 or written into by the program.
3729 @kindex info watchpoints @r{[}@var{n}@r{]}
3730 @item info watchpoints
3731 This command prints a list of watchpoints, using the same format as
3732 @code{info break} (@pxref{Set Breaks}).
3735 If you watch for a change in a numerically entered address you need to
3736 dereference it, as the address itself is just a constant number which will
3737 never change. @value{GDBN} refuses to create a watchpoint that watches
3738 a never-changing value:
3741 (@value{GDBP}) watch 0x600850
3742 Cannot watch constant value 0x600850.
3743 (@value{GDBP}) watch *(int *) 0x600850
3744 Watchpoint 1: *(int *) 6293584
3747 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3748 watchpoints execute very quickly, and the debugger reports a change in
3749 value at the exact instruction where the change occurs. If @value{GDBN}
3750 cannot set a hardware watchpoint, it sets a software watchpoint, which
3751 executes more slowly and reports the change in value at the next
3752 @emph{statement}, not the instruction, after the change occurs.
3754 @cindex use only software watchpoints
3755 You can force @value{GDBN} to use only software watchpoints with the
3756 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3757 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3758 the underlying system supports them. (Note that hardware-assisted
3759 watchpoints that were set @emph{before} setting
3760 @code{can-use-hw-watchpoints} to zero will still use the hardware
3761 mechanism of watching expression values.)
3764 @item set can-use-hw-watchpoints
3765 @kindex set can-use-hw-watchpoints
3766 Set whether or not to use hardware watchpoints.
3768 @item show can-use-hw-watchpoints
3769 @kindex show can-use-hw-watchpoints
3770 Show the current mode of using hardware watchpoints.
3773 For remote targets, you can restrict the number of hardware
3774 watchpoints @value{GDBN} will use, see @ref{set remote
3775 hardware-breakpoint-limit}.
3777 When you issue the @code{watch} command, @value{GDBN} reports
3780 Hardware watchpoint @var{num}: @var{expr}
3784 if it was able to set a hardware watchpoint.
3786 Currently, the @code{awatch} and @code{rwatch} commands can only set
3787 hardware watchpoints, because accesses to data that don't change the
3788 value of the watched expression cannot be detected without examining
3789 every instruction as it is being executed, and @value{GDBN} does not do
3790 that currently. If @value{GDBN} finds that it is unable to set a
3791 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3792 will print a message like this:
3795 Expression cannot be implemented with read/access watchpoint.
3798 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3799 data type of the watched expression is wider than what a hardware
3800 watchpoint on the target machine can handle. For example, some systems
3801 can only watch regions that are up to 4 bytes wide; on such systems you
3802 cannot set hardware watchpoints for an expression that yields a
3803 double-precision floating-point number (which is typically 8 bytes
3804 wide). As a work-around, it might be possible to break the large region
3805 into a series of smaller ones and watch them with separate watchpoints.
3807 If you set too many hardware watchpoints, @value{GDBN} might be unable
3808 to insert all of them when you resume the execution of your program.
3809 Since the precise number of active watchpoints is unknown until such
3810 time as the program is about to be resumed, @value{GDBN} might not be
3811 able to warn you about this when you set the watchpoints, and the
3812 warning will be printed only when the program is resumed:
3815 Hardware watchpoint @var{num}: Could not insert watchpoint
3819 If this happens, delete or disable some of the watchpoints.
3821 Watching complex expressions that reference many variables can also
3822 exhaust the resources available for hardware-assisted watchpoints.
3823 That's because @value{GDBN} needs to watch every variable in the
3824 expression with separately allocated resources.
3826 If you call a function interactively using @code{print} or @code{call},
3827 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3828 kind of breakpoint or the call completes.
3830 @value{GDBN} automatically deletes watchpoints that watch local
3831 (automatic) variables, or expressions that involve such variables, when
3832 they go out of scope, that is, when the execution leaves the block in
3833 which these variables were defined. In particular, when the program
3834 being debugged terminates, @emph{all} local variables go out of scope,
3835 and so only watchpoints that watch global variables remain set. If you
3836 rerun the program, you will need to set all such watchpoints again. One
3837 way of doing that would be to set a code breakpoint at the entry to the
3838 @code{main} function and when it breaks, set all the watchpoints.
3840 @cindex watchpoints and threads
3841 @cindex threads and watchpoints
3842 In multi-threaded programs, watchpoints will detect changes to the
3843 watched expression from every thread.
3846 @emph{Warning:} In multi-threaded programs, software watchpoints
3847 have only limited usefulness. If @value{GDBN} creates a software
3848 watchpoint, it can only watch the value of an expression @emph{in a
3849 single thread}. If you are confident that the expression can only
3850 change due to the current thread's activity (and if you are also
3851 confident that no other thread can become current), then you can use
3852 software watchpoints as usual. However, @value{GDBN} may not notice
3853 when a non-current thread's activity changes the expression. (Hardware
3854 watchpoints, in contrast, watch an expression in all threads.)
3857 @xref{set remote hardware-watchpoint-limit}.
3859 @node Set Catchpoints
3860 @subsection Setting Catchpoints
3861 @cindex catchpoints, setting
3862 @cindex exception handlers
3863 @cindex event handling
3865 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3866 kinds of program events, such as C@t{++} exceptions or the loading of a
3867 shared library. Use the @code{catch} command to set a catchpoint.
3871 @item catch @var{event}
3872 Stop when @var{event} occurs. @var{event} can be any of the following:
3875 @cindex stop on C@t{++} exceptions
3876 The throwing of a C@t{++} exception.
3879 The catching of a C@t{++} exception.
3882 @cindex Ada exception catching
3883 @cindex catch Ada exceptions
3884 An Ada exception being raised. If an exception name is specified
3885 at the end of the command (eg @code{catch exception Program_Error}),
3886 the debugger will stop only when this specific exception is raised.
3887 Otherwise, the debugger stops execution when any Ada exception is raised.
3889 When inserting an exception catchpoint on a user-defined exception whose
3890 name is identical to one of the exceptions defined by the language, the
3891 fully qualified name must be used as the exception name. Otherwise,
3892 @value{GDBN} will assume that it should stop on the pre-defined exception
3893 rather than the user-defined one. For instance, assuming an exception
3894 called @code{Constraint_Error} is defined in package @code{Pck}, then
3895 the command to use to catch such exceptions is @kbd{catch exception
3896 Pck.Constraint_Error}.
3898 @item exception unhandled
3899 An exception that was raised but is not handled by the program.
3902 A failed Ada assertion.
3905 @cindex break on fork/exec
3906 A call to @code{exec}. This is currently only available for HP-UX
3910 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
3911 @cindex break on a system call.
3912 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
3913 syscall is a mechanism for application programs to request a service
3914 from the operating system (OS) or one of the OS system services.
3915 @value{GDBN} can catch some or all of the syscalls issued by the
3916 debuggee, and show the related information for each syscall. If no
3917 argument is specified, calls to and returns from all system calls
3920 @var{name} can be any system call name that is valid for the
3921 underlying OS. Just what syscalls are valid depends on the OS. On
3922 GNU and Unix systems, you can find the full list of valid syscall
3923 names on @file{/usr/include/asm/unistd.h}.
3925 @c For MS-Windows, the syscall names and the corresponding numbers
3926 @c can be found, e.g., on this URL:
3927 @c http://www.metasploit.com/users/opcode/syscalls.html
3928 @c but we don't support Windows syscalls yet.
3930 Normally, @value{GDBN} knows in advance which syscalls are valid for
3931 each OS, so you can use the @value{GDBN} command-line completion
3932 facilities (@pxref{Completion,, command completion}) to list the
3935 You may also specify the system call numerically. A syscall's
3936 number is the value passed to the OS's syscall dispatcher to
3937 identify the requested service. When you specify the syscall by its
3938 name, @value{GDBN} uses its database of syscalls to convert the name
3939 into the corresponding numeric code, but using the number directly
3940 may be useful if @value{GDBN}'s database does not have the complete
3941 list of syscalls on your system (e.g., because @value{GDBN} lags
3942 behind the OS upgrades).
3944 The example below illustrates how this command works if you don't provide
3948 (@value{GDBP}) catch syscall
3949 Catchpoint 1 (syscall)
3951 Starting program: /tmp/catch-syscall
3953 Catchpoint 1 (call to syscall 'close'), \
3954 0xffffe424 in __kernel_vsyscall ()
3958 Catchpoint 1 (returned from syscall 'close'), \
3959 0xffffe424 in __kernel_vsyscall ()
3963 Here is an example of catching a system call by name:
3966 (@value{GDBP}) catch syscall chroot
3967 Catchpoint 1 (syscall 'chroot' [61])
3969 Starting program: /tmp/catch-syscall
3971 Catchpoint 1 (call to syscall 'chroot'), \
3972 0xffffe424 in __kernel_vsyscall ()
3976 Catchpoint 1 (returned from syscall 'chroot'), \
3977 0xffffe424 in __kernel_vsyscall ()
3981 An example of specifying a system call numerically. In the case
3982 below, the syscall number has a corresponding entry in the XML
3983 file, so @value{GDBN} finds its name and prints it:
3986 (@value{GDBP}) catch syscall 252
3987 Catchpoint 1 (syscall(s) 'exit_group')
3989 Starting program: /tmp/catch-syscall
3991 Catchpoint 1 (call to syscall 'exit_group'), \
3992 0xffffe424 in __kernel_vsyscall ()
3996 Program exited normally.
4000 However, there can be situations when there is no corresponding name
4001 in XML file for that syscall number. In this case, @value{GDBN} prints
4002 a warning message saying that it was not able to find the syscall name,
4003 but the catchpoint will be set anyway. See the example below:
4006 (@value{GDBP}) catch syscall 764
4007 warning: The number '764' does not represent a known syscall.
4008 Catchpoint 2 (syscall 764)
4012 If you configure @value{GDBN} using the @samp{--without-expat} option,
4013 it will not be able to display syscall names. Also, if your
4014 architecture does not have an XML file describing its system calls,
4015 you will not be able to see the syscall names. It is important to
4016 notice that these two features are used for accessing the syscall
4017 name database. In either case, you will see a warning like this:
4020 (@value{GDBP}) catch syscall
4021 warning: Could not open "syscalls/i386-linux.xml"
4022 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4023 GDB will not be able to display syscall names.
4024 Catchpoint 1 (syscall)
4028 Of course, the file name will change depending on your architecture and system.
4030 Still using the example above, you can also try to catch a syscall by its
4031 number. In this case, you would see something like:
4034 (@value{GDBP}) catch syscall 252
4035 Catchpoint 1 (syscall(s) 252)
4038 Again, in this case @value{GDBN} would not be able to display syscall's names.
4041 A call to @code{fork}. This is currently only available for HP-UX
4045 A call to @code{vfork}. This is currently only available for HP-UX
4050 @item tcatch @var{event}
4051 Set a catchpoint that is enabled only for one stop. The catchpoint is
4052 automatically deleted after the first time the event is caught.
4056 Use the @code{info break} command to list the current catchpoints.
4058 There are currently some limitations to C@t{++} exception handling
4059 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4063 If you call a function interactively, @value{GDBN} normally returns
4064 control to you when the function has finished executing. If the call
4065 raises an exception, however, the call may bypass the mechanism that
4066 returns control to you and cause your program either to abort or to
4067 simply continue running until it hits a breakpoint, catches a signal
4068 that @value{GDBN} is listening for, or exits. This is the case even if
4069 you set a catchpoint for the exception; catchpoints on exceptions are
4070 disabled within interactive calls.
4073 You cannot raise an exception interactively.
4076 You cannot install an exception handler interactively.
4079 @cindex raise exceptions
4080 Sometimes @code{catch} is not the best way to debug exception handling:
4081 if you need to know exactly where an exception is raised, it is better to
4082 stop @emph{before} the exception handler is called, since that way you
4083 can see the stack before any unwinding takes place. If you set a
4084 breakpoint in an exception handler instead, it may not be easy to find
4085 out where the exception was raised.
4087 To stop just before an exception handler is called, you need some
4088 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4089 raised by calling a library function named @code{__raise_exception}
4090 which has the following ANSI C interface:
4093 /* @var{addr} is where the exception identifier is stored.
4094 @var{id} is the exception identifier. */
4095 void __raise_exception (void **addr, void *id);
4099 To make the debugger catch all exceptions before any stack
4100 unwinding takes place, set a breakpoint on @code{__raise_exception}
4101 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4103 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4104 that depends on the value of @var{id}, you can stop your program when
4105 a specific exception is raised. You can use multiple conditional
4106 breakpoints to stop your program when any of a number of exceptions are
4111 @subsection Deleting Breakpoints
4113 @cindex clearing breakpoints, watchpoints, catchpoints
4114 @cindex deleting breakpoints, watchpoints, catchpoints
4115 It is often necessary to eliminate a breakpoint, watchpoint, or
4116 catchpoint once it has done its job and you no longer want your program
4117 to stop there. This is called @dfn{deleting} the breakpoint. A
4118 breakpoint that has been deleted no longer exists; it is forgotten.
4120 With the @code{clear} command you can delete breakpoints according to
4121 where they are in your program. With the @code{delete} command you can
4122 delete individual breakpoints, watchpoints, or catchpoints by specifying
4123 their breakpoint numbers.
4125 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4126 automatically ignores breakpoints on the first instruction to be executed
4127 when you continue execution without changing the execution address.
4132 Delete any breakpoints at the next instruction to be executed in the
4133 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4134 the innermost frame is selected, this is a good way to delete a
4135 breakpoint where your program just stopped.
4137 @item clear @var{location}
4138 Delete any breakpoints set at the specified @var{location}.
4139 @xref{Specify Location}, for the various forms of @var{location}; the
4140 most useful ones are listed below:
4143 @item clear @var{function}
4144 @itemx clear @var{filename}:@var{function}
4145 Delete any breakpoints set at entry to the named @var{function}.
4147 @item clear @var{linenum}
4148 @itemx clear @var{filename}:@var{linenum}
4149 Delete any breakpoints set at or within the code of the specified
4150 @var{linenum} of the specified @var{filename}.
4153 @cindex delete breakpoints
4155 @kindex d @r{(@code{delete})}
4156 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4157 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4158 ranges specified as arguments. If no argument is specified, delete all
4159 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4160 confirm off}). You can abbreviate this command as @code{d}.
4164 @subsection Disabling Breakpoints
4166 @cindex enable/disable a breakpoint
4167 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4168 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4169 it had been deleted, but remembers the information on the breakpoint so
4170 that you can @dfn{enable} it again later.
4172 You disable and enable breakpoints, watchpoints, and catchpoints with
4173 the @code{enable} and @code{disable} commands, optionally specifying
4174 one or more breakpoint numbers as arguments. Use @code{info break} to
4175 print a list of all breakpoints, watchpoints, and catchpoints if you
4176 do not know which numbers to use.
4178 Disabling and enabling a breakpoint that has multiple locations
4179 affects all of its locations.
4181 A breakpoint, watchpoint, or catchpoint can have any of four different
4182 states of enablement:
4186 Enabled. The breakpoint stops your program. A breakpoint set
4187 with the @code{break} command starts out in this state.
4189 Disabled. The breakpoint has no effect on your program.
4191 Enabled once. The breakpoint stops your program, but then becomes
4194 Enabled for deletion. The breakpoint stops your program, but
4195 immediately after it does so it is deleted permanently. A breakpoint
4196 set with the @code{tbreak} command starts out in this state.
4199 You can use the following commands to enable or disable breakpoints,
4200 watchpoints, and catchpoints:
4204 @kindex dis @r{(@code{disable})}
4205 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4206 Disable the specified breakpoints---or all breakpoints, if none are
4207 listed. A disabled breakpoint has no effect but is not forgotten. All
4208 options such as ignore-counts, conditions and commands are remembered in
4209 case the breakpoint is enabled again later. You may abbreviate
4210 @code{disable} as @code{dis}.
4213 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4214 Enable the specified breakpoints (or all defined breakpoints). They
4215 become effective once again in stopping your program.
4217 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4218 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4219 of these breakpoints immediately after stopping your program.
4221 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4222 Enable the specified breakpoints to work once, then die. @value{GDBN}
4223 deletes any of these breakpoints as soon as your program stops there.
4224 Breakpoints set by the @code{tbreak} command start out in this state.
4227 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4228 @c confusing: tbreak is also initially enabled.
4229 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4230 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4231 subsequently, they become disabled or enabled only when you use one of
4232 the commands above. (The command @code{until} can set and delete a
4233 breakpoint of its own, but it does not change the state of your other
4234 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4238 @subsection Break Conditions
4239 @cindex conditional breakpoints
4240 @cindex breakpoint conditions
4242 @c FIXME what is scope of break condition expr? Context where wanted?
4243 @c in particular for a watchpoint?
4244 The simplest sort of breakpoint breaks every time your program reaches a
4245 specified place. You can also specify a @dfn{condition} for a
4246 breakpoint. A condition is just a Boolean expression in your
4247 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4248 a condition evaluates the expression each time your program reaches it,
4249 and your program stops only if the condition is @emph{true}.
4251 This is the converse of using assertions for program validation; in that
4252 situation, you want to stop when the assertion is violated---that is,
4253 when the condition is false. In C, if you want to test an assertion expressed
4254 by the condition @var{assert}, you should set the condition
4255 @samp{! @var{assert}} on the appropriate breakpoint.
4257 Conditions are also accepted for watchpoints; you may not need them,
4258 since a watchpoint is inspecting the value of an expression anyhow---but
4259 it might be simpler, say, to just set a watchpoint on a variable name,
4260 and specify a condition that tests whether the new value is an interesting
4263 Break conditions can have side effects, and may even call functions in
4264 your program. This can be useful, for example, to activate functions
4265 that log program progress, or to use your own print functions to
4266 format special data structures. The effects are completely predictable
4267 unless there is another enabled breakpoint at the same address. (In
4268 that case, @value{GDBN} might see the other breakpoint first and stop your
4269 program without checking the condition of this one.) Note that
4270 breakpoint commands are usually more convenient and flexible than break
4272 purpose of performing side effects when a breakpoint is reached
4273 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4275 Break conditions can be specified when a breakpoint is set, by using
4276 @samp{if} in the arguments to the @code{break} command. @xref{Set
4277 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4278 with the @code{condition} command.
4280 You can also use the @code{if} keyword with the @code{watch} command.
4281 The @code{catch} command does not recognize the @code{if} keyword;
4282 @code{condition} is the only way to impose a further condition on a
4287 @item condition @var{bnum} @var{expression}
4288 Specify @var{expression} as the break condition for breakpoint,
4289 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4290 breakpoint @var{bnum} stops your program only if the value of
4291 @var{expression} is true (nonzero, in C). When you use
4292 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4293 syntactic correctness, and to determine whether symbols in it have
4294 referents in the context of your breakpoint. If @var{expression} uses
4295 symbols not referenced in the context of the breakpoint, @value{GDBN}
4296 prints an error message:
4299 No symbol "foo" in current context.
4304 not actually evaluate @var{expression} at the time the @code{condition}
4305 command (or a command that sets a breakpoint with a condition, like
4306 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4308 @item condition @var{bnum}
4309 Remove the condition from breakpoint number @var{bnum}. It becomes
4310 an ordinary unconditional breakpoint.
4313 @cindex ignore count (of breakpoint)
4314 A special case of a breakpoint condition is to stop only when the
4315 breakpoint has been reached a certain number of times. This is so
4316 useful that there is a special way to do it, using the @dfn{ignore
4317 count} of the breakpoint. Every breakpoint has an ignore count, which
4318 is an integer. Most of the time, the ignore count is zero, and
4319 therefore has no effect. But if your program reaches a breakpoint whose
4320 ignore count is positive, then instead of stopping, it just decrements
4321 the ignore count by one and continues. As a result, if the ignore count
4322 value is @var{n}, the breakpoint does not stop the next @var{n} times
4323 your program reaches it.
4327 @item ignore @var{bnum} @var{count}
4328 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4329 The next @var{count} times the breakpoint is reached, your program's
4330 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4333 To make the breakpoint stop the next time it is reached, specify
4336 When you use @code{continue} to resume execution of your program from a
4337 breakpoint, you can specify an ignore count directly as an argument to
4338 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4339 Stepping,,Continuing and Stepping}.
4341 If a breakpoint has a positive ignore count and a condition, the
4342 condition is not checked. Once the ignore count reaches zero,
4343 @value{GDBN} resumes checking the condition.
4345 You could achieve the effect of the ignore count with a condition such
4346 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4347 is decremented each time. @xref{Convenience Vars, ,Convenience
4351 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4354 @node Break Commands
4355 @subsection Breakpoint Command Lists
4357 @cindex breakpoint commands
4358 You can give any breakpoint (or watchpoint or catchpoint) a series of
4359 commands to execute when your program stops due to that breakpoint. For
4360 example, you might want to print the values of certain expressions, or
4361 enable other breakpoints.
4365 @kindex end@r{ (breakpoint commands)}
4366 @item commands @r{[}@var{range}@dots{}@r{]}
4367 @itemx @dots{} @var{command-list} @dots{}
4369 Specify a list of commands for the given breakpoints. The commands
4370 themselves appear on the following lines. Type a line containing just
4371 @code{end} to terminate the commands.
4373 To remove all commands from a breakpoint, type @code{commands} and
4374 follow it immediately with @code{end}; that is, give no commands.
4376 With no argument, @code{commands} refers to the last breakpoint,
4377 watchpoint, or catchpoint set (not to the breakpoint most recently
4378 encountered). If the most recent breakpoints were set with a single
4379 command, then the @code{commands} will apply to all the breakpoints
4380 set by that command. This applies to breakpoints set by
4381 @code{rbreak}, and also applies when a single @code{break} command
4382 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4386 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4387 disabled within a @var{command-list}.
4389 You can use breakpoint commands to start your program up again. Simply
4390 use the @code{continue} command, or @code{step}, or any other command
4391 that resumes execution.
4393 Any other commands in the command list, after a command that resumes
4394 execution, are ignored. This is because any time you resume execution
4395 (even with a simple @code{next} or @code{step}), you may encounter
4396 another breakpoint---which could have its own command list, leading to
4397 ambiguities about which list to execute.
4400 If the first command you specify in a command list is @code{silent}, the
4401 usual message about stopping at a breakpoint is not printed. This may
4402 be desirable for breakpoints that are to print a specific message and
4403 then continue. If none of the remaining commands print anything, you
4404 see no sign that the breakpoint was reached. @code{silent} is
4405 meaningful only at the beginning of a breakpoint command list.
4407 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4408 print precisely controlled output, and are often useful in silent
4409 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4411 For example, here is how you could use breakpoint commands to print the
4412 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4418 printf "x is %d\n",x
4423 One application for breakpoint commands is to compensate for one bug so
4424 you can test for another. Put a breakpoint just after the erroneous line
4425 of code, give it a condition to detect the case in which something
4426 erroneous has been done, and give it commands to assign correct values
4427 to any variables that need them. End with the @code{continue} command
4428 so that your program does not stop, and start with the @code{silent}
4429 command so that no output is produced. Here is an example:
4440 @node Save Breakpoints
4441 @subsection How to save breakpoints to a file
4443 To save breakpoint definitions to a file use the @w{@code{save
4444 breakpoints}} command.
4447 @kindex save breakpoints
4448 @cindex save breakpoints to a file for future sessions
4449 @item save breakpoints [@var{filename}]
4450 This command saves all current breakpoint definitions together with
4451 their commands and ignore counts, into a file @file{@var{filename}}
4452 suitable for use in a later debugging session. This includes all
4453 types of breakpoints (breakpoints, watchpoints, catchpoints,
4454 tracepoints). To read the saved breakpoint definitions, use the
4455 @code{source} command (@pxref{Command Files}). Note that watchpoints
4456 with expressions involving local variables may fail to be recreated
4457 because it may not be possible to access the context where the
4458 watchpoint is valid anymore. Because the saved breakpoint definitions
4459 are simply a sequence of @value{GDBN} commands that recreate the
4460 breakpoints, you can edit the file in your favorite editing program,
4461 and remove the breakpoint definitions you're not interested in, or
4462 that can no longer be recreated.
4465 @c @ifclear BARETARGET
4466 @node Error in Breakpoints
4467 @subsection ``Cannot insert breakpoints''
4469 If you request too many active hardware-assisted breakpoints and
4470 watchpoints, you will see this error message:
4472 @c FIXME: the precise wording of this message may change; the relevant
4473 @c source change is not committed yet (Sep 3, 1999).
4475 Stopped; cannot insert breakpoints.
4476 You may have requested too many hardware breakpoints and watchpoints.
4480 This message is printed when you attempt to resume the program, since
4481 only then @value{GDBN} knows exactly how many hardware breakpoints and
4482 watchpoints it needs to insert.
4484 When this message is printed, you need to disable or remove some of the
4485 hardware-assisted breakpoints and watchpoints, and then continue.
4487 @node Breakpoint-related Warnings
4488 @subsection ``Breakpoint address adjusted...''
4489 @cindex breakpoint address adjusted
4491 Some processor architectures place constraints on the addresses at
4492 which breakpoints may be placed. For architectures thus constrained,
4493 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4494 with the constraints dictated by the architecture.
4496 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4497 a VLIW architecture in which a number of RISC-like instructions may be
4498 bundled together for parallel execution. The FR-V architecture
4499 constrains the location of a breakpoint instruction within such a
4500 bundle to the instruction with the lowest address. @value{GDBN}
4501 honors this constraint by adjusting a breakpoint's address to the
4502 first in the bundle.
4504 It is not uncommon for optimized code to have bundles which contain
4505 instructions from different source statements, thus it may happen that
4506 a breakpoint's address will be adjusted from one source statement to
4507 another. Since this adjustment may significantly alter @value{GDBN}'s
4508 breakpoint related behavior from what the user expects, a warning is
4509 printed when the breakpoint is first set and also when the breakpoint
4512 A warning like the one below is printed when setting a breakpoint
4513 that's been subject to address adjustment:
4516 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4519 Such warnings are printed both for user settable and @value{GDBN}'s
4520 internal breakpoints. If you see one of these warnings, you should
4521 verify that a breakpoint set at the adjusted address will have the
4522 desired affect. If not, the breakpoint in question may be removed and
4523 other breakpoints may be set which will have the desired behavior.
4524 E.g., it may be sufficient to place the breakpoint at a later
4525 instruction. A conditional breakpoint may also be useful in some
4526 cases to prevent the breakpoint from triggering too often.
4528 @value{GDBN} will also issue a warning when stopping at one of these
4529 adjusted breakpoints:
4532 warning: Breakpoint 1 address previously adjusted from 0x00010414
4536 When this warning is encountered, it may be too late to take remedial
4537 action except in cases where the breakpoint is hit earlier or more
4538 frequently than expected.
4540 @node Continuing and Stepping
4541 @section Continuing and Stepping
4545 @cindex resuming execution
4546 @dfn{Continuing} means resuming program execution until your program
4547 completes normally. In contrast, @dfn{stepping} means executing just
4548 one more ``step'' of your program, where ``step'' may mean either one
4549 line of source code, or one machine instruction (depending on what
4550 particular command you use). Either when continuing or when stepping,
4551 your program may stop even sooner, due to a breakpoint or a signal. (If
4552 it stops due to a signal, you may want to use @code{handle}, or use
4553 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4557 @kindex c @r{(@code{continue})}
4558 @kindex fg @r{(resume foreground execution)}
4559 @item continue @r{[}@var{ignore-count}@r{]}
4560 @itemx c @r{[}@var{ignore-count}@r{]}
4561 @itemx fg @r{[}@var{ignore-count}@r{]}
4562 Resume program execution, at the address where your program last stopped;
4563 any breakpoints set at that address are bypassed. The optional argument
4564 @var{ignore-count} allows you to specify a further number of times to
4565 ignore a breakpoint at this location; its effect is like that of
4566 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4568 The argument @var{ignore-count} is meaningful only when your program
4569 stopped due to a breakpoint. At other times, the argument to
4570 @code{continue} is ignored.
4572 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4573 debugged program is deemed to be the foreground program) are provided
4574 purely for convenience, and have exactly the same behavior as
4578 To resume execution at a different place, you can use @code{return}
4579 (@pxref{Returning, ,Returning from a Function}) to go back to the
4580 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4581 Different Address}) to go to an arbitrary location in your program.
4583 A typical technique for using stepping is to set a breakpoint
4584 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4585 beginning of the function or the section of your program where a problem
4586 is believed to lie, run your program until it stops at that breakpoint,
4587 and then step through the suspect area, examining the variables that are
4588 interesting, until you see the problem happen.
4592 @kindex s @r{(@code{step})}
4594 Continue running your program until control reaches a different source
4595 line, then stop it and return control to @value{GDBN}. This command is
4596 abbreviated @code{s}.
4599 @c "without debugging information" is imprecise; actually "without line
4600 @c numbers in the debugging information". (gcc -g1 has debugging info but
4601 @c not line numbers). But it seems complex to try to make that
4602 @c distinction here.
4603 @emph{Warning:} If you use the @code{step} command while control is
4604 within a function that was compiled without debugging information,
4605 execution proceeds until control reaches a function that does have
4606 debugging information. Likewise, it will not step into a function which
4607 is compiled without debugging information. To step through functions
4608 without debugging information, use the @code{stepi} command, described
4612 The @code{step} command only stops at the first instruction of a source
4613 line. This prevents the multiple stops that could otherwise occur in
4614 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4615 to stop if a function that has debugging information is called within
4616 the line. In other words, @code{step} @emph{steps inside} any functions
4617 called within the line.
4619 Also, the @code{step} command only enters a function if there is line
4620 number information for the function. Otherwise it acts like the
4621 @code{next} command. This avoids problems when using @code{cc -gl}
4622 on MIPS machines. Previously, @code{step} entered subroutines if there
4623 was any debugging information about the routine.
4625 @item step @var{count}
4626 Continue running as in @code{step}, but do so @var{count} times. If a
4627 breakpoint is reached, or a signal not related to stepping occurs before
4628 @var{count} steps, stepping stops right away.
4631 @kindex n @r{(@code{next})}
4632 @item next @r{[}@var{count}@r{]}
4633 Continue to the next source line in the current (innermost) stack frame.
4634 This is similar to @code{step}, but function calls that appear within
4635 the line of code are executed without stopping. Execution stops when
4636 control reaches a different line of code at the original stack level
4637 that was executing when you gave the @code{next} command. This command
4638 is abbreviated @code{n}.
4640 An argument @var{count} is a repeat count, as for @code{step}.
4643 @c FIX ME!! Do we delete this, or is there a way it fits in with
4644 @c the following paragraph? --- Vctoria
4646 @c @code{next} within a function that lacks debugging information acts like
4647 @c @code{step}, but any function calls appearing within the code of the
4648 @c function are executed without stopping.
4650 The @code{next} command only stops at the first instruction of a
4651 source line. This prevents multiple stops that could otherwise occur in
4652 @code{switch} statements, @code{for} loops, etc.
4654 @kindex set step-mode
4656 @cindex functions without line info, and stepping
4657 @cindex stepping into functions with no line info
4658 @itemx set step-mode on
4659 The @code{set step-mode on} command causes the @code{step} command to
4660 stop at the first instruction of a function which contains no debug line
4661 information rather than stepping over it.
4663 This is useful in cases where you may be interested in inspecting the
4664 machine instructions of a function which has no symbolic info and do not
4665 want @value{GDBN} to automatically skip over this function.
4667 @item set step-mode off
4668 Causes the @code{step} command to step over any functions which contains no
4669 debug information. This is the default.
4671 @item show step-mode
4672 Show whether @value{GDBN} will stop in or step over functions without
4673 source line debug information.
4676 @kindex fin @r{(@code{finish})}
4678 Continue running until just after function in the selected stack frame
4679 returns. Print the returned value (if any). This command can be
4680 abbreviated as @code{fin}.
4682 Contrast this with the @code{return} command (@pxref{Returning,
4683 ,Returning from a Function}).
4686 @kindex u @r{(@code{until})}
4687 @cindex run until specified location
4690 Continue running until a source line past the current line, in the
4691 current stack frame, is reached. This command is used to avoid single
4692 stepping through a loop more than once. It is like the @code{next}
4693 command, except that when @code{until} encounters a jump, it
4694 automatically continues execution until the program counter is greater
4695 than the address of the jump.
4697 This means that when you reach the end of a loop after single stepping
4698 though it, @code{until} makes your program continue execution until it
4699 exits the loop. In contrast, a @code{next} command at the end of a loop
4700 simply steps back to the beginning of the loop, which forces you to step
4701 through the next iteration.
4703 @code{until} always stops your program if it attempts to exit the current
4706 @code{until} may produce somewhat counterintuitive results if the order
4707 of machine code does not match the order of the source lines. For
4708 example, in the following excerpt from a debugging session, the @code{f}
4709 (@code{frame}) command shows that execution is stopped at line
4710 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4714 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4716 (@value{GDBP}) until
4717 195 for ( ; argc > 0; NEXTARG) @{
4720 This happened because, for execution efficiency, the compiler had
4721 generated code for the loop closure test at the end, rather than the
4722 start, of the loop---even though the test in a C @code{for}-loop is
4723 written before the body of the loop. The @code{until} command appeared
4724 to step back to the beginning of the loop when it advanced to this
4725 expression; however, it has not really gone to an earlier
4726 statement---not in terms of the actual machine code.
4728 @code{until} with no argument works by means of single
4729 instruction stepping, and hence is slower than @code{until} with an
4732 @item until @var{location}
4733 @itemx u @var{location}
4734 Continue running your program until either the specified location is
4735 reached, or the current stack frame returns. @var{location} is any of
4736 the forms described in @ref{Specify Location}.
4737 This form of the command uses temporary breakpoints, and
4738 hence is quicker than @code{until} without an argument. The specified
4739 location is actually reached only if it is in the current frame. This
4740 implies that @code{until} can be used to skip over recursive function
4741 invocations. For instance in the code below, if the current location is
4742 line @code{96}, issuing @code{until 99} will execute the program up to
4743 line @code{99} in the same invocation of factorial, i.e., after the inner
4744 invocations have returned.
4747 94 int factorial (int value)
4749 96 if (value > 1) @{
4750 97 value *= factorial (value - 1);
4757 @kindex advance @var{location}
4758 @itemx advance @var{location}
4759 Continue running the program up to the given @var{location}. An argument is
4760 required, which should be of one of the forms described in
4761 @ref{Specify Location}.
4762 Execution will also stop upon exit from the current stack
4763 frame. This command is similar to @code{until}, but @code{advance} will
4764 not skip over recursive function calls, and the target location doesn't
4765 have to be in the same frame as the current one.
4769 @kindex si @r{(@code{stepi})}
4771 @itemx stepi @var{arg}
4773 Execute one machine instruction, then stop and return to the debugger.
4775 It is often useful to do @samp{display/i $pc} when stepping by machine
4776 instructions. This makes @value{GDBN} automatically display the next
4777 instruction to be executed, each time your program stops. @xref{Auto
4778 Display,, Automatic Display}.
4780 An argument is a repeat count, as in @code{step}.
4784 @kindex ni @r{(@code{nexti})}
4786 @itemx nexti @var{arg}
4788 Execute one machine instruction, but if it is a function call,
4789 proceed until the function returns.
4791 An argument is a repeat count, as in @code{next}.
4798 A signal is an asynchronous event that can happen in a program. The
4799 operating system defines the possible kinds of signals, and gives each
4800 kind a name and a number. For example, in Unix @code{SIGINT} is the
4801 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4802 @code{SIGSEGV} is the signal a program gets from referencing a place in
4803 memory far away from all the areas in use; @code{SIGALRM} occurs when
4804 the alarm clock timer goes off (which happens only if your program has
4805 requested an alarm).
4807 @cindex fatal signals
4808 Some signals, including @code{SIGALRM}, are a normal part of the
4809 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4810 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4811 program has not specified in advance some other way to handle the signal.
4812 @code{SIGINT} does not indicate an error in your program, but it is normally
4813 fatal so it can carry out the purpose of the interrupt: to kill the program.
4815 @value{GDBN} has the ability to detect any occurrence of a signal in your
4816 program. You can tell @value{GDBN} in advance what to do for each kind of
4819 @cindex handling signals
4820 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4821 @code{SIGALRM} be silently passed to your program
4822 (so as not to interfere with their role in the program's functioning)
4823 but to stop your program immediately whenever an error signal happens.
4824 You can change these settings with the @code{handle} command.
4827 @kindex info signals
4831 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4832 handle each one. You can use this to see the signal numbers of all
4833 the defined types of signals.
4835 @item info signals @var{sig}
4836 Similar, but print information only about the specified signal number.
4838 @code{info handle} is an alias for @code{info signals}.
4841 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4842 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4843 can be the number of a signal or its name (with or without the
4844 @samp{SIG} at the beginning); a list of signal numbers of the form
4845 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4846 known signals. Optional arguments @var{keywords}, described below,
4847 say what change to make.
4851 The keywords allowed by the @code{handle} command can be abbreviated.
4852 Their full names are:
4856 @value{GDBN} should not stop your program when this signal happens. It may
4857 still print a message telling you that the signal has come in.
4860 @value{GDBN} should stop your program when this signal happens. This implies
4861 the @code{print} keyword as well.
4864 @value{GDBN} should print a message when this signal happens.
4867 @value{GDBN} should not mention the occurrence of the signal at all. This
4868 implies the @code{nostop} keyword as well.
4872 @value{GDBN} should allow your program to see this signal; your program
4873 can handle the signal, or else it may terminate if the signal is fatal
4874 and not handled. @code{pass} and @code{noignore} are synonyms.
4878 @value{GDBN} should not allow your program to see this signal.
4879 @code{nopass} and @code{ignore} are synonyms.
4883 When a signal stops your program, the signal is not visible to the
4885 continue. Your program sees the signal then, if @code{pass} is in
4886 effect for the signal in question @emph{at that time}. In other words,
4887 after @value{GDBN} reports a signal, you can use the @code{handle}
4888 command with @code{pass} or @code{nopass} to control whether your
4889 program sees that signal when you continue.
4891 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4892 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4893 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4896 You can also use the @code{signal} command to prevent your program from
4897 seeing a signal, or cause it to see a signal it normally would not see,
4898 or to give it any signal at any time. For example, if your program stopped
4899 due to some sort of memory reference error, you might store correct
4900 values into the erroneous variables and continue, hoping to see more
4901 execution; but your program would probably terminate immediately as
4902 a result of the fatal signal once it saw the signal. To prevent this,
4903 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4906 @cindex extra signal information
4907 @anchor{extra signal information}
4909 On some targets, @value{GDBN} can inspect extra signal information
4910 associated with the intercepted signal, before it is actually
4911 delivered to the program being debugged. This information is exported
4912 by the convenience variable @code{$_siginfo}, and consists of data
4913 that is passed by the kernel to the signal handler at the time of the
4914 receipt of a signal. The data type of the information itself is
4915 target dependent. You can see the data type using the @code{ptype
4916 $_siginfo} command. On Unix systems, it typically corresponds to the
4917 standard @code{siginfo_t} type, as defined in the @file{signal.h}
4920 Here's an example, on a @sc{gnu}/Linux system, printing the stray
4921 referenced address that raised a segmentation fault.
4925 (@value{GDBP}) continue
4926 Program received signal SIGSEGV, Segmentation fault.
4927 0x0000000000400766 in main ()
4929 (@value{GDBP}) ptype $_siginfo
4936 struct @{...@} _kill;
4937 struct @{...@} _timer;
4939 struct @{...@} _sigchld;
4940 struct @{...@} _sigfault;
4941 struct @{...@} _sigpoll;
4944 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
4948 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
4949 $1 = (void *) 0x7ffff7ff7000
4953 Depending on target support, @code{$_siginfo} may also be writable.
4956 @section Stopping and Starting Multi-thread Programs
4958 @cindex stopped threads
4959 @cindex threads, stopped
4961 @cindex continuing threads
4962 @cindex threads, continuing
4964 @value{GDBN} supports debugging programs with multiple threads
4965 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
4966 are two modes of controlling execution of your program within the
4967 debugger. In the default mode, referred to as @dfn{all-stop mode},
4968 when any thread in your program stops (for example, at a breakpoint
4969 or while being stepped), all other threads in the program are also stopped by
4970 @value{GDBN}. On some targets, @value{GDBN} also supports
4971 @dfn{non-stop mode}, in which other threads can continue to run freely while
4972 you examine the stopped thread in the debugger.
4975 * All-Stop Mode:: All threads stop when GDB takes control
4976 * Non-Stop Mode:: Other threads continue to execute
4977 * Background Execution:: Running your program asynchronously
4978 * Thread-Specific Breakpoints:: Controlling breakpoints
4979 * Interrupted System Calls:: GDB may interfere with system calls
4980 * Observer Mode:: GDB does not alter program behavior
4984 @subsection All-Stop Mode
4986 @cindex all-stop mode
4988 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
4989 @emph{all} threads of execution stop, not just the current thread. This
4990 allows you to examine the overall state of the program, including
4991 switching between threads, without worrying that things may change
4994 Conversely, whenever you restart the program, @emph{all} threads start
4995 executing. @emph{This is true even when single-stepping} with commands
4996 like @code{step} or @code{next}.
4998 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4999 Since thread scheduling is up to your debugging target's operating
5000 system (not controlled by @value{GDBN}), other threads may
5001 execute more than one statement while the current thread completes a
5002 single step. Moreover, in general other threads stop in the middle of a
5003 statement, rather than at a clean statement boundary, when the program
5006 You might even find your program stopped in another thread after
5007 continuing or even single-stepping. This happens whenever some other
5008 thread runs into a breakpoint, a signal, or an exception before the
5009 first thread completes whatever you requested.
5011 @cindex automatic thread selection
5012 @cindex switching threads automatically
5013 @cindex threads, automatic switching
5014 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5015 signal, it automatically selects the thread where that breakpoint or
5016 signal happened. @value{GDBN} alerts you to the context switch with a
5017 message such as @samp{[Switching to Thread @var{n}]} to identify the
5020 On some OSes, you can modify @value{GDBN}'s default behavior by
5021 locking the OS scheduler to allow only a single thread to run.
5024 @item set scheduler-locking @var{mode}
5025 @cindex scheduler locking mode
5026 @cindex lock scheduler
5027 Set the scheduler locking mode. If it is @code{off}, then there is no
5028 locking and any thread may run at any time. If @code{on}, then only the
5029 current thread may run when the inferior is resumed. The @code{step}
5030 mode optimizes for single-stepping; it prevents other threads
5031 from preempting the current thread while you are stepping, so that
5032 the focus of debugging does not change unexpectedly.
5033 Other threads only rarely (or never) get a chance to run
5034 when you step. They are more likely to run when you @samp{next} over a
5035 function call, and they are completely free to run when you use commands
5036 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5037 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5038 the current thread away from the thread that you are debugging.
5040 @item show scheduler-locking
5041 Display the current scheduler locking mode.
5044 @cindex resume threads of multiple processes simultaneously
5045 By default, when you issue one of the execution commands such as
5046 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5047 threads of the current inferior to run. For example, if @value{GDBN}
5048 is attached to two inferiors, each with two threads, the
5049 @code{continue} command resumes only the two threads of the current
5050 inferior. This is useful, for example, when you debug a program that
5051 forks and you want to hold the parent stopped (so that, for instance,
5052 it doesn't run to exit), while you debug the child. In other
5053 situations, you may not be interested in inspecting the current state
5054 of any of the processes @value{GDBN} is attached to, and you may want
5055 to resume them all until some breakpoint is hit. In the latter case,
5056 you can instruct @value{GDBN} to allow all threads of all the
5057 inferiors to run with the @w{@code{set schedule-multiple}} command.
5060 @kindex set schedule-multiple
5061 @item set schedule-multiple
5062 Set the mode for allowing threads of multiple processes to be resumed
5063 when an execution command is issued. When @code{on}, all threads of
5064 all processes are allowed to run. When @code{off}, only the threads
5065 of the current process are resumed. The default is @code{off}. The
5066 @code{scheduler-locking} mode takes precedence when set to @code{on},
5067 or while you are stepping and set to @code{step}.
5069 @item show schedule-multiple
5070 Display the current mode for resuming the execution of threads of
5075 @subsection Non-Stop Mode
5077 @cindex non-stop mode
5079 @c This section is really only a place-holder, and needs to be expanded
5080 @c with more details.
5082 For some multi-threaded targets, @value{GDBN} supports an optional
5083 mode of operation in which you can examine stopped program threads in
5084 the debugger while other threads continue to execute freely. This
5085 minimizes intrusion when debugging live systems, such as programs
5086 where some threads have real-time constraints or must continue to
5087 respond to external events. This is referred to as @dfn{non-stop} mode.
5089 In non-stop mode, when a thread stops to report a debugging event,
5090 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5091 threads as well, in contrast to the all-stop mode behavior. Additionally,
5092 execution commands such as @code{continue} and @code{step} apply by default
5093 only to the current thread in non-stop mode, rather than all threads as
5094 in all-stop mode. This allows you to control threads explicitly in
5095 ways that are not possible in all-stop mode --- for example, stepping
5096 one thread while allowing others to run freely, stepping
5097 one thread while holding all others stopped, or stepping several threads
5098 independently and simultaneously.
5100 To enter non-stop mode, use this sequence of commands before you run
5101 or attach to your program:
5104 # Enable the async interface.
5107 # If using the CLI, pagination breaks non-stop.
5110 # Finally, turn it on!
5114 You can use these commands to manipulate the non-stop mode setting:
5117 @kindex set non-stop
5118 @item set non-stop on
5119 Enable selection of non-stop mode.
5120 @item set non-stop off
5121 Disable selection of non-stop mode.
5122 @kindex show non-stop
5124 Show the current non-stop enablement setting.
5127 Note these commands only reflect whether non-stop mode is enabled,
5128 not whether the currently-executing program is being run in non-stop mode.
5129 In particular, the @code{set non-stop} preference is only consulted when
5130 @value{GDBN} starts or connects to the target program, and it is generally
5131 not possible to switch modes once debugging has started. Furthermore,
5132 since not all targets support non-stop mode, even when you have enabled
5133 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5136 In non-stop mode, all execution commands apply only to the current thread
5137 by default. That is, @code{continue} only continues one thread.
5138 To continue all threads, issue @code{continue -a} or @code{c -a}.
5140 You can use @value{GDBN}'s background execution commands
5141 (@pxref{Background Execution}) to run some threads in the background
5142 while you continue to examine or step others from @value{GDBN}.
5143 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5144 always executed asynchronously in non-stop mode.
5146 Suspending execution is done with the @code{interrupt} command when
5147 running in the background, or @kbd{Ctrl-c} during foreground execution.
5148 In all-stop mode, this stops the whole process;
5149 but in non-stop mode the interrupt applies only to the current thread.
5150 To stop the whole program, use @code{interrupt -a}.
5152 Other execution commands do not currently support the @code{-a} option.
5154 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5155 that thread current, as it does in all-stop mode. This is because the
5156 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5157 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5158 changed to a different thread just as you entered a command to operate on the
5159 previously current thread.
5161 @node Background Execution
5162 @subsection Background Execution
5164 @cindex foreground execution
5165 @cindex background execution
5166 @cindex asynchronous execution
5167 @cindex execution, foreground, background and asynchronous
5169 @value{GDBN}'s execution commands have two variants: the normal
5170 foreground (synchronous) behavior, and a background
5171 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5172 the program to report that some thread has stopped before prompting for
5173 another command. In background execution, @value{GDBN} immediately gives
5174 a command prompt so that you can issue other commands while your program runs.
5176 You need to explicitly enable asynchronous mode before you can use
5177 background execution commands. You can use these commands to
5178 manipulate the asynchronous mode setting:
5181 @kindex set target-async
5182 @item set target-async on
5183 Enable asynchronous mode.
5184 @item set target-async off
5185 Disable asynchronous mode.
5186 @kindex show target-async
5187 @item show target-async
5188 Show the current target-async setting.
5191 If the target doesn't support async mode, @value{GDBN} issues an error
5192 message if you attempt to use the background execution commands.
5194 To specify background execution, add a @code{&} to the command. For example,
5195 the background form of the @code{continue} command is @code{continue&}, or
5196 just @code{c&}. The execution commands that accept background execution
5202 @xref{Starting, , Starting your Program}.
5206 @xref{Attach, , Debugging an Already-running Process}.
5210 @xref{Continuing and Stepping, step}.
5214 @xref{Continuing and Stepping, stepi}.
5218 @xref{Continuing and Stepping, next}.
5222 @xref{Continuing and Stepping, nexti}.
5226 @xref{Continuing and Stepping, continue}.
5230 @xref{Continuing and Stepping, finish}.
5234 @xref{Continuing and Stepping, until}.
5238 Background execution is especially useful in conjunction with non-stop
5239 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5240 However, you can also use these commands in the normal all-stop mode with
5241 the restriction that you cannot issue another execution command until the
5242 previous one finishes. Examples of commands that are valid in all-stop
5243 mode while the program is running include @code{help} and @code{info break}.
5245 You can interrupt your program while it is running in the background by
5246 using the @code{interrupt} command.
5253 Suspend execution of the running program. In all-stop mode,
5254 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5255 only the current thread. To stop the whole program in non-stop mode,
5256 use @code{interrupt -a}.
5259 @node Thread-Specific Breakpoints
5260 @subsection Thread-Specific Breakpoints
5262 When your program has multiple threads (@pxref{Threads,, Debugging
5263 Programs with Multiple Threads}), you can choose whether to set
5264 breakpoints on all threads, or on a particular thread.
5267 @cindex breakpoints and threads
5268 @cindex thread breakpoints
5269 @kindex break @dots{} thread @var{threadno}
5270 @item break @var{linespec} thread @var{threadno}
5271 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5272 @var{linespec} specifies source lines; there are several ways of
5273 writing them (@pxref{Specify Location}), but the effect is always to
5274 specify some source line.
5276 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5277 to specify that you only want @value{GDBN} to stop the program when a
5278 particular thread reaches this breakpoint. @var{threadno} is one of the
5279 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5280 column of the @samp{info threads} display.
5282 If you do not specify @samp{thread @var{threadno}} when you set a
5283 breakpoint, the breakpoint applies to @emph{all} threads of your
5286 You can use the @code{thread} qualifier on conditional breakpoints as
5287 well; in this case, place @samp{thread @var{threadno}} before or
5288 after the breakpoint condition, like this:
5291 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5296 @node Interrupted System Calls
5297 @subsection Interrupted System Calls
5299 @cindex thread breakpoints and system calls
5300 @cindex system calls and thread breakpoints
5301 @cindex premature return from system calls
5302 There is an unfortunate side effect when using @value{GDBN} to debug
5303 multi-threaded programs. If one thread stops for a
5304 breakpoint, or for some other reason, and another thread is blocked in a
5305 system call, then the system call may return prematurely. This is a
5306 consequence of the interaction between multiple threads and the signals
5307 that @value{GDBN} uses to implement breakpoints and other events that
5310 To handle this problem, your program should check the return value of
5311 each system call and react appropriately. This is good programming
5314 For example, do not write code like this:
5320 The call to @code{sleep} will return early if a different thread stops
5321 at a breakpoint or for some other reason.
5323 Instead, write this:
5328 unslept = sleep (unslept);
5331 A system call is allowed to return early, so the system is still
5332 conforming to its specification. But @value{GDBN} does cause your
5333 multi-threaded program to behave differently than it would without
5336 Also, @value{GDBN} uses internal breakpoints in the thread library to
5337 monitor certain events such as thread creation and thread destruction.
5338 When such an event happens, a system call in another thread may return
5339 prematurely, even though your program does not appear to stop.
5342 @subsection Observer Mode
5344 If you want to build on non-stop mode and observe program behavior
5345 without any chance of disruption by @value{GDBN}, you can set
5346 variables to disable all of the debugger's attempts to modify state,
5347 whether by writing memory, inserting breakpoints, etc. These operate
5348 at a low level, intercepting operations from all commands.
5350 When all of these are set to @code{off}, then @value{GDBN} is said to
5351 be @dfn{observer mode}. As a convenience, the variable
5352 @code{observer} can be set to disable these, plus enable non-stop
5355 Note that @value{GDBN} will not prevent you from making nonsensical
5356 combinations of these settings. For instance, if you have enabled
5357 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5358 then breakpoints that work by writing trap instructions into the code
5359 stream will still not be able to be placed.
5364 @item set observer on
5365 @itemx set observer off
5366 When set to @code{on}, this disables all the permission variables
5367 below (except for @code{insert-fast-tracepoints}), plus enables
5368 non-stop debugging. Setting this to @code{off} switches back to
5369 normal debugging, though remaining in non-stop mode.
5372 Show whether observer mode is on or off.
5374 @kindex may-write-registers
5375 @item set may-write-registers on
5376 @itemx set may-write-registers off
5377 This controls whether @value{GDBN} will attempt to alter the values of
5378 registers, such as with assignment expressions in @code{print}, or the
5379 @code{jump} command. It defaults to @code{on}.
5381 @item show may-write-registers
5382 Show the current permission to write registers.
5384 @kindex may-write-memory
5385 @item set may-write-memory on
5386 @itemx set may-write-memory off
5387 This controls whether @value{GDBN} will attempt to alter the contents
5388 of memory, such as with assignment expressions in @code{print}. It
5389 defaults to @code{on}.
5391 @item show may-write-memory
5392 Show the current permission to write memory.
5394 @kindex may-insert-breakpoints
5395 @item set may-insert-breakpoints on
5396 @itemx set may-insert-breakpoints off
5397 This controls whether @value{GDBN} will attempt to insert breakpoints.
5398 This affects all breakpoints, including internal breakpoints defined
5399 by @value{GDBN}. It defaults to @code{on}.
5401 @item show may-insert-breakpoints
5402 Show the current permission to insert breakpoints.
5404 @kindex may-insert-tracepoints
5405 @item set may-insert-tracepoints on
5406 @itemx set may-insert-tracepoints off
5407 This controls whether @value{GDBN} will attempt to insert (regular)
5408 tracepoints at the beginning of a tracing experiment. It affects only
5409 non-fast tracepoints, fast tracepoints being under the control of
5410 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5412 @item show may-insert-tracepoints
5413 Show the current permission to insert tracepoints.
5415 @kindex may-insert-fast-tracepoints
5416 @item set may-insert-fast-tracepoints on
5417 @itemx set may-insert-fast-tracepoints off
5418 This controls whether @value{GDBN} will attempt to insert fast
5419 tracepoints at the beginning of a tracing experiment. It affects only
5420 fast tracepoints, regular (non-fast) tracepoints being under the
5421 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5423 @item show may-insert-fast-tracepoints
5424 Show the current permission to insert fast tracepoints.
5426 @kindex may-interrupt
5427 @item set may-interrupt on
5428 @itemx set may-interrupt off
5429 This controls whether @value{GDBN} will attempt to interrupt or stop
5430 program execution. When this variable is @code{off}, the
5431 @code{interrupt} command will have no effect, nor will
5432 @kbd{Ctrl-c}. It defaults to @code{on}.
5434 @item show may-interrupt
5435 Show the current permission to interrupt or stop the program.
5439 @node Reverse Execution
5440 @chapter Running programs backward
5441 @cindex reverse execution
5442 @cindex running programs backward
5444 When you are debugging a program, it is not unusual to realize that
5445 you have gone too far, and some event of interest has already happened.
5446 If the target environment supports it, @value{GDBN} can allow you to
5447 ``rewind'' the program by running it backward.
5449 A target environment that supports reverse execution should be able
5450 to ``undo'' the changes in machine state that have taken place as the
5451 program was executing normally. Variables, registers etc.@: should
5452 revert to their previous values. Obviously this requires a great
5453 deal of sophistication on the part of the target environment; not
5454 all target environments can support reverse execution.
5456 When a program is executed in reverse, the instructions that
5457 have most recently been executed are ``un-executed'', in reverse
5458 order. The program counter runs backward, following the previous
5459 thread of execution in reverse. As each instruction is ``un-executed'',
5460 the values of memory and/or registers that were changed by that
5461 instruction are reverted to their previous states. After executing
5462 a piece of source code in reverse, all side effects of that code
5463 should be ``undone'', and all variables should be returned to their
5464 prior values@footnote{
5465 Note that some side effects are easier to undo than others. For instance,
5466 memory and registers are relatively easy, but device I/O is hard. Some
5467 targets may be able undo things like device I/O, and some may not.
5469 The contract between @value{GDBN} and the reverse executing target
5470 requires only that the target do something reasonable when
5471 @value{GDBN} tells it to execute backwards, and then report the
5472 results back to @value{GDBN}. Whatever the target reports back to
5473 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5474 assumes that the memory and registers that the target reports are in a
5475 consistant state, but @value{GDBN} accepts whatever it is given.
5478 If you are debugging in a target environment that supports
5479 reverse execution, @value{GDBN} provides the following commands.
5482 @kindex reverse-continue
5483 @kindex rc @r{(@code{reverse-continue})}
5484 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5485 @itemx rc @r{[}@var{ignore-count}@r{]}
5486 Beginning at the point where your program last stopped, start executing
5487 in reverse. Reverse execution will stop for breakpoints and synchronous
5488 exceptions (signals), just like normal execution. Behavior of
5489 asynchronous signals depends on the target environment.
5491 @kindex reverse-step
5492 @kindex rs @r{(@code{step})}
5493 @item reverse-step @r{[}@var{count}@r{]}
5494 Run the program backward until control reaches the start of a
5495 different source line; then stop it, and return control to @value{GDBN}.
5497 Like the @code{step} command, @code{reverse-step} will only stop
5498 at the beginning of a source line. It ``un-executes'' the previously
5499 executed source line. If the previous source line included calls to
5500 debuggable functions, @code{reverse-step} will step (backward) into
5501 the called function, stopping at the beginning of the @emph{last}
5502 statement in the called function (typically a return statement).
5504 Also, as with the @code{step} command, if non-debuggable functions are
5505 called, @code{reverse-step} will run thru them backward without stopping.
5507 @kindex reverse-stepi
5508 @kindex rsi @r{(@code{reverse-stepi})}
5509 @item reverse-stepi @r{[}@var{count}@r{]}
5510 Reverse-execute one machine instruction. Note that the instruction
5511 to be reverse-executed is @emph{not} the one pointed to by the program
5512 counter, but the instruction executed prior to that one. For instance,
5513 if the last instruction was a jump, @code{reverse-stepi} will take you
5514 back from the destination of the jump to the jump instruction itself.
5516 @kindex reverse-next
5517 @kindex rn @r{(@code{reverse-next})}
5518 @item reverse-next @r{[}@var{count}@r{]}
5519 Run backward to the beginning of the previous line executed in
5520 the current (innermost) stack frame. If the line contains function
5521 calls, they will be ``un-executed'' without stopping. Starting from
5522 the first line of a function, @code{reverse-next} will take you back
5523 to the caller of that function, @emph{before} the function was called,
5524 just as the normal @code{next} command would take you from the last
5525 line of a function back to its return to its caller
5526 @footnote{Unless the code is too heavily optimized.}.
5528 @kindex reverse-nexti
5529 @kindex rni @r{(@code{reverse-nexti})}
5530 @item reverse-nexti @r{[}@var{count}@r{]}
5531 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5532 in reverse, except that called functions are ``un-executed'' atomically.
5533 That is, if the previously executed instruction was a return from
5534 another function, @code{reverse-nexti} will continue to execute
5535 in reverse until the call to that function (from the current stack
5538 @kindex reverse-finish
5539 @item reverse-finish
5540 Just as the @code{finish} command takes you to the point where the
5541 current function returns, @code{reverse-finish} takes you to the point
5542 where it was called. Instead of ending up at the end of the current
5543 function invocation, you end up at the beginning.
5545 @kindex set exec-direction
5546 @item set exec-direction
5547 Set the direction of target execution.
5548 @itemx set exec-direction reverse
5549 @cindex execute forward or backward in time
5550 @value{GDBN} will perform all execution commands in reverse, until the
5551 exec-direction mode is changed to ``forward''. Affected commands include
5552 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5553 command cannot be used in reverse mode.
5554 @item set exec-direction forward
5555 @value{GDBN} will perform all execution commands in the normal fashion.
5556 This is the default.
5560 @node Process Record and Replay
5561 @chapter Recording Inferior's Execution and Replaying It
5562 @cindex process record and replay
5563 @cindex recording inferior's execution and replaying it
5565 On some platforms, @value{GDBN} provides a special @dfn{process record
5566 and replay} target that can record a log of the process execution, and
5567 replay it later with both forward and reverse execution commands.
5570 When this target is in use, if the execution log includes the record
5571 for the next instruction, @value{GDBN} will debug in @dfn{replay
5572 mode}. In the replay mode, the inferior does not really execute code
5573 instructions. Instead, all the events that normally happen during
5574 code execution are taken from the execution log. While code is not
5575 really executed in replay mode, the values of registers (including the
5576 program counter register) and the memory of the inferior are still
5577 changed as they normally would. Their contents are taken from the
5581 If the record for the next instruction is not in the execution log,
5582 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5583 inferior executes normally, and @value{GDBN} records the execution log
5586 The process record and replay target supports reverse execution
5587 (@pxref{Reverse Execution}), even if the platform on which the
5588 inferior runs does not. However, the reverse execution is limited in
5589 this case by the range of the instructions recorded in the execution
5590 log. In other words, reverse execution on platforms that don't
5591 support it directly can only be done in the replay mode.
5593 When debugging in the reverse direction, @value{GDBN} will work in
5594 replay mode as long as the execution log includes the record for the
5595 previous instruction; otherwise, it will work in record mode, if the
5596 platform supports reverse execution, or stop if not.
5598 For architecture environments that support process record and replay,
5599 @value{GDBN} provides the following commands:
5602 @kindex target record
5606 This command starts the process record and replay target. The process
5607 record and replay target can only debug a process that is already
5608 running. Therefore, you need first to start the process with the
5609 @kbd{run} or @kbd{start} commands, and then start the recording with
5610 the @kbd{target record} command.
5612 Both @code{record} and @code{rec} are aliases of @code{target record}.
5614 @cindex displaced stepping, and process record and replay
5615 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5616 will be automatically disabled when process record and replay target
5617 is started. That's because the process record and replay target
5618 doesn't support displaced stepping.
5620 @cindex non-stop mode, and process record and replay
5621 @cindex asynchronous execution, and process record and replay
5622 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5623 the asynchronous execution mode (@pxref{Background Execution}), the
5624 process record and replay target cannot be started because it doesn't
5625 support these two modes.
5630 Stop the process record and replay target. When process record and
5631 replay target stops, the entire execution log will be deleted and the
5632 inferior will either be terminated, or will remain in its final state.
5634 When you stop the process record and replay target in record mode (at
5635 the end of the execution log), the inferior will be stopped at the
5636 next instruction that would have been recorded. In other words, if
5637 you record for a while and then stop recording, the inferior process
5638 will be left in the same state as if the recording never happened.
5640 On the other hand, if the process record and replay target is stopped
5641 while in replay mode (that is, not at the end of the execution log,
5642 but at some earlier point), the inferior process will become ``live''
5643 at that earlier state, and it will then be possible to continue the
5644 usual ``live'' debugging of the process from that state.
5646 When the inferior process exits, or @value{GDBN} detaches from it,
5647 process record and replay target will automatically stop itself.
5650 @item record save @var{filename}
5651 Save the execution log to a file @file{@var{filename}}.
5652 Default filename is @file{gdb_record.@var{process_id}}, where
5653 @var{process_id} is the process ID of the inferior.
5655 @kindex record restore
5656 @item record restore @var{filename}
5657 Restore the execution log from a file @file{@var{filename}}.
5658 File must have been created with @code{record save}.
5660 @kindex set record insn-number-max
5661 @item set record insn-number-max @var{limit}
5662 Set the limit of instructions to be recorded. Default value is 200000.
5664 If @var{limit} is a positive number, then @value{GDBN} will start
5665 deleting instructions from the log once the number of the record
5666 instructions becomes greater than @var{limit}. For every new recorded
5667 instruction, @value{GDBN} will delete the earliest recorded
5668 instruction to keep the number of recorded instructions at the limit.
5669 (Since deleting recorded instructions loses information, @value{GDBN}
5670 lets you control what happens when the limit is reached, by means of
5671 the @code{stop-at-limit} option, described below.)
5673 If @var{limit} is zero, @value{GDBN} will never delete recorded
5674 instructions from the execution log. The number of recorded
5675 instructions is unlimited in this case.
5677 @kindex show record insn-number-max
5678 @item show record insn-number-max
5679 Show the limit of instructions to be recorded.
5681 @kindex set record stop-at-limit
5682 @item set record stop-at-limit
5683 Control the behavior when the number of recorded instructions reaches
5684 the limit. If ON (the default), @value{GDBN} will stop when the limit
5685 is reached for the first time and ask you whether you want to stop the
5686 inferior or continue running it and recording the execution log. If
5687 you decide to continue recording, each new recorded instruction will
5688 cause the oldest one to be deleted.
5690 If this option is OFF, @value{GDBN} will automatically delete the
5691 oldest record to make room for each new one, without asking.
5693 @kindex show record stop-at-limit
5694 @item show record stop-at-limit
5695 Show the current setting of @code{stop-at-limit}.
5697 @kindex set record memory-query
5698 @item set record memory-query
5699 Control the behavior when @value{GDBN} is unable to record memory
5700 changes caused by an instruction. If ON, @value{GDBN} will query
5701 whether to stop the inferior in that case.
5703 If this option is OFF (the default), @value{GDBN} will automatically
5704 ignore the effect of such instructions on memory. Later, when
5705 @value{GDBN} replays this execution log, it will mark the log of this
5706 instruction as not accessible, and it will not affect the replay
5709 @kindex show record memory-query
5710 @item show record memory-query
5711 Show the current setting of @code{memory-query}.
5715 Show various statistics about the state of process record and its
5716 in-memory execution log buffer, including:
5720 Whether in record mode or replay mode.
5722 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
5724 Highest recorded instruction number.
5726 Current instruction about to be replayed (if in replay mode).
5728 Number of instructions contained in the execution log.
5730 Maximum number of instructions that may be contained in the execution log.
5733 @kindex record delete
5736 When record target runs in replay mode (``in the past''), delete the
5737 subsequent execution log and begin to record a new execution log starting
5738 from the current address. This means you will abandon the previously
5739 recorded ``future'' and begin recording a new ``future''.
5744 @chapter Examining the Stack
5746 When your program has stopped, the first thing you need to know is where it
5747 stopped and how it got there.
5750 Each time your program performs a function call, information about the call
5752 That information includes the location of the call in your program,
5753 the arguments of the call,
5754 and the local variables of the function being called.
5755 The information is saved in a block of data called a @dfn{stack frame}.
5756 The stack frames are allocated in a region of memory called the @dfn{call
5759 When your program stops, the @value{GDBN} commands for examining the
5760 stack allow you to see all of this information.
5762 @cindex selected frame
5763 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5764 @value{GDBN} commands refer implicitly to the selected frame. In
5765 particular, whenever you ask @value{GDBN} for the value of a variable in
5766 your program, the value is found in the selected frame. There are
5767 special @value{GDBN} commands to select whichever frame you are
5768 interested in. @xref{Selection, ,Selecting a Frame}.
5770 When your program stops, @value{GDBN} automatically selects the
5771 currently executing frame and describes it briefly, similar to the
5772 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5775 * Frames:: Stack frames
5776 * Backtrace:: Backtraces
5777 * Selection:: Selecting a frame
5778 * Frame Info:: Information on a frame
5783 @section Stack Frames
5785 @cindex frame, definition
5787 The call stack is divided up into contiguous pieces called @dfn{stack
5788 frames}, or @dfn{frames} for short; each frame is the data associated
5789 with one call to one function. The frame contains the arguments given
5790 to the function, the function's local variables, and the address at
5791 which the function is executing.
5793 @cindex initial frame
5794 @cindex outermost frame
5795 @cindex innermost frame
5796 When your program is started, the stack has only one frame, that of the
5797 function @code{main}. This is called the @dfn{initial} frame or the
5798 @dfn{outermost} frame. Each time a function is called, a new frame is
5799 made. Each time a function returns, the frame for that function invocation
5800 is eliminated. If a function is recursive, there can be many frames for
5801 the same function. The frame for the function in which execution is
5802 actually occurring is called the @dfn{innermost} frame. This is the most
5803 recently created of all the stack frames that still exist.
5805 @cindex frame pointer
5806 Inside your program, stack frames are identified by their addresses. A
5807 stack frame consists of many bytes, each of which has its own address; each
5808 kind of computer has a convention for choosing one byte whose
5809 address serves as the address of the frame. Usually this address is kept
5810 in a register called the @dfn{frame pointer register}
5811 (@pxref{Registers, $fp}) while execution is going on in that frame.
5813 @cindex frame number
5814 @value{GDBN} assigns numbers to all existing stack frames, starting with
5815 zero for the innermost frame, one for the frame that called it,
5816 and so on upward. These numbers do not really exist in your program;
5817 they are assigned by @value{GDBN} to give you a way of designating stack
5818 frames in @value{GDBN} commands.
5820 @c The -fomit-frame-pointer below perennially causes hbox overflow
5821 @c underflow problems.
5822 @cindex frameless execution
5823 Some compilers provide a way to compile functions so that they operate
5824 without stack frames. (For example, the @value{NGCC} option
5826 @samp{-fomit-frame-pointer}
5828 generates functions without a frame.)
5829 This is occasionally done with heavily used library functions to save
5830 the frame setup time. @value{GDBN} has limited facilities for dealing
5831 with these function invocations. If the innermost function invocation
5832 has no stack frame, @value{GDBN} nevertheless regards it as though
5833 it had a separate frame, which is numbered zero as usual, allowing
5834 correct tracing of the function call chain. However, @value{GDBN} has
5835 no provision for frameless functions elsewhere in the stack.
5838 @kindex frame@r{, command}
5839 @cindex current stack frame
5840 @item frame @var{args}
5841 The @code{frame} command allows you to move from one stack frame to another,
5842 and to print the stack frame you select. @var{args} may be either the
5843 address of the frame or the stack frame number. Without an argument,
5844 @code{frame} prints the current stack frame.
5846 @kindex select-frame
5847 @cindex selecting frame silently
5849 The @code{select-frame} command allows you to move from one stack frame
5850 to another without printing the frame. This is the silent version of
5858 @cindex call stack traces
5859 A backtrace is a summary of how your program got where it is. It shows one
5860 line per frame, for many frames, starting with the currently executing
5861 frame (frame zero), followed by its caller (frame one), and on up the
5866 @kindex bt @r{(@code{backtrace})}
5869 Print a backtrace of the entire stack: one line per frame for all
5870 frames in the stack.
5872 You can stop the backtrace at any time by typing the system interrupt
5873 character, normally @kbd{Ctrl-c}.
5875 @item backtrace @var{n}
5877 Similar, but print only the innermost @var{n} frames.
5879 @item backtrace -@var{n}
5881 Similar, but print only the outermost @var{n} frames.
5883 @item backtrace full
5885 @itemx bt full @var{n}
5886 @itemx bt full -@var{n}
5887 Print the values of the local variables also. @var{n} specifies the
5888 number of frames to print, as described above.
5893 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5894 are additional aliases for @code{backtrace}.
5896 @cindex multiple threads, backtrace
5897 In a multi-threaded program, @value{GDBN} by default shows the
5898 backtrace only for the current thread. To display the backtrace for
5899 several or all of the threads, use the command @code{thread apply}
5900 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5901 apply all backtrace}, @value{GDBN} will display the backtrace for all
5902 the threads; this is handy when you debug a core dump of a
5903 multi-threaded program.
5905 Each line in the backtrace shows the frame number and the function name.
5906 The program counter value is also shown---unless you use @code{set
5907 print address off}. The backtrace also shows the source file name and
5908 line number, as well as the arguments to the function. The program
5909 counter value is omitted if it is at the beginning of the code for that
5912 Here is an example of a backtrace. It was made with the command
5913 @samp{bt 3}, so it shows the innermost three frames.
5917 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5919 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
5920 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5922 (More stack frames follow...)
5927 The display for frame zero does not begin with a program counter
5928 value, indicating that your program has stopped at the beginning of the
5929 code for line @code{993} of @code{builtin.c}.
5932 The value of parameter @code{data} in frame 1 has been replaced by
5933 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
5934 only if it is a scalar (integer, pointer, enumeration, etc). See command
5935 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
5936 on how to configure the way function parameter values are printed.
5938 @cindex value optimized out, in backtrace
5939 @cindex function call arguments, optimized out
5940 If your program was compiled with optimizations, some compilers will
5941 optimize away arguments passed to functions if those arguments are
5942 never used after the call. Such optimizations generate code that
5943 passes arguments through registers, but doesn't store those arguments
5944 in the stack frame. @value{GDBN} has no way of displaying such
5945 arguments in stack frames other than the innermost one. Here's what
5946 such a backtrace might look like:
5950 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5952 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
5953 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
5955 (More stack frames follow...)
5960 The values of arguments that were not saved in their stack frames are
5961 shown as @samp{<value optimized out>}.
5963 If you need to display the values of such optimized-out arguments,
5964 either deduce that from other variables whose values depend on the one
5965 you are interested in, or recompile without optimizations.
5967 @cindex backtrace beyond @code{main} function
5968 @cindex program entry point
5969 @cindex startup code, and backtrace
5970 Most programs have a standard user entry point---a place where system
5971 libraries and startup code transition into user code. For C this is
5972 @code{main}@footnote{
5973 Note that embedded programs (the so-called ``free-standing''
5974 environment) are not required to have a @code{main} function as the
5975 entry point. They could even have multiple entry points.}.
5976 When @value{GDBN} finds the entry function in a backtrace
5977 it will terminate the backtrace, to avoid tracing into highly
5978 system-specific (and generally uninteresting) code.
5980 If you need to examine the startup code, or limit the number of levels
5981 in a backtrace, you can change this behavior:
5984 @item set backtrace past-main
5985 @itemx set backtrace past-main on
5986 @kindex set backtrace
5987 Backtraces will continue past the user entry point.
5989 @item set backtrace past-main off
5990 Backtraces will stop when they encounter the user entry point. This is the
5993 @item show backtrace past-main
5994 @kindex show backtrace
5995 Display the current user entry point backtrace policy.
5997 @item set backtrace past-entry
5998 @itemx set backtrace past-entry on
5999 Backtraces will continue past the internal entry point of an application.
6000 This entry point is encoded by the linker when the application is built,
6001 and is likely before the user entry point @code{main} (or equivalent) is called.
6003 @item set backtrace past-entry off
6004 Backtraces will stop when they encounter the internal entry point of an
6005 application. This is the default.
6007 @item show backtrace past-entry
6008 Display the current internal entry point backtrace policy.
6010 @item set backtrace limit @var{n}
6011 @itemx set backtrace limit 0
6012 @cindex backtrace limit
6013 Limit the backtrace to @var{n} levels. A value of zero means
6016 @item show backtrace limit
6017 Display the current limit on backtrace levels.
6021 @section Selecting a Frame
6023 Most commands for examining the stack and other data in your program work on
6024 whichever stack frame is selected at the moment. Here are the commands for
6025 selecting a stack frame; all of them finish by printing a brief description
6026 of the stack frame just selected.
6029 @kindex frame@r{, selecting}
6030 @kindex f @r{(@code{frame})}
6033 Select frame number @var{n}. Recall that frame zero is the innermost
6034 (currently executing) frame, frame one is the frame that called the
6035 innermost one, and so on. The highest-numbered frame is the one for
6038 @item frame @var{addr}
6040 Select the frame at address @var{addr}. This is useful mainly if the
6041 chaining of stack frames has been damaged by a bug, making it
6042 impossible for @value{GDBN} to assign numbers properly to all frames. In
6043 addition, this can be useful when your program has multiple stacks and
6044 switches between them.
6046 On the SPARC architecture, @code{frame} needs two addresses to
6047 select an arbitrary frame: a frame pointer and a stack pointer.
6049 On the MIPS and Alpha architecture, it needs two addresses: a stack
6050 pointer and a program counter.
6052 On the 29k architecture, it needs three addresses: a register stack
6053 pointer, a program counter, and a memory stack pointer.
6057 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6058 advances toward the outermost frame, to higher frame numbers, to frames
6059 that have existed longer. @var{n} defaults to one.
6062 @kindex do @r{(@code{down})}
6064 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6065 advances toward the innermost frame, to lower frame numbers, to frames
6066 that were created more recently. @var{n} defaults to one. You may
6067 abbreviate @code{down} as @code{do}.
6070 All of these commands end by printing two lines of output describing the
6071 frame. The first line shows the frame number, the function name, the
6072 arguments, and the source file and line number of execution in that
6073 frame. The second line shows the text of that source line.
6081 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6083 10 read_input_file (argv[i]);
6087 After such a printout, the @code{list} command with no arguments
6088 prints ten lines centered on the point of execution in the frame.
6089 You can also edit the program at the point of execution with your favorite
6090 editing program by typing @code{edit}.
6091 @xref{List, ,Printing Source Lines},
6095 @kindex down-silently
6097 @item up-silently @var{n}
6098 @itemx down-silently @var{n}
6099 These two commands are variants of @code{up} and @code{down},
6100 respectively; they differ in that they do their work silently, without
6101 causing display of the new frame. They are intended primarily for use
6102 in @value{GDBN} command scripts, where the output might be unnecessary and
6107 @section Information About a Frame
6109 There are several other commands to print information about the selected
6115 When used without any argument, this command does not change which
6116 frame is selected, but prints a brief description of the currently
6117 selected stack frame. It can be abbreviated @code{f}. With an
6118 argument, this command is used to select a stack frame.
6119 @xref{Selection, ,Selecting a Frame}.
6122 @kindex info f @r{(@code{info frame})}
6125 This command prints a verbose description of the selected stack frame,
6130 the address of the frame
6132 the address of the next frame down (called by this frame)
6134 the address of the next frame up (caller of this frame)
6136 the language in which the source code corresponding to this frame is written
6138 the address of the frame's arguments
6140 the address of the frame's local variables
6142 the program counter saved in it (the address of execution in the caller frame)
6144 which registers were saved in the frame
6147 @noindent The verbose description is useful when
6148 something has gone wrong that has made the stack format fail to fit
6149 the usual conventions.
6151 @item info frame @var{addr}
6152 @itemx info f @var{addr}
6153 Print a verbose description of the frame at address @var{addr}, without
6154 selecting that frame. The selected frame remains unchanged by this
6155 command. This requires the same kind of address (more than one for some
6156 architectures) that you specify in the @code{frame} command.
6157 @xref{Selection, ,Selecting a Frame}.
6161 Print the arguments of the selected frame, each on a separate line.
6165 Print the local variables of the selected frame, each on a separate
6166 line. These are all variables (declared either static or automatic)
6167 accessible at the point of execution of the selected frame.
6170 @cindex catch exceptions, list active handlers
6171 @cindex exception handlers, how to list
6173 Print a list of all the exception handlers that are active in the
6174 current stack frame at the current point of execution. To see other
6175 exception handlers, visit the associated frame (using the @code{up},
6176 @code{down}, or @code{frame} commands); then type @code{info catch}.
6177 @xref{Set Catchpoints, , Setting Catchpoints}.
6183 @chapter Examining Source Files
6185 @value{GDBN} can print parts of your program's source, since the debugging
6186 information recorded in the program tells @value{GDBN} what source files were
6187 used to build it. When your program stops, @value{GDBN} spontaneously prints
6188 the line where it stopped. Likewise, when you select a stack frame
6189 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6190 execution in that frame has stopped. You can print other portions of
6191 source files by explicit command.
6193 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6194 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6195 @value{GDBN} under @sc{gnu} Emacs}.
6198 * List:: Printing source lines
6199 * Specify Location:: How to specify code locations
6200 * Edit:: Editing source files
6201 * Search:: Searching source files
6202 * Source Path:: Specifying source directories
6203 * Machine Code:: Source and machine code
6207 @section Printing Source Lines
6210 @kindex l @r{(@code{list})}
6211 To print lines from a source file, use the @code{list} command
6212 (abbreviated @code{l}). By default, ten lines are printed.
6213 There are several ways to specify what part of the file you want to
6214 print; see @ref{Specify Location}, for the full list.
6216 Here are the forms of the @code{list} command most commonly used:
6219 @item list @var{linenum}
6220 Print lines centered around line number @var{linenum} in the
6221 current source file.
6223 @item list @var{function}
6224 Print lines centered around the beginning of function
6228 Print more lines. If the last lines printed were printed with a
6229 @code{list} command, this prints lines following the last lines
6230 printed; however, if the last line printed was a solitary line printed
6231 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6232 Stack}), this prints lines centered around that line.
6235 Print lines just before the lines last printed.
6238 @cindex @code{list}, how many lines to display
6239 By default, @value{GDBN} prints ten source lines with any of these forms of
6240 the @code{list} command. You can change this using @code{set listsize}:
6243 @kindex set listsize
6244 @item set listsize @var{count}
6245 Make the @code{list} command display @var{count} source lines (unless
6246 the @code{list} argument explicitly specifies some other number).
6248 @kindex show listsize
6250 Display the number of lines that @code{list} prints.
6253 Repeating a @code{list} command with @key{RET} discards the argument,
6254 so it is equivalent to typing just @code{list}. This is more useful
6255 than listing the same lines again. An exception is made for an
6256 argument of @samp{-}; that argument is preserved in repetition so that
6257 each repetition moves up in the source file.
6259 In general, the @code{list} command expects you to supply zero, one or two
6260 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6261 of writing them (@pxref{Specify Location}), but the effect is always
6262 to specify some source line.
6264 Here is a complete description of the possible arguments for @code{list}:
6267 @item list @var{linespec}
6268 Print lines centered around the line specified by @var{linespec}.
6270 @item list @var{first},@var{last}
6271 Print lines from @var{first} to @var{last}. Both arguments are
6272 linespecs. When a @code{list} command has two linespecs, and the
6273 source file of the second linespec is omitted, this refers to
6274 the same source file as the first linespec.
6276 @item list ,@var{last}
6277 Print lines ending with @var{last}.
6279 @item list @var{first},
6280 Print lines starting with @var{first}.
6283 Print lines just after the lines last printed.
6286 Print lines just before the lines last printed.
6289 As described in the preceding table.
6292 @node Specify Location
6293 @section Specifying a Location
6294 @cindex specifying location
6297 Several @value{GDBN} commands accept arguments that specify a location
6298 of your program's code. Since @value{GDBN} is a source-level
6299 debugger, a location usually specifies some line in the source code;
6300 for that reason, locations are also known as @dfn{linespecs}.
6302 Here are all the different ways of specifying a code location that
6303 @value{GDBN} understands:
6307 Specifies the line number @var{linenum} of the current source file.
6310 @itemx +@var{offset}
6311 Specifies the line @var{offset} lines before or after the @dfn{current
6312 line}. For the @code{list} command, the current line is the last one
6313 printed; for the breakpoint commands, this is the line at which
6314 execution stopped in the currently selected @dfn{stack frame}
6315 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6316 used as the second of the two linespecs in a @code{list} command,
6317 this specifies the line @var{offset} lines up or down from the first
6320 @item @var{filename}:@var{linenum}
6321 Specifies the line @var{linenum} in the source file @var{filename}.
6323 @item @var{function}
6324 Specifies the line that begins the body of the function @var{function}.
6325 For example, in C, this is the line with the open brace.
6327 @item @var{filename}:@var{function}
6328 Specifies the line that begins the body of the function @var{function}
6329 in the file @var{filename}. You only need the file name with a
6330 function name to avoid ambiguity when there are identically named
6331 functions in different source files.
6333 @item *@var{address}
6334 Specifies the program address @var{address}. For line-oriented
6335 commands, such as @code{list} and @code{edit}, this specifies a source
6336 line that contains @var{address}. For @code{break} and other
6337 breakpoint oriented commands, this can be used to set breakpoints in
6338 parts of your program which do not have debugging information or
6341 Here @var{address} may be any expression valid in the current working
6342 language (@pxref{Languages, working language}) that specifies a code
6343 address. In addition, as a convenience, @value{GDBN} extends the
6344 semantics of expressions used in locations to cover the situations
6345 that frequently happen during debugging. Here are the various forms
6349 @item @var{expression}
6350 Any expression valid in the current working language.
6352 @item @var{funcaddr}
6353 An address of a function or procedure derived from its name. In C,
6354 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6355 simply the function's name @var{function} (and actually a special case
6356 of a valid expression). In Pascal and Modula-2, this is
6357 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6358 (although the Pascal form also works).
6360 This form specifies the address of the function's first instruction,
6361 before the stack frame and arguments have been set up.
6363 @item '@var{filename}'::@var{funcaddr}
6364 Like @var{funcaddr} above, but also specifies the name of the source
6365 file explicitly. This is useful if the name of the function does not
6366 specify the function unambiguously, e.g., if there are several
6367 functions with identical names in different source files.
6374 @section Editing Source Files
6375 @cindex editing source files
6378 @kindex e @r{(@code{edit})}
6379 To edit the lines in a source file, use the @code{edit} command.
6380 The editing program of your choice
6381 is invoked with the current line set to
6382 the active line in the program.
6383 Alternatively, there are several ways to specify what part of the file you
6384 want to print if you want to see other parts of the program:
6387 @item edit @var{location}
6388 Edit the source file specified by @code{location}. Editing starts at
6389 that @var{location}, e.g., at the specified source line of the
6390 specified file. @xref{Specify Location}, for all the possible forms
6391 of the @var{location} argument; here are the forms of the @code{edit}
6392 command most commonly used:
6395 @item edit @var{number}
6396 Edit the current source file with @var{number} as the active line number.
6398 @item edit @var{function}
6399 Edit the file containing @var{function} at the beginning of its definition.
6404 @subsection Choosing your Editor
6405 You can customize @value{GDBN} to use any editor you want
6407 The only restriction is that your editor (say @code{ex}), recognizes the
6408 following command-line syntax:
6410 ex +@var{number} file
6412 The optional numeric value +@var{number} specifies the number of the line in
6413 the file where to start editing.}.
6414 By default, it is @file{@value{EDITOR}}, but you can change this
6415 by setting the environment variable @code{EDITOR} before using
6416 @value{GDBN}. For example, to configure @value{GDBN} to use the
6417 @code{vi} editor, you could use these commands with the @code{sh} shell:
6423 or in the @code{csh} shell,
6425 setenv EDITOR /usr/bin/vi
6430 @section Searching Source Files
6431 @cindex searching source files
6433 There are two commands for searching through the current source file for a
6438 @kindex forward-search
6439 @item forward-search @var{regexp}
6440 @itemx search @var{regexp}
6441 The command @samp{forward-search @var{regexp}} checks each line,
6442 starting with the one following the last line listed, for a match for
6443 @var{regexp}. It lists the line that is found. You can use the
6444 synonym @samp{search @var{regexp}} or abbreviate the command name as
6447 @kindex reverse-search
6448 @item reverse-search @var{regexp}
6449 The command @samp{reverse-search @var{regexp}} checks each line, starting
6450 with the one before the last line listed and going backward, for a match
6451 for @var{regexp}. It lists the line that is found. You can abbreviate
6452 this command as @code{rev}.
6456 @section Specifying Source Directories
6459 @cindex directories for source files
6460 Executable programs sometimes do not record the directories of the source
6461 files from which they were compiled, just the names. Even when they do,
6462 the directories could be moved between the compilation and your debugging
6463 session. @value{GDBN} has a list of directories to search for source files;
6464 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6465 it tries all the directories in the list, in the order they are present
6466 in the list, until it finds a file with the desired name.
6468 For example, suppose an executable references the file
6469 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6470 @file{/mnt/cross}. The file is first looked up literally; if this
6471 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6472 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6473 message is printed. @value{GDBN} does not look up the parts of the
6474 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6475 Likewise, the subdirectories of the source path are not searched: if
6476 the source path is @file{/mnt/cross}, and the binary refers to
6477 @file{foo.c}, @value{GDBN} would not find it under
6478 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6480 Plain file names, relative file names with leading directories, file
6481 names containing dots, etc.@: are all treated as described above; for
6482 instance, if the source path is @file{/mnt/cross}, and the source file
6483 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6484 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6485 that---@file{/mnt/cross/foo.c}.
6487 Note that the executable search path is @emph{not} used to locate the
6490 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6491 any information it has cached about where source files are found and where
6492 each line is in the file.
6496 When you start @value{GDBN}, its source path includes only @samp{cdir}
6497 and @samp{cwd}, in that order.
6498 To add other directories, use the @code{directory} command.
6500 The search path is used to find both program source files and @value{GDBN}
6501 script files (read using the @samp{-command} option and @samp{source} command).
6503 In addition to the source path, @value{GDBN} provides a set of commands
6504 that manage a list of source path substitution rules. A @dfn{substitution
6505 rule} specifies how to rewrite source directories stored in the program's
6506 debug information in case the sources were moved to a different
6507 directory between compilation and debugging. A rule is made of
6508 two strings, the first specifying what needs to be rewritten in
6509 the path, and the second specifying how it should be rewritten.
6510 In @ref{set substitute-path}, we name these two parts @var{from} and
6511 @var{to} respectively. @value{GDBN} does a simple string replacement
6512 of @var{from} with @var{to} at the start of the directory part of the
6513 source file name, and uses that result instead of the original file
6514 name to look up the sources.
6516 Using the previous example, suppose the @file{foo-1.0} tree has been
6517 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6518 @value{GDBN} to replace @file{/usr/src} in all source path names with
6519 @file{/mnt/cross}. The first lookup will then be
6520 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6521 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6522 substitution rule, use the @code{set substitute-path} command
6523 (@pxref{set substitute-path}).
6525 To avoid unexpected substitution results, a rule is applied only if the
6526 @var{from} part of the directory name ends at a directory separator.
6527 For instance, a rule substituting @file{/usr/source} into
6528 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6529 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6530 is applied only at the beginning of the directory name, this rule will
6531 not be applied to @file{/root/usr/source/baz.c} either.
6533 In many cases, you can achieve the same result using the @code{directory}
6534 command. However, @code{set substitute-path} can be more efficient in
6535 the case where the sources are organized in a complex tree with multiple
6536 subdirectories. With the @code{directory} command, you need to add each
6537 subdirectory of your project. If you moved the entire tree while
6538 preserving its internal organization, then @code{set substitute-path}
6539 allows you to direct the debugger to all the sources with one single
6542 @code{set substitute-path} is also more than just a shortcut command.
6543 The source path is only used if the file at the original location no
6544 longer exists. On the other hand, @code{set substitute-path} modifies
6545 the debugger behavior to look at the rewritten location instead. So, if
6546 for any reason a source file that is not relevant to your executable is
6547 located at the original location, a substitution rule is the only
6548 method available to point @value{GDBN} at the new location.
6550 @cindex @samp{--with-relocated-sources}
6551 @cindex default source path substitution
6552 You can configure a default source path substitution rule by
6553 configuring @value{GDBN} with the
6554 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6555 should be the name of a directory under @value{GDBN}'s configured
6556 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6557 directory names in debug information under @var{dir} will be adjusted
6558 automatically if the installed @value{GDBN} is moved to a new
6559 location. This is useful if @value{GDBN}, libraries or executables
6560 with debug information and corresponding source code are being moved
6564 @item directory @var{dirname} @dots{}
6565 @item dir @var{dirname} @dots{}
6566 Add directory @var{dirname} to the front of the source path. Several
6567 directory names may be given to this command, separated by @samp{:}
6568 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6569 part of absolute file names) or
6570 whitespace. You may specify a directory that is already in the source
6571 path; this moves it forward, so @value{GDBN} searches it sooner.
6575 @vindex $cdir@r{, convenience variable}
6576 @vindex $cwd@r{, convenience variable}
6577 @cindex compilation directory
6578 @cindex current directory
6579 @cindex working directory
6580 @cindex directory, current
6581 @cindex directory, compilation
6582 You can use the string @samp{$cdir} to refer to the compilation
6583 directory (if one is recorded), and @samp{$cwd} to refer to the current
6584 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6585 tracks the current working directory as it changes during your @value{GDBN}
6586 session, while the latter is immediately expanded to the current
6587 directory at the time you add an entry to the source path.
6590 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6592 @c RET-repeat for @code{directory} is explicitly disabled, but since
6593 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6595 @item show directories
6596 @kindex show directories
6597 Print the source path: show which directories it contains.
6599 @anchor{set substitute-path}
6600 @item set substitute-path @var{from} @var{to}
6601 @kindex set substitute-path
6602 Define a source path substitution rule, and add it at the end of the
6603 current list of existing substitution rules. If a rule with the same
6604 @var{from} was already defined, then the old rule is also deleted.
6606 For example, if the file @file{/foo/bar/baz.c} was moved to
6607 @file{/mnt/cross/baz.c}, then the command
6610 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6614 will tell @value{GDBN} to replace @samp{/usr/src} with
6615 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6616 @file{baz.c} even though it was moved.
6618 In the case when more than one substitution rule have been defined,
6619 the rules are evaluated one by one in the order where they have been
6620 defined. The first one matching, if any, is selected to perform
6623 For instance, if we had entered the following commands:
6626 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6627 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6631 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6632 @file{/mnt/include/defs.h} by using the first rule. However, it would
6633 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6634 @file{/mnt/src/lib/foo.c}.
6637 @item unset substitute-path [path]
6638 @kindex unset substitute-path
6639 If a path is specified, search the current list of substitution rules
6640 for a rule that would rewrite that path. Delete that rule if found.
6641 A warning is emitted by the debugger if no rule could be found.
6643 If no path is specified, then all substitution rules are deleted.
6645 @item show substitute-path [path]
6646 @kindex show substitute-path
6647 If a path is specified, then print the source path substitution rule
6648 which would rewrite that path, if any.
6650 If no path is specified, then print all existing source path substitution
6655 If your source path is cluttered with directories that are no longer of
6656 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6657 versions of source. You can correct the situation as follows:
6661 Use @code{directory} with no argument to reset the source path to its default value.
6664 Use @code{directory} with suitable arguments to reinstall the
6665 directories you want in the source path. You can add all the
6666 directories in one command.
6670 @section Source and Machine Code
6671 @cindex source line and its code address
6673 You can use the command @code{info line} to map source lines to program
6674 addresses (and vice versa), and the command @code{disassemble} to display
6675 a range of addresses as machine instructions. You can use the command
6676 @code{set disassemble-next-line} to set whether to disassemble next
6677 source line when execution stops. When run under @sc{gnu} Emacs
6678 mode, the @code{info line} command causes the arrow to point to the
6679 line specified. Also, @code{info line} prints addresses in symbolic form as
6684 @item info line @var{linespec}
6685 Print the starting and ending addresses of the compiled code for
6686 source line @var{linespec}. You can specify source lines in any of
6687 the ways documented in @ref{Specify Location}.
6690 For example, we can use @code{info line} to discover the location of
6691 the object code for the first line of function
6692 @code{m4_changequote}:
6694 @c FIXME: I think this example should also show the addresses in
6695 @c symbolic form, as they usually would be displayed.
6697 (@value{GDBP}) info line m4_changequote
6698 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6702 @cindex code address and its source line
6703 We can also inquire (using @code{*@var{addr}} as the form for
6704 @var{linespec}) what source line covers a particular address:
6706 (@value{GDBP}) info line *0x63ff
6707 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6710 @cindex @code{$_} and @code{info line}
6711 @cindex @code{x} command, default address
6712 @kindex x@r{(examine), and} info line
6713 After @code{info line}, the default address for the @code{x} command
6714 is changed to the starting address of the line, so that @samp{x/i} is
6715 sufficient to begin examining the machine code (@pxref{Memory,
6716 ,Examining Memory}). Also, this address is saved as the value of the
6717 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6722 @cindex assembly instructions
6723 @cindex instructions, assembly
6724 @cindex machine instructions
6725 @cindex listing machine instructions
6727 @itemx disassemble /m
6728 @itemx disassemble /r
6729 This specialized command dumps a range of memory as machine
6730 instructions. It can also print mixed source+disassembly by specifying
6731 the @code{/m} modifier and print the raw instructions in hex as well as
6732 in symbolic form by specifying the @code{/r}.
6733 The default memory range is the function surrounding the
6734 program counter of the selected frame. A single argument to this
6735 command is a program counter value; @value{GDBN} dumps the function
6736 surrounding this value. When two arguments are given, they should
6737 be separated by a comma, possibly surrounded by whitespace. The
6738 arguments specify a range of addresses (first inclusive, second exclusive)
6739 to dump. In that case, the name of the function is also printed (since
6740 there could be several functions in the given range).
6742 The argument(s) can be any expression yielding a numeric value, such as
6743 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
6745 If the range of memory being disassembled contains current program counter,
6746 the instruction at that location is shown with a @code{=>} marker.
6749 The following example shows the disassembly of a range of addresses of
6750 HP PA-RISC 2.0 code:
6753 (@value{GDBP}) disas 0x32c4, 0x32e4
6754 Dump of assembler code from 0x32c4 to 0x32e4:
6755 0x32c4 <main+204>: addil 0,dp
6756 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6757 0x32cc <main+212>: ldil 0x3000,r31
6758 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6759 0x32d4 <main+220>: ldo 0(r31),rp
6760 0x32d8 <main+224>: addil -0x800,dp
6761 0x32dc <main+228>: ldo 0x588(r1),r26
6762 0x32e0 <main+232>: ldil 0x3000,r31
6763 End of assembler dump.
6766 Here is an example showing mixed source+assembly for Intel x86, when the
6767 program is stopped just after function prologue:
6770 (@value{GDBP}) disas /m main
6771 Dump of assembler code for function main:
6773 0x08048330 <+0>: push %ebp
6774 0x08048331 <+1>: mov %esp,%ebp
6775 0x08048333 <+3>: sub $0x8,%esp
6776 0x08048336 <+6>: and $0xfffffff0,%esp
6777 0x08048339 <+9>: sub $0x10,%esp
6779 6 printf ("Hello.\n");
6780 => 0x0804833c <+12>: movl $0x8048440,(%esp)
6781 0x08048343 <+19>: call 0x8048284 <puts@@plt>
6785 0x08048348 <+24>: mov $0x0,%eax
6786 0x0804834d <+29>: leave
6787 0x0804834e <+30>: ret
6789 End of assembler dump.
6792 Some architectures have more than one commonly-used set of instruction
6793 mnemonics or other syntax.
6795 For programs that were dynamically linked and use shared libraries,
6796 instructions that call functions or branch to locations in the shared
6797 libraries might show a seemingly bogus location---it's actually a
6798 location of the relocation table. On some architectures, @value{GDBN}
6799 might be able to resolve these to actual function names.
6802 @kindex set disassembly-flavor
6803 @cindex Intel disassembly flavor
6804 @cindex AT&T disassembly flavor
6805 @item set disassembly-flavor @var{instruction-set}
6806 Select the instruction set to use when disassembling the
6807 program via the @code{disassemble} or @code{x/i} commands.
6809 Currently this command is only defined for the Intel x86 family. You
6810 can set @var{instruction-set} to either @code{intel} or @code{att}.
6811 The default is @code{att}, the AT&T flavor used by default by Unix
6812 assemblers for x86-based targets.
6814 @kindex show disassembly-flavor
6815 @item show disassembly-flavor
6816 Show the current setting of the disassembly flavor.
6820 @kindex set disassemble-next-line
6821 @kindex show disassemble-next-line
6822 @item set disassemble-next-line
6823 @itemx show disassemble-next-line
6824 Control whether or not @value{GDBN} will disassemble the next source
6825 line or instruction when execution stops. If ON, @value{GDBN} will
6826 display disassembly of the next source line when execution of the
6827 program being debugged stops. This is @emph{in addition} to
6828 displaying the source line itself, which @value{GDBN} always does if
6829 possible. If the next source line cannot be displayed for some reason
6830 (e.g., if @value{GDBN} cannot find the source file, or there's no line
6831 info in the debug info), @value{GDBN} will display disassembly of the
6832 next @emph{instruction} instead of showing the next source line. If
6833 AUTO, @value{GDBN} will display disassembly of next instruction only
6834 if the source line cannot be displayed. This setting causes
6835 @value{GDBN} to display some feedback when you step through a function
6836 with no line info or whose source file is unavailable. The default is
6837 OFF, which means never display the disassembly of the next line or
6843 @chapter Examining Data
6845 @cindex printing data
6846 @cindex examining data
6849 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6850 @c document because it is nonstandard... Under Epoch it displays in a
6851 @c different window or something like that.
6852 The usual way to examine data in your program is with the @code{print}
6853 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6854 evaluates and prints the value of an expression of the language your
6855 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6856 Different Languages}). It may also print the expression using a
6857 Python-based pretty-printer (@pxref{Pretty Printing}).
6860 @item print @var{expr}
6861 @itemx print /@var{f} @var{expr}
6862 @var{expr} is an expression (in the source language). By default the
6863 value of @var{expr} is printed in a format appropriate to its data type;
6864 you can choose a different format by specifying @samp{/@var{f}}, where
6865 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6869 @itemx print /@var{f}
6870 @cindex reprint the last value
6871 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6872 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6873 conveniently inspect the same value in an alternative format.
6876 A more low-level way of examining data is with the @code{x} command.
6877 It examines data in memory at a specified address and prints it in a
6878 specified format. @xref{Memory, ,Examining Memory}.
6880 If you are interested in information about types, or about how the
6881 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6882 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6886 * Expressions:: Expressions
6887 * Ambiguous Expressions:: Ambiguous Expressions
6888 * Variables:: Program variables
6889 * Arrays:: Artificial arrays
6890 * Output Formats:: Output formats
6891 * Memory:: Examining memory
6892 * Auto Display:: Automatic display
6893 * Print Settings:: Print settings
6894 * Pretty Printing:: Python pretty printing
6895 * Value History:: Value history
6896 * Convenience Vars:: Convenience variables
6897 * Registers:: Registers
6898 * Floating Point Hardware:: Floating point hardware
6899 * Vector Unit:: Vector Unit
6900 * OS Information:: Auxiliary data provided by operating system
6901 * Memory Region Attributes:: Memory region attributes
6902 * Dump/Restore Files:: Copy between memory and a file
6903 * Core File Generation:: Cause a program dump its core
6904 * Character Sets:: Debugging programs that use a different
6905 character set than GDB does
6906 * Caching Remote Data:: Data caching for remote targets
6907 * Searching Memory:: Searching memory for a sequence of bytes
6911 @section Expressions
6914 @code{print} and many other @value{GDBN} commands accept an expression and
6915 compute its value. Any kind of constant, variable or operator defined
6916 by the programming language you are using is valid in an expression in
6917 @value{GDBN}. This includes conditional expressions, function calls,
6918 casts, and string constants. It also includes preprocessor macros, if
6919 you compiled your program to include this information; see
6922 @cindex arrays in expressions
6923 @value{GDBN} supports array constants in expressions input by
6924 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
6925 you can use the command @code{print @{1, 2, 3@}} to create an array
6926 of three integers. If you pass an array to a function or assign it
6927 to a program variable, @value{GDBN} copies the array to memory that
6928 is @code{malloc}ed in the target program.
6930 Because C is so widespread, most of the expressions shown in examples in
6931 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
6932 Languages}, for information on how to use expressions in other
6935 In this section, we discuss operators that you can use in @value{GDBN}
6936 expressions regardless of your programming language.
6938 @cindex casts, in expressions
6939 Casts are supported in all languages, not just in C, because it is so
6940 useful to cast a number into a pointer in order to examine a structure
6941 at that address in memory.
6942 @c FIXME: casts supported---Mod2 true?
6944 @value{GDBN} supports these operators, in addition to those common
6945 to programming languages:
6949 @samp{@@} is a binary operator for treating parts of memory as arrays.
6950 @xref{Arrays, ,Artificial Arrays}, for more information.
6953 @samp{::} allows you to specify a variable in terms of the file or
6954 function where it is defined. @xref{Variables, ,Program Variables}.
6956 @cindex @{@var{type}@}
6957 @cindex type casting memory
6958 @cindex memory, viewing as typed object
6959 @cindex casts, to view memory
6960 @item @{@var{type}@} @var{addr}
6961 Refers to an object of type @var{type} stored at address @var{addr} in
6962 memory. @var{addr} may be any expression whose value is an integer or
6963 pointer (but parentheses are required around binary operators, just as in
6964 a cast). This construct is allowed regardless of what kind of data is
6965 normally supposed to reside at @var{addr}.
6968 @node Ambiguous Expressions
6969 @section Ambiguous Expressions
6970 @cindex ambiguous expressions
6972 Expressions can sometimes contain some ambiguous elements. For instance,
6973 some programming languages (notably Ada, C@t{++} and Objective-C) permit
6974 a single function name to be defined several times, for application in
6975 different contexts. This is called @dfn{overloading}. Another example
6976 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
6977 templates and is typically instantiated several times, resulting in
6978 the same function name being defined in different contexts.
6980 In some cases and depending on the language, it is possible to adjust
6981 the expression to remove the ambiguity. For instance in C@t{++}, you
6982 can specify the signature of the function you want to break on, as in
6983 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
6984 qualified name of your function often makes the expression unambiguous
6987 When an ambiguity that needs to be resolved is detected, the debugger
6988 has the capability to display a menu of numbered choices for each
6989 possibility, and then waits for the selection with the prompt @samp{>}.
6990 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
6991 aborts the current command. If the command in which the expression was
6992 used allows more than one choice to be selected, the next option in the
6993 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
6996 For example, the following session excerpt shows an attempt to set a
6997 breakpoint at the overloaded symbol @code{String::after}.
6998 We choose three particular definitions of that function name:
7000 @c FIXME! This is likely to change to show arg type lists, at least
7003 (@value{GDBP}) b String::after
7006 [2] file:String.cc; line number:867
7007 [3] file:String.cc; line number:860
7008 [4] file:String.cc; line number:875
7009 [5] file:String.cc; line number:853
7010 [6] file:String.cc; line number:846
7011 [7] file:String.cc; line number:735
7013 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7014 Breakpoint 2 at 0xb344: file String.cc, line 875.
7015 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7016 Multiple breakpoints were set.
7017 Use the "delete" command to delete unwanted
7024 @kindex set multiple-symbols
7025 @item set multiple-symbols @var{mode}
7026 @cindex multiple-symbols menu
7028 This option allows you to adjust the debugger behavior when an expression
7031 By default, @var{mode} is set to @code{all}. If the command with which
7032 the expression is used allows more than one choice, then @value{GDBN}
7033 automatically selects all possible choices. For instance, inserting
7034 a breakpoint on a function using an ambiguous name results in a breakpoint
7035 inserted on each possible match. However, if a unique choice must be made,
7036 then @value{GDBN} uses the menu to help you disambiguate the expression.
7037 For instance, printing the address of an overloaded function will result
7038 in the use of the menu.
7040 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7041 when an ambiguity is detected.
7043 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7044 an error due to the ambiguity and the command is aborted.
7046 @kindex show multiple-symbols
7047 @item show multiple-symbols
7048 Show the current value of the @code{multiple-symbols} setting.
7052 @section Program Variables
7054 The most common kind of expression to use is the name of a variable
7057 Variables in expressions are understood in the selected stack frame
7058 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7062 global (or file-static)
7069 visible according to the scope rules of the
7070 programming language from the point of execution in that frame
7073 @noindent This means that in the function
7088 you can examine and use the variable @code{a} whenever your program is
7089 executing within the function @code{foo}, but you can only use or
7090 examine the variable @code{b} while your program is executing inside
7091 the block where @code{b} is declared.
7093 @cindex variable name conflict
7094 There is an exception: you can refer to a variable or function whose
7095 scope is a single source file even if the current execution point is not
7096 in this file. But it is possible to have more than one such variable or
7097 function with the same name (in different source files). If that
7098 happens, referring to that name has unpredictable effects. If you wish,
7099 you can specify a static variable in a particular function or file,
7100 using the colon-colon (@code{::}) notation:
7102 @cindex colon-colon, context for variables/functions
7104 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7105 @cindex @code{::}, context for variables/functions
7108 @var{file}::@var{variable}
7109 @var{function}::@var{variable}
7113 Here @var{file} or @var{function} is the name of the context for the
7114 static @var{variable}. In the case of file names, you can use quotes to
7115 make sure @value{GDBN} parses the file name as a single word---for example,
7116 to print a global value of @code{x} defined in @file{f2.c}:
7119 (@value{GDBP}) p 'f2.c'::x
7122 @cindex C@t{++} scope resolution
7123 This use of @samp{::} is very rarely in conflict with the very similar
7124 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7125 scope resolution operator in @value{GDBN} expressions.
7126 @c FIXME: Um, so what happens in one of those rare cases where it's in
7129 @cindex wrong values
7130 @cindex variable values, wrong
7131 @cindex function entry/exit, wrong values of variables
7132 @cindex optimized code, wrong values of variables
7134 @emph{Warning:} Occasionally, a local variable may appear to have the
7135 wrong value at certain points in a function---just after entry to a new
7136 scope, and just before exit.
7138 You may see this problem when you are stepping by machine instructions.
7139 This is because, on most machines, it takes more than one instruction to
7140 set up a stack frame (including local variable definitions); if you are
7141 stepping by machine instructions, variables may appear to have the wrong
7142 values until the stack frame is completely built. On exit, it usually
7143 also takes more than one machine instruction to destroy a stack frame;
7144 after you begin stepping through that group of instructions, local
7145 variable definitions may be gone.
7147 This may also happen when the compiler does significant optimizations.
7148 To be sure of always seeing accurate values, turn off all optimization
7151 @cindex ``No symbol "foo" in current context''
7152 Another possible effect of compiler optimizations is to optimize
7153 unused variables out of existence, or assign variables to registers (as
7154 opposed to memory addresses). Depending on the support for such cases
7155 offered by the debug info format used by the compiler, @value{GDBN}
7156 might not be able to display values for such local variables. If that
7157 happens, @value{GDBN} will print a message like this:
7160 No symbol "foo" in current context.
7163 To solve such problems, either recompile without optimizations, or use a
7164 different debug info format, if the compiler supports several such
7165 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
7166 usually supports the @option{-gstabs+} option. @option{-gstabs+}
7167 produces debug info in a format that is superior to formats such as
7168 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
7169 an effective form for debug info. @xref{Debugging Options,,Options
7170 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
7171 Compiler Collection (GCC)}.
7172 @xref{C, ,C and C@t{++}}, for more information about debug info formats
7173 that are best suited to C@t{++} programs.
7175 If you ask to print an object whose contents are unknown to
7176 @value{GDBN}, e.g., because its data type is not completely specified
7177 by the debug information, @value{GDBN} will say @samp{<incomplete
7178 type>}. @xref{Symbols, incomplete type}, for more about this.
7180 Strings are identified as arrays of @code{char} values without specified
7181 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7182 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7183 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7184 defines literal string type @code{"char"} as @code{char} without a sign.
7189 signed char var1[] = "A";
7192 You get during debugging
7197 $2 = @{65 'A', 0 '\0'@}
7201 @section Artificial Arrays
7203 @cindex artificial array
7205 @kindex @@@r{, referencing memory as an array}
7206 It is often useful to print out several successive objects of the
7207 same type in memory; a section of an array, or an array of
7208 dynamically determined size for which only a pointer exists in the
7211 You can do this by referring to a contiguous span of memory as an
7212 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7213 operand of @samp{@@} should be the first element of the desired array
7214 and be an individual object. The right operand should be the desired length
7215 of the array. The result is an array value whose elements are all of
7216 the type of the left argument. The first element is actually the left
7217 argument; the second element comes from bytes of memory immediately
7218 following those that hold the first element, and so on. Here is an
7219 example. If a program says
7222 int *array = (int *) malloc (len * sizeof (int));
7226 you can print the contents of @code{array} with
7232 The left operand of @samp{@@} must reside in memory. Array values made
7233 with @samp{@@} in this way behave just like other arrays in terms of
7234 subscripting, and are coerced to pointers when used in expressions.
7235 Artificial arrays most often appear in expressions via the value history
7236 (@pxref{Value History, ,Value History}), after printing one out.
7238 Another way to create an artificial array is to use a cast.
7239 This re-interprets a value as if it were an array.
7240 The value need not be in memory:
7242 (@value{GDBP}) p/x (short[2])0x12345678
7243 $1 = @{0x1234, 0x5678@}
7246 As a convenience, if you leave the array length out (as in
7247 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7248 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7250 (@value{GDBP}) p/x (short[])0x12345678
7251 $2 = @{0x1234, 0x5678@}
7254 Sometimes the artificial array mechanism is not quite enough; in
7255 moderately complex data structures, the elements of interest may not
7256 actually be adjacent---for example, if you are interested in the values
7257 of pointers in an array. One useful work-around in this situation is
7258 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7259 Variables}) as a counter in an expression that prints the first
7260 interesting value, and then repeat that expression via @key{RET}. For
7261 instance, suppose you have an array @code{dtab} of pointers to
7262 structures, and you are interested in the values of a field @code{fv}
7263 in each structure. Here is an example of what you might type:
7273 @node Output Formats
7274 @section Output Formats
7276 @cindex formatted output
7277 @cindex output formats
7278 By default, @value{GDBN} prints a value according to its data type. Sometimes
7279 this is not what you want. For example, you might want to print a number
7280 in hex, or a pointer in decimal. Or you might want to view data in memory
7281 at a certain address as a character string or as an instruction. To do
7282 these things, specify an @dfn{output format} when you print a value.
7284 The simplest use of output formats is to say how to print a value
7285 already computed. This is done by starting the arguments of the
7286 @code{print} command with a slash and a format letter. The format
7287 letters supported are:
7291 Regard the bits of the value as an integer, and print the integer in
7295 Print as integer in signed decimal.
7298 Print as integer in unsigned decimal.
7301 Print as integer in octal.
7304 Print as integer in binary. The letter @samp{t} stands for ``two''.
7305 @footnote{@samp{b} cannot be used because these format letters are also
7306 used with the @code{x} command, where @samp{b} stands for ``byte'';
7307 see @ref{Memory,,Examining Memory}.}
7310 @cindex unknown address, locating
7311 @cindex locate address
7312 Print as an address, both absolute in hexadecimal and as an offset from
7313 the nearest preceding symbol. You can use this format used to discover
7314 where (in what function) an unknown address is located:
7317 (@value{GDBP}) p/a 0x54320
7318 $3 = 0x54320 <_initialize_vx+396>
7322 The command @code{info symbol 0x54320} yields similar results.
7323 @xref{Symbols, info symbol}.
7326 Regard as an integer and print it as a character constant. This
7327 prints both the numerical value and its character representation. The
7328 character representation is replaced with the octal escape @samp{\nnn}
7329 for characters outside the 7-bit @sc{ascii} range.
7331 Without this format, @value{GDBN} displays @code{char},
7332 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7333 constants. Single-byte members of vectors are displayed as integer
7337 Regard the bits of the value as a floating point number and print
7338 using typical floating point syntax.
7341 @cindex printing strings
7342 @cindex printing byte arrays
7343 Regard as a string, if possible. With this format, pointers to single-byte
7344 data are displayed as null-terminated strings and arrays of single-byte data
7345 are displayed as fixed-length strings. Other values are displayed in their
7348 Without this format, @value{GDBN} displays pointers to and arrays of
7349 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7350 strings. Single-byte members of a vector are displayed as an integer
7354 @cindex raw printing
7355 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7356 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7357 Printing}). This typically results in a higher-level display of the
7358 value's contents. The @samp{r} format bypasses any Python
7359 pretty-printer which might exist.
7362 For example, to print the program counter in hex (@pxref{Registers}), type
7369 Note that no space is required before the slash; this is because command
7370 names in @value{GDBN} cannot contain a slash.
7372 To reprint the last value in the value history with a different format,
7373 you can use the @code{print} command with just a format and no
7374 expression. For example, @samp{p/x} reprints the last value in hex.
7377 @section Examining Memory
7379 You can use the command @code{x} (for ``examine'') to examine memory in
7380 any of several formats, independently of your program's data types.
7382 @cindex examining memory
7384 @kindex x @r{(examine memory)}
7385 @item x/@var{nfu} @var{addr}
7388 Use the @code{x} command to examine memory.
7391 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7392 much memory to display and how to format it; @var{addr} is an
7393 expression giving the address where you want to start displaying memory.
7394 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7395 Several commands set convenient defaults for @var{addr}.
7398 @item @var{n}, the repeat count
7399 The repeat count is a decimal integer; the default is 1. It specifies
7400 how much memory (counting by units @var{u}) to display.
7401 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7404 @item @var{f}, the display format
7405 The display format is one of the formats used by @code{print}
7406 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7407 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7408 The default is @samp{x} (hexadecimal) initially. The default changes
7409 each time you use either @code{x} or @code{print}.
7411 @item @var{u}, the unit size
7412 The unit size is any of
7418 Halfwords (two bytes).
7420 Words (four bytes). This is the initial default.
7422 Giant words (eight bytes).
7425 Each time you specify a unit size with @code{x}, that size becomes the
7426 default unit the next time you use @code{x}. For the @samp{i} format,
7427 the unit size is ignored and is normally not written. For the @samp{s} format,
7428 the unit size defaults to @samp{b}, unless it is explicitly given.
7429 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
7430 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
7431 Note that the results depend on the programming language of the
7432 current compilation unit. If the language is C, the @samp{s}
7433 modifier will use the UTF-16 encoding while @samp{w} will use
7434 UTF-32. The encoding is set by the programming language and cannot
7437 @item @var{addr}, starting display address
7438 @var{addr} is the address where you want @value{GDBN} to begin displaying
7439 memory. The expression need not have a pointer value (though it may);
7440 it is always interpreted as an integer address of a byte of memory.
7441 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7442 @var{addr} is usually just after the last address examined---but several
7443 other commands also set the default address: @code{info breakpoints} (to
7444 the address of the last breakpoint listed), @code{info line} (to the
7445 starting address of a line), and @code{print} (if you use it to display
7446 a value from memory).
7449 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7450 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7451 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7452 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7453 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7455 Since the letters indicating unit sizes are all distinct from the
7456 letters specifying output formats, you do not have to remember whether
7457 unit size or format comes first; either order works. The output
7458 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7459 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7461 Even though the unit size @var{u} is ignored for the formats @samp{s}
7462 and @samp{i}, you might still want to use a count @var{n}; for example,
7463 @samp{3i} specifies that you want to see three machine instructions,
7464 including any operands. For convenience, especially when used with
7465 the @code{display} command, the @samp{i} format also prints branch delay
7466 slot instructions, if any, beyond the count specified, which immediately
7467 follow the last instruction that is within the count. The command
7468 @code{disassemble} gives an alternative way of inspecting machine
7469 instructions; see @ref{Machine Code,,Source and Machine Code}.
7471 All the defaults for the arguments to @code{x} are designed to make it
7472 easy to continue scanning memory with minimal specifications each time
7473 you use @code{x}. For example, after you have inspected three machine
7474 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7475 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7476 the repeat count @var{n} is used again; the other arguments default as
7477 for successive uses of @code{x}.
7479 When examining machine instructions, the instruction at current program
7480 counter is shown with a @code{=>} marker. For example:
7483 (@value{GDBP}) x/5i $pc-6
7484 0x804837f <main+11>: mov %esp,%ebp
7485 0x8048381 <main+13>: push %ecx
7486 0x8048382 <main+14>: sub $0x4,%esp
7487 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7488 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7491 @cindex @code{$_}, @code{$__}, and value history
7492 The addresses and contents printed by the @code{x} command are not saved
7493 in the value history because there is often too much of them and they
7494 would get in the way. Instead, @value{GDBN} makes these values available for
7495 subsequent use in expressions as values of the convenience variables
7496 @code{$_} and @code{$__}. After an @code{x} command, the last address
7497 examined is available for use in expressions in the convenience variable
7498 @code{$_}. The contents of that address, as examined, are available in
7499 the convenience variable @code{$__}.
7501 If the @code{x} command has a repeat count, the address and contents saved
7502 are from the last memory unit printed; this is not the same as the last
7503 address printed if several units were printed on the last line of output.
7505 @cindex remote memory comparison
7506 @cindex verify remote memory image
7507 When you are debugging a program running on a remote target machine
7508 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7509 remote machine's memory against the executable file you downloaded to
7510 the target. The @code{compare-sections} command is provided for such
7514 @kindex compare-sections
7515 @item compare-sections @r{[}@var{section-name}@r{]}
7516 Compare the data of a loadable section @var{section-name} in the
7517 executable file of the program being debugged with the same section in
7518 the remote machine's memory, and report any mismatches. With no
7519 arguments, compares all loadable sections. This command's
7520 availability depends on the target's support for the @code{"qCRC"}
7525 @section Automatic Display
7526 @cindex automatic display
7527 @cindex display of expressions
7529 If you find that you want to print the value of an expression frequently
7530 (to see how it changes), you might want to add it to the @dfn{automatic
7531 display list} so that @value{GDBN} prints its value each time your program stops.
7532 Each expression added to the list is given a number to identify it;
7533 to remove an expression from the list, you specify that number.
7534 The automatic display looks like this:
7538 3: bar[5] = (struct hack *) 0x3804
7542 This display shows item numbers, expressions and their current values. As with
7543 displays you request manually using @code{x} or @code{print}, you can
7544 specify the output format you prefer; in fact, @code{display} decides
7545 whether to use @code{print} or @code{x} depending your format
7546 specification---it uses @code{x} if you specify either the @samp{i}
7547 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7551 @item display @var{expr}
7552 Add the expression @var{expr} to the list of expressions to display
7553 each time your program stops. @xref{Expressions, ,Expressions}.
7555 @code{display} does not repeat if you press @key{RET} again after using it.
7557 @item display/@var{fmt} @var{expr}
7558 For @var{fmt} specifying only a display format and not a size or
7559 count, add the expression @var{expr} to the auto-display list but
7560 arrange to display it each time in the specified format @var{fmt}.
7561 @xref{Output Formats,,Output Formats}.
7563 @item display/@var{fmt} @var{addr}
7564 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7565 number of units, add the expression @var{addr} as a memory address to
7566 be examined each time your program stops. Examining means in effect
7567 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7570 For example, @samp{display/i $pc} can be helpful, to see the machine
7571 instruction about to be executed each time execution stops (@samp{$pc}
7572 is a common name for the program counter; @pxref{Registers, ,Registers}).
7575 @kindex delete display
7577 @item undisplay @var{dnums}@dots{}
7578 @itemx delete display @var{dnums}@dots{}
7579 Remove item numbers @var{dnums} from the list of expressions to display.
7581 @code{undisplay} does not repeat if you press @key{RET} after using it.
7582 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7584 @kindex disable display
7585 @item disable display @var{dnums}@dots{}
7586 Disable the display of item numbers @var{dnums}. A disabled display
7587 item is not printed automatically, but is not forgotten. It may be
7588 enabled again later.
7590 @kindex enable display
7591 @item enable display @var{dnums}@dots{}
7592 Enable display of item numbers @var{dnums}. It becomes effective once
7593 again in auto display of its expression, until you specify otherwise.
7596 Display the current values of the expressions on the list, just as is
7597 done when your program stops.
7599 @kindex info display
7601 Print the list of expressions previously set up to display
7602 automatically, each one with its item number, but without showing the
7603 values. This includes disabled expressions, which are marked as such.
7604 It also includes expressions which would not be displayed right now
7605 because they refer to automatic variables not currently available.
7608 @cindex display disabled out of scope
7609 If a display expression refers to local variables, then it does not make
7610 sense outside the lexical context for which it was set up. Such an
7611 expression is disabled when execution enters a context where one of its
7612 variables is not defined. For example, if you give the command
7613 @code{display last_char} while inside a function with an argument
7614 @code{last_char}, @value{GDBN} displays this argument while your program
7615 continues to stop inside that function. When it stops elsewhere---where
7616 there is no variable @code{last_char}---the display is disabled
7617 automatically. The next time your program stops where @code{last_char}
7618 is meaningful, you can enable the display expression once again.
7620 @node Print Settings
7621 @section Print Settings
7623 @cindex format options
7624 @cindex print settings
7625 @value{GDBN} provides the following ways to control how arrays, structures,
7626 and symbols are printed.
7629 These settings are useful for debugging programs in any language:
7633 @item set print address
7634 @itemx set print address on
7635 @cindex print/don't print memory addresses
7636 @value{GDBN} prints memory addresses showing the location of stack
7637 traces, structure values, pointer values, breakpoints, and so forth,
7638 even when it also displays the contents of those addresses. The default
7639 is @code{on}. For example, this is what a stack frame display looks like with
7640 @code{set print address on}:
7645 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7647 530 if (lquote != def_lquote)
7651 @item set print address off
7652 Do not print addresses when displaying their contents. For example,
7653 this is the same stack frame displayed with @code{set print address off}:
7657 (@value{GDBP}) set print addr off
7659 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7660 530 if (lquote != def_lquote)
7664 You can use @samp{set print address off} to eliminate all machine
7665 dependent displays from the @value{GDBN} interface. For example, with
7666 @code{print address off}, you should get the same text for backtraces on
7667 all machines---whether or not they involve pointer arguments.
7670 @item show print address
7671 Show whether or not addresses are to be printed.
7674 When @value{GDBN} prints a symbolic address, it normally prints the
7675 closest earlier symbol plus an offset. If that symbol does not uniquely
7676 identify the address (for example, it is a name whose scope is a single
7677 source file), you may need to clarify. One way to do this is with
7678 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7679 you can set @value{GDBN} to print the source file and line number when
7680 it prints a symbolic address:
7683 @item set print symbol-filename on
7684 @cindex source file and line of a symbol
7685 @cindex symbol, source file and line
7686 Tell @value{GDBN} to print the source file name and line number of a
7687 symbol in the symbolic form of an address.
7689 @item set print symbol-filename off
7690 Do not print source file name and line number of a symbol. This is the
7693 @item show print symbol-filename
7694 Show whether or not @value{GDBN} will print the source file name and
7695 line number of a symbol in the symbolic form of an address.
7698 Another situation where it is helpful to show symbol filenames and line
7699 numbers is when disassembling code; @value{GDBN} shows you the line
7700 number and source file that corresponds to each instruction.
7702 Also, you may wish to see the symbolic form only if the address being
7703 printed is reasonably close to the closest earlier symbol:
7706 @item set print max-symbolic-offset @var{max-offset}
7707 @cindex maximum value for offset of closest symbol
7708 Tell @value{GDBN} to only display the symbolic form of an address if the
7709 offset between the closest earlier symbol and the address is less than
7710 @var{max-offset}. The default is 0, which tells @value{GDBN}
7711 to always print the symbolic form of an address if any symbol precedes it.
7713 @item show print max-symbolic-offset
7714 Ask how large the maximum offset is that @value{GDBN} prints in a
7718 @cindex wild pointer, interpreting
7719 @cindex pointer, finding referent
7720 If you have a pointer and you are not sure where it points, try
7721 @samp{set print symbol-filename on}. Then you can determine the name
7722 and source file location of the variable where it points, using
7723 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7724 For example, here @value{GDBN} shows that a variable @code{ptt} points
7725 at another variable @code{t}, defined in @file{hi2.c}:
7728 (@value{GDBP}) set print symbol-filename on
7729 (@value{GDBP}) p/a ptt
7730 $4 = 0xe008 <t in hi2.c>
7734 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
7735 does not show the symbol name and filename of the referent, even with
7736 the appropriate @code{set print} options turned on.
7739 Other settings control how different kinds of objects are printed:
7742 @item set print array
7743 @itemx set print array on
7744 @cindex pretty print arrays
7745 Pretty print arrays. This format is more convenient to read,
7746 but uses more space. The default is off.
7748 @item set print array off
7749 Return to compressed format for arrays.
7751 @item show print array
7752 Show whether compressed or pretty format is selected for displaying
7755 @cindex print array indexes
7756 @item set print array-indexes
7757 @itemx set print array-indexes on
7758 Print the index of each element when displaying arrays. May be more
7759 convenient to locate a given element in the array or quickly find the
7760 index of a given element in that printed array. The default is off.
7762 @item set print array-indexes off
7763 Stop printing element indexes when displaying arrays.
7765 @item show print array-indexes
7766 Show whether the index of each element is printed when displaying
7769 @item set print elements @var{number-of-elements}
7770 @cindex number of array elements to print
7771 @cindex limit on number of printed array elements
7772 Set a limit on how many elements of an array @value{GDBN} will print.
7773 If @value{GDBN} is printing a large array, it stops printing after it has
7774 printed the number of elements set by the @code{set print elements} command.
7775 This limit also applies to the display of strings.
7776 When @value{GDBN} starts, this limit is set to 200.
7777 Setting @var{number-of-elements} to zero means that the printing is unlimited.
7779 @item show print elements
7780 Display the number of elements of a large array that @value{GDBN} will print.
7781 If the number is 0, then the printing is unlimited.
7783 @item set print frame-arguments @var{value}
7784 @kindex set print frame-arguments
7785 @cindex printing frame argument values
7786 @cindex print all frame argument values
7787 @cindex print frame argument values for scalars only
7788 @cindex do not print frame argument values
7789 This command allows to control how the values of arguments are printed
7790 when the debugger prints a frame (@pxref{Frames}). The possible
7795 The values of all arguments are printed.
7798 Print the value of an argument only if it is a scalar. The value of more
7799 complex arguments such as arrays, structures, unions, etc, is replaced
7800 by @code{@dots{}}. This is the default. Here is an example where
7801 only scalar arguments are shown:
7804 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
7809 None of the argument values are printed. Instead, the value of each argument
7810 is replaced by @code{@dots{}}. In this case, the example above now becomes:
7813 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
7818 By default, only scalar arguments are printed. This command can be used
7819 to configure the debugger to print the value of all arguments, regardless
7820 of their type. However, it is often advantageous to not print the value
7821 of more complex parameters. For instance, it reduces the amount of
7822 information printed in each frame, making the backtrace more readable.
7823 Also, it improves performance when displaying Ada frames, because
7824 the computation of large arguments can sometimes be CPU-intensive,
7825 especially in large applications. Setting @code{print frame-arguments}
7826 to @code{scalars} (the default) or @code{none} avoids this computation,
7827 thus speeding up the display of each Ada frame.
7829 @item show print frame-arguments
7830 Show how the value of arguments should be displayed when printing a frame.
7832 @item set print repeats
7833 @cindex repeated array elements
7834 Set the threshold for suppressing display of repeated array
7835 elements. When the number of consecutive identical elements of an
7836 array exceeds the threshold, @value{GDBN} prints the string
7837 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
7838 identical repetitions, instead of displaying the identical elements
7839 themselves. Setting the threshold to zero will cause all elements to
7840 be individually printed. The default threshold is 10.
7842 @item show print repeats
7843 Display the current threshold for printing repeated identical
7846 @item set print null-stop
7847 @cindex @sc{null} elements in arrays
7848 Cause @value{GDBN} to stop printing the characters of an array when the first
7849 @sc{null} is encountered. This is useful when large arrays actually
7850 contain only short strings.
7853 @item show print null-stop
7854 Show whether @value{GDBN} stops printing an array on the first
7855 @sc{null} character.
7857 @item set print pretty on
7858 @cindex print structures in indented form
7859 @cindex indentation in structure display
7860 Cause @value{GDBN} to print structures in an indented format with one member
7861 per line, like this:
7876 @item set print pretty off
7877 Cause @value{GDBN} to print structures in a compact format, like this:
7881 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
7882 meat = 0x54 "Pork"@}
7887 This is the default format.
7889 @item show print pretty
7890 Show which format @value{GDBN} is using to print structures.
7892 @item set print sevenbit-strings on
7893 @cindex eight-bit characters in strings
7894 @cindex octal escapes in strings
7895 Print using only seven-bit characters; if this option is set,
7896 @value{GDBN} displays any eight-bit characters (in strings or
7897 character values) using the notation @code{\}@var{nnn}. This setting is
7898 best if you are working in English (@sc{ascii}) and you use the
7899 high-order bit of characters as a marker or ``meta'' bit.
7901 @item set print sevenbit-strings off
7902 Print full eight-bit characters. This allows the use of more
7903 international character sets, and is the default.
7905 @item show print sevenbit-strings
7906 Show whether or not @value{GDBN} is printing only seven-bit characters.
7908 @item set print union on
7909 @cindex unions in structures, printing
7910 Tell @value{GDBN} to print unions which are contained in structures
7911 and other unions. This is the default setting.
7913 @item set print union off
7914 Tell @value{GDBN} not to print unions which are contained in
7915 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
7918 @item show print union
7919 Ask @value{GDBN} whether or not it will print unions which are contained in
7920 structures and other unions.
7922 For example, given the declarations
7925 typedef enum @{Tree, Bug@} Species;
7926 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
7927 typedef enum @{Caterpillar, Cocoon, Butterfly@}
7938 struct thing foo = @{Tree, @{Acorn@}@};
7942 with @code{set print union on} in effect @samp{p foo} would print
7945 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
7949 and with @code{set print union off} in effect it would print
7952 $1 = @{it = Tree, form = @{...@}@}
7956 @code{set print union} affects programs written in C-like languages
7962 These settings are of interest when debugging C@t{++} programs:
7965 @cindex demangling C@t{++} names
7966 @item set print demangle
7967 @itemx set print demangle on
7968 Print C@t{++} names in their source form rather than in the encoded
7969 (``mangled'') form passed to the assembler and linker for type-safe
7970 linkage. The default is on.
7972 @item show print demangle
7973 Show whether C@t{++} names are printed in mangled or demangled form.
7975 @item set print asm-demangle
7976 @itemx set print asm-demangle on
7977 Print C@t{++} names in their source form rather than their mangled form, even
7978 in assembler code printouts such as instruction disassemblies.
7981 @item show print asm-demangle
7982 Show whether C@t{++} names in assembly listings are printed in mangled
7985 @cindex C@t{++} symbol decoding style
7986 @cindex symbol decoding style, C@t{++}
7987 @kindex set demangle-style
7988 @item set demangle-style @var{style}
7989 Choose among several encoding schemes used by different compilers to
7990 represent C@t{++} names. The choices for @var{style} are currently:
7994 Allow @value{GDBN} to choose a decoding style by inspecting your program.
7997 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
7998 This is the default.
8001 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
8004 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
8007 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
8008 @strong{Warning:} this setting alone is not sufficient to allow
8009 debugging @code{cfront}-generated executables. @value{GDBN} would
8010 require further enhancement to permit that.
8013 If you omit @var{style}, you will see a list of possible formats.
8015 @item show demangle-style
8016 Display the encoding style currently in use for decoding C@t{++} symbols.
8018 @item set print object
8019 @itemx set print object on
8020 @cindex derived type of an object, printing
8021 @cindex display derived types
8022 When displaying a pointer to an object, identify the @emph{actual}
8023 (derived) type of the object rather than the @emph{declared} type, using
8024 the virtual function table.
8026 @item set print object off
8027 Display only the declared type of objects, without reference to the
8028 virtual function table. This is the default setting.
8030 @item show print object
8031 Show whether actual, or declared, object types are displayed.
8033 @item set print static-members
8034 @itemx set print static-members on
8035 @cindex static members of C@t{++} objects
8036 Print static members when displaying a C@t{++} object. The default is on.
8038 @item set print static-members off
8039 Do not print static members when displaying a C@t{++} object.
8041 @item show print static-members
8042 Show whether C@t{++} static members are printed or not.
8044 @item set print pascal_static-members
8045 @itemx set print pascal_static-members on
8046 @cindex static members of Pascal objects
8047 @cindex Pascal objects, static members display
8048 Print static members when displaying a Pascal object. The default is on.
8050 @item set print pascal_static-members off
8051 Do not print static members when displaying a Pascal object.
8053 @item show print pascal_static-members
8054 Show whether Pascal static members are printed or not.
8056 @c These don't work with HP ANSI C++ yet.
8057 @item set print vtbl
8058 @itemx set print vtbl on
8059 @cindex pretty print C@t{++} virtual function tables
8060 @cindex virtual functions (C@t{++}) display
8061 @cindex VTBL display
8062 Pretty print C@t{++} virtual function tables. The default is off.
8063 (The @code{vtbl} commands do not work on programs compiled with the HP
8064 ANSI C@t{++} compiler (@code{aCC}).)
8066 @item set print vtbl off
8067 Do not pretty print C@t{++} virtual function tables.
8069 @item show print vtbl
8070 Show whether C@t{++} virtual function tables are pretty printed, or not.
8073 @node Pretty Printing
8074 @section Pretty Printing
8076 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8077 Python code. It greatly simplifies the display of complex objects. This
8078 mechanism works for both MI and the CLI.
8080 For example, here is how a C@t{++} @code{std::string} looks without a
8084 (@value{GDBP}) print s
8086 static npos = 4294967295,
8088 <std::allocator<char>> = @{
8089 <__gnu_cxx::new_allocator<char>> = @{
8090 <No data fields>@}, <No data fields>
8092 members of std::basic_string<char, std::char_traits<char>,
8093 std::allocator<char> >::_Alloc_hider:
8094 _M_p = 0x804a014 "abcd"
8099 With a pretty-printer for @code{std::string} only the contents are printed:
8102 (@value{GDBP}) print s
8106 For implementing pretty printers for new types you should read the Python API
8107 details (@pxref{Pretty Printing API}).
8110 @section Value History
8112 @cindex value history
8113 @cindex history of values printed by @value{GDBN}
8114 Values printed by the @code{print} command are saved in the @value{GDBN}
8115 @dfn{value history}. This allows you to refer to them in other expressions.
8116 Values are kept until the symbol table is re-read or discarded
8117 (for example with the @code{file} or @code{symbol-file} commands).
8118 When the symbol table changes, the value history is discarded,
8119 since the values may contain pointers back to the types defined in the
8124 @cindex history number
8125 The values printed are given @dfn{history numbers} by which you can
8126 refer to them. These are successive integers starting with one.
8127 @code{print} shows you the history number assigned to a value by
8128 printing @samp{$@var{num} = } before the value; here @var{num} is the
8131 To refer to any previous value, use @samp{$} followed by the value's
8132 history number. The way @code{print} labels its output is designed to
8133 remind you of this. Just @code{$} refers to the most recent value in
8134 the history, and @code{$$} refers to the value before that.
8135 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
8136 is the value just prior to @code{$$}, @code{$$1} is equivalent to
8137 @code{$$}, and @code{$$0} is equivalent to @code{$}.
8139 For example, suppose you have just printed a pointer to a structure and
8140 want to see the contents of the structure. It suffices to type
8146 If you have a chain of structures where the component @code{next} points
8147 to the next one, you can print the contents of the next one with this:
8154 You can print successive links in the chain by repeating this
8155 command---which you can do by just typing @key{RET}.
8157 Note that the history records values, not expressions. If the value of
8158 @code{x} is 4 and you type these commands:
8166 then the value recorded in the value history by the @code{print} command
8167 remains 4 even though the value of @code{x} has changed.
8172 Print the last ten values in the value history, with their item numbers.
8173 This is like @samp{p@ $$9} repeated ten times, except that @code{show
8174 values} does not change the history.
8176 @item show values @var{n}
8177 Print ten history values centered on history item number @var{n}.
8180 Print ten history values just after the values last printed. If no more
8181 values are available, @code{show values +} produces no display.
8184 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
8185 same effect as @samp{show values +}.
8187 @node Convenience Vars
8188 @section Convenience Variables
8190 @cindex convenience variables
8191 @cindex user-defined variables
8192 @value{GDBN} provides @dfn{convenience variables} that you can use within
8193 @value{GDBN} to hold on to a value and refer to it later. These variables
8194 exist entirely within @value{GDBN}; they are not part of your program, and
8195 setting a convenience variable has no direct effect on further execution
8196 of your program. That is why you can use them freely.
8198 Convenience variables are prefixed with @samp{$}. Any name preceded by
8199 @samp{$} can be used for a convenience variable, unless it is one of
8200 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
8201 (Value history references, in contrast, are @emph{numbers} preceded
8202 by @samp{$}. @xref{Value History, ,Value History}.)
8204 You can save a value in a convenience variable with an assignment
8205 expression, just as you would set a variable in your program.
8209 set $foo = *object_ptr
8213 would save in @code{$foo} the value contained in the object pointed to by
8216 Using a convenience variable for the first time creates it, but its
8217 value is @code{void} until you assign a new value. You can alter the
8218 value with another assignment at any time.
8220 Convenience variables have no fixed types. You can assign a convenience
8221 variable any type of value, including structures and arrays, even if
8222 that variable already has a value of a different type. The convenience
8223 variable, when used as an expression, has the type of its current value.
8226 @kindex show convenience
8227 @cindex show all user variables
8228 @item show convenience
8229 Print a list of convenience variables used so far, and their values.
8230 Abbreviated @code{show conv}.
8232 @kindex init-if-undefined
8233 @cindex convenience variables, initializing
8234 @item init-if-undefined $@var{variable} = @var{expression}
8235 Set a convenience variable if it has not already been set. This is useful
8236 for user-defined commands that keep some state. It is similar, in concept,
8237 to using local static variables with initializers in C (except that
8238 convenience variables are global). It can also be used to allow users to
8239 override default values used in a command script.
8241 If the variable is already defined then the expression is not evaluated so
8242 any side-effects do not occur.
8245 One of the ways to use a convenience variable is as a counter to be
8246 incremented or a pointer to be advanced. For example, to print
8247 a field from successive elements of an array of structures:
8251 print bar[$i++]->contents
8255 Repeat that command by typing @key{RET}.
8257 Some convenience variables are created automatically by @value{GDBN} and given
8258 values likely to be useful.
8261 @vindex $_@r{, convenience variable}
8263 The variable @code{$_} is automatically set by the @code{x} command to
8264 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8265 commands which provide a default address for @code{x} to examine also
8266 set @code{$_} to that address; these commands include @code{info line}
8267 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8268 except when set by the @code{x} command, in which case it is a pointer
8269 to the type of @code{$__}.
8271 @vindex $__@r{, convenience variable}
8273 The variable @code{$__} is automatically set by the @code{x} command
8274 to the value found in the last address examined. Its type is chosen
8275 to match the format in which the data was printed.
8278 @vindex $_exitcode@r{, convenience variable}
8279 The variable @code{$_exitcode} is automatically set to the exit code when
8280 the program being debugged terminates.
8283 @vindex $_sdata@r{, inspect, convenience variable}
8284 The variable @code{$_sdata} contains extra collected static tracepoint
8285 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
8286 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
8287 if extra static tracepoint data has not been collected.
8290 @vindex $_siginfo@r{, convenience variable}
8291 The variable @code{$_siginfo} contains extra signal information
8292 (@pxref{extra signal information}). Note that @code{$_siginfo}
8293 could be empty, if the application has not yet received any signals.
8294 For example, it will be empty before you execute the @code{run} command.
8297 @vindex $_tlb@r{, convenience variable}
8298 The variable @code{$_tlb} is automatically set when debugging
8299 applications running on MS-Windows in native mode or connected to
8300 gdbserver that supports the @code{qGetTIBAddr} request.
8301 @xref{General Query Packets}.
8302 This variable contains the address of the thread information block.
8306 On HP-UX systems, if you refer to a function or variable name that
8307 begins with a dollar sign, @value{GDBN} searches for a user or system
8308 name first, before it searches for a convenience variable.
8310 @cindex convenience functions
8311 @value{GDBN} also supplies some @dfn{convenience functions}. These
8312 have a syntax similar to convenience variables. A convenience
8313 function can be used in an expression just like an ordinary function;
8314 however, a convenience function is implemented internally to
8319 @kindex help function
8320 @cindex show all convenience functions
8321 Print a list of all convenience functions.
8328 You can refer to machine register contents, in expressions, as variables
8329 with names starting with @samp{$}. The names of registers are different
8330 for each machine; use @code{info registers} to see the names used on
8334 @kindex info registers
8335 @item info registers
8336 Print the names and values of all registers except floating-point
8337 and vector registers (in the selected stack frame).
8339 @kindex info all-registers
8340 @cindex floating point registers
8341 @item info all-registers
8342 Print the names and values of all registers, including floating-point
8343 and vector registers (in the selected stack frame).
8345 @item info registers @var{regname} @dots{}
8346 Print the @dfn{relativized} value of each specified register @var{regname}.
8347 As discussed in detail below, register values are normally relative to
8348 the selected stack frame. @var{regname} may be any register name valid on
8349 the machine you are using, with or without the initial @samp{$}.
8352 @cindex stack pointer register
8353 @cindex program counter register
8354 @cindex process status register
8355 @cindex frame pointer register
8356 @cindex standard registers
8357 @value{GDBN} has four ``standard'' register names that are available (in
8358 expressions) on most machines---whenever they do not conflict with an
8359 architecture's canonical mnemonics for registers. The register names
8360 @code{$pc} and @code{$sp} are used for the program counter register and
8361 the stack pointer. @code{$fp} is used for a register that contains a
8362 pointer to the current stack frame, and @code{$ps} is used for a
8363 register that contains the processor status. For example,
8364 you could print the program counter in hex with
8371 or print the instruction to be executed next with
8378 or add four to the stack pointer@footnote{This is a way of removing
8379 one word from the stack, on machines where stacks grow downward in
8380 memory (most machines, nowadays). This assumes that the innermost
8381 stack frame is selected; setting @code{$sp} is not allowed when other
8382 stack frames are selected. To pop entire frames off the stack,
8383 regardless of machine architecture, use @code{return};
8384 see @ref{Returning, ,Returning from a Function}.} with
8390 Whenever possible, these four standard register names are available on
8391 your machine even though the machine has different canonical mnemonics,
8392 so long as there is no conflict. The @code{info registers} command
8393 shows the canonical names. For example, on the SPARC, @code{info
8394 registers} displays the processor status register as @code{$psr} but you
8395 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
8396 is an alias for the @sc{eflags} register.
8398 @value{GDBN} always considers the contents of an ordinary register as an
8399 integer when the register is examined in this way. Some machines have
8400 special registers which can hold nothing but floating point; these
8401 registers are considered to have floating point values. There is no way
8402 to refer to the contents of an ordinary register as floating point value
8403 (although you can @emph{print} it as a floating point value with
8404 @samp{print/f $@var{regname}}).
8406 Some registers have distinct ``raw'' and ``virtual'' data formats. This
8407 means that the data format in which the register contents are saved by
8408 the operating system is not the same one that your program normally
8409 sees. For example, the registers of the 68881 floating point
8410 coprocessor are always saved in ``extended'' (raw) format, but all C
8411 programs expect to work with ``double'' (virtual) format. In such
8412 cases, @value{GDBN} normally works with the virtual format only (the format
8413 that makes sense for your program), but the @code{info registers} command
8414 prints the data in both formats.
8416 @cindex SSE registers (x86)
8417 @cindex MMX registers (x86)
8418 Some machines have special registers whose contents can be interpreted
8419 in several different ways. For example, modern x86-based machines
8420 have SSE and MMX registers that can hold several values packed
8421 together in several different formats. @value{GDBN} refers to such
8422 registers in @code{struct} notation:
8425 (@value{GDBP}) print $xmm1
8427 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
8428 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
8429 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
8430 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
8431 v4_int32 = @{0, 20657912, 11, 13@},
8432 v2_int64 = @{88725056443645952, 55834574859@},
8433 uint128 = 0x0000000d0000000b013b36f800000000
8438 To set values of such registers, you need to tell @value{GDBN} which
8439 view of the register you wish to change, as if you were assigning
8440 value to a @code{struct} member:
8443 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
8446 Normally, register values are relative to the selected stack frame
8447 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
8448 value that the register would contain if all stack frames farther in
8449 were exited and their saved registers restored. In order to see the
8450 true contents of hardware registers, you must select the innermost
8451 frame (with @samp{frame 0}).
8453 However, @value{GDBN} must deduce where registers are saved, from the machine
8454 code generated by your compiler. If some registers are not saved, or if
8455 @value{GDBN} is unable to locate the saved registers, the selected stack
8456 frame makes no difference.
8458 @node Floating Point Hardware
8459 @section Floating Point Hardware
8460 @cindex floating point
8462 Depending on the configuration, @value{GDBN} may be able to give
8463 you more information about the status of the floating point hardware.
8468 Display hardware-dependent information about the floating
8469 point unit. The exact contents and layout vary depending on the
8470 floating point chip. Currently, @samp{info float} is supported on
8471 the ARM and x86 machines.
8475 @section Vector Unit
8478 Depending on the configuration, @value{GDBN} may be able to give you
8479 more information about the status of the vector unit.
8484 Display information about the vector unit. The exact contents and
8485 layout vary depending on the hardware.
8488 @node OS Information
8489 @section Operating System Auxiliary Information
8490 @cindex OS information
8492 @value{GDBN} provides interfaces to useful OS facilities that can help
8493 you debug your program.
8495 @cindex @code{ptrace} system call
8496 @cindex @code{struct user} contents
8497 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
8498 machines), it interfaces with the inferior via the @code{ptrace}
8499 system call. The operating system creates a special sata structure,
8500 called @code{struct user}, for this interface. You can use the
8501 command @code{info udot} to display the contents of this data
8507 Display the contents of the @code{struct user} maintained by the OS
8508 kernel for the program being debugged. @value{GDBN} displays the
8509 contents of @code{struct user} as a list of hex numbers, similar to
8510 the @code{examine} command.
8513 @cindex auxiliary vector
8514 @cindex vector, auxiliary
8515 Some operating systems supply an @dfn{auxiliary vector} to programs at
8516 startup. This is akin to the arguments and environment that you
8517 specify for a program, but contains a system-dependent variety of
8518 binary values that tell system libraries important details about the
8519 hardware, operating system, and process. Each value's purpose is
8520 identified by an integer tag; the meanings are well-known but system-specific.
8521 Depending on the configuration and operating system facilities,
8522 @value{GDBN} may be able to show you this information. For remote
8523 targets, this functionality may further depend on the remote stub's
8524 support of the @samp{qXfer:auxv:read} packet, see
8525 @ref{qXfer auxiliary vector read}.
8530 Display the auxiliary vector of the inferior, which can be either a
8531 live process or a core dump file. @value{GDBN} prints each tag value
8532 numerically, and also shows names and text descriptions for recognized
8533 tags. Some values in the vector are numbers, some bit masks, and some
8534 pointers to strings or other data. @value{GDBN} displays each value in the
8535 most appropriate form for a recognized tag, and in hexadecimal for
8536 an unrecognized tag.
8539 On some targets, @value{GDBN} can access operating-system-specific information
8540 and display it to user, without interpretation. For remote targets,
8541 this functionality depends on the remote stub's support of the
8542 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
8547 List the types of OS information available for the target. If the
8548 target does not return a list of possible types, this command will
8551 @kindex info os processes
8552 @item info os processes
8553 Display the list of processes on the target. For each process,
8554 @value{GDBN} prints the process identifier, the name of the user, and
8555 the command corresponding to the process.
8558 @node Memory Region Attributes
8559 @section Memory Region Attributes
8560 @cindex memory region attributes
8562 @dfn{Memory region attributes} allow you to describe special handling
8563 required by regions of your target's memory. @value{GDBN} uses
8564 attributes to determine whether to allow certain types of memory
8565 accesses; whether to use specific width accesses; and whether to cache
8566 target memory. By default the description of memory regions is
8567 fetched from the target (if the current target supports this), but the
8568 user can override the fetched regions.
8570 Defined memory regions can be individually enabled and disabled. When a
8571 memory region is disabled, @value{GDBN} uses the default attributes when
8572 accessing memory in that region. Similarly, if no memory regions have
8573 been defined, @value{GDBN} uses the default attributes when accessing
8576 When a memory region is defined, it is given a number to identify it;
8577 to enable, disable, or remove a memory region, you specify that number.
8581 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
8582 Define a memory region bounded by @var{lower} and @var{upper} with
8583 attributes @var{attributes}@dots{}, and add it to the list of regions
8584 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
8585 case: it is treated as the target's maximum memory address.
8586 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
8589 Discard any user changes to the memory regions and use target-supplied
8590 regions, if available, or no regions if the target does not support.
8593 @item delete mem @var{nums}@dots{}
8594 Remove memory regions @var{nums}@dots{} from the list of regions
8595 monitored by @value{GDBN}.
8598 @item disable mem @var{nums}@dots{}
8599 Disable monitoring of memory regions @var{nums}@dots{}.
8600 A disabled memory region is not forgotten.
8601 It may be enabled again later.
8604 @item enable mem @var{nums}@dots{}
8605 Enable monitoring of memory regions @var{nums}@dots{}.
8609 Print a table of all defined memory regions, with the following columns
8613 @item Memory Region Number
8614 @item Enabled or Disabled.
8615 Enabled memory regions are marked with @samp{y}.
8616 Disabled memory regions are marked with @samp{n}.
8619 The address defining the inclusive lower bound of the memory region.
8622 The address defining the exclusive upper bound of the memory region.
8625 The list of attributes set for this memory region.
8630 @subsection Attributes
8632 @subsubsection Memory Access Mode
8633 The access mode attributes set whether @value{GDBN} may make read or
8634 write accesses to a memory region.
8636 While these attributes prevent @value{GDBN} from performing invalid
8637 memory accesses, they do nothing to prevent the target system, I/O DMA,
8638 etc.@: from accessing memory.
8642 Memory is read only.
8644 Memory is write only.
8646 Memory is read/write. This is the default.
8649 @subsubsection Memory Access Size
8650 The access size attribute tells @value{GDBN} to use specific sized
8651 accesses in the memory region. Often memory mapped device registers
8652 require specific sized accesses. If no access size attribute is
8653 specified, @value{GDBN} may use accesses of any size.
8657 Use 8 bit memory accesses.
8659 Use 16 bit memory accesses.
8661 Use 32 bit memory accesses.
8663 Use 64 bit memory accesses.
8666 @c @subsubsection Hardware/Software Breakpoints
8667 @c The hardware/software breakpoint attributes set whether @value{GDBN}
8668 @c will use hardware or software breakpoints for the internal breakpoints
8669 @c used by the step, next, finish, until, etc. commands.
8673 @c Always use hardware breakpoints
8674 @c @item swbreak (default)
8677 @subsubsection Data Cache
8678 The data cache attributes set whether @value{GDBN} will cache target
8679 memory. While this generally improves performance by reducing debug
8680 protocol overhead, it can lead to incorrect results because @value{GDBN}
8681 does not know about volatile variables or memory mapped device
8686 Enable @value{GDBN} to cache target memory.
8688 Disable @value{GDBN} from caching target memory. This is the default.
8691 @subsection Memory Access Checking
8692 @value{GDBN} can be instructed to refuse accesses to memory that is
8693 not explicitly described. This can be useful if accessing such
8694 regions has undesired effects for a specific target, or to provide
8695 better error checking. The following commands control this behaviour.
8698 @kindex set mem inaccessible-by-default
8699 @item set mem inaccessible-by-default [on|off]
8700 If @code{on} is specified, make @value{GDBN} treat memory not
8701 explicitly described by the memory ranges as non-existent and refuse accesses
8702 to such memory. The checks are only performed if there's at least one
8703 memory range defined. If @code{off} is specified, make @value{GDBN}
8704 treat the memory not explicitly described by the memory ranges as RAM.
8705 The default value is @code{on}.
8706 @kindex show mem inaccessible-by-default
8707 @item show mem inaccessible-by-default
8708 Show the current handling of accesses to unknown memory.
8712 @c @subsubsection Memory Write Verification
8713 @c The memory write verification attributes set whether @value{GDBN}
8714 @c will re-reads data after each write to verify the write was successful.
8718 @c @item noverify (default)
8721 @node Dump/Restore Files
8722 @section Copy Between Memory and a File
8723 @cindex dump/restore files
8724 @cindex append data to a file
8725 @cindex dump data to a file
8726 @cindex restore data from a file
8728 You can use the commands @code{dump}, @code{append}, and
8729 @code{restore} to copy data between target memory and a file. The
8730 @code{dump} and @code{append} commands write data to a file, and the
8731 @code{restore} command reads data from a file back into the inferior's
8732 memory. Files may be in binary, Motorola S-record, Intel hex, or
8733 Tektronix Hex format; however, @value{GDBN} can only append to binary
8739 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8740 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
8741 Dump the contents of memory from @var{start_addr} to @var{end_addr},
8742 or the value of @var{expr}, to @var{filename} in the given format.
8744 The @var{format} parameter may be any one of:
8751 Motorola S-record format.
8753 Tektronix Hex format.
8756 @value{GDBN} uses the same definitions of these formats as the
8757 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
8758 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
8762 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8763 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
8764 Append the contents of memory from @var{start_addr} to @var{end_addr},
8765 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
8766 (@value{GDBN} can only append data to files in raw binary form.)
8769 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
8770 Restore the contents of file @var{filename} into memory. The
8771 @code{restore} command can automatically recognize any known @sc{bfd}
8772 file format, except for raw binary. To restore a raw binary file you
8773 must specify the optional keyword @code{binary} after the filename.
8775 If @var{bias} is non-zero, its value will be added to the addresses
8776 contained in the file. Binary files always start at address zero, so
8777 they will be restored at address @var{bias}. Other bfd files have
8778 a built-in location; they will be restored at offset @var{bias}
8781 If @var{start} and/or @var{end} are non-zero, then only data between
8782 file offset @var{start} and file offset @var{end} will be restored.
8783 These offsets are relative to the addresses in the file, before
8784 the @var{bias} argument is applied.
8788 @node Core File Generation
8789 @section How to Produce a Core File from Your Program
8790 @cindex dump core from inferior
8792 A @dfn{core file} or @dfn{core dump} is a file that records the memory
8793 image of a running process and its process status (register values
8794 etc.). Its primary use is post-mortem debugging of a program that
8795 crashed while it ran outside a debugger. A program that crashes
8796 automatically produces a core file, unless this feature is disabled by
8797 the user. @xref{Files}, for information on invoking @value{GDBN} in
8798 the post-mortem debugging mode.
8800 Occasionally, you may wish to produce a core file of the program you
8801 are debugging in order to preserve a snapshot of its state.
8802 @value{GDBN} has a special command for that.
8806 @kindex generate-core-file
8807 @item generate-core-file [@var{file}]
8808 @itemx gcore [@var{file}]
8809 Produce a core dump of the inferior process. The optional argument
8810 @var{file} specifies the file name where to put the core dump. If not
8811 specified, the file name defaults to @file{core.@var{pid}}, where
8812 @var{pid} is the inferior process ID.
8814 Note that this command is implemented only for some systems (as of
8815 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
8818 @node Character Sets
8819 @section Character Sets
8820 @cindex character sets
8822 @cindex translating between character sets
8823 @cindex host character set
8824 @cindex target character set
8826 If the program you are debugging uses a different character set to
8827 represent characters and strings than the one @value{GDBN} uses itself,
8828 @value{GDBN} can automatically translate between the character sets for
8829 you. The character set @value{GDBN} uses we call the @dfn{host
8830 character set}; the one the inferior program uses we call the
8831 @dfn{target character set}.
8833 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
8834 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
8835 remote protocol (@pxref{Remote Debugging}) to debug a program
8836 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
8837 then the host character set is Latin-1, and the target character set is
8838 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
8839 target-charset EBCDIC-US}, then @value{GDBN} translates between
8840 @sc{ebcdic} and Latin 1 as you print character or string values, or use
8841 character and string literals in expressions.
8843 @value{GDBN} has no way to automatically recognize which character set
8844 the inferior program uses; you must tell it, using the @code{set
8845 target-charset} command, described below.
8847 Here are the commands for controlling @value{GDBN}'s character set
8851 @item set target-charset @var{charset}
8852 @kindex set target-charset
8853 Set the current target character set to @var{charset}. To display the
8854 list of supported target character sets, type
8855 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
8857 @item set host-charset @var{charset}
8858 @kindex set host-charset
8859 Set the current host character set to @var{charset}.
8861 By default, @value{GDBN} uses a host character set appropriate to the
8862 system it is running on; you can override that default using the
8863 @code{set host-charset} command. On some systems, @value{GDBN} cannot
8864 automatically determine the appropriate host character set. In this
8865 case, @value{GDBN} uses @samp{UTF-8}.
8867 @value{GDBN} can only use certain character sets as its host character
8868 set. If you type @kbd{@w{set target-charset @key{TAB}@key{TAB}}},
8869 @value{GDBN} will list the host character sets it supports.
8871 @item set charset @var{charset}
8873 Set the current host and target character sets to @var{charset}. As
8874 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
8875 @value{GDBN} will list the names of the character sets that can be used
8876 for both host and target.
8879 @kindex show charset
8880 Show the names of the current host and target character sets.
8882 @item show host-charset
8883 @kindex show host-charset
8884 Show the name of the current host character set.
8886 @item show target-charset
8887 @kindex show target-charset
8888 Show the name of the current target character set.
8890 @item set target-wide-charset @var{charset}
8891 @kindex set target-wide-charset
8892 Set the current target's wide character set to @var{charset}. This is
8893 the character set used by the target's @code{wchar_t} type. To
8894 display the list of supported wide character sets, type
8895 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
8897 @item show target-wide-charset
8898 @kindex show target-wide-charset
8899 Show the name of the current target's wide character set.
8902 Here is an example of @value{GDBN}'s character set support in action.
8903 Assume that the following source code has been placed in the file
8904 @file{charset-test.c}:
8910 = @{72, 101, 108, 108, 111, 44, 32, 119,
8911 111, 114, 108, 100, 33, 10, 0@};
8912 char ibm1047_hello[]
8913 = @{200, 133, 147, 147, 150, 107, 64, 166,
8914 150, 153, 147, 132, 90, 37, 0@};
8918 printf ("Hello, world!\n");
8922 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
8923 containing the string @samp{Hello, world!} followed by a newline,
8924 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
8926 We compile the program, and invoke the debugger on it:
8929 $ gcc -g charset-test.c -o charset-test
8930 $ gdb -nw charset-test
8931 GNU gdb 2001-12-19-cvs
8932 Copyright 2001 Free Software Foundation, Inc.
8937 We can use the @code{show charset} command to see what character sets
8938 @value{GDBN} is currently using to interpret and display characters and
8942 (@value{GDBP}) show charset
8943 The current host and target character set is `ISO-8859-1'.
8947 For the sake of printing this manual, let's use @sc{ascii} as our
8948 initial character set:
8950 (@value{GDBP}) set charset ASCII
8951 (@value{GDBP}) show charset
8952 The current host and target character set is `ASCII'.
8956 Let's assume that @sc{ascii} is indeed the correct character set for our
8957 host system --- in other words, let's assume that if @value{GDBN} prints
8958 characters using the @sc{ascii} character set, our terminal will display
8959 them properly. Since our current target character set is also
8960 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
8963 (@value{GDBP}) print ascii_hello
8964 $1 = 0x401698 "Hello, world!\n"
8965 (@value{GDBP}) print ascii_hello[0]
8970 @value{GDBN} uses the target character set for character and string
8971 literals you use in expressions:
8974 (@value{GDBP}) print '+'
8979 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
8982 @value{GDBN} relies on the user to tell it which character set the
8983 target program uses. If we print @code{ibm1047_hello} while our target
8984 character set is still @sc{ascii}, we get jibberish:
8987 (@value{GDBP}) print ibm1047_hello
8988 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
8989 (@value{GDBP}) print ibm1047_hello[0]
8994 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
8995 @value{GDBN} tells us the character sets it supports:
8998 (@value{GDBP}) set target-charset
8999 ASCII EBCDIC-US IBM1047 ISO-8859-1
9000 (@value{GDBP}) set target-charset
9003 We can select @sc{ibm1047} as our target character set, and examine the
9004 program's strings again. Now the @sc{ascii} string is wrong, but
9005 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
9006 target character set, @sc{ibm1047}, to the host character set,
9007 @sc{ascii}, and they display correctly:
9010 (@value{GDBP}) set target-charset IBM1047
9011 (@value{GDBP}) show charset
9012 The current host character set is `ASCII'.
9013 The current target character set is `IBM1047'.
9014 (@value{GDBP}) print ascii_hello
9015 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
9016 (@value{GDBP}) print ascii_hello[0]
9018 (@value{GDBP}) print ibm1047_hello
9019 $8 = 0x4016a8 "Hello, world!\n"
9020 (@value{GDBP}) print ibm1047_hello[0]
9025 As above, @value{GDBN} uses the target character set for character and
9026 string literals you use in expressions:
9029 (@value{GDBP}) print '+'
9034 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
9037 @node Caching Remote Data
9038 @section Caching Data of Remote Targets
9039 @cindex caching data of remote targets
9041 @value{GDBN} caches data exchanged between the debugger and a
9042 remote target (@pxref{Remote Debugging}). Such caching generally improves
9043 performance, because it reduces the overhead of the remote protocol by
9044 bundling memory reads and writes into large chunks. Unfortunately, simply
9045 caching everything would lead to incorrect results, since @value{GDBN}
9046 does not necessarily know anything about volatile values, memory-mapped I/O
9047 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
9048 memory can be changed @emph{while} a gdb command is executing.
9049 Therefore, by default, @value{GDBN} only caches data
9050 known to be on the stack@footnote{In non-stop mode, it is moderately
9051 rare for a running thread to modify the stack of a stopped thread
9052 in a way that would interfere with a backtrace, and caching of
9053 stack reads provides a significant speed up of remote backtraces.}.
9054 Other regions of memory can be explicitly marked as
9055 cacheable; see @pxref{Memory Region Attributes}.
9058 @kindex set remotecache
9059 @item set remotecache on
9060 @itemx set remotecache off
9061 This option no longer does anything; it exists for compatibility
9064 @kindex show remotecache
9065 @item show remotecache
9066 Show the current state of the obsolete remotecache flag.
9068 @kindex set stack-cache
9069 @item set stack-cache on
9070 @itemx set stack-cache off
9071 Enable or disable caching of stack accesses. When @code{ON}, use
9072 caching. By default, this option is @code{ON}.
9074 @kindex show stack-cache
9075 @item show stack-cache
9076 Show the current state of data caching for memory accesses.
9079 @item info dcache @r{[}line@r{]}
9080 Print the information about the data cache performance. The
9081 information displayed includes the dcache width and depth, and for
9082 each cache line, its number, address, and how many times it was
9083 referenced. This command is useful for debugging the data cache
9086 If a line number is specified, the contents of that line will be
9090 @node Searching Memory
9091 @section Search Memory
9092 @cindex searching memory
9094 Memory can be searched for a particular sequence of bytes with the
9095 @code{find} command.
9099 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9100 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9101 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
9102 etc. The search begins at address @var{start_addr} and continues for either
9103 @var{len} bytes or through to @var{end_addr} inclusive.
9106 @var{s} and @var{n} are optional parameters.
9107 They may be specified in either order, apart or together.
9110 @item @var{s}, search query size
9111 The size of each search query value.
9117 halfwords (two bytes)
9121 giant words (eight bytes)
9124 All values are interpreted in the current language.
9125 This means, for example, that if the current source language is C/C@t{++}
9126 then searching for the string ``hello'' includes the trailing '\0'.
9128 If the value size is not specified, it is taken from the
9129 value's type in the current language.
9130 This is useful when one wants to specify the search
9131 pattern as a mixture of types.
9132 Note that this means, for example, that in the case of C-like languages
9133 a search for an untyped 0x42 will search for @samp{(int) 0x42}
9134 which is typically four bytes.
9136 @item @var{n}, maximum number of finds
9137 The maximum number of matches to print. The default is to print all finds.
9140 You can use strings as search values. Quote them with double-quotes
9142 The string value is copied into the search pattern byte by byte,
9143 regardless of the endianness of the target and the size specification.
9145 The address of each match found is printed as well as a count of the
9146 number of matches found.
9148 The address of the last value found is stored in convenience variable
9150 A count of the number of matches is stored in @samp{$numfound}.
9152 For example, if stopped at the @code{printf} in this function:
9158 static char hello[] = "hello-hello";
9159 static struct @{ char c; short s; int i; @}
9160 __attribute__ ((packed)) mixed
9161 = @{ 'c', 0x1234, 0x87654321 @};
9162 printf ("%s\n", hello);
9167 you get during debugging:
9170 (gdb) find &hello[0], +sizeof(hello), "hello"
9171 0x804956d <hello.1620+6>
9173 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
9174 0x8049567 <hello.1620>
9175 0x804956d <hello.1620+6>
9177 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
9178 0x8049567 <hello.1620>
9180 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
9181 0x8049560 <mixed.1625>
9183 (gdb) print $numfound
9186 $2 = (void *) 0x8049560
9189 @node Optimized Code
9190 @chapter Debugging Optimized Code
9191 @cindex optimized code, debugging
9192 @cindex debugging optimized code
9194 Almost all compilers support optimization. With optimization
9195 disabled, the compiler generates assembly code that corresponds
9196 directly to your source code, in a simplistic way. As the compiler
9197 applies more powerful optimizations, the generated assembly code
9198 diverges from your original source code. With help from debugging
9199 information generated by the compiler, @value{GDBN} can map from
9200 the running program back to constructs from your original source.
9202 @value{GDBN} is more accurate with optimization disabled. If you
9203 can recompile without optimization, it is easier to follow the
9204 progress of your program during debugging. But, there are many cases
9205 where you may need to debug an optimized version.
9207 When you debug a program compiled with @samp{-g -O}, remember that the
9208 optimizer has rearranged your code; the debugger shows you what is
9209 really there. Do not be too surprised when the execution path does not
9210 exactly match your source file! An extreme example: if you define a
9211 variable, but never use it, @value{GDBN} never sees that
9212 variable---because the compiler optimizes it out of existence.
9214 Some things do not work as well with @samp{-g -O} as with just
9215 @samp{-g}, particularly on machines with instruction scheduling. If in
9216 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
9217 please report it to us as a bug (including a test case!).
9218 @xref{Variables}, for more information about debugging optimized code.
9221 * Inline Functions:: How @value{GDBN} presents inlining
9224 @node Inline Functions
9225 @section Inline Functions
9226 @cindex inline functions, debugging
9228 @dfn{Inlining} is an optimization that inserts a copy of the function
9229 body directly at each call site, instead of jumping to a shared
9230 routine. @value{GDBN} displays inlined functions just like
9231 non-inlined functions. They appear in backtraces. You can view their
9232 arguments and local variables, step into them with @code{step}, skip
9233 them with @code{next}, and escape from them with @code{finish}.
9234 You can check whether a function was inlined by using the
9235 @code{info frame} command.
9237 For @value{GDBN} to support inlined functions, the compiler must
9238 record information about inlining in the debug information ---
9239 @value{NGCC} using the @sc{dwarf 2} format does this, and several
9240 other compilers do also. @value{GDBN} only supports inlined functions
9241 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
9242 do not emit two required attributes (@samp{DW_AT_call_file} and
9243 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
9244 function calls with earlier versions of @value{NGCC}. It instead
9245 displays the arguments and local variables of inlined functions as
9246 local variables in the caller.
9248 The body of an inlined function is directly included at its call site;
9249 unlike a non-inlined function, there are no instructions devoted to
9250 the call. @value{GDBN} still pretends that the call site and the
9251 start of the inlined function are different instructions. Stepping to
9252 the call site shows the call site, and then stepping again shows
9253 the first line of the inlined function, even though no additional
9254 instructions are executed.
9256 This makes source-level debugging much clearer; you can see both the
9257 context of the call and then the effect of the call. Only stepping by
9258 a single instruction using @code{stepi} or @code{nexti} does not do
9259 this; single instruction steps always show the inlined body.
9261 There are some ways that @value{GDBN} does not pretend that inlined
9262 function calls are the same as normal calls:
9266 You cannot set breakpoints on inlined functions. @value{GDBN}
9267 either reports that there is no symbol with that name, or else sets the
9268 breakpoint only on non-inlined copies of the function. This limitation
9269 will be removed in a future version of @value{GDBN}; until then,
9270 set a breakpoint by line number on the first line of the inlined
9274 Setting breakpoints at the call site of an inlined function may not
9275 work, because the call site does not contain any code. @value{GDBN}
9276 may incorrectly move the breakpoint to the next line of the enclosing
9277 function, after the call. This limitation will be removed in a future
9278 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9279 or inside the inlined function instead.
9282 @value{GDBN} cannot locate the return value of inlined calls after
9283 using the @code{finish} command. This is a limitation of compiler-generated
9284 debugging information; after @code{finish}, you can step to the next line
9285 and print a variable where your program stored the return value.
9291 @chapter C Preprocessor Macros
9293 Some languages, such as C and C@t{++}, provide a way to define and invoke
9294 ``preprocessor macros'' which expand into strings of tokens.
9295 @value{GDBN} can evaluate expressions containing macro invocations, show
9296 the result of macro expansion, and show a macro's definition, including
9297 where it was defined.
9299 You may need to compile your program specially to provide @value{GDBN}
9300 with information about preprocessor macros. Most compilers do not
9301 include macros in their debugging information, even when you compile
9302 with the @option{-g} flag. @xref{Compilation}.
9304 A program may define a macro at one point, remove that definition later,
9305 and then provide a different definition after that. Thus, at different
9306 points in the program, a macro may have different definitions, or have
9307 no definition at all. If there is a current stack frame, @value{GDBN}
9308 uses the macros in scope at that frame's source code line. Otherwise,
9309 @value{GDBN} uses the macros in scope at the current listing location;
9312 Whenever @value{GDBN} evaluates an expression, it always expands any
9313 macro invocations present in the expression. @value{GDBN} also provides
9314 the following commands for working with macros explicitly.
9318 @kindex macro expand
9319 @cindex macro expansion, showing the results of preprocessor
9320 @cindex preprocessor macro expansion, showing the results of
9321 @cindex expanding preprocessor macros
9322 @item macro expand @var{expression}
9323 @itemx macro exp @var{expression}
9324 Show the results of expanding all preprocessor macro invocations in
9325 @var{expression}. Since @value{GDBN} simply expands macros, but does
9326 not parse the result, @var{expression} need not be a valid expression;
9327 it can be any string of tokens.
9330 @item macro expand-once @var{expression}
9331 @itemx macro exp1 @var{expression}
9332 @cindex expand macro once
9333 @i{(This command is not yet implemented.)} Show the results of
9334 expanding those preprocessor macro invocations that appear explicitly in
9335 @var{expression}. Macro invocations appearing in that expansion are
9336 left unchanged. This command allows you to see the effect of a
9337 particular macro more clearly, without being confused by further
9338 expansions. Since @value{GDBN} simply expands macros, but does not
9339 parse the result, @var{expression} need not be a valid expression; it
9340 can be any string of tokens.
9343 @cindex macro definition, showing
9344 @cindex definition, showing a macro's
9345 @item info macro @var{macro}
9346 Show the definition of the macro named @var{macro}, and describe the
9347 source location or compiler command-line where that definition was established.
9349 @kindex macro define
9350 @cindex user-defined macros
9351 @cindex defining macros interactively
9352 @cindex macros, user-defined
9353 @item macro define @var{macro} @var{replacement-list}
9354 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
9355 Introduce a definition for a preprocessor macro named @var{macro},
9356 invocations of which are replaced by the tokens given in
9357 @var{replacement-list}. The first form of this command defines an
9358 ``object-like'' macro, which takes no arguments; the second form
9359 defines a ``function-like'' macro, which takes the arguments given in
9362 A definition introduced by this command is in scope in every
9363 expression evaluated in @value{GDBN}, until it is removed with the
9364 @code{macro undef} command, described below. The definition overrides
9365 all definitions for @var{macro} present in the program being debugged,
9366 as well as any previous user-supplied definition.
9369 @item macro undef @var{macro}
9370 Remove any user-supplied definition for the macro named @var{macro}.
9371 This command only affects definitions provided with the @code{macro
9372 define} command, described above; it cannot remove definitions present
9373 in the program being debugged.
9377 List all the macros defined using the @code{macro define} command.
9380 @cindex macros, example of debugging with
9381 Here is a transcript showing the above commands in action. First, we
9382 show our source files:
9390 #define ADD(x) (M + x)
9395 printf ("Hello, world!\n");
9397 printf ("We're so creative.\n");
9399 printf ("Goodbye, world!\n");
9406 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
9407 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
9408 compiler includes information about preprocessor macros in the debugging
9412 $ gcc -gdwarf-2 -g3 sample.c -o sample
9416 Now, we start @value{GDBN} on our sample program:
9420 GNU gdb 2002-05-06-cvs
9421 Copyright 2002 Free Software Foundation, Inc.
9422 GDB is free software, @dots{}
9426 We can expand macros and examine their definitions, even when the
9427 program is not running. @value{GDBN} uses the current listing position
9428 to decide which macro definitions are in scope:
9431 (@value{GDBP}) list main
9434 5 #define ADD(x) (M + x)
9439 10 printf ("Hello, world!\n");
9441 12 printf ("We're so creative.\n");
9442 (@value{GDBP}) info macro ADD
9443 Defined at /home/jimb/gdb/macros/play/sample.c:5
9444 #define ADD(x) (M + x)
9445 (@value{GDBP}) info macro Q
9446 Defined at /home/jimb/gdb/macros/play/sample.h:1
9447 included at /home/jimb/gdb/macros/play/sample.c:2
9449 (@value{GDBP}) macro expand ADD(1)
9450 expands to: (42 + 1)
9451 (@value{GDBP}) macro expand-once ADD(1)
9452 expands to: once (M + 1)
9456 In the example above, note that @code{macro expand-once} expands only
9457 the macro invocation explicit in the original text --- the invocation of
9458 @code{ADD} --- but does not expand the invocation of the macro @code{M},
9459 which was introduced by @code{ADD}.
9461 Once the program is running, @value{GDBN} uses the macro definitions in
9462 force at the source line of the current stack frame:
9465 (@value{GDBP}) break main
9466 Breakpoint 1 at 0x8048370: file sample.c, line 10.
9468 Starting program: /home/jimb/gdb/macros/play/sample
9470 Breakpoint 1, main () at sample.c:10
9471 10 printf ("Hello, world!\n");
9475 At line 10, the definition of the macro @code{N} at line 9 is in force:
9478 (@value{GDBP}) info macro N
9479 Defined at /home/jimb/gdb/macros/play/sample.c:9
9481 (@value{GDBP}) macro expand N Q M
9483 (@value{GDBP}) print N Q M
9488 As we step over directives that remove @code{N}'s definition, and then
9489 give it a new definition, @value{GDBN} finds the definition (or lack
9490 thereof) in force at each point:
9495 12 printf ("We're so creative.\n");
9496 (@value{GDBP}) info macro N
9497 The symbol `N' has no definition as a C/C++ preprocessor macro
9498 at /home/jimb/gdb/macros/play/sample.c:12
9501 14 printf ("Goodbye, world!\n");
9502 (@value{GDBP}) info macro N
9503 Defined at /home/jimb/gdb/macros/play/sample.c:13
9505 (@value{GDBP}) macro expand N Q M
9506 expands to: 1729 < 42
9507 (@value{GDBP}) print N Q M
9512 In addition to source files, macros can be defined on the compilation command
9513 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
9514 such a way, @value{GDBN} displays the location of their definition as line zero
9515 of the source file submitted to the compiler.
9518 (@value{GDBP}) info macro __STDC__
9519 Defined at /home/jimb/gdb/macros/play/sample.c:0
9526 @chapter Tracepoints
9527 @c This chapter is based on the documentation written by Michael
9528 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
9531 In some applications, it is not feasible for the debugger to interrupt
9532 the program's execution long enough for the developer to learn
9533 anything helpful about its behavior. If the program's correctness
9534 depends on its real-time behavior, delays introduced by a debugger
9535 might cause the program to change its behavior drastically, or perhaps
9536 fail, even when the code itself is correct. It is useful to be able
9537 to observe the program's behavior without interrupting it.
9539 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
9540 specify locations in the program, called @dfn{tracepoints}, and
9541 arbitrary expressions to evaluate when those tracepoints are reached.
9542 Later, using the @code{tfind} command, you can examine the values
9543 those expressions had when the program hit the tracepoints. The
9544 expressions may also denote objects in memory---structures or arrays,
9545 for example---whose values @value{GDBN} should record; while visiting
9546 a particular tracepoint, you may inspect those objects as if they were
9547 in memory at that moment. However, because @value{GDBN} records these
9548 values without interacting with you, it can do so quickly and
9549 unobtrusively, hopefully not disturbing the program's behavior.
9551 The tracepoint facility is currently available only for remote
9552 targets. @xref{Targets}. In addition, your remote target must know
9553 how to collect trace data. This functionality is implemented in the
9554 remote stub; however, none of the stubs distributed with @value{GDBN}
9555 support tracepoints as of this writing. The format of the remote
9556 packets used to implement tracepoints are described in @ref{Tracepoint
9559 It is also possible to get trace data from a file, in a manner reminiscent
9560 of corefiles; you specify the filename, and use @code{tfind} to search
9561 through the file. @xref{Trace Files}, for more details.
9563 This chapter describes the tracepoint commands and features.
9567 * Analyze Collected Data::
9568 * Tracepoint Variables::
9572 @node Set Tracepoints
9573 @section Commands to Set Tracepoints
9575 Before running such a @dfn{trace experiment}, an arbitrary number of
9576 tracepoints can be set. A tracepoint is actually a special type of
9577 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
9578 standard breakpoint commands. For instance, as with breakpoints,
9579 tracepoint numbers are successive integers starting from one, and many
9580 of the commands associated with tracepoints take the tracepoint number
9581 as their argument, to identify which tracepoint to work on.
9583 For each tracepoint, you can specify, in advance, some arbitrary set
9584 of data that you want the target to collect in the trace buffer when
9585 it hits that tracepoint. The collected data can include registers,
9586 local variables, or global data. Later, you can use @value{GDBN}
9587 commands to examine the values these data had at the time the
9590 Tracepoints do not support every breakpoint feature. Ignore counts on
9591 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
9592 commands when they are hit. Tracepoints may not be thread-specific
9595 @cindex fast tracepoints
9596 Some targets may support @dfn{fast tracepoints}, which are inserted in
9597 a different way (such as with a jump instead of a trap), that is
9598 faster but possibly restricted in where they may be installed.
9600 @cindex static tracepoints
9601 @cindex markers, static tracepoints
9602 @cindex probing markers, static tracepoints
9603 Regular and fast tracepoints are dynamic tracing facilities, meaning
9604 that they can be used to insert tracepoints at (almost) any location
9605 in the target. Some targets may also support controlling @dfn{static
9606 tracepoints} from @value{GDBN}. With static tracing, a set of
9607 instrumentation points, also known as @dfn{markers}, are embedded in
9608 the target program, and can be activated or deactivated by name or
9609 address. These are usually placed at locations which facilitate
9610 investigating what the target is actually doing. @value{GDBN}'s
9611 support for static tracing includes being able to list instrumentation
9612 points, and attach them with @value{GDBN} defined high level
9613 tracepoints that expose the whole range of convenience of
9614 @value{GDBN}'s tracepoints support. Namelly, support for collecting
9615 registers values and values of global or local (to the instrumentation
9616 point) variables; tracepoint conditions and trace state variables.
9617 The act of installing a @value{GDBN} static tracepoint on an
9618 instrumentation point, or marker, is referred to as @dfn{probing} a
9619 static tracepoint marker.
9621 @code{gdbserver} supports tracepoints on some target systems.
9622 @xref{Server,,Tracepoints support in @code{gdbserver}}.
9624 This section describes commands to set tracepoints and associated
9625 conditions and actions.
9628 * Create and Delete Tracepoints::
9629 * Enable and Disable Tracepoints::
9630 * Tracepoint Passcounts::
9631 * Tracepoint Conditions::
9632 * Trace State Variables::
9633 * Tracepoint Actions::
9634 * Listing Tracepoints::
9635 * Listing Static Tracepoint Markers::
9636 * Starting and Stopping Trace Experiments::
9637 * Tracepoint Restrictions::
9640 @node Create and Delete Tracepoints
9641 @subsection Create and Delete Tracepoints
9644 @cindex set tracepoint
9646 @item trace @var{location}
9647 The @code{trace} command is very similar to the @code{break} command.
9648 Its argument @var{location} can be a source line, a function name, or
9649 an address in the target program. @xref{Specify Location}. The
9650 @code{trace} command defines a tracepoint, which is a point in the
9651 target program where the debugger will briefly stop, collect some
9652 data, and then allow the program to continue. Setting a tracepoint or
9653 changing its actions doesn't take effect until the next @code{tstart}
9654 command, and once a trace experiment is running, further changes will
9655 not have any effect until the next trace experiment starts.
9657 Here are some examples of using the @code{trace} command:
9660 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
9662 (@value{GDBP}) @b{trace +2} // 2 lines forward
9664 (@value{GDBP}) @b{trace my_function} // first source line of function
9666 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
9668 (@value{GDBP}) @b{trace *0x2117c4} // an address
9672 You can abbreviate @code{trace} as @code{tr}.
9674 @item trace @var{location} if @var{cond}
9675 Set a tracepoint with condition @var{cond}; evaluate the expression
9676 @var{cond} each time the tracepoint is reached, and collect data only
9677 if the value is nonzero---that is, if @var{cond} evaluates as true.
9678 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
9679 information on tracepoint conditions.
9681 @item ftrace @var{location} [ if @var{cond} ]
9682 @cindex set fast tracepoint
9684 The @code{ftrace} command sets a fast tracepoint. For targets that
9685 support them, fast tracepoints will use a more efficient but possibly
9686 less general technique to trigger data collection, such as a jump
9687 instruction instead of a trap, or some sort of hardware support. It
9688 may not be possible to create a fast tracepoint at the desired
9689 location, in which case the command will exit with an explanatory
9692 @value{GDBN} handles arguments to @code{ftrace} exactly as for
9695 @item strace @var{location} [ if @var{cond} ]
9696 @cindex static tracepoint, setting
9698 The @code{strace} command sets a static tracepoint. For targets that
9699 support it, setting a static tracepoint probes a static
9700 instrumentation point, or marker, found at @var{location}. It may not
9701 be possible to set a static tracepoint at the desired location, in
9702 which case the command will exit with an explanatory message.
9704 @value{GDBN} handles arguments to @code{strace} exactly as for
9705 @code{trace}, with the addition that the user can also specify
9706 @code{-m @var{marker}} as @var{location}. This probes the marker
9707 identified by the @var{marker} string identifier. This identifier
9708 depends on the static tracepoint backend library your program is
9709 using. You can find all the marker identifiers in the @samp{ID} field
9710 of the @code{info static-tracepoint-markers} command output.
9711 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
9712 Markers}. For example, in the following small program using the UST
9718 trace_mark(ust, bar33, "str %s", "FOOBAZ");
9723 the marker id is composed of joining the first two arguments to the
9724 @code{trace_mark} call with a slash, which translates to:
9727 (@value{GDBP}) info static-tracepoint-markers
9728 Cnt Enb ID Address What
9729 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
9735 so you may probe the marker above with:
9738 (@value{GDBP}) strace -m ust/bar33
9741 Static tracepoints accept an extra collect action --- @code{collect
9742 $_sdata}. This collects arbitrary user data passed in the probe point
9743 call to the tracing library. In the UST example above, you'll see
9744 that the third argument to @code{trace_mark} is a printf-like format
9745 string. The user data is then the result of running that formating
9746 string against the following arguments. Note that @code{info
9747 static-tracepoint-markers} command output lists that format string in
9748 the @samp{Data:} field.
9750 You can inspect this data when analyzing the trace buffer, by printing
9751 the $_sdata variable like any other variable available to
9752 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
9755 @cindex last tracepoint number
9756 @cindex recent tracepoint number
9757 @cindex tracepoint number
9758 The convenience variable @code{$tpnum} records the tracepoint number
9759 of the most recently set tracepoint.
9761 @kindex delete tracepoint
9762 @cindex tracepoint deletion
9763 @item delete tracepoint @r{[}@var{num}@r{]}
9764 Permanently delete one or more tracepoints. With no argument, the
9765 default is to delete all tracepoints. Note that the regular
9766 @code{delete} command can remove tracepoints also.
9771 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
9773 (@value{GDBP}) @b{delete trace} // remove all tracepoints
9777 You can abbreviate this command as @code{del tr}.
9780 @node Enable and Disable Tracepoints
9781 @subsection Enable and Disable Tracepoints
9783 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
9786 @kindex disable tracepoint
9787 @item disable tracepoint @r{[}@var{num}@r{]}
9788 Disable tracepoint @var{num}, or all tracepoints if no argument
9789 @var{num} is given. A disabled tracepoint will have no effect during
9790 the next trace experiment, but it is not forgotten. You can re-enable
9791 a disabled tracepoint using the @code{enable tracepoint} command.
9793 @kindex enable tracepoint
9794 @item enable tracepoint @r{[}@var{num}@r{]}
9795 Enable tracepoint @var{num}, or all tracepoints. The enabled
9796 tracepoints will become effective the next time a trace experiment is
9800 @node Tracepoint Passcounts
9801 @subsection Tracepoint Passcounts
9805 @cindex tracepoint pass count
9806 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
9807 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
9808 automatically stop a trace experiment. If a tracepoint's passcount is
9809 @var{n}, then the trace experiment will be automatically stopped on
9810 the @var{n}'th time that tracepoint is hit. If the tracepoint number
9811 @var{num} is not specified, the @code{passcount} command sets the
9812 passcount of the most recently defined tracepoint. If no passcount is
9813 given, the trace experiment will run until stopped explicitly by the
9819 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
9820 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
9822 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
9823 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
9824 (@value{GDBP}) @b{trace foo}
9825 (@value{GDBP}) @b{pass 3}
9826 (@value{GDBP}) @b{trace bar}
9827 (@value{GDBP}) @b{pass 2}
9828 (@value{GDBP}) @b{trace baz}
9829 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
9830 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
9831 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
9832 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
9836 @node Tracepoint Conditions
9837 @subsection Tracepoint Conditions
9838 @cindex conditional tracepoints
9839 @cindex tracepoint conditions
9841 The simplest sort of tracepoint collects data every time your program
9842 reaches a specified place. You can also specify a @dfn{condition} for
9843 a tracepoint. A condition is just a Boolean expression in your
9844 programming language (@pxref{Expressions, ,Expressions}). A
9845 tracepoint with a condition evaluates the expression each time your
9846 program reaches it, and data collection happens only if the condition
9849 Tracepoint conditions can be specified when a tracepoint is set, by
9850 using @samp{if} in the arguments to the @code{trace} command.
9851 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
9852 also be set or changed at any time with the @code{condition} command,
9853 just as with breakpoints.
9855 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
9856 the conditional expression itself. Instead, @value{GDBN} encodes the
9857 expression into an agent expression (@pxref{Agent Expressions}
9858 suitable for execution on the target, independently of @value{GDBN}.
9859 Global variables become raw memory locations, locals become stack
9860 accesses, and so forth.
9862 For instance, suppose you have a function that is usually called
9863 frequently, but should not be called after an error has occurred. You
9864 could use the following tracepoint command to collect data about calls
9865 of that function that happen while the error code is propagating
9866 through the program; an unconditional tracepoint could end up
9867 collecting thousands of useless trace frames that you would have to
9871 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
9874 @node Trace State Variables
9875 @subsection Trace State Variables
9876 @cindex trace state variables
9878 A @dfn{trace state variable} is a special type of variable that is
9879 created and managed by target-side code. The syntax is the same as
9880 that for GDB's convenience variables (a string prefixed with ``$''),
9881 but they are stored on the target. They must be created explicitly,
9882 using a @code{tvariable} command. They are always 64-bit signed
9885 Trace state variables are remembered by @value{GDBN}, and downloaded
9886 to the target along with tracepoint information when the trace
9887 experiment starts. There are no intrinsic limits on the number of
9888 trace state variables, beyond memory limitations of the target.
9890 @cindex convenience variables, and trace state variables
9891 Although trace state variables are managed by the target, you can use
9892 them in print commands and expressions as if they were convenience
9893 variables; @value{GDBN} will get the current value from the target
9894 while the trace experiment is running. Trace state variables share
9895 the same namespace as other ``$'' variables, which means that you
9896 cannot have trace state variables with names like @code{$23} or
9897 @code{$pc}, nor can you have a trace state variable and a convenience
9898 variable with the same name.
9902 @item tvariable $@var{name} [ = @var{expression} ]
9904 The @code{tvariable} command creates a new trace state variable named
9905 @code{$@var{name}}, and optionally gives it an initial value of
9906 @var{expression}. @var{expression} is evaluated when this command is
9907 entered; the result will be converted to an integer if possible,
9908 otherwise @value{GDBN} will report an error. A subsequent
9909 @code{tvariable} command specifying the same name does not create a
9910 variable, but instead assigns the supplied initial value to the
9911 existing variable of that name, overwriting any previous initial
9912 value. The default initial value is 0.
9914 @item info tvariables
9915 @kindex info tvariables
9916 List all the trace state variables along with their initial values.
9917 Their current values may also be displayed, if the trace experiment is
9920 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
9921 @kindex delete tvariable
9922 Delete the given trace state variables, or all of them if no arguments
9927 @node Tracepoint Actions
9928 @subsection Tracepoint Action Lists
9932 @cindex tracepoint actions
9933 @item actions @r{[}@var{num}@r{]}
9934 This command will prompt for a list of actions to be taken when the
9935 tracepoint is hit. If the tracepoint number @var{num} is not
9936 specified, this command sets the actions for the one that was most
9937 recently defined (so that you can define a tracepoint and then say
9938 @code{actions} without bothering about its number). You specify the
9939 actions themselves on the following lines, one action at a time, and
9940 terminate the actions list with a line containing just @code{end}. So
9941 far, the only defined actions are @code{collect}, @code{teval}, and
9942 @code{while-stepping}.
9944 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
9945 Commands, ,Breakpoint Command Lists}), except that only the defined
9946 actions are allowed; any other @value{GDBN} command is rejected.
9948 @cindex remove actions from a tracepoint
9949 To remove all actions from a tracepoint, type @samp{actions @var{num}}
9950 and follow it immediately with @samp{end}.
9953 (@value{GDBP}) @b{collect @var{data}} // collect some data
9955 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
9957 (@value{GDBP}) @b{end} // signals the end of actions.
9960 In the following example, the action list begins with @code{collect}
9961 commands indicating the things to be collected when the tracepoint is
9962 hit. Then, in order to single-step and collect additional data
9963 following the tracepoint, a @code{while-stepping} command is used,
9964 followed by the list of things to be collected after each step in a
9965 sequence of single steps. The @code{while-stepping} command is
9966 terminated by its own separate @code{end} command. Lastly, the action
9967 list is terminated by an @code{end} command.
9970 (@value{GDBP}) @b{trace foo}
9971 (@value{GDBP}) @b{actions}
9972 Enter actions for tracepoint 1, one per line:
9976 > collect $pc, arr[i]
9981 @kindex collect @r{(tracepoints)}
9982 @item collect @var{expr1}, @var{expr2}, @dots{}
9983 Collect values of the given expressions when the tracepoint is hit.
9984 This command accepts a comma-separated list of any valid expressions.
9985 In addition to global, static, or local variables, the following
9986 special arguments are supported:
9990 Collect all registers.
9993 Collect all function arguments.
9996 Collect all local variables.
9999 @vindex $_sdata@r{, collect}
10000 Collect static tracepoint marker specific data. Only available for
10001 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
10002 Lists}. On the UST static tracepoints library backend, an
10003 instrumentation point resembles a @code{printf} function call. The
10004 tracing library is able to collect user specified data formatted to a
10005 character string using the format provided by the programmer that
10006 instrumented the program. Other backends have similar mechanisms.
10007 Here's an example of a UST marker call:
10010 const char master_name[] = "$your_name";
10011 trace_mark(channel1, marker1, "hello %s", master_name)
10014 In this case, collecting @code{$_sdata} collects the string
10015 @samp{hello $yourname}. When analyzing the trace buffer, you can
10016 inspect @samp{$_sdata} like any other variable available to
10020 You can give several consecutive @code{collect} commands, each one
10021 with a single argument, or one @code{collect} command with several
10022 arguments separated by commas; the effect is the same.
10024 The command @code{info scope} (@pxref{Symbols, info scope}) is
10025 particularly useful for figuring out what data to collect.
10027 @kindex teval @r{(tracepoints)}
10028 @item teval @var{expr1}, @var{expr2}, @dots{}
10029 Evaluate the given expressions when the tracepoint is hit. This
10030 command accepts a comma-separated list of expressions. The results
10031 are discarded, so this is mainly useful for assigning values to trace
10032 state variables (@pxref{Trace State Variables}) without adding those
10033 values to the trace buffer, as would be the case if the @code{collect}
10036 @kindex while-stepping @r{(tracepoints)}
10037 @item while-stepping @var{n}
10038 Perform @var{n} single-step instruction traces after the tracepoint,
10039 collecting new data after each step. The @code{while-stepping}
10040 command is followed by the list of what to collect while stepping
10041 (followed by its own @code{end} command):
10044 > while-stepping 12
10045 > collect $regs, myglobal
10051 Note that @code{$pc} is not automatically collected by
10052 @code{while-stepping}; you need to explicitly collect that register if
10053 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
10056 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
10057 @kindex set default-collect
10058 @cindex default collection action
10059 This variable is a list of expressions to collect at each tracepoint
10060 hit. It is effectively an additional @code{collect} action prepended
10061 to every tracepoint action list. The expressions are parsed
10062 individually for each tracepoint, so for instance a variable named
10063 @code{xyz} may be interpreted as a global for one tracepoint, and a
10064 local for another, as appropriate to the tracepoint's location.
10066 @item show default-collect
10067 @kindex show default-collect
10068 Show the list of expressions that are collected by default at each
10073 @node Listing Tracepoints
10074 @subsection Listing Tracepoints
10077 @kindex info tracepoints
10079 @cindex information about tracepoints
10080 @item info tracepoints @r{[}@var{num}@r{]}
10081 Display information about the tracepoint @var{num}. If you don't
10082 specify a tracepoint number, displays information about all the
10083 tracepoints defined so far. The format is similar to that used for
10084 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
10085 command, simply restricting itself to tracepoints.
10087 A tracepoint's listing may include additional information specific to
10092 its passcount as given by the @code{passcount @var{n}} command
10096 (@value{GDBP}) @b{info trace}
10097 Num Type Disp Enb Address What
10098 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
10100 collect globfoo, $regs
10109 This command can be abbreviated @code{info tp}.
10112 @node Listing Static Tracepoint Markers
10113 @subsection Listing Static Tracepoint Markers
10116 @kindex info static-tracepoint-markers
10117 @cindex information about static tracepoint markers
10118 @item info static-tracepoint-markers
10119 Display information about all static tracepoint markers defined in the
10122 For each marker, the following columns are printed:
10126 An incrementing counter, output to help readability. This is not a
10129 The marker ID, as reported by the target.
10130 @item Enabled or Disabled
10131 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
10132 that are not enabled.
10134 Where the marker is in your program, as a memory address.
10136 Where the marker is in the source for your program, as a file and line
10137 number. If the debug information included in the program does not
10138 allow @value{GDBN} to locate the source of the marker, this column
10139 will be left blank.
10143 In addition, the following information may be printed for each marker:
10147 User data passed to the tracing library by the marker call. In the
10148 UST backend, this is the format string passed as argument to the
10150 @item Static tracepoints probing the marker
10151 The list of static tracepoints attached to the marker.
10155 (@value{GDBP}) info static-tracepoint-markers
10156 Cnt ID Enb Address What
10157 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
10158 Data: number1 %d number2 %d
10159 Probed by static tracepoints: #2
10160 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
10166 @node Starting and Stopping Trace Experiments
10167 @subsection Starting and Stopping Trace Experiments
10171 @cindex start a new trace experiment
10172 @cindex collected data discarded
10174 This command takes no arguments. It starts the trace experiment, and
10175 begins collecting data. This has the side effect of discarding all
10176 the data collected in the trace buffer during the previous trace
10180 @cindex stop a running trace experiment
10182 This command takes no arguments. It ends the trace experiment, and
10183 stops collecting data.
10185 @strong{Note}: a trace experiment and data collection may stop
10186 automatically if any tracepoint's passcount is reached
10187 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
10190 @cindex status of trace data collection
10191 @cindex trace experiment, status of
10193 This command displays the status of the current trace data
10197 Here is an example of the commands we described so far:
10200 (@value{GDBP}) @b{trace gdb_c_test}
10201 (@value{GDBP}) @b{actions}
10202 Enter actions for tracepoint #1, one per line.
10203 > collect $regs,$locals,$args
10204 > while-stepping 11
10208 (@value{GDBP}) @b{tstart}
10209 [time passes @dots{}]
10210 (@value{GDBP}) @b{tstop}
10213 @cindex disconnected tracing
10214 You can choose to continue running the trace experiment even if
10215 @value{GDBN} disconnects from the target, voluntarily or
10216 involuntarily. For commands such as @code{detach}, the debugger will
10217 ask what you want to do with the trace. But for unexpected
10218 terminations (@value{GDBN} crash, network outage), it would be
10219 unfortunate to lose hard-won trace data, so the variable
10220 @code{disconnected-tracing} lets you decide whether the trace should
10221 continue running without @value{GDBN}.
10224 @item set disconnected-tracing on
10225 @itemx set disconnected-tracing off
10226 @kindex set disconnected-tracing
10227 Choose whether a tracing run should continue to run if @value{GDBN}
10228 has disconnected from the target. Note that @code{detach} or
10229 @code{quit} will ask you directly what to do about a running trace no
10230 matter what this variable's setting, so the variable is mainly useful
10231 for handling unexpected situations, such as loss of the network.
10233 @item show disconnected-tracing
10234 @kindex show disconnected-tracing
10235 Show the current choice for disconnected tracing.
10239 When you reconnect to the target, the trace experiment may or may not
10240 still be running; it might have filled the trace buffer in the
10241 meantime, or stopped for one of the other reasons. If it is running,
10242 it will continue after reconnection.
10244 Upon reconnection, the target will upload information about the
10245 tracepoints in effect. @value{GDBN} will then compare that
10246 information to the set of tracepoints currently defined, and attempt
10247 to match them up, allowing for the possibility that the numbers may
10248 have changed due to creation and deletion in the meantime. If one of
10249 the target's tracepoints does not match any in @value{GDBN}, the
10250 debugger will create a new tracepoint, so that you have a number with
10251 which to specify that tracepoint. This matching-up process is
10252 necessarily heuristic, and it may result in useless tracepoints being
10253 created; you may simply delete them if they are of no use.
10255 @cindex circular trace buffer
10256 If your target agent supports a @dfn{circular trace buffer}, then you
10257 can run a trace experiment indefinitely without filling the trace
10258 buffer; when space runs out, the agent deletes already-collected trace
10259 frames, oldest first, until there is enough room to continue
10260 collecting. This is especially useful if your tracepoints are being
10261 hit too often, and your trace gets terminated prematurely because the
10262 buffer is full. To ask for a circular trace buffer, simply set
10263 @samp{circular_trace_buffer} to on. You can set this at any time,
10264 including during tracing; if the agent can do it, it will change
10265 buffer handling on the fly, otherwise it will not take effect until
10269 @item set circular-trace-buffer on
10270 @itemx set circular-trace-buffer off
10271 @kindex set circular-trace-buffer
10272 Choose whether a tracing run should use a linear or circular buffer
10273 for trace data. A linear buffer will not lose any trace data, but may
10274 fill up prematurely, while a circular buffer will discard old trace
10275 data, but it will have always room for the latest tracepoint hits.
10277 @item show circular-trace-buffer
10278 @kindex show circular-trace-buffer
10279 Show the current choice for the trace buffer. Note that this may not
10280 match the agent's current buffer handling, nor is it guaranteed to
10281 match the setting that might have been in effect during a past run,
10282 for instance if you are looking at frames from a trace file.
10286 @node Tracepoint Restrictions
10287 @subsection Tracepoint Restrictions
10289 @cindex tracepoint restrictions
10290 There are a number of restrictions on the use of tracepoints. As
10291 described above, tracepoint data gathering occurs on the target
10292 without interaction from @value{GDBN}. Thus the full capabilities of
10293 the debugger are not available during data gathering, and then at data
10294 examination time, you will be limited by only having what was
10295 collected. The following items describe some common problems, but it
10296 is not exhaustive, and you may run into additional difficulties not
10302 Tracepoint expressions are intended to gather objects (lvalues). Thus
10303 the full flexibility of GDB's expression evaluator is not available.
10304 You cannot call functions, cast objects to aggregate types, access
10305 convenience variables or modify values (except by assignment to trace
10306 state variables). Some language features may implicitly call
10307 functions (for instance Objective-C fields with accessors), and therefore
10308 cannot be collected either.
10311 Collection of local variables, either individually or in bulk with
10312 @code{$locals} or @code{$args}, during @code{while-stepping} may
10313 behave erratically. The stepping action may enter a new scope (for
10314 instance by stepping into a function), or the location of the variable
10315 may change (for instance it is loaded into a register). The
10316 tracepoint data recorded uses the location information for the
10317 variables that is correct for the tracepoint location. When the
10318 tracepoint is created, it is not possible, in general, to determine
10319 where the steps of a @code{while-stepping} sequence will advance the
10320 program---particularly if a conditional branch is stepped.
10323 Collection of an incompletely-initialized or partially-destroyed object
10324 may result in something that @value{GDBN} cannot display, or displays
10325 in a misleading way.
10328 When @value{GDBN} displays a pointer to character it automatically
10329 dereferences the pointer to also display characters of the string
10330 being pointed to. However, collecting the pointer during tracing does
10331 not automatically collect the string. You need to explicitly
10332 dereference the pointer and provide size information if you want to
10333 collect not only the pointer, but the memory pointed to. For example,
10334 @code{*ptr@@50} can be used to collect the 50 element array pointed to
10338 It is not possible to collect a complete stack backtrace at a
10339 tracepoint. Instead, you may collect the registers and a few hundred
10340 bytes from the stack pointer with something like @code{*$esp@@300}
10341 (adjust to use the name of the actual stack pointer register on your
10342 target architecture, and the amount of stack you wish to capture).
10343 Then the @code{backtrace} command will show a partial backtrace when
10344 using a trace frame. The number of stack frames that can be examined
10345 depends on the sizes of the frames in the collected stack. Note that
10346 if you ask for a block so large that it goes past the bottom of the
10347 stack, the target agent may report an error trying to read from an
10351 If you do not collect registers at a tracepoint, @value{GDBN} can
10352 infer that the value of @code{$pc} must be the same as the address of
10353 the tracepoint and use that when you are looking at a trace frame
10354 for that tracepoint. However, this cannot work if the tracepoint has
10355 multiple locations (for instance if it was set in a function that was
10356 inlined), or if it has a @code{while-stepping} loop. In those cases
10357 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
10362 @node Analyze Collected Data
10363 @section Using the Collected Data
10365 After the tracepoint experiment ends, you use @value{GDBN} commands
10366 for examining the trace data. The basic idea is that each tracepoint
10367 collects a trace @dfn{snapshot} every time it is hit and another
10368 snapshot every time it single-steps. All these snapshots are
10369 consecutively numbered from zero and go into a buffer, and you can
10370 examine them later. The way you examine them is to @dfn{focus} on a
10371 specific trace snapshot. When the remote stub is focused on a trace
10372 snapshot, it will respond to all @value{GDBN} requests for memory and
10373 registers by reading from the buffer which belongs to that snapshot,
10374 rather than from @emph{real} memory or registers of the program being
10375 debugged. This means that @strong{all} @value{GDBN} commands
10376 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
10377 behave as if we were currently debugging the program state as it was
10378 when the tracepoint occurred. Any requests for data that are not in
10379 the buffer will fail.
10382 * tfind:: How to select a trace snapshot
10383 * tdump:: How to display all data for a snapshot
10384 * save tracepoints:: How to save tracepoints for a future run
10388 @subsection @code{tfind @var{n}}
10391 @cindex select trace snapshot
10392 @cindex find trace snapshot
10393 The basic command for selecting a trace snapshot from the buffer is
10394 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
10395 counting from zero. If no argument @var{n} is given, the next
10396 snapshot is selected.
10398 Here are the various forms of using the @code{tfind} command.
10402 Find the first snapshot in the buffer. This is a synonym for
10403 @code{tfind 0} (since 0 is the number of the first snapshot).
10406 Stop debugging trace snapshots, resume @emph{live} debugging.
10409 Same as @samp{tfind none}.
10412 No argument means find the next trace snapshot.
10415 Find the previous trace snapshot before the current one. This permits
10416 retracing earlier steps.
10418 @item tfind tracepoint @var{num}
10419 Find the next snapshot associated with tracepoint @var{num}. Search
10420 proceeds forward from the last examined trace snapshot. If no
10421 argument @var{num} is given, it means find the next snapshot collected
10422 for the same tracepoint as the current snapshot.
10424 @item tfind pc @var{addr}
10425 Find the next snapshot associated with the value @var{addr} of the
10426 program counter. Search proceeds forward from the last examined trace
10427 snapshot. If no argument @var{addr} is given, it means find the next
10428 snapshot with the same value of PC as the current snapshot.
10430 @item tfind outside @var{addr1}, @var{addr2}
10431 Find the next snapshot whose PC is outside the given range of
10432 addresses (exclusive).
10434 @item tfind range @var{addr1}, @var{addr2}
10435 Find the next snapshot whose PC is between @var{addr1} and
10436 @var{addr2} (inclusive).
10438 @item tfind line @r{[}@var{file}:@r{]}@var{n}
10439 Find the next snapshot associated with the source line @var{n}. If
10440 the optional argument @var{file} is given, refer to line @var{n} in
10441 that source file. Search proceeds forward from the last examined
10442 trace snapshot. If no argument @var{n} is given, it means find the
10443 next line other than the one currently being examined; thus saying
10444 @code{tfind line} repeatedly can appear to have the same effect as
10445 stepping from line to line in a @emph{live} debugging session.
10448 The default arguments for the @code{tfind} commands are specifically
10449 designed to make it easy to scan through the trace buffer. For
10450 instance, @code{tfind} with no argument selects the next trace
10451 snapshot, and @code{tfind -} with no argument selects the previous
10452 trace snapshot. So, by giving one @code{tfind} command, and then
10453 simply hitting @key{RET} repeatedly you can examine all the trace
10454 snapshots in order. Or, by saying @code{tfind -} and then hitting
10455 @key{RET} repeatedly you can examine the snapshots in reverse order.
10456 The @code{tfind line} command with no argument selects the snapshot
10457 for the next source line executed. The @code{tfind pc} command with
10458 no argument selects the next snapshot with the same program counter
10459 (PC) as the current frame. The @code{tfind tracepoint} command with
10460 no argument selects the next trace snapshot collected by the same
10461 tracepoint as the current one.
10463 In addition to letting you scan through the trace buffer manually,
10464 these commands make it easy to construct @value{GDBN} scripts that
10465 scan through the trace buffer and print out whatever collected data
10466 you are interested in. Thus, if we want to examine the PC, FP, and SP
10467 registers from each trace frame in the buffer, we can say this:
10470 (@value{GDBP}) @b{tfind start}
10471 (@value{GDBP}) @b{while ($trace_frame != -1)}
10472 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
10473 $trace_frame, $pc, $sp, $fp
10477 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
10478 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
10479 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
10480 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
10481 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
10482 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
10483 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
10484 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
10485 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
10486 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
10487 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
10490 Or, if we want to examine the variable @code{X} at each source line in
10494 (@value{GDBP}) @b{tfind start}
10495 (@value{GDBP}) @b{while ($trace_frame != -1)}
10496 > printf "Frame %d, X == %d\n", $trace_frame, X
10506 @subsection @code{tdump}
10508 @cindex dump all data collected at tracepoint
10509 @cindex tracepoint data, display
10511 This command takes no arguments. It prints all the data collected at
10512 the current trace snapshot.
10515 (@value{GDBP}) @b{trace 444}
10516 (@value{GDBP}) @b{actions}
10517 Enter actions for tracepoint #2, one per line:
10518 > collect $regs, $locals, $args, gdb_long_test
10521 (@value{GDBP}) @b{tstart}
10523 (@value{GDBP}) @b{tfind line 444}
10524 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
10526 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
10528 (@value{GDBP}) @b{tdump}
10529 Data collected at tracepoint 2, trace frame 1:
10530 d0 0xc4aa0085 -995491707
10534 d4 0x71aea3d 119204413
10537 d7 0x380035 3670069
10538 a0 0x19e24a 1696330
10539 a1 0x3000668 50333288
10541 a3 0x322000 3284992
10542 a4 0x3000698 50333336
10543 a5 0x1ad3cc 1758156
10544 fp 0x30bf3c 0x30bf3c
10545 sp 0x30bf34 0x30bf34
10547 pc 0x20b2c8 0x20b2c8
10551 p = 0x20e5b4 "gdb-test"
10558 gdb_long_test = 17 '\021'
10563 @code{tdump} works by scanning the tracepoint's current collection
10564 actions and printing the value of each expression listed. So
10565 @code{tdump} can fail, if after a run, you change the tracepoint's
10566 actions to mention variables that were not collected during the run.
10568 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
10569 uses the collected value of @code{$pc} to distinguish between trace
10570 frames that were collected at the tracepoint hit, and frames that were
10571 collected while stepping. This allows it to correctly choose whether
10572 to display the basic list of collections, or the collections from the
10573 body of the while-stepping loop. However, if @code{$pc} was not collected,
10574 then @code{tdump} will always attempt to dump using the basic collection
10575 list, and may fail if a while-stepping frame does not include all the
10576 same data that is collected at the tracepoint hit.
10577 @c This is getting pretty arcane, example would be good.
10579 @node save tracepoints
10580 @subsection @code{save tracepoints @var{filename}}
10581 @kindex save tracepoints
10582 @kindex save-tracepoints
10583 @cindex save tracepoints for future sessions
10585 This command saves all current tracepoint definitions together with
10586 their actions and passcounts, into a file @file{@var{filename}}
10587 suitable for use in a later debugging session. To read the saved
10588 tracepoint definitions, use the @code{source} command (@pxref{Command
10589 Files}). The @w{@code{save-tracepoints}} command is a deprecated
10590 alias for @w{@code{save tracepoints}}
10592 @node Tracepoint Variables
10593 @section Convenience Variables for Tracepoints
10594 @cindex tracepoint variables
10595 @cindex convenience variables for tracepoints
10598 @vindex $trace_frame
10599 @item (int) $trace_frame
10600 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
10601 snapshot is selected.
10603 @vindex $tracepoint
10604 @item (int) $tracepoint
10605 The tracepoint for the current trace snapshot.
10607 @vindex $trace_line
10608 @item (int) $trace_line
10609 The line number for the current trace snapshot.
10611 @vindex $trace_file
10612 @item (char []) $trace_file
10613 The source file for the current trace snapshot.
10615 @vindex $trace_func
10616 @item (char []) $trace_func
10617 The name of the function containing @code{$tracepoint}.
10620 Note: @code{$trace_file} is not suitable for use in @code{printf},
10621 use @code{output} instead.
10623 Here's a simple example of using these convenience variables for
10624 stepping through all the trace snapshots and printing some of their
10625 data. Note that these are not the same as trace state variables,
10626 which are managed by the target.
10629 (@value{GDBP}) @b{tfind start}
10631 (@value{GDBP}) @b{while $trace_frame != -1}
10632 > output $trace_file
10633 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
10639 @section Using Trace Files
10640 @cindex trace files
10642 In some situations, the target running a trace experiment may no
10643 longer be available; perhaps it crashed, or the hardware was needed
10644 for a different activity. To handle these cases, you can arrange to
10645 dump the trace data into a file, and later use that file as a source
10646 of trace data, via the @code{target tfile} command.
10651 @item tsave [ -r ] @var{filename}
10652 Save the trace data to @var{filename}. By default, this command
10653 assumes that @var{filename} refers to the host filesystem, so if
10654 necessary @value{GDBN} will copy raw trace data up from the target and
10655 then save it. If the target supports it, you can also supply the
10656 optional argument @code{-r} (``remote'') to direct the target to save
10657 the data directly into @var{filename} in its own filesystem, which may be
10658 more efficient if the trace buffer is very large. (Note, however, that
10659 @code{target tfile} can only read from files accessible to the host.)
10661 @kindex target tfile
10663 @item target tfile @var{filename}
10664 Use the file named @var{filename} as a source of trace data. Commands
10665 that examine data work as they do with a live target, but it is not
10666 possible to run any new trace experiments. @code{tstatus} will report
10667 the state of the trace run at the moment the data was saved, as well
10668 as the current trace frame you are examining. @var{filename} must be
10669 on a filesystem accessible to the host.
10674 @chapter Debugging Programs That Use Overlays
10677 If your program is too large to fit completely in your target system's
10678 memory, you can sometimes use @dfn{overlays} to work around this
10679 problem. @value{GDBN} provides some support for debugging programs that
10683 * How Overlays Work:: A general explanation of overlays.
10684 * Overlay Commands:: Managing overlays in @value{GDBN}.
10685 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
10686 mapped by asking the inferior.
10687 * Overlay Sample Program:: A sample program using overlays.
10690 @node How Overlays Work
10691 @section How Overlays Work
10692 @cindex mapped overlays
10693 @cindex unmapped overlays
10694 @cindex load address, overlay's
10695 @cindex mapped address
10696 @cindex overlay area
10698 Suppose you have a computer whose instruction address space is only 64
10699 kilobytes long, but which has much more memory which can be accessed by
10700 other means: special instructions, segment registers, or memory
10701 management hardware, for example. Suppose further that you want to
10702 adapt a program which is larger than 64 kilobytes to run on this system.
10704 One solution is to identify modules of your program which are relatively
10705 independent, and need not call each other directly; call these modules
10706 @dfn{overlays}. Separate the overlays from the main program, and place
10707 their machine code in the larger memory. Place your main program in
10708 instruction memory, but leave at least enough space there to hold the
10709 largest overlay as well.
10711 Now, to call a function located in an overlay, you must first copy that
10712 overlay's machine code from the large memory into the space set aside
10713 for it in the instruction memory, and then jump to its entry point
10716 @c NB: In the below the mapped area's size is greater or equal to the
10717 @c size of all overlays. This is intentional to remind the developer
10718 @c that overlays don't necessarily need to be the same size.
10722 Data Instruction Larger
10723 Address Space Address Space Address Space
10724 +-----------+ +-----------+ +-----------+
10726 +-----------+ +-----------+ +-----------+<-- overlay 1
10727 | program | | main | .----| overlay 1 | load address
10728 | variables | | program | | +-----------+
10729 | and heap | | | | | |
10730 +-----------+ | | | +-----------+<-- overlay 2
10731 | | +-----------+ | | | load address
10732 +-----------+ | | | .-| overlay 2 |
10734 mapped --->+-----------+ | | +-----------+
10735 address | | | | | |
10736 | overlay | <-' | | |
10737 | area | <---' +-----------+<-- overlay 3
10738 | | <---. | | load address
10739 +-----------+ `--| overlay 3 |
10746 @anchor{A code overlay}A code overlay
10750 The diagram (@pxref{A code overlay}) shows a system with separate data
10751 and instruction address spaces. To map an overlay, the program copies
10752 its code from the larger address space to the instruction address space.
10753 Since the overlays shown here all use the same mapped address, only one
10754 may be mapped at a time. For a system with a single address space for
10755 data and instructions, the diagram would be similar, except that the
10756 program variables and heap would share an address space with the main
10757 program and the overlay area.
10759 An overlay loaded into instruction memory and ready for use is called a
10760 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
10761 instruction memory. An overlay not present (or only partially present)
10762 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
10763 is its address in the larger memory. The mapped address is also called
10764 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
10765 called the @dfn{load memory address}, or @dfn{LMA}.
10767 Unfortunately, overlays are not a completely transparent way to adapt a
10768 program to limited instruction memory. They introduce a new set of
10769 global constraints you must keep in mind as you design your program:
10774 Before calling or returning to a function in an overlay, your program
10775 must make sure that overlay is actually mapped. Otherwise, the call or
10776 return will transfer control to the right address, but in the wrong
10777 overlay, and your program will probably crash.
10780 If the process of mapping an overlay is expensive on your system, you
10781 will need to choose your overlays carefully to minimize their effect on
10782 your program's performance.
10785 The executable file you load onto your system must contain each
10786 overlay's instructions, appearing at the overlay's load address, not its
10787 mapped address. However, each overlay's instructions must be relocated
10788 and its symbols defined as if the overlay were at its mapped address.
10789 You can use GNU linker scripts to specify different load and relocation
10790 addresses for pieces of your program; see @ref{Overlay Description,,,
10791 ld.info, Using ld: the GNU linker}.
10794 The procedure for loading executable files onto your system must be able
10795 to load their contents into the larger address space as well as the
10796 instruction and data spaces.
10800 The overlay system described above is rather simple, and could be
10801 improved in many ways:
10806 If your system has suitable bank switch registers or memory management
10807 hardware, you could use those facilities to make an overlay's load area
10808 contents simply appear at their mapped address in instruction space.
10809 This would probably be faster than copying the overlay to its mapped
10810 area in the usual way.
10813 If your overlays are small enough, you could set aside more than one
10814 overlay area, and have more than one overlay mapped at a time.
10817 You can use overlays to manage data, as well as instructions. In
10818 general, data overlays are even less transparent to your design than
10819 code overlays: whereas code overlays only require care when you call or
10820 return to functions, data overlays require care every time you access
10821 the data. Also, if you change the contents of a data overlay, you
10822 must copy its contents back out to its load address before you can copy a
10823 different data overlay into the same mapped area.
10828 @node Overlay Commands
10829 @section Overlay Commands
10831 To use @value{GDBN}'s overlay support, each overlay in your program must
10832 correspond to a separate section of the executable file. The section's
10833 virtual memory address and load memory address must be the overlay's
10834 mapped and load addresses. Identifying overlays with sections allows
10835 @value{GDBN} to determine the appropriate address of a function or
10836 variable, depending on whether the overlay is mapped or not.
10838 @value{GDBN}'s overlay commands all start with the word @code{overlay};
10839 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
10844 Disable @value{GDBN}'s overlay support. When overlay support is
10845 disabled, @value{GDBN} assumes that all functions and variables are
10846 always present at their mapped addresses. By default, @value{GDBN}'s
10847 overlay support is disabled.
10849 @item overlay manual
10850 @cindex manual overlay debugging
10851 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
10852 relies on you to tell it which overlays are mapped, and which are not,
10853 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
10854 commands described below.
10856 @item overlay map-overlay @var{overlay}
10857 @itemx overlay map @var{overlay}
10858 @cindex map an overlay
10859 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
10860 be the name of the object file section containing the overlay. When an
10861 overlay is mapped, @value{GDBN} assumes it can find the overlay's
10862 functions and variables at their mapped addresses. @value{GDBN} assumes
10863 that any other overlays whose mapped ranges overlap that of
10864 @var{overlay} are now unmapped.
10866 @item overlay unmap-overlay @var{overlay}
10867 @itemx overlay unmap @var{overlay}
10868 @cindex unmap an overlay
10869 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
10870 must be the name of the object file section containing the overlay.
10871 When an overlay is unmapped, @value{GDBN} assumes it can find the
10872 overlay's functions and variables at their load addresses.
10875 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
10876 consults a data structure the overlay manager maintains in the inferior
10877 to see which overlays are mapped. For details, see @ref{Automatic
10878 Overlay Debugging}.
10880 @item overlay load-target
10881 @itemx overlay load
10882 @cindex reloading the overlay table
10883 Re-read the overlay table from the inferior. Normally, @value{GDBN}
10884 re-reads the table @value{GDBN} automatically each time the inferior
10885 stops, so this command should only be necessary if you have changed the
10886 overlay mapping yourself using @value{GDBN}. This command is only
10887 useful when using automatic overlay debugging.
10889 @item overlay list-overlays
10890 @itemx overlay list
10891 @cindex listing mapped overlays
10892 Display a list of the overlays currently mapped, along with their mapped
10893 addresses, load addresses, and sizes.
10897 Normally, when @value{GDBN} prints a code address, it includes the name
10898 of the function the address falls in:
10901 (@value{GDBP}) print main
10902 $3 = @{int ()@} 0x11a0 <main>
10905 When overlay debugging is enabled, @value{GDBN} recognizes code in
10906 unmapped overlays, and prints the names of unmapped functions with
10907 asterisks around them. For example, if @code{foo} is a function in an
10908 unmapped overlay, @value{GDBN} prints it this way:
10911 (@value{GDBP}) overlay list
10912 No sections are mapped.
10913 (@value{GDBP}) print foo
10914 $5 = @{int (int)@} 0x100000 <*foo*>
10917 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
10921 (@value{GDBP}) overlay list
10922 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
10923 mapped at 0x1016 - 0x104a
10924 (@value{GDBP}) print foo
10925 $6 = @{int (int)@} 0x1016 <foo>
10928 When overlay debugging is enabled, @value{GDBN} can find the correct
10929 address for functions and variables in an overlay, whether or not the
10930 overlay is mapped. This allows most @value{GDBN} commands, like
10931 @code{break} and @code{disassemble}, to work normally, even on unmapped
10932 code. However, @value{GDBN}'s breakpoint support has some limitations:
10936 @cindex breakpoints in overlays
10937 @cindex overlays, setting breakpoints in
10938 You can set breakpoints in functions in unmapped overlays, as long as
10939 @value{GDBN} can write to the overlay at its load address.
10941 @value{GDBN} can not set hardware or simulator-based breakpoints in
10942 unmapped overlays. However, if you set a breakpoint at the end of your
10943 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
10944 you are using manual overlay management), @value{GDBN} will re-set its
10945 breakpoints properly.
10949 @node Automatic Overlay Debugging
10950 @section Automatic Overlay Debugging
10951 @cindex automatic overlay debugging
10953 @value{GDBN} can automatically track which overlays are mapped and which
10954 are not, given some simple co-operation from the overlay manager in the
10955 inferior. If you enable automatic overlay debugging with the
10956 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
10957 looks in the inferior's memory for certain variables describing the
10958 current state of the overlays.
10960 Here are the variables your overlay manager must define to support
10961 @value{GDBN}'s automatic overlay debugging:
10965 @item @code{_ovly_table}:
10966 This variable must be an array of the following structures:
10971 /* The overlay's mapped address. */
10974 /* The size of the overlay, in bytes. */
10975 unsigned long size;
10977 /* The overlay's load address. */
10980 /* Non-zero if the overlay is currently mapped;
10982 unsigned long mapped;
10986 @item @code{_novlys}:
10987 This variable must be a four-byte signed integer, holding the total
10988 number of elements in @code{_ovly_table}.
10992 To decide whether a particular overlay is mapped or not, @value{GDBN}
10993 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
10994 @code{lma} members equal the VMA and LMA of the overlay's section in the
10995 executable file. When @value{GDBN} finds a matching entry, it consults
10996 the entry's @code{mapped} member to determine whether the overlay is
10999 In addition, your overlay manager may define a function called
11000 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
11001 will silently set a breakpoint there. If the overlay manager then
11002 calls this function whenever it has changed the overlay table, this
11003 will enable @value{GDBN} to accurately keep track of which overlays
11004 are in program memory, and update any breakpoints that may be set
11005 in overlays. This will allow breakpoints to work even if the
11006 overlays are kept in ROM or other non-writable memory while they
11007 are not being executed.
11009 @node Overlay Sample Program
11010 @section Overlay Sample Program
11011 @cindex overlay example program
11013 When linking a program which uses overlays, you must place the overlays
11014 at their load addresses, while relocating them to run at their mapped
11015 addresses. To do this, you must write a linker script (@pxref{Overlay
11016 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
11017 since linker scripts are specific to a particular host system, target
11018 architecture, and target memory layout, this manual cannot provide
11019 portable sample code demonstrating @value{GDBN}'s overlay support.
11021 However, the @value{GDBN} source distribution does contain an overlaid
11022 program, with linker scripts for a few systems, as part of its test
11023 suite. The program consists of the following files from
11024 @file{gdb/testsuite/gdb.base}:
11028 The main program file.
11030 A simple overlay manager, used by @file{overlays.c}.
11035 Overlay modules, loaded and used by @file{overlays.c}.
11038 Linker scripts for linking the test program on the @code{d10v-elf}
11039 and @code{m32r-elf} targets.
11042 You can build the test program using the @code{d10v-elf} GCC
11043 cross-compiler like this:
11046 $ d10v-elf-gcc -g -c overlays.c
11047 $ d10v-elf-gcc -g -c ovlymgr.c
11048 $ d10v-elf-gcc -g -c foo.c
11049 $ d10v-elf-gcc -g -c bar.c
11050 $ d10v-elf-gcc -g -c baz.c
11051 $ d10v-elf-gcc -g -c grbx.c
11052 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
11053 baz.o grbx.o -Wl,-Td10v.ld -o overlays
11056 The build process is identical for any other architecture, except that
11057 you must substitute the appropriate compiler and linker script for the
11058 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
11062 @chapter Using @value{GDBN} with Different Languages
11065 Although programming languages generally have common aspects, they are
11066 rarely expressed in the same manner. For instance, in ANSI C,
11067 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
11068 Modula-2, it is accomplished by @code{p^}. Values can also be
11069 represented (and displayed) differently. Hex numbers in C appear as
11070 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
11072 @cindex working language
11073 Language-specific information is built into @value{GDBN} for some languages,
11074 allowing you to express operations like the above in your program's
11075 native language, and allowing @value{GDBN} to output values in a manner
11076 consistent with the syntax of your program's native language. The
11077 language you use to build expressions is called the @dfn{working
11081 * Setting:: Switching between source languages
11082 * Show:: Displaying the language
11083 * Checks:: Type and range checks
11084 * Supported Languages:: Supported languages
11085 * Unsupported Languages:: Unsupported languages
11089 @section Switching Between Source Languages
11091 There are two ways to control the working language---either have @value{GDBN}
11092 set it automatically, or select it manually yourself. You can use the
11093 @code{set language} command for either purpose. On startup, @value{GDBN}
11094 defaults to setting the language automatically. The working language is
11095 used to determine how expressions you type are interpreted, how values
11098 In addition to the working language, every source file that
11099 @value{GDBN} knows about has its own working language. For some object
11100 file formats, the compiler might indicate which language a particular
11101 source file is in. However, most of the time @value{GDBN} infers the
11102 language from the name of the file. The language of a source file
11103 controls whether C@t{++} names are demangled---this way @code{backtrace} can
11104 show each frame appropriately for its own language. There is no way to
11105 set the language of a source file from within @value{GDBN}, but you can
11106 set the language associated with a filename extension. @xref{Show, ,
11107 Displaying the Language}.
11109 This is most commonly a problem when you use a program, such
11110 as @code{cfront} or @code{f2c}, that generates C but is written in
11111 another language. In that case, make the
11112 program use @code{#line} directives in its C output; that way
11113 @value{GDBN} will know the correct language of the source code of the original
11114 program, and will display that source code, not the generated C code.
11117 * Filenames:: Filename extensions and languages.
11118 * Manually:: Setting the working language manually
11119 * Automatically:: Having @value{GDBN} infer the source language
11123 @subsection List of Filename Extensions and Languages
11125 If a source file name ends in one of the following extensions, then
11126 @value{GDBN} infers that its language is the one indicated.
11144 C@t{++} source file
11150 Objective-C source file
11154 Fortran source file
11157 Modula-2 source file
11161 Assembler source file. This actually behaves almost like C, but
11162 @value{GDBN} does not skip over function prologues when stepping.
11165 In addition, you may set the language associated with a filename
11166 extension. @xref{Show, , Displaying the Language}.
11169 @subsection Setting the Working Language
11171 If you allow @value{GDBN} to set the language automatically,
11172 expressions are interpreted the same way in your debugging session and
11175 @kindex set language
11176 If you wish, you may set the language manually. To do this, issue the
11177 command @samp{set language @var{lang}}, where @var{lang} is the name of
11178 a language, such as
11179 @code{c} or @code{modula-2}.
11180 For a list of the supported languages, type @samp{set language}.
11182 Setting the language manually prevents @value{GDBN} from updating the working
11183 language automatically. This can lead to confusion if you try
11184 to debug a program when the working language is not the same as the
11185 source language, when an expression is acceptable to both
11186 languages---but means different things. For instance, if the current
11187 source file were written in C, and @value{GDBN} was parsing Modula-2, a
11195 might not have the effect you intended. In C, this means to add
11196 @code{b} and @code{c} and place the result in @code{a}. The result
11197 printed would be the value of @code{a}. In Modula-2, this means to compare
11198 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
11200 @node Automatically
11201 @subsection Having @value{GDBN} Infer the Source Language
11203 To have @value{GDBN} set the working language automatically, use
11204 @samp{set language local} or @samp{set language auto}. @value{GDBN}
11205 then infers the working language. That is, when your program stops in a
11206 frame (usually by encountering a breakpoint), @value{GDBN} sets the
11207 working language to the language recorded for the function in that
11208 frame. If the language for a frame is unknown (that is, if the function
11209 or block corresponding to the frame was defined in a source file that
11210 does not have a recognized extension), the current working language is
11211 not changed, and @value{GDBN} issues a warning.
11213 This may not seem necessary for most programs, which are written
11214 entirely in one source language. However, program modules and libraries
11215 written in one source language can be used by a main program written in
11216 a different source language. Using @samp{set language auto} in this
11217 case frees you from having to set the working language manually.
11220 @section Displaying the Language
11222 The following commands help you find out which language is the
11223 working language, and also what language source files were written in.
11226 @item show language
11227 @kindex show language
11228 Display the current working language. This is the
11229 language you can use with commands such as @code{print} to
11230 build and compute expressions that may involve variables in your program.
11233 @kindex info frame@r{, show the source language}
11234 Display the source language for this frame. This language becomes the
11235 working language if you use an identifier from this frame.
11236 @xref{Frame Info, ,Information about a Frame}, to identify the other
11237 information listed here.
11240 @kindex info source@r{, show the source language}
11241 Display the source language of this source file.
11242 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
11243 information listed here.
11246 In unusual circumstances, you may have source files with extensions
11247 not in the standard list. You can then set the extension associated
11248 with a language explicitly:
11251 @item set extension-language @var{ext} @var{language}
11252 @kindex set extension-language
11253 Tell @value{GDBN} that source files with extension @var{ext} are to be
11254 assumed as written in the source language @var{language}.
11256 @item info extensions
11257 @kindex info extensions
11258 List all the filename extensions and the associated languages.
11262 @section Type and Range Checking
11265 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
11266 checking are included, but they do not yet have any effect. This
11267 section documents the intended facilities.
11269 @c FIXME remove warning when type/range code added
11271 Some languages are designed to guard you against making seemingly common
11272 errors through a series of compile- and run-time checks. These include
11273 checking the type of arguments to functions and operators, and making
11274 sure mathematical overflows are caught at run time. Checks such as
11275 these help to ensure a program's correctness once it has been compiled
11276 by eliminating type mismatches, and providing active checks for range
11277 errors when your program is running.
11279 @value{GDBN} can check for conditions like the above if you wish.
11280 Although @value{GDBN} does not check the statements in your program,
11281 it can check expressions entered directly into @value{GDBN} for
11282 evaluation via the @code{print} command, for example. As with the
11283 working language, @value{GDBN} can also decide whether or not to check
11284 automatically based on your program's source language.
11285 @xref{Supported Languages, ,Supported Languages}, for the default
11286 settings of supported languages.
11289 * Type Checking:: An overview of type checking
11290 * Range Checking:: An overview of range checking
11293 @cindex type checking
11294 @cindex checks, type
11295 @node Type Checking
11296 @subsection An Overview of Type Checking
11298 Some languages, such as Modula-2, are strongly typed, meaning that the
11299 arguments to operators and functions have to be of the correct type,
11300 otherwise an error occurs. These checks prevent type mismatch
11301 errors from ever causing any run-time problems. For example,
11309 The second example fails because the @code{CARDINAL} 1 is not
11310 type-compatible with the @code{REAL} 2.3.
11312 For the expressions you use in @value{GDBN} commands, you can tell the
11313 @value{GDBN} type checker to skip checking;
11314 to treat any mismatches as errors and abandon the expression;
11315 or to only issue warnings when type mismatches occur,
11316 but evaluate the expression anyway. When you choose the last of
11317 these, @value{GDBN} evaluates expressions like the second example above, but
11318 also issues a warning.
11320 Even if you turn type checking off, there may be other reasons
11321 related to type that prevent @value{GDBN} from evaluating an expression.
11322 For instance, @value{GDBN} does not know how to add an @code{int} and
11323 a @code{struct foo}. These particular type errors have nothing to do
11324 with the language in use, and usually arise from expressions, such as
11325 the one described above, which make little sense to evaluate anyway.
11327 Each language defines to what degree it is strict about type. For
11328 instance, both Modula-2 and C require the arguments to arithmetical
11329 operators to be numbers. In C, enumerated types and pointers can be
11330 represented as numbers, so that they are valid arguments to mathematical
11331 operators. @xref{Supported Languages, ,Supported Languages}, for further
11332 details on specific languages.
11334 @value{GDBN} provides some additional commands for controlling the type checker:
11336 @kindex set check type
11337 @kindex show check type
11339 @item set check type auto
11340 Set type checking on or off based on the current working language.
11341 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11344 @item set check type on
11345 @itemx set check type off
11346 Set type checking on or off, overriding the default setting for the
11347 current working language. Issue a warning if the setting does not
11348 match the language default. If any type mismatches occur in
11349 evaluating an expression while type checking is on, @value{GDBN} prints a
11350 message and aborts evaluation of the expression.
11352 @item set check type warn
11353 Cause the type checker to issue warnings, but to always attempt to
11354 evaluate the expression. Evaluating the expression may still
11355 be impossible for other reasons. For example, @value{GDBN} cannot add
11356 numbers and structures.
11359 Show the current setting of the type checker, and whether or not @value{GDBN}
11360 is setting it automatically.
11363 @cindex range checking
11364 @cindex checks, range
11365 @node Range Checking
11366 @subsection An Overview of Range Checking
11368 In some languages (such as Modula-2), it is an error to exceed the
11369 bounds of a type; this is enforced with run-time checks. Such range
11370 checking is meant to ensure program correctness by making sure
11371 computations do not overflow, or indices on an array element access do
11372 not exceed the bounds of the array.
11374 For expressions you use in @value{GDBN} commands, you can tell
11375 @value{GDBN} to treat range errors in one of three ways: ignore them,
11376 always treat them as errors and abandon the expression, or issue
11377 warnings but evaluate the expression anyway.
11379 A range error can result from numerical overflow, from exceeding an
11380 array index bound, or when you type a constant that is not a member
11381 of any type. Some languages, however, do not treat overflows as an
11382 error. In many implementations of C, mathematical overflow causes the
11383 result to ``wrap around'' to lower values---for example, if @var{m} is
11384 the largest integer value, and @var{s} is the smallest, then
11387 @var{m} + 1 @result{} @var{s}
11390 This, too, is specific to individual languages, and in some cases
11391 specific to individual compilers or machines. @xref{Supported Languages, ,
11392 Supported Languages}, for further details on specific languages.
11394 @value{GDBN} provides some additional commands for controlling the range checker:
11396 @kindex set check range
11397 @kindex show check range
11399 @item set check range auto
11400 Set range checking on or off based on the current working language.
11401 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11404 @item set check range on
11405 @itemx set check range off
11406 Set range checking on or off, overriding the default setting for the
11407 current working language. A warning is issued if the setting does not
11408 match the language default. If a range error occurs and range checking is on,
11409 then a message is printed and evaluation of the expression is aborted.
11411 @item set check range warn
11412 Output messages when the @value{GDBN} range checker detects a range error,
11413 but attempt to evaluate the expression anyway. Evaluating the
11414 expression may still be impossible for other reasons, such as accessing
11415 memory that the process does not own (a typical example from many Unix
11419 Show the current setting of the range checker, and whether or not it is
11420 being set automatically by @value{GDBN}.
11423 @node Supported Languages
11424 @section Supported Languages
11426 @value{GDBN} supports C, C@t{++}, D, Objective-C, Fortran, Java, Pascal,
11427 assembly, Modula-2, and Ada.
11428 @c This is false ...
11429 Some @value{GDBN} features may be used in expressions regardless of the
11430 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
11431 and the @samp{@{type@}addr} construct (@pxref{Expressions,
11432 ,Expressions}) can be used with the constructs of any supported
11435 The following sections detail to what degree each source language is
11436 supported by @value{GDBN}. These sections are not meant to be language
11437 tutorials or references, but serve only as a reference guide to what the
11438 @value{GDBN} expression parser accepts, and what input and output
11439 formats should look like for different languages. There are many good
11440 books written on each of these languages; please look to these for a
11441 language reference or tutorial.
11444 * C:: C and C@t{++}
11446 * Objective-C:: Objective-C
11447 * Fortran:: Fortran
11449 * Modula-2:: Modula-2
11454 @subsection C and C@t{++}
11456 @cindex C and C@t{++}
11457 @cindex expressions in C or C@t{++}
11459 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
11460 to both languages. Whenever this is the case, we discuss those languages
11464 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
11465 @cindex @sc{gnu} C@t{++}
11466 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
11467 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
11468 effectively, you must compile your C@t{++} programs with a supported
11469 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
11470 compiler (@code{aCC}).
11472 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
11473 format; if it doesn't work on your system, try the stabs+ debugging
11474 format. You can select those formats explicitly with the @code{g++}
11475 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
11476 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
11477 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
11480 * C Operators:: C and C@t{++} operators
11481 * C Constants:: C and C@t{++} constants
11482 * C Plus Plus Expressions:: C@t{++} expressions
11483 * C Defaults:: Default settings for C and C@t{++}
11484 * C Checks:: C and C@t{++} type and range checks
11485 * Debugging C:: @value{GDBN} and C
11486 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
11487 * Decimal Floating Point:: Numbers in Decimal Floating Point format
11491 @subsubsection C and C@t{++} Operators
11493 @cindex C and C@t{++} operators
11495 Operators must be defined on values of specific types. For instance,
11496 @code{+} is defined on numbers, but not on structures. Operators are
11497 often defined on groups of types.
11499 For the purposes of C and C@t{++}, the following definitions hold:
11504 @emph{Integral types} include @code{int} with any of its storage-class
11505 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
11508 @emph{Floating-point types} include @code{float}, @code{double}, and
11509 @code{long double} (if supported by the target platform).
11512 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
11515 @emph{Scalar types} include all of the above.
11520 The following operators are supported. They are listed here
11521 in order of increasing precedence:
11525 The comma or sequencing operator. Expressions in a comma-separated list
11526 are evaluated from left to right, with the result of the entire
11527 expression being the last expression evaluated.
11530 Assignment. The value of an assignment expression is the value
11531 assigned. Defined on scalar types.
11534 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
11535 and translated to @w{@code{@var{a} = @var{a op b}}}.
11536 @w{@code{@var{op}=}} and @code{=} have the same precedence.
11537 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
11538 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
11541 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
11542 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
11546 Logical @sc{or}. Defined on integral types.
11549 Logical @sc{and}. Defined on integral types.
11552 Bitwise @sc{or}. Defined on integral types.
11555 Bitwise exclusive-@sc{or}. Defined on integral types.
11558 Bitwise @sc{and}. Defined on integral types.
11561 Equality and inequality. Defined on scalar types. The value of these
11562 expressions is 0 for false and non-zero for true.
11564 @item <@r{, }>@r{, }<=@r{, }>=
11565 Less than, greater than, less than or equal, greater than or equal.
11566 Defined on scalar types. The value of these expressions is 0 for false
11567 and non-zero for true.
11570 left shift, and right shift. Defined on integral types.
11573 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
11576 Addition and subtraction. Defined on integral types, floating-point types and
11579 @item *@r{, }/@r{, }%
11580 Multiplication, division, and modulus. Multiplication and division are
11581 defined on integral and floating-point types. Modulus is defined on
11585 Increment and decrement. When appearing before a variable, the
11586 operation is performed before the variable is used in an expression;
11587 when appearing after it, the variable's value is used before the
11588 operation takes place.
11591 Pointer dereferencing. Defined on pointer types. Same precedence as
11595 Address operator. Defined on variables. Same precedence as @code{++}.
11597 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
11598 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
11599 to examine the address
11600 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
11604 Negative. Defined on integral and floating-point types. Same
11605 precedence as @code{++}.
11608 Logical negation. Defined on integral types. Same precedence as
11612 Bitwise complement operator. Defined on integral types. Same precedence as
11617 Structure member, and pointer-to-structure member. For convenience,
11618 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
11619 pointer based on the stored type information.
11620 Defined on @code{struct} and @code{union} data.
11623 Dereferences of pointers to members.
11626 Array indexing. @code{@var{a}[@var{i}]} is defined as
11627 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
11630 Function parameter list. Same precedence as @code{->}.
11633 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
11634 and @code{class} types.
11637 Doubled colons also represent the @value{GDBN} scope operator
11638 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
11642 If an operator is redefined in the user code, @value{GDBN} usually
11643 attempts to invoke the redefined version instead of using the operator's
11644 predefined meaning.
11647 @subsubsection C and C@t{++} Constants
11649 @cindex C and C@t{++} constants
11651 @value{GDBN} allows you to express the constants of C and C@t{++} in the
11656 Integer constants are a sequence of digits. Octal constants are
11657 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
11658 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
11659 @samp{l}, specifying that the constant should be treated as a
11663 Floating point constants are a sequence of digits, followed by a decimal
11664 point, followed by a sequence of digits, and optionally followed by an
11665 exponent. An exponent is of the form:
11666 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
11667 sequence of digits. The @samp{+} is optional for positive exponents.
11668 A floating-point constant may also end with a letter @samp{f} or
11669 @samp{F}, specifying that the constant should be treated as being of
11670 the @code{float} (as opposed to the default @code{double}) type; or with
11671 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
11675 Enumerated constants consist of enumerated identifiers, or their
11676 integral equivalents.
11679 Character constants are a single character surrounded by single quotes
11680 (@code{'}), or a number---the ordinal value of the corresponding character
11681 (usually its @sc{ascii} value). Within quotes, the single character may
11682 be represented by a letter or by @dfn{escape sequences}, which are of
11683 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
11684 of the character's ordinal value; or of the form @samp{\@var{x}}, where
11685 @samp{@var{x}} is a predefined special character---for example,
11686 @samp{\n} for newline.
11689 String constants are a sequence of character constants surrounded by
11690 double quotes (@code{"}). Any valid character constant (as described
11691 above) may appear. Double quotes within the string must be preceded by
11692 a backslash, so for instance @samp{"a\"b'c"} is a string of five
11696 Pointer constants are an integral value. You can also write pointers
11697 to constants using the C operator @samp{&}.
11700 Array constants are comma-separated lists surrounded by braces @samp{@{}
11701 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
11702 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
11703 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
11706 @node C Plus Plus Expressions
11707 @subsubsection C@t{++} Expressions
11709 @cindex expressions in C@t{++}
11710 @value{GDBN} expression handling can interpret most C@t{++} expressions.
11712 @cindex debugging C@t{++} programs
11713 @cindex C@t{++} compilers
11714 @cindex debug formats and C@t{++}
11715 @cindex @value{NGCC} and C@t{++}
11717 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
11718 proper compiler and the proper debug format. Currently, @value{GDBN}
11719 works best when debugging C@t{++} code that is compiled with
11720 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
11721 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
11722 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
11723 stabs+ as their default debug format, so you usually don't need to
11724 specify a debug format explicitly. Other compilers and/or debug formats
11725 are likely to work badly or not at all when using @value{GDBN} to debug
11731 @cindex member functions
11733 Member function calls are allowed; you can use expressions like
11736 count = aml->GetOriginal(x, y)
11739 @vindex this@r{, inside C@t{++} member functions}
11740 @cindex namespace in C@t{++}
11742 While a member function is active (in the selected stack frame), your
11743 expressions have the same namespace available as the member function;
11744 that is, @value{GDBN} allows implicit references to the class instance
11745 pointer @code{this} following the same rules as C@t{++}.
11747 @cindex call overloaded functions
11748 @cindex overloaded functions, calling
11749 @cindex type conversions in C@t{++}
11751 You can call overloaded functions; @value{GDBN} resolves the function
11752 call to the right definition, with some restrictions. @value{GDBN} does not
11753 perform overload resolution involving user-defined type conversions,
11754 calls to constructors, or instantiations of templates that do not exist
11755 in the program. It also cannot handle ellipsis argument lists or
11758 It does perform integral conversions and promotions, floating-point
11759 promotions, arithmetic conversions, pointer conversions, conversions of
11760 class objects to base classes, and standard conversions such as those of
11761 functions or arrays to pointers; it requires an exact match on the
11762 number of function arguments.
11764 Overload resolution is always performed, unless you have specified
11765 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
11766 ,@value{GDBN} Features for C@t{++}}.
11768 You must specify @code{set overload-resolution off} in order to use an
11769 explicit function signature to call an overloaded function, as in
11771 p 'foo(char,int)'('x', 13)
11774 The @value{GDBN} command-completion facility can simplify this;
11775 see @ref{Completion, ,Command Completion}.
11777 @cindex reference declarations
11779 @value{GDBN} understands variables declared as C@t{++} references; you can use
11780 them in expressions just as you do in C@t{++} source---they are automatically
11783 In the parameter list shown when @value{GDBN} displays a frame, the values of
11784 reference variables are not displayed (unlike other variables); this
11785 avoids clutter, since references are often used for large structures.
11786 The @emph{address} of a reference variable is always shown, unless
11787 you have specified @samp{set print address off}.
11790 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
11791 expressions can use it just as expressions in your program do. Since
11792 one scope may be defined in another, you can use @code{::} repeatedly if
11793 necessary, for example in an expression like
11794 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
11795 resolving name scope by reference to source files, in both C and C@t{++}
11796 debugging (@pxref{Variables, ,Program Variables}).
11799 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
11800 calling virtual functions correctly, printing out virtual bases of
11801 objects, calling functions in a base subobject, casting objects, and
11802 invoking user-defined operators.
11805 @subsubsection C and C@t{++} Defaults
11807 @cindex C and C@t{++} defaults
11809 If you allow @value{GDBN} to set type and range checking automatically, they
11810 both default to @code{off} whenever the working language changes to
11811 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
11812 selects the working language.
11814 If you allow @value{GDBN} to set the language automatically, it
11815 recognizes source files whose names end with @file{.c}, @file{.C}, or
11816 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
11817 these files, it sets the working language to C or C@t{++}.
11818 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
11819 for further details.
11821 @c Type checking is (a) primarily motivated by Modula-2, and (b)
11822 @c unimplemented. If (b) changes, it might make sense to let this node
11823 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
11826 @subsubsection C and C@t{++} Type and Range Checks
11828 @cindex C and C@t{++} checks
11830 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
11831 is not used. However, if you turn type checking on, @value{GDBN}
11832 considers two variables type equivalent if:
11836 The two variables are structured and have the same structure, union, or
11840 The two variables have the same type name, or types that have been
11841 declared equivalent through @code{typedef}.
11844 @c leaving this out because neither J Gilmore nor R Pesch understand it.
11847 The two @code{struct}, @code{union}, or @code{enum} variables are
11848 declared in the same declaration. (Note: this may not be true for all C
11853 Range checking, if turned on, is done on mathematical operations. Array
11854 indices are not checked, since they are often used to index a pointer
11855 that is not itself an array.
11858 @subsubsection @value{GDBN} and C
11860 The @code{set print union} and @code{show print union} commands apply to
11861 the @code{union} type. When set to @samp{on}, any @code{union} that is
11862 inside a @code{struct} or @code{class} is also printed. Otherwise, it
11863 appears as @samp{@{...@}}.
11865 The @code{@@} operator aids in the debugging of dynamic arrays, formed
11866 with pointers and a memory allocation function. @xref{Expressions,
11869 @node Debugging C Plus Plus
11870 @subsubsection @value{GDBN} Features for C@t{++}
11872 @cindex commands for C@t{++}
11874 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
11875 designed specifically for use with C@t{++}. Here is a summary:
11878 @cindex break in overloaded functions
11879 @item @r{breakpoint menus}
11880 When you want a breakpoint in a function whose name is overloaded,
11881 @value{GDBN} has the capability to display a menu of possible breakpoint
11882 locations to help you specify which function definition you want.
11883 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
11885 @cindex overloading in C@t{++}
11886 @item rbreak @var{regex}
11887 Setting breakpoints using regular expressions is helpful for setting
11888 breakpoints on overloaded functions that are not members of any special
11890 @xref{Set Breaks, ,Setting Breakpoints}.
11892 @cindex C@t{++} exception handling
11895 Debug C@t{++} exception handling using these commands. @xref{Set
11896 Catchpoints, , Setting Catchpoints}.
11898 @cindex inheritance
11899 @item ptype @var{typename}
11900 Print inheritance relationships as well as other information for type
11902 @xref{Symbols, ,Examining the Symbol Table}.
11904 @cindex C@t{++} symbol display
11905 @item set print demangle
11906 @itemx show print demangle
11907 @itemx set print asm-demangle
11908 @itemx show print asm-demangle
11909 Control whether C@t{++} symbols display in their source form, both when
11910 displaying code as C@t{++} source and when displaying disassemblies.
11911 @xref{Print Settings, ,Print Settings}.
11913 @item set print object
11914 @itemx show print object
11915 Choose whether to print derived (actual) or declared types of objects.
11916 @xref{Print Settings, ,Print Settings}.
11918 @item set print vtbl
11919 @itemx show print vtbl
11920 Control the format for printing virtual function tables.
11921 @xref{Print Settings, ,Print Settings}.
11922 (The @code{vtbl} commands do not work on programs compiled with the HP
11923 ANSI C@t{++} compiler (@code{aCC}).)
11925 @kindex set overload-resolution
11926 @cindex overloaded functions, overload resolution
11927 @item set overload-resolution on
11928 Enable overload resolution for C@t{++} expression evaluation. The default
11929 is on. For overloaded functions, @value{GDBN} evaluates the arguments
11930 and searches for a function whose signature matches the argument types,
11931 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
11932 Expressions, ,C@t{++} Expressions}, for details).
11933 If it cannot find a match, it emits a message.
11935 @item set overload-resolution off
11936 Disable overload resolution for C@t{++} expression evaluation. For
11937 overloaded functions that are not class member functions, @value{GDBN}
11938 chooses the first function of the specified name that it finds in the
11939 symbol table, whether or not its arguments are of the correct type. For
11940 overloaded functions that are class member functions, @value{GDBN}
11941 searches for a function whose signature @emph{exactly} matches the
11944 @kindex show overload-resolution
11945 @item show overload-resolution
11946 Show the current setting of overload resolution.
11948 @item @r{Overloaded symbol names}
11949 You can specify a particular definition of an overloaded symbol, using
11950 the same notation that is used to declare such symbols in C@t{++}: type
11951 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
11952 also use the @value{GDBN} command-line word completion facilities to list the
11953 available choices, or to finish the type list for you.
11954 @xref{Completion,, Command Completion}, for details on how to do this.
11957 @node Decimal Floating Point
11958 @subsubsection Decimal Floating Point format
11959 @cindex decimal floating point format
11961 @value{GDBN} can examine, set and perform computations with numbers in
11962 decimal floating point format, which in the C language correspond to the
11963 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
11964 specified by the extension to support decimal floating-point arithmetic.
11966 There are two encodings in use, depending on the architecture: BID (Binary
11967 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
11968 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
11971 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
11972 to manipulate decimal floating point numbers, it is not possible to convert
11973 (using a cast, for example) integers wider than 32-bit to decimal float.
11975 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
11976 point computations, error checking in decimal float operations ignores
11977 underflow, overflow and divide by zero exceptions.
11979 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
11980 to inspect @code{_Decimal128} values stored in floating point registers.
11981 See @ref{PowerPC,,PowerPC} for more details.
11987 @value{GDBN} can be used to debug programs written in D and compiled with
11988 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
11989 specific feature --- dynamic arrays.
11992 @subsection Objective-C
11994 @cindex Objective-C
11995 This section provides information about some commands and command
11996 options that are useful for debugging Objective-C code. See also
11997 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
11998 few more commands specific to Objective-C support.
12001 * Method Names in Commands::
12002 * The Print Command with Objective-C::
12005 @node Method Names in Commands
12006 @subsubsection Method Names in Commands
12008 The following commands have been extended to accept Objective-C method
12009 names as line specifications:
12011 @kindex clear@r{, and Objective-C}
12012 @kindex break@r{, and Objective-C}
12013 @kindex info line@r{, and Objective-C}
12014 @kindex jump@r{, and Objective-C}
12015 @kindex list@r{, and Objective-C}
12019 @item @code{info line}
12024 A fully qualified Objective-C method name is specified as
12027 -[@var{Class} @var{methodName}]
12030 where the minus sign is used to indicate an instance method and a
12031 plus sign (not shown) is used to indicate a class method. The class
12032 name @var{Class} and method name @var{methodName} are enclosed in
12033 brackets, similar to the way messages are specified in Objective-C
12034 source code. For example, to set a breakpoint at the @code{create}
12035 instance method of class @code{Fruit} in the program currently being
12039 break -[Fruit create]
12042 To list ten program lines around the @code{initialize} class method,
12046 list +[NSText initialize]
12049 In the current version of @value{GDBN}, the plus or minus sign is
12050 required. In future versions of @value{GDBN}, the plus or minus
12051 sign will be optional, but you can use it to narrow the search. It
12052 is also possible to specify just a method name:
12058 You must specify the complete method name, including any colons. If
12059 your program's source files contain more than one @code{create} method,
12060 you'll be presented with a numbered list of classes that implement that
12061 method. Indicate your choice by number, or type @samp{0} to exit if
12064 As another example, to clear a breakpoint established at the
12065 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
12068 clear -[NSWindow makeKeyAndOrderFront:]
12071 @node The Print Command with Objective-C
12072 @subsubsection The Print Command With Objective-C
12073 @cindex Objective-C, print objects
12074 @kindex print-object
12075 @kindex po @r{(@code{print-object})}
12077 The print command has also been extended to accept methods. For example:
12080 print -[@var{object} hash]
12083 @cindex print an Objective-C object description
12084 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
12086 will tell @value{GDBN} to send the @code{hash} message to @var{object}
12087 and print the result. Also, an additional command has been added,
12088 @code{print-object} or @code{po} for short, which is meant to print
12089 the description of an object. However, this command may only work
12090 with certain Objective-C libraries that have a particular hook
12091 function, @code{_NSPrintForDebugger}, defined.
12094 @subsection Fortran
12095 @cindex Fortran-specific support in @value{GDBN}
12097 @value{GDBN} can be used to debug programs written in Fortran, but it
12098 currently supports only the features of Fortran 77 language.
12100 @cindex trailing underscore, in Fortran symbols
12101 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
12102 among them) append an underscore to the names of variables and
12103 functions. When you debug programs compiled by those compilers, you
12104 will need to refer to variables and functions with a trailing
12108 * Fortran Operators:: Fortran operators and expressions
12109 * Fortran Defaults:: Default settings for Fortran
12110 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
12113 @node Fortran Operators
12114 @subsubsection Fortran Operators and Expressions
12116 @cindex Fortran operators and expressions
12118 Operators must be defined on values of specific types. For instance,
12119 @code{+} is defined on numbers, but not on characters or other non-
12120 arithmetic types. Operators are often defined on groups of types.
12124 The exponentiation operator. It raises the first operand to the power
12128 The range operator. Normally used in the form of array(low:high) to
12129 represent a section of array.
12132 The access component operator. Normally used to access elements in derived
12133 types. Also suitable for unions. As unions aren't part of regular Fortran,
12134 this can only happen when accessing a register that uses a gdbarch-defined
12138 @node Fortran Defaults
12139 @subsubsection Fortran Defaults
12141 @cindex Fortran Defaults
12143 Fortran symbols are usually case-insensitive, so @value{GDBN} by
12144 default uses case-insensitive matches for Fortran symbols. You can
12145 change that with the @samp{set case-insensitive} command, see
12146 @ref{Symbols}, for the details.
12148 @node Special Fortran Commands
12149 @subsubsection Special Fortran Commands
12151 @cindex Special Fortran commands
12153 @value{GDBN} has some commands to support Fortran-specific features,
12154 such as displaying common blocks.
12157 @cindex @code{COMMON} blocks, Fortran
12158 @kindex info common
12159 @item info common @r{[}@var{common-name}@r{]}
12160 This command prints the values contained in the Fortran @code{COMMON}
12161 block whose name is @var{common-name}. With no argument, the names of
12162 all @code{COMMON} blocks visible at the current program location are
12169 @cindex Pascal support in @value{GDBN}, limitations
12170 Debugging Pascal programs which use sets, subranges, file variables, or
12171 nested functions does not currently work. @value{GDBN} does not support
12172 entering expressions, printing values, or similar features using Pascal
12175 The Pascal-specific command @code{set print pascal_static-members}
12176 controls whether static members of Pascal objects are displayed.
12177 @xref{Print Settings, pascal_static-members}.
12180 @subsection Modula-2
12182 @cindex Modula-2, @value{GDBN} support
12184 The extensions made to @value{GDBN} to support Modula-2 only support
12185 output from the @sc{gnu} Modula-2 compiler (which is currently being
12186 developed). Other Modula-2 compilers are not currently supported, and
12187 attempting to debug executables produced by them is most likely
12188 to give an error as @value{GDBN} reads in the executable's symbol
12191 @cindex expressions in Modula-2
12193 * M2 Operators:: Built-in operators
12194 * Built-In Func/Proc:: Built-in functions and procedures
12195 * M2 Constants:: Modula-2 constants
12196 * M2 Types:: Modula-2 types
12197 * M2 Defaults:: Default settings for Modula-2
12198 * Deviations:: Deviations from standard Modula-2
12199 * M2 Checks:: Modula-2 type and range checks
12200 * M2 Scope:: The scope operators @code{::} and @code{.}
12201 * GDB/M2:: @value{GDBN} and Modula-2
12205 @subsubsection Operators
12206 @cindex Modula-2 operators
12208 Operators must be defined on values of specific types. For instance,
12209 @code{+} is defined on numbers, but not on structures. Operators are
12210 often defined on groups of types. For the purposes of Modula-2, the
12211 following definitions hold:
12216 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
12220 @emph{Character types} consist of @code{CHAR} and its subranges.
12223 @emph{Floating-point types} consist of @code{REAL}.
12226 @emph{Pointer types} consist of anything declared as @code{POINTER TO
12230 @emph{Scalar types} consist of all of the above.
12233 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
12236 @emph{Boolean types} consist of @code{BOOLEAN}.
12240 The following operators are supported, and appear in order of
12241 increasing precedence:
12245 Function argument or array index separator.
12248 Assignment. The value of @var{var} @code{:=} @var{value} is
12252 Less than, greater than on integral, floating-point, or enumerated
12256 Less than or equal to, greater than or equal to
12257 on integral, floating-point and enumerated types, or set inclusion on
12258 set types. Same precedence as @code{<}.
12260 @item =@r{, }<>@r{, }#
12261 Equality and two ways of expressing inequality, valid on scalar types.
12262 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
12263 available for inequality, since @code{#} conflicts with the script
12267 Set membership. Defined on set types and the types of their members.
12268 Same precedence as @code{<}.
12271 Boolean disjunction. Defined on boolean types.
12274 Boolean conjunction. Defined on boolean types.
12277 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12280 Addition and subtraction on integral and floating-point types, or union
12281 and difference on set types.
12284 Multiplication on integral and floating-point types, or set intersection
12288 Division on floating-point types, or symmetric set difference on set
12289 types. Same precedence as @code{*}.
12292 Integer division and remainder. Defined on integral types. Same
12293 precedence as @code{*}.
12296 Negative. Defined on @code{INTEGER} and @code{REAL} data.
12299 Pointer dereferencing. Defined on pointer types.
12302 Boolean negation. Defined on boolean types. Same precedence as
12306 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
12307 precedence as @code{^}.
12310 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
12313 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
12317 @value{GDBN} and Modula-2 scope operators.
12321 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
12322 treats the use of the operator @code{IN}, or the use of operators
12323 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
12324 @code{<=}, and @code{>=} on sets as an error.
12328 @node Built-In Func/Proc
12329 @subsubsection Built-in Functions and Procedures
12330 @cindex Modula-2 built-ins
12332 Modula-2 also makes available several built-in procedures and functions.
12333 In describing these, the following metavariables are used:
12338 represents an @code{ARRAY} variable.
12341 represents a @code{CHAR} constant or variable.
12344 represents a variable or constant of integral type.
12347 represents an identifier that belongs to a set. Generally used in the
12348 same function with the metavariable @var{s}. The type of @var{s} should
12349 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
12352 represents a variable or constant of integral or floating-point type.
12355 represents a variable or constant of floating-point type.
12361 represents a variable.
12364 represents a variable or constant of one of many types. See the
12365 explanation of the function for details.
12368 All Modula-2 built-in procedures also return a result, described below.
12372 Returns the absolute value of @var{n}.
12375 If @var{c} is a lower case letter, it returns its upper case
12376 equivalent, otherwise it returns its argument.
12379 Returns the character whose ordinal value is @var{i}.
12382 Decrements the value in the variable @var{v} by one. Returns the new value.
12384 @item DEC(@var{v},@var{i})
12385 Decrements the value in the variable @var{v} by @var{i}. Returns the
12388 @item EXCL(@var{m},@var{s})
12389 Removes the element @var{m} from the set @var{s}. Returns the new
12392 @item FLOAT(@var{i})
12393 Returns the floating point equivalent of the integer @var{i}.
12395 @item HIGH(@var{a})
12396 Returns the index of the last member of @var{a}.
12399 Increments the value in the variable @var{v} by one. Returns the new value.
12401 @item INC(@var{v},@var{i})
12402 Increments the value in the variable @var{v} by @var{i}. Returns the
12405 @item INCL(@var{m},@var{s})
12406 Adds the element @var{m} to the set @var{s} if it is not already
12407 there. Returns the new set.
12410 Returns the maximum value of the type @var{t}.
12413 Returns the minimum value of the type @var{t}.
12416 Returns boolean TRUE if @var{i} is an odd number.
12419 Returns the ordinal value of its argument. For example, the ordinal
12420 value of a character is its @sc{ascii} value (on machines supporting the
12421 @sc{ascii} character set). @var{x} must be of an ordered type, which include
12422 integral, character and enumerated types.
12424 @item SIZE(@var{x})
12425 Returns the size of its argument. @var{x} can be a variable or a type.
12427 @item TRUNC(@var{r})
12428 Returns the integral part of @var{r}.
12430 @item TSIZE(@var{x})
12431 Returns the size of its argument. @var{x} can be a variable or a type.
12433 @item VAL(@var{t},@var{i})
12434 Returns the member of the type @var{t} whose ordinal value is @var{i}.
12438 @emph{Warning:} Sets and their operations are not yet supported, so
12439 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
12443 @cindex Modula-2 constants
12445 @subsubsection Constants
12447 @value{GDBN} allows you to express the constants of Modula-2 in the following
12453 Integer constants are simply a sequence of digits. When used in an
12454 expression, a constant is interpreted to be type-compatible with the
12455 rest of the expression. Hexadecimal integers are specified by a
12456 trailing @samp{H}, and octal integers by a trailing @samp{B}.
12459 Floating point constants appear as a sequence of digits, followed by a
12460 decimal point and another sequence of digits. An optional exponent can
12461 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
12462 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
12463 digits of the floating point constant must be valid decimal (base 10)
12467 Character constants consist of a single character enclosed by a pair of
12468 like quotes, either single (@code{'}) or double (@code{"}). They may
12469 also be expressed by their ordinal value (their @sc{ascii} value, usually)
12470 followed by a @samp{C}.
12473 String constants consist of a sequence of characters enclosed by a
12474 pair of like quotes, either single (@code{'}) or double (@code{"}).
12475 Escape sequences in the style of C are also allowed. @xref{C
12476 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
12480 Enumerated constants consist of an enumerated identifier.
12483 Boolean constants consist of the identifiers @code{TRUE} and
12487 Pointer constants consist of integral values only.
12490 Set constants are not yet supported.
12494 @subsubsection Modula-2 Types
12495 @cindex Modula-2 types
12497 Currently @value{GDBN} can print the following data types in Modula-2
12498 syntax: array types, record types, set types, pointer types, procedure
12499 types, enumerated types, subrange types and base types. You can also
12500 print the contents of variables declared using these type.
12501 This section gives a number of simple source code examples together with
12502 sample @value{GDBN} sessions.
12504 The first example contains the following section of code:
12513 and you can request @value{GDBN} to interrogate the type and value of
12514 @code{r} and @code{s}.
12517 (@value{GDBP}) print s
12519 (@value{GDBP}) ptype s
12521 (@value{GDBP}) print r
12523 (@value{GDBP}) ptype r
12528 Likewise if your source code declares @code{s} as:
12532 s: SET ['A'..'Z'] ;
12536 then you may query the type of @code{s} by:
12539 (@value{GDBP}) ptype s
12540 type = SET ['A'..'Z']
12544 Note that at present you cannot interactively manipulate set
12545 expressions using the debugger.
12547 The following example shows how you might declare an array in Modula-2
12548 and how you can interact with @value{GDBN} to print its type and contents:
12552 s: ARRAY [-10..10] OF CHAR ;
12556 (@value{GDBP}) ptype s
12557 ARRAY [-10..10] OF CHAR
12560 Note that the array handling is not yet complete and although the type
12561 is printed correctly, expression handling still assumes that all
12562 arrays have a lower bound of zero and not @code{-10} as in the example
12565 Here are some more type related Modula-2 examples:
12569 colour = (blue, red, yellow, green) ;
12570 t = [blue..yellow] ;
12578 The @value{GDBN} interaction shows how you can query the data type
12579 and value of a variable.
12582 (@value{GDBP}) print s
12584 (@value{GDBP}) ptype t
12585 type = [blue..yellow]
12589 In this example a Modula-2 array is declared and its contents
12590 displayed. Observe that the contents are written in the same way as
12591 their @code{C} counterparts.
12595 s: ARRAY [1..5] OF CARDINAL ;
12601 (@value{GDBP}) print s
12602 $1 = @{1, 0, 0, 0, 0@}
12603 (@value{GDBP}) ptype s
12604 type = ARRAY [1..5] OF CARDINAL
12607 The Modula-2 language interface to @value{GDBN} also understands
12608 pointer types as shown in this example:
12612 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
12619 and you can request that @value{GDBN} describes the type of @code{s}.
12622 (@value{GDBP}) ptype s
12623 type = POINTER TO ARRAY [1..5] OF CARDINAL
12626 @value{GDBN} handles compound types as we can see in this example.
12627 Here we combine array types, record types, pointer types and subrange
12638 myarray = ARRAY myrange OF CARDINAL ;
12639 myrange = [-2..2] ;
12641 s: POINTER TO ARRAY myrange OF foo ;
12645 and you can ask @value{GDBN} to describe the type of @code{s} as shown
12649 (@value{GDBP}) ptype s
12650 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
12653 f3 : ARRAY [-2..2] OF CARDINAL;
12658 @subsubsection Modula-2 Defaults
12659 @cindex Modula-2 defaults
12661 If type and range checking are set automatically by @value{GDBN}, they
12662 both default to @code{on} whenever the working language changes to
12663 Modula-2. This happens regardless of whether you or @value{GDBN}
12664 selected the working language.
12666 If you allow @value{GDBN} to set the language automatically, then entering
12667 code compiled from a file whose name ends with @file{.mod} sets the
12668 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
12669 Infer the Source Language}, for further details.
12672 @subsubsection Deviations from Standard Modula-2
12673 @cindex Modula-2, deviations from
12675 A few changes have been made to make Modula-2 programs easier to debug.
12676 This is done primarily via loosening its type strictness:
12680 Unlike in standard Modula-2, pointer constants can be formed by
12681 integers. This allows you to modify pointer variables during
12682 debugging. (In standard Modula-2, the actual address contained in a
12683 pointer variable is hidden from you; it can only be modified
12684 through direct assignment to another pointer variable or expression that
12685 returned a pointer.)
12688 C escape sequences can be used in strings and characters to represent
12689 non-printable characters. @value{GDBN} prints out strings with these
12690 escape sequences embedded. Single non-printable characters are
12691 printed using the @samp{CHR(@var{nnn})} format.
12694 The assignment operator (@code{:=}) returns the value of its right-hand
12698 All built-in procedures both modify @emph{and} return their argument.
12702 @subsubsection Modula-2 Type and Range Checks
12703 @cindex Modula-2 checks
12706 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
12709 @c FIXME remove warning when type/range checks added
12711 @value{GDBN} considers two Modula-2 variables type equivalent if:
12715 They are of types that have been declared equivalent via a @code{TYPE
12716 @var{t1} = @var{t2}} statement
12719 They have been declared on the same line. (Note: This is true of the
12720 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
12723 As long as type checking is enabled, any attempt to combine variables
12724 whose types are not equivalent is an error.
12726 Range checking is done on all mathematical operations, assignment, array
12727 index bounds, and all built-in functions and procedures.
12730 @subsubsection The Scope Operators @code{::} and @code{.}
12732 @cindex @code{.}, Modula-2 scope operator
12733 @cindex colon, doubled as scope operator
12735 @vindex colon-colon@r{, in Modula-2}
12736 @c Info cannot handle :: but TeX can.
12739 @vindex ::@r{, in Modula-2}
12742 There are a few subtle differences between the Modula-2 scope operator
12743 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
12748 @var{module} . @var{id}
12749 @var{scope} :: @var{id}
12753 where @var{scope} is the name of a module or a procedure,
12754 @var{module} the name of a module, and @var{id} is any declared
12755 identifier within your program, except another module.
12757 Using the @code{::} operator makes @value{GDBN} search the scope
12758 specified by @var{scope} for the identifier @var{id}. If it is not
12759 found in the specified scope, then @value{GDBN} searches all scopes
12760 enclosing the one specified by @var{scope}.
12762 Using the @code{.} operator makes @value{GDBN} search the current scope for
12763 the identifier specified by @var{id} that was imported from the
12764 definition module specified by @var{module}. With this operator, it is
12765 an error if the identifier @var{id} was not imported from definition
12766 module @var{module}, or if @var{id} is not an identifier in
12770 @subsubsection @value{GDBN} and Modula-2
12772 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
12773 Five subcommands of @code{set print} and @code{show print} apply
12774 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
12775 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
12776 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
12777 analogue in Modula-2.
12779 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
12780 with any language, is not useful with Modula-2. Its
12781 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
12782 created in Modula-2 as they can in C or C@t{++}. However, because an
12783 address can be specified by an integral constant, the construct
12784 @samp{@{@var{type}@}@var{adrexp}} is still useful.
12786 @cindex @code{#} in Modula-2
12787 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
12788 interpreted as the beginning of a comment. Use @code{<>} instead.
12794 The extensions made to @value{GDBN} for Ada only support
12795 output from the @sc{gnu} Ada (GNAT) compiler.
12796 Other Ada compilers are not currently supported, and
12797 attempting to debug executables produced by them is most likely
12801 @cindex expressions in Ada
12803 * Ada Mode Intro:: General remarks on the Ada syntax
12804 and semantics supported by Ada mode
12806 * Omissions from Ada:: Restrictions on the Ada expression syntax.
12807 * Additions to Ada:: Extensions of the Ada expression syntax.
12808 * Stopping Before Main Program:: Debugging the program during elaboration.
12809 * Ada Tasks:: Listing and setting breakpoints in tasks.
12810 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
12811 * Ada Glitches:: Known peculiarities of Ada mode.
12814 @node Ada Mode Intro
12815 @subsubsection Introduction
12816 @cindex Ada mode, general
12818 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
12819 syntax, with some extensions.
12820 The philosophy behind the design of this subset is
12824 That @value{GDBN} should provide basic literals and access to operations for
12825 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
12826 leaving more sophisticated computations to subprograms written into the
12827 program (which therefore may be called from @value{GDBN}).
12830 That type safety and strict adherence to Ada language restrictions
12831 are not particularly important to the @value{GDBN} user.
12834 That brevity is important to the @value{GDBN} user.
12837 Thus, for brevity, the debugger acts as if all names declared in
12838 user-written packages are directly visible, even if they are not visible
12839 according to Ada rules, thus making it unnecessary to fully qualify most
12840 names with their packages, regardless of context. Where this causes
12841 ambiguity, @value{GDBN} asks the user's intent.
12843 The debugger will start in Ada mode if it detects an Ada main program.
12844 As for other languages, it will enter Ada mode when stopped in a program that
12845 was translated from an Ada source file.
12847 While in Ada mode, you may use `@t{--}' for comments. This is useful
12848 mostly for documenting command files. The standard @value{GDBN} comment
12849 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
12850 middle (to allow based literals).
12852 The debugger supports limited overloading. Given a subprogram call in which
12853 the function symbol has multiple definitions, it will use the number of
12854 actual parameters and some information about their types to attempt to narrow
12855 the set of definitions. It also makes very limited use of context, preferring
12856 procedures to functions in the context of the @code{call} command, and
12857 functions to procedures elsewhere.
12859 @node Omissions from Ada
12860 @subsubsection Omissions from Ada
12861 @cindex Ada, omissions from
12863 Here are the notable omissions from the subset:
12867 Only a subset of the attributes are supported:
12871 @t{'First}, @t{'Last}, and @t{'Length}
12872 on array objects (not on types and subtypes).
12875 @t{'Min} and @t{'Max}.
12878 @t{'Pos} and @t{'Val}.
12884 @t{'Range} on array objects (not subtypes), but only as the right
12885 operand of the membership (@code{in}) operator.
12888 @t{'Access}, @t{'Unchecked_Access}, and
12889 @t{'Unrestricted_Access} (a GNAT extension).
12897 @code{Characters.Latin_1} are not available and
12898 concatenation is not implemented. Thus, escape characters in strings are
12899 not currently available.
12902 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
12903 equality of representations. They will generally work correctly
12904 for strings and arrays whose elements have integer or enumeration types.
12905 They may not work correctly for arrays whose element
12906 types have user-defined equality, for arrays of real values
12907 (in particular, IEEE-conformant floating point, because of negative
12908 zeroes and NaNs), and for arrays whose elements contain unused bits with
12909 indeterminate values.
12912 The other component-by-component array operations (@code{and}, @code{or},
12913 @code{xor}, @code{not}, and relational tests other than equality)
12914 are not implemented.
12917 @cindex array aggregates (Ada)
12918 @cindex record aggregates (Ada)
12919 @cindex aggregates (Ada)
12920 There is limited support for array and record aggregates. They are
12921 permitted only on the right sides of assignments, as in these examples:
12924 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
12925 (@value{GDBP}) set An_Array := (1, others => 0)
12926 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
12927 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
12928 (@value{GDBP}) set A_Record := (1, "Peter", True);
12929 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
12933 discriminant's value by assigning an aggregate has an
12934 undefined effect if that discriminant is used within the record.
12935 However, you can first modify discriminants by directly assigning to
12936 them (which normally would not be allowed in Ada), and then performing an
12937 aggregate assignment. For example, given a variable @code{A_Rec}
12938 declared to have a type such as:
12941 type Rec (Len : Small_Integer := 0) is record
12943 Vals : IntArray (1 .. Len);
12947 you can assign a value with a different size of @code{Vals} with two
12951 (@value{GDBP}) set A_Rec.Len := 4
12952 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
12955 As this example also illustrates, @value{GDBN} is very loose about the usual
12956 rules concerning aggregates. You may leave out some of the
12957 components of an array or record aggregate (such as the @code{Len}
12958 component in the assignment to @code{A_Rec} above); they will retain their
12959 original values upon assignment. You may freely use dynamic values as
12960 indices in component associations. You may even use overlapping or
12961 redundant component associations, although which component values are
12962 assigned in such cases is not defined.
12965 Calls to dispatching subprograms are not implemented.
12968 The overloading algorithm is much more limited (i.e., less selective)
12969 than that of real Ada. It makes only limited use of the context in
12970 which a subexpression appears to resolve its meaning, and it is much
12971 looser in its rules for allowing type matches. As a result, some
12972 function calls will be ambiguous, and the user will be asked to choose
12973 the proper resolution.
12976 The @code{new} operator is not implemented.
12979 Entry calls are not implemented.
12982 Aside from printing, arithmetic operations on the native VAX floating-point
12983 formats are not supported.
12986 It is not possible to slice a packed array.
12989 The names @code{True} and @code{False}, when not part of a qualified name,
12990 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
12992 Should your program
12993 redefine these names in a package or procedure (at best a dubious practice),
12994 you will have to use fully qualified names to access their new definitions.
12997 @node Additions to Ada
12998 @subsubsection Additions to Ada
12999 @cindex Ada, deviations from
13001 As it does for other languages, @value{GDBN} makes certain generic
13002 extensions to Ada (@pxref{Expressions}):
13006 If the expression @var{E} is a variable residing in memory (typically
13007 a local variable or array element) and @var{N} is a positive integer,
13008 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
13009 @var{N}-1 adjacent variables following it in memory as an array. In
13010 Ada, this operator is generally not necessary, since its prime use is
13011 in displaying parts of an array, and slicing will usually do this in
13012 Ada. However, there are occasional uses when debugging programs in
13013 which certain debugging information has been optimized away.
13016 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
13017 appears in function or file @var{B}.'' When @var{B} is a file name,
13018 you must typically surround it in single quotes.
13021 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
13022 @var{type} that appears at address @var{addr}.''
13025 A name starting with @samp{$} is a convenience variable
13026 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
13029 In addition, @value{GDBN} provides a few other shortcuts and outright
13030 additions specific to Ada:
13034 The assignment statement is allowed as an expression, returning
13035 its right-hand operand as its value. Thus, you may enter
13038 (@value{GDBP}) set x := y + 3
13039 (@value{GDBP}) print A(tmp := y + 1)
13043 The semicolon is allowed as an ``operator,'' returning as its value
13044 the value of its right-hand operand.
13045 This allows, for example,
13046 complex conditional breaks:
13049 (@value{GDBP}) break f
13050 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
13054 Rather than use catenation and symbolic character names to introduce special
13055 characters into strings, one may instead use a special bracket notation,
13056 which is also used to print strings. A sequence of characters of the form
13057 @samp{["@var{XX}"]} within a string or character literal denotes the
13058 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
13059 sequence of characters @samp{["""]} also denotes a single quotation mark
13060 in strings. For example,
13062 "One line.["0a"]Next line.["0a"]"
13065 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
13069 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
13070 @t{'Max} is optional (and is ignored in any case). For example, it is valid
13074 (@value{GDBP}) print 'max(x, y)
13078 When printing arrays, @value{GDBN} uses positional notation when the
13079 array has a lower bound of 1, and uses a modified named notation otherwise.
13080 For example, a one-dimensional array of three integers with a lower bound
13081 of 3 might print as
13088 That is, in contrast to valid Ada, only the first component has a @code{=>}
13092 You may abbreviate attributes in expressions with any unique,
13093 multi-character subsequence of
13094 their names (an exact match gets preference).
13095 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
13096 in place of @t{a'length}.
13099 @cindex quoting Ada internal identifiers
13100 Since Ada is case-insensitive, the debugger normally maps identifiers you type
13101 to lower case. The GNAT compiler uses upper-case characters for
13102 some of its internal identifiers, which are normally of no interest to users.
13103 For the rare occasions when you actually have to look at them,
13104 enclose them in angle brackets to avoid the lower-case mapping.
13107 (@value{GDBP}) print <JMPBUF_SAVE>[0]
13111 Printing an object of class-wide type or dereferencing an
13112 access-to-class-wide value will display all the components of the object's
13113 specific type (as indicated by its run-time tag). Likewise, component
13114 selection on such a value will operate on the specific type of the
13119 @node Stopping Before Main Program
13120 @subsubsection Stopping at the Very Beginning
13122 @cindex breakpointing Ada elaboration code
13123 It is sometimes necessary to debug the program during elaboration, and
13124 before reaching the main procedure.
13125 As defined in the Ada Reference
13126 Manual, the elaboration code is invoked from a procedure called
13127 @code{adainit}. To run your program up to the beginning of
13128 elaboration, simply use the following two commands:
13129 @code{tbreak adainit} and @code{run}.
13132 @subsubsection Extensions for Ada Tasks
13133 @cindex Ada, tasking
13135 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
13136 @value{GDBN} provides the following task-related commands:
13141 This command shows a list of current Ada tasks, as in the following example:
13148 (@value{GDBP}) info tasks
13149 ID TID P-ID Pri State Name
13150 1 8088000 0 15 Child Activation Wait main_task
13151 2 80a4000 1 15 Accept Statement b
13152 3 809a800 1 15 Child Activation Wait a
13153 * 4 80ae800 3 15 Runnable c
13158 In this listing, the asterisk before the last task indicates it to be the
13159 task currently being inspected.
13163 Represents @value{GDBN}'s internal task number.
13169 The parent's task ID (@value{GDBN}'s internal task number).
13172 The base priority of the task.
13175 Current state of the task.
13179 The task has been created but has not been activated. It cannot be
13183 The task is not blocked for any reason known to Ada. (It may be waiting
13184 for a mutex, though.) It is conceptually "executing" in normal mode.
13187 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
13188 that were waiting on terminate alternatives have been awakened and have
13189 terminated themselves.
13191 @item Child Activation Wait
13192 The task is waiting for created tasks to complete activation.
13194 @item Accept Statement
13195 The task is waiting on an accept or selective wait statement.
13197 @item Waiting on entry call
13198 The task is waiting on an entry call.
13200 @item Async Select Wait
13201 The task is waiting to start the abortable part of an asynchronous
13205 The task is waiting on a select statement with only a delay
13208 @item Child Termination Wait
13209 The task is sleeping having completed a master within itself, and is
13210 waiting for the tasks dependent on that master to become terminated or
13211 waiting on a terminate Phase.
13213 @item Wait Child in Term Alt
13214 The task is sleeping waiting for tasks on terminate alternatives to
13215 finish terminating.
13217 @item Accepting RV with @var{taskno}
13218 The task is accepting a rendez-vous with the task @var{taskno}.
13222 Name of the task in the program.
13226 @kindex info task @var{taskno}
13227 @item info task @var{taskno}
13228 This command shows detailled informations on the specified task, as in
13229 the following example:
13234 (@value{GDBP}) info tasks
13235 ID TID P-ID Pri State Name
13236 1 8077880 0 15 Child Activation Wait main_task
13237 * 2 807c468 1 15 Runnable task_1
13238 (@value{GDBP}) info task 2
13239 Ada Task: 0x807c468
13242 Parent: 1 (main_task)
13248 @kindex task@r{ (Ada)}
13249 @cindex current Ada task ID
13250 This command prints the ID of the current task.
13256 (@value{GDBP}) info tasks
13257 ID TID P-ID Pri State Name
13258 1 8077870 0 15 Child Activation Wait main_task
13259 * 2 807c458 1 15 Runnable t
13260 (@value{GDBP}) task
13261 [Current task is 2]
13264 @item task @var{taskno}
13265 @cindex Ada task switching
13266 This command is like the @code{thread @var{threadno}}
13267 command (@pxref{Threads}). It switches the context of debugging
13268 from the current task to the given task.
13274 (@value{GDBP}) info tasks
13275 ID TID P-ID Pri State Name
13276 1 8077870 0 15 Child Activation Wait main_task
13277 * 2 807c458 1 15 Runnable t
13278 (@value{GDBP}) task 1
13279 [Switching to task 1]
13280 #0 0x8067726 in pthread_cond_wait ()
13282 #0 0x8067726 in pthread_cond_wait ()
13283 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
13284 #2 0x805cb63 in system.task_primitives.operations.sleep ()
13285 #3 0x806153e in system.tasking.stages.activate_tasks ()
13286 #4 0x804aacc in un () at un.adb:5
13289 @item break @var{linespec} task @var{taskno}
13290 @itemx break @var{linespec} task @var{taskno} if @dots{}
13291 @cindex breakpoints and tasks, in Ada
13292 @cindex task breakpoints, in Ada
13293 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
13294 These commands are like the @code{break @dots{} thread @dots{}}
13295 command (@pxref{Thread Stops}).
13296 @var{linespec} specifies source lines, as described
13297 in @ref{Specify Location}.
13299 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
13300 to specify that you only want @value{GDBN} to stop the program when a
13301 particular Ada task reaches this breakpoint. @var{taskno} is one of the
13302 numeric task identifiers assigned by @value{GDBN}, shown in the first
13303 column of the @samp{info tasks} display.
13305 If you do not specify @samp{task @var{taskno}} when you set a
13306 breakpoint, the breakpoint applies to @emph{all} tasks of your
13309 You can use the @code{task} qualifier on conditional breakpoints as
13310 well; in this case, place @samp{task @var{taskno}} before the
13311 breakpoint condition (before the @code{if}).
13319 (@value{GDBP}) info tasks
13320 ID TID P-ID Pri State Name
13321 1 140022020 0 15 Child Activation Wait main_task
13322 2 140045060 1 15 Accept/Select Wait t2
13323 3 140044840 1 15 Runnable t1
13324 * 4 140056040 1 15 Runnable t3
13325 (@value{GDBP}) b 15 task 2
13326 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
13327 (@value{GDBP}) cont
13332 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
13334 (@value{GDBP}) info tasks
13335 ID TID P-ID Pri State Name
13336 1 140022020 0 15 Child Activation Wait main_task
13337 * 2 140045060 1 15 Runnable t2
13338 3 140044840 1 15 Runnable t1
13339 4 140056040 1 15 Delay Sleep t3
13343 @node Ada Tasks and Core Files
13344 @subsubsection Tasking Support when Debugging Core Files
13345 @cindex Ada tasking and core file debugging
13347 When inspecting a core file, as opposed to debugging a live program,
13348 tasking support may be limited or even unavailable, depending on
13349 the platform being used.
13350 For instance, on x86-linux, the list of tasks is available, but task
13351 switching is not supported. On Tru64, however, task switching will work
13354 On certain platforms, including Tru64, the debugger needs to perform some
13355 memory writes in order to provide Ada tasking support. When inspecting
13356 a core file, this means that the core file must be opened with read-write
13357 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
13358 Under these circumstances, you should make a backup copy of the core
13359 file before inspecting it with @value{GDBN}.
13362 @subsubsection Known Peculiarities of Ada Mode
13363 @cindex Ada, problems
13365 Besides the omissions listed previously (@pxref{Omissions from Ada}),
13366 we know of several problems with and limitations of Ada mode in
13368 some of which will be fixed with planned future releases of the debugger
13369 and the GNU Ada compiler.
13373 Currently, the debugger
13374 has insufficient information to determine whether certain pointers represent
13375 pointers to objects or the objects themselves.
13376 Thus, the user may have to tack an extra @code{.all} after an expression
13377 to get it printed properly.
13380 Static constants that the compiler chooses not to materialize as objects in
13381 storage are invisible to the debugger.
13384 Named parameter associations in function argument lists are ignored (the
13385 argument lists are treated as positional).
13388 Many useful library packages are currently invisible to the debugger.
13391 Fixed-point arithmetic, conversions, input, and output is carried out using
13392 floating-point arithmetic, and may give results that only approximate those on
13396 The GNAT compiler never generates the prefix @code{Standard} for any of
13397 the standard symbols defined by the Ada language. @value{GDBN} knows about
13398 this: it will strip the prefix from names when you use it, and will never
13399 look for a name you have so qualified among local symbols, nor match against
13400 symbols in other packages or subprograms. If you have
13401 defined entities anywhere in your program other than parameters and
13402 local variables whose simple names match names in @code{Standard},
13403 GNAT's lack of qualification here can cause confusion. When this happens,
13404 you can usually resolve the confusion
13405 by qualifying the problematic names with package
13406 @code{Standard} explicitly.
13409 Older versions of the compiler sometimes generate erroneous debugging
13410 information, resulting in the debugger incorrectly printing the value
13411 of affected entities. In some cases, the debugger is able to work
13412 around an issue automatically. In other cases, the debugger is able
13413 to work around the issue, but the work-around has to be specifically
13416 @kindex set ada trust-PAD-over-XVS
13417 @kindex show ada trust-PAD-over-XVS
13420 @item set ada trust-PAD-over-XVS on
13421 Configure GDB to strictly follow the GNAT encoding when computing the
13422 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
13423 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
13424 a complete description of the encoding used by the GNAT compiler).
13425 This is the default.
13427 @item set ada trust-PAD-over-XVS off
13428 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
13429 sometimes prints the wrong value for certain entities, changing @code{ada
13430 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
13431 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
13432 @code{off}, but this incurs a slight performance penalty, so it is
13433 recommended to leave this setting to @code{on} unless necessary.
13437 @node Unsupported Languages
13438 @section Unsupported Languages
13440 @cindex unsupported languages
13441 @cindex minimal language
13442 In addition to the other fully-supported programming languages,
13443 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
13444 It does not represent a real programming language, but provides a set
13445 of capabilities close to what the C or assembly languages provide.
13446 This should allow most simple operations to be performed while debugging
13447 an application that uses a language currently not supported by @value{GDBN}.
13449 If the language is set to @code{auto}, @value{GDBN} will automatically
13450 select this language if the current frame corresponds to an unsupported
13454 @chapter Examining the Symbol Table
13456 The commands described in this chapter allow you to inquire about the
13457 symbols (names of variables, functions and types) defined in your
13458 program. This information is inherent in the text of your program and
13459 does not change as your program executes. @value{GDBN} finds it in your
13460 program's symbol table, in the file indicated when you started @value{GDBN}
13461 (@pxref{File Options, ,Choosing Files}), or by one of the
13462 file-management commands (@pxref{Files, ,Commands to Specify Files}).
13464 @cindex symbol names
13465 @cindex names of symbols
13466 @cindex quoting names
13467 Occasionally, you may need to refer to symbols that contain unusual
13468 characters, which @value{GDBN} ordinarily treats as word delimiters. The
13469 most frequent case is in referring to static variables in other
13470 source files (@pxref{Variables,,Program Variables}). File names
13471 are recorded in object files as debugging symbols, but @value{GDBN} would
13472 ordinarily parse a typical file name, like @file{foo.c}, as the three words
13473 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
13474 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
13481 looks up the value of @code{x} in the scope of the file @file{foo.c}.
13484 @cindex case-insensitive symbol names
13485 @cindex case sensitivity in symbol names
13486 @kindex set case-sensitive
13487 @item set case-sensitive on
13488 @itemx set case-sensitive off
13489 @itemx set case-sensitive auto
13490 Normally, when @value{GDBN} looks up symbols, it matches their names
13491 with case sensitivity determined by the current source language.
13492 Occasionally, you may wish to control that. The command @code{set
13493 case-sensitive} lets you do that by specifying @code{on} for
13494 case-sensitive matches or @code{off} for case-insensitive ones. If
13495 you specify @code{auto}, case sensitivity is reset to the default
13496 suitable for the source language. The default is case-sensitive
13497 matches for all languages except for Fortran, for which the default is
13498 case-insensitive matches.
13500 @kindex show case-sensitive
13501 @item show case-sensitive
13502 This command shows the current setting of case sensitivity for symbols
13505 @kindex info address
13506 @cindex address of a symbol
13507 @item info address @var{symbol}
13508 Describe where the data for @var{symbol} is stored. For a register
13509 variable, this says which register it is kept in. For a non-register
13510 local variable, this prints the stack-frame offset at which the variable
13513 Note the contrast with @samp{print &@var{symbol}}, which does not work
13514 at all for a register variable, and for a stack local variable prints
13515 the exact address of the current instantiation of the variable.
13517 @kindex info symbol
13518 @cindex symbol from address
13519 @cindex closest symbol and offset for an address
13520 @item info symbol @var{addr}
13521 Print the name of a symbol which is stored at the address @var{addr}.
13522 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
13523 nearest symbol and an offset from it:
13526 (@value{GDBP}) info symbol 0x54320
13527 _initialize_vx + 396 in section .text
13531 This is the opposite of the @code{info address} command. You can use
13532 it to find out the name of a variable or a function given its address.
13534 For dynamically linked executables, the name of executable or shared
13535 library containing the symbol is also printed:
13538 (@value{GDBP}) info symbol 0x400225
13539 _start + 5 in section .text of /tmp/a.out
13540 (@value{GDBP}) info symbol 0x2aaaac2811cf
13541 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
13545 @item whatis [@var{arg}]
13546 Print the data type of @var{arg}, which can be either an expression or
13547 a data type. With no argument, print the data type of @code{$}, the
13548 last value in the value history. If @var{arg} is an expression, it is
13549 not actually evaluated, and any side-effecting operations (such as
13550 assignments or function calls) inside it do not take place. If
13551 @var{arg} is a type name, it may be the name of a type or typedef, or
13552 for C code it may have the form @samp{class @var{class-name}},
13553 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
13554 @samp{enum @var{enum-tag}}.
13555 @xref{Expressions, ,Expressions}.
13558 @item ptype [@var{arg}]
13559 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
13560 detailed description of the type, instead of just the name of the type.
13561 @xref{Expressions, ,Expressions}.
13563 For example, for this variable declaration:
13566 struct complex @{double real; double imag;@} v;
13570 the two commands give this output:
13574 (@value{GDBP}) whatis v
13575 type = struct complex
13576 (@value{GDBP}) ptype v
13577 type = struct complex @{
13585 As with @code{whatis}, using @code{ptype} without an argument refers to
13586 the type of @code{$}, the last value in the value history.
13588 @cindex incomplete type
13589 Sometimes, programs use opaque data types or incomplete specifications
13590 of complex data structure. If the debug information included in the
13591 program does not allow @value{GDBN} to display a full declaration of
13592 the data type, it will say @samp{<incomplete type>}. For example,
13593 given these declarations:
13597 struct foo *fooptr;
13601 but no definition for @code{struct foo} itself, @value{GDBN} will say:
13604 (@value{GDBP}) ptype foo
13605 $1 = <incomplete type>
13609 ``Incomplete type'' is C terminology for data types that are not
13610 completely specified.
13613 @item info types @var{regexp}
13615 Print a brief description of all types whose names match the regular
13616 expression @var{regexp} (or all types in your program, if you supply
13617 no argument). Each complete typename is matched as though it were a
13618 complete line; thus, @samp{i type value} gives information on all
13619 types in your program whose names include the string @code{value}, but
13620 @samp{i type ^value$} gives information only on types whose complete
13621 name is @code{value}.
13623 This command differs from @code{ptype} in two ways: first, like
13624 @code{whatis}, it does not print a detailed description; second, it
13625 lists all source files where a type is defined.
13628 @cindex local variables
13629 @item info scope @var{location}
13630 List all the variables local to a particular scope. This command
13631 accepts a @var{location} argument---a function name, a source line, or
13632 an address preceded by a @samp{*}, and prints all the variables local
13633 to the scope defined by that location. (@xref{Specify Location}, for
13634 details about supported forms of @var{location}.) For example:
13637 (@value{GDBP}) @b{info scope command_line_handler}
13638 Scope for command_line_handler:
13639 Symbol rl is an argument at stack/frame offset 8, length 4.
13640 Symbol linebuffer is in static storage at address 0x150a18, length 4.
13641 Symbol linelength is in static storage at address 0x150a1c, length 4.
13642 Symbol p is a local variable in register $esi, length 4.
13643 Symbol p1 is a local variable in register $ebx, length 4.
13644 Symbol nline is a local variable in register $edx, length 4.
13645 Symbol repeat is a local variable at frame offset -8, length 4.
13649 This command is especially useful for determining what data to collect
13650 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
13653 @kindex info source
13655 Show information about the current source file---that is, the source file for
13656 the function containing the current point of execution:
13659 the name of the source file, and the directory containing it,
13661 the directory it was compiled in,
13663 its length, in lines,
13665 which programming language it is written in,
13667 whether the executable includes debugging information for that file, and
13668 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
13670 whether the debugging information includes information about
13671 preprocessor macros.
13675 @kindex info sources
13677 Print the names of all source files in your program for which there is
13678 debugging information, organized into two lists: files whose symbols
13679 have already been read, and files whose symbols will be read when needed.
13681 @kindex info functions
13682 @item info functions
13683 Print the names and data types of all defined functions.
13685 @item info functions @var{regexp}
13686 Print the names and data types of all defined functions
13687 whose names contain a match for regular expression @var{regexp}.
13688 Thus, @samp{info fun step} finds all functions whose names
13689 include @code{step}; @samp{info fun ^step} finds those whose names
13690 start with @code{step}. If a function name contains characters
13691 that conflict with the regular expression language (e.g.@:
13692 @samp{operator*()}), they may be quoted with a backslash.
13694 @kindex info variables
13695 @item info variables
13696 Print the names and data types of all variables that are defined
13697 outside of functions (i.e.@: excluding local variables).
13699 @item info variables @var{regexp}
13700 Print the names and data types of all variables (except for local
13701 variables) whose names contain a match for regular expression
13704 @kindex info classes
13705 @cindex Objective-C, classes and selectors
13707 @itemx info classes @var{regexp}
13708 Display all Objective-C classes in your program, or
13709 (with the @var{regexp} argument) all those matching a particular regular
13712 @kindex info selectors
13713 @item info selectors
13714 @itemx info selectors @var{regexp}
13715 Display all Objective-C selectors in your program, or
13716 (with the @var{regexp} argument) all those matching a particular regular
13720 This was never implemented.
13721 @kindex info methods
13723 @itemx info methods @var{regexp}
13724 The @code{info methods} command permits the user to examine all defined
13725 methods within C@t{++} program, or (with the @var{regexp} argument) a
13726 specific set of methods found in the various C@t{++} classes. Many
13727 C@t{++} classes provide a large number of methods. Thus, the output
13728 from the @code{ptype} command can be overwhelming and hard to use. The
13729 @code{info-methods} command filters the methods, printing only those
13730 which match the regular-expression @var{regexp}.
13733 @cindex reloading symbols
13734 Some systems allow individual object files that make up your program to
13735 be replaced without stopping and restarting your program. For example,
13736 in VxWorks you can simply recompile a defective object file and keep on
13737 running. If you are running on one of these systems, you can allow
13738 @value{GDBN} to reload the symbols for automatically relinked modules:
13741 @kindex set symbol-reloading
13742 @item set symbol-reloading on
13743 Replace symbol definitions for the corresponding source file when an
13744 object file with a particular name is seen again.
13746 @item set symbol-reloading off
13747 Do not replace symbol definitions when encountering object files of the
13748 same name more than once. This is the default state; if you are not
13749 running on a system that permits automatic relinking of modules, you
13750 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
13751 may discard symbols when linking large programs, that may contain
13752 several modules (from different directories or libraries) with the same
13755 @kindex show symbol-reloading
13756 @item show symbol-reloading
13757 Show the current @code{on} or @code{off} setting.
13760 @cindex opaque data types
13761 @kindex set opaque-type-resolution
13762 @item set opaque-type-resolution on
13763 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
13764 declared as a pointer to a @code{struct}, @code{class}, or
13765 @code{union}---for example, @code{struct MyType *}---that is used in one
13766 source file although the full declaration of @code{struct MyType} is in
13767 another source file. The default is on.
13769 A change in the setting of this subcommand will not take effect until
13770 the next time symbols for a file are loaded.
13772 @item set opaque-type-resolution off
13773 Tell @value{GDBN} not to resolve opaque types. In this case, the type
13774 is printed as follows:
13776 @{<no data fields>@}
13779 @kindex show opaque-type-resolution
13780 @item show opaque-type-resolution
13781 Show whether opaque types are resolved or not.
13783 @kindex maint print symbols
13784 @cindex symbol dump
13785 @kindex maint print psymbols
13786 @cindex partial symbol dump
13787 @item maint print symbols @var{filename}
13788 @itemx maint print psymbols @var{filename}
13789 @itemx maint print msymbols @var{filename}
13790 Write a dump of debugging symbol data into the file @var{filename}.
13791 These commands are used to debug the @value{GDBN} symbol-reading code. Only
13792 symbols with debugging data are included. If you use @samp{maint print
13793 symbols}, @value{GDBN} includes all the symbols for which it has already
13794 collected full details: that is, @var{filename} reflects symbols for
13795 only those files whose symbols @value{GDBN} has read. You can use the
13796 command @code{info sources} to find out which files these are. If you
13797 use @samp{maint print psymbols} instead, the dump shows information about
13798 symbols that @value{GDBN} only knows partially---that is, symbols defined in
13799 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
13800 @samp{maint print msymbols} dumps just the minimal symbol information
13801 required for each object file from which @value{GDBN} has read some symbols.
13802 @xref{Files, ,Commands to Specify Files}, for a discussion of how
13803 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
13805 @kindex maint info symtabs
13806 @kindex maint info psymtabs
13807 @cindex listing @value{GDBN}'s internal symbol tables
13808 @cindex symbol tables, listing @value{GDBN}'s internal
13809 @cindex full symbol tables, listing @value{GDBN}'s internal
13810 @cindex partial symbol tables, listing @value{GDBN}'s internal
13811 @item maint info symtabs @r{[} @var{regexp} @r{]}
13812 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
13814 List the @code{struct symtab} or @code{struct partial_symtab}
13815 structures whose names match @var{regexp}. If @var{regexp} is not
13816 given, list them all. The output includes expressions which you can
13817 copy into a @value{GDBN} debugging this one to examine a particular
13818 structure in more detail. For example:
13821 (@value{GDBP}) maint info psymtabs dwarf2read
13822 @{ objfile /home/gnu/build/gdb/gdb
13823 ((struct objfile *) 0x82e69d0)
13824 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
13825 ((struct partial_symtab *) 0x8474b10)
13828 text addresses 0x814d3c8 -- 0x8158074
13829 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
13830 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
13831 dependencies (none)
13834 (@value{GDBP}) maint info symtabs
13838 We see that there is one partial symbol table whose filename contains
13839 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
13840 and we see that @value{GDBN} has not read in any symtabs yet at all.
13841 If we set a breakpoint on a function, that will cause @value{GDBN} to
13842 read the symtab for the compilation unit containing that function:
13845 (@value{GDBP}) break dwarf2_psymtab_to_symtab
13846 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
13848 (@value{GDBP}) maint info symtabs
13849 @{ objfile /home/gnu/build/gdb/gdb
13850 ((struct objfile *) 0x82e69d0)
13851 @{ symtab /home/gnu/src/gdb/dwarf2read.c
13852 ((struct symtab *) 0x86c1f38)
13855 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
13856 linetable ((struct linetable *) 0x8370fa0)
13857 debugformat DWARF 2
13866 @chapter Altering Execution
13868 Once you think you have found an error in your program, you might want to
13869 find out for certain whether correcting the apparent error would lead to
13870 correct results in the rest of the run. You can find the answer by
13871 experiment, using the @value{GDBN} features for altering execution of the
13874 For example, you can store new values into variables or memory
13875 locations, give your program a signal, restart it at a different
13876 address, or even return prematurely from a function.
13879 * Assignment:: Assignment to variables
13880 * Jumping:: Continuing at a different address
13881 * Signaling:: Giving your program a signal
13882 * Returning:: Returning from a function
13883 * Calling:: Calling your program's functions
13884 * Patching:: Patching your program
13888 @section Assignment to Variables
13891 @cindex setting variables
13892 To alter the value of a variable, evaluate an assignment expression.
13893 @xref{Expressions, ,Expressions}. For example,
13900 stores the value 4 into the variable @code{x}, and then prints the
13901 value of the assignment expression (which is 4).
13902 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
13903 information on operators in supported languages.
13905 @kindex set variable
13906 @cindex variables, setting
13907 If you are not interested in seeing the value of the assignment, use the
13908 @code{set} command instead of the @code{print} command. @code{set} is
13909 really the same as @code{print} except that the expression's value is
13910 not printed and is not put in the value history (@pxref{Value History,
13911 ,Value History}). The expression is evaluated only for its effects.
13913 If the beginning of the argument string of the @code{set} command
13914 appears identical to a @code{set} subcommand, use the @code{set
13915 variable} command instead of just @code{set}. This command is identical
13916 to @code{set} except for its lack of subcommands. For example, if your
13917 program has a variable @code{width}, you get an error if you try to set
13918 a new value with just @samp{set width=13}, because @value{GDBN} has the
13919 command @code{set width}:
13922 (@value{GDBP}) whatis width
13924 (@value{GDBP}) p width
13926 (@value{GDBP}) set width=47
13927 Invalid syntax in expression.
13931 The invalid expression, of course, is @samp{=47}. In
13932 order to actually set the program's variable @code{width}, use
13935 (@value{GDBP}) set var width=47
13938 Because the @code{set} command has many subcommands that can conflict
13939 with the names of program variables, it is a good idea to use the
13940 @code{set variable} command instead of just @code{set}. For example, if
13941 your program has a variable @code{g}, you run into problems if you try
13942 to set a new value with just @samp{set g=4}, because @value{GDBN} has
13943 the command @code{set gnutarget}, abbreviated @code{set g}:
13947 (@value{GDBP}) whatis g
13951 (@value{GDBP}) set g=4
13955 The program being debugged has been started already.
13956 Start it from the beginning? (y or n) y
13957 Starting program: /home/smith/cc_progs/a.out
13958 "/home/smith/cc_progs/a.out": can't open to read symbols:
13959 Invalid bfd target.
13960 (@value{GDBP}) show g
13961 The current BFD target is "=4".
13966 The program variable @code{g} did not change, and you silently set the
13967 @code{gnutarget} to an invalid value. In order to set the variable
13971 (@value{GDBP}) set var g=4
13974 @value{GDBN} allows more implicit conversions in assignments than C; you can
13975 freely store an integer value into a pointer variable or vice versa,
13976 and you can convert any structure to any other structure that is the
13977 same length or shorter.
13978 @comment FIXME: how do structs align/pad in these conversions?
13979 @comment /doc@cygnus.com 18dec1990
13981 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
13982 construct to generate a value of specified type at a specified address
13983 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
13984 to memory location @code{0x83040} as an integer (which implies a certain size
13985 and representation in memory), and
13988 set @{int@}0x83040 = 4
13992 stores the value 4 into that memory location.
13995 @section Continuing at a Different Address
13997 Ordinarily, when you continue your program, you do so at the place where
13998 it stopped, with the @code{continue} command. You can instead continue at
13999 an address of your own choosing, with the following commands:
14003 @item jump @var{linespec}
14004 @itemx jump @var{location}
14005 Resume execution at line @var{linespec} or at address given by
14006 @var{location}. Execution stops again immediately if there is a
14007 breakpoint there. @xref{Specify Location}, for a description of the
14008 different forms of @var{linespec} and @var{location}. It is common
14009 practice to use the @code{tbreak} command in conjunction with
14010 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
14012 The @code{jump} command does not change the current stack frame, or
14013 the stack pointer, or the contents of any memory location or any
14014 register other than the program counter. If line @var{linespec} is in
14015 a different function from the one currently executing, the results may
14016 be bizarre if the two functions expect different patterns of arguments or
14017 of local variables. For this reason, the @code{jump} command requests
14018 confirmation if the specified line is not in the function currently
14019 executing. However, even bizarre results are predictable if you are
14020 well acquainted with the machine-language code of your program.
14023 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
14024 On many systems, you can get much the same effect as the @code{jump}
14025 command by storing a new value into the register @code{$pc}. The
14026 difference is that this does not start your program running; it only
14027 changes the address of where it @emph{will} run when you continue. For
14035 makes the next @code{continue} command or stepping command execute at
14036 address @code{0x485}, rather than at the address where your program stopped.
14037 @xref{Continuing and Stepping, ,Continuing and Stepping}.
14039 The most common occasion to use the @code{jump} command is to back
14040 up---perhaps with more breakpoints set---over a portion of a program
14041 that has already executed, in order to examine its execution in more
14046 @section Giving your Program a Signal
14047 @cindex deliver a signal to a program
14051 @item signal @var{signal}
14052 Resume execution where your program stopped, but immediately give it the
14053 signal @var{signal}. @var{signal} can be the name or the number of a
14054 signal. For example, on many systems @code{signal 2} and @code{signal
14055 SIGINT} are both ways of sending an interrupt signal.
14057 Alternatively, if @var{signal} is zero, continue execution without
14058 giving a signal. This is useful when your program stopped on account of
14059 a signal and would ordinary see the signal when resumed with the
14060 @code{continue} command; @samp{signal 0} causes it to resume without a
14063 @code{signal} does not repeat when you press @key{RET} a second time
14064 after executing the command.
14068 Invoking the @code{signal} command is not the same as invoking the
14069 @code{kill} utility from the shell. Sending a signal with @code{kill}
14070 causes @value{GDBN} to decide what to do with the signal depending on
14071 the signal handling tables (@pxref{Signals}). The @code{signal} command
14072 passes the signal directly to your program.
14076 @section Returning from a Function
14079 @cindex returning from a function
14082 @itemx return @var{expression}
14083 You can cancel execution of a function call with the @code{return}
14084 command. If you give an
14085 @var{expression} argument, its value is used as the function's return
14089 When you use @code{return}, @value{GDBN} discards the selected stack frame
14090 (and all frames within it). You can think of this as making the
14091 discarded frame return prematurely. If you wish to specify a value to
14092 be returned, give that value as the argument to @code{return}.
14094 This pops the selected stack frame (@pxref{Selection, ,Selecting a
14095 Frame}), and any other frames inside of it, leaving its caller as the
14096 innermost remaining frame. That frame becomes selected. The
14097 specified value is stored in the registers used for returning values
14100 The @code{return} command does not resume execution; it leaves the
14101 program stopped in the state that would exist if the function had just
14102 returned. In contrast, the @code{finish} command (@pxref{Continuing
14103 and Stepping, ,Continuing and Stepping}) resumes execution until the
14104 selected stack frame returns naturally.
14106 @value{GDBN} needs to know how the @var{expression} argument should be set for
14107 the inferior. The concrete registers assignment depends on the OS ABI and the
14108 type being returned by the selected stack frame. For example it is common for
14109 OS ABI to return floating point values in FPU registers while integer values in
14110 CPU registers. Still some ABIs return even floating point values in CPU
14111 registers. Larger integer widths (such as @code{long long int}) also have
14112 specific placement rules. @value{GDBN} already knows the OS ABI from its
14113 current target so it needs to find out also the type being returned to make the
14114 assignment into the right register(s).
14116 Normally, the selected stack frame has debug info. @value{GDBN} will always
14117 use the debug info instead of the implicit type of @var{expression} when the
14118 debug info is available. For example, if you type @kbd{return -1}, and the
14119 function in the current stack frame is declared to return a @code{long long
14120 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
14121 into a @code{long long int}:
14124 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
14126 (@value{GDBP}) return -1
14127 Make func return now? (y or n) y
14128 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
14129 43 printf ("result=%lld\n", func ());
14133 However, if the selected stack frame does not have a debug info, e.g., if the
14134 function was compiled without debug info, @value{GDBN} has to find out the type
14135 to return from user. Specifying a different type by mistake may set the value
14136 in different inferior registers than the caller code expects. For example,
14137 typing @kbd{return -1} with its implicit type @code{int} would set only a part
14138 of a @code{long long int} result for a debug info less function (on 32-bit
14139 architectures). Therefore the user is required to specify the return type by
14140 an appropriate cast explicitly:
14143 Breakpoint 2, 0x0040050b in func ()
14144 (@value{GDBP}) return -1
14145 Return value type not available for selected stack frame.
14146 Please use an explicit cast of the value to return.
14147 (@value{GDBP}) return (long long int) -1
14148 Make selected stack frame return now? (y or n) y
14149 #0 0x00400526 in main ()
14154 @section Calling Program Functions
14157 @cindex calling functions
14158 @cindex inferior functions, calling
14159 @item print @var{expr}
14160 Evaluate the expression @var{expr} and display the resulting value.
14161 @var{expr} may include calls to functions in the program being
14165 @item call @var{expr}
14166 Evaluate the expression @var{expr} without displaying @code{void}
14169 You can use this variant of the @code{print} command if you want to
14170 execute a function from your program that does not return anything
14171 (a.k.a.@: @dfn{a void function}), but without cluttering the output
14172 with @code{void} returned values that @value{GDBN} will otherwise
14173 print. If the result is not void, it is printed and saved in the
14177 It is possible for the function you call via the @code{print} or
14178 @code{call} command to generate a signal (e.g., if there's a bug in
14179 the function, or if you passed it incorrect arguments). What happens
14180 in that case is controlled by the @code{set unwindonsignal} command.
14182 Similarly, with a C@t{++} program it is possible for the function you
14183 call via the @code{print} or @code{call} command to generate an
14184 exception that is not handled due to the constraints of the dummy
14185 frame. In this case, any exception that is raised in the frame, but has
14186 an out-of-frame exception handler will not be found. GDB builds a
14187 dummy-frame for the inferior function call, and the unwinder cannot
14188 seek for exception handlers outside of this dummy-frame. What happens
14189 in that case is controlled by the
14190 @code{set unwind-on-terminating-exception} command.
14193 @item set unwindonsignal
14194 @kindex set unwindonsignal
14195 @cindex unwind stack in called functions
14196 @cindex call dummy stack unwinding
14197 Set unwinding of the stack if a signal is received while in a function
14198 that @value{GDBN} called in the program being debugged. If set to on,
14199 @value{GDBN} unwinds the stack it created for the call and restores
14200 the context to what it was before the call. If set to off (the
14201 default), @value{GDBN} stops in the frame where the signal was
14204 @item show unwindonsignal
14205 @kindex show unwindonsignal
14206 Show the current setting of stack unwinding in the functions called by
14209 @item set unwind-on-terminating-exception
14210 @kindex set unwind-on-terminating-exception
14211 @cindex unwind stack in called functions with unhandled exceptions
14212 @cindex call dummy stack unwinding on unhandled exception.
14213 Set unwinding of the stack if a C@t{++} exception is raised, but left
14214 unhandled while in a function that @value{GDBN} called in the program being
14215 debugged. If set to on (the default), @value{GDBN} unwinds the stack
14216 it created for the call and restores the context to what it was before
14217 the call. If set to off, @value{GDBN} the exception is delivered to
14218 the default C@t{++} exception handler and the inferior terminated.
14220 @item show unwind-on-terminating-exception
14221 @kindex show unwind-on-terminating-exception
14222 Show the current setting of stack unwinding in the functions called by
14227 @cindex weak alias functions
14228 Sometimes, a function you wish to call is actually a @dfn{weak alias}
14229 for another function. In such case, @value{GDBN} might not pick up
14230 the type information, including the types of the function arguments,
14231 which causes @value{GDBN} to call the inferior function incorrectly.
14232 As a result, the called function will function erroneously and may
14233 even crash. A solution to that is to use the name of the aliased
14237 @section Patching Programs
14239 @cindex patching binaries
14240 @cindex writing into executables
14241 @cindex writing into corefiles
14243 By default, @value{GDBN} opens the file containing your program's
14244 executable code (or the corefile) read-only. This prevents accidental
14245 alterations to machine code; but it also prevents you from intentionally
14246 patching your program's binary.
14248 If you'd like to be able to patch the binary, you can specify that
14249 explicitly with the @code{set write} command. For example, you might
14250 want to turn on internal debugging flags, or even to make emergency
14256 @itemx set write off
14257 If you specify @samp{set write on}, @value{GDBN} opens executable and
14258 core files for both reading and writing; if you specify @kbd{set write
14259 off} (the default), @value{GDBN} opens them read-only.
14261 If you have already loaded a file, you must load it again (using the
14262 @code{exec-file} or @code{core-file} command) after changing @code{set
14263 write}, for your new setting to take effect.
14267 Display whether executable files and core files are opened for writing
14268 as well as reading.
14272 @chapter @value{GDBN} Files
14274 @value{GDBN} needs to know the file name of the program to be debugged,
14275 both in order to read its symbol table and in order to start your
14276 program. To debug a core dump of a previous run, you must also tell
14277 @value{GDBN} the name of the core dump file.
14280 * Files:: Commands to specify files
14281 * Separate Debug Files:: Debugging information in separate files
14282 * Symbol Errors:: Errors reading symbol files
14283 * Data Files:: GDB data files
14287 @section Commands to Specify Files
14289 @cindex symbol table
14290 @cindex core dump file
14292 You may want to specify executable and core dump file names. The usual
14293 way to do this is at start-up time, using the arguments to
14294 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
14295 Out of @value{GDBN}}).
14297 Occasionally it is necessary to change to a different file during a
14298 @value{GDBN} session. Or you may run @value{GDBN} and forget to
14299 specify a file you want to use. Or you are debugging a remote target
14300 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
14301 Program}). In these situations the @value{GDBN} commands to specify
14302 new files are useful.
14305 @cindex executable file
14307 @item file @var{filename}
14308 Use @var{filename} as the program to be debugged. It is read for its
14309 symbols and for the contents of pure memory. It is also the program
14310 executed when you use the @code{run} command. If you do not specify a
14311 directory and the file is not found in the @value{GDBN} working directory,
14312 @value{GDBN} uses the environment variable @code{PATH} as a list of
14313 directories to search, just as the shell does when looking for a program
14314 to run. You can change the value of this variable, for both @value{GDBN}
14315 and your program, using the @code{path} command.
14317 @cindex unlinked object files
14318 @cindex patching object files
14319 You can load unlinked object @file{.o} files into @value{GDBN} using
14320 the @code{file} command. You will not be able to ``run'' an object
14321 file, but you can disassemble functions and inspect variables. Also,
14322 if the underlying BFD functionality supports it, you could use
14323 @kbd{gdb -write} to patch object files using this technique. Note
14324 that @value{GDBN} can neither interpret nor modify relocations in this
14325 case, so branches and some initialized variables will appear to go to
14326 the wrong place. But this feature is still handy from time to time.
14329 @code{file} with no argument makes @value{GDBN} discard any information it
14330 has on both executable file and the symbol table.
14333 @item exec-file @r{[} @var{filename} @r{]}
14334 Specify that the program to be run (but not the symbol table) is found
14335 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
14336 if necessary to locate your program. Omitting @var{filename} means to
14337 discard information on the executable file.
14339 @kindex symbol-file
14340 @item symbol-file @r{[} @var{filename} @r{]}
14341 Read symbol table information from file @var{filename}. @code{PATH} is
14342 searched when necessary. Use the @code{file} command to get both symbol
14343 table and program to run from the same file.
14345 @code{symbol-file} with no argument clears out @value{GDBN} information on your
14346 program's symbol table.
14348 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
14349 some breakpoints and auto-display expressions. This is because they may
14350 contain pointers to the internal data recording symbols and data types,
14351 which are part of the old symbol table data being discarded inside
14354 @code{symbol-file} does not repeat if you press @key{RET} again after
14357 When @value{GDBN} is configured for a particular environment, it
14358 understands debugging information in whatever format is the standard
14359 generated for that environment; you may use either a @sc{gnu} compiler, or
14360 other compilers that adhere to the local conventions.
14361 Best results are usually obtained from @sc{gnu} compilers; for example,
14362 using @code{@value{NGCC}} you can generate debugging information for
14365 For most kinds of object files, with the exception of old SVR3 systems
14366 using COFF, the @code{symbol-file} command does not normally read the
14367 symbol table in full right away. Instead, it scans the symbol table
14368 quickly to find which source files and which symbols are present. The
14369 details are read later, one source file at a time, as they are needed.
14371 The purpose of this two-stage reading strategy is to make @value{GDBN}
14372 start up faster. For the most part, it is invisible except for
14373 occasional pauses while the symbol table details for a particular source
14374 file are being read. (The @code{set verbose} command can turn these
14375 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
14376 Warnings and Messages}.)
14378 We have not implemented the two-stage strategy for COFF yet. When the
14379 symbol table is stored in COFF format, @code{symbol-file} reads the
14380 symbol table data in full right away. Note that ``stabs-in-COFF''
14381 still does the two-stage strategy, since the debug info is actually
14385 @cindex reading symbols immediately
14386 @cindex symbols, reading immediately
14387 @item symbol-file @r{[} -readnow @r{]} @var{filename}
14388 @itemx file @r{[} -readnow @r{]} @var{filename}
14389 You can override the @value{GDBN} two-stage strategy for reading symbol
14390 tables by using the @samp{-readnow} option with any of the commands that
14391 load symbol table information, if you want to be sure @value{GDBN} has the
14392 entire symbol table available.
14394 @c FIXME: for now no mention of directories, since this seems to be in
14395 @c flux. 13mar1992 status is that in theory GDB would look either in
14396 @c current dir or in same dir as myprog; but issues like competing
14397 @c GDB's, or clutter in system dirs, mean that in practice right now
14398 @c only current dir is used. FFish says maybe a special GDB hierarchy
14399 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
14403 @item core-file @r{[}@var{filename}@r{]}
14405 Specify the whereabouts of a core dump file to be used as the ``contents
14406 of memory''. Traditionally, core files contain only some parts of the
14407 address space of the process that generated them; @value{GDBN} can access the
14408 executable file itself for other parts.
14410 @code{core-file} with no argument specifies that no core file is
14413 Note that the core file is ignored when your program is actually running
14414 under @value{GDBN}. So, if you have been running your program and you
14415 wish to debug a core file instead, you must kill the subprocess in which
14416 the program is running. To do this, use the @code{kill} command
14417 (@pxref{Kill Process, ,Killing the Child Process}).
14419 @kindex add-symbol-file
14420 @cindex dynamic linking
14421 @item add-symbol-file @var{filename} @var{address}
14422 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
14423 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
14424 The @code{add-symbol-file} command reads additional symbol table
14425 information from the file @var{filename}. You would use this command
14426 when @var{filename} has been dynamically loaded (by some other means)
14427 into the program that is running. @var{address} should be the memory
14428 address at which the file has been loaded; @value{GDBN} cannot figure
14429 this out for itself. You can additionally specify an arbitrary number
14430 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
14431 section name and base address for that section. You can specify any
14432 @var{address} as an expression.
14434 The symbol table of the file @var{filename} is added to the symbol table
14435 originally read with the @code{symbol-file} command. You can use the
14436 @code{add-symbol-file} command any number of times; the new symbol data
14437 thus read keeps adding to the old. To discard all old symbol data
14438 instead, use the @code{symbol-file} command without any arguments.
14440 @cindex relocatable object files, reading symbols from
14441 @cindex object files, relocatable, reading symbols from
14442 @cindex reading symbols from relocatable object files
14443 @cindex symbols, reading from relocatable object files
14444 @cindex @file{.o} files, reading symbols from
14445 Although @var{filename} is typically a shared library file, an
14446 executable file, or some other object file which has been fully
14447 relocated for loading into a process, you can also load symbolic
14448 information from relocatable @file{.o} files, as long as:
14452 the file's symbolic information refers only to linker symbols defined in
14453 that file, not to symbols defined by other object files,
14455 every section the file's symbolic information refers to has actually
14456 been loaded into the inferior, as it appears in the file, and
14458 you can determine the address at which every section was loaded, and
14459 provide these to the @code{add-symbol-file} command.
14463 Some embedded operating systems, like Sun Chorus and VxWorks, can load
14464 relocatable files into an already running program; such systems
14465 typically make the requirements above easy to meet. However, it's
14466 important to recognize that many native systems use complex link
14467 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
14468 assembly, for example) that make the requirements difficult to meet. In
14469 general, one cannot assume that using @code{add-symbol-file} to read a
14470 relocatable object file's symbolic information will have the same effect
14471 as linking the relocatable object file into the program in the normal
14474 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
14476 @kindex add-symbol-file-from-memory
14477 @cindex @code{syscall DSO}
14478 @cindex load symbols from memory
14479 @item add-symbol-file-from-memory @var{address}
14480 Load symbols from the given @var{address} in a dynamically loaded
14481 object file whose image is mapped directly into the inferior's memory.
14482 For example, the Linux kernel maps a @code{syscall DSO} into each
14483 process's address space; this DSO provides kernel-specific code for
14484 some system calls. The argument can be any expression whose
14485 evaluation yields the address of the file's shared object file header.
14486 For this command to work, you must have used @code{symbol-file} or
14487 @code{exec-file} commands in advance.
14489 @kindex add-shared-symbol-files
14491 @item add-shared-symbol-files @var{library-file}
14492 @itemx assf @var{library-file}
14493 The @code{add-shared-symbol-files} command can currently be used only
14494 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
14495 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
14496 @value{GDBN} automatically looks for shared libraries, however if
14497 @value{GDBN} does not find yours, you can invoke
14498 @code{add-shared-symbol-files}. It takes one argument: the shared
14499 library's file name. @code{assf} is a shorthand alias for
14500 @code{add-shared-symbol-files}.
14503 @item section @var{section} @var{addr}
14504 The @code{section} command changes the base address of the named
14505 @var{section} of the exec file to @var{addr}. This can be used if the
14506 exec file does not contain section addresses, (such as in the
14507 @code{a.out} format), or when the addresses specified in the file
14508 itself are wrong. Each section must be changed separately. The
14509 @code{info files} command, described below, lists all the sections and
14513 @kindex info target
14516 @code{info files} and @code{info target} are synonymous; both print the
14517 current target (@pxref{Targets, ,Specifying a Debugging Target}),
14518 including the names of the executable and core dump files currently in
14519 use by @value{GDBN}, and the files from which symbols were loaded. The
14520 command @code{help target} lists all possible targets rather than
14523 @kindex maint info sections
14524 @item maint info sections
14525 Another command that can give you extra information about program sections
14526 is @code{maint info sections}. In addition to the section information
14527 displayed by @code{info files}, this command displays the flags and file
14528 offset of each section in the executable and core dump files. In addition,
14529 @code{maint info sections} provides the following command options (which
14530 may be arbitrarily combined):
14534 Display sections for all loaded object files, including shared libraries.
14535 @item @var{sections}
14536 Display info only for named @var{sections}.
14537 @item @var{section-flags}
14538 Display info only for sections for which @var{section-flags} are true.
14539 The section flags that @value{GDBN} currently knows about are:
14542 Section will have space allocated in the process when loaded.
14543 Set for all sections except those containing debug information.
14545 Section will be loaded from the file into the child process memory.
14546 Set for pre-initialized code and data, clear for @code{.bss} sections.
14548 Section needs to be relocated before loading.
14550 Section cannot be modified by the child process.
14552 Section contains executable code only.
14554 Section contains data only (no executable code).
14556 Section will reside in ROM.
14558 Section contains data for constructor/destructor lists.
14560 Section is not empty.
14562 An instruction to the linker to not output the section.
14563 @item COFF_SHARED_LIBRARY
14564 A notification to the linker that the section contains
14565 COFF shared library information.
14567 Section contains common symbols.
14570 @kindex set trust-readonly-sections
14571 @cindex read-only sections
14572 @item set trust-readonly-sections on
14573 Tell @value{GDBN} that readonly sections in your object file
14574 really are read-only (i.e.@: that their contents will not change).
14575 In that case, @value{GDBN} can fetch values from these sections
14576 out of the object file, rather than from the target program.
14577 For some targets (notably embedded ones), this can be a significant
14578 enhancement to debugging performance.
14580 The default is off.
14582 @item set trust-readonly-sections off
14583 Tell @value{GDBN} not to trust readonly sections. This means that
14584 the contents of the section might change while the program is running,
14585 and must therefore be fetched from the target when needed.
14587 @item show trust-readonly-sections
14588 Show the current setting of trusting readonly sections.
14591 All file-specifying commands allow both absolute and relative file names
14592 as arguments. @value{GDBN} always converts the file name to an absolute file
14593 name and remembers it that way.
14595 @cindex shared libraries
14596 @anchor{Shared Libraries}
14597 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
14598 and IBM RS/6000 AIX shared libraries.
14600 On MS-Windows @value{GDBN} must be linked with the Expat library to support
14601 shared libraries. @xref{Expat}.
14603 @value{GDBN} automatically loads symbol definitions from shared libraries
14604 when you use the @code{run} command, or when you examine a core file.
14605 (Before you issue the @code{run} command, @value{GDBN} does not understand
14606 references to a function in a shared library, however---unless you are
14607 debugging a core file).
14609 On HP-UX, if the program loads a library explicitly, @value{GDBN}
14610 automatically loads the symbols at the time of the @code{shl_load} call.
14612 @c FIXME: some @value{GDBN} release may permit some refs to undef
14613 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
14614 @c FIXME...lib; check this from time to time when updating manual
14616 There are times, however, when you may wish to not automatically load
14617 symbol definitions from shared libraries, such as when they are
14618 particularly large or there are many of them.
14620 To control the automatic loading of shared library symbols, use the
14624 @kindex set auto-solib-add
14625 @item set auto-solib-add @var{mode}
14626 If @var{mode} is @code{on}, symbols from all shared object libraries
14627 will be loaded automatically when the inferior begins execution, you
14628 attach to an independently started inferior, or when the dynamic linker
14629 informs @value{GDBN} that a new library has been loaded. If @var{mode}
14630 is @code{off}, symbols must be loaded manually, using the
14631 @code{sharedlibrary} command. The default value is @code{on}.
14633 @cindex memory used for symbol tables
14634 If your program uses lots of shared libraries with debug info that
14635 takes large amounts of memory, you can decrease the @value{GDBN}
14636 memory footprint by preventing it from automatically loading the
14637 symbols from shared libraries. To that end, type @kbd{set
14638 auto-solib-add off} before running the inferior, then load each
14639 library whose debug symbols you do need with @kbd{sharedlibrary
14640 @var{regexp}}, where @var{regexp} is a regular expression that matches
14641 the libraries whose symbols you want to be loaded.
14643 @kindex show auto-solib-add
14644 @item show auto-solib-add
14645 Display the current autoloading mode.
14648 @cindex load shared library
14649 To explicitly load shared library symbols, use the @code{sharedlibrary}
14653 @kindex info sharedlibrary
14655 @item info share @var{regex}
14656 @itemx info sharedlibrary @var{regex}
14657 Print the names of the shared libraries which are currently loaded
14658 that match @var{regex}. If @var{regex} is omitted then print
14659 all shared libraries that are loaded.
14661 @kindex sharedlibrary
14663 @item sharedlibrary @var{regex}
14664 @itemx share @var{regex}
14665 Load shared object library symbols for files matching a
14666 Unix regular expression.
14667 As with files loaded automatically, it only loads shared libraries
14668 required by your program for a core file or after typing @code{run}. If
14669 @var{regex} is omitted all shared libraries required by your program are
14672 @item nosharedlibrary
14673 @kindex nosharedlibrary
14674 @cindex unload symbols from shared libraries
14675 Unload all shared object library symbols. This discards all symbols
14676 that have been loaded from all shared libraries. Symbols from shared
14677 libraries that were loaded by explicit user requests are not
14681 Sometimes you may wish that @value{GDBN} stops and gives you control
14682 when any of shared library events happen. Use the @code{set
14683 stop-on-solib-events} command for this:
14686 @item set stop-on-solib-events
14687 @kindex set stop-on-solib-events
14688 This command controls whether @value{GDBN} should give you control
14689 when the dynamic linker notifies it about some shared library event.
14690 The most common event of interest is loading or unloading of a new
14693 @item show stop-on-solib-events
14694 @kindex show stop-on-solib-events
14695 Show whether @value{GDBN} stops and gives you control when shared
14696 library events happen.
14699 Shared libraries are also supported in many cross or remote debugging
14700 configurations. @value{GDBN} needs to have access to the target's libraries;
14701 this can be accomplished either by providing copies of the libraries
14702 on the host system, or by asking @value{GDBN} to automatically retrieve the
14703 libraries from the target. If copies of the target libraries are
14704 provided, they need to be the same as the target libraries, although the
14705 copies on the target can be stripped as long as the copies on the host are
14708 @cindex where to look for shared libraries
14709 For remote debugging, you need to tell @value{GDBN} where the target
14710 libraries are, so that it can load the correct copies---otherwise, it
14711 may try to load the host's libraries. @value{GDBN} has two variables
14712 to specify the search directories for target libraries.
14715 @cindex prefix for shared library file names
14716 @cindex system root, alternate
14717 @kindex set solib-absolute-prefix
14718 @kindex set sysroot
14719 @item set sysroot @var{path}
14720 Use @var{path} as the system root for the program being debugged. Any
14721 absolute shared library paths will be prefixed with @var{path}; many
14722 runtime loaders store the absolute paths to the shared library in the
14723 target program's memory. If you use @code{set sysroot} to find shared
14724 libraries, they need to be laid out in the same way that they are on
14725 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
14728 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
14729 retrieve the target libraries from the remote system. This is only
14730 supported when using a remote target that supports the @code{remote get}
14731 command (@pxref{File Transfer,,Sending files to a remote system}).
14732 The part of @var{path} following the initial @file{remote:}
14733 (if present) is used as system root prefix on the remote file system.
14734 @footnote{If you want to specify a local system root using a directory
14735 that happens to be named @file{remote:}, you need to use some equivalent
14736 variant of the name like @file{./remote:}.}
14738 For targets with an MS-DOS based filesystem, such as MS-Windows and
14739 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
14740 absolute file name with @var{path}. But first, on Unix hosts,
14741 @value{GDBN} converts all backslash directory separators into forward
14742 slashes, because the backslash is not a directory separator on Unix:
14745 c:\foo\bar.dll @result{} c:/foo/bar.dll
14748 Then, @value{GDBN} attempts prefixing the target file name with
14749 @var{path}, and looks for the resulting file name in the host file
14753 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
14756 If that does not find the shared library, @value{GDBN} tries removing
14757 the @samp{:} character from the drive spec, both for convenience, and,
14758 for the case of the host file system not supporting file names with
14762 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
14765 This makes it possible to have a system root that mirrors a target
14766 with more than one drive. E.g., you may want to setup your local
14767 copies of the target system shared libraries like so (note @samp{c} vs
14771 @file{/path/to/sysroot/c/sys/bin/foo.dll}
14772 @file{/path/to/sysroot/c/sys/bin/bar.dll}
14773 @file{/path/to/sysroot/z/sys/bin/bar.dll}
14777 and point the system root at @file{/path/to/sysroot}, so that
14778 @value{GDBN} can find the correct copies of both
14779 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
14781 If that still does not find the shared library, @value{GDBN} tries
14782 removing the whole drive spec from the target file name:
14785 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
14788 This last lookup makes it possible to not care about the drive name,
14789 if you don't want or need to.
14791 The @code{set solib-absolute-prefix} command is an alias for @code{set
14794 @cindex default system root
14795 @cindex @samp{--with-sysroot}
14796 You can set the default system root by using the configure-time
14797 @samp{--with-sysroot} option. If the system root is inside
14798 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
14799 @samp{--exec-prefix}), then the default system root will be updated
14800 automatically if the installed @value{GDBN} is moved to a new
14803 @kindex show sysroot
14805 Display the current shared library prefix.
14807 @kindex set solib-search-path
14808 @item set solib-search-path @var{path}
14809 If this variable is set, @var{path} is a colon-separated list of
14810 directories to search for shared libraries. @samp{solib-search-path}
14811 is used after @samp{sysroot} fails to locate the library, or if the
14812 path to the library is relative instead of absolute. If you want to
14813 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
14814 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
14815 finding your host's libraries. @samp{sysroot} is preferred; setting
14816 it to a nonexistent directory may interfere with automatic loading
14817 of shared library symbols.
14819 @kindex show solib-search-path
14820 @item show solib-search-path
14821 Display the current shared library search path.
14823 @cindex DOS file-name semantics of file names.
14824 @kindex set target-file-system-kind (unix|dos-based|auto)
14825 @kindex show target-file-system-kind
14826 @item set target-file-system-kind @var{kind}
14827 Set assumed file system kind for target reported file names.
14829 Shared library file names as reported by the target system may not
14830 make sense as is on the system @value{GDBN} is running on. For
14831 example, when remote debugging a target that has MS-DOS based file
14832 system semantics, from a Unix host, the target may be reporting to
14833 @value{GDBN} a list of loaded shared libraries with file names such as
14834 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
14835 drive letters, so the @samp{c:\} prefix is not normally understood as
14836 indicating an absolute file name, and neither is the backslash
14837 normally considered a directory separator character. In that case,
14838 the native file system would interpret this whole absolute file name
14839 as a relative file name with no directory components. This would make
14840 it impossible to point @value{GDBN} at a copy of the remote target's
14841 shared libraries on the host using @code{set sysroot}, and impractical
14842 with @code{set solib-search-path}. Setting
14843 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
14844 to interpret such file names similarly to how the target would, and to
14845 map them to file names valid on @value{GDBN}'s native file system
14846 semantics. The value of @var{kind} can be @code{"auto"}, in addition
14847 to one of the supported file system kinds. In that case, @value{GDBN}
14848 tries to determine the appropriate file system variant based on the
14849 current target's operating system (@pxref{ABI, ,Configuring the
14850 Current ABI}). The supported file system settings are:
14854 Instruct @value{GDBN} to assume the target file system is of Unix
14855 kind. Only file names starting the forward slash (@samp{/}) character
14856 are considered absolute, and the directory separator character is also
14860 Instruct @value{GDBN} to assume the target file system is DOS based.
14861 File names starting with either a forward slash, or a drive letter
14862 followed by a colon (e.g., @samp{c:}), are considered absolute, and
14863 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
14864 considered directory separators.
14867 Instruct @value{GDBN} to use the file system kind associated with the
14868 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
14869 This is the default.
14874 @node Separate Debug Files
14875 @section Debugging Information in Separate Files
14876 @cindex separate debugging information files
14877 @cindex debugging information in separate files
14878 @cindex @file{.debug} subdirectories
14879 @cindex debugging information directory, global
14880 @cindex global debugging information directory
14881 @cindex build ID, and separate debugging files
14882 @cindex @file{.build-id} directory
14884 @value{GDBN} allows you to put a program's debugging information in a
14885 file separate from the executable itself, in a way that allows
14886 @value{GDBN} to find and load the debugging information automatically.
14887 Since debugging information can be very large---sometimes larger
14888 than the executable code itself---some systems distribute debugging
14889 information for their executables in separate files, which users can
14890 install only when they need to debug a problem.
14892 @value{GDBN} supports two ways of specifying the separate debug info
14897 The executable contains a @dfn{debug link} that specifies the name of
14898 the separate debug info file. The separate debug file's name is
14899 usually @file{@var{executable}.debug}, where @var{executable} is the
14900 name of the corresponding executable file without leading directories
14901 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
14902 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
14903 checksum for the debug file, which @value{GDBN} uses to validate that
14904 the executable and the debug file came from the same build.
14907 The executable contains a @dfn{build ID}, a unique bit string that is
14908 also present in the corresponding debug info file. (This is supported
14909 only on some operating systems, notably those which use the ELF format
14910 for binary files and the @sc{gnu} Binutils.) For more details about
14911 this feature, see the description of the @option{--build-id}
14912 command-line option in @ref{Options, , Command Line Options, ld.info,
14913 The GNU Linker}. The debug info file's name is not specified
14914 explicitly by the build ID, but can be computed from the build ID, see
14918 Depending on the way the debug info file is specified, @value{GDBN}
14919 uses two different methods of looking for the debug file:
14923 For the ``debug link'' method, @value{GDBN} looks up the named file in
14924 the directory of the executable file, then in a subdirectory of that
14925 directory named @file{.debug}, and finally under the global debug
14926 directory, in a subdirectory whose name is identical to the leading
14927 directories of the executable's absolute file name.
14930 For the ``build ID'' method, @value{GDBN} looks in the
14931 @file{.build-id} subdirectory of the global debug directory for a file
14932 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
14933 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
14934 are the rest of the bit string. (Real build ID strings are 32 or more
14935 hex characters, not 10.)
14938 So, for example, suppose you ask @value{GDBN} to debug
14939 @file{/usr/bin/ls}, which has a debug link that specifies the
14940 file @file{ls.debug}, and a build ID whose value in hex is
14941 @code{abcdef1234}. If the global debug directory is
14942 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
14943 debug information files, in the indicated order:
14947 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
14949 @file{/usr/bin/ls.debug}
14951 @file{/usr/bin/.debug/ls.debug}
14953 @file{/usr/lib/debug/usr/bin/ls.debug}.
14956 You can set the global debugging info directory's name, and view the
14957 name @value{GDBN} is currently using.
14961 @kindex set debug-file-directory
14962 @item set debug-file-directory @var{directories}
14963 Set the directories which @value{GDBN} searches for separate debugging
14964 information files to @var{directory}. Multiple directory components can be set
14965 concatenating them by a directory separator.
14967 @kindex show debug-file-directory
14968 @item show debug-file-directory
14969 Show the directories @value{GDBN} searches for separate debugging
14974 @cindex @code{.gnu_debuglink} sections
14975 @cindex debug link sections
14976 A debug link is a special section of the executable file named
14977 @code{.gnu_debuglink}. The section must contain:
14981 A filename, with any leading directory components removed, followed by
14984 zero to three bytes of padding, as needed to reach the next four-byte
14985 boundary within the section, and
14987 a four-byte CRC checksum, stored in the same endianness used for the
14988 executable file itself. The checksum is computed on the debugging
14989 information file's full contents by the function given below, passing
14990 zero as the @var{crc} argument.
14993 Any executable file format can carry a debug link, as long as it can
14994 contain a section named @code{.gnu_debuglink} with the contents
14997 @cindex @code{.note.gnu.build-id} sections
14998 @cindex build ID sections
14999 The build ID is a special section in the executable file (and in other
15000 ELF binary files that @value{GDBN} may consider). This section is
15001 often named @code{.note.gnu.build-id}, but that name is not mandatory.
15002 It contains unique identification for the built files---the ID remains
15003 the same across multiple builds of the same build tree. The default
15004 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
15005 content for the build ID string. The same section with an identical
15006 value is present in the original built binary with symbols, in its
15007 stripped variant, and in the separate debugging information file.
15009 The debugging information file itself should be an ordinary
15010 executable, containing a full set of linker symbols, sections, and
15011 debugging information. The sections of the debugging information file
15012 should have the same names, addresses, and sizes as the original file,
15013 but they need not contain any data---much like a @code{.bss} section
15014 in an ordinary executable.
15016 The @sc{gnu} binary utilities (Binutils) package includes the
15017 @samp{objcopy} utility that can produce
15018 the separated executable / debugging information file pairs using the
15019 following commands:
15022 @kbd{objcopy --only-keep-debug foo foo.debug}
15027 These commands remove the debugging
15028 information from the executable file @file{foo} and place it in the file
15029 @file{foo.debug}. You can use the first, second or both methods to link the
15034 The debug link method needs the following additional command to also leave
15035 behind a debug link in @file{foo}:
15038 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
15041 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
15042 a version of the @code{strip} command such that the command @kbd{strip foo -f
15043 foo.debug} has the same functionality as the two @code{objcopy} commands and
15044 the @code{ln -s} command above, together.
15047 Build ID gets embedded into the main executable using @code{ld --build-id} or
15048 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
15049 compatibility fixes for debug files separation are present in @sc{gnu} binary
15050 utilities (Binutils) package since version 2.18.
15055 @cindex CRC algorithm definition
15056 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
15057 IEEE 802.3 using the polynomial:
15059 @c TexInfo requires naked braces for multi-digit exponents for Tex
15060 @c output, but this causes HTML output to barf. HTML has to be set using
15061 @c raw commands. So we end up having to specify this equation in 2
15066 <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>
15067 + <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
15073 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
15074 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
15078 The function is computed byte at a time, taking the least
15079 significant bit of each byte first. The initial pattern
15080 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
15081 the final result is inverted to ensure trailing zeros also affect the
15084 @emph{Note:} This is the same CRC polynomial as used in handling the
15085 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
15086 , @value{GDBN} Remote Serial Protocol}). However in the
15087 case of the Remote Serial Protocol, the CRC is computed @emph{most}
15088 significant bit first, and the result is not inverted, so trailing
15089 zeros have no effect on the CRC value.
15091 To complete the description, we show below the code of the function
15092 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
15093 initially supplied @code{crc} argument means that an initial call to
15094 this function passing in zero will start computing the CRC using
15097 @kindex gnu_debuglink_crc32
15100 gnu_debuglink_crc32 (unsigned long crc,
15101 unsigned char *buf, size_t len)
15103 static const unsigned long crc32_table[256] =
15105 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
15106 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
15107 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
15108 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
15109 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
15110 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
15111 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
15112 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
15113 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
15114 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
15115 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
15116 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
15117 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
15118 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
15119 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
15120 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
15121 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
15122 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
15123 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
15124 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
15125 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
15126 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
15127 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
15128 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
15129 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
15130 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
15131 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
15132 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
15133 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
15134 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
15135 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
15136 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
15137 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
15138 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
15139 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
15140 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
15141 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
15142 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
15143 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
15144 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
15145 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
15146 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
15147 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
15148 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
15149 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
15150 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
15151 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
15152 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
15153 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
15154 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
15155 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
15158 unsigned char *end;
15160 crc = ~crc & 0xffffffff;
15161 for (end = buf + len; buf < end; ++buf)
15162 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
15163 return ~crc & 0xffffffff;
15168 This computation does not apply to the ``build ID'' method.
15171 @node Symbol Errors
15172 @section Errors Reading Symbol Files
15174 While reading a symbol file, @value{GDBN} occasionally encounters problems,
15175 such as symbol types it does not recognize, or known bugs in compiler
15176 output. By default, @value{GDBN} does not notify you of such problems, since
15177 they are relatively common and primarily of interest to people
15178 debugging compilers. If you are interested in seeing information
15179 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
15180 only one message about each such type of problem, no matter how many
15181 times the problem occurs; or you can ask @value{GDBN} to print more messages,
15182 to see how many times the problems occur, with the @code{set
15183 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
15186 The messages currently printed, and their meanings, include:
15189 @item inner block not inside outer block in @var{symbol}
15191 The symbol information shows where symbol scopes begin and end
15192 (such as at the start of a function or a block of statements). This
15193 error indicates that an inner scope block is not fully contained
15194 in its outer scope blocks.
15196 @value{GDBN} circumvents the problem by treating the inner block as if it had
15197 the same scope as the outer block. In the error message, @var{symbol}
15198 may be shown as ``@code{(don't know)}'' if the outer block is not a
15201 @item block at @var{address} out of order
15203 The symbol information for symbol scope blocks should occur in
15204 order of increasing addresses. This error indicates that it does not
15207 @value{GDBN} does not circumvent this problem, and has trouble
15208 locating symbols in the source file whose symbols it is reading. (You
15209 can often determine what source file is affected by specifying
15210 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
15213 @item bad block start address patched
15215 The symbol information for a symbol scope block has a start address
15216 smaller than the address of the preceding source line. This is known
15217 to occur in the SunOS 4.1.1 (and earlier) C compiler.
15219 @value{GDBN} circumvents the problem by treating the symbol scope block as
15220 starting on the previous source line.
15222 @item bad string table offset in symbol @var{n}
15225 Symbol number @var{n} contains a pointer into the string table which is
15226 larger than the size of the string table.
15228 @value{GDBN} circumvents the problem by considering the symbol to have the
15229 name @code{foo}, which may cause other problems if many symbols end up
15232 @item unknown symbol type @code{0x@var{nn}}
15234 The symbol information contains new data types that @value{GDBN} does
15235 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
15236 uncomprehended information, in hexadecimal.
15238 @value{GDBN} circumvents the error by ignoring this symbol information.
15239 This usually allows you to debug your program, though certain symbols
15240 are not accessible. If you encounter such a problem and feel like
15241 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
15242 on @code{complain}, then go up to the function @code{read_dbx_symtab}
15243 and examine @code{*bufp} to see the symbol.
15245 @item stub type has NULL name
15247 @value{GDBN} could not find the full definition for a struct or class.
15249 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
15250 The symbol information for a C@t{++} member function is missing some
15251 information that recent versions of the compiler should have output for
15254 @item info mismatch between compiler and debugger
15256 @value{GDBN} could not parse a type specification output by the compiler.
15261 @section GDB Data Files
15263 @cindex prefix for data files
15264 @value{GDBN} will sometimes read an auxiliary data file. These files
15265 are kept in a directory known as the @dfn{data directory}.
15267 You can set the data directory's name, and view the name @value{GDBN}
15268 is currently using.
15271 @kindex set data-directory
15272 @item set data-directory @var{directory}
15273 Set the directory which @value{GDBN} searches for auxiliary data files
15274 to @var{directory}.
15276 @kindex show data-directory
15277 @item show data-directory
15278 Show the directory @value{GDBN} searches for auxiliary data files.
15281 @cindex default data directory
15282 @cindex @samp{--with-gdb-datadir}
15283 You can set the default data directory by using the configure-time
15284 @samp{--with-gdb-datadir} option. If the data directory is inside
15285 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15286 @samp{--exec-prefix}), then the default data directory will be updated
15287 automatically if the installed @value{GDBN} is moved to a new
15291 @chapter Specifying a Debugging Target
15293 @cindex debugging target
15294 A @dfn{target} is the execution environment occupied by your program.
15296 Often, @value{GDBN} runs in the same host environment as your program;
15297 in that case, the debugging target is specified as a side effect when
15298 you use the @code{file} or @code{core} commands. When you need more
15299 flexibility---for example, running @value{GDBN} on a physically separate
15300 host, or controlling a standalone system over a serial port or a
15301 realtime system over a TCP/IP connection---you can use the @code{target}
15302 command to specify one of the target types configured for @value{GDBN}
15303 (@pxref{Target Commands, ,Commands for Managing Targets}).
15305 @cindex target architecture
15306 It is possible to build @value{GDBN} for several different @dfn{target
15307 architectures}. When @value{GDBN} is built like that, you can choose
15308 one of the available architectures with the @kbd{set architecture}
15312 @kindex set architecture
15313 @kindex show architecture
15314 @item set architecture @var{arch}
15315 This command sets the current target architecture to @var{arch}. The
15316 value of @var{arch} can be @code{"auto"}, in addition to one of the
15317 supported architectures.
15319 @item show architecture
15320 Show the current target architecture.
15322 @item set processor
15324 @kindex set processor
15325 @kindex show processor
15326 These are alias commands for, respectively, @code{set architecture}
15327 and @code{show architecture}.
15331 * Active Targets:: Active targets
15332 * Target Commands:: Commands for managing targets
15333 * Byte Order:: Choosing target byte order
15336 @node Active Targets
15337 @section Active Targets
15339 @cindex stacking targets
15340 @cindex active targets
15341 @cindex multiple targets
15343 There are three classes of targets: processes, core files, and
15344 executable files. @value{GDBN} can work concurrently on up to three
15345 active targets, one in each class. This allows you to (for example)
15346 start a process and inspect its activity without abandoning your work on
15349 For example, if you execute @samp{gdb a.out}, then the executable file
15350 @code{a.out} is the only active target. If you designate a core file as
15351 well---presumably from a prior run that crashed and coredumped---then
15352 @value{GDBN} has two active targets and uses them in tandem, looking
15353 first in the corefile target, then in the executable file, to satisfy
15354 requests for memory addresses. (Typically, these two classes of target
15355 are complementary, since core files contain only a program's
15356 read-write memory---variables and so on---plus machine status, while
15357 executable files contain only the program text and initialized data.)
15359 When you type @code{run}, your executable file becomes an active process
15360 target as well. When a process target is active, all @value{GDBN}
15361 commands requesting memory addresses refer to that target; addresses in
15362 an active core file or executable file target are obscured while the
15363 process target is active.
15365 Use the @code{core-file} and @code{exec-file} commands to select a new
15366 core file or executable target (@pxref{Files, ,Commands to Specify
15367 Files}). To specify as a target a process that is already running, use
15368 the @code{attach} command (@pxref{Attach, ,Debugging an Already-running
15371 @node Target Commands
15372 @section Commands for Managing Targets
15375 @item target @var{type} @var{parameters}
15376 Connects the @value{GDBN} host environment to a target machine or
15377 process. A target is typically a protocol for talking to debugging
15378 facilities. You use the argument @var{type} to specify the type or
15379 protocol of the target machine.
15381 Further @var{parameters} are interpreted by the target protocol, but
15382 typically include things like device names or host names to connect
15383 with, process numbers, and baud rates.
15385 The @code{target} command does not repeat if you press @key{RET} again
15386 after executing the command.
15388 @kindex help target
15390 Displays the names of all targets available. To display targets
15391 currently selected, use either @code{info target} or @code{info files}
15392 (@pxref{Files, ,Commands to Specify Files}).
15394 @item help target @var{name}
15395 Describe a particular target, including any parameters necessary to
15398 @kindex set gnutarget
15399 @item set gnutarget @var{args}
15400 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
15401 knows whether it is reading an @dfn{executable},
15402 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
15403 with the @code{set gnutarget} command. Unlike most @code{target} commands,
15404 with @code{gnutarget} the @code{target} refers to a program, not a machine.
15407 @emph{Warning:} To specify a file format with @code{set gnutarget},
15408 you must know the actual BFD name.
15412 @xref{Files, , Commands to Specify Files}.
15414 @kindex show gnutarget
15415 @item show gnutarget
15416 Use the @code{show gnutarget} command to display what file format
15417 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
15418 @value{GDBN} will determine the file format for each file automatically,
15419 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
15422 @cindex common targets
15423 Here are some common targets (available, or not, depending on the GDB
15428 @item target exec @var{program}
15429 @cindex executable file target
15430 An executable file. @samp{target exec @var{program}} is the same as
15431 @samp{exec-file @var{program}}.
15433 @item target core @var{filename}
15434 @cindex core dump file target
15435 A core dump file. @samp{target core @var{filename}} is the same as
15436 @samp{core-file @var{filename}}.
15438 @item target remote @var{medium}
15439 @cindex remote target
15440 A remote system connected to @value{GDBN} via a serial line or network
15441 connection. This command tells @value{GDBN} to use its own remote
15442 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
15444 For example, if you have a board connected to @file{/dev/ttya} on the
15445 machine running @value{GDBN}, you could say:
15448 target remote /dev/ttya
15451 @code{target remote} supports the @code{load} command. This is only
15452 useful if you have some other way of getting the stub to the target
15453 system, and you can put it somewhere in memory where it won't get
15454 clobbered by the download.
15456 @item target sim @r{[}@var{simargs}@r{]} @dots{}
15457 @cindex built-in simulator target
15458 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
15466 works; however, you cannot assume that a specific memory map, device
15467 drivers, or even basic I/O is available, although some simulators do
15468 provide these. For info about any processor-specific simulator details,
15469 see the appropriate section in @ref{Embedded Processors, ,Embedded
15474 Some configurations may include these targets as well:
15478 @item target nrom @var{dev}
15479 @cindex NetROM ROM emulator target
15480 NetROM ROM emulator. This target only supports downloading.
15484 Different targets are available on different configurations of @value{GDBN};
15485 your configuration may have more or fewer targets.
15487 Many remote targets require you to download the executable's code once
15488 you've successfully established a connection. You may wish to control
15489 various aspects of this process.
15494 @kindex set hash@r{, for remote monitors}
15495 @cindex hash mark while downloading
15496 This command controls whether a hash mark @samp{#} is displayed while
15497 downloading a file to the remote monitor. If on, a hash mark is
15498 displayed after each S-record is successfully downloaded to the
15502 @kindex show hash@r{, for remote monitors}
15503 Show the current status of displaying the hash mark.
15505 @item set debug monitor
15506 @kindex set debug monitor
15507 @cindex display remote monitor communications
15508 Enable or disable display of communications messages between
15509 @value{GDBN} and the remote monitor.
15511 @item show debug monitor
15512 @kindex show debug monitor
15513 Show the current status of displaying communications between
15514 @value{GDBN} and the remote monitor.
15519 @kindex load @var{filename}
15520 @item load @var{filename}
15522 Depending on what remote debugging facilities are configured into
15523 @value{GDBN}, the @code{load} command may be available. Where it exists, it
15524 is meant to make @var{filename} (an executable) available for debugging
15525 on the remote system---by downloading, or dynamic linking, for example.
15526 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
15527 the @code{add-symbol-file} command.
15529 If your @value{GDBN} does not have a @code{load} command, attempting to
15530 execute it gets the error message ``@code{You can't do that when your
15531 target is @dots{}}''
15533 The file is loaded at whatever address is specified in the executable.
15534 For some object file formats, you can specify the load address when you
15535 link the program; for other formats, like a.out, the object file format
15536 specifies a fixed address.
15537 @c FIXME! This would be a good place for an xref to the GNU linker doc.
15539 Depending on the remote side capabilities, @value{GDBN} may be able to
15540 load programs into flash memory.
15542 @code{load} does not repeat if you press @key{RET} again after using it.
15546 @section Choosing Target Byte Order
15548 @cindex choosing target byte order
15549 @cindex target byte order
15551 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
15552 offer the ability to run either big-endian or little-endian byte
15553 orders. Usually the executable or symbol will include a bit to
15554 designate the endian-ness, and you will not need to worry about
15555 which to use. However, you may still find it useful to adjust
15556 @value{GDBN}'s idea of processor endian-ness manually.
15560 @item set endian big
15561 Instruct @value{GDBN} to assume the target is big-endian.
15563 @item set endian little
15564 Instruct @value{GDBN} to assume the target is little-endian.
15566 @item set endian auto
15567 Instruct @value{GDBN} to use the byte order associated with the
15571 Display @value{GDBN}'s current idea of the target byte order.
15575 Note that these commands merely adjust interpretation of symbolic
15576 data on the host, and that they have absolutely no effect on the
15580 @node Remote Debugging
15581 @chapter Debugging Remote Programs
15582 @cindex remote debugging
15584 If you are trying to debug a program running on a machine that cannot run
15585 @value{GDBN} in the usual way, it is often useful to use remote debugging.
15586 For example, you might use remote debugging on an operating system kernel,
15587 or on a small system which does not have a general purpose operating system
15588 powerful enough to run a full-featured debugger.
15590 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
15591 to make this work with particular debugging targets. In addition,
15592 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
15593 but not specific to any particular target system) which you can use if you
15594 write the remote stubs---the code that runs on the remote system to
15595 communicate with @value{GDBN}.
15597 Other remote targets may be available in your
15598 configuration of @value{GDBN}; use @code{help target} to list them.
15601 * Connecting:: Connecting to a remote target
15602 * File Transfer:: Sending files to a remote system
15603 * Server:: Using the gdbserver program
15604 * Remote Configuration:: Remote configuration
15605 * Remote Stub:: Implementing a remote stub
15609 @section Connecting to a Remote Target
15611 On the @value{GDBN} host machine, you will need an unstripped copy of
15612 your program, since @value{GDBN} needs symbol and debugging information.
15613 Start up @value{GDBN} as usual, using the name of the local copy of your
15614 program as the first argument.
15616 @cindex @code{target remote}
15617 @value{GDBN} can communicate with the target over a serial line, or
15618 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
15619 each case, @value{GDBN} uses the same protocol for debugging your
15620 program; only the medium carrying the debugging packets varies. The
15621 @code{target remote} command establishes a connection to the target.
15622 Its arguments indicate which medium to use:
15626 @item target remote @var{serial-device}
15627 @cindex serial line, @code{target remote}
15628 Use @var{serial-device} to communicate with the target. For example,
15629 to use a serial line connected to the device named @file{/dev/ttyb}:
15632 target remote /dev/ttyb
15635 If you're using a serial line, you may want to give @value{GDBN} the
15636 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
15637 (@pxref{Remote Configuration, set remotebaud}) before the
15638 @code{target} command.
15640 @item target remote @code{@var{host}:@var{port}}
15641 @itemx target remote @code{tcp:@var{host}:@var{port}}
15642 @cindex @acronym{TCP} port, @code{target remote}
15643 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
15644 The @var{host} may be either a host name or a numeric @acronym{IP}
15645 address; @var{port} must be a decimal number. The @var{host} could be
15646 the target machine itself, if it is directly connected to the net, or
15647 it might be a terminal server which in turn has a serial line to the
15650 For example, to connect to port 2828 on a terminal server named
15654 target remote manyfarms:2828
15657 If your remote target is actually running on the same machine as your
15658 debugger session (e.g.@: a simulator for your target running on the
15659 same host), you can omit the hostname. For example, to connect to
15660 port 1234 on your local machine:
15663 target remote :1234
15667 Note that the colon is still required here.
15669 @item target remote @code{udp:@var{host}:@var{port}}
15670 @cindex @acronym{UDP} port, @code{target remote}
15671 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
15672 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
15675 target remote udp:manyfarms:2828
15678 When using a @acronym{UDP} connection for remote debugging, you should
15679 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
15680 can silently drop packets on busy or unreliable networks, which will
15681 cause havoc with your debugging session.
15683 @item target remote | @var{command}
15684 @cindex pipe, @code{target remote} to
15685 Run @var{command} in the background and communicate with it using a
15686 pipe. The @var{command} is a shell command, to be parsed and expanded
15687 by the system's command shell, @code{/bin/sh}; it should expect remote
15688 protocol packets on its standard input, and send replies on its
15689 standard output. You could use this to run a stand-alone simulator
15690 that speaks the remote debugging protocol, to make net connections
15691 using programs like @code{ssh}, or for other similar tricks.
15693 If @var{command} closes its standard output (perhaps by exiting),
15694 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
15695 program has already exited, this will have no effect.)
15699 Once the connection has been established, you can use all the usual
15700 commands to examine and change data. The remote program is already
15701 running; you can use @kbd{step} and @kbd{continue}, and you do not
15702 need to use @kbd{run}.
15704 @cindex interrupting remote programs
15705 @cindex remote programs, interrupting
15706 Whenever @value{GDBN} is waiting for the remote program, if you type the
15707 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
15708 program. This may or may not succeed, depending in part on the hardware
15709 and the serial drivers the remote system uses. If you type the
15710 interrupt character once again, @value{GDBN} displays this prompt:
15713 Interrupted while waiting for the program.
15714 Give up (and stop debugging it)? (y or n)
15717 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
15718 (If you decide you want to try again later, you can use @samp{target
15719 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
15720 goes back to waiting.
15723 @kindex detach (remote)
15725 When you have finished debugging the remote program, you can use the
15726 @code{detach} command to release it from @value{GDBN} control.
15727 Detaching from the target normally resumes its execution, but the results
15728 will depend on your particular remote stub. After the @code{detach}
15729 command, @value{GDBN} is free to connect to another target.
15733 The @code{disconnect} command behaves like @code{detach}, except that
15734 the target is generally not resumed. It will wait for @value{GDBN}
15735 (this instance or another one) to connect and continue debugging. After
15736 the @code{disconnect} command, @value{GDBN} is again free to connect to
15739 @cindex send command to remote monitor
15740 @cindex extend @value{GDBN} for remote targets
15741 @cindex add new commands for external monitor
15743 @item monitor @var{cmd}
15744 This command allows you to send arbitrary commands directly to the
15745 remote monitor. Since @value{GDBN} doesn't care about the commands it
15746 sends like this, this command is the way to extend @value{GDBN}---you
15747 can add new commands that only the external monitor will understand
15751 @node File Transfer
15752 @section Sending files to a remote system
15753 @cindex remote target, file transfer
15754 @cindex file transfer
15755 @cindex sending files to remote systems
15757 Some remote targets offer the ability to transfer files over the same
15758 connection used to communicate with @value{GDBN}. This is convenient
15759 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
15760 running @code{gdbserver} over a network interface. For other targets,
15761 e.g.@: embedded devices with only a single serial port, this may be
15762 the only way to upload or download files.
15764 Not all remote targets support these commands.
15768 @item remote put @var{hostfile} @var{targetfile}
15769 Copy file @var{hostfile} from the host system (the machine running
15770 @value{GDBN}) to @var{targetfile} on the target system.
15773 @item remote get @var{targetfile} @var{hostfile}
15774 Copy file @var{targetfile} from the target system to @var{hostfile}
15775 on the host system.
15777 @kindex remote delete
15778 @item remote delete @var{targetfile}
15779 Delete @var{targetfile} from the target system.
15784 @section Using the @code{gdbserver} Program
15787 @cindex remote connection without stubs
15788 @code{gdbserver} is a control program for Unix-like systems, which
15789 allows you to connect your program with a remote @value{GDBN} via
15790 @code{target remote}---but without linking in the usual debugging stub.
15792 @code{gdbserver} is not a complete replacement for the debugging stubs,
15793 because it requires essentially the same operating-system facilities
15794 that @value{GDBN} itself does. In fact, a system that can run
15795 @code{gdbserver} to connect to a remote @value{GDBN} could also run
15796 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
15797 because it is a much smaller program than @value{GDBN} itself. It is
15798 also easier to port than all of @value{GDBN}, so you may be able to get
15799 started more quickly on a new system by using @code{gdbserver}.
15800 Finally, if you develop code for real-time systems, you may find that
15801 the tradeoffs involved in real-time operation make it more convenient to
15802 do as much development work as possible on another system, for example
15803 by cross-compiling. You can use @code{gdbserver} to make a similar
15804 choice for debugging.
15806 @value{GDBN} and @code{gdbserver} communicate via either a serial line
15807 or a TCP connection, using the standard @value{GDBN} remote serial
15811 @emph{Warning:} @code{gdbserver} does not have any built-in security.
15812 Do not run @code{gdbserver} connected to any public network; a
15813 @value{GDBN} connection to @code{gdbserver} provides access to the
15814 target system with the same privileges as the user running
15818 @subsection Running @code{gdbserver}
15819 @cindex arguments, to @code{gdbserver}
15821 Run @code{gdbserver} on the target system. You need a copy of the
15822 program you want to debug, including any libraries it requires.
15823 @code{gdbserver} does not need your program's symbol table, so you can
15824 strip the program if necessary to save space. @value{GDBN} on the host
15825 system does all the symbol handling.
15827 To use the server, you must tell it how to communicate with @value{GDBN};
15828 the name of your program; and the arguments for your program. The usual
15832 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
15835 @var{comm} is either a device name (to use a serial line) or a TCP
15836 hostname and portnumber. For example, to debug Emacs with the argument
15837 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
15841 target> gdbserver /dev/com1 emacs foo.txt
15844 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
15847 To use a TCP connection instead of a serial line:
15850 target> gdbserver host:2345 emacs foo.txt
15853 The only difference from the previous example is the first argument,
15854 specifying that you are communicating with the host @value{GDBN} via
15855 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
15856 expect a TCP connection from machine @samp{host} to local TCP port 2345.
15857 (Currently, the @samp{host} part is ignored.) You can choose any number
15858 you want for the port number as long as it does not conflict with any
15859 TCP ports already in use on the target system (for example, @code{23} is
15860 reserved for @code{telnet}).@footnote{If you choose a port number that
15861 conflicts with another service, @code{gdbserver} prints an error message
15862 and exits.} You must use the same port number with the host @value{GDBN}
15863 @code{target remote} command.
15865 @subsubsection Attaching to a Running Program
15867 On some targets, @code{gdbserver} can also attach to running programs.
15868 This is accomplished via the @code{--attach} argument. The syntax is:
15871 target> gdbserver --attach @var{comm} @var{pid}
15874 @var{pid} is the process ID of a currently running process. It isn't necessary
15875 to point @code{gdbserver} at a binary for the running process.
15878 @cindex attach to a program by name
15879 You can debug processes by name instead of process ID if your target has the
15880 @code{pidof} utility:
15883 target> gdbserver --attach @var{comm} `pidof @var{program}`
15886 In case more than one copy of @var{program} is running, or @var{program}
15887 has multiple threads, most versions of @code{pidof} support the
15888 @code{-s} option to only return the first process ID.
15890 @subsubsection Multi-Process Mode for @code{gdbserver}
15891 @cindex gdbserver, multiple processes
15892 @cindex multiple processes with gdbserver
15894 When you connect to @code{gdbserver} using @code{target remote},
15895 @code{gdbserver} debugs the specified program only once. When the
15896 program exits, or you detach from it, @value{GDBN} closes the connection
15897 and @code{gdbserver} exits.
15899 If you connect using @kbd{target extended-remote}, @code{gdbserver}
15900 enters multi-process mode. When the debugged program exits, or you
15901 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
15902 though no program is running. The @code{run} and @code{attach}
15903 commands instruct @code{gdbserver} to run or attach to a new program.
15904 The @code{run} command uses @code{set remote exec-file} (@pxref{set
15905 remote exec-file}) to select the program to run. Command line
15906 arguments are supported, except for wildcard expansion and I/O
15907 redirection (@pxref{Arguments}).
15909 To start @code{gdbserver} without supplying an initial command to run
15910 or process ID to attach, use the @option{--multi} command line option.
15911 Then you can connect using @kbd{target extended-remote} and start
15912 the program you want to debug.
15914 @code{gdbserver} does not automatically exit in multi-process mode.
15915 You can terminate it by using @code{monitor exit}
15916 (@pxref{Monitor Commands for gdbserver}).
15918 @subsubsection Other Command-Line Arguments for @code{gdbserver}
15920 The @option{--debug} option tells @code{gdbserver} to display extra
15921 status information about the debugging process. The
15922 @option{--remote-debug} option tells @code{gdbserver} to display
15923 remote protocol debug output. These options are intended for
15924 @code{gdbserver} development and for bug reports to the developers.
15926 The @option{--wrapper} option specifies a wrapper to launch programs
15927 for debugging. The option should be followed by the name of the
15928 wrapper, then any command-line arguments to pass to the wrapper, then
15929 @kbd{--} indicating the end of the wrapper arguments.
15931 @code{gdbserver} runs the specified wrapper program with a combined
15932 command line including the wrapper arguments, then the name of the
15933 program to debug, then any arguments to the program. The wrapper
15934 runs until it executes your program, and then @value{GDBN} gains control.
15936 You can use any program that eventually calls @code{execve} with
15937 its arguments as a wrapper. Several standard Unix utilities do
15938 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
15939 with @code{exec "$@@"} will also work.
15941 For example, you can use @code{env} to pass an environment variable to
15942 the debugged program, without setting the variable in @code{gdbserver}'s
15946 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
15949 @subsection Connecting to @code{gdbserver}
15951 Run @value{GDBN} on the host system.
15953 First make sure you have the necessary symbol files. Load symbols for
15954 your application using the @code{file} command before you connect. Use
15955 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
15956 was compiled with the correct sysroot using @code{--with-sysroot}).
15958 The symbol file and target libraries must exactly match the executable
15959 and libraries on the target, with one exception: the files on the host
15960 system should not be stripped, even if the files on the target system
15961 are. Mismatched or missing files will lead to confusing results
15962 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
15963 files may also prevent @code{gdbserver} from debugging multi-threaded
15966 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
15967 For TCP connections, you must start up @code{gdbserver} prior to using
15968 the @code{target remote} command. Otherwise you may get an error whose
15969 text depends on the host system, but which usually looks something like
15970 @samp{Connection refused}. Don't use the @code{load}
15971 command in @value{GDBN} when using @code{gdbserver}, since the program is
15972 already on the target.
15974 @subsection Monitor Commands for @code{gdbserver}
15975 @cindex monitor commands, for @code{gdbserver}
15976 @anchor{Monitor Commands for gdbserver}
15978 During a @value{GDBN} session using @code{gdbserver}, you can use the
15979 @code{monitor} command to send special requests to @code{gdbserver}.
15980 Here are the available commands.
15984 List the available monitor commands.
15986 @item monitor set debug 0
15987 @itemx monitor set debug 1
15988 Disable or enable general debugging messages.
15990 @item monitor set remote-debug 0
15991 @itemx monitor set remote-debug 1
15992 Disable or enable specific debugging messages associated with the remote
15993 protocol (@pxref{Remote Protocol}).
15995 @item monitor set libthread-db-search-path [PATH]
15996 @cindex gdbserver, search path for @code{libthread_db}
15997 When this command is issued, @var{path} is a colon-separated list of
15998 directories to search for @code{libthread_db} (@pxref{Threads,,set
15999 libthread-db-search-path}). If you omit @var{path},
16000 @samp{libthread-db-search-path} will be reset to an empty list.
16003 Tell gdbserver to exit immediately. This command should be followed by
16004 @code{disconnect} to close the debugging session. @code{gdbserver} will
16005 detach from any attached processes and kill any processes it created.
16006 Use @code{monitor exit} to terminate @code{gdbserver} at the end
16007 of a multi-process mode debug session.
16011 @subsection Tracepoints support in @code{gdbserver}
16012 @cindex tracepoints support in @code{gdbserver}
16014 On some targets, @code{gdbserver} supports tracepoints, fast
16015 tracepoints and static tracepoints.
16017 For fast or static tracepoints to work, a special library called the
16018 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
16019 This library is built and distributed as an integral part of
16020 @code{gdbserver}. In addition, support for static tracepoints
16021 requires building the in-process agent library with static tracepoints
16022 support. At present, the UST (LTTng Userspace Tracer,
16023 @url{http://lttng.org/ust}) tracing engine is supported. This support
16024 is automatically available if UST development headers are found in the
16025 standard include path when @code{gdbserver} is built, or if
16026 @code{gdbserver} was explicitly configured using @option{--with-ust}
16027 to point at such headers. You can explicitly disable the support
16028 using @option{--with-ust=no}.
16030 There are several ways to load the in-process agent in your program:
16033 @item Specifying it as dependency at link time
16035 You can link your program dynamically with the in-process agent
16036 library. On most systems, this is accomplished by adding
16037 @code{-linproctrace} to the link command.
16039 @item Using the system's preloading mechanisms
16041 You can force loading the in-process agent at startup time by using
16042 your system's support for preloading shared libraries. Many Unixes
16043 support the concept of preloading user defined libraries. In most
16044 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
16045 in the environment. See also the description of @code{gdbserver}'s
16046 @option{--wrapper} command line option.
16048 @item Using @value{GDBN} to force loading the agent at run time
16050 On some systems, you can force the inferior to load a shared library,
16051 by calling a dynamic loader function in the inferior that takes care
16052 of dynamically looking up and loading a shared library. On most Unix
16053 systems, the function is @code{dlopen}. You'll use the @code{call}
16054 command for that. For example:
16057 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
16060 Note that on most Unix systems, for the @code{dlopen} function to be
16061 available, the program needs to be linked with @code{-ldl}.
16064 On systems that have a userspace dynamic loader, like most Unix
16065 systems, when you connect to @code{gdbserver} using @code{target
16066 remote}, you'll find that the program is stopped at the dynamic
16067 loader's entry point, and no shared library has been loaded in the
16068 program's address space yet, including the in-process agent. In that
16069 case, before being able to use any of the fast or static tracepoints
16070 features, you need to let the loader run and load the shared
16071 libraries. The simplest way to do that is to run the program to the
16072 main procedure. E.g., if debugging a C or C@t{++} program, start
16073 @code{gdbserver} like so:
16076 $ gdbserver :9999 myprogram
16079 Start GDB and connect to @code{gdbserver} like so, and run to main:
16083 (@value{GDBP}) target remote myhost:9999
16084 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
16085 (@value{GDBP}) b main
16086 (@value{GDBP}) continue
16089 The in-process tracing agent library should now be loaded into the
16090 process; you can confirm it with the @code{info sharedlibrary}
16091 command, which will list @file{libinproctrace.so} as loaded in the
16092 process. You are now ready to install fast tracepoints, list static
16093 tracepoint markers, probe static tracepoints markers, and start
16096 @node Remote Configuration
16097 @section Remote Configuration
16100 @kindex show remote
16101 This section documents the configuration options available when
16102 debugging remote programs. For the options related to the File I/O
16103 extensions of the remote protocol, see @ref{system,
16104 system-call-allowed}.
16107 @item set remoteaddresssize @var{bits}
16108 @cindex address size for remote targets
16109 @cindex bits in remote address
16110 Set the maximum size of address in a memory packet to the specified
16111 number of bits. @value{GDBN} will mask off the address bits above
16112 that number, when it passes addresses to the remote target. The
16113 default value is the number of bits in the target's address.
16115 @item show remoteaddresssize
16116 Show the current value of remote address size in bits.
16118 @item set remotebaud @var{n}
16119 @cindex baud rate for remote targets
16120 Set the baud rate for the remote serial I/O to @var{n} baud. The
16121 value is used to set the speed of the serial port used for debugging
16124 @item show remotebaud
16125 Show the current speed of the remote connection.
16127 @item set remotebreak
16128 @cindex interrupt remote programs
16129 @cindex BREAK signal instead of Ctrl-C
16130 @anchor{set remotebreak}
16131 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
16132 when you type @kbd{Ctrl-c} to interrupt the program running
16133 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
16134 character instead. The default is off, since most remote systems
16135 expect to see @samp{Ctrl-C} as the interrupt signal.
16137 @item show remotebreak
16138 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
16139 interrupt the remote program.
16141 @item set remoteflow on
16142 @itemx set remoteflow off
16143 @kindex set remoteflow
16144 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
16145 on the serial port used to communicate to the remote target.
16147 @item show remoteflow
16148 @kindex show remoteflow
16149 Show the current setting of hardware flow control.
16151 @item set remotelogbase @var{base}
16152 Set the base (a.k.a.@: radix) of logging serial protocol
16153 communications to @var{base}. Supported values of @var{base} are:
16154 @code{ascii}, @code{octal}, and @code{hex}. The default is
16157 @item show remotelogbase
16158 Show the current setting of the radix for logging remote serial
16161 @item set remotelogfile @var{file}
16162 @cindex record serial communications on file
16163 Record remote serial communications on the named @var{file}. The
16164 default is not to record at all.
16166 @item show remotelogfile.
16167 Show the current setting of the file name on which to record the
16168 serial communications.
16170 @item set remotetimeout @var{num}
16171 @cindex timeout for serial communications
16172 @cindex remote timeout
16173 Set the timeout limit to wait for the remote target to respond to
16174 @var{num} seconds. The default is 2 seconds.
16176 @item show remotetimeout
16177 Show the current number of seconds to wait for the remote target
16180 @cindex limit hardware breakpoints and watchpoints
16181 @cindex remote target, limit break- and watchpoints
16182 @anchor{set remote hardware-watchpoint-limit}
16183 @anchor{set remote hardware-breakpoint-limit}
16184 @item set remote hardware-watchpoint-limit @var{limit}
16185 @itemx set remote hardware-breakpoint-limit @var{limit}
16186 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
16187 watchpoints. A limit of -1, the default, is treated as unlimited.
16189 @item set remote exec-file @var{filename}
16190 @itemx show remote exec-file
16191 @anchor{set remote exec-file}
16192 @cindex executable file, for remote target
16193 Select the file used for @code{run} with @code{target
16194 extended-remote}. This should be set to a filename valid on the
16195 target system. If it is not set, the target will use a default
16196 filename (e.g.@: the last program run).
16198 @item set remote interrupt-sequence
16199 @cindex interrupt remote programs
16200 @cindex select Ctrl-C, BREAK or BREAK-g
16201 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
16202 @samp{BREAK-g} as the
16203 sequence to the remote target in order to interrupt the execution.
16204 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
16205 is high level of serial line for some certain time.
16206 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
16207 It is @code{BREAK} signal followed by character @code{g}.
16209 @item show interrupt-sequence
16210 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
16211 is sent by @value{GDBN} to interrupt the remote program.
16212 @code{BREAK-g} is BREAK signal followed by @code{g} and
16213 also known as Magic SysRq g.
16215 @item set remote interrupt-on-connect
16216 @cindex send interrupt-sequence on start
16217 Specify whether interrupt-sequence is sent to remote target when
16218 @value{GDBN} connects to it. This is mostly needed when you debug
16219 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
16220 which is known as Magic SysRq g in order to connect @value{GDBN}.
16222 @item show interrupt-on-connect
16223 Show whether interrupt-sequence is sent
16224 to remote target when @value{GDBN} connects to it.
16228 @item set tcp auto-retry on
16229 @cindex auto-retry, for remote TCP target
16230 Enable auto-retry for remote TCP connections. This is useful if the remote
16231 debugging agent is launched in parallel with @value{GDBN}; there is a race
16232 condition because the agent may not become ready to accept the connection
16233 before @value{GDBN} attempts to connect. When auto-retry is
16234 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
16235 to establish the connection using the timeout specified by
16236 @code{set tcp connect-timeout}.
16238 @item set tcp auto-retry off
16239 Do not auto-retry failed TCP connections.
16241 @item show tcp auto-retry
16242 Show the current auto-retry setting.
16244 @item set tcp connect-timeout @var{seconds}
16245 @cindex connection timeout, for remote TCP target
16246 @cindex timeout, for remote target connection
16247 Set the timeout for establishing a TCP connection to the remote target to
16248 @var{seconds}. The timeout affects both polling to retry failed connections
16249 (enabled by @code{set tcp auto-retry on}) and waiting for connections
16250 that are merely slow to complete, and represents an approximate cumulative
16253 @item show tcp connect-timeout
16254 Show the current connection timeout setting.
16257 @cindex remote packets, enabling and disabling
16258 The @value{GDBN} remote protocol autodetects the packets supported by
16259 your debugging stub. If you need to override the autodetection, you
16260 can use these commands to enable or disable individual packets. Each
16261 packet can be set to @samp{on} (the remote target supports this
16262 packet), @samp{off} (the remote target does not support this packet),
16263 or @samp{auto} (detect remote target support for this packet). They
16264 all default to @samp{auto}. For more information about each packet,
16265 see @ref{Remote Protocol}.
16267 During normal use, you should not have to use any of these commands.
16268 If you do, that may be a bug in your remote debugging stub, or a bug
16269 in @value{GDBN}. You may want to report the problem to the
16270 @value{GDBN} developers.
16272 For each packet @var{name}, the command to enable or disable the
16273 packet is @code{set remote @var{name}-packet}. The available settings
16276 @multitable @columnfractions 0.28 0.32 0.25
16279 @tab Related Features
16281 @item @code{fetch-register}
16283 @tab @code{info registers}
16285 @item @code{set-register}
16289 @item @code{binary-download}
16291 @tab @code{load}, @code{set}
16293 @item @code{read-aux-vector}
16294 @tab @code{qXfer:auxv:read}
16295 @tab @code{info auxv}
16297 @item @code{symbol-lookup}
16298 @tab @code{qSymbol}
16299 @tab Detecting multiple threads
16301 @item @code{attach}
16302 @tab @code{vAttach}
16305 @item @code{verbose-resume}
16307 @tab Stepping or resuming multiple threads
16313 @item @code{software-breakpoint}
16317 @item @code{hardware-breakpoint}
16321 @item @code{write-watchpoint}
16325 @item @code{read-watchpoint}
16329 @item @code{access-watchpoint}
16333 @item @code{target-features}
16334 @tab @code{qXfer:features:read}
16335 @tab @code{set architecture}
16337 @item @code{library-info}
16338 @tab @code{qXfer:libraries:read}
16339 @tab @code{info sharedlibrary}
16341 @item @code{memory-map}
16342 @tab @code{qXfer:memory-map:read}
16343 @tab @code{info mem}
16345 @item @code{read-sdata-object}
16346 @tab @code{qXfer:sdata:read}
16347 @tab @code{print $_sdata}
16349 @item @code{read-spu-object}
16350 @tab @code{qXfer:spu:read}
16351 @tab @code{info spu}
16353 @item @code{write-spu-object}
16354 @tab @code{qXfer:spu:write}
16355 @tab @code{info spu}
16357 @item @code{read-siginfo-object}
16358 @tab @code{qXfer:siginfo:read}
16359 @tab @code{print $_siginfo}
16361 @item @code{write-siginfo-object}
16362 @tab @code{qXfer:siginfo:write}
16363 @tab @code{set $_siginfo}
16365 @item @code{threads}
16366 @tab @code{qXfer:threads:read}
16367 @tab @code{info threads}
16369 @item @code{get-thread-local-@*storage-address}
16370 @tab @code{qGetTLSAddr}
16371 @tab Displaying @code{__thread} variables
16373 @item @code{get-thread-information-block-address}
16374 @tab @code{qGetTIBAddr}
16375 @tab Display MS-Windows Thread Information Block.
16377 @item @code{search-memory}
16378 @tab @code{qSearch:memory}
16381 @item @code{supported-packets}
16382 @tab @code{qSupported}
16383 @tab Remote communications parameters
16385 @item @code{pass-signals}
16386 @tab @code{QPassSignals}
16387 @tab @code{handle @var{signal}}
16389 @item @code{hostio-close-packet}
16390 @tab @code{vFile:close}
16391 @tab @code{remote get}, @code{remote put}
16393 @item @code{hostio-open-packet}
16394 @tab @code{vFile:open}
16395 @tab @code{remote get}, @code{remote put}
16397 @item @code{hostio-pread-packet}
16398 @tab @code{vFile:pread}
16399 @tab @code{remote get}, @code{remote put}
16401 @item @code{hostio-pwrite-packet}
16402 @tab @code{vFile:pwrite}
16403 @tab @code{remote get}, @code{remote put}
16405 @item @code{hostio-unlink-packet}
16406 @tab @code{vFile:unlink}
16407 @tab @code{remote delete}
16409 @item @code{noack-packet}
16410 @tab @code{QStartNoAckMode}
16411 @tab Packet acknowledgment
16413 @item @code{osdata}
16414 @tab @code{qXfer:osdata:read}
16415 @tab @code{info os}
16417 @item @code{query-attached}
16418 @tab @code{qAttached}
16419 @tab Querying remote process attach state.
16423 @section Implementing a Remote Stub
16425 @cindex debugging stub, example
16426 @cindex remote stub, example
16427 @cindex stub example, remote debugging
16428 The stub files provided with @value{GDBN} implement the target side of the
16429 communication protocol, and the @value{GDBN} side is implemented in the
16430 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
16431 these subroutines to communicate, and ignore the details. (If you're
16432 implementing your own stub file, you can still ignore the details: start
16433 with one of the existing stub files. @file{sparc-stub.c} is the best
16434 organized, and therefore the easiest to read.)
16436 @cindex remote serial debugging, overview
16437 To debug a program running on another machine (the debugging
16438 @dfn{target} machine), you must first arrange for all the usual
16439 prerequisites for the program to run by itself. For example, for a C
16444 A startup routine to set up the C runtime environment; these usually
16445 have a name like @file{crt0}. The startup routine may be supplied by
16446 your hardware supplier, or you may have to write your own.
16449 A C subroutine library to support your program's
16450 subroutine calls, notably managing input and output.
16453 A way of getting your program to the other machine---for example, a
16454 download program. These are often supplied by the hardware
16455 manufacturer, but you may have to write your own from hardware
16459 The next step is to arrange for your program to use a serial port to
16460 communicate with the machine where @value{GDBN} is running (the @dfn{host}
16461 machine). In general terms, the scheme looks like this:
16465 @value{GDBN} already understands how to use this protocol; when everything
16466 else is set up, you can simply use the @samp{target remote} command
16467 (@pxref{Targets,,Specifying a Debugging Target}).
16469 @item On the target,
16470 you must link with your program a few special-purpose subroutines that
16471 implement the @value{GDBN} remote serial protocol. The file containing these
16472 subroutines is called a @dfn{debugging stub}.
16474 On certain remote targets, you can use an auxiliary program
16475 @code{gdbserver} instead of linking a stub into your program.
16476 @xref{Server,,Using the @code{gdbserver} Program}, for details.
16479 The debugging stub is specific to the architecture of the remote
16480 machine; for example, use @file{sparc-stub.c} to debug programs on
16483 @cindex remote serial stub list
16484 These working remote stubs are distributed with @value{GDBN}:
16489 @cindex @file{i386-stub.c}
16492 For Intel 386 and compatible architectures.
16495 @cindex @file{m68k-stub.c}
16496 @cindex Motorola 680x0
16498 For Motorola 680x0 architectures.
16501 @cindex @file{sh-stub.c}
16504 For Renesas SH architectures.
16507 @cindex @file{sparc-stub.c}
16509 For @sc{sparc} architectures.
16511 @item sparcl-stub.c
16512 @cindex @file{sparcl-stub.c}
16515 For Fujitsu @sc{sparclite} architectures.
16519 The @file{README} file in the @value{GDBN} distribution may list other
16520 recently added stubs.
16523 * Stub Contents:: What the stub can do for you
16524 * Bootstrapping:: What you must do for the stub
16525 * Debug Session:: Putting it all together
16528 @node Stub Contents
16529 @subsection What the Stub Can Do for You
16531 @cindex remote serial stub
16532 The debugging stub for your architecture supplies these three
16536 @item set_debug_traps
16537 @findex set_debug_traps
16538 @cindex remote serial stub, initialization
16539 This routine arranges for @code{handle_exception} to run when your
16540 program stops. You must call this subroutine explicitly near the
16541 beginning of your program.
16543 @item handle_exception
16544 @findex handle_exception
16545 @cindex remote serial stub, main routine
16546 This is the central workhorse, but your program never calls it
16547 explicitly---the setup code arranges for @code{handle_exception} to
16548 run when a trap is triggered.
16550 @code{handle_exception} takes control when your program stops during
16551 execution (for example, on a breakpoint), and mediates communications
16552 with @value{GDBN} on the host machine. This is where the communications
16553 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
16554 representative on the target machine. It begins by sending summary
16555 information on the state of your program, then continues to execute,
16556 retrieving and transmitting any information @value{GDBN} needs, until you
16557 execute a @value{GDBN} command that makes your program resume; at that point,
16558 @code{handle_exception} returns control to your own code on the target
16562 @cindex @code{breakpoint} subroutine, remote
16563 Use this auxiliary subroutine to make your program contain a
16564 breakpoint. Depending on the particular situation, this may be the only
16565 way for @value{GDBN} to get control. For instance, if your target
16566 machine has some sort of interrupt button, you won't need to call this;
16567 pressing the interrupt button transfers control to
16568 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
16569 simply receiving characters on the serial port may also trigger a trap;
16570 again, in that situation, you don't need to call @code{breakpoint} from
16571 your own program---simply running @samp{target remote} from the host
16572 @value{GDBN} session gets control.
16574 Call @code{breakpoint} if none of these is true, or if you simply want
16575 to make certain your program stops at a predetermined point for the
16576 start of your debugging session.
16579 @node Bootstrapping
16580 @subsection What You Must Do for the Stub
16582 @cindex remote stub, support routines
16583 The debugging stubs that come with @value{GDBN} are set up for a particular
16584 chip architecture, but they have no information about the rest of your
16585 debugging target machine.
16587 First of all you need to tell the stub how to communicate with the
16591 @item int getDebugChar()
16592 @findex getDebugChar
16593 Write this subroutine to read a single character from the serial port.
16594 It may be identical to @code{getchar} for your target system; a
16595 different name is used to allow you to distinguish the two if you wish.
16597 @item void putDebugChar(int)
16598 @findex putDebugChar
16599 Write this subroutine to write a single character to the serial port.
16600 It may be identical to @code{putchar} for your target system; a
16601 different name is used to allow you to distinguish the two if you wish.
16604 @cindex control C, and remote debugging
16605 @cindex interrupting remote targets
16606 If you want @value{GDBN} to be able to stop your program while it is
16607 running, you need to use an interrupt-driven serial driver, and arrange
16608 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
16609 character). That is the character which @value{GDBN} uses to tell the
16610 remote system to stop.
16612 Getting the debugging target to return the proper status to @value{GDBN}
16613 probably requires changes to the standard stub; one quick and dirty way
16614 is to just execute a breakpoint instruction (the ``dirty'' part is that
16615 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
16617 Other routines you need to supply are:
16620 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
16621 @findex exceptionHandler
16622 Write this function to install @var{exception_address} in the exception
16623 handling tables. You need to do this because the stub does not have any
16624 way of knowing what the exception handling tables on your target system
16625 are like (for example, the processor's table might be in @sc{rom},
16626 containing entries which point to a table in @sc{ram}).
16627 @var{exception_number} is the exception number which should be changed;
16628 its meaning is architecture-dependent (for example, different numbers
16629 might represent divide by zero, misaligned access, etc). When this
16630 exception occurs, control should be transferred directly to
16631 @var{exception_address}, and the processor state (stack, registers,
16632 and so on) should be just as it is when a processor exception occurs. So if
16633 you want to use a jump instruction to reach @var{exception_address}, it
16634 should be a simple jump, not a jump to subroutine.
16636 For the 386, @var{exception_address} should be installed as an interrupt
16637 gate so that interrupts are masked while the handler runs. The gate
16638 should be at privilege level 0 (the most privileged level). The
16639 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
16640 help from @code{exceptionHandler}.
16642 @item void flush_i_cache()
16643 @findex flush_i_cache
16644 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
16645 instruction cache, if any, on your target machine. If there is no
16646 instruction cache, this subroutine may be a no-op.
16648 On target machines that have instruction caches, @value{GDBN} requires this
16649 function to make certain that the state of your program is stable.
16653 You must also make sure this library routine is available:
16656 @item void *memset(void *, int, int)
16658 This is the standard library function @code{memset} that sets an area of
16659 memory to a known value. If you have one of the free versions of
16660 @code{libc.a}, @code{memset} can be found there; otherwise, you must
16661 either obtain it from your hardware manufacturer, or write your own.
16664 If you do not use the GNU C compiler, you may need other standard
16665 library subroutines as well; this varies from one stub to another,
16666 but in general the stubs are likely to use any of the common library
16667 subroutines which @code{@value{NGCC}} generates as inline code.
16670 @node Debug Session
16671 @subsection Putting it All Together
16673 @cindex remote serial debugging summary
16674 In summary, when your program is ready to debug, you must follow these
16679 Make sure you have defined the supporting low-level routines
16680 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
16682 @code{getDebugChar}, @code{putDebugChar},
16683 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
16687 Insert these lines near the top of your program:
16695 For the 680x0 stub only, you need to provide a variable called
16696 @code{exceptionHook}. Normally you just use:
16699 void (*exceptionHook)() = 0;
16703 but if before calling @code{set_debug_traps}, you set it to point to a
16704 function in your program, that function is called when
16705 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
16706 error). The function indicated by @code{exceptionHook} is called with
16707 one parameter: an @code{int} which is the exception number.
16710 Compile and link together: your program, the @value{GDBN} debugging stub for
16711 your target architecture, and the supporting subroutines.
16714 Make sure you have a serial connection between your target machine and
16715 the @value{GDBN} host, and identify the serial port on the host.
16718 @c The "remote" target now provides a `load' command, so we should
16719 @c document that. FIXME.
16720 Download your program to your target machine (or get it there by
16721 whatever means the manufacturer provides), and start it.
16724 Start @value{GDBN} on the host, and connect to the target
16725 (@pxref{Connecting,,Connecting to a Remote Target}).
16729 @node Configurations
16730 @chapter Configuration-Specific Information
16732 While nearly all @value{GDBN} commands are available for all native and
16733 cross versions of the debugger, there are some exceptions. This chapter
16734 describes things that are only available in certain configurations.
16736 There are three major categories of configurations: native
16737 configurations, where the host and target are the same, embedded
16738 operating system configurations, which are usually the same for several
16739 different processor architectures, and bare embedded processors, which
16740 are quite different from each other.
16745 * Embedded Processors::
16752 This section describes details specific to particular native
16757 * BSD libkvm Interface:: Debugging BSD kernel memory images
16758 * SVR4 Process Information:: SVR4 process information
16759 * DJGPP Native:: Features specific to the DJGPP port
16760 * Cygwin Native:: Features specific to the Cygwin port
16761 * Hurd Native:: Features specific to @sc{gnu} Hurd
16762 * Neutrino:: Features specific to QNX Neutrino
16763 * Darwin:: Features specific to Darwin
16769 On HP-UX systems, if you refer to a function or variable name that
16770 begins with a dollar sign, @value{GDBN} searches for a user or system
16771 name first, before it searches for a convenience variable.
16774 @node BSD libkvm Interface
16775 @subsection BSD libkvm Interface
16778 @cindex kernel memory image
16779 @cindex kernel crash dump
16781 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
16782 interface that provides a uniform interface for accessing kernel virtual
16783 memory images, including live systems and crash dumps. @value{GDBN}
16784 uses this interface to allow you to debug live kernels and kernel crash
16785 dumps on many native BSD configurations. This is implemented as a
16786 special @code{kvm} debugging target. For debugging a live system, load
16787 the currently running kernel into @value{GDBN} and connect to the
16791 (@value{GDBP}) @b{target kvm}
16794 For debugging crash dumps, provide the file name of the crash dump as an
16798 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
16801 Once connected to the @code{kvm} target, the following commands are
16807 Set current context from the @dfn{Process Control Block} (PCB) address.
16810 Set current context from proc address. This command isn't available on
16811 modern FreeBSD systems.
16814 @node SVR4 Process Information
16815 @subsection SVR4 Process Information
16817 @cindex examine process image
16818 @cindex process info via @file{/proc}
16820 Many versions of SVR4 and compatible systems provide a facility called
16821 @samp{/proc} that can be used to examine the image of a running
16822 process using file-system subroutines. If @value{GDBN} is configured
16823 for an operating system with this facility, the command @code{info
16824 proc} is available to report information about the process running
16825 your program, or about any process running on your system. @code{info
16826 proc} works only on SVR4 systems that include the @code{procfs} code.
16827 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
16828 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
16834 @itemx info proc @var{process-id}
16835 Summarize available information about any running process. If a
16836 process ID is specified by @var{process-id}, display information about
16837 that process; otherwise display information about the program being
16838 debugged. The summary includes the debugged process ID, the command
16839 line used to invoke it, its current working directory, and its
16840 executable file's absolute file name.
16842 On some systems, @var{process-id} can be of the form
16843 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
16844 within a process. If the optional @var{pid} part is missing, it means
16845 a thread from the process being debugged (the leading @samp{/} still
16846 needs to be present, or else @value{GDBN} will interpret the number as
16847 a process ID rather than a thread ID).
16849 @item info proc mappings
16850 @cindex memory address space mappings
16851 Report the memory address space ranges accessible in the program, with
16852 information on whether the process has read, write, or execute access
16853 rights to each range. On @sc{gnu}/Linux systems, each memory range
16854 includes the object file which is mapped to that range, instead of the
16855 memory access rights to that range.
16857 @item info proc stat
16858 @itemx info proc status
16859 @cindex process detailed status information
16860 These subcommands are specific to @sc{gnu}/Linux systems. They show
16861 the process-related information, including the user ID and group ID;
16862 how many threads are there in the process; its virtual memory usage;
16863 the signals that are pending, blocked, and ignored; its TTY; its
16864 consumption of system and user time; its stack size; its @samp{nice}
16865 value; etc. For more information, see the @samp{proc} man page
16866 (type @kbd{man 5 proc} from your shell prompt).
16868 @item info proc all
16869 Show all the information about the process described under all of the
16870 above @code{info proc} subcommands.
16873 @comment These sub-options of 'info proc' were not included when
16874 @comment procfs.c was re-written. Keep their descriptions around
16875 @comment against the day when someone finds the time to put them back in.
16876 @kindex info proc times
16877 @item info proc times
16878 Starting time, user CPU time, and system CPU time for your program and
16881 @kindex info proc id
16883 Report on the process IDs related to your program: its own process ID,
16884 the ID of its parent, the process group ID, and the session ID.
16887 @item set procfs-trace
16888 @kindex set procfs-trace
16889 @cindex @code{procfs} API calls
16890 This command enables and disables tracing of @code{procfs} API calls.
16892 @item show procfs-trace
16893 @kindex show procfs-trace
16894 Show the current state of @code{procfs} API call tracing.
16896 @item set procfs-file @var{file}
16897 @kindex set procfs-file
16898 Tell @value{GDBN} to write @code{procfs} API trace to the named
16899 @var{file}. @value{GDBN} appends the trace info to the previous
16900 contents of the file. The default is to display the trace on the
16903 @item show procfs-file
16904 @kindex show procfs-file
16905 Show the file to which @code{procfs} API trace is written.
16907 @item proc-trace-entry
16908 @itemx proc-trace-exit
16909 @itemx proc-untrace-entry
16910 @itemx proc-untrace-exit
16911 @kindex proc-trace-entry
16912 @kindex proc-trace-exit
16913 @kindex proc-untrace-entry
16914 @kindex proc-untrace-exit
16915 These commands enable and disable tracing of entries into and exits
16916 from the @code{syscall} interface.
16919 @kindex info pidlist
16920 @cindex process list, QNX Neutrino
16921 For QNX Neutrino only, this command displays the list of all the
16922 processes and all the threads within each process.
16925 @kindex info meminfo
16926 @cindex mapinfo list, QNX Neutrino
16927 For QNX Neutrino only, this command displays the list of all mapinfos.
16931 @subsection Features for Debugging @sc{djgpp} Programs
16932 @cindex @sc{djgpp} debugging
16933 @cindex native @sc{djgpp} debugging
16934 @cindex MS-DOS-specific commands
16937 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
16938 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
16939 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
16940 top of real-mode DOS systems and their emulations.
16942 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
16943 defines a few commands specific to the @sc{djgpp} port. This
16944 subsection describes those commands.
16949 This is a prefix of @sc{djgpp}-specific commands which print
16950 information about the target system and important OS structures.
16953 @cindex MS-DOS system info
16954 @cindex free memory information (MS-DOS)
16955 @item info dos sysinfo
16956 This command displays assorted information about the underlying
16957 platform: the CPU type and features, the OS version and flavor, the
16958 DPMI version, and the available conventional and DPMI memory.
16963 @cindex segment descriptor tables
16964 @cindex descriptor tables display
16966 @itemx info dos ldt
16967 @itemx info dos idt
16968 These 3 commands display entries from, respectively, Global, Local,
16969 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
16970 tables are data structures which store a descriptor for each segment
16971 that is currently in use. The segment's selector is an index into a
16972 descriptor table; the table entry for that index holds the
16973 descriptor's base address and limit, and its attributes and access
16976 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
16977 segment (used for both data and the stack), and a DOS segment (which
16978 allows access to DOS/BIOS data structures and absolute addresses in
16979 conventional memory). However, the DPMI host will usually define
16980 additional segments in order to support the DPMI environment.
16982 @cindex garbled pointers
16983 These commands allow to display entries from the descriptor tables.
16984 Without an argument, all entries from the specified table are
16985 displayed. An argument, which should be an integer expression, means
16986 display a single entry whose index is given by the argument. For
16987 example, here's a convenient way to display information about the
16988 debugged program's data segment:
16991 @exdent @code{(@value{GDBP}) info dos ldt $ds}
16992 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
16996 This comes in handy when you want to see whether a pointer is outside
16997 the data segment's limit (i.e.@: @dfn{garbled}).
16999 @cindex page tables display (MS-DOS)
17001 @itemx info dos pte
17002 These two commands display entries from, respectively, the Page
17003 Directory and the Page Tables. Page Directories and Page Tables are
17004 data structures which control how virtual memory addresses are mapped
17005 into physical addresses. A Page Table includes an entry for every
17006 page of memory that is mapped into the program's address space; there
17007 may be several Page Tables, each one holding up to 4096 entries. A
17008 Page Directory has up to 4096 entries, one each for every Page Table
17009 that is currently in use.
17011 Without an argument, @kbd{info dos pde} displays the entire Page
17012 Directory, and @kbd{info dos pte} displays all the entries in all of
17013 the Page Tables. An argument, an integer expression, given to the
17014 @kbd{info dos pde} command means display only that entry from the Page
17015 Directory table. An argument given to the @kbd{info dos pte} command
17016 means display entries from a single Page Table, the one pointed to by
17017 the specified entry in the Page Directory.
17019 @cindex direct memory access (DMA) on MS-DOS
17020 These commands are useful when your program uses @dfn{DMA} (Direct
17021 Memory Access), which needs physical addresses to program the DMA
17024 These commands are supported only with some DPMI servers.
17026 @cindex physical address from linear address
17027 @item info dos address-pte @var{addr}
17028 This command displays the Page Table entry for a specified linear
17029 address. The argument @var{addr} is a linear address which should
17030 already have the appropriate segment's base address added to it,
17031 because this command accepts addresses which may belong to @emph{any}
17032 segment. For example, here's how to display the Page Table entry for
17033 the page where a variable @code{i} is stored:
17036 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
17037 @exdent @code{Page Table entry for address 0x11a00d30:}
17038 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
17042 This says that @code{i} is stored at offset @code{0xd30} from the page
17043 whose physical base address is @code{0x02698000}, and shows all the
17044 attributes of that page.
17046 Note that you must cast the addresses of variables to a @code{char *},
17047 since otherwise the value of @code{__djgpp_base_address}, the base
17048 address of all variables and functions in a @sc{djgpp} program, will
17049 be added using the rules of C pointer arithmetics: if @code{i} is
17050 declared an @code{int}, @value{GDBN} will add 4 times the value of
17051 @code{__djgpp_base_address} to the address of @code{i}.
17053 Here's another example, it displays the Page Table entry for the
17057 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
17058 @exdent @code{Page Table entry for address 0x29110:}
17059 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
17063 (The @code{+ 3} offset is because the transfer buffer's address is the
17064 3rd member of the @code{_go32_info_block} structure.) The output
17065 clearly shows that this DPMI server maps the addresses in conventional
17066 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
17067 linear (@code{0x29110}) addresses are identical.
17069 This command is supported only with some DPMI servers.
17072 @cindex DOS serial data link, remote debugging
17073 In addition to native debugging, the DJGPP port supports remote
17074 debugging via a serial data link. The following commands are specific
17075 to remote serial debugging in the DJGPP port of @value{GDBN}.
17078 @kindex set com1base
17079 @kindex set com1irq
17080 @kindex set com2base
17081 @kindex set com2irq
17082 @kindex set com3base
17083 @kindex set com3irq
17084 @kindex set com4base
17085 @kindex set com4irq
17086 @item set com1base @var{addr}
17087 This command sets the base I/O port address of the @file{COM1} serial
17090 @item set com1irq @var{irq}
17091 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
17092 for the @file{COM1} serial port.
17094 There are similar commands @samp{set com2base}, @samp{set com3irq},
17095 etc.@: for setting the port address and the @code{IRQ} lines for the
17098 @kindex show com1base
17099 @kindex show com1irq
17100 @kindex show com2base
17101 @kindex show com2irq
17102 @kindex show com3base
17103 @kindex show com3irq
17104 @kindex show com4base
17105 @kindex show com4irq
17106 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
17107 display the current settings of the base address and the @code{IRQ}
17108 lines used by the COM ports.
17111 @kindex info serial
17112 @cindex DOS serial port status
17113 This command prints the status of the 4 DOS serial ports. For each
17114 port, it prints whether it's active or not, its I/O base address and
17115 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
17116 counts of various errors encountered so far.
17120 @node Cygwin Native
17121 @subsection Features for Debugging MS Windows PE Executables
17122 @cindex MS Windows debugging
17123 @cindex native Cygwin debugging
17124 @cindex Cygwin-specific commands
17126 @value{GDBN} supports native debugging of MS Windows programs, including
17127 DLLs with and without symbolic debugging information.
17129 @cindex Ctrl-BREAK, MS-Windows
17130 @cindex interrupt debuggee on MS-Windows
17131 MS-Windows programs that call @code{SetConsoleMode} to switch off the
17132 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
17133 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
17134 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
17135 sequence, which can be used to interrupt the debuggee even if it
17138 There are various additional Cygwin-specific commands, described in
17139 this section. Working with DLLs that have no debugging symbols is
17140 described in @ref{Non-debug DLL Symbols}.
17145 This is a prefix of MS Windows-specific commands which print
17146 information about the target system and important OS structures.
17148 @item info w32 selector
17149 This command displays information returned by
17150 the Win32 API @code{GetThreadSelectorEntry} function.
17151 It takes an optional argument that is evaluated to
17152 a long value to give the information about this given selector.
17153 Without argument, this command displays information
17154 about the six segment registers.
17156 @item info w32 thread-information-block
17157 This command displays thread specific information stored in the
17158 Thread Information Block (readable on the X86 CPU family using @code{$fs}
17159 selector for 32-bit programs and @code{$gs} for 64-bit programs).
17163 This is a Cygwin-specific alias of @code{info shared}.
17165 @kindex dll-symbols
17167 This command loads symbols from a dll similarly to
17168 add-sym command but without the need to specify a base address.
17170 @kindex set cygwin-exceptions
17171 @cindex debugging the Cygwin DLL
17172 @cindex Cygwin DLL, debugging
17173 @item set cygwin-exceptions @var{mode}
17174 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
17175 happen inside the Cygwin DLL. If @var{mode} is @code{off},
17176 @value{GDBN} will delay recognition of exceptions, and may ignore some
17177 exceptions which seem to be caused by internal Cygwin DLL
17178 ``bookkeeping''. This option is meant primarily for debugging the
17179 Cygwin DLL itself; the default value is @code{off} to avoid annoying
17180 @value{GDBN} users with false @code{SIGSEGV} signals.
17182 @kindex show cygwin-exceptions
17183 @item show cygwin-exceptions
17184 Displays whether @value{GDBN} will break on exceptions that happen
17185 inside the Cygwin DLL itself.
17187 @kindex set new-console
17188 @item set new-console @var{mode}
17189 If @var{mode} is @code{on} the debuggee will
17190 be started in a new console on next start.
17191 If @var{mode} is @code{off}, the debuggee will
17192 be started in the same console as the debugger.
17194 @kindex show new-console
17195 @item show new-console
17196 Displays whether a new console is used
17197 when the debuggee is started.
17199 @kindex set new-group
17200 @item set new-group @var{mode}
17201 This boolean value controls whether the debuggee should
17202 start a new group or stay in the same group as the debugger.
17203 This affects the way the Windows OS handles
17206 @kindex show new-group
17207 @item show new-group
17208 Displays current value of new-group boolean.
17210 @kindex set debugevents
17211 @item set debugevents
17212 This boolean value adds debug output concerning kernel events related
17213 to the debuggee seen by the debugger. This includes events that
17214 signal thread and process creation and exit, DLL loading and
17215 unloading, console interrupts, and debugging messages produced by the
17216 Windows @code{OutputDebugString} API call.
17218 @kindex set debugexec
17219 @item set debugexec
17220 This boolean value adds debug output concerning execute events
17221 (such as resume thread) seen by the debugger.
17223 @kindex set debugexceptions
17224 @item set debugexceptions
17225 This boolean value adds debug output concerning exceptions in the
17226 debuggee seen by the debugger.
17228 @kindex set debugmemory
17229 @item set debugmemory
17230 This boolean value adds debug output concerning debuggee memory reads
17231 and writes by the debugger.
17235 This boolean values specifies whether the debuggee is called
17236 via a shell or directly (default value is on).
17240 Displays if the debuggee will be started with a shell.
17245 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
17248 @node Non-debug DLL Symbols
17249 @subsubsection Support for DLLs without Debugging Symbols
17250 @cindex DLLs with no debugging symbols
17251 @cindex Minimal symbols and DLLs
17253 Very often on windows, some of the DLLs that your program relies on do
17254 not include symbolic debugging information (for example,
17255 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
17256 symbols in a DLL, it relies on the minimal amount of symbolic
17257 information contained in the DLL's export table. This section
17258 describes working with such symbols, known internally to @value{GDBN} as
17259 ``minimal symbols''.
17261 Note that before the debugged program has started execution, no DLLs
17262 will have been loaded. The easiest way around this problem is simply to
17263 start the program --- either by setting a breakpoint or letting the
17264 program run once to completion. It is also possible to force
17265 @value{GDBN} to load a particular DLL before starting the executable ---
17266 see the shared library information in @ref{Files}, or the
17267 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
17268 explicitly loading symbols from a DLL with no debugging information will
17269 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
17270 which may adversely affect symbol lookup performance.
17272 @subsubsection DLL Name Prefixes
17274 In keeping with the naming conventions used by the Microsoft debugging
17275 tools, DLL export symbols are made available with a prefix based on the
17276 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
17277 also entered into the symbol table, so @code{CreateFileA} is often
17278 sufficient. In some cases there will be name clashes within a program
17279 (particularly if the executable itself includes full debugging symbols)
17280 necessitating the use of the fully qualified name when referring to the
17281 contents of the DLL. Use single-quotes around the name to avoid the
17282 exclamation mark (``!'') being interpreted as a language operator.
17284 Note that the internal name of the DLL may be all upper-case, even
17285 though the file name of the DLL is lower-case, or vice-versa. Since
17286 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
17287 some confusion. If in doubt, try the @code{info functions} and
17288 @code{info variables} commands or even @code{maint print msymbols}
17289 (@pxref{Symbols}). Here's an example:
17292 (@value{GDBP}) info function CreateFileA
17293 All functions matching regular expression "CreateFileA":
17295 Non-debugging symbols:
17296 0x77e885f4 CreateFileA
17297 0x77e885f4 KERNEL32!CreateFileA
17301 (@value{GDBP}) info function !
17302 All functions matching regular expression "!":
17304 Non-debugging symbols:
17305 0x6100114c cygwin1!__assert
17306 0x61004034 cygwin1!_dll_crt0@@0
17307 0x61004240 cygwin1!dll_crt0(per_process *)
17311 @subsubsection Working with Minimal Symbols
17313 Symbols extracted from a DLL's export table do not contain very much
17314 type information. All that @value{GDBN} can do is guess whether a symbol
17315 refers to a function or variable depending on the linker section that
17316 contains the symbol. Also note that the actual contents of the memory
17317 contained in a DLL are not available unless the program is running. This
17318 means that you cannot examine the contents of a variable or disassemble
17319 a function within a DLL without a running program.
17321 Variables are generally treated as pointers and dereferenced
17322 automatically. For this reason, it is often necessary to prefix a
17323 variable name with the address-of operator (``&'') and provide explicit
17324 type information in the command. Here's an example of the type of
17328 (@value{GDBP}) print 'cygwin1!__argv'
17333 (@value{GDBP}) x 'cygwin1!__argv'
17334 0x10021610: "\230y\""
17337 And two possible solutions:
17340 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
17341 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
17345 (@value{GDBP}) x/2x &'cygwin1!__argv'
17346 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
17347 (@value{GDBP}) x/x 0x10021608
17348 0x10021608: 0x0022fd98
17349 (@value{GDBP}) x/s 0x0022fd98
17350 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
17353 Setting a break point within a DLL is possible even before the program
17354 starts execution. However, under these circumstances, @value{GDBN} can't
17355 examine the initial instructions of the function in order to skip the
17356 function's frame set-up code. You can work around this by using ``*&''
17357 to set the breakpoint at a raw memory address:
17360 (@value{GDBP}) break *&'python22!PyOS_Readline'
17361 Breakpoint 1 at 0x1e04eff0
17364 The author of these extensions is not entirely convinced that setting a
17365 break point within a shared DLL like @file{kernel32.dll} is completely
17369 @subsection Commands Specific to @sc{gnu} Hurd Systems
17370 @cindex @sc{gnu} Hurd debugging
17372 This subsection describes @value{GDBN} commands specific to the
17373 @sc{gnu} Hurd native debugging.
17378 @kindex set signals@r{, Hurd command}
17379 @kindex set sigs@r{, Hurd command}
17380 This command toggles the state of inferior signal interception by
17381 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
17382 affected by this command. @code{sigs} is a shorthand alias for
17387 @kindex show signals@r{, Hurd command}
17388 @kindex show sigs@r{, Hurd command}
17389 Show the current state of intercepting inferior's signals.
17391 @item set signal-thread
17392 @itemx set sigthread
17393 @kindex set signal-thread
17394 @kindex set sigthread
17395 This command tells @value{GDBN} which thread is the @code{libc} signal
17396 thread. That thread is run when a signal is delivered to a running
17397 process. @code{set sigthread} is the shorthand alias of @code{set
17400 @item show signal-thread
17401 @itemx show sigthread
17402 @kindex show signal-thread
17403 @kindex show sigthread
17404 These two commands show which thread will run when the inferior is
17405 delivered a signal.
17408 @kindex set stopped@r{, Hurd command}
17409 This commands tells @value{GDBN} that the inferior process is stopped,
17410 as with the @code{SIGSTOP} signal. The stopped process can be
17411 continued by delivering a signal to it.
17414 @kindex show stopped@r{, Hurd command}
17415 This command shows whether @value{GDBN} thinks the debuggee is
17418 @item set exceptions
17419 @kindex set exceptions@r{, Hurd command}
17420 Use this command to turn off trapping of exceptions in the inferior.
17421 When exception trapping is off, neither breakpoints nor
17422 single-stepping will work. To restore the default, set exception
17425 @item show exceptions
17426 @kindex show exceptions@r{, Hurd command}
17427 Show the current state of trapping exceptions in the inferior.
17429 @item set task pause
17430 @kindex set task@r{, Hurd commands}
17431 @cindex task attributes (@sc{gnu} Hurd)
17432 @cindex pause current task (@sc{gnu} Hurd)
17433 This command toggles task suspension when @value{GDBN} has control.
17434 Setting it to on takes effect immediately, and the task is suspended
17435 whenever @value{GDBN} gets control. Setting it to off will take
17436 effect the next time the inferior is continued. If this option is set
17437 to off, you can use @code{set thread default pause on} or @code{set
17438 thread pause on} (see below) to pause individual threads.
17440 @item show task pause
17441 @kindex show task@r{, Hurd commands}
17442 Show the current state of task suspension.
17444 @item set task detach-suspend-count
17445 @cindex task suspend count
17446 @cindex detach from task, @sc{gnu} Hurd
17447 This command sets the suspend count the task will be left with when
17448 @value{GDBN} detaches from it.
17450 @item show task detach-suspend-count
17451 Show the suspend count the task will be left with when detaching.
17453 @item set task exception-port
17454 @itemx set task excp
17455 @cindex task exception port, @sc{gnu} Hurd
17456 This command sets the task exception port to which @value{GDBN} will
17457 forward exceptions. The argument should be the value of the @dfn{send
17458 rights} of the task. @code{set task excp} is a shorthand alias.
17460 @item set noninvasive
17461 @cindex noninvasive task options
17462 This command switches @value{GDBN} to a mode that is the least
17463 invasive as far as interfering with the inferior is concerned. This
17464 is the same as using @code{set task pause}, @code{set exceptions}, and
17465 @code{set signals} to values opposite to the defaults.
17467 @item info send-rights
17468 @itemx info receive-rights
17469 @itemx info port-rights
17470 @itemx info port-sets
17471 @itemx info dead-names
17474 @cindex send rights, @sc{gnu} Hurd
17475 @cindex receive rights, @sc{gnu} Hurd
17476 @cindex port rights, @sc{gnu} Hurd
17477 @cindex port sets, @sc{gnu} Hurd
17478 @cindex dead names, @sc{gnu} Hurd
17479 These commands display information about, respectively, send rights,
17480 receive rights, port rights, port sets, and dead names of a task.
17481 There are also shorthand aliases: @code{info ports} for @code{info
17482 port-rights} and @code{info psets} for @code{info port-sets}.
17484 @item set thread pause
17485 @kindex set thread@r{, Hurd command}
17486 @cindex thread properties, @sc{gnu} Hurd
17487 @cindex pause current thread (@sc{gnu} Hurd)
17488 This command toggles current thread suspension when @value{GDBN} has
17489 control. Setting it to on takes effect immediately, and the current
17490 thread is suspended whenever @value{GDBN} gets control. Setting it to
17491 off will take effect the next time the inferior is continued.
17492 Normally, this command has no effect, since when @value{GDBN} has
17493 control, the whole task is suspended. However, if you used @code{set
17494 task pause off} (see above), this command comes in handy to suspend
17495 only the current thread.
17497 @item show thread pause
17498 @kindex show thread@r{, Hurd command}
17499 This command shows the state of current thread suspension.
17501 @item set thread run
17502 This command sets whether the current thread is allowed to run.
17504 @item show thread run
17505 Show whether the current thread is allowed to run.
17507 @item set thread detach-suspend-count
17508 @cindex thread suspend count, @sc{gnu} Hurd
17509 @cindex detach from thread, @sc{gnu} Hurd
17510 This command sets the suspend count @value{GDBN} will leave on a
17511 thread when detaching. This number is relative to the suspend count
17512 found by @value{GDBN} when it notices the thread; use @code{set thread
17513 takeover-suspend-count} to force it to an absolute value.
17515 @item show thread detach-suspend-count
17516 Show the suspend count @value{GDBN} will leave on the thread when
17519 @item set thread exception-port
17520 @itemx set thread excp
17521 Set the thread exception port to which to forward exceptions. This
17522 overrides the port set by @code{set task exception-port} (see above).
17523 @code{set thread excp} is the shorthand alias.
17525 @item set thread takeover-suspend-count
17526 Normally, @value{GDBN}'s thread suspend counts are relative to the
17527 value @value{GDBN} finds when it notices each thread. This command
17528 changes the suspend counts to be absolute instead.
17530 @item set thread default
17531 @itemx show thread default
17532 @cindex thread default settings, @sc{gnu} Hurd
17533 Each of the above @code{set thread} commands has a @code{set thread
17534 default} counterpart (e.g., @code{set thread default pause}, @code{set
17535 thread default exception-port}, etc.). The @code{thread default}
17536 variety of commands sets the default thread properties for all
17537 threads; you can then change the properties of individual threads with
17538 the non-default commands.
17543 @subsection QNX Neutrino
17544 @cindex QNX Neutrino
17546 @value{GDBN} provides the following commands specific to the QNX
17550 @item set debug nto-debug
17551 @kindex set debug nto-debug
17552 When set to on, enables debugging messages specific to the QNX
17555 @item show debug nto-debug
17556 @kindex show debug nto-debug
17557 Show the current state of QNX Neutrino messages.
17564 @value{GDBN} provides the following commands specific to the Darwin target:
17567 @item set debug darwin @var{num}
17568 @kindex set debug darwin
17569 When set to a non zero value, enables debugging messages specific to
17570 the Darwin support. Higher values produce more verbose output.
17572 @item show debug darwin
17573 @kindex show debug darwin
17574 Show the current state of Darwin messages.
17576 @item set debug mach-o @var{num}
17577 @kindex set debug mach-o
17578 When set to a non zero value, enables debugging messages while
17579 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
17580 file format used on Darwin for object and executable files.) Higher
17581 values produce more verbose output. This is a command to diagnose
17582 problems internal to @value{GDBN} and should not be needed in normal
17585 @item show debug mach-o
17586 @kindex show debug mach-o
17587 Show the current state of Mach-O file messages.
17589 @item set mach-exceptions on
17590 @itemx set mach-exceptions off
17591 @kindex set mach-exceptions
17592 On Darwin, faults are first reported as a Mach exception and are then
17593 mapped to a Posix signal. Use this command to turn on trapping of
17594 Mach exceptions in the inferior. This might be sometimes useful to
17595 better understand the cause of a fault. The default is off.
17597 @item show mach-exceptions
17598 @kindex show mach-exceptions
17599 Show the current state of exceptions trapping.
17604 @section Embedded Operating Systems
17606 This section describes configurations involving the debugging of
17607 embedded operating systems that are available for several different
17611 * VxWorks:: Using @value{GDBN} with VxWorks
17614 @value{GDBN} includes the ability to debug programs running on
17615 various real-time operating systems.
17618 @subsection Using @value{GDBN} with VxWorks
17624 @kindex target vxworks
17625 @item target vxworks @var{machinename}
17626 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
17627 is the target system's machine name or IP address.
17631 On VxWorks, @code{load} links @var{filename} dynamically on the
17632 current target system as well as adding its symbols in @value{GDBN}.
17634 @value{GDBN} enables developers to spawn and debug tasks running on networked
17635 VxWorks targets from a Unix host. Already-running tasks spawned from
17636 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
17637 both the Unix host and on the VxWorks target. The program
17638 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
17639 installed with the name @code{vxgdb}, to distinguish it from a
17640 @value{GDBN} for debugging programs on the host itself.)
17643 @item VxWorks-timeout @var{args}
17644 @kindex vxworks-timeout
17645 All VxWorks-based targets now support the option @code{vxworks-timeout}.
17646 This option is set by the user, and @var{args} represents the number of
17647 seconds @value{GDBN} waits for responses to rpc's. You might use this if
17648 your VxWorks target is a slow software simulator or is on the far side
17649 of a thin network line.
17652 The following information on connecting to VxWorks was current when
17653 this manual was produced; newer releases of VxWorks may use revised
17656 @findex INCLUDE_RDB
17657 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
17658 to include the remote debugging interface routines in the VxWorks
17659 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
17660 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
17661 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
17662 source debugging task @code{tRdbTask} when VxWorks is booted. For more
17663 information on configuring and remaking VxWorks, see the manufacturer's
17665 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
17667 Once you have included @file{rdb.a} in your VxWorks system image and set
17668 your Unix execution search path to find @value{GDBN}, you are ready to
17669 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
17670 @code{vxgdb}, depending on your installation).
17672 @value{GDBN} comes up showing the prompt:
17679 * VxWorks Connection:: Connecting to VxWorks
17680 * VxWorks Download:: VxWorks download
17681 * VxWorks Attach:: Running tasks
17684 @node VxWorks Connection
17685 @subsubsection Connecting to VxWorks
17687 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
17688 network. To connect to a target whose host name is ``@code{tt}'', type:
17691 (vxgdb) target vxworks tt
17695 @value{GDBN} displays messages like these:
17698 Attaching remote machine across net...
17703 @value{GDBN} then attempts to read the symbol tables of any object modules
17704 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
17705 these files by searching the directories listed in the command search
17706 path (@pxref{Environment, ,Your Program's Environment}); if it fails
17707 to find an object file, it displays a message such as:
17710 prog.o: No such file or directory.
17713 When this happens, add the appropriate directory to the search path with
17714 the @value{GDBN} command @code{path}, and execute the @code{target}
17717 @node VxWorks Download
17718 @subsubsection VxWorks Download
17720 @cindex download to VxWorks
17721 If you have connected to the VxWorks target and you want to debug an
17722 object that has not yet been loaded, you can use the @value{GDBN}
17723 @code{load} command to download a file from Unix to VxWorks
17724 incrementally. The object file given as an argument to the @code{load}
17725 command is actually opened twice: first by the VxWorks target in order
17726 to download the code, then by @value{GDBN} in order to read the symbol
17727 table. This can lead to problems if the current working directories on
17728 the two systems differ. If both systems have NFS mounted the same
17729 filesystems, you can avoid these problems by using absolute paths.
17730 Otherwise, it is simplest to set the working directory on both systems
17731 to the directory in which the object file resides, and then to reference
17732 the file by its name, without any path. For instance, a program
17733 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
17734 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
17735 program, type this on VxWorks:
17738 -> cd "@var{vxpath}/vw/demo/rdb"
17742 Then, in @value{GDBN}, type:
17745 (vxgdb) cd @var{hostpath}/vw/demo/rdb
17746 (vxgdb) load prog.o
17749 @value{GDBN} displays a response similar to this:
17752 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
17755 You can also use the @code{load} command to reload an object module
17756 after editing and recompiling the corresponding source file. Note that
17757 this makes @value{GDBN} delete all currently-defined breakpoints,
17758 auto-displays, and convenience variables, and to clear the value
17759 history. (This is necessary in order to preserve the integrity of
17760 debugger's data structures that reference the target system's symbol
17763 @node VxWorks Attach
17764 @subsubsection Running Tasks
17766 @cindex running VxWorks tasks
17767 You can also attach to an existing task using the @code{attach} command as
17771 (vxgdb) attach @var{task}
17775 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
17776 or suspended when you attach to it. Running tasks are suspended at
17777 the time of attachment.
17779 @node Embedded Processors
17780 @section Embedded Processors
17782 This section goes into details specific to particular embedded
17785 @cindex send command to simulator
17786 Whenever a specific embedded processor has a simulator, @value{GDBN}
17787 allows to send an arbitrary command to the simulator.
17790 @item sim @var{command}
17791 @kindex sim@r{, a command}
17792 Send an arbitrary @var{command} string to the simulator. Consult the
17793 documentation for the specific simulator in use for information about
17794 acceptable commands.
17800 * M32R/D:: Renesas M32R/D
17801 * M68K:: Motorola M68K
17802 * MicroBlaze:: Xilinx MicroBlaze
17803 * MIPS Embedded:: MIPS Embedded
17804 * OpenRISC 1000:: OpenRisc 1000
17805 * PA:: HP PA Embedded
17806 * PowerPC Embedded:: PowerPC Embedded
17807 * Sparclet:: Tsqware Sparclet
17808 * Sparclite:: Fujitsu Sparclite
17809 * Z8000:: Zilog Z8000
17812 * Super-H:: Renesas Super-H
17821 @item target rdi @var{dev}
17822 ARM Angel monitor, via RDI library interface to ADP protocol. You may
17823 use this target to communicate with both boards running the Angel
17824 monitor, or with the EmbeddedICE JTAG debug device.
17827 @item target rdp @var{dev}
17832 @value{GDBN} provides the following ARM-specific commands:
17835 @item set arm disassembler
17837 This commands selects from a list of disassembly styles. The
17838 @code{"std"} style is the standard style.
17840 @item show arm disassembler
17842 Show the current disassembly style.
17844 @item set arm apcs32
17845 @cindex ARM 32-bit mode
17846 This command toggles ARM operation mode between 32-bit and 26-bit.
17848 @item show arm apcs32
17849 Display the current usage of the ARM 32-bit mode.
17851 @item set arm fpu @var{fputype}
17852 This command sets the ARM floating-point unit (FPU) type. The
17853 argument @var{fputype} can be one of these:
17857 Determine the FPU type by querying the OS ABI.
17859 Software FPU, with mixed-endian doubles on little-endian ARM
17862 GCC-compiled FPA co-processor.
17864 Software FPU with pure-endian doubles.
17870 Show the current type of the FPU.
17873 This command forces @value{GDBN} to use the specified ABI.
17876 Show the currently used ABI.
17878 @item set arm fallback-mode (arm|thumb|auto)
17879 @value{GDBN} uses the symbol table, when available, to determine
17880 whether instructions are ARM or Thumb. This command controls
17881 @value{GDBN}'s default behavior when the symbol table is not
17882 available. The default is @samp{auto}, which causes @value{GDBN} to
17883 use the current execution mode (from the @code{T} bit in the @code{CPSR}
17886 @item show arm fallback-mode
17887 Show the current fallback instruction mode.
17889 @item set arm force-mode (arm|thumb|auto)
17890 This command overrides use of the symbol table to determine whether
17891 instructions are ARM or Thumb. The default is @samp{auto}, which
17892 causes @value{GDBN} to use the symbol table and then the setting
17893 of @samp{set arm fallback-mode}.
17895 @item show arm force-mode
17896 Show the current forced instruction mode.
17898 @item set debug arm
17899 Toggle whether to display ARM-specific debugging messages from the ARM
17900 target support subsystem.
17902 @item show debug arm
17903 Show whether ARM-specific debugging messages are enabled.
17906 The following commands are available when an ARM target is debugged
17907 using the RDI interface:
17910 @item rdilogfile @r{[}@var{file}@r{]}
17912 @cindex ADP (Angel Debugger Protocol) logging
17913 Set the filename for the ADP (Angel Debugger Protocol) packet log.
17914 With an argument, sets the log file to the specified @var{file}. With
17915 no argument, show the current log file name. The default log file is
17918 @item rdilogenable @r{[}@var{arg}@r{]}
17919 @kindex rdilogenable
17920 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
17921 enables logging, with an argument 0 or @code{"no"} disables it. With
17922 no arguments displays the current setting. When logging is enabled,
17923 ADP packets exchanged between @value{GDBN} and the RDI target device
17924 are logged to a file.
17926 @item set rdiromatzero
17927 @kindex set rdiromatzero
17928 @cindex ROM at zero address, RDI
17929 Tell @value{GDBN} whether the target has ROM at address 0. If on,
17930 vector catching is disabled, so that zero address can be used. If off
17931 (the default), vector catching is enabled. For this command to take
17932 effect, it needs to be invoked prior to the @code{target rdi} command.
17934 @item show rdiromatzero
17935 @kindex show rdiromatzero
17936 Show the current setting of ROM at zero address.
17938 @item set rdiheartbeat
17939 @kindex set rdiheartbeat
17940 @cindex RDI heartbeat
17941 Enable or disable RDI heartbeat packets. It is not recommended to
17942 turn on this option, since it confuses ARM and EPI JTAG interface, as
17943 well as the Angel monitor.
17945 @item show rdiheartbeat
17946 @kindex show rdiheartbeat
17947 Show the setting of RDI heartbeat packets.
17951 @item target sim @r{[}@var{simargs}@r{]} @dots{}
17952 The @value{GDBN} ARM simulator accepts the following optional arguments.
17955 @item --swi-support=@var{type}
17956 Tell the simulator which SWI interfaces to support.
17957 @var{type} may be a comma separated list of the following values.
17958 The default value is @code{all}.
17971 @subsection Renesas M32R/D and M32R/SDI
17974 @kindex target m32r
17975 @item target m32r @var{dev}
17976 Renesas M32R/D ROM monitor.
17978 @kindex target m32rsdi
17979 @item target m32rsdi @var{dev}
17980 Renesas M32R SDI server, connected via parallel port to the board.
17983 The following @value{GDBN} commands are specific to the M32R monitor:
17986 @item set download-path @var{path}
17987 @kindex set download-path
17988 @cindex find downloadable @sc{srec} files (M32R)
17989 Set the default path for finding downloadable @sc{srec} files.
17991 @item show download-path
17992 @kindex show download-path
17993 Show the default path for downloadable @sc{srec} files.
17995 @item set board-address @var{addr}
17996 @kindex set board-address
17997 @cindex M32-EVA target board address
17998 Set the IP address for the M32R-EVA target board.
18000 @item show board-address
18001 @kindex show board-address
18002 Show the current IP address of the target board.
18004 @item set server-address @var{addr}
18005 @kindex set server-address
18006 @cindex download server address (M32R)
18007 Set the IP address for the download server, which is the @value{GDBN}'s
18010 @item show server-address
18011 @kindex show server-address
18012 Display the IP address of the download server.
18014 @item upload @r{[}@var{file}@r{]}
18015 @kindex upload@r{, M32R}
18016 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
18017 upload capability. If no @var{file} argument is given, the current
18018 executable file is uploaded.
18020 @item tload @r{[}@var{file}@r{]}
18021 @kindex tload@r{, M32R}
18022 Test the @code{upload} command.
18025 The following commands are available for M32R/SDI:
18030 @cindex reset SDI connection, M32R
18031 This command resets the SDI connection.
18035 This command shows the SDI connection status.
18038 @kindex debug_chaos
18039 @cindex M32R/Chaos debugging
18040 Instructs the remote that M32R/Chaos debugging is to be used.
18042 @item use_debug_dma
18043 @kindex use_debug_dma
18044 Instructs the remote to use the DEBUG_DMA method of accessing memory.
18047 @kindex use_mon_code
18048 Instructs the remote to use the MON_CODE method of accessing memory.
18051 @kindex use_ib_break
18052 Instructs the remote to set breakpoints by IB break.
18054 @item use_dbt_break
18055 @kindex use_dbt_break
18056 Instructs the remote to set breakpoints by DBT.
18062 The Motorola m68k configuration includes ColdFire support, and a
18063 target command for the following ROM monitor.
18067 @kindex target dbug
18068 @item target dbug @var{dev}
18069 dBUG ROM monitor for Motorola ColdFire.
18074 @subsection MicroBlaze
18075 @cindex Xilinx MicroBlaze
18076 @cindex XMD, Xilinx Microprocessor Debugger
18078 The MicroBlaze is a soft-core processor supported on various Xilinx
18079 FPGAs, such as Spartan or Virtex series. Boards with these processors
18080 usually have JTAG ports which connect to a host system running the Xilinx
18081 Embedded Development Kit (EDK) or Software Development Kit (SDK).
18082 This host system is used to download the configuration bitstream to
18083 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
18084 communicates with the target board using the JTAG interface and
18085 presents a @code{gdbserver} interface to the board. By default
18086 @code{xmd} uses port @code{1234}. (While it is possible to change
18087 this default port, it requires the use of undocumented @code{xmd}
18088 commands. Contact Xilinx support if you need to do this.)
18090 Use these GDB commands to connect to the MicroBlaze target processor.
18093 @item target remote :1234
18094 Use this command to connect to the target if you are running @value{GDBN}
18095 on the same system as @code{xmd}.
18097 @item target remote @var{xmd-host}:1234
18098 Use this command to connect to the target if it is connected to @code{xmd}
18099 running on a different system named @var{xmd-host}.
18102 Use this command to download a program to the MicroBlaze target.
18104 @item set debug microblaze @var{n}
18105 Enable MicroBlaze-specific debugging messages if non-zero.
18107 @item show debug microblaze @var{n}
18108 Show MicroBlaze-specific debugging level.
18111 @node MIPS Embedded
18112 @subsection MIPS Embedded
18114 @cindex MIPS boards
18115 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
18116 MIPS board attached to a serial line. This is available when
18117 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
18120 Use these @value{GDBN} commands to specify the connection to your target board:
18123 @item target mips @var{port}
18124 @kindex target mips @var{port}
18125 To run a program on the board, start up @code{@value{GDBP}} with the
18126 name of your program as the argument. To connect to the board, use the
18127 command @samp{target mips @var{port}}, where @var{port} is the name of
18128 the serial port connected to the board. If the program has not already
18129 been downloaded to the board, you may use the @code{load} command to
18130 download it. You can then use all the usual @value{GDBN} commands.
18132 For example, this sequence connects to the target board through a serial
18133 port, and loads and runs a program called @var{prog} through the
18137 host$ @value{GDBP} @var{prog}
18138 @value{GDBN} is free software and @dots{}
18139 (@value{GDBP}) target mips /dev/ttyb
18140 (@value{GDBP}) load @var{prog}
18144 @item target mips @var{hostname}:@var{portnumber}
18145 On some @value{GDBN} host configurations, you can specify a TCP
18146 connection (for instance, to a serial line managed by a terminal
18147 concentrator) instead of a serial port, using the syntax
18148 @samp{@var{hostname}:@var{portnumber}}.
18150 @item target pmon @var{port}
18151 @kindex target pmon @var{port}
18154 @item target ddb @var{port}
18155 @kindex target ddb @var{port}
18156 NEC's DDB variant of PMON for Vr4300.
18158 @item target lsi @var{port}
18159 @kindex target lsi @var{port}
18160 LSI variant of PMON.
18162 @kindex target r3900
18163 @item target r3900 @var{dev}
18164 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
18166 @kindex target array
18167 @item target array @var{dev}
18168 Array Tech LSI33K RAID controller board.
18174 @value{GDBN} also supports these special commands for MIPS targets:
18177 @item set mipsfpu double
18178 @itemx set mipsfpu single
18179 @itemx set mipsfpu none
18180 @itemx set mipsfpu auto
18181 @itemx show mipsfpu
18182 @kindex set mipsfpu
18183 @kindex show mipsfpu
18184 @cindex MIPS remote floating point
18185 @cindex floating point, MIPS remote
18186 If your target board does not support the MIPS floating point
18187 coprocessor, you should use the command @samp{set mipsfpu none} (if you
18188 need this, you may wish to put the command in your @value{GDBN} init
18189 file). This tells @value{GDBN} how to find the return value of
18190 functions which return floating point values. It also allows
18191 @value{GDBN} to avoid saving the floating point registers when calling
18192 functions on the board. If you are using a floating point coprocessor
18193 with only single precision floating point support, as on the @sc{r4650}
18194 processor, use the command @samp{set mipsfpu single}. The default
18195 double precision floating point coprocessor may be selected using
18196 @samp{set mipsfpu double}.
18198 In previous versions the only choices were double precision or no
18199 floating point, so @samp{set mipsfpu on} will select double precision
18200 and @samp{set mipsfpu off} will select no floating point.
18202 As usual, you can inquire about the @code{mipsfpu} variable with
18203 @samp{show mipsfpu}.
18205 @item set timeout @var{seconds}
18206 @itemx set retransmit-timeout @var{seconds}
18207 @itemx show timeout
18208 @itemx show retransmit-timeout
18209 @cindex @code{timeout}, MIPS protocol
18210 @cindex @code{retransmit-timeout}, MIPS protocol
18211 @kindex set timeout
18212 @kindex show timeout
18213 @kindex set retransmit-timeout
18214 @kindex show retransmit-timeout
18215 You can control the timeout used while waiting for a packet, in the MIPS
18216 remote protocol, with the @code{set timeout @var{seconds}} command. The
18217 default is 5 seconds. Similarly, you can control the timeout used while
18218 waiting for an acknowledgment of a packet with the @code{set
18219 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
18220 You can inspect both values with @code{show timeout} and @code{show
18221 retransmit-timeout}. (These commands are @emph{only} available when
18222 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
18224 The timeout set by @code{set timeout} does not apply when @value{GDBN}
18225 is waiting for your program to stop. In that case, @value{GDBN} waits
18226 forever because it has no way of knowing how long the program is going
18227 to run before stopping.
18229 @item set syn-garbage-limit @var{num}
18230 @kindex set syn-garbage-limit@r{, MIPS remote}
18231 @cindex synchronize with remote MIPS target
18232 Limit the maximum number of characters @value{GDBN} should ignore when
18233 it tries to synchronize with the remote target. The default is 10
18234 characters. Setting the limit to -1 means there's no limit.
18236 @item show syn-garbage-limit
18237 @kindex show syn-garbage-limit@r{, MIPS remote}
18238 Show the current limit on the number of characters to ignore when
18239 trying to synchronize with the remote system.
18241 @item set monitor-prompt @var{prompt}
18242 @kindex set monitor-prompt@r{, MIPS remote}
18243 @cindex remote monitor prompt
18244 Tell @value{GDBN} to expect the specified @var{prompt} string from the
18245 remote monitor. The default depends on the target:
18255 @item show monitor-prompt
18256 @kindex show monitor-prompt@r{, MIPS remote}
18257 Show the current strings @value{GDBN} expects as the prompt from the
18260 @item set monitor-warnings
18261 @kindex set monitor-warnings@r{, MIPS remote}
18262 Enable or disable monitor warnings about hardware breakpoints. This
18263 has effect only for the @code{lsi} target. When on, @value{GDBN} will
18264 display warning messages whose codes are returned by the @code{lsi}
18265 PMON monitor for breakpoint commands.
18267 @item show monitor-warnings
18268 @kindex show monitor-warnings@r{, MIPS remote}
18269 Show the current setting of printing monitor warnings.
18271 @item pmon @var{command}
18272 @kindex pmon@r{, MIPS remote}
18273 @cindex send PMON command
18274 This command allows sending an arbitrary @var{command} string to the
18275 monitor. The monitor must be in debug mode for this to work.
18278 @node OpenRISC 1000
18279 @subsection OpenRISC 1000
18280 @cindex OpenRISC 1000
18282 @cindex or1k boards
18283 See OR1k Architecture document (@uref{www.opencores.org}) for more information
18284 about platform and commands.
18288 @kindex target jtag
18289 @item target jtag jtag://@var{host}:@var{port}
18291 Connects to remote JTAG server.
18292 JTAG remote server can be either an or1ksim or JTAG server,
18293 connected via parallel port to the board.
18295 Example: @code{target jtag jtag://localhost:9999}
18298 @item or1ksim @var{command}
18299 If connected to @code{or1ksim} OpenRISC 1000 Architectural
18300 Simulator, proprietary commands can be executed.
18302 @kindex info or1k spr
18303 @item info or1k spr
18304 Displays spr groups.
18306 @item info or1k spr @var{group}
18307 @itemx info or1k spr @var{groupno}
18308 Displays register names in selected group.
18310 @item info or1k spr @var{group} @var{register}
18311 @itemx info or1k spr @var{register}
18312 @itemx info or1k spr @var{groupno} @var{registerno}
18313 @itemx info or1k spr @var{registerno}
18314 Shows information about specified spr register.
18317 @item spr @var{group} @var{register} @var{value}
18318 @itemx spr @var{register @var{value}}
18319 @itemx spr @var{groupno} @var{registerno @var{value}}
18320 @itemx spr @var{registerno @var{value}}
18321 Writes @var{value} to specified spr register.
18324 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
18325 It is very similar to @value{GDBN} trace, except it does not interfere with normal
18326 program execution and is thus much faster. Hardware breakpoints/watchpoint
18327 triggers can be set using:
18330 Load effective address/data
18332 Store effective address/data
18334 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
18339 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
18340 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
18342 @code{htrace} commands:
18343 @cindex OpenRISC 1000 htrace
18346 @item hwatch @var{conditional}
18347 Set hardware watchpoint on combination of Load/Store Effective Address(es)
18348 or Data. For example:
18350 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
18352 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
18356 Display information about current HW trace configuration.
18358 @item htrace trigger @var{conditional}
18359 Set starting criteria for HW trace.
18361 @item htrace qualifier @var{conditional}
18362 Set acquisition qualifier for HW trace.
18364 @item htrace stop @var{conditional}
18365 Set HW trace stopping criteria.
18367 @item htrace record [@var{data}]*
18368 Selects the data to be recorded, when qualifier is met and HW trace was
18371 @item htrace enable
18372 @itemx htrace disable
18373 Enables/disables the HW trace.
18375 @item htrace rewind [@var{filename}]
18376 Clears currently recorded trace data.
18378 If filename is specified, new trace file is made and any newly collected data
18379 will be written there.
18381 @item htrace print [@var{start} [@var{len}]]
18382 Prints trace buffer, using current record configuration.
18384 @item htrace mode continuous
18385 Set continuous trace mode.
18387 @item htrace mode suspend
18388 Set suspend trace mode.
18392 @node PowerPC Embedded
18393 @subsection PowerPC Embedded
18395 @value{GDBN} provides the following PowerPC-specific commands:
18398 @kindex set powerpc
18399 @item set powerpc soft-float
18400 @itemx show powerpc soft-float
18401 Force @value{GDBN} to use (or not use) a software floating point calling
18402 convention. By default, @value{GDBN} selects the calling convention based
18403 on the selected architecture and the provided executable file.
18405 @item set powerpc vector-abi
18406 @itemx show powerpc vector-abi
18407 Force @value{GDBN} to use the specified calling convention for vector
18408 arguments and return values. The valid options are @samp{auto};
18409 @samp{generic}, to avoid vector registers even if they are present;
18410 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
18411 registers. By default, @value{GDBN} selects the calling convention
18412 based on the selected architecture and the provided executable file.
18414 @kindex target dink32
18415 @item target dink32 @var{dev}
18416 DINK32 ROM monitor.
18418 @kindex target ppcbug
18419 @item target ppcbug @var{dev}
18420 @kindex target ppcbug1
18421 @item target ppcbug1 @var{dev}
18422 PPCBUG ROM monitor for PowerPC.
18425 @item target sds @var{dev}
18426 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
18429 @cindex SDS protocol
18430 The following commands specific to the SDS protocol are supported
18434 @item set sdstimeout @var{nsec}
18435 @kindex set sdstimeout
18436 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
18437 default is 2 seconds.
18439 @item show sdstimeout
18440 @kindex show sdstimeout
18441 Show the current value of the SDS timeout.
18443 @item sds @var{command}
18444 @kindex sds@r{, a command}
18445 Send the specified @var{command} string to the SDS monitor.
18450 @subsection HP PA Embedded
18454 @kindex target op50n
18455 @item target op50n @var{dev}
18456 OP50N monitor, running on an OKI HPPA board.
18458 @kindex target w89k
18459 @item target w89k @var{dev}
18460 W89K monitor, running on a Winbond HPPA board.
18465 @subsection Tsqware Sparclet
18469 @value{GDBN} enables developers to debug tasks running on
18470 Sparclet targets from a Unix host.
18471 @value{GDBN} uses code that runs on
18472 both the Unix host and on the Sparclet target. The program
18473 @code{@value{GDBP}} is installed and executed on the Unix host.
18476 @item remotetimeout @var{args}
18477 @kindex remotetimeout
18478 @value{GDBN} supports the option @code{remotetimeout}.
18479 This option is set by the user, and @var{args} represents the number of
18480 seconds @value{GDBN} waits for responses.
18483 @cindex compiling, on Sparclet
18484 When compiling for debugging, include the options @samp{-g} to get debug
18485 information and @samp{-Ttext} to relocate the program to where you wish to
18486 load it on the target. You may also want to add the options @samp{-n} or
18487 @samp{-N} in order to reduce the size of the sections. Example:
18490 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
18493 You can use @code{objdump} to verify that the addresses are what you intended:
18496 sparclet-aout-objdump --headers --syms prog
18499 @cindex running, on Sparclet
18501 your Unix execution search path to find @value{GDBN}, you are ready to
18502 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
18503 (or @code{sparclet-aout-gdb}, depending on your installation).
18505 @value{GDBN} comes up showing the prompt:
18512 * Sparclet File:: Setting the file to debug
18513 * Sparclet Connection:: Connecting to Sparclet
18514 * Sparclet Download:: Sparclet download
18515 * Sparclet Execution:: Running and debugging
18518 @node Sparclet File
18519 @subsubsection Setting File to Debug
18521 The @value{GDBN} command @code{file} lets you choose with program to debug.
18524 (gdbslet) file prog
18528 @value{GDBN} then attempts to read the symbol table of @file{prog}.
18529 @value{GDBN} locates
18530 the file by searching the directories listed in the command search
18532 If the file was compiled with debug information (option @samp{-g}), source
18533 files will be searched as well.
18534 @value{GDBN} locates
18535 the source files by searching the directories listed in the directory search
18536 path (@pxref{Environment, ,Your Program's Environment}).
18538 to find a file, it displays a message such as:
18541 prog: No such file or directory.
18544 When this happens, add the appropriate directories to the search paths with
18545 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
18546 @code{target} command again.
18548 @node Sparclet Connection
18549 @subsubsection Connecting to Sparclet
18551 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
18552 To connect to a target on serial port ``@code{ttya}'', type:
18555 (gdbslet) target sparclet /dev/ttya
18556 Remote target sparclet connected to /dev/ttya
18557 main () at ../prog.c:3
18561 @value{GDBN} displays messages like these:
18567 @node Sparclet Download
18568 @subsubsection Sparclet Download
18570 @cindex download to Sparclet
18571 Once connected to the Sparclet target,
18572 you can use the @value{GDBN}
18573 @code{load} command to download the file from the host to the target.
18574 The file name and load offset should be given as arguments to the @code{load}
18576 Since the file format is aout, the program must be loaded to the starting
18577 address. You can use @code{objdump} to find out what this value is. The load
18578 offset is an offset which is added to the VMA (virtual memory address)
18579 of each of the file's sections.
18580 For instance, if the program
18581 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
18582 and bss at 0x12010170, in @value{GDBN}, type:
18585 (gdbslet) load prog 0x12010000
18586 Loading section .text, size 0xdb0 vma 0x12010000
18589 If the code is loaded at a different address then what the program was linked
18590 to, you may need to use the @code{section} and @code{add-symbol-file} commands
18591 to tell @value{GDBN} where to map the symbol table.
18593 @node Sparclet Execution
18594 @subsubsection Running and Debugging
18596 @cindex running and debugging Sparclet programs
18597 You can now begin debugging the task using @value{GDBN}'s execution control
18598 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
18599 manual for the list of commands.
18603 Breakpoint 1 at 0x12010000: file prog.c, line 3.
18605 Starting program: prog
18606 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
18607 3 char *symarg = 0;
18609 4 char *execarg = "hello!";
18614 @subsection Fujitsu Sparclite
18618 @kindex target sparclite
18619 @item target sparclite @var{dev}
18620 Fujitsu sparclite boards, used only for the purpose of loading.
18621 You must use an additional command to debug the program.
18622 For example: target remote @var{dev} using @value{GDBN} standard
18628 @subsection Zilog Z8000
18631 @cindex simulator, Z8000
18632 @cindex Zilog Z8000 simulator
18634 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
18637 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
18638 unsegmented variant of the Z8000 architecture) or the Z8001 (the
18639 segmented variant). The simulator recognizes which architecture is
18640 appropriate by inspecting the object code.
18643 @item target sim @var{args}
18645 @kindex target sim@r{, with Z8000}
18646 Debug programs on a simulated CPU. If the simulator supports setup
18647 options, specify them via @var{args}.
18651 After specifying this target, you can debug programs for the simulated
18652 CPU in the same style as programs for your host computer; use the
18653 @code{file} command to load a new program image, the @code{run} command
18654 to run your program, and so on.
18656 As well as making available all the usual machine registers
18657 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
18658 additional items of information as specially named registers:
18663 Counts clock-ticks in the simulator.
18666 Counts instructions run in the simulator.
18669 Execution time in 60ths of a second.
18673 You can refer to these values in @value{GDBN} expressions with the usual
18674 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
18675 conditional breakpoint that suspends only after at least 5000
18676 simulated clock ticks.
18679 @subsection Atmel AVR
18682 When configured for debugging the Atmel AVR, @value{GDBN} supports the
18683 following AVR-specific commands:
18686 @item info io_registers
18687 @kindex info io_registers@r{, AVR}
18688 @cindex I/O registers (Atmel AVR)
18689 This command displays information about the AVR I/O registers. For
18690 each register, @value{GDBN} prints its number and value.
18697 When configured for debugging CRIS, @value{GDBN} provides the
18698 following CRIS-specific commands:
18701 @item set cris-version @var{ver}
18702 @cindex CRIS version
18703 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
18704 The CRIS version affects register names and sizes. This command is useful in
18705 case autodetection of the CRIS version fails.
18707 @item show cris-version
18708 Show the current CRIS version.
18710 @item set cris-dwarf2-cfi
18711 @cindex DWARF-2 CFI and CRIS
18712 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
18713 Change to @samp{off} when using @code{gcc-cris} whose version is below
18716 @item show cris-dwarf2-cfi
18717 Show the current state of using DWARF-2 CFI.
18719 @item set cris-mode @var{mode}
18721 Set the current CRIS mode to @var{mode}. It should only be changed when
18722 debugging in guru mode, in which case it should be set to
18723 @samp{guru} (the default is @samp{normal}).
18725 @item show cris-mode
18726 Show the current CRIS mode.
18730 @subsection Renesas Super-H
18733 For the Renesas Super-H processor, @value{GDBN} provides these
18738 @kindex regs@r{, Super-H}
18739 Show the values of all Super-H registers.
18741 @item set sh calling-convention @var{convention}
18742 @kindex set sh calling-convention
18743 Set the calling-convention used when calling functions from @value{GDBN}.
18744 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
18745 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
18746 convention. If the DWARF-2 information of the called function specifies
18747 that the function follows the Renesas calling convention, the function
18748 is called using the Renesas calling convention. If the calling convention
18749 is set to @samp{renesas}, the Renesas calling convention is always used,
18750 regardless of the DWARF-2 information. This can be used to override the
18751 default of @samp{gcc} if debug information is missing, or the compiler
18752 does not emit the DWARF-2 calling convention entry for a function.
18754 @item show sh calling-convention
18755 @kindex show sh calling-convention
18756 Show the current calling convention setting.
18761 @node Architectures
18762 @section Architectures
18764 This section describes characteristics of architectures that affect
18765 all uses of @value{GDBN} with the architecture, both native and cross.
18772 * HPPA:: HP PA architecture
18773 * SPU:: Cell Broadband Engine SPU architecture
18778 @subsection x86 Architecture-specific Issues
18781 @item set struct-convention @var{mode}
18782 @kindex set struct-convention
18783 @cindex struct return convention
18784 @cindex struct/union returned in registers
18785 Set the convention used by the inferior to return @code{struct}s and
18786 @code{union}s from functions to @var{mode}. Possible values of
18787 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
18788 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
18789 are returned on the stack, while @code{"reg"} means that a
18790 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
18791 be returned in a register.
18793 @item show struct-convention
18794 @kindex show struct-convention
18795 Show the current setting of the convention to return @code{struct}s
18804 @kindex set rstack_high_address
18805 @cindex AMD 29K register stack
18806 @cindex register stack, AMD29K
18807 @item set rstack_high_address @var{address}
18808 On AMD 29000 family processors, registers are saved in a separate
18809 @dfn{register stack}. There is no way for @value{GDBN} to determine the
18810 extent of this stack. Normally, @value{GDBN} just assumes that the
18811 stack is ``large enough''. This may result in @value{GDBN} referencing
18812 memory locations that do not exist. If necessary, you can get around
18813 this problem by specifying the ending address of the register stack with
18814 the @code{set rstack_high_address} command. The argument should be an
18815 address, which you probably want to precede with @samp{0x} to specify in
18818 @kindex show rstack_high_address
18819 @item show rstack_high_address
18820 Display the current limit of the register stack, on AMD 29000 family
18828 See the following section.
18833 @cindex stack on Alpha
18834 @cindex stack on MIPS
18835 @cindex Alpha stack
18837 Alpha- and MIPS-based computers use an unusual stack frame, which
18838 sometimes requires @value{GDBN} to search backward in the object code to
18839 find the beginning of a function.
18841 @cindex response time, MIPS debugging
18842 To improve response time (especially for embedded applications, where
18843 @value{GDBN} may be restricted to a slow serial line for this search)
18844 you may want to limit the size of this search, using one of these
18848 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
18849 @item set heuristic-fence-post @var{limit}
18850 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
18851 search for the beginning of a function. A value of @var{0} (the
18852 default) means there is no limit. However, except for @var{0}, the
18853 larger the limit the more bytes @code{heuristic-fence-post} must search
18854 and therefore the longer it takes to run. You should only need to use
18855 this command when debugging a stripped executable.
18857 @item show heuristic-fence-post
18858 Display the current limit.
18862 These commands are available @emph{only} when @value{GDBN} is configured
18863 for debugging programs on Alpha or MIPS processors.
18865 Several MIPS-specific commands are available when debugging MIPS
18869 @item set mips abi @var{arg}
18870 @kindex set mips abi
18871 @cindex set ABI for MIPS
18872 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
18873 values of @var{arg} are:
18877 The default ABI associated with the current binary (this is the
18888 @item show mips abi
18889 @kindex show mips abi
18890 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
18893 @itemx show mipsfpu
18894 @xref{MIPS Embedded, set mipsfpu}.
18896 @item set mips mask-address @var{arg}
18897 @kindex set mips mask-address
18898 @cindex MIPS addresses, masking
18899 This command determines whether the most-significant 32 bits of 64-bit
18900 MIPS addresses are masked off. The argument @var{arg} can be
18901 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
18902 setting, which lets @value{GDBN} determine the correct value.
18904 @item show mips mask-address
18905 @kindex show mips mask-address
18906 Show whether the upper 32 bits of MIPS addresses are masked off or
18909 @item set remote-mips64-transfers-32bit-regs
18910 @kindex set remote-mips64-transfers-32bit-regs
18911 This command controls compatibility with 64-bit MIPS targets that
18912 transfer data in 32-bit quantities. If you have an old MIPS 64 target
18913 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
18914 and 64 bits for other registers, set this option to @samp{on}.
18916 @item show remote-mips64-transfers-32bit-regs
18917 @kindex show remote-mips64-transfers-32bit-regs
18918 Show the current setting of compatibility with older MIPS 64 targets.
18920 @item set debug mips
18921 @kindex set debug mips
18922 This command turns on and off debugging messages for the MIPS-specific
18923 target code in @value{GDBN}.
18925 @item show debug mips
18926 @kindex show debug mips
18927 Show the current setting of MIPS debugging messages.
18933 @cindex HPPA support
18935 When @value{GDBN} is debugging the HP PA architecture, it provides the
18936 following special commands:
18939 @item set debug hppa
18940 @kindex set debug hppa
18941 This command determines whether HPPA architecture-specific debugging
18942 messages are to be displayed.
18944 @item show debug hppa
18945 Show whether HPPA debugging messages are displayed.
18947 @item maint print unwind @var{address}
18948 @kindex maint print unwind@r{, HPPA}
18949 This command displays the contents of the unwind table entry at the
18950 given @var{address}.
18956 @subsection Cell Broadband Engine SPU architecture
18957 @cindex Cell Broadband Engine
18960 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
18961 it provides the following special commands:
18964 @item info spu event
18966 Display SPU event facility status. Shows current event mask
18967 and pending event status.
18969 @item info spu signal
18970 Display SPU signal notification facility status. Shows pending
18971 signal-control word and signal notification mode of both signal
18972 notification channels.
18974 @item info spu mailbox
18975 Display SPU mailbox facility status. Shows all pending entries,
18976 in order of processing, in each of the SPU Write Outbound,
18977 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
18980 Display MFC DMA status. Shows all pending commands in the MFC
18981 DMA queue. For each entry, opcode, tag, class IDs, effective
18982 and local store addresses and transfer size are shown.
18984 @item info spu proxydma
18985 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
18986 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
18987 and local store addresses and transfer size are shown.
18991 When @value{GDBN} is debugging a combined PowerPC/SPU application
18992 on the Cell Broadband Engine, it provides in addition the following
18996 @item set spu stop-on-load @var{arg}
18998 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
18999 will give control to the user when a new SPE thread enters its @code{main}
19000 function. The default is @code{off}.
19002 @item show spu stop-on-load
19004 Show whether to stop for new SPE threads.
19006 @item set spu auto-flush-cache @var{arg}
19007 Set whether to automatically flush the software-managed cache. When set to
19008 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
19009 cache to be flushed whenever SPE execution stops. This provides a consistent
19010 view of PowerPC memory that is accessed via the cache. If an application
19011 does not use the software-managed cache, this option has no effect.
19013 @item show spu auto-flush-cache
19014 Show whether to automatically flush the software-managed cache.
19019 @subsection PowerPC
19020 @cindex PowerPC architecture
19022 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
19023 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
19024 numbers stored in the floating point registers. These values must be stored
19025 in two consecutive registers, always starting at an even register like
19026 @code{f0} or @code{f2}.
19028 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
19029 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
19030 @code{f2} and @code{f3} for @code{$dl1} and so on.
19032 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
19033 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
19036 @node Controlling GDB
19037 @chapter Controlling @value{GDBN}
19039 You can alter the way @value{GDBN} interacts with you by using the
19040 @code{set} command. For commands controlling how @value{GDBN} displays
19041 data, see @ref{Print Settings, ,Print Settings}. Other settings are
19046 * Editing:: Command editing
19047 * Command History:: Command history
19048 * Screen Size:: Screen size
19049 * Numbers:: Numbers
19050 * ABI:: Configuring the current ABI
19051 * Messages/Warnings:: Optional warnings and messages
19052 * Debugging Output:: Optional messages about internal happenings
19053 * Other Misc Settings:: Other Miscellaneous Settings
19061 @value{GDBN} indicates its readiness to read a command by printing a string
19062 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
19063 can change the prompt string with the @code{set prompt} command. For
19064 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
19065 the prompt in one of the @value{GDBN} sessions so that you can always tell
19066 which one you are talking to.
19068 @emph{Note:} @code{set prompt} does not add a space for you after the
19069 prompt you set. This allows you to set a prompt which ends in a space
19070 or a prompt that does not.
19074 @item set prompt @var{newprompt}
19075 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
19077 @kindex show prompt
19079 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
19083 @section Command Editing
19085 @cindex command line editing
19087 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
19088 @sc{gnu} library provides consistent behavior for programs which provide a
19089 command line interface to the user. Advantages are @sc{gnu} Emacs-style
19090 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
19091 substitution, and a storage and recall of command history across
19092 debugging sessions.
19094 You may control the behavior of command line editing in @value{GDBN} with the
19095 command @code{set}.
19098 @kindex set editing
19101 @itemx set editing on
19102 Enable command line editing (enabled by default).
19104 @item set editing off
19105 Disable command line editing.
19107 @kindex show editing
19109 Show whether command line editing is enabled.
19112 @xref{Command Line Editing}, for more details about the Readline
19113 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
19114 encouraged to read that chapter.
19116 @node Command History
19117 @section Command History
19118 @cindex command history
19120 @value{GDBN} can keep track of the commands you type during your
19121 debugging sessions, so that you can be certain of precisely what
19122 happened. Use these commands to manage the @value{GDBN} command
19125 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
19126 package, to provide the history facility. @xref{Using History
19127 Interactively}, for the detailed description of the History library.
19129 To issue a command to @value{GDBN} without affecting certain aspects of
19130 the state which is seen by users, prefix it with @samp{server }
19131 (@pxref{Server Prefix}). This
19132 means that this command will not affect the command history, nor will it
19133 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
19134 pressed on a line by itself.
19136 @cindex @code{server}, command prefix
19137 The server prefix does not affect the recording of values into the value
19138 history; to print a value without recording it into the value history,
19139 use the @code{output} command instead of the @code{print} command.
19141 Here is the description of @value{GDBN} commands related to command
19145 @cindex history substitution
19146 @cindex history file
19147 @kindex set history filename
19148 @cindex @env{GDBHISTFILE}, environment variable
19149 @item set history filename @var{fname}
19150 Set the name of the @value{GDBN} command history file to @var{fname}.
19151 This is the file where @value{GDBN} reads an initial command history
19152 list, and where it writes the command history from this session when it
19153 exits. You can access this list through history expansion or through
19154 the history command editing characters listed below. This file defaults
19155 to the value of the environment variable @code{GDBHISTFILE}, or to
19156 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
19159 @cindex save command history
19160 @kindex set history save
19161 @item set history save
19162 @itemx set history save on
19163 Record command history in a file, whose name may be specified with the
19164 @code{set history filename} command. By default, this option is disabled.
19166 @item set history save off
19167 Stop recording command history in a file.
19169 @cindex history size
19170 @kindex set history size
19171 @cindex @env{HISTSIZE}, environment variable
19172 @item set history size @var{size}
19173 Set the number of commands which @value{GDBN} keeps in its history list.
19174 This defaults to the value of the environment variable
19175 @code{HISTSIZE}, or to 256 if this variable is not set.
19178 History expansion assigns special meaning to the character @kbd{!}.
19179 @xref{Event Designators}, for more details.
19181 @cindex history expansion, turn on/off
19182 Since @kbd{!} is also the logical not operator in C, history expansion
19183 is off by default. If you decide to enable history expansion with the
19184 @code{set history expansion on} command, you may sometimes need to
19185 follow @kbd{!} (when it is used as logical not, in an expression) with
19186 a space or a tab to prevent it from being expanded. The readline
19187 history facilities do not attempt substitution on the strings
19188 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
19190 The commands to control history expansion are:
19193 @item set history expansion on
19194 @itemx set history expansion
19195 @kindex set history expansion
19196 Enable history expansion. History expansion is off by default.
19198 @item set history expansion off
19199 Disable history expansion.
19202 @kindex show history
19204 @itemx show history filename
19205 @itemx show history save
19206 @itemx show history size
19207 @itemx show history expansion
19208 These commands display the state of the @value{GDBN} history parameters.
19209 @code{show history} by itself displays all four states.
19214 @kindex show commands
19215 @cindex show last commands
19216 @cindex display command history
19217 @item show commands
19218 Display the last ten commands in the command history.
19220 @item show commands @var{n}
19221 Print ten commands centered on command number @var{n}.
19223 @item show commands +
19224 Print ten commands just after the commands last printed.
19228 @section Screen Size
19229 @cindex size of screen
19230 @cindex pauses in output
19232 Certain commands to @value{GDBN} may produce large amounts of
19233 information output to the screen. To help you read all of it,
19234 @value{GDBN} pauses and asks you for input at the end of each page of
19235 output. Type @key{RET} when you want to continue the output, or @kbd{q}
19236 to discard the remaining output. Also, the screen width setting
19237 determines when to wrap lines of output. Depending on what is being
19238 printed, @value{GDBN} tries to break the line at a readable place,
19239 rather than simply letting it overflow onto the following line.
19241 Normally @value{GDBN} knows the size of the screen from the terminal
19242 driver software. For example, on Unix @value{GDBN} uses the termcap data base
19243 together with the value of the @code{TERM} environment variable and the
19244 @code{stty rows} and @code{stty cols} settings. If this is not correct,
19245 you can override it with the @code{set height} and @code{set
19252 @kindex show height
19253 @item set height @var{lpp}
19255 @itemx set width @var{cpl}
19257 These @code{set} commands specify a screen height of @var{lpp} lines and
19258 a screen width of @var{cpl} characters. The associated @code{show}
19259 commands display the current settings.
19261 If you specify a height of zero lines, @value{GDBN} does not pause during
19262 output no matter how long the output is. This is useful if output is to a
19263 file or to an editor buffer.
19265 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
19266 from wrapping its output.
19268 @item set pagination on
19269 @itemx set pagination off
19270 @kindex set pagination
19271 Turn the output pagination on or off; the default is on. Turning
19272 pagination off is the alternative to @code{set height 0}. Note that
19273 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
19274 Options, -batch}) also automatically disables pagination.
19276 @item show pagination
19277 @kindex show pagination
19278 Show the current pagination mode.
19283 @cindex number representation
19284 @cindex entering numbers
19286 You can always enter numbers in octal, decimal, or hexadecimal in
19287 @value{GDBN} by the usual conventions: octal numbers begin with
19288 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
19289 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
19290 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
19291 10; likewise, the default display for numbers---when no particular
19292 format is specified---is base 10. You can change the default base for
19293 both input and output with the commands described below.
19296 @kindex set input-radix
19297 @item set input-radix @var{base}
19298 Set the default base for numeric input. Supported choices
19299 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
19300 specified either unambiguously or using the current input radix; for
19304 set input-radix 012
19305 set input-radix 10.
19306 set input-radix 0xa
19310 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
19311 leaves the input radix unchanged, no matter what it was, since
19312 @samp{10}, being without any leading or trailing signs of its base, is
19313 interpreted in the current radix. Thus, if the current radix is 16,
19314 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
19317 @kindex set output-radix
19318 @item set output-radix @var{base}
19319 Set the default base for numeric display. Supported choices
19320 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
19321 specified either unambiguously or using the current input radix.
19323 @kindex show input-radix
19324 @item show input-radix
19325 Display the current default base for numeric input.
19327 @kindex show output-radix
19328 @item show output-radix
19329 Display the current default base for numeric display.
19331 @item set radix @r{[}@var{base}@r{]}
19335 These commands set and show the default base for both input and output
19336 of numbers. @code{set radix} sets the radix of input and output to
19337 the same base; without an argument, it resets the radix back to its
19338 default value of 10.
19343 @section Configuring the Current ABI
19345 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
19346 application automatically. However, sometimes you need to override its
19347 conclusions. Use these commands to manage @value{GDBN}'s view of the
19354 One @value{GDBN} configuration can debug binaries for multiple operating
19355 system targets, either via remote debugging or native emulation.
19356 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
19357 but you can override its conclusion using the @code{set osabi} command.
19358 One example where this is useful is in debugging of binaries which use
19359 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
19360 not have the same identifying marks that the standard C library for your
19365 Show the OS ABI currently in use.
19368 With no argument, show the list of registered available OS ABI's.
19370 @item set osabi @var{abi}
19371 Set the current OS ABI to @var{abi}.
19374 @cindex float promotion
19376 Generally, the way that an argument of type @code{float} is passed to a
19377 function depends on whether the function is prototyped. For a prototyped
19378 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
19379 according to the architecture's convention for @code{float}. For unprototyped
19380 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
19381 @code{double} and then passed.
19383 Unfortunately, some forms of debug information do not reliably indicate whether
19384 a function is prototyped. If @value{GDBN} calls a function that is not marked
19385 as prototyped, it consults @kbd{set coerce-float-to-double}.
19388 @kindex set coerce-float-to-double
19389 @item set coerce-float-to-double
19390 @itemx set coerce-float-to-double on
19391 Arguments of type @code{float} will be promoted to @code{double} when passed
19392 to an unprototyped function. This is the default setting.
19394 @item set coerce-float-to-double off
19395 Arguments of type @code{float} will be passed directly to unprototyped
19398 @kindex show coerce-float-to-double
19399 @item show coerce-float-to-double
19400 Show the current setting of promoting @code{float} to @code{double}.
19404 @kindex show cp-abi
19405 @value{GDBN} needs to know the ABI used for your program's C@t{++}
19406 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
19407 used to build your application. @value{GDBN} only fully supports
19408 programs with a single C@t{++} ABI; if your program contains code using
19409 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
19410 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
19411 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
19412 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
19413 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
19414 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
19419 Show the C@t{++} ABI currently in use.
19422 With no argument, show the list of supported C@t{++} ABI's.
19424 @item set cp-abi @var{abi}
19425 @itemx set cp-abi auto
19426 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
19429 @node Messages/Warnings
19430 @section Optional Warnings and Messages
19432 @cindex verbose operation
19433 @cindex optional warnings
19434 By default, @value{GDBN} is silent about its inner workings. If you are
19435 running on a slow machine, you may want to use the @code{set verbose}
19436 command. This makes @value{GDBN} tell you when it does a lengthy
19437 internal operation, so you will not think it has crashed.
19439 Currently, the messages controlled by @code{set verbose} are those
19440 which announce that the symbol table for a source file is being read;
19441 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
19444 @kindex set verbose
19445 @item set verbose on
19446 Enables @value{GDBN} output of certain informational messages.
19448 @item set verbose off
19449 Disables @value{GDBN} output of certain informational messages.
19451 @kindex show verbose
19453 Displays whether @code{set verbose} is on or off.
19456 By default, if @value{GDBN} encounters bugs in the symbol table of an
19457 object file, it is silent; but if you are debugging a compiler, you may
19458 find this information useful (@pxref{Symbol Errors, ,Errors Reading
19463 @kindex set complaints
19464 @item set complaints @var{limit}
19465 Permits @value{GDBN} to output @var{limit} complaints about each type of
19466 unusual symbols before becoming silent about the problem. Set
19467 @var{limit} to zero to suppress all complaints; set it to a large number
19468 to prevent complaints from being suppressed.
19470 @kindex show complaints
19471 @item show complaints
19472 Displays how many symbol complaints @value{GDBN} is permitted to produce.
19476 @anchor{confirmation requests}
19477 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
19478 lot of stupid questions to confirm certain commands. For example, if
19479 you try to run a program which is already running:
19483 The program being debugged has been started already.
19484 Start it from the beginning? (y or n)
19487 If you are willing to unflinchingly face the consequences of your own
19488 commands, you can disable this ``feature'':
19492 @kindex set confirm
19494 @cindex confirmation
19495 @cindex stupid questions
19496 @item set confirm off
19497 Disables confirmation requests. Note that running @value{GDBN} with
19498 the @option{--batch} option (@pxref{Mode Options, -batch}) also
19499 automatically disables confirmation requests.
19501 @item set confirm on
19502 Enables confirmation requests (the default).
19504 @kindex show confirm
19506 Displays state of confirmation requests.
19510 @cindex command tracing
19511 If you need to debug user-defined commands or sourced files you may find it
19512 useful to enable @dfn{command tracing}. In this mode each command will be
19513 printed as it is executed, prefixed with one or more @samp{+} symbols, the
19514 quantity denoting the call depth of each command.
19517 @kindex set trace-commands
19518 @cindex command scripts, debugging
19519 @item set trace-commands on
19520 Enable command tracing.
19521 @item set trace-commands off
19522 Disable command tracing.
19523 @item show trace-commands
19524 Display the current state of command tracing.
19527 @node Debugging Output
19528 @section Optional Messages about Internal Happenings
19529 @cindex optional debugging messages
19531 @value{GDBN} has commands that enable optional debugging messages from
19532 various @value{GDBN} subsystems; normally these commands are of
19533 interest to @value{GDBN} maintainers, or when reporting a bug. This
19534 section documents those commands.
19537 @kindex set exec-done-display
19538 @item set exec-done-display
19539 Turns on or off the notification of asynchronous commands'
19540 completion. When on, @value{GDBN} will print a message when an
19541 asynchronous command finishes its execution. The default is off.
19542 @kindex show exec-done-display
19543 @item show exec-done-display
19544 Displays the current setting of asynchronous command completion
19547 @cindex gdbarch debugging info
19548 @cindex architecture debugging info
19549 @item set debug arch
19550 Turns on or off display of gdbarch debugging info. The default is off
19552 @item show debug arch
19553 Displays the current state of displaying gdbarch debugging info.
19554 @item set debug aix-thread
19555 @cindex AIX threads
19556 Display debugging messages about inner workings of the AIX thread
19558 @item show debug aix-thread
19559 Show the current state of AIX thread debugging info display.
19560 @item set debug dwarf2-die
19561 @cindex DWARF2 DIEs
19562 Dump DWARF2 DIEs after they are read in.
19563 The value is the number of nesting levels to print.
19564 A value of zero turns off the display.
19565 @item show debug dwarf2-die
19566 Show the current state of DWARF2 DIE debugging.
19567 @item set debug displaced
19568 @cindex displaced stepping debugging info
19569 Turns on or off display of @value{GDBN} debugging info for the
19570 displaced stepping support. The default is off.
19571 @item show debug displaced
19572 Displays the current state of displaying @value{GDBN} debugging info
19573 related to displaced stepping.
19574 @item set debug event
19575 @cindex event debugging info
19576 Turns on or off display of @value{GDBN} event debugging info. The
19578 @item show debug event
19579 Displays the current state of displaying @value{GDBN} event debugging
19581 @item set debug expression
19582 @cindex expression debugging info
19583 Turns on or off display of debugging info about @value{GDBN}
19584 expression parsing. The default is off.
19585 @item show debug expression
19586 Displays the current state of displaying debugging info about
19587 @value{GDBN} expression parsing.
19588 @item set debug frame
19589 @cindex frame debugging info
19590 Turns on or off display of @value{GDBN} frame debugging info. The
19592 @item show debug frame
19593 Displays the current state of displaying @value{GDBN} frame debugging
19595 @item set debug gnu-nat
19596 @cindex @sc{gnu}/Hurd debug messages
19597 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
19598 @item show debug gnu-nat
19599 Show the current state of @sc{gnu}/Hurd debugging messages.
19600 @item set debug infrun
19601 @cindex inferior debugging info
19602 Turns on or off display of @value{GDBN} debugging info for running the inferior.
19603 The default is off. @file{infrun.c} contains GDB's runtime state machine used
19604 for implementing operations such as single-stepping the inferior.
19605 @item show debug infrun
19606 Displays the current state of @value{GDBN} inferior debugging.
19607 @item set debug lin-lwp
19608 @cindex @sc{gnu}/Linux LWP debug messages
19609 @cindex Linux lightweight processes
19610 Turns on or off debugging messages from the Linux LWP debug support.
19611 @item show debug lin-lwp
19612 Show the current state of Linux LWP debugging messages.
19613 @item set debug lin-lwp-async
19614 @cindex @sc{gnu}/Linux LWP async debug messages
19615 @cindex Linux lightweight processes
19616 Turns on or off debugging messages from the Linux LWP async debug support.
19617 @item show debug lin-lwp-async
19618 Show the current state of Linux LWP async debugging messages.
19619 @item set debug observer
19620 @cindex observer debugging info
19621 Turns on or off display of @value{GDBN} observer debugging. This
19622 includes info such as the notification of observable events.
19623 @item show debug observer
19624 Displays the current state of observer debugging.
19625 @item set debug overload
19626 @cindex C@t{++} overload debugging info
19627 Turns on or off display of @value{GDBN} C@t{++} overload debugging
19628 info. This includes info such as ranking of functions, etc. The default
19630 @item show debug overload
19631 Displays the current state of displaying @value{GDBN} C@t{++} overload
19633 @cindex expression parser, debugging info
19634 @cindex debug expression parser
19635 @item set debug parser
19636 Turns on or off the display of expression parser debugging output.
19637 Internally, this sets the @code{yydebug} variable in the expression
19638 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
19639 details. The default is off.
19640 @item show debug parser
19641 Show the current state of expression parser debugging.
19642 @cindex packets, reporting on stdout
19643 @cindex serial connections, debugging
19644 @cindex debug remote protocol
19645 @cindex remote protocol debugging
19646 @cindex display remote packets
19647 @item set debug remote
19648 Turns on or off display of reports on all packets sent back and forth across
19649 the serial line to the remote machine. The info is printed on the
19650 @value{GDBN} standard output stream. The default is off.
19651 @item show debug remote
19652 Displays the state of display of remote packets.
19653 @item set debug serial
19654 Turns on or off display of @value{GDBN} serial debugging info. The
19656 @item show debug serial
19657 Displays the current state of displaying @value{GDBN} serial debugging
19659 @item set debug solib-frv
19660 @cindex FR-V shared-library debugging
19661 Turns on or off debugging messages for FR-V shared-library code.
19662 @item show debug solib-frv
19663 Display the current state of FR-V shared-library code debugging
19665 @item set debug target
19666 @cindex target debugging info
19667 Turns on or off display of @value{GDBN} target debugging info. This info
19668 includes what is going on at the target level of GDB, as it happens. The
19669 default is 0. Set it to 1 to track events, and to 2 to also track the
19670 value of large memory transfers. Changes to this flag do not take effect
19671 until the next time you connect to a target or use the @code{run} command.
19672 @item show debug target
19673 Displays the current state of displaying @value{GDBN} target debugging
19675 @item set debug timestamp
19676 @cindex timestampping debugging info
19677 Turns on or off display of timestamps with @value{GDBN} debugging info.
19678 When enabled, seconds and microseconds are displayed before each debugging
19680 @item show debug timestamp
19681 Displays the current state of displaying timestamps with @value{GDBN}
19683 @item set debugvarobj
19684 @cindex variable object debugging info
19685 Turns on or off display of @value{GDBN} variable object debugging
19686 info. The default is off.
19687 @item show debugvarobj
19688 Displays the current state of displaying @value{GDBN} variable object
19690 @item set debug xml
19691 @cindex XML parser debugging
19692 Turns on or off debugging messages for built-in XML parsers.
19693 @item show debug xml
19694 Displays the current state of XML debugging messages.
19697 @node Other Misc Settings
19698 @section Other Miscellaneous Settings
19699 @cindex miscellaneous settings
19702 @kindex set interactive-mode
19703 @item set interactive-mode
19704 If @code{on}, forces @value{GDBN} to operate interactively.
19705 If @code{off}, forces @value{GDBN} to operate non-interactively,
19706 If @code{auto} (the default), @value{GDBN} guesses which mode to use,
19707 based on whether the debugger was started in a terminal or not.
19709 In the vast majority of cases, the debugger should be able to guess
19710 correctly which mode should be used. But this setting can be useful
19711 in certain specific cases, such as running a MinGW @value{GDBN}
19712 inside a cygwin window.
19714 @kindex show interactive-mode
19715 @item show interactive-mode
19716 Displays whether the debugger is operating in interactive mode or not.
19719 @node Extending GDB
19720 @chapter Extending @value{GDBN}
19721 @cindex extending GDB
19723 @value{GDBN} provides two mechanisms for extension. The first is based
19724 on composition of @value{GDBN} commands, and the second is based on the
19725 Python scripting language.
19727 To facilitate the use of these extensions, @value{GDBN} is capable
19728 of evaluating the contents of a file. When doing so, @value{GDBN}
19729 can recognize which scripting language is being used by looking at
19730 the filename extension. Files with an unrecognized filename extension
19731 are always treated as a @value{GDBN} Command Files.
19732 @xref{Command Files,, Command files}.
19734 You can control how @value{GDBN} evaluates these files with the following
19738 @kindex set script-extension
19739 @kindex show script-extension
19740 @item set script-extension off
19741 All scripts are always evaluated as @value{GDBN} Command Files.
19743 @item set script-extension soft
19744 The debugger determines the scripting language based on filename
19745 extension. If this scripting language is supported, @value{GDBN}
19746 evaluates the script using that language. Otherwise, it evaluates
19747 the file as a @value{GDBN} Command File.
19749 @item set script-extension strict
19750 The debugger determines the scripting language based on filename
19751 extension, and evaluates the script using that language. If the
19752 language is not supported, then the evaluation fails.
19754 @item show script-extension
19755 Display the current value of the @code{script-extension} option.
19760 * Sequences:: Canned Sequences of Commands
19761 * Python:: Scripting @value{GDBN} using Python
19765 @section Canned Sequences of Commands
19767 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
19768 Command Lists}), @value{GDBN} provides two ways to store sequences of
19769 commands for execution as a unit: user-defined commands and command
19773 * Define:: How to define your own commands
19774 * Hooks:: Hooks for user-defined commands
19775 * Command Files:: How to write scripts of commands to be stored in a file
19776 * Output:: Commands for controlled output
19780 @subsection User-defined Commands
19782 @cindex user-defined command
19783 @cindex arguments, to user-defined commands
19784 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
19785 which you assign a new name as a command. This is done with the
19786 @code{define} command. User commands may accept up to 10 arguments
19787 separated by whitespace. Arguments are accessed within the user command
19788 via @code{$arg0@dots{}$arg9}. A trivial example:
19792 print $arg0 + $arg1 + $arg2
19797 To execute the command use:
19804 This defines the command @code{adder}, which prints the sum of
19805 its three arguments. Note the arguments are text substitutions, so they may
19806 reference variables, use complex expressions, or even perform inferior
19809 @cindex argument count in user-defined commands
19810 @cindex how many arguments (user-defined commands)
19811 In addition, @code{$argc} may be used to find out how many arguments have
19812 been passed. This expands to a number in the range 0@dots{}10.
19817 print $arg0 + $arg1
19820 print $arg0 + $arg1 + $arg2
19828 @item define @var{commandname}
19829 Define a command named @var{commandname}. If there is already a command
19830 by that name, you are asked to confirm that you want to redefine it.
19831 @var{commandname} may be a bare command name consisting of letters,
19832 numbers, dashes, and underscores. It may also start with any predefined
19833 prefix command. For example, @samp{define target my-target} creates
19834 a user-defined @samp{target my-target} command.
19836 The definition of the command is made up of other @value{GDBN} command lines,
19837 which are given following the @code{define} command. The end of these
19838 commands is marked by a line containing @code{end}.
19841 @kindex end@r{ (user-defined commands)}
19842 @item document @var{commandname}
19843 Document the user-defined command @var{commandname}, so that it can be
19844 accessed by @code{help}. The command @var{commandname} must already be
19845 defined. This command reads lines of documentation just as @code{define}
19846 reads the lines of the command definition, ending with @code{end}.
19847 After the @code{document} command is finished, @code{help} on command
19848 @var{commandname} displays the documentation you have written.
19850 You may use the @code{document} command again to change the
19851 documentation of a command. Redefining the command with @code{define}
19852 does not change the documentation.
19854 @kindex dont-repeat
19855 @cindex don't repeat command
19857 Used inside a user-defined command, this tells @value{GDBN} that this
19858 command should not be repeated when the user hits @key{RET}
19859 (@pxref{Command Syntax, repeat last command}).
19861 @kindex help user-defined
19862 @item help user-defined
19863 List all user-defined commands, with the first line of the documentation
19868 @itemx show user @var{commandname}
19869 Display the @value{GDBN} commands used to define @var{commandname} (but
19870 not its documentation). If no @var{commandname} is given, display the
19871 definitions for all user-defined commands.
19873 @cindex infinite recursion in user-defined commands
19874 @kindex show max-user-call-depth
19875 @kindex set max-user-call-depth
19876 @item show max-user-call-depth
19877 @itemx set max-user-call-depth
19878 The value of @code{max-user-call-depth} controls how many recursion
19879 levels are allowed in user-defined commands before @value{GDBN} suspects an
19880 infinite recursion and aborts the command.
19883 In addition to the above commands, user-defined commands frequently
19884 use control flow commands, described in @ref{Command Files}.
19886 When user-defined commands are executed, the
19887 commands of the definition are not printed. An error in any command
19888 stops execution of the user-defined command.
19890 If used interactively, commands that would ask for confirmation proceed
19891 without asking when used inside a user-defined command. Many @value{GDBN}
19892 commands that normally print messages to say what they are doing omit the
19893 messages when used in a user-defined command.
19896 @subsection User-defined Command Hooks
19897 @cindex command hooks
19898 @cindex hooks, for commands
19899 @cindex hooks, pre-command
19902 You may define @dfn{hooks}, which are a special kind of user-defined
19903 command. Whenever you run the command @samp{foo}, if the user-defined
19904 command @samp{hook-foo} exists, it is executed (with no arguments)
19905 before that command.
19907 @cindex hooks, post-command
19909 A hook may also be defined which is run after the command you executed.
19910 Whenever you run the command @samp{foo}, if the user-defined command
19911 @samp{hookpost-foo} exists, it is executed (with no arguments) after
19912 that command. Post-execution hooks may exist simultaneously with
19913 pre-execution hooks, for the same command.
19915 It is valid for a hook to call the command which it hooks. If this
19916 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
19918 @c It would be nice if hookpost could be passed a parameter indicating
19919 @c if the command it hooks executed properly or not. FIXME!
19921 @kindex stop@r{, a pseudo-command}
19922 In addition, a pseudo-command, @samp{stop} exists. Defining
19923 (@samp{hook-stop}) makes the associated commands execute every time
19924 execution stops in your program: before breakpoint commands are run,
19925 displays are printed, or the stack frame is printed.
19927 For example, to ignore @code{SIGALRM} signals while
19928 single-stepping, but treat them normally during normal execution,
19933 handle SIGALRM nopass
19937 handle SIGALRM pass
19940 define hook-continue
19941 handle SIGALRM pass
19945 As a further example, to hook at the beginning and end of the @code{echo}
19946 command, and to add extra text to the beginning and end of the message,
19954 define hookpost-echo
19958 (@value{GDBP}) echo Hello World
19959 <<<---Hello World--->>>
19964 You can define a hook for any single-word command in @value{GDBN}, but
19965 not for command aliases; you should define a hook for the basic command
19966 name, e.g.@: @code{backtrace} rather than @code{bt}.
19967 @c FIXME! So how does Joe User discover whether a command is an alias
19969 You can hook a multi-word command by adding @code{hook-} or
19970 @code{hookpost-} to the last word of the command, e.g.@:
19971 @samp{define target hook-remote} to add a hook to @samp{target remote}.
19973 If an error occurs during the execution of your hook, execution of
19974 @value{GDBN} commands stops and @value{GDBN} issues a prompt
19975 (before the command that you actually typed had a chance to run).
19977 If you try to define a hook which does not match any known command, you
19978 get a warning from the @code{define} command.
19980 @node Command Files
19981 @subsection Command Files
19983 @cindex command files
19984 @cindex scripting commands
19985 A command file for @value{GDBN} is a text file made of lines that are
19986 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
19987 also be included. An empty line in a command file does nothing; it
19988 does not mean to repeat the last command, as it would from the
19991 You can request the execution of a command file with the @code{source}
19992 command. Note that the @code{source} command is also used to evaluate
19993 scripts that are not Command Files. The exact behavior can be configured
19994 using the @code{script-extension} setting.
19995 @xref{Extending GDB,, Extending GDB}.
19999 @cindex execute commands from a file
20000 @item source [-s] [-v] @var{filename}
20001 Execute the command file @var{filename}.
20004 The lines in a command file are generally executed sequentially,
20005 unless the order of execution is changed by one of the
20006 @emph{flow-control commands} described below. The commands are not
20007 printed as they are executed. An error in any command terminates
20008 execution of the command file and control is returned to the console.
20010 @value{GDBN} first searches for @var{filename} in the current directory.
20011 If the file is not found there, and @var{filename} does not specify a
20012 directory, then @value{GDBN} also looks for the file on the source search path
20013 (specified with the @samp{directory} command);
20014 except that @file{$cdir} is not searched because the compilation directory
20015 is not relevant to scripts.
20017 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
20018 on the search path even if @var{filename} specifies a directory.
20019 The search is done by appending @var{filename} to each element of the
20020 search path. So, for example, if @var{filename} is @file{mylib/myscript}
20021 and the search path contains @file{/home/user} then @value{GDBN} will
20022 look for the script @file{/home/user/mylib/myscript}.
20023 The search is also done if @var{filename} is an absolute path.
20024 For example, if @var{filename} is @file{/tmp/myscript} and
20025 the search path contains @file{/home/user} then @value{GDBN} will
20026 look for the script @file{/home/user/tmp/myscript}.
20027 For DOS-like systems, if @var{filename} contains a drive specification,
20028 it is stripped before concatenation. For example, if @var{filename} is
20029 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
20030 will look for the script @file{c:/tmp/myscript}.
20032 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
20033 each command as it is executed. The option must be given before
20034 @var{filename}, and is interpreted as part of the filename anywhere else.
20036 Commands that would ask for confirmation if used interactively proceed
20037 without asking when used in a command file. Many @value{GDBN} commands that
20038 normally print messages to say what they are doing omit the messages
20039 when called from command files.
20041 @value{GDBN} also accepts command input from standard input. In this
20042 mode, normal output goes to standard output and error output goes to
20043 standard error. Errors in a command file supplied on standard input do
20044 not terminate execution of the command file---execution continues with
20048 gdb < cmds > log 2>&1
20051 (The syntax above will vary depending on the shell used.) This example
20052 will execute commands from the file @file{cmds}. All output and errors
20053 would be directed to @file{log}.
20055 Since commands stored on command files tend to be more general than
20056 commands typed interactively, they frequently need to deal with
20057 complicated situations, such as different or unexpected values of
20058 variables and symbols, changes in how the program being debugged is
20059 built, etc. @value{GDBN} provides a set of flow-control commands to
20060 deal with these complexities. Using these commands, you can write
20061 complex scripts that loop over data structures, execute commands
20062 conditionally, etc.
20069 This command allows to include in your script conditionally executed
20070 commands. The @code{if} command takes a single argument, which is an
20071 expression to evaluate. It is followed by a series of commands that
20072 are executed only if the expression is true (its value is nonzero).
20073 There can then optionally be an @code{else} line, followed by a series
20074 of commands that are only executed if the expression was false. The
20075 end of the list is marked by a line containing @code{end}.
20079 This command allows to write loops. Its syntax is similar to
20080 @code{if}: the command takes a single argument, which is an expression
20081 to evaluate, and must be followed by the commands to execute, one per
20082 line, terminated by an @code{end}. These commands are called the
20083 @dfn{body} of the loop. The commands in the body of @code{while} are
20084 executed repeatedly as long as the expression evaluates to true.
20088 This command exits the @code{while} loop in whose body it is included.
20089 Execution of the script continues after that @code{while}s @code{end}
20092 @kindex loop_continue
20093 @item loop_continue
20094 This command skips the execution of the rest of the body of commands
20095 in the @code{while} loop in whose body it is included. Execution
20096 branches to the beginning of the @code{while} loop, where it evaluates
20097 the controlling expression.
20099 @kindex end@r{ (if/else/while commands)}
20101 Terminate the block of commands that are the body of @code{if},
20102 @code{else}, or @code{while} flow-control commands.
20107 @subsection Commands for Controlled Output
20109 During the execution of a command file or a user-defined command, normal
20110 @value{GDBN} output is suppressed; the only output that appears is what is
20111 explicitly printed by the commands in the definition. This section
20112 describes three commands useful for generating exactly the output you
20117 @item echo @var{text}
20118 @c I do not consider backslash-space a standard C escape sequence
20119 @c because it is not in ANSI.
20120 Print @var{text}. Nonprinting characters can be included in
20121 @var{text} using C escape sequences, such as @samp{\n} to print a
20122 newline. @strong{No newline is printed unless you specify one.}
20123 In addition to the standard C escape sequences, a backslash followed
20124 by a space stands for a space. This is useful for displaying a
20125 string with spaces at the beginning or the end, since leading and
20126 trailing spaces are otherwise trimmed from all arguments.
20127 To print @samp{@w{ }and foo =@w{ }}, use the command
20128 @samp{echo \@w{ }and foo = \@w{ }}.
20130 A backslash at the end of @var{text} can be used, as in C, to continue
20131 the command onto subsequent lines. For example,
20134 echo This is some text\n\
20135 which is continued\n\
20136 onto several lines.\n
20139 produces the same output as
20142 echo This is some text\n
20143 echo which is continued\n
20144 echo onto several lines.\n
20148 @item output @var{expression}
20149 Print the value of @var{expression} and nothing but that value: no
20150 newlines, no @samp{$@var{nn} = }. The value is not entered in the
20151 value history either. @xref{Expressions, ,Expressions}, for more information
20154 @item output/@var{fmt} @var{expression}
20155 Print the value of @var{expression} in format @var{fmt}. You can use
20156 the same formats as for @code{print}. @xref{Output Formats,,Output
20157 Formats}, for more information.
20160 @item printf @var{template}, @var{expressions}@dots{}
20161 Print the values of one or more @var{expressions} under the control of
20162 the string @var{template}. To print several values, make
20163 @var{expressions} be a comma-separated list of individual expressions,
20164 which may be either numbers or pointers. Their values are printed as
20165 specified by @var{template}, exactly as a C program would do by
20166 executing the code below:
20169 printf (@var{template}, @var{expressions}@dots{});
20172 As in @code{C} @code{printf}, ordinary characters in @var{template}
20173 are printed verbatim, while @dfn{conversion specification} introduced
20174 by the @samp{%} character cause subsequent @var{expressions} to be
20175 evaluated, their values converted and formatted according to type and
20176 style information encoded in the conversion specifications, and then
20179 For example, you can print two values in hex like this:
20182 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
20185 @code{printf} supports all the standard @code{C} conversion
20186 specifications, including the flags and modifiers between the @samp{%}
20187 character and the conversion letter, with the following exceptions:
20191 The argument-ordering modifiers, such as @samp{2$}, are not supported.
20194 The modifier @samp{*} is not supported for specifying precision or
20198 The @samp{'} flag (for separation of digits into groups according to
20199 @code{LC_NUMERIC'}) is not supported.
20202 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
20206 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
20209 The conversion letters @samp{a} and @samp{A} are not supported.
20213 Note that the @samp{ll} type modifier is supported only if the
20214 underlying @code{C} implementation used to build @value{GDBN} supports
20215 the @code{long long int} type, and the @samp{L} type modifier is
20216 supported only if @code{long double} type is available.
20218 As in @code{C}, @code{printf} supports simple backslash-escape
20219 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
20220 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
20221 single character. Octal and hexadecimal escape sequences are not
20224 Additionally, @code{printf} supports conversion specifications for DFP
20225 (@dfn{Decimal Floating Point}) types using the following length modifiers
20226 together with a floating point specifier.
20231 @samp{H} for printing @code{Decimal32} types.
20234 @samp{D} for printing @code{Decimal64} types.
20237 @samp{DD} for printing @code{Decimal128} types.
20240 If the underlying @code{C} implementation used to build @value{GDBN} has
20241 support for the three length modifiers for DFP types, other modifiers
20242 such as width and precision will also be available for @value{GDBN} to use.
20244 In case there is no such @code{C} support, no additional modifiers will be
20245 available and the value will be printed in the standard way.
20247 Here's an example of printing DFP types using the above conversion letters:
20249 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
20253 @item eval @var{template}, @var{expressions}@dots{}
20254 Convert the values of one or more @var{expressions} under the control of
20255 the string @var{template} to a command line, and call it.
20260 @section Scripting @value{GDBN} using Python
20261 @cindex python scripting
20262 @cindex scripting with python
20264 You can script @value{GDBN} using the @uref{http://www.python.org/,
20265 Python programming language}. This feature is available only if
20266 @value{GDBN} was configured using @option{--with-python}.
20268 @cindex python directory
20269 Python scripts used by @value{GDBN} should be installed in
20270 @file{@var{data-directory}/python}, where @var{data-directory} is
20271 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}). This directory, known as the @dfn{python directory},
20272 is automatically added to the Python Search Path in order to allow
20273 the Python interpreter to locate all scripts installed at this location.
20276 * Python Commands:: Accessing Python from @value{GDBN}.
20277 * Python API:: Accessing @value{GDBN} from Python.
20278 * Auto-loading:: Automatically loading Python code.
20281 @node Python Commands
20282 @subsection Python Commands
20283 @cindex python commands
20284 @cindex commands to access python
20286 @value{GDBN} provides one command for accessing the Python interpreter,
20287 and one related setting:
20291 @item python @r{[}@var{code}@r{]}
20292 The @code{python} command can be used to evaluate Python code.
20294 If given an argument, the @code{python} command will evaluate the
20295 argument as a Python command. For example:
20298 (@value{GDBP}) python print 23
20302 If you do not provide an argument to @code{python}, it will act as a
20303 multi-line command, like @code{define}. In this case, the Python
20304 script is made up of subsequent command lines, given after the
20305 @code{python} command. This command list is terminated using a line
20306 containing @code{end}. For example:
20309 (@value{GDBP}) python
20311 End with a line saying just "end".
20317 @kindex maint set python print-stack
20318 @item maint set python print-stack
20319 By default, @value{GDBN} will print a stack trace when an error occurs
20320 in a Python script. This can be controlled using @code{maint set
20321 python print-stack}: if @code{on}, the default, then Python stack
20322 printing is enabled; if @code{off}, then Python stack printing is
20326 It is also possible to execute a Python script from the @value{GDBN}
20330 @item source @file{script-name}
20331 The script name must end with @samp{.py} and @value{GDBN} must be configured
20332 to recognize the script language based on filename extension using
20333 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
20335 @item python execfile ("script-name")
20336 This method is based on the @code{execfile} Python built-in function,
20337 and thus is always available.
20341 @subsection Python API
20343 @cindex programming in python
20345 @cindex python stdout
20346 @cindex python pagination
20347 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
20348 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
20349 A Python program which outputs to one of these streams may have its
20350 output interrupted by the user (@pxref{Screen Size}). In this
20351 situation, a Python @code{KeyboardInterrupt} exception is thrown.
20354 * Basic Python:: Basic Python Functions.
20355 * Exception Handling::
20356 * Values From Inferior::
20357 * Types In Python:: Python representation of types.
20358 * Pretty Printing API:: Pretty-printing values.
20359 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
20360 * Disabling Pretty-Printers:: Disabling broken printers.
20361 * Inferiors In Python:: Python representation of inferiors (processes)
20362 * Threads In Python:: Accessing inferior threads from Python.
20363 * Commands In Python:: Implementing new commands in Python.
20364 * Parameters In Python:: Adding new @value{GDBN} parameters.
20365 * Functions In Python:: Writing new convenience functions.
20366 * Progspaces In Python:: Program spaces.
20367 * Objfiles In Python:: Object files.
20368 * Frames In Python:: Accessing inferior stack frames from Python.
20369 * Blocks In Python:: Accessing frame blocks from Python.
20370 * Symbols In Python:: Python representation of symbols.
20371 * Symbol Tables In Python:: Python representation of symbol tables.
20372 * Lazy Strings In Python:: Python representation of lazy strings.
20373 * Breakpoints In Python:: Manipulating breakpoints using Python.
20377 @subsubsection Basic Python
20379 @cindex python functions
20380 @cindex python module
20382 @value{GDBN} introduces a new Python module, named @code{gdb}. All
20383 methods and classes added by @value{GDBN} are placed in this module.
20384 @value{GDBN} automatically @code{import}s the @code{gdb} module for
20385 use in all scripts evaluated by the @code{python} command.
20387 @findex gdb.PYTHONDIR
20389 A string containing the python directory (@pxref{Python}).
20392 @findex gdb.execute
20393 @defun execute command [from_tty] [to_string]
20394 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
20395 If a GDB exception happens while @var{command} runs, it is
20396 translated as described in @ref{Exception Handling,,Exception Handling}.
20398 @var{from_tty} specifies whether @value{GDBN} ought to consider this
20399 command as having originated from the user invoking it interactively.
20400 It must be a boolean value. If omitted, it defaults to @code{False}.
20402 By default, any output produced by @var{command} is sent to
20403 @value{GDBN}'s standard output. If the @var{to_string} parameter is
20404 @code{True}, then output will be collected by @code{gdb.execute} and
20405 returned as a string. The default is @code{False}, in which case the
20406 return value is @code{None}.
20409 @findex gdb.breakpoints
20411 Return a sequence holding all of @value{GDBN}'s breakpoints.
20412 @xref{Breakpoints In Python}, for more information.
20415 @findex gdb.parameter
20416 @defun parameter parameter
20417 Return the value of a @value{GDBN} parameter. @var{parameter} is a
20418 string naming the parameter to look up; @var{parameter} may contain
20419 spaces if the parameter has a multi-part name. For example,
20420 @samp{print object} is a valid parameter name.
20422 If the named parameter does not exist, this function throws a
20423 @code{RuntimeError}. Otherwise, the parameter's value is converted to
20424 a Python value of the appropriate type, and returned.
20427 @findex gdb.history
20428 @defun history number
20429 Return a value from @value{GDBN}'s value history (@pxref{Value
20430 History}). @var{number} indicates which history element to return.
20431 If @var{number} is negative, then @value{GDBN} will take its absolute value
20432 and count backward from the last element (i.e., the most recent element) to
20433 find the value to return. If @var{number} is zero, then @value{GDBN} will
20434 return the most recent element. If the element specified by @var{number}
20435 doesn't exist in the value history, a @code{RuntimeError} exception will be
20438 If no exception is raised, the return value is always an instance of
20439 @code{gdb.Value} (@pxref{Values From Inferior}).
20442 @findex gdb.parse_and_eval
20443 @defun parse_and_eval expression
20444 Parse @var{expression} as an expression in the current language,
20445 evaluate it, and return the result as a @code{gdb.Value}.
20446 @var{expression} must be a string.
20448 This function can be useful when implementing a new command
20449 (@pxref{Commands In Python}), as it provides a way to parse the
20450 command's argument as an expression. It is also useful simply to
20451 compute values, for example, it is the only way to get the value of a
20452 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
20456 @defun write string
20457 Print a string to @value{GDBN}'s paginated standard output stream.
20458 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
20459 call this function.
20464 Flush @value{GDBN}'s paginated standard output stream. Flushing
20465 @code{sys.stdout} or @code{sys.stderr} will automatically call this
20469 @findex gdb.target_charset
20470 @defun target_charset
20471 Return the name of the current target character set (@pxref{Character
20472 Sets}). This differs from @code{gdb.parameter('target-charset')} in
20473 that @samp{auto} is never returned.
20476 @findex gdb.target_wide_charset
20477 @defun target_wide_charset
20478 Return the name of the current target wide character set
20479 (@pxref{Character Sets}). This differs from
20480 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
20484 @node Exception Handling
20485 @subsubsection Exception Handling
20486 @cindex python exceptions
20487 @cindex exceptions, python
20489 When executing the @code{python} command, Python exceptions
20490 uncaught within the Python code are translated to calls to
20491 @value{GDBN} error-reporting mechanism. If the command that called
20492 @code{python} does not handle the error, @value{GDBN} will
20493 terminate it and print an error message containing the Python
20494 exception name, the associated value, and the Python call stack
20495 backtrace at the point where the exception was raised. Example:
20498 (@value{GDBP}) python print foo
20499 Traceback (most recent call last):
20500 File "<string>", line 1, in <module>
20501 NameError: name 'foo' is not defined
20504 @value{GDBN} errors that happen in @value{GDBN} commands invoked by Python
20505 code are converted to Python @code{RuntimeError} exceptions. User
20506 interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
20507 prompt) is translated to a Python @code{KeyboardInterrupt}
20508 exception. If you catch these exceptions in your Python code, your
20509 exception handler will see @code{RuntimeError} or
20510 @code{KeyboardInterrupt} as the exception type, the @value{GDBN} error
20511 message as its value, and the Python call stack backtrace at the
20512 Python statement closest to where the @value{GDBN} error occured as the
20515 @findex gdb.GdbError
20516 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
20517 it is useful to be able to throw an exception that doesn't cause a
20518 traceback to be printed. For example, the user may have invoked the
20519 command incorrectly. Use the @code{gdb.GdbError} exception
20520 to handle this case. Example:
20524 >class HelloWorld (gdb.Command):
20525 > """Greet the whole world."""
20526 > def __init__ (self):
20527 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
20528 > def invoke (self, args, from_tty):
20529 > argv = gdb.string_to_argv (args)
20530 > if len (argv) != 0:
20531 > raise gdb.GdbError ("hello-world takes no arguments")
20532 > print "Hello, World!"
20535 (gdb) hello-world 42
20536 hello-world takes no arguments
20539 @node Values From Inferior
20540 @subsubsection Values From Inferior
20541 @cindex values from inferior, with Python
20542 @cindex python, working with values from inferior
20544 @cindex @code{gdb.Value}
20545 @value{GDBN} provides values it obtains from the inferior program in
20546 an object of type @code{gdb.Value}. @value{GDBN} uses this object
20547 for its internal bookkeeping of the inferior's values, and for
20548 fetching values when necessary.
20550 Inferior values that are simple scalars can be used directly in
20551 Python expressions that are valid for the value's data type. Here's
20552 an example for an integer or floating-point value @code{some_val}:
20559 As result of this, @code{bar} will also be a @code{gdb.Value} object
20560 whose values are of the same type as those of @code{some_val}.
20562 Inferior values that are structures or instances of some class can
20563 be accessed using the Python @dfn{dictionary syntax}. For example, if
20564 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
20565 can access its @code{foo} element with:
20568 bar = some_val['foo']
20571 Again, @code{bar} will also be a @code{gdb.Value} object.
20573 The following attributes are provided:
20576 @defivar Value address
20577 If this object is addressable, this read-only attribute holds a
20578 @code{gdb.Value} object representing the address. Otherwise,
20579 this attribute holds @code{None}.
20582 @cindex optimized out value in Python
20583 @defivar Value is_optimized_out
20584 This read-only boolean attribute is true if the compiler optimized out
20585 this value, thus it is not available for fetching from the inferior.
20588 @defivar Value type
20589 The type of this @code{gdb.Value}. The value of this attribute is a
20590 @code{gdb.Type} object.
20594 The following methods are provided:
20597 @defmethod Value cast type
20598 Return a new instance of @code{gdb.Value} that is the result of
20599 casting this instance to the type described by @var{type}, which must
20600 be a @code{gdb.Type} object. If the cast cannot be performed for some
20601 reason, this method throws an exception.
20604 @defmethod Value dereference
20605 For pointer data types, this method returns a new @code{gdb.Value} object
20606 whose contents is the object pointed to by the pointer. For example, if
20607 @code{foo} is a C pointer to an @code{int}, declared in your C program as
20614 then you can use the corresponding @code{gdb.Value} to access what
20615 @code{foo} points to like this:
20618 bar = foo.dereference ()
20621 The result @code{bar} will be a @code{gdb.Value} object holding the
20622 value pointed to by @code{foo}.
20625 @defmethod Value string @r{[}encoding@r{]} @r{[}errors@r{]} @r{[}length@r{]}
20626 If this @code{gdb.Value} represents a string, then this method
20627 converts the contents to a Python string. Otherwise, this method will
20628 throw an exception.
20630 Strings are recognized in a language-specific way; whether a given
20631 @code{gdb.Value} represents a string is determined by the current
20634 For C-like languages, a value is a string if it is a pointer to or an
20635 array of characters or ints. The string is assumed to be terminated
20636 by a zero of the appropriate width. However if the optional length
20637 argument is given, the string will be converted to that given length,
20638 ignoring any embedded zeros that the string may contain.
20640 If the optional @var{encoding} argument is given, it must be a string
20641 naming the encoding of the string in the @code{gdb.Value}, such as
20642 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
20643 the same encodings as the corresponding argument to Python's
20644 @code{string.decode} method, and the Python codec machinery will be used
20645 to convert the string. If @var{encoding} is not given, or if
20646 @var{encoding} is the empty string, then either the @code{target-charset}
20647 (@pxref{Character Sets}) will be used, or a language-specific encoding
20648 will be used, if the current language is able to supply one.
20650 The optional @var{errors} argument is the same as the corresponding
20651 argument to Python's @code{string.decode} method.
20653 If the optional @var{length} argument is given, the string will be
20654 fetched and converted to the given length.
20657 @defmethod Value lazy_string @r{[}encoding@r{]} @r{[}length@r{]}
20658 If this @code{gdb.Value} represents a string, then this method
20659 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
20660 In Python}). Otherwise, this method will throw an exception.
20662 If the optional @var{encoding} argument is given, it must be a string
20663 naming the encoding of the @code{gdb.LazyString}. Some examples are:
20664 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
20665 @var{encoding} argument is an encoding that @value{GDBN} does
20666 recognize, @value{GDBN} will raise an error.
20668 When a lazy string is printed, the @value{GDBN} encoding machinery is
20669 used to convert the string during printing. If the optional
20670 @var{encoding} argument is not provided, or is an empty string,
20671 @value{GDBN} will automatically select the encoding most suitable for
20672 the string type. For further information on encoding in @value{GDBN}
20673 please see @ref{Character Sets}.
20675 If the optional @var{length} argument is given, the string will be
20676 fetched and encoded to the length of characters specified. If
20677 the @var{length} argument is not provided, the string will be fetched
20678 and encoded until a null of appropriate width is found.
20682 @node Types In Python
20683 @subsubsection Types In Python
20684 @cindex types in Python
20685 @cindex Python, working with types
20688 @value{GDBN} represents types from the inferior using the class
20691 The following type-related functions are available in the @code{gdb}
20694 @findex gdb.lookup_type
20695 @defun lookup_type name [block]
20696 This function looks up a type by name. @var{name} is the name of the
20697 type to look up. It must be a string.
20699 If @var{block} is given, then @var{name} is looked up in that scope.
20700 Otherwise, it is searched for globally.
20702 Ordinarily, this function will return an instance of @code{gdb.Type}.
20703 If the named type cannot be found, it will throw an exception.
20706 An instance of @code{Type} has the following attributes:
20710 The type code for this type. The type code will be one of the
20711 @code{TYPE_CODE_} constants defined below.
20714 @defivar Type sizeof
20715 The size of this type, in target @code{char} units. Usually, a
20716 target's @code{char} type will be an 8-bit byte. However, on some
20717 unusual platforms, this type may have a different size.
20721 The tag name for this type. The tag name is the name after
20722 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
20723 languages have this concept. If this type has no tag name, then
20724 @code{None} is returned.
20728 The following methods are provided:
20731 @defmethod Type fields
20732 For structure and union types, this method returns the fields. Range
20733 types have two fields, the minimum and maximum values. Enum types
20734 have one field per enum constant. Function and method types have one
20735 field per parameter. The base types of C@t{++} classes are also
20736 represented as fields. If the type has no fields, or does not fit
20737 into one of these categories, an empty sequence will be returned.
20739 Each field is an object, with some pre-defined attributes:
20742 This attribute is not available for @code{static} fields (as in
20743 C@t{++} or Java). For non-@code{static} fields, the value is the bit
20744 position of the field.
20747 The name of the field, or @code{None} for anonymous fields.
20750 This is @code{True} if the field is artificial, usually meaning that
20751 it was provided by the compiler and not the user. This attribute is
20752 always provided, and is @code{False} if the field is not artificial.
20754 @item is_base_class
20755 This is @code{True} if the field represents a base class of a C@t{++}
20756 structure. This attribute is always provided, and is @code{False}
20757 if the field is not a base class of the type that is the argument of
20758 @code{fields}, or if that type was not a C@t{++} class.
20761 If the field is packed, or is a bitfield, then this will have a
20762 non-zero value, which is the size of the field in bits. Otherwise,
20763 this will be zero; in this case the field's size is given by its type.
20766 The type of the field. This is usually an instance of @code{Type},
20767 but it can be @code{None} in some situations.
20771 @defmethod Type const
20772 Return a new @code{gdb.Type} object which represents a
20773 @code{const}-qualified variant of this type.
20776 @defmethod Type volatile
20777 Return a new @code{gdb.Type} object which represents a
20778 @code{volatile}-qualified variant of this type.
20781 @defmethod Type unqualified
20782 Return a new @code{gdb.Type} object which represents an unqualified
20783 variant of this type. That is, the result is neither @code{const} nor
20787 @defmethod Type range
20788 Return a Python @code{Tuple} object that contains two elements: the
20789 low bound of the argument type and the high bound of that type. If
20790 the type does not have a range, @value{GDBN} will raise a
20791 @code{RuntimeError} exception.
20794 @defmethod Type reference
20795 Return a new @code{gdb.Type} object which represents a reference to this
20799 @defmethod Type pointer
20800 Return a new @code{gdb.Type} object which represents a pointer to this
20804 @defmethod Type strip_typedefs
20805 Return a new @code{gdb.Type} that represents the real type,
20806 after removing all layers of typedefs.
20809 @defmethod Type target
20810 Return a new @code{gdb.Type} object which represents the target type
20813 For a pointer type, the target type is the type of the pointed-to
20814 object. For an array type (meaning C-like arrays), the target type is
20815 the type of the elements of the array. For a function or method type,
20816 the target type is the type of the return value. For a complex type,
20817 the target type is the type of the elements. For a typedef, the
20818 target type is the aliased type.
20820 If the type does not have a target, this method will throw an
20824 @defmethod Type template_argument n [block]
20825 If this @code{gdb.Type} is an instantiation of a template, this will
20826 return a new @code{gdb.Type} which represents the type of the
20827 @var{n}th template argument.
20829 If this @code{gdb.Type} is not a template type, this will throw an
20830 exception. Ordinarily, only C@t{++} code will have template types.
20832 If @var{block} is given, then @var{name} is looked up in that scope.
20833 Otherwise, it is searched for globally.
20838 Each type has a code, which indicates what category this type falls
20839 into. The available type categories are represented by constants
20840 defined in the @code{gdb} module:
20843 @findex TYPE_CODE_PTR
20844 @findex gdb.TYPE_CODE_PTR
20845 @item TYPE_CODE_PTR
20846 The type is a pointer.
20848 @findex TYPE_CODE_ARRAY
20849 @findex gdb.TYPE_CODE_ARRAY
20850 @item TYPE_CODE_ARRAY
20851 The type is an array.
20853 @findex TYPE_CODE_STRUCT
20854 @findex gdb.TYPE_CODE_STRUCT
20855 @item TYPE_CODE_STRUCT
20856 The type is a structure.
20858 @findex TYPE_CODE_UNION
20859 @findex gdb.TYPE_CODE_UNION
20860 @item TYPE_CODE_UNION
20861 The type is a union.
20863 @findex TYPE_CODE_ENUM
20864 @findex gdb.TYPE_CODE_ENUM
20865 @item TYPE_CODE_ENUM
20866 The type is an enum.
20868 @findex TYPE_CODE_FLAGS
20869 @findex gdb.TYPE_CODE_FLAGS
20870 @item TYPE_CODE_FLAGS
20871 A bit flags type, used for things such as status registers.
20873 @findex TYPE_CODE_FUNC
20874 @findex gdb.TYPE_CODE_FUNC
20875 @item TYPE_CODE_FUNC
20876 The type is a function.
20878 @findex TYPE_CODE_INT
20879 @findex gdb.TYPE_CODE_INT
20880 @item TYPE_CODE_INT
20881 The type is an integer type.
20883 @findex TYPE_CODE_FLT
20884 @findex gdb.TYPE_CODE_FLT
20885 @item TYPE_CODE_FLT
20886 A floating point type.
20888 @findex TYPE_CODE_VOID
20889 @findex gdb.TYPE_CODE_VOID
20890 @item TYPE_CODE_VOID
20891 The special type @code{void}.
20893 @findex TYPE_CODE_SET
20894 @findex gdb.TYPE_CODE_SET
20895 @item TYPE_CODE_SET
20898 @findex TYPE_CODE_RANGE
20899 @findex gdb.TYPE_CODE_RANGE
20900 @item TYPE_CODE_RANGE
20901 A range type, that is, an integer type with bounds.
20903 @findex TYPE_CODE_STRING
20904 @findex gdb.TYPE_CODE_STRING
20905 @item TYPE_CODE_STRING
20906 A string type. Note that this is only used for certain languages with
20907 language-defined string types; C strings are not represented this way.
20909 @findex TYPE_CODE_BITSTRING
20910 @findex gdb.TYPE_CODE_BITSTRING
20911 @item TYPE_CODE_BITSTRING
20914 @findex TYPE_CODE_ERROR
20915 @findex gdb.TYPE_CODE_ERROR
20916 @item TYPE_CODE_ERROR
20917 An unknown or erroneous type.
20919 @findex TYPE_CODE_METHOD
20920 @findex gdb.TYPE_CODE_METHOD
20921 @item TYPE_CODE_METHOD
20922 A method type, as found in C@t{++} or Java.
20924 @findex TYPE_CODE_METHODPTR
20925 @findex gdb.TYPE_CODE_METHODPTR
20926 @item TYPE_CODE_METHODPTR
20927 A pointer-to-member-function.
20929 @findex TYPE_CODE_MEMBERPTR
20930 @findex gdb.TYPE_CODE_MEMBERPTR
20931 @item TYPE_CODE_MEMBERPTR
20932 A pointer-to-member.
20934 @findex TYPE_CODE_REF
20935 @findex gdb.TYPE_CODE_REF
20936 @item TYPE_CODE_REF
20939 @findex TYPE_CODE_CHAR
20940 @findex gdb.TYPE_CODE_CHAR
20941 @item TYPE_CODE_CHAR
20944 @findex TYPE_CODE_BOOL
20945 @findex gdb.TYPE_CODE_BOOL
20946 @item TYPE_CODE_BOOL
20949 @findex TYPE_CODE_COMPLEX
20950 @findex gdb.TYPE_CODE_COMPLEX
20951 @item TYPE_CODE_COMPLEX
20952 A complex float type.
20954 @findex TYPE_CODE_TYPEDEF
20955 @findex gdb.TYPE_CODE_TYPEDEF
20956 @item TYPE_CODE_TYPEDEF
20957 A typedef to some other type.
20959 @findex TYPE_CODE_NAMESPACE
20960 @findex gdb.TYPE_CODE_NAMESPACE
20961 @item TYPE_CODE_NAMESPACE
20962 A C@t{++} namespace.
20964 @findex TYPE_CODE_DECFLOAT
20965 @findex gdb.TYPE_CODE_DECFLOAT
20966 @item TYPE_CODE_DECFLOAT
20967 A decimal floating point type.
20969 @findex TYPE_CODE_INTERNAL_FUNCTION
20970 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
20971 @item TYPE_CODE_INTERNAL_FUNCTION
20972 A function internal to @value{GDBN}. This is the type used to represent
20973 convenience functions.
20976 @node Pretty Printing API
20977 @subsubsection Pretty Printing API
20979 An example output is provided (@pxref{Pretty Printing}).
20981 A pretty-printer is just an object that holds a value and implements a
20982 specific interface, defined here.
20984 @defop Operation {pretty printer} children (self)
20985 @value{GDBN} will call this method on a pretty-printer to compute the
20986 children of the pretty-printer's value.
20988 This method must return an object conforming to the Python iterator
20989 protocol. Each item returned by the iterator must be a tuple holding
20990 two elements. The first element is the ``name'' of the child; the
20991 second element is the child's value. The value can be any Python
20992 object which is convertible to a @value{GDBN} value.
20994 This method is optional. If it does not exist, @value{GDBN} will act
20995 as though the value has no children.
20998 @defop Operation {pretty printer} display_hint (self)
20999 The CLI may call this method and use its result to change the
21000 formatting of a value. The result will also be supplied to an MI
21001 consumer as a @samp{displayhint} attribute of the variable being
21004 This method is optional. If it does exist, this method must return a
21007 Some display hints are predefined by @value{GDBN}:
21011 Indicate that the object being printed is ``array-like''. The CLI
21012 uses this to respect parameters such as @code{set print elements} and
21013 @code{set print array}.
21016 Indicate that the object being printed is ``map-like'', and that the
21017 children of this value can be assumed to alternate between keys and
21021 Indicate that the object being printed is ``string-like''. If the
21022 printer's @code{to_string} method returns a Python string of some
21023 kind, then @value{GDBN} will call its internal language-specific
21024 string-printing function to format the string. For the CLI this means
21025 adding quotation marks, possibly escaping some characters, respecting
21026 @code{set print elements}, and the like.
21030 @defop Operation {pretty printer} to_string (self)
21031 @value{GDBN} will call this method to display the string
21032 representation of the value passed to the object's constructor.
21034 When printing from the CLI, if the @code{to_string} method exists,
21035 then @value{GDBN} will prepend its result to the values returned by
21036 @code{children}. Exactly how this formatting is done is dependent on
21037 the display hint, and may change as more hints are added. Also,
21038 depending on the print settings (@pxref{Print Settings}), the CLI may
21039 print just the result of @code{to_string} in a stack trace, omitting
21040 the result of @code{children}.
21042 If this method returns a string, it is printed verbatim.
21044 Otherwise, if this method returns an instance of @code{gdb.Value},
21045 then @value{GDBN} prints this value. This may result in a call to
21046 another pretty-printer.
21048 If instead the method returns a Python value which is convertible to a
21049 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
21050 the resulting value. Again, this may result in a call to another
21051 pretty-printer. Python scalars (integers, floats, and booleans) and
21052 strings are convertible to @code{gdb.Value}; other types are not.
21054 Finally, if this method returns @code{None} then no further operations
21055 are peformed in this method and nothing is printed.
21057 If the result is not one of these types, an exception is raised.
21060 @node Selecting Pretty-Printers
21061 @subsubsection Selecting Pretty-Printers
21063 The Python list @code{gdb.pretty_printers} contains an array of
21064 functions or callable objects that have been registered via addition
21065 as a pretty-printer.
21066 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
21067 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
21070 A function on one of these lists is passed a single @code{gdb.Value}
21071 argument and should return a pretty-printer object conforming to the
21072 interface definition above (@pxref{Pretty Printing API}). If a function
21073 cannot create a pretty-printer for the value, it should return
21076 @value{GDBN} first checks the @code{pretty_printers} attribute of each
21077 @code{gdb.Objfile} in the current program space and iteratively calls
21078 each enabled function (@pxref{Disabling Pretty-Printers})
21079 in the list for that @code{gdb.Objfile} until it receives
21080 a pretty-printer object.
21081 If no pretty-printer is found in the objfile lists, @value{GDBN} then
21082 searches the pretty-printer list of the current program space,
21083 calling each enabled function until an object is returned.
21084 After these lists have been exhausted, it tries the global
21085 @code{gdb.pretty_printers} list, again calling each enabled function until an
21086 object is returned.
21088 The order in which the objfiles are searched is not specified. For a
21089 given list, functions are always invoked from the head of the list,
21090 and iterated over sequentially until the end of the list, or a printer
21091 object is returned.
21093 Here is an example showing how a @code{std::string} printer might be
21097 class StdStringPrinter:
21098 "Print a std::string"
21100 def __init__ (self, val):
21103 def to_string (self):
21104 return self.val['_M_dataplus']['_M_p']
21106 def display_hint (self):
21110 And here is an example showing how a lookup function for the printer
21111 example above might be written.
21114 def str_lookup_function (val):
21116 lookup_tag = val.type.tag
21117 regex = re.compile ("^std::basic_string<char,.*>$")
21118 if lookup_tag == None:
21120 if regex.match (lookup_tag):
21121 return StdStringPrinter (val)
21126 The example lookup function extracts the value's type, and attempts to
21127 match it to a type that it can pretty-print. If it is a type the
21128 printer can pretty-print, it will return a printer object. If not, it
21129 returns @code{None}.
21131 We recommend that you put your core pretty-printers into a Python
21132 package. If your pretty-printers are for use with a library, we
21133 further recommend embedding a version number into the package name.
21134 This practice will enable @value{GDBN} to load multiple versions of
21135 your pretty-printers at the same time, because they will have
21138 You should write auto-loaded code (@pxref{Auto-loading}) such that it
21139 can be evaluated multiple times without changing its meaning. An
21140 ideal auto-load file will consist solely of @code{import}s of your
21141 printer modules, followed by a call to a register pretty-printers with
21142 the current objfile.
21144 Taken as a whole, this approach will scale nicely to multiple
21145 inferiors, each potentially using a different library version.
21146 Embedding a version number in the Python package name will ensure that
21147 @value{GDBN} is able to load both sets of printers simultaneously.
21148 Then, because the search for pretty-printers is done by objfile, and
21149 because your auto-loaded code took care to register your library's
21150 printers with a specific objfile, @value{GDBN} will find the correct
21151 printers for the specific version of the library used by each
21154 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
21155 this code might appear in @code{gdb.libstdcxx.v6}:
21158 def register_printers (objfile):
21159 objfile.pretty_printers.add (str_lookup_function)
21163 And then the corresponding contents of the auto-load file would be:
21166 import gdb.libstdcxx.v6
21167 gdb.libstdcxx.v6.register_printers (gdb.current_objfile ())
21170 @node Disabling Pretty-Printers
21171 @subsubsection Disabling Pretty-Printers
21172 @cindex disabling pretty-printers
21174 For various reasons a pretty-printer may not work.
21175 For example, the underlying data structure may have changed and
21176 the pretty-printer is out of date.
21178 The consequences of a broken pretty-printer are severe enough that
21179 @value{GDBN} provides support for enabling and disabling individual
21180 printers. For example, if @code{print frame-arguments} is on,
21181 a backtrace can become highly illegible if any argument is printed
21182 with a broken printer.
21184 Pretty-printers are enabled and disabled by attaching an @code{enabled}
21185 attribute to the registered function or callable object. If this attribute
21186 is present and its value is @code{False}, the printer is disabled, otherwise
21187 the printer is enabled.
21189 @node Inferiors In Python
21190 @subsubsection Inferiors In Python
21191 @cindex inferiors in python
21193 @findex gdb.Inferior
21194 Programs which are being run under @value{GDBN} are called inferiors
21195 (@pxref{Inferiors and Programs}). Python scripts can access
21196 information about and manipulate inferiors controlled by @value{GDBN}
21197 via objects of the @code{gdb.Inferior} class.
21199 The following inferior-related functions are available in the @code{gdb}
21203 Return a tuple containing all inferior objects.
21206 A @code{gdb.Inferior} object has the following attributes:
21209 @defivar Inferior num
21210 ID of inferior, as assigned by GDB.
21213 @defivar Inferior pid
21214 Process ID of the inferior, as assigned by the underlying operating
21218 @defivar Inferior was_attached
21219 Boolean signaling whether the inferior was created using `attach', or
21220 started by @value{GDBN} itself.
21224 A @code{gdb.Inferior} object has the following methods:
21227 @defmethod Inferior threads
21228 This method returns a tuple holding all the threads which are valid
21229 when it is called. If there are no valid threads, the method will
21230 return an empty tuple.
21233 @findex gdb.read_memory
21234 @defmethod Inferior read_memory address length
21235 Read @var{length} bytes of memory from the inferior, starting at
21236 @var{address}. Returns a buffer object, which behaves much like an array
21237 or a string. It can be modified and given to the @code{gdb.write_memory}
21241 @findex gdb.write_memory
21242 @defmethod Inferior write_memory address buffer @r{[}length@r{]}
21243 Write the contents of @var{buffer} to the inferior, starting at
21244 @var{address}. The @var{buffer} parameter must be a Python object
21245 which supports the buffer protocol, i.e., a string, an array or the
21246 object returned from @code{gdb.read_memory}. If given, @var{length}
21247 determines the number of bytes from @var{buffer} to be written.
21250 @findex gdb.search_memory
21251 @defmethod Inferior search_memory address length pattern
21252 Search a region of the inferior memory starting at @var{address} with
21253 the given @var{length} using the search pattern supplied in
21254 @var{pattern}. The @var{pattern} parameter must be a Python object
21255 which supports the buffer protocol, i.e., a string, an array or the
21256 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
21257 containing the address where the pattern was found, or @code{None} if
21258 the pattern could not be found.
21262 @node Threads In Python
21263 @subsubsection Threads In Python
21264 @cindex threads in python
21266 @findex gdb.InferiorThread
21267 Python scripts can access information about, and manipulate inferior threads
21268 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
21270 The following thread-related functions are available in the @code{gdb}
21273 @findex gdb.selected_thread
21274 @defun selected_thread
21275 This function returns the thread object for the selected thread. If there
21276 is no selected thread, this will return @code{None}.
21279 A @code{gdb.InferiorThread} object has the following attributes:
21282 @defivar InferiorThread num
21283 ID of the thread, as assigned by GDB.
21286 @defivar InferiorThread ptid
21287 ID of the thread, as assigned by the operating system. This attribute is a
21288 tuple containing three integers. The first is the Process ID (PID); the second
21289 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
21290 Either the LWPID or TID may be 0, which indicates that the operating system
21291 does not use that identifier.
21295 A @code{gdb.InferiorThread} object has the following methods:
21298 @defmethod InferiorThread switch
21299 This changes @value{GDBN}'s currently selected thread to the one represented
21303 @defmethod InferiorThread is_stopped
21304 Return a Boolean indicating whether the thread is stopped.
21307 @defmethod InferiorThread is_running
21308 Return a Boolean indicating whether the thread is running.
21311 @defmethod InferiorThread is_exited
21312 Return a Boolean indicating whether the thread is exited.
21316 @node Commands In Python
21317 @subsubsection Commands In Python
21319 @cindex commands in python
21320 @cindex python commands
21321 You can implement new @value{GDBN} CLI commands in Python. A CLI
21322 command is implemented using an instance of the @code{gdb.Command}
21323 class, most commonly using a subclass.
21325 @defmethod Command __init__ name @var{command_class} @r{[}@var{completer_class}@r{]} @r{[}@var{prefix}@r{]}
21326 The object initializer for @code{Command} registers the new command
21327 with @value{GDBN}. This initializer is normally invoked from the
21328 subclass' own @code{__init__} method.
21330 @var{name} is the name of the command. If @var{name} consists of
21331 multiple words, then the initial words are looked for as prefix
21332 commands. In this case, if one of the prefix commands does not exist,
21333 an exception is raised.
21335 There is no support for multi-line commands.
21337 @var{command_class} should be one of the @samp{COMMAND_} constants
21338 defined below. This argument tells @value{GDBN} how to categorize the
21339 new command in the help system.
21341 @var{completer_class} is an optional argument. If given, it should be
21342 one of the @samp{COMPLETE_} constants defined below. This argument
21343 tells @value{GDBN} how to perform completion for this command. If not
21344 given, @value{GDBN} will attempt to complete using the object's
21345 @code{complete} method (see below); if no such method is found, an
21346 error will occur when completion is attempted.
21348 @var{prefix} is an optional argument. If @code{True}, then the new
21349 command is a prefix command; sub-commands of this command may be
21352 The help text for the new command is taken from the Python
21353 documentation string for the command's class, if there is one. If no
21354 documentation string is provided, the default value ``This command is
21355 not documented.'' is used.
21358 @cindex don't repeat Python command
21359 @defmethod Command dont_repeat
21360 By default, a @value{GDBN} command is repeated when the user enters a
21361 blank line at the command prompt. A command can suppress this
21362 behavior by invoking the @code{dont_repeat} method. This is similar
21363 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
21366 @defmethod Command invoke argument from_tty
21367 This method is called by @value{GDBN} when this command is invoked.
21369 @var{argument} is a string. It is the argument to the command, after
21370 leading and trailing whitespace has been stripped.
21372 @var{from_tty} is a boolean argument. When true, this means that the
21373 command was entered by the user at the terminal; when false it means
21374 that the command came from elsewhere.
21376 If this method throws an exception, it is turned into a @value{GDBN}
21377 @code{error} call. Otherwise, the return value is ignored.
21379 @findex gdb.string_to_argv
21380 To break @var{argument} up into an argv-like string use
21381 @code{gdb.string_to_argv}. This function behaves identically to
21382 @value{GDBN}'s internal argument lexer @code{buildargv}.
21383 It is recommended to use this for consistency.
21384 Arguments are separated by spaces and may be quoted.
21388 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
21389 ['1', '2 "3', '4 "5', "6 '7"]
21394 @cindex completion of Python commands
21395 @defmethod Command complete text word
21396 This method is called by @value{GDBN} when the user attempts
21397 completion on this command. All forms of completion are handled by
21398 this method, that is, the @key{TAB} and @key{M-?} key bindings
21399 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
21402 The arguments @var{text} and @var{word} are both strings. @var{text}
21403 holds the complete command line up to the cursor's location.
21404 @var{word} holds the last word of the command line; this is computed
21405 using a word-breaking heuristic.
21407 The @code{complete} method can return several values:
21410 If the return value is a sequence, the contents of the sequence are
21411 used as the completions. It is up to @code{complete} to ensure that the
21412 contents actually do complete the word. A zero-length sequence is
21413 allowed, it means that there were no completions available. Only
21414 string elements of the sequence are used; other elements in the
21415 sequence are ignored.
21418 If the return value is one of the @samp{COMPLETE_} constants defined
21419 below, then the corresponding @value{GDBN}-internal completion
21420 function is invoked, and its result is used.
21423 All other results are treated as though there were no available
21428 When a new command is registered, it must be declared as a member of
21429 some general class of commands. This is used to classify top-level
21430 commands in the on-line help system; note that prefix commands are not
21431 listed under their own category but rather that of their top-level
21432 command. The available classifications are represented by constants
21433 defined in the @code{gdb} module:
21436 @findex COMMAND_NONE
21437 @findex gdb.COMMAND_NONE
21439 The command does not belong to any particular class. A command in
21440 this category will not be displayed in any of the help categories.
21442 @findex COMMAND_RUNNING
21443 @findex gdb.COMMAND_RUNNING
21444 @item COMMAND_RUNNING
21445 The command is related to running the inferior. For example,
21446 @code{start}, @code{step}, and @code{continue} are in this category.
21447 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
21448 commands in this category.
21450 @findex COMMAND_DATA
21451 @findex gdb.COMMAND_DATA
21453 The command is related to data or variables. For example,
21454 @code{call}, @code{find}, and @code{print} are in this category. Type
21455 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
21458 @findex COMMAND_STACK
21459 @findex gdb.COMMAND_STACK
21460 @item COMMAND_STACK
21461 The command has to do with manipulation of the stack. For example,
21462 @code{backtrace}, @code{frame}, and @code{return} are in this
21463 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
21464 list of commands in this category.
21466 @findex COMMAND_FILES
21467 @findex gdb.COMMAND_FILES
21468 @item COMMAND_FILES
21469 This class is used for file-related commands. For example,
21470 @code{file}, @code{list} and @code{section} are in this category.
21471 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
21472 commands in this category.
21474 @findex COMMAND_SUPPORT
21475 @findex gdb.COMMAND_SUPPORT
21476 @item COMMAND_SUPPORT
21477 This should be used for ``support facilities'', generally meaning
21478 things that are useful to the user when interacting with @value{GDBN},
21479 but not related to the state of the inferior. For example,
21480 @code{help}, @code{make}, and @code{shell} are in this category. Type
21481 @kbd{help support} at the @value{GDBN} prompt to see a list of
21482 commands in this category.
21484 @findex COMMAND_STATUS
21485 @findex gdb.COMMAND_STATUS
21486 @item COMMAND_STATUS
21487 The command is an @samp{info}-related command, that is, related to the
21488 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
21489 and @code{show} are in this category. Type @kbd{help status} at the
21490 @value{GDBN} prompt to see a list of commands in this category.
21492 @findex COMMAND_BREAKPOINTS
21493 @findex gdb.COMMAND_BREAKPOINTS
21494 @item COMMAND_BREAKPOINTS
21495 The command has to do with breakpoints. For example, @code{break},
21496 @code{clear}, and @code{delete} are in this category. Type @kbd{help
21497 breakpoints} at the @value{GDBN} prompt to see a list of commands in
21500 @findex COMMAND_TRACEPOINTS
21501 @findex gdb.COMMAND_TRACEPOINTS
21502 @item COMMAND_TRACEPOINTS
21503 The command has to do with tracepoints. For example, @code{trace},
21504 @code{actions}, and @code{tfind} are in this category. Type
21505 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
21506 commands in this category.
21508 @findex COMMAND_OBSCURE
21509 @findex gdb.COMMAND_OBSCURE
21510 @item COMMAND_OBSCURE
21511 The command is only used in unusual circumstances, or is not of
21512 general interest to users. For example, @code{checkpoint},
21513 @code{fork}, and @code{stop} are in this category. Type @kbd{help
21514 obscure} at the @value{GDBN} prompt to see a list of commands in this
21517 @findex COMMAND_MAINTENANCE
21518 @findex gdb.COMMAND_MAINTENANCE
21519 @item COMMAND_MAINTENANCE
21520 The command is only useful to @value{GDBN} maintainers. The
21521 @code{maintenance} and @code{flushregs} commands are in this category.
21522 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
21523 commands in this category.
21526 A new command can use a predefined completion function, either by
21527 specifying it via an argument at initialization, or by returning it
21528 from the @code{complete} method. These predefined completion
21529 constants are all defined in the @code{gdb} module:
21532 @findex COMPLETE_NONE
21533 @findex gdb.COMPLETE_NONE
21534 @item COMPLETE_NONE
21535 This constant means that no completion should be done.
21537 @findex COMPLETE_FILENAME
21538 @findex gdb.COMPLETE_FILENAME
21539 @item COMPLETE_FILENAME
21540 This constant means that filename completion should be performed.
21542 @findex COMPLETE_LOCATION
21543 @findex gdb.COMPLETE_LOCATION
21544 @item COMPLETE_LOCATION
21545 This constant means that location completion should be done.
21546 @xref{Specify Location}.
21548 @findex COMPLETE_COMMAND
21549 @findex gdb.COMPLETE_COMMAND
21550 @item COMPLETE_COMMAND
21551 This constant means that completion should examine @value{GDBN}
21554 @findex COMPLETE_SYMBOL
21555 @findex gdb.COMPLETE_SYMBOL
21556 @item COMPLETE_SYMBOL
21557 This constant means that completion should be done using symbol names
21561 The following code snippet shows how a trivial CLI command can be
21562 implemented in Python:
21565 class HelloWorld (gdb.Command):
21566 """Greet the whole world."""
21568 def __init__ (self):
21569 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
21571 def invoke (self, arg, from_tty):
21572 print "Hello, World!"
21577 The last line instantiates the class, and is necessary to trigger the
21578 registration of the command with @value{GDBN}. Depending on how the
21579 Python code is read into @value{GDBN}, you may need to import the
21580 @code{gdb} module explicitly.
21582 @node Parameters In Python
21583 @subsubsection Parameters In Python
21585 @cindex parameters in python
21586 @cindex python parameters
21587 @tindex gdb.Parameter
21589 You can implement new @value{GDBN} parameters using Python. A new
21590 parameter is implemented as an instance of the @code{gdb.Parameter}
21593 Parameters are exposed to the user via the @code{set} and
21594 @code{show} commands. @xref{Help}.
21596 There are many parameters that already exist and can be set in
21597 @value{GDBN}. Two examples are: @code{set follow fork} and
21598 @code{set charset}. Setting these parameters influences certain
21599 behavior in @value{GDBN}. Similarly, you can define parameters that
21600 can be used to influence behavior in custom Python scripts and commands.
21602 @defmethod Parameter __init__ name @var{command-class} @var{parameter-class} @r{[}@var{enum-sequence}@r{]}
21603 The object initializer for @code{Parameter} registers the new
21604 parameter with @value{GDBN}. This initializer is normally invoked
21605 from the subclass' own @code{__init__} method.
21607 @var{name} is the name of the new parameter. If @var{name} consists
21608 of multiple words, then the initial words are looked for as prefix
21609 parameters. An example of this can be illustrated with the
21610 @code{set print} set of parameters. If @var{name} is
21611 @code{print foo}, then @code{print} will be searched as the prefix
21612 parameter. In this case the parameter can subsequently be accessed in
21613 @value{GDBN} as @code{set print foo}.
21615 If @var{name} consists of multiple words, and no prefix parameter group
21616 can be found, an exception is raised.
21618 @var{command-class} should be one of the @samp{COMMAND_} constants
21619 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
21620 categorize the new parameter in the help system.
21622 @var{parameter-class} should be one of the @samp{PARAM_} constants
21623 defined below. This argument tells @value{GDBN} the type of the new
21624 parameter; this information is used for input validation and
21627 If @var{parameter-class} is @code{PARAM_ENUM}, then
21628 @var{enum-sequence} must be a sequence of strings. These strings
21629 represent the possible values for the parameter.
21631 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
21632 of a fourth argument will cause an exception to be thrown.
21634 The help text for the new parameter is taken from the Python
21635 documentation string for the parameter's class, if there is one. If
21636 there is no documentation string, a default value is used.
21639 @defivar Parameter set_doc
21640 If this attribute exists, and is a string, then its value is used as
21641 the help text for this parameter's @code{set} command. The value is
21642 examined when @code{Parameter.__init__} is invoked; subsequent changes
21646 @defivar Parameter show_doc
21647 If this attribute exists, and is a string, then its value is used as
21648 the help text for this parameter's @code{show} command. The value is
21649 examined when @code{Parameter.__init__} is invoked; subsequent changes
21653 @defivar Parameter value
21654 The @code{value} attribute holds the underlying value of the
21655 parameter. It can be read and assigned to just as any other
21656 attribute. @value{GDBN} does validation when assignments are made.
21660 When a new parameter is defined, its type must be specified. The
21661 available types are represented by constants defined in the @code{gdb}
21665 @findex PARAM_BOOLEAN
21666 @findex gdb.PARAM_BOOLEAN
21667 @item PARAM_BOOLEAN
21668 The value is a plain boolean. The Python boolean values, @code{True}
21669 and @code{False} are the only valid values.
21671 @findex PARAM_AUTO_BOOLEAN
21672 @findex gdb.PARAM_AUTO_BOOLEAN
21673 @item PARAM_AUTO_BOOLEAN
21674 The value has three possible states: true, false, and @samp{auto}. In
21675 Python, true and false are represented using boolean constants, and
21676 @samp{auto} is represented using @code{None}.
21678 @findex PARAM_UINTEGER
21679 @findex gdb.PARAM_UINTEGER
21680 @item PARAM_UINTEGER
21681 The value is an unsigned integer. The value of 0 should be
21682 interpreted to mean ``unlimited''.
21684 @findex PARAM_INTEGER
21685 @findex gdb.PARAM_INTEGER
21686 @item PARAM_INTEGER
21687 The value is a signed integer. The value of 0 should be interpreted
21688 to mean ``unlimited''.
21690 @findex PARAM_STRING
21691 @findex gdb.PARAM_STRING
21693 The value is a string. When the user modifies the string, any escape
21694 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
21695 translated into corresponding characters and encoded into the current
21698 @findex PARAM_STRING_NOESCAPE
21699 @findex gdb.PARAM_STRING_NOESCAPE
21700 @item PARAM_STRING_NOESCAPE
21701 The value is a string. When the user modifies the string, escapes are
21702 passed through untranslated.
21704 @findex PARAM_OPTIONAL_FILENAME
21705 @findex gdb.PARAM_OPTIONAL_FILENAME
21706 @item PARAM_OPTIONAL_FILENAME
21707 The value is a either a filename (a string), or @code{None}.
21709 @findex PARAM_FILENAME
21710 @findex gdb.PARAM_FILENAME
21711 @item PARAM_FILENAME
21712 The value is a filename. This is just like
21713 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
21715 @findex PARAM_ZINTEGER
21716 @findex gdb.PARAM_ZINTEGER
21717 @item PARAM_ZINTEGER
21718 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
21719 is interpreted as itself.
21722 @findex gdb.PARAM_ENUM
21724 The value is a string, which must be one of a collection string
21725 constants provided when the parameter is created.
21728 @node Functions In Python
21729 @subsubsection Writing new convenience functions
21731 @cindex writing convenience functions
21732 @cindex convenience functions in python
21733 @cindex python convenience functions
21734 @tindex gdb.Function
21736 You can implement new convenience functions (@pxref{Convenience Vars})
21737 in Python. A convenience function is an instance of a subclass of the
21738 class @code{gdb.Function}.
21740 @defmethod Function __init__ name
21741 The initializer for @code{Function} registers the new function with
21742 @value{GDBN}. The argument @var{name} is the name of the function,
21743 a string. The function will be visible to the user as a convenience
21744 variable of type @code{internal function}, whose name is the same as
21745 the given @var{name}.
21747 The documentation for the new function is taken from the documentation
21748 string for the new class.
21751 @defmethod Function invoke @var{*args}
21752 When a convenience function is evaluated, its arguments are converted
21753 to instances of @code{gdb.Value}, and then the function's
21754 @code{invoke} method is called. Note that @value{GDBN} does not
21755 predetermine the arity of convenience functions. Instead, all
21756 available arguments are passed to @code{invoke}, following the
21757 standard Python calling convention. In particular, a convenience
21758 function can have default values for parameters without ill effect.
21760 The return value of this method is used as its value in the enclosing
21761 expression. If an ordinary Python value is returned, it is converted
21762 to a @code{gdb.Value} following the usual rules.
21765 The following code snippet shows how a trivial convenience function can
21766 be implemented in Python:
21769 class Greet (gdb.Function):
21770 """Return string to greet someone.
21771 Takes a name as argument."""
21773 def __init__ (self):
21774 super (Greet, self).__init__ ("greet")
21776 def invoke (self, name):
21777 return "Hello, %s!" % name.string ()
21782 The last line instantiates the class, and is necessary to trigger the
21783 registration of the function with @value{GDBN}. Depending on how the
21784 Python code is read into @value{GDBN}, you may need to import the
21785 @code{gdb} module explicitly.
21787 @node Progspaces In Python
21788 @subsubsection Program Spaces In Python
21790 @cindex progspaces in python
21791 @tindex gdb.Progspace
21793 A program space, or @dfn{progspace}, represents a symbolic view
21794 of an address space.
21795 It consists of all of the objfiles of the program.
21796 @xref{Objfiles In Python}.
21797 @xref{Inferiors and Programs, program spaces}, for more details
21798 about program spaces.
21800 The following progspace-related functions are available in the
21803 @findex gdb.current_progspace
21804 @defun current_progspace
21805 This function returns the program space of the currently selected inferior.
21806 @xref{Inferiors and Programs}.
21809 @findex gdb.progspaces
21811 Return a sequence of all the progspaces currently known to @value{GDBN}.
21814 Each progspace is represented by an instance of the @code{gdb.Progspace}
21817 @defivar Progspace filename
21818 The file name of the progspace as a string.
21821 @defivar Progspace pretty_printers
21822 The @code{pretty_printers} attribute is a list of functions. It is
21823 used to look up pretty-printers. A @code{Value} is passed to each
21824 function in order; if the function returns @code{None}, then the
21825 search continues. Otherwise, the return value should be an object
21826 which is used to format the value. @xref{Pretty Printing API}, for more
21830 @node Objfiles In Python
21831 @subsubsection Objfiles In Python
21833 @cindex objfiles in python
21834 @tindex gdb.Objfile
21836 @value{GDBN} loads symbols for an inferior from various
21837 symbol-containing files (@pxref{Files}). These include the primary
21838 executable file, any shared libraries used by the inferior, and any
21839 separate debug info files (@pxref{Separate Debug Files}).
21840 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
21842 The following objfile-related functions are available in the
21845 @findex gdb.current_objfile
21846 @defun current_objfile
21847 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
21848 sets the ``current objfile'' to the corresponding objfile. This
21849 function returns the current objfile. If there is no current objfile,
21850 this function returns @code{None}.
21853 @findex gdb.objfiles
21855 Return a sequence of all the objfiles current known to @value{GDBN}.
21856 @xref{Objfiles In Python}.
21859 Each objfile is represented by an instance of the @code{gdb.Objfile}
21862 @defivar Objfile filename
21863 The file name of the objfile as a string.
21866 @defivar Objfile pretty_printers
21867 The @code{pretty_printers} attribute is a list of functions. It is
21868 used to look up pretty-printers. A @code{Value} is passed to each
21869 function in order; if the function returns @code{None}, then the
21870 search continues. Otherwise, the return value should be an object
21871 which is used to format the value. @xref{Pretty Printing API}, for more
21875 @node Frames In Python
21876 @subsubsection Accessing inferior stack frames from Python.
21878 @cindex frames in python
21879 When the debugged program stops, @value{GDBN} is able to analyze its call
21880 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
21881 represents a frame in the stack. A @code{gdb.Frame} object is only valid
21882 while its corresponding frame exists in the inferior's stack. If you try
21883 to use an invalid frame object, @value{GDBN} will throw a @code{RuntimeError}
21886 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
21890 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
21894 The following frame-related functions are available in the @code{gdb} module:
21896 @findex gdb.selected_frame
21897 @defun selected_frame
21898 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
21901 @defun frame_stop_reason_string reason
21902 Return a string explaining the reason why @value{GDBN} stopped unwinding
21903 frames, as expressed by the given @var{reason} code (an integer, see the
21904 @code{unwind_stop_reason} method further down in this section).
21907 A @code{gdb.Frame} object has the following methods:
21910 @defmethod Frame is_valid
21911 Returns true if the @code{gdb.Frame} object is valid, false if not.
21912 A frame object can become invalid if the frame it refers to doesn't
21913 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
21914 an exception if it is invalid at the time the method is called.
21917 @defmethod Frame name
21918 Returns the function name of the frame, or @code{None} if it can't be
21922 @defmethod Frame type
21923 Returns the type of the frame. The value can be one of
21924 @code{gdb.NORMAL_FRAME}, @code{gdb.DUMMY_FRAME}, @code{gdb.SIGTRAMP_FRAME}
21925 or @code{gdb.SENTINEL_FRAME}.
21928 @defmethod Frame unwind_stop_reason
21929 Return an integer representing the reason why it's not possible to find
21930 more frames toward the outermost frame. Use
21931 @code{gdb.frame_stop_reason_string} to convert the value returned by this
21932 function to a string.
21935 @defmethod Frame pc
21936 Returns the frame's resume address.
21939 @defmethod Frame block
21940 Return the frame's code block. @xref{Blocks In Python}.
21943 @defmethod Frame function
21944 Return the symbol for the function corresponding to this frame.
21945 @xref{Symbols In Python}.
21948 @defmethod Frame older
21949 Return the frame that called this frame.
21952 @defmethod Frame newer
21953 Return the frame called by this frame.
21956 @defmethod Frame find_sal
21957 Return the frame's symtab and line object.
21958 @xref{Symbol Tables In Python}.
21961 @defmethod Frame read_var variable @r{[}block@r{]}
21962 Return the value of @var{variable} in this frame. If the optional
21963 argument @var{block} is provided, search for the variable from that
21964 block; otherwise start at the frame's current block (which is
21965 determined by the frame's current program counter). @var{variable}
21966 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
21967 @code{gdb.Block} object.
21970 @defmethod Frame select
21971 Set this frame to be the selected frame. @xref{Stack, ,Examining the
21976 @node Blocks In Python
21977 @subsubsection Accessing frame blocks from Python.
21979 @cindex blocks in python
21982 Within each frame, @value{GDBN} maintains information on each block
21983 stored in that frame. These blocks are organized hierarchically, and
21984 are represented individually in Python as a @code{gdb.Block}.
21985 Please see @ref{Frames In Python}, for a more in-depth discussion on
21986 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
21987 detailed technical information on @value{GDBN}'s book-keeping of the
21990 The following block-related functions are available in the @code{gdb}
21993 @findex gdb.block_for_pc
21994 @defun block_for_pc pc
21995 Return the @code{gdb.Block} containing the given @var{pc} value. If the
21996 block cannot be found for the @var{pc} value specified, the function
21997 will return @code{None}.
22000 A @code{gdb.Block} object has the following attributes:
22003 @defivar Block start
22004 The start address of the block. This attribute is not writable.
22008 The end address of the block. This attribute is not writable.
22011 @defivar Block function
22012 The name of the block represented as a @code{gdb.Symbol}. If the
22013 block is not named, then this attribute holds @code{None}. This
22014 attribute is not writable.
22017 @defivar Block superblock
22018 The block containing this block. If this parent block does not exist,
22019 this attribute holds @code{None}. This attribute is not writable.
22023 @node Symbols In Python
22024 @subsubsection Python representation of Symbols.
22026 @cindex symbols in python
22029 @value{GDBN} represents every variable, function and type as an
22030 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
22031 Similarly, Python represents these symbols in @value{GDBN} with the
22032 @code{gdb.Symbol} object.
22034 The following symbol-related functions are available in the @code{gdb}
22037 @findex gdb.lookup_symbol
22038 @defun lookup_symbol name [block] [domain]
22039 This function searches for a symbol by name. The search scope can be
22040 restricted to the parameters defined in the optional domain and block
22043 @var{name} is the name of the symbol. It must be a string. The
22044 optional @var{block} argument restricts the search to symbols visible
22045 in that @var{block}. The @var{block} argument must be a
22046 @code{gdb.Block} object. The optional @var{domain} argument restricts
22047 the search to the domain type. The @var{domain} argument must be a
22048 domain constant defined in the @code{gdb} module and described later
22052 A @code{gdb.Symbol} object has the following attributes:
22055 @defivar Symbol symtab
22056 The symbol table in which the symbol appears. This attribute is
22057 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
22058 Python}. This attribute is not writable.
22061 @defivar Symbol name
22062 The name of the symbol as a string. This attribute is not writable.
22065 @defivar Symbol linkage_name
22066 The name of the symbol, as used by the linker (i.e., may be mangled).
22067 This attribute is not writable.
22070 @defivar Symbol print_name
22071 The name of the symbol in a form suitable for output. This is either
22072 @code{name} or @code{linkage_name}, depending on whether the user
22073 asked @value{GDBN} to display demangled or mangled names.
22076 @defivar Symbol addr_class
22077 The address class of the symbol. This classifies how to find the value
22078 of a symbol. Each address class is a constant defined in the
22079 @code{gdb} module and described later in this chapter.
22082 @defivar Symbol is_argument
22083 @code{True} if the symbol is an argument of a function.
22086 @defivar Symbol is_constant
22087 @code{True} if the symbol is a constant.
22090 @defivar Symbol is_function
22091 @code{True} if the symbol is a function or a method.
22094 @defivar Symbol is_variable
22095 @code{True} if the symbol is a variable.
22099 The available domain categories in @code{gdb.Symbol} are represented
22100 as constants in the @code{gdb} module:
22103 @findex SYMBOL_UNDEF_DOMAIN
22104 @findex gdb.SYMBOL_UNDEF_DOMAIN
22105 @item SYMBOL_UNDEF_DOMAIN
22106 This is used when a domain has not been discovered or none of the
22107 following domains apply. This usually indicates an error either
22108 in the symbol information or in @value{GDBN}'s handling of symbols.
22109 @findex SYMBOL_VAR_DOMAIN
22110 @findex gdb.SYMBOL_VAR_DOMAIN
22111 @item SYMBOL_VAR_DOMAIN
22112 This domain contains variables, function names, typedef names and enum
22114 @findex SYMBOL_STRUCT_DOMAIN
22115 @findex gdb.SYMBOL_STRUCT_DOMAIN
22116 @item SYMBOL_STRUCT_DOMAIN
22117 This domain holds struct, union and enum type names.
22118 @findex SYMBOL_LABEL_DOMAIN
22119 @findex gdb.SYMBOL_LABEL_DOMAIN
22120 @item SYMBOL_LABEL_DOMAIN
22121 This domain contains names of labels (for gotos).
22122 @findex SYMBOL_VARIABLES_DOMAIN
22123 @findex gdb.SYMBOL_VARIABLES_DOMAIN
22124 @item SYMBOL_VARIABLES_DOMAIN
22125 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
22126 contains everything minus functions and types.
22127 @findex SYMBOL_FUNCTIONS_DOMAIN
22128 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
22129 @item SYMBOL_FUNCTION_DOMAIN
22130 This domain contains all functions.
22131 @findex SYMBOL_TYPES_DOMAIN
22132 @findex gdb.SYMBOL_TYPES_DOMAIN
22133 @item SYMBOL_TYPES_DOMAIN
22134 This domain contains all types.
22137 The available address class categories in @code{gdb.Symbol} are represented
22138 as constants in the @code{gdb} module:
22141 @findex SYMBOL_LOC_UNDEF
22142 @findex gdb.SYMBOL_LOC_UNDEF
22143 @item SYMBOL_LOC_UNDEF
22144 If this is returned by address class, it indicates an error either in
22145 the symbol information or in @value{GDBN}'s handling of symbols.
22146 @findex SYMBOL_LOC_CONST
22147 @findex gdb.SYMBOL_LOC_CONST
22148 @item SYMBOL_LOC_CONST
22149 Value is constant int.
22150 @findex SYMBOL_LOC_STATIC
22151 @findex gdb.SYMBOL_LOC_STATIC
22152 @item SYMBOL_LOC_STATIC
22153 Value is at a fixed address.
22154 @findex SYMBOL_LOC_REGISTER
22155 @findex gdb.SYMBOL_LOC_REGISTER
22156 @item SYMBOL_LOC_REGISTER
22157 Value is in a register.
22158 @findex SYMBOL_LOC_ARG
22159 @findex gdb.SYMBOL_LOC_ARG
22160 @item SYMBOL_LOC_ARG
22161 Value is an argument. This value is at the offset stored within the
22162 symbol inside the frame's argument list.
22163 @findex SYMBOL_LOC_REF_ARG
22164 @findex gdb.SYMBOL_LOC_REF_ARG
22165 @item SYMBOL_LOC_REF_ARG
22166 Value address is stored in the frame's argument list. Just like
22167 @code{LOC_ARG} except that the value's address is stored at the
22168 offset, not the value itself.
22169 @findex SYMBOL_LOC_REGPARM_ADDR
22170 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
22171 @item SYMBOL_LOC_REGPARM_ADDR
22172 Value is a specified register. Just like @code{LOC_REGISTER} except
22173 the register holds the address of the argument instead of the argument
22175 @findex SYMBOL_LOC_LOCAL
22176 @findex gdb.SYMBOL_LOC_LOCAL
22177 @item SYMBOL_LOC_LOCAL
22178 Value is a local variable.
22179 @findex SYMBOL_LOC_TYPEDEF
22180 @findex gdb.SYMBOL_LOC_TYPEDEF
22181 @item SYMBOL_LOC_TYPEDEF
22182 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
22184 @findex SYMBOL_LOC_BLOCK
22185 @findex gdb.SYMBOL_LOC_BLOCK
22186 @item SYMBOL_LOC_BLOCK
22188 @findex SYMBOL_LOC_CONST_BYTES
22189 @findex gdb.SYMBOL_LOC_CONST_BYTES
22190 @item SYMBOL_LOC_CONST_BYTES
22191 Value is a byte-sequence.
22192 @findex SYMBOL_LOC_UNRESOLVED
22193 @findex gdb.SYMBOL_LOC_UNRESOLVED
22194 @item SYMBOL_LOC_UNRESOLVED
22195 Value is at a fixed address, but the address of the variable has to be
22196 determined from the minimal symbol table whenever the variable is
22198 @findex SYMBOL_LOC_OPTIMIZED_OUT
22199 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
22200 @item SYMBOL_LOC_OPTIMIZED_OUT
22201 The value does not actually exist in the program.
22202 @findex SYMBOL_LOC_COMPUTED
22203 @findex gdb.SYMBOL_LOC_COMPUTED
22204 @item SYMBOL_LOC_COMPUTED
22205 The value's address is a computed location.
22208 @node Symbol Tables In Python
22209 @subsubsection Symbol table representation in Python.
22211 @cindex symbol tables in python
22213 @tindex gdb.Symtab_and_line
22215 Access to symbol table data maintained by @value{GDBN} on the inferior
22216 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
22217 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
22218 from the @code{find_sal} method in @code{gdb.Frame} object.
22219 @xref{Frames In Python}.
22221 For more information on @value{GDBN}'s symbol table management, see
22222 @ref{Symbols, ,Examining the Symbol Table}, for more information.
22224 A @code{gdb.Symtab_and_line} object has the following attributes:
22227 @defivar Symtab_and_line symtab
22228 The symbol table object (@code{gdb.Symtab}) for this frame.
22229 This attribute is not writable.
22232 @defivar Symtab_and_line pc
22233 Indicates the current program counter address. This attribute is not
22237 @defivar Symtab_and_line line
22238 Indicates the current line number for this object. This
22239 attribute is not writable.
22243 A @code{gdb.Symtab} object has the following attributes:
22246 @defivar Symtab filename
22247 The symbol table's source filename. This attribute is not writable.
22250 @defivar Symtab objfile
22251 The symbol table's backing object file. @xref{Objfiles In Python}.
22252 This attribute is not writable.
22256 The following methods are provided:
22259 @defmethod Symtab fullname
22260 Return the symbol table's source absolute file name.
22264 @node Breakpoints In Python
22265 @subsubsection Manipulating breakpoints using Python
22267 @cindex breakpoints in python
22268 @tindex gdb.Breakpoint
22270 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
22273 @defmethod Breakpoint __init__ spec @r{[}type@r{]} @r{[}wp_class@r{]}
22274 Create a new breakpoint. @var{spec} is a string naming the
22275 location of the breakpoint, or an expression that defines a
22276 watchpoint. The contents can be any location recognized by the
22277 @code{break} command, or in the case of a watchpoint, by the @code{watch}
22278 command. The optional @var{type} denotes the breakpoint to create
22279 from the types defined later in this chapter. This argument can be
22280 either: @code{BP_BREAKPOINT} or @code{BP_WATCHPOINT}. @var{type}
22281 defaults to @code{BP_BREAKPOINT}. The optional @var{wp_class}
22282 argument defines the class of watchpoint to create, if @var{type} is
22283 defined as @code{BP_WATCHPOINT}. If a watchpoint class is not
22284 provided, it is assumed to be a @var{WP_WRITE} class.
22287 The available watchpoint types represented by constants are defined in the
22292 @findex gdb.WP_READ
22294 Read only watchpoint.
22297 @findex gdb.WP_WRITE
22299 Write only watchpoint.
22302 @findex gdb.WP_ACCESS
22304 Read/Write watchpoint.
22307 @defmethod Breakpoint is_valid
22308 Return @code{True} if this @code{Breakpoint} object is valid,
22309 @code{False} otherwise. A @code{Breakpoint} object can become invalid
22310 if the user deletes the breakpoint. In this case, the object still
22311 exists, but the underlying breakpoint does not. In the cases of
22312 watchpoint scope, the watchpoint remains valid even if execution of the
22313 inferior leaves the scope of that watchpoint.
22316 @defivar Breakpoint enabled
22317 This attribute is @code{True} if the breakpoint is enabled, and
22318 @code{False} otherwise. This attribute is writable.
22321 @defivar Breakpoint silent
22322 This attribute is @code{True} if the breakpoint is silent, and
22323 @code{False} otherwise. This attribute is writable.
22325 Note that a breakpoint can also be silent if it has commands and the
22326 first command is @code{silent}. This is not reported by the
22327 @code{silent} attribute.
22330 @defivar Breakpoint thread
22331 If the breakpoint is thread-specific, this attribute holds the thread
22332 id. If the breakpoint is not thread-specific, this attribute is
22333 @code{None}. This attribute is writable.
22336 @defivar Breakpoint task
22337 If the breakpoint is Ada task-specific, this attribute holds the Ada task
22338 id. If the breakpoint is not task-specific (or the underlying
22339 language is not Ada), this attribute is @code{None}. This attribute
22343 @defivar Breakpoint ignore_count
22344 This attribute holds the ignore count for the breakpoint, an integer.
22345 This attribute is writable.
22348 @defivar Breakpoint number
22349 This attribute holds the breakpoint's number --- the identifier used by
22350 the user to manipulate the breakpoint. This attribute is not writable.
22353 @defivar Breakpoint type
22354 This attribute holds the breakpoint's type --- the identifier used to
22355 determine the actual breakpoint type or use-case. This attribute is not
22359 The available types are represented by constants defined in the @code{gdb}
22363 @findex BP_BREAKPOINT
22364 @findex gdb.BP_BREAKPOINT
22365 @item BP_BREAKPOINT
22366 Normal code breakpoint.
22368 @findex BP_WATCHPOINT
22369 @findex gdb.BP_WATCHPOINT
22370 @item BP_WATCHPOINT
22371 Watchpoint breakpoint.
22373 @findex BP_HARDWARE_WATCHPOINT
22374 @findex gdb.BP_HARDWARE_WATCHPOINT
22375 @item BP_HARDWARE_WATCHPOINT
22376 Hardware assisted watchpoint.
22378 @findex BP_READ_WATCHPOINT
22379 @findex gdb.BP_READ_WATCHPOINT
22380 @item BP_READ_WATCHPOINT
22381 Hardware assisted read watchpoint.
22383 @findex BP_ACCESS_WATCHPOINT
22384 @findex gdb.BP_ACCESS_WATCHPOINT
22385 @item BP_ACCESS_WATCHPOINT
22386 Hardware assisted access watchpoint.
22389 @defivar Breakpoint hit_count
22390 This attribute holds the hit count for the breakpoint, an integer.
22391 This attribute is writable, but currently it can only be set to zero.
22394 @defivar Breakpoint location
22395 This attribute holds the location of the breakpoint, as specified by
22396 the user. It is a string. If the breakpoint does not have a location
22397 (that is, it is a watchpoint) the attribute's value is @code{None}. This
22398 attribute is not writable.
22401 @defivar Breakpoint expression
22402 This attribute holds a breakpoint expression, as specified by
22403 the user. It is a string. If the breakpoint does not have an
22404 expression (the breakpoint is not a watchpoint) the attribute's value
22405 is @code{None}. This attribute is not writable.
22408 @defivar Breakpoint condition
22409 This attribute holds the condition of the breakpoint, as specified by
22410 the user. It is a string. If there is no condition, this attribute's
22411 value is @code{None}. This attribute is writable.
22414 @defivar Breakpoint commands
22415 This attribute holds the commands attached to the breakpoint. If
22416 there are commands, this attribute's value is a string holding all the
22417 commands, separated by newlines. If there are no commands, this
22418 attribute is @code{None}. This attribute is not writable.
22421 @node Lazy Strings In Python
22422 @subsubsection Python representation of lazy strings.
22424 @cindex lazy strings in python
22425 @tindex gdb.LazyString
22427 A @dfn{lazy string} is a string whose contents is not retrieved or
22428 encoded until it is needed.
22430 A @code{gdb.LazyString} is represented in @value{GDBN} as an
22431 @code{address} that points to a region of memory, an @code{encoding}
22432 that will be used to encode that region of memory, and a @code{length}
22433 to delimit the region of memory that represents the string. The
22434 difference between a @code{gdb.LazyString} and a string wrapped within
22435 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
22436 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
22437 retrieved and encoded during printing, while a @code{gdb.Value}
22438 wrapping a string is immediately retrieved and encoded on creation.
22440 A @code{gdb.LazyString} object has the following functions:
22442 @defmethod LazyString value
22443 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
22444 will point to the string in memory, but will lose all the delayed
22445 retrieval, encoding and handling that @value{GDBN} applies to a
22446 @code{gdb.LazyString}.
22449 @defivar LazyString address
22450 This attribute holds the address of the string. This attribute is not
22454 @defivar LazyString length
22455 This attribute holds the length of the string in characters. If the
22456 length is -1, then the string will be fetched and encoded up to the
22457 first null of appropriate width. This attribute is not writable.
22460 @defivar LazyString encoding
22461 This attribute holds the encoding that will be applied to the string
22462 when the string is printed by @value{GDBN}. If the encoding is not
22463 set, or contains an empty string, then @value{GDBN} will select the
22464 most appropriate encoding when the string is printed. This attribute
22468 @defivar LazyString type
22469 This attribute holds the type that is represented by the lazy string's
22470 type. For a lazy string this will always be a pointer type. To
22471 resolve this to the lazy string's character type, use the type's
22472 @code{target} method. @xref{Types In Python}. This attribute is not
22477 @subsection Auto-loading
22478 @cindex auto-loading, Python
22480 When a new object file is read (for example, due to the @code{file}
22481 command, or because the inferior has loaded a shared library),
22482 @value{GDBN} will look for Python support scripts in several ways:
22483 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
22486 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
22487 * .debug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
22488 * Which flavor to choose?::
22491 The auto-loading feature is useful for supplying application-specific
22492 debugging commands and scripts.
22494 Auto-loading can be enabled or disabled.
22497 @kindex maint set python auto-load
22498 @item maint set python auto-load [yes|no]
22499 Enable or disable the Python auto-loading feature.
22501 @kindex maint show python auto-load
22502 @item maint show python auto-load
22503 Show whether Python auto-loading is enabled or disabled.
22506 When reading an auto-loaded file, @value{GDBN} sets the
22507 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
22508 function (@pxref{Objfiles In Python}). This can be useful for
22509 registering objfile-specific pretty-printers.
22511 @node objfile-gdb.py file
22512 @subsubsection The @file{@var{objfile}-gdb.py} file
22513 @cindex @file{@var{objfile}-gdb.py}
22515 When a new object file is read, @value{GDBN} looks for
22516 a file named @file{@var{objfile}-gdb.py},
22517 where @var{objfile} is the object file's real name, formed by ensuring
22518 that the file name is absolute, following all symlinks, and resolving
22519 @code{.} and @code{..} components. If this file exists and is
22520 readable, @value{GDBN} will evaluate it as a Python script.
22522 If this file does not exist, and if the parameter
22523 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
22524 then @value{GDBN} will look for @var{real-name} in all of the
22525 directories mentioned in the value of @code{debug-file-directory}.
22527 Finally, if this file does not exist, then @value{GDBN} will look for
22528 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
22529 @var{data-directory} is @value{GDBN}'s data directory (available via
22530 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
22531 is the object file's real name, as described above.
22533 @value{GDBN} does not track which files it has already auto-loaded this way.
22534 @value{GDBN} will load the associated script every time the corresponding
22535 @var{objfile} is opened.
22536 So your @file{-gdb.py} file should be careful to avoid errors if it
22537 is evaluated more than once.
22539 @node .debug_gdb_scripts section
22540 @subsubsection The @code{.debug_gdb_scripts} section
22541 @cindex @code{.debug_gdb_scripts} section
22543 For systems using file formats like ELF and COFF,
22544 when @value{GDBN} loads a new object file
22545 it will look for a special section named @samp{.debug_gdb_scripts}.
22546 If this section exists, its contents is a list of names of scripts to load.
22548 @value{GDBN} will look for each specified script file first in the
22549 current directory and then along the source search path
22550 (@pxref{Source Path, ,Specifying Source Directories}),
22551 except that @file{$cdir} is not searched, since the compilation
22552 directory is not relevant to scripts.
22554 Entries can be placed in section @code{.debug_gdb_scripts} with,
22555 for example, this GCC macro:
22558 /* Note: The "MS" section flags are to remote duplicates. */
22559 #define DEFINE_GDB_SCRIPT(script_name) \
22561 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
22563 .asciz \"" script_name "\"\n\
22569 Then one can reference the macro in a header or source file like this:
22572 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
22575 The script name may include directories if desired.
22577 If the macro is put in a header, any application or library
22578 using this header will get a reference to the specified script.
22580 @node Which flavor to choose?
22581 @subsubsection Which flavor to choose?
22583 Given the multiple ways of auto-loading Python scripts, it might not always
22584 be clear which one to choose. This section provides some guidance.
22586 Benefits of the @file{-gdb.py} way:
22590 Can be used with file formats that don't support multiple sections.
22593 Ease of finding scripts for public libraries.
22595 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
22596 in the source search path.
22597 For publicly installed libraries, e.g., @file{libstdc++}, there typically
22598 isn't a source directory in which to find the script.
22601 Doesn't require source code additions.
22604 Benefits of the @code{.debug_gdb_scripts} way:
22608 Works with static linking.
22610 Scripts for libraries done the @file{-gdb.py} way require an objfile to
22611 trigger their loading. When an application is statically linked the only
22612 objfile available is the executable, and it is cumbersome to attach all the
22613 scripts from all the input libraries to the executable's @file{-gdb.py} script.
22616 Works with classes that are entirely inlined.
22618 Some classes can be entirely inlined, and thus there may not be an associated
22619 shared library to attach a @file{-gdb.py} script to.
22622 Scripts needn't be copied out of the source tree.
22624 In some circumstances, apps can be built out of large collections of internal
22625 libraries, and the build infrastructure necessary to install the
22626 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
22627 cumbersome. It may be easier to specify the scripts in the
22628 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
22629 top of the source tree to the source search path.
22633 @chapter Command Interpreters
22634 @cindex command interpreters
22636 @value{GDBN} supports multiple command interpreters, and some command
22637 infrastructure to allow users or user interface writers to switch
22638 between interpreters or run commands in other interpreters.
22640 @value{GDBN} currently supports two command interpreters, the console
22641 interpreter (sometimes called the command-line interpreter or @sc{cli})
22642 and the machine interface interpreter (or @sc{gdb/mi}). This manual
22643 describes both of these interfaces in great detail.
22645 By default, @value{GDBN} will start with the console interpreter.
22646 However, the user may choose to start @value{GDBN} with another
22647 interpreter by specifying the @option{-i} or @option{--interpreter}
22648 startup options. Defined interpreters include:
22652 @cindex console interpreter
22653 The traditional console or command-line interpreter. This is the most often
22654 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
22655 @value{GDBN} will use this interpreter.
22658 @cindex mi interpreter
22659 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
22660 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
22661 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
22665 @cindex mi2 interpreter
22666 The current @sc{gdb/mi} interface.
22669 @cindex mi1 interpreter
22670 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
22674 @cindex invoke another interpreter
22675 The interpreter being used by @value{GDBN} may not be dynamically
22676 switched at runtime. Although possible, this could lead to a very
22677 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
22678 enters the command "interpreter-set console" in a console view,
22679 @value{GDBN} would switch to using the console interpreter, rendering
22680 the IDE inoperable!
22682 @kindex interpreter-exec
22683 Although you may only choose a single interpreter at startup, you may execute
22684 commands in any interpreter from the current interpreter using the appropriate
22685 command. If you are running the console interpreter, simply use the
22686 @code{interpreter-exec} command:
22689 interpreter-exec mi "-data-list-register-names"
22692 @sc{gdb/mi} has a similar command, although it is only available in versions of
22693 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
22696 @chapter @value{GDBN} Text User Interface
22698 @cindex Text User Interface
22701 * TUI Overview:: TUI overview
22702 * TUI Keys:: TUI key bindings
22703 * TUI Single Key Mode:: TUI single key mode
22704 * TUI Commands:: TUI-specific commands
22705 * TUI Configuration:: TUI configuration variables
22708 The @value{GDBN} Text User Interface (TUI) is a terminal
22709 interface which uses the @code{curses} library to show the source
22710 file, the assembly output, the program registers and @value{GDBN}
22711 commands in separate text windows. The TUI mode is supported only
22712 on platforms where a suitable version of the @code{curses} library
22715 @pindex @value{GDBTUI}
22716 The TUI mode is enabled by default when you invoke @value{GDBN} as
22717 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
22718 You can also switch in and out of TUI mode while @value{GDBN} runs by
22719 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
22720 @xref{TUI Keys, ,TUI Key Bindings}.
22723 @section TUI Overview
22725 In TUI mode, @value{GDBN} can display several text windows:
22729 This window is the @value{GDBN} command window with the @value{GDBN}
22730 prompt and the @value{GDBN} output. The @value{GDBN} input is still
22731 managed using readline.
22734 The source window shows the source file of the program. The current
22735 line and active breakpoints are displayed in this window.
22738 The assembly window shows the disassembly output of the program.
22741 This window shows the processor registers. Registers are highlighted
22742 when their values change.
22745 The source and assembly windows show the current program position
22746 by highlighting the current line and marking it with a @samp{>} marker.
22747 Breakpoints are indicated with two markers. The first marker
22748 indicates the breakpoint type:
22752 Breakpoint which was hit at least once.
22755 Breakpoint which was never hit.
22758 Hardware breakpoint which was hit at least once.
22761 Hardware breakpoint which was never hit.
22764 The second marker indicates whether the breakpoint is enabled or not:
22768 Breakpoint is enabled.
22771 Breakpoint is disabled.
22774 The source, assembly and register windows are updated when the current
22775 thread changes, when the frame changes, or when the program counter
22778 These windows are not all visible at the same time. The command
22779 window is always visible. The others can be arranged in several
22790 source and assembly,
22793 source and registers, or
22796 assembly and registers.
22799 A status line above the command window shows the following information:
22803 Indicates the current @value{GDBN} target.
22804 (@pxref{Targets, ,Specifying a Debugging Target}).
22807 Gives the current process or thread number.
22808 When no process is being debugged, this field is set to @code{No process}.
22811 Gives the current function name for the selected frame.
22812 The name is demangled if demangling is turned on (@pxref{Print Settings}).
22813 When there is no symbol corresponding to the current program counter,
22814 the string @code{??} is displayed.
22817 Indicates the current line number for the selected frame.
22818 When the current line number is not known, the string @code{??} is displayed.
22821 Indicates the current program counter address.
22825 @section TUI Key Bindings
22826 @cindex TUI key bindings
22828 The TUI installs several key bindings in the readline keymaps
22829 (@pxref{Command Line Editing}). The following key bindings
22830 are installed for both TUI mode and the @value{GDBN} standard mode.
22839 Enter or leave the TUI mode. When leaving the TUI mode,
22840 the curses window management stops and @value{GDBN} operates using
22841 its standard mode, writing on the terminal directly. When reentering
22842 the TUI mode, control is given back to the curses windows.
22843 The screen is then refreshed.
22847 Use a TUI layout with only one window. The layout will
22848 either be @samp{source} or @samp{assembly}. When the TUI mode
22849 is not active, it will switch to the TUI mode.
22851 Think of this key binding as the Emacs @kbd{C-x 1} binding.
22855 Use a TUI layout with at least two windows. When the current
22856 layout already has two windows, the next layout with two windows is used.
22857 When a new layout is chosen, one window will always be common to the
22858 previous layout and the new one.
22860 Think of it as the Emacs @kbd{C-x 2} binding.
22864 Change the active window. The TUI associates several key bindings
22865 (like scrolling and arrow keys) with the active window. This command
22866 gives the focus to the next TUI window.
22868 Think of it as the Emacs @kbd{C-x o} binding.
22872 Switch in and out of the TUI SingleKey mode that binds single
22873 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
22876 The following key bindings only work in the TUI mode:
22881 Scroll the active window one page up.
22885 Scroll the active window one page down.
22889 Scroll the active window one line up.
22893 Scroll the active window one line down.
22897 Scroll the active window one column left.
22901 Scroll the active window one column right.
22905 Refresh the screen.
22908 Because the arrow keys scroll the active window in the TUI mode, they
22909 are not available for their normal use by readline unless the command
22910 window has the focus. When another window is active, you must use
22911 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
22912 and @kbd{C-f} to control the command window.
22914 @node TUI Single Key Mode
22915 @section TUI Single Key Mode
22916 @cindex TUI single key mode
22918 The TUI also provides a @dfn{SingleKey} mode, which binds several
22919 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
22920 switch into this mode, where the following key bindings are used:
22923 @kindex c @r{(SingleKey TUI key)}
22927 @kindex d @r{(SingleKey TUI key)}
22931 @kindex f @r{(SingleKey TUI key)}
22935 @kindex n @r{(SingleKey TUI key)}
22939 @kindex q @r{(SingleKey TUI key)}
22941 exit the SingleKey mode.
22943 @kindex r @r{(SingleKey TUI key)}
22947 @kindex s @r{(SingleKey TUI key)}
22951 @kindex u @r{(SingleKey TUI key)}
22955 @kindex v @r{(SingleKey TUI key)}
22959 @kindex w @r{(SingleKey TUI key)}
22964 Other keys temporarily switch to the @value{GDBN} command prompt.
22965 The key that was pressed is inserted in the editing buffer so that
22966 it is possible to type most @value{GDBN} commands without interaction
22967 with the TUI SingleKey mode. Once the command is entered the TUI
22968 SingleKey mode is restored. The only way to permanently leave
22969 this mode is by typing @kbd{q} or @kbd{C-x s}.
22973 @section TUI-specific Commands
22974 @cindex TUI commands
22976 The TUI has specific commands to control the text windows.
22977 These commands are always available, even when @value{GDBN} is not in
22978 the TUI mode. When @value{GDBN} is in the standard mode, most
22979 of these commands will automatically switch to the TUI mode.
22981 Note that if @value{GDBN}'s @code{stdout} is not connected to a
22982 terminal, or @value{GDBN} has been started with the machine interface
22983 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
22984 these commands will fail with an error, because it would not be
22985 possible or desirable to enable curses window management.
22990 List and give the size of all displayed windows.
22994 Display the next layout.
22997 Display the previous layout.
23000 Display the source window only.
23003 Display the assembly window only.
23006 Display the source and assembly window.
23009 Display the register window together with the source or assembly window.
23013 Make the next window active for scrolling.
23016 Make the previous window active for scrolling.
23019 Make the source window active for scrolling.
23022 Make the assembly window active for scrolling.
23025 Make the register window active for scrolling.
23028 Make the command window active for scrolling.
23032 Refresh the screen. This is similar to typing @kbd{C-L}.
23034 @item tui reg float
23036 Show the floating point registers in the register window.
23038 @item tui reg general
23039 Show the general registers in the register window.
23042 Show the next register group. The list of register groups as well as
23043 their order is target specific. The predefined register groups are the
23044 following: @code{general}, @code{float}, @code{system}, @code{vector},
23045 @code{all}, @code{save}, @code{restore}.
23047 @item tui reg system
23048 Show the system registers in the register window.
23052 Update the source window and the current execution point.
23054 @item winheight @var{name} +@var{count}
23055 @itemx winheight @var{name} -@var{count}
23057 Change the height of the window @var{name} by @var{count}
23058 lines. Positive counts increase the height, while negative counts
23061 @item tabset @var{nchars}
23063 Set the width of tab stops to be @var{nchars} characters.
23066 @node TUI Configuration
23067 @section TUI Configuration Variables
23068 @cindex TUI configuration variables
23070 Several configuration variables control the appearance of TUI windows.
23073 @item set tui border-kind @var{kind}
23074 @kindex set tui border-kind
23075 Select the border appearance for the source, assembly and register windows.
23076 The possible values are the following:
23079 Use a space character to draw the border.
23082 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
23085 Use the Alternate Character Set to draw the border. The border is
23086 drawn using character line graphics if the terminal supports them.
23089 @item set tui border-mode @var{mode}
23090 @kindex set tui border-mode
23091 @itemx set tui active-border-mode @var{mode}
23092 @kindex set tui active-border-mode
23093 Select the display attributes for the borders of the inactive windows
23094 or the active window. The @var{mode} can be one of the following:
23097 Use normal attributes to display the border.
23103 Use reverse video mode.
23106 Use half bright mode.
23108 @item half-standout
23109 Use half bright and standout mode.
23112 Use extra bright or bold mode.
23114 @item bold-standout
23115 Use extra bright or bold and standout mode.
23120 @chapter Using @value{GDBN} under @sc{gnu} Emacs
23123 @cindex @sc{gnu} Emacs
23124 A special interface allows you to use @sc{gnu} Emacs to view (and
23125 edit) the source files for the program you are debugging with
23128 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
23129 executable file you want to debug as an argument. This command starts
23130 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
23131 created Emacs buffer.
23132 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
23134 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
23139 All ``terminal'' input and output goes through an Emacs buffer, called
23142 This applies both to @value{GDBN} commands and their output, and to the input
23143 and output done by the program you are debugging.
23145 This is useful because it means that you can copy the text of previous
23146 commands and input them again; you can even use parts of the output
23149 All the facilities of Emacs' Shell mode are available for interacting
23150 with your program. In particular, you can send signals the usual
23151 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
23155 @value{GDBN} displays source code through Emacs.
23157 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
23158 source file for that frame and puts an arrow (@samp{=>}) at the
23159 left margin of the current line. Emacs uses a separate buffer for
23160 source display, and splits the screen to show both your @value{GDBN} session
23163 Explicit @value{GDBN} @code{list} or search commands still produce output as
23164 usual, but you probably have no reason to use them from Emacs.
23167 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
23168 a graphical mode, enabled by default, which provides further buffers
23169 that can control the execution and describe the state of your program.
23170 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
23172 If you specify an absolute file name when prompted for the @kbd{M-x
23173 gdb} argument, then Emacs sets your current working directory to where
23174 your program resides. If you only specify the file name, then Emacs
23175 sets your current working directory to to the directory associated
23176 with the previous buffer. In this case, @value{GDBN} may find your
23177 program by searching your environment's @code{PATH} variable, but on
23178 some operating systems it might not find the source. So, although the
23179 @value{GDBN} input and output session proceeds normally, the auxiliary
23180 buffer does not display the current source and line of execution.
23182 The initial working directory of @value{GDBN} is printed on the top
23183 line of the GUD buffer and this serves as a default for the commands
23184 that specify files for @value{GDBN} to operate on. @xref{Files,
23185 ,Commands to Specify Files}.
23187 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
23188 need to call @value{GDBN} by a different name (for example, if you
23189 keep several configurations around, with different names) you can
23190 customize the Emacs variable @code{gud-gdb-command-name} to run the
23193 In the GUD buffer, you can use these special Emacs commands in
23194 addition to the standard Shell mode commands:
23198 Describe the features of Emacs' GUD Mode.
23201 Execute to another source line, like the @value{GDBN} @code{step} command; also
23202 update the display window to show the current file and location.
23205 Execute to next source line in this function, skipping all function
23206 calls, like the @value{GDBN} @code{next} command. Then update the display window
23207 to show the current file and location.
23210 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
23211 display window accordingly.
23214 Execute until exit from the selected stack frame, like the @value{GDBN}
23215 @code{finish} command.
23218 Continue execution of your program, like the @value{GDBN} @code{continue}
23222 Go up the number of frames indicated by the numeric argument
23223 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
23224 like the @value{GDBN} @code{up} command.
23227 Go down the number of frames indicated by the numeric argument, like the
23228 @value{GDBN} @code{down} command.
23231 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
23232 tells @value{GDBN} to set a breakpoint on the source line point is on.
23234 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
23235 separate frame which shows a backtrace when the GUD buffer is current.
23236 Move point to any frame in the stack and type @key{RET} to make it
23237 become the current frame and display the associated source in the
23238 source buffer. Alternatively, click @kbd{Mouse-2} to make the
23239 selected frame become the current one. In graphical mode, the
23240 speedbar displays watch expressions.
23242 If you accidentally delete the source-display buffer, an easy way to get
23243 it back is to type the command @code{f} in the @value{GDBN} buffer, to
23244 request a frame display; when you run under Emacs, this recreates
23245 the source buffer if necessary to show you the context of the current
23248 The source files displayed in Emacs are in ordinary Emacs buffers
23249 which are visiting the source files in the usual way. You can edit
23250 the files with these buffers if you wish; but keep in mind that @value{GDBN}
23251 communicates with Emacs in terms of line numbers. If you add or
23252 delete lines from the text, the line numbers that @value{GDBN} knows cease
23253 to correspond properly with the code.
23255 A more detailed description of Emacs' interaction with @value{GDBN} is
23256 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
23259 @c The following dropped because Epoch is nonstandard. Reactivate
23260 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
23262 @kindex Emacs Epoch environment
23266 Version 18 of @sc{gnu} Emacs has a built-in window system
23267 called the @code{epoch}
23268 environment. Users of this environment can use a new command,
23269 @code{inspect} which performs identically to @code{print} except that
23270 each value is printed in its own window.
23275 @chapter The @sc{gdb/mi} Interface
23277 @unnumberedsec Function and Purpose
23279 @cindex @sc{gdb/mi}, its purpose
23280 @sc{gdb/mi} is a line based machine oriented text interface to
23281 @value{GDBN} and is activated by specifying using the
23282 @option{--interpreter} command line option (@pxref{Mode Options}). It
23283 is specifically intended to support the development of systems which
23284 use the debugger as just one small component of a larger system.
23286 This chapter is a specification of the @sc{gdb/mi} interface. It is written
23287 in the form of a reference manual.
23289 Note that @sc{gdb/mi} is still under construction, so some of the
23290 features described below are incomplete and subject to change
23291 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
23293 @unnumberedsec Notation and Terminology
23295 @cindex notational conventions, for @sc{gdb/mi}
23296 This chapter uses the following notation:
23300 @code{|} separates two alternatives.
23303 @code{[ @var{something} ]} indicates that @var{something} is optional:
23304 it may or may not be given.
23307 @code{( @var{group} )*} means that @var{group} inside the parentheses
23308 may repeat zero or more times.
23311 @code{( @var{group} )+} means that @var{group} inside the parentheses
23312 may repeat one or more times.
23315 @code{"@var{string}"} means a literal @var{string}.
23319 @heading Dependencies
23323 * GDB/MI General Design::
23324 * GDB/MI Command Syntax::
23325 * GDB/MI Compatibility with CLI::
23326 * GDB/MI Development and Front Ends::
23327 * GDB/MI Output Records::
23328 * GDB/MI Simple Examples::
23329 * GDB/MI Command Description Format::
23330 * GDB/MI Breakpoint Commands::
23331 * GDB/MI Program Context::
23332 * GDB/MI Thread Commands::
23333 * GDB/MI Program Execution::
23334 * GDB/MI Stack Manipulation::
23335 * GDB/MI Variable Objects::
23336 * GDB/MI Data Manipulation::
23337 * GDB/MI Tracepoint Commands::
23338 * GDB/MI Symbol Query::
23339 * GDB/MI File Commands::
23341 * GDB/MI Kod Commands::
23342 * GDB/MI Memory Overlay Commands::
23343 * GDB/MI Signal Handling Commands::
23345 * GDB/MI Target Manipulation::
23346 * GDB/MI File Transfer Commands::
23347 * GDB/MI Miscellaneous Commands::
23350 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23351 @node GDB/MI General Design
23352 @section @sc{gdb/mi} General Design
23353 @cindex GDB/MI General Design
23355 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
23356 parts---commands sent to @value{GDBN}, responses to those commands
23357 and notifications. Each command results in exactly one response,
23358 indicating either successful completion of the command, or an error.
23359 For the commands that do not resume the target, the response contains the
23360 requested information. For the commands that resume the target, the
23361 response only indicates whether the target was successfully resumed.
23362 Notifications is the mechanism for reporting changes in the state of the
23363 target, or in @value{GDBN} state, that cannot conveniently be associated with
23364 a command and reported as part of that command response.
23366 The important examples of notifications are:
23370 Exec notifications. These are used to report changes in
23371 target state---when a target is resumed, or stopped. It would not
23372 be feasible to include this information in response of resuming
23373 commands, because one resume commands can result in multiple events in
23374 different threads. Also, quite some time may pass before any event
23375 happens in the target, while a frontend needs to know whether the resuming
23376 command itself was successfully executed.
23379 Console output, and status notifications. Console output
23380 notifications are used to report output of CLI commands, as well as
23381 diagnostics for other commands. Status notifications are used to
23382 report the progress of a long-running operation. Naturally, including
23383 this information in command response would mean no output is produced
23384 until the command is finished, which is undesirable.
23387 General notifications. Commands may have various side effects on
23388 the @value{GDBN} or target state beyond their official purpose. For example,
23389 a command may change the selected thread. Although such changes can
23390 be included in command response, using notification allows for more
23391 orthogonal frontend design.
23395 There's no guarantee that whenever an MI command reports an error,
23396 @value{GDBN} or the target are in any specific state, and especially,
23397 the state is not reverted to the state before the MI command was
23398 processed. Therefore, whenever an MI command results in an error,
23399 we recommend that the frontend refreshes all the information shown in
23400 the user interface.
23404 * Context management::
23405 * Asynchronous and non-stop modes::
23409 @node Context management
23410 @subsection Context management
23412 In most cases when @value{GDBN} accesses the target, this access is
23413 done in context of a specific thread and frame (@pxref{Frames}).
23414 Often, even when accessing global data, the target requires that a thread
23415 be specified. The CLI interface maintains the selected thread and frame,
23416 and supplies them to target on each command. This is convenient,
23417 because a command line user would not want to specify that information
23418 explicitly on each command, and because user interacts with
23419 @value{GDBN} via a single terminal, so no confusion is possible as
23420 to what thread and frame are the current ones.
23422 In the case of MI, the concept of selected thread and frame is less
23423 useful. First, a frontend can easily remember this information
23424 itself. Second, a graphical frontend can have more than one window,
23425 each one used for debugging a different thread, and the frontend might
23426 want to access additional threads for internal purposes. This
23427 increases the risk that by relying on implicitly selected thread, the
23428 frontend may be operating on a wrong one. Therefore, each MI command
23429 should explicitly specify which thread and frame to operate on. To
23430 make it possible, each MI command accepts the @samp{--thread} and
23431 @samp{--frame} options, the value to each is @value{GDBN} identifier
23432 for thread and frame to operate on.
23434 Usually, each top-level window in a frontend allows the user to select
23435 a thread and a frame, and remembers the user selection for further
23436 operations. However, in some cases @value{GDBN} may suggest that the
23437 current thread be changed. For example, when stopping on a breakpoint
23438 it is reasonable to switch to the thread where breakpoint is hit. For
23439 another example, if the user issues the CLI @samp{thread} command via
23440 the frontend, it is desirable to change the frontend's selected thread to the
23441 one specified by user. @value{GDBN} communicates the suggestion to
23442 change current thread using the @samp{=thread-selected} notification.
23443 No such notification is available for the selected frame at the moment.
23445 Note that historically, MI shares the selected thread with CLI, so
23446 frontends used the @code{-thread-select} to execute commands in the
23447 right context. However, getting this to work right is cumbersome. The
23448 simplest way is for frontend to emit @code{-thread-select} command
23449 before every command. This doubles the number of commands that need
23450 to be sent. The alternative approach is to suppress @code{-thread-select}
23451 if the selected thread in @value{GDBN} is supposed to be identical to the
23452 thread the frontend wants to operate on. However, getting this
23453 optimization right can be tricky. In particular, if the frontend
23454 sends several commands to @value{GDBN}, and one of the commands changes the
23455 selected thread, then the behaviour of subsequent commands will
23456 change. So, a frontend should either wait for response from such
23457 problematic commands, or explicitly add @code{-thread-select} for
23458 all subsequent commands. No frontend is known to do this exactly
23459 right, so it is suggested to just always pass the @samp{--thread} and
23460 @samp{--frame} options.
23462 @node Asynchronous and non-stop modes
23463 @subsection Asynchronous command execution and non-stop mode
23465 On some targets, @value{GDBN} is capable of processing MI commands
23466 even while the target is running. This is called @dfn{asynchronous
23467 command execution} (@pxref{Background Execution}). The frontend may
23468 specify a preferrence for asynchronous execution using the
23469 @code{-gdb-set target-async 1} command, which should be emitted before
23470 either running the executable or attaching to the target. After the
23471 frontend has started the executable or attached to the target, it can
23472 find if asynchronous execution is enabled using the
23473 @code{-list-target-features} command.
23475 Even if @value{GDBN} can accept a command while target is running,
23476 many commands that access the target do not work when the target is
23477 running. Therefore, asynchronous command execution is most useful
23478 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
23479 it is possible to examine the state of one thread, while other threads
23482 When a given thread is running, MI commands that try to access the
23483 target in the context of that thread may not work, or may work only on
23484 some targets. In particular, commands that try to operate on thread's
23485 stack will not work, on any target. Commands that read memory, or
23486 modify breakpoints, may work or not work, depending on the target. Note
23487 that even commands that operate on global state, such as @code{print},
23488 @code{set}, and breakpoint commands, still access the target in the
23489 context of a specific thread, so frontend should try to find a
23490 stopped thread and perform the operation on that thread (using the
23491 @samp{--thread} option).
23493 Which commands will work in the context of a running thread is
23494 highly target dependent. However, the two commands
23495 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
23496 to find the state of a thread, will always work.
23498 @node Thread groups
23499 @subsection Thread groups
23500 @value{GDBN} may be used to debug several processes at the same time.
23501 On some platfroms, @value{GDBN} may support debugging of several
23502 hardware systems, each one having several cores with several different
23503 processes running on each core. This section describes the MI
23504 mechanism to support such debugging scenarios.
23506 The key observation is that regardless of the structure of the
23507 target, MI can have a global list of threads, because most commands that
23508 accept the @samp{--thread} option do not need to know what process that
23509 thread belongs to. Therefore, it is not necessary to introduce
23510 neither additional @samp{--process} option, nor an notion of the
23511 current process in the MI interface. The only strictly new feature
23512 that is required is the ability to find how the threads are grouped
23515 To allow the user to discover such grouping, and to support arbitrary
23516 hierarchy of machines/cores/processes, MI introduces the concept of a
23517 @dfn{thread group}. Thread group is a collection of threads and other
23518 thread groups. A thread group always has a string identifier, a type,
23519 and may have additional attributes specific to the type. A new
23520 command, @code{-list-thread-groups}, returns the list of top-level
23521 thread groups, which correspond to processes that @value{GDBN} is
23522 debugging at the moment. By passing an identifier of a thread group
23523 to the @code{-list-thread-groups} command, it is possible to obtain
23524 the members of specific thread group.
23526 To allow the user to easily discover processes, and other objects, he
23527 wishes to debug, a concept of @dfn{available thread group} is
23528 introduced. Available thread group is an thread group that
23529 @value{GDBN} is not debugging, but that can be attached to, using the
23530 @code{-target-attach} command. The list of available top-level thread
23531 groups can be obtained using @samp{-list-thread-groups --available}.
23532 In general, the content of a thread group may be only retrieved only
23533 after attaching to that thread group.
23535 Thread groups are related to inferiors (@pxref{Inferiors and
23536 Programs}). Each inferior corresponds to a thread group of a special
23537 type @samp{process}, and some additional operations are permitted on
23538 such thread groups.
23540 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23541 @node GDB/MI Command Syntax
23542 @section @sc{gdb/mi} Command Syntax
23545 * GDB/MI Input Syntax::
23546 * GDB/MI Output Syntax::
23549 @node GDB/MI Input Syntax
23550 @subsection @sc{gdb/mi} Input Syntax
23552 @cindex input syntax for @sc{gdb/mi}
23553 @cindex @sc{gdb/mi}, input syntax
23555 @item @var{command} @expansion{}
23556 @code{@var{cli-command} | @var{mi-command}}
23558 @item @var{cli-command} @expansion{}
23559 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
23560 @var{cli-command} is any existing @value{GDBN} CLI command.
23562 @item @var{mi-command} @expansion{}
23563 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
23564 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
23566 @item @var{token} @expansion{}
23567 "any sequence of digits"
23569 @item @var{option} @expansion{}
23570 @code{"-" @var{parameter} [ " " @var{parameter} ]}
23572 @item @var{parameter} @expansion{}
23573 @code{@var{non-blank-sequence} | @var{c-string}}
23575 @item @var{operation} @expansion{}
23576 @emph{any of the operations described in this chapter}
23578 @item @var{non-blank-sequence} @expansion{}
23579 @emph{anything, provided it doesn't contain special characters such as
23580 "-", @var{nl}, """ and of course " "}
23582 @item @var{c-string} @expansion{}
23583 @code{""" @var{seven-bit-iso-c-string-content} """}
23585 @item @var{nl} @expansion{}
23594 The CLI commands are still handled by the @sc{mi} interpreter; their
23595 output is described below.
23598 The @code{@var{token}}, when present, is passed back when the command
23602 Some @sc{mi} commands accept optional arguments as part of the parameter
23603 list. Each option is identified by a leading @samp{-} (dash) and may be
23604 followed by an optional argument parameter. Options occur first in the
23605 parameter list and can be delimited from normal parameters using
23606 @samp{--} (this is useful when some parameters begin with a dash).
23613 We want easy access to the existing CLI syntax (for debugging).
23616 We want it to be easy to spot a @sc{mi} operation.
23619 @node GDB/MI Output Syntax
23620 @subsection @sc{gdb/mi} Output Syntax
23622 @cindex output syntax of @sc{gdb/mi}
23623 @cindex @sc{gdb/mi}, output syntax
23624 The output from @sc{gdb/mi} consists of zero or more out-of-band records
23625 followed, optionally, by a single result record. This result record
23626 is for the most recent command. The sequence of output records is
23627 terminated by @samp{(gdb)}.
23629 If an input command was prefixed with a @code{@var{token}} then the
23630 corresponding output for that command will also be prefixed by that same
23634 @item @var{output} @expansion{}
23635 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
23637 @item @var{result-record} @expansion{}
23638 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
23640 @item @var{out-of-band-record} @expansion{}
23641 @code{@var{async-record} | @var{stream-record}}
23643 @item @var{async-record} @expansion{}
23644 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
23646 @item @var{exec-async-output} @expansion{}
23647 @code{[ @var{token} ] "*" @var{async-output}}
23649 @item @var{status-async-output} @expansion{}
23650 @code{[ @var{token} ] "+" @var{async-output}}
23652 @item @var{notify-async-output} @expansion{}
23653 @code{[ @var{token} ] "=" @var{async-output}}
23655 @item @var{async-output} @expansion{}
23656 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
23658 @item @var{result-class} @expansion{}
23659 @code{"done" | "running" | "connected" | "error" | "exit"}
23661 @item @var{async-class} @expansion{}
23662 @code{"stopped" | @var{others}} (where @var{others} will be added
23663 depending on the needs---this is still in development).
23665 @item @var{result} @expansion{}
23666 @code{ @var{variable} "=" @var{value}}
23668 @item @var{variable} @expansion{}
23669 @code{ @var{string} }
23671 @item @var{value} @expansion{}
23672 @code{ @var{const} | @var{tuple} | @var{list} }
23674 @item @var{const} @expansion{}
23675 @code{@var{c-string}}
23677 @item @var{tuple} @expansion{}
23678 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
23680 @item @var{list} @expansion{}
23681 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
23682 @var{result} ( "," @var{result} )* "]" }
23684 @item @var{stream-record} @expansion{}
23685 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
23687 @item @var{console-stream-output} @expansion{}
23688 @code{"~" @var{c-string}}
23690 @item @var{target-stream-output} @expansion{}
23691 @code{"@@" @var{c-string}}
23693 @item @var{log-stream-output} @expansion{}
23694 @code{"&" @var{c-string}}
23696 @item @var{nl} @expansion{}
23699 @item @var{token} @expansion{}
23700 @emph{any sequence of digits}.
23708 All output sequences end in a single line containing a period.
23711 The @code{@var{token}} is from the corresponding request. Note that
23712 for all async output, while the token is allowed by the grammar and
23713 may be output by future versions of @value{GDBN} for select async
23714 output messages, it is generally omitted. Frontends should treat
23715 all async output as reporting general changes in the state of the
23716 target and there should be no need to associate async output to any
23720 @cindex status output in @sc{gdb/mi}
23721 @var{status-async-output} contains on-going status information about the
23722 progress of a slow operation. It can be discarded. All status output is
23723 prefixed by @samp{+}.
23726 @cindex async output in @sc{gdb/mi}
23727 @var{exec-async-output} contains asynchronous state change on the target
23728 (stopped, started, disappeared). All async output is prefixed by
23732 @cindex notify output in @sc{gdb/mi}
23733 @var{notify-async-output} contains supplementary information that the
23734 client should handle (e.g., a new breakpoint information). All notify
23735 output is prefixed by @samp{=}.
23738 @cindex console output in @sc{gdb/mi}
23739 @var{console-stream-output} is output that should be displayed as is in the
23740 console. It is the textual response to a CLI command. All the console
23741 output is prefixed by @samp{~}.
23744 @cindex target output in @sc{gdb/mi}
23745 @var{target-stream-output} is the output produced by the target program.
23746 All the target output is prefixed by @samp{@@}.
23749 @cindex log output in @sc{gdb/mi}
23750 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
23751 instance messages that should be displayed as part of an error log. All
23752 the log output is prefixed by @samp{&}.
23755 @cindex list output in @sc{gdb/mi}
23756 New @sc{gdb/mi} commands should only output @var{lists} containing
23762 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
23763 details about the various output records.
23765 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23766 @node GDB/MI Compatibility with CLI
23767 @section @sc{gdb/mi} Compatibility with CLI
23769 @cindex compatibility, @sc{gdb/mi} and CLI
23770 @cindex @sc{gdb/mi}, compatibility with CLI
23772 For the developers convenience CLI commands can be entered directly,
23773 but there may be some unexpected behaviour. For example, commands
23774 that query the user will behave as if the user replied yes, breakpoint
23775 command lists are not executed and some CLI commands, such as
23776 @code{if}, @code{when} and @code{define}, prompt for further input with
23777 @samp{>}, which is not valid MI output.
23779 This feature may be removed at some stage in the future and it is
23780 recommended that front ends use the @code{-interpreter-exec} command
23781 (@pxref{-interpreter-exec}).
23783 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23784 @node GDB/MI Development and Front Ends
23785 @section @sc{gdb/mi} Development and Front Ends
23786 @cindex @sc{gdb/mi} development
23788 The application which takes the MI output and presents the state of the
23789 program being debugged to the user is called a @dfn{front end}.
23791 Although @sc{gdb/mi} is still incomplete, it is currently being used
23792 by a variety of front ends to @value{GDBN}. This makes it difficult
23793 to introduce new functionality without breaking existing usage. This
23794 section tries to minimize the problems by describing how the protocol
23797 Some changes in MI need not break a carefully designed front end, and
23798 for these the MI version will remain unchanged. The following is a
23799 list of changes that may occur within one level, so front ends should
23800 parse MI output in a way that can handle them:
23804 New MI commands may be added.
23807 New fields may be added to the output of any MI command.
23810 The range of values for fields with specified values, e.g.,
23811 @code{in_scope} (@pxref{-var-update}) may be extended.
23813 @c The format of field's content e.g type prefix, may change so parse it
23814 @c at your own risk. Yes, in general?
23816 @c The order of fields may change? Shouldn't really matter but it might
23817 @c resolve inconsistencies.
23820 If the changes are likely to break front ends, the MI version level
23821 will be increased by one. This will allow the front end to parse the
23822 output according to the MI version. Apart from mi0, new versions of
23823 @value{GDBN} will not support old versions of MI and it will be the
23824 responsibility of the front end to work with the new one.
23826 @c Starting with mi3, add a new command -mi-version that prints the MI
23829 The best way to avoid unexpected changes in MI that might break your front
23830 end is to make your project known to @value{GDBN} developers and
23831 follow development on @email{gdb@@sourceware.org} and
23832 @email{gdb-patches@@sourceware.org}.
23833 @cindex mailing lists
23835 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
23836 @node GDB/MI Output Records
23837 @section @sc{gdb/mi} Output Records
23840 * GDB/MI Result Records::
23841 * GDB/MI Stream Records::
23842 * GDB/MI Async Records::
23843 * GDB/MI Frame Information::
23844 * GDB/MI Thread Information::
23847 @node GDB/MI Result Records
23848 @subsection @sc{gdb/mi} Result Records
23850 @cindex result records in @sc{gdb/mi}
23851 @cindex @sc{gdb/mi}, result records
23852 In addition to a number of out-of-band notifications, the response to a
23853 @sc{gdb/mi} command includes one of the following result indications:
23857 @item "^done" [ "," @var{results} ]
23858 The synchronous operation was successful, @code{@var{results}} are the return
23863 This result record is equivalent to @samp{^done}. Historically, it
23864 was output instead of @samp{^done} if the command has resumed the
23865 target. This behaviour is maintained for backward compatibility, but
23866 all frontends should treat @samp{^done} and @samp{^running}
23867 identically and rely on the @samp{*running} output record to determine
23868 which threads are resumed.
23872 @value{GDBN} has connected to a remote target.
23874 @item "^error" "," @var{c-string}
23876 The operation failed. The @code{@var{c-string}} contains the corresponding
23881 @value{GDBN} has terminated.
23885 @node GDB/MI Stream Records
23886 @subsection @sc{gdb/mi} Stream Records
23888 @cindex @sc{gdb/mi}, stream records
23889 @cindex stream records in @sc{gdb/mi}
23890 @value{GDBN} internally maintains a number of output streams: the console, the
23891 target, and the log. The output intended for each of these streams is
23892 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
23894 Each stream record begins with a unique @dfn{prefix character} which
23895 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
23896 Syntax}). In addition to the prefix, each stream record contains a
23897 @code{@var{string-output}}. This is either raw text (with an implicit new
23898 line) or a quoted C string (which does not contain an implicit newline).
23901 @item "~" @var{string-output}
23902 The console output stream contains text that should be displayed in the
23903 CLI console window. It contains the textual responses to CLI commands.
23905 @item "@@" @var{string-output}
23906 The target output stream contains any textual output from the running
23907 target. This is only present when GDB's event loop is truly
23908 asynchronous, which is currently only the case for remote targets.
23910 @item "&" @var{string-output}
23911 The log stream contains debugging messages being produced by @value{GDBN}'s
23915 @node GDB/MI Async Records
23916 @subsection @sc{gdb/mi} Async Records
23918 @cindex async records in @sc{gdb/mi}
23919 @cindex @sc{gdb/mi}, async records
23920 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
23921 additional changes that have occurred. Those changes can either be a
23922 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
23923 target activity (e.g., target stopped).
23925 The following is the list of possible async records:
23929 @item *running,thread-id="@var{thread}"
23930 The target is now running. The @var{thread} field tells which
23931 specific thread is now running, and can be @samp{all} if all threads
23932 are running. The frontend should assume that no interaction with a
23933 running thread is possible after this notification is produced.
23934 The frontend should not assume that this notification is output
23935 only once for any command. @value{GDBN} may emit this notification
23936 several times, either for different threads, because it cannot resume
23937 all threads together, or even for a single thread, if the thread must
23938 be stepped though some code before letting it run freely.
23940 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
23941 The target has stopped. The @var{reason} field can have one of the
23945 @item breakpoint-hit
23946 A breakpoint was reached.
23947 @item watchpoint-trigger
23948 A watchpoint was triggered.
23949 @item read-watchpoint-trigger
23950 A read watchpoint was triggered.
23951 @item access-watchpoint-trigger
23952 An access watchpoint was triggered.
23953 @item function-finished
23954 An -exec-finish or similar CLI command was accomplished.
23955 @item location-reached
23956 An -exec-until or similar CLI command was accomplished.
23957 @item watchpoint-scope
23958 A watchpoint has gone out of scope.
23959 @item end-stepping-range
23960 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
23961 similar CLI command was accomplished.
23962 @item exited-signalled
23963 The inferior exited because of a signal.
23965 The inferior exited.
23966 @item exited-normally
23967 The inferior exited normally.
23968 @item signal-received
23969 A signal was received by the inferior.
23972 The @var{id} field identifies the thread that directly caused the stop
23973 -- for example by hitting a breakpoint. Depending on whether all-stop
23974 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
23975 stop all threads, or only the thread that directly triggered the stop.
23976 If all threads are stopped, the @var{stopped} field will have the
23977 value of @code{"all"}. Otherwise, the value of the @var{stopped}
23978 field will be a list of thread identifiers. Presently, this list will
23979 always include a single thread, but frontend should be prepared to see
23980 several threads in the list. The @var{core} field reports the
23981 processor core on which the stop event has happened. This field may be absent
23982 if such information is not available.
23984 @item =thread-group-added,id="@var{id}"
23985 @itemx =thread-group-removed,id="@var{id}"
23986 A thread group was either added or removed. The @var{id} field
23987 contains the @value{GDBN} identifier of the thread group. When a thread
23988 group is added, it generally might not be associated with a running
23989 process. When a thread group is removed, its id becomes invalid and
23990 cannot be used in any way.
23992 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
23993 A thread group became associated with a running program,
23994 either because the program was just started or the thread group
23995 was attached to a program. The @var{id} field contains the
23996 @value{GDBN} identifier of the thread group. The @var{pid} field
23997 contains process identifier, specific to the operating system.
23999 @itemx =thread-group-exited,id="@var{id}"
24000 A thread group is no longer associated with a running program,
24001 either because the program has exited, or because it was detached
24002 from. The @var{id} field contains the @value{GDBN} identifier of the
24005 @item =thread-created,id="@var{id}",group-id="@var{gid}"
24006 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
24007 A thread either was created, or has exited. The @var{id} field
24008 contains the @value{GDBN} identifier of the thread. The @var{gid}
24009 field identifies the thread group this thread belongs to.
24011 @item =thread-selected,id="@var{id}"
24012 Informs that the selected thread was changed as result of the last
24013 command. This notification is not emitted as result of @code{-thread-select}
24014 command but is emitted whenever an MI command that is not documented
24015 to change the selected thread actually changes it. In particular,
24016 invoking, directly or indirectly (via user-defined command), the CLI
24017 @code{thread} command, will generate this notification.
24019 We suggest that in response to this notification, front ends
24020 highlight the selected thread and cause subsequent commands to apply to
24023 @item =library-loaded,...
24024 Reports that a new library file was loaded by the program. This
24025 notification has 4 fields---@var{id}, @var{target-name},
24026 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
24027 opaque identifier of the library. For remote debugging case,
24028 @var{target-name} and @var{host-name} fields give the name of the
24029 library file on the target, and on the host respectively. For native
24030 debugging, both those fields have the same value. The
24031 @var{symbols-loaded} field reports if the debug symbols for this
24032 library are loaded. The @var{thread-group} field, if present,
24033 specifies the id of the thread group in whose context the library was loaded.
24034 If the field is absent, it means the library was loaded in the context
24035 of all present thread groups.
24037 @item =library-unloaded,...
24038 Reports that a library was unloaded by the program. This notification
24039 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
24040 the same meaning as for the @code{=library-loaded} notification.
24041 The @var{thread-group} field, if present, specifies the id of the
24042 thread group in whose context the library was unloaded. If the field is
24043 absent, it means the library was unloaded in the context of all present
24048 @node GDB/MI Frame Information
24049 @subsection @sc{gdb/mi} Frame Information
24051 Response from many MI commands includes an information about stack
24052 frame. This information is a tuple that may have the following
24057 The level of the stack frame. The innermost frame has the level of
24058 zero. This field is always present.
24061 The name of the function corresponding to the frame. This field may
24062 be absent if @value{GDBN} is unable to determine the function name.
24065 The code address for the frame. This field is always present.
24068 The name of the source files that correspond to the frame's code
24069 address. This field may be absent.
24072 The source line corresponding to the frames' code address. This field
24076 The name of the binary file (either executable or shared library) the
24077 corresponds to the frame's code address. This field may be absent.
24081 @node GDB/MI Thread Information
24082 @subsection @sc{gdb/mi} Thread Information
24084 Whenever @value{GDBN} has to report an information about a thread, it
24085 uses a tuple with the following fields:
24089 The numeric id assigned to the thread by @value{GDBN}. This field is
24093 Target-specific string identifying the thread. This field is always present.
24096 Additional information about the thread provided by the target.
24097 It is supposed to be human-readable and not interpreted by the
24098 frontend. This field is optional.
24101 Either @samp{stopped} or @samp{running}, depending on whether the
24102 thread is presently running. This field is always present.
24105 The value of this field is an integer number of the processor core the
24106 thread was last seen on. This field is optional.
24110 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24111 @node GDB/MI Simple Examples
24112 @section Simple Examples of @sc{gdb/mi} Interaction
24113 @cindex @sc{gdb/mi}, simple examples
24115 This subsection presents several simple examples of interaction using
24116 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
24117 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
24118 the output received from @sc{gdb/mi}.
24120 Note the line breaks shown in the examples are here only for
24121 readability, they don't appear in the real output.
24123 @subheading Setting a Breakpoint
24125 Setting a breakpoint generates synchronous output which contains detailed
24126 information of the breakpoint.
24129 -> -break-insert main
24130 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
24131 enabled="y",addr="0x08048564",func="main",file="myprog.c",
24132 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
24136 @subheading Program Execution
24138 Program execution generates asynchronous records and MI gives the
24139 reason that execution stopped.
24145 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
24146 frame=@{addr="0x08048564",func="main",
24147 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
24148 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
24153 <- *stopped,reason="exited-normally"
24157 @subheading Quitting @value{GDBN}
24159 Quitting @value{GDBN} just prints the result class @samp{^exit}.
24167 Please note that @samp{^exit} is printed immediately, but it might
24168 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
24169 performs necessary cleanups, including killing programs being debugged
24170 or disconnecting from debug hardware, so the frontend should wait till
24171 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
24172 fails to exit in reasonable time.
24174 @subheading A Bad Command
24176 Here's what happens if you pass a non-existent command:
24180 <- ^error,msg="Undefined MI command: rubbish"
24185 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24186 @node GDB/MI Command Description Format
24187 @section @sc{gdb/mi} Command Description Format
24189 The remaining sections describe blocks of commands. Each block of
24190 commands is laid out in a fashion similar to this section.
24192 @subheading Motivation
24194 The motivation for this collection of commands.
24196 @subheading Introduction
24198 A brief introduction to this collection of commands as a whole.
24200 @subheading Commands
24202 For each command in the block, the following is described:
24204 @subsubheading Synopsis
24207 -command @var{args}@dots{}
24210 @subsubheading Result
24212 @subsubheading @value{GDBN} Command
24214 The corresponding @value{GDBN} CLI command(s), if any.
24216 @subsubheading Example
24218 Example(s) formatted for readability. Some of the described commands have
24219 not been implemented yet and these are labeled N.A.@: (not available).
24222 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24223 @node GDB/MI Breakpoint Commands
24224 @section @sc{gdb/mi} Breakpoint Commands
24226 @cindex breakpoint commands for @sc{gdb/mi}
24227 @cindex @sc{gdb/mi}, breakpoint commands
24228 This section documents @sc{gdb/mi} commands for manipulating
24231 @subheading The @code{-break-after} Command
24232 @findex -break-after
24234 @subsubheading Synopsis
24237 -break-after @var{number} @var{count}
24240 The breakpoint number @var{number} is not in effect until it has been
24241 hit @var{count} times. To see how this is reflected in the output of
24242 the @samp{-break-list} command, see the description of the
24243 @samp{-break-list} command below.
24245 @subsubheading @value{GDBN} Command
24247 The corresponding @value{GDBN} command is @samp{ignore}.
24249 @subsubheading Example
24254 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
24255 enabled="y",addr="0x000100d0",func="main",file="hello.c",
24256 fullname="/home/foo/hello.c",line="5",times="0"@}
24263 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24264 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24265 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24266 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24267 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24268 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24269 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24270 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24271 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
24272 line="5",times="0",ignore="3"@}]@}
24277 @subheading The @code{-break-catch} Command
24278 @findex -break-catch
24281 @subheading The @code{-break-commands} Command
24282 @findex -break-commands
24284 @subsubheading Synopsis
24287 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
24290 Specifies the CLI commands that should be executed when breakpoint
24291 @var{number} is hit. The parameters @var{command1} to @var{commandN}
24292 are the commands. If no command is specified, any previously-set
24293 commands are cleared. @xref{Break Commands}. Typical use of this
24294 functionality is tracing a program, that is, printing of values of
24295 some variables whenever breakpoint is hit and then continuing.
24297 @subsubheading @value{GDBN} Command
24299 The corresponding @value{GDBN} command is @samp{commands}.
24301 @subsubheading Example
24306 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
24307 enabled="y",addr="0x000100d0",func="main",file="hello.c",
24308 fullname="/home/foo/hello.c",line="5",times="0"@}
24310 -break-commands 1 "print v" "continue"
24315 @subheading The @code{-break-condition} Command
24316 @findex -break-condition
24318 @subsubheading Synopsis
24321 -break-condition @var{number} @var{expr}
24324 Breakpoint @var{number} will stop the program only if the condition in
24325 @var{expr} is true. The condition becomes part of the
24326 @samp{-break-list} output (see the description of the @samp{-break-list}
24329 @subsubheading @value{GDBN} Command
24331 The corresponding @value{GDBN} command is @samp{condition}.
24333 @subsubheading Example
24337 -break-condition 1 1
24341 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24342 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24343 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24344 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24345 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24346 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24347 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24348 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24349 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
24350 line="5",cond="1",times="0",ignore="3"@}]@}
24354 @subheading The @code{-break-delete} Command
24355 @findex -break-delete
24357 @subsubheading Synopsis
24360 -break-delete ( @var{breakpoint} )+
24363 Delete the breakpoint(s) whose number(s) are specified in the argument
24364 list. This is obviously reflected in the breakpoint list.
24366 @subsubheading @value{GDBN} Command
24368 The corresponding @value{GDBN} command is @samp{delete}.
24370 @subsubheading Example
24378 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
24379 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24380 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24381 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24382 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24383 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24384 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24389 @subheading The @code{-break-disable} Command
24390 @findex -break-disable
24392 @subsubheading Synopsis
24395 -break-disable ( @var{breakpoint} )+
24398 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
24399 break list is now set to @samp{n} for the named @var{breakpoint}(s).
24401 @subsubheading @value{GDBN} Command
24403 The corresponding @value{GDBN} command is @samp{disable}.
24405 @subsubheading Example
24413 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24414 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24415 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24416 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24417 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24418 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24419 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24420 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
24421 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
24422 line="5",times="0"@}]@}
24426 @subheading The @code{-break-enable} Command
24427 @findex -break-enable
24429 @subsubheading Synopsis
24432 -break-enable ( @var{breakpoint} )+
24435 Enable (previously disabled) @var{breakpoint}(s).
24437 @subsubheading @value{GDBN} Command
24439 The corresponding @value{GDBN} command is @samp{enable}.
24441 @subsubheading Example
24449 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24450 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24451 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24452 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24453 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24454 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24455 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24456 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
24457 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
24458 line="5",times="0"@}]@}
24462 @subheading The @code{-break-info} Command
24463 @findex -break-info
24465 @subsubheading Synopsis
24468 -break-info @var{breakpoint}
24472 Get information about a single breakpoint.
24474 @subsubheading @value{GDBN} Command
24476 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
24478 @subsubheading Example
24481 @subheading The @code{-break-insert} Command
24482 @findex -break-insert
24484 @subsubheading Synopsis
24487 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
24488 [ -c @var{condition} ] [ -i @var{ignore-count} ]
24489 [ -p @var{thread} ] [ @var{location} ]
24493 If specified, @var{location}, can be one of:
24500 @item filename:linenum
24501 @item filename:function
24505 The possible optional parameters of this command are:
24509 Insert a temporary breakpoint.
24511 Insert a hardware breakpoint.
24512 @item -c @var{condition}
24513 Make the breakpoint conditional on @var{condition}.
24514 @item -i @var{ignore-count}
24515 Initialize the @var{ignore-count}.
24517 If @var{location} cannot be parsed (for example if it
24518 refers to unknown files or functions), create a pending
24519 breakpoint. Without this flag, @value{GDBN} will report
24520 an error, and won't create a breakpoint, if @var{location}
24523 Create a disabled breakpoint.
24525 Create a tracepoint. @xref{Tracepoints}. When this parameter
24526 is used together with @samp{-h}, a fast tracepoint is created.
24529 @subsubheading Result
24531 The result is in the form:
24534 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
24535 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
24536 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
24537 times="@var{times}"@}
24541 where @var{number} is the @value{GDBN} number for this breakpoint,
24542 @var{funcname} is the name of the function where the breakpoint was
24543 inserted, @var{filename} is the name of the source file which contains
24544 this function, @var{lineno} is the source line number within that file
24545 and @var{times} the number of times that the breakpoint has been hit
24546 (always 0 for -break-insert but may be greater for -break-info or -break-list
24547 which use the same output).
24549 Note: this format is open to change.
24550 @c An out-of-band breakpoint instead of part of the result?
24552 @subsubheading @value{GDBN} Command
24554 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
24555 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
24557 @subsubheading Example
24562 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
24563 fullname="/home/foo/recursive2.c,line="4",times="0"@}
24565 -break-insert -t foo
24566 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
24567 fullname="/home/foo/recursive2.c,line="11",times="0"@}
24570 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
24571 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24572 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24573 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24574 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24575 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24576 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24577 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24578 addr="0x0001072c", func="main",file="recursive2.c",
24579 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
24580 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
24581 addr="0x00010774",func="foo",file="recursive2.c",
24582 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
24584 -break-insert -r foo.*
24585 ~int foo(int, int);
24586 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
24587 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
24591 @subheading The @code{-break-list} Command
24592 @findex -break-list
24594 @subsubheading Synopsis
24600 Displays the list of inserted breakpoints, showing the following fields:
24604 number of the breakpoint
24606 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
24608 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
24611 is the breakpoint enabled or no: @samp{y} or @samp{n}
24613 memory location at which the breakpoint is set
24615 logical location of the breakpoint, expressed by function name, file
24618 number of times the breakpoint has been hit
24621 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
24622 @code{body} field is an empty list.
24624 @subsubheading @value{GDBN} Command
24626 The corresponding @value{GDBN} command is @samp{info break}.
24628 @subsubheading Example
24633 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
24634 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24635 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24636 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24637 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24638 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24639 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24640 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24641 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
24642 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
24643 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
24644 line="13",times="0"@}]@}
24648 Here's an example of the result when there are no breakpoints:
24653 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
24654 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24655 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24656 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24657 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24658 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24659 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24664 @subheading The @code{-break-passcount} Command
24665 @findex -break-passcount
24667 @subsubheading Synopsis
24670 -break-passcount @var{tracepoint-number} @var{passcount}
24673 Set the passcount for tracepoint @var{tracepoint-number} to
24674 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
24675 is not a tracepoint, error is emitted. This corresponds to CLI
24676 command @samp{passcount}.
24678 @subheading The @code{-break-watch} Command
24679 @findex -break-watch
24681 @subsubheading Synopsis
24684 -break-watch [ -a | -r ]
24687 Create a watchpoint. With the @samp{-a} option it will create an
24688 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
24689 read from or on a write to the memory location. With the @samp{-r}
24690 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
24691 trigger only when the memory location is accessed for reading. Without
24692 either of the options, the watchpoint created is a regular watchpoint,
24693 i.e., it will trigger when the memory location is accessed for writing.
24694 @xref{Set Watchpoints, , Setting Watchpoints}.
24696 Note that @samp{-break-list} will report a single list of watchpoints and
24697 breakpoints inserted.
24699 @subsubheading @value{GDBN} Command
24701 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
24704 @subsubheading Example
24706 Setting a watchpoint on a variable in the @code{main} function:
24711 ^done,wpt=@{number="2",exp="x"@}
24716 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
24717 value=@{old="-268439212",new="55"@},
24718 frame=@{func="main",args=[],file="recursive2.c",
24719 fullname="/home/foo/bar/recursive2.c",line="5"@}
24723 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
24724 the program execution twice: first for the variable changing value, then
24725 for the watchpoint going out of scope.
24730 ^done,wpt=@{number="5",exp="C"@}
24735 *stopped,reason="watchpoint-trigger",
24736 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
24737 frame=@{func="callee4",args=[],
24738 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24739 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
24744 *stopped,reason="watchpoint-scope",wpnum="5",
24745 frame=@{func="callee3",args=[@{name="strarg",
24746 value="0x11940 \"A string argument.\""@}],
24747 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24748 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
24752 Listing breakpoints and watchpoints, at different points in the program
24753 execution. Note that once the watchpoint goes out of scope, it is
24759 ^done,wpt=@{number="2",exp="C"@}
24762 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
24763 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24764 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24765 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24766 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24767 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24768 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24769 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24770 addr="0x00010734",func="callee4",
24771 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24772 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
24773 bkpt=@{number="2",type="watchpoint",disp="keep",
24774 enabled="y",addr="",what="C",times="0"@}]@}
24779 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
24780 value=@{old="-276895068",new="3"@},
24781 frame=@{func="callee4",args=[],
24782 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24783 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
24786 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
24787 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24788 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24789 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24790 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24791 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24792 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24793 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24794 addr="0x00010734",func="callee4",
24795 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24796 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
24797 bkpt=@{number="2",type="watchpoint",disp="keep",
24798 enabled="y",addr="",what="C",times="-5"@}]@}
24802 ^done,reason="watchpoint-scope",wpnum="2",
24803 frame=@{func="callee3",args=[@{name="strarg",
24804 value="0x11940 \"A string argument.\""@}],
24805 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24806 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
24809 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24810 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24811 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24812 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24813 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24814 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24815 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24816 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24817 addr="0x00010734",func="callee4",
24818 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
24819 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
24824 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24825 @node GDB/MI Program Context
24826 @section @sc{gdb/mi} Program Context
24828 @subheading The @code{-exec-arguments} Command
24829 @findex -exec-arguments
24832 @subsubheading Synopsis
24835 -exec-arguments @var{args}
24838 Set the inferior program arguments, to be used in the next
24841 @subsubheading @value{GDBN} Command
24843 The corresponding @value{GDBN} command is @samp{set args}.
24845 @subsubheading Example
24849 -exec-arguments -v word
24856 @subheading The @code{-exec-show-arguments} Command
24857 @findex -exec-show-arguments
24859 @subsubheading Synopsis
24862 -exec-show-arguments
24865 Print the arguments of the program.
24867 @subsubheading @value{GDBN} Command
24869 The corresponding @value{GDBN} command is @samp{show args}.
24871 @subsubheading Example
24876 @subheading The @code{-environment-cd} Command
24877 @findex -environment-cd
24879 @subsubheading Synopsis
24882 -environment-cd @var{pathdir}
24885 Set @value{GDBN}'s working directory.
24887 @subsubheading @value{GDBN} Command
24889 The corresponding @value{GDBN} command is @samp{cd}.
24891 @subsubheading Example
24895 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
24901 @subheading The @code{-environment-directory} Command
24902 @findex -environment-directory
24904 @subsubheading Synopsis
24907 -environment-directory [ -r ] [ @var{pathdir} ]+
24910 Add directories @var{pathdir} to beginning of search path for source files.
24911 If the @samp{-r} option is used, the search path is reset to the default
24912 search path. If directories @var{pathdir} are supplied in addition to the
24913 @samp{-r} option, the search path is first reset and then addition
24915 Multiple directories may be specified, separated by blanks. Specifying
24916 multiple directories in a single command
24917 results in the directories added to the beginning of the
24918 search path in the same order they were presented in the command.
24919 If blanks are needed as
24920 part of a directory name, double-quotes should be used around
24921 the name. In the command output, the path will show up separated
24922 by the system directory-separator character. The directory-separator
24923 character must not be used
24924 in any directory name.
24925 If no directories are specified, the current search path is displayed.
24927 @subsubheading @value{GDBN} Command
24929 The corresponding @value{GDBN} command is @samp{dir}.
24931 @subsubheading Example
24935 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
24936 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
24938 -environment-directory ""
24939 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
24941 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
24942 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
24944 -environment-directory -r
24945 ^done,source-path="$cdir:$cwd"
24950 @subheading The @code{-environment-path} Command
24951 @findex -environment-path
24953 @subsubheading Synopsis
24956 -environment-path [ -r ] [ @var{pathdir} ]+
24959 Add directories @var{pathdir} to beginning of search path for object files.
24960 If the @samp{-r} option is used, the search path is reset to the original
24961 search path that existed at gdb start-up. If directories @var{pathdir} are
24962 supplied in addition to the
24963 @samp{-r} option, the search path is first reset and then addition
24965 Multiple directories may be specified, separated by blanks. Specifying
24966 multiple directories in a single command
24967 results in the directories added to the beginning of the
24968 search path in the same order they were presented in the command.
24969 If blanks are needed as
24970 part of a directory name, double-quotes should be used around
24971 the name. In the command output, the path will show up separated
24972 by the system directory-separator character. The directory-separator
24973 character must not be used
24974 in any directory name.
24975 If no directories are specified, the current path is displayed.
24978 @subsubheading @value{GDBN} Command
24980 The corresponding @value{GDBN} command is @samp{path}.
24982 @subsubheading Example
24987 ^done,path="/usr/bin"
24989 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
24990 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
24992 -environment-path -r /usr/local/bin
24993 ^done,path="/usr/local/bin:/usr/bin"
24998 @subheading The @code{-environment-pwd} Command
24999 @findex -environment-pwd
25001 @subsubheading Synopsis
25007 Show the current working directory.
25009 @subsubheading @value{GDBN} Command
25011 The corresponding @value{GDBN} command is @samp{pwd}.
25013 @subsubheading Example
25018 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
25022 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25023 @node GDB/MI Thread Commands
25024 @section @sc{gdb/mi} Thread Commands
25027 @subheading The @code{-thread-info} Command
25028 @findex -thread-info
25030 @subsubheading Synopsis
25033 -thread-info [ @var{thread-id} ]
25036 Reports information about either a specific thread, if
25037 the @var{thread-id} parameter is present, or about all
25038 threads. When printing information about all threads,
25039 also reports the current thread.
25041 @subsubheading @value{GDBN} Command
25043 The @samp{info thread} command prints the same information
25046 @subsubheading Example
25051 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
25052 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
25053 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
25054 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
25055 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}],
25056 current-thread-id="1"
25060 The @samp{state} field may have the following values:
25064 The thread is stopped. Frame information is available for stopped
25068 The thread is running. There's no frame information for running
25073 @subheading The @code{-thread-list-ids} Command
25074 @findex -thread-list-ids
25076 @subsubheading Synopsis
25082 Produces a list of the currently known @value{GDBN} thread ids. At the
25083 end of the list it also prints the total number of such threads.
25085 This command is retained for historical reasons, the
25086 @code{-thread-info} command should be used instead.
25088 @subsubheading @value{GDBN} Command
25090 Part of @samp{info threads} supplies the same information.
25092 @subsubheading Example
25097 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
25098 current-thread-id="1",number-of-threads="3"
25103 @subheading The @code{-thread-select} Command
25104 @findex -thread-select
25106 @subsubheading Synopsis
25109 -thread-select @var{threadnum}
25112 Make @var{threadnum} the current thread. It prints the number of the new
25113 current thread, and the topmost frame for that thread.
25115 This command is deprecated in favor of explicitly using the
25116 @samp{--thread} option to each command.
25118 @subsubheading @value{GDBN} Command
25120 The corresponding @value{GDBN} command is @samp{thread}.
25122 @subsubheading Example
25129 *stopped,reason="end-stepping-range",thread-id="2",line="187",
25130 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
25134 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
25135 number-of-threads="3"
25138 ^done,new-thread-id="3",
25139 frame=@{level="0",func="vprintf",
25140 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
25141 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
25145 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25146 @node GDB/MI Program Execution
25147 @section @sc{gdb/mi} Program Execution
25149 These are the asynchronous commands which generate the out-of-band
25150 record @samp{*stopped}. Currently @value{GDBN} only really executes
25151 asynchronously with remote targets and this interaction is mimicked in
25154 @subheading The @code{-exec-continue} Command
25155 @findex -exec-continue
25157 @subsubheading Synopsis
25160 -exec-continue [--reverse] [--all|--thread-group N]
25163 Resumes the execution of the inferior program, which will continue
25164 to execute until it reaches a debugger stop event. If the
25165 @samp{--reverse} option is specified, execution resumes in reverse until
25166 it reaches a stop event. Stop events may include
25169 breakpoints or watchpoints
25171 signals or exceptions
25173 the end of the process (or its beginning under @samp{--reverse})
25175 the end or beginning of a replay log if one is being used.
25177 In all-stop mode (@pxref{All-Stop
25178 Mode}), may resume only one thread, or all threads, depending on the
25179 value of the @samp{scheduler-locking} variable. If @samp{--all} is
25180 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
25181 ignored in all-stop mode. If the @samp{--thread-group} options is
25182 specified, then all threads in that thread group are resumed.
25184 @subsubheading @value{GDBN} Command
25186 The corresponding @value{GDBN} corresponding is @samp{continue}.
25188 @subsubheading Example
25195 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
25196 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
25202 @subheading The @code{-exec-finish} Command
25203 @findex -exec-finish
25205 @subsubheading Synopsis
25208 -exec-finish [--reverse]
25211 Resumes the execution of the inferior program until the current
25212 function is exited. Displays the results returned by the function.
25213 If the @samp{--reverse} option is specified, resumes the reverse
25214 execution of the inferior program until the point where current
25215 function was called.
25217 @subsubheading @value{GDBN} Command
25219 The corresponding @value{GDBN} command is @samp{finish}.
25221 @subsubheading Example
25223 Function returning @code{void}.
25230 *stopped,reason="function-finished",frame=@{func="main",args=[],
25231 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
25235 Function returning other than @code{void}. The name of the internal
25236 @value{GDBN} variable storing the result is printed, together with the
25243 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
25244 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
25245 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25246 gdb-result-var="$1",return-value="0"
25251 @subheading The @code{-exec-interrupt} Command
25252 @findex -exec-interrupt
25254 @subsubheading Synopsis
25257 -exec-interrupt [--all|--thread-group N]
25260 Interrupts the background execution of the target. Note how the token
25261 associated with the stop message is the one for the execution command
25262 that has been interrupted. The token for the interrupt itself only
25263 appears in the @samp{^done} output. If the user is trying to
25264 interrupt a non-running program, an error message will be printed.
25266 Note that when asynchronous execution is enabled, this command is
25267 asynchronous just like other execution commands. That is, first the
25268 @samp{^done} response will be printed, and the target stop will be
25269 reported after that using the @samp{*stopped} notification.
25271 In non-stop mode, only the context thread is interrupted by default.
25272 All threads (in all inferiors) will be interrupted if the
25273 @samp{--all} option is specified. If the @samp{--thread-group}
25274 option is specified, all threads in that group will be interrupted.
25276 @subsubheading @value{GDBN} Command
25278 The corresponding @value{GDBN} command is @samp{interrupt}.
25280 @subsubheading Example
25291 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
25292 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
25293 fullname="/home/foo/bar/try.c",line="13"@}
25298 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
25302 @subheading The @code{-exec-jump} Command
25305 @subsubheading Synopsis
25308 -exec-jump @var{location}
25311 Resumes execution of the inferior program at the location specified by
25312 parameter. @xref{Specify Location}, for a description of the
25313 different forms of @var{location}.
25315 @subsubheading @value{GDBN} Command
25317 The corresponding @value{GDBN} command is @samp{jump}.
25319 @subsubheading Example
25322 -exec-jump foo.c:10
25323 *running,thread-id="all"
25328 @subheading The @code{-exec-next} Command
25331 @subsubheading Synopsis
25334 -exec-next [--reverse]
25337 Resumes execution of the inferior program, stopping when the beginning
25338 of the next source line is reached.
25340 If the @samp{--reverse} option is specified, resumes reverse execution
25341 of the inferior program, stopping at the beginning of the previous
25342 source line. If you issue this command on the first line of a
25343 function, it will take you back to the caller of that function, to the
25344 source line where the function was called.
25347 @subsubheading @value{GDBN} Command
25349 The corresponding @value{GDBN} command is @samp{next}.
25351 @subsubheading Example
25357 *stopped,reason="end-stepping-range",line="8",file="hello.c"
25362 @subheading The @code{-exec-next-instruction} Command
25363 @findex -exec-next-instruction
25365 @subsubheading Synopsis
25368 -exec-next-instruction [--reverse]
25371 Executes one machine instruction. If the instruction is a function
25372 call, continues until the function returns. If the program stops at an
25373 instruction in the middle of a source line, the address will be
25376 If the @samp{--reverse} option is specified, resumes reverse execution
25377 of the inferior program, stopping at the previous instruction. If the
25378 previously executed instruction was a return from another function,
25379 it will continue to execute in reverse until the call to that function
25380 (from the current stack frame) is reached.
25382 @subsubheading @value{GDBN} Command
25384 The corresponding @value{GDBN} command is @samp{nexti}.
25386 @subsubheading Example
25390 -exec-next-instruction
25394 *stopped,reason="end-stepping-range",
25395 addr="0x000100d4",line="5",file="hello.c"
25400 @subheading The @code{-exec-return} Command
25401 @findex -exec-return
25403 @subsubheading Synopsis
25409 Makes current function return immediately. Doesn't execute the inferior.
25410 Displays the new current frame.
25412 @subsubheading @value{GDBN} Command
25414 The corresponding @value{GDBN} command is @samp{return}.
25416 @subsubheading Example
25420 200-break-insert callee4
25421 200^done,bkpt=@{number="1",addr="0x00010734",
25422 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
25427 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
25428 frame=@{func="callee4",args=[],
25429 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25430 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
25436 111^done,frame=@{level="0",func="callee3",
25437 args=[@{name="strarg",
25438 value="0x11940 \"A string argument.\""@}],
25439 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25440 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
25445 @subheading The @code{-exec-run} Command
25448 @subsubheading Synopsis
25451 -exec-run [--all | --thread-group N]
25454 Starts execution of the inferior from the beginning. The inferior
25455 executes until either a breakpoint is encountered or the program
25456 exits. In the latter case the output will include an exit code, if
25457 the program has exited exceptionally.
25459 When no option is specified, the current inferior is started. If the
25460 @samp{--thread-group} option is specified, it should refer to a thread
25461 group of type @samp{process}, and that thread group will be started.
25462 If the @samp{--all} option is specified, then all inferiors will be started.
25464 @subsubheading @value{GDBN} Command
25466 The corresponding @value{GDBN} command is @samp{run}.
25468 @subsubheading Examples
25473 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
25478 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
25479 frame=@{func="main",args=[],file="recursive2.c",
25480 fullname="/home/foo/bar/recursive2.c",line="4"@}
25485 Program exited normally:
25493 *stopped,reason="exited-normally"
25498 Program exited exceptionally:
25506 *stopped,reason="exited",exit-code="01"
25510 Another way the program can terminate is if it receives a signal such as
25511 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
25515 *stopped,reason="exited-signalled",signal-name="SIGINT",
25516 signal-meaning="Interrupt"
25520 @c @subheading -exec-signal
25523 @subheading The @code{-exec-step} Command
25526 @subsubheading Synopsis
25529 -exec-step [--reverse]
25532 Resumes execution of the inferior program, stopping when the beginning
25533 of the next source line is reached, if the next source line is not a
25534 function call. If it is, stop at the first instruction of the called
25535 function. If the @samp{--reverse} option is specified, resumes reverse
25536 execution of the inferior program, stopping at the beginning of the
25537 previously executed source line.
25539 @subsubheading @value{GDBN} Command
25541 The corresponding @value{GDBN} command is @samp{step}.
25543 @subsubheading Example
25545 Stepping into a function:
25551 *stopped,reason="end-stepping-range",
25552 frame=@{func="foo",args=[@{name="a",value="10"@},
25553 @{name="b",value="0"@}],file="recursive2.c",
25554 fullname="/home/foo/bar/recursive2.c",line="11"@}
25564 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
25569 @subheading The @code{-exec-step-instruction} Command
25570 @findex -exec-step-instruction
25572 @subsubheading Synopsis
25575 -exec-step-instruction [--reverse]
25578 Resumes the inferior which executes one machine instruction. If the
25579 @samp{--reverse} option is specified, resumes reverse execution of the
25580 inferior program, stopping at the previously executed instruction.
25581 The output, once @value{GDBN} has stopped, will vary depending on
25582 whether we have stopped in the middle of a source line or not. In the
25583 former case, the address at which the program stopped will be printed
25586 @subsubheading @value{GDBN} Command
25588 The corresponding @value{GDBN} command is @samp{stepi}.
25590 @subsubheading Example
25594 -exec-step-instruction
25598 *stopped,reason="end-stepping-range",
25599 frame=@{func="foo",args=[],file="try.c",
25600 fullname="/home/foo/bar/try.c",line="10"@}
25602 -exec-step-instruction
25606 *stopped,reason="end-stepping-range",
25607 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
25608 fullname="/home/foo/bar/try.c",line="10"@}
25613 @subheading The @code{-exec-until} Command
25614 @findex -exec-until
25616 @subsubheading Synopsis
25619 -exec-until [ @var{location} ]
25622 Executes the inferior until the @var{location} specified in the
25623 argument is reached. If there is no argument, the inferior executes
25624 until a source line greater than the current one is reached. The
25625 reason for stopping in this case will be @samp{location-reached}.
25627 @subsubheading @value{GDBN} Command
25629 The corresponding @value{GDBN} command is @samp{until}.
25631 @subsubheading Example
25635 -exec-until recursive2.c:6
25639 *stopped,reason="location-reached",frame=@{func="main",args=[],
25640 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
25645 @subheading -file-clear
25646 Is this going away????
25649 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25650 @node GDB/MI Stack Manipulation
25651 @section @sc{gdb/mi} Stack Manipulation Commands
25654 @subheading The @code{-stack-info-frame} Command
25655 @findex -stack-info-frame
25657 @subsubheading Synopsis
25663 Get info on the selected frame.
25665 @subsubheading @value{GDBN} Command
25667 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
25668 (without arguments).
25670 @subsubheading Example
25675 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
25676 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25677 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
25681 @subheading The @code{-stack-info-depth} Command
25682 @findex -stack-info-depth
25684 @subsubheading Synopsis
25687 -stack-info-depth [ @var{max-depth} ]
25690 Return the depth of the stack. If the integer argument @var{max-depth}
25691 is specified, do not count beyond @var{max-depth} frames.
25693 @subsubheading @value{GDBN} Command
25695 There's no equivalent @value{GDBN} command.
25697 @subsubheading Example
25699 For a stack with frame levels 0 through 11:
25706 -stack-info-depth 4
25709 -stack-info-depth 12
25712 -stack-info-depth 11
25715 -stack-info-depth 13
25720 @subheading The @code{-stack-list-arguments} Command
25721 @findex -stack-list-arguments
25723 @subsubheading Synopsis
25726 -stack-list-arguments @var{print-values}
25727 [ @var{low-frame} @var{high-frame} ]
25730 Display a list of the arguments for the frames between @var{low-frame}
25731 and @var{high-frame} (inclusive). If @var{low-frame} and
25732 @var{high-frame} are not provided, list the arguments for the whole
25733 call stack. If the two arguments are equal, show the single frame
25734 at the corresponding level. It is an error if @var{low-frame} is
25735 larger than the actual number of frames. On the other hand,
25736 @var{high-frame} may be larger than the actual number of frames, in
25737 which case only existing frames will be returned.
25739 If @var{print-values} is 0 or @code{--no-values}, print only the names of
25740 the variables; if it is 1 or @code{--all-values}, print also their
25741 values; and if it is 2 or @code{--simple-values}, print the name,
25742 type and value for simple data types, and the name and type for arrays,
25743 structures and unions.
25745 Use of this command to obtain arguments in a single frame is
25746 deprecated in favor of the @samp{-stack-list-variables} command.
25748 @subsubheading @value{GDBN} Command
25750 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
25751 @samp{gdb_get_args} command which partially overlaps with the
25752 functionality of @samp{-stack-list-arguments}.
25754 @subsubheading Example
25761 frame=@{level="0",addr="0x00010734",func="callee4",
25762 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25763 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
25764 frame=@{level="1",addr="0x0001076c",func="callee3",
25765 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25766 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
25767 frame=@{level="2",addr="0x0001078c",func="callee2",
25768 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25769 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
25770 frame=@{level="3",addr="0x000107b4",func="callee1",
25771 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25772 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
25773 frame=@{level="4",addr="0x000107e0",func="main",
25774 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25775 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
25777 -stack-list-arguments 0
25780 frame=@{level="0",args=[]@},
25781 frame=@{level="1",args=[name="strarg"]@},
25782 frame=@{level="2",args=[name="intarg",name="strarg"]@},
25783 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
25784 frame=@{level="4",args=[]@}]
25786 -stack-list-arguments 1
25789 frame=@{level="0",args=[]@},
25791 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
25792 frame=@{level="2",args=[
25793 @{name="intarg",value="2"@},
25794 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
25795 @{frame=@{level="3",args=[
25796 @{name="intarg",value="2"@},
25797 @{name="strarg",value="0x11940 \"A string argument.\""@},
25798 @{name="fltarg",value="3.5"@}]@},
25799 frame=@{level="4",args=[]@}]
25801 -stack-list-arguments 0 2 2
25802 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
25804 -stack-list-arguments 1 2 2
25805 ^done,stack-args=[frame=@{level="2",
25806 args=[@{name="intarg",value="2"@},
25807 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
25811 @c @subheading -stack-list-exception-handlers
25814 @subheading The @code{-stack-list-frames} Command
25815 @findex -stack-list-frames
25817 @subsubheading Synopsis
25820 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
25823 List the frames currently on the stack. For each frame it displays the
25828 The frame number, 0 being the topmost frame, i.e., the innermost function.
25830 The @code{$pc} value for that frame.
25834 File name of the source file where the function lives.
25836 Line number corresponding to the @code{$pc}.
25839 If invoked without arguments, this command prints a backtrace for the
25840 whole stack. If given two integer arguments, it shows the frames whose
25841 levels are between the two arguments (inclusive). If the two arguments
25842 are equal, it shows the single frame at the corresponding level. It is
25843 an error if @var{low-frame} is larger than the actual number of
25844 frames. On the other hand, @var{high-frame} may be larger than the
25845 actual number of frames, in which case only existing frames will be returned.
25847 @subsubheading @value{GDBN} Command
25849 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
25851 @subsubheading Example
25853 Full stack backtrace:
25859 [frame=@{level="0",addr="0x0001076c",func="foo",
25860 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
25861 frame=@{level="1",addr="0x000107a4",func="foo",
25862 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25863 frame=@{level="2",addr="0x000107a4",func="foo",
25864 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25865 frame=@{level="3",addr="0x000107a4",func="foo",
25866 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25867 frame=@{level="4",addr="0x000107a4",func="foo",
25868 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25869 frame=@{level="5",addr="0x000107a4",func="foo",
25870 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25871 frame=@{level="6",addr="0x000107a4",func="foo",
25872 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25873 frame=@{level="7",addr="0x000107a4",func="foo",
25874 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25875 frame=@{level="8",addr="0x000107a4",func="foo",
25876 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25877 frame=@{level="9",addr="0x000107a4",func="foo",
25878 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25879 frame=@{level="10",addr="0x000107a4",func="foo",
25880 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25881 frame=@{level="11",addr="0x00010738",func="main",
25882 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
25886 Show frames between @var{low_frame} and @var{high_frame}:
25890 -stack-list-frames 3 5
25892 [frame=@{level="3",addr="0x000107a4",func="foo",
25893 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25894 frame=@{level="4",addr="0x000107a4",func="foo",
25895 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25896 frame=@{level="5",addr="0x000107a4",func="foo",
25897 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
25901 Show a single frame:
25905 -stack-list-frames 3 3
25907 [frame=@{level="3",addr="0x000107a4",func="foo",
25908 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
25913 @subheading The @code{-stack-list-locals} Command
25914 @findex -stack-list-locals
25916 @subsubheading Synopsis
25919 -stack-list-locals @var{print-values}
25922 Display the local variable names for the selected frame. If
25923 @var{print-values} is 0 or @code{--no-values}, print only the names of
25924 the variables; if it is 1 or @code{--all-values}, print also their
25925 values; and if it is 2 or @code{--simple-values}, print the name,
25926 type and value for simple data types, and the name and type for arrays,
25927 structures and unions. In this last case, a frontend can immediately
25928 display the value of simple data types and create variable objects for
25929 other data types when the user wishes to explore their values in
25932 This command is deprecated in favor of the
25933 @samp{-stack-list-variables} command.
25935 @subsubheading @value{GDBN} Command
25937 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
25939 @subsubheading Example
25943 -stack-list-locals 0
25944 ^done,locals=[name="A",name="B",name="C"]
25946 -stack-list-locals --all-values
25947 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
25948 @{name="C",value="@{1, 2, 3@}"@}]
25949 -stack-list-locals --simple-values
25950 ^done,locals=[@{name="A",type="int",value="1"@},
25951 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
25955 @subheading The @code{-stack-list-variables} Command
25956 @findex -stack-list-variables
25958 @subsubheading Synopsis
25961 -stack-list-variables @var{print-values}
25964 Display the names of local variables and function arguments for the selected frame. If
25965 @var{print-values} is 0 or @code{--no-values}, print only the names of
25966 the variables; if it is 1 or @code{--all-values}, print also their
25967 values; and if it is 2 or @code{--simple-values}, print the name,
25968 type and value for simple data types, and the name and type for arrays,
25969 structures and unions.
25971 @subsubheading Example
25975 -stack-list-variables --thread 1 --frame 0 --all-values
25976 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
25981 @subheading The @code{-stack-select-frame} Command
25982 @findex -stack-select-frame
25984 @subsubheading Synopsis
25987 -stack-select-frame @var{framenum}
25990 Change the selected frame. Select a different frame @var{framenum} on
25993 This command in deprecated in favor of passing the @samp{--frame}
25994 option to every command.
25996 @subsubheading @value{GDBN} Command
25998 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
25999 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
26001 @subsubheading Example
26005 -stack-select-frame 2
26010 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26011 @node GDB/MI Variable Objects
26012 @section @sc{gdb/mi} Variable Objects
26016 @subheading Motivation for Variable Objects in @sc{gdb/mi}
26018 For the implementation of a variable debugger window (locals, watched
26019 expressions, etc.), we are proposing the adaptation of the existing code
26020 used by @code{Insight}.
26022 The two main reasons for that are:
26026 It has been proven in practice (it is already on its second generation).
26029 It will shorten development time (needless to say how important it is
26033 The original interface was designed to be used by Tcl code, so it was
26034 slightly changed so it could be used through @sc{gdb/mi}. This section
26035 describes the @sc{gdb/mi} operations that will be available and gives some
26036 hints about their use.
26038 @emph{Note}: In addition to the set of operations described here, we
26039 expect the @sc{gui} implementation of a variable window to require, at
26040 least, the following operations:
26043 @item @code{-gdb-show} @code{output-radix}
26044 @item @code{-stack-list-arguments}
26045 @item @code{-stack-list-locals}
26046 @item @code{-stack-select-frame}
26051 @subheading Introduction to Variable Objects
26053 @cindex variable objects in @sc{gdb/mi}
26055 Variable objects are "object-oriented" MI interface for examining and
26056 changing values of expressions. Unlike some other MI interfaces that
26057 work with expressions, variable objects are specifically designed for
26058 simple and efficient presentation in the frontend. A variable object
26059 is identified by string name. When a variable object is created, the
26060 frontend specifies the expression for that variable object. The
26061 expression can be a simple variable, or it can be an arbitrary complex
26062 expression, and can even involve CPU registers. After creating a
26063 variable object, the frontend can invoke other variable object
26064 operations---for example to obtain or change the value of a variable
26065 object, or to change display format.
26067 Variable objects have hierarchical tree structure. Any variable object
26068 that corresponds to a composite type, such as structure in C, has
26069 a number of child variable objects, for example corresponding to each
26070 element of a structure. A child variable object can itself have
26071 children, recursively. Recursion ends when we reach
26072 leaf variable objects, which always have built-in types. Child variable
26073 objects are created only by explicit request, so if a frontend
26074 is not interested in the children of a particular variable object, no
26075 child will be created.
26077 For a leaf variable object it is possible to obtain its value as a
26078 string, or set the value from a string. String value can be also
26079 obtained for a non-leaf variable object, but it's generally a string
26080 that only indicates the type of the object, and does not list its
26081 contents. Assignment to a non-leaf variable object is not allowed.
26083 A frontend does not need to read the values of all variable objects each time
26084 the program stops. Instead, MI provides an update command that lists all
26085 variable objects whose values has changed since the last update
26086 operation. This considerably reduces the amount of data that must
26087 be transferred to the frontend. As noted above, children variable
26088 objects are created on demand, and only leaf variable objects have a
26089 real value. As result, gdb will read target memory only for leaf
26090 variables that frontend has created.
26092 The automatic update is not always desirable. For example, a frontend
26093 might want to keep a value of some expression for future reference,
26094 and never update it. For another example, fetching memory is
26095 relatively slow for embedded targets, so a frontend might want
26096 to disable automatic update for the variables that are either not
26097 visible on the screen, or ``closed''. This is possible using so
26098 called ``frozen variable objects''. Such variable objects are never
26099 implicitly updated.
26101 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
26102 fixed variable object, the expression is parsed when the variable
26103 object is created, including associating identifiers to specific
26104 variables. The meaning of expression never changes. For a floating
26105 variable object the values of variables whose names appear in the
26106 expressions are re-evaluated every time in the context of the current
26107 frame. Consider this example:
26112 struct work_state state;
26119 If a fixed variable object for the @code{state} variable is created in
26120 this function, and we enter the recursive call, the the variable
26121 object will report the value of @code{state} in the top-level
26122 @code{do_work} invocation. On the other hand, a floating variable
26123 object will report the value of @code{state} in the current frame.
26125 If an expression specified when creating a fixed variable object
26126 refers to a local variable, the variable object becomes bound to the
26127 thread and frame in which the variable object is created. When such
26128 variable object is updated, @value{GDBN} makes sure that the
26129 thread/frame combination the variable object is bound to still exists,
26130 and re-evaluates the variable object in context of that thread/frame.
26132 The following is the complete set of @sc{gdb/mi} operations defined to
26133 access this functionality:
26135 @multitable @columnfractions .4 .6
26136 @item @strong{Operation}
26137 @tab @strong{Description}
26139 @item @code{-enable-pretty-printing}
26140 @tab enable Python-based pretty-printing
26141 @item @code{-var-create}
26142 @tab create a variable object
26143 @item @code{-var-delete}
26144 @tab delete the variable object and/or its children
26145 @item @code{-var-set-format}
26146 @tab set the display format of this variable
26147 @item @code{-var-show-format}
26148 @tab show the display format of this variable
26149 @item @code{-var-info-num-children}
26150 @tab tells how many children this object has
26151 @item @code{-var-list-children}
26152 @tab return a list of the object's children
26153 @item @code{-var-info-type}
26154 @tab show the type of this variable object
26155 @item @code{-var-info-expression}
26156 @tab print parent-relative expression that this variable object represents
26157 @item @code{-var-info-path-expression}
26158 @tab print full expression that this variable object represents
26159 @item @code{-var-show-attributes}
26160 @tab is this variable editable? does it exist here?
26161 @item @code{-var-evaluate-expression}
26162 @tab get the value of this variable
26163 @item @code{-var-assign}
26164 @tab set the value of this variable
26165 @item @code{-var-update}
26166 @tab update the variable and its children
26167 @item @code{-var-set-frozen}
26168 @tab set frozeness attribute
26169 @item @code{-var-set-update-range}
26170 @tab set range of children to display on update
26173 In the next subsection we describe each operation in detail and suggest
26174 how it can be used.
26176 @subheading Description And Use of Operations on Variable Objects
26178 @subheading The @code{-enable-pretty-printing} Command
26179 @findex -enable-pretty-printing
26182 -enable-pretty-printing
26185 @value{GDBN} allows Python-based visualizers to affect the output of the
26186 MI variable object commands. However, because there was no way to
26187 implement this in a fully backward-compatible way, a front end must
26188 request that this functionality be enabled.
26190 Once enabled, this feature cannot be disabled.
26192 Note that if Python support has not been compiled into @value{GDBN},
26193 this command will still succeed (and do nothing).
26195 This feature is currently (as of @value{GDBN} 7.0) experimental, and
26196 may work differently in future versions of @value{GDBN}.
26198 @subheading The @code{-var-create} Command
26199 @findex -var-create
26201 @subsubheading Synopsis
26204 -var-create @{@var{name} | "-"@}
26205 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
26208 This operation creates a variable object, which allows the monitoring of
26209 a variable, the result of an expression, a memory cell or a CPU
26212 The @var{name} parameter is the string by which the object can be
26213 referenced. It must be unique. If @samp{-} is specified, the varobj
26214 system will generate a string ``varNNNNNN'' automatically. It will be
26215 unique provided that one does not specify @var{name} of that format.
26216 The command fails if a duplicate name is found.
26218 The frame under which the expression should be evaluated can be
26219 specified by @var{frame-addr}. A @samp{*} indicates that the current
26220 frame should be used. A @samp{@@} indicates that a floating variable
26221 object must be created.
26223 @var{expression} is any expression valid on the current language set (must not
26224 begin with a @samp{*}), or one of the following:
26228 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
26231 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
26234 @samp{$@var{regname}} --- a CPU register name
26237 @cindex dynamic varobj
26238 A varobj's contents may be provided by a Python-based pretty-printer. In this
26239 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
26240 have slightly different semantics in some cases. If the
26241 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
26242 will never create a dynamic varobj. This ensures backward
26243 compatibility for existing clients.
26245 @subsubheading Result
26247 This operation returns attributes of the newly-created varobj. These
26252 The name of the varobj.
26255 The number of children of the varobj. This number is not necessarily
26256 reliable for a dynamic varobj. Instead, you must examine the
26257 @samp{has_more} attribute.
26260 The varobj's scalar value. For a varobj whose type is some sort of
26261 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
26262 will not be interesting.
26265 The varobj's type. This is a string representation of the type, as
26266 would be printed by the @value{GDBN} CLI.
26269 If a variable object is bound to a specific thread, then this is the
26270 thread's identifier.
26273 For a dynamic varobj, this indicates whether there appear to be any
26274 children available. For a non-dynamic varobj, this will be 0.
26277 This attribute will be present and have the value @samp{1} if the
26278 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
26279 then this attribute will not be present.
26282 A dynamic varobj can supply a display hint to the front end. The
26283 value comes directly from the Python pretty-printer object's
26284 @code{display_hint} method. @xref{Pretty Printing API}.
26287 Typical output will look like this:
26290 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
26291 has_more="@var{has_more}"
26295 @subheading The @code{-var-delete} Command
26296 @findex -var-delete
26298 @subsubheading Synopsis
26301 -var-delete [ -c ] @var{name}
26304 Deletes a previously created variable object and all of its children.
26305 With the @samp{-c} option, just deletes the children.
26307 Returns an error if the object @var{name} is not found.
26310 @subheading The @code{-var-set-format} Command
26311 @findex -var-set-format
26313 @subsubheading Synopsis
26316 -var-set-format @var{name} @var{format-spec}
26319 Sets the output format for the value of the object @var{name} to be
26322 @anchor{-var-set-format}
26323 The syntax for the @var{format-spec} is as follows:
26326 @var{format-spec} @expansion{}
26327 @{binary | decimal | hexadecimal | octal | natural@}
26330 The natural format is the default format choosen automatically
26331 based on the variable type (like decimal for an @code{int}, hex
26332 for pointers, etc.).
26334 For a variable with children, the format is set only on the
26335 variable itself, and the children are not affected.
26337 @subheading The @code{-var-show-format} Command
26338 @findex -var-show-format
26340 @subsubheading Synopsis
26343 -var-show-format @var{name}
26346 Returns the format used to display the value of the object @var{name}.
26349 @var{format} @expansion{}
26354 @subheading The @code{-var-info-num-children} Command
26355 @findex -var-info-num-children
26357 @subsubheading Synopsis
26360 -var-info-num-children @var{name}
26363 Returns the number of children of a variable object @var{name}:
26369 Note that this number is not completely reliable for a dynamic varobj.
26370 It will return the current number of children, but more children may
26374 @subheading The @code{-var-list-children} Command
26375 @findex -var-list-children
26377 @subsubheading Synopsis
26380 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
26382 @anchor{-var-list-children}
26384 Return a list of the children of the specified variable object and
26385 create variable objects for them, if they do not already exist. With
26386 a single argument or if @var{print-values} has a value for of 0 or
26387 @code{--no-values}, print only the names of the variables; if
26388 @var{print-values} is 1 or @code{--all-values}, also print their
26389 values; and if it is 2 or @code{--simple-values} print the name and
26390 value for simple data types and just the name for arrays, structures
26393 @var{from} and @var{to}, if specified, indicate the range of children
26394 to report. If @var{from} or @var{to} is less than zero, the range is
26395 reset and all children will be reported. Otherwise, children starting
26396 at @var{from} (zero-based) and up to and excluding @var{to} will be
26399 If a child range is requested, it will only affect the current call to
26400 @code{-var-list-children}, but not future calls to @code{-var-update}.
26401 For this, you must instead use @code{-var-set-update-range}. The
26402 intent of this approach is to enable a front end to implement any
26403 update approach it likes; for example, scrolling a view may cause the
26404 front end to request more children with @code{-var-list-children}, and
26405 then the front end could call @code{-var-set-update-range} with a
26406 different range to ensure that future updates are restricted to just
26409 For each child the following results are returned:
26414 Name of the variable object created for this child.
26417 The expression to be shown to the user by the front end to designate this child.
26418 For example this may be the name of a structure member.
26420 For a dynamic varobj, this value cannot be used to form an
26421 expression. There is no way to do this at all with a dynamic varobj.
26423 For C/C@t{++} structures there are several pseudo children returned to
26424 designate access qualifiers. For these pseudo children @var{exp} is
26425 @samp{public}, @samp{private}, or @samp{protected}. In this case the
26426 type and value are not present.
26428 A dynamic varobj will not report the access qualifying
26429 pseudo-children, regardless of the language. This information is not
26430 available at all with a dynamic varobj.
26433 Number of children this child has. For a dynamic varobj, this will be
26437 The type of the child.
26440 If values were requested, this is the value.
26443 If this variable object is associated with a thread, this is the thread id.
26444 Otherwise this result is not present.
26447 If the variable object is frozen, this variable will be present with a value of 1.
26450 The result may have its own attributes:
26454 A dynamic varobj can supply a display hint to the front end. The
26455 value comes directly from the Python pretty-printer object's
26456 @code{display_hint} method. @xref{Pretty Printing API}.
26459 This is an integer attribute which is nonzero if there are children
26460 remaining after the end of the selected range.
26463 @subsubheading Example
26467 -var-list-children n
26468 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
26469 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
26471 -var-list-children --all-values n
26472 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
26473 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
26477 @subheading The @code{-var-info-type} Command
26478 @findex -var-info-type
26480 @subsubheading Synopsis
26483 -var-info-type @var{name}
26486 Returns the type of the specified variable @var{name}. The type is
26487 returned as a string in the same format as it is output by the
26491 type=@var{typename}
26495 @subheading The @code{-var-info-expression} Command
26496 @findex -var-info-expression
26498 @subsubheading Synopsis
26501 -var-info-expression @var{name}
26504 Returns a string that is suitable for presenting this
26505 variable object in user interface. The string is generally
26506 not valid expression in the current language, and cannot be evaluated.
26508 For example, if @code{a} is an array, and variable object
26509 @code{A} was created for @code{a}, then we'll get this output:
26512 (gdb) -var-info-expression A.1
26513 ^done,lang="C",exp="1"
26517 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
26519 Note that the output of the @code{-var-list-children} command also
26520 includes those expressions, so the @code{-var-info-expression} command
26523 @subheading The @code{-var-info-path-expression} Command
26524 @findex -var-info-path-expression
26526 @subsubheading Synopsis
26529 -var-info-path-expression @var{name}
26532 Returns an expression that can be evaluated in the current
26533 context and will yield the same value that a variable object has.
26534 Compare this with the @code{-var-info-expression} command, which
26535 result can be used only for UI presentation. Typical use of
26536 the @code{-var-info-path-expression} command is creating a
26537 watchpoint from a variable object.
26539 This command is currently not valid for children of a dynamic varobj,
26540 and will give an error when invoked on one.
26542 For example, suppose @code{C} is a C@t{++} class, derived from class
26543 @code{Base}, and that the @code{Base} class has a member called
26544 @code{m_size}. Assume a variable @code{c} is has the type of
26545 @code{C} and a variable object @code{C} was created for variable
26546 @code{c}. Then, we'll get this output:
26548 (gdb) -var-info-path-expression C.Base.public.m_size
26549 ^done,path_expr=((Base)c).m_size)
26552 @subheading The @code{-var-show-attributes} Command
26553 @findex -var-show-attributes
26555 @subsubheading Synopsis
26558 -var-show-attributes @var{name}
26561 List attributes of the specified variable object @var{name}:
26564 status=@var{attr} [ ( ,@var{attr} )* ]
26568 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
26570 @subheading The @code{-var-evaluate-expression} Command
26571 @findex -var-evaluate-expression
26573 @subsubheading Synopsis
26576 -var-evaluate-expression [-f @var{format-spec}] @var{name}
26579 Evaluates the expression that is represented by the specified variable
26580 object and returns its value as a string. The format of the string
26581 can be specified with the @samp{-f} option. The possible values of
26582 this option are the same as for @code{-var-set-format}
26583 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
26584 the current display format will be used. The current display format
26585 can be changed using the @code{-var-set-format} command.
26591 Note that one must invoke @code{-var-list-children} for a variable
26592 before the value of a child variable can be evaluated.
26594 @subheading The @code{-var-assign} Command
26595 @findex -var-assign
26597 @subsubheading Synopsis
26600 -var-assign @var{name} @var{expression}
26603 Assigns the value of @var{expression} to the variable object specified
26604 by @var{name}. The object must be @samp{editable}. If the variable's
26605 value is altered by the assign, the variable will show up in any
26606 subsequent @code{-var-update} list.
26608 @subsubheading Example
26616 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
26620 @subheading The @code{-var-update} Command
26621 @findex -var-update
26623 @subsubheading Synopsis
26626 -var-update [@var{print-values}] @{@var{name} | "*"@}
26629 Reevaluate the expressions corresponding to the variable object
26630 @var{name} and all its direct and indirect children, and return the
26631 list of variable objects whose values have changed; @var{name} must
26632 be a root variable object. Here, ``changed'' means that the result of
26633 @code{-var-evaluate-expression} before and after the
26634 @code{-var-update} is different. If @samp{*} is used as the variable
26635 object names, all existing variable objects are updated, except
26636 for frozen ones (@pxref{-var-set-frozen}). The option
26637 @var{print-values} determines whether both names and values, or just
26638 names are printed. The possible values of this option are the same
26639 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
26640 recommended to use the @samp{--all-values} option, to reduce the
26641 number of MI commands needed on each program stop.
26643 With the @samp{*} parameter, if a variable object is bound to a
26644 currently running thread, it will not be updated, without any
26647 If @code{-var-set-update-range} was previously used on a varobj, then
26648 only the selected range of children will be reported.
26650 @code{-var-update} reports all the changed varobjs in a tuple named
26653 Each item in the change list is itself a tuple holding:
26657 The name of the varobj.
26660 If values were requested for this update, then this field will be
26661 present and will hold the value of the varobj.
26664 @anchor{-var-update}
26665 This field is a string which may take one of three values:
26669 The variable object's current value is valid.
26672 The variable object does not currently hold a valid value but it may
26673 hold one in the future if its associated expression comes back into
26677 The variable object no longer holds a valid value.
26678 This can occur when the executable file being debugged has changed,
26679 either through recompilation or by using the @value{GDBN} @code{file}
26680 command. The front end should normally choose to delete these variable
26684 In the future new values may be added to this list so the front should
26685 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
26688 This is only present if the varobj is still valid. If the type
26689 changed, then this will be the string @samp{true}; otherwise it will
26693 If the varobj's type changed, then this field will be present and will
26696 @item new_num_children
26697 For a dynamic varobj, if the number of children changed, or if the
26698 type changed, this will be the new number of children.
26700 The @samp{numchild} field in other varobj responses is generally not
26701 valid for a dynamic varobj -- it will show the number of children that
26702 @value{GDBN} knows about, but because dynamic varobjs lazily
26703 instantiate their children, this will not reflect the number of
26704 children which may be available.
26706 The @samp{new_num_children} attribute only reports changes to the
26707 number of children known by @value{GDBN}. This is the only way to
26708 detect whether an update has removed children (which necessarily can
26709 only happen at the end of the update range).
26712 The display hint, if any.
26715 This is an integer value, which will be 1 if there are more children
26716 available outside the varobj's update range.
26719 This attribute will be present and have the value @samp{1} if the
26720 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
26721 then this attribute will not be present.
26724 If new children were added to a dynamic varobj within the selected
26725 update range (as set by @code{-var-set-update-range}), then they will
26726 be listed in this attribute.
26729 @subsubheading Example
26736 -var-update --all-values var1
26737 ^done,changelist=[@{name="var1",value="3",in_scope="true",
26738 type_changed="false"@}]
26742 @subheading The @code{-var-set-frozen} Command
26743 @findex -var-set-frozen
26744 @anchor{-var-set-frozen}
26746 @subsubheading Synopsis
26749 -var-set-frozen @var{name} @var{flag}
26752 Set the frozenness flag on the variable object @var{name}. The
26753 @var{flag} parameter should be either @samp{1} to make the variable
26754 frozen or @samp{0} to make it unfrozen. If a variable object is
26755 frozen, then neither itself, nor any of its children, are
26756 implicitly updated by @code{-var-update} of
26757 a parent variable or by @code{-var-update *}. Only
26758 @code{-var-update} of the variable itself will update its value and
26759 values of its children. After a variable object is unfrozen, it is
26760 implicitly updated by all subsequent @code{-var-update} operations.
26761 Unfreezing a variable does not update it, only subsequent
26762 @code{-var-update} does.
26764 @subsubheading Example
26768 -var-set-frozen V 1
26773 @subheading The @code{-var-set-update-range} command
26774 @findex -var-set-update-range
26775 @anchor{-var-set-update-range}
26777 @subsubheading Synopsis
26780 -var-set-update-range @var{name} @var{from} @var{to}
26783 Set the range of children to be returned by future invocations of
26784 @code{-var-update}.
26786 @var{from} and @var{to} indicate the range of children to report. If
26787 @var{from} or @var{to} is less than zero, the range is reset and all
26788 children will be reported. Otherwise, children starting at @var{from}
26789 (zero-based) and up to and excluding @var{to} will be reported.
26791 @subsubheading Example
26795 -var-set-update-range V 1 2
26799 @subheading The @code{-var-set-visualizer} command
26800 @findex -var-set-visualizer
26801 @anchor{-var-set-visualizer}
26803 @subsubheading Synopsis
26806 -var-set-visualizer @var{name} @var{visualizer}
26809 Set a visualizer for the variable object @var{name}.
26811 @var{visualizer} is the visualizer to use. The special value
26812 @samp{None} means to disable any visualizer in use.
26814 If not @samp{None}, @var{visualizer} must be a Python expression.
26815 This expression must evaluate to a callable object which accepts a
26816 single argument. @value{GDBN} will call this object with the value of
26817 the varobj @var{name} as an argument (this is done so that the same
26818 Python pretty-printing code can be used for both the CLI and MI).
26819 When called, this object must return an object which conforms to the
26820 pretty-printing interface (@pxref{Pretty Printing API}).
26822 The pre-defined function @code{gdb.default_visualizer} may be used to
26823 select a visualizer by following the built-in process
26824 (@pxref{Selecting Pretty-Printers}). This is done automatically when
26825 a varobj is created, and so ordinarily is not needed.
26827 This feature is only available if Python support is enabled. The MI
26828 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
26829 can be used to check this.
26831 @subsubheading Example
26833 Resetting the visualizer:
26837 -var-set-visualizer V None
26841 Reselecting the default (type-based) visualizer:
26845 -var-set-visualizer V gdb.default_visualizer
26849 Suppose @code{SomeClass} is a visualizer class. A lambda expression
26850 can be used to instantiate this class for a varobj:
26854 -var-set-visualizer V "lambda val: SomeClass()"
26858 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26859 @node GDB/MI Data Manipulation
26860 @section @sc{gdb/mi} Data Manipulation
26862 @cindex data manipulation, in @sc{gdb/mi}
26863 @cindex @sc{gdb/mi}, data manipulation
26864 This section describes the @sc{gdb/mi} commands that manipulate data:
26865 examine memory and registers, evaluate expressions, etc.
26867 @c REMOVED FROM THE INTERFACE.
26868 @c @subheading -data-assign
26869 @c Change the value of a program variable. Plenty of side effects.
26870 @c @subsubheading GDB Command
26872 @c @subsubheading Example
26875 @subheading The @code{-data-disassemble} Command
26876 @findex -data-disassemble
26878 @subsubheading Synopsis
26882 [ -s @var{start-addr} -e @var{end-addr} ]
26883 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
26891 @item @var{start-addr}
26892 is the beginning address (or @code{$pc})
26893 @item @var{end-addr}
26895 @item @var{filename}
26896 is the name of the file to disassemble
26897 @item @var{linenum}
26898 is the line number to disassemble around
26900 is the number of disassembly lines to be produced. If it is -1,
26901 the whole function will be disassembled, in case no @var{end-addr} is
26902 specified. If @var{end-addr} is specified as a non-zero value, and
26903 @var{lines} is lower than the number of disassembly lines between
26904 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
26905 displayed; if @var{lines} is higher than the number of lines between
26906 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
26909 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
26913 @subsubheading Result
26915 The output for each instruction is composed of four fields:
26924 Note that whatever included in the instruction field, is not manipulated
26925 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
26927 @subsubheading @value{GDBN} Command
26929 There's no direct mapping from this command to the CLI.
26931 @subsubheading Example
26933 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
26937 -data-disassemble -s $pc -e "$pc + 20" -- 0
26940 @{address="0x000107c0",func-name="main",offset="4",
26941 inst="mov 2, %o0"@},
26942 @{address="0x000107c4",func-name="main",offset="8",
26943 inst="sethi %hi(0x11800), %o2"@},
26944 @{address="0x000107c8",func-name="main",offset="12",
26945 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
26946 @{address="0x000107cc",func-name="main",offset="16",
26947 inst="sethi %hi(0x11800), %o2"@},
26948 @{address="0x000107d0",func-name="main",offset="20",
26949 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
26953 Disassemble the whole @code{main} function. Line 32 is part of
26957 -data-disassemble -f basics.c -l 32 -- 0
26959 @{address="0x000107bc",func-name="main",offset="0",
26960 inst="save %sp, -112, %sp"@},
26961 @{address="0x000107c0",func-name="main",offset="4",
26962 inst="mov 2, %o0"@},
26963 @{address="0x000107c4",func-name="main",offset="8",
26964 inst="sethi %hi(0x11800), %o2"@},
26966 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
26967 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
26971 Disassemble 3 instructions from the start of @code{main}:
26975 -data-disassemble -f basics.c -l 32 -n 3 -- 0
26977 @{address="0x000107bc",func-name="main",offset="0",
26978 inst="save %sp, -112, %sp"@},
26979 @{address="0x000107c0",func-name="main",offset="4",
26980 inst="mov 2, %o0"@},
26981 @{address="0x000107c4",func-name="main",offset="8",
26982 inst="sethi %hi(0x11800), %o2"@}]
26986 Disassemble 3 instructions from the start of @code{main} in mixed mode:
26990 -data-disassemble -f basics.c -l 32 -n 3 -- 1
26992 src_and_asm_line=@{line="31",
26993 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
26994 testsuite/gdb.mi/basics.c",line_asm_insn=[
26995 @{address="0x000107bc",func-name="main",offset="0",
26996 inst="save %sp, -112, %sp"@}]@},
26997 src_and_asm_line=@{line="32",
26998 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
26999 testsuite/gdb.mi/basics.c",line_asm_insn=[
27000 @{address="0x000107c0",func-name="main",offset="4",
27001 inst="mov 2, %o0"@},
27002 @{address="0x000107c4",func-name="main",offset="8",
27003 inst="sethi %hi(0x11800), %o2"@}]@}]
27008 @subheading The @code{-data-evaluate-expression} Command
27009 @findex -data-evaluate-expression
27011 @subsubheading Synopsis
27014 -data-evaluate-expression @var{expr}
27017 Evaluate @var{expr} as an expression. The expression could contain an
27018 inferior function call. The function call will execute synchronously.
27019 If the expression contains spaces, it must be enclosed in double quotes.
27021 @subsubheading @value{GDBN} Command
27023 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
27024 @samp{call}. In @code{gdbtk} only, there's a corresponding
27025 @samp{gdb_eval} command.
27027 @subsubheading Example
27029 In the following example, the numbers that precede the commands are the
27030 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
27031 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
27035 211-data-evaluate-expression A
27038 311-data-evaluate-expression &A
27039 311^done,value="0xefffeb7c"
27041 411-data-evaluate-expression A+3
27044 511-data-evaluate-expression "A + 3"
27050 @subheading The @code{-data-list-changed-registers} Command
27051 @findex -data-list-changed-registers
27053 @subsubheading Synopsis
27056 -data-list-changed-registers
27059 Display a list of the registers that have changed.
27061 @subsubheading @value{GDBN} Command
27063 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
27064 has the corresponding command @samp{gdb_changed_register_list}.
27066 @subsubheading Example
27068 On a PPC MBX board:
27076 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
27077 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
27080 -data-list-changed-registers
27081 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
27082 "10","11","13","14","15","16","17","18","19","20","21","22","23",
27083 "24","25","26","27","28","30","31","64","65","66","67","69"]
27088 @subheading The @code{-data-list-register-names} Command
27089 @findex -data-list-register-names
27091 @subsubheading Synopsis
27094 -data-list-register-names [ ( @var{regno} )+ ]
27097 Show a list of register names for the current target. If no arguments
27098 are given, it shows a list of the names of all the registers. If
27099 integer numbers are given as arguments, it will print a list of the
27100 names of the registers corresponding to the arguments. To ensure
27101 consistency between a register name and its number, the output list may
27102 include empty register names.
27104 @subsubheading @value{GDBN} Command
27106 @value{GDBN} does not have a command which corresponds to
27107 @samp{-data-list-register-names}. In @code{gdbtk} there is a
27108 corresponding command @samp{gdb_regnames}.
27110 @subsubheading Example
27112 For the PPC MBX board:
27115 -data-list-register-names
27116 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
27117 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
27118 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
27119 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
27120 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
27121 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
27122 "", "pc","ps","cr","lr","ctr","xer"]
27124 -data-list-register-names 1 2 3
27125 ^done,register-names=["r1","r2","r3"]
27129 @subheading The @code{-data-list-register-values} Command
27130 @findex -data-list-register-values
27132 @subsubheading Synopsis
27135 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
27138 Display the registers' contents. @var{fmt} is the format according to
27139 which the registers' contents are to be returned, followed by an optional
27140 list of numbers specifying the registers to display. A missing list of
27141 numbers indicates that the contents of all the registers must be returned.
27143 Allowed formats for @var{fmt} are:
27160 @subsubheading @value{GDBN} Command
27162 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
27163 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
27165 @subsubheading Example
27167 For a PPC MBX board (note: line breaks are for readability only, they
27168 don't appear in the actual output):
27172 -data-list-register-values r 64 65
27173 ^done,register-values=[@{number="64",value="0xfe00a300"@},
27174 @{number="65",value="0x00029002"@}]
27176 -data-list-register-values x
27177 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
27178 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
27179 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
27180 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
27181 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
27182 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
27183 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
27184 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
27185 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
27186 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
27187 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
27188 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
27189 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
27190 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
27191 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
27192 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
27193 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
27194 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
27195 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
27196 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
27197 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
27198 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
27199 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
27200 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
27201 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
27202 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
27203 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
27204 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
27205 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
27206 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
27207 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
27208 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
27209 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
27210 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
27211 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
27212 @{number="69",value="0x20002b03"@}]
27217 @subheading The @code{-data-read-memory} Command
27218 @findex -data-read-memory
27220 @subsubheading Synopsis
27223 -data-read-memory [ -o @var{byte-offset} ]
27224 @var{address} @var{word-format} @var{word-size}
27225 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
27232 @item @var{address}
27233 An expression specifying the address of the first memory word to be
27234 read. Complex expressions containing embedded white space should be
27235 quoted using the C convention.
27237 @item @var{word-format}
27238 The format to be used to print the memory words. The notation is the
27239 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
27242 @item @var{word-size}
27243 The size of each memory word in bytes.
27245 @item @var{nr-rows}
27246 The number of rows in the output table.
27248 @item @var{nr-cols}
27249 The number of columns in the output table.
27252 If present, indicates that each row should include an @sc{ascii} dump. The
27253 value of @var{aschar} is used as a padding character when a byte is not a
27254 member of the printable @sc{ascii} character set (printable @sc{ascii}
27255 characters are those whose code is between 32 and 126, inclusively).
27257 @item @var{byte-offset}
27258 An offset to add to the @var{address} before fetching memory.
27261 This command displays memory contents as a table of @var{nr-rows} by
27262 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
27263 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
27264 (returned as @samp{total-bytes}). Should less than the requested number
27265 of bytes be returned by the target, the missing words are identified
27266 using @samp{N/A}. The number of bytes read from the target is returned
27267 in @samp{nr-bytes} and the starting address used to read memory in
27270 The address of the next/previous row or page is available in
27271 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
27274 @subsubheading @value{GDBN} Command
27276 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
27277 @samp{gdb_get_mem} memory read command.
27279 @subsubheading Example
27281 Read six bytes of memory starting at @code{bytes+6} but then offset by
27282 @code{-6} bytes. Format as three rows of two columns. One byte per
27283 word. Display each word in hex.
27287 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
27288 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
27289 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
27290 prev-page="0x0000138a",memory=[
27291 @{addr="0x00001390",data=["0x00","0x01"]@},
27292 @{addr="0x00001392",data=["0x02","0x03"]@},
27293 @{addr="0x00001394",data=["0x04","0x05"]@}]
27297 Read two bytes of memory starting at address @code{shorts + 64} and
27298 display as a single word formatted in decimal.
27302 5-data-read-memory shorts+64 d 2 1 1
27303 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
27304 next-row="0x00001512",prev-row="0x0000150e",
27305 next-page="0x00001512",prev-page="0x0000150e",memory=[
27306 @{addr="0x00001510",data=["128"]@}]
27310 Read thirty two bytes of memory starting at @code{bytes+16} and format
27311 as eight rows of four columns. Include a string encoding with @samp{x}
27312 used as the non-printable character.
27316 4-data-read-memory bytes+16 x 1 8 4 x
27317 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
27318 next-row="0x000013c0",prev-row="0x0000139c",
27319 next-page="0x000013c0",prev-page="0x00001380",memory=[
27320 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
27321 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
27322 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
27323 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
27324 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
27325 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
27326 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
27327 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
27331 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27332 @node GDB/MI Tracepoint Commands
27333 @section @sc{gdb/mi} Tracepoint Commands
27335 The commands defined in this section implement MI support for
27336 tracepoints. For detailed introduction, see @ref{Tracepoints}.
27338 @subheading The @code{-trace-find} Command
27339 @findex -trace-find
27341 @subsubheading Synopsis
27344 -trace-find @var{mode} [@var{parameters}@dots{}]
27347 Find a trace frame using criteria defined by @var{mode} and
27348 @var{parameters}. The following table lists permissible
27349 modes and their parameters. For details of operation, see @ref{tfind}.
27354 No parameters are required. Stops examining trace frames.
27357 An integer is required as parameter. Selects tracepoint frame with
27360 @item tracepoint-number
27361 An integer is required as parameter. Finds next
27362 trace frame that corresponds to tracepoint with the specified number.
27365 An address is required as parameter. Finds
27366 next trace frame that corresponds to any tracepoint at the specified
27369 @item pc-inside-range
27370 Two addresses are required as parameters. Finds next trace
27371 frame that corresponds to a tracepoint at an address inside the
27372 specified range. Both bounds are considered to be inside the range.
27374 @item pc-outside-range
27375 Two addresses are required as parameters. Finds
27376 next trace frame that corresponds to a tracepoint at an address outside
27377 the specified range. Both bounds are considered to be inside the range.
27380 Line specification is required as parameter. @xref{Specify Location}.
27381 Finds next trace frame that corresponds to a tracepoint at
27382 the specified location.
27386 If @samp{none} was passed as @var{mode}, the response does not
27387 have fields. Otherwise, the response may have the following fields:
27391 This field has either @samp{0} or @samp{1} as the value, depending
27392 on whether a matching tracepoint was found.
27395 The index of the found traceframe. This field is present iff
27396 the @samp{found} field has value of @samp{1}.
27399 The index of the found tracepoint. This field is present iff
27400 the @samp{found} field has value of @samp{1}.
27403 The information about the frame corresponding to the found trace
27404 frame. This field is present only if a trace frame was found.
27405 @xref{GDB/MI Frame Information}, for description of this field.
27409 @subsubheading @value{GDBN} Command
27411 The corresponding @value{GDBN} command is @samp{tfind}.
27413 @subheading -trace-define-variable
27414 @findex -trace-define-variable
27416 @subsubheading Synopsis
27419 -trace-define-variable @var{name} [ @var{value} ]
27422 Create trace variable @var{name} if it does not exist. If
27423 @var{value} is specified, sets the initial value of the specified
27424 trace variable to that value. Note that the @var{name} should start
27425 with the @samp{$} character.
27427 @subsubheading @value{GDBN} Command
27429 The corresponding @value{GDBN} command is @samp{tvariable}.
27431 @subheading -trace-list-variables
27432 @findex -trace-list-variables
27434 @subsubheading Synopsis
27437 -trace-list-variables
27440 Return a table of all defined trace variables. Each element of the
27441 table has the following fields:
27445 The name of the trace variable. This field is always present.
27448 The initial value. This is a 64-bit signed integer. This
27449 field is always present.
27452 The value the trace variable has at the moment. This is a 64-bit
27453 signed integer. This field is absent iff current value is
27454 not defined, for example if the trace was never run, or is
27459 @subsubheading @value{GDBN} Command
27461 The corresponding @value{GDBN} command is @samp{tvariables}.
27463 @subsubheading Example
27467 -trace-list-variables
27468 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
27469 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
27470 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
27471 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
27472 body=[variable=@{name="$trace_timestamp",initial="0"@}
27473 variable=@{name="$foo",initial="10",current="15"@}]@}
27477 @subheading -trace-save
27478 @findex -trace-save
27480 @subsubheading Synopsis
27483 -trace-save [-r ] @var{filename}
27486 Saves the collected trace data to @var{filename}. Without the
27487 @samp{-r} option, the data is downloaded from the target and saved
27488 in a local file. With the @samp{-r} option the target is asked
27489 to perform the save.
27491 @subsubheading @value{GDBN} Command
27493 The corresponding @value{GDBN} command is @samp{tsave}.
27496 @subheading -trace-start
27497 @findex -trace-start
27499 @subsubheading Synopsis
27505 Starts a tracing experiments. The result of this command does not
27508 @subsubheading @value{GDBN} Command
27510 The corresponding @value{GDBN} command is @samp{tstart}.
27512 @subheading -trace-status
27513 @findex -trace-status
27515 @subsubheading Synopsis
27521 Obtains the status of a tracing experiment. The result may include
27522 the following fields:
27527 May have a value of either @samp{0}, when no tracing operations are
27528 supported, @samp{1}, when all tracing operations are supported, or
27529 @samp{file} when examining trace file. In the latter case, examining
27530 of trace frame is possible but new tracing experiement cannot be
27531 started. This field is always present.
27534 May have a value of either @samp{0} or @samp{1} depending on whether
27535 tracing experiement is in progress on target. This field is present
27536 if @samp{supported} field is not @samp{0}.
27539 Report the reason why the tracing was stopped last time. This field
27540 may be absent iff tracing was never stopped on target yet. The
27541 value of @samp{request} means the tracing was stopped as result of
27542 the @code{-trace-stop} command. The value of @samp{overflow} means
27543 the tracing buffer is full. The value of @samp{disconnection} means
27544 tracing was automatically stopped when @value{GDBN} has disconnected.
27545 The value of @samp{passcount} means tracing was stopped when a
27546 tracepoint was passed a maximal number of times for that tracepoint.
27547 This field is present if @samp{supported} field is not @samp{0}.
27549 @item stopping-tracepoint
27550 The number of tracepoint whose passcount as exceeded. This field is
27551 present iff the @samp{stop-reason} field has the value of
27555 @itemx frames-created
27556 The @samp{frames} field is a count of the total number of trace frames
27557 in the trace buffer, while @samp{frames-created} is the total created
27558 during the run, including ones that were discarded, such as when a
27559 circular trace buffer filled up. Both fields are optional.
27563 These fields tell the current size of the tracing buffer and the
27564 remaining space. These fields are optional.
27567 The value of the circular trace buffer flag. @code{1} means that the
27568 trace buffer is circular and old trace frames will be discarded if
27569 necessary to make room, @code{0} means that the trace buffer is linear
27573 The value of the disconnected tracing flag. @code{1} means that
27574 tracing will continue after @value{GDBN} disconnects, @code{0} means
27575 that the trace run will stop.
27579 @subsubheading @value{GDBN} Command
27581 The corresponding @value{GDBN} command is @samp{tstatus}.
27583 @subheading -trace-stop
27584 @findex -trace-stop
27586 @subsubheading Synopsis
27592 Stops a tracing experiment. The result of this command has the same
27593 fields as @code{-trace-status}, except that the @samp{supported} and
27594 @samp{running} fields are not output.
27596 @subsubheading @value{GDBN} Command
27598 The corresponding @value{GDBN} command is @samp{tstop}.
27601 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27602 @node GDB/MI Symbol Query
27603 @section @sc{gdb/mi} Symbol Query Commands
27607 @subheading The @code{-symbol-info-address} Command
27608 @findex -symbol-info-address
27610 @subsubheading Synopsis
27613 -symbol-info-address @var{symbol}
27616 Describe where @var{symbol} is stored.
27618 @subsubheading @value{GDBN} Command
27620 The corresponding @value{GDBN} command is @samp{info address}.
27622 @subsubheading Example
27626 @subheading The @code{-symbol-info-file} Command
27627 @findex -symbol-info-file
27629 @subsubheading Synopsis
27635 Show the file for the symbol.
27637 @subsubheading @value{GDBN} Command
27639 There's no equivalent @value{GDBN} command. @code{gdbtk} has
27640 @samp{gdb_find_file}.
27642 @subsubheading Example
27646 @subheading The @code{-symbol-info-function} Command
27647 @findex -symbol-info-function
27649 @subsubheading Synopsis
27652 -symbol-info-function
27655 Show which function the symbol lives in.
27657 @subsubheading @value{GDBN} Command
27659 @samp{gdb_get_function} in @code{gdbtk}.
27661 @subsubheading Example
27665 @subheading The @code{-symbol-info-line} Command
27666 @findex -symbol-info-line
27668 @subsubheading Synopsis
27674 Show the core addresses of the code for a source line.
27676 @subsubheading @value{GDBN} Command
27678 The corresponding @value{GDBN} command is @samp{info line}.
27679 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
27681 @subsubheading Example
27685 @subheading The @code{-symbol-info-symbol} Command
27686 @findex -symbol-info-symbol
27688 @subsubheading Synopsis
27691 -symbol-info-symbol @var{addr}
27694 Describe what symbol is at location @var{addr}.
27696 @subsubheading @value{GDBN} Command
27698 The corresponding @value{GDBN} command is @samp{info symbol}.
27700 @subsubheading Example
27704 @subheading The @code{-symbol-list-functions} Command
27705 @findex -symbol-list-functions
27707 @subsubheading Synopsis
27710 -symbol-list-functions
27713 List the functions in the executable.
27715 @subsubheading @value{GDBN} Command
27717 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
27718 @samp{gdb_search} in @code{gdbtk}.
27720 @subsubheading Example
27725 @subheading The @code{-symbol-list-lines} Command
27726 @findex -symbol-list-lines
27728 @subsubheading Synopsis
27731 -symbol-list-lines @var{filename}
27734 Print the list of lines that contain code and their associated program
27735 addresses for the given source filename. The entries are sorted in
27736 ascending PC order.
27738 @subsubheading @value{GDBN} Command
27740 There is no corresponding @value{GDBN} command.
27742 @subsubheading Example
27745 -symbol-list-lines basics.c
27746 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
27752 @subheading The @code{-symbol-list-types} Command
27753 @findex -symbol-list-types
27755 @subsubheading Synopsis
27761 List all the type names.
27763 @subsubheading @value{GDBN} Command
27765 The corresponding commands are @samp{info types} in @value{GDBN},
27766 @samp{gdb_search} in @code{gdbtk}.
27768 @subsubheading Example
27772 @subheading The @code{-symbol-list-variables} Command
27773 @findex -symbol-list-variables
27775 @subsubheading Synopsis
27778 -symbol-list-variables
27781 List all the global and static variable names.
27783 @subsubheading @value{GDBN} Command
27785 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
27787 @subsubheading Example
27791 @subheading The @code{-symbol-locate} Command
27792 @findex -symbol-locate
27794 @subsubheading Synopsis
27800 @subsubheading @value{GDBN} Command
27802 @samp{gdb_loc} in @code{gdbtk}.
27804 @subsubheading Example
27808 @subheading The @code{-symbol-type} Command
27809 @findex -symbol-type
27811 @subsubheading Synopsis
27814 -symbol-type @var{variable}
27817 Show type of @var{variable}.
27819 @subsubheading @value{GDBN} Command
27821 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
27822 @samp{gdb_obj_variable}.
27824 @subsubheading Example
27829 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27830 @node GDB/MI File Commands
27831 @section @sc{gdb/mi} File Commands
27833 This section describes the GDB/MI commands to specify executable file names
27834 and to read in and obtain symbol table information.
27836 @subheading The @code{-file-exec-and-symbols} Command
27837 @findex -file-exec-and-symbols
27839 @subsubheading Synopsis
27842 -file-exec-and-symbols @var{file}
27845 Specify the executable file to be debugged. This file is the one from
27846 which the symbol table is also read. If no file is specified, the
27847 command clears the executable and symbol information. If breakpoints
27848 are set when using this command with no arguments, @value{GDBN} will produce
27849 error messages. Otherwise, no output is produced, except a completion
27852 @subsubheading @value{GDBN} Command
27854 The corresponding @value{GDBN} command is @samp{file}.
27856 @subsubheading Example
27860 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
27866 @subheading The @code{-file-exec-file} Command
27867 @findex -file-exec-file
27869 @subsubheading Synopsis
27872 -file-exec-file @var{file}
27875 Specify the executable file to be debugged. Unlike
27876 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
27877 from this file. If used without argument, @value{GDBN} clears the information
27878 about the executable file. No output is produced, except a completion
27881 @subsubheading @value{GDBN} Command
27883 The corresponding @value{GDBN} command is @samp{exec-file}.
27885 @subsubheading Example
27889 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
27896 @subheading The @code{-file-list-exec-sections} Command
27897 @findex -file-list-exec-sections
27899 @subsubheading Synopsis
27902 -file-list-exec-sections
27905 List the sections of the current executable file.
27907 @subsubheading @value{GDBN} Command
27909 The @value{GDBN} command @samp{info file} shows, among the rest, the same
27910 information as this command. @code{gdbtk} has a corresponding command
27911 @samp{gdb_load_info}.
27913 @subsubheading Example
27918 @subheading The @code{-file-list-exec-source-file} Command
27919 @findex -file-list-exec-source-file
27921 @subsubheading Synopsis
27924 -file-list-exec-source-file
27927 List the line number, the current source file, and the absolute path
27928 to the current source file for the current executable. The macro
27929 information field has a value of @samp{1} or @samp{0} depending on
27930 whether or not the file includes preprocessor macro information.
27932 @subsubheading @value{GDBN} Command
27934 The @value{GDBN} equivalent is @samp{info source}
27936 @subsubheading Example
27940 123-file-list-exec-source-file
27941 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
27946 @subheading The @code{-file-list-exec-source-files} Command
27947 @findex -file-list-exec-source-files
27949 @subsubheading Synopsis
27952 -file-list-exec-source-files
27955 List the source files for the current executable.
27957 It will always output the filename, but only when @value{GDBN} can find
27958 the absolute file name of a source file, will it output the fullname.
27960 @subsubheading @value{GDBN} Command
27962 The @value{GDBN} equivalent is @samp{info sources}.
27963 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
27965 @subsubheading Example
27968 -file-list-exec-source-files
27970 @{file=foo.c,fullname=/home/foo.c@},
27971 @{file=/home/bar.c,fullname=/home/bar.c@},
27972 @{file=gdb_could_not_find_fullpath.c@}]
27977 @subheading The @code{-file-list-shared-libraries} Command
27978 @findex -file-list-shared-libraries
27980 @subsubheading Synopsis
27983 -file-list-shared-libraries
27986 List the shared libraries in the program.
27988 @subsubheading @value{GDBN} Command
27990 The corresponding @value{GDBN} command is @samp{info shared}.
27992 @subsubheading Example
27996 @subheading The @code{-file-list-symbol-files} Command
27997 @findex -file-list-symbol-files
27999 @subsubheading Synopsis
28002 -file-list-symbol-files
28007 @subsubheading @value{GDBN} Command
28009 The corresponding @value{GDBN} command is @samp{info file} (part of it).
28011 @subsubheading Example
28016 @subheading The @code{-file-symbol-file} Command
28017 @findex -file-symbol-file
28019 @subsubheading Synopsis
28022 -file-symbol-file @var{file}
28025 Read symbol table info from the specified @var{file} argument. When
28026 used without arguments, clears @value{GDBN}'s symbol table info. No output is
28027 produced, except for a completion notification.
28029 @subsubheading @value{GDBN} Command
28031 The corresponding @value{GDBN} command is @samp{symbol-file}.
28033 @subsubheading Example
28037 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
28043 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28044 @node GDB/MI Memory Overlay Commands
28045 @section @sc{gdb/mi} Memory Overlay Commands
28047 The memory overlay commands are not implemented.
28049 @c @subheading -overlay-auto
28051 @c @subheading -overlay-list-mapping-state
28053 @c @subheading -overlay-list-overlays
28055 @c @subheading -overlay-map
28057 @c @subheading -overlay-off
28059 @c @subheading -overlay-on
28061 @c @subheading -overlay-unmap
28063 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28064 @node GDB/MI Signal Handling Commands
28065 @section @sc{gdb/mi} Signal Handling Commands
28067 Signal handling commands are not implemented.
28069 @c @subheading -signal-handle
28071 @c @subheading -signal-list-handle-actions
28073 @c @subheading -signal-list-signal-types
28077 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28078 @node GDB/MI Target Manipulation
28079 @section @sc{gdb/mi} Target Manipulation Commands
28082 @subheading The @code{-target-attach} Command
28083 @findex -target-attach
28085 @subsubheading Synopsis
28088 -target-attach @var{pid} | @var{gid} | @var{file}
28091 Attach to a process @var{pid} or a file @var{file} outside of
28092 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
28093 group, the id previously returned by
28094 @samp{-list-thread-groups --available} must be used.
28096 @subsubheading @value{GDBN} Command
28098 The corresponding @value{GDBN} command is @samp{attach}.
28100 @subsubheading Example
28104 =thread-created,id="1"
28105 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
28111 @subheading The @code{-target-compare-sections} Command
28112 @findex -target-compare-sections
28114 @subsubheading Synopsis
28117 -target-compare-sections [ @var{section} ]
28120 Compare data of section @var{section} on target to the exec file.
28121 Without the argument, all sections are compared.
28123 @subsubheading @value{GDBN} Command
28125 The @value{GDBN} equivalent is @samp{compare-sections}.
28127 @subsubheading Example
28132 @subheading The @code{-target-detach} Command
28133 @findex -target-detach
28135 @subsubheading Synopsis
28138 -target-detach [ @var{pid} | @var{gid} ]
28141 Detach from the remote target which normally resumes its execution.
28142 If either @var{pid} or @var{gid} is specified, detaches from either
28143 the specified process, or specified thread group. There's no output.
28145 @subsubheading @value{GDBN} Command
28147 The corresponding @value{GDBN} command is @samp{detach}.
28149 @subsubheading Example
28159 @subheading The @code{-target-disconnect} Command
28160 @findex -target-disconnect
28162 @subsubheading Synopsis
28168 Disconnect from the remote target. There's no output and the target is
28169 generally not resumed.
28171 @subsubheading @value{GDBN} Command
28173 The corresponding @value{GDBN} command is @samp{disconnect}.
28175 @subsubheading Example
28185 @subheading The @code{-target-download} Command
28186 @findex -target-download
28188 @subsubheading Synopsis
28194 Loads the executable onto the remote target.
28195 It prints out an update message every half second, which includes the fields:
28199 The name of the section.
28201 The size of what has been sent so far for that section.
28203 The size of the section.
28205 The total size of what was sent so far (the current and the previous sections).
28207 The size of the overall executable to download.
28211 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
28212 @sc{gdb/mi} Output Syntax}).
28214 In addition, it prints the name and size of the sections, as they are
28215 downloaded. These messages include the following fields:
28219 The name of the section.
28221 The size of the section.
28223 The size of the overall executable to download.
28227 At the end, a summary is printed.
28229 @subsubheading @value{GDBN} Command
28231 The corresponding @value{GDBN} command is @samp{load}.
28233 @subsubheading Example
28235 Note: each status message appears on a single line. Here the messages
28236 have been broken down so that they can fit onto a page.
28241 +download,@{section=".text",section-size="6668",total-size="9880"@}
28242 +download,@{section=".text",section-sent="512",section-size="6668",
28243 total-sent="512",total-size="9880"@}
28244 +download,@{section=".text",section-sent="1024",section-size="6668",
28245 total-sent="1024",total-size="9880"@}
28246 +download,@{section=".text",section-sent="1536",section-size="6668",
28247 total-sent="1536",total-size="9880"@}
28248 +download,@{section=".text",section-sent="2048",section-size="6668",
28249 total-sent="2048",total-size="9880"@}
28250 +download,@{section=".text",section-sent="2560",section-size="6668",
28251 total-sent="2560",total-size="9880"@}
28252 +download,@{section=".text",section-sent="3072",section-size="6668",
28253 total-sent="3072",total-size="9880"@}
28254 +download,@{section=".text",section-sent="3584",section-size="6668",
28255 total-sent="3584",total-size="9880"@}
28256 +download,@{section=".text",section-sent="4096",section-size="6668",
28257 total-sent="4096",total-size="9880"@}
28258 +download,@{section=".text",section-sent="4608",section-size="6668",
28259 total-sent="4608",total-size="9880"@}
28260 +download,@{section=".text",section-sent="5120",section-size="6668",
28261 total-sent="5120",total-size="9880"@}
28262 +download,@{section=".text",section-sent="5632",section-size="6668",
28263 total-sent="5632",total-size="9880"@}
28264 +download,@{section=".text",section-sent="6144",section-size="6668",
28265 total-sent="6144",total-size="9880"@}
28266 +download,@{section=".text",section-sent="6656",section-size="6668",
28267 total-sent="6656",total-size="9880"@}
28268 +download,@{section=".init",section-size="28",total-size="9880"@}
28269 +download,@{section=".fini",section-size="28",total-size="9880"@}
28270 +download,@{section=".data",section-size="3156",total-size="9880"@}
28271 +download,@{section=".data",section-sent="512",section-size="3156",
28272 total-sent="7236",total-size="9880"@}
28273 +download,@{section=".data",section-sent="1024",section-size="3156",
28274 total-sent="7748",total-size="9880"@}
28275 +download,@{section=".data",section-sent="1536",section-size="3156",
28276 total-sent="8260",total-size="9880"@}
28277 +download,@{section=".data",section-sent="2048",section-size="3156",
28278 total-sent="8772",total-size="9880"@}
28279 +download,@{section=".data",section-sent="2560",section-size="3156",
28280 total-sent="9284",total-size="9880"@}
28281 +download,@{section=".data",section-sent="3072",section-size="3156",
28282 total-sent="9796",total-size="9880"@}
28283 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
28290 @subheading The @code{-target-exec-status} Command
28291 @findex -target-exec-status
28293 @subsubheading Synopsis
28296 -target-exec-status
28299 Provide information on the state of the target (whether it is running or
28300 not, for instance).
28302 @subsubheading @value{GDBN} Command
28304 There's no equivalent @value{GDBN} command.
28306 @subsubheading Example
28310 @subheading The @code{-target-list-available-targets} Command
28311 @findex -target-list-available-targets
28313 @subsubheading Synopsis
28316 -target-list-available-targets
28319 List the possible targets to connect to.
28321 @subsubheading @value{GDBN} Command
28323 The corresponding @value{GDBN} command is @samp{help target}.
28325 @subsubheading Example
28329 @subheading The @code{-target-list-current-targets} Command
28330 @findex -target-list-current-targets
28332 @subsubheading Synopsis
28335 -target-list-current-targets
28338 Describe the current target.
28340 @subsubheading @value{GDBN} Command
28342 The corresponding information is printed by @samp{info file} (among
28345 @subsubheading Example
28349 @subheading The @code{-target-list-parameters} Command
28350 @findex -target-list-parameters
28352 @subsubheading Synopsis
28355 -target-list-parameters
28361 @subsubheading @value{GDBN} Command
28365 @subsubheading Example
28369 @subheading The @code{-target-select} Command
28370 @findex -target-select
28372 @subsubheading Synopsis
28375 -target-select @var{type} @var{parameters @dots{}}
28378 Connect @value{GDBN} to the remote target. This command takes two args:
28382 The type of target, for instance @samp{remote}, etc.
28383 @item @var{parameters}
28384 Device names, host names and the like. @xref{Target Commands, ,
28385 Commands for Managing Targets}, for more details.
28388 The output is a connection notification, followed by the address at
28389 which the target program is, in the following form:
28392 ^connected,addr="@var{address}",func="@var{function name}",
28393 args=[@var{arg list}]
28396 @subsubheading @value{GDBN} Command
28398 The corresponding @value{GDBN} command is @samp{target}.
28400 @subsubheading Example
28404 -target-select remote /dev/ttya
28405 ^connected,addr="0xfe00a300",func="??",args=[]
28409 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28410 @node GDB/MI File Transfer Commands
28411 @section @sc{gdb/mi} File Transfer Commands
28414 @subheading The @code{-target-file-put} Command
28415 @findex -target-file-put
28417 @subsubheading Synopsis
28420 -target-file-put @var{hostfile} @var{targetfile}
28423 Copy file @var{hostfile} from the host system (the machine running
28424 @value{GDBN}) to @var{targetfile} on the target system.
28426 @subsubheading @value{GDBN} Command
28428 The corresponding @value{GDBN} command is @samp{remote put}.
28430 @subsubheading Example
28434 -target-file-put localfile remotefile
28440 @subheading The @code{-target-file-get} Command
28441 @findex -target-file-get
28443 @subsubheading Synopsis
28446 -target-file-get @var{targetfile} @var{hostfile}
28449 Copy file @var{targetfile} from the target system to @var{hostfile}
28450 on the host system.
28452 @subsubheading @value{GDBN} Command
28454 The corresponding @value{GDBN} command is @samp{remote get}.
28456 @subsubheading Example
28460 -target-file-get remotefile localfile
28466 @subheading The @code{-target-file-delete} Command
28467 @findex -target-file-delete
28469 @subsubheading Synopsis
28472 -target-file-delete @var{targetfile}
28475 Delete @var{targetfile} from the target system.
28477 @subsubheading @value{GDBN} Command
28479 The corresponding @value{GDBN} command is @samp{remote delete}.
28481 @subsubheading Example
28485 -target-file-delete remotefile
28491 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28492 @node GDB/MI Miscellaneous Commands
28493 @section Miscellaneous @sc{gdb/mi} Commands
28495 @c @subheading -gdb-complete
28497 @subheading The @code{-gdb-exit} Command
28500 @subsubheading Synopsis
28506 Exit @value{GDBN} immediately.
28508 @subsubheading @value{GDBN} Command
28510 Approximately corresponds to @samp{quit}.
28512 @subsubheading Example
28522 @subheading The @code{-exec-abort} Command
28523 @findex -exec-abort
28525 @subsubheading Synopsis
28531 Kill the inferior running program.
28533 @subsubheading @value{GDBN} Command
28535 The corresponding @value{GDBN} command is @samp{kill}.
28537 @subsubheading Example
28542 @subheading The @code{-gdb-set} Command
28545 @subsubheading Synopsis
28551 Set an internal @value{GDBN} variable.
28552 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
28554 @subsubheading @value{GDBN} Command
28556 The corresponding @value{GDBN} command is @samp{set}.
28558 @subsubheading Example
28568 @subheading The @code{-gdb-show} Command
28571 @subsubheading Synopsis
28577 Show the current value of a @value{GDBN} variable.
28579 @subsubheading @value{GDBN} Command
28581 The corresponding @value{GDBN} command is @samp{show}.
28583 @subsubheading Example
28592 @c @subheading -gdb-source
28595 @subheading The @code{-gdb-version} Command
28596 @findex -gdb-version
28598 @subsubheading Synopsis
28604 Show version information for @value{GDBN}. Used mostly in testing.
28606 @subsubheading @value{GDBN} Command
28608 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
28609 default shows this information when you start an interactive session.
28611 @subsubheading Example
28613 @c This example modifies the actual output from GDB to avoid overfull
28619 ~Copyright 2000 Free Software Foundation, Inc.
28620 ~GDB is free software, covered by the GNU General Public License, and
28621 ~you are welcome to change it and/or distribute copies of it under
28622 ~ certain conditions.
28623 ~Type "show copying" to see the conditions.
28624 ~There is absolutely no warranty for GDB. Type "show warranty" for
28626 ~This GDB was configured as
28627 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
28632 @subheading The @code{-list-features} Command
28633 @findex -list-features
28635 Returns a list of particular features of the MI protocol that
28636 this version of gdb implements. A feature can be a command,
28637 or a new field in an output of some command, or even an
28638 important bugfix. While a frontend can sometimes detect presence
28639 of a feature at runtime, it is easier to perform detection at debugger
28642 The command returns a list of strings, with each string naming an
28643 available feature. Each returned string is just a name, it does not
28644 have any internal structure. The list of possible feature names
28650 (gdb) -list-features
28651 ^done,result=["feature1","feature2"]
28654 The current list of features is:
28657 @item frozen-varobjs
28658 Indicates presence of the @code{-var-set-frozen} command, as well
28659 as possible presense of the @code{frozen} field in the output
28660 of @code{-varobj-create}.
28661 @item pending-breakpoints
28662 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
28664 Indicates presence of Python scripting support, Python-based
28665 pretty-printing commands, and possible presence of the
28666 @samp{display_hint} field in the output of @code{-var-list-children}
28668 Indicates presence of the @code{-thread-info} command.
28672 @subheading The @code{-list-target-features} Command
28673 @findex -list-target-features
28675 Returns a list of particular features that are supported by the
28676 target. Those features affect the permitted MI commands, but
28677 unlike the features reported by the @code{-list-features} command, the
28678 features depend on which target GDB is using at the moment. Whenever
28679 a target can change, due to commands such as @code{-target-select},
28680 @code{-target-attach} or @code{-exec-run}, the list of target features
28681 may change, and the frontend should obtain it again.
28685 (gdb) -list-features
28686 ^done,result=["async"]
28689 The current list of features is:
28693 Indicates that the target is capable of asynchronous command
28694 execution, which means that @value{GDBN} will accept further commands
28695 while the target is running.
28699 @subheading The @code{-list-thread-groups} Command
28700 @findex -list-thread-groups
28702 @subheading Synopsis
28705 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
28708 Lists thread groups (@pxref{Thread groups}). When a single thread
28709 group is passed as the argument, lists the children of that group.
28710 When several thread group are passed, lists information about those
28711 thread groups. Without any parameters, lists information about all
28712 top-level thread groups.
28714 Normally, thread groups that are being debugged are reported.
28715 With the @samp{--available} option, @value{GDBN} reports thread groups
28716 available on the target.
28718 The output of this command may have either a @samp{threads} result or
28719 a @samp{groups} result. The @samp{thread} result has a list of tuples
28720 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
28721 Information}). The @samp{groups} result has a list of tuples as value,
28722 each tuple describing a thread group. If top-level groups are
28723 requested (that is, no parameter is passed), or when several groups
28724 are passed, the output always has a @samp{groups} result. The format
28725 of the @samp{group} result is described below.
28727 To reduce the number of roundtrips it's possible to list thread groups
28728 together with their children, by passing the @samp{--recurse} option
28729 and the recursion depth. Presently, only recursion depth of 1 is
28730 permitted. If this option is present, then every reported thread group
28731 will also include its children, either as @samp{group} or
28732 @samp{threads} field.
28734 In general, any combination of option and parameters is permitted, with
28735 the following caveats:
28739 When a single thread group is passed, the output will typically
28740 be the @samp{threads} result. Because threads may not contain
28741 anything, the @samp{recurse} option will be ignored.
28744 When the @samp{--available} option is passed, limited information may
28745 be available. In particular, the list of threads of a process might
28746 be inaccessible. Further, specifying specific thread groups might
28747 not give any performance advantage over listing all thread groups.
28748 The frontend should assume that @samp{-list-thread-groups --available}
28749 is always an expensive operation and cache the results.
28753 The @samp{groups} result is a list of tuples, where each tuple may
28754 have the following fields:
28758 Identifier of the thread group. This field is always present.
28759 The identifier is an opaque string; frontends should not try to
28760 convert it to an integer, even though it might look like one.
28763 The type of the thread group. At present, only @samp{process} is a
28767 The target-specific process identifier. This field is only present
28768 for thread groups of type @samp{process} and only if the process exists.
28771 The number of children this thread group has. This field may be
28772 absent for an available thread group.
28775 This field has a list of tuples as value, each tuple describing a
28776 thread. It may be present if the @samp{--recurse} option is
28777 specified, and it's actually possible to obtain the threads.
28780 This field is a list of integers, each identifying a core that one
28781 thread of the group is running on. This field may be absent if
28782 such information is not available.
28785 The name of the executable file that corresponds to this thread group.
28786 The field is only present for thread groups of type @samp{process},
28787 and only if there is a corresponding executable file.
28791 @subheading Example
28795 -list-thread-groups
28796 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
28797 -list-thread-groups 17
28798 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
28799 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
28800 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
28801 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
28802 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
28803 -list-thread-groups --available
28804 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
28805 -list-thread-groups --available --recurse 1
28806 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
28807 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
28808 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
28809 -list-thread-groups --available --recurse 1 17 18
28810 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
28811 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
28812 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
28816 @subheading The @code{-add-inferior} Command
28817 @findex -add-inferior
28819 @subheading Synopsis
28825 Creates a new inferior (@pxref{Inferiors and Programs}). The created
28826 inferior is not associated with any executable. Such association may
28827 be established with the @samp{-file-exec-and-symbols} command
28828 (@pxref{GDB/MI File Commands}). The command response has a single
28829 field, @samp{thread-group}, whose value is the identifier of the
28830 thread group corresponding to the new inferior.
28832 @subheading Example
28837 ^done,thread-group="i3"
28840 @subheading The @code{-interpreter-exec} Command
28841 @findex -interpreter-exec
28843 @subheading Synopsis
28846 -interpreter-exec @var{interpreter} @var{command}
28848 @anchor{-interpreter-exec}
28850 Execute the specified @var{command} in the given @var{interpreter}.
28852 @subheading @value{GDBN} Command
28854 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
28856 @subheading Example
28860 -interpreter-exec console "break main"
28861 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
28862 &"During symbol reading, bad structure-type format.\n"
28863 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
28868 @subheading The @code{-inferior-tty-set} Command
28869 @findex -inferior-tty-set
28871 @subheading Synopsis
28874 -inferior-tty-set /dev/pts/1
28877 Set terminal for future runs of the program being debugged.
28879 @subheading @value{GDBN} Command
28881 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
28883 @subheading Example
28887 -inferior-tty-set /dev/pts/1
28892 @subheading The @code{-inferior-tty-show} Command
28893 @findex -inferior-tty-show
28895 @subheading Synopsis
28901 Show terminal for future runs of program being debugged.
28903 @subheading @value{GDBN} Command
28905 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
28907 @subheading Example
28911 -inferior-tty-set /dev/pts/1
28915 ^done,inferior_tty_terminal="/dev/pts/1"
28919 @subheading The @code{-enable-timings} Command
28920 @findex -enable-timings
28922 @subheading Synopsis
28925 -enable-timings [yes | no]
28928 Toggle the printing of the wallclock, user and system times for an MI
28929 command as a field in its output. This command is to help frontend
28930 developers optimize the performance of their code. No argument is
28931 equivalent to @samp{yes}.
28933 @subheading @value{GDBN} Command
28937 @subheading Example
28945 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28946 addr="0x080484ed",func="main",file="myprog.c",
28947 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
28948 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
28956 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
28957 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
28958 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
28959 fullname="/home/nickrob/myprog.c",line="73"@}
28964 @chapter @value{GDBN} Annotations
28966 This chapter describes annotations in @value{GDBN}. Annotations were
28967 designed to interface @value{GDBN} to graphical user interfaces or other
28968 similar programs which want to interact with @value{GDBN} at a
28969 relatively high level.
28971 The annotation mechanism has largely been superseded by @sc{gdb/mi}
28975 This is Edition @value{EDITION}, @value{DATE}.
28979 * Annotations Overview:: What annotations are; the general syntax.
28980 * Server Prefix:: Issuing a command without affecting user state.
28981 * Prompting:: Annotations marking @value{GDBN}'s need for input.
28982 * Errors:: Annotations for error messages.
28983 * Invalidation:: Some annotations describe things now invalid.
28984 * Annotations for Running::
28985 Whether the program is running, how it stopped, etc.
28986 * Source Annotations:: Annotations describing source code.
28989 @node Annotations Overview
28990 @section What is an Annotation?
28991 @cindex annotations
28993 Annotations start with a newline character, two @samp{control-z}
28994 characters, and the name of the annotation. If there is no additional
28995 information associated with this annotation, the name of the annotation
28996 is followed immediately by a newline. If there is additional
28997 information, the name of the annotation is followed by a space, the
28998 additional information, and a newline. The additional information
28999 cannot contain newline characters.
29001 Any output not beginning with a newline and two @samp{control-z}
29002 characters denotes literal output from @value{GDBN}. Currently there is
29003 no need for @value{GDBN} to output a newline followed by two
29004 @samp{control-z} characters, but if there was such a need, the
29005 annotations could be extended with an @samp{escape} annotation which
29006 means those three characters as output.
29008 The annotation @var{level}, which is specified using the
29009 @option{--annotate} command line option (@pxref{Mode Options}), controls
29010 how much information @value{GDBN} prints together with its prompt,
29011 values of expressions, source lines, and other types of output. Level 0
29012 is for no annotations, level 1 is for use when @value{GDBN} is run as a
29013 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
29014 for programs that control @value{GDBN}, and level 2 annotations have
29015 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
29016 Interface, annotate, GDB's Obsolete Annotations}).
29019 @kindex set annotate
29020 @item set annotate @var{level}
29021 The @value{GDBN} command @code{set annotate} sets the level of
29022 annotations to the specified @var{level}.
29024 @item show annotate
29025 @kindex show annotate
29026 Show the current annotation level.
29029 This chapter describes level 3 annotations.
29031 A simple example of starting up @value{GDBN} with annotations is:
29034 $ @kbd{gdb --annotate=3}
29036 Copyright 2003 Free Software Foundation, Inc.
29037 GDB is free software, covered by the GNU General Public License,
29038 and you are welcome to change it and/or distribute copies of it
29039 under certain conditions.
29040 Type "show copying" to see the conditions.
29041 There is absolutely no warranty for GDB. Type "show warranty"
29043 This GDB was configured as "i386-pc-linux-gnu"
29054 Here @samp{quit} is input to @value{GDBN}; the rest is output from
29055 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
29056 denotes a @samp{control-z} character) are annotations; the rest is
29057 output from @value{GDBN}.
29059 @node Server Prefix
29060 @section The Server Prefix
29061 @cindex server prefix
29063 If you prefix a command with @samp{server } then it will not affect
29064 the command history, nor will it affect @value{GDBN}'s notion of which
29065 command to repeat if @key{RET} is pressed on a line by itself. This
29066 means that commands can be run behind a user's back by a front-end in
29067 a transparent manner.
29069 The @code{server } prefix does not affect the recording of values into
29070 the value history; to print a value without recording it into the
29071 value history, use the @code{output} command instead of the
29072 @code{print} command.
29074 Using this prefix also disables confirmation requests
29075 (@pxref{confirmation requests}).
29078 @section Annotation for @value{GDBN} Input
29080 @cindex annotations for prompts
29081 When @value{GDBN} prompts for input, it annotates this fact so it is possible
29082 to know when to send output, when the output from a given command is
29085 Different kinds of input each have a different @dfn{input type}. Each
29086 input type has three annotations: a @code{pre-} annotation, which
29087 denotes the beginning of any prompt which is being output, a plain
29088 annotation, which denotes the end of the prompt, and then a @code{post-}
29089 annotation which denotes the end of any echo which may (or may not) be
29090 associated with the input. For example, the @code{prompt} input type
29091 features the following annotations:
29099 The input types are
29102 @findex pre-prompt annotation
29103 @findex prompt annotation
29104 @findex post-prompt annotation
29106 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
29108 @findex pre-commands annotation
29109 @findex commands annotation
29110 @findex post-commands annotation
29112 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
29113 command. The annotations are repeated for each command which is input.
29115 @findex pre-overload-choice annotation
29116 @findex overload-choice annotation
29117 @findex post-overload-choice annotation
29118 @item overload-choice
29119 When @value{GDBN} wants the user to select between various overloaded functions.
29121 @findex pre-query annotation
29122 @findex query annotation
29123 @findex post-query annotation
29125 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
29127 @findex pre-prompt-for-continue annotation
29128 @findex prompt-for-continue annotation
29129 @findex post-prompt-for-continue annotation
29130 @item prompt-for-continue
29131 When @value{GDBN} is asking the user to press return to continue. Note: Don't
29132 expect this to work well; instead use @code{set height 0} to disable
29133 prompting. This is because the counting of lines is buggy in the
29134 presence of annotations.
29139 @cindex annotations for errors, warnings and interrupts
29141 @findex quit annotation
29146 This annotation occurs right before @value{GDBN} responds to an interrupt.
29148 @findex error annotation
29153 This annotation occurs right before @value{GDBN} responds to an error.
29155 Quit and error annotations indicate that any annotations which @value{GDBN} was
29156 in the middle of may end abruptly. For example, if a
29157 @code{value-history-begin} annotation is followed by a @code{error}, one
29158 cannot expect to receive the matching @code{value-history-end}. One
29159 cannot expect not to receive it either, however; an error annotation
29160 does not necessarily mean that @value{GDBN} is immediately returning all the way
29163 @findex error-begin annotation
29164 A quit or error annotation may be preceded by
29170 Any output between that and the quit or error annotation is the error
29173 Warning messages are not yet annotated.
29174 @c If we want to change that, need to fix warning(), type_error(),
29175 @c range_error(), and possibly other places.
29178 @section Invalidation Notices
29180 @cindex annotations for invalidation messages
29181 The following annotations say that certain pieces of state may have
29185 @findex frames-invalid annotation
29186 @item ^Z^Zframes-invalid
29188 The frames (for example, output from the @code{backtrace} command) may
29191 @findex breakpoints-invalid annotation
29192 @item ^Z^Zbreakpoints-invalid
29194 The breakpoints may have changed. For example, the user just added or
29195 deleted a breakpoint.
29198 @node Annotations for Running
29199 @section Running the Program
29200 @cindex annotations for running programs
29202 @findex starting annotation
29203 @findex stopping annotation
29204 When the program starts executing due to a @value{GDBN} command such as
29205 @code{step} or @code{continue},
29211 is output. When the program stops,
29217 is output. Before the @code{stopped} annotation, a variety of
29218 annotations describe how the program stopped.
29221 @findex exited annotation
29222 @item ^Z^Zexited @var{exit-status}
29223 The program exited, and @var{exit-status} is the exit status (zero for
29224 successful exit, otherwise nonzero).
29226 @findex signalled annotation
29227 @findex signal-name annotation
29228 @findex signal-name-end annotation
29229 @findex signal-string annotation
29230 @findex signal-string-end annotation
29231 @item ^Z^Zsignalled
29232 The program exited with a signal. After the @code{^Z^Zsignalled}, the
29233 annotation continues:
29239 ^Z^Zsignal-name-end
29243 ^Z^Zsignal-string-end
29248 where @var{name} is the name of the signal, such as @code{SIGILL} or
29249 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
29250 as @code{Illegal Instruction} or @code{Segmentation fault}.
29251 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
29252 user's benefit and have no particular format.
29254 @findex signal annotation
29256 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
29257 just saying that the program received the signal, not that it was
29258 terminated with it.
29260 @findex breakpoint annotation
29261 @item ^Z^Zbreakpoint @var{number}
29262 The program hit breakpoint number @var{number}.
29264 @findex watchpoint annotation
29265 @item ^Z^Zwatchpoint @var{number}
29266 The program hit watchpoint number @var{number}.
29269 @node Source Annotations
29270 @section Displaying Source
29271 @cindex annotations for source display
29273 @findex source annotation
29274 The following annotation is used instead of displaying source code:
29277 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
29280 where @var{filename} is an absolute file name indicating which source
29281 file, @var{line} is the line number within that file (where 1 is the
29282 first line in the file), @var{character} is the character position
29283 within the file (where 0 is the first character in the file) (for most
29284 debug formats this will necessarily point to the beginning of a line),
29285 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
29286 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
29287 @var{addr} is the address in the target program associated with the
29288 source which is being displayed. @var{addr} is in the form @samp{0x}
29289 followed by one or more lowercase hex digits (note that this does not
29290 depend on the language).
29292 @node JIT Interface
29293 @chapter JIT Compilation Interface
29294 @cindex just-in-time compilation
29295 @cindex JIT compilation interface
29297 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
29298 interface. A JIT compiler is a program or library that generates native
29299 executable code at runtime and executes it, usually in order to achieve good
29300 performance while maintaining platform independence.
29302 Programs that use JIT compilation are normally difficult to debug because
29303 portions of their code are generated at runtime, instead of being loaded from
29304 object files, which is where @value{GDBN} normally finds the program's symbols
29305 and debug information. In order to debug programs that use JIT compilation,
29306 @value{GDBN} has an interface that allows the program to register in-memory
29307 symbol files with @value{GDBN} at runtime.
29309 If you are using @value{GDBN} to debug a program that uses this interface, then
29310 it should work transparently so long as you have not stripped the binary. If
29311 you are developing a JIT compiler, then the interface is documented in the rest
29312 of this chapter. At this time, the only known client of this interface is the
29315 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
29316 JIT compiler communicates with @value{GDBN} by writing data into a global
29317 variable and calling a fuction at a well-known symbol. When @value{GDBN}
29318 attaches, it reads a linked list of symbol files from the global variable to
29319 find existing code, and puts a breakpoint in the function so that it can find
29320 out about additional code.
29323 * Declarations:: Relevant C struct declarations
29324 * Registering Code:: Steps to register code
29325 * Unregistering Code:: Steps to unregister code
29329 @section JIT Declarations
29331 These are the relevant struct declarations that a C program should include to
29332 implement the interface:
29342 struct jit_code_entry
29344 struct jit_code_entry *next_entry;
29345 struct jit_code_entry *prev_entry;
29346 const char *symfile_addr;
29347 uint64_t symfile_size;
29350 struct jit_descriptor
29353 /* This type should be jit_actions_t, but we use uint32_t
29354 to be explicit about the bitwidth. */
29355 uint32_t action_flag;
29356 struct jit_code_entry *relevant_entry;
29357 struct jit_code_entry *first_entry;
29360 /* GDB puts a breakpoint in this function. */
29361 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
29363 /* Make sure to specify the version statically, because the
29364 debugger may check the version before we can set it. */
29365 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
29368 If the JIT is multi-threaded, then it is important that the JIT synchronize any
29369 modifications to this global data properly, which can easily be done by putting
29370 a global mutex around modifications to these structures.
29372 @node Registering Code
29373 @section Registering Code
29375 To register code with @value{GDBN}, the JIT should follow this protocol:
29379 Generate an object file in memory with symbols and other desired debug
29380 information. The file must include the virtual addresses of the sections.
29383 Create a code entry for the file, which gives the start and size of the symbol
29387 Add it to the linked list in the JIT descriptor.
29390 Point the relevant_entry field of the descriptor at the entry.
29393 Set @code{action_flag} to @code{JIT_REGISTER} and call
29394 @code{__jit_debug_register_code}.
29397 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
29398 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
29399 new code. However, the linked list must still be maintained in order to allow
29400 @value{GDBN} to attach to a running process and still find the symbol files.
29402 @node Unregistering Code
29403 @section Unregistering Code
29405 If code is freed, then the JIT should use the following protocol:
29409 Remove the code entry corresponding to the code from the linked list.
29412 Point the @code{relevant_entry} field of the descriptor at the code entry.
29415 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
29416 @code{__jit_debug_register_code}.
29419 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
29420 and the JIT will leak the memory used for the associated symbol files.
29423 @chapter Reporting Bugs in @value{GDBN}
29424 @cindex bugs in @value{GDBN}
29425 @cindex reporting bugs in @value{GDBN}
29427 Your bug reports play an essential role in making @value{GDBN} reliable.
29429 Reporting a bug may help you by bringing a solution to your problem, or it
29430 may not. But in any case the principal function of a bug report is to help
29431 the entire community by making the next version of @value{GDBN} work better. Bug
29432 reports are your contribution to the maintenance of @value{GDBN}.
29434 In order for a bug report to serve its purpose, you must include the
29435 information that enables us to fix the bug.
29438 * Bug Criteria:: Have you found a bug?
29439 * Bug Reporting:: How to report bugs
29443 @section Have You Found a Bug?
29444 @cindex bug criteria
29446 If you are not sure whether you have found a bug, here are some guidelines:
29449 @cindex fatal signal
29450 @cindex debugger crash
29451 @cindex crash of debugger
29453 If the debugger gets a fatal signal, for any input whatever, that is a
29454 @value{GDBN} bug. Reliable debuggers never crash.
29456 @cindex error on valid input
29458 If @value{GDBN} produces an error message for valid input, that is a
29459 bug. (Note that if you're cross debugging, the problem may also be
29460 somewhere in the connection to the target.)
29462 @cindex invalid input
29464 If @value{GDBN} does not produce an error message for invalid input,
29465 that is a bug. However, you should note that your idea of
29466 ``invalid input'' might be our idea of ``an extension'' or ``support
29467 for traditional practice''.
29470 If you are an experienced user of debugging tools, your suggestions
29471 for improvement of @value{GDBN} are welcome in any case.
29474 @node Bug Reporting
29475 @section How to Report Bugs
29476 @cindex bug reports
29477 @cindex @value{GDBN} bugs, reporting
29479 A number of companies and individuals offer support for @sc{gnu} products.
29480 If you obtained @value{GDBN} from a support organization, we recommend you
29481 contact that organization first.
29483 You can find contact information for many support companies and
29484 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
29486 @c should add a web page ref...
29489 @ifset BUGURL_DEFAULT
29490 In any event, we also recommend that you submit bug reports for
29491 @value{GDBN}. The preferred method is to submit them directly using
29492 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
29493 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
29496 @strong{Do not send bug reports to @samp{info-gdb}, or to
29497 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
29498 not want to receive bug reports. Those that do have arranged to receive
29501 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
29502 serves as a repeater. The mailing list and the newsgroup carry exactly
29503 the same messages. Often people think of posting bug reports to the
29504 newsgroup instead of mailing them. This appears to work, but it has one
29505 problem which can be crucial: a newsgroup posting often lacks a mail
29506 path back to the sender. Thus, if we need to ask for more information,
29507 we may be unable to reach you. For this reason, it is better to send
29508 bug reports to the mailing list.
29510 @ifclear BUGURL_DEFAULT
29511 In any event, we also recommend that you submit bug reports for
29512 @value{GDBN} to @value{BUGURL}.
29516 The fundamental principle of reporting bugs usefully is this:
29517 @strong{report all the facts}. If you are not sure whether to state a
29518 fact or leave it out, state it!
29520 Often people omit facts because they think they know what causes the
29521 problem and assume that some details do not matter. Thus, you might
29522 assume that the name of the variable you use in an example does not matter.
29523 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
29524 stray memory reference which happens to fetch from the location where that
29525 name is stored in memory; perhaps, if the name were different, the contents
29526 of that location would fool the debugger into doing the right thing despite
29527 the bug. Play it safe and give a specific, complete example. That is the
29528 easiest thing for you to do, and the most helpful.
29530 Keep in mind that the purpose of a bug report is to enable us to fix the
29531 bug. It may be that the bug has been reported previously, but neither
29532 you nor we can know that unless your bug report is complete and
29535 Sometimes people give a few sketchy facts and ask, ``Does this ring a
29536 bell?'' Those bug reports are useless, and we urge everyone to
29537 @emph{refuse to respond to them} except to chide the sender to report
29540 To enable us to fix the bug, you should include all these things:
29544 The version of @value{GDBN}. @value{GDBN} announces it if you start
29545 with no arguments; you can also print it at any time using @code{show
29548 Without this, we will not know whether there is any point in looking for
29549 the bug in the current version of @value{GDBN}.
29552 The type of machine you are using, and the operating system name and
29556 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
29557 ``@value{GCC}--2.8.1''.
29560 What compiler (and its version) was used to compile the program you are
29561 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
29562 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
29563 to get this information; for other compilers, see the documentation for
29567 The command arguments you gave the compiler to compile your example and
29568 observe the bug. For example, did you use @samp{-O}? To guarantee
29569 you will not omit something important, list them all. A copy of the
29570 Makefile (or the output from make) is sufficient.
29572 If we were to try to guess the arguments, we would probably guess wrong
29573 and then we might not encounter the bug.
29576 A complete input script, and all necessary source files, that will
29580 A description of what behavior you observe that you believe is
29581 incorrect. For example, ``It gets a fatal signal.''
29583 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
29584 will certainly notice it. But if the bug is incorrect output, we might
29585 not notice unless it is glaringly wrong. You might as well not give us
29586 a chance to make a mistake.
29588 Even if the problem you experience is a fatal signal, you should still
29589 say so explicitly. Suppose something strange is going on, such as, your
29590 copy of @value{GDBN} is out of synch, or you have encountered a bug in
29591 the C library on your system. (This has happened!) Your copy might
29592 crash and ours would not. If you told us to expect a crash, then when
29593 ours fails to crash, we would know that the bug was not happening for
29594 us. If you had not told us to expect a crash, then we would not be able
29595 to draw any conclusion from our observations.
29598 @cindex recording a session script
29599 To collect all this information, you can use a session recording program
29600 such as @command{script}, which is available on many Unix systems.
29601 Just run your @value{GDBN} session inside @command{script} and then
29602 include the @file{typescript} file with your bug report.
29604 Another way to record a @value{GDBN} session is to run @value{GDBN}
29605 inside Emacs and then save the entire buffer to a file.
29608 If you wish to suggest changes to the @value{GDBN} source, send us context
29609 diffs. If you even discuss something in the @value{GDBN} source, refer to
29610 it by context, not by line number.
29612 The line numbers in our development sources will not match those in your
29613 sources. Your line numbers would convey no useful information to us.
29617 Here are some things that are not necessary:
29621 A description of the envelope of the bug.
29623 Often people who encounter a bug spend a lot of time investigating
29624 which changes to the input file will make the bug go away and which
29625 changes will not affect it.
29627 This is often time consuming and not very useful, because the way we
29628 will find the bug is by running a single example under the debugger
29629 with breakpoints, not by pure deduction from a series of examples.
29630 We recommend that you save your time for something else.
29632 Of course, if you can find a simpler example to report @emph{instead}
29633 of the original one, that is a convenience for us. Errors in the
29634 output will be easier to spot, running under the debugger will take
29635 less time, and so on.
29637 However, simplification is not vital; if you do not want to do this,
29638 report the bug anyway and send us the entire test case you used.
29641 A patch for the bug.
29643 A patch for the bug does help us if it is a good one. But do not omit
29644 the necessary information, such as the test case, on the assumption that
29645 a patch is all we need. We might see problems with your patch and decide
29646 to fix the problem another way, or we might not understand it at all.
29648 Sometimes with a program as complicated as @value{GDBN} it is very hard to
29649 construct an example that will make the program follow a certain path
29650 through the code. If you do not send us the example, we will not be able
29651 to construct one, so we will not be able to verify that the bug is fixed.
29653 And if we cannot understand what bug you are trying to fix, or why your
29654 patch should be an improvement, we will not install it. A test case will
29655 help us to understand.
29658 A guess about what the bug is or what it depends on.
29660 Such guesses are usually wrong. Even we cannot guess right about such
29661 things without first using the debugger to find the facts.
29664 @c The readline documentation is distributed with the readline code
29665 @c and consists of the two following files:
29667 @c inc-hist.texinfo
29668 @c Use -I with makeinfo to point to the appropriate directory,
29669 @c environment var TEXINPUTS with TeX.
29670 @include rluser.texi
29671 @include inc-hist.texinfo
29674 @node Formatting Documentation
29675 @appendix Formatting Documentation
29677 @cindex @value{GDBN} reference card
29678 @cindex reference card
29679 The @value{GDBN} 4 release includes an already-formatted reference card, ready
29680 for printing with PostScript or Ghostscript, in the @file{gdb}
29681 subdirectory of the main source directory@footnote{In
29682 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
29683 release.}. If you can use PostScript or Ghostscript with your printer,
29684 you can print the reference card immediately with @file{refcard.ps}.
29686 The release also includes the source for the reference card. You
29687 can format it, using @TeX{}, by typing:
29693 The @value{GDBN} reference card is designed to print in @dfn{landscape}
29694 mode on US ``letter'' size paper;
29695 that is, on a sheet 11 inches wide by 8.5 inches
29696 high. You will need to specify this form of printing as an option to
29697 your @sc{dvi} output program.
29699 @cindex documentation
29701 All the documentation for @value{GDBN} comes as part of the machine-readable
29702 distribution. The documentation is written in Texinfo format, which is
29703 a documentation system that uses a single source file to produce both
29704 on-line information and a printed manual. You can use one of the Info
29705 formatting commands to create the on-line version of the documentation
29706 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
29708 @value{GDBN} includes an already formatted copy of the on-line Info
29709 version of this manual in the @file{gdb} subdirectory. The main Info
29710 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
29711 subordinate files matching @samp{gdb.info*} in the same directory. If
29712 necessary, you can print out these files, or read them with any editor;
29713 but they are easier to read using the @code{info} subsystem in @sc{gnu}
29714 Emacs or the standalone @code{info} program, available as part of the
29715 @sc{gnu} Texinfo distribution.
29717 If you want to format these Info files yourself, you need one of the
29718 Info formatting programs, such as @code{texinfo-format-buffer} or
29721 If you have @code{makeinfo} installed, and are in the top level
29722 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
29723 version @value{GDBVN}), you can make the Info file by typing:
29730 If you want to typeset and print copies of this manual, you need @TeX{},
29731 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
29732 Texinfo definitions file.
29734 @TeX{} is a typesetting program; it does not print files directly, but
29735 produces output files called @sc{dvi} files. To print a typeset
29736 document, you need a program to print @sc{dvi} files. If your system
29737 has @TeX{} installed, chances are it has such a program. The precise
29738 command to use depends on your system; @kbd{lpr -d} is common; another
29739 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
29740 require a file name without any extension or a @samp{.dvi} extension.
29742 @TeX{} also requires a macro definitions file called
29743 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
29744 written in Texinfo format. On its own, @TeX{} cannot either read or
29745 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
29746 and is located in the @file{gdb-@var{version-number}/texinfo}
29749 If you have @TeX{} and a @sc{dvi} printer program installed, you can
29750 typeset and print this manual. First switch to the @file{gdb}
29751 subdirectory of the main source directory (for example, to
29752 @file{gdb-@value{GDBVN}/gdb}) and type:
29758 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
29760 @node Installing GDB
29761 @appendix Installing @value{GDBN}
29762 @cindex installation
29765 * Requirements:: Requirements for building @value{GDBN}
29766 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
29767 * Separate Objdir:: Compiling @value{GDBN} in another directory
29768 * Config Names:: Specifying names for hosts and targets
29769 * Configure Options:: Summary of options for configure
29770 * System-wide configuration:: Having a system-wide init file
29774 @section Requirements for Building @value{GDBN}
29775 @cindex building @value{GDBN}, requirements for
29777 Building @value{GDBN} requires various tools and packages to be available.
29778 Other packages will be used only if they are found.
29780 @heading Tools/Packages Necessary for Building @value{GDBN}
29782 @item ISO C90 compiler
29783 @value{GDBN} is written in ISO C90. It should be buildable with any
29784 working C90 compiler, e.g.@: GCC.
29788 @heading Tools/Packages Optional for Building @value{GDBN}
29792 @value{GDBN} can use the Expat XML parsing library. This library may be
29793 included with your operating system distribution; if it is not, you
29794 can get the latest version from @url{http://expat.sourceforge.net}.
29795 The @file{configure} script will search for this library in several
29796 standard locations; if it is installed in an unusual path, you can
29797 use the @option{--with-libexpat-prefix} option to specify its location.
29803 Remote protocol memory maps (@pxref{Memory Map Format})
29805 Target descriptions (@pxref{Target Descriptions})
29807 Remote shared library lists (@pxref{Library List Format})
29809 MS-Windows shared libraries (@pxref{Shared Libraries})
29813 @cindex compressed debug sections
29814 @value{GDBN} will use the @samp{zlib} library, if available, to read
29815 compressed debug sections. Some linkers, such as GNU gold, are capable
29816 of producing binaries with compressed debug sections. If @value{GDBN}
29817 is compiled with @samp{zlib}, it will be able to read the debug
29818 information in such binaries.
29820 The @samp{zlib} library is likely included with your operating system
29821 distribution; if it is not, you can get the latest version from
29822 @url{http://zlib.net}.
29825 @value{GDBN}'s features related to character sets (@pxref{Character
29826 Sets}) require a functioning @code{iconv} implementation. If you are
29827 on a GNU system, then this is provided by the GNU C Library. Some
29828 other systems also provide a working @code{iconv}.
29830 On systems with @code{iconv}, you can install GNU Libiconv. If you
29831 have previously installed Libiconv, you can use the
29832 @option{--with-libiconv-prefix} option to configure.
29834 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
29835 arrange to build Libiconv if a directory named @file{libiconv} appears
29836 in the top-most source directory. If Libiconv is built this way, and
29837 if the operating system does not provide a suitable @code{iconv}
29838 implementation, then the just-built library will automatically be used
29839 by @value{GDBN}. One easy way to set this up is to download GNU
29840 Libiconv, unpack it, and then rename the directory holding the
29841 Libiconv source code to @samp{libiconv}.
29844 @node Running Configure
29845 @section Invoking the @value{GDBN} @file{configure} Script
29846 @cindex configuring @value{GDBN}
29847 @value{GDBN} comes with a @file{configure} script that automates the process
29848 of preparing @value{GDBN} for installation; you can then use @code{make} to
29849 build the @code{gdb} program.
29851 @c irrelevant in info file; it's as current as the code it lives with.
29852 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
29853 look at the @file{README} file in the sources; we may have improved the
29854 installation procedures since publishing this manual.}
29857 The @value{GDBN} distribution includes all the source code you need for
29858 @value{GDBN} in a single directory, whose name is usually composed by
29859 appending the version number to @samp{gdb}.
29861 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
29862 @file{gdb-@value{GDBVN}} directory. That directory contains:
29865 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
29866 script for configuring @value{GDBN} and all its supporting libraries
29868 @item gdb-@value{GDBVN}/gdb
29869 the source specific to @value{GDBN} itself
29871 @item gdb-@value{GDBVN}/bfd
29872 source for the Binary File Descriptor library
29874 @item gdb-@value{GDBVN}/include
29875 @sc{gnu} include files
29877 @item gdb-@value{GDBVN}/libiberty
29878 source for the @samp{-liberty} free software library
29880 @item gdb-@value{GDBVN}/opcodes
29881 source for the library of opcode tables and disassemblers
29883 @item gdb-@value{GDBVN}/readline
29884 source for the @sc{gnu} command-line interface
29886 @item gdb-@value{GDBVN}/glob
29887 source for the @sc{gnu} filename pattern-matching subroutine
29889 @item gdb-@value{GDBVN}/mmalloc
29890 source for the @sc{gnu} memory-mapped malloc package
29893 The simplest way to configure and build @value{GDBN} is to run @file{configure}
29894 from the @file{gdb-@var{version-number}} source directory, which in
29895 this example is the @file{gdb-@value{GDBVN}} directory.
29897 First switch to the @file{gdb-@var{version-number}} source directory
29898 if you are not already in it; then run @file{configure}. Pass the
29899 identifier for the platform on which @value{GDBN} will run as an
29905 cd gdb-@value{GDBVN}
29906 ./configure @var{host}
29911 where @var{host} is an identifier such as @samp{sun4} or
29912 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
29913 (You can often leave off @var{host}; @file{configure} tries to guess the
29914 correct value by examining your system.)
29916 Running @samp{configure @var{host}} and then running @code{make} builds the
29917 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
29918 libraries, then @code{gdb} itself. The configured source files, and the
29919 binaries, are left in the corresponding source directories.
29922 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
29923 system does not recognize this automatically when you run a different
29924 shell, you may need to run @code{sh} on it explicitly:
29927 sh configure @var{host}
29930 If you run @file{configure} from a directory that contains source
29931 directories for multiple libraries or programs, such as the
29932 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
29934 creates configuration files for every directory level underneath (unless
29935 you tell it not to, with the @samp{--norecursion} option).
29937 You should run the @file{configure} script from the top directory in the
29938 source tree, the @file{gdb-@var{version-number}} directory. If you run
29939 @file{configure} from one of the subdirectories, you will configure only
29940 that subdirectory. That is usually not what you want. In particular,
29941 if you run the first @file{configure} from the @file{gdb} subdirectory
29942 of the @file{gdb-@var{version-number}} directory, you will omit the
29943 configuration of @file{bfd}, @file{readline}, and other sibling
29944 directories of the @file{gdb} subdirectory. This leads to build errors
29945 about missing include files such as @file{bfd/bfd.h}.
29947 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
29948 However, you should make sure that the shell on your path (named by
29949 the @samp{SHELL} environment variable) is publicly readable. Remember
29950 that @value{GDBN} uses the shell to start your program---some systems refuse to
29951 let @value{GDBN} debug child processes whose programs are not readable.
29953 @node Separate Objdir
29954 @section Compiling @value{GDBN} in Another Directory
29956 If you want to run @value{GDBN} versions for several host or target machines,
29957 you need a different @code{gdb} compiled for each combination of
29958 host and target. @file{configure} is designed to make this easy by
29959 allowing you to generate each configuration in a separate subdirectory,
29960 rather than in the source directory. If your @code{make} program
29961 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
29962 @code{make} in each of these directories builds the @code{gdb}
29963 program specified there.
29965 To build @code{gdb} in a separate directory, run @file{configure}
29966 with the @samp{--srcdir} option to specify where to find the source.
29967 (You also need to specify a path to find @file{configure}
29968 itself from your working directory. If the path to @file{configure}
29969 would be the same as the argument to @samp{--srcdir}, you can leave out
29970 the @samp{--srcdir} option; it is assumed.)
29972 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
29973 separate directory for a Sun 4 like this:
29977 cd gdb-@value{GDBVN}
29980 ../gdb-@value{GDBVN}/configure sun4
29985 When @file{configure} builds a configuration using a remote source
29986 directory, it creates a tree for the binaries with the same structure
29987 (and using the same names) as the tree under the source directory. In
29988 the example, you'd find the Sun 4 library @file{libiberty.a} in the
29989 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
29990 @file{gdb-sun4/gdb}.
29992 Make sure that your path to the @file{configure} script has just one
29993 instance of @file{gdb} in it. If your path to @file{configure} looks
29994 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
29995 one subdirectory of @value{GDBN}, not the whole package. This leads to
29996 build errors about missing include files such as @file{bfd/bfd.h}.
29998 One popular reason to build several @value{GDBN} configurations in separate
29999 directories is to configure @value{GDBN} for cross-compiling (where
30000 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
30001 programs that run on another machine---the @dfn{target}).
30002 You specify a cross-debugging target by
30003 giving the @samp{--target=@var{target}} option to @file{configure}.
30005 When you run @code{make} to build a program or library, you must run
30006 it in a configured directory---whatever directory you were in when you
30007 called @file{configure} (or one of its subdirectories).
30009 The @code{Makefile} that @file{configure} generates in each source
30010 directory also runs recursively. If you type @code{make} in a source
30011 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
30012 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
30013 will build all the required libraries, and then build GDB.
30015 When you have multiple hosts or targets configured in separate
30016 directories, you can run @code{make} on them in parallel (for example,
30017 if they are NFS-mounted on each of the hosts); they will not interfere
30021 @section Specifying Names for Hosts and Targets
30023 The specifications used for hosts and targets in the @file{configure}
30024 script are based on a three-part naming scheme, but some short predefined
30025 aliases are also supported. The full naming scheme encodes three pieces
30026 of information in the following pattern:
30029 @var{architecture}-@var{vendor}-@var{os}
30032 For example, you can use the alias @code{sun4} as a @var{host} argument,
30033 or as the value for @var{target} in a @code{--target=@var{target}}
30034 option. The equivalent full name is @samp{sparc-sun-sunos4}.
30036 The @file{configure} script accompanying @value{GDBN} does not provide
30037 any query facility to list all supported host and target names or
30038 aliases. @file{configure} calls the Bourne shell script
30039 @code{config.sub} to map abbreviations to full names; you can read the
30040 script, if you wish, or you can use it to test your guesses on
30041 abbreviations---for example:
30044 % sh config.sub i386-linux
30046 % sh config.sub alpha-linux
30047 alpha-unknown-linux-gnu
30048 % sh config.sub hp9k700
30050 % sh config.sub sun4
30051 sparc-sun-sunos4.1.1
30052 % sh config.sub sun3
30053 m68k-sun-sunos4.1.1
30054 % sh config.sub i986v
30055 Invalid configuration `i986v': machine `i986v' not recognized
30059 @code{config.sub} is also distributed in the @value{GDBN} source
30060 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
30062 @node Configure Options
30063 @section @file{configure} Options
30065 Here is a summary of the @file{configure} options and arguments that
30066 are most often useful for building @value{GDBN}. @file{configure} also has
30067 several other options not listed here. @inforef{What Configure
30068 Does,,configure.info}, for a full explanation of @file{configure}.
30071 configure @r{[}--help@r{]}
30072 @r{[}--prefix=@var{dir}@r{]}
30073 @r{[}--exec-prefix=@var{dir}@r{]}
30074 @r{[}--srcdir=@var{dirname}@r{]}
30075 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
30076 @r{[}--target=@var{target}@r{]}
30081 You may introduce options with a single @samp{-} rather than
30082 @samp{--} if you prefer; but you may abbreviate option names if you use
30087 Display a quick summary of how to invoke @file{configure}.
30089 @item --prefix=@var{dir}
30090 Configure the source to install programs and files under directory
30093 @item --exec-prefix=@var{dir}
30094 Configure the source to install programs under directory
30097 @c avoid splitting the warning from the explanation:
30099 @item --srcdir=@var{dirname}
30100 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
30101 @code{make} that implements the @code{VPATH} feature.}@*
30102 Use this option to make configurations in directories separate from the
30103 @value{GDBN} source directories. Among other things, you can use this to
30104 build (or maintain) several configurations simultaneously, in separate
30105 directories. @file{configure} writes configuration-specific files in
30106 the current directory, but arranges for them to use the source in the
30107 directory @var{dirname}. @file{configure} creates directories under
30108 the working directory in parallel to the source directories below
30111 @item --norecursion
30112 Configure only the directory level where @file{configure} is executed; do not
30113 propagate configuration to subdirectories.
30115 @item --target=@var{target}
30116 Configure @value{GDBN} for cross-debugging programs running on the specified
30117 @var{target}. Without this option, @value{GDBN} is configured to debug
30118 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
30120 There is no convenient way to generate a list of all available targets.
30122 @item @var{host} @dots{}
30123 Configure @value{GDBN} to run on the specified @var{host}.
30125 There is no convenient way to generate a list of all available hosts.
30128 There are many other options available as well, but they are generally
30129 needed for special purposes only.
30131 @node System-wide configuration
30132 @section System-wide configuration and settings
30133 @cindex system-wide init file
30135 @value{GDBN} can be configured to have a system-wide init file;
30136 this file will be read and executed at startup (@pxref{Startup, , What
30137 @value{GDBN} does during startup}).
30139 Here is the corresponding configure option:
30142 @item --with-system-gdbinit=@var{file}
30143 Specify that the default location of the system-wide init file is
30147 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
30148 it may be subject to relocation. Two possible cases:
30152 If the default location of this init file contains @file{$prefix},
30153 it will be subject to relocation. Suppose that the configure options
30154 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
30155 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
30156 init file is looked for as @file{$install/etc/gdbinit} instead of
30157 @file{$prefix/etc/gdbinit}.
30160 By contrast, if the default location does not contain the prefix,
30161 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
30162 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
30163 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
30164 wherever @value{GDBN} is installed.
30167 @node Maintenance Commands
30168 @appendix Maintenance Commands
30169 @cindex maintenance commands
30170 @cindex internal commands
30172 In addition to commands intended for @value{GDBN} users, @value{GDBN}
30173 includes a number of commands intended for @value{GDBN} developers,
30174 that are not documented elsewhere in this manual. These commands are
30175 provided here for reference. (For commands that turn on debugging
30176 messages, see @ref{Debugging Output}.)
30179 @kindex maint agent
30180 @kindex maint agent-eval
30181 @item maint agent @var{expression}
30182 @itemx maint agent-eval @var{expression}
30183 Translate the given @var{expression} into remote agent bytecodes.
30184 This command is useful for debugging the Agent Expression mechanism
30185 (@pxref{Agent Expressions}). The @samp{agent} version produces an
30186 expression useful for data collection, such as by tracepoints, while
30187 @samp{maint agent-eval} produces an expression that evaluates directly
30188 to a result. For instance, a collection expression for @code{globa +
30189 globb} will include bytecodes to record four bytes of memory at each
30190 of the addresses of @code{globa} and @code{globb}, while discarding
30191 the result of the addition, while an evaluation expression will do the
30192 addition and return the sum.
30194 @kindex maint info breakpoints
30195 @item @anchor{maint info breakpoints}maint info breakpoints
30196 Using the same format as @samp{info breakpoints}, display both the
30197 breakpoints you've set explicitly, and those @value{GDBN} is using for
30198 internal purposes. Internal breakpoints are shown with negative
30199 breakpoint numbers. The type column identifies what kind of breakpoint
30204 Normal, explicitly set breakpoint.
30207 Normal, explicitly set watchpoint.
30210 Internal breakpoint, used to handle correctly stepping through
30211 @code{longjmp} calls.
30213 @item longjmp resume
30214 Internal breakpoint at the target of a @code{longjmp}.
30217 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
30220 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
30223 Shared library events.
30227 @kindex set displaced-stepping
30228 @kindex show displaced-stepping
30229 @cindex displaced stepping support
30230 @cindex out-of-line single-stepping
30231 @item set displaced-stepping
30232 @itemx show displaced-stepping
30233 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
30234 if the target supports it. Displaced stepping is a way to single-step
30235 over breakpoints without removing them from the inferior, by executing
30236 an out-of-line copy of the instruction that was originally at the
30237 breakpoint location. It is also known as out-of-line single-stepping.
30240 @item set displaced-stepping on
30241 If the target architecture supports it, @value{GDBN} will use
30242 displaced stepping to step over breakpoints.
30244 @item set displaced-stepping off
30245 @value{GDBN} will not use displaced stepping to step over breakpoints,
30246 even if such is supported by the target architecture.
30248 @cindex non-stop mode, and @samp{set displaced-stepping}
30249 @item set displaced-stepping auto
30250 This is the default mode. @value{GDBN} will use displaced stepping
30251 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
30252 architecture supports displaced stepping.
30255 @kindex maint check-symtabs
30256 @item maint check-symtabs
30257 Check the consistency of psymtabs and symtabs.
30259 @kindex maint cplus first_component
30260 @item maint cplus first_component @var{name}
30261 Print the first C@t{++} class/namespace component of @var{name}.
30263 @kindex maint cplus namespace
30264 @item maint cplus namespace
30265 Print the list of possible C@t{++} namespaces.
30267 @kindex maint demangle
30268 @item maint demangle @var{name}
30269 Demangle a C@t{++} or Objective-C mangled @var{name}.
30271 @kindex maint deprecate
30272 @kindex maint undeprecate
30273 @cindex deprecated commands
30274 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
30275 @itemx maint undeprecate @var{command}
30276 Deprecate or undeprecate the named @var{command}. Deprecated commands
30277 cause @value{GDBN} to issue a warning when you use them. The optional
30278 argument @var{replacement} says which newer command should be used in
30279 favor of the deprecated one; if it is given, @value{GDBN} will mention
30280 the replacement as part of the warning.
30282 @kindex maint dump-me
30283 @item maint dump-me
30284 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
30285 Cause a fatal signal in the debugger and force it to dump its core.
30286 This is supported only on systems which support aborting a program
30287 with the @code{SIGQUIT} signal.
30289 @kindex maint internal-error
30290 @kindex maint internal-warning
30291 @item maint internal-error @r{[}@var{message-text}@r{]}
30292 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
30293 Cause @value{GDBN} to call the internal function @code{internal_error}
30294 or @code{internal_warning} and hence behave as though an internal error
30295 or internal warning has been detected. In addition to reporting the
30296 internal problem, these functions give the user the opportunity to
30297 either quit @value{GDBN} or create a core file of the current
30298 @value{GDBN} session.
30300 These commands take an optional parameter @var{message-text} that is
30301 used as the text of the error or warning message.
30303 Here's an example of using @code{internal-error}:
30306 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
30307 @dots{}/maint.c:121: internal-error: testing, 1, 2
30308 A problem internal to GDB has been detected. Further
30309 debugging may prove unreliable.
30310 Quit this debugging session? (y or n) @kbd{n}
30311 Create a core file? (y or n) @kbd{n}
30315 @cindex @value{GDBN} internal error
30316 @cindex internal errors, control of @value{GDBN} behavior
30318 @kindex maint set internal-error
30319 @kindex maint show internal-error
30320 @kindex maint set internal-warning
30321 @kindex maint show internal-warning
30322 @item maint set internal-error @var{action} [ask|yes|no]
30323 @itemx maint show internal-error @var{action}
30324 @itemx maint set internal-warning @var{action} [ask|yes|no]
30325 @itemx maint show internal-warning @var{action}
30326 When @value{GDBN} reports an internal problem (error or warning) it
30327 gives the user the opportunity to both quit @value{GDBN} and create a
30328 core file of the current @value{GDBN} session. These commands let you
30329 override the default behaviour for each particular @var{action},
30330 described in the table below.
30334 You can specify that @value{GDBN} should always (yes) or never (no)
30335 quit. The default is to ask the user what to do.
30338 You can specify that @value{GDBN} should always (yes) or never (no)
30339 create a core file. The default is to ask the user what to do.
30342 @kindex maint packet
30343 @item maint packet @var{text}
30344 If @value{GDBN} is talking to an inferior via the serial protocol,
30345 then this command sends the string @var{text} to the inferior, and
30346 displays the response packet. @value{GDBN} supplies the initial
30347 @samp{$} character, the terminating @samp{#} character, and the
30350 @kindex maint print architecture
30351 @item maint print architecture @r{[}@var{file}@r{]}
30352 Print the entire architecture configuration. The optional argument
30353 @var{file} names the file where the output goes.
30355 @kindex maint print c-tdesc
30356 @item maint print c-tdesc
30357 Print the current target description (@pxref{Target Descriptions}) as
30358 a C source file. The created source file can be used in @value{GDBN}
30359 when an XML parser is not available to parse the description.
30361 @kindex maint print dummy-frames
30362 @item maint print dummy-frames
30363 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
30366 (@value{GDBP}) @kbd{b add}
30368 (@value{GDBP}) @kbd{print add(2,3)}
30369 Breakpoint 2, add (a=2, b=3) at @dots{}
30371 The program being debugged stopped while in a function called from GDB.
30373 (@value{GDBP}) @kbd{maint print dummy-frames}
30374 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
30375 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
30376 call_lo=0x01014000 call_hi=0x01014001
30380 Takes an optional file parameter.
30382 @kindex maint print registers
30383 @kindex maint print raw-registers
30384 @kindex maint print cooked-registers
30385 @kindex maint print register-groups
30386 @item maint print registers @r{[}@var{file}@r{]}
30387 @itemx maint print raw-registers @r{[}@var{file}@r{]}
30388 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
30389 @itemx maint print register-groups @r{[}@var{file}@r{]}
30390 Print @value{GDBN}'s internal register data structures.
30392 The command @code{maint print raw-registers} includes the contents of
30393 the raw register cache; the command @code{maint print cooked-registers}
30394 includes the (cooked) value of all registers, including registers which
30395 aren't available on the target nor visible to user; and the
30396 command @code{maint print register-groups} includes the groups that each
30397 register is a member of. @xref{Registers,, Registers, gdbint,
30398 @value{GDBN} Internals}.
30400 These commands take an optional parameter, a file name to which to
30401 write the information.
30403 @kindex maint print reggroups
30404 @item maint print reggroups @r{[}@var{file}@r{]}
30405 Print @value{GDBN}'s internal register group data structures. The
30406 optional argument @var{file} tells to what file to write the
30409 The register groups info looks like this:
30412 (@value{GDBP}) @kbd{maint print reggroups}
30425 This command forces @value{GDBN} to flush its internal register cache.
30427 @kindex maint print objfiles
30428 @cindex info for known object files
30429 @item maint print objfiles
30430 Print a dump of all known object files. For each object file, this
30431 command prints its name, address in memory, and all of its psymtabs
30434 @kindex maint print section-scripts
30435 @cindex info for known .debug_gdb_scripts-loaded scripts
30436 @item maint print section-scripts [@var{regexp}]
30437 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
30438 If @var{regexp} is specified, only print scripts loaded by object files
30439 matching @var{regexp}.
30440 For each script, this command prints its name as specified in the objfile,
30441 and the full path if known.
30442 @xref{.debug_gdb_scripts section}.
30444 @kindex maint print statistics
30445 @cindex bcache statistics
30446 @item maint print statistics
30447 This command prints, for each object file in the program, various data
30448 about that object file followed by the byte cache (@dfn{bcache})
30449 statistics for the object file. The objfile data includes the number
30450 of minimal, partial, full, and stabs symbols, the number of types
30451 defined by the objfile, the number of as yet unexpanded psym tables,
30452 the number of line tables and string tables, and the amount of memory
30453 used by the various tables. The bcache statistics include the counts,
30454 sizes, and counts of duplicates of all and unique objects, max,
30455 average, and median entry size, total memory used and its overhead and
30456 savings, and various measures of the hash table size and chain
30459 @kindex maint print target-stack
30460 @cindex target stack description
30461 @item maint print target-stack
30462 A @dfn{target} is an interface between the debugger and a particular
30463 kind of file or process. Targets can be stacked in @dfn{strata},
30464 so that more than one target can potentially respond to a request.
30465 In particular, memory accesses will walk down the stack of targets
30466 until they find a target that is interested in handling that particular
30469 This command prints a short description of each layer that was pushed on
30470 the @dfn{target stack}, starting from the top layer down to the bottom one.
30472 @kindex maint print type
30473 @cindex type chain of a data type
30474 @item maint print type @var{expr}
30475 Print the type chain for a type specified by @var{expr}. The argument
30476 can be either a type name or a symbol. If it is a symbol, the type of
30477 that symbol is described. The type chain produced by this command is
30478 a recursive definition of the data type as stored in @value{GDBN}'s
30479 data structures, including its flags and contained types.
30481 @kindex maint set dwarf2 always-disassemble
30482 @kindex maint show dwarf2 always-disassemble
30483 @item maint set dwarf2 always-disassemble
30484 @item maint show dwarf2 always-disassemble
30485 Control the behavior of @code{info address} when using DWARF debugging
30488 The default is @code{off}, which means that @value{GDBN} should try to
30489 describe a variable's location in an easily readable format. When
30490 @code{on}, @value{GDBN} will instead display the DWARF location
30491 expression in an assembly-like format. Note that some locations are
30492 too complex for @value{GDBN} to describe simply; in this case you will
30493 always see the disassembly form.
30495 Here is an example of the resulting disassembly:
30498 (gdb) info addr argc
30499 Symbol "argc" is a complex DWARF expression:
30503 For more information on these expressions, see
30504 @uref{http://www.dwarfstd.org/, the DWARF standard}.
30506 @kindex maint set dwarf2 max-cache-age
30507 @kindex maint show dwarf2 max-cache-age
30508 @item maint set dwarf2 max-cache-age
30509 @itemx maint show dwarf2 max-cache-age
30510 Control the DWARF 2 compilation unit cache.
30512 @cindex DWARF 2 compilation units cache
30513 In object files with inter-compilation-unit references, such as those
30514 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
30515 reader needs to frequently refer to previously read compilation units.
30516 This setting controls how long a compilation unit will remain in the
30517 cache if it is not referenced. A higher limit means that cached
30518 compilation units will be stored in memory longer, and more total
30519 memory will be used. Setting it to zero disables caching, which will
30520 slow down @value{GDBN} startup, but reduce memory consumption.
30522 @kindex maint set profile
30523 @kindex maint show profile
30524 @cindex profiling GDB
30525 @item maint set profile
30526 @itemx maint show profile
30527 Control profiling of @value{GDBN}.
30529 Profiling will be disabled until you use the @samp{maint set profile}
30530 command to enable it. When you enable profiling, the system will begin
30531 collecting timing and execution count data; when you disable profiling or
30532 exit @value{GDBN}, the results will be written to a log file. Remember that
30533 if you use profiling, @value{GDBN} will overwrite the profiling log file
30534 (often called @file{gmon.out}). If you have a record of important profiling
30535 data in a @file{gmon.out} file, be sure to move it to a safe location.
30537 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
30538 compiled with the @samp{-pg} compiler option.
30540 @kindex maint set show-debug-regs
30541 @kindex maint show show-debug-regs
30542 @cindex hardware debug registers
30543 @item maint set show-debug-regs
30544 @itemx maint show show-debug-regs
30545 Control whether to show variables that mirror the hardware debug
30546 registers. Use @code{ON} to enable, @code{OFF} to disable. If
30547 enabled, the debug registers values are shown when @value{GDBN} inserts or
30548 removes a hardware breakpoint or watchpoint, and when the inferior
30549 triggers a hardware-assisted breakpoint or watchpoint.
30551 @kindex maint set show-all-tib
30552 @kindex maint show show-all-tib
30553 @item maint set show-all-tib
30554 @itemx maint show show-all-tib
30555 Control whether to show all non zero areas within a 1k block starting
30556 at thread local base, when using the @samp{info w32 thread-information-block}
30559 @kindex maint space
30560 @cindex memory used by commands
30562 Control whether to display memory usage for each command. If set to a
30563 nonzero value, @value{GDBN} will display how much memory each command
30564 took, following the command's own output. This can also be requested
30565 by invoking @value{GDBN} with the @option{--statistics} command-line
30566 switch (@pxref{Mode Options}).
30569 @cindex time of command execution
30571 Control whether to display the execution time for each command. If
30572 set to a nonzero value, @value{GDBN} will display how much time it
30573 took to execute each command, following the command's own output.
30574 The time is not printed for the commands that run the target, since
30575 there's no mechanism currently to compute how much time was spend
30576 by @value{GDBN} and how much time was spend by the program been debugged.
30577 it's not possibly currently
30578 This can also be requested by invoking @value{GDBN} with the
30579 @option{--statistics} command-line switch (@pxref{Mode Options}).
30581 @kindex maint translate-address
30582 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
30583 Find the symbol stored at the location specified by the address
30584 @var{addr} and an optional section name @var{section}. If found,
30585 @value{GDBN} prints the name of the closest symbol and an offset from
30586 the symbol's location to the specified address. This is similar to
30587 the @code{info address} command (@pxref{Symbols}), except that this
30588 command also allows to find symbols in other sections.
30590 If section was not specified, the section in which the symbol was found
30591 is also printed. For dynamically linked executables, the name of
30592 executable or shared library containing the symbol is printed as well.
30596 The following command is useful for non-interactive invocations of
30597 @value{GDBN}, such as in the test suite.
30600 @item set watchdog @var{nsec}
30601 @kindex set watchdog
30602 @cindex watchdog timer
30603 @cindex timeout for commands
30604 Set the maximum number of seconds @value{GDBN} will wait for the
30605 target operation to finish. If this time expires, @value{GDBN}
30606 reports and error and the command is aborted.
30608 @item show watchdog
30609 Show the current setting of the target wait timeout.
30612 @node Remote Protocol
30613 @appendix @value{GDBN} Remote Serial Protocol
30618 * Stop Reply Packets::
30619 * General Query Packets::
30620 * Architecture-Specific Protocol Details::
30621 * Tracepoint Packets::
30622 * Host I/O Packets::
30624 * Notification Packets::
30625 * Remote Non-Stop::
30626 * Packet Acknowledgment::
30628 * File-I/O Remote Protocol Extension::
30629 * Library List Format::
30630 * Memory Map Format::
30631 * Thread List Format::
30637 There may be occasions when you need to know something about the
30638 protocol---for example, if there is only one serial port to your target
30639 machine, you might want your program to do something special if it
30640 recognizes a packet meant for @value{GDBN}.
30642 In the examples below, @samp{->} and @samp{<-} are used to indicate
30643 transmitted and received data, respectively.
30645 @cindex protocol, @value{GDBN} remote serial
30646 @cindex serial protocol, @value{GDBN} remote
30647 @cindex remote serial protocol
30648 All @value{GDBN} commands and responses (other than acknowledgments
30649 and notifications, see @ref{Notification Packets}) are sent as a
30650 @var{packet}. A @var{packet} is introduced with the character
30651 @samp{$}, the actual @var{packet-data}, and the terminating character
30652 @samp{#} followed by a two-digit @var{checksum}:
30655 @code{$}@var{packet-data}@code{#}@var{checksum}
30659 @cindex checksum, for @value{GDBN} remote
30661 The two-digit @var{checksum} is computed as the modulo 256 sum of all
30662 characters between the leading @samp{$} and the trailing @samp{#} (an
30663 eight bit unsigned checksum).
30665 Implementors should note that prior to @value{GDBN} 5.0 the protocol
30666 specification also included an optional two-digit @var{sequence-id}:
30669 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
30672 @cindex sequence-id, for @value{GDBN} remote
30674 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
30675 has never output @var{sequence-id}s. Stubs that handle packets added
30676 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
30678 When either the host or the target machine receives a packet, the first
30679 response expected is an acknowledgment: either @samp{+} (to indicate
30680 the package was received correctly) or @samp{-} (to request
30684 -> @code{$}@var{packet-data}@code{#}@var{checksum}
30689 The @samp{+}/@samp{-} acknowledgments can be disabled
30690 once a connection is established.
30691 @xref{Packet Acknowledgment}, for details.
30693 The host (@value{GDBN}) sends @var{command}s, and the target (the
30694 debugging stub incorporated in your program) sends a @var{response}. In
30695 the case of step and continue @var{command}s, the response is only sent
30696 when the operation has completed, and the target has again stopped all
30697 threads in all attached processes. This is the default all-stop mode
30698 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
30699 execution mode; see @ref{Remote Non-Stop}, for details.
30701 @var{packet-data} consists of a sequence of characters with the
30702 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
30705 @cindex remote protocol, field separator
30706 Fields within the packet should be separated using @samp{,} @samp{;} or
30707 @samp{:}. Except where otherwise noted all numbers are represented in
30708 @sc{hex} with leading zeros suppressed.
30710 Implementors should note that prior to @value{GDBN} 5.0, the character
30711 @samp{:} could not appear as the third character in a packet (as it
30712 would potentially conflict with the @var{sequence-id}).
30714 @cindex remote protocol, binary data
30715 @anchor{Binary Data}
30716 Binary data in most packets is encoded either as two hexadecimal
30717 digits per byte of binary data. This allowed the traditional remote
30718 protocol to work over connections which were only seven-bit clean.
30719 Some packets designed more recently assume an eight-bit clean
30720 connection, and use a more efficient encoding to send and receive
30723 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
30724 as an escape character. Any escaped byte is transmitted as the escape
30725 character followed by the original character XORed with @code{0x20}.
30726 For example, the byte @code{0x7d} would be transmitted as the two
30727 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
30728 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
30729 @samp{@}}) must always be escaped. Responses sent by the stub
30730 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
30731 is not interpreted as the start of a run-length encoded sequence
30734 Response @var{data} can be run-length encoded to save space.
30735 Run-length encoding replaces runs of identical characters with one
30736 instance of the repeated character, followed by a @samp{*} and a
30737 repeat count. The repeat count is itself sent encoded, to avoid
30738 binary characters in @var{data}: a value of @var{n} is sent as
30739 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
30740 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
30741 code 32) for a repeat count of 3. (This is because run-length
30742 encoding starts to win for counts 3 or more.) Thus, for example,
30743 @samp{0* } is a run-length encoding of ``0000'': the space character
30744 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
30747 The printable characters @samp{#} and @samp{$} or with a numeric value
30748 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
30749 seven repeats (@samp{$}) can be expanded using a repeat count of only
30750 five (@samp{"}). For example, @samp{00000000} can be encoded as
30753 The error response returned for some packets includes a two character
30754 error number. That number is not well defined.
30756 @cindex empty response, for unsupported packets
30757 For any @var{command} not supported by the stub, an empty response
30758 (@samp{$#00}) should be returned. That way it is possible to extend the
30759 protocol. A newer @value{GDBN} can tell if a packet is supported based
30762 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
30763 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
30769 The following table provides a complete list of all currently defined
30770 @var{command}s and their corresponding response @var{data}.
30771 @xref{File-I/O Remote Protocol Extension}, for details about the File
30772 I/O extension of the remote protocol.
30774 Each packet's description has a template showing the packet's overall
30775 syntax, followed by an explanation of the packet's meaning. We
30776 include spaces in some of the templates for clarity; these are not
30777 part of the packet's syntax. No @value{GDBN} packet uses spaces to
30778 separate its components. For example, a template like @samp{foo
30779 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
30780 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
30781 @var{baz}. @value{GDBN} does not transmit a space character between the
30782 @samp{foo} and the @var{bar}, or between the @var{bar} and the
30785 @cindex @var{thread-id}, in remote protocol
30786 @anchor{thread-id syntax}
30787 Several packets and replies include a @var{thread-id} field to identify
30788 a thread. Normally these are positive numbers with a target-specific
30789 interpretation, formatted as big-endian hex strings. A @var{thread-id}
30790 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
30793 In addition, the remote protocol supports a multiprocess feature in
30794 which the @var{thread-id} syntax is extended to optionally include both
30795 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
30796 The @var{pid} (process) and @var{tid} (thread) components each have the
30797 format described above: a positive number with target-specific
30798 interpretation formatted as a big-endian hex string, literal @samp{-1}
30799 to indicate all processes or threads (respectively), or @samp{0} to
30800 indicate an arbitrary process or thread. Specifying just a process, as
30801 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
30802 error to specify all processes but a specific thread, such as
30803 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
30804 for those packets and replies explicitly documented to include a process
30805 ID, rather than a @var{thread-id}.
30807 The multiprocess @var{thread-id} syntax extensions are only used if both
30808 @value{GDBN} and the stub report support for the @samp{multiprocess}
30809 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
30812 Note that all packet forms beginning with an upper- or lower-case
30813 letter, other than those described here, are reserved for future use.
30815 Here are the packet descriptions.
30820 @cindex @samp{!} packet
30821 @anchor{extended mode}
30822 Enable extended mode. In extended mode, the remote server is made
30823 persistent. The @samp{R} packet is used to restart the program being
30829 The remote target both supports and has enabled extended mode.
30833 @cindex @samp{?} packet
30834 Indicate the reason the target halted. The reply is the same as for
30835 step and continue. This packet has a special interpretation when the
30836 target is in non-stop mode; see @ref{Remote Non-Stop}.
30839 @xref{Stop Reply Packets}, for the reply specifications.
30841 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
30842 @cindex @samp{A} packet
30843 Initialized @code{argv[]} array passed into program. @var{arglen}
30844 specifies the number of bytes in the hex encoded byte stream
30845 @var{arg}. See @code{gdbserver} for more details.
30850 The arguments were set.
30856 @cindex @samp{b} packet
30857 (Don't use this packet; its behavior is not well-defined.)
30858 Change the serial line speed to @var{baud}.
30860 JTC: @emph{When does the transport layer state change? When it's
30861 received, or after the ACK is transmitted. In either case, there are
30862 problems if the command or the acknowledgment packet is dropped.}
30864 Stan: @emph{If people really wanted to add something like this, and get
30865 it working for the first time, they ought to modify ser-unix.c to send
30866 some kind of out-of-band message to a specially-setup stub and have the
30867 switch happen "in between" packets, so that from remote protocol's point
30868 of view, nothing actually happened.}
30870 @item B @var{addr},@var{mode}
30871 @cindex @samp{B} packet
30872 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
30873 breakpoint at @var{addr}.
30875 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
30876 (@pxref{insert breakpoint or watchpoint packet}).
30878 @cindex @samp{bc} packet
30881 Backward continue. Execute the target system in reverse. No parameter.
30882 @xref{Reverse Execution}, for more information.
30885 @xref{Stop Reply Packets}, for the reply specifications.
30887 @cindex @samp{bs} packet
30890 Backward single step. Execute one instruction in reverse. No parameter.
30891 @xref{Reverse Execution}, for more information.
30894 @xref{Stop Reply Packets}, for the reply specifications.
30896 @item c @r{[}@var{addr}@r{]}
30897 @cindex @samp{c} packet
30898 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
30899 resume at current address.
30902 @xref{Stop Reply Packets}, for the reply specifications.
30904 @item C @var{sig}@r{[};@var{addr}@r{]}
30905 @cindex @samp{C} packet
30906 Continue with signal @var{sig} (hex signal number). If
30907 @samp{;@var{addr}} is omitted, resume at same address.
30910 @xref{Stop Reply Packets}, for the reply specifications.
30913 @cindex @samp{d} packet
30916 Don't use this packet; instead, define a general set packet
30917 (@pxref{General Query Packets}).
30921 @cindex @samp{D} packet
30922 The first form of the packet is used to detach @value{GDBN} from the
30923 remote system. It is sent to the remote target
30924 before @value{GDBN} disconnects via the @code{detach} command.
30926 The second form, including a process ID, is used when multiprocess
30927 protocol extensions are enabled (@pxref{multiprocess extensions}), to
30928 detach only a specific process. The @var{pid} is specified as a
30929 big-endian hex string.
30939 @item F @var{RC},@var{EE},@var{CF};@var{XX}
30940 @cindex @samp{F} packet
30941 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
30942 This is part of the File-I/O protocol extension. @xref{File-I/O
30943 Remote Protocol Extension}, for the specification.
30946 @anchor{read registers packet}
30947 @cindex @samp{g} packet
30948 Read general registers.
30952 @item @var{XX@dots{}}
30953 Each byte of register data is described by two hex digits. The bytes
30954 with the register are transmitted in target byte order. The size of
30955 each register and their position within the @samp{g} packet are
30956 determined by the @value{GDBN} internal gdbarch functions
30957 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
30958 specification of several standard @samp{g} packets is specified below.
30963 @item G @var{XX@dots{}}
30964 @cindex @samp{G} packet
30965 Write general registers. @xref{read registers packet}, for a
30966 description of the @var{XX@dots{}} data.
30976 @item H @var{c} @var{thread-id}
30977 @cindex @samp{H} packet
30978 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
30979 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
30980 should be @samp{c} for step and continue operations, @samp{g} for other
30981 operations. The thread designator @var{thread-id} has the format and
30982 interpretation described in @ref{thread-id syntax}.
30993 @c 'H': How restrictive (or permissive) is the thread model. If a
30994 @c thread is selected and stopped, are other threads allowed
30995 @c to continue to execute? As I mentioned above, I think the
30996 @c semantics of each command when a thread is selected must be
30997 @c described. For example:
30999 @c 'g': If the stub supports threads and a specific thread is
31000 @c selected, returns the register block from that thread;
31001 @c otherwise returns current registers.
31003 @c 'G' If the stub supports threads and a specific thread is
31004 @c selected, sets the registers of the register block of
31005 @c that thread; otherwise sets current registers.
31007 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
31008 @anchor{cycle step packet}
31009 @cindex @samp{i} packet
31010 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
31011 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
31012 step starting at that address.
31015 @cindex @samp{I} packet
31016 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
31020 @cindex @samp{k} packet
31023 FIXME: @emph{There is no description of how to operate when a specific
31024 thread context has been selected (i.e.@: does 'k' kill only that
31027 @item m @var{addr},@var{length}
31028 @cindex @samp{m} packet
31029 Read @var{length} bytes of memory starting at address @var{addr}.
31030 Note that @var{addr} may not be aligned to any particular boundary.
31032 The stub need not use any particular size or alignment when gathering
31033 data from memory for the response; even if @var{addr} is word-aligned
31034 and @var{length} is a multiple of the word size, the stub is free to
31035 use byte accesses, or not. For this reason, this packet may not be
31036 suitable for accessing memory-mapped I/O devices.
31037 @cindex alignment of remote memory accesses
31038 @cindex size of remote memory accesses
31039 @cindex memory, alignment and size of remote accesses
31043 @item @var{XX@dots{}}
31044 Memory contents; each byte is transmitted as a two-digit hexadecimal
31045 number. The reply may contain fewer bytes than requested if the
31046 server was able to read only part of the region of memory.
31051 @item M @var{addr},@var{length}:@var{XX@dots{}}
31052 @cindex @samp{M} packet
31053 Write @var{length} bytes of memory starting at address @var{addr}.
31054 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
31055 hexadecimal number.
31062 for an error (this includes the case where only part of the data was
31067 @cindex @samp{p} packet
31068 Read the value of register @var{n}; @var{n} is in hex.
31069 @xref{read registers packet}, for a description of how the returned
31070 register value is encoded.
31074 @item @var{XX@dots{}}
31075 the register's value
31079 Indicating an unrecognized @var{query}.
31082 @item P @var{n@dots{}}=@var{r@dots{}}
31083 @anchor{write register packet}
31084 @cindex @samp{P} packet
31085 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
31086 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
31087 digits for each byte in the register (target byte order).
31097 @item q @var{name} @var{params}@dots{}
31098 @itemx Q @var{name} @var{params}@dots{}
31099 @cindex @samp{q} packet
31100 @cindex @samp{Q} packet
31101 General query (@samp{q}) and set (@samp{Q}). These packets are
31102 described fully in @ref{General Query Packets}.
31105 @cindex @samp{r} packet
31106 Reset the entire system.
31108 Don't use this packet; use the @samp{R} packet instead.
31111 @cindex @samp{R} packet
31112 Restart the program being debugged. @var{XX}, while needed, is ignored.
31113 This packet is only available in extended mode (@pxref{extended mode}).
31115 The @samp{R} packet has no reply.
31117 @item s @r{[}@var{addr}@r{]}
31118 @cindex @samp{s} packet
31119 Single step. @var{addr} is the address at which to resume. If
31120 @var{addr} is omitted, resume at same address.
31123 @xref{Stop Reply Packets}, for the reply specifications.
31125 @item S @var{sig}@r{[};@var{addr}@r{]}
31126 @anchor{step with signal packet}
31127 @cindex @samp{S} packet
31128 Step with signal. This is analogous to the @samp{C} packet, but
31129 requests a single-step, rather than a normal resumption of execution.
31132 @xref{Stop Reply Packets}, for the reply specifications.
31134 @item t @var{addr}:@var{PP},@var{MM}
31135 @cindex @samp{t} packet
31136 Search backwards starting at address @var{addr} for a match with pattern
31137 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
31138 @var{addr} must be at least 3 digits.
31140 @item T @var{thread-id}
31141 @cindex @samp{T} packet
31142 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
31147 thread is still alive
31153 Packets starting with @samp{v} are identified by a multi-letter name,
31154 up to the first @samp{;} or @samp{?} (or the end of the packet).
31156 @item vAttach;@var{pid}
31157 @cindex @samp{vAttach} packet
31158 Attach to a new process with the specified process ID @var{pid}.
31159 The process ID is a
31160 hexadecimal integer identifying the process. In all-stop mode, all
31161 threads in the attached process are stopped; in non-stop mode, it may be
31162 attached without being stopped if that is supported by the target.
31164 @c In non-stop mode, on a successful vAttach, the stub should set the
31165 @c current thread to a thread of the newly-attached process. After
31166 @c attaching, GDB queries for the attached process's thread ID with qC.
31167 @c Also note that, from a user perspective, whether or not the
31168 @c target is stopped on attach in non-stop mode depends on whether you
31169 @c use the foreground or background version of the attach command, not
31170 @c on what vAttach does; GDB does the right thing with respect to either
31171 @c stopping or restarting threads.
31173 This packet is only available in extended mode (@pxref{extended mode}).
31179 @item @r{Any stop packet}
31180 for success in all-stop mode (@pxref{Stop Reply Packets})
31182 for success in non-stop mode (@pxref{Remote Non-Stop})
31185 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
31186 @cindex @samp{vCont} packet
31187 Resume the inferior, specifying different actions for each thread.
31188 If an action is specified with no @var{thread-id}, then it is applied to any
31189 threads that don't have a specific action specified; if no default action is
31190 specified then other threads should remain stopped in all-stop mode and
31191 in their current state in non-stop mode.
31192 Specifying multiple
31193 default actions is an error; specifying no actions is also an error.
31194 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
31196 Currently supported actions are:
31202 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
31206 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
31211 The optional argument @var{addr} normally associated with the
31212 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
31213 not supported in @samp{vCont}.
31215 The @samp{t} action is only relevant in non-stop mode
31216 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
31217 A stop reply should be generated for any affected thread not already stopped.
31218 When a thread is stopped by means of a @samp{t} action,
31219 the corresponding stop reply should indicate that the thread has stopped with
31220 signal @samp{0}, regardless of whether the target uses some other signal
31221 as an implementation detail.
31224 @xref{Stop Reply Packets}, for the reply specifications.
31227 @cindex @samp{vCont?} packet
31228 Request a list of actions supported by the @samp{vCont} packet.
31232 @item vCont@r{[};@var{action}@dots{}@r{]}
31233 The @samp{vCont} packet is supported. Each @var{action} is a supported
31234 command in the @samp{vCont} packet.
31236 The @samp{vCont} packet is not supported.
31239 @item vFile:@var{operation}:@var{parameter}@dots{}
31240 @cindex @samp{vFile} packet
31241 Perform a file operation on the target system. For details,
31242 see @ref{Host I/O Packets}.
31244 @item vFlashErase:@var{addr},@var{length}
31245 @cindex @samp{vFlashErase} packet
31246 Direct the stub to erase @var{length} bytes of flash starting at
31247 @var{addr}. The region may enclose any number of flash blocks, but
31248 its start and end must fall on block boundaries, as indicated by the
31249 flash block size appearing in the memory map (@pxref{Memory Map
31250 Format}). @value{GDBN} groups flash memory programming operations
31251 together, and sends a @samp{vFlashDone} request after each group; the
31252 stub is allowed to delay erase operation until the @samp{vFlashDone}
31253 packet is received.
31255 The stub must support @samp{vCont} if it reports support for
31256 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
31257 this case @samp{vCont} actions can be specified to apply to all threads
31258 in a process by using the @samp{p@var{pid}.-1} form of the
31269 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
31270 @cindex @samp{vFlashWrite} packet
31271 Direct the stub to write data to flash address @var{addr}. The data
31272 is passed in binary form using the same encoding as for the @samp{X}
31273 packet (@pxref{Binary Data}). The memory ranges specified by
31274 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
31275 not overlap, and must appear in order of increasing addresses
31276 (although @samp{vFlashErase} packets for higher addresses may already
31277 have been received; the ordering is guaranteed only between
31278 @samp{vFlashWrite} packets). If a packet writes to an address that was
31279 neither erased by a preceding @samp{vFlashErase} packet nor by some other
31280 target-specific method, the results are unpredictable.
31288 for vFlashWrite addressing non-flash memory
31294 @cindex @samp{vFlashDone} packet
31295 Indicate to the stub that flash programming operation is finished.
31296 The stub is permitted to delay or batch the effects of a group of
31297 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
31298 @samp{vFlashDone} packet is received. The contents of the affected
31299 regions of flash memory are unpredictable until the @samp{vFlashDone}
31300 request is completed.
31302 @item vKill;@var{pid}
31303 @cindex @samp{vKill} packet
31304 Kill the process with the specified process ID. @var{pid} is a
31305 hexadecimal integer identifying the process. This packet is used in
31306 preference to @samp{k} when multiprocess protocol extensions are
31307 supported; see @ref{multiprocess extensions}.
31317 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
31318 @cindex @samp{vRun} packet
31319 Run the program @var{filename}, passing it each @var{argument} on its
31320 command line. The file and arguments are hex-encoded strings. If
31321 @var{filename} is an empty string, the stub may use a default program
31322 (e.g.@: the last program run). The program is created in the stopped
31325 @c FIXME: What about non-stop mode?
31327 This packet is only available in extended mode (@pxref{extended mode}).
31333 @item @r{Any stop packet}
31334 for success (@pxref{Stop Reply Packets})
31338 @anchor{vStopped packet}
31339 @cindex @samp{vStopped} packet
31341 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
31342 reply and prompt for the stub to report another one.
31346 @item @r{Any stop packet}
31347 if there is another unreported stop event (@pxref{Stop Reply Packets})
31349 if there are no unreported stop events
31352 @item X @var{addr},@var{length}:@var{XX@dots{}}
31354 @cindex @samp{X} packet
31355 Write data to memory, where the data is transmitted in binary.
31356 @var{addr} is address, @var{length} is number of bytes,
31357 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
31367 @item z @var{type},@var{addr},@var{kind}
31368 @itemx Z @var{type},@var{addr},@var{kind}
31369 @anchor{insert breakpoint or watchpoint packet}
31370 @cindex @samp{z} packet
31371 @cindex @samp{Z} packets
31372 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
31373 watchpoint starting at address @var{address} of kind @var{kind}.
31375 Each breakpoint and watchpoint packet @var{type} is documented
31378 @emph{Implementation notes: A remote target shall return an empty string
31379 for an unrecognized breakpoint or watchpoint packet @var{type}. A
31380 remote target shall support either both or neither of a given
31381 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
31382 avoid potential problems with duplicate packets, the operations should
31383 be implemented in an idempotent way.}
31385 @item z0,@var{addr},@var{kind}
31386 @itemx Z0,@var{addr},@var{kind}
31387 @cindex @samp{z0} packet
31388 @cindex @samp{Z0} packet
31389 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
31390 @var{addr} of type @var{kind}.
31392 A memory breakpoint is implemented by replacing the instruction at
31393 @var{addr} with a software breakpoint or trap instruction. The
31394 @var{kind} is target-specific and typically indicates the size of
31395 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
31396 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
31397 architectures have additional meanings for @var{kind};
31398 see @ref{Architecture-Specific Protocol Details}.
31400 @emph{Implementation note: It is possible for a target to copy or move
31401 code that contains memory breakpoints (e.g., when implementing
31402 overlays). The behavior of this packet, in the presence of such a
31403 target, is not defined.}
31415 @item z1,@var{addr},@var{kind}
31416 @itemx Z1,@var{addr},@var{kind}
31417 @cindex @samp{z1} packet
31418 @cindex @samp{Z1} packet
31419 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
31420 address @var{addr}.
31422 A hardware breakpoint is implemented using a mechanism that is not
31423 dependant on being able to modify the target's memory. @var{kind}
31424 has the same meaning as in @samp{Z0} packets.
31426 @emph{Implementation note: A hardware breakpoint is not affected by code
31439 @item z2,@var{addr},@var{kind}
31440 @itemx Z2,@var{addr},@var{kind}
31441 @cindex @samp{z2} packet
31442 @cindex @samp{Z2} packet
31443 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
31444 @var{kind} is interpreted as the number of bytes to watch.
31456 @item z3,@var{addr},@var{kind}
31457 @itemx Z3,@var{addr},@var{kind}
31458 @cindex @samp{z3} packet
31459 @cindex @samp{Z3} packet
31460 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
31461 @var{kind} is interpreted as the number of bytes to watch.
31473 @item z4,@var{addr},@var{kind}
31474 @itemx Z4,@var{addr},@var{kind}
31475 @cindex @samp{z4} packet
31476 @cindex @samp{Z4} packet
31477 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
31478 @var{kind} is interpreted as the number of bytes to watch.
31492 @node Stop Reply Packets
31493 @section Stop Reply Packets
31494 @cindex stop reply packets
31496 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
31497 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
31498 receive any of the below as a reply. Except for @samp{?}
31499 and @samp{vStopped}, that reply is only returned
31500 when the target halts. In the below the exact meaning of @dfn{signal
31501 number} is defined by the header @file{include/gdb/signals.h} in the
31502 @value{GDBN} source code.
31504 As in the description of request packets, we include spaces in the
31505 reply templates for clarity; these are not part of the reply packet's
31506 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
31512 The program received signal number @var{AA} (a two-digit hexadecimal
31513 number). This is equivalent to a @samp{T} response with no
31514 @var{n}:@var{r} pairs.
31516 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
31517 @cindex @samp{T} packet reply
31518 The program received signal number @var{AA} (a two-digit hexadecimal
31519 number). This is equivalent to an @samp{S} response, except that the
31520 @samp{@var{n}:@var{r}} pairs can carry values of important registers
31521 and other information directly in the stop reply packet, reducing
31522 round-trip latency. Single-step and breakpoint traps are reported
31523 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
31527 If @var{n} is a hexadecimal number, it is a register number, and the
31528 corresponding @var{r} gives that register's value. @var{r} is a
31529 series of bytes in target byte order, with each byte given by a
31530 two-digit hex number.
31533 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
31534 the stopped thread, as specified in @ref{thread-id syntax}.
31537 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
31538 the core on which the stop event was detected.
31541 If @var{n} is a recognized @dfn{stop reason}, it describes a more
31542 specific event that stopped the target. The currently defined stop
31543 reasons are listed below. @var{aa} should be @samp{05}, the trap
31544 signal. At most one stop reason should be present.
31547 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
31548 and go on to the next; this allows us to extend the protocol in the
31552 The currently defined stop reasons are:
31558 The packet indicates a watchpoint hit, and @var{r} is the data address, in
31561 @cindex shared library events, remote reply
31563 The packet indicates that the loaded libraries have changed.
31564 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
31565 list of loaded libraries. @var{r} is ignored.
31567 @cindex replay log events, remote reply
31569 The packet indicates that the target cannot continue replaying
31570 logged execution events, because it has reached the end (or the
31571 beginning when executing backward) of the log. The value of @var{r}
31572 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
31573 for more information.
31577 @itemx W @var{AA} ; process:@var{pid}
31578 The process exited, and @var{AA} is the exit status. This is only
31579 applicable to certain targets.
31581 The second form of the response, including the process ID of the exited
31582 process, can be used only when @value{GDBN} has reported support for
31583 multiprocess protocol extensions; see @ref{multiprocess extensions}.
31584 The @var{pid} is formatted as a big-endian hex string.
31587 @itemx X @var{AA} ; process:@var{pid}
31588 The process terminated with signal @var{AA}.
31590 The second form of the response, including the process ID of the
31591 terminated process, can be used only when @value{GDBN} has reported
31592 support for multiprocess protocol extensions; see @ref{multiprocess
31593 extensions}. The @var{pid} is formatted as a big-endian hex string.
31595 @item O @var{XX}@dots{}
31596 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
31597 written as the program's console output. This can happen at any time
31598 while the program is running and the debugger should continue to wait
31599 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
31601 @item F @var{call-id},@var{parameter}@dots{}
31602 @var{call-id} is the identifier which says which host system call should
31603 be called. This is just the name of the function. Translation into the
31604 correct system call is only applicable as it's defined in @value{GDBN}.
31605 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
31608 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
31609 this very system call.
31611 The target replies with this packet when it expects @value{GDBN} to
31612 call a host system call on behalf of the target. @value{GDBN} replies
31613 with an appropriate @samp{F} packet and keeps up waiting for the next
31614 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
31615 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
31616 Protocol Extension}, for more details.
31620 @node General Query Packets
31621 @section General Query Packets
31622 @cindex remote query requests
31624 Packets starting with @samp{q} are @dfn{general query packets};
31625 packets starting with @samp{Q} are @dfn{general set packets}. General
31626 query and set packets are a semi-unified form for retrieving and
31627 sending information to and from the stub.
31629 The initial letter of a query or set packet is followed by a name
31630 indicating what sort of thing the packet applies to. For example,
31631 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
31632 definitions with the stub. These packet names follow some
31637 The name must not contain commas, colons or semicolons.
31639 Most @value{GDBN} query and set packets have a leading upper case
31642 The names of custom vendor packets should use a company prefix, in
31643 lower case, followed by a period. For example, packets designed at
31644 the Acme Corporation might begin with @samp{qacme.foo} (for querying
31645 foos) or @samp{Qacme.bar} (for setting bars).
31648 The name of a query or set packet should be separated from any
31649 parameters by a @samp{:}; the parameters themselves should be
31650 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
31651 full packet name, and check for a separator or the end of the packet,
31652 in case two packet names share a common prefix. New packets should not begin
31653 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
31654 packets predate these conventions, and have arguments without any terminator
31655 for the packet name; we suspect they are in widespread use in places that
31656 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
31657 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
31660 Like the descriptions of the other packets, each description here
31661 has a template showing the packet's overall syntax, followed by an
31662 explanation of the packet's meaning. We include spaces in some of the
31663 templates for clarity; these are not part of the packet's syntax. No
31664 @value{GDBN} packet uses spaces to separate its components.
31666 Here are the currently defined query and set packets:
31670 @item QAllow:@var{op}:@var{val}@dots{}
31671 @cindex @samp{QAllow} packet
31672 Specify which operations @value{GDBN} expects to request of the
31673 target, as a semicolon-separated list of operation name and value
31674 pairs. Possible values for @var{op} include @samp{WriteReg},
31675 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
31676 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
31677 indicating that @value{GDBN} will not request the operation, or 1,
31678 indicating that it may. (The target can then use this to set up its
31679 own internals optimally, for instance if the debugger never expects to
31680 insert breakpoints, it may not need to install its own trap handler.)
31683 @cindex current thread, remote request
31684 @cindex @samp{qC} packet
31685 Return the current thread ID.
31689 @item QC @var{thread-id}
31690 Where @var{thread-id} is a thread ID as documented in
31691 @ref{thread-id syntax}.
31692 @item @r{(anything else)}
31693 Any other reply implies the old thread ID.
31696 @item qCRC:@var{addr},@var{length}
31697 @cindex CRC of memory block, remote request
31698 @cindex @samp{qCRC} packet
31699 Compute the CRC checksum of a block of memory using CRC-32 defined in
31700 IEEE 802.3. The CRC is computed byte at a time, taking the most
31701 significant bit of each byte first. The initial pattern code
31702 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
31704 @emph{Note:} This is the same CRC used in validating separate debug
31705 files (@pxref{Separate Debug Files, , Debugging Information in Separate
31706 Files}). However the algorithm is slightly different. When validating
31707 separate debug files, the CRC is computed taking the @emph{least}
31708 significant bit of each byte first, and the final result is inverted to
31709 detect trailing zeros.
31714 An error (such as memory fault)
31715 @item C @var{crc32}
31716 The specified memory region's checksum is @var{crc32}.
31720 @itemx qsThreadInfo
31721 @cindex list active threads, remote request
31722 @cindex @samp{qfThreadInfo} packet
31723 @cindex @samp{qsThreadInfo} packet
31724 Obtain a list of all active thread IDs from the target (OS). Since there
31725 may be too many active threads to fit into one reply packet, this query
31726 works iteratively: it may require more than one query/reply sequence to
31727 obtain the entire list of threads. The first query of the sequence will
31728 be the @samp{qfThreadInfo} query; subsequent queries in the
31729 sequence will be the @samp{qsThreadInfo} query.
31731 NOTE: This packet replaces the @samp{qL} query (see below).
31735 @item m @var{thread-id}
31737 @item m @var{thread-id},@var{thread-id}@dots{}
31738 a comma-separated list of thread IDs
31740 (lower case letter @samp{L}) denotes end of list.
31743 In response to each query, the target will reply with a list of one or
31744 more thread IDs, separated by commas.
31745 @value{GDBN} will respond to each reply with a request for more thread
31746 ids (using the @samp{qs} form of the query), until the target responds
31747 with @samp{l} (lower-case el, for @dfn{last}).
31748 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
31751 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
31752 @cindex get thread-local storage address, remote request
31753 @cindex @samp{qGetTLSAddr} packet
31754 Fetch the address associated with thread local storage specified
31755 by @var{thread-id}, @var{offset}, and @var{lm}.
31757 @var{thread-id} is the thread ID associated with the
31758 thread for which to fetch the TLS address. @xref{thread-id syntax}.
31760 @var{offset} is the (big endian, hex encoded) offset associated with the
31761 thread local variable. (This offset is obtained from the debug
31762 information associated with the variable.)
31764 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
31765 the load module associated with the thread local storage. For example,
31766 a @sc{gnu}/Linux system will pass the link map address of the shared
31767 object associated with the thread local storage under consideration.
31768 Other operating environments may choose to represent the load module
31769 differently, so the precise meaning of this parameter will vary.
31773 @item @var{XX}@dots{}
31774 Hex encoded (big endian) bytes representing the address of the thread
31775 local storage requested.
31778 An error occurred. @var{nn} are hex digits.
31781 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
31784 @item qGetTIBAddr:@var{thread-id}
31785 @cindex get thread information block address
31786 @cindex @samp{qGetTIBAddr} packet
31787 Fetch address of the Windows OS specific Thread Information Block.
31789 @var{thread-id} is the thread ID associated with the thread.
31793 @item @var{XX}@dots{}
31794 Hex encoded (big endian) bytes representing the linear address of the
31795 thread information block.
31798 An error occured. This means that either the thread was not found, or the
31799 address could not be retrieved.
31802 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
31805 @item qL @var{startflag} @var{threadcount} @var{nextthread}
31806 Obtain thread information from RTOS. Where: @var{startflag} (one hex
31807 digit) is one to indicate the first query and zero to indicate a
31808 subsequent query; @var{threadcount} (two hex digits) is the maximum
31809 number of threads the response packet can contain; and @var{nextthread}
31810 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
31811 returned in the response as @var{argthread}.
31813 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
31817 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
31818 Where: @var{count} (two hex digits) is the number of threads being
31819 returned; @var{done} (one hex digit) is zero to indicate more threads
31820 and one indicates no further threads; @var{argthreadid} (eight hex
31821 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
31822 is a sequence of thread IDs from the target. @var{threadid} (eight hex
31823 digits). See @code{remote.c:parse_threadlist_response()}.
31827 @cindex section offsets, remote request
31828 @cindex @samp{qOffsets} packet
31829 Get section offsets that the target used when relocating the downloaded
31834 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
31835 Relocate the @code{Text} section by @var{xxx} from its original address.
31836 Relocate the @code{Data} section by @var{yyy} from its original address.
31837 If the object file format provides segment information (e.g.@: @sc{elf}
31838 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
31839 segments by the supplied offsets.
31841 @emph{Note: while a @code{Bss} offset may be included in the response,
31842 @value{GDBN} ignores this and instead applies the @code{Data} offset
31843 to the @code{Bss} section.}
31845 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
31846 Relocate the first segment of the object file, which conventionally
31847 contains program code, to a starting address of @var{xxx}. If
31848 @samp{DataSeg} is specified, relocate the second segment, which
31849 conventionally contains modifiable data, to a starting address of
31850 @var{yyy}. @value{GDBN} will report an error if the object file
31851 does not contain segment information, or does not contain at least
31852 as many segments as mentioned in the reply. Extra segments are
31853 kept at fixed offsets relative to the last relocated segment.
31856 @item qP @var{mode} @var{thread-id}
31857 @cindex thread information, remote request
31858 @cindex @samp{qP} packet
31859 Returns information on @var{thread-id}. Where: @var{mode} is a hex
31860 encoded 32 bit mode; @var{thread-id} is a thread ID
31861 (@pxref{thread-id syntax}).
31863 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
31866 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
31870 @cindex non-stop mode, remote request
31871 @cindex @samp{QNonStop} packet
31873 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
31874 @xref{Remote Non-Stop}, for more information.
31879 The request succeeded.
31882 An error occurred. @var{nn} are hex digits.
31885 An empty reply indicates that @samp{QNonStop} is not supported by
31889 This packet is not probed by default; the remote stub must request it,
31890 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31891 Use of this packet is controlled by the @code{set non-stop} command;
31892 @pxref{Non-Stop Mode}.
31894 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
31895 @cindex pass signals to inferior, remote request
31896 @cindex @samp{QPassSignals} packet
31897 @anchor{QPassSignals}
31898 Each listed @var{signal} should be passed directly to the inferior process.
31899 Signals are numbered identically to continue packets and stop replies
31900 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
31901 strictly greater than the previous item. These signals do not need to stop
31902 the inferior, or be reported to @value{GDBN}. All other signals should be
31903 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
31904 combine; any earlier @samp{QPassSignals} list is completely replaced by the
31905 new list. This packet improves performance when using @samp{handle
31906 @var{signal} nostop noprint pass}.
31911 The request succeeded.
31914 An error occurred. @var{nn} are hex digits.
31917 An empty reply indicates that @samp{QPassSignals} is not supported by
31921 Use of this packet is controlled by the @code{set remote pass-signals}
31922 command (@pxref{Remote Configuration, set remote pass-signals}).
31923 This packet is not probed by default; the remote stub must request it,
31924 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
31926 @item qRcmd,@var{command}
31927 @cindex execute remote command, remote request
31928 @cindex @samp{qRcmd} packet
31929 @var{command} (hex encoded) is passed to the local interpreter for
31930 execution. Invalid commands should be reported using the output
31931 string. Before the final result packet, the target may also respond
31932 with a number of intermediate @samp{O@var{output}} console output
31933 packets. @emph{Implementors should note that providing access to a
31934 stubs's interpreter may have security implications}.
31939 A command response with no output.
31941 A command response with the hex encoded output string @var{OUTPUT}.
31943 Indicate a badly formed request.
31945 An empty reply indicates that @samp{qRcmd} is not recognized.
31948 (Note that the @code{qRcmd} packet's name is separated from the
31949 command by a @samp{,}, not a @samp{:}, contrary to the naming
31950 conventions above. Please don't use this packet as a model for new
31953 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
31954 @cindex searching memory, in remote debugging
31955 @cindex @samp{qSearch:memory} packet
31956 @anchor{qSearch memory}
31957 Search @var{length} bytes at @var{address} for @var{search-pattern}.
31958 @var{address} and @var{length} are encoded in hex.
31959 @var{search-pattern} is a sequence of bytes, hex encoded.
31964 The pattern was not found.
31966 The pattern was found at @var{address}.
31968 A badly formed request or an error was encountered while searching memory.
31970 An empty reply indicates that @samp{qSearch:memory} is not recognized.
31973 @item QStartNoAckMode
31974 @cindex @samp{QStartNoAckMode} packet
31975 @anchor{QStartNoAckMode}
31976 Request that the remote stub disable the normal @samp{+}/@samp{-}
31977 protocol acknowledgments (@pxref{Packet Acknowledgment}).
31982 The stub has switched to no-acknowledgment mode.
31983 @value{GDBN} acknowledges this reponse,
31984 but neither the stub nor @value{GDBN} shall send or expect further
31985 @samp{+}/@samp{-} acknowledgments in the current connection.
31987 An empty reply indicates that the stub does not support no-acknowledgment mode.
31990 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
31991 @cindex supported packets, remote query
31992 @cindex features of the remote protocol
31993 @cindex @samp{qSupported} packet
31994 @anchor{qSupported}
31995 Tell the remote stub about features supported by @value{GDBN}, and
31996 query the stub for features it supports. This packet allows
31997 @value{GDBN} and the remote stub to take advantage of each others'
31998 features. @samp{qSupported} also consolidates multiple feature probes
31999 at startup, to improve @value{GDBN} performance---a single larger
32000 packet performs better than multiple smaller probe packets on
32001 high-latency links. Some features may enable behavior which must not
32002 be on by default, e.g.@: because it would confuse older clients or
32003 stubs. Other features may describe packets which could be
32004 automatically probed for, but are not. These features must be
32005 reported before @value{GDBN} will use them. This ``default
32006 unsupported'' behavior is not appropriate for all packets, but it
32007 helps to keep the initial connection time under control with new
32008 versions of @value{GDBN} which support increasing numbers of packets.
32012 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
32013 The stub supports or does not support each returned @var{stubfeature},
32014 depending on the form of each @var{stubfeature} (see below for the
32017 An empty reply indicates that @samp{qSupported} is not recognized,
32018 or that no features needed to be reported to @value{GDBN}.
32021 The allowed forms for each feature (either a @var{gdbfeature} in the
32022 @samp{qSupported} packet, or a @var{stubfeature} in the response)
32026 @item @var{name}=@var{value}
32027 The remote protocol feature @var{name} is supported, and associated
32028 with the specified @var{value}. The format of @var{value} depends
32029 on the feature, but it must not include a semicolon.
32031 The remote protocol feature @var{name} is supported, and does not
32032 need an associated value.
32034 The remote protocol feature @var{name} is not supported.
32036 The remote protocol feature @var{name} may be supported, and
32037 @value{GDBN} should auto-detect support in some other way when it is
32038 needed. This form will not be used for @var{gdbfeature} notifications,
32039 but may be used for @var{stubfeature} responses.
32042 Whenever the stub receives a @samp{qSupported} request, the
32043 supplied set of @value{GDBN} features should override any previous
32044 request. This allows @value{GDBN} to put the stub in a known
32045 state, even if the stub had previously been communicating with
32046 a different version of @value{GDBN}.
32048 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
32053 This feature indicates whether @value{GDBN} supports multiprocess
32054 extensions to the remote protocol. @value{GDBN} does not use such
32055 extensions unless the stub also reports that it supports them by
32056 including @samp{multiprocess+} in its @samp{qSupported} reply.
32057 @xref{multiprocess extensions}, for details.
32060 This feature indicates that @value{GDBN} supports the XML target
32061 description. If the stub sees @samp{xmlRegisters=} with target
32062 specific strings separated by a comma, it will report register
32066 This feature indicates whether @value{GDBN} supports the
32067 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
32068 instruction reply packet}).
32071 Stubs should ignore any unknown values for
32072 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
32073 packet supports receiving packets of unlimited length (earlier
32074 versions of @value{GDBN} may reject overly long responses). Additional values
32075 for @var{gdbfeature} may be defined in the future to let the stub take
32076 advantage of new features in @value{GDBN}, e.g.@: incompatible
32077 improvements in the remote protocol---the @samp{multiprocess} feature is
32078 an example of such a feature. The stub's reply should be independent
32079 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
32080 describes all the features it supports, and then the stub replies with
32081 all the features it supports.
32083 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
32084 responses, as long as each response uses one of the standard forms.
32086 Some features are flags. A stub which supports a flag feature
32087 should respond with a @samp{+} form response. Other features
32088 require values, and the stub should respond with an @samp{=}
32091 Each feature has a default value, which @value{GDBN} will use if
32092 @samp{qSupported} is not available or if the feature is not mentioned
32093 in the @samp{qSupported} response. The default values are fixed; a
32094 stub is free to omit any feature responses that match the defaults.
32096 Not all features can be probed, but for those which can, the probing
32097 mechanism is useful: in some cases, a stub's internal
32098 architecture may not allow the protocol layer to know some information
32099 about the underlying target in advance. This is especially common in
32100 stubs which may be configured for multiple targets.
32102 These are the currently defined stub features and their properties:
32104 @multitable @columnfractions 0.35 0.2 0.12 0.2
32105 @c NOTE: The first row should be @headitem, but we do not yet require
32106 @c a new enough version of Texinfo (4.7) to use @headitem.
32108 @tab Value Required
32112 @item @samp{PacketSize}
32117 @item @samp{qXfer:auxv:read}
32122 @item @samp{qXfer:features:read}
32127 @item @samp{qXfer:libraries:read}
32132 @item @samp{qXfer:memory-map:read}
32137 @item @samp{qXfer:sdata:read}
32142 @item @samp{qXfer:spu:read}
32147 @item @samp{qXfer:spu:write}
32152 @item @samp{qXfer:siginfo:read}
32157 @item @samp{qXfer:siginfo:write}
32162 @item @samp{qXfer:threads:read}
32168 @item @samp{QNonStop}
32173 @item @samp{QPassSignals}
32178 @item @samp{QStartNoAckMode}
32183 @item @samp{multiprocess}
32188 @item @samp{ConditionalTracepoints}
32193 @item @samp{ReverseContinue}
32198 @item @samp{ReverseStep}
32203 @item @samp{TracepointSource}
32208 @item @samp{QAllow}
32215 These are the currently defined stub features, in more detail:
32218 @cindex packet size, remote protocol
32219 @item PacketSize=@var{bytes}
32220 The remote stub can accept packets up to at least @var{bytes} in
32221 length. @value{GDBN} will send packets up to this size for bulk
32222 transfers, and will never send larger packets. This is a limit on the
32223 data characters in the packet, including the frame and checksum.
32224 There is no trailing NUL byte in a remote protocol packet; if the stub
32225 stores packets in a NUL-terminated format, it should allow an extra
32226 byte in its buffer for the NUL. If this stub feature is not supported,
32227 @value{GDBN} guesses based on the size of the @samp{g} packet response.
32229 @item qXfer:auxv:read
32230 The remote stub understands the @samp{qXfer:auxv:read} packet
32231 (@pxref{qXfer auxiliary vector read}).
32233 @item qXfer:features:read
32234 The remote stub understands the @samp{qXfer:features:read} packet
32235 (@pxref{qXfer target description read}).
32237 @item qXfer:libraries:read
32238 The remote stub understands the @samp{qXfer:libraries:read} packet
32239 (@pxref{qXfer library list read}).
32241 @item qXfer:memory-map:read
32242 The remote stub understands the @samp{qXfer:memory-map:read} packet
32243 (@pxref{qXfer memory map read}).
32245 @item qXfer:sdata:read
32246 The remote stub understands the @samp{qXfer:sdata:read} packet
32247 (@pxref{qXfer sdata read}).
32249 @item qXfer:spu:read
32250 The remote stub understands the @samp{qXfer:spu:read} packet
32251 (@pxref{qXfer spu read}).
32253 @item qXfer:spu:write
32254 The remote stub understands the @samp{qXfer:spu:write} packet
32255 (@pxref{qXfer spu write}).
32257 @item qXfer:siginfo:read
32258 The remote stub understands the @samp{qXfer:siginfo:read} packet
32259 (@pxref{qXfer siginfo read}).
32261 @item qXfer:siginfo:write
32262 The remote stub understands the @samp{qXfer:siginfo:write} packet
32263 (@pxref{qXfer siginfo write}).
32265 @item qXfer:threads:read
32266 The remote stub understands the @samp{qXfer:threads:read} packet
32267 (@pxref{qXfer threads read}).
32270 The remote stub understands the @samp{QNonStop} packet
32271 (@pxref{QNonStop}).
32274 The remote stub understands the @samp{QPassSignals} packet
32275 (@pxref{QPassSignals}).
32277 @item QStartNoAckMode
32278 The remote stub understands the @samp{QStartNoAckMode} packet and
32279 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
32282 @anchor{multiprocess extensions}
32283 @cindex multiprocess extensions, in remote protocol
32284 The remote stub understands the multiprocess extensions to the remote
32285 protocol syntax. The multiprocess extensions affect the syntax of
32286 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
32287 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
32288 replies. Note that reporting this feature indicates support for the
32289 syntactic extensions only, not that the stub necessarily supports
32290 debugging of more than one process at a time. The stub must not use
32291 multiprocess extensions in packet replies unless @value{GDBN} has also
32292 indicated it supports them in its @samp{qSupported} request.
32294 @item qXfer:osdata:read
32295 The remote stub understands the @samp{qXfer:osdata:read} packet
32296 ((@pxref{qXfer osdata read}).
32298 @item ConditionalTracepoints
32299 The remote stub accepts and implements conditional expressions defined
32300 for tracepoints (@pxref{Tracepoint Conditions}).
32302 @item ReverseContinue
32303 The remote stub accepts and implements the reverse continue packet
32307 The remote stub accepts and implements the reverse step packet
32310 @item TracepointSource
32311 The remote stub understands the @samp{QTDPsrc} packet that supplies
32312 the source form of tracepoint definitions.
32315 The remote stub understands the @samp{QAllow} packet.
32317 @item StaticTracepoint
32318 @cindex static tracepoints, in remote protocol
32319 The remote stub supports static tracepoints.
32324 @cindex symbol lookup, remote request
32325 @cindex @samp{qSymbol} packet
32326 Notify the target that @value{GDBN} is prepared to serve symbol lookup
32327 requests. Accept requests from the target for the values of symbols.
32332 The target does not need to look up any (more) symbols.
32333 @item qSymbol:@var{sym_name}
32334 The target requests the value of symbol @var{sym_name} (hex encoded).
32335 @value{GDBN} may provide the value by using the
32336 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
32340 @item qSymbol:@var{sym_value}:@var{sym_name}
32341 Set the value of @var{sym_name} to @var{sym_value}.
32343 @var{sym_name} (hex encoded) is the name of a symbol whose value the
32344 target has previously requested.
32346 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
32347 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
32353 The target does not need to look up any (more) symbols.
32354 @item qSymbol:@var{sym_name}
32355 The target requests the value of a new symbol @var{sym_name} (hex
32356 encoded). @value{GDBN} will continue to supply the values of symbols
32357 (if available), until the target ceases to request them.
32362 @item QTDisconnected
32369 @xref{Tracepoint Packets}.
32371 @item qThreadExtraInfo,@var{thread-id}
32372 @cindex thread attributes info, remote request
32373 @cindex @samp{qThreadExtraInfo} packet
32374 Obtain a printable string description of a thread's attributes from
32375 the target OS. @var{thread-id} is a thread ID;
32376 see @ref{thread-id syntax}. This
32377 string may contain anything that the target OS thinks is interesting
32378 for @value{GDBN} to tell the user about the thread. The string is
32379 displayed in @value{GDBN}'s @code{info threads} display. Some
32380 examples of possible thread extra info strings are @samp{Runnable}, or
32381 @samp{Blocked on Mutex}.
32385 @item @var{XX}@dots{}
32386 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
32387 comprising the printable string containing the extra information about
32388 the thread's attributes.
32391 (Note that the @code{qThreadExtraInfo} packet's name is separated from
32392 the command by a @samp{,}, not a @samp{:}, contrary to the naming
32393 conventions above. Please don't use this packet as a model for new
32408 @xref{Tracepoint Packets}.
32410 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
32411 @cindex read special object, remote request
32412 @cindex @samp{qXfer} packet
32413 @anchor{qXfer read}
32414 Read uninterpreted bytes from the target's special data area
32415 identified by the keyword @var{object}. Request @var{length} bytes
32416 starting at @var{offset} bytes into the data. The content and
32417 encoding of @var{annex} is specific to @var{object}; it can supply
32418 additional details about what data to access.
32420 Here are the specific requests of this form defined so far. All
32421 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
32422 formats, listed below.
32425 @item qXfer:auxv:read::@var{offset},@var{length}
32426 @anchor{qXfer auxiliary vector read}
32427 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
32428 auxiliary vector}. Note @var{annex} must be empty.
32430 This packet is not probed by default; the remote stub must request it,
32431 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32433 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
32434 @anchor{qXfer target description read}
32435 Access the @dfn{target description}. @xref{Target Descriptions}. The
32436 annex specifies which XML document to access. The main description is
32437 always loaded from the @samp{target.xml} annex.
32439 This packet is not probed by default; the remote stub must request it,
32440 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32442 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
32443 @anchor{qXfer library list read}
32444 Access the target's list of loaded libraries. @xref{Library List Format}.
32445 The annex part of the generic @samp{qXfer} packet must be empty
32446 (@pxref{qXfer read}).
32448 Targets which maintain a list of libraries in the program's memory do
32449 not need to implement this packet; it is designed for platforms where
32450 the operating system manages the list of loaded libraries.
32452 This packet is not probed by default; the remote stub must request it,
32453 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32455 @item qXfer:memory-map:read::@var{offset},@var{length}
32456 @anchor{qXfer memory map read}
32457 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
32458 annex part of the generic @samp{qXfer} packet must be empty
32459 (@pxref{qXfer read}).
32461 This packet is not probed by default; the remote stub must request it,
32462 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32464 @item qXfer:sdata:read::@var{offset},@var{length}
32465 @anchor{qXfer sdata read}
32467 Read contents of the extra collected static tracepoint marker
32468 information. The annex part of the generic @samp{qXfer} packet must
32469 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
32472 This packet is not probed by default; the remote stub must request it,
32473 by supplying an appropriate @samp{qSupported} response
32474 (@pxref{qSupported}).
32476 @item qXfer:siginfo:read::@var{offset},@var{length}
32477 @anchor{qXfer siginfo read}
32478 Read contents of the extra signal information on the target
32479 system. The annex part of the generic @samp{qXfer} packet must be
32480 empty (@pxref{qXfer read}).
32482 This packet is not probed by default; the remote stub must request it,
32483 by supplying an appropriate @samp{qSupported} response
32484 (@pxref{qSupported}).
32486 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
32487 @anchor{qXfer spu read}
32488 Read contents of an @code{spufs} file on the target system. The
32489 annex specifies which file to read; it must be of the form
32490 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
32491 in the target process, and @var{name} identifes the @code{spufs} file
32492 in that context to be accessed.
32494 This packet is not probed by default; the remote stub must request it,
32495 by supplying an appropriate @samp{qSupported} response
32496 (@pxref{qSupported}).
32498 @item qXfer:threads:read::@var{offset},@var{length}
32499 @anchor{qXfer threads read}
32500 Access the list of threads on target. @xref{Thread List Format}. The
32501 annex part of the generic @samp{qXfer} packet must be empty
32502 (@pxref{qXfer read}).
32504 This packet is not probed by default; the remote stub must request it,
32505 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32507 @item qXfer:osdata:read::@var{offset},@var{length}
32508 @anchor{qXfer osdata read}
32509 Access the target's @dfn{operating system information}.
32510 @xref{Operating System Information}.
32517 Data @var{data} (@pxref{Binary Data}) has been read from the
32518 target. There may be more data at a higher address (although
32519 it is permitted to return @samp{m} even for the last valid
32520 block of data, as long as at least one byte of data was read).
32521 @var{data} may have fewer bytes than the @var{length} in the
32525 Data @var{data} (@pxref{Binary Data}) has been read from the target.
32526 There is no more data to be read. @var{data} may have fewer bytes
32527 than the @var{length} in the request.
32530 The @var{offset} in the request is at the end of the data.
32531 There is no more data to be read.
32534 The request was malformed, or @var{annex} was invalid.
32537 The offset was invalid, or there was an error encountered reading the data.
32538 @var{nn} is a hex-encoded @code{errno} value.
32541 An empty reply indicates the @var{object} string was not recognized by
32542 the stub, or that the object does not support reading.
32545 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
32546 @cindex write data into object, remote request
32547 @anchor{qXfer write}
32548 Write uninterpreted bytes into the target's special data area
32549 identified by the keyword @var{object}, starting at @var{offset} bytes
32550 into the data. @var{data}@dots{} is the binary-encoded data
32551 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
32552 is specific to @var{object}; it can supply additional details about what data
32555 Here are the specific requests of this form defined so far. All
32556 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
32557 formats, listed below.
32560 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
32561 @anchor{qXfer siginfo write}
32562 Write @var{data} to the extra signal information on the target system.
32563 The annex part of the generic @samp{qXfer} packet must be
32564 empty (@pxref{qXfer write}).
32566 This packet is not probed by default; the remote stub must request it,
32567 by supplying an appropriate @samp{qSupported} response
32568 (@pxref{qSupported}).
32570 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
32571 @anchor{qXfer spu write}
32572 Write @var{data} to an @code{spufs} file on the target system. The
32573 annex specifies which file to write; it must be of the form
32574 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
32575 in the target process, and @var{name} identifes the @code{spufs} file
32576 in that context to be accessed.
32578 This packet is not probed by default; the remote stub must request it,
32579 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32585 @var{nn} (hex encoded) is the number of bytes written.
32586 This may be fewer bytes than supplied in the request.
32589 The request was malformed, or @var{annex} was invalid.
32592 The offset was invalid, or there was an error encountered writing the data.
32593 @var{nn} is a hex-encoded @code{errno} value.
32596 An empty reply indicates the @var{object} string was not
32597 recognized by the stub, or that the object does not support writing.
32600 @item qXfer:@var{object}:@var{operation}:@dots{}
32601 Requests of this form may be added in the future. When a stub does
32602 not recognize the @var{object} keyword, or its support for
32603 @var{object} does not recognize the @var{operation} keyword, the stub
32604 must respond with an empty packet.
32606 @item qAttached:@var{pid}
32607 @cindex query attached, remote request
32608 @cindex @samp{qAttached} packet
32609 Return an indication of whether the remote server attached to an
32610 existing process or created a new process. When the multiprocess
32611 protocol extensions are supported (@pxref{multiprocess extensions}),
32612 @var{pid} is an integer in hexadecimal format identifying the target
32613 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
32614 the query packet will be simplified as @samp{qAttached}.
32616 This query is used, for example, to know whether the remote process
32617 should be detached or killed when a @value{GDBN} session is ended with
32618 the @code{quit} command.
32623 The remote server attached to an existing process.
32625 The remote server created a new process.
32627 A badly formed request or an error was encountered.
32632 @node Architecture-Specific Protocol Details
32633 @section Architecture-Specific Protocol Details
32635 This section describes how the remote protocol is applied to specific
32636 target architectures. Also see @ref{Standard Target Features}, for
32637 details of XML target descriptions for each architecture.
32641 @subsubsection Breakpoint Kinds
32643 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
32648 16-bit Thumb mode breakpoint.
32651 32-bit Thumb mode (Thumb-2) breakpoint.
32654 32-bit ARM mode breakpoint.
32660 @subsubsection Register Packet Format
32662 The following @code{g}/@code{G} packets have previously been defined.
32663 In the below, some thirty-two bit registers are transferred as
32664 sixty-four bits. Those registers should be zero/sign extended (which?)
32665 to fill the space allocated. Register bytes are transferred in target
32666 byte order. The two nibbles within a register byte are transferred
32667 most-significant - least-significant.
32673 All registers are transferred as thirty-two bit quantities in the order:
32674 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
32675 registers; fsr; fir; fp.
32679 All registers are transferred as sixty-four bit quantities (including
32680 thirty-two bit registers such as @code{sr}). The ordering is the same
32685 @node Tracepoint Packets
32686 @section Tracepoint Packets
32687 @cindex tracepoint packets
32688 @cindex packets, tracepoint
32690 Here we describe the packets @value{GDBN} uses to implement
32691 tracepoints (@pxref{Tracepoints}).
32695 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
32696 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
32697 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
32698 the tracepoint is disabled. @var{step} is the tracepoint's step
32699 count, and @var{pass} is its pass count. If an @samp{F} is present,
32700 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
32701 the number of bytes that the target should copy elsewhere to make room
32702 for the tracepoint. If an @samp{X} is present, it introduces a
32703 tracepoint condition, which consists of a hexadecimal length, followed
32704 by a comma and hex-encoded bytes, in a manner similar to action
32705 encodings as described below. If the trailing @samp{-} is present,
32706 further @samp{QTDP} packets will follow to specify this tracepoint's
32712 The packet was understood and carried out.
32714 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
32716 The packet was not recognized.
32719 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
32720 Define actions to be taken when a tracepoint is hit. @var{n} and
32721 @var{addr} must be the same as in the initial @samp{QTDP} packet for
32722 this tracepoint. This packet may only be sent immediately after
32723 another @samp{QTDP} packet that ended with a @samp{-}. If the
32724 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
32725 specifying more actions for this tracepoint.
32727 In the series of action packets for a given tracepoint, at most one
32728 can have an @samp{S} before its first @var{action}. If such a packet
32729 is sent, it and the following packets define ``while-stepping''
32730 actions. Any prior packets define ordinary actions --- that is, those
32731 taken when the tracepoint is first hit. If no action packet has an
32732 @samp{S}, then all the packets in the series specify ordinary
32733 tracepoint actions.
32735 The @samp{@var{action}@dots{}} portion of the packet is a series of
32736 actions, concatenated without separators. Each action has one of the
32742 Collect the registers whose bits are set in @var{mask}. @var{mask} is
32743 a hexadecimal number whose @var{i}'th bit is set if register number
32744 @var{i} should be collected. (The least significant bit is numbered
32745 zero.) Note that @var{mask} may be any number of digits long; it may
32746 not fit in a 32-bit word.
32748 @item M @var{basereg},@var{offset},@var{len}
32749 Collect @var{len} bytes of memory starting at the address in register
32750 number @var{basereg}, plus @var{offset}. If @var{basereg} is
32751 @samp{-1}, then the range has a fixed address: @var{offset} is the
32752 address of the lowest byte to collect. The @var{basereg},
32753 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
32754 values (the @samp{-1} value for @var{basereg} is a special case).
32756 @item X @var{len},@var{expr}
32757 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
32758 it directs. @var{expr} is an agent expression, as described in
32759 @ref{Agent Expressions}. Each byte of the expression is encoded as a
32760 two-digit hex number in the packet; @var{len} is the number of bytes
32761 in the expression (and thus one-half the number of hex digits in the
32766 Any number of actions may be packed together in a single @samp{QTDP}
32767 packet, as long as the packet does not exceed the maximum packet
32768 length (400 bytes, for many stubs). There may be only one @samp{R}
32769 action per tracepoint, and it must precede any @samp{M} or @samp{X}
32770 actions. Any registers referred to by @samp{M} and @samp{X} actions
32771 must be collected by a preceding @samp{R} action. (The
32772 ``while-stepping'' actions are treated as if they were attached to a
32773 separate tracepoint, as far as these restrictions are concerned.)
32778 The packet was understood and carried out.
32780 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
32782 The packet was not recognized.
32785 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
32786 @cindex @samp{QTDPsrc} packet
32787 Specify a source string of tracepoint @var{n} at address @var{addr}.
32788 This is useful to get accurate reproduction of the tracepoints
32789 originally downloaded at the beginning of the trace run. @var{type}
32790 is the name of the tracepoint part, such as @samp{cond} for the
32791 tracepoint's conditional expression (see below for a list of types), while
32792 @var{bytes} is the string, encoded in hexadecimal.
32794 @var{start} is the offset of the @var{bytes} within the overall source
32795 string, while @var{slen} is the total length of the source string.
32796 This is intended for handling source strings that are longer than will
32797 fit in a single packet.
32798 @c Add detailed example when this info is moved into a dedicated
32799 @c tracepoint descriptions section.
32801 The available string types are @samp{at} for the location,
32802 @samp{cond} for the conditional, and @samp{cmd} for an action command.
32803 @value{GDBN} sends a separate packet for each command in the action
32804 list, in the same order in which the commands are stored in the list.
32806 The target does not need to do anything with source strings except
32807 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
32810 Although this packet is optional, and @value{GDBN} will only send it
32811 if the target replies with @samp{TracepointSource} @xref{General
32812 Query Packets}, it makes both disconnected tracing and trace files
32813 much easier to use. Otherwise the user must be careful that the
32814 tracepoints in effect while looking at trace frames are identical to
32815 the ones in effect during the trace run; even a small discrepancy
32816 could cause @samp{tdump} not to work, or a particular trace frame not
32819 @item QTDV:@var{n}:@var{value}
32820 @cindex define trace state variable, remote request
32821 @cindex @samp{QTDV} packet
32822 Create a new trace state variable, number @var{n}, with an initial
32823 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
32824 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
32825 the option of not using this packet for initial values of zero; the
32826 target should simply create the trace state variables as they are
32827 mentioned in expressions.
32829 @item QTFrame:@var{n}
32830 Select the @var{n}'th tracepoint frame from the buffer, and use the
32831 register and memory contents recorded there to answer subsequent
32832 request packets from @value{GDBN}.
32834 A successful reply from the stub indicates that the stub has found the
32835 requested frame. The response is a series of parts, concatenated
32836 without separators, describing the frame we selected. Each part has
32837 one of the following forms:
32841 The selected frame is number @var{n} in the trace frame buffer;
32842 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
32843 was no frame matching the criteria in the request packet.
32846 The selected trace frame records a hit of tracepoint number @var{t};
32847 @var{t} is a hexadecimal number.
32851 @item QTFrame:pc:@var{addr}
32852 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
32853 currently selected frame whose PC is @var{addr};
32854 @var{addr} is a hexadecimal number.
32856 @item QTFrame:tdp:@var{t}
32857 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
32858 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
32859 is a hexadecimal number.
32861 @item QTFrame:range:@var{start}:@var{end}
32862 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
32863 currently selected frame whose PC is between @var{start} (inclusive)
32864 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
32867 @item QTFrame:outside:@var{start}:@var{end}
32868 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
32869 frame @emph{outside} the given range of addresses (exclusive).
32872 Begin the tracepoint experiment. Begin collecting data from
32873 tracepoint hits in the trace frame buffer. This packet supports the
32874 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
32875 instruction reply packet}).
32878 End the tracepoint experiment. Stop collecting trace frames.
32881 Clear the table of tracepoints, and empty the trace frame buffer.
32883 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
32884 Establish the given ranges of memory as ``transparent''. The stub
32885 will answer requests for these ranges from memory's current contents,
32886 if they were not collected as part of the tracepoint hit.
32888 @value{GDBN} uses this to mark read-only regions of memory, like those
32889 containing program code. Since these areas never change, they should
32890 still have the same contents they did when the tracepoint was hit, so
32891 there's no reason for the stub to refuse to provide their contents.
32893 @item QTDisconnected:@var{value}
32894 Set the choice to what to do with the tracing run when @value{GDBN}
32895 disconnects from the target. A @var{value} of 1 directs the target to
32896 continue the tracing run, while 0 tells the target to stop tracing if
32897 @value{GDBN} is no longer in the picture.
32900 Ask the stub if there is a trace experiment running right now.
32902 The reply has the form:
32906 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
32907 @var{running} is a single digit @code{1} if the trace is presently
32908 running, or @code{0} if not. It is followed by semicolon-separated
32909 optional fields that an agent may use to report additional status.
32913 If the trace is not running, the agent may report any of several
32914 explanations as one of the optional fields:
32919 No trace has been run yet.
32922 The trace was stopped by a user-originated stop command.
32925 The trace stopped because the trace buffer filled up.
32927 @item tdisconnected:0
32928 The trace stopped because @value{GDBN} disconnected from the target.
32930 @item tpasscount:@var{tpnum}
32931 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
32933 @item terror:@var{text}:@var{tpnum}
32934 The trace stopped because tracepoint @var{tpnum} had an error. The
32935 string @var{text} is available to describe the nature of the error
32936 (for instance, a divide by zero in the condition expression).
32937 @var{text} is hex encoded.
32940 The trace stopped for some other reason.
32944 Additional optional fields supply statistical and other information.
32945 Although not required, they are extremely useful for users monitoring
32946 the progress of a trace run. If a trace has stopped, and these
32947 numbers are reported, they must reflect the state of the just-stopped
32952 @item tframes:@var{n}
32953 The number of trace frames in the buffer.
32955 @item tcreated:@var{n}
32956 The total number of trace frames created during the run. This may
32957 be larger than the trace frame count, if the buffer is circular.
32959 @item tsize:@var{n}
32960 The total size of the trace buffer, in bytes.
32962 @item tfree:@var{n}
32963 The number of bytes still unused in the buffer.
32965 @item circular:@var{n}
32966 The value of the circular trace buffer flag. @code{1} means that the
32967 trace buffer is circular and old trace frames will be discarded if
32968 necessary to make room, @code{0} means that the trace buffer is linear
32971 @item disconn:@var{n}
32972 The value of the disconnected tracing flag. @code{1} means that
32973 tracing will continue after @value{GDBN} disconnects, @code{0} means
32974 that the trace run will stop.
32978 @item qTV:@var{var}
32979 @cindex trace state variable value, remote request
32980 @cindex @samp{qTV} packet
32981 Ask the stub for the value of the trace state variable number @var{var}.
32986 The value of the variable is @var{value}. This will be the current
32987 value of the variable if the user is examining a running target, or a
32988 saved value if the variable was collected in the trace frame that the
32989 user is looking at. Note that multiple requests may result in
32990 different reply values, such as when requesting values while the
32991 program is running.
32994 The value of the variable is unknown. This would occur, for example,
32995 if the user is examining a trace frame in which the requested variable
33001 These packets request data about tracepoints that are being used by
33002 the target. @value{GDBN} sends @code{qTfP} to get the first piece
33003 of data, and multiple @code{qTsP} to get additional pieces. Replies
33004 to these packets generally take the form of the @code{QTDP} packets
33005 that define tracepoints. (FIXME add detailed syntax)
33009 These packets request data about trace state variables that are on the
33010 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
33011 and multiple @code{qTsV} to get additional variables. Replies to
33012 these packets follow the syntax of the @code{QTDV} packets that define
33013 trace state variables.
33017 These packets request data about static tracepoint markers that exist
33018 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
33019 first piece of data, and multiple @code{qTsSTM} to get additional
33020 pieces. Replies to these packets take the following form:
33024 @item m @var{address}:@var{id}:@var{extra}
33026 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
33027 a comma-separated list of markers
33029 (lower case letter @samp{L}) denotes end of list.
33031 An error occurred. @var{nn} are hex digits.
33033 An empty reply indicates that the request is not supported by the
33037 @var{address} is encoded in hex.
33038 @var{id} and @var{extra} are strings encoded in hex.
33040 In response to each query, the target will reply with a list of one or
33041 more markers, separated by commas. @value{GDBN} will respond to each
33042 reply with a request for more markers (using the @samp{qs} form of the
33043 query), until the target responds with @samp{l} (lower-case ell, for
33046 @item qTSTMat:@var{address}
33047 This packets requests data about static tracepoint markers in the
33048 target program at @var{address}. Replies to this packet follow the
33049 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
33050 tracepoint markers.
33052 @item QTSave:@var{filename}
33053 This packet directs the target to save trace data to the file name
33054 @var{filename} in the target's filesystem. @var{filename} is encoded
33055 as a hex string; the interpretation of the file name (relative vs
33056 absolute, wild cards, etc) is up to the target.
33058 @item qTBuffer:@var{offset},@var{len}
33059 Return up to @var{len} bytes of the current contents of trace buffer,
33060 starting at @var{offset}. The trace buffer is treated as if it were
33061 a contiguous collection of traceframes, as per the trace file format.
33062 The reply consists as many hex-encoded bytes as the target can deliver
33063 in a packet; it is not an error to return fewer than were asked for.
33064 A reply consisting of just @code{l} indicates that no bytes are
33067 @item QTBuffer:circular:@var{value}
33068 This packet directs the target to use a circular trace buffer if
33069 @var{value} is 1, or a linear buffer if the value is 0.
33073 @subsection Relocate instruction reply packet
33074 When installing fast tracepoints in memory, the target may need to
33075 relocate the instruction currently at the tracepoint address to a
33076 different address in memory. For most instructions, a simple copy is
33077 enough, but, for example, call instructions that implicitly push the
33078 return address on the stack, and relative branches or other
33079 PC-relative instructions require offset adjustment, so that the effect
33080 of executing the instruction at a different address is the same as if
33081 it had executed in the original location.
33083 In response to several of the tracepoint packets, the target may also
33084 respond with a number of intermediate @samp{qRelocInsn} request
33085 packets before the final result packet, to have @value{GDBN} handle
33086 this relocation operation. If a packet supports this mechanism, its
33087 documentation will explicitly say so. See for example the above
33088 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
33089 format of the request is:
33092 @item qRelocInsn:@var{from};@var{to}
33094 This requests @value{GDBN} to copy instruction at address @var{from}
33095 to address @var{to}, possibly adjusted so that executing the
33096 instruction at @var{to} has the same effect as executing it at
33097 @var{from}. @value{GDBN} writes the adjusted instruction to target
33098 memory starting at @var{to}.
33103 @item qRelocInsn:@var{adjusted_size}
33104 Informs the stub the relocation is complete. @var{adjusted_size} is
33105 the length in bytes of resulting relocated instruction sequence.
33107 A badly formed request was detected, or an error was encountered while
33108 relocating the instruction.
33111 @node Host I/O Packets
33112 @section Host I/O Packets
33113 @cindex Host I/O, remote protocol
33114 @cindex file transfer, remote protocol
33116 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
33117 operations on the far side of a remote link. For example, Host I/O is
33118 used to upload and download files to a remote target with its own
33119 filesystem. Host I/O uses the same constant values and data structure
33120 layout as the target-initiated File-I/O protocol. However, the
33121 Host I/O packets are structured differently. The target-initiated
33122 protocol relies on target memory to store parameters and buffers.
33123 Host I/O requests are initiated by @value{GDBN}, and the
33124 target's memory is not involved. @xref{File-I/O Remote Protocol
33125 Extension}, for more details on the target-initiated protocol.
33127 The Host I/O request packets all encode a single operation along with
33128 its arguments. They have this format:
33132 @item vFile:@var{operation}: @var{parameter}@dots{}
33133 @var{operation} is the name of the particular request; the target
33134 should compare the entire packet name up to the second colon when checking
33135 for a supported operation. The format of @var{parameter} depends on
33136 the operation. Numbers are always passed in hexadecimal. Negative
33137 numbers have an explicit minus sign (i.e.@: two's complement is not
33138 used). Strings (e.g.@: filenames) are encoded as a series of
33139 hexadecimal bytes. The last argument to a system call may be a
33140 buffer of escaped binary data (@pxref{Binary Data}).
33144 The valid responses to Host I/O packets are:
33148 @item F @var{result} [, @var{errno}] [; @var{attachment}]
33149 @var{result} is the integer value returned by this operation, usually
33150 non-negative for success and -1 for errors. If an error has occured,
33151 @var{errno} will be included in the result. @var{errno} will have a
33152 value defined by the File-I/O protocol (@pxref{Errno Values}). For
33153 operations which return data, @var{attachment} supplies the data as a
33154 binary buffer. Binary buffers in response packets are escaped in the
33155 normal way (@pxref{Binary Data}). See the individual packet
33156 documentation for the interpretation of @var{result} and
33160 An empty response indicates that this operation is not recognized.
33164 These are the supported Host I/O operations:
33167 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
33168 Open a file at @var{pathname} and return a file descriptor for it, or
33169 return -1 if an error occurs. @var{pathname} is a string,
33170 @var{flags} is an integer indicating a mask of open flags
33171 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
33172 of mode bits to use if the file is created (@pxref{mode_t Values}).
33173 @xref{open}, for details of the open flags and mode values.
33175 @item vFile:close: @var{fd}
33176 Close the open file corresponding to @var{fd} and return 0, or
33177 -1 if an error occurs.
33179 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
33180 Read data from the open file corresponding to @var{fd}. Up to
33181 @var{count} bytes will be read from the file, starting at @var{offset}
33182 relative to the start of the file. The target may read fewer bytes;
33183 common reasons include packet size limits and an end-of-file
33184 condition. The number of bytes read is returned. Zero should only be
33185 returned for a successful read at the end of the file, or if
33186 @var{count} was zero.
33188 The data read should be returned as a binary attachment on success.
33189 If zero bytes were read, the response should include an empty binary
33190 attachment (i.e.@: a trailing semicolon). The return value is the
33191 number of target bytes read; the binary attachment may be longer if
33192 some characters were escaped.
33194 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
33195 Write @var{data} (a binary buffer) to the open file corresponding
33196 to @var{fd}. Start the write at @var{offset} from the start of the
33197 file. Unlike many @code{write} system calls, there is no
33198 separate @var{count} argument; the length of @var{data} in the
33199 packet is used. @samp{vFile:write} returns the number of bytes written,
33200 which may be shorter than the length of @var{data}, or -1 if an
33203 @item vFile:unlink: @var{pathname}
33204 Delete the file at @var{pathname} on the target. Return 0,
33205 or -1 if an error occurs. @var{pathname} is a string.
33210 @section Interrupts
33211 @cindex interrupts (remote protocol)
33213 When a program on the remote target is running, @value{GDBN} may
33214 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
33215 a @code{BREAK} followed by @code{g},
33216 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
33218 The precise meaning of @code{BREAK} is defined by the transport
33219 mechanism and may, in fact, be undefined. @value{GDBN} does not
33220 currently define a @code{BREAK} mechanism for any of the network
33221 interfaces except for TCP, in which case @value{GDBN} sends the
33222 @code{telnet} BREAK sequence.
33224 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
33225 transport mechanisms. It is represented by sending the single byte
33226 @code{0x03} without any of the usual packet overhead described in
33227 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
33228 transmitted as part of a packet, it is considered to be packet data
33229 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
33230 (@pxref{X packet}), used for binary downloads, may include an unescaped
33231 @code{0x03} as part of its packet.
33233 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
33234 When Linux kernel receives this sequence from serial port,
33235 it stops execution and connects to gdb.
33237 Stubs are not required to recognize these interrupt mechanisms and the
33238 precise meaning associated with receipt of the interrupt is
33239 implementation defined. If the target supports debugging of multiple
33240 threads and/or processes, it should attempt to interrupt all
33241 currently-executing threads and processes.
33242 If the stub is successful at interrupting the
33243 running program, it should send one of the stop
33244 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
33245 of successfully stopping the program in all-stop mode, and a stop reply
33246 for each stopped thread in non-stop mode.
33247 Interrupts received while the
33248 program is stopped are discarded.
33250 @node Notification Packets
33251 @section Notification Packets
33252 @cindex notification packets
33253 @cindex packets, notification
33255 The @value{GDBN} remote serial protocol includes @dfn{notifications},
33256 packets that require no acknowledgment. Both the GDB and the stub
33257 may send notifications (although the only notifications defined at
33258 present are sent by the stub). Notifications carry information
33259 without incurring the round-trip latency of an acknowledgment, and so
33260 are useful for low-impact communications where occasional packet loss
33263 A notification packet has the form @samp{% @var{data} #
33264 @var{checksum}}, where @var{data} is the content of the notification,
33265 and @var{checksum} is a checksum of @var{data}, computed and formatted
33266 as for ordinary @value{GDBN} packets. A notification's @var{data}
33267 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
33268 receiving a notification, the recipient sends no @samp{+} or @samp{-}
33269 to acknowledge the notification's receipt or to report its corruption.
33271 Every notification's @var{data} begins with a name, which contains no
33272 colon characters, followed by a colon character.
33274 Recipients should silently ignore corrupted notifications and
33275 notifications they do not understand. Recipients should restart
33276 timeout periods on receipt of a well-formed notification, whether or
33277 not they understand it.
33279 Senders should only send the notifications described here when this
33280 protocol description specifies that they are permitted. In the
33281 future, we may extend the protocol to permit existing notifications in
33282 new contexts; this rule helps older senders avoid confusing newer
33285 (Older versions of @value{GDBN} ignore bytes received until they see
33286 the @samp{$} byte that begins an ordinary packet, so new stubs may
33287 transmit notifications without fear of confusing older clients. There
33288 are no notifications defined for @value{GDBN} to send at the moment, but we
33289 assume that most older stubs would ignore them, as well.)
33291 The following notification packets from the stub to @value{GDBN} are
33295 @item Stop: @var{reply}
33296 Report an asynchronous stop event in non-stop mode.
33297 The @var{reply} has the form of a stop reply, as
33298 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
33299 for information on how these notifications are acknowledged by
33303 @node Remote Non-Stop
33304 @section Remote Protocol Support for Non-Stop Mode
33306 @value{GDBN}'s remote protocol supports non-stop debugging of
33307 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
33308 supports non-stop mode, it should report that to @value{GDBN} by including
33309 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
33311 @value{GDBN} typically sends a @samp{QNonStop} packet only when
33312 establishing a new connection with the stub. Entering non-stop mode
33313 does not alter the state of any currently-running threads, but targets
33314 must stop all threads in any already-attached processes when entering
33315 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
33316 probe the target state after a mode change.
33318 In non-stop mode, when an attached process encounters an event that
33319 would otherwise be reported with a stop reply, it uses the
33320 asynchronous notification mechanism (@pxref{Notification Packets}) to
33321 inform @value{GDBN}. In contrast to all-stop mode, where all threads
33322 in all processes are stopped when a stop reply is sent, in non-stop
33323 mode only the thread reporting the stop event is stopped. That is,
33324 when reporting a @samp{S} or @samp{T} response to indicate completion
33325 of a step operation, hitting a breakpoint, or a fault, only the
33326 affected thread is stopped; any other still-running threads continue
33327 to run. When reporting a @samp{W} or @samp{X} response, all running
33328 threads belonging to other attached processes continue to run.
33330 Only one stop reply notification at a time may be pending; if
33331 additional stop events occur before @value{GDBN} has acknowledged the
33332 previous notification, they must be queued by the stub for later
33333 synchronous transmission in response to @samp{vStopped} packets from
33334 @value{GDBN}. Because the notification mechanism is unreliable,
33335 the stub is permitted to resend a stop reply notification
33336 if it believes @value{GDBN} may not have received it. @value{GDBN}
33337 ignores additional stop reply notifications received before it has
33338 finished processing a previous notification and the stub has completed
33339 sending any queued stop events.
33341 Otherwise, @value{GDBN} must be prepared to receive a stop reply
33342 notification at any time. Specifically, they may appear when
33343 @value{GDBN} is not otherwise reading input from the stub, or when
33344 @value{GDBN} is expecting to read a normal synchronous response or a
33345 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
33346 Notification packets are distinct from any other communication from
33347 the stub so there is no ambiguity.
33349 After receiving a stop reply notification, @value{GDBN} shall
33350 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
33351 as a regular, synchronous request to the stub. Such acknowledgment
33352 is not required to happen immediately, as @value{GDBN} is permitted to
33353 send other, unrelated packets to the stub first, which the stub should
33356 Upon receiving a @samp{vStopped} packet, if the stub has other queued
33357 stop events to report to @value{GDBN}, it shall respond by sending a
33358 normal stop reply response. @value{GDBN} shall then send another
33359 @samp{vStopped} packet to solicit further responses; again, it is
33360 permitted to send other, unrelated packets as well which the stub
33361 should process normally.
33363 If the stub receives a @samp{vStopped} packet and there are no
33364 additional stop events to report, the stub shall return an @samp{OK}
33365 response. At this point, if further stop events occur, the stub shall
33366 send a new stop reply notification, @value{GDBN} shall accept the
33367 notification, and the process shall be repeated.
33369 In non-stop mode, the target shall respond to the @samp{?} packet as
33370 follows. First, any incomplete stop reply notification/@samp{vStopped}
33371 sequence in progress is abandoned. The target must begin a new
33372 sequence reporting stop events for all stopped threads, whether or not
33373 it has previously reported those events to @value{GDBN}. The first
33374 stop reply is sent as a synchronous reply to the @samp{?} packet, and
33375 subsequent stop replies are sent as responses to @samp{vStopped} packets
33376 using the mechanism described above. The target must not send
33377 asynchronous stop reply notifications until the sequence is complete.
33378 If all threads are running when the target receives the @samp{?} packet,
33379 or if the target is not attached to any process, it shall respond
33382 @node Packet Acknowledgment
33383 @section Packet Acknowledgment
33385 @cindex acknowledgment, for @value{GDBN} remote
33386 @cindex packet acknowledgment, for @value{GDBN} remote
33387 By default, when either the host or the target machine receives a packet,
33388 the first response expected is an acknowledgment: either @samp{+} (to indicate
33389 the package was received correctly) or @samp{-} (to request retransmission).
33390 This mechanism allows the @value{GDBN} remote protocol to operate over
33391 unreliable transport mechanisms, such as a serial line.
33393 In cases where the transport mechanism is itself reliable (such as a pipe or
33394 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
33395 It may be desirable to disable them in that case to reduce communication
33396 overhead, or for other reasons. This can be accomplished by means of the
33397 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
33399 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
33400 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
33401 and response format still includes the normal checksum, as described in
33402 @ref{Overview}, but the checksum may be ignored by the receiver.
33404 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
33405 no-acknowledgment mode, it should report that to @value{GDBN}
33406 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
33407 @pxref{qSupported}.
33408 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
33409 disabled via the @code{set remote noack-packet off} command
33410 (@pxref{Remote Configuration}),
33411 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
33412 Only then may the stub actually turn off packet acknowledgments.
33413 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
33414 response, which can be safely ignored by the stub.
33416 Note that @code{set remote noack-packet} command only affects negotiation
33417 between @value{GDBN} and the stub when subsequent connections are made;
33418 it does not affect the protocol acknowledgment state for any current
33420 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
33421 new connection is established,
33422 there is also no protocol request to re-enable the acknowledgments
33423 for the current connection, once disabled.
33428 Example sequence of a target being re-started. Notice how the restart
33429 does not get any direct output:
33434 @emph{target restarts}
33437 <- @code{T001:1234123412341234}
33441 Example sequence of a target being stepped by a single instruction:
33444 -> @code{G1445@dots{}}
33449 <- @code{T001:1234123412341234}
33453 <- @code{1455@dots{}}
33457 @node File-I/O Remote Protocol Extension
33458 @section File-I/O Remote Protocol Extension
33459 @cindex File-I/O remote protocol extension
33462 * File-I/O Overview::
33463 * Protocol Basics::
33464 * The F Request Packet::
33465 * The F Reply Packet::
33466 * The Ctrl-C Message::
33468 * List of Supported Calls::
33469 * Protocol-specific Representation of Datatypes::
33471 * File-I/O Examples::
33474 @node File-I/O Overview
33475 @subsection File-I/O Overview
33476 @cindex file-i/o overview
33478 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
33479 target to use the host's file system and console I/O to perform various
33480 system calls. System calls on the target system are translated into a
33481 remote protocol packet to the host system, which then performs the needed
33482 actions and returns a response packet to the target system.
33483 This simulates file system operations even on targets that lack file systems.
33485 The protocol is defined to be independent of both the host and target systems.
33486 It uses its own internal representation of datatypes and values. Both
33487 @value{GDBN} and the target's @value{GDBN} stub are responsible for
33488 translating the system-dependent value representations into the internal
33489 protocol representations when data is transmitted.
33491 The communication is synchronous. A system call is possible only when
33492 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
33493 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
33494 the target is stopped to allow deterministic access to the target's
33495 memory. Therefore File-I/O is not interruptible by target signals. On
33496 the other hand, it is possible to interrupt File-I/O by a user interrupt
33497 (@samp{Ctrl-C}) within @value{GDBN}.
33499 The target's request to perform a host system call does not finish
33500 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
33501 after finishing the system call, the target returns to continuing the
33502 previous activity (continue, step). No additional continue or step
33503 request from @value{GDBN} is required.
33506 (@value{GDBP}) continue
33507 <- target requests 'system call X'
33508 target is stopped, @value{GDBN} executes system call
33509 -> @value{GDBN} returns result
33510 ... target continues, @value{GDBN} returns to wait for the target
33511 <- target hits breakpoint and sends a Txx packet
33514 The protocol only supports I/O on the console and to regular files on
33515 the host file system. Character or block special devices, pipes,
33516 named pipes, sockets or any other communication method on the host
33517 system are not supported by this protocol.
33519 File I/O is not supported in non-stop mode.
33521 @node Protocol Basics
33522 @subsection Protocol Basics
33523 @cindex protocol basics, file-i/o
33525 The File-I/O protocol uses the @code{F} packet as the request as well
33526 as reply packet. Since a File-I/O system call can only occur when
33527 @value{GDBN} is waiting for a response from the continuing or stepping target,
33528 the File-I/O request is a reply that @value{GDBN} has to expect as a result
33529 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
33530 This @code{F} packet contains all information needed to allow @value{GDBN}
33531 to call the appropriate host system call:
33535 A unique identifier for the requested system call.
33538 All parameters to the system call. Pointers are given as addresses
33539 in the target memory address space. Pointers to strings are given as
33540 pointer/length pair. Numerical values are given as they are.
33541 Numerical control flags are given in a protocol-specific representation.
33545 At this point, @value{GDBN} has to perform the following actions.
33549 If the parameters include pointer values to data needed as input to a
33550 system call, @value{GDBN} requests this data from the target with a
33551 standard @code{m} packet request. This additional communication has to be
33552 expected by the target implementation and is handled as any other @code{m}
33556 @value{GDBN} translates all value from protocol representation to host
33557 representation as needed. Datatypes are coerced into the host types.
33560 @value{GDBN} calls the system call.
33563 It then coerces datatypes back to protocol representation.
33566 If the system call is expected to return data in buffer space specified
33567 by pointer parameters to the call, the data is transmitted to the
33568 target using a @code{M} or @code{X} packet. This packet has to be expected
33569 by the target implementation and is handled as any other @code{M} or @code{X}
33574 Eventually @value{GDBN} replies with another @code{F} packet which contains all
33575 necessary information for the target to continue. This at least contains
33582 @code{errno}, if has been changed by the system call.
33589 After having done the needed type and value coercion, the target continues
33590 the latest continue or step action.
33592 @node The F Request Packet
33593 @subsection The @code{F} Request Packet
33594 @cindex file-i/o request packet
33595 @cindex @code{F} request packet
33597 The @code{F} request packet has the following format:
33600 @item F@var{call-id},@var{parameter@dots{}}
33602 @var{call-id} is the identifier to indicate the host system call to be called.
33603 This is just the name of the function.
33605 @var{parameter@dots{}} are the parameters to the system call.
33606 Parameters are hexadecimal integer values, either the actual values in case
33607 of scalar datatypes, pointers to target buffer space in case of compound
33608 datatypes and unspecified memory areas, or pointer/length pairs in case
33609 of string parameters. These are appended to the @var{call-id} as a
33610 comma-delimited list. All values are transmitted in ASCII
33611 string representation, pointer/length pairs separated by a slash.
33617 @node The F Reply Packet
33618 @subsection The @code{F} Reply Packet
33619 @cindex file-i/o reply packet
33620 @cindex @code{F} reply packet
33622 The @code{F} reply packet has the following format:
33626 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
33628 @var{retcode} is the return code of the system call as hexadecimal value.
33630 @var{errno} is the @code{errno} set by the call, in protocol-specific
33632 This parameter can be omitted if the call was successful.
33634 @var{Ctrl-C flag} is only sent if the user requested a break. In this
33635 case, @var{errno} must be sent as well, even if the call was successful.
33636 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
33643 or, if the call was interrupted before the host call has been performed:
33650 assuming 4 is the protocol-specific representation of @code{EINTR}.
33655 @node The Ctrl-C Message
33656 @subsection The @samp{Ctrl-C} Message
33657 @cindex ctrl-c message, in file-i/o protocol
33659 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
33660 reply packet (@pxref{The F Reply Packet}),
33661 the target should behave as if it had
33662 gotten a break message. The meaning for the target is ``system call
33663 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
33664 (as with a break message) and return to @value{GDBN} with a @code{T02}
33667 It's important for the target to know in which
33668 state the system call was interrupted. There are two possible cases:
33672 The system call hasn't been performed on the host yet.
33675 The system call on the host has been finished.
33679 These two states can be distinguished by the target by the value of the
33680 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
33681 call hasn't been performed. This is equivalent to the @code{EINTR} handling
33682 on POSIX systems. In any other case, the target may presume that the
33683 system call has been finished --- successfully or not --- and should behave
33684 as if the break message arrived right after the system call.
33686 @value{GDBN} must behave reliably. If the system call has not been called
33687 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
33688 @code{errno} in the packet. If the system call on the host has been finished
33689 before the user requests a break, the full action must be finished by
33690 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
33691 The @code{F} packet may only be sent when either nothing has happened
33692 or the full action has been completed.
33695 @subsection Console I/O
33696 @cindex console i/o as part of file-i/o
33698 By default and if not explicitly closed by the target system, the file
33699 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
33700 on the @value{GDBN} console is handled as any other file output operation
33701 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
33702 by @value{GDBN} so that after the target read request from file descriptor
33703 0 all following typing is buffered until either one of the following
33708 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
33710 system call is treated as finished.
33713 The user presses @key{RET}. This is treated as end of input with a trailing
33717 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
33718 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
33722 If the user has typed more characters than fit in the buffer given to
33723 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
33724 either another @code{read(0, @dots{})} is requested by the target, or debugging
33725 is stopped at the user's request.
33728 @node List of Supported Calls
33729 @subsection List of Supported Calls
33730 @cindex list of supported file-i/o calls
33747 @unnumberedsubsubsec open
33748 @cindex open, file-i/o system call
33753 int open(const char *pathname, int flags);
33754 int open(const char *pathname, int flags, mode_t mode);
33758 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
33761 @var{flags} is the bitwise @code{OR} of the following values:
33765 If the file does not exist it will be created. The host
33766 rules apply as far as file ownership and time stamps
33770 When used with @code{O_CREAT}, if the file already exists it is
33771 an error and open() fails.
33774 If the file already exists and the open mode allows
33775 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
33776 truncated to zero length.
33779 The file is opened in append mode.
33782 The file is opened for reading only.
33785 The file is opened for writing only.
33788 The file is opened for reading and writing.
33792 Other bits are silently ignored.
33796 @var{mode} is the bitwise @code{OR} of the following values:
33800 User has read permission.
33803 User has write permission.
33806 Group has read permission.
33809 Group has write permission.
33812 Others have read permission.
33815 Others have write permission.
33819 Other bits are silently ignored.
33822 @item Return value:
33823 @code{open} returns the new file descriptor or -1 if an error
33830 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
33833 @var{pathname} refers to a directory.
33836 The requested access is not allowed.
33839 @var{pathname} was too long.
33842 A directory component in @var{pathname} does not exist.
33845 @var{pathname} refers to a device, pipe, named pipe or socket.
33848 @var{pathname} refers to a file on a read-only filesystem and
33849 write access was requested.
33852 @var{pathname} is an invalid pointer value.
33855 No space on device to create the file.
33858 The process already has the maximum number of files open.
33861 The limit on the total number of files open on the system
33865 The call was interrupted by the user.
33871 @unnumberedsubsubsec close
33872 @cindex close, file-i/o system call
33881 @samp{Fclose,@var{fd}}
33883 @item Return value:
33884 @code{close} returns zero on success, or -1 if an error occurred.
33890 @var{fd} isn't a valid open file descriptor.
33893 The call was interrupted by the user.
33899 @unnumberedsubsubsec read
33900 @cindex read, file-i/o system call
33905 int read(int fd, void *buf, unsigned int count);
33909 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
33911 @item Return value:
33912 On success, the number of bytes read is returned.
33913 Zero indicates end of file. If count is zero, read
33914 returns zero as well. On error, -1 is returned.
33920 @var{fd} is not a valid file descriptor or is not open for
33924 @var{bufptr} is an invalid pointer value.
33927 The call was interrupted by the user.
33933 @unnumberedsubsubsec write
33934 @cindex write, file-i/o system call
33939 int write(int fd, const void *buf, unsigned int count);
33943 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
33945 @item Return value:
33946 On success, the number of bytes written are returned.
33947 Zero indicates nothing was written. On error, -1
33954 @var{fd} is not a valid file descriptor or is not open for
33958 @var{bufptr} is an invalid pointer value.
33961 An attempt was made to write a file that exceeds the
33962 host-specific maximum file size allowed.
33965 No space on device to write the data.
33968 The call was interrupted by the user.
33974 @unnumberedsubsubsec lseek
33975 @cindex lseek, file-i/o system call
33980 long lseek (int fd, long offset, int flag);
33984 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
33986 @var{flag} is one of:
33990 The offset is set to @var{offset} bytes.
33993 The offset is set to its current location plus @var{offset}
33997 The offset is set to the size of the file plus @var{offset}
34001 @item Return value:
34002 On success, the resulting unsigned offset in bytes from
34003 the beginning of the file is returned. Otherwise, a
34004 value of -1 is returned.
34010 @var{fd} is not a valid open file descriptor.
34013 @var{fd} is associated with the @value{GDBN} console.
34016 @var{flag} is not a proper value.
34019 The call was interrupted by the user.
34025 @unnumberedsubsubsec rename
34026 @cindex rename, file-i/o system call
34031 int rename(const char *oldpath, const char *newpath);
34035 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
34037 @item Return value:
34038 On success, zero is returned. On error, -1 is returned.
34044 @var{newpath} is an existing directory, but @var{oldpath} is not a
34048 @var{newpath} is a non-empty directory.
34051 @var{oldpath} or @var{newpath} is a directory that is in use by some
34055 An attempt was made to make a directory a subdirectory
34059 A component used as a directory in @var{oldpath} or new
34060 path is not a directory. Or @var{oldpath} is a directory
34061 and @var{newpath} exists but is not a directory.
34064 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
34067 No access to the file or the path of the file.
34071 @var{oldpath} or @var{newpath} was too long.
34074 A directory component in @var{oldpath} or @var{newpath} does not exist.
34077 The file is on a read-only filesystem.
34080 The device containing the file has no room for the new
34084 The call was interrupted by the user.
34090 @unnumberedsubsubsec unlink
34091 @cindex unlink, file-i/o system call
34096 int unlink(const char *pathname);
34100 @samp{Funlink,@var{pathnameptr}/@var{len}}
34102 @item Return value:
34103 On success, zero is returned. On error, -1 is returned.
34109 No access to the file or the path of the file.
34112 The system does not allow unlinking of directories.
34115 The file @var{pathname} cannot be unlinked because it's
34116 being used by another process.
34119 @var{pathnameptr} is an invalid pointer value.
34122 @var{pathname} was too long.
34125 A directory component in @var{pathname} does not exist.
34128 A component of the path is not a directory.
34131 The file is on a read-only filesystem.
34134 The call was interrupted by the user.
34140 @unnumberedsubsubsec stat/fstat
34141 @cindex fstat, file-i/o system call
34142 @cindex stat, file-i/o system call
34147 int stat(const char *pathname, struct stat *buf);
34148 int fstat(int fd, struct stat *buf);
34152 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
34153 @samp{Ffstat,@var{fd},@var{bufptr}}
34155 @item Return value:
34156 On success, zero is returned. On error, -1 is returned.
34162 @var{fd} is not a valid open file.
34165 A directory component in @var{pathname} does not exist or the
34166 path is an empty string.
34169 A component of the path is not a directory.
34172 @var{pathnameptr} is an invalid pointer value.
34175 No access to the file or the path of the file.
34178 @var{pathname} was too long.
34181 The call was interrupted by the user.
34187 @unnumberedsubsubsec gettimeofday
34188 @cindex gettimeofday, file-i/o system call
34193 int gettimeofday(struct timeval *tv, void *tz);
34197 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
34199 @item Return value:
34200 On success, 0 is returned, -1 otherwise.
34206 @var{tz} is a non-NULL pointer.
34209 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
34215 @unnumberedsubsubsec isatty
34216 @cindex isatty, file-i/o system call
34221 int isatty(int fd);
34225 @samp{Fisatty,@var{fd}}
34227 @item Return value:
34228 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
34234 The call was interrupted by the user.
34239 Note that the @code{isatty} call is treated as a special case: it returns
34240 1 to the target if the file descriptor is attached
34241 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
34242 would require implementing @code{ioctl} and would be more complex than
34247 @unnumberedsubsubsec system
34248 @cindex system, file-i/o system call
34253 int system(const char *command);
34257 @samp{Fsystem,@var{commandptr}/@var{len}}
34259 @item Return value:
34260 If @var{len} is zero, the return value indicates whether a shell is
34261 available. A zero return value indicates a shell is not available.
34262 For non-zero @var{len}, the value returned is -1 on error and the
34263 return status of the command otherwise. Only the exit status of the
34264 command is returned, which is extracted from the host's @code{system}
34265 return value by calling @code{WEXITSTATUS(retval)}. In case
34266 @file{/bin/sh} could not be executed, 127 is returned.
34272 The call was interrupted by the user.
34277 @value{GDBN} takes over the full task of calling the necessary host calls
34278 to perform the @code{system} call. The return value of @code{system} on
34279 the host is simplified before it's returned
34280 to the target. Any termination signal information from the child process
34281 is discarded, and the return value consists
34282 entirely of the exit status of the called command.
34284 Due to security concerns, the @code{system} call is by default refused
34285 by @value{GDBN}. The user has to allow this call explicitly with the
34286 @code{set remote system-call-allowed 1} command.
34289 @item set remote system-call-allowed
34290 @kindex set remote system-call-allowed
34291 Control whether to allow the @code{system} calls in the File I/O
34292 protocol for the remote target. The default is zero (disabled).
34294 @item show remote system-call-allowed
34295 @kindex show remote system-call-allowed
34296 Show whether the @code{system} calls are allowed in the File I/O
34300 @node Protocol-specific Representation of Datatypes
34301 @subsection Protocol-specific Representation of Datatypes
34302 @cindex protocol-specific representation of datatypes, in file-i/o protocol
34305 * Integral Datatypes::
34307 * Memory Transfer::
34312 @node Integral Datatypes
34313 @unnumberedsubsubsec Integral Datatypes
34314 @cindex integral datatypes, in file-i/o protocol
34316 The integral datatypes used in the system calls are @code{int},
34317 @code{unsigned int}, @code{long}, @code{unsigned long},
34318 @code{mode_t}, and @code{time_t}.
34320 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
34321 implemented as 32 bit values in this protocol.
34323 @code{long} and @code{unsigned long} are implemented as 64 bit types.
34325 @xref{Limits}, for corresponding MIN and MAX values (similar to those
34326 in @file{limits.h}) to allow range checking on host and target.
34328 @code{time_t} datatypes are defined as seconds since the Epoch.
34330 All integral datatypes transferred as part of a memory read or write of a
34331 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
34334 @node Pointer Values
34335 @unnumberedsubsubsec Pointer Values
34336 @cindex pointer values, in file-i/o protocol
34338 Pointers to target data are transmitted as they are. An exception
34339 is made for pointers to buffers for which the length isn't
34340 transmitted as part of the function call, namely strings. Strings
34341 are transmitted as a pointer/length pair, both as hex values, e.g.@:
34348 which is a pointer to data of length 18 bytes at position 0x1aaf.
34349 The length is defined as the full string length in bytes, including
34350 the trailing null byte. For example, the string @code{"hello world"}
34351 at address 0x123456 is transmitted as
34357 @node Memory Transfer
34358 @unnumberedsubsubsec Memory Transfer
34359 @cindex memory transfer, in file-i/o protocol
34361 Structured data which is transferred using a memory read or write (for
34362 example, a @code{struct stat}) is expected to be in a protocol-specific format
34363 with all scalar multibyte datatypes being big endian. Translation to
34364 this representation needs to be done both by the target before the @code{F}
34365 packet is sent, and by @value{GDBN} before
34366 it transfers memory to the target. Transferred pointers to structured
34367 data should point to the already-coerced data at any time.
34371 @unnumberedsubsubsec struct stat
34372 @cindex struct stat, in file-i/o protocol
34374 The buffer of type @code{struct stat} used by the target and @value{GDBN}
34375 is defined as follows:
34379 unsigned int st_dev; /* device */
34380 unsigned int st_ino; /* inode */
34381 mode_t st_mode; /* protection */
34382 unsigned int st_nlink; /* number of hard links */
34383 unsigned int st_uid; /* user ID of owner */
34384 unsigned int st_gid; /* group ID of owner */
34385 unsigned int st_rdev; /* device type (if inode device) */
34386 unsigned long st_size; /* total size, in bytes */
34387 unsigned long st_blksize; /* blocksize for filesystem I/O */
34388 unsigned long st_blocks; /* number of blocks allocated */
34389 time_t st_atime; /* time of last access */
34390 time_t st_mtime; /* time of last modification */
34391 time_t st_ctime; /* time of last change */
34395 The integral datatypes conform to the definitions given in the
34396 appropriate section (see @ref{Integral Datatypes}, for details) so this
34397 structure is of size 64 bytes.
34399 The values of several fields have a restricted meaning and/or
34405 A value of 0 represents a file, 1 the console.
34408 No valid meaning for the target. Transmitted unchanged.
34411 Valid mode bits are described in @ref{Constants}. Any other
34412 bits have currently no meaning for the target.
34417 No valid meaning for the target. Transmitted unchanged.
34422 These values have a host and file system dependent
34423 accuracy. Especially on Windows hosts, the file system may not
34424 support exact timing values.
34427 The target gets a @code{struct stat} of the above representation and is
34428 responsible for coercing it to the target representation before
34431 Note that due to size differences between the host, target, and protocol
34432 representations of @code{struct stat} members, these members could eventually
34433 get truncated on the target.
34435 @node struct timeval
34436 @unnumberedsubsubsec struct timeval
34437 @cindex struct timeval, in file-i/o protocol
34439 The buffer of type @code{struct timeval} used by the File-I/O protocol
34440 is defined as follows:
34444 time_t tv_sec; /* second */
34445 long tv_usec; /* microsecond */
34449 The integral datatypes conform to the definitions given in the
34450 appropriate section (see @ref{Integral Datatypes}, for details) so this
34451 structure is of size 8 bytes.
34454 @subsection Constants
34455 @cindex constants, in file-i/o protocol
34457 The following values are used for the constants inside of the
34458 protocol. @value{GDBN} and target are responsible for translating these
34459 values before and after the call as needed.
34470 @unnumberedsubsubsec Open Flags
34471 @cindex open flags, in file-i/o protocol
34473 All values are given in hexadecimal representation.
34485 @node mode_t Values
34486 @unnumberedsubsubsec mode_t Values
34487 @cindex mode_t values, in file-i/o protocol
34489 All values are given in octal representation.
34506 @unnumberedsubsubsec Errno Values
34507 @cindex errno values, in file-i/o protocol
34509 All values are given in decimal representation.
34534 @code{EUNKNOWN} is used as a fallback error value if a host system returns
34535 any error value not in the list of supported error numbers.
34538 @unnumberedsubsubsec Lseek Flags
34539 @cindex lseek flags, in file-i/o protocol
34548 @unnumberedsubsubsec Limits
34549 @cindex limits, in file-i/o protocol
34551 All values are given in decimal representation.
34554 INT_MIN -2147483648
34556 UINT_MAX 4294967295
34557 LONG_MIN -9223372036854775808
34558 LONG_MAX 9223372036854775807
34559 ULONG_MAX 18446744073709551615
34562 @node File-I/O Examples
34563 @subsection File-I/O Examples
34564 @cindex file-i/o examples
34566 Example sequence of a write call, file descriptor 3, buffer is at target
34567 address 0x1234, 6 bytes should be written:
34570 <- @code{Fwrite,3,1234,6}
34571 @emph{request memory read from target}
34574 @emph{return "6 bytes written"}
34578 Example sequence of a read call, file descriptor 3, buffer is at target
34579 address 0x1234, 6 bytes should be read:
34582 <- @code{Fread,3,1234,6}
34583 @emph{request memory write to target}
34584 -> @code{X1234,6:XXXXXX}
34585 @emph{return "6 bytes read"}
34589 Example sequence of a read call, call fails on the host due to invalid
34590 file descriptor (@code{EBADF}):
34593 <- @code{Fread,3,1234,6}
34597 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
34601 <- @code{Fread,3,1234,6}
34606 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
34610 <- @code{Fread,3,1234,6}
34611 -> @code{X1234,6:XXXXXX}
34615 @node Library List Format
34616 @section Library List Format
34617 @cindex library list format, remote protocol
34619 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
34620 same process as your application to manage libraries. In this case,
34621 @value{GDBN} can use the loader's symbol table and normal memory
34622 operations to maintain a list of shared libraries. On other
34623 platforms, the operating system manages loaded libraries.
34624 @value{GDBN} can not retrieve the list of currently loaded libraries
34625 through memory operations, so it uses the @samp{qXfer:libraries:read}
34626 packet (@pxref{qXfer library list read}) instead. The remote stub
34627 queries the target's operating system and reports which libraries
34630 The @samp{qXfer:libraries:read} packet returns an XML document which
34631 lists loaded libraries and their offsets. Each library has an
34632 associated name and one or more segment or section base addresses,
34633 which report where the library was loaded in memory.
34635 For the common case of libraries that are fully linked binaries, the
34636 library should have a list of segments. If the target supports
34637 dynamic linking of a relocatable object file, its library XML element
34638 should instead include a list of allocated sections. The segment or
34639 section bases are start addresses, not relocation offsets; they do not
34640 depend on the library's link-time base addresses.
34642 @value{GDBN} must be linked with the Expat library to support XML
34643 library lists. @xref{Expat}.
34645 A simple memory map, with one loaded library relocated by a single
34646 offset, looks like this:
34650 <library name="/lib/libc.so.6">
34651 <segment address="0x10000000"/>
34656 Another simple memory map, with one loaded library with three
34657 allocated sections (.text, .data, .bss), looks like this:
34661 <library name="sharedlib.o">
34662 <section address="0x10000000"/>
34663 <section address="0x20000000"/>
34664 <section address="0x30000000"/>
34669 The format of a library list is described by this DTD:
34672 <!-- library-list: Root element with versioning -->
34673 <!ELEMENT library-list (library)*>
34674 <!ATTLIST library-list version CDATA #FIXED "1.0">
34675 <!ELEMENT library (segment*, section*)>
34676 <!ATTLIST library name CDATA #REQUIRED>
34677 <!ELEMENT segment EMPTY>
34678 <!ATTLIST segment address CDATA #REQUIRED>
34679 <!ELEMENT section EMPTY>
34680 <!ATTLIST section address CDATA #REQUIRED>
34683 In addition, segments and section descriptors cannot be mixed within a
34684 single library element, and you must supply at least one segment or
34685 section for each library.
34687 @node Memory Map Format
34688 @section Memory Map Format
34689 @cindex memory map format
34691 To be able to write into flash memory, @value{GDBN} needs to obtain a
34692 memory map from the target. This section describes the format of the
34695 The memory map is obtained using the @samp{qXfer:memory-map:read}
34696 (@pxref{qXfer memory map read}) packet and is an XML document that
34697 lists memory regions.
34699 @value{GDBN} must be linked with the Expat library to support XML
34700 memory maps. @xref{Expat}.
34702 The top-level structure of the document is shown below:
34705 <?xml version="1.0"?>
34706 <!DOCTYPE memory-map
34707 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
34708 "http://sourceware.org/gdb/gdb-memory-map.dtd">
34714 Each region can be either:
34719 A region of RAM starting at @var{addr} and extending for @var{length}
34723 <memory type="ram" start="@var{addr}" length="@var{length}"/>
34728 A region of read-only memory:
34731 <memory type="rom" start="@var{addr}" length="@var{length}"/>
34736 A region of flash memory, with erasure blocks @var{blocksize}
34740 <memory type="flash" start="@var{addr}" length="@var{length}">
34741 <property name="blocksize">@var{blocksize}</property>
34747 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
34748 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
34749 packets to write to addresses in such ranges.
34751 The formal DTD for memory map format is given below:
34754 <!-- ................................................... -->
34755 <!-- Memory Map XML DTD ................................ -->
34756 <!-- File: memory-map.dtd .............................. -->
34757 <!-- .................................... .............. -->
34758 <!-- memory-map.dtd -->
34759 <!-- memory-map: Root element with versioning -->
34760 <!ELEMENT memory-map (memory | property)>
34761 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
34762 <!ELEMENT memory (property)>
34763 <!-- memory: Specifies a memory region,
34764 and its type, or device. -->
34765 <!ATTLIST memory type CDATA #REQUIRED
34766 start CDATA #REQUIRED
34767 length CDATA #REQUIRED
34768 device CDATA #IMPLIED>
34769 <!-- property: Generic attribute tag -->
34770 <!ELEMENT property (#PCDATA | property)*>
34771 <!ATTLIST property name CDATA #REQUIRED>
34774 @node Thread List Format
34775 @section Thread List Format
34776 @cindex thread list format
34778 To efficiently update the list of threads and their attributes,
34779 @value{GDBN} issues the @samp{qXfer:threads:read} packet
34780 (@pxref{qXfer threads read}) and obtains the XML document with
34781 the following structure:
34784 <?xml version="1.0"?>
34786 <thread id="id" core="0">
34787 ... description ...
34792 Each @samp{thread} element must have the @samp{id} attribute that
34793 identifies the thread (@pxref{thread-id syntax}). The
34794 @samp{core} attribute, if present, specifies which processor core
34795 the thread was last executing on. The content of the of @samp{thread}
34796 element is interpreted as human-readable auxilliary information.
34798 @include agentexpr.texi
34800 @node Trace File Format
34801 @appendix Trace File Format
34802 @cindex trace file format
34804 The trace file comes in three parts: a header, a textual description
34805 section, and a trace frame section with binary data.
34807 The header has the form @code{\x7fTRACE0\n}. The first byte is
34808 @code{0x7f} so as to indicate that the file contains binary data,
34809 while the @code{0} is a version number that may have different values
34812 The description section consists of multiple lines of @sc{ascii} text
34813 separated by newline characters (@code{0xa}). The lines may include a
34814 variety of optional descriptive or context-setting information, such
34815 as tracepoint definitions or register set size. @value{GDBN} will
34816 ignore any line that it does not recognize. An empty line marks the end
34819 @c FIXME add some specific types of data
34821 The trace frame section consists of a number of consecutive frames.
34822 Each frame begins with a two-byte tracepoint number, followed by a
34823 four-byte size giving the amount of data in the frame. The data in
34824 the frame consists of a number of blocks, each introduced by a
34825 character indicating its type (at least register, memory, and trace
34826 state variable). The data in this section is raw binary, not a
34827 hexadecimal or other encoding; its endianness matches the target's
34830 @c FIXME bi-arch may require endianness/arch info in description section
34833 @item R @var{bytes}
34834 Register block. The number and ordering of bytes matches that of a
34835 @code{g} packet in the remote protocol. Note that these are the
34836 actual bytes, in target order and @value{GDBN} register order, not a
34837 hexadecimal encoding.
34839 @item M @var{address} @var{length} @var{bytes}...
34840 Memory block. This is a contiguous block of memory, at the 8-byte
34841 address @var{address}, with a 2-byte length @var{length}, followed by
34842 @var{length} bytes.
34844 @item V @var{number} @var{value}
34845 Trace state variable block. This records the 8-byte signed value
34846 @var{value} of trace state variable numbered @var{number}.
34850 Future enhancements of the trace file format may include additional types
34853 @node Target Descriptions
34854 @appendix Target Descriptions
34855 @cindex target descriptions
34857 @strong{Warning:} target descriptions are still under active development,
34858 and the contents and format may change between @value{GDBN} releases.
34859 The format is expected to stabilize in the future.
34861 One of the challenges of using @value{GDBN} to debug embedded systems
34862 is that there are so many minor variants of each processor
34863 architecture in use. It is common practice for vendors to start with
34864 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
34865 and then make changes to adapt it to a particular market niche. Some
34866 architectures have hundreds of variants, available from dozens of
34867 vendors. This leads to a number of problems:
34871 With so many different customized processors, it is difficult for
34872 the @value{GDBN} maintainers to keep up with the changes.
34874 Since individual variants may have short lifetimes or limited
34875 audiences, it may not be worthwhile to carry information about every
34876 variant in the @value{GDBN} source tree.
34878 When @value{GDBN} does support the architecture of the embedded system
34879 at hand, the task of finding the correct architecture name to give the
34880 @command{set architecture} command can be error-prone.
34883 To address these problems, the @value{GDBN} remote protocol allows a
34884 target system to not only identify itself to @value{GDBN}, but to
34885 actually describe its own features. This lets @value{GDBN} support
34886 processor variants it has never seen before --- to the extent that the
34887 descriptions are accurate, and that @value{GDBN} understands them.
34889 @value{GDBN} must be linked with the Expat library to support XML
34890 target descriptions. @xref{Expat}.
34893 * Retrieving Descriptions:: How descriptions are fetched from a target.
34894 * Target Description Format:: The contents of a target description.
34895 * Predefined Target Types:: Standard types available for target
34897 * Standard Target Features:: Features @value{GDBN} knows about.
34900 @node Retrieving Descriptions
34901 @section Retrieving Descriptions
34903 Target descriptions can be read from the target automatically, or
34904 specified by the user manually. The default behavior is to read the
34905 description from the target. @value{GDBN} retrieves it via the remote
34906 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
34907 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
34908 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
34909 XML document, of the form described in @ref{Target Description
34912 Alternatively, you can specify a file to read for the target description.
34913 If a file is set, the target will not be queried. The commands to
34914 specify a file are:
34917 @cindex set tdesc filename
34918 @item set tdesc filename @var{path}
34919 Read the target description from @var{path}.
34921 @cindex unset tdesc filename
34922 @item unset tdesc filename
34923 Do not read the XML target description from a file. @value{GDBN}
34924 will use the description supplied by the current target.
34926 @cindex show tdesc filename
34927 @item show tdesc filename
34928 Show the filename to read for a target description, if any.
34932 @node Target Description Format
34933 @section Target Description Format
34934 @cindex target descriptions, XML format
34936 A target description annex is an @uref{http://www.w3.org/XML/, XML}
34937 document which complies with the Document Type Definition provided in
34938 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
34939 means you can use generally available tools like @command{xmllint} to
34940 check that your feature descriptions are well-formed and valid.
34941 However, to help people unfamiliar with XML write descriptions for
34942 their targets, we also describe the grammar here.
34944 Target descriptions can identify the architecture of the remote target
34945 and (for some architectures) provide information about custom register
34946 sets. They can also identify the OS ABI of the remote target.
34947 @value{GDBN} can use this information to autoconfigure for your
34948 target, or to warn you if you connect to an unsupported target.
34950 Here is a simple target description:
34953 <target version="1.0">
34954 <architecture>i386:x86-64</architecture>
34959 This minimal description only says that the target uses
34960 the x86-64 architecture.
34962 A target description has the following overall form, with [ ] marking
34963 optional elements and @dots{} marking repeatable elements. The elements
34964 are explained further below.
34967 <?xml version="1.0"?>
34968 <!DOCTYPE target SYSTEM "gdb-target.dtd">
34969 <target version="1.0">
34970 @r{[}@var{architecture}@r{]}
34971 @r{[}@var{osabi}@r{]}
34972 @r{[}@var{compatible}@r{]}
34973 @r{[}@var{feature}@dots{}@r{]}
34978 The description is generally insensitive to whitespace and line
34979 breaks, under the usual common-sense rules. The XML version
34980 declaration and document type declaration can generally be omitted
34981 (@value{GDBN} does not require them), but specifying them may be
34982 useful for XML validation tools. The @samp{version} attribute for
34983 @samp{<target>} may also be omitted, but we recommend
34984 including it; if future versions of @value{GDBN} use an incompatible
34985 revision of @file{gdb-target.dtd}, they will detect and report
34986 the version mismatch.
34988 @subsection Inclusion
34989 @cindex target descriptions, inclusion
34992 @cindex <xi:include>
34995 It can sometimes be valuable to split a target description up into
34996 several different annexes, either for organizational purposes, or to
34997 share files between different possible target descriptions. You can
34998 divide a description into multiple files by replacing any element of
34999 the target description with an inclusion directive of the form:
35002 <xi:include href="@var{document}"/>
35006 When @value{GDBN} encounters an element of this form, it will retrieve
35007 the named XML @var{document}, and replace the inclusion directive with
35008 the contents of that document. If the current description was read
35009 using @samp{qXfer}, then so will be the included document;
35010 @var{document} will be interpreted as the name of an annex. If the
35011 current description was read from a file, @value{GDBN} will look for
35012 @var{document} as a file in the same directory where it found the
35013 original description.
35015 @subsection Architecture
35016 @cindex <architecture>
35018 An @samp{<architecture>} element has this form:
35021 <architecture>@var{arch}</architecture>
35024 @var{arch} is one of the architectures from the set accepted by
35025 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
35028 @cindex @code{<osabi>}
35030 This optional field was introduced in @value{GDBN} version 7.0.
35031 Previous versions of @value{GDBN} ignore it.
35033 An @samp{<osabi>} element has this form:
35036 <osabi>@var{abi-name}</osabi>
35039 @var{abi-name} is an OS ABI name from the same selection accepted by
35040 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
35042 @subsection Compatible Architecture
35043 @cindex @code{<compatible>}
35045 This optional field was introduced in @value{GDBN} version 7.0.
35046 Previous versions of @value{GDBN} ignore it.
35048 A @samp{<compatible>} element has this form:
35051 <compatible>@var{arch}</compatible>
35054 @var{arch} is one of the architectures from the set accepted by
35055 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
35057 A @samp{<compatible>} element is used to specify that the target
35058 is able to run binaries in some other than the main target architecture
35059 given by the @samp{<architecture>} element. For example, on the
35060 Cell Broadband Engine, the main architecture is @code{powerpc:common}
35061 or @code{powerpc:common64}, but the system is able to run binaries
35062 in the @code{spu} architecture as well. The way to describe this
35063 capability with @samp{<compatible>} is as follows:
35066 <architecture>powerpc:common</architecture>
35067 <compatible>spu</compatible>
35070 @subsection Features
35073 Each @samp{<feature>} describes some logical portion of the target
35074 system. Features are currently used to describe available CPU
35075 registers and the types of their contents. A @samp{<feature>} element
35079 <feature name="@var{name}">
35080 @r{[}@var{type}@dots{}@r{]}
35086 Each feature's name should be unique within the description. The name
35087 of a feature does not matter unless @value{GDBN} has some special
35088 knowledge of the contents of that feature; if it does, the feature
35089 should have its standard name. @xref{Standard Target Features}.
35093 Any register's value is a collection of bits which @value{GDBN} must
35094 interpret. The default interpretation is a two's complement integer,
35095 but other types can be requested by name in the register description.
35096 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
35097 Target Types}), and the description can define additional composite types.
35099 Each type element must have an @samp{id} attribute, which gives
35100 a unique (within the containing @samp{<feature>}) name to the type.
35101 Types must be defined before they are used.
35104 Some targets offer vector registers, which can be treated as arrays
35105 of scalar elements. These types are written as @samp{<vector>} elements,
35106 specifying the array element type, @var{type}, and the number of elements,
35110 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
35114 If a register's value is usefully viewed in multiple ways, define it
35115 with a union type containing the useful representations. The
35116 @samp{<union>} element contains one or more @samp{<field>} elements,
35117 each of which has a @var{name} and a @var{type}:
35120 <union id="@var{id}">
35121 <field name="@var{name}" type="@var{type}"/>
35127 If a register's value is composed from several separate values, define
35128 it with a structure type. There are two forms of the @samp{<struct>}
35129 element; a @samp{<struct>} element must either contain only bitfields
35130 or contain no bitfields. If the structure contains only bitfields,
35131 its total size in bytes must be specified, each bitfield must have an
35132 explicit start and end, and bitfields are automatically assigned an
35133 integer type. The field's @var{start} should be less than or
35134 equal to its @var{end}, and zero represents the least significant bit.
35137 <struct id="@var{id}" size="@var{size}">
35138 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
35143 If the structure contains no bitfields, then each field has an
35144 explicit type, and no implicit padding is added.
35147 <struct id="@var{id}">
35148 <field name="@var{name}" type="@var{type}"/>
35154 If a register's value is a series of single-bit flags, define it with
35155 a flags type. The @samp{<flags>} element has an explicit @var{size}
35156 and contains one or more @samp{<field>} elements. Each field has a
35157 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
35161 <flags id="@var{id}" size="@var{size}">
35162 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
35167 @subsection Registers
35170 Each register is represented as an element with this form:
35173 <reg name="@var{name}"
35174 bitsize="@var{size}"
35175 @r{[}regnum="@var{num}"@r{]}
35176 @r{[}save-restore="@var{save-restore}"@r{]}
35177 @r{[}type="@var{type}"@r{]}
35178 @r{[}group="@var{group}"@r{]}/>
35182 The components are as follows:
35187 The register's name; it must be unique within the target description.
35190 The register's size, in bits.
35193 The register's number. If omitted, a register's number is one greater
35194 than that of the previous register (either in the current feature or in
35195 a preceeding feature); the first register in the target description
35196 defaults to zero. This register number is used to read or write
35197 the register; e.g.@: it is used in the remote @code{p} and @code{P}
35198 packets, and registers appear in the @code{g} and @code{G} packets
35199 in order of increasing register number.
35202 Whether the register should be preserved across inferior function
35203 calls; this must be either @code{yes} or @code{no}. The default is
35204 @code{yes}, which is appropriate for most registers except for
35205 some system control registers; this is not related to the target's
35209 The type of the register. @var{type} may be a predefined type, a type
35210 defined in the current feature, or one of the special types @code{int}
35211 and @code{float}. @code{int} is an integer type of the correct size
35212 for @var{bitsize}, and @code{float} is a floating point type (in the
35213 architecture's normal floating point format) of the correct size for
35214 @var{bitsize}. The default is @code{int}.
35217 The register group to which this register belongs. @var{group} must
35218 be either @code{general}, @code{float}, or @code{vector}. If no
35219 @var{group} is specified, @value{GDBN} will not display the register
35220 in @code{info registers}.
35224 @node Predefined Target Types
35225 @section Predefined Target Types
35226 @cindex target descriptions, predefined types
35228 Type definitions in the self-description can build up composite types
35229 from basic building blocks, but can not define fundamental types. Instead,
35230 standard identifiers are provided by @value{GDBN} for the fundamental
35231 types. The currently supported types are:
35240 Signed integer types holding the specified number of bits.
35247 Unsigned integer types holding the specified number of bits.
35251 Pointers to unspecified code and data. The program counter and
35252 any dedicated return address register may be marked as code
35253 pointers; printing a code pointer converts it into a symbolic
35254 address. The stack pointer and any dedicated address registers
35255 may be marked as data pointers.
35258 Single precision IEEE floating point.
35261 Double precision IEEE floating point.
35264 The 12-byte extended precision format used by ARM FPA registers.
35267 The 10-byte extended precision format used by x87 registers.
35270 32bit @sc{eflags} register used by x86.
35273 32bit @sc{mxcsr} register used by x86.
35277 @node Standard Target Features
35278 @section Standard Target Features
35279 @cindex target descriptions, standard features
35281 A target description must contain either no registers or all the
35282 target's registers. If the description contains no registers, then
35283 @value{GDBN} will assume a default register layout, selected based on
35284 the architecture. If the description contains any registers, the
35285 default layout will not be used; the standard registers must be
35286 described in the target description, in such a way that @value{GDBN}
35287 can recognize them.
35289 This is accomplished by giving specific names to feature elements
35290 which contain standard registers. @value{GDBN} will look for features
35291 with those names and verify that they contain the expected registers;
35292 if any known feature is missing required registers, or if any required
35293 feature is missing, @value{GDBN} will reject the target
35294 description. You can add additional registers to any of the
35295 standard features --- @value{GDBN} will display them just as if
35296 they were added to an unrecognized feature.
35298 This section lists the known features and their expected contents.
35299 Sample XML documents for these features are included in the
35300 @value{GDBN} source tree, in the directory @file{gdb/features}.
35302 Names recognized by @value{GDBN} should include the name of the
35303 company or organization which selected the name, and the overall
35304 architecture to which the feature applies; so e.g.@: the feature
35305 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
35307 The names of registers are not case sensitive for the purpose
35308 of recognizing standard features, but @value{GDBN} will only display
35309 registers using the capitalization used in the description.
35316 * PowerPC Features::
35321 @subsection ARM Features
35322 @cindex target descriptions, ARM features
35324 The @samp{org.gnu.gdb.arm.core} feature is required for ARM targets.
35325 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
35326 @samp{lr}, @samp{pc}, and @samp{cpsr}.
35328 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
35329 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
35331 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
35332 it should contain at least registers @samp{wR0} through @samp{wR15} and
35333 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
35334 @samp{wCSSF}, and @samp{wCASF} registers are optional.
35336 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
35337 should contain at least registers @samp{d0} through @samp{d15}. If
35338 they are present, @samp{d16} through @samp{d31} should also be included.
35339 @value{GDBN} will synthesize the single-precision registers from
35340 halves of the double-precision registers.
35342 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
35343 need to contain registers; it instructs @value{GDBN} to display the
35344 VFP double-precision registers as vectors and to synthesize the
35345 quad-precision registers from pairs of double-precision registers.
35346 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
35347 be present and include 32 double-precision registers.
35349 @node i386 Features
35350 @subsection i386 Features
35351 @cindex target descriptions, i386 features
35353 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
35354 targets. It should describe the following registers:
35358 @samp{eax} through @samp{edi} plus @samp{eip} for i386
35360 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
35362 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
35363 @samp{fs}, @samp{gs}
35365 @samp{st0} through @samp{st7}
35367 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
35368 @samp{foseg}, @samp{fooff} and @samp{fop}
35371 The register sets may be different, depending on the target.
35373 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
35374 describe registers:
35378 @samp{xmm0} through @samp{xmm7} for i386
35380 @samp{xmm0} through @samp{xmm15} for amd64
35385 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
35386 @samp{org.gnu.gdb.i386.sse} feature. It should
35387 describe the upper 128 bits of @sc{ymm} registers:
35391 @samp{ymm0h} through @samp{ymm7h} for i386
35393 @samp{ymm0h} through @samp{ymm15h} for amd64
35397 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
35398 describe a single register, @samp{orig_eax}.
35400 @node MIPS Features
35401 @subsection MIPS Features
35402 @cindex target descriptions, MIPS features
35404 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
35405 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
35406 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
35409 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
35410 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
35411 registers. They may be 32-bit or 64-bit depending on the target.
35413 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
35414 it may be optional in a future version of @value{GDBN}. It should
35415 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
35416 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
35418 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
35419 contain a single register, @samp{restart}, which is used by the
35420 Linux kernel to control restartable syscalls.
35422 @node M68K Features
35423 @subsection M68K Features
35424 @cindex target descriptions, M68K features
35427 @item @samp{org.gnu.gdb.m68k.core}
35428 @itemx @samp{org.gnu.gdb.coldfire.core}
35429 @itemx @samp{org.gnu.gdb.fido.core}
35430 One of those features must be always present.
35431 The feature that is present determines which flavor of m68k is
35432 used. The feature that is present should contain registers
35433 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
35434 @samp{sp}, @samp{ps} and @samp{pc}.
35436 @item @samp{org.gnu.gdb.coldfire.fp}
35437 This feature is optional. If present, it should contain registers
35438 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
35442 @node PowerPC Features
35443 @subsection PowerPC Features
35444 @cindex target descriptions, PowerPC features
35446 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
35447 targets. It should contain registers @samp{r0} through @samp{r31},
35448 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
35449 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
35451 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
35452 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
35454 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
35455 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
35458 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
35459 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
35460 will combine these registers with the floating point registers
35461 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
35462 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
35463 through @samp{vs63}, the set of vector registers for POWER7.
35465 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
35466 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
35467 @samp{spefscr}. SPE targets should provide 32-bit registers in
35468 @samp{org.gnu.gdb.power.core} and provide the upper halves in
35469 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
35470 these to present registers @samp{ev0} through @samp{ev31} to the
35473 @node Operating System Information
35474 @appendix Operating System Information
35475 @cindex operating system information
35481 Users of @value{GDBN} often wish to obtain information about the state of
35482 the operating system running on the target---for example the list of
35483 processes, or the list of open files. This section describes the
35484 mechanism that makes it possible. This mechanism is similar to the
35485 target features mechanism (@pxref{Target Descriptions}), but focuses
35486 on a different aspect of target.
35488 Operating system information is retrived from the target via the
35489 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
35490 read}). The object name in the request should be @samp{osdata}, and
35491 the @var{annex} identifies the data to be fetched.
35494 @appendixsection Process list
35495 @cindex operating system information, process list
35497 When requesting the process list, the @var{annex} field in the
35498 @samp{qXfer} request should be @samp{processes}. The returned data is
35499 an XML document. The formal syntax of this document is defined in
35500 @file{gdb/features/osdata.dtd}.
35502 An example document is:
35505 <?xml version="1.0"?>
35506 <!DOCTYPE target SYSTEM "osdata.dtd">
35507 <osdata type="processes">
35509 <column name="pid">1</column>
35510 <column name="user">root</column>
35511 <column name="command">/sbin/init</column>
35512 <column name="cores">1,2,3</column>
35517 Each item should include a column whose name is @samp{pid}. The value
35518 of that column should identify the process on the target. The
35519 @samp{user} and @samp{command} columns are optional, and will be
35520 displayed by @value{GDBN}. The @samp{cores} column, if present,
35521 should contain a comma-separated list of cores that this process
35522 is running on. Target may provide additional columns,
35523 which @value{GDBN} currently ignores.
35527 @node GNU Free Documentation License
35528 @appendix GNU Free Documentation License
35537 % I think something like @colophon should be in texinfo. In the
35539 \long\def\colophon{\hbox to0pt{}\vfill
35540 \centerline{The body of this manual is set in}
35541 \centerline{\fontname\tenrm,}
35542 \centerline{with headings in {\bf\fontname\tenbf}}
35543 \centerline{and examples in {\tt\fontname\tentt}.}
35544 \centerline{{\it\fontname\tenit\/},}
35545 \centerline{{\bf\fontname\tenbf}, and}
35546 \centerline{{\sl\fontname\tensl\/}}
35547 \centerline{are used for emphasis.}\vfill}
35549 % Blame: doc@cygnus.com, 1991.