1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988-1996, 1998-2012 Free Software Foundation, Inc.
5 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
6 @c of @set vars. However, you can override filename with makeinfo -o.
11 @settitle Debugging with @value{GDBN}
12 @setchapternewpage odd
24 @c readline appendices use @vindex, @findex and @ftable,
25 @c annotate.texi and gdbmi use @findex.
29 @c !!set GDB manual's edition---not the same as GDB version!
30 @c This is updated by GNU Press.
33 @c !!set GDB edit command default editor
36 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
38 @c This is a dir.info fragment to support semi-automated addition of
39 @c manuals to an info tree.
40 @dircategory Software development
42 * Gdb: (gdb). The GNU debugger.
46 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
47 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
48 Free Software Foundation, Inc.
50 Permission is granted to copy, distribute and/or modify this document
51 under the terms of the GNU Free Documentation License, Version 1.3 or
52 any later version published by the Free Software Foundation; with the
53 Invariant Sections being ``Free Software'' and ``Free Software Needs
54 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
55 and with the Back-Cover Texts as in (a) below.
57 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
58 this GNU Manual. Buying copies from GNU Press supports the FSF in
59 developing GNU and promoting software freedom.''
63 This file documents the @sc{gnu} debugger @value{GDBN}.
65 This is the @value{EDITION} Edition, of @cite{Debugging with
66 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
67 @ifset VERSION_PACKAGE
68 @value{VERSION_PACKAGE}
70 Version @value{GDBVN}.
76 @title Debugging with @value{GDBN}
77 @subtitle The @sc{gnu} Source-Level Debugger
79 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
80 @ifset VERSION_PACKAGE
82 @subtitle @value{VERSION_PACKAGE}
84 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
88 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
89 \hfill {\it Debugging with @value{GDBN}}\par
90 \hfill \TeX{}info \texinfoversion\par
94 @vskip 0pt plus 1filll
95 Published by the Free Software Foundation @*
96 51 Franklin Street, Fifth Floor,
97 Boston, MA 02110-1301, USA@*
98 ISBN 978-0-9831592-3-0 @*
105 @node Top, Summary, (dir), (dir)
107 @top Debugging with @value{GDBN}
109 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
111 This is the @value{EDITION} Edition, for @value{GDBN}
112 @ifset VERSION_PACKAGE
113 @value{VERSION_PACKAGE}
115 Version @value{GDBVN}.
117 Copyright (C) 1988-2010 Free Software Foundation, Inc.
119 This edition of the GDB manual is dedicated to the memory of Fred
120 Fish. Fred was a long-standing contributor to GDB and to Free
121 software in general. We will miss him.
124 * Summary:: Summary of @value{GDBN}
125 * Sample Session:: A sample @value{GDBN} session
127 * Invocation:: Getting in and out of @value{GDBN}
128 * Commands:: @value{GDBN} commands
129 * Running:: Running programs under @value{GDBN}
130 * Stopping:: Stopping and continuing
131 * Reverse Execution:: Running programs backward
132 * Process Record and Replay:: Recording inferior's execution and replaying it
133 * Stack:: Examining the stack
134 * Source:: Examining source files
135 * Data:: Examining data
136 * Optimized Code:: Debugging optimized code
137 * Macros:: Preprocessor Macros
138 * Tracepoints:: Debugging remote targets non-intrusively
139 * Overlays:: Debugging programs that use overlays
141 * Languages:: Using @value{GDBN} with different languages
143 * Symbols:: Examining the symbol table
144 * Altering:: Altering execution
145 * GDB Files:: @value{GDBN} files
146 * Targets:: Specifying a debugging target
147 * Remote Debugging:: Debugging remote programs
148 * Configurations:: Configuration-specific information
149 * Controlling GDB:: Controlling @value{GDBN}
150 * Extending GDB:: Extending @value{GDBN}
151 * Interpreters:: Command Interpreters
152 * TUI:: @value{GDBN} Text User Interface
153 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
154 * GDB/MI:: @value{GDBN}'s Machine Interface.
155 * Annotations:: @value{GDBN}'s annotation interface.
156 * JIT Interface:: Using the JIT debugging interface.
157 * In-Process Agent:: In-Process Agent
159 * GDB Bugs:: Reporting bugs in @value{GDBN}
161 @ifset SYSTEM_READLINE
162 * Command Line Editing: (rluserman). Command Line Editing
163 * Using History Interactively: (history). Using History Interactively
165 @ifclear SYSTEM_READLINE
166 * Command Line Editing:: Command Line Editing
167 * Using History Interactively:: Using History Interactively
169 * In Memoriam:: In Memoriam
170 * Formatting Documentation:: How to format and print @value{GDBN} documentation
171 * Installing GDB:: Installing GDB
172 * Maintenance Commands:: Maintenance Commands
173 * Remote Protocol:: GDB Remote Serial Protocol
174 * Agent Expressions:: The GDB Agent Expression Mechanism
175 * Target Descriptions:: How targets can describe themselves to
177 * Operating System Information:: Getting additional information from
179 * Trace File Format:: GDB trace file format
180 * Index Section Format:: .gdb_index section format
181 * Copying:: GNU General Public License says
182 how you can copy and share GDB
183 * GNU Free Documentation License:: The license for this documentation
192 @unnumbered Summary of @value{GDBN}
194 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
195 going on ``inside'' another program while it executes---or what another
196 program was doing at the moment it crashed.
198 @value{GDBN} can do four main kinds of things (plus other things in support of
199 these) to help you catch bugs in the act:
203 Start your program, specifying anything that might affect its behavior.
206 Make your program stop on specified conditions.
209 Examine what has happened, when your program has stopped.
212 Change things in your program, so you can experiment with correcting the
213 effects of one bug and go on to learn about another.
216 You can use @value{GDBN} to debug programs written in C and C@t{++}.
217 For more information, see @ref{Supported Languages,,Supported Languages}.
218 For more information, see @ref{C,,C and C++}.
220 Support for D is partial. For information on D, see
224 Support for Modula-2 is partial. For information on Modula-2, see
225 @ref{Modula-2,,Modula-2}.
227 Support for OpenCL C is partial. For information on OpenCL C, see
228 @ref{OpenCL C,,OpenCL C}.
231 Debugging Pascal programs which use sets, subranges, file variables, or
232 nested functions does not currently work. @value{GDBN} does not support
233 entering expressions, printing values, or similar features using Pascal
237 @value{GDBN} can be used to debug programs written in Fortran, although
238 it may be necessary to refer to some variables with a trailing
241 @value{GDBN} can be used to debug programs written in Objective-C,
242 using either the Apple/NeXT or the GNU Objective-C runtime.
245 * Free Software:: Freely redistributable software
246 * Contributors:: Contributors to GDB
250 @unnumberedsec Free Software
252 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
253 General Public License
254 (GPL). The GPL gives you the freedom to copy or adapt a licensed
255 program---but every person getting a copy also gets with it the
256 freedom to modify that copy (which means that they must get access to
257 the source code), and the freedom to distribute further copies.
258 Typical software companies use copyrights to limit your freedoms; the
259 Free Software Foundation uses the GPL to preserve these freedoms.
261 Fundamentally, the General Public License is a license which says that
262 you have these freedoms and that you cannot take these freedoms away
265 @unnumberedsec Free Software Needs Free Documentation
267 The biggest deficiency in the free software community today is not in
268 the software---it is the lack of good free documentation that we can
269 include with the free software. Many of our most important
270 programs do not come with free reference manuals and free introductory
271 texts. Documentation is an essential part of any software package;
272 when an important free software package does not come with a free
273 manual and a free tutorial, that is a major gap. We have many such
276 Consider Perl, for instance. The tutorial manuals that people
277 normally use are non-free. How did this come about? Because the
278 authors of those manuals published them with restrictive terms---no
279 copying, no modification, source files not available---which exclude
280 them from the free software world.
282 That wasn't the first time this sort of thing happened, and it was far
283 from the last. Many times we have heard a GNU user eagerly describe a
284 manual that he is writing, his intended contribution to the community,
285 only to learn that he had ruined everything by signing a publication
286 contract to make it non-free.
288 Free documentation, like free software, is a matter of freedom, not
289 price. The problem with the non-free manual is not that publishers
290 charge a price for printed copies---that in itself is fine. (The Free
291 Software Foundation sells printed copies of manuals, too.) The
292 problem is the restrictions on the use of the manual. Free manuals
293 are available in source code form, and give you permission to copy and
294 modify. Non-free manuals do not allow this.
296 The criteria of freedom for a free manual are roughly the same as for
297 free software. Redistribution (including the normal kinds of
298 commercial redistribution) must be permitted, so that the manual can
299 accompany every copy of the program, both on-line and on paper.
301 Permission for modification of the technical content is crucial too.
302 When people modify the software, adding or changing features, if they
303 are conscientious they will change the manual too---so they can
304 provide accurate and clear documentation for the modified program. A
305 manual that leaves you no choice but to write a new manual to document
306 a changed version of the program is not really available to our
309 Some kinds of limits on the way modification is handled are
310 acceptable. For example, requirements to preserve the original
311 author's copyright notice, the distribution terms, or the list of
312 authors, are ok. It is also no problem to require modified versions
313 to include notice that they were modified. Even entire sections that
314 may not be deleted or changed are acceptable, as long as they deal
315 with nontechnical topics (like this one). These kinds of restrictions
316 are acceptable because they don't obstruct the community's normal use
319 However, it must be possible to modify all the @emph{technical}
320 content of the manual, and then distribute the result in all the usual
321 media, through all the usual channels. Otherwise, the restrictions
322 obstruct the use of the manual, it is not free, and we need another
323 manual to replace it.
325 Please spread the word about this issue. Our community continues to
326 lose manuals to proprietary publishing. If we spread the word that
327 free software needs free reference manuals and free tutorials, perhaps
328 the next person who wants to contribute by writing documentation will
329 realize, before it is too late, that only free manuals contribute to
330 the free software community.
332 If you are writing documentation, please insist on publishing it under
333 the GNU Free Documentation License or another free documentation
334 license. Remember that this decision requires your approval---you
335 don't have to let the publisher decide. Some commercial publishers
336 will use a free license if you insist, but they will not propose the
337 option; it is up to you to raise the issue and say firmly that this is
338 what you want. If the publisher you are dealing with refuses, please
339 try other publishers. If you're not sure whether a proposed license
340 is free, write to @email{licensing@@gnu.org}.
342 You can encourage commercial publishers to sell more free, copylefted
343 manuals and tutorials by buying them, and particularly by buying
344 copies from the publishers that paid for their writing or for major
345 improvements. Meanwhile, try to avoid buying non-free documentation
346 at all. Check the distribution terms of a manual before you buy it,
347 and insist that whoever seeks your business must respect your freedom.
348 Check the history of the book, and try to reward the publishers that
349 have paid or pay the authors to work on it.
351 The Free Software Foundation maintains a list of free documentation
352 published by other publishers, at
353 @url{http://www.fsf.org/doc/other-free-books.html}.
356 @unnumberedsec Contributors to @value{GDBN}
358 Richard Stallman was the original author of @value{GDBN}, and of many
359 other @sc{gnu} programs. Many others have contributed to its
360 development. This section attempts to credit major contributors. One
361 of the virtues of free software is that everyone is free to contribute
362 to it; with regret, we cannot actually acknowledge everyone here. The
363 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
364 blow-by-blow account.
366 Changes much prior to version 2.0 are lost in the mists of time.
369 @emph{Plea:} Additions to this section are particularly welcome. If you
370 or your friends (or enemies, to be evenhanded) have been unfairly
371 omitted from this list, we would like to add your names!
374 So that they may not regard their many labors as thankless, we
375 particularly thank those who shepherded @value{GDBN} through major
377 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
378 Jim Blandy (release 4.18);
379 Jason Molenda (release 4.17);
380 Stan Shebs (release 4.14);
381 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
382 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
383 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
384 Jim Kingdon (releases 3.5, 3.4, and 3.3);
385 and Randy Smith (releases 3.2, 3.1, and 3.0).
387 Richard Stallman, assisted at various times by Peter TerMaat, Chris
388 Hanson, and Richard Mlynarik, handled releases through 2.8.
390 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
391 in @value{GDBN}, with significant additional contributions from Per
392 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
393 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
394 much general update work leading to release 3.0).
396 @value{GDBN} uses the BFD subroutine library to examine multiple
397 object-file formats; BFD was a joint project of David V.
398 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
400 David Johnson wrote the original COFF support; Pace Willison did
401 the original support for encapsulated COFF.
403 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
405 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
406 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
408 Jean-Daniel Fekete contributed Sun 386i support.
409 Chris Hanson improved the HP9000 support.
410 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
411 David Johnson contributed Encore Umax support.
412 Jyrki Kuoppala contributed Altos 3068 support.
413 Jeff Law contributed HP PA and SOM support.
414 Keith Packard contributed NS32K support.
415 Doug Rabson contributed Acorn Risc Machine support.
416 Bob Rusk contributed Harris Nighthawk CX-UX support.
417 Chris Smith contributed Convex support (and Fortran debugging).
418 Jonathan Stone contributed Pyramid support.
419 Michael Tiemann contributed SPARC support.
420 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
421 Pace Willison contributed Intel 386 support.
422 Jay Vosburgh contributed Symmetry support.
423 Marko Mlinar contributed OpenRISC 1000 support.
425 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
427 Rich Schaefer and Peter Schauer helped with support of SunOS shared
430 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
431 about several machine instruction sets.
433 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
434 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
435 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
436 and RDI targets, respectively.
438 Brian Fox is the author of the readline libraries providing
439 command-line editing and command history.
441 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
442 Modula-2 support, and contributed the Languages chapter of this manual.
444 Fred Fish wrote most of the support for Unix System Vr4.
445 He also enhanced the command-completion support to cover C@t{++} overloaded
448 Hitachi America (now Renesas America), Ltd. sponsored the support for
449 H8/300, H8/500, and Super-H processors.
451 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
453 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
456 Toshiba sponsored the support for the TX39 Mips processor.
458 Matsushita sponsored the support for the MN10200 and MN10300 processors.
460 Fujitsu sponsored the support for SPARClite and FR30 processors.
462 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
465 Michael Snyder added support for tracepoints.
467 Stu Grossman wrote gdbserver.
469 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
470 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
472 The following people at the Hewlett-Packard Company contributed
473 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
474 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
475 compiler, and the Text User Interface (nee Terminal User Interface):
476 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
477 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
478 provided HP-specific information in this manual.
480 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
481 Robert Hoehne made significant contributions to the DJGPP port.
483 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
484 development since 1991. Cygnus engineers who have worked on @value{GDBN}
485 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
486 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
487 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
488 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
489 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
490 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
491 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
492 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
493 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
494 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
495 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
496 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
497 Zuhn have made contributions both large and small.
499 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
500 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
502 Jim Blandy added support for preprocessor macros, while working for Red
505 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
506 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
507 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
508 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
509 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
510 with the migration of old architectures to this new framework.
512 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
513 unwinder framework, this consisting of a fresh new design featuring
514 frame IDs, independent frame sniffers, and the sentinel frame. Mark
515 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
516 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
517 trad unwinders. The architecture-specific changes, each involving a
518 complete rewrite of the architecture's frame code, were carried out by
519 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
520 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
521 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
522 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
525 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
526 Tensilica, Inc.@: contributed support for Xtensa processors. Others
527 who have worked on the Xtensa port of @value{GDBN} in the past include
528 Steve Tjiang, John Newlin, and Scott Foehner.
530 Michael Eager and staff of Xilinx, Inc., contributed support for the
531 Xilinx MicroBlaze architecture.
534 @chapter A Sample @value{GDBN} Session
536 You can use this manual at your leisure to read all about @value{GDBN}.
537 However, a handful of commands are enough to get started using the
538 debugger. This chapter illustrates those commands.
541 In this sample session, we emphasize user input like this: @b{input},
542 to make it easier to pick out from the surrounding output.
545 @c FIXME: this example may not be appropriate for some configs, where
546 @c FIXME...primary interest is in remote use.
548 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
549 processor) exhibits the following bug: sometimes, when we change its
550 quote strings from the default, the commands used to capture one macro
551 definition within another stop working. In the following short @code{m4}
552 session, we define a macro @code{foo} which expands to @code{0000}; we
553 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
554 same thing. However, when we change the open quote string to
555 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
556 procedure fails to define a new synonym @code{baz}:
565 @b{define(bar,defn(`foo'))}
569 @b{changequote(<QUOTE>,<UNQUOTE>)}
571 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
574 m4: End of input: 0: fatal error: EOF in string
578 Let us use @value{GDBN} to try to see what is going on.
581 $ @b{@value{GDBP} m4}
582 @c FIXME: this falsifies the exact text played out, to permit smallbook
583 @c FIXME... format to come out better.
584 @value{GDBN} is free software and you are welcome to distribute copies
585 of it under certain conditions; type "show copying" to see
587 There is absolutely no warranty for @value{GDBN}; type "show warranty"
590 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
595 @value{GDBN} reads only enough symbol data to know where to find the
596 rest when needed; as a result, the first prompt comes up very quickly.
597 We now tell @value{GDBN} to use a narrower display width than usual, so
598 that examples fit in this manual.
601 (@value{GDBP}) @b{set width 70}
605 We need to see how the @code{m4} built-in @code{changequote} works.
606 Having looked at the source, we know the relevant subroutine is
607 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
608 @code{break} command.
611 (@value{GDBP}) @b{break m4_changequote}
612 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
616 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
617 control; as long as control does not reach the @code{m4_changequote}
618 subroutine, the program runs as usual:
621 (@value{GDBP}) @b{run}
622 Starting program: /work/Editorial/gdb/gnu/m4/m4
630 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
631 suspends execution of @code{m4}, displaying information about the
632 context where it stops.
635 @b{changequote(<QUOTE>,<UNQUOTE>)}
637 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
639 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
643 Now we use the command @code{n} (@code{next}) to advance execution to
644 the next line of the current function.
648 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
653 @code{set_quotes} looks like a promising subroutine. We can go into it
654 by using the command @code{s} (@code{step}) instead of @code{next}.
655 @code{step} goes to the next line to be executed in @emph{any}
656 subroutine, so it steps into @code{set_quotes}.
660 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
662 530 if (lquote != def_lquote)
666 The display that shows the subroutine where @code{m4} is now
667 suspended (and its arguments) is called a stack frame display. It
668 shows a summary of the stack. We can use the @code{backtrace}
669 command (which can also be spelled @code{bt}), to see where we are
670 in the stack as a whole: the @code{backtrace} command displays a
671 stack frame for each active subroutine.
674 (@value{GDBP}) @b{bt}
675 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
677 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
679 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
680 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
682 #4 0x79dc in expand_input () at macro.c:40
683 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
687 We step through a few more lines to see what happens. The first two
688 times, we can use @samp{s}; the next two times we use @code{n} to avoid
689 falling into the @code{xstrdup} subroutine.
693 0x3b5c 532 if (rquote != def_rquote)
695 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
696 def_lquote : xstrdup(lq);
698 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
701 538 len_lquote = strlen(rquote);
705 The last line displayed looks a little odd; we can examine the variables
706 @code{lquote} and @code{rquote} to see if they are in fact the new left
707 and right quotes we specified. We use the command @code{p}
708 (@code{print}) to see their values.
711 (@value{GDBP}) @b{p lquote}
712 $1 = 0x35d40 "<QUOTE>"
713 (@value{GDBP}) @b{p rquote}
714 $2 = 0x35d50 "<UNQUOTE>"
718 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
719 To look at some context, we can display ten lines of source
720 surrounding the current line with the @code{l} (@code{list}) command.
726 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
728 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
731 538 len_lquote = strlen(rquote);
732 539 len_rquote = strlen(lquote);
739 Let us step past the two lines that set @code{len_lquote} and
740 @code{len_rquote}, and then examine the values of those variables.
744 539 len_rquote = strlen(lquote);
747 (@value{GDBP}) @b{p len_lquote}
749 (@value{GDBP}) @b{p len_rquote}
754 That certainly looks wrong, assuming @code{len_lquote} and
755 @code{len_rquote} are meant to be the lengths of @code{lquote} and
756 @code{rquote} respectively. We can set them to better values using
757 the @code{p} command, since it can print the value of
758 any expression---and that expression can include subroutine calls and
762 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
764 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
769 Is that enough to fix the problem of using the new quotes with the
770 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
771 executing with the @code{c} (@code{continue}) command, and then try the
772 example that caused trouble initially:
778 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
785 Success! The new quotes now work just as well as the default ones. The
786 problem seems to have been just the two typos defining the wrong
787 lengths. We allow @code{m4} exit by giving it an EOF as input:
791 Program exited normally.
795 The message @samp{Program exited normally.} is from @value{GDBN}; it
796 indicates @code{m4} has finished executing. We can end our @value{GDBN}
797 session with the @value{GDBN} @code{quit} command.
800 (@value{GDBP}) @b{quit}
804 @chapter Getting In and Out of @value{GDBN}
806 This chapter discusses how to start @value{GDBN}, and how to get out of it.
810 type @samp{@value{GDBP}} to start @value{GDBN}.
812 type @kbd{quit} or @kbd{Ctrl-d} to exit.
816 * Invoking GDB:: How to start @value{GDBN}
817 * Quitting GDB:: How to quit @value{GDBN}
818 * Shell Commands:: How to use shell commands inside @value{GDBN}
819 * Logging Output:: How to log @value{GDBN}'s output to a file
823 @section Invoking @value{GDBN}
825 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
826 @value{GDBN} reads commands from the terminal until you tell it to exit.
828 You can also run @code{@value{GDBP}} with a variety of arguments and options,
829 to specify more of your debugging environment at the outset.
831 The command-line options described here are designed
832 to cover a variety of situations; in some environments, some of these
833 options may effectively be unavailable.
835 The most usual way to start @value{GDBN} is with one argument,
836 specifying an executable program:
839 @value{GDBP} @var{program}
843 You can also start with both an executable program and a core file
847 @value{GDBP} @var{program} @var{core}
850 You can, instead, specify a process ID as a second argument, if you want
851 to debug a running process:
854 @value{GDBP} @var{program} 1234
858 would attach @value{GDBN} to process @code{1234} (unless you also have a file
859 named @file{1234}; @value{GDBN} does check for a core file first).
861 Taking advantage of the second command-line argument requires a fairly
862 complete operating system; when you use @value{GDBN} as a remote
863 debugger attached to a bare board, there may not be any notion of
864 ``process'', and there is often no way to get a core dump. @value{GDBN}
865 will warn you if it is unable to attach or to read core dumps.
867 You can optionally have @code{@value{GDBP}} pass any arguments after the
868 executable file to the inferior using @code{--args}. This option stops
871 @value{GDBP} --args gcc -O2 -c foo.c
873 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
874 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
876 You can run @code{@value{GDBP}} without printing the front material, which describes
877 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
884 You can further control how @value{GDBN} starts up by using command-line
885 options. @value{GDBN} itself can remind you of the options available.
895 to display all available options and briefly describe their use
896 (@samp{@value{GDBP} -h} is a shorter equivalent).
898 All options and command line arguments you give are processed
899 in sequential order. The order makes a difference when the
900 @samp{-x} option is used.
904 * File Options:: Choosing files
905 * Mode Options:: Choosing modes
906 * Startup:: What @value{GDBN} does during startup
910 @subsection Choosing Files
912 When @value{GDBN} starts, it reads any arguments other than options as
913 specifying an executable file and core file (or process ID). This is
914 the same as if the arguments were specified by the @samp{-se} and
915 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
916 first argument that does not have an associated option flag as
917 equivalent to the @samp{-se} option followed by that argument; and the
918 second argument that does not have an associated option flag, if any, as
919 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
920 If the second argument begins with a decimal digit, @value{GDBN} will
921 first attempt to attach to it as a process, and if that fails, attempt
922 to open it as a corefile. If you have a corefile whose name begins with
923 a digit, you can prevent @value{GDBN} from treating it as a pid by
924 prefixing it with @file{./}, e.g.@: @file{./12345}.
926 If @value{GDBN} has not been configured to included core file support,
927 such as for most embedded targets, then it will complain about a second
928 argument and ignore it.
930 Many options have both long and short forms; both are shown in the
931 following list. @value{GDBN} also recognizes the long forms if you truncate
932 them, so long as enough of the option is present to be unambiguous.
933 (If you prefer, you can flag option arguments with @samp{--} rather
934 than @samp{-}, though we illustrate the more usual convention.)
936 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
937 @c way, both those who look for -foo and --foo in the index, will find
941 @item -symbols @var{file}
943 @cindex @code{--symbols}
945 Read symbol table from file @var{file}.
947 @item -exec @var{file}
949 @cindex @code{--exec}
951 Use file @var{file} as the executable file to execute when appropriate,
952 and for examining pure data in conjunction with a core dump.
956 Read symbol table from file @var{file} and use it as the executable
959 @item -core @var{file}
961 @cindex @code{--core}
963 Use file @var{file} as a core dump to examine.
965 @item -pid @var{number}
966 @itemx -p @var{number}
969 Connect to process ID @var{number}, as with the @code{attach} command.
971 @item -command @var{file}
973 @cindex @code{--command}
975 Execute commands from file @var{file}. The contents of this file is
976 evaluated exactly as the @code{source} command would.
977 @xref{Command Files,, Command files}.
979 @item -eval-command @var{command}
980 @itemx -ex @var{command}
981 @cindex @code{--eval-command}
983 Execute a single @value{GDBN} command.
985 This option may be used multiple times to call multiple commands. It may
986 also be interleaved with @samp{-command} as required.
989 @value{GDBP} -ex 'target sim' -ex 'load' \
990 -x setbreakpoints -ex 'run' a.out
993 @item -directory @var{directory}
994 @itemx -d @var{directory}
995 @cindex @code{--directory}
997 Add @var{directory} to the path to search for source and script files.
1001 @cindex @code{--readnow}
1003 Read each symbol file's entire symbol table immediately, rather than
1004 the default, which is to read it incrementally as it is needed.
1005 This makes startup slower, but makes future operations faster.
1010 @subsection Choosing Modes
1012 You can run @value{GDBN} in various alternative modes---for example, in
1013 batch mode or quiet mode.
1020 Do not execute commands found in any initialization files. Normally,
1021 @value{GDBN} executes the commands in these files after all the command
1022 options and arguments have been processed. @xref{Command Files,,Command
1028 @cindex @code{--quiet}
1029 @cindex @code{--silent}
1031 ``Quiet''. Do not print the introductory and copyright messages. These
1032 messages are also suppressed in batch mode.
1035 @cindex @code{--batch}
1036 Run in batch mode. Exit with status @code{0} after processing all the
1037 command files specified with @samp{-x} (and all commands from
1038 initialization files, if not inhibited with @samp{-n}). Exit with
1039 nonzero status if an error occurs in executing the @value{GDBN} commands
1040 in the command files. Batch mode also disables pagination, sets unlimited
1041 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1042 off} were in effect (@pxref{Messages/Warnings}).
1044 Batch mode may be useful for running @value{GDBN} as a filter, for
1045 example to download and run a program on another computer; in order to
1046 make this more useful, the message
1049 Program exited normally.
1053 (which is ordinarily issued whenever a program running under
1054 @value{GDBN} control terminates) is not issued when running in batch
1058 @cindex @code{--batch-silent}
1059 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1060 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1061 unaffected). This is much quieter than @samp{-silent} and would be useless
1062 for an interactive session.
1064 This is particularly useful when using targets that give @samp{Loading section}
1065 messages, for example.
1067 Note that targets that give their output via @value{GDBN}, as opposed to
1068 writing directly to @code{stdout}, will also be made silent.
1070 @item -return-child-result
1071 @cindex @code{--return-child-result}
1072 The return code from @value{GDBN} will be the return code from the child
1073 process (the process being debugged), with the following exceptions:
1077 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1078 internal error. In this case the exit code is the same as it would have been
1079 without @samp{-return-child-result}.
1081 The user quits with an explicit value. E.g., @samp{quit 1}.
1083 The child process never runs, or is not allowed to terminate, in which case
1084 the exit code will be -1.
1087 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1088 when @value{GDBN} is being used as a remote program loader or simulator
1093 @cindex @code{--nowindows}
1095 ``No windows''. If @value{GDBN} comes with a graphical user interface
1096 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1097 interface. If no GUI is available, this option has no effect.
1101 @cindex @code{--windows}
1103 If @value{GDBN} includes a GUI, then this option requires it to be
1106 @item -cd @var{directory}
1108 Run @value{GDBN} using @var{directory} as its working directory,
1109 instead of the current directory.
1111 @item -data-directory @var{directory}
1112 @cindex @code{--data-directory}
1113 Run @value{GDBN} using @var{directory} as its data directory.
1114 The data directory is where @value{GDBN} searches for its
1115 auxiliary files. @xref{Data Files}.
1119 @cindex @code{--fullname}
1121 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1122 subprocess. It tells @value{GDBN} to output the full file name and line
1123 number in a standard, recognizable fashion each time a stack frame is
1124 displayed (which includes each time your program stops). This
1125 recognizable format looks like two @samp{\032} characters, followed by
1126 the file name, line number and character position separated by colons,
1127 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1128 @samp{\032} characters as a signal to display the source code for the
1132 @cindex @code{--epoch}
1133 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1134 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1135 routines so as to allow Epoch to display values of expressions in a
1138 @item -annotate @var{level}
1139 @cindex @code{--annotate}
1140 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1141 effect is identical to using @samp{set annotate @var{level}}
1142 (@pxref{Annotations}). The annotation @var{level} controls how much
1143 information @value{GDBN} prints together with its prompt, values of
1144 expressions, source lines, and other types of output. Level 0 is the
1145 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1146 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1147 that control @value{GDBN}, and level 2 has been deprecated.
1149 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1153 @cindex @code{--args}
1154 Change interpretation of command line so that arguments following the
1155 executable file are passed as command line arguments to the inferior.
1156 This option stops option processing.
1158 @item -baud @var{bps}
1160 @cindex @code{--baud}
1162 Set the line speed (baud rate or bits per second) of any serial
1163 interface used by @value{GDBN} for remote debugging.
1165 @item -l @var{timeout}
1167 Set the timeout (in seconds) of any communication used by @value{GDBN}
1168 for remote debugging.
1170 @item -tty @var{device}
1171 @itemx -t @var{device}
1172 @cindex @code{--tty}
1174 Run using @var{device} for your program's standard input and output.
1175 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1177 @c resolve the situation of these eventually
1179 @cindex @code{--tui}
1180 Activate the @dfn{Text User Interface} when starting. The Text User
1181 Interface manages several text windows on the terminal, showing
1182 source, assembly, registers and @value{GDBN} command outputs
1183 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1184 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1185 Using @value{GDBN} under @sc{gnu} Emacs}).
1188 @c @cindex @code{--xdb}
1189 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1190 @c For information, see the file @file{xdb_trans.html}, which is usually
1191 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1194 @item -interpreter @var{interp}
1195 @cindex @code{--interpreter}
1196 Use the interpreter @var{interp} for interface with the controlling
1197 program or device. This option is meant to be set by programs which
1198 communicate with @value{GDBN} using it as a back end.
1199 @xref{Interpreters, , Command Interpreters}.
1201 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1202 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1203 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1204 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1205 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1206 @sc{gdb/mi} interfaces are no longer supported.
1209 @cindex @code{--write}
1210 Open the executable and core files for both reading and writing. This
1211 is equivalent to the @samp{set write on} command inside @value{GDBN}
1215 @cindex @code{--statistics}
1216 This option causes @value{GDBN} to print statistics about time and
1217 memory usage after it completes each command and returns to the prompt.
1220 @cindex @code{--version}
1221 This option causes @value{GDBN} to print its version number and
1222 no-warranty blurb, and exit.
1227 @subsection What @value{GDBN} Does During Startup
1228 @cindex @value{GDBN} startup
1230 Here's the description of what @value{GDBN} does during session startup:
1234 Sets up the command interpreter as specified by the command line
1235 (@pxref{Mode Options, interpreter}).
1239 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1240 used when building @value{GDBN}; @pxref{System-wide configuration,
1241 ,System-wide configuration and settings}) and executes all the commands in
1245 Reads the init file (if any) in your home directory@footnote{On
1246 DOS/Windows systems, the home directory is the one pointed to by the
1247 @code{HOME} environment variable.} and executes all the commands in
1251 Processes command line options and operands.
1254 Reads and executes the commands from init file (if any) in the current
1255 working directory. This is only done if the current directory is
1256 different from your home directory. Thus, you can have more than one
1257 init file, one generic in your home directory, and another, specific
1258 to the program you are debugging, in the directory where you invoke
1262 If the command line specified a program to debug, or a process to
1263 attach to, or a core file, @value{GDBN} loads any auto-loaded
1264 scripts provided for the program or for its loaded shared libraries.
1265 @xref{Auto-loading}.
1267 If you wish to disable the auto-loading during startup,
1268 you must do something like the following:
1271 $ gdb -ex "set auto-load-scripts off" -ex "file myprogram"
1274 The following does not work because the auto-loading is turned off too late:
1277 $ gdb -ex "set auto-load-scripts off" myprogram
1281 Executes commands and command files specified by the @samp{-ex} and
1282 @samp{-x} options in their specified order. @xref{Command Files}, for
1283 more details about @value{GDBN} command files.
1286 Reads the command history recorded in the @dfn{history file}.
1287 @xref{Command History}, for more details about the command history and the
1288 files where @value{GDBN} records it.
1291 Init files use the same syntax as @dfn{command files} (@pxref{Command
1292 Files}) and are processed by @value{GDBN} in the same way. The init
1293 file in your home directory can set options (such as @samp{set
1294 complaints}) that affect subsequent processing of command line options
1295 and operands. Init files are not executed if you use the @samp{-nx}
1296 option (@pxref{Mode Options, ,Choosing Modes}).
1298 To display the list of init files loaded by gdb at startup, you
1299 can use @kbd{gdb --help}.
1301 @cindex init file name
1302 @cindex @file{.gdbinit}
1303 @cindex @file{gdb.ini}
1304 The @value{GDBN} init files are normally called @file{.gdbinit}.
1305 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1306 the limitations of file names imposed by DOS filesystems. The Windows
1307 ports of @value{GDBN} use the standard name, but if they find a
1308 @file{gdb.ini} file, they warn you about that and suggest to rename
1309 the file to the standard name.
1313 @section Quitting @value{GDBN}
1314 @cindex exiting @value{GDBN}
1315 @cindex leaving @value{GDBN}
1318 @kindex quit @r{[}@var{expression}@r{]}
1319 @kindex q @r{(@code{quit})}
1320 @item quit @r{[}@var{expression}@r{]}
1322 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1323 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1324 do not supply @var{expression}, @value{GDBN} will terminate normally;
1325 otherwise it will terminate using the result of @var{expression} as the
1330 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1331 terminates the action of any @value{GDBN} command that is in progress and
1332 returns to @value{GDBN} command level. It is safe to type the interrupt
1333 character at any time because @value{GDBN} does not allow it to take effect
1334 until a time when it is safe.
1336 If you have been using @value{GDBN} to control an attached process or
1337 device, you can release it with the @code{detach} command
1338 (@pxref{Attach, ,Debugging an Already-running Process}).
1340 @node Shell Commands
1341 @section Shell Commands
1343 If you need to execute occasional shell commands during your
1344 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1345 just use the @code{shell} command.
1350 @cindex shell escape
1351 @item shell @var{command-string}
1352 @itemx !@var{command-string}
1353 Invoke a standard shell to execute @var{command-string}.
1354 Note that no space is needed between @code{!} and @var{command-string}.
1355 If it exists, the environment variable @code{SHELL} determines which
1356 shell to run. Otherwise @value{GDBN} uses the default shell
1357 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1360 The utility @code{make} is often needed in development environments.
1361 You do not have to use the @code{shell} command for this purpose in
1366 @cindex calling make
1367 @item make @var{make-args}
1368 Execute the @code{make} program with the specified
1369 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1372 @node Logging Output
1373 @section Logging Output
1374 @cindex logging @value{GDBN} output
1375 @cindex save @value{GDBN} output to a file
1377 You may want to save the output of @value{GDBN} commands to a file.
1378 There are several commands to control @value{GDBN}'s logging.
1382 @item set logging on
1384 @item set logging off
1386 @cindex logging file name
1387 @item set logging file @var{file}
1388 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1389 @item set logging overwrite [on|off]
1390 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1391 you want @code{set logging on} to overwrite the logfile instead.
1392 @item set logging redirect [on|off]
1393 By default, @value{GDBN} output will go to both the terminal and the logfile.
1394 Set @code{redirect} if you want output to go only to the log file.
1395 @kindex show logging
1397 Show the current values of the logging settings.
1401 @chapter @value{GDBN} Commands
1403 You can abbreviate a @value{GDBN} command to the first few letters of the command
1404 name, if that abbreviation is unambiguous; and you can repeat certain
1405 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1406 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1407 show you the alternatives available, if there is more than one possibility).
1410 * Command Syntax:: How to give commands to @value{GDBN}
1411 * Completion:: Command completion
1412 * Help:: How to ask @value{GDBN} for help
1415 @node Command Syntax
1416 @section Command Syntax
1418 A @value{GDBN} command is a single line of input. There is no limit on
1419 how long it can be. It starts with a command name, which is followed by
1420 arguments whose meaning depends on the command name. For example, the
1421 command @code{step} accepts an argument which is the number of times to
1422 step, as in @samp{step 5}. You can also use the @code{step} command
1423 with no arguments. Some commands do not allow any arguments.
1425 @cindex abbreviation
1426 @value{GDBN} command names may always be truncated if that abbreviation is
1427 unambiguous. Other possible command abbreviations are listed in the
1428 documentation for individual commands. In some cases, even ambiguous
1429 abbreviations are allowed; for example, @code{s} is specially defined as
1430 equivalent to @code{step} even though there are other commands whose
1431 names start with @code{s}. You can test abbreviations by using them as
1432 arguments to the @code{help} command.
1434 @cindex repeating commands
1435 @kindex RET @r{(repeat last command)}
1436 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1437 repeat the previous command. Certain commands (for example, @code{run})
1438 will not repeat this way; these are commands whose unintentional
1439 repetition might cause trouble and which you are unlikely to want to
1440 repeat. User-defined commands can disable this feature; see
1441 @ref{Define, dont-repeat}.
1443 The @code{list} and @code{x} commands, when you repeat them with
1444 @key{RET}, construct new arguments rather than repeating
1445 exactly as typed. This permits easy scanning of source or memory.
1447 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1448 output, in a way similar to the common utility @code{more}
1449 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1450 @key{RET} too many in this situation, @value{GDBN} disables command
1451 repetition after any command that generates this sort of display.
1453 @kindex # @r{(a comment)}
1455 Any text from a @kbd{#} to the end of the line is a comment; it does
1456 nothing. This is useful mainly in command files (@pxref{Command
1457 Files,,Command Files}).
1459 @cindex repeating command sequences
1460 @kindex Ctrl-o @r{(operate-and-get-next)}
1461 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1462 commands. This command accepts the current line, like @key{RET}, and
1463 then fetches the next line relative to the current line from the history
1467 @section Command Completion
1470 @cindex word completion
1471 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1472 only one possibility; it can also show you what the valid possibilities
1473 are for the next word in a command, at any time. This works for @value{GDBN}
1474 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1476 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1477 of a word. If there is only one possibility, @value{GDBN} fills in the
1478 word, and waits for you to finish the command (or press @key{RET} to
1479 enter it). For example, if you type
1481 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1482 @c complete accuracy in these examples; space introduced for clarity.
1483 @c If texinfo enhancements make it unnecessary, it would be nice to
1484 @c replace " @key" by "@key" in the following...
1486 (@value{GDBP}) info bre @key{TAB}
1490 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1491 the only @code{info} subcommand beginning with @samp{bre}:
1494 (@value{GDBP}) info breakpoints
1498 You can either press @key{RET} at this point, to run the @code{info
1499 breakpoints} command, or backspace and enter something else, if
1500 @samp{breakpoints} does not look like the command you expected. (If you
1501 were sure you wanted @code{info breakpoints} in the first place, you
1502 might as well just type @key{RET} immediately after @samp{info bre},
1503 to exploit command abbreviations rather than command completion).
1505 If there is more than one possibility for the next word when you press
1506 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1507 characters and try again, or just press @key{TAB} a second time;
1508 @value{GDBN} displays all the possible completions for that word. For
1509 example, you might want to set a breakpoint on a subroutine whose name
1510 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1511 just sounds the bell. Typing @key{TAB} again displays all the
1512 function names in your program that begin with those characters, for
1516 (@value{GDBP}) b make_ @key{TAB}
1517 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1518 make_a_section_from_file make_environ
1519 make_abs_section make_function_type
1520 make_blockvector make_pointer_type
1521 make_cleanup make_reference_type
1522 make_command make_symbol_completion_list
1523 (@value{GDBP}) b make_
1527 After displaying the available possibilities, @value{GDBN} copies your
1528 partial input (@samp{b make_} in the example) so you can finish the
1531 If you just want to see the list of alternatives in the first place, you
1532 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1533 means @kbd{@key{META} ?}. You can type this either by holding down a
1534 key designated as the @key{META} shift on your keyboard (if there is
1535 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1537 @cindex quotes in commands
1538 @cindex completion of quoted strings
1539 Sometimes the string you need, while logically a ``word'', may contain
1540 parentheses or other characters that @value{GDBN} normally excludes from
1541 its notion of a word. To permit word completion to work in this
1542 situation, you may enclose words in @code{'} (single quote marks) in
1543 @value{GDBN} commands.
1545 The most likely situation where you might need this is in typing the
1546 name of a C@t{++} function. This is because C@t{++} allows function
1547 overloading (multiple definitions of the same function, distinguished
1548 by argument type). For example, when you want to set a breakpoint you
1549 may need to distinguish whether you mean the version of @code{name}
1550 that takes an @code{int} parameter, @code{name(int)}, or the version
1551 that takes a @code{float} parameter, @code{name(float)}. To use the
1552 word-completion facilities in this situation, type a single quote
1553 @code{'} at the beginning of the function name. This alerts
1554 @value{GDBN} that it may need to consider more information than usual
1555 when you press @key{TAB} or @kbd{M-?} to request word completion:
1558 (@value{GDBP}) b 'bubble( @kbd{M-?}
1559 bubble(double,double) bubble(int,int)
1560 (@value{GDBP}) b 'bubble(
1563 In some cases, @value{GDBN} can tell that completing a name requires using
1564 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1565 completing as much as it can) if you do not type the quote in the first
1569 (@value{GDBP}) b bub @key{TAB}
1570 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1571 (@value{GDBP}) b 'bubble(
1575 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1576 you have not yet started typing the argument list when you ask for
1577 completion on an overloaded symbol.
1579 For more information about overloaded functions, see @ref{C Plus Plus
1580 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1581 overload-resolution off} to disable overload resolution;
1582 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1584 @cindex completion of structure field names
1585 @cindex structure field name completion
1586 @cindex completion of union field names
1587 @cindex union field name completion
1588 When completing in an expression which looks up a field in a
1589 structure, @value{GDBN} also tries@footnote{The completer can be
1590 confused by certain kinds of invalid expressions. Also, it only
1591 examines the static type of the expression, not the dynamic type.} to
1592 limit completions to the field names available in the type of the
1596 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1597 magic to_fputs to_rewind
1598 to_data to_isatty to_write
1599 to_delete to_put to_write_async_safe
1604 This is because the @code{gdb_stdout} is a variable of the type
1605 @code{struct ui_file} that is defined in @value{GDBN} sources as
1612 ui_file_flush_ftype *to_flush;
1613 ui_file_write_ftype *to_write;
1614 ui_file_write_async_safe_ftype *to_write_async_safe;
1615 ui_file_fputs_ftype *to_fputs;
1616 ui_file_read_ftype *to_read;
1617 ui_file_delete_ftype *to_delete;
1618 ui_file_isatty_ftype *to_isatty;
1619 ui_file_rewind_ftype *to_rewind;
1620 ui_file_put_ftype *to_put;
1627 @section Getting Help
1628 @cindex online documentation
1631 You can always ask @value{GDBN} itself for information on its commands,
1632 using the command @code{help}.
1635 @kindex h @r{(@code{help})}
1638 You can use @code{help} (abbreviated @code{h}) with no arguments to
1639 display a short list of named classes of commands:
1643 List of classes of commands:
1645 aliases -- Aliases of other commands
1646 breakpoints -- Making program stop at certain points
1647 data -- Examining data
1648 files -- Specifying and examining files
1649 internals -- Maintenance commands
1650 obscure -- Obscure features
1651 running -- Running the program
1652 stack -- Examining the stack
1653 status -- Status inquiries
1654 support -- Support facilities
1655 tracepoints -- Tracing of program execution without
1656 stopping the program
1657 user-defined -- User-defined commands
1659 Type "help" followed by a class name for a list of
1660 commands in that class.
1661 Type "help" followed by command name for full
1663 Command name abbreviations are allowed if unambiguous.
1666 @c the above line break eliminates huge line overfull...
1668 @item help @var{class}
1669 Using one of the general help classes as an argument, you can get a
1670 list of the individual commands in that class. For example, here is the
1671 help display for the class @code{status}:
1674 (@value{GDBP}) help status
1679 @c Line break in "show" line falsifies real output, but needed
1680 @c to fit in smallbook page size.
1681 info -- Generic command for showing things
1682 about the program being debugged
1683 show -- Generic command for showing things
1686 Type "help" followed by command name for full
1688 Command name abbreviations are allowed if unambiguous.
1692 @item help @var{command}
1693 With a command name as @code{help} argument, @value{GDBN} displays a
1694 short paragraph on how to use that command.
1697 @item apropos @var{args}
1698 The @code{apropos} command searches through all of the @value{GDBN}
1699 commands, and their documentation, for the regular expression specified in
1700 @var{args}. It prints out all matches found. For example:
1711 set symbol-reloading -- Set dynamic symbol table reloading
1712 multiple times in one run
1713 show symbol-reloading -- Show dynamic symbol table reloading
1714 multiple times in one run
1719 @item complete @var{args}
1720 The @code{complete @var{args}} command lists all the possible completions
1721 for the beginning of a command. Use @var{args} to specify the beginning of the
1722 command you want completed. For example:
1728 @noindent results in:
1739 @noindent This is intended for use by @sc{gnu} Emacs.
1742 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1743 and @code{show} to inquire about the state of your program, or the state
1744 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1745 manual introduces each of them in the appropriate context. The listings
1746 under @code{info} and under @code{show} in the Index point to
1747 all the sub-commands. @xref{Index}.
1752 @kindex i @r{(@code{info})}
1754 This command (abbreviated @code{i}) is for describing the state of your
1755 program. For example, you can show the arguments passed to a function
1756 with @code{info args}, list the registers currently in use with @code{info
1757 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1758 You can get a complete list of the @code{info} sub-commands with
1759 @w{@code{help info}}.
1763 You can assign the result of an expression to an environment variable with
1764 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1765 @code{set prompt $}.
1769 In contrast to @code{info}, @code{show} is for describing the state of
1770 @value{GDBN} itself.
1771 You can change most of the things you can @code{show}, by using the
1772 related command @code{set}; for example, you can control what number
1773 system is used for displays with @code{set radix}, or simply inquire
1774 which is currently in use with @code{show radix}.
1777 To display all the settable parameters and their current
1778 values, you can use @code{show} with no arguments; you may also use
1779 @code{info set}. Both commands produce the same display.
1780 @c FIXME: "info set" violates the rule that "info" is for state of
1781 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1782 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1786 Here are three miscellaneous @code{show} subcommands, all of which are
1787 exceptional in lacking corresponding @code{set} commands:
1790 @kindex show version
1791 @cindex @value{GDBN} version number
1793 Show what version of @value{GDBN} is running. You should include this
1794 information in @value{GDBN} bug-reports. If multiple versions of
1795 @value{GDBN} are in use at your site, you may need to determine which
1796 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1797 commands are introduced, and old ones may wither away. Also, many
1798 system vendors ship variant versions of @value{GDBN}, and there are
1799 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1800 The version number is the same as the one announced when you start
1803 @kindex show copying
1804 @kindex info copying
1805 @cindex display @value{GDBN} copyright
1808 Display information about permission for copying @value{GDBN}.
1810 @kindex show warranty
1811 @kindex info warranty
1813 @itemx info warranty
1814 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1815 if your version of @value{GDBN} comes with one.
1820 @chapter Running Programs Under @value{GDBN}
1822 When you run a program under @value{GDBN}, you must first generate
1823 debugging information when you compile it.
1825 You may start @value{GDBN} with its arguments, if any, in an environment
1826 of your choice. If you are doing native debugging, you may redirect
1827 your program's input and output, debug an already running process, or
1828 kill a child process.
1831 * Compilation:: Compiling for debugging
1832 * Starting:: Starting your program
1833 * Arguments:: Your program's arguments
1834 * Environment:: Your program's environment
1836 * Working Directory:: Your program's working directory
1837 * Input/Output:: Your program's input and output
1838 * Attach:: Debugging an already-running process
1839 * Kill Process:: Killing the child process
1841 * Inferiors and Programs:: Debugging multiple inferiors and programs
1842 * Threads:: Debugging programs with multiple threads
1843 * Forks:: Debugging forks
1844 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1848 @section Compiling for Debugging
1850 In order to debug a program effectively, you need to generate
1851 debugging information when you compile it. This debugging information
1852 is stored in the object file; it describes the data type of each
1853 variable or function and the correspondence between source line numbers
1854 and addresses in the executable code.
1856 To request debugging information, specify the @samp{-g} option when you run
1859 Programs that are to be shipped to your customers are compiled with
1860 optimizations, using the @samp{-O} compiler option. However, some
1861 compilers are unable to handle the @samp{-g} and @samp{-O} options
1862 together. Using those compilers, you cannot generate optimized
1863 executables containing debugging information.
1865 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1866 without @samp{-O}, making it possible to debug optimized code. We
1867 recommend that you @emph{always} use @samp{-g} whenever you compile a
1868 program. You may think your program is correct, but there is no sense
1869 in pushing your luck. For more information, see @ref{Optimized Code}.
1871 Older versions of the @sc{gnu} C compiler permitted a variant option
1872 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1873 format; if your @sc{gnu} C compiler has this option, do not use it.
1875 @value{GDBN} knows about preprocessor macros and can show you their
1876 expansion (@pxref{Macros}). Most compilers do not include information
1877 about preprocessor macros in the debugging information if you specify
1878 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1879 the @sc{gnu} C compiler, provides macro information if you are using
1880 the DWARF debugging format, and specify the option @option{-g3}.
1882 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1883 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1884 information on @value{NGCC} options affecting debug information.
1886 You will have the best debugging experience if you use the latest
1887 version of the DWARF debugging format that your compiler supports.
1888 DWARF is currently the most expressive and best supported debugging
1889 format in @value{GDBN}.
1893 @section Starting your Program
1899 @kindex r @r{(@code{run})}
1902 Use the @code{run} command to start your program under @value{GDBN}.
1903 You must first specify the program name (except on VxWorks) with an
1904 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1905 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1906 (@pxref{Files, ,Commands to Specify Files}).
1910 If you are running your program in an execution environment that
1911 supports processes, @code{run} creates an inferior process and makes
1912 that process run your program. In some environments without processes,
1913 @code{run} jumps to the start of your program. Other targets,
1914 like @samp{remote}, are always running. If you get an error
1915 message like this one:
1918 The "remote" target does not support "run".
1919 Try "help target" or "continue".
1923 then use @code{continue} to run your program. You may need @code{load}
1924 first (@pxref{load}).
1926 The execution of a program is affected by certain information it
1927 receives from its superior. @value{GDBN} provides ways to specify this
1928 information, which you must do @emph{before} starting your program. (You
1929 can change it after starting your program, but such changes only affect
1930 your program the next time you start it.) This information may be
1931 divided into four categories:
1934 @item The @emph{arguments.}
1935 Specify the arguments to give your program as the arguments of the
1936 @code{run} command. If a shell is available on your target, the shell
1937 is used to pass the arguments, so that you may use normal conventions
1938 (such as wildcard expansion or variable substitution) in describing
1940 In Unix systems, you can control which shell is used with the
1941 @code{SHELL} environment variable.
1942 @xref{Arguments, ,Your Program's Arguments}.
1944 @item The @emph{environment.}
1945 Your program normally inherits its environment from @value{GDBN}, but you can
1946 use the @value{GDBN} commands @code{set environment} and @code{unset
1947 environment} to change parts of the environment that affect
1948 your program. @xref{Environment, ,Your Program's Environment}.
1950 @item The @emph{working directory.}
1951 Your program inherits its working directory from @value{GDBN}. You can set
1952 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1953 @xref{Working Directory, ,Your Program's Working Directory}.
1955 @item The @emph{standard input and output.}
1956 Your program normally uses the same device for standard input and
1957 standard output as @value{GDBN} is using. You can redirect input and output
1958 in the @code{run} command line, or you can use the @code{tty} command to
1959 set a different device for your program.
1960 @xref{Input/Output, ,Your Program's Input and Output}.
1963 @emph{Warning:} While input and output redirection work, you cannot use
1964 pipes to pass the output of the program you are debugging to another
1965 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1969 When you issue the @code{run} command, your program begins to execute
1970 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1971 of how to arrange for your program to stop. Once your program has
1972 stopped, you may call functions in your program, using the @code{print}
1973 or @code{call} commands. @xref{Data, ,Examining Data}.
1975 If the modification time of your symbol file has changed since the last
1976 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1977 table, and reads it again. When it does this, @value{GDBN} tries to retain
1978 your current breakpoints.
1983 @cindex run to main procedure
1984 The name of the main procedure can vary from language to language.
1985 With C or C@t{++}, the main procedure name is always @code{main}, but
1986 other languages such as Ada do not require a specific name for their
1987 main procedure. The debugger provides a convenient way to start the
1988 execution of the program and to stop at the beginning of the main
1989 procedure, depending on the language used.
1991 The @samp{start} command does the equivalent of setting a temporary
1992 breakpoint at the beginning of the main procedure and then invoking
1993 the @samp{run} command.
1995 @cindex elaboration phase
1996 Some programs contain an @dfn{elaboration} phase where some startup code is
1997 executed before the main procedure is called. This depends on the
1998 languages used to write your program. In C@t{++}, for instance,
1999 constructors for static and global objects are executed before
2000 @code{main} is called. It is therefore possible that the debugger stops
2001 before reaching the main procedure. However, the temporary breakpoint
2002 will remain to halt execution.
2004 Specify the arguments to give to your program as arguments to the
2005 @samp{start} command. These arguments will be given verbatim to the
2006 underlying @samp{run} command. Note that the same arguments will be
2007 reused if no argument is provided during subsequent calls to
2008 @samp{start} or @samp{run}.
2010 It is sometimes necessary to debug the program during elaboration. In
2011 these cases, using the @code{start} command would stop the execution of
2012 your program too late, as the program would have already completed the
2013 elaboration phase. Under these circumstances, insert breakpoints in your
2014 elaboration code before running your program.
2016 @kindex set exec-wrapper
2017 @item set exec-wrapper @var{wrapper}
2018 @itemx show exec-wrapper
2019 @itemx unset exec-wrapper
2020 When @samp{exec-wrapper} is set, the specified wrapper is used to
2021 launch programs for debugging. @value{GDBN} starts your program
2022 with a shell command of the form @kbd{exec @var{wrapper}
2023 @var{program}}. Quoting is added to @var{program} and its
2024 arguments, but not to @var{wrapper}, so you should add quotes if
2025 appropriate for your shell. The wrapper runs until it executes
2026 your program, and then @value{GDBN} takes control.
2028 You can use any program that eventually calls @code{execve} with
2029 its arguments as a wrapper. Several standard Unix utilities do
2030 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2031 with @code{exec "$@@"} will also work.
2033 For example, you can use @code{env} to pass an environment variable to
2034 the debugged program, without setting the variable in your shell's
2038 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2042 This command is available when debugging locally on most targets, excluding
2043 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2045 @kindex set disable-randomization
2046 @item set disable-randomization
2047 @itemx set disable-randomization on
2048 This option (enabled by default in @value{GDBN}) will turn off the native
2049 randomization of the virtual address space of the started program. This option
2050 is useful for multiple debugging sessions to make the execution better
2051 reproducible and memory addresses reusable across debugging sessions.
2053 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2054 On @sc{gnu}/Linux you can get the same behavior using
2057 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2060 @item set disable-randomization off
2061 Leave the behavior of the started executable unchanged. Some bugs rear their
2062 ugly heads only when the program is loaded at certain addresses. If your bug
2063 disappears when you run the program under @value{GDBN}, that might be because
2064 @value{GDBN} by default disables the address randomization on platforms, such
2065 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2066 disable-randomization off} to try to reproduce such elusive bugs.
2068 On targets where it is available, virtual address space randomization
2069 protects the programs against certain kinds of security attacks. In these
2070 cases the attacker needs to know the exact location of a concrete executable
2071 code. Randomizing its location makes it impossible to inject jumps misusing
2072 a code at its expected addresses.
2074 Prelinking shared libraries provides a startup performance advantage but it
2075 makes addresses in these libraries predictable for privileged processes by
2076 having just unprivileged access at the target system. Reading the shared
2077 library binary gives enough information for assembling the malicious code
2078 misusing it. Still even a prelinked shared library can get loaded at a new
2079 random address just requiring the regular relocation process during the
2080 startup. Shared libraries not already prelinked are always loaded at
2081 a randomly chosen address.
2083 Position independent executables (PIE) contain position independent code
2084 similar to the shared libraries and therefore such executables get loaded at
2085 a randomly chosen address upon startup. PIE executables always load even
2086 already prelinked shared libraries at a random address. You can build such
2087 executable using @command{gcc -fPIE -pie}.
2089 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2090 (as long as the randomization is enabled).
2092 @item show disable-randomization
2093 Show the current setting of the explicit disable of the native randomization of
2094 the virtual address space of the started program.
2099 @section Your Program's Arguments
2101 @cindex arguments (to your program)
2102 The arguments to your program can be specified by the arguments of the
2104 They are passed to a shell, which expands wildcard characters and
2105 performs redirection of I/O, and thence to your program. Your
2106 @code{SHELL} environment variable (if it exists) specifies what shell
2107 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2108 the default shell (@file{/bin/sh} on Unix).
2110 On non-Unix systems, the program is usually invoked directly by
2111 @value{GDBN}, which emulates I/O redirection via the appropriate system
2112 calls, and the wildcard characters are expanded by the startup code of
2113 the program, not by the shell.
2115 @code{run} with no arguments uses the same arguments used by the previous
2116 @code{run}, or those set by the @code{set args} command.
2121 Specify the arguments to be used the next time your program is run. If
2122 @code{set args} has no arguments, @code{run} executes your program
2123 with no arguments. Once you have run your program with arguments,
2124 using @code{set args} before the next @code{run} is the only way to run
2125 it again without arguments.
2129 Show the arguments to give your program when it is started.
2133 @section Your Program's Environment
2135 @cindex environment (of your program)
2136 The @dfn{environment} consists of a set of environment variables and
2137 their values. Environment variables conventionally record such things as
2138 your user name, your home directory, your terminal type, and your search
2139 path for programs to run. Usually you set up environment variables with
2140 the shell and they are inherited by all the other programs you run. When
2141 debugging, it can be useful to try running your program with a modified
2142 environment without having to start @value{GDBN} over again.
2146 @item path @var{directory}
2147 Add @var{directory} to the front of the @code{PATH} environment variable
2148 (the search path for executables) that will be passed to your program.
2149 The value of @code{PATH} used by @value{GDBN} does not change.
2150 You may specify several directory names, separated by whitespace or by a
2151 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2152 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2153 is moved to the front, so it is searched sooner.
2155 You can use the string @samp{$cwd} to refer to whatever is the current
2156 working directory at the time @value{GDBN} searches the path. If you
2157 use @samp{.} instead, it refers to the directory where you executed the
2158 @code{path} command. @value{GDBN} replaces @samp{.} in the
2159 @var{directory} argument (with the current path) before adding
2160 @var{directory} to the search path.
2161 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2162 @c document that, since repeating it would be a no-op.
2166 Display the list of search paths for executables (the @code{PATH}
2167 environment variable).
2169 @kindex show environment
2170 @item show environment @r{[}@var{varname}@r{]}
2171 Print the value of environment variable @var{varname} to be given to
2172 your program when it starts. If you do not supply @var{varname},
2173 print the names and values of all environment variables to be given to
2174 your program. You can abbreviate @code{environment} as @code{env}.
2176 @kindex set environment
2177 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2178 Set environment variable @var{varname} to @var{value}. The value
2179 changes for your program only, not for @value{GDBN} itself. @var{value} may
2180 be any string; the values of environment variables are just strings, and
2181 any interpretation is supplied by your program itself. The @var{value}
2182 parameter is optional; if it is eliminated, the variable is set to a
2184 @c "any string" here does not include leading, trailing
2185 @c blanks. Gnu asks: does anyone care?
2187 For example, this command:
2194 tells the debugged program, when subsequently run, that its user is named
2195 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2196 are not actually required.)
2198 @kindex unset environment
2199 @item unset environment @var{varname}
2200 Remove variable @var{varname} from the environment to be passed to your
2201 program. This is different from @samp{set env @var{varname} =};
2202 @code{unset environment} removes the variable from the environment,
2203 rather than assigning it an empty value.
2206 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2208 by your @code{SHELL} environment variable if it exists (or
2209 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2210 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2211 @file{.bashrc} for BASH---any variables you set in that file affect
2212 your program. You may wish to move setting of environment variables to
2213 files that are only run when you sign on, such as @file{.login} or
2216 @node Working Directory
2217 @section Your Program's Working Directory
2219 @cindex working directory (of your program)
2220 Each time you start your program with @code{run}, it inherits its
2221 working directory from the current working directory of @value{GDBN}.
2222 The @value{GDBN} working directory is initially whatever it inherited
2223 from its parent process (typically the shell), but you can specify a new
2224 working directory in @value{GDBN} with the @code{cd} command.
2226 The @value{GDBN} working directory also serves as a default for the commands
2227 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2232 @cindex change working directory
2233 @item cd @var{directory}
2234 Set the @value{GDBN} working directory to @var{directory}.
2238 Print the @value{GDBN} working directory.
2241 It is generally impossible to find the current working directory of
2242 the process being debugged (since a program can change its directory
2243 during its run). If you work on a system where @value{GDBN} is
2244 configured with the @file{/proc} support, you can use the @code{info
2245 proc} command (@pxref{SVR4 Process Information}) to find out the
2246 current working directory of the debuggee.
2249 @section Your Program's Input and Output
2254 By default, the program you run under @value{GDBN} does input and output to
2255 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2256 to its own terminal modes to interact with you, but it records the terminal
2257 modes your program was using and switches back to them when you continue
2258 running your program.
2261 @kindex info terminal
2263 Displays information recorded by @value{GDBN} about the terminal modes your
2267 You can redirect your program's input and/or output using shell
2268 redirection with the @code{run} command. For example,
2275 starts your program, diverting its output to the file @file{outfile}.
2278 @cindex controlling terminal
2279 Another way to specify where your program should do input and output is
2280 with the @code{tty} command. This command accepts a file name as
2281 argument, and causes this file to be the default for future @code{run}
2282 commands. It also resets the controlling terminal for the child
2283 process, for future @code{run} commands. For example,
2290 directs that processes started with subsequent @code{run} commands
2291 default to do input and output on the terminal @file{/dev/ttyb} and have
2292 that as their controlling terminal.
2294 An explicit redirection in @code{run} overrides the @code{tty} command's
2295 effect on the input/output device, but not its effect on the controlling
2298 When you use the @code{tty} command or redirect input in the @code{run}
2299 command, only the input @emph{for your program} is affected. The input
2300 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2301 for @code{set inferior-tty}.
2303 @cindex inferior tty
2304 @cindex set inferior controlling terminal
2305 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2306 display the name of the terminal that will be used for future runs of your
2310 @item set inferior-tty /dev/ttyb
2311 @kindex set inferior-tty
2312 Set the tty for the program being debugged to /dev/ttyb.
2314 @item show inferior-tty
2315 @kindex show inferior-tty
2316 Show the current tty for the program being debugged.
2320 @section Debugging an Already-running Process
2325 @item attach @var{process-id}
2326 This command attaches to a running process---one that was started
2327 outside @value{GDBN}. (@code{info files} shows your active
2328 targets.) The command takes as argument a process ID. The usual way to
2329 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2330 or with the @samp{jobs -l} shell command.
2332 @code{attach} does not repeat if you press @key{RET} a second time after
2333 executing the command.
2336 To use @code{attach}, your program must be running in an environment
2337 which supports processes; for example, @code{attach} does not work for
2338 programs on bare-board targets that lack an operating system. You must
2339 also have permission to send the process a signal.
2341 When you use @code{attach}, the debugger finds the program running in
2342 the process first by looking in the current working directory, then (if
2343 the program is not found) by using the source file search path
2344 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2345 the @code{file} command to load the program. @xref{Files, ,Commands to
2348 The first thing @value{GDBN} does after arranging to debug the specified
2349 process is to stop it. You can examine and modify an attached process
2350 with all the @value{GDBN} commands that are ordinarily available when
2351 you start processes with @code{run}. You can insert breakpoints; you
2352 can step and continue; you can modify storage. If you would rather the
2353 process continue running, you may use the @code{continue} command after
2354 attaching @value{GDBN} to the process.
2359 When you have finished debugging the attached process, you can use the
2360 @code{detach} command to release it from @value{GDBN} control. Detaching
2361 the process continues its execution. After the @code{detach} command,
2362 that process and @value{GDBN} become completely independent once more, and you
2363 are ready to @code{attach} another process or start one with @code{run}.
2364 @code{detach} does not repeat if you press @key{RET} again after
2365 executing the command.
2368 If you exit @value{GDBN} while you have an attached process, you detach
2369 that process. If you use the @code{run} command, you kill that process.
2370 By default, @value{GDBN} asks for confirmation if you try to do either of these
2371 things; you can control whether or not you need to confirm by using the
2372 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2376 @section Killing the Child Process
2381 Kill the child process in which your program is running under @value{GDBN}.
2384 This command is useful if you wish to debug a core dump instead of a
2385 running process. @value{GDBN} ignores any core dump file while your program
2388 On some operating systems, a program cannot be executed outside @value{GDBN}
2389 while you have breakpoints set on it inside @value{GDBN}. You can use the
2390 @code{kill} command in this situation to permit running your program
2391 outside the debugger.
2393 The @code{kill} command is also useful if you wish to recompile and
2394 relink your program, since on many systems it is impossible to modify an
2395 executable file while it is running in a process. In this case, when you
2396 next type @code{run}, @value{GDBN} notices that the file has changed, and
2397 reads the symbol table again (while trying to preserve your current
2398 breakpoint settings).
2400 @node Inferiors and Programs
2401 @section Debugging Multiple Inferiors and Programs
2403 @value{GDBN} lets you run and debug multiple programs in a single
2404 session. In addition, @value{GDBN} on some systems may let you run
2405 several programs simultaneously (otherwise you have to exit from one
2406 before starting another). In the most general case, you can have
2407 multiple threads of execution in each of multiple processes, launched
2408 from multiple executables.
2411 @value{GDBN} represents the state of each program execution with an
2412 object called an @dfn{inferior}. An inferior typically corresponds to
2413 a process, but is more general and applies also to targets that do not
2414 have processes. Inferiors may be created before a process runs, and
2415 may be retained after a process exits. Inferiors have unique
2416 identifiers that are different from process ids. Usually each
2417 inferior will also have its own distinct address space, although some
2418 embedded targets may have several inferiors running in different parts
2419 of a single address space. Each inferior may in turn have multiple
2420 threads running in it.
2422 To find out what inferiors exist at any moment, use @w{@code{info
2426 @kindex info inferiors
2427 @item info inferiors
2428 Print a list of all inferiors currently being managed by @value{GDBN}.
2430 @value{GDBN} displays for each inferior (in this order):
2434 the inferior number assigned by @value{GDBN}
2437 the target system's inferior identifier
2440 the name of the executable the inferior is running.
2445 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2446 indicates the current inferior.
2450 @c end table here to get a little more width for example
2453 (@value{GDBP}) info inferiors
2454 Num Description Executable
2455 2 process 2307 hello
2456 * 1 process 3401 goodbye
2459 To switch focus between inferiors, use the @code{inferior} command:
2462 @kindex inferior @var{infno}
2463 @item inferior @var{infno}
2464 Make inferior number @var{infno} the current inferior. The argument
2465 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2466 in the first field of the @samp{info inferiors} display.
2470 You can get multiple executables into a debugging session via the
2471 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2472 systems @value{GDBN} can add inferiors to the debug session
2473 automatically by following calls to @code{fork} and @code{exec}. To
2474 remove inferiors from the debugging session use the
2475 @w{@code{remove-inferiors}} command.
2478 @kindex add-inferior
2479 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2480 Adds @var{n} inferiors to be run using @var{executable} as the
2481 executable. @var{n} defaults to 1. If no executable is specified,
2482 the inferiors begins empty, with no program. You can still assign or
2483 change the program assigned to the inferior at any time by using the
2484 @code{file} command with the executable name as its argument.
2486 @kindex clone-inferior
2487 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2488 Adds @var{n} inferiors ready to execute the same program as inferior
2489 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2490 number of the current inferior. This is a convenient command when you
2491 want to run another instance of the inferior you are debugging.
2494 (@value{GDBP}) info inferiors
2495 Num Description Executable
2496 * 1 process 29964 helloworld
2497 (@value{GDBP}) clone-inferior
2500 (@value{GDBP}) info inferiors
2501 Num Description Executable
2503 * 1 process 29964 helloworld
2506 You can now simply switch focus to inferior 2 and run it.
2508 @kindex remove-inferiors
2509 @item remove-inferiors @var{infno}@dots{}
2510 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2511 possible to remove an inferior that is running with this command. For
2512 those, use the @code{kill} or @code{detach} command first.
2516 To quit debugging one of the running inferiors that is not the current
2517 inferior, you can either detach from it by using the @w{@code{detach
2518 inferior}} command (allowing it to run independently), or kill it
2519 using the @w{@code{kill inferiors}} command:
2522 @kindex detach inferiors @var{infno}@dots{}
2523 @item detach inferior @var{infno}@dots{}
2524 Detach from the inferior or inferiors identified by @value{GDBN}
2525 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2526 still stays on the list of inferiors shown by @code{info inferiors},
2527 but its Description will show @samp{<null>}.
2529 @kindex kill inferiors @var{infno}@dots{}
2530 @item kill inferiors @var{infno}@dots{}
2531 Kill the inferior or inferiors identified by @value{GDBN} inferior
2532 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2533 stays on the list of inferiors shown by @code{info inferiors}, but its
2534 Description will show @samp{<null>}.
2537 After the successful completion of a command such as @code{detach},
2538 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2539 a normal process exit, the inferior is still valid and listed with
2540 @code{info inferiors}, ready to be restarted.
2543 To be notified when inferiors are started or exit under @value{GDBN}'s
2544 control use @w{@code{set print inferior-events}}:
2547 @kindex set print inferior-events
2548 @cindex print messages on inferior start and exit
2549 @item set print inferior-events
2550 @itemx set print inferior-events on
2551 @itemx set print inferior-events off
2552 The @code{set print inferior-events} command allows you to enable or
2553 disable printing of messages when @value{GDBN} notices that new
2554 inferiors have started or that inferiors have exited or have been
2555 detached. By default, these messages will not be printed.
2557 @kindex show print inferior-events
2558 @item show print inferior-events
2559 Show whether messages will be printed when @value{GDBN} detects that
2560 inferiors have started, exited or have been detached.
2563 Many commands will work the same with multiple programs as with a
2564 single program: e.g., @code{print myglobal} will simply display the
2565 value of @code{myglobal} in the current inferior.
2568 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2569 get more info about the relationship of inferiors, programs, address
2570 spaces in a debug session. You can do that with the @w{@code{maint
2571 info program-spaces}} command.
2574 @kindex maint info program-spaces
2575 @item maint info program-spaces
2576 Print a list of all program spaces currently being managed by
2579 @value{GDBN} displays for each program space (in this order):
2583 the program space number assigned by @value{GDBN}
2586 the name of the executable loaded into the program space, with e.g.,
2587 the @code{file} command.
2592 An asterisk @samp{*} preceding the @value{GDBN} program space number
2593 indicates the current program space.
2595 In addition, below each program space line, @value{GDBN} prints extra
2596 information that isn't suitable to display in tabular form. For
2597 example, the list of inferiors bound to the program space.
2600 (@value{GDBP}) maint info program-spaces
2603 Bound inferiors: ID 1 (process 21561)
2607 Here we can see that no inferior is running the program @code{hello},
2608 while @code{process 21561} is running the program @code{goodbye}. On
2609 some targets, it is possible that multiple inferiors are bound to the
2610 same program space. The most common example is that of debugging both
2611 the parent and child processes of a @code{vfork} call. For example,
2614 (@value{GDBP}) maint info program-spaces
2617 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2620 Here, both inferior 2 and inferior 1 are running in the same program
2621 space as a result of inferior 1 having executed a @code{vfork} call.
2625 @section Debugging Programs with Multiple Threads
2627 @cindex threads of execution
2628 @cindex multiple threads
2629 @cindex switching threads
2630 In some operating systems, such as HP-UX and Solaris, a single program
2631 may have more than one @dfn{thread} of execution. The precise semantics
2632 of threads differ from one operating system to another, but in general
2633 the threads of a single program are akin to multiple processes---except
2634 that they share one address space (that is, they can all examine and
2635 modify the same variables). On the other hand, each thread has its own
2636 registers and execution stack, and perhaps private memory.
2638 @value{GDBN} provides these facilities for debugging multi-thread
2642 @item automatic notification of new threads
2643 @item @samp{thread @var{threadno}}, a command to switch among threads
2644 @item @samp{info threads}, a command to inquire about existing threads
2645 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2646 a command to apply a command to a list of threads
2647 @item thread-specific breakpoints
2648 @item @samp{set print thread-events}, which controls printing of
2649 messages on thread start and exit.
2650 @item @samp{set libthread-db-search-path @var{path}}, which lets
2651 the user specify which @code{libthread_db} to use if the default choice
2652 isn't compatible with the program.
2656 @emph{Warning:} These facilities are not yet available on every
2657 @value{GDBN} configuration where the operating system supports threads.
2658 If your @value{GDBN} does not support threads, these commands have no
2659 effect. For example, a system without thread support shows no output
2660 from @samp{info threads}, and always rejects the @code{thread} command,
2664 (@value{GDBP}) info threads
2665 (@value{GDBP}) thread 1
2666 Thread ID 1 not known. Use the "info threads" command to
2667 see the IDs of currently known threads.
2669 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2670 @c doesn't support threads"?
2673 @cindex focus of debugging
2674 @cindex current thread
2675 The @value{GDBN} thread debugging facility allows you to observe all
2676 threads while your program runs---but whenever @value{GDBN} takes
2677 control, one thread in particular is always the focus of debugging.
2678 This thread is called the @dfn{current thread}. Debugging commands show
2679 program information from the perspective of the current thread.
2681 @cindex @code{New} @var{systag} message
2682 @cindex thread identifier (system)
2683 @c FIXME-implementors!! It would be more helpful if the [New...] message
2684 @c included GDB's numeric thread handle, so you could just go to that
2685 @c thread without first checking `info threads'.
2686 Whenever @value{GDBN} detects a new thread in your program, it displays
2687 the target system's identification for the thread with a message in the
2688 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2689 whose form varies depending on the particular system. For example, on
2690 @sc{gnu}/Linux, you might see
2693 [New Thread 0x41e02940 (LWP 25582)]
2697 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2698 the @var{systag} is simply something like @samp{process 368}, with no
2701 @c FIXME!! (1) Does the [New...] message appear even for the very first
2702 @c thread of a program, or does it only appear for the
2703 @c second---i.e.@: when it becomes obvious we have a multithread
2705 @c (2) *Is* there necessarily a first thread always? Or do some
2706 @c multithread systems permit starting a program with multiple
2707 @c threads ab initio?
2709 @cindex thread number
2710 @cindex thread identifier (GDB)
2711 For debugging purposes, @value{GDBN} associates its own thread
2712 number---always a single integer---with each thread in your program.
2715 @kindex info threads
2716 @item info threads @r{[}@var{id}@dots{}@r{]}
2717 Display a summary of all threads currently in your program. Optional
2718 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2719 means to print information only about the specified thread or threads.
2720 @value{GDBN} displays for each thread (in this order):
2724 the thread number assigned by @value{GDBN}
2727 the target system's thread identifier (@var{systag})
2730 the thread's name, if one is known. A thread can either be named by
2731 the user (see @code{thread name}, below), or, in some cases, by the
2735 the current stack frame summary for that thread
2739 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2740 indicates the current thread.
2744 @c end table here to get a little more width for example
2747 (@value{GDBP}) info threads
2749 3 process 35 thread 27 0x34e5 in sigpause ()
2750 2 process 35 thread 23 0x34e5 in sigpause ()
2751 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2755 On Solaris, you can display more information about user threads with a
2756 Solaris-specific command:
2759 @item maint info sol-threads
2760 @kindex maint info sol-threads
2761 @cindex thread info (Solaris)
2762 Display info on Solaris user threads.
2766 @kindex thread @var{threadno}
2767 @item thread @var{threadno}
2768 Make thread number @var{threadno} the current thread. The command
2769 argument @var{threadno} is the internal @value{GDBN} thread number, as
2770 shown in the first field of the @samp{info threads} display.
2771 @value{GDBN} responds by displaying the system identifier of the thread
2772 you selected, and its current stack frame summary:
2775 (@value{GDBP}) thread 2
2776 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2777 #0 some_function (ignore=0x0) at example.c:8
2778 8 printf ("hello\n");
2782 As with the @samp{[New @dots{}]} message, the form of the text after
2783 @samp{Switching to} depends on your system's conventions for identifying
2786 @vindex $_thread@r{, convenience variable}
2787 The debugger convenience variable @samp{$_thread} contains the number
2788 of the current thread. You may find this useful in writing breakpoint
2789 conditional expressions, command scripts, and so forth. See
2790 @xref{Convenience Vars,, Convenience Variables}, for general
2791 information on convenience variables.
2793 @kindex thread apply
2794 @cindex apply command to several threads
2795 @item thread apply [@var{threadno} | all] @var{command}
2796 The @code{thread apply} command allows you to apply the named
2797 @var{command} to one or more threads. Specify the numbers of the
2798 threads that you want affected with the command argument
2799 @var{threadno}. It can be a single thread number, one of the numbers
2800 shown in the first field of the @samp{info threads} display; or it
2801 could be a range of thread numbers, as in @code{2-4}. To apply a
2802 command to all threads, type @kbd{thread apply all @var{command}}.
2805 @cindex name a thread
2806 @item thread name [@var{name}]
2807 This command assigns a name to the current thread. If no argument is
2808 given, any existing user-specified name is removed. The thread name
2809 appears in the @samp{info threads} display.
2811 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2812 determine the name of the thread as given by the OS. On these
2813 systems, a name specified with @samp{thread name} will override the
2814 system-give name, and removing the user-specified name will cause
2815 @value{GDBN} to once again display the system-specified name.
2818 @cindex search for a thread
2819 @item thread find [@var{regexp}]
2820 Search for and display thread ids whose name or @var{systag}
2821 matches the supplied regular expression.
2823 As well as being the complement to the @samp{thread name} command,
2824 this command also allows you to identify a thread by its target
2825 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2829 (@value{GDBN}) thread find 26688
2830 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2831 (@value{GDBN}) info thread 4
2833 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
2836 @kindex set print thread-events
2837 @cindex print messages on thread start and exit
2838 @item set print thread-events
2839 @itemx set print thread-events on
2840 @itemx set print thread-events off
2841 The @code{set print thread-events} command allows you to enable or
2842 disable printing of messages when @value{GDBN} notices that new threads have
2843 started or that threads have exited. By default, these messages will
2844 be printed if detection of these events is supported by the target.
2845 Note that these messages cannot be disabled on all targets.
2847 @kindex show print thread-events
2848 @item show print thread-events
2849 Show whether messages will be printed when @value{GDBN} detects that threads
2850 have started and exited.
2853 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2854 more information about how @value{GDBN} behaves when you stop and start
2855 programs with multiple threads.
2857 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2858 watchpoints in programs with multiple threads.
2861 @kindex set libthread-db-search-path
2862 @cindex search path for @code{libthread_db}
2863 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2864 If this variable is set, @var{path} is a colon-separated list of
2865 directories @value{GDBN} will use to search for @code{libthread_db}.
2866 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2867 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
2868 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
2871 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2872 @code{libthread_db} library to obtain information about threads in the
2873 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2874 to find @code{libthread_db}.
2876 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
2877 refers to the default system directories that are
2878 normally searched for loading shared libraries.
2880 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
2881 refers to the directory from which @code{libpthread}
2882 was loaded in the inferior process.
2884 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2885 @value{GDBN} attempts to initialize it with the current inferior process.
2886 If this initialization fails (which could happen because of a version
2887 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2888 will unload @code{libthread_db}, and continue with the next directory.
2889 If none of @code{libthread_db} libraries initialize successfully,
2890 @value{GDBN} will issue a warning and thread debugging will be disabled.
2892 Setting @code{libthread-db-search-path} is currently implemented
2893 only on some platforms.
2895 @kindex show libthread-db-search-path
2896 @item show libthread-db-search-path
2897 Display current libthread_db search path.
2899 @kindex set debug libthread-db
2900 @kindex show debug libthread-db
2901 @cindex debugging @code{libthread_db}
2902 @item set debug libthread-db
2903 @itemx show debug libthread-db
2904 Turns on or off display of @code{libthread_db}-related events.
2905 Use @code{1} to enable, @code{0} to disable.
2909 @section Debugging Forks
2911 @cindex fork, debugging programs which call
2912 @cindex multiple processes
2913 @cindex processes, multiple
2914 On most systems, @value{GDBN} has no special support for debugging
2915 programs which create additional processes using the @code{fork}
2916 function. When a program forks, @value{GDBN} will continue to debug the
2917 parent process and the child process will run unimpeded. If you have
2918 set a breakpoint in any code which the child then executes, the child
2919 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2920 will cause it to terminate.
2922 However, if you want to debug the child process there is a workaround
2923 which isn't too painful. Put a call to @code{sleep} in the code which
2924 the child process executes after the fork. It may be useful to sleep
2925 only if a certain environment variable is set, or a certain file exists,
2926 so that the delay need not occur when you don't want to run @value{GDBN}
2927 on the child. While the child is sleeping, use the @code{ps} program to
2928 get its process ID. Then tell @value{GDBN} (a new invocation of
2929 @value{GDBN} if you are also debugging the parent process) to attach to
2930 the child process (@pxref{Attach}). From that point on you can debug
2931 the child process just like any other process which you attached to.
2933 On some systems, @value{GDBN} provides support for debugging programs that
2934 create additional processes using the @code{fork} or @code{vfork} functions.
2935 Currently, the only platforms with this feature are HP-UX (11.x and later
2936 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2938 By default, when a program forks, @value{GDBN} will continue to debug
2939 the parent process and the child process will run unimpeded.
2941 If you want to follow the child process instead of the parent process,
2942 use the command @w{@code{set follow-fork-mode}}.
2945 @kindex set follow-fork-mode
2946 @item set follow-fork-mode @var{mode}
2947 Set the debugger response to a program call of @code{fork} or
2948 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2949 process. The @var{mode} argument can be:
2953 The original process is debugged after a fork. The child process runs
2954 unimpeded. This is the default.
2957 The new process is debugged after a fork. The parent process runs
2962 @kindex show follow-fork-mode
2963 @item show follow-fork-mode
2964 Display the current debugger response to a @code{fork} or @code{vfork} call.
2967 @cindex debugging multiple processes
2968 On Linux, if you want to debug both the parent and child processes, use the
2969 command @w{@code{set detach-on-fork}}.
2972 @kindex set detach-on-fork
2973 @item set detach-on-fork @var{mode}
2974 Tells gdb whether to detach one of the processes after a fork, or
2975 retain debugger control over them both.
2979 The child process (or parent process, depending on the value of
2980 @code{follow-fork-mode}) will be detached and allowed to run
2981 independently. This is the default.
2984 Both processes will be held under the control of @value{GDBN}.
2985 One process (child or parent, depending on the value of
2986 @code{follow-fork-mode}) is debugged as usual, while the other
2991 @kindex show detach-on-fork
2992 @item show detach-on-fork
2993 Show whether detach-on-fork mode is on/off.
2996 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
2997 will retain control of all forked processes (including nested forks).
2998 You can list the forked processes under the control of @value{GDBN} by
2999 using the @w{@code{info inferiors}} command, and switch from one fork
3000 to another by using the @code{inferior} command (@pxref{Inferiors and
3001 Programs, ,Debugging Multiple Inferiors and Programs}).
3003 To quit debugging one of the forked processes, you can either detach
3004 from it by using the @w{@code{detach inferiors}} command (allowing it
3005 to run independently), or kill it using the @w{@code{kill inferiors}}
3006 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3009 If you ask to debug a child process and a @code{vfork} is followed by an
3010 @code{exec}, @value{GDBN} executes the new target up to the first
3011 breakpoint in the new target. If you have a breakpoint set on
3012 @code{main} in your original program, the breakpoint will also be set on
3013 the child process's @code{main}.
3015 On some systems, when a child process is spawned by @code{vfork}, you
3016 cannot debug the child or parent until an @code{exec} call completes.
3018 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3019 call executes, the new target restarts. To restart the parent
3020 process, use the @code{file} command with the parent executable name
3021 as its argument. By default, after an @code{exec} call executes,
3022 @value{GDBN} discards the symbols of the previous executable image.
3023 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3027 @kindex set follow-exec-mode
3028 @item set follow-exec-mode @var{mode}
3030 Set debugger response to a program call of @code{exec}. An
3031 @code{exec} call replaces the program image of a process.
3033 @code{follow-exec-mode} can be:
3037 @value{GDBN} creates a new inferior and rebinds the process to this
3038 new inferior. The program the process was running before the
3039 @code{exec} call can be restarted afterwards by restarting the
3045 (@value{GDBP}) info inferiors
3047 Id Description Executable
3050 process 12020 is executing new program: prog2
3051 Program exited normally.
3052 (@value{GDBP}) info inferiors
3053 Id Description Executable
3059 @value{GDBN} keeps the process bound to the same inferior. The new
3060 executable image replaces the previous executable loaded in the
3061 inferior. Restarting the inferior after the @code{exec} call, with
3062 e.g., the @code{run} command, restarts the executable the process was
3063 running after the @code{exec} call. This is the default mode.
3068 (@value{GDBP}) info inferiors
3069 Id Description Executable
3072 process 12020 is executing new program: prog2
3073 Program exited normally.
3074 (@value{GDBP}) info inferiors
3075 Id Description Executable
3082 You can use the @code{catch} command to make @value{GDBN} stop whenever
3083 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3084 Catchpoints, ,Setting Catchpoints}.
3086 @node Checkpoint/Restart
3087 @section Setting a @emph{Bookmark} to Return to Later
3092 @cindex snapshot of a process
3093 @cindex rewind program state
3095 On certain operating systems@footnote{Currently, only
3096 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3097 program's state, called a @dfn{checkpoint}, and come back to it
3100 Returning to a checkpoint effectively undoes everything that has
3101 happened in the program since the @code{checkpoint} was saved. This
3102 includes changes in memory, registers, and even (within some limits)
3103 system state. Effectively, it is like going back in time to the
3104 moment when the checkpoint was saved.
3106 Thus, if you're stepping thru a program and you think you're
3107 getting close to the point where things go wrong, you can save
3108 a checkpoint. Then, if you accidentally go too far and miss
3109 the critical statement, instead of having to restart your program
3110 from the beginning, you can just go back to the checkpoint and
3111 start again from there.
3113 This can be especially useful if it takes a lot of time or
3114 steps to reach the point where you think the bug occurs.
3116 To use the @code{checkpoint}/@code{restart} method of debugging:
3121 Save a snapshot of the debugged program's current execution state.
3122 The @code{checkpoint} command takes no arguments, but each checkpoint
3123 is assigned a small integer id, similar to a breakpoint id.
3125 @kindex info checkpoints
3126 @item info checkpoints
3127 List the checkpoints that have been saved in the current debugging
3128 session. For each checkpoint, the following information will be
3135 @item Source line, or label
3138 @kindex restart @var{checkpoint-id}
3139 @item restart @var{checkpoint-id}
3140 Restore the program state that was saved as checkpoint number
3141 @var{checkpoint-id}. All program variables, registers, stack frames
3142 etc.@: will be returned to the values that they had when the checkpoint
3143 was saved. In essence, gdb will ``wind back the clock'' to the point
3144 in time when the checkpoint was saved.
3146 Note that breakpoints, @value{GDBN} variables, command history etc.
3147 are not affected by restoring a checkpoint. In general, a checkpoint
3148 only restores things that reside in the program being debugged, not in
3151 @kindex delete checkpoint @var{checkpoint-id}
3152 @item delete checkpoint @var{checkpoint-id}
3153 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3157 Returning to a previously saved checkpoint will restore the user state
3158 of the program being debugged, plus a significant subset of the system
3159 (OS) state, including file pointers. It won't ``un-write'' data from
3160 a file, but it will rewind the file pointer to the previous location,
3161 so that the previously written data can be overwritten. For files
3162 opened in read mode, the pointer will also be restored so that the
3163 previously read data can be read again.
3165 Of course, characters that have been sent to a printer (or other
3166 external device) cannot be ``snatched back'', and characters received
3167 from eg.@: a serial device can be removed from internal program buffers,
3168 but they cannot be ``pushed back'' into the serial pipeline, ready to
3169 be received again. Similarly, the actual contents of files that have
3170 been changed cannot be restored (at this time).
3172 However, within those constraints, you actually can ``rewind'' your
3173 program to a previously saved point in time, and begin debugging it
3174 again --- and you can change the course of events so as to debug a
3175 different execution path this time.
3177 @cindex checkpoints and process id
3178 Finally, there is one bit of internal program state that will be
3179 different when you return to a checkpoint --- the program's process
3180 id. Each checkpoint will have a unique process id (or @var{pid}),
3181 and each will be different from the program's original @var{pid}.
3182 If your program has saved a local copy of its process id, this could
3183 potentially pose a problem.
3185 @subsection A Non-obvious Benefit of Using Checkpoints
3187 On some systems such as @sc{gnu}/Linux, address space randomization
3188 is performed on new processes for security reasons. This makes it
3189 difficult or impossible to set a breakpoint, or watchpoint, on an
3190 absolute address if you have to restart the program, since the
3191 absolute location of a symbol will change from one execution to the
3194 A checkpoint, however, is an @emph{identical} copy of a process.
3195 Therefore if you create a checkpoint at (eg.@:) the start of main,
3196 and simply return to that checkpoint instead of restarting the
3197 process, you can avoid the effects of address randomization and
3198 your symbols will all stay in the same place.
3201 @chapter Stopping and Continuing
3203 The principal purposes of using a debugger are so that you can stop your
3204 program before it terminates; or so that, if your program runs into
3205 trouble, you can investigate and find out why.
3207 Inside @value{GDBN}, your program may stop for any of several reasons,
3208 such as a signal, a breakpoint, or reaching a new line after a
3209 @value{GDBN} command such as @code{step}. You may then examine and
3210 change variables, set new breakpoints or remove old ones, and then
3211 continue execution. Usually, the messages shown by @value{GDBN} provide
3212 ample explanation of the status of your program---but you can also
3213 explicitly request this information at any time.
3216 @kindex info program
3218 Display information about the status of your program: whether it is
3219 running or not, what process it is, and why it stopped.
3223 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3224 * Continuing and Stepping:: Resuming execution
3225 * Skipping Over Functions and Files::
3226 Skipping over functions and files
3228 * Thread Stops:: Stopping and starting multi-thread programs
3232 @section Breakpoints, Watchpoints, and Catchpoints
3235 A @dfn{breakpoint} makes your program stop whenever a certain point in
3236 the program is reached. For each breakpoint, you can add conditions to
3237 control in finer detail whether your program stops. You can set
3238 breakpoints with the @code{break} command and its variants (@pxref{Set
3239 Breaks, ,Setting Breakpoints}), to specify the place where your program
3240 should stop by line number, function name or exact address in the
3243 On some systems, you can set breakpoints in shared libraries before
3244 the executable is run. There is a minor limitation on HP-UX systems:
3245 you must wait until the executable is run in order to set breakpoints
3246 in shared library routines that are not called directly by the program
3247 (for example, routines that are arguments in a @code{pthread_create}
3251 @cindex data breakpoints
3252 @cindex memory tracing
3253 @cindex breakpoint on memory address
3254 @cindex breakpoint on variable modification
3255 A @dfn{watchpoint} is a special breakpoint that stops your program
3256 when the value of an expression changes. The expression may be a value
3257 of a variable, or it could involve values of one or more variables
3258 combined by operators, such as @samp{a + b}. This is sometimes called
3259 @dfn{data breakpoints}. You must use a different command to set
3260 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3261 from that, you can manage a watchpoint like any other breakpoint: you
3262 enable, disable, and delete both breakpoints and watchpoints using the
3265 You can arrange to have values from your program displayed automatically
3266 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3270 @cindex breakpoint on events
3271 A @dfn{catchpoint} is another special breakpoint that stops your program
3272 when a certain kind of event occurs, such as the throwing of a C@t{++}
3273 exception or the loading of a library. As with watchpoints, you use a
3274 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3275 Catchpoints}), but aside from that, you can manage a catchpoint like any
3276 other breakpoint. (To stop when your program receives a signal, use the
3277 @code{handle} command; see @ref{Signals, ,Signals}.)
3279 @cindex breakpoint numbers
3280 @cindex numbers for breakpoints
3281 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3282 catchpoint when you create it; these numbers are successive integers
3283 starting with one. In many of the commands for controlling various
3284 features of breakpoints you use the breakpoint number to say which
3285 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3286 @dfn{disabled}; if disabled, it has no effect on your program until you
3289 @cindex breakpoint ranges
3290 @cindex ranges of breakpoints
3291 Some @value{GDBN} commands accept a range of breakpoints on which to
3292 operate. A breakpoint range is either a single breakpoint number, like
3293 @samp{5}, or two such numbers, in increasing order, separated by a
3294 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3295 all breakpoints in that range are operated on.
3298 * Set Breaks:: Setting breakpoints
3299 * Set Watchpoints:: Setting watchpoints
3300 * Set Catchpoints:: Setting catchpoints
3301 * Delete Breaks:: Deleting breakpoints
3302 * Disabling:: Disabling breakpoints
3303 * Conditions:: Break conditions
3304 * Break Commands:: Breakpoint command lists
3305 * Save Breakpoints:: How to save breakpoints in a file
3306 * Error in Breakpoints:: ``Cannot insert breakpoints''
3307 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3311 @subsection Setting Breakpoints
3313 @c FIXME LMB what does GDB do if no code on line of breakpt?
3314 @c consider in particular declaration with/without initialization.
3316 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3319 @kindex b @r{(@code{break})}
3320 @vindex $bpnum@r{, convenience variable}
3321 @cindex latest breakpoint
3322 Breakpoints are set with the @code{break} command (abbreviated
3323 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3324 number of the breakpoint you've set most recently; see @ref{Convenience
3325 Vars,, Convenience Variables}, for a discussion of what you can do with
3326 convenience variables.
3329 @item break @var{location}
3330 Set a breakpoint at the given @var{location}, which can specify a
3331 function name, a line number, or an address of an instruction.
3332 (@xref{Specify Location}, for a list of all the possible ways to
3333 specify a @var{location}.) The breakpoint will stop your program just
3334 before it executes any of the code in the specified @var{location}.
3336 When using source languages that permit overloading of symbols, such as
3337 C@t{++}, a function name may refer to more than one possible place to break.
3338 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3341 It is also possible to insert a breakpoint that will stop the program
3342 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3343 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3346 When called without any arguments, @code{break} sets a breakpoint at
3347 the next instruction to be executed in the selected stack frame
3348 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3349 innermost, this makes your program stop as soon as control
3350 returns to that frame. This is similar to the effect of a
3351 @code{finish} command in the frame inside the selected frame---except
3352 that @code{finish} does not leave an active breakpoint. If you use
3353 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3354 the next time it reaches the current location; this may be useful
3357 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3358 least one instruction has been executed. If it did not do this, you
3359 would be unable to proceed past a breakpoint without first disabling the
3360 breakpoint. This rule applies whether or not the breakpoint already
3361 existed when your program stopped.
3363 @item break @dots{} if @var{cond}
3364 Set a breakpoint with condition @var{cond}; evaluate the expression
3365 @var{cond} each time the breakpoint is reached, and stop only if the
3366 value is nonzero---that is, if @var{cond} evaluates as true.
3367 @samp{@dots{}} stands for one of the possible arguments described
3368 above (or no argument) specifying where to break. @xref{Conditions,
3369 ,Break Conditions}, for more information on breakpoint conditions.
3372 @item tbreak @var{args}
3373 Set a breakpoint enabled only for one stop. @var{args} are the
3374 same as for the @code{break} command, and the breakpoint is set in the same
3375 way, but the breakpoint is automatically deleted after the first time your
3376 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3379 @cindex hardware breakpoints
3380 @item hbreak @var{args}
3381 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3382 @code{break} command and the breakpoint is set in the same way, but the
3383 breakpoint requires hardware support and some target hardware may not
3384 have this support. The main purpose of this is EPROM/ROM code
3385 debugging, so you can set a breakpoint at an instruction without
3386 changing the instruction. This can be used with the new trap-generation
3387 provided by SPARClite DSU and most x86-based targets. These targets
3388 will generate traps when a program accesses some data or instruction
3389 address that is assigned to the debug registers. However the hardware
3390 breakpoint registers can take a limited number of breakpoints. For
3391 example, on the DSU, only two data breakpoints can be set at a time, and
3392 @value{GDBN} will reject this command if more than two are used. Delete
3393 or disable unused hardware breakpoints before setting new ones
3394 (@pxref{Disabling, ,Disabling Breakpoints}).
3395 @xref{Conditions, ,Break Conditions}.
3396 For remote targets, you can restrict the number of hardware
3397 breakpoints @value{GDBN} will use, see @ref{set remote
3398 hardware-breakpoint-limit}.
3401 @item thbreak @var{args}
3402 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3403 are the same as for the @code{hbreak} command and the breakpoint is set in
3404 the same way. However, like the @code{tbreak} command,
3405 the breakpoint is automatically deleted after the
3406 first time your program stops there. Also, like the @code{hbreak}
3407 command, the breakpoint requires hardware support and some target hardware
3408 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3409 See also @ref{Conditions, ,Break Conditions}.
3412 @cindex regular expression
3413 @cindex breakpoints at functions matching a regexp
3414 @cindex set breakpoints in many functions
3415 @item rbreak @var{regex}
3416 Set breakpoints on all functions matching the regular expression
3417 @var{regex}. This command sets an unconditional breakpoint on all
3418 matches, printing a list of all breakpoints it set. Once these
3419 breakpoints are set, they are treated just like the breakpoints set with
3420 the @code{break} command. You can delete them, disable them, or make
3421 them conditional the same way as any other breakpoint.
3423 The syntax of the regular expression is the standard one used with tools
3424 like @file{grep}. Note that this is different from the syntax used by
3425 shells, so for instance @code{foo*} matches all functions that include
3426 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3427 @code{.*} leading and trailing the regular expression you supply, so to
3428 match only functions that begin with @code{foo}, use @code{^foo}.
3430 @cindex non-member C@t{++} functions, set breakpoint in
3431 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3432 breakpoints on overloaded functions that are not members of any special
3435 @cindex set breakpoints on all functions
3436 The @code{rbreak} command can be used to set breakpoints in
3437 @strong{all} the functions in a program, like this:
3440 (@value{GDBP}) rbreak .
3443 @item rbreak @var{file}:@var{regex}
3444 If @code{rbreak} is called with a filename qualification, it limits
3445 the search for functions matching the given regular expression to the
3446 specified @var{file}. This can be used, for example, to set breakpoints on
3447 every function in a given file:
3450 (@value{GDBP}) rbreak file.c:.
3453 The colon separating the filename qualifier from the regex may
3454 optionally be surrounded by spaces.
3456 @kindex info breakpoints
3457 @cindex @code{$_} and @code{info breakpoints}
3458 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3459 @itemx info break @r{[}@var{n}@dots{}@r{]}
3460 Print a table of all breakpoints, watchpoints, and catchpoints set and
3461 not deleted. Optional argument @var{n} means print information only
3462 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3463 For each breakpoint, following columns are printed:
3466 @item Breakpoint Numbers
3468 Breakpoint, watchpoint, or catchpoint.
3470 Whether the breakpoint is marked to be disabled or deleted when hit.
3471 @item Enabled or Disabled
3472 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3473 that are not enabled.
3475 Where the breakpoint is in your program, as a memory address. For a
3476 pending breakpoint whose address is not yet known, this field will
3477 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3478 library that has the symbol or line referred by breakpoint is loaded.
3479 See below for details. A breakpoint with several locations will
3480 have @samp{<MULTIPLE>} in this field---see below for details.
3482 Where the breakpoint is in the source for your program, as a file and
3483 line number. For a pending breakpoint, the original string passed to
3484 the breakpoint command will be listed as it cannot be resolved until
3485 the appropriate shared library is loaded in the future.
3489 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3490 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3491 @value{GDBN} on the host's side. If it is ``target'', then the condition
3492 is evaluated by the target. The @code{info break} command shows
3493 the condition on the line following the affected breakpoint, together with
3494 its condition evaluation mode in between parentheses.
3496 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3497 allowed to have a condition specified for it. The condition is not parsed for
3498 validity until a shared library is loaded that allows the pending
3499 breakpoint to resolve to a valid location.
3502 @code{info break} with a breakpoint
3503 number @var{n} as argument lists only that breakpoint. The
3504 convenience variable @code{$_} and the default examining-address for
3505 the @code{x} command are set to the address of the last breakpoint
3506 listed (@pxref{Memory, ,Examining Memory}).
3509 @code{info break} displays a count of the number of times the breakpoint
3510 has been hit. This is especially useful in conjunction with the
3511 @code{ignore} command. You can ignore a large number of breakpoint
3512 hits, look at the breakpoint info to see how many times the breakpoint
3513 was hit, and then run again, ignoring one less than that number. This
3514 will get you quickly to the last hit of that breakpoint.
3517 For a breakpoints with an enable count (xref) greater than 1,
3518 @code{info break} also displays that count.
3522 @value{GDBN} allows you to set any number of breakpoints at the same place in
3523 your program. There is nothing silly or meaningless about this. When
3524 the breakpoints are conditional, this is even useful
3525 (@pxref{Conditions, ,Break Conditions}).
3527 @cindex multiple locations, breakpoints
3528 @cindex breakpoints, multiple locations
3529 It is possible that a breakpoint corresponds to several locations
3530 in your program. Examples of this situation are:
3534 Multiple functions in the program may have the same name.
3537 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3538 instances of the function body, used in different cases.
3541 For a C@t{++} template function, a given line in the function can
3542 correspond to any number of instantiations.
3545 For an inlined function, a given source line can correspond to
3546 several places where that function is inlined.
3549 In all those cases, @value{GDBN} will insert a breakpoint at all
3550 the relevant locations.
3552 A breakpoint with multiple locations is displayed in the breakpoint
3553 table using several rows---one header row, followed by one row for
3554 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3555 address column. The rows for individual locations contain the actual
3556 addresses for locations, and show the functions to which those
3557 locations belong. The number column for a location is of the form
3558 @var{breakpoint-number}.@var{location-number}.
3563 Num Type Disp Enb Address What
3564 1 breakpoint keep y <MULTIPLE>
3566 breakpoint already hit 1 time
3567 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3568 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3571 Each location can be individually enabled or disabled by passing
3572 @var{breakpoint-number}.@var{location-number} as argument to the
3573 @code{enable} and @code{disable} commands. Note that you cannot
3574 delete the individual locations from the list, you can only delete the
3575 entire list of locations that belong to their parent breakpoint (with
3576 the @kbd{delete @var{num}} command, where @var{num} is the number of
3577 the parent breakpoint, 1 in the above example). Disabling or enabling
3578 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3579 that belong to that breakpoint.
3581 @cindex pending breakpoints
3582 It's quite common to have a breakpoint inside a shared library.
3583 Shared libraries can be loaded and unloaded explicitly,
3584 and possibly repeatedly, as the program is executed. To support
3585 this use case, @value{GDBN} updates breakpoint locations whenever
3586 any shared library is loaded or unloaded. Typically, you would
3587 set a breakpoint in a shared library at the beginning of your
3588 debugging session, when the library is not loaded, and when the
3589 symbols from the library are not available. When you try to set
3590 breakpoint, @value{GDBN} will ask you if you want to set
3591 a so called @dfn{pending breakpoint}---breakpoint whose address
3592 is not yet resolved.
3594 After the program is run, whenever a new shared library is loaded,
3595 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3596 shared library contains the symbol or line referred to by some
3597 pending breakpoint, that breakpoint is resolved and becomes an
3598 ordinary breakpoint. When a library is unloaded, all breakpoints
3599 that refer to its symbols or source lines become pending again.
3601 This logic works for breakpoints with multiple locations, too. For
3602 example, if you have a breakpoint in a C@t{++} template function, and
3603 a newly loaded shared library has an instantiation of that template,
3604 a new location is added to the list of locations for the breakpoint.
3606 Except for having unresolved address, pending breakpoints do not
3607 differ from regular breakpoints. You can set conditions or commands,
3608 enable and disable them and perform other breakpoint operations.
3610 @value{GDBN} provides some additional commands for controlling what
3611 happens when the @samp{break} command cannot resolve breakpoint
3612 address specification to an address:
3614 @kindex set breakpoint pending
3615 @kindex show breakpoint pending
3617 @item set breakpoint pending auto
3618 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3619 location, it queries you whether a pending breakpoint should be created.
3621 @item set breakpoint pending on
3622 This indicates that an unrecognized breakpoint location should automatically
3623 result in a pending breakpoint being created.
3625 @item set breakpoint pending off
3626 This indicates that pending breakpoints are not to be created. Any
3627 unrecognized breakpoint location results in an error. This setting does
3628 not affect any pending breakpoints previously created.
3630 @item show breakpoint pending
3631 Show the current behavior setting for creating pending breakpoints.
3634 The settings above only affect the @code{break} command and its
3635 variants. Once breakpoint is set, it will be automatically updated
3636 as shared libraries are loaded and unloaded.
3638 @cindex automatic hardware breakpoints
3639 For some targets, @value{GDBN} can automatically decide if hardware or
3640 software breakpoints should be used, depending on whether the
3641 breakpoint address is read-only or read-write. This applies to
3642 breakpoints set with the @code{break} command as well as to internal
3643 breakpoints set by commands like @code{next} and @code{finish}. For
3644 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3647 You can control this automatic behaviour with the following commands::
3649 @kindex set breakpoint auto-hw
3650 @kindex show breakpoint auto-hw
3652 @item set breakpoint auto-hw on
3653 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3654 will try to use the target memory map to decide if software or hardware
3655 breakpoint must be used.
3657 @item set breakpoint auto-hw off
3658 This indicates @value{GDBN} should not automatically select breakpoint
3659 type. If the target provides a memory map, @value{GDBN} will warn when
3660 trying to set software breakpoint at a read-only address.
3663 @value{GDBN} normally implements breakpoints by replacing the program code
3664 at the breakpoint address with a special instruction, which, when
3665 executed, given control to the debugger. By default, the program
3666 code is so modified only when the program is resumed. As soon as
3667 the program stops, @value{GDBN} restores the original instructions. This
3668 behaviour guards against leaving breakpoints inserted in the
3669 target should gdb abrubptly disconnect. However, with slow remote
3670 targets, inserting and removing breakpoint can reduce the performance.
3671 This behavior can be controlled with the following commands::
3673 @kindex set breakpoint always-inserted
3674 @kindex show breakpoint always-inserted
3676 @item set breakpoint always-inserted off
3677 All breakpoints, including newly added by the user, are inserted in
3678 the target only when the target is resumed. All breakpoints are
3679 removed from the target when it stops.
3681 @item set breakpoint always-inserted on
3682 Causes all breakpoints to be inserted in the target at all times. If
3683 the user adds a new breakpoint, or changes an existing breakpoint, the
3684 breakpoints in the target are updated immediately. A breakpoint is
3685 removed from the target only when breakpoint itself is removed.
3687 @cindex non-stop mode, and @code{breakpoint always-inserted}
3688 @item set breakpoint always-inserted auto
3689 This is the default mode. If @value{GDBN} is controlling the inferior
3690 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3691 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3692 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3693 @code{breakpoint always-inserted} mode is off.
3696 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3697 when a breakpoint breaks. If the condition is true, then the process being
3698 debugged stops, otherwise the process is resumed.
3700 If the target supports evaluating conditions on its end, @value{GDBN} may
3701 download the breakpoint, together with its conditions, to it.
3703 This feature can be controlled via the following commands:
3705 @kindex set breakpoint condition-evaluation
3706 @kindex show breakpoint condition-evaluation
3708 @item set breakpoint condition-evaluation host
3709 This option commands @value{GDBN} to evaluate the breakpoint
3710 conditions on the host's side. Unconditional breakpoints are sent to
3711 the target which in turn receives the triggers and reports them back to GDB
3712 for condition evaluation. This is the standard evaluation mode.
3714 @item set breakpoint condition-evaluation target
3715 This option commands @value{GDBN} to download breakpoint conditions
3716 to the target at the moment of their insertion. The target
3717 is responsible for evaluating the conditional expression and reporting
3718 breakpoint stop events back to @value{GDBN} whenever the condition
3719 is true. Due to limitations of target-side evaluation, some conditions
3720 cannot be evaluated there, e.g., conditions that depend on local data
3721 that is only known to the host. Examples include
3722 conditional expressions involving convenience variables, complex types
3723 that cannot be handled by the agent expression parser and expressions
3724 that are too long to be sent over to the target, specially when the
3725 target is a remote system. In these cases, the conditions will be
3726 evaluated by @value{GDBN}.
3728 @item set breakpoint condition-evaluation auto
3729 This is the default mode. If the target supports evaluating breakpoint
3730 conditions on its end, @value{GDBN} will download breakpoint conditions to
3731 the target (limitations mentioned previously apply). If the target does
3732 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3733 to evaluating all these conditions on the host's side.
3737 @cindex negative breakpoint numbers
3738 @cindex internal @value{GDBN} breakpoints
3739 @value{GDBN} itself sometimes sets breakpoints in your program for
3740 special purposes, such as proper handling of @code{longjmp} (in C
3741 programs). These internal breakpoints are assigned negative numbers,
3742 starting with @code{-1}; @samp{info breakpoints} does not display them.
3743 You can see these breakpoints with the @value{GDBN} maintenance command
3744 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3747 @node Set Watchpoints
3748 @subsection Setting Watchpoints
3750 @cindex setting watchpoints
3751 You can use a watchpoint to stop execution whenever the value of an
3752 expression changes, without having to predict a particular place where
3753 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3754 The expression may be as simple as the value of a single variable, or
3755 as complex as many variables combined by operators. Examples include:
3759 A reference to the value of a single variable.
3762 An address cast to an appropriate data type. For example,
3763 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3764 address (assuming an @code{int} occupies 4 bytes).
3767 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3768 expression can use any operators valid in the program's native
3769 language (@pxref{Languages}).
3772 You can set a watchpoint on an expression even if the expression can
3773 not be evaluated yet. For instance, you can set a watchpoint on
3774 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3775 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3776 the expression produces a valid value. If the expression becomes
3777 valid in some other way than changing a variable (e.g.@: if the memory
3778 pointed to by @samp{*global_ptr} becomes readable as the result of a
3779 @code{malloc} call), @value{GDBN} may not stop until the next time
3780 the expression changes.
3782 @cindex software watchpoints
3783 @cindex hardware watchpoints
3784 Depending on your system, watchpoints may be implemented in software or
3785 hardware. @value{GDBN} does software watchpointing by single-stepping your
3786 program and testing the variable's value each time, which is hundreds of
3787 times slower than normal execution. (But this may still be worth it, to
3788 catch errors where you have no clue what part of your program is the
3791 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3792 x86-based targets, @value{GDBN} includes support for hardware
3793 watchpoints, which do not slow down the running of your program.
3797 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3798 Set a watchpoint for an expression. @value{GDBN} will break when the
3799 expression @var{expr} is written into by the program and its value
3800 changes. The simplest (and the most popular) use of this command is
3801 to watch the value of a single variable:
3804 (@value{GDBP}) watch foo
3807 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3808 argument, @value{GDBN} breaks only when the thread identified by
3809 @var{threadnum} changes the value of @var{expr}. If any other threads
3810 change the value of @var{expr}, @value{GDBN} will not break. Note
3811 that watchpoints restricted to a single thread in this way only work
3812 with Hardware Watchpoints.
3814 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3815 (see below). The @code{-location} argument tells @value{GDBN} to
3816 instead watch the memory referred to by @var{expr}. In this case,
3817 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3818 and watch the memory at that address. The type of the result is used
3819 to determine the size of the watched memory. If the expression's
3820 result does not have an address, then @value{GDBN} will print an
3823 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3824 of masked watchpoints, if the current architecture supports this
3825 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3826 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3827 to an address to watch. The mask specifies that some bits of an address
3828 (the bits which are reset in the mask) should be ignored when matching
3829 the address accessed by the inferior against the watchpoint address.
3830 Thus, a masked watchpoint watches many addresses simultaneously---those
3831 addresses whose unmasked bits are identical to the unmasked bits in the
3832 watchpoint address. The @code{mask} argument implies @code{-location}.
3836 (@value{GDBP}) watch foo mask 0xffff00ff
3837 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
3841 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3842 Set a watchpoint that will break when the value of @var{expr} is read
3846 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3847 Set a watchpoint that will break when @var{expr} is either read from
3848 or written into by the program.
3850 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
3851 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
3852 This command prints a list of watchpoints, using the same format as
3853 @code{info break} (@pxref{Set Breaks}).
3856 If you watch for a change in a numerically entered address you need to
3857 dereference it, as the address itself is just a constant number which will
3858 never change. @value{GDBN} refuses to create a watchpoint that watches
3859 a never-changing value:
3862 (@value{GDBP}) watch 0x600850
3863 Cannot watch constant value 0x600850.
3864 (@value{GDBP}) watch *(int *) 0x600850
3865 Watchpoint 1: *(int *) 6293584
3868 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3869 watchpoints execute very quickly, and the debugger reports a change in
3870 value at the exact instruction where the change occurs. If @value{GDBN}
3871 cannot set a hardware watchpoint, it sets a software watchpoint, which
3872 executes more slowly and reports the change in value at the next
3873 @emph{statement}, not the instruction, after the change occurs.
3875 @cindex use only software watchpoints
3876 You can force @value{GDBN} to use only software watchpoints with the
3877 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3878 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3879 the underlying system supports them. (Note that hardware-assisted
3880 watchpoints that were set @emph{before} setting
3881 @code{can-use-hw-watchpoints} to zero will still use the hardware
3882 mechanism of watching expression values.)
3885 @item set can-use-hw-watchpoints
3886 @kindex set can-use-hw-watchpoints
3887 Set whether or not to use hardware watchpoints.
3889 @item show can-use-hw-watchpoints
3890 @kindex show can-use-hw-watchpoints
3891 Show the current mode of using hardware watchpoints.
3894 For remote targets, you can restrict the number of hardware
3895 watchpoints @value{GDBN} will use, see @ref{set remote
3896 hardware-breakpoint-limit}.
3898 When you issue the @code{watch} command, @value{GDBN} reports
3901 Hardware watchpoint @var{num}: @var{expr}
3905 if it was able to set a hardware watchpoint.
3907 Currently, the @code{awatch} and @code{rwatch} commands can only set
3908 hardware watchpoints, because accesses to data that don't change the
3909 value of the watched expression cannot be detected without examining
3910 every instruction as it is being executed, and @value{GDBN} does not do
3911 that currently. If @value{GDBN} finds that it is unable to set a
3912 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3913 will print a message like this:
3916 Expression cannot be implemented with read/access watchpoint.
3919 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3920 data type of the watched expression is wider than what a hardware
3921 watchpoint on the target machine can handle. For example, some systems
3922 can only watch regions that are up to 4 bytes wide; on such systems you
3923 cannot set hardware watchpoints for an expression that yields a
3924 double-precision floating-point number (which is typically 8 bytes
3925 wide). As a work-around, it might be possible to break the large region
3926 into a series of smaller ones and watch them with separate watchpoints.
3928 If you set too many hardware watchpoints, @value{GDBN} might be unable
3929 to insert all of them when you resume the execution of your program.
3930 Since the precise number of active watchpoints is unknown until such
3931 time as the program is about to be resumed, @value{GDBN} might not be
3932 able to warn you about this when you set the watchpoints, and the
3933 warning will be printed only when the program is resumed:
3936 Hardware watchpoint @var{num}: Could not insert watchpoint
3940 If this happens, delete or disable some of the watchpoints.
3942 Watching complex expressions that reference many variables can also
3943 exhaust the resources available for hardware-assisted watchpoints.
3944 That's because @value{GDBN} needs to watch every variable in the
3945 expression with separately allocated resources.
3947 If you call a function interactively using @code{print} or @code{call},
3948 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3949 kind of breakpoint or the call completes.
3951 @value{GDBN} automatically deletes watchpoints that watch local
3952 (automatic) variables, or expressions that involve such variables, when
3953 they go out of scope, that is, when the execution leaves the block in
3954 which these variables were defined. In particular, when the program
3955 being debugged terminates, @emph{all} local variables go out of scope,
3956 and so only watchpoints that watch global variables remain set. If you
3957 rerun the program, you will need to set all such watchpoints again. One
3958 way of doing that would be to set a code breakpoint at the entry to the
3959 @code{main} function and when it breaks, set all the watchpoints.
3961 @cindex watchpoints and threads
3962 @cindex threads and watchpoints
3963 In multi-threaded programs, watchpoints will detect changes to the
3964 watched expression from every thread.
3967 @emph{Warning:} In multi-threaded programs, software watchpoints
3968 have only limited usefulness. If @value{GDBN} creates a software
3969 watchpoint, it can only watch the value of an expression @emph{in a
3970 single thread}. If you are confident that the expression can only
3971 change due to the current thread's activity (and if you are also
3972 confident that no other thread can become current), then you can use
3973 software watchpoints as usual. However, @value{GDBN} may not notice
3974 when a non-current thread's activity changes the expression. (Hardware
3975 watchpoints, in contrast, watch an expression in all threads.)
3978 @xref{set remote hardware-watchpoint-limit}.
3980 @node Set Catchpoints
3981 @subsection Setting Catchpoints
3982 @cindex catchpoints, setting
3983 @cindex exception handlers
3984 @cindex event handling
3986 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3987 kinds of program events, such as C@t{++} exceptions or the loading of a
3988 shared library. Use the @code{catch} command to set a catchpoint.
3992 @item catch @var{event}
3993 Stop when @var{event} occurs. @var{event} can be any of the following:
3996 @cindex stop on C@t{++} exceptions
3997 The throwing of a C@t{++} exception.
4000 The catching of a C@t{++} exception.
4003 @cindex Ada exception catching
4004 @cindex catch Ada exceptions
4005 An Ada exception being raised. If an exception name is specified
4006 at the end of the command (eg @code{catch exception Program_Error}),
4007 the debugger will stop only when this specific exception is raised.
4008 Otherwise, the debugger stops execution when any Ada exception is raised.
4010 When inserting an exception catchpoint on a user-defined exception whose
4011 name is identical to one of the exceptions defined by the language, the
4012 fully qualified name must be used as the exception name. Otherwise,
4013 @value{GDBN} will assume that it should stop on the pre-defined exception
4014 rather than the user-defined one. For instance, assuming an exception
4015 called @code{Constraint_Error} is defined in package @code{Pck}, then
4016 the command to use to catch such exceptions is @kbd{catch exception
4017 Pck.Constraint_Error}.
4019 @item exception unhandled
4020 An exception that was raised but is not handled by the program.
4023 A failed Ada assertion.
4026 @cindex break on fork/exec
4027 A call to @code{exec}. This is currently only available for HP-UX
4031 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4032 @cindex break on a system call.
4033 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4034 syscall is a mechanism for application programs to request a service
4035 from the operating system (OS) or one of the OS system services.
4036 @value{GDBN} can catch some or all of the syscalls issued by the
4037 debuggee, and show the related information for each syscall. If no
4038 argument is specified, calls to and returns from all system calls
4041 @var{name} can be any system call name that is valid for the
4042 underlying OS. Just what syscalls are valid depends on the OS. On
4043 GNU and Unix systems, you can find the full list of valid syscall
4044 names on @file{/usr/include/asm/unistd.h}.
4046 @c For MS-Windows, the syscall names and the corresponding numbers
4047 @c can be found, e.g., on this URL:
4048 @c http://www.metasploit.com/users/opcode/syscalls.html
4049 @c but we don't support Windows syscalls yet.
4051 Normally, @value{GDBN} knows in advance which syscalls are valid for
4052 each OS, so you can use the @value{GDBN} command-line completion
4053 facilities (@pxref{Completion,, command completion}) to list the
4056 You may also specify the system call numerically. A syscall's
4057 number is the value passed to the OS's syscall dispatcher to
4058 identify the requested service. When you specify the syscall by its
4059 name, @value{GDBN} uses its database of syscalls to convert the name
4060 into the corresponding numeric code, but using the number directly
4061 may be useful if @value{GDBN}'s database does not have the complete
4062 list of syscalls on your system (e.g., because @value{GDBN} lags
4063 behind the OS upgrades).
4065 The example below illustrates how this command works if you don't provide
4069 (@value{GDBP}) catch syscall
4070 Catchpoint 1 (syscall)
4072 Starting program: /tmp/catch-syscall
4074 Catchpoint 1 (call to syscall 'close'), \
4075 0xffffe424 in __kernel_vsyscall ()
4079 Catchpoint 1 (returned from syscall 'close'), \
4080 0xffffe424 in __kernel_vsyscall ()
4084 Here is an example of catching a system call by name:
4087 (@value{GDBP}) catch syscall chroot
4088 Catchpoint 1 (syscall 'chroot' [61])
4090 Starting program: /tmp/catch-syscall
4092 Catchpoint 1 (call to syscall 'chroot'), \
4093 0xffffe424 in __kernel_vsyscall ()
4097 Catchpoint 1 (returned from syscall 'chroot'), \
4098 0xffffe424 in __kernel_vsyscall ()
4102 An example of specifying a system call numerically. In the case
4103 below, the syscall number has a corresponding entry in the XML
4104 file, so @value{GDBN} finds its name and prints it:
4107 (@value{GDBP}) catch syscall 252
4108 Catchpoint 1 (syscall(s) 'exit_group')
4110 Starting program: /tmp/catch-syscall
4112 Catchpoint 1 (call to syscall 'exit_group'), \
4113 0xffffe424 in __kernel_vsyscall ()
4117 Program exited normally.
4121 However, there can be situations when there is no corresponding name
4122 in XML file for that syscall number. In this case, @value{GDBN} prints
4123 a warning message saying that it was not able to find the syscall name,
4124 but the catchpoint will be set anyway. See the example below:
4127 (@value{GDBP}) catch syscall 764
4128 warning: The number '764' does not represent a known syscall.
4129 Catchpoint 2 (syscall 764)
4133 If you configure @value{GDBN} using the @samp{--without-expat} option,
4134 it will not be able to display syscall names. Also, if your
4135 architecture does not have an XML file describing its system calls,
4136 you will not be able to see the syscall names. It is important to
4137 notice that these two features are used for accessing the syscall
4138 name database. In either case, you will see a warning like this:
4141 (@value{GDBP}) catch syscall
4142 warning: Could not open "syscalls/i386-linux.xml"
4143 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4144 GDB will not be able to display syscall names.
4145 Catchpoint 1 (syscall)
4149 Of course, the file name will change depending on your architecture and system.
4151 Still using the example above, you can also try to catch a syscall by its
4152 number. In this case, you would see something like:
4155 (@value{GDBP}) catch syscall 252
4156 Catchpoint 1 (syscall(s) 252)
4159 Again, in this case @value{GDBN} would not be able to display syscall's names.
4162 A call to @code{fork}. This is currently only available for HP-UX
4166 A call to @code{vfork}. This is currently only available for HP-UX
4169 @item load @r{[}regexp@r{]}
4170 @itemx unload @r{[}regexp@r{]}
4171 The loading or unloading of a shared library. If @var{regexp} is
4172 given, then the catchpoint will stop only if the regular expression
4173 matches one of the affected libraries.
4177 @item tcatch @var{event}
4178 Set a catchpoint that is enabled only for one stop. The catchpoint is
4179 automatically deleted after the first time the event is caught.
4183 Use the @code{info break} command to list the current catchpoints.
4185 There are currently some limitations to C@t{++} exception handling
4186 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4190 If you call a function interactively, @value{GDBN} normally returns
4191 control to you when the function has finished executing. If the call
4192 raises an exception, however, the call may bypass the mechanism that
4193 returns control to you and cause your program either to abort or to
4194 simply continue running until it hits a breakpoint, catches a signal
4195 that @value{GDBN} is listening for, or exits. This is the case even if
4196 you set a catchpoint for the exception; catchpoints on exceptions are
4197 disabled within interactive calls.
4200 You cannot raise an exception interactively.
4203 You cannot install an exception handler interactively.
4206 @cindex raise exceptions
4207 Sometimes @code{catch} is not the best way to debug exception handling:
4208 if you need to know exactly where an exception is raised, it is better to
4209 stop @emph{before} the exception handler is called, since that way you
4210 can see the stack before any unwinding takes place. If you set a
4211 breakpoint in an exception handler instead, it may not be easy to find
4212 out where the exception was raised.
4214 To stop just before an exception handler is called, you need some
4215 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4216 raised by calling a library function named @code{__raise_exception}
4217 which has the following ANSI C interface:
4220 /* @var{addr} is where the exception identifier is stored.
4221 @var{id} is the exception identifier. */
4222 void __raise_exception (void **addr, void *id);
4226 To make the debugger catch all exceptions before any stack
4227 unwinding takes place, set a breakpoint on @code{__raise_exception}
4228 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4230 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4231 that depends on the value of @var{id}, you can stop your program when
4232 a specific exception is raised. You can use multiple conditional
4233 breakpoints to stop your program when any of a number of exceptions are
4238 @subsection Deleting Breakpoints
4240 @cindex clearing breakpoints, watchpoints, catchpoints
4241 @cindex deleting breakpoints, watchpoints, catchpoints
4242 It is often necessary to eliminate a breakpoint, watchpoint, or
4243 catchpoint once it has done its job and you no longer want your program
4244 to stop there. This is called @dfn{deleting} the breakpoint. A
4245 breakpoint that has been deleted no longer exists; it is forgotten.
4247 With the @code{clear} command you can delete breakpoints according to
4248 where they are in your program. With the @code{delete} command you can
4249 delete individual breakpoints, watchpoints, or catchpoints by specifying
4250 their breakpoint numbers.
4252 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4253 automatically ignores breakpoints on the first instruction to be executed
4254 when you continue execution without changing the execution address.
4259 Delete any breakpoints at the next instruction to be executed in the
4260 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4261 the innermost frame is selected, this is a good way to delete a
4262 breakpoint where your program just stopped.
4264 @item clear @var{location}
4265 Delete any breakpoints set at the specified @var{location}.
4266 @xref{Specify Location}, for the various forms of @var{location}; the
4267 most useful ones are listed below:
4270 @item clear @var{function}
4271 @itemx clear @var{filename}:@var{function}
4272 Delete any breakpoints set at entry to the named @var{function}.
4274 @item clear @var{linenum}
4275 @itemx clear @var{filename}:@var{linenum}
4276 Delete any breakpoints set at or within the code of the specified
4277 @var{linenum} of the specified @var{filename}.
4280 @cindex delete breakpoints
4282 @kindex d @r{(@code{delete})}
4283 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4284 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4285 ranges specified as arguments. If no argument is specified, delete all
4286 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4287 confirm off}). You can abbreviate this command as @code{d}.
4291 @subsection Disabling Breakpoints
4293 @cindex enable/disable a breakpoint
4294 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4295 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4296 it had been deleted, but remembers the information on the breakpoint so
4297 that you can @dfn{enable} it again later.
4299 You disable and enable breakpoints, watchpoints, and catchpoints with
4300 the @code{enable} and @code{disable} commands, optionally specifying
4301 one or more breakpoint numbers as arguments. Use @code{info break} to
4302 print a list of all breakpoints, watchpoints, and catchpoints if you
4303 do not know which numbers to use.
4305 Disabling and enabling a breakpoint that has multiple locations
4306 affects all of its locations.
4308 A breakpoint, watchpoint, or catchpoint can have any of several
4309 different states of enablement:
4313 Enabled. The breakpoint stops your program. A breakpoint set
4314 with the @code{break} command starts out in this state.
4316 Disabled. The breakpoint has no effect on your program.
4318 Enabled once. The breakpoint stops your program, but then becomes
4321 Enabled for a count. The breakpoint stops your program for the next
4322 N times, then becomes disabled.
4324 Enabled for deletion. The breakpoint stops your program, but
4325 immediately after it does so it is deleted permanently. A breakpoint
4326 set with the @code{tbreak} command starts out in this state.
4329 You can use the following commands to enable or disable breakpoints,
4330 watchpoints, and catchpoints:
4334 @kindex dis @r{(@code{disable})}
4335 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4336 Disable the specified breakpoints---or all breakpoints, if none are
4337 listed. A disabled breakpoint has no effect but is not forgotten. All
4338 options such as ignore-counts, conditions and commands are remembered in
4339 case the breakpoint is enabled again later. You may abbreviate
4340 @code{disable} as @code{dis}.
4343 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4344 Enable the specified breakpoints (or all defined breakpoints). They
4345 become effective once again in stopping your program.
4347 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4348 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4349 of these breakpoints immediately after stopping your program.
4351 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4352 Enable the specified breakpoints temporarily. @value{GDBN} records
4353 @var{count} with each of the specified breakpoints, and decrements a
4354 breakpoint's count when it is hit. When any count reaches 0,
4355 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4356 count (@pxref{Conditions, ,Break Conditions}), that will be
4357 decremented to 0 before @var{count} is affected.
4359 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4360 Enable the specified breakpoints to work once, then die. @value{GDBN}
4361 deletes any of these breakpoints as soon as your program stops there.
4362 Breakpoints set by the @code{tbreak} command start out in this state.
4365 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4366 @c confusing: tbreak is also initially enabled.
4367 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4368 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4369 subsequently, they become disabled or enabled only when you use one of
4370 the commands above. (The command @code{until} can set and delete a
4371 breakpoint of its own, but it does not change the state of your other
4372 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4376 @subsection Break Conditions
4377 @cindex conditional breakpoints
4378 @cindex breakpoint conditions
4380 @c FIXME what is scope of break condition expr? Context where wanted?
4381 @c in particular for a watchpoint?
4382 The simplest sort of breakpoint breaks every time your program reaches a
4383 specified place. You can also specify a @dfn{condition} for a
4384 breakpoint. A condition is just a Boolean expression in your
4385 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4386 a condition evaluates the expression each time your program reaches it,
4387 and your program stops only if the condition is @emph{true}.
4389 This is the converse of using assertions for program validation; in that
4390 situation, you want to stop when the assertion is violated---that is,
4391 when the condition is false. In C, if you want to test an assertion expressed
4392 by the condition @var{assert}, you should set the condition
4393 @samp{! @var{assert}} on the appropriate breakpoint.
4395 Conditions are also accepted for watchpoints; you may not need them,
4396 since a watchpoint is inspecting the value of an expression anyhow---but
4397 it might be simpler, say, to just set a watchpoint on a variable name,
4398 and specify a condition that tests whether the new value is an interesting
4401 Break conditions can have side effects, and may even call functions in
4402 your program. This can be useful, for example, to activate functions
4403 that log program progress, or to use your own print functions to
4404 format special data structures. The effects are completely predictable
4405 unless there is another enabled breakpoint at the same address. (In
4406 that case, @value{GDBN} might see the other breakpoint first and stop your
4407 program without checking the condition of this one.) Note that
4408 breakpoint commands are usually more convenient and flexible than break
4410 purpose of performing side effects when a breakpoint is reached
4411 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4413 Breakpoint conditions can also be evaluated on the target's side if
4414 the target supports it. Instead of evaluating the conditions locally,
4415 @value{GDBN} encodes the expression into an agent expression
4416 (@pxref{Agent Expressions}) suitable for execution on the target,
4417 independently of @value{GDBN}. Global variables become raw memory
4418 locations, locals become stack accesses, and so forth.
4420 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4421 when its condition evaluates to true. This mechanism may provide faster
4422 response times depending on the performance characteristics of the target
4423 since it does not need to keep @value{GDBN} informed about
4424 every breakpoint trigger, even those with false conditions.
4426 Break conditions can be specified when a breakpoint is set, by using
4427 @samp{if} in the arguments to the @code{break} command. @xref{Set
4428 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4429 with the @code{condition} command.
4431 You can also use the @code{if} keyword with the @code{watch} command.
4432 The @code{catch} command does not recognize the @code{if} keyword;
4433 @code{condition} is the only way to impose a further condition on a
4438 @item condition @var{bnum} @var{expression}
4439 Specify @var{expression} as the break condition for breakpoint,
4440 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4441 breakpoint @var{bnum} stops your program only if the value of
4442 @var{expression} is true (nonzero, in C). When you use
4443 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4444 syntactic correctness, and to determine whether symbols in it have
4445 referents in the context of your breakpoint. If @var{expression} uses
4446 symbols not referenced in the context of the breakpoint, @value{GDBN}
4447 prints an error message:
4450 No symbol "foo" in current context.
4455 not actually evaluate @var{expression} at the time the @code{condition}
4456 command (or a command that sets a breakpoint with a condition, like
4457 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4459 @item condition @var{bnum}
4460 Remove the condition from breakpoint number @var{bnum}. It becomes
4461 an ordinary unconditional breakpoint.
4464 @cindex ignore count (of breakpoint)
4465 A special case of a breakpoint condition is to stop only when the
4466 breakpoint has been reached a certain number of times. This is so
4467 useful that there is a special way to do it, using the @dfn{ignore
4468 count} of the breakpoint. Every breakpoint has an ignore count, which
4469 is an integer. Most of the time, the ignore count is zero, and
4470 therefore has no effect. But if your program reaches a breakpoint whose
4471 ignore count is positive, then instead of stopping, it just decrements
4472 the ignore count by one and continues. As a result, if the ignore count
4473 value is @var{n}, the breakpoint does not stop the next @var{n} times
4474 your program reaches it.
4478 @item ignore @var{bnum} @var{count}
4479 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4480 The next @var{count} times the breakpoint is reached, your program's
4481 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4484 To make the breakpoint stop the next time it is reached, specify
4487 When you use @code{continue} to resume execution of your program from a
4488 breakpoint, you can specify an ignore count directly as an argument to
4489 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4490 Stepping,,Continuing and Stepping}.
4492 If a breakpoint has a positive ignore count and a condition, the
4493 condition is not checked. Once the ignore count reaches zero,
4494 @value{GDBN} resumes checking the condition.
4496 You could achieve the effect of the ignore count with a condition such
4497 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4498 is decremented each time. @xref{Convenience Vars, ,Convenience
4502 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4505 @node Break Commands
4506 @subsection Breakpoint Command Lists
4508 @cindex breakpoint commands
4509 You can give any breakpoint (or watchpoint or catchpoint) a series of
4510 commands to execute when your program stops due to that breakpoint. For
4511 example, you might want to print the values of certain expressions, or
4512 enable other breakpoints.
4516 @kindex end@r{ (breakpoint commands)}
4517 @item commands @r{[}@var{range}@dots{}@r{]}
4518 @itemx @dots{} @var{command-list} @dots{}
4520 Specify a list of commands for the given breakpoints. The commands
4521 themselves appear on the following lines. Type a line containing just
4522 @code{end} to terminate the commands.
4524 To remove all commands from a breakpoint, type @code{commands} and
4525 follow it immediately with @code{end}; that is, give no commands.
4527 With no argument, @code{commands} refers to the last breakpoint,
4528 watchpoint, or catchpoint set (not to the breakpoint most recently
4529 encountered). If the most recent breakpoints were set with a single
4530 command, then the @code{commands} will apply to all the breakpoints
4531 set by that command. This applies to breakpoints set by
4532 @code{rbreak}, and also applies when a single @code{break} command
4533 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4537 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4538 disabled within a @var{command-list}.
4540 You can use breakpoint commands to start your program up again. Simply
4541 use the @code{continue} command, or @code{step}, or any other command
4542 that resumes execution.
4544 Any other commands in the command list, after a command that resumes
4545 execution, are ignored. This is because any time you resume execution
4546 (even with a simple @code{next} or @code{step}), you may encounter
4547 another breakpoint---which could have its own command list, leading to
4548 ambiguities about which list to execute.
4551 If the first command you specify in a command list is @code{silent}, the
4552 usual message about stopping at a breakpoint is not printed. This may
4553 be desirable for breakpoints that are to print a specific message and
4554 then continue. If none of the remaining commands print anything, you
4555 see no sign that the breakpoint was reached. @code{silent} is
4556 meaningful only at the beginning of a breakpoint command list.
4558 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4559 print precisely controlled output, and are often useful in silent
4560 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4562 For example, here is how you could use breakpoint commands to print the
4563 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4569 printf "x is %d\n",x
4574 One application for breakpoint commands is to compensate for one bug so
4575 you can test for another. Put a breakpoint just after the erroneous line
4576 of code, give it a condition to detect the case in which something
4577 erroneous has been done, and give it commands to assign correct values
4578 to any variables that need them. End with the @code{continue} command
4579 so that your program does not stop, and start with the @code{silent}
4580 command so that no output is produced. Here is an example:
4591 @node Save Breakpoints
4592 @subsection How to save breakpoints to a file
4594 To save breakpoint definitions to a file use the @w{@code{save
4595 breakpoints}} command.
4598 @kindex save breakpoints
4599 @cindex save breakpoints to a file for future sessions
4600 @item save breakpoints [@var{filename}]
4601 This command saves all current breakpoint definitions together with
4602 their commands and ignore counts, into a file @file{@var{filename}}
4603 suitable for use in a later debugging session. This includes all
4604 types of breakpoints (breakpoints, watchpoints, catchpoints,
4605 tracepoints). To read the saved breakpoint definitions, use the
4606 @code{source} command (@pxref{Command Files}). Note that watchpoints
4607 with expressions involving local variables may fail to be recreated
4608 because it may not be possible to access the context where the
4609 watchpoint is valid anymore. Because the saved breakpoint definitions
4610 are simply a sequence of @value{GDBN} commands that recreate the
4611 breakpoints, you can edit the file in your favorite editing program,
4612 and remove the breakpoint definitions you're not interested in, or
4613 that can no longer be recreated.
4616 @c @ifclear BARETARGET
4617 @node Error in Breakpoints
4618 @subsection ``Cannot insert breakpoints''
4620 If you request too many active hardware-assisted breakpoints and
4621 watchpoints, you will see this error message:
4623 @c FIXME: the precise wording of this message may change; the relevant
4624 @c source change is not committed yet (Sep 3, 1999).
4626 Stopped; cannot insert breakpoints.
4627 You may have requested too many hardware breakpoints and watchpoints.
4631 This message is printed when you attempt to resume the program, since
4632 only then @value{GDBN} knows exactly how many hardware breakpoints and
4633 watchpoints it needs to insert.
4635 When this message is printed, you need to disable or remove some of the
4636 hardware-assisted breakpoints and watchpoints, and then continue.
4638 @node Breakpoint-related Warnings
4639 @subsection ``Breakpoint address adjusted...''
4640 @cindex breakpoint address adjusted
4642 Some processor architectures place constraints on the addresses at
4643 which breakpoints may be placed. For architectures thus constrained,
4644 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4645 with the constraints dictated by the architecture.
4647 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4648 a VLIW architecture in which a number of RISC-like instructions may be
4649 bundled together for parallel execution. The FR-V architecture
4650 constrains the location of a breakpoint instruction within such a
4651 bundle to the instruction with the lowest address. @value{GDBN}
4652 honors this constraint by adjusting a breakpoint's address to the
4653 first in the bundle.
4655 It is not uncommon for optimized code to have bundles which contain
4656 instructions from different source statements, thus it may happen that
4657 a breakpoint's address will be adjusted from one source statement to
4658 another. Since this adjustment may significantly alter @value{GDBN}'s
4659 breakpoint related behavior from what the user expects, a warning is
4660 printed when the breakpoint is first set and also when the breakpoint
4663 A warning like the one below is printed when setting a breakpoint
4664 that's been subject to address adjustment:
4667 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4670 Such warnings are printed both for user settable and @value{GDBN}'s
4671 internal breakpoints. If you see one of these warnings, you should
4672 verify that a breakpoint set at the adjusted address will have the
4673 desired affect. If not, the breakpoint in question may be removed and
4674 other breakpoints may be set which will have the desired behavior.
4675 E.g., it may be sufficient to place the breakpoint at a later
4676 instruction. A conditional breakpoint may also be useful in some
4677 cases to prevent the breakpoint from triggering too often.
4679 @value{GDBN} will also issue a warning when stopping at one of these
4680 adjusted breakpoints:
4683 warning: Breakpoint 1 address previously adjusted from 0x00010414
4687 When this warning is encountered, it may be too late to take remedial
4688 action except in cases where the breakpoint is hit earlier or more
4689 frequently than expected.
4691 @node Continuing and Stepping
4692 @section Continuing and Stepping
4696 @cindex resuming execution
4697 @dfn{Continuing} means resuming program execution until your program
4698 completes normally. In contrast, @dfn{stepping} means executing just
4699 one more ``step'' of your program, where ``step'' may mean either one
4700 line of source code, or one machine instruction (depending on what
4701 particular command you use). Either when continuing or when stepping,
4702 your program may stop even sooner, due to a breakpoint or a signal. (If
4703 it stops due to a signal, you may want to use @code{handle}, or use
4704 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4708 @kindex c @r{(@code{continue})}
4709 @kindex fg @r{(resume foreground execution)}
4710 @item continue @r{[}@var{ignore-count}@r{]}
4711 @itemx c @r{[}@var{ignore-count}@r{]}
4712 @itemx fg @r{[}@var{ignore-count}@r{]}
4713 Resume program execution, at the address where your program last stopped;
4714 any breakpoints set at that address are bypassed. The optional argument
4715 @var{ignore-count} allows you to specify a further number of times to
4716 ignore a breakpoint at this location; its effect is like that of
4717 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4719 The argument @var{ignore-count} is meaningful only when your program
4720 stopped due to a breakpoint. At other times, the argument to
4721 @code{continue} is ignored.
4723 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4724 debugged program is deemed to be the foreground program) are provided
4725 purely for convenience, and have exactly the same behavior as
4729 To resume execution at a different place, you can use @code{return}
4730 (@pxref{Returning, ,Returning from a Function}) to go back to the
4731 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4732 Different Address}) to go to an arbitrary location in your program.
4734 A typical technique for using stepping is to set a breakpoint
4735 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4736 beginning of the function or the section of your program where a problem
4737 is believed to lie, run your program until it stops at that breakpoint,
4738 and then step through the suspect area, examining the variables that are
4739 interesting, until you see the problem happen.
4743 @kindex s @r{(@code{step})}
4745 Continue running your program until control reaches a different source
4746 line, then stop it and return control to @value{GDBN}. This command is
4747 abbreviated @code{s}.
4750 @c "without debugging information" is imprecise; actually "without line
4751 @c numbers in the debugging information". (gcc -g1 has debugging info but
4752 @c not line numbers). But it seems complex to try to make that
4753 @c distinction here.
4754 @emph{Warning:} If you use the @code{step} command while control is
4755 within a function that was compiled without debugging information,
4756 execution proceeds until control reaches a function that does have
4757 debugging information. Likewise, it will not step into a function which
4758 is compiled without debugging information. To step through functions
4759 without debugging information, use the @code{stepi} command, described
4763 The @code{step} command only stops at the first instruction of a source
4764 line. This prevents the multiple stops that could otherwise occur in
4765 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4766 to stop if a function that has debugging information is called within
4767 the line. In other words, @code{step} @emph{steps inside} any functions
4768 called within the line.
4770 Also, the @code{step} command only enters a function if there is line
4771 number information for the function. Otherwise it acts like the
4772 @code{next} command. This avoids problems when using @code{cc -gl}
4773 on MIPS machines. Previously, @code{step} entered subroutines if there
4774 was any debugging information about the routine.
4776 @item step @var{count}
4777 Continue running as in @code{step}, but do so @var{count} times. If a
4778 breakpoint is reached, or a signal not related to stepping occurs before
4779 @var{count} steps, stepping stops right away.
4782 @kindex n @r{(@code{next})}
4783 @item next @r{[}@var{count}@r{]}
4784 Continue to the next source line in the current (innermost) stack frame.
4785 This is similar to @code{step}, but function calls that appear within
4786 the line of code are executed without stopping. Execution stops when
4787 control reaches a different line of code at the original stack level
4788 that was executing when you gave the @code{next} command. This command
4789 is abbreviated @code{n}.
4791 An argument @var{count} is a repeat count, as for @code{step}.
4794 @c FIX ME!! Do we delete this, or is there a way it fits in with
4795 @c the following paragraph? --- Vctoria
4797 @c @code{next} within a function that lacks debugging information acts like
4798 @c @code{step}, but any function calls appearing within the code of the
4799 @c function are executed without stopping.
4801 The @code{next} command only stops at the first instruction of a
4802 source line. This prevents multiple stops that could otherwise occur in
4803 @code{switch} statements, @code{for} loops, etc.
4805 @kindex set step-mode
4807 @cindex functions without line info, and stepping
4808 @cindex stepping into functions with no line info
4809 @itemx set step-mode on
4810 The @code{set step-mode on} command causes the @code{step} command to
4811 stop at the first instruction of a function which contains no debug line
4812 information rather than stepping over it.
4814 This is useful in cases where you may be interested in inspecting the
4815 machine instructions of a function which has no symbolic info and do not
4816 want @value{GDBN} to automatically skip over this function.
4818 @item set step-mode off
4819 Causes the @code{step} command to step over any functions which contains no
4820 debug information. This is the default.
4822 @item show step-mode
4823 Show whether @value{GDBN} will stop in or step over functions without
4824 source line debug information.
4827 @kindex fin @r{(@code{finish})}
4829 Continue running until just after function in the selected stack frame
4830 returns. Print the returned value (if any). This command can be
4831 abbreviated as @code{fin}.
4833 Contrast this with the @code{return} command (@pxref{Returning,
4834 ,Returning from a Function}).
4837 @kindex u @r{(@code{until})}
4838 @cindex run until specified location
4841 Continue running until a source line past the current line, in the
4842 current stack frame, is reached. This command is used to avoid single
4843 stepping through a loop more than once. It is like the @code{next}
4844 command, except that when @code{until} encounters a jump, it
4845 automatically continues execution until the program counter is greater
4846 than the address of the jump.
4848 This means that when you reach the end of a loop after single stepping
4849 though it, @code{until} makes your program continue execution until it
4850 exits the loop. In contrast, a @code{next} command at the end of a loop
4851 simply steps back to the beginning of the loop, which forces you to step
4852 through the next iteration.
4854 @code{until} always stops your program if it attempts to exit the current
4857 @code{until} may produce somewhat counterintuitive results if the order
4858 of machine code does not match the order of the source lines. For
4859 example, in the following excerpt from a debugging session, the @code{f}
4860 (@code{frame}) command shows that execution is stopped at line
4861 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4865 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4867 (@value{GDBP}) until
4868 195 for ( ; argc > 0; NEXTARG) @{
4871 This happened because, for execution efficiency, the compiler had
4872 generated code for the loop closure test at the end, rather than the
4873 start, of the loop---even though the test in a C @code{for}-loop is
4874 written before the body of the loop. The @code{until} command appeared
4875 to step back to the beginning of the loop when it advanced to this
4876 expression; however, it has not really gone to an earlier
4877 statement---not in terms of the actual machine code.
4879 @code{until} with no argument works by means of single
4880 instruction stepping, and hence is slower than @code{until} with an
4883 @item until @var{location}
4884 @itemx u @var{location}
4885 Continue running your program until either the specified location is
4886 reached, or the current stack frame returns. @var{location} is any of
4887 the forms described in @ref{Specify Location}.
4888 This form of the command uses temporary breakpoints, and
4889 hence is quicker than @code{until} without an argument. The specified
4890 location is actually reached only if it is in the current frame. This
4891 implies that @code{until} can be used to skip over recursive function
4892 invocations. For instance in the code below, if the current location is
4893 line @code{96}, issuing @code{until 99} will execute the program up to
4894 line @code{99} in the same invocation of factorial, i.e., after the inner
4895 invocations have returned.
4898 94 int factorial (int value)
4900 96 if (value > 1) @{
4901 97 value *= factorial (value - 1);
4908 @kindex advance @var{location}
4909 @itemx advance @var{location}
4910 Continue running the program up to the given @var{location}. An argument is
4911 required, which should be of one of the forms described in
4912 @ref{Specify Location}.
4913 Execution will also stop upon exit from the current stack
4914 frame. This command is similar to @code{until}, but @code{advance} will
4915 not skip over recursive function calls, and the target location doesn't
4916 have to be in the same frame as the current one.
4920 @kindex si @r{(@code{stepi})}
4922 @itemx stepi @var{arg}
4924 Execute one machine instruction, then stop and return to the debugger.
4926 It is often useful to do @samp{display/i $pc} when stepping by machine
4927 instructions. This makes @value{GDBN} automatically display the next
4928 instruction to be executed, each time your program stops. @xref{Auto
4929 Display,, Automatic Display}.
4931 An argument is a repeat count, as in @code{step}.
4935 @kindex ni @r{(@code{nexti})}
4937 @itemx nexti @var{arg}
4939 Execute one machine instruction, but if it is a function call,
4940 proceed until the function returns.
4942 An argument is a repeat count, as in @code{next}.
4945 @node Skipping Over Functions and Files
4946 @section Skipping Over Functions and Files
4947 @cindex skipping over functions and files
4949 The program you are debugging may contain some functions which are
4950 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
4951 skip a function or all functions in a file when stepping.
4953 For example, consider the following C function:
4964 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
4965 are not interested in stepping through @code{boring}. If you run @code{step}
4966 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
4967 step over both @code{foo} and @code{boring}!
4969 One solution is to @code{step} into @code{boring} and use the @code{finish}
4970 command to immediately exit it. But this can become tedious if @code{boring}
4971 is called from many places.
4973 A more flexible solution is to execute @kbd{skip boring}. This instructs
4974 @value{GDBN} never to step into @code{boring}. Now when you execute
4975 @code{step} at line 103, you'll step over @code{boring} and directly into
4978 You can also instruct @value{GDBN} to skip all functions in a file, with, for
4979 example, @code{skip file boring.c}.
4982 @kindex skip function
4983 @item skip @r{[}@var{linespec}@r{]}
4984 @itemx skip function @r{[}@var{linespec}@r{]}
4985 After running this command, the function named by @var{linespec} or the
4986 function containing the line named by @var{linespec} will be skipped over when
4987 stepping. @xref{Specify Location}.
4989 If you do not specify @var{linespec}, the function you're currently debugging
4992 (If you have a function called @code{file} that you want to skip, use
4993 @kbd{skip function file}.)
4996 @item skip file @r{[}@var{filename}@r{]}
4997 After running this command, any function whose source lives in @var{filename}
4998 will be skipped over when stepping.
5000 If you do not specify @var{filename}, functions whose source lives in the file
5001 you're currently debugging will be skipped.
5004 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5005 These are the commands for managing your list of skips:
5009 @item info skip @r{[}@var{range}@r{]}
5010 Print details about the specified skip(s). If @var{range} is not specified,
5011 print a table with details about all functions and files marked for skipping.
5012 @code{info skip} prints the following information about each skip:
5016 A number identifying this skip.
5018 The type of this skip, either @samp{function} or @samp{file}.
5019 @item Enabled or Disabled
5020 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5022 For function skips, this column indicates the address in memory of the function
5023 being skipped. If you've set a function skip on a function which has not yet
5024 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5025 which has the function is loaded, @code{info skip} will show the function's
5028 For file skips, this field contains the filename being skipped. For functions
5029 skips, this field contains the function name and its line number in the file
5030 where it is defined.
5034 @item skip delete @r{[}@var{range}@r{]}
5035 Delete the specified skip(s). If @var{range} is not specified, delete all
5039 @item skip enable @r{[}@var{range}@r{]}
5040 Enable the specified skip(s). If @var{range} is not specified, enable all
5043 @kindex skip disable
5044 @item skip disable @r{[}@var{range}@r{]}
5045 Disable the specified skip(s). If @var{range} is not specified, disable all
5054 A signal is an asynchronous event that can happen in a program. The
5055 operating system defines the possible kinds of signals, and gives each
5056 kind a name and a number. For example, in Unix @code{SIGINT} is the
5057 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5058 @code{SIGSEGV} is the signal a program gets from referencing a place in
5059 memory far away from all the areas in use; @code{SIGALRM} occurs when
5060 the alarm clock timer goes off (which happens only if your program has
5061 requested an alarm).
5063 @cindex fatal signals
5064 Some signals, including @code{SIGALRM}, are a normal part of the
5065 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5066 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5067 program has not specified in advance some other way to handle the signal.
5068 @code{SIGINT} does not indicate an error in your program, but it is normally
5069 fatal so it can carry out the purpose of the interrupt: to kill the program.
5071 @value{GDBN} has the ability to detect any occurrence of a signal in your
5072 program. You can tell @value{GDBN} in advance what to do for each kind of
5075 @cindex handling signals
5076 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5077 @code{SIGALRM} be silently passed to your program
5078 (so as not to interfere with their role in the program's functioning)
5079 but to stop your program immediately whenever an error signal happens.
5080 You can change these settings with the @code{handle} command.
5083 @kindex info signals
5087 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5088 handle each one. You can use this to see the signal numbers of all
5089 the defined types of signals.
5091 @item info signals @var{sig}
5092 Similar, but print information only about the specified signal number.
5094 @code{info handle} is an alias for @code{info signals}.
5097 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5098 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
5099 can be the number of a signal or its name (with or without the
5100 @samp{SIG} at the beginning); a list of signal numbers of the form
5101 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5102 known signals. Optional arguments @var{keywords}, described below,
5103 say what change to make.
5107 The keywords allowed by the @code{handle} command can be abbreviated.
5108 Their full names are:
5112 @value{GDBN} should not stop your program when this signal happens. It may
5113 still print a message telling you that the signal has come in.
5116 @value{GDBN} should stop your program when this signal happens. This implies
5117 the @code{print} keyword as well.
5120 @value{GDBN} should print a message when this signal happens.
5123 @value{GDBN} should not mention the occurrence of the signal at all. This
5124 implies the @code{nostop} keyword as well.
5128 @value{GDBN} should allow your program to see this signal; your program
5129 can handle the signal, or else it may terminate if the signal is fatal
5130 and not handled. @code{pass} and @code{noignore} are synonyms.
5134 @value{GDBN} should not allow your program to see this signal.
5135 @code{nopass} and @code{ignore} are synonyms.
5139 When a signal stops your program, the signal is not visible to the
5141 continue. Your program sees the signal then, if @code{pass} is in
5142 effect for the signal in question @emph{at that time}. In other words,
5143 after @value{GDBN} reports a signal, you can use the @code{handle}
5144 command with @code{pass} or @code{nopass} to control whether your
5145 program sees that signal when you continue.
5147 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5148 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5149 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5152 You can also use the @code{signal} command to prevent your program from
5153 seeing a signal, or cause it to see a signal it normally would not see,
5154 or to give it any signal at any time. For example, if your program stopped
5155 due to some sort of memory reference error, you might store correct
5156 values into the erroneous variables and continue, hoping to see more
5157 execution; but your program would probably terminate immediately as
5158 a result of the fatal signal once it saw the signal. To prevent this,
5159 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5162 @cindex extra signal information
5163 @anchor{extra signal information}
5165 On some targets, @value{GDBN} can inspect extra signal information
5166 associated with the intercepted signal, before it is actually
5167 delivered to the program being debugged. This information is exported
5168 by the convenience variable @code{$_siginfo}, and consists of data
5169 that is passed by the kernel to the signal handler at the time of the
5170 receipt of a signal. The data type of the information itself is
5171 target dependent. You can see the data type using the @code{ptype
5172 $_siginfo} command. On Unix systems, it typically corresponds to the
5173 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5176 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5177 referenced address that raised a segmentation fault.
5181 (@value{GDBP}) continue
5182 Program received signal SIGSEGV, Segmentation fault.
5183 0x0000000000400766 in main ()
5185 (@value{GDBP}) ptype $_siginfo
5192 struct @{...@} _kill;
5193 struct @{...@} _timer;
5195 struct @{...@} _sigchld;
5196 struct @{...@} _sigfault;
5197 struct @{...@} _sigpoll;
5200 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5204 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5205 $1 = (void *) 0x7ffff7ff7000
5209 Depending on target support, @code{$_siginfo} may also be writable.
5212 @section Stopping and Starting Multi-thread Programs
5214 @cindex stopped threads
5215 @cindex threads, stopped
5217 @cindex continuing threads
5218 @cindex threads, continuing
5220 @value{GDBN} supports debugging programs with multiple threads
5221 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5222 are two modes of controlling execution of your program within the
5223 debugger. In the default mode, referred to as @dfn{all-stop mode},
5224 when any thread in your program stops (for example, at a breakpoint
5225 or while being stepped), all other threads in the program are also stopped by
5226 @value{GDBN}. On some targets, @value{GDBN} also supports
5227 @dfn{non-stop mode}, in which other threads can continue to run freely while
5228 you examine the stopped thread in the debugger.
5231 * All-Stop Mode:: All threads stop when GDB takes control
5232 * Non-Stop Mode:: Other threads continue to execute
5233 * Background Execution:: Running your program asynchronously
5234 * Thread-Specific Breakpoints:: Controlling breakpoints
5235 * Interrupted System Calls:: GDB may interfere with system calls
5236 * Observer Mode:: GDB does not alter program behavior
5240 @subsection All-Stop Mode
5242 @cindex all-stop mode
5244 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5245 @emph{all} threads of execution stop, not just the current thread. This
5246 allows you to examine the overall state of the program, including
5247 switching between threads, without worrying that things may change
5250 Conversely, whenever you restart the program, @emph{all} threads start
5251 executing. @emph{This is true even when single-stepping} with commands
5252 like @code{step} or @code{next}.
5254 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5255 Since thread scheduling is up to your debugging target's operating
5256 system (not controlled by @value{GDBN}), other threads may
5257 execute more than one statement while the current thread completes a
5258 single step. Moreover, in general other threads stop in the middle of a
5259 statement, rather than at a clean statement boundary, when the program
5262 You might even find your program stopped in another thread after
5263 continuing or even single-stepping. This happens whenever some other
5264 thread runs into a breakpoint, a signal, or an exception before the
5265 first thread completes whatever you requested.
5267 @cindex automatic thread selection
5268 @cindex switching threads automatically
5269 @cindex threads, automatic switching
5270 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5271 signal, it automatically selects the thread where that breakpoint or
5272 signal happened. @value{GDBN} alerts you to the context switch with a
5273 message such as @samp{[Switching to Thread @var{n}]} to identify the
5276 On some OSes, you can modify @value{GDBN}'s default behavior by
5277 locking the OS scheduler to allow only a single thread to run.
5280 @item set scheduler-locking @var{mode}
5281 @cindex scheduler locking mode
5282 @cindex lock scheduler
5283 Set the scheduler locking mode. If it is @code{off}, then there is no
5284 locking and any thread may run at any time. If @code{on}, then only the
5285 current thread may run when the inferior is resumed. The @code{step}
5286 mode optimizes for single-stepping; it prevents other threads
5287 from preempting the current thread while you are stepping, so that
5288 the focus of debugging does not change unexpectedly.
5289 Other threads only rarely (or never) get a chance to run
5290 when you step. They are more likely to run when you @samp{next} over a
5291 function call, and they are completely free to run when you use commands
5292 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5293 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5294 the current thread away from the thread that you are debugging.
5296 @item show scheduler-locking
5297 Display the current scheduler locking mode.
5300 @cindex resume threads of multiple processes simultaneously
5301 By default, when you issue one of the execution commands such as
5302 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5303 threads of the current inferior to run. For example, if @value{GDBN}
5304 is attached to two inferiors, each with two threads, the
5305 @code{continue} command resumes only the two threads of the current
5306 inferior. This is useful, for example, when you debug a program that
5307 forks and you want to hold the parent stopped (so that, for instance,
5308 it doesn't run to exit), while you debug the child. In other
5309 situations, you may not be interested in inspecting the current state
5310 of any of the processes @value{GDBN} is attached to, and you may want
5311 to resume them all until some breakpoint is hit. In the latter case,
5312 you can instruct @value{GDBN} to allow all threads of all the
5313 inferiors to run with the @w{@code{set schedule-multiple}} command.
5316 @kindex set schedule-multiple
5317 @item set schedule-multiple
5318 Set the mode for allowing threads of multiple processes to be resumed
5319 when an execution command is issued. When @code{on}, all threads of
5320 all processes are allowed to run. When @code{off}, only the threads
5321 of the current process are resumed. The default is @code{off}. The
5322 @code{scheduler-locking} mode takes precedence when set to @code{on},
5323 or while you are stepping and set to @code{step}.
5325 @item show schedule-multiple
5326 Display the current mode for resuming the execution of threads of
5331 @subsection Non-Stop Mode
5333 @cindex non-stop mode
5335 @c This section is really only a place-holder, and needs to be expanded
5336 @c with more details.
5338 For some multi-threaded targets, @value{GDBN} supports an optional
5339 mode of operation in which you can examine stopped program threads in
5340 the debugger while other threads continue to execute freely. This
5341 minimizes intrusion when debugging live systems, such as programs
5342 where some threads have real-time constraints or must continue to
5343 respond to external events. This is referred to as @dfn{non-stop} mode.
5345 In non-stop mode, when a thread stops to report a debugging event,
5346 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5347 threads as well, in contrast to the all-stop mode behavior. Additionally,
5348 execution commands such as @code{continue} and @code{step} apply by default
5349 only to the current thread in non-stop mode, rather than all threads as
5350 in all-stop mode. This allows you to control threads explicitly in
5351 ways that are not possible in all-stop mode --- for example, stepping
5352 one thread while allowing others to run freely, stepping
5353 one thread while holding all others stopped, or stepping several threads
5354 independently and simultaneously.
5356 To enter non-stop mode, use this sequence of commands before you run
5357 or attach to your program:
5360 # Enable the async interface.
5363 # If using the CLI, pagination breaks non-stop.
5366 # Finally, turn it on!
5370 You can use these commands to manipulate the non-stop mode setting:
5373 @kindex set non-stop
5374 @item set non-stop on
5375 Enable selection of non-stop mode.
5376 @item set non-stop off
5377 Disable selection of non-stop mode.
5378 @kindex show non-stop
5380 Show the current non-stop enablement setting.
5383 Note these commands only reflect whether non-stop mode is enabled,
5384 not whether the currently-executing program is being run in non-stop mode.
5385 In particular, the @code{set non-stop} preference is only consulted when
5386 @value{GDBN} starts or connects to the target program, and it is generally
5387 not possible to switch modes once debugging has started. Furthermore,
5388 since not all targets support non-stop mode, even when you have enabled
5389 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5392 In non-stop mode, all execution commands apply only to the current thread
5393 by default. That is, @code{continue} only continues one thread.
5394 To continue all threads, issue @code{continue -a} or @code{c -a}.
5396 You can use @value{GDBN}'s background execution commands
5397 (@pxref{Background Execution}) to run some threads in the background
5398 while you continue to examine or step others from @value{GDBN}.
5399 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5400 always executed asynchronously in non-stop mode.
5402 Suspending execution is done with the @code{interrupt} command when
5403 running in the background, or @kbd{Ctrl-c} during foreground execution.
5404 In all-stop mode, this stops the whole process;
5405 but in non-stop mode the interrupt applies only to the current thread.
5406 To stop the whole program, use @code{interrupt -a}.
5408 Other execution commands do not currently support the @code{-a} option.
5410 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5411 that thread current, as it does in all-stop mode. This is because the
5412 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5413 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5414 changed to a different thread just as you entered a command to operate on the
5415 previously current thread.
5417 @node Background Execution
5418 @subsection Background Execution
5420 @cindex foreground execution
5421 @cindex background execution
5422 @cindex asynchronous execution
5423 @cindex execution, foreground, background and asynchronous
5425 @value{GDBN}'s execution commands have two variants: the normal
5426 foreground (synchronous) behavior, and a background
5427 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5428 the program to report that some thread has stopped before prompting for
5429 another command. In background execution, @value{GDBN} immediately gives
5430 a command prompt so that you can issue other commands while your program runs.
5432 You need to explicitly enable asynchronous mode before you can use
5433 background execution commands. You can use these commands to
5434 manipulate the asynchronous mode setting:
5437 @kindex set target-async
5438 @item set target-async on
5439 Enable asynchronous mode.
5440 @item set target-async off
5441 Disable asynchronous mode.
5442 @kindex show target-async
5443 @item show target-async
5444 Show the current target-async setting.
5447 If the target doesn't support async mode, @value{GDBN} issues an error
5448 message if you attempt to use the background execution commands.
5450 To specify background execution, add a @code{&} to the command. For example,
5451 the background form of the @code{continue} command is @code{continue&}, or
5452 just @code{c&}. The execution commands that accept background execution
5458 @xref{Starting, , Starting your Program}.
5462 @xref{Attach, , Debugging an Already-running Process}.
5466 @xref{Continuing and Stepping, step}.
5470 @xref{Continuing and Stepping, stepi}.
5474 @xref{Continuing and Stepping, next}.
5478 @xref{Continuing and Stepping, nexti}.
5482 @xref{Continuing and Stepping, continue}.
5486 @xref{Continuing and Stepping, finish}.
5490 @xref{Continuing and Stepping, until}.
5494 Background execution is especially useful in conjunction with non-stop
5495 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5496 However, you can also use these commands in the normal all-stop mode with
5497 the restriction that you cannot issue another execution command until the
5498 previous one finishes. Examples of commands that are valid in all-stop
5499 mode while the program is running include @code{help} and @code{info break}.
5501 You can interrupt your program while it is running in the background by
5502 using the @code{interrupt} command.
5509 Suspend execution of the running program. In all-stop mode,
5510 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5511 only the current thread. To stop the whole program in non-stop mode,
5512 use @code{interrupt -a}.
5515 @node Thread-Specific Breakpoints
5516 @subsection Thread-Specific Breakpoints
5518 When your program has multiple threads (@pxref{Threads,, Debugging
5519 Programs with Multiple Threads}), you can choose whether to set
5520 breakpoints on all threads, or on a particular thread.
5523 @cindex breakpoints and threads
5524 @cindex thread breakpoints
5525 @kindex break @dots{} thread @var{threadno}
5526 @item break @var{linespec} thread @var{threadno}
5527 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5528 @var{linespec} specifies source lines; there are several ways of
5529 writing them (@pxref{Specify Location}), but the effect is always to
5530 specify some source line.
5532 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5533 to specify that you only want @value{GDBN} to stop the program when a
5534 particular thread reaches this breakpoint. @var{threadno} is one of the
5535 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5536 column of the @samp{info threads} display.
5538 If you do not specify @samp{thread @var{threadno}} when you set a
5539 breakpoint, the breakpoint applies to @emph{all} threads of your
5542 You can use the @code{thread} qualifier on conditional breakpoints as
5543 well; in this case, place @samp{thread @var{threadno}} before or
5544 after the breakpoint condition, like this:
5547 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5552 @node Interrupted System Calls
5553 @subsection Interrupted System Calls
5555 @cindex thread breakpoints and system calls
5556 @cindex system calls and thread breakpoints
5557 @cindex premature return from system calls
5558 There is an unfortunate side effect when using @value{GDBN} to debug
5559 multi-threaded programs. If one thread stops for a
5560 breakpoint, or for some other reason, and another thread is blocked in a
5561 system call, then the system call may return prematurely. This is a
5562 consequence of the interaction between multiple threads and the signals
5563 that @value{GDBN} uses to implement breakpoints and other events that
5566 To handle this problem, your program should check the return value of
5567 each system call and react appropriately. This is good programming
5570 For example, do not write code like this:
5576 The call to @code{sleep} will return early if a different thread stops
5577 at a breakpoint or for some other reason.
5579 Instead, write this:
5584 unslept = sleep (unslept);
5587 A system call is allowed to return early, so the system is still
5588 conforming to its specification. But @value{GDBN} does cause your
5589 multi-threaded program to behave differently than it would without
5592 Also, @value{GDBN} uses internal breakpoints in the thread library to
5593 monitor certain events such as thread creation and thread destruction.
5594 When such an event happens, a system call in another thread may return
5595 prematurely, even though your program does not appear to stop.
5598 @subsection Observer Mode
5600 If you want to build on non-stop mode and observe program behavior
5601 without any chance of disruption by @value{GDBN}, you can set
5602 variables to disable all of the debugger's attempts to modify state,
5603 whether by writing memory, inserting breakpoints, etc. These operate
5604 at a low level, intercepting operations from all commands.
5606 When all of these are set to @code{off}, then @value{GDBN} is said to
5607 be @dfn{observer mode}. As a convenience, the variable
5608 @code{observer} can be set to disable these, plus enable non-stop
5611 Note that @value{GDBN} will not prevent you from making nonsensical
5612 combinations of these settings. For instance, if you have enabled
5613 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5614 then breakpoints that work by writing trap instructions into the code
5615 stream will still not be able to be placed.
5620 @item set observer on
5621 @itemx set observer off
5622 When set to @code{on}, this disables all the permission variables
5623 below (except for @code{insert-fast-tracepoints}), plus enables
5624 non-stop debugging. Setting this to @code{off} switches back to
5625 normal debugging, though remaining in non-stop mode.
5628 Show whether observer mode is on or off.
5630 @kindex may-write-registers
5631 @item set may-write-registers on
5632 @itemx set may-write-registers off
5633 This controls whether @value{GDBN} will attempt to alter the values of
5634 registers, such as with assignment expressions in @code{print}, or the
5635 @code{jump} command. It defaults to @code{on}.
5637 @item show may-write-registers
5638 Show the current permission to write registers.
5640 @kindex may-write-memory
5641 @item set may-write-memory on
5642 @itemx set may-write-memory off
5643 This controls whether @value{GDBN} will attempt to alter the contents
5644 of memory, such as with assignment expressions in @code{print}. It
5645 defaults to @code{on}.
5647 @item show may-write-memory
5648 Show the current permission to write memory.
5650 @kindex may-insert-breakpoints
5651 @item set may-insert-breakpoints on
5652 @itemx set may-insert-breakpoints off
5653 This controls whether @value{GDBN} will attempt to insert breakpoints.
5654 This affects all breakpoints, including internal breakpoints defined
5655 by @value{GDBN}. It defaults to @code{on}.
5657 @item show may-insert-breakpoints
5658 Show the current permission to insert breakpoints.
5660 @kindex may-insert-tracepoints
5661 @item set may-insert-tracepoints on
5662 @itemx set may-insert-tracepoints off
5663 This controls whether @value{GDBN} will attempt to insert (regular)
5664 tracepoints at the beginning of a tracing experiment. It affects only
5665 non-fast tracepoints, fast tracepoints being under the control of
5666 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5668 @item show may-insert-tracepoints
5669 Show the current permission to insert tracepoints.
5671 @kindex may-insert-fast-tracepoints
5672 @item set may-insert-fast-tracepoints on
5673 @itemx set may-insert-fast-tracepoints off
5674 This controls whether @value{GDBN} will attempt to insert fast
5675 tracepoints at the beginning of a tracing experiment. It affects only
5676 fast tracepoints, regular (non-fast) tracepoints being under the
5677 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5679 @item show may-insert-fast-tracepoints
5680 Show the current permission to insert fast tracepoints.
5682 @kindex may-interrupt
5683 @item set may-interrupt on
5684 @itemx set may-interrupt off
5685 This controls whether @value{GDBN} will attempt to interrupt or stop
5686 program execution. When this variable is @code{off}, the
5687 @code{interrupt} command will have no effect, nor will
5688 @kbd{Ctrl-c}. It defaults to @code{on}.
5690 @item show may-interrupt
5691 Show the current permission to interrupt or stop the program.
5695 @node Reverse Execution
5696 @chapter Running programs backward
5697 @cindex reverse execution
5698 @cindex running programs backward
5700 When you are debugging a program, it is not unusual to realize that
5701 you have gone too far, and some event of interest has already happened.
5702 If the target environment supports it, @value{GDBN} can allow you to
5703 ``rewind'' the program by running it backward.
5705 A target environment that supports reverse execution should be able
5706 to ``undo'' the changes in machine state that have taken place as the
5707 program was executing normally. Variables, registers etc.@: should
5708 revert to their previous values. Obviously this requires a great
5709 deal of sophistication on the part of the target environment; not
5710 all target environments can support reverse execution.
5712 When a program is executed in reverse, the instructions that
5713 have most recently been executed are ``un-executed'', in reverse
5714 order. The program counter runs backward, following the previous
5715 thread of execution in reverse. As each instruction is ``un-executed'',
5716 the values of memory and/or registers that were changed by that
5717 instruction are reverted to their previous states. After executing
5718 a piece of source code in reverse, all side effects of that code
5719 should be ``undone'', and all variables should be returned to their
5720 prior values@footnote{
5721 Note that some side effects are easier to undo than others. For instance,
5722 memory and registers are relatively easy, but device I/O is hard. Some
5723 targets may be able undo things like device I/O, and some may not.
5725 The contract between @value{GDBN} and the reverse executing target
5726 requires only that the target do something reasonable when
5727 @value{GDBN} tells it to execute backwards, and then report the
5728 results back to @value{GDBN}. Whatever the target reports back to
5729 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5730 assumes that the memory and registers that the target reports are in a
5731 consistant state, but @value{GDBN} accepts whatever it is given.
5734 If you are debugging in a target environment that supports
5735 reverse execution, @value{GDBN} provides the following commands.
5738 @kindex reverse-continue
5739 @kindex rc @r{(@code{reverse-continue})}
5740 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5741 @itemx rc @r{[}@var{ignore-count}@r{]}
5742 Beginning at the point where your program last stopped, start executing
5743 in reverse. Reverse execution will stop for breakpoints and synchronous
5744 exceptions (signals), just like normal execution. Behavior of
5745 asynchronous signals depends on the target environment.
5747 @kindex reverse-step
5748 @kindex rs @r{(@code{step})}
5749 @item reverse-step @r{[}@var{count}@r{]}
5750 Run the program backward until control reaches the start of a
5751 different source line; then stop it, and return control to @value{GDBN}.
5753 Like the @code{step} command, @code{reverse-step} will only stop
5754 at the beginning of a source line. It ``un-executes'' the previously
5755 executed source line. If the previous source line included calls to
5756 debuggable functions, @code{reverse-step} will step (backward) into
5757 the called function, stopping at the beginning of the @emph{last}
5758 statement in the called function (typically a return statement).
5760 Also, as with the @code{step} command, if non-debuggable functions are
5761 called, @code{reverse-step} will run thru them backward without stopping.
5763 @kindex reverse-stepi
5764 @kindex rsi @r{(@code{reverse-stepi})}
5765 @item reverse-stepi @r{[}@var{count}@r{]}
5766 Reverse-execute one machine instruction. Note that the instruction
5767 to be reverse-executed is @emph{not} the one pointed to by the program
5768 counter, but the instruction executed prior to that one. For instance,
5769 if the last instruction was a jump, @code{reverse-stepi} will take you
5770 back from the destination of the jump to the jump instruction itself.
5772 @kindex reverse-next
5773 @kindex rn @r{(@code{reverse-next})}
5774 @item reverse-next @r{[}@var{count}@r{]}
5775 Run backward to the beginning of the previous line executed in
5776 the current (innermost) stack frame. If the line contains function
5777 calls, they will be ``un-executed'' without stopping. Starting from
5778 the first line of a function, @code{reverse-next} will take you back
5779 to the caller of that function, @emph{before} the function was called,
5780 just as the normal @code{next} command would take you from the last
5781 line of a function back to its return to its caller
5782 @footnote{Unless the code is too heavily optimized.}.
5784 @kindex reverse-nexti
5785 @kindex rni @r{(@code{reverse-nexti})}
5786 @item reverse-nexti @r{[}@var{count}@r{]}
5787 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5788 in reverse, except that called functions are ``un-executed'' atomically.
5789 That is, if the previously executed instruction was a return from
5790 another function, @code{reverse-nexti} will continue to execute
5791 in reverse until the call to that function (from the current stack
5794 @kindex reverse-finish
5795 @item reverse-finish
5796 Just as the @code{finish} command takes you to the point where the
5797 current function returns, @code{reverse-finish} takes you to the point
5798 where it was called. Instead of ending up at the end of the current
5799 function invocation, you end up at the beginning.
5801 @kindex set exec-direction
5802 @item set exec-direction
5803 Set the direction of target execution.
5804 @itemx set exec-direction reverse
5805 @cindex execute forward or backward in time
5806 @value{GDBN} will perform all execution commands in reverse, until the
5807 exec-direction mode is changed to ``forward''. Affected commands include
5808 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5809 command cannot be used in reverse mode.
5810 @item set exec-direction forward
5811 @value{GDBN} will perform all execution commands in the normal fashion.
5812 This is the default.
5816 @node Process Record and Replay
5817 @chapter Recording Inferior's Execution and Replaying It
5818 @cindex process record and replay
5819 @cindex recording inferior's execution and replaying it
5821 On some platforms, @value{GDBN} provides a special @dfn{process record
5822 and replay} target that can record a log of the process execution, and
5823 replay it later with both forward and reverse execution commands.
5826 When this target is in use, if the execution log includes the record
5827 for the next instruction, @value{GDBN} will debug in @dfn{replay
5828 mode}. In the replay mode, the inferior does not really execute code
5829 instructions. Instead, all the events that normally happen during
5830 code execution are taken from the execution log. While code is not
5831 really executed in replay mode, the values of registers (including the
5832 program counter register) and the memory of the inferior are still
5833 changed as they normally would. Their contents are taken from the
5837 If the record for the next instruction is not in the execution log,
5838 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5839 inferior executes normally, and @value{GDBN} records the execution log
5842 The process record and replay target supports reverse execution
5843 (@pxref{Reverse Execution}), even if the platform on which the
5844 inferior runs does not. However, the reverse execution is limited in
5845 this case by the range of the instructions recorded in the execution
5846 log. In other words, reverse execution on platforms that don't
5847 support it directly can only be done in the replay mode.
5849 When debugging in the reverse direction, @value{GDBN} will work in
5850 replay mode as long as the execution log includes the record for the
5851 previous instruction; otherwise, it will work in record mode, if the
5852 platform supports reverse execution, or stop if not.
5854 For architecture environments that support process record and replay,
5855 @value{GDBN} provides the following commands:
5858 @kindex target record
5862 This command starts the process record and replay target. The process
5863 record and replay target can only debug a process that is already
5864 running. Therefore, you need first to start the process with the
5865 @kbd{run} or @kbd{start} commands, and then start the recording with
5866 the @kbd{target record} command.
5868 Both @code{record} and @code{rec} are aliases of @code{target record}.
5870 @cindex displaced stepping, and process record and replay
5871 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5872 will be automatically disabled when process record and replay target
5873 is started. That's because the process record and replay target
5874 doesn't support displaced stepping.
5876 @cindex non-stop mode, and process record and replay
5877 @cindex asynchronous execution, and process record and replay
5878 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5879 the asynchronous execution mode (@pxref{Background Execution}), the
5880 process record and replay target cannot be started because it doesn't
5881 support these two modes.
5886 Stop the process record and replay target. When process record and
5887 replay target stops, the entire execution log will be deleted and the
5888 inferior will either be terminated, or will remain in its final state.
5890 When you stop the process record and replay target in record mode (at
5891 the end of the execution log), the inferior will be stopped at the
5892 next instruction that would have been recorded. In other words, if
5893 you record for a while and then stop recording, the inferior process
5894 will be left in the same state as if the recording never happened.
5896 On the other hand, if the process record and replay target is stopped
5897 while in replay mode (that is, not at the end of the execution log,
5898 but at some earlier point), the inferior process will become ``live''
5899 at that earlier state, and it will then be possible to continue the
5900 usual ``live'' debugging of the process from that state.
5902 When the inferior process exits, or @value{GDBN} detaches from it,
5903 process record and replay target will automatically stop itself.
5906 @item record save @var{filename}
5907 Save the execution log to a file @file{@var{filename}}.
5908 Default filename is @file{gdb_record.@var{process_id}}, where
5909 @var{process_id} is the process ID of the inferior.
5911 @kindex record restore
5912 @item record restore @var{filename}
5913 Restore the execution log from a file @file{@var{filename}}.
5914 File must have been created with @code{record save}.
5916 @kindex set record insn-number-max
5917 @item set record insn-number-max @var{limit}
5918 Set the limit of instructions to be recorded. Default value is 200000.
5920 If @var{limit} is a positive number, then @value{GDBN} will start
5921 deleting instructions from the log once the number of the record
5922 instructions becomes greater than @var{limit}. For every new recorded
5923 instruction, @value{GDBN} will delete the earliest recorded
5924 instruction to keep the number of recorded instructions at the limit.
5925 (Since deleting recorded instructions loses information, @value{GDBN}
5926 lets you control what happens when the limit is reached, by means of
5927 the @code{stop-at-limit} option, described below.)
5929 If @var{limit} is zero, @value{GDBN} will never delete recorded
5930 instructions from the execution log. The number of recorded
5931 instructions is unlimited in this case.
5933 @kindex show record insn-number-max
5934 @item show record insn-number-max
5935 Show the limit of instructions to be recorded.
5937 @kindex set record stop-at-limit
5938 @item set record stop-at-limit
5939 Control the behavior when the number of recorded instructions reaches
5940 the limit. If ON (the default), @value{GDBN} will stop when the limit
5941 is reached for the first time and ask you whether you want to stop the
5942 inferior or continue running it and recording the execution log. If
5943 you decide to continue recording, each new recorded instruction will
5944 cause the oldest one to be deleted.
5946 If this option is OFF, @value{GDBN} will automatically delete the
5947 oldest record to make room for each new one, without asking.
5949 @kindex show record stop-at-limit
5950 @item show record stop-at-limit
5951 Show the current setting of @code{stop-at-limit}.
5953 @kindex set record memory-query
5954 @item set record memory-query
5955 Control the behavior when @value{GDBN} is unable to record memory
5956 changes caused by an instruction. If ON, @value{GDBN} will query
5957 whether to stop the inferior in that case.
5959 If this option is OFF (the default), @value{GDBN} will automatically
5960 ignore the effect of such instructions on memory. Later, when
5961 @value{GDBN} replays this execution log, it will mark the log of this
5962 instruction as not accessible, and it will not affect the replay
5965 @kindex show record memory-query
5966 @item show record memory-query
5967 Show the current setting of @code{memory-query}.
5971 Show various statistics about the state of process record and its
5972 in-memory execution log buffer, including:
5976 Whether in record mode or replay mode.
5978 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
5980 Highest recorded instruction number.
5982 Current instruction about to be replayed (if in replay mode).
5984 Number of instructions contained in the execution log.
5986 Maximum number of instructions that may be contained in the execution log.
5989 @kindex record delete
5992 When record target runs in replay mode (``in the past''), delete the
5993 subsequent execution log and begin to record a new execution log starting
5994 from the current address. This means you will abandon the previously
5995 recorded ``future'' and begin recording a new ``future''.
6000 @chapter Examining the Stack
6002 When your program has stopped, the first thing you need to know is where it
6003 stopped and how it got there.
6006 Each time your program performs a function call, information about the call
6008 That information includes the location of the call in your program,
6009 the arguments of the call,
6010 and the local variables of the function being called.
6011 The information is saved in a block of data called a @dfn{stack frame}.
6012 The stack frames are allocated in a region of memory called the @dfn{call
6015 When your program stops, the @value{GDBN} commands for examining the
6016 stack allow you to see all of this information.
6018 @cindex selected frame
6019 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6020 @value{GDBN} commands refer implicitly to the selected frame. In
6021 particular, whenever you ask @value{GDBN} for the value of a variable in
6022 your program, the value is found in the selected frame. There are
6023 special @value{GDBN} commands to select whichever frame you are
6024 interested in. @xref{Selection, ,Selecting a Frame}.
6026 When your program stops, @value{GDBN} automatically selects the
6027 currently executing frame and describes it briefly, similar to the
6028 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6031 * Frames:: Stack frames
6032 * Backtrace:: Backtraces
6033 * Selection:: Selecting a frame
6034 * Frame Info:: Information on a frame
6039 @section Stack Frames
6041 @cindex frame, definition
6043 The call stack is divided up into contiguous pieces called @dfn{stack
6044 frames}, or @dfn{frames} for short; each frame is the data associated
6045 with one call to one function. The frame contains the arguments given
6046 to the function, the function's local variables, and the address at
6047 which the function is executing.
6049 @cindex initial frame
6050 @cindex outermost frame
6051 @cindex innermost frame
6052 When your program is started, the stack has only one frame, that of the
6053 function @code{main}. This is called the @dfn{initial} frame or the
6054 @dfn{outermost} frame. Each time a function is called, a new frame is
6055 made. Each time a function returns, the frame for that function invocation
6056 is eliminated. If a function is recursive, there can be many frames for
6057 the same function. The frame for the function in which execution is
6058 actually occurring is called the @dfn{innermost} frame. This is the most
6059 recently created of all the stack frames that still exist.
6061 @cindex frame pointer
6062 Inside your program, stack frames are identified by their addresses. A
6063 stack frame consists of many bytes, each of which has its own address; each
6064 kind of computer has a convention for choosing one byte whose
6065 address serves as the address of the frame. Usually this address is kept
6066 in a register called the @dfn{frame pointer register}
6067 (@pxref{Registers, $fp}) while execution is going on in that frame.
6069 @cindex frame number
6070 @value{GDBN} assigns numbers to all existing stack frames, starting with
6071 zero for the innermost frame, one for the frame that called it,
6072 and so on upward. These numbers do not really exist in your program;
6073 they are assigned by @value{GDBN} to give you a way of designating stack
6074 frames in @value{GDBN} commands.
6076 @c The -fomit-frame-pointer below perennially causes hbox overflow
6077 @c underflow problems.
6078 @cindex frameless execution
6079 Some compilers provide a way to compile functions so that they operate
6080 without stack frames. (For example, the @value{NGCC} option
6082 @samp{-fomit-frame-pointer}
6084 generates functions without a frame.)
6085 This is occasionally done with heavily used library functions to save
6086 the frame setup time. @value{GDBN} has limited facilities for dealing
6087 with these function invocations. If the innermost function invocation
6088 has no stack frame, @value{GDBN} nevertheless regards it as though
6089 it had a separate frame, which is numbered zero as usual, allowing
6090 correct tracing of the function call chain. However, @value{GDBN} has
6091 no provision for frameless functions elsewhere in the stack.
6094 @kindex frame@r{, command}
6095 @cindex current stack frame
6096 @item frame @var{args}
6097 The @code{frame} command allows you to move from one stack frame to another,
6098 and to print the stack frame you select. @var{args} may be either the
6099 address of the frame or the stack frame number. Without an argument,
6100 @code{frame} prints the current stack frame.
6102 @kindex select-frame
6103 @cindex selecting frame silently
6105 The @code{select-frame} command allows you to move from one stack frame
6106 to another without printing the frame. This is the silent version of
6114 @cindex call stack traces
6115 A backtrace is a summary of how your program got where it is. It shows one
6116 line per frame, for many frames, starting with the currently executing
6117 frame (frame zero), followed by its caller (frame one), and on up the
6122 @kindex bt @r{(@code{backtrace})}
6125 Print a backtrace of the entire stack: one line per frame for all
6126 frames in the stack.
6128 You can stop the backtrace at any time by typing the system interrupt
6129 character, normally @kbd{Ctrl-c}.
6131 @item backtrace @var{n}
6133 Similar, but print only the innermost @var{n} frames.
6135 @item backtrace -@var{n}
6137 Similar, but print only the outermost @var{n} frames.
6139 @item backtrace full
6141 @itemx bt full @var{n}
6142 @itemx bt full -@var{n}
6143 Print the values of the local variables also. @var{n} specifies the
6144 number of frames to print, as described above.
6149 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6150 are additional aliases for @code{backtrace}.
6152 @cindex multiple threads, backtrace
6153 In a multi-threaded program, @value{GDBN} by default shows the
6154 backtrace only for the current thread. To display the backtrace for
6155 several or all of the threads, use the command @code{thread apply}
6156 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6157 apply all backtrace}, @value{GDBN} will display the backtrace for all
6158 the threads; this is handy when you debug a core dump of a
6159 multi-threaded program.
6161 Each line in the backtrace shows the frame number and the function name.
6162 The program counter value is also shown---unless you use @code{set
6163 print address off}. The backtrace also shows the source file name and
6164 line number, as well as the arguments to the function. The program
6165 counter value is omitted if it is at the beginning of the code for that
6168 Here is an example of a backtrace. It was made with the command
6169 @samp{bt 3}, so it shows the innermost three frames.
6173 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6175 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6176 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6178 (More stack frames follow...)
6183 The display for frame zero does not begin with a program counter
6184 value, indicating that your program has stopped at the beginning of the
6185 code for line @code{993} of @code{builtin.c}.
6188 The value of parameter @code{data} in frame 1 has been replaced by
6189 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6190 only if it is a scalar (integer, pointer, enumeration, etc). See command
6191 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6192 on how to configure the way function parameter values are printed.
6194 @cindex optimized out, in backtrace
6195 @cindex function call arguments, optimized out
6196 If your program was compiled with optimizations, some compilers will
6197 optimize away arguments passed to functions if those arguments are
6198 never used after the call. Such optimizations generate code that
6199 passes arguments through registers, but doesn't store those arguments
6200 in the stack frame. @value{GDBN} has no way of displaying such
6201 arguments in stack frames other than the innermost one. Here's what
6202 such a backtrace might look like:
6206 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6208 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6209 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6211 (More stack frames follow...)
6216 The values of arguments that were not saved in their stack frames are
6217 shown as @samp{<optimized out>}.
6219 If you need to display the values of such optimized-out arguments,
6220 either deduce that from other variables whose values depend on the one
6221 you are interested in, or recompile without optimizations.
6223 @cindex backtrace beyond @code{main} function
6224 @cindex program entry point
6225 @cindex startup code, and backtrace
6226 Most programs have a standard user entry point---a place where system
6227 libraries and startup code transition into user code. For C this is
6228 @code{main}@footnote{
6229 Note that embedded programs (the so-called ``free-standing''
6230 environment) are not required to have a @code{main} function as the
6231 entry point. They could even have multiple entry points.}.
6232 When @value{GDBN} finds the entry function in a backtrace
6233 it will terminate the backtrace, to avoid tracing into highly
6234 system-specific (and generally uninteresting) code.
6236 If you need to examine the startup code, or limit the number of levels
6237 in a backtrace, you can change this behavior:
6240 @item set backtrace past-main
6241 @itemx set backtrace past-main on
6242 @kindex set backtrace
6243 Backtraces will continue past the user entry point.
6245 @item set backtrace past-main off
6246 Backtraces will stop when they encounter the user entry point. This is the
6249 @item show backtrace past-main
6250 @kindex show backtrace
6251 Display the current user entry point backtrace policy.
6253 @item set backtrace past-entry
6254 @itemx set backtrace past-entry on
6255 Backtraces will continue past the internal entry point of an application.
6256 This entry point is encoded by the linker when the application is built,
6257 and is likely before the user entry point @code{main} (or equivalent) is called.
6259 @item set backtrace past-entry off
6260 Backtraces will stop when they encounter the internal entry point of an
6261 application. This is the default.
6263 @item show backtrace past-entry
6264 Display the current internal entry point backtrace policy.
6266 @item set backtrace limit @var{n}
6267 @itemx set backtrace limit 0
6268 @cindex backtrace limit
6269 Limit the backtrace to @var{n} levels. A value of zero means
6272 @item show backtrace limit
6273 Display the current limit on backtrace levels.
6277 @section Selecting a Frame
6279 Most commands for examining the stack and other data in your program work on
6280 whichever stack frame is selected at the moment. Here are the commands for
6281 selecting a stack frame; all of them finish by printing a brief description
6282 of the stack frame just selected.
6285 @kindex frame@r{, selecting}
6286 @kindex f @r{(@code{frame})}
6289 Select frame number @var{n}. Recall that frame zero is the innermost
6290 (currently executing) frame, frame one is the frame that called the
6291 innermost one, and so on. The highest-numbered frame is the one for
6294 @item frame @var{addr}
6296 Select the frame at address @var{addr}. This is useful mainly if the
6297 chaining of stack frames has been damaged by a bug, making it
6298 impossible for @value{GDBN} to assign numbers properly to all frames. In
6299 addition, this can be useful when your program has multiple stacks and
6300 switches between them.
6302 On the SPARC architecture, @code{frame} needs two addresses to
6303 select an arbitrary frame: a frame pointer and a stack pointer.
6305 On the MIPS and Alpha architecture, it needs two addresses: a stack
6306 pointer and a program counter.
6308 On the 29k architecture, it needs three addresses: a register stack
6309 pointer, a program counter, and a memory stack pointer.
6313 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6314 advances toward the outermost frame, to higher frame numbers, to frames
6315 that have existed longer. @var{n} defaults to one.
6318 @kindex do @r{(@code{down})}
6320 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6321 advances toward the innermost frame, to lower frame numbers, to frames
6322 that were created more recently. @var{n} defaults to one. You may
6323 abbreviate @code{down} as @code{do}.
6326 All of these commands end by printing two lines of output describing the
6327 frame. The first line shows the frame number, the function name, the
6328 arguments, and the source file and line number of execution in that
6329 frame. The second line shows the text of that source line.
6337 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6339 10 read_input_file (argv[i]);
6343 After such a printout, the @code{list} command with no arguments
6344 prints ten lines centered on the point of execution in the frame.
6345 You can also edit the program at the point of execution with your favorite
6346 editing program by typing @code{edit}.
6347 @xref{List, ,Printing Source Lines},
6351 @kindex down-silently
6353 @item up-silently @var{n}
6354 @itemx down-silently @var{n}
6355 These two commands are variants of @code{up} and @code{down},
6356 respectively; they differ in that they do their work silently, without
6357 causing display of the new frame. They are intended primarily for use
6358 in @value{GDBN} command scripts, where the output might be unnecessary and
6363 @section Information About a Frame
6365 There are several other commands to print information about the selected
6371 When used without any argument, this command does not change which
6372 frame is selected, but prints a brief description of the currently
6373 selected stack frame. It can be abbreviated @code{f}. With an
6374 argument, this command is used to select a stack frame.
6375 @xref{Selection, ,Selecting a Frame}.
6378 @kindex info f @r{(@code{info frame})}
6381 This command prints a verbose description of the selected stack frame,
6386 the address of the frame
6388 the address of the next frame down (called by this frame)
6390 the address of the next frame up (caller of this frame)
6392 the language in which the source code corresponding to this frame is written
6394 the address of the frame's arguments
6396 the address of the frame's local variables
6398 the program counter saved in it (the address of execution in the caller frame)
6400 which registers were saved in the frame
6403 @noindent The verbose description is useful when
6404 something has gone wrong that has made the stack format fail to fit
6405 the usual conventions.
6407 @item info frame @var{addr}
6408 @itemx info f @var{addr}
6409 Print a verbose description of the frame at address @var{addr}, without
6410 selecting that frame. The selected frame remains unchanged by this
6411 command. This requires the same kind of address (more than one for some
6412 architectures) that you specify in the @code{frame} command.
6413 @xref{Selection, ,Selecting a Frame}.
6417 Print the arguments of the selected frame, each on a separate line.
6421 Print the local variables of the selected frame, each on a separate
6422 line. These are all variables (declared either static or automatic)
6423 accessible at the point of execution of the selected frame.
6429 @chapter Examining Source Files
6431 @value{GDBN} can print parts of your program's source, since the debugging
6432 information recorded in the program tells @value{GDBN} what source files were
6433 used to build it. When your program stops, @value{GDBN} spontaneously prints
6434 the line where it stopped. Likewise, when you select a stack frame
6435 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6436 execution in that frame has stopped. You can print other portions of
6437 source files by explicit command.
6439 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6440 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6441 @value{GDBN} under @sc{gnu} Emacs}.
6444 * List:: Printing source lines
6445 * Specify Location:: How to specify code locations
6446 * Edit:: Editing source files
6447 * Search:: Searching source files
6448 * Source Path:: Specifying source directories
6449 * Machine Code:: Source and machine code
6453 @section Printing Source Lines
6456 @kindex l @r{(@code{list})}
6457 To print lines from a source file, use the @code{list} command
6458 (abbreviated @code{l}). By default, ten lines are printed.
6459 There are several ways to specify what part of the file you want to
6460 print; see @ref{Specify Location}, for the full list.
6462 Here are the forms of the @code{list} command most commonly used:
6465 @item list @var{linenum}
6466 Print lines centered around line number @var{linenum} in the
6467 current source file.
6469 @item list @var{function}
6470 Print lines centered around the beginning of function
6474 Print more lines. If the last lines printed were printed with a
6475 @code{list} command, this prints lines following the last lines
6476 printed; however, if the last line printed was a solitary line printed
6477 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6478 Stack}), this prints lines centered around that line.
6481 Print lines just before the lines last printed.
6484 @cindex @code{list}, how many lines to display
6485 By default, @value{GDBN} prints ten source lines with any of these forms of
6486 the @code{list} command. You can change this using @code{set listsize}:
6489 @kindex set listsize
6490 @item set listsize @var{count}
6491 Make the @code{list} command display @var{count} source lines (unless
6492 the @code{list} argument explicitly specifies some other number).
6494 @kindex show listsize
6496 Display the number of lines that @code{list} prints.
6499 Repeating a @code{list} command with @key{RET} discards the argument,
6500 so it is equivalent to typing just @code{list}. This is more useful
6501 than listing the same lines again. An exception is made for an
6502 argument of @samp{-}; that argument is preserved in repetition so that
6503 each repetition moves up in the source file.
6505 In general, the @code{list} command expects you to supply zero, one or two
6506 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6507 of writing them (@pxref{Specify Location}), but the effect is always
6508 to specify some source line.
6510 Here is a complete description of the possible arguments for @code{list}:
6513 @item list @var{linespec}
6514 Print lines centered around the line specified by @var{linespec}.
6516 @item list @var{first},@var{last}
6517 Print lines from @var{first} to @var{last}. Both arguments are
6518 linespecs. When a @code{list} command has two linespecs, and the
6519 source file of the second linespec is omitted, this refers to
6520 the same source file as the first linespec.
6522 @item list ,@var{last}
6523 Print lines ending with @var{last}.
6525 @item list @var{first},
6526 Print lines starting with @var{first}.
6529 Print lines just after the lines last printed.
6532 Print lines just before the lines last printed.
6535 As described in the preceding table.
6538 @node Specify Location
6539 @section Specifying a Location
6540 @cindex specifying location
6543 Several @value{GDBN} commands accept arguments that specify a location
6544 of your program's code. Since @value{GDBN} is a source-level
6545 debugger, a location usually specifies some line in the source code;
6546 for that reason, locations are also known as @dfn{linespecs}.
6548 Here are all the different ways of specifying a code location that
6549 @value{GDBN} understands:
6553 Specifies the line number @var{linenum} of the current source file.
6556 @itemx +@var{offset}
6557 Specifies the line @var{offset} lines before or after the @dfn{current
6558 line}. For the @code{list} command, the current line is the last one
6559 printed; for the breakpoint commands, this is the line at which
6560 execution stopped in the currently selected @dfn{stack frame}
6561 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6562 used as the second of the two linespecs in a @code{list} command,
6563 this specifies the line @var{offset} lines up or down from the first
6566 @item @var{filename}:@var{linenum}
6567 Specifies the line @var{linenum} in the source file @var{filename}.
6568 If @var{filename} is a relative file name, then it will match any
6569 source file name with the same trailing components. For example, if
6570 @var{filename} is @samp{gcc/expr.c}, then it will match source file
6571 name of @file{/build/trunk/gcc/expr.c}, but not
6572 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
6574 @item @var{function}
6575 Specifies the line that begins the body of the function @var{function}.
6576 For example, in C, this is the line with the open brace.
6578 @item @var{function}:@var{label}
6579 Specifies the line where @var{label} appears in @var{function}.
6581 @item @var{filename}:@var{function}
6582 Specifies the line that begins the body of the function @var{function}
6583 in the file @var{filename}. You only need the file name with a
6584 function name to avoid ambiguity when there are identically named
6585 functions in different source files.
6588 Specifies the line at which the label named @var{label} appears.
6589 @value{GDBN} searches for the label in the function corresponding to
6590 the currently selected stack frame. If there is no current selected
6591 stack frame (for instance, if the inferior is not running), then
6592 @value{GDBN} will not search for a label.
6594 @item *@var{address}
6595 Specifies the program address @var{address}. For line-oriented
6596 commands, such as @code{list} and @code{edit}, this specifies a source
6597 line that contains @var{address}. For @code{break} and other
6598 breakpoint oriented commands, this can be used to set breakpoints in
6599 parts of your program which do not have debugging information or
6602 Here @var{address} may be any expression valid in the current working
6603 language (@pxref{Languages, working language}) that specifies a code
6604 address. In addition, as a convenience, @value{GDBN} extends the
6605 semantics of expressions used in locations to cover the situations
6606 that frequently happen during debugging. Here are the various forms
6610 @item @var{expression}
6611 Any expression valid in the current working language.
6613 @item @var{funcaddr}
6614 An address of a function or procedure derived from its name. In C,
6615 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6616 simply the function's name @var{function} (and actually a special case
6617 of a valid expression). In Pascal and Modula-2, this is
6618 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6619 (although the Pascal form also works).
6621 This form specifies the address of the function's first instruction,
6622 before the stack frame and arguments have been set up.
6624 @item '@var{filename}'::@var{funcaddr}
6625 Like @var{funcaddr} above, but also specifies the name of the source
6626 file explicitly. This is useful if the name of the function does not
6627 specify the function unambiguously, e.g., if there are several
6628 functions with identical names in different source files.
6635 @section Editing Source Files
6636 @cindex editing source files
6639 @kindex e @r{(@code{edit})}
6640 To edit the lines in a source file, use the @code{edit} command.
6641 The editing program of your choice
6642 is invoked with the current line set to
6643 the active line in the program.
6644 Alternatively, there are several ways to specify what part of the file you
6645 want to print if you want to see other parts of the program:
6648 @item edit @var{location}
6649 Edit the source file specified by @code{location}. Editing starts at
6650 that @var{location}, e.g., at the specified source line of the
6651 specified file. @xref{Specify Location}, for all the possible forms
6652 of the @var{location} argument; here are the forms of the @code{edit}
6653 command most commonly used:
6656 @item edit @var{number}
6657 Edit the current source file with @var{number} as the active line number.
6659 @item edit @var{function}
6660 Edit the file containing @var{function} at the beginning of its definition.
6665 @subsection Choosing your Editor
6666 You can customize @value{GDBN} to use any editor you want
6668 The only restriction is that your editor (say @code{ex}), recognizes the
6669 following command-line syntax:
6671 ex +@var{number} file
6673 The optional numeric value +@var{number} specifies the number of the line in
6674 the file where to start editing.}.
6675 By default, it is @file{@value{EDITOR}}, but you can change this
6676 by setting the environment variable @code{EDITOR} before using
6677 @value{GDBN}. For example, to configure @value{GDBN} to use the
6678 @code{vi} editor, you could use these commands with the @code{sh} shell:
6684 or in the @code{csh} shell,
6686 setenv EDITOR /usr/bin/vi
6691 @section Searching Source Files
6692 @cindex searching source files
6694 There are two commands for searching through the current source file for a
6699 @kindex forward-search
6700 @item forward-search @var{regexp}
6701 @itemx search @var{regexp}
6702 The command @samp{forward-search @var{regexp}} checks each line,
6703 starting with the one following the last line listed, for a match for
6704 @var{regexp}. It lists the line that is found. You can use the
6705 synonym @samp{search @var{regexp}} or abbreviate the command name as
6708 @kindex reverse-search
6709 @item reverse-search @var{regexp}
6710 The command @samp{reverse-search @var{regexp}} checks each line, starting
6711 with the one before the last line listed and going backward, for a match
6712 for @var{regexp}. It lists the line that is found. You can abbreviate
6713 this command as @code{rev}.
6717 @section Specifying Source Directories
6720 @cindex directories for source files
6721 Executable programs sometimes do not record the directories of the source
6722 files from which they were compiled, just the names. Even when they do,
6723 the directories could be moved between the compilation and your debugging
6724 session. @value{GDBN} has a list of directories to search for source files;
6725 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6726 it tries all the directories in the list, in the order they are present
6727 in the list, until it finds a file with the desired name.
6729 For example, suppose an executable references the file
6730 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6731 @file{/mnt/cross}. The file is first looked up literally; if this
6732 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6733 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6734 message is printed. @value{GDBN} does not look up the parts of the
6735 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6736 Likewise, the subdirectories of the source path are not searched: if
6737 the source path is @file{/mnt/cross}, and the binary refers to
6738 @file{foo.c}, @value{GDBN} would not find it under
6739 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6741 Plain file names, relative file names with leading directories, file
6742 names containing dots, etc.@: are all treated as described above; for
6743 instance, if the source path is @file{/mnt/cross}, and the source file
6744 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6745 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6746 that---@file{/mnt/cross/foo.c}.
6748 Note that the executable search path is @emph{not} used to locate the
6751 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6752 any information it has cached about where source files are found and where
6753 each line is in the file.
6757 When you start @value{GDBN}, its source path includes only @samp{cdir}
6758 and @samp{cwd}, in that order.
6759 To add other directories, use the @code{directory} command.
6761 The search path is used to find both program source files and @value{GDBN}
6762 script files (read using the @samp{-command} option and @samp{source} command).
6764 In addition to the source path, @value{GDBN} provides a set of commands
6765 that manage a list of source path substitution rules. A @dfn{substitution
6766 rule} specifies how to rewrite source directories stored in the program's
6767 debug information in case the sources were moved to a different
6768 directory between compilation and debugging. A rule is made of
6769 two strings, the first specifying what needs to be rewritten in
6770 the path, and the second specifying how it should be rewritten.
6771 In @ref{set substitute-path}, we name these two parts @var{from} and
6772 @var{to} respectively. @value{GDBN} does a simple string replacement
6773 of @var{from} with @var{to} at the start of the directory part of the
6774 source file name, and uses that result instead of the original file
6775 name to look up the sources.
6777 Using the previous example, suppose the @file{foo-1.0} tree has been
6778 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6779 @value{GDBN} to replace @file{/usr/src} in all source path names with
6780 @file{/mnt/cross}. The first lookup will then be
6781 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6782 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6783 substitution rule, use the @code{set substitute-path} command
6784 (@pxref{set substitute-path}).
6786 To avoid unexpected substitution results, a rule is applied only if the
6787 @var{from} part of the directory name ends at a directory separator.
6788 For instance, a rule substituting @file{/usr/source} into
6789 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6790 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6791 is applied only at the beginning of the directory name, this rule will
6792 not be applied to @file{/root/usr/source/baz.c} either.
6794 In many cases, you can achieve the same result using the @code{directory}
6795 command. However, @code{set substitute-path} can be more efficient in
6796 the case where the sources are organized in a complex tree with multiple
6797 subdirectories. With the @code{directory} command, you need to add each
6798 subdirectory of your project. If you moved the entire tree while
6799 preserving its internal organization, then @code{set substitute-path}
6800 allows you to direct the debugger to all the sources with one single
6803 @code{set substitute-path} is also more than just a shortcut command.
6804 The source path is only used if the file at the original location no
6805 longer exists. On the other hand, @code{set substitute-path} modifies
6806 the debugger behavior to look at the rewritten location instead. So, if
6807 for any reason a source file that is not relevant to your executable is
6808 located at the original location, a substitution rule is the only
6809 method available to point @value{GDBN} at the new location.
6811 @cindex @samp{--with-relocated-sources}
6812 @cindex default source path substitution
6813 You can configure a default source path substitution rule by
6814 configuring @value{GDBN} with the
6815 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6816 should be the name of a directory under @value{GDBN}'s configured
6817 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6818 directory names in debug information under @var{dir} will be adjusted
6819 automatically if the installed @value{GDBN} is moved to a new
6820 location. This is useful if @value{GDBN}, libraries or executables
6821 with debug information and corresponding source code are being moved
6825 @item directory @var{dirname} @dots{}
6826 @item dir @var{dirname} @dots{}
6827 Add directory @var{dirname} to the front of the source path. Several
6828 directory names may be given to this command, separated by @samp{:}
6829 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6830 part of absolute file names) or
6831 whitespace. You may specify a directory that is already in the source
6832 path; this moves it forward, so @value{GDBN} searches it sooner.
6836 @vindex $cdir@r{, convenience variable}
6837 @vindex $cwd@r{, convenience variable}
6838 @cindex compilation directory
6839 @cindex current directory
6840 @cindex working directory
6841 @cindex directory, current
6842 @cindex directory, compilation
6843 You can use the string @samp{$cdir} to refer to the compilation
6844 directory (if one is recorded), and @samp{$cwd} to refer to the current
6845 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6846 tracks the current working directory as it changes during your @value{GDBN}
6847 session, while the latter is immediately expanded to the current
6848 directory at the time you add an entry to the source path.
6851 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6853 @c RET-repeat for @code{directory} is explicitly disabled, but since
6854 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6856 @item set directories @var{path-list}
6857 @kindex set directories
6858 Set the source path to @var{path-list}.
6859 @samp{$cdir:$cwd} are added if missing.
6861 @item show directories
6862 @kindex show directories
6863 Print the source path: show which directories it contains.
6865 @anchor{set substitute-path}
6866 @item set substitute-path @var{from} @var{to}
6867 @kindex set substitute-path
6868 Define a source path substitution rule, and add it at the end of the
6869 current list of existing substitution rules. If a rule with the same
6870 @var{from} was already defined, then the old rule is also deleted.
6872 For example, if the file @file{/foo/bar/baz.c} was moved to
6873 @file{/mnt/cross/baz.c}, then the command
6876 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6880 will tell @value{GDBN} to replace @samp{/usr/src} with
6881 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6882 @file{baz.c} even though it was moved.
6884 In the case when more than one substitution rule have been defined,
6885 the rules are evaluated one by one in the order where they have been
6886 defined. The first one matching, if any, is selected to perform
6889 For instance, if we had entered the following commands:
6892 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6893 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6897 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6898 @file{/mnt/include/defs.h} by using the first rule. However, it would
6899 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6900 @file{/mnt/src/lib/foo.c}.
6903 @item unset substitute-path [path]
6904 @kindex unset substitute-path
6905 If a path is specified, search the current list of substitution rules
6906 for a rule that would rewrite that path. Delete that rule if found.
6907 A warning is emitted by the debugger if no rule could be found.
6909 If no path is specified, then all substitution rules are deleted.
6911 @item show substitute-path [path]
6912 @kindex show substitute-path
6913 If a path is specified, then print the source path substitution rule
6914 which would rewrite that path, if any.
6916 If no path is specified, then print all existing source path substitution
6921 If your source path is cluttered with directories that are no longer of
6922 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6923 versions of source. You can correct the situation as follows:
6927 Use @code{directory} with no argument to reset the source path to its default value.
6930 Use @code{directory} with suitable arguments to reinstall the
6931 directories you want in the source path. You can add all the
6932 directories in one command.
6936 @section Source and Machine Code
6937 @cindex source line and its code address
6939 You can use the command @code{info line} to map source lines to program
6940 addresses (and vice versa), and the command @code{disassemble} to display
6941 a range of addresses as machine instructions. You can use the command
6942 @code{set disassemble-next-line} to set whether to disassemble next
6943 source line when execution stops. When run under @sc{gnu} Emacs
6944 mode, the @code{info line} command causes the arrow to point to the
6945 line specified. Also, @code{info line} prints addresses in symbolic form as
6950 @item info line @var{linespec}
6951 Print the starting and ending addresses of the compiled code for
6952 source line @var{linespec}. You can specify source lines in any of
6953 the ways documented in @ref{Specify Location}.
6956 For example, we can use @code{info line} to discover the location of
6957 the object code for the first line of function
6958 @code{m4_changequote}:
6960 @c FIXME: I think this example should also show the addresses in
6961 @c symbolic form, as they usually would be displayed.
6963 (@value{GDBP}) info line m4_changequote
6964 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6968 @cindex code address and its source line
6969 We can also inquire (using @code{*@var{addr}} as the form for
6970 @var{linespec}) what source line covers a particular address:
6972 (@value{GDBP}) info line *0x63ff
6973 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6976 @cindex @code{$_} and @code{info line}
6977 @cindex @code{x} command, default address
6978 @kindex x@r{(examine), and} info line
6979 After @code{info line}, the default address for the @code{x} command
6980 is changed to the starting address of the line, so that @samp{x/i} is
6981 sufficient to begin examining the machine code (@pxref{Memory,
6982 ,Examining Memory}). Also, this address is saved as the value of the
6983 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6988 @cindex assembly instructions
6989 @cindex instructions, assembly
6990 @cindex machine instructions
6991 @cindex listing machine instructions
6993 @itemx disassemble /m
6994 @itemx disassemble /r
6995 This specialized command dumps a range of memory as machine
6996 instructions. It can also print mixed source+disassembly by specifying
6997 the @code{/m} modifier and print the raw instructions in hex as well as
6998 in symbolic form by specifying the @code{/r}.
6999 The default memory range is the function surrounding the
7000 program counter of the selected frame. A single argument to this
7001 command is a program counter value; @value{GDBN} dumps the function
7002 surrounding this value. When two arguments are given, they should
7003 be separated by a comma, possibly surrounded by whitespace. The
7004 arguments specify a range of addresses to dump, in one of two forms:
7007 @item @var{start},@var{end}
7008 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
7009 @item @var{start},+@var{length}
7010 the addresses from @var{start} (inclusive) to
7011 @code{@var{start}+@var{length}} (exclusive).
7015 When 2 arguments are specified, the name of the function is also
7016 printed (since there could be several functions in the given range).
7018 The argument(s) can be any expression yielding a numeric value, such as
7019 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
7021 If the range of memory being disassembled contains current program counter,
7022 the instruction at that location is shown with a @code{=>} marker.
7025 The following example shows the disassembly of a range of addresses of
7026 HP PA-RISC 2.0 code:
7029 (@value{GDBP}) disas 0x32c4, 0x32e4
7030 Dump of assembler code from 0x32c4 to 0x32e4:
7031 0x32c4 <main+204>: addil 0,dp
7032 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
7033 0x32cc <main+212>: ldil 0x3000,r31
7034 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
7035 0x32d4 <main+220>: ldo 0(r31),rp
7036 0x32d8 <main+224>: addil -0x800,dp
7037 0x32dc <main+228>: ldo 0x588(r1),r26
7038 0x32e0 <main+232>: ldil 0x3000,r31
7039 End of assembler dump.
7042 Here is an example showing mixed source+assembly for Intel x86, when the
7043 program is stopped just after function prologue:
7046 (@value{GDBP}) disas /m main
7047 Dump of assembler code for function main:
7049 0x08048330 <+0>: push %ebp
7050 0x08048331 <+1>: mov %esp,%ebp
7051 0x08048333 <+3>: sub $0x8,%esp
7052 0x08048336 <+6>: and $0xfffffff0,%esp
7053 0x08048339 <+9>: sub $0x10,%esp
7055 6 printf ("Hello.\n");
7056 => 0x0804833c <+12>: movl $0x8048440,(%esp)
7057 0x08048343 <+19>: call 0x8048284 <puts@@plt>
7061 0x08048348 <+24>: mov $0x0,%eax
7062 0x0804834d <+29>: leave
7063 0x0804834e <+30>: ret
7065 End of assembler dump.
7068 Here is another example showing raw instructions in hex for AMD x86-64,
7071 (gdb) disas /r 0x400281,+10
7072 Dump of assembler code from 0x400281 to 0x40028b:
7073 0x0000000000400281: 38 36 cmp %dh,(%rsi)
7074 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
7075 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
7076 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7077 End of assembler dump.
7080 Some architectures have more than one commonly-used set of instruction
7081 mnemonics or other syntax.
7083 For programs that were dynamically linked and use shared libraries,
7084 instructions that call functions or branch to locations in the shared
7085 libraries might show a seemingly bogus location---it's actually a
7086 location of the relocation table. On some architectures, @value{GDBN}
7087 might be able to resolve these to actual function names.
7090 @kindex set disassembly-flavor
7091 @cindex Intel disassembly flavor
7092 @cindex AT&T disassembly flavor
7093 @item set disassembly-flavor @var{instruction-set}
7094 Select the instruction set to use when disassembling the
7095 program via the @code{disassemble} or @code{x/i} commands.
7097 Currently this command is only defined for the Intel x86 family. You
7098 can set @var{instruction-set} to either @code{intel} or @code{att}.
7099 The default is @code{att}, the AT&T flavor used by default by Unix
7100 assemblers for x86-based targets.
7102 @kindex show disassembly-flavor
7103 @item show disassembly-flavor
7104 Show the current setting of the disassembly flavor.
7108 @kindex set disassemble-next-line
7109 @kindex show disassemble-next-line
7110 @item set disassemble-next-line
7111 @itemx show disassemble-next-line
7112 Control whether or not @value{GDBN} will disassemble the next source
7113 line or instruction when execution stops. If ON, @value{GDBN} will
7114 display disassembly of the next source line when execution of the
7115 program being debugged stops. This is @emph{in addition} to
7116 displaying the source line itself, which @value{GDBN} always does if
7117 possible. If the next source line cannot be displayed for some reason
7118 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7119 info in the debug info), @value{GDBN} will display disassembly of the
7120 next @emph{instruction} instead of showing the next source line. If
7121 AUTO, @value{GDBN} will display disassembly of next instruction only
7122 if the source line cannot be displayed. This setting causes
7123 @value{GDBN} to display some feedback when you step through a function
7124 with no line info or whose source file is unavailable. The default is
7125 OFF, which means never display the disassembly of the next line or
7131 @chapter Examining Data
7133 @cindex printing data
7134 @cindex examining data
7137 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
7138 @c document because it is nonstandard... Under Epoch it displays in a
7139 @c different window or something like that.
7140 The usual way to examine data in your program is with the @code{print}
7141 command (abbreviated @code{p}), or its synonym @code{inspect}. It
7142 evaluates and prints the value of an expression of the language your
7143 program is written in (@pxref{Languages, ,Using @value{GDBN} with
7144 Different Languages}). It may also print the expression using a
7145 Python-based pretty-printer (@pxref{Pretty Printing}).
7148 @item print @var{expr}
7149 @itemx print /@var{f} @var{expr}
7150 @var{expr} is an expression (in the source language). By default the
7151 value of @var{expr} is printed in a format appropriate to its data type;
7152 you can choose a different format by specifying @samp{/@var{f}}, where
7153 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
7157 @itemx print /@var{f}
7158 @cindex reprint the last value
7159 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
7160 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
7161 conveniently inspect the same value in an alternative format.
7164 A more low-level way of examining data is with the @code{x} command.
7165 It examines data in memory at a specified address and prints it in a
7166 specified format. @xref{Memory, ,Examining Memory}.
7168 If you are interested in information about types, or about how the
7169 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
7170 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7174 * Expressions:: Expressions
7175 * Ambiguous Expressions:: Ambiguous Expressions
7176 * Variables:: Program variables
7177 * Arrays:: Artificial arrays
7178 * Output Formats:: Output formats
7179 * Memory:: Examining memory
7180 * Auto Display:: Automatic display
7181 * Print Settings:: Print settings
7182 * Pretty Printing:: Python pretty printing
7183 * Value History:: Value history
7184 * Convenience Vars:: Convenience variables
7185 * Registers:: Registers
7186 * Floating Point Hardware:: Floating point hardware
7187 * Vector Unit:: Vector Unit
7188 * OS Information:: Auxiliary data provided by operating system
7189 * Memory Region Attributes:: Memory region attributes
7190 * Dump/Restore Files:: Copy between memory and a file
7191 * Core File Generation:: Cause a program dump its core
7192 * Character Sets:: Debugging programs that use a different
7193 character set than GDB does
7194 * Caching Remote Data:: Data caching for remote targets
7195 * Searching Memory:: Searching memory for a sequence of bytes
7199 @section Expressions
7202 @code{print} and many other @value{GDBN} commands accept an expression and
7203 compute its value. Any kind of constant, variable or operator defined
7204 by the programming language you are using is valid in an expression in
7205 @value{GDBN}. This includes conditional expressions, function calls,
7206 casts, and string constants. It also includes preprocessor macros, if
7207 you compiled your program to include this information; see
7210 @cindex arrays in expressions
7211 @value{GDBN} supports array constants in expressions input by
7212 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
7213 you can use the command @code{print @{1, 2, 3@}} to create an array
7214 of three integers. If you pass an array to a function or assign it
7215 to a program variable, @value{GDBN} copies the array to memory that
7216 is @code{malloc}ed in the target program.
7218 Because C is so widespread, most of the expressions shown in examples in
7219 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
7220 Languages}, for information on how to use expressions in other
7223 In this section, we discuss operators that you can use in @value{GDBN}
7224 expressions regardless of your programming language.
7226 @cindex casts, in expressions
7227 Casts are supported in all languages, not just in C, because it is so
7228 useful to cast a number into a pointer in order to examine a structure
7229 at that address in memory.
7230 @c FIXME: casts supported---Mod2 true?
7232 @value{GDBN} supports these operators, in addition to those common
7233 to programming languages:
7237 @samp{@@} is a binary operator for treating parts of memory as arrays.
7238 @xref{Arrays, ,Artificial Arrays}, for more information.
7241 @samp{::} allows you to specify a variable in terms of the file or
7242 function where it is defined. @xref{Variables, ,Program Variables}.
7244 @cindex @{@var{type}@}
7245 @cindex type casting memory
7246 @cindex memory, viewing as typed object
7247 @cindex casts, to view memory
7248 @item @{@var{type}@} @var{addr}
7249 Refers to an object of type @var{type} stored at address @var{addr} in
7250 memory. @var{addr} may be any expression whose value is an integer or
7251 pointer (but parentheses are required around binary operators, just as in
7252 a cast). This construct is allowed regardless of what kind of data is
7253 normally supposed to reside at @var{addr}.
7256 @node Ambiguous Expressions
7257 @section Ambiguous Expressions
7258 @cindex ambiguous expressions
7260 Expressions can sometimes contain some ambiguous elements. For instance,
7261 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7262 a single function name to be defined several times, for application in
7263 different contexts. This is called @dfn{overloading}. Another example
7264 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7265 templates and is typically instantiated several times, resulting in
7266 the same function name being defined in different contexts.
7268 In some cases and depending on the language, it is possible to adjust
7269 the expression to remove the ambiguity. For instance in C@t{++}, you
7270 can specify the signature of the function you want to break on, as in
7271 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7272 qualified name of your function often makes the expression unambiguous
7275 When an ambiguity that needs to be resolved is detected, the debugger
7276 has the capability to display a menu of numbered choices for each
7277 possibility, and then waits for the selection with the prompt @samp{>}.
7278 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7279 aborts the current command. If the command in which the expression was
7280 used allows more than one choice to be selected, the next option in the
7281 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7284 For example, the following session excerpt shows an attempt to set a
7285 breakpoint at the overloaded symbol @code{String::after}.
7286 We choose three particular definitions of that function name:
7288 @c FIXME! This is likely to change to show arg type lists, at least
7291 (@value{GDBP}) b String::after
7294 [2] file:String.cc; line number:867
7295 [3] file:String.cc; line number:860
7296 [4] file:String.cc; line number:875
7297 [5] file:String.cc; line number:853
7298 [6] file:String.cc; line number:846
7299 [7] file:String.cc; line number:735
7301 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7302 Breakpoint 2 at 0xb344: file String.cc, line 875.
7303 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7304 Multiple breakpoints were set.
7305 Use the "delete" command to delete unwanted
7312 @kindex set multiple-symbols
7313 @item set multiple-symbols @var{mode}
7314 @cindex multiple-symbols menu
7316 This option allows you to adjust the debugger behavior when an expression
7319 By default, @var{mode} is set to @code{all}. If the command with which
7320 the expression is used allows more than one choice, then @value{GDBN}
7321 automatically selects all possible choices. For instance, inserting
7322 a breakpoint on a function using an ambiguous name results in a breakpoint
7323 inserted on each possible match. However, if a unique choice must be made,
7324 then @value{GDBN} uses the menu to help you disambiguate the expression.
7325 For instance, printing the address of an overloaded function will result
7326 in the use of the menu.
7328 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7329 when an ambiguity is detected.
7331 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7332 an error due to the ambiguity and the command is aborted.
7334 @kindex show multiple-symbols
7335 @item show multiple-symbols
7336 Show the current value of the @code{multiple-symbols} setting.
7340 @section Program Variables
7342 The most common kind of expression to use is the name of a variable
7345 Variables in expressions are understood in the selected stack frame
7346 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7350 global (or file-static)
7357 visible according to the scope rules of the
7358 programming language from the point of execution in that frame
7361 @noindent This means that in the function
7376 you can examine and use the variable @code{a} whenever your program is
7377 executing within the function @code{foo}, but you can only use or
7378 examine the variable @code{b} while your program is executing inside
7379 the block where @code{b} is declared.
7381 @cindex variable name conflict
7382 There is an exception: you can refer to a variable or function whose
7383 scope is a single source file even if the current execution point is not
7384 in this file. But it is possible to have more than one such variable or
7385 function with the same name (in different source files). If that
7386 happens, referring to that name has unpredictable effects. If you wish,
7387 you can specify a static variable in a particular function or file by
7388 using the colon-colon (@code{::}) notation:
7390 @cindex colon-colon, context for variables/functions
7392 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7393 @cindex @code{::}, context for variables/functions
7396 @var{file}::@var{variable}
7397 @var{function}::@var{variable}
7401 Here @var{file} or @var{function} is the name of the context for the
7402 static @var{variable}. In the case of file names, you can use quotes to
7403 make sure @value{GDBN} parses the file name as a single word---for example,
7404 to print a global value of @code{x} defined in @file{f2.c}:
7407 (@value{GDBP}) p 'f2.c'::x
7410 The @code{::} notation is normally used for referring to
7411 static variables, since you typically disambiguate uses of local variables
7412 in functions by selecting the appropriate frame and using the
7413 simple name of the variable. However, you may also use this notation
7414 to refer to local variables in frames enclosing the selected frame:
7423 process (a); /* Stop here */
7434 For example, if there is a breakpoint at the commented line,
7435 here is what you might see
7436 when the program stops after executing the call @code{bar(0)}:
7441 (@value{GDBP}) p bar::a
7444 #2 0x080483d0 in foo (a=5) at foobar.c:12
7447 (@value{GDBP}) p bar::a
7451 @cindex C@t{++} scope resolution
7452 These uses of @samp{::} are very rarely in conflict with the very similar
7453 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7454 scope resolution operator in @value{GDBN} expressions.
7455 @c FIXME: Um, so what happens in one of those rare cases where it's in
7458 @cindex wrong values
7459 @cindex variable values, wrong
7460 @cindex function entry/exit, wrong values of variables
7461 @cindex optimized code, wrong values of variables
7463 @emph{Warning:} Occasionally, a local variable may appear to have the
7464 wrong value at certain points in a function---just after entry to a new
7465 scope, and just before exit.
7467 You may see this problem when you are stepping by machine instructions.
7468 This is because, on most machines, it takes more than one instruction to
7469 set up a stack frame (including local variable definitions); if you are
7470 stepping by machine instructions, variables may appear to have the wrong
7471 values until the stack frame is completely built. On exit, it usually
7472 also takes more than one machine instruction to destroy a stack frame;
7473 after you begin stepping through that group of instructions, local
7474 variable definitions may be gone.
7476 This may also happen when the compiler does significant optimizations.
7477 To be sure of always seeing accurate values, turn off all optimization
7480 @cindex ``No symbol "foo" in current context''
7481 Another possible effect of compiler optimizations is to optimize
7482 unused variables out of existence, or assign variables to registers (as
7483 opposed to memory addresses). Depending on the support for such cases
7484 offered by the debug info format used by the compiler, @value{GDBN}
7485 might not be able to display values for such local variables. If that
7486 happens, @value{GDBN} will print a message like this:
7489 No symbol "foo" in current context.
7492 To solve such problems, either recompile without optimizations, or use a
7493 different debug info format, if the compiler supports several such
7494 formats. @xref{Compilation}, for more information on choosing compiler
7495 options. @xref{C, ,C and C@t{++}}, for more information about debug
7496 info formats that are best suited to C@t{++} programs.
7498 If you ask to print an object whose contents are unknown to
7499 @value{GDBN}, e.g., because its data type is not completely specified
7500 by the debug information, @value{GDBN} will say @samp{<incomplete
7501 type>}. @xref{Symbols, incomplete type}, for more about this.
7503 If you append @kbd{@@entry} string to a function parameter name you get its
7504 value at the time the function got called. If the value is not available an
7505 error message is printed. Entry values are available only with some compilers.
7506 Entry values are normally also printed at the function parameter list according
7507 to @ref{set print entry-values}.
7510 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
7516 (gdb) print i@@entry
7520 Strings are identified as arrays of @code{char} values without specified
7521 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7522 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7523 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7524 defines literal string type @code{"char"} as @code{char} without a sign.
7529 signed char var1[] = "A";
7532 You get during debugging
7537 $2 = @{65 'A', 0 '\0'@}
7541 @section Artificial Arrays
7543 @cindex artificial array
7545 @kindex @@@r{, referencing memory as an array}
7546 It is often useful to print out several successive objects of the
7547 same type in memory; a section of an array, or an array of
7548 dynamically determined size for which only a pointer exists in the
7551 You can do this by referring to a contiguous span of memory as an
7552 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7553 operand of @samp{@@} should be the first element of the desired array
7554 and be an individual object. The right operand should be the desired length
7555 of the array. The result is an array value whose elements are all of
7556 the type of the left argument. The first element is actually the left
7557 argument; the second element comes from bytes of memory immediately
7558 following those that hold the first element, and so on. Here is an
7559 example. If a program says
7562 int *array = (int *) malloc (len * sizeof (int));
7566 you can print the contents of @code{array} with
7572 The left operand of @samp{@@} must reside in memory. Array values made
7573 with @samp{@@} in this way behave just like other arrays in terms of
7574 subscripting, and are coerced to pointers when used in expressions.
7575 Artificial arrays most often appear in expressions via the value history
7576 (@pxref{Value History, ,Value History}), after printing one out.
7578 Another way to create an artificial array is to use a cast.
7579 This re-interprets a value as if it were an array.
7580 The value need not be in memory:
7582 (@value{GDBP}) p/x (short[2])0x12345678
7583 $1 = @{0x1234, 0x5678@}
7586 As a convenience, if you leave the array length out (as in
7587 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7588 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7590 (@value{GDBP}) p/x (short[])0x12345678
7591 $2 = @{0x1234, 0x5678@}
7594 Sometimes the artificial array mechanism is not quite enough; in
7595 moderately complex data structures, the elements of interest may not
7596 actually be adjacent---for example, if you are interested in the values
7597 of pointers in an array. One useful work-around in this situation is
7598 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7599 Variables}) as a counter in an expression that prints the first
7600 interesting value, and then repeat that expression via @key{RET}. For
7601 instance, suppose you have an array @code{dtab} of pointers to
7602 structures, and you are interested in the values of a field @code{fv}
7603 in each structure. Here is an example of what you might type:
7613 @node Output Formats
7614 @section Output Formats
7616 @cindex formatted output
7617 @cindex output formats
7618 By default, @value{GDBN} prints a value according to its data type. Sometimes
7619 this is not what you want. For example, you might want to print a number
7620 in hex, or a pointer in decimal. Or you might want to view data in memory
7621 at a certain address as a character string or as an instruction. To do
7622 these things, specify an @dfn{output format} when you print a value.
7624 The simplest use of output formats is to say how to print a value
7625 already computed. This is done by starting the arguments of the
7626 @code{print} command with a slash and a format letter. The format
7627 letters supported are:
7631 Regard the bits of the value as an integer, and print the integer in
7635 Print as integer in signed decimal.
7638 Print as integer in unsigned decimal.
7641 Print as integer in octal.
7644 Print as integer in binary. The letter @samp{t} stands for ``two''.
7645 @footnote{@samp{b} cannot be used because these format letters are also
7646 used with the @code{x} command, where @samp{b} stands for ``byte'';
7647 see @ref{Memory,,Examining Memory}.}
7650 @cindex unknown address, locating
7651 @cindex locate address
7652 Print as an address, both absolute in hexadecimal and as an offset from
7653 the nearest preceding symbol. You can use this format used to discover
7654 where (in what function) an unknown address is located:
7657 (@value{GDBP}) p/a 0x54320
7658 $3 = 0x54320 <_initialize_vx+396>
7662 The command @code{info symbol 0x54320} yields similar results.
7663 @xref{Symbols, info symbol}.
7666 Regard as an integer and print it as a character constant. This
7667 prints both the numerical value and its character representation. The
7668 character representation is replaced with the octal escape @samp{\nnn}
7669 for characters outside the 7-bit @sc{ascii} range.
7671 Without this format, @value{GDBN} displays @code{char},
7672 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7673 constants. Single-byte members of vectors are displayed as integer
7677 Regard the bits of the value as a floating point number and print
7678 using typical floating point syntax.
7681 @cindex printing strings
7682 @cindex printing byte arrays
7683 Regard as a string, if possible. With this format, pointers to single-byte
7684 data are displayed as null-terminated strings and arrays of single-byte data
7685 are displayed as fixed-length strings. Other values are displayed in their
7688 Without this format, @value{GDBN} displays pointers to and arrays of
7689 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7690 strings. Single-byte members of a vector are displayed as an integer
7694 @cindex raw printing
7695 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7696 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7697 Printing}). This typically results in a higher-level display of the
7698 value's contents. The @samp{r} format bypasses any Python
7699 pretty-printer which might exist.
7702 For example, to print the program counter in hex (@pxref{Registers}), type
7709 Note that no space is required before the slash; this is because command
7710 names in @value{GDBN} cannot contain a slash.
7712 To reprint the last value in the value history with a different format,
7713 you can use the @code{print} command with just a format and no
7714 expression. For example, @samp{p/x} reprints the last value in hex.
7717 @section Examining Memory
7719 You can use the command @code{x} (for ``examine'') to examine memory in
7720 any of several formats, independently of your program's data types.
7722 @cindex examining memory
7724 @kindex x @r{(examine memory)}
7725 @item x/@var{nfu} @var{addr}
7728 Use the @code{x} command to examine memory.
7731 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7732 much memory to display and how to format it; @var{addr} is an
7733 expression giving the address where you want to start displaying memory.
7734 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7735 Several commands set convenient defaults for @var{addr}.
7738 @item @var{n}, the repeat count
7739 The repeat count is a decimal integer; the default is 1. It specifies
7740 how much memory (counting by units @var{u}) to display.
7741 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7744 @item @var{f}, the display format
7745 The display format is one of the formats used by @code{print}
7746 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7747 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7748 The default is @samp{x} (hexadecimal) initially. The default changes
7749 each time you use either @code{x} or @code{print}.
7751 @item @var{u}, the unit size
7752 The unit size is any of
7758 Halfwords (two bytes).
7760 Words (four bytes). This is the initial default.
7762 Giant words (eight bytes).
7765 Each time you specify a unit size with @code{x}, that size becomes the
7766 default unit the next time you use @code{x}. For the @samp{i} format,
7767 the unit size is ignored and is normally not written. For the @samp{s} format,
7768 the unit size defaults to @samp{b}, unless it is explicitly given.
7769 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
7770 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
7771 Note that the results depend on the programming language of the
7772 current compilation unit. If the language is C, the @samp{s}
7773 modifier will use the UTF-16 encoding while @samp{w} will use
7774 UTF-32. The encoding is set by the programming language and cannot
7777 @item @var{addr}, starting display address
7778 @var{addr} is the address where you want @value{GDBN} to begin displaying
7779 memory. The expression need not have a pointer value (though it may);
7780 it is always interpreted as an integer address of a byte of memory.
7781 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7782 @var{addr} is usually just after the last address examined---but several
7783 other commands also set the default address: @code{info breakpoints} (to
7784 the address of the last breakpoint listed), @code{info line} (to the
7785 starting address of a line), and @code{print} (if you use it to display
7786 a value from memory).
7789 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7790 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7791 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7792 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7793 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7795 Since the letters indicating unit sizes are all distinct from the
7796 letters specifying output formats, you do not have to remember whether
7797 unit size or format comes first; either order works. The output
7798 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7799 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7801 Even though the unit size @var{u} is ignored for the formats @samp{s}
7802 and @samp{i}, you might still want to use a count @var{n}; for example,
7803 @samp{3i} specifies that you want to see three machine instructions,
7804 including any operands. For convenience, especially when used with
7805 the @code{display} command, the @samp{i} format also prints branch delay
7806 slot instructions, if any, beyond the count specified, which immediately
7807 follow the last instruction that is within the count. The command
7808 @code{disassemble} gives an alternative way of inspecting machine
7809 instructions; see @ref{Machine Code,,Source and Machine Code}.
7811 All the defaults for the arguments to @code{x} are designed to make it
7812 easy to continue scanning memory with minimal specifications each time
7813 you use @code{x}. For example, after you have inspected three machine
7814 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7815 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7816 the repeat count @var{n} is used again; the other arguments default as
7817 for successive uses of @code{x}.
7819 When examining machine instructions, the instruction at current program
7820 counter is shown with a @code{=>} marker. For example:
7823 (@value{GDBP}) x/5i $pc-6
7824 0x804837f <main+11>: mov %esp,%ebp
7825 0x8048381 <main+13>: push %ecx
7826 0x8048382 <main+14>: sub $0x4,%esp
7827 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7828 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7831 @cindex @code{$_}, @code{$__}, and value history
7832 The addresses and contents printed by the @code{x} command are not saved
7833 in the value history because there is often too much of them and they
7834 would get in the way. Instead, @value{GDBN} makes these values available for
7835 subsequent use in expressions as values of the convenience variables
7836 @code{$_} and @code{$__}. After an @code{x} command, the last address
7837 examined is available for use in expressions in the convenience variable
7838 @code{$_}. The contents of that address, as examined, are available in
7839 the convenience variable @code{$__}.
7841 If the @code{x} command has a repeat count, the address and contents saved
7842 are from the last memory unit printed; this is not the same as the last
7843 address printed if several units were printed on the last line of output.
7845 @cindex remote memory comparison
7846 @cindex verify remote memory image
7847 When you are debugging a program running on a remote target machine
7848 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7849 remote machine's memory against the executable file you downloaded to
7850 the target. The @code{compare-sections} command is provided for such
7854 @kindex compare-sections
7855 @item compare-sections @r{[}@var{section-name}@r{]}
7856 Compare the data of a loadable section @var{section-name} in the
7857 executable file of the program being debugged with the same section in
7858 the remote machine's memory, and report any mismatches. With no
7859 arguments, compares all loadable sections. This command's
7860 availability depends on the target's support for the @code{"qCRC"}
7865 @section Automatic Display
7866 @cindex automatic display
7867 @cindex display of expressions
7869 If you find that you want to print the value of an expression frequently
7870 (to see how it changes), you might want to add it to the @dfn{automatic
7871 display list} so that @value{GDBN} prints its value each time your program stops.
7872 Each expression added to the list is given a number to identify it;
7873 to remove an expression from the list, you specify that number.
7874 The automatic display looks like this:
7878 3: bar[5] = (struct hack *) 0x3804
7882 This display shows item numbers, expressions and their current values. As with
7883 displays you request manually using @code{x} or @code{print}, you can
7884 specify the output format you prefer; in fact, @code{display} decides
7885 whether to use @code{print} or @code{x} depending your format
7886 specification---it uses @code{x} if you specify either the @samp{i}
7887 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7891 @item display @var{expr}
7892 Add the expression @var{expr} to the list of expressions to display
7893 each time your program stops. @xref{Expressions, ,Expressions}.
7895 @code{display} does not repeat if you press @key{RET} again after using it.
7897 @item display/@var{fmt} @var{expr}
7898 For @var{fmt} specifying only a display format and not a size or
7899 count, add the expression @var{expr} to the auto-display list but
7900 arrange to display it each time in the specified format @var{fmt}.
7901 @xref{Output Formats,,Output Formats}.
7903 @item display/@var{fmt} @var{addr}
7904 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7905 number of units, add the expression @var{addr} as a memory address to
7906 be examined each time your program stops. Examining means in effect
7907 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7910 For example, @samp{display/i $pc} can be helpful, to see the machine
7911 instruction about to be executed each time execution stops (@samp{$pc}
7912 is a common name for the program counter; @pxref{Registers, ,Registers}).
7915 @kindex delete display
7917 @item undisplay @var{dnums}@dots{}
7918 @itemx delete display @var{dnums}@dots{}
7919 Remove items from the list of expressions to display. Specify the
7920 numbers of the displays that you want affected with the command
7921 argument @var{dnums}. It can be a single display number, one of the
7922 numbers shown in the first field of the @samp{info display} display;
7923 or it could be a range of display numbers, as in @code{2-4}.
7925 @code{undisplay} does not repeat if you press @key{RET} after using it.
7926 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7928 @kindex disable display
7929 @item disable display @var{dnums}@dots{}
7930 Disable the display of item numbers @var{dnums}. A disabled display
7931 item is not printed automatically, but is not forgotten. It may be
7932 enabled again later. Specify the numbers of the displays that you
7933 want affected with the command argument @var{dnums}. It can be a
7934 single display number, one of the numbers shown in the first field of
7935 the @samp{info display} display; or it could be a range of display
7936 numbers, as in @code{2-4}.
7938 @kindex enable display
7939 @item enable display @var{dnums}@dots{}
7940 Enable display of item numbers @var{dnums}. It becomes effective once
7941 again in auto display of its expression, until you specify otherwise.
7942 Specify the numbers of the displays that you want affected with the
7943 command argument @var{dnums}. It can be a single display number, one
7944 of the numbers shown in the first field of the @samp{info display}
7945 display; or it could be a range of display numbers, as in @code{2-4}.
7948 Display the current values of the expressions on the list, just as is
7949 done when your program stops.
7951 @kindex info display
7953 Print the list of expressions previously set up to display
7954 automatically, each one with its item number, but without showing the
7955 values. This includes disabled expressions, which are marked as such.
7956 It also includes expressions which would not be displayed right now
7957 because they refer to automatic variables not currently available.
7960 @cindex display disabled out of scope
7961 If a display expression refers to local variables, then it does not make
7962 sense outside the lexical context for which it was set up. Such an
7963 expression is disabled when execution enters a context where one of its
7964 variables is not defined. For example, if you give the command
7965 @code{display last_char} while inside a function with an argument
7966 @code{last_char}, @value{GDBN} displays this argument while your program
7967 continues to stop inside that function. When it stops elsewhere---where
7968 there is no variable @code{last_char}---the display is disabled
7969 automatically. The next time your program stops where @code{last_char}
7970 is meaningful, you can enable the display expression once again.
7972 @node Print Settings
7973 @section Print Settings
7975 @cindex format options
7976 @cindex print settings
7977 @value{GDBN} provides the following ways to control how arrays, structures,
7978 and symbols are printed.
7981 These settings are useful for debugging programs in any language:
7985 @item set print address
7986 @itemx set print address on
7987 @cindex print/don't print memory addresses
7988 @value{GDBN} prints memory addresses showing the location of stack
7989 traces, structure values, pointer values, breakpoints, and so forth,
7990 even when it also displays the contents of those addresses. The default
7991 is @code{on}. For example, this is what a stack frame display looks like with
7992 @code{set print address on}:
7997 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7999 530 if (lquote != def_lquote)
8003 @item set print address off
8004 Do not print addresses when displaying their contents. For example,
8005 this is the same stack frame displayed with @code{set print address off}:
8009 (@value{GDBP}) set print addr off
8011 #0 set_quotes (lq="<<", rq=">>") at input.c:530
8012 530 if (lquote != def_lquote)
8016 You can use @samp{set print address off} to eliminate all machine
8017 dependent displays from the @value{GDBN} interface. For example, with
8018 @code{print address off}, you should get the same text for backtraces on
8019 all machines---whether or not they involve pointer arguments.
8022 @item show print address
8023 Show whether or not addresses are to be printed.
8026 When @value{GDBN} prints a symbolic address, it normally prints the
8027 closest earlier symbol plus an offset. If that symbol does not uniquely
8028 identify the address (for example, it is a name whose scope is a single
8029 source file), you may need to clarify. One way to do this is with
8030 @code{info line}, for example @samp{info line *0x4537}. Alternately,
8031 you can set @value{GDBN} to print the source file and line number when
8032 it prints a symbolic address:
8035 @item set print symbol-filename on
8036 @cindex source file and line of a symbol
8037 @cindex symbol, source file and line
8038 Tell @value{GDBN} to print the source file name and line number of a
8039 symbol in the symbolic form of an address.
8041 @item set print symbol-filename off
8042 Do not print source file name and line number of a symbol. This is the
8045 @item show print symbol-filename
8046 Show whether or not @value{GDBN} will print the source file name and
8047 line number of a symbol in the symbolic form of an address.
8050 Another situation where it is helpful to show symbol filenames and line
8051 numbers is when disassembling code; @value{GDBN} shows you the line
8052 number and source file that corresponds to each instruction.
8054 Also, you may wish to see the symbolic form only if the address being
8055 printed is reasonably close to the closest earlier symbol:
8058 @item set print max-symbolic-offset @var{max-offset}
8059 @cindex maximum value for offset of closest symbol
8060 Tell @value{GDBN} to only display the symbolic form of an address if the
8061 offset between the closest earlier symbol and the address is less than
8062 @var{max-offset}. The default is 0, which tells @value{GDBN}
8063 to always print the symbolic form of an address if any symbol precedes it.
8065 @item show print max-symbolic-offset
8066 Ask how large the maximum offset is that @value{GDBN} prints in a
8070 @cindex wild pointer, interpreting
8071 @cindex pointer, finding referent
8072 If you have a pointer and you are not sure where it points, try
8073 @samp{set print symbol-filename on}. Then you can determine the name
8074 and source file location of the variable where it points, using
8075 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
8076 For example, here @value{GDBN} shows that a variable @code{ptt} points
8077 at another variable @code{t}, defined in @file{hi2.c}:
8080 (@value{GDBP}) set print symbol-filename on
8081 (@value{GDBP}) p/a ptt
8082 $4 = 0xe008 <t in hi2.c>
8086 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
8087 does not show the symbol name and filename of the referent, even with
8088 the appropriate @code{set print} options turned on.
8091 Other settings control how different kinds of objects are printed:
8094 @item set print array
8095 @itemx set print array on
8096 @cindex pretty print arrays
8097 Pretty print arrays. This format is more convenient to read,
8098 but uses more space. The default is off.
8100 @item set print array off
8101 Return to compressed format for arrays.
8103 @item show print array
8104 Show whether compressed or pretty format is selected for displaying
8107 @cindex print array indexes
8108 @item set print array-indexes
8109 @itemx set print array-indexes on
8110 Print the index of each element when displaying arrays. May be more
8111 convenient to locate a given element in the array or quickly find the
8112 index of a given element in that printed array. The default is off.
8114 @item set print array-indexes off
8115 Stop printing element indexes when displaying arrays.
8117 @item show print array-indexes
8118 Show whether the index of each element is printed when displaying
8121 @item set print elements @var{number-of-elements}
8122 @cindex number of array elements to print
8123 @cindex limit on number of printed array elements
8124 Set a limit on how many elements of an array @value{GDBN} will print.
8125 If @value{GDBN} is printing a large array, it stops printing after it has
8126 printed the number of elements set by the @code{set print elements} command.
8127 This limit also applies to the display of strings.
8128 When @value{GDBN} starts, this limit is set to 200.
8129 Setting @var{number-of-elements} to zero means that the printing is unlimited.
8131 @item show print elements
8132 Display the number of elements of a large array that @value{GDBN} will print.
8133 If the number is 0, then the printing is unlimited.
8135 @item set print frame-arguments @var{value}
8136 @kindex set print frame-arguments
8137 @cindex printing frame argument values
8138 @cindex print all frame argument values
8139 @cindex print frame argument values for scalars only
8140 @cindex do not print frame argument values
8141 This command allows to control how the values of arguments are printed
8142 when the debugger prints a frame (@pxref{Frames}). The possible
8147 The values of all arguments are printed.
8150 Print the value of an argument only if it is a scalar. The value of more
8151 complex arguments such as arrays, structures, unions, etc, is replaced
8152 by @code{@dots{}}. This is the default. Here is an example where
8153 only scalar arguments are shown:
8156 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
8161 None of the argument values are printed. Instead, the value of each argument
8162 is replaced by @code{@dots{}}. In this case, the example above now becomes:
8165 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
8170 By default, only scalar arguments are printed. This command can be used
8171 to configure the debugger to print the value of all arguments, regardless
8172 of their type. However, it is often advantageous to not print the value
8173 of more complex parameters. For instance, it reduces the amount of
8174 information printed in each frame, making the backtrace more readable.
8175 Also, it improves performance when displaying Ada frames, because
8176 the computation of large arguments can sometimes be CPU-intensive,
8177 especially in large applications. Setting @code{print frame-arguments}
8178 to @code{scalars} (the default) or @code{none} avoids this computation,
8179 thus speeding up the display of each Ada frame.
8181 @item show print frame-arguments
8182 Show how the value of arguments should be displayed when printing a frame.
8184 @anchor{set print entry-values}
8185 @item set print entry-values @var{value}
8186 @kindex set print entry-values
8187 Set printing of frame argument values at function entry. In some cases
8188 @value{GDBN} can determine the value of function argument which was passed by
8189 the function caller, even if the value was modified inside the called function
8190 and therefore is different. With optimized code, the current value could be
8191 unavailable, but the entry value may still be known.
8193 The default value is @code{default} (see below for its description). Older
8194 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
8195 this feature will behave in the @code{default} setting the same way as with the
8198 This functionality is currently supported only by DWARF 2 debugging format and
8199 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
8200 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
8203 The @var{value} parameter can be one of the following:
8207 Print only actual parameter values, never print values from function entry
8211 #0 different (val=6)
8212 #0 lost (val=<optimized out>)
8214 #0 invalid (val=<optimized out>)
8218 Print only parameter values from function entry point. The actual parameter
8219 values are never printed.
8221 #0 equal (val@@entry=5)
8222 #0 different (val@@entry=5)
8223 #0 lost (val@@entry=5)
8224 #0 born (val@@entry=<optimized out>)
8225 #0 invalid (val@@entry=<optimized out>)
8229 Print only parameter values from function entry point. If value from function
8230 entry point is not known while the actual value is known, print the actual
8231 value for such parameter.
8233 #0 equal (val@@entry=5)
8234 #0 different (val@@entry=5)
8235 #0 lost (val@@entry=5)
8237 #0 invalid (val@@entry=<optimized out>)
8241 Print actual parameter values. If actual parameter value is not known while
8242 value from function entry point is known, print the entry point value for such
8246 #0 different (val=6)
8247 #0 lost (val@@entry=5)
8249 #0 invalid (val=<optimized out>)
8253 Always print both the actual parameter value and its value from function entry
8254 point, even if values of one or both are not available due to compiler
8257 #0 equal (val=5, val@@entry=5)
8258 #0 different (val=6, val@@entry=5)
8259 #0 lost (val=<optimized out>, val@@entry=5)
8260 #0 born (val=10, val@@entry=<optimized out>)
8261 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
8265 Print the actual parameter value if it is known and also its value from
8266 function entry point if it is known. If neither is known, print for the actual
8267 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
8268 values are known and identical, print the shortened
8269 @code{param=param@@entry=VALUE} notation.
8271 #0 equal (val=val@@entry=5)
8272 #0 different (val=6, val@@entry=5)
8273 #0 lost (val@@entry=5)
8275 #0 invalid (val=<optimized out>)
8279 Always print the actual parameter value. Print also its value from function
8280 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
8281 if both values are known and identical, print the shortened
8282 @code{param=param@@entry=VALUE} notation.
8284 #0 equal (val=val@@entry=5)
8285 #0 different (val=6, val@@entry=5)
8286 #0 lost (val=<optimized out>, val@@entry=5)
8288 #0 invalid (val=<optimized out>)
8292 For analysis messages on possible failures of frame argument values at function
8293 entry resolution see @ref{set debug entry-values}.
8295 @item show print entry-values
8296 Show the method being used for printing of frame argument values at function
8299 @item set print repeats
8300 @cindex repeated array elements
8301 Set the threshold for suppressing display of repeated array
8302 elements. When the number of consecutive identical elements of an
8303 array exceeds the threshold, @value{GDBN} prints the string
8304 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
8305 identical repetitions, instead of displaying the identical elements
8306 themselves. Setting the threshold to zero will cause all elements to
8307 be individually printed. The default threshold is 10.
8309 @item show print repeats
8310 Display the current threshold for printing repeated identical
8313 @item set print null-stop
8314 @cindex @sc{null} elements in arrays
8315 Cause @value{GDBN} to stop printing the characters of an array when the first
8316 @sc{null} is encountered. This is useful when large arrays actually
8317 contain only short strings.
8320 @item show print null-stop
8321 Show whether @value{GDBN} stops printing an array on the first
8322 @sc{null} character.
8324 @item set print pretty on
8325 @cindex print structures in indented form
8326 @cindex indentation in structure display
8327 Cause @value{GDBN} to print structures in an indented format with one member
8328 per line, like this:
8343 @item set print pretty off
8344 Cause @value{GDBN} to print structures in a compact format, like this:
8348 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
8349 meat = 0x54 "Pork"@}
8354 This is the default format.
8356 @item show print pretty
8357 Show which format @value{GDBN} is using to print structures.
8359 @item set print sevenbit-strings on
8360 @cindex eight-bit characters in strings
8361 @cindex octal escapes in strings
8362 Print using only seven-bit characters; if this option is set,
8363 @value{GDBN} displays any eight-bit characters (in strings or
8364 character values) using the notation @code{\}@var{nnn}. This setting is
8365 best if you are working in English (@sc{ascii}) and you use the
8366 high-order bit of characters as a marker or ``meta'' bit.
8368 @item set print sevenbit-strings off
8369 Print full eight-bit characters. This allows the use of more
8370 international character sets, and is the default.
8372 @item show print sevenbit-strings
8373 Show whether or not @value{GDBN} is printing only seven-bit characters.
8375 @item set print union on
8376 @cindex unions in structures, printing
8377 Tell @value{GDBN} to print unions which are contained in structures
8378 and other unions. This is the default setting.
8380 @item set print union off
8381 Tell @value{GDBN} not to print unions which are contained in
8382 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
8385 @item show print union
8386 Ask @value{GDBN} whether or not it will print unions which are contained in
8387 structures and other unions.
8389 For example, given the declarations
8392 typedef enum @{Tree, Bug@} Species;
8393 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
8394 typedef enum @{Caterpillar, Cocoon, Butterfly@}
8405 struct thing foo = @{Tree, @{Acorn@}@};
8409 with @code{set print union on} in effect @samp{p foo} would print
8412 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
8416 and with @code{set print union off} in effect it would print
8419 $1 = @{it = Tree, form = @{...@}@}
8423 @code{set print union} affects programs written in C-like languages
8429 These settings are of interest when debugging C@t{++} programs:
8432 @cindex demangling C@t{++} names
8433 @item set print demangle
8434 @itemx set print demangle on
8435 Print C@t{++} names in their source form rather than in the encoded
8436 (``mangled'') form passed to the assembler and linker for type-safe
8437 linkage. The default is on.
8439 @item show print demangle
8440 Show whether C@t{++} names are printed in mangled or demangled form.
8442 @item set print asm-demangle
8443 @itemx set print asm-demangle on
8444 Print C@t{++} names in their source form rather than their mangled form, even
8445 in assembler code printouts such as instruction disassemblies.
8448 @item show print asm-demangle
8449 Show whether C@t{++} names in assembly listings are printed in mangled
8452 @cindex C@t{++} symbol decoding style
8453 @cindex symbol decoding style, C@t{++}
8454 @kindex set demangle-style
8455 @item set demangle-style @var{style}
8456 Choose among several encoding schemes used by different compilers to
8457 represent C@t{++} names. The choices for @var{style} are currently:
8461 Allow @value{GDBN} to choose a decoding style by inspecting your program.
8464 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
8465 This is the default.
8468 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
8471 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
8474 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
8475 @strong{Warning:} this setting alone is not sufficient to allow
8476 debugging @code{cfront}-generated executables. @value{GDBN} would
8477 require further enhancement to permit that.
8480 If you omit @var{style}, you will see a list of possible formats.
8482 @item show demangle-style
8483 Display the encoding style currently in use for decoding C@t{++} symbols.
8485 @item set print object
8486 @itemx set print object on
8487 @cindex derived type of an object, printing
8488 @cindex display derived types
8489 When displaying a pointer to an object, identify the @emph{actual}
8490 (derived) type of the object rather than the @emph{declared} type, using
8491 the virtual function table. Note that the virtual function table is
8492 required---this feature can only work for objects that have run-time
8493 type identification; a single virtual method in the object's declared
8496 @item set print object off
8497 Display only the declared type of objects, without reference to the
8498 virtual function table. This is the default setting.
8500 @item show print object
8501 Show whether actual, or declared, object types are displayed.
8503 @item set print static-members
8504 @itemx set print static-members on
8505 @cindex static members of C@t{++} objects
8506 Print static members when displaying a C@t{++} object. The default is on.
8508 @item set print static-members off
8509 Do not print static members when displaying a C@t{++} object.
8511 @item show print static-members
8512 Show whether C@t{++} static members are printed or not.
8514 @item set print pascal_static-members
8515 @itemx set print pascal_static-members on
8516 @cindex static members of Pascal objects
8517 @cindex Pascal objects, static members display
8518 Print static members when displaying a Pascal object. The default is on.
8520 @item set print pascal_static-members off
8521 Do not print static members when displaying a Pascal object.
8523 @item show print pascal_static-members
8524 Show whether Pascal static members are printed or not.
8526 @c These don't work with HP ANSI C++ yet.
8527 @item set print vtbl
8528 @itemx set print vtbl on
8529 @cindex pretty print C@t{++} virtual function tables
8530 @cindex virtual functions (C@t{++}) display
8531 @cindex VTBL display
8532 Pretty print C@t{++} virtual function tables. The default is off.
8533 (The @code{vtbl} commands do not work on programs compiled with the HP
8534 ANSI C@t{++} compiler (@code{aCC}).)
8536 @item set print vtbl off
8537 Do not pretty print C@t{++} virtual function tables.
8539 @item show print vtbl
8540 Show whether C@t{++} virtual function tables are pretty printed, or not.
8543 @node Pretty Printing
8544 @section Pretty Printing
8546 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8547 Python code. It greatly simplifies the display of complex objects. This
8548 mechanism works for both MI and the CLI.
8551 * Pretty-Printer Introduction:: Introduction to pretty-printers
8552 * Pretty-Printer Example:: An example pretty-printer
8553 * Pretty-Printer Commands:: Pretty-printer commands
8556 @node Pretty-Printer Introduction
8557 @subsection Pretty-Printer Introduction
8559 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
8560 registered for the value. If there is then @value{GDBN} invokes the
8561 pretty-printer to print the value. Otherwise the value is printed normally.
8563 Pretty-printers are normally named. This makes them easy to manage.
8564 The @samp{info pretty-printer} command will list all the installed
8565 pretty-printers with their names.
8566 If a pretty-printer can handle multiple data types, then its
8567 @dfn{subprinters} are the printers for the individual data types.
8568 Each such subprinter has its own name.
8569 The format of the name is @var{printer-name};@var{subprinter-name}.
8571 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
8572 Typically they are automatically loaded and registered when the corresponding
8573 debug information is loaded, thus making them available without having to
8574 do anything special.
8576 There are three places where a pretty-printer can be registered.
8580 Pretty-printers registered globally are available when debugging
8584 Pretty-printers registered with a program space are available only
8585 when debugging that program.
8586 @xref{Progspaces In Python}, for more details on program spaces in Python.
8589 Pretty-printers registered with an objfile are loaded and unloaded
8590 with the corresponding objfile (e.g., shared library).
8591 @xref{Objfiles In Python}, for more details on objfiles in Python.
8594 @xref{Selecting Pretty-Printers}, for further information on how
8595 pretty-printers are selected,
8597 @xref{Writing a Pretty-Printer}, for implementing pretty printers
8600 @node Pretty-Printer Example
8601 @subsection Pretty-Printer Example
8603 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
8606 (@value{GDBP}) print s
8608 static npos = 4294967295,
8610 <std::allocator<char>> = @{
8611 <__gnu_cxx::new_allocator<char>> = @{
8612 <No data fields>@}, <No data fields>
8614 members of std::basic_string<char, std::char_traits<char>,
8615 std::allocator<char> >::_Alloc_hider:
8616 _M_p = 0x804a014 "abcd"
8621 With a pretty-printer for @code{std::string} only the contents are printed:
8624 (@value{GDBP}) print s
8628 @node Pretty-Printer Commands
8629 @subsection Pretty-Printer Commands
8630 @cindex pretty-printer commands
8633 @kindex info pretty-printer
8634 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8635 Print the list of installed pretty-printers.
8636 This includes disabled pretty-printers, which are marked as such.
8638 @var{object-regexp} is a regular expression matching the objects
8639 whose pretty-printers to list.
8640 Objects can be @code{global}, the program space's file
8641 (@pxref{Progspaces In Python}),
8642 and the object files within that program space (@pxref{Objfiles In Python}).
8643 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
8644 looks up a printer from these three objects.
8646 @var{name-regexp} is a regular expression matching the name of the printers
8649 @kindex disable pretty-printer
8650 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8651 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8652 A disabled pretty-printer is not forgotten, it may be enabled again later.
8654 @kindex enable pretty-printer
8655 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8656 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8661 Suppose we have three pretty-printers installed: one from library1.so
8662 named @code{foo} that prints objects of type @code{foo}, and
8663 another from library2.so named @code{bar} that prints two types of objects,
8664 @code{bar1} and @code{bar2}.
8667 (gdb) info pretty-printer
8674 (gdb) info pretty-printer library2
8679 (gdb) disable pretty-printer library1
8681 2 of 3 printers enabled
8682 (gdb) info pretty-printer
8689 (gdb) disable pretty-printer library2 bar:bar1
8691 1 of 3 printers enabled
8692 (gdb) info pretty-printer library2
8699 (gdb) disable pretty-printer library2 bar
8701 0 of 3 printers enabled
8702 (gdb) info pretty-printer library2
8711 Note that for @code{bar} the entire printer can be disabled,
8712 as can each individual subprinter.
8715 @section Value History
8717 @cindex value history
8718 @cindex history of values printed by @value{GDBN}
8719 Values printed by the @code{print} command are saved in the @value{GDBN}
8720 @dfn{value history}. This allows you to refer to them in other expressions.
8721 Values are kept until the symbol table is re-read or discarded
8722 (for example with the @code{file} or @code{symbol-file} commands).
8723 When the symbol table changes, the value history is discarded,
8724 since the values may contain pointers back to the types defined in the
8729 @cindex history number
8730 The values printed are given @dfn{history numbers} by which you can
8731 refer to them. These are successive integers starting with one.
8732 @code{print} shows you the history number assigned to a value by
8733 printing @samp{$@var{num} = } before the value; here @var{num} is the
8736 To refer to any previous value, use @samp{$} followed by the value's
8737 history number. The way @code{print} labels its output is designed to
8738 remind you of this. Just @code{$} refers to the most recent value in
8739 the history, and @code{$$} refers to the value before that.
8740 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
8741 is the value just prior to @code{$$}, @code{$$1} is equivalent to
8742 @code{$$}, and @code{$$0} is equivalent to @code{$}.
8744 For example, suppose you have just printed a pointer to a structure and
8745 want to see the contents of the structure. It suffices to type
8751 If you have a chain of structures where the component @code{next} points
8752 to the next one, you can print the contents of the next one with this:
8759 You can print successive links in the chain by repeating this
8760 command---which you can do by just typing @key{RET}.
8762 Note that the history records values, not expressions. If the value of
8763 @code{x} is 4 and you type these commands:
8771 then the value recorded in the value history by the @code{print} command
8772 remains 4 even though the value of @code{x} has changed.
8777 Print the last ten values in the value history, with their item numbers.
8778 This is like @samp{p@ $$9} repeated ten times, except that @code{show
8779 values} does not change the history.
8781 @item show values @var{n}
8782 Print ten history values centered on history item number @var{n}.
8785 Print ten history values just after the values last printed. If no more
8786 values are available, @code{show values +} produces no display.
8789 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
8790 same effect as @samp{show values +}.
8792 @node Convenience Vars
8793 @section Convenience Variables
8795 @cindex convenience variables
8796 @cindex user-defined variables
8797 @value{GDBN} provides @dfn{convenience variables} that you can use within
8798 @value{GDBN} to hold on to a value and refer to it later. These variables
8799 exist entirely within @value{GDBN}; they are not part of your program, and
8800 setting a convenience variable has no direct effect on further execution
8801 of your program. That is why you can use them freely.
8803 Convenience variables are prefixed with @samp{$}. Any name preceded by
8804 @samp{$} can be used for a convenience variable, unless it is one of
8805 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
8806 (Value history references, in contrast, are @emph{numbers} preceded
8807 by @samp{$}. @xref{Value History, ,Value History}.)
8809 You can save a value in a convenience variable with an assignment
8810 expression, just as you would set a variable in your program.
8814 set $foo = *object_ptr
8818 would save in @code{$foo} the value contained in the object pointed to by
8821 Using a convenience variable for the first time creates it, but its
8822 value is @code{void} until you assign a new value. You can alter the
8823 value with another assignment at any time.
8825 Convenience variables have no fixed types. You can assign a convenience
8826 variable any type of value, including structures and arrays, even if
8827 that variable already has a value of a different type. The convenience
8828 variable, when used as an expression, has the type of its current value.
8831 @kindex show convenience
8832 @cindex show all user variables
8833 @item show convenience
8834 Print a list of convenience variables used so far, and their values.
8835 Abbreviated @code{show conv}.
8837 @kindex init-if-undefined
8838 @cindex convenience variables, initializing
8839 @item init-if-undefined $@var{variable} = @var{expression}
8840 Set a convenience variable if it has not already been set. This is useful
8841 for user-defined commands that keep some state. It is similar, in concept,
8842 to using local static variables with initializers in C (except that
8843 convenience variables are global). It can also be used to allow users to
8844 override default values used in a command script.
8846 If the variable is already defined then the expression is not evaluated so
8847 any side-effects do not occur.
8850 One of the ways to use a convenience variable is as a counter to be
8851 incremented or a pointer to be advanced. For example, to print
8852 a field from successive elements of an array of structures:
8856 print bar[$i++]->contents
8860 Repeat that command by typing @key{RET}.
8862 Some convenience variables are created automatically by @value{GDBN} and given
8863 values likely to be useful.
8866 @vindex $_@r{, convenience variable}
8868 The variable @code{$_} is automatically set by the @code{x} command to
8869 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8870 commands which provide a default address for @code{x} to examine also
8871 set @code{$_} to that address; these commands include @code{info line}
8872 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8873 except when set by the @code{x} command, in which case it is a pointer
8874 to the type of @code{$__}.
8876 @vindex $__@r{, convenience variable}
8878 The variable @code{$__} is automatically set by the @code{x} command
8879 to the value found in the last address examined. Its type is chosen
8880 to match the format in which the data was printed.
8883 @vindex $_exitcode@r{, convenience variable}
8884 The variable @code{$_exitcode} is automatically set to the exit code when
8885 the program being debugged terminates.
8888 @vindex $_sdata@r{, inspect, convenience variable}
8889 The variable @code{$_sdata} contains extra collected static tracepoint
8890 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
8891 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
8892 if extra static tracepoint data has not been collected.
8895 @vindex $_siginfo@r{, convenience variable}
8896 The variable @code{$_siginfo} contains extra signal information
8897 (@pxref{extra signal information}). Note that @code{$_siginfo}
8898 could be empty, if the application has not yet received any signals.
8899 For example, it will be empty before you execute the @code{run} command.
8902 @vindex $_tlb@r{, convenience variable}
8903 The variable @code{$_tlb} is automatically set when debugging
8904 applications running on MS-Windows in native mode or connected to
8905 gdbserver that supports the @code{qGetTIBAddr} request.
8906 @xref{General Query Packets}.
8907 This variable contains the address of the thread information block.
8911 On HP-UX systems, if you refer to a function or variable name that
8912 begins with a dollar sign, @value{GDBN} searches for a user or system
8913 name first, before it searches for a convenience variable.
8915 @cindex convenience functions
8916 @value{GDBN} also supplies some @dfn{convenience functions}. These
8917 have a syntax similar to convenience variables. A convenience
8918 function can be used in an expression just like an ordinary function;
8919 however, a convenience function is implemented internally to
8924 @kindex help function
8925 @cindex show all convenience functions
8926 Print a list of all convenience functions.
8933 You can refer to machine register contents, in expressions, as variables
8934 with names starting with @samp{$}. The names of registers are different
8935 for each machine; use @code{info registers} to see the names used on
8939 @kindex info registers
8940 @item info registers
8941 Print the names and values of all registers except floating-point
8942 and vector registers (in the selected stack frame).
8944 @kindex info all-registers
8945 @cindex floating point registers
8946 @item info all-registers
8947 Print the names and values of all registers, including floating-point
8948 and vector registers (in the selected stack frame).
8950 @item info registers @var{regname} @dots{}
8951 Print the @dfn{relativized} value of each specified register @var{regname}.
8952 As discussed in detail below, register values are normally relative to
8953 the selected stack frame. @var{regname} may be any register name valid on
8954 the machine you are using, with or without the initial @samp{$}.
8957 @cindex stack pointer register
8958 @cindex program counter register
8959 @cindex process status register
8960 @cindex frame pointer register
8961 @cindex standard registers
8962 @value{GDBN} has four ``standard'' register names that are available (in
8963 expressions) on most machines---whenever they do not conflict with an
8964 architecture's canonical mnemonics for registers. The register names
8965 @code{$pc} and @code{$sp} are used for the program counter register and
8966 the stack pointer. @code{$fp} is used for a register that contains a
8967 pointer to the current stack frame, and @code{$ps} is used for a
8968 register that contains the processor status. For example,
8969 you could print the program counter in hex with
8976 or print the instruction to be executed next with
8983 or add four to the stack pointer@footnote{This is a way of removing
8984 one word from the stack, on machines where stacks grow downward in
8985 memory (most machines, nowadays). This assumes that the innermost
8986 stack frame is selected; setting @code{$sp} is not allowed when other
8987 stack frames are selected. To pop entire frames off the stack,
8988 regardless of machine architecture, use @code{return};
8989 see @ref{Returning, ,Returning from a Function}.} with
8995 Whenever possible, these four standard register names are available on
8996 your machine even though the machine has different canonical mnemonics,
8997 so long as there is no conflict. The @code{info registers} command
8998 shows the canonical names. For example, on the SPARC, @code{info
8999 registers} displays the processor status register as @code{$psr} but you
9000 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
9001 is an alias for the @sc{eflags} register.
9003 @value{GDBN} always considers the contents of an ordinary register as an
9004 integer when the register is examined in this way. Some machines have
9005 special registers which can hold nothing but floating point; these
9006 registers are considered to have floating point values. There is no way
9007 to refer to the contents of an ordinary register as floating point value
9008 (although you can @emph{print} it as a floating point value with
9009 @samp{print/f $@var{regname}}).
9011 Some registers have distinct ``raw'' and ``virtual'' data formats. This
9012 means that the data format in which the register contents are saved by
9013 the operating system is not the same one that your program normally
9014 sees. For example, the registers of the 68881 floating point
9015 coprocessor are always saved in ``extended'' (raw) format, but all C
9016 programs expect to work with ``double'' (virtual) format. In such
9017 cases, @value{GDBN} normally works with the virtual format only (the format
9018 that makes sense for your program), but the @code{info registers} command
9019 prints the data in both formats.
9021 @cindex SSE registers (x86)
9022 @cindex MMX registers (x86)
9023 Some machines have special registers whose contents can be interpreted
9024 in several different ways. For example, modern x86-based machines
9025 have SSE and MMX registers that can hold several values packed
9026 together in several different formats. @value{GDBN} refers to such
9027 registers in @code{struct} notation:
9030 (@value{GDBP}) print $xmm1
9032 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
9033 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
9034 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
9035 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
9036 v4_int32 = @{0, 20657912, 11, 13@},
9037 v2_int64 = @{88725056443645952, 55834574859@},
9038 uint128 = 0x0000000d0000000b013b36f800000000
9043 To set values of such registers, you need to tell @value{GDBN} which
9044 view of the register you wish to change, as if you were assigning
9045 value to a @code{struct} member:
9048 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
9051 Normally, register values are relative to the selected stack frame
9052 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
9053 value that the register would contain if all stack frames farther in
9054 were exited and their saved registers restored. In order to see the
9055 true contents of hardware registers, you must select the innermost
9056 frame (with @samp{frame 0}).
9058 However, @value{GDBN} must deduce where registers are saved, from the machine
9059 code generated by your compiler. If some registers are not saved, or if
9060 @value{GDBN} is unable to locate the saved registers, the selected stack
9061 frame makes no difference.
9063 @node Floating Point Hardware
9064 @section Floating Point Hardware
9065 @cindex floating point
9067 Depending on the configuration, @value{GDBN} may be able to give
9068 you more information about the status of the floating point hardware.
9073 Display hardware-dependent information about the floating
9074 point unit. The exact contents and layout vary depending on the
9075 floating point chip. Currently, @samp{info float} is supported on
9076 the ARM and x86 machines.
9080 @section Vector Unit
9083 Depending on the configuration, @value{GDBN} may be able to give you
9084 more information about the status of the vector unit.
9089 Display information about the vector unit. The exact contents and
9090 layout vary depending on the hardware.
9093 @node OS Information
9094 @section Operating System Auxiliary Information
9095 @cindex OS information
9097 @value{GDBN} provides interfaces to useful OS facilities that can help
9098 you debug your program.
9100 @cindex @code{ptrace} system call
9101 @cindex @code{struct user} contents
9102 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
9103 machines), it interfaces with the inferior via the @code{ptrace}
9104 system call. The operating system creates a special sata structure,
9105 called @code{struct user}, for this interface. You can use the
9106 command @code{info udot} to display the contents of this data
9112 Display the contents of the @code{struct user} maintained by the OS
9113 kernel for the program being debugged. @value{GDBN} displays the
9114 contents of @code{struct user} as a list of hex numbers, similar to
9115 the @code{examine} command.
9118 @cindex auxiliary vector
9119 @cindex vector, auxiliary
9120 Some operating systems supply an @dfn{auxiliary vector} to programs at
9121 startup. This is akin to the arguments and environment that you
9122 specify for a program, but contains a system-dependent variety of
9123 binary values that tell system libraries important details about the
9124 hardware, operating system, and process. Each value's purpose is
9125 identified by an integer tag; the meanings are well-known but system-specific.
9126 Depending on the configuration and operating system facilities,
9127 @value{GDBN} may be able to show you this information. For remote
9128 targets, this functionality may further depend on the remote stub's
9129 support of the @samp{qXfer:auxv:read} packet, see
9130 @ref{qXfer auxiliary vector read}.
9135 Display the auxiliary vector of the inferior, which can be either a
9136 live process or a core dump file. @value{GDBN} prints each tag value
9137 numerically, and also shows names and text descriptions for recognized
9138 tags. Some values in the vector are numbers, some bit masks, and some
9139 pointers to strings or other data. @value{GDBN} displays each value in the
9140 most appropriate form for a recognized tag, and in hexadecimal for
9141 an unrecognized tag.
9144 On some targets, @value{GDBN} can access operating-system-specific information
9145 and display it to user, without interpretation. For remote targets,
9146 this functionality depends on the remote stub's support of the
9147 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
9152 List the types of OS information available for the target. If the
9153 target does not return a list of possible types, this command will
9156 @kindex info os processes
9157 @item info os processes
9158 Display the list of processes on the target. For each process,
9159 @value{GDBN} prints the process identifier, the name of the user, and
9160 the command corresponding to the process.
9163 @node Memory Region Attributes
9164 @section Memory Region Attributes
9165 @cindex memory region attributes
9167 @dfn{Memory region attributes} allow you to describe special handling
9168 required by regions of your target's memory. @value{GDBN} uses
9169 attributes to determine whether to allow certain types of memory
9170 accesses; whether to use specific width accesses; and whether to cache
9171 target memory. By default the description of memory regions is
9172 fetched from the target (if the current target supports this), but the
9173 user can override the fetched regions.
9175 Defined memory regions can be individually enabled and disabled. When a
9176 memory region is disabled, @value{GDBN} uses the default attributes when
9177 accessing memory in that region. Similarly, if no memory regions have
9178 been defined, @value{GDBN} uses the default attributes when accessing
9181 When a memory region is defined, it is given a number to identify it;
9182 to enable, disable, or remove a memory region, you specify that number.
9186 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
9187 Define a memory region bounded by @var{lower} and @var{upper} with
9188 attributes @var{attributes}@dots{}, and add it to the list of regions
9189 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
9190 case: it is treated as the target's maximum memory address.
9191 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
9194 Discard any user changes to the memory regions and use target-supplied
9195 regions, if available, or no regions if the target does not support.
9198 @item delete mem @var{nums}@dots{}
9199 Remove memory regions @var{nums}@dots{} from the list of regions
9200 monitored by @value{GDBN}.
9203 @item disable mem @var{nums}@dots{}
9204 Disable monitoring of memory regions @var{nums}@dots{}.
9205 A disabled memory region is not forgotten.
9206 It may be enabled again later.
9209 @item enable mem @var{nums}@dots{}
9210 Enable monitoring of memory regions @var{nums}@dots{}.
9214 Print a table of all defined memory regions, with the following columns
9218 @item Memory Region Number
9219 @item Enabled or Disabled.
9220 Enabled memory regions are marked with @samp{y}.
9221 Disabled memory regions are marked with @samp{n}.
9224 The address defining the inclusive lower bound of the memory region.
9227 The address defining the exclusive upper bound of the memory region.
9230 The list of attributes set for this memory region.
9235 @subsection Attributes
9237 @subsubsection Memory Access Mode
9238 The access mode attributes set whether @value{GDBN} may make read or
9239 write accesses to a memory region.
9241 While these attributes prevent @value{GDBN} from performing invalid
9242 memory accesses, they do nothing to prevent the target system, I/O DMA,
9243 etc.@: from accessing memory.
9247 Memory is read only.
9249 Memory is write only.
9251 Memory is read/write. This is the default.
9254 @subsubsection Memory Access Size
9255 The access size attribute tells @value{GDBN} to use specific sized
9256 accesses in the memory region. Often memory mapped device registers
9257 require specific sized accesses. If no access size attribute is
9258 specified, @value{GDBN} may use accesses of any size.
9262 Use 8 bit memory accesses.
9264 Use 16 bit memory accesses.
9266 Use 32 bit memory accesses.
9268 Use 64 bit memory accesses.
9271 @c @subsubsection Hardware/Software Breakpoints
9272 @c The hardware/software breakpoint attributes set whether @value{GDBN}
9273 @c will use hardware or software breakpoints for the internal breakpoints
9274 @c used by the step, next, finish, until, etc. commands.
9278 @c Always use hardware breakpoints
9279 @c @item swbreak (default)
9282 @subsubsection Data Cache
9283 The data cache attributes set whether @value{GDBN} will cache target
9284 memory. While this generally improves performance by reducing debug
9285 protocol overhead, it can lead to incorrect results because @value{GDBN}
9286 does not know about volatile variables or memory mapped device
9291 Enable @value{GDBN} to cache target memory.
9293 Disable @value{GDBN} from caching target memory. This is the default.
9296 @subsection Memory Access Checking
9297 @value{GDBN} can be instructed to refuse accesses to memory that is
9298 not explicitly described. This can be useful if accessing such
9299 regions has undesired effects for a specific target, or to provide
9300 better error checking. The following commands control this behaviour.
9303 @kindex set mem inaccessible-by-default
9304 @item set mem inaccessible-by-default [on|off]
9305 If @code{on} is specified, make @value{GDBN} treat memory not
9306 explicitly described by the memory ranges as non-existent and refuse accesses
9307 to such memory. The checks are only performed if there's at least one
9308 memory range defined. If @code{off} is specified, make @value{GDBN}
9309 treat the memory not explicitly described by the memory ranges as RAM.
9310 The default value is @code{on}.
9311 @kindex show mem inaccessible-by-default
9312 @item show mem inaccessible-by-default
9313 Show the current handling of accesses to unknown memory.
9317 @c @subsubsection Memory Write Verification
9318 @c The memory write verification attributes set whether @value{GDBN}
9319 @c will re-reads data after each write to verify the write was successful.
9323 @c @item noverify (default)
9326 @node Dump/Restore Files
9327 @section Copy Between Memory and a File
9328 @cindex dump/restore files
9329 @cindex append data to a file
9330 @cindex dump data to a file
9331 @cindex restore data from a file
9333 You can use the commands @code{dump}, @code{append}, and
9334 @code{restore} to copy data between target memory and a file. The
9335 @code{dump} and @code{append} commands write data to a file, and the
9336 @code{restore} command reads data from a file back into the inferior's
9337 memory. Files may be in binary, Motorola S-record, Intel hex, or
9338 Tektronix Hex format; however, @value{GDBN} can only append to binary
9344 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9345 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
9346 Dump the contents of memory from @var{start_addr} to @var{end_addr},
9347 or the value of @var{expr}, to @var{filename} in the given format.
9349 The @var{format} parameter may be any one of:
9356 Motorola S-record format.
9358 Tektronix Hex format.
9361 @value{GDBN} uses the same definitions of these formats as the
9362 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
9363 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
9367 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9368 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
9369 Append the contents of memory from @var{start_addr} to @var{end_addr},
9370 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
9371 (@value{GDBN} can only append data to files in raw binary form.)
9374 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
9375 Restore the contents of file @var{filename} into memory. The
9376 @code{restore} command can automatically recognize any known @sc{bfd}
9377 file format, except for raw binary. To restore a raw binary file you
9378 must specify the optional keyword @code{binary} after the filename.
9380 If @var{bias} is non-zero, its value will be added to the addresses
9381 contained in the file. Binary files always start at address zero, so
9382 they will be restored at address @var{bias}. Other bfd files have
9383 a built-in location; they will be restored at offset @var{bias}
9386 If @var{start} and/or @var{end} are non-zero, then only data between
9387 file offset @var{start} and file offset @var{end} will be restored.
9388 These offsets are relative to the addresses in the file, before
9389 the @var{bias} argument is applied.
9393 @node Core File Generation
9394 @section How to Produce a Core File from Your Program
9395 @cindex dump core from inferior
9397 A @dfn{core file} or @dfn{core dump} is a file that records the memory
9398 image of a running process and its process status (register values
9399 etc.). Its primary use is post-mortem debugging of a program that
9400 crashed while it ran outside a debugger. A program that crashes
9401 automatically produces a core file, unless this feature is disabled by
9402 the user. @xref{Files}, for information on invoking @value{GDBN} in
9403 the post-mortem debugging mode.
9405 Occasionally, you may wish to produce a core file of the program you
9406 are debugging in order to preserve a snapshot of its state.
9407 @value{GDBN} has a special command for that.
9411 @kindex generate-core-file
9412 @item generate-core-file [@var{file}]
9413 @itemx gcore [@var{file}]
9414 Produce a core dump of the inferior process. The optional argument
9415 @var{file} specifies the file name where to put the core dump. If not
9416 specified, the file name defaults to @file{core.@var{pid}}, where
9417 @var{pid} is the inferior process ID.
9419 Note that this command is implemented only for some systems (as of
9420 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
9423 @node Character Sets
9424 @section Character Sets
9425 @cindex character sets
9427 @cindex translating between character sets
9428 @cindex host character set
9429 @cindex target character set
9431 If the program you are debugging uses a different character set to
9432 represent characters and strings than the one @value{GDBN} uses itself,
9433 @value{GDBN} can automatically translate between the character sets for
9434 you. The character set @value{GDBN} uses we call the @dfn{host
9435 character set}; the one the inferior program uses we call the
9436 @dfn{target character set}.
9438 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
9439 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
9440 remote protocol (@pxref{Remote Debugging}) to debug a program
9441 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
9442 then the host character set is Latin-1, and the target character set is
9443 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
9444 target-charset EBCDIC-US}, then @value{GDBN} translates between
9445 @sc{ebcdic} and Latin 1 as you print character or string values, or use
9446 character and string literals in expressions.
9448 @value{GDBN} has no way to automatically recognize which character set
9449 the inferior program uses; you must tell it, using the @code{set
9450 target-charset} command, described below.
9452 Here are the commands for controlling @value{GDBN}'s character set
9456 @item set target-charset @var{charset}
9457 @kindex set target-charset
9458 Set the current target character set to @var{charset}. To display the
9459 list of supported target character sets, type
9460 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
9462 @item set host-charset @var{charset}
9463 @kindex set host-charset
9464 Set the current host character set to @var{charset}.
9466 By default, @value{GDBN} uses a host character set appropriate to the
9467 system it is running on; you can override that default using the
9468 @code{set host-charset} command. On some systems, @value{GDBN} cannot
9469 automatically determine the appropriate host character set. In this
9470 case, @value{GDBN} uses @samp{UTF-8}.
9472 @value{GDBN} can only use certain character sets as its host character
9473 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
9474 @value{GDBN} will list the host character sets it supports.
9476 @item set charset @var{charset}
9478 Set the current host and target character sets to @var{charset}. As
9479 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
9480 @value{GDBN} will list the names of the character sets that can be used
9481 for both host and target.
9484 @kindex show charset
9485 Show the names of the current host and target character sets.
9487 @item show host-charset
9488 @kindex show host-charset
9489 Show the name of the current host character set.
9491 @item show target-charset
9492 @kindex show target-charset
9493 Show the name of the current target character set.
9495 @item set target-wide-charset @var{charset}
9496 @kindex set target-wide-charset
9497 Set the current target's wide character set to @var{charset}. This is
9498 the character set used by the target's @code{wchar_t} type. To
9499 display the list of supported wide character sets, type
9500 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
9502 @item show target-wide-charset
9503 @kindex show target-wide-charset
9504 Show the name of the current target's wide character set.
9507 Here is an example of @value{GDBN}'s character set support in action.
9508 Assume that the following source code has been placed in the file
9509 @file{charset-test.c}:
9515 = @{72, 101, 108, 108, 111, 44, 32, 119,
9516 111, 114, 108, 100, 33, 10, 0@};
9517 char ibm1047_hello[]
9518 = @{200, 133, 147, 147, 150, 107, 64, 166,
9519 150, 153, 147, 132, 90, 37, 0@};
9523 printf ("Hello, world!\n");
9527 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
9528 containing the string @samp{Hello, world!} followed by a newline,
9529 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
9531 We compile the program, and invoke the debugger on it:
9534 $ gcc -g charset-test.c -o charset-test
9535 $ gdb -nw charset-test
9536 GNU gdb 2001-12-19-cvs
9537 Copyright 2001 Free Software Foundation, Inc.
9542 We can use the @code{show charset} command to see what character sets
9543 @value{GDBN} is currently using to interpret and display characters and
9547 (@value{GDBP}) show charset
9548 The current host and target character set is `ISO-8859-1'.
9552 For the sake of printing this manual, let's use @sc{ascii} as our
9553 initial character set:
9555 (@value{GDBP}) set charset ASCII
9556 (@value{GDBP}) show charset
9557 The current host and target character set is `ASCII'.
9561 Let's assume that @sc{ascii} is indeed the correct character set for our
9562 host system --- in other words, let's assume that if @value{GDBN} prints
9563 characters using the @sc{ascii} character set, our terminal will display
9564 them properly. Since our current target character set is also
9565 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
9568 (@value{GDBP}) print ascii_hello
9569 $1 = 0x401698 "Hello, world!\n"
9570 (@value{GDBP}) print ascii_hello[0]
9575 @value{GDBN} uses the target character set for character and string
9576 literals you use in expressions:
9579 (@value{GDBP}) print '+'
9584 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
9587 @value{GDBN} relies on the user to tell it which character set the
9588 target program uses. If we print @code{ibm1047_hello} while our target
9589 character set is still @sc{ascii}, we get jibberish:
9592 (@value{GDBP}) print ibm1047_hello
9593 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
9594 (@value{GDBP}) print ibm1047_hello[0]
9599 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
9600 @value{GDBN} tells us the character sets it supports:
9603 (@value{GDBP}) set target-charset
9604 ASCII EBCDIC-US IBM1047 ISO-8859-1
9605 (@value{GDBP}) set target-charset
9608 We can select @sc{ibm1047} as our target character set, and examine the
9609 program's strings again. Now the @sc{ascii} string is wrong, but
9610 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
9611 target character set, @sc{ibm1047}, to the host character set,
9612 @sc{ascii}, and they display correctly:
9615 (@value{GDBP}) set target-charset IBM1047
9616 (@value{GDBP}) show charset
9617 The current host character set is `ASCII'.
9618 The current target character set is `IBM1047'.
9619 (@value{GDBP}) print ascii_hello
9620 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
9621 (@value{GDBP}) print ascii_hello[0]
9623 (@value{GDBP}) print ibm1047_hello
9624 $8 = 0x4016a8 "Hello, world!\n"
9625 (@value{GDBP}) print ibm1047_hello[0]
9630 As above, @value{GDBN} uses the target character set for character and
9631 string literals you use in expressions:
9634 (@value{GDBP}) print '+'
9639 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
9642 @node Caching Remote Data
9643 @section Caching Data of Remote Targets
9644 @cindex caching data of remote targets
9646 @value{GDBN} caches data exchanged between the debugger and a
9647 remote target (@pxref{Remote Debugging}). Such caching generally improves
9648 performance, because it reduces the overhead of the remote protocol by
9649 bundling memory reads and writes into large chunks. Unfortunately, simply
9650 caching everything would lead to incorrect results, since @value{GDBN}
9651 does not necessarily know anything about volatile values, memory-mapped I/O
9652 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
9653 memory can be changed @emph{while} a gdb command is executing.
9654 Therefore, by default, @value{GDBN} only caches data
9655 known to be on the stack@footnote{In non-stop mode, it is moderately
9656 rare for a running thread to modify the stack of a stopped thread
9657 in a way that would interfere with a backtrace, and caching of
9658 stack reads provides a significant speed up of remote backtraces.}.
9659 Other regions of memory can be explicitly marked as
9660 cacheable; see @pxref{Memory Region Attributes}.
9663 @kindex set remotecache
9664 @item set remotecache on
9665 @itemx set remotecache off
9666 This option no longer does anything; it exists for compatibility
9669 @kindex show remotecache
9670 @item show remotecache
9671 Show the current state of the obsolete remotecache flag.
9673 @kindex set stack-cache
9674 @item set stack-cache on
9675 @itemx set stack-cache off
9676 Enable or disable caching of stack accesses. When @code{ON}, use
9677 caching. By default, this option is @code{ON}.
9679 @kindex show stack-cache
9680 @item show stack-cache
9681 Show the current state of data caching for memory accesses.
9684 @item info dcache @r{[}line@r{]}
9685 Print the information about the data cache performance. The
9686 information displayed includes the dcache width and depth, and for
9687 each cache line, its number, address, and how many times it was
9688 referenced. This command is useful for debugging the data cache
9691 If a line number is specified, the contents of that line will be
9694 @item set dcache size @var{size}
9696 @kindex set dcache size
9697 Set maximum number of entries in dcache (dcache depth above).
9699 @item set dcache line-size @var{line-size}
9700 @cindex dcache line-size
9701 @kindex set dcache line-size
9702 Set number of bytes each dcache entry caches (dcache width above).
9703 Must be a power of 2.
9705 @item show dcache size
9706 @kindex show dcache size
9707 Show maximum number of dcache entries. See also @ref{Caching Remote Data, info dcache}.
9709 @item show dcache line-size
9710 @kindex show dcache line-size
9711 Show default size of dcache lines. See also @ref{Caching Remote Data, info dcache}.
9715 @node Searching Memory
9716 @section Search Memory
9717 @cindex searching memory
9719 Memory can be searched for a particular sequence of bytes with the
9720 @code{find} command.
9724 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9725 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9726 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
9727 etc. The search begins at address @var{start_addr} and continues for either
9728 @var{len} bytes or through to @var{end_addr} inclusive.
9731 @var{s} and @var{n} are optional parameters.
9732 They may be specified in either order, apart or together.
9735 @item @var{s}, search query size
9736 The size of each search query value.
9742 halfwords (two bytes)
9746 giant words (eight bytes)
9749 All values are interpreted in the current language.
9750 This means, for example, that if the current source language is C/C@t{++}
9751 then searching for the string ``hello'' includes the trailing '\0'.
9753 If the value size is not specified, it is taken from the
9754 value's type in the current language.
9755 This is useful when one wants to specify the search
9756 pattern as a mixture of types.
9757 Note that this means, for example, that in the case of C-like languages
9758 a search for an untyped 0x42 will search for @samp{(int) 0x42}
9759 which is typically four bytes.
9761 @item @var{n}, maximum number of finds
9762 The maximum number of matches to print. The default is to print all finds.
9765 You can use strings as search values. Quote them with double-quotes
9767 The string value is copied into the search pattern byte by byte,
9768 regardless of the endianness of the target and the size specification.
9770 The address of each match found is printed as well as a count of the
9771 number of matches found.
9773 The address of the last value found is stored in convenience variable
9775 A count of the number of matches is stored in @samp{$numfound}.
9777 For example, if stopped at the @code{printf} in this function:
9783 static char hello[] = "hello-hello";
9784 static struct @{ char c; short s; int i; @}
9785 __attribute__ ((packed)) mixed
9786 = @{ 'c', 0x1234, 0x87654321 @};
9787 printf ("%s\n", hello);
9792 you get during debugging:
9795 (gdb) find &hello[0], +sizeof(hello), "hello"
9796 0x804956d <hello.1620+6>
9798 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
9799 0x8049567 <hello.1620>
9800 0x804956d <hello.1620+6>
9802 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
9803 0x8049567 <hello.1620>
9805 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
9806 0x8049560 <mixed.1625>
9808 (gdb) print $numfound
9811 $2 = (void *) 0x8049560
9814 @node Optimized Code
9815 @chapter Debugging Optimized Code
9816 @cindex optimized code, debugging
9817 @cindex debugging optimized code
9819 Almost all compilers support optimization. With optimization
9820 disabled, the compiler generates assembly code that corresponds
9821 directly to your source code, in a simplistic way. As the compiler
9822 applies more powerful optimizations, the generated assembly code
9823 diverges from your original source code. With help from debugging
9824 information generated by the compiler, @value{GDBN} can map from
9825 the running program back to constructs from your original source.
9827 @value{GDBN} is more accurate with optimization disabled. If you
9828 can recompile without optimization, it is easier to follow the
9829 progress of your program during debugging. But, there are many cases
9830 where you may need to debug an optimized version.
9832 When you debug a program compiled with @samp{-g -O}, remember that the
9833 optimizer has rearranged your code; the debugger shows you what is
9834 really there. Do not be too surprised when the execution path does not
9835 exactly match your source file! An extreme example: if you define a
9836 variable, but never use it, @value{GDBN} never sees that
9837 variable---because the compiler optimizes it out of existence.
9839 Some things do not work as well with @samp{-g -O} as with just
9840 @samp{-g}, particularly on machines with instruction scheduling. If in
9841 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
9842 please report it to us as a bug (including a test case!).
9843 @xref{Variables}, for more information about debugging optimized code.
9846 * Inline Functions:: How @value{GDBN} presents inlining
9847 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
9850 @node Inline Functions
9851 @section Inline Functions
9852 @cindex inline functions, debugging
9854 @dfn{Inlining} is an optimization that inserts a copy of the function
9855 body directly at each call site, instead of jumping to a shared
9856 routine. @value{GDBN} displays inlined functions just like
9857 non-inlined functions. They appear in backtraces. You can view their
9858 arguments and local variables, step into them with @code{step}, skip
9859 them with @code{next}, and escape from them with @code{finish}.
9860 You can check whether a function was inlined by using the
9861 @code{info frame} command.
9863 For @value{GDBN} to support inlined functions, the compiler must
9864 record information about inlining in the debug information ---
9865 @value{NGCC} using the @sc{dwarf 2} format does this, and several
9866 other compilers do also. @value{GDBN} only supports inlined functions
9867 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
9868 do not emit two required attributes (@samp{DW_AT_call_file} and
9869 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
9870 function calls with earlier versions of @value{NGCC}. It instead
9871 displays the arguments and local variables of inlined functions as
9872 local variables in the caller.
9874 The body of an inlined function is directly included at its call site;
9875 unlike a non-inlined function, there are no instructions devoted to
9876 the call. @value{GDBN} still pretends that the call site and the
9877 start of the inlined function are different instructions. Stepping to
9878 the call site shows the call site, and then stepping again shows
9879 the first line of the inlined function, even though no additional
9880 instructions are executed.
9882 This makes source-level debugging much clearer; you can see both the
9883 context of the call and then the effect of the call. Only stepping by
9884 a single instruction using @code{stepi} or @code{nexti} does not do
9885 this; single instruction steps always show the inlined body.
9887 There are some ways that @value{GDBN} does not pretend that inlined
9888 function calls are the same as normal calls:
9892 You cannot set breakpoints on inlined functions. @value{GDBN}
9893 either reports that there is no symbol with that name, or else sets the
9894 breakpoint only on non-inlined copies of the function. This limitation
9895 will be removed in a future version of @value{GDBN}; until then,
9896 set a breakpoint by line number on the first line of the inlined
9900 Setting breakpoints at the call site of an inlined function may not
9901 work, because the call site does not contain any code. @value{GDBN}
9902 may incorrectly move the breakpoint to the next line of the enclosing
9903 function, after the call. This limitation will be removed in a future
9904 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9905 or inside the inlined function instead.
9908 @value{GDBN} cannot locate the return value of inlined calls after
9909 using the @code{finish} command. This is a limitation of compiler-generated
9910 debugging information; after @code{finish}, you can step to the next line
9911 and print a variable where your program stored the return value.
9915 @node Tail Call Frames
9916 @section Tail Call Frames
9917 @cindex tail call frames, debugging
9919 Function @code{B} can call function @code{C} in its very last statement. In
9920 unoptimized compilation the call of @code{C} is immediately followed by return
9921 instruction at the end of @code{B} code. Optimizing compiler may replace the
9922 call and return in function @code{B} into one jump to function @code{C}
9923 instead. Such use of a jump instruction is called @dfn{tail call}.
9925 During execution of function @code{C}, there will be no indication in the
9926 function call stack frames that it was tail-called from @code{B}. If function
9927 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
9928 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
9929 some cases @value{GDBN} can determine that @code{C} was tail-called from
9930 @code{B}, and it will then create fictitious call frame for that, with the
9931 return address set up as if @code{B} called @code{C} normally.
9933 This functionality is currently supported only by DWARF 2 debugging format and
9934 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9935 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9938 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
9939 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
9943 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
9945 Stack level 1, frame at 0x7fffffffda30:
9946 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
9947 tail call frame, caller of frame at 0x7fffffffda30
9948 source language c++.
9949 Arglist at unknown address.
9950 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
9953 The detection of all the possible code path executions can find them ambiguous.
9954 There is no execution history stored (possible @ref{Reverse Execution} is never
9955 used for this purpose) and the last known caller could have reached the known
9956 callee by multiple different jump sequences. In such case @value{GDBN} still
9957 tries to show at least all the unambiguous top tail callers and all the
9958 unambiguous bottom tail calees, if any.
9961 @anchor{set debug entry-values}
9962 @item set debug entry-values
9963 @kindex set debug entry-values
9964 When set to on, enables printing of analysis messages for both frame argument
9965 values at function entry and tail calls. It will show all the possible valid
9966 tail calls code paths it has considered. It will also print the intersection
9967 of them with the final unambiguous (possibly partial or even empty) code path
9970 @item show debug entry-values
9971 @kindex show debug entry-values
9972 Show the current state of analysis messages printing for both frame argument
9973 values at function entry and tail calls.
9976 The analysis messages for tail calls can for example show why the virtual tail
9977 call frame for function @code{c} has not been recognized (due to the indirect
9978 reference by variable @code{x}):
9981 static void __attribute__((noinline, noclone)) c (void);
9982 void (*x) (void) = c;
9983 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
9984 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
9985 int main (void) @{ x (); return 0; @}
9987 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
9988 DW_TAG_GNU_call_site 0x40039a in main
9990 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
9993 #1 0x000000000040039a in main () at t.c:5
9996 Another possibility is an ambiguous virtual tail call frames resolution:
10000 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
10001 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
10002 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
10003 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
10004 static void __attribute__((noinline, noclone)) b (void)
10005 @{ if (i) c (); else e (); @}
10006 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
10007 int main (void) @{ a (); return 0; @}
10009 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
10010 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
10011 tailcall: reduced: 0x4004d2(a) |
10014 #1 0x00000000004004d2 in a () at t.c:8
10015 #2 0x0000000000400395 in main () at t.c:9
10018 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
10019 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
10021 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
10022 @ifset HAVE_MAKEINFO_CLICK
10023 @set ARROW @click{}
10024 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
10025 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
10027 @ifclear HAVE_MAKEINFO_CLICK
10029 @set CALLSEQ1B @value{CALLSEQ1A}
10030 @set CALLSEQ2B @value{CALLSEQ2A}
10033 Frames #0 and #2 are real, #1 is a virtual tail call frame.
10034 The code can have possible execution paths @value{CALLSEQ1B} or
10035 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
10037 @code{initial:} state shows some random possible calling sequence @value{GDBN}
10038 has found. It then finds another possible calling sequcen - that one is
10039 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
10040 printed as the @code{reduced:} calling sequence. That one could have many
10041 futher @code{compare:} and @code{reduced:} statements as long as there remain
10042 any non-ambiguous sequence entries.
10044 For the frame of function @code{b} in both cases there are different possible
10045 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
10046 also ambigous. The only non-ambiguous frame is the one for function @code{a},
10047 therefore this one is displayed to the user while the ambiguous frames are
10050 There can be also reasons why printing of frame argument values at function
10055 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
10056 static void __attribute__((noinline, noclone)) a (int i);
10057 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
10058 static void __attribute__((noinline, noclone)) a (int i)
10059 @{ if (i) b (i - 1); else c (0); @}
10060 int main (void) @{ a (5); return 0; @}
10063 #0 c (i=i@@entry=0) at t.c:2
10064 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
10065 function "a" at 0x400420 can call itself via tail calls
10066 i=<optimized out>) at t.c:6
10067 #2 0x000000000040036e in main () at t.c:7
10070 @value{GDBN} cannot find out from the inferior state if and how many times did
10071 function @code{a} call itself (via function @code{b}) as these calls would be
10072 tail calls. Such tail calls would modify thue @code{i} variable, therefore
10073 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
10074 prints @code{<optimized out>} instead.
10077 @chapter C Preprocessor Macros
10079 Some languages, such as C and C@t{++}, provide a way to define and invoke
10080 ``preprocessor macros'' which expand into strings of tokens.
10081 @value{GDBN} can evaluate expressions containing macro invocations, show
10082 the result of macro expansion, and show a macro's definition, including
10083 where it was defined.
10085 You may need to compile your program specially to provide @value{GDBN}
10086 with information about preprocessor macros. Most compilers do not
10087 include macros in their debugging information, even when you compile
10088 with the @option{-g} flag. @xref{Compilation}.
10090 A program may define a macro at one point, remove that definition later,
10091 and then provide a different definition after that. Thus, at different
10092 points in the program, a macro may have different definitions, or have
10093 no definition at all. If there is a current stack frame, @value{GDBN}
10094 uses the macros in scope at that frame's source code line. Otherwise,
10095 @value{GDBN} uses the macros in scope at the current listing location;
10098 Whenever @value{GDBN} evaluates an expression, it always expands any
10099 macro invocations present in the expression. @value{GDBN} also provides
10100 the following commands for working with macros explicitly.
10104 @kindex macro expand
10105 @cindex macro expansion, showing the results of preprocessor
10106 @cindex preprocessor macro expansion, showing the results of
10107 @cindex expanding preprocessor macros
10108 @item macro expand @var{expression}
10109 @itemx macro exp @var{expression}
10110 Show the results of expanding all preprocessor macro invocations in
10111 @var{expression}. Since @value{GDBN} simply expands macros, but does
10112 not parse the result, @var{expression} need not be a valid expression;
10113 it can be any string of tokens.
10116 @item macro expand-once @var{expression}
10117 @itemx macro exp1 @var{expression}
10118 @cindex expand macro once
10119 @i{(This command is not yet implemented.)} Show the results of
10120 expanding those preprocessor macro invocations that appear explicitly in
10121 @var{expression}. Macro invocations appearing in that expansion are
10122 left unchanged. This command allows you to see the effect of a
10123 particular macro more clearly, without being confused by further
10124 expansions. Since @value{GDBN} simply expands macros, but does not
10125 parse the result, @var{expression} need not be a valid expression; it
10126 can be any string of tokens.
10129 @cindex macro definition, showing
10130 @cindex definition of a macro, showing
10131 @cindex macros, from debug info
10132 @item info macro [-a|-all] [--] @var{macro}
10133 Show the current definition or all definitions of the named @var{macro},
10134 and describe the source location or compiler command-line where that
10135 definition was established. The optional double dash is to signify the end of
10136 argument processing and the beginning of @var{macro} for non C-like macros where
10137 the macro may begin with a hyphen.
10139 @kindex info macros
10140 @item info macros @var{linespec}
10141 Show all macro definitions that are in effect at the location specified
10142 by @var{linespec}, and describe the source location or compiler
10143 command-line where those definitions were established.
10145 @kindex macro define
10146 @cindex user-defined macros
10147 @cindex defining macros interactively
10148 @cindex macros, user-defined
10149 @item macro define @var{macro} @var{replacement-list}
10150 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
10151 Introduce a definition for a preprocessor macro named @var{macro},
10152 invocations of which are replaced by the tokens given in
10153 @var{replacement-list}. The first form of this command defines an
10154 ``object-like'' macro, which takes no arguments; the second form
10155 defines a ``function-like'' macro, which takes the arguments given in
10158 A definition introduced by this command is in scope in every
10159 expression evaluated in @value{GDBN}, until it is removed with the
10160 @code{macro undef} command, described below. The definition overrides
10161 all definitions for @var{macro} present in the program being debugged,
10162 as well as any previous user-supplied definition.
10164 @kindex macro undef
10165 @item macro undef @var{macro}
10166 Remove any user-supplied definition for the macro named @var{macro}.
10167 This command only affects definitions provided with the @code{macro
10168 define} command, described above; it cannot remove definitions present
10169 in the program being debugged.
10173 List all the macros defined using the @code{macro define} command.
10176 @cindex macros, example of debugging with
10177 Here is a transcript showing the above commands in action. First, we
10178 show our source files:
10183 #include "sample.h"
10186 #define ADD(x) (M + x)
10191 printf ("Hello, world!\n");
10193 printf ("We're so creative.\n");
10195 printf ("Goodbye, world!\n");
10202 Now, we compile the program using the @sc{gnu} C compiler,
10203 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
10204 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
10205 and @option{-gdwarf-4}; we recommend always choosing the most recent
10206 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
10207 includes information about preprocessor macros in the debugging
10211 $ gcc -gdwarf-2 -g3 sample.c -o sample
10215 Now, we start @value{GDBN} on our sample program:
10219 GNU gdb 2002-05-06-cvs
10220 Copyright 2002 Free Software Foundation, Inc.
10221 GDB is free software, @dots{}
10225 We can expand macros and examine their definitions, even when the
10226 program is not running. @value{GDBN} uses the current listing position
10227 to decide which macro definitions are in scope:
10230 (@value{GDBP}) list main
10233 5 #define ADD(x) (M + x)
10238 10 printf ("Hello, world!\n");
10240 12 printf ("We're so creative.\n");
10241 (@value{GDBP}) info macro ADD
10242 Defined at /home/jimb/gdb/macros/play/sample.c:5
10243 #define ADD(x) (M + x)
10244 (@value{GDBP}) info macro Q
10245 Defined at /home/jimb/gdb/macros/play/sample.h:1
10246 included at /home/jimb/gdb/macros/play/sample.c:2
10248 (@value{GDBP}) macro expand ADD(1)
10249 expands to: (42 + 1)
10250 (@value{GDBP}) macro expand-once ADD(1)
10251 expands to: once (M + 1)
10255 In the example above, note that @code{macro expand-once} expands only
10256 the macro invocation explicit in the original text --- the invocation of
10257 @code{ADD} --- but does not expand the invocation of the macro @code{M},
10258 which was introduced by @code{ADD}.
10260 Once the program is running, @value{GDBN} uses the macro definitions in
10261 force at the source line of the current stack frame:
10264 (@value{GDBP}) break main
10265 Breakpoint 1 at 0x8048370: file sample.c, line 10.
10267 Starting program: /home/jimb/gdb/macros/play/sample
10269 Breakpoint 1, main () at sample.c:10
10270 10 printf ("Hello, world!\n");
10274 At line 10, the definition of the macro @code{N} at line 9 is in force:
10277 (@value{GDBP}) info macro N
10278 Defined at /home/jimb/gdb/macros/play/sample.c:9
10280 (@value{GDBP}) macro expand N Q M
10281 expands to: 28 < 42
10282 (@value{GDBP}) print N Q M
10287 As we step over directives that remove @code{N}'s definition, and then
10288 give it a new definition, @value{GDBN} finds the definition (or lack
10289 thereof) in force at each point:
10292 (@value{GDBP}) next
10294 12 printf ("We're so creative.\n");
10295 (@value{GDBP}) info macro N
10296 The symbol `N' has no definition as a C/C++ preprocessor macro
10297 at /home/jimb/gdb/macros/play/sample.c:12
10298 (@value{GDBP}) next
10300 14 printf ("Goodbye, world!\n");
10301 (@value{GDBP}) info macro N
10302 Defined at /home/jimb/gdb/macros/play/sample.c:13
10304 (@value{GDBP}) macro expand N Q M
10305 expands to: 1729 < 42
10306 (@value{GDBP}) print N Q M
10311 In addition to source files, macros can be defined on the compilation command
10312 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
10313 such a way, @value{GDBN} displays the location of their definition as line zero
10314 of the source file submitted to the compiler.
10317 (@value{GDBP}) info macro __STDC__
10318 Defined at /home/jimb/gdb/macros/play/sample.c:0
10325 @chapter Tracepoints
10326 @c This chapter is based on the documentation written by Michael
10327 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
10329 @cindex tracepoints
10330 In some applications, it is not feasible for the debugger to interrupt
10331 the program's execution long enough for the developer to learn
10332 anything helpful about its behavior. If the program's correctness
10333 depends on its real-time behavior, delays introduced by a debugger
10334 might cause the program to change its behavior drastically, or perhaps
10335 fail, even when the code itself is correct. It is useful to be able
10336 to observe the program's behavior without interrupting it.
10338 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
10339 specify locations in the program, called @dfn{tracepoints}, and
10340 arbitrary expressions to evaluate when those tracepoints are reached.
10341 Later, using the @code{tfind} command, you can examine the values
10342 those expressions had when the program hit the tracepoints. The
10343 expressions may also denote objects in memory---structures or arrays,
10344 for example---whose values @value{GDBN} should record; while visiting
10345 a particular tracepoint, you may inspect those objects as if they were
10346 in memory at that moment. However, because @value{GDBN} records these
10347 values without interacting with you, it can do so quickly and
10348 unobtrusively, hopefully not disturbing the program's behavior.
10350 The tracepoint facility is currently available only for remote
10351 targets. @xref{Targets}. In addition, your remote target must know
10352 how to collect trace data. This functionality is implemented in the
10353 remote stub; however, none of the stubs distributed with @value{GDBN}
10354 support tracepoints as of this writing. The format of the remote
10355 packets used to implement tracepoints are described in @ref{Tracepoint
10358 It is also possible to get trace data from a file, in a manner reminiscent
10359 of corefiles; you specify the filename, and use @code{tfind} to search
10360 through the file. @xref{Trace Files}, for more details.
10362 This chapter describes the tracepoint commands and features.
10365 * Set Tracepoints::
10366 * Analyze Collected Data::
10367 * Tracepoint Variables::
10371 @node Set Tracepoints
10372 @section Commands to Set Tracepoints
10374 Before running such a @dfn{trace experiment}, an arbitrary number of
10375 tracepoints can be set. A tracepoint is actually a special type of
10376 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
10377 standard breakpoint commands. For instance, as with breakpoints,
10378 tracepoint numbers are successive integers starting from one, and many
10379 of the commands associated with tracepoints take the tracepoint number
10380 as their argument, to identify which tracepoint to work on.
10382 For each tracepoint, you can specify, in advance, some arbitrary set
10383 of data that you want the target to collect in the trace buffer when
10384 it hits that tracepoint. The collected data can include registers,
10385 local variables, or global data. Later, you can use @value{GDBN}
10386 commands to examine the values these data had at the time the
10387 tracepoint was hit.
10389 Tracepoints do not support every breakpoint feature. Ignore counts on
10390 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
10391 commands when they are hit. Tracepoints may not be thread-specific
10394 @cindex fast tracepoints
10395 Some targets may support @dfn{fast tracepoints}, which are inserted in
10396 a different way (such as with a jump instead of a trap), that is
10397 faster but possibly restricted in where they may be installed.
10399 @cindex static tracepoints
10400 @cindex markers, static tracepoints
10401 @cindex probing markers, static tracepoints
10402 Regular and fast tracepoints are dynamic tracing facilities, meaning
10403 that they can be used to insert tracepoints at (almost) any location
10404 in the target. Some targets may also support controlling @dfn{static
10405 tracepoints} from @value{GDBN}. With static tracing, a set of
10406 instrumentation points, also known as @dfn{markers}, are embedded in
10407 the target program, and can be activated or deactivated by name or
10408 address. These are usually placed at locations which facilitate
10409 investigating what the target is actually doing. @value{GDBN}'s
10410 support for static tracing includes being able to list instrumentation
10411 points, and attach them with @value{GDBN} defined high level
10412 tracepoints that expose the whole range of convenience of
10413 @value{GDBN}'s tracepoints support. Namely, support for collecting
10414 registers values and values of global or local (to the instrumentation
10415 point) variables; tracepoint conditions and trace state variables.
10416 The act of installing a @value{GDBN} static tracepoint on an
10417 instrumentation point, or marker, is referred to as @dfn{probing} a
10418 static tracepoint marker.
10420 @code{gdbserver} supports tracepoints on some target systems.
10421 @xref{Server,,Tracepoints support in @code{gdbserver}}.
10423 This section describes commands to set tracepoints and associated
10424 conditions and actions.
10427 * Create and Delete Tracepoints::
10428 * Enable and Disable Tracepoints::
10429 * Tracepoint Passcounts::
10430 * Tracepoint Conditions::
10431 * Trace State Variables::
10432 * Tracepoint Actions::
10433 * Listing Tracepoints::
10434 * Listing Static Tracepoint Markers::
10435 * Starting and Stopping Trace Experiments::
10436 * Tracepoint Restrictions::
10439 @node Create and Delete Tracepoints
10440 @subsection Create and Delete Tracepoints
10443 @cindex set tracepoint
10445 @item trace @var{location}
10446 The @code{trace} command is very similar to the @code{break} command.
10447 Its argument @var{location} can be a source line, a function name, or
10448 an address in the target program. @xref{Specify Location}. The
10449 @code{trace} command defines a tracepoint, which is a point in the
10450 target program where the debugger will briefly stop, collect some
10451 data, and then allow the program to continue. Setting a tracepoint or
10452 changing its actions takes effect immediately if the remote stub
10453 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
10455 If remote stub doesn't support the @samp{InstallInTrace} feature, all
10456 these changes don't take effect until the next @code{tstart}
10457 command, and once a trace experiment is running, further changes will
10458 not have any effect until the next trace experiment starts. In addition,
10459 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
10460 address is not yet resolved. (This is similar to pending breakpoints.)
10461 Pending tracepoints are not downloaded to the target and not installed
10462 until they are resolved. The resolution of pending tracepoints requires
10463 @value{GDBN} support---when debugging with the remote target, and
10464 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
10465 tracing}), pending tracepoints can not be resolved (and downloaded to
10466 the remote stub) while @value{GDBN} is disconnected.
10468 Here are some examples of using the @code{trace} command:
10471 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
10473 (@value{GDBP}) @b{trace +2} // 2 lines forward
10475 (@value{GDBP}) @b{trace my_function} // first source line of function
10477 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
10479 (@value{GDBP}) @b{trace *0x2117c4} // an address
10483 You can abbreviate @code{trace} as @code{tr}.
10485 @item trace @var{location} if @var{cond}
10486 Set a tracepoint with condition @var{cond}; evaluate the expression
10487 @var{cond} each time the tracepoint is reached, and collect data only
10488 if the value is nonzero---that is, if @var{cond} evaluates as true.
10489 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
10490 information on tracepoint conditions.
10492 @item ftrace @var{location} [ if @var{cond} ]
10493 @cindex set fast tracepoint
10494 @cindex fast tracepoints, setting
10496 The @code{ftrace} command sets a fast tracepoint. For targets that
10497 support them, fast tracepoints will use a more efficient but possibly
10498 less general technique to trigger data collection, such as a jump
10499 instruction instead of a trap, or some sort of hardware support. It
10500 may not be possible to create a fast tracepoint at the desired
10501 location, in which case the command will exit with an explanatory
10504 @value{GDBN} handles arguments to @code{ftrace} exactly as for
10507 On 32-bit x86-architecture systems, fast tracepoints normally need to
10508 be placed at an instruction that is 5 bytes or longer, but can be
10509 placed at 4-byte instructions if the low 64K of memory of the target
10510 program is available to install trampolines. Some Unix-type systems,
10511 such as @sc{gnu}/Linux, exclude low addresses from the program's
10512 address space; but for instance with the Linux kernel it is possible
10513 to let @value{GDBN} use this area by doing a @command{sysctl} command
10514 to set the @code{mmap_min_addr} kernel parameter, as in
10517 sudo sysctl -w vm.mmap_min_addr=32768
10521 which sets the low address to 32K, which leaves plenty of room for
10522 trampolines. The minimum address should be set to a page boundary.
10524 @item strace @var{location} [ if @var{cond} ]
10525 @cindex set static tracepoint
10526 @cindex static tracepoints, setting
10527 @cindex probe static tracepoint marker
10529 The @code{strace} command sets a static tracepoint. For targets that
10530 support it, setting a static tracepoint probes a static
10531 instrumentation point, or marker, found at @var{location}. It may not
10532 be possible to set a static tracepoint at the desired location, in
10533 which case the command will exit with an explanatory message.
10535 @value{GDBN} handles arguments to @code{strace} exactly as for
10536 @code{trace}, with the addition that the user can also specify
10537 @code{-m @var{marker}} as @var{location}. This probes the marker
10538 identified by the @var{marker} string identifier. This identifier
10539 depends on the static tracepoint backend library your program is
10540 using. You can find all the marker identifiers in the @samp{ID} field
10541 of the @code{info static-tracepoint-markers} command output.
10542 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
10543 Markers}. For example, in the following small program using the UST
10549 trace_mark(ust, bar33, "str %s", "FOOBAZ");
10554 the marker id is composed of joining the first two arguments to the
10555 @code{trace_mark} call with a slash, which translates to:
10558 (@value{GDBP}) info static-tracepoint-markers
10559 Cnt Enb ID Address What
10560 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
10566 so you may probe the marker above with:
10569 (@value{GDBP}) strace -m ust/bar33
10572 Static tracepoints accept an extra collect action --- @code{collect
10573 $_sdata}. This collects arbitrary user data passed in the probe point
10574 call to the tracing library. In the UST example above, you'll see
10575 that the third argument to @code{trace_mark} is a printf-like format
10576 string. The user data is then the result of running that formating
10577 string against the following arguments. Note that @code{info
10578 static-tracepoint-markers} command output lists that format string in
10579 the @samp{Data:} field.
10581 You can inspect this data when analyzing the trace buffer, by printing
10582 the $_sdata variable like any other variable available to
10583 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
10586 @cindex last tracepoint number
10587 @cindex recent tracepoint number
10588 @cindex tracepoint number
10589 The convenience variable @code{$tpnum} records the tracepoint number
10590 of the most recently set tracepoint.
10592 @kindex delete tracepoint
10593 @cindex tracepoint deletion
10594 @item delete tracepoint @r{[}@var{num}@r{]}
10595 Permanently delete one or more tracepoints. With no argument, the
10596 default is to delete all tracepoints. Note that the regular
10597 @code{delete} command can remove tracepoints also.
10602 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
10604 (@value{GDBP}) @b{delete trace} // remove all tracepoints
10608 You can abbreviate this command as @code{del tr}.
10611 @node Enable and Disable Tracepoints
10612 @subsection Enable and Disable Tracepoints
10614 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
10617 @kindex disable tracepoint
10618 @item disable tracepoint @r{[}@var{num}@r{]}
10619 Disable tracepoint @var{num}, or all tracepoints if no argument
10620 @var{num} is given. A disabled tracepoint will have no effect during
10621 a trace experiment, but it is not forgotten. You can re-enable
10622 a disabled tracepoint using the @code{enable tracepoint} command.
10623 If the command is issued during a trace experiment and the debug target
10624 has support for disabling tracepoints during a trace experiment, then the
10625 change will be effective immediately. Otherwise, it will be applied to the
10626 next trace experiment.
10628 @kindex enable tracepoint
10629 @item enable tracepoint @r{[}@var{num}@r{]}
10630 Enable tracepoint @var{num}, or all tracepoints. If this command is
10631 issued during a trace experiment and the debug target supports enabling
10632 tracepoints during a trace experiment, then the enabled tracepoints will
10633 become effective immediately. Otherwise, they will become effective the
10634 next time a trace experiment is run.
10637 @node Tracepoint Passcounts
10638 @subsection Tracepoint Passcounts
10642 @cindex tracepoint pass count
10643 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
10644 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
10645 automatically stop a trace experiment. If a tracepoint's passcount is
10646 @var{n}, then the trace experiment will be automatically stopped on
10647 the @var{n}'th time that tracepoint is hit. If the tracepoint number
10648 @var{num} is not specified, the @code{passcount} command sets the
10649 passcount of the most recently defined tracepoint. If no passcount is
10650 given, the trace experiment will run until stopped explicitly by the
10656 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
10657 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
10659 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
10660 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
10661 (@value{GDBP}) @b{trace foo}
10662 (@value{GDBP}) @b{pass 3}
10663 (@value{GDBP}) @b{trace bar}
10664 (@value{GDBP}) @b{pass 2}
10665 (@value{GDBP}) @b{trace baz}
10666 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
10667 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
10668 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
10669 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
10673 @node Tracepoint Conditions
10674 @subsection Tracepoint Conditions
10675 @cindex conditional tracepoints
10676 @cindex tracepoint conditions
10678 The simplest sort of tracepoint collects data every time your program
10679 reaches a specified place. You can also specify a @dfn{condition} for
10680 a tracepoint. A condition is just a Boolean expression in your
10681 programming language (@pxref{Expressions, ,Expressions}). A
10682 tracepoint with a condition evaluates the expression each time your
10683 program reaches it, and data collection happens only if the condition
10686 Tracepoint conditions can be specified when a tracepoint is set, by
10687 using @samp{if} in the arguments to the @code{trace} command.
10688 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
10689 also be set or changed at any time with the @code{condition} command,
10690 just as with breakpoints.
10692 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
10693 the conditional expression itself. Instead, @value{GDBN} encodes the
10694 expression into an agent expression (@pxref{Agent Expressions})
10695 suitable for execution on the target, independently of @value{GDBN}.
10696 Global variables become raw memory locations, locals become stack
10697 accesses, and so forth.
10699 For instance, suppose you have a function that is usually called
10700 frequently, but should not be called after an error has occurred. You
10701 could use the following tracepoint command to collect data about calls
10702 of that function that happen while the error code is propagating
10703 through the program; an unconditional tracepoint could end up
10704 collecting thousands of useless trace frames that you would have to
10708 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
10711 @node Trace State Variables
10712 @subsection Trace State Variables
10713 @cindex trace state variables
10715 A @dfn{trace state variable} is a special type of variable that is
10716 created and managed by target-side code. The syntax is the same as
10717 that for GDB's convenience variables (a string prefixed with ``$''),
10718 but they are stored on the target. They must be created explicitly,
10719 using a @code{tvariable} command. They are always 64-bit signed
10722 Trace state variables are remembered by @value{GDBN}, and downloaded
10723 to the target along with tracepoint information when the trace
10724 experiment starts. There are no intrinsic limits on the number of
10725 trace state variables, beyond memory limitations of the target.
10727 @cindex convenience variables, and trace state variables
10728 Although trace state variables are managed by the target, you can use
10729 them in print commands and expressions as if they were convenience
10730 variables; @value{GDBN} will get the current value from the target
10731 while the trace experiment is running. Trace state variables share
10732 the same namespace as other ``$'' variables, which means that you
10733 cannot have trace state variables with names like @code{$23} or
10734 @code{$pc}, nor can you have a trace state variable and a convenience
10735 variable with the same name.
10739 @item tvariable $@var{name} [ = @var{expression} ]
10741 The @code{tvariable} command creates a new trace state variable named
10742 @code{$@var{name}}, and optionally gives it an initial value of
10743 @var{expression}. @var{expression} is evaluated when this command is
10744 entered; the result will be converted to an integer if possible,
10745 otherwise @value{GDBN} will report an error. A subsequent
10746 @code{tvariable} command specifying the same name does not create a
10747 variable, but instead assigns the supplied initial value to the
10748 existing variable of that name, overwriting any previous initial
10749 value. The default initial value is 0.
10751 @item info tvariables
10752 @kindex info tvariables
10753 List all the trace state variables along with their initial values.
10754 Their current values may also be displayed, if the trace experiment is
10757 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
10758 @kindex delete tvariable
10759 Delete the given trace state variables, or all of them if no arguments
10764 @node Tracepoint Actions
10765 @subsection Tracepoint Action Lists
10769 @cindex tracepoint actions
10770 @item actions @r{[}@var{num}@r{]}
10771 This command will prompt for a list of actions to be taken when the
10772 tracepoint is hit. If the tracepoint number @var{num} is not
10773 specified, this command sets the actions for the one that was most
10774 recently defined (so that you can define a tracepoint and then say
10775 @code{actions} without bothering about its number). You specify the
10776 actions themselves on the following lines, one action at a time, and
10777 terminate the actions list with a line containing just @code{end}. So
10778 far, the only defined actions are @code{collect}, @code{teval}, and
10779 @code{while-stepping}.
10781 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
10782 Commands, ,Breakpoint Command Lists}), except that only the defined
10783 actions are allowed; any other @value{GDBN} command is rejected.
10785 @cindex remove actions from a tracepoint
10786 To remove all actions from a tracepoint, type @samp{actions @var{num}}
10787 and follow it immediately with @samp{end}.
10790 (@value{GDBP}) @b{collect @var{data}} // collect some data
10792 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
10794 (@value{GDBP}) @b{end} // signals the end of actions.
10797 In the following example, the action list begins with @code{collect}
10798 commands indicating the things to be collected when the tracepoint is
10799 hit. Then, in order to single-step and collect additional data
10800 following the tracepoint, a @code{while-stepping} command is used,
10801 followed by the list of things to be collected after each step in a
10802 sequence of single steps. The @code{while-stepping} command is
10803 terminated by its own separate @code{end} command. Lastly, the action
10804 list is terminated by an @code{end} command.
10807 (@value{GDBP}) @b{trace foo}
10808 (@value{GDBP}) @b{actions}
10809 Enter actions for tracepoint 1, one per line:
10812 > while-stepping 12
10813 > collect $pc, arr[i]
10818 @kindex collect @r{(tracepoints)}
10819 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
10820 Collect values of the given expressions when the tracepoint is hit.
10821 This command accepts a comma-separated list of any valid expressions.
10822 In addition to global, static, or local variables, the following
10823 special arguments are supported:
10827 Collect all registers.
10830 Collect all function arguments.
10833 Collect all local variables.
10836 Collect the return address. This is helpful if you want to see more
10840 @vindex $_sdata@r{, collect}
10841 Collect static tracepoint marker specific data. Only available for
10842 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
10843 Lists}. On the UST static tracepoints library backend, an
10844 instrumentation point resembles a @code{printf} function call. The
10845 tracing library is able to collect user specified data formatted to a
10846 character string using the format provided by the programmer that
10847 instrumented the program. Other backends have similar mechanisms.
10848 Here's an example of a UST marker call:
10851 const char master_name[] = "$your_name";
10852 trace_mark(channel1, marker1, "hello %s", master_name)
10855 In this case, collecting @code{$_sdata} collects the string
10856 @samp{hello $yourname}. When analyzing the trace buffer, you can
10857 inspect @samp{$_sdata} like any other variable available to
10861 You can give several consecutive @code{collect} commands, each one
10862 with a single argument, or one @code{collect} command with several
10863 arguments separated by commas; the effect is the same.
10865 The optional @var{mods} changes the usual handling of the arguments.
10866 @code{s} requests that pointers to chars be handled as strings, in
10867 particular collecting the contents of the memory being pointed at, up
10868 to the first zero. The upper bound is by default the value of the
10869 @code{print elements} variable; if @code{s} is followed by a decimal
10870 number, that is the upper bound instead. So for instance
10871 @samp{collect/s25 mystr} collects as many as 25 characters at
10874 The command @code{info scope} (@pxref{Symbols, info scope}) is
10875 particularly useful for figuring out what data to collect.
10877 @kindex teval @r{(tracepoints)}
10878 @item teval @var{expr1}, @var{expr2}, @dots{}
10879 Evaluate the given expressions when the tracepoint is hit. This
10880 command accepts a comma-separated list of expressions. The results
10881 are discarded, so this is mainly useful for assigning values to trace
10882 state variables (@pxref{Trace State Variables}) without adding those
10883 values to the trace buffer, as would be the case if the @code{collect}
10886 @kindex while-stepping @r{(tracepoints)}
10887 @item while-stepping @var{n}
10888 Perform @var{n} single-step instruction traces after the tracepoint,
10889 collecting new data after each step. The @code{while-stepping}
10890 command is followed by the list of what to collect while stepping
10891 (followed by its own @code{end} command):
10894 > while-stepping 12
10895 > collect $regs, myglobal
10901 Note that @code{$pc} is not automatically collected by
10902 @code{while-stepping}; you need to explicitly collect that register if
10903 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
10906 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
10907 @kindex set default-collect
10908 @cindex default collection action
10909 This variable is a list of expressions to collect at each tracepoint
10910 hit. It is effectively an additional @code{collect} action prepended
10911 to every tracepoint action list. The expressions are parsed
10912 individually for each tracepoint, so for instance a variable named
10913 @code{xyz} may be interpreted as a global for one tracepoint, and a
10914 local for another, as appropriate to the tracepoint's location.
10916 @item show default-collect
10917 @kindex show default-collect
10918 Show the list of expressions that are collected by default at each
10923 @node Listing Tracepoints
10924 @subsection Listing Tracepoints
10927 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
10928 @kindex info tp @r{[}@var{n}@dots{}@r{]}
10929 @cindex information about tracepoints
10930 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
10931 Display information about the tracepoint @var{num}. If you don't
10932 specify a tracepoint number, displays information about all the
10933 tracepoints defined so far. The format is similar to that used for
10934 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
10935 command, simply restricting itself to tracepoints.
10937 A tracepoint's listing may include additional information specific to
10942 its passcount as given by the @code{passcount @var{n}} command
10946 (@value{GDBP}) @b{info trace}
10947 Num Type Disp Enb Address What
10948 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
10950 collect globfoo, $regs
10959 This command can be abbreviated @code{info tp}.
10962 @node Listing Static Tracepoint Markers
10963 @subsection Listing Static Tracepoint Markers
10966 @kindex info static-tracepoint-markers
10967 @cindex information about static tracepoint markers
10968 @item info static-tracepoint-markers
10969 Display information about all static tracepoint markers defined in the
10972 For each marker, the following columns are printed:
10976 An incrementing counter, output to help readability. This is not a
10979 The marker ID, as reported by the target.
10980 @item Enabled or Disabled
10981 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
10982 that are not enabled.
10984 Where the marker is in your program, as a memory address.
10986 Where the marker is in the source for your program, as a file and line
10987 number. If the debug information included in the program does not
10988 allow @value{GDBN} to locate the source of the marker, this column
10989 will be left blank.
10993 In addition, the following information may be printed for each marker:
10997 User data passed to the tracing library by the marker call. In the
10998 UST backend, this is the format string passed as argument to the
11000 @item Static tracepoints probing the marker
11001 The list of static tracepoints attached to the marker.
11005 (@value{GDBP}) info static-tracepoint-markers
11006 Cnt ID Enb Address What
11007 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
11008 Data: number1 %d number2 %d
11009 Probed by static tracepoints: #2
11010 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
11016 @node Starting and Stopping Trace Experiments
11017 @subsection Starting and Stopping Trace Experiments
11020 @kindex tstart [ @var{notes} ]
11021 @cindex start a new trace experiment
11022 @cindex collected data discarded
11024 This command starts the trace experiment, and begins collecting data.
11025 It has the side effect of discarding all the data collected in the
11026 trace buffer during the previous trace experiment. If any arguments
11027 are supplied, they are taken as a note and stored with the trace
11028 experiment's state. The notes may be arbitrary text, and are
11029 especially useful with disconnected tracing in a multi-user context;
11030 the notes can explain what the trace is doing, supply user contact
11031 information, and so forth.
11033 @kindex tstop [ @var{notes} ]
11034 @cindex stop a running trace experiment
11036 This command stops the trace experiment. If any arguments are
11037 supplied, they are recorded with the experiment as a note. This is
11038 useful if you are stopping a trace started by someone else, for
11039 instance if the trace is interfering with the system's behavior and
11040 needs to be stopped quickly.
11042 @strong{Note}: a trace experiment and data collection may stop
11043 automatically if any tracepoint's passcount is reached
11044 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
11047 @cindex status of trace data collection
11048 @cindex trace experiment, status of
11050 This command displays the status of the current trace data
11054 Here is an example of the commands we described so far:
11057 (@value{GDBP}) @b{trace gdb_c_test}
11058 (@value{GDBP}) @b{actions}
11059 Enter actions for tracepoint #1, one per line.
11060 > collect $regs,$locals,$args
11061 > while-stepping 11
11065 (@value{GDBP}) @b{tstart}
11066 [time passes @dots{}]
11067 (@value{GDBP}) @b{tstop}
11070 @anchor{disconnected tracing}
11071 @cindex disconnected tracing
11072 You can choose to continue running the trace experiment even if
11073 @value{GDBN} disconnects from the target, voluntarily or
11074 involuntarily. For commands such as @code{detach}, the debugger will
11075 ask what you want to do with the trace. But for unexpected
11076 terminations (@value{GDBN} crash, network outage), it would be
11077 unfortunate to lose hard-won trace data, so the variable
11078 @code{disconnected-tracing} lets you decide whether the trace should
11079 continue running without @value{GDBN}.
11082 @item set disconnected-tracing on
11083 @itemx set disconnected-tracing off
11084 @kindex set disconnected-tracing
11085 Choose whether a tracing run should continue to run if @value{GDBN}
11086 has disconnected from the target. Note that @code{detach} or
11087 @code{quit} will ask you directly what to do about a running trace no
11088 matter what this variable's setting, so the variable is mainly useful
11089 for handling unexpected situations, such as loss of the network.
11091 @item show disconnected-tracing
11092 @kindex show disconnected-tracing
11093 Show the current choice for disconnected tracing.
11097 When you reconnect to the target, the trace experiment may or may not
11098 still be running; it might have filled the trace buffer in the
11099 meantime, or stopped for one of the other reasons. If it is running,
11100 it will continue after reconnection.
11102 Upon reconnection, the target will upload information about the
11103 tracepoints in effect. @value{GDBN} will then compare that
11104 information to the set of tracepoints currently defined, and attempt
11105 to match them up, allowing for the possibility that the numbers may
11106 have changed due to creation and deletion in the meantime. If one of
11107 the target's tracepoints does not match any in @value{GDBN}, the
11108 debugger will create a new tracepoint, so that you have a number with
11109 which to specify that tracepoint. This matching-up process is
11110 necessarily heuristic, and it may result in useless tracepoints being
11111 created; you may simply delete them if they are of no use.
11113 @cindex circular trace buffer
11114 If your target agent supports a @dfn{circular trace buffer}, then you
11115 can run a trace experiment indefinitely without filling the trace
11116 buffer; when space runs out, the agent deletes already-collected trace
11117 frames, oldest first, until there is enough room to continue
11118 collecting. This is especially useful if your tracepoints are being
11119 hit too often, and your trace gets terminated prematurely because the
11120 buffer is full. To ask for a circular trace buffer, simply set
11121 @samp{circular-trace-buffer} to on. You can set this at any time,
11122 including during tracing; if the agent can do it, it will change
11123 buffer handling on the fly, otherwise it will not take effect until
11127 @item set circular-trace-buffer on
11128 @itemx set circular-trace-buffer off
11129 @kindex set circular-trace-buffer
11130 Choose whether a tracing run should use a linear or circular buffer
11131 for trace data. A linear buffer will not lose any trace data, but may
11132 fill up prematurely, while a circular buffer will discard old trace
11133 data, but it will have always room for the latest tracepoint hits.
11135 @item show circular-trace-buffer
11136 @kindex show circular-trace-buffer
11137 Show the current choice for the trace buffer. Note that this may not
11138 match the agent's current buffer handling, nor is it guaranteed to
11139 match the setting that might have been in effect during a past run,
11140 for instance if you are looking at frames from a trace file.
11145 @item set trace-user @var{text}
11146 @kindex set trace-user
11148 @item show trace-user
11149 @kindex show trace-user
11151 @item set trace-notes @var{text}
11152 @kindex set trace-notes
11153 Set the trace run's notes.
11155 @item show trace-notes
11156 @kindex show trace-notes
11157 Show the trace run's notes.
11159 @item set trace-stop-notes @var{text}
11160 @kindex set trace-stop-notes
11161 Set the trace run's stop notes. The handling of the note is as for
11162 @code{tstop} arguments; the set command is convenient way to fix a
11163 stop note that is mistaken or incomplete.
11165 @item show trace-stop-notes
11166 @kindex show trace-stop-notes
11167 Show the trace run's stop notes.
11171 @node Tracepoint Restrictions
11172 @subsection Tracepoint Restrictions
11174 @cindex tracepoint restrictions
11175 There are a number of restrictions on the use of tracepoints. As
11176 described above, tracepoint data gathering occurs on the target
11177 without interaction from @value{GDBN}. Thus the full capabilities of
11178 the debugger are not available during data gathering, and then at data
11179 examination time, you will be limited by only having what was
11180 collected. The following items describe some common problems, but it
11181 is not exhaustive, and you may run into additional difficulties not
11187 Tracepoint expressions are intended to gather objects (lvalues). Thus
11188 the full flexibility of GDB's expression evaluator is not available.
11189 You cannot call functions, cast objects to aggregate types, access
11190 convenience variables or modify values (except by assignment to trace
11191 state variables). Some language features may implicitly call
11192 functions (for instance Objective-C fields with accessors), and therefore
11193 cannot be collected either.
11196 Collection of local variables, either individually or in bulk with
11197 @code{$locals} or @code{$args}, during @code{while-stepping} may
11198 behave erratically. The stepping action may enter a new scope (for
11199 instance by stepping into a function), or the location of the variable
11200 may change (for instance it is loaded into a register). The
11201 tracepoint data recorded uses the location information for the
11202 variables that is correct for the tracepoint location. When the
11203 tracepoint is created, it is not possible, in general, to determine
11204 where the steps of a @code{while-stepping} sequence will advance the
11205 program---particularly if a conditional branch is stepped.
11208 Collection of an incompletely-initialized or partially-destroyed object
11209 may result in something that @value{GDBN} cannot display, or displays
11210 in a misleading way.
11213 When @value{GDBN} displays a pointer to character it automatically
11214 dereferences the pointer to also display characters of the string
11215 being pointed to. However, collecting the pointer during tracing does
11216 not automatically collect the string. You need to explicitly
11217 dereference the pointer and provide size information if you want to
11218 collect not only the pointer, but the memory pointed to. For example,
11219 @code{*ptr@@50} can be used to collect the 50 element array pointed to
11223 It is not possible to collect a complete stack backtrace at a
11224 tracepoint. Instead, you may collect the registers and a few hundred
11225 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
11226 (adjust to use the name of the actual stack pointer register on your
11227 target architecture, and the amount of stack you wish to capture).
11228 Then the @code{backtrace} command will show a partial backtrace when
11229 using a trace frame. The number of stack frames that can be examined
11230 depends on the sizes of the frames in the collected stack. Note that
11231 if you ask for a block so large that it goes past the bottom of the
11232 stack, the target agent may report an error trying to read from an
11236 If you do not collect registers at a tracepoint, @value{GDBN} can
11237 infer that the value of @code{$pc} must be the same as the address of
11238 the tracepoint and use that when you are looking at a trace frame
11239 for that tracepoint. However, this cannot work if the tracepoint has
11240 multiple locations (for instance if it was set in a function that was
11241 inlined), or if it has a @code{while-stepping} loop. In those cases
11242 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
11247 @node Analyze Collected Data
11248 @section Using the Collected Data
11250 After the tracepoint experiment ends, you use @value{GDBN} commands
11251 for examining the trace data. The basic idea is that each tracepoint
11252 collects a trace @dfn{snapshot} every time it is hit and another
11253 snapshot every time it single-steps. All these snapshots are
11254 consecutively numbered from zero and go into a buffer, and you can
11255 examine them later. The way you examine them is to @dfn{focus} on a
11256 specific trace snapshot. When the remote stub is focused on a trace
11257 snapshot, it will respond to all @value{GDBN} requests for memory and
11258 registers by reading from the buffer which belongs to that snapshot,
11259 rather than from @emph{real} memory or registers of the program being
11260 debugged. This means that @strong{all} @value{GDBN} commands
11261 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
11262 behave as if we were currently debugging the program state as it was
11263 when the tracepoint occurred. Any requests for data that are not in
11264 the buffer will fail.
11267 * tfind:: How to select a trace snapshot
11268 * tdump:: How to display all data for a snapshot
11269 * save tracepoints:: How to save tracepoints for a future run
11273 @subsection @code{tfind @var{n}}
11276 @cindex select trace snapshot
11277 @cindex find trace snapshot
11278 The basic command for selecting a trace snapshot from the buffer is
11279 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
11280 counting from zero. If no argument @var{n} is given, the next
11281 snapshot is selected.
11283 Here are the various forms of using the @code{tfind} command.
11287 Find the first snapshot in the buffer. This is a synonym for
11288 @code{tfind 0} (since 0 is the number of the first snapshot).
11291 Stop debugging trace snapshots, resume @emph{live} debugging.
11294 Same as @samp{tfind none}.
11297 No argument means find the next trace snapshot.
11300 Find the previous trace snapshot before the current one. This permits
11301 retracing earlier steps.
11303 @item tfind tracepoint @var{num}
11304 Find the next snapshot associated with tracepoint @var{num}. Search
11305 proceeds forward from the last examined trace snapshot. If no
11306 argument @var{num} is given, it means find the next snapshot collected
11307 for the same tracepoint as the current snapshot.
11309 @item tfind pc @var{addr}
11310 Find the next snapshot associated with the value @var{addr} of the
11311 program counter. Search proceeds forward from the last examined trace
11312 snapshot. If no argument @var{addr} is given, it means find the next
11313 snapshot with the same value of PC as the current snapshot.
11315 @item tfind outside @var{addr1}, @var{addr2}
11316 Find the next snapshot whose PC is outside the given range of
11317 addresses (exclusive).
11319 @item tfind range @var{addr1}, @var{addr2}
11320 Find the next snapshot whose PC is between @var{addr1} and
11321 @var{addr2} (inclusive).
11323 @item tfind line @r{[}@var{file}:@r{]}@var{n}
11324 Find the next snapshot associated with the source line @var{n}. If
11325 the optional argument @var{file} is given, refer to line @var{n} in
11326 that source file. Search proceeds forward from the last examined
11327 trace snapshot. If no argument @var{n} is given, it means find the
11328 next line other than the one currently being examined; thus saying
11329 @code{tfind line} repeatedly can appear to have the same effect as
11330 stepping from line to line in a @emph{live} debugging session.
11333 The default arguments for the @code{tfind} commands are specifically
11334 designed to make it easy to scan through the trace buffer. For
11335 instance, @code{tfind} with no argument selects the next trace
11336 snapshot, and @code{tfind -} with no argument selects the previous
11337 trace snapshot. So, by giving one @code{tfind} command, and then
11338 simply hitting @key{RET} repeatedly you can examine all the trace
11339 snapshots in order. Or, by saying @code{tfind -} and then hitting
11340 @key{RET} repeatedly you can examine the snapshots in reverse order.
11341 The @code{tfind line} command with no argument selects the snapshot
11342 for the next source line executed. The @code{tfind pc} command with
11343 no argument selects the next snapshot with the same program counter
11344 (PC) as the current frame. The @code{tfind tracepoint} command with
11345 no argument selects the next trace snapshot collected by the same
11346 tracepoint as the current one.
11348 In addition to letting you scan through the trace buffer manually,
11349 these commands make it easy to construct @value{GDBN} scripts that
11350 scan through the trace buffer and print out whatever collected data
11351 you are interested in. Thus, if we want to examine the PC, FP, and SP
11352 registers from each trace frame in the buffer, we can say this:
11355 (@value{GDBP}) @b{tfind start}
11356 (@value{GDBP}) @b{while ($trace_frame != -1)}
11357 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
11358 $trace_frame, $pc, $sp, $fp
11362 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
11363 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
11364 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
11365 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
11366 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
11367 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
11368 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
11369 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
11370 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
11371 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
11372 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
11375 Or, if we want to examine the variable @code{X} at each source line in
11379 (@value{GDBP}) @b{tfind start}
11380 (@value{GDBP}) @b{while ($trace_frame != -1)}
11381 > printf "Frame %d, X == %d\n", $trace_frame, X
11391 @subsection @code{tdump}
11393 @cindex dump all data collected at tracepoint
11394 @cindex tracepoint data, display
11396 This command takes no arguments. It prints all the data collected at
11397 the current trace snapshot.
11400 (@value{GDBP}) @b{trace 444}
11401 (@value{GDBP}) @b{actions}
11402 Enter actions for tracepoint #2, one per line:
11403 > collect $regs, $locals, $args, gdb_long_test
11406 (@value{GDBP}) @b{tstart}
11408 (@value{GDBP}) @b{tfind line 444}
11409 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
11411 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
11413 (@value{GDBP}) @b{tdump}
11414 Data collected at tracepoint 2, trace frame 1:
11415 d0 0xc4aa0085 -995491707
11419 d4 0x71aea3d 119204413
11422 d7 0x380035 3670069
11423 a0 0x19e24a 1696330
11424 a1 0x3000668 50333288
11426 a3 0x322000 3284992
11427 a4 0x3000698 50333336
11428 a5 0x1ad3cc 1758156
11429 fp 0x30bf3c 0x30bf3c
11430 sp 0x30bf34 0x30bf34
11432 pc 0x20b2c8 0x20b2c8
11436 p = 0x20e5b4 "gdb-test"
11443 gdb_long_test = 17 '\021'
11448 @code{tdump} works by scanning the tracepoint's current collection
11449 actions and printing the value of each expression listed. So
11450 @code{tdump} can fail, if after a run, you change the tracepoint's
11451 actions to mention variables that were not collected during the run.
11453 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
11454 uses the collected value of @code{$pc} to distinguish between trace
11455 frames that were collected at the tracepoint hit, and frames that were
11456 collected while stepping. This allows it to correctly choose whether
11457 to display the basic list of collections, or the collections from the
11458 body of the while-stepping loop. However, if @code{$pc} was not collected,
11459 then @code{tdump} will always attempt to dump using the basic collection
11460 list, and may fail if a while-stepping frame does not include all the
11461 same data that is collected at the tracepoint hit.
11462 @c This is getting pretty arcane, example would be good.
11464 @node save tracepoints
11465 @subsection @code{save tracepoints @var{filename}}
11466 @kindex save tracepoints
11467 @kindex save-tracepoints
11468 @cindex save tracepoints for future sessions
11470 This command saves all current tracepoint definitions together with
11471 their actions and passcounts, into a file @file{@var{filename}}
11472 suitable for use in a later debugging session. To read the saved
11473 tracepoint definitions, use the @code{source} command (@pxref{Command
11474 Files}). The @w{@code{save-tracepoints}} command is a deprecated
11475 alias for @w{@code{save tracepoints}}
11477 @node Tracepoint Variables
11478 @section Convenience Variables for Tracepoints
11479 @cindex tracepoint variables
11480 @cindex convenience variables for tracepoints
11483 @vindex $trace_frame
11484 @item (int) $trace_frame
11485 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
11486 snapshot is selected.
11488 @vindex $tracepoint
11489 @item (int) $tracepoint
11490 The tracepoint for the current trace snapshot.
11492 @vindex $trace_line
11493 @item (int) $trace_line
11494 The line number for the current trace snapshot.
11496 @vindex $trace_file
11497 @item (char []) $trace_file
11498 The source file for the current trace snapshot.
11500 @vindex $trace_func
11501 @item (char []) $trace_func
11502 The name of the function containing @code{$tracepoint}.
11505 Note: @code{$trace_file} is not suitable for use in @code{printf},
11506 use @code{output} instead.
11508 Here's a simple example of using these convenience variables for
11509 stepping through all the trace snapshots and printing some of their
11510 data. Note that these are not the same as trace state variables,
11511 which are managed by the target.
11514 (@value{GDBP}) @b{tfind start}
11516 (@value{GDBP}) @b{while $trace_frame != -1}
11517 > output $trace_file
11518 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
11524 @section Using Trace Files
11525 @cindex trace files
11527 In some situations, the target running a trace experiment may no
11528 longer be available; perhaps it crashed, or the hardware was needed
11529 for a different activity. To handle these cases, you can arrange to
11530 dump the trace data into a file, and later use that file as a source
11531 of trace data, via the @code{target tfile} command.
11536 @item tsave [ -r ] @var{filename}
11537 Save the trace data to @var{filename}. By default, this command
11538 assumes that @var{filename} refers to the host filesystem, so if
11539 necessary @value{GDBN} will copy raw trace data up from the target and
11540 then save it. If the target supports it, you can also supply the
11541 optional argument @code{-r} (``remote'') to direct the target to save
11542 the data directly into @var{filename} in its own filesystem, which may be
11543 more efficient if the trace buffer is very large. (Note, however, that
11544 @code{target tfile} can only read from files accessible to the host.)
11546 @kindex target tfile
11548 @item target tfile @var{filename}
11549 Use the file named @var{filename} as a source of trace data. Commands
11550 that examine data work as they do with a live target, but it is not
11551 possible to run any new trace experiments. @code{tstatus} will report
11552 the state of the trace run at the moment the data was saved, as well
11553 as the current trace frame you are examining. @var{filename} must be
11554 on a filesystem accessible to the host.
11559 @chapter Debugging Programs That Use Overlays
11562 If your program is too large to fit completely in your target system's
11563 memory, you can sometimes use @dfn{overlays} to work around this
11564 problem. @value{GDBN} provides some support for debugging programs that
11568 * How Overlays Work:: A general explanation of overlays.
11569 * Overlay Commands:: Managing overlays in @value{GDBN}.
11570 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
11571 mapped by asking the inferior.
11572 * Overlay Sample Program:: A sample program using overlays.
11575 @node How Overlays Work
11576 @section How Overlays Work
11577 @cindex mapped overlays
11578 @cindex unmapped overlays
11579 @cindex load address, overlay's
11580 @cindex mapped address
11581 @cindex overlay area
11583 Suppose you have a computer whose instruction address space is only 64
11584 kilobytes long, but which has much more memory which can be accessed by
11585 other means: special instructions, segment registers, or memory
11586 management hardware, for example. Suppose further that you want to
11587 adapt a program which is larger than 64 kilobytes to run on this system.
11589 One solution is to identify modules of your program which are relatively
11590 independent, and need not call each other directly; call these modules
11591 @dfn{overlays}. Separate the overlays from the main program, and place
11592 their machine code in the larger memory. Place your main program in
11593 instruction memory, but leave at least enough space there to hold the
11594 largest overlay as well.
11596 Now, to call a function located in an overlay, you must first copy that
11597 overlay's machine code from the large memory into the space set aside
11598 for it in the instruction memory, and then jump to its entry point
11601 @c NB: In the below the mapped area's size is greater or equal to the
11602 @c size of all overlays. This is intentional to remind the developer
11603 @c that overlays don't necessarily need to be the same size.
11607 Data Instruction Larger
11608 Address Space Address Space Address Space
11609 +-----------+ +-----------+ +-----------+
11611 +-----------+ +-----------+ +-----------+<-- overlay 1
11612 | program | | main | .----| overlay 1 | load address
11613 | variables | | program | | +-----------+
11614 | and heap | | | | | |
11615 +-----------+ | | | +-----------+<-- overlay 2
11616 | | +-----------+ | | | load address
11617 +-----------+ | | | .-| overlay 2 |
11619 mapped --->+-----------+ | | +-----------+
11620 address | | | | | |
11621 | overlay | <-' | | |
11622 | area | <---' +-----------+<-- overlay 3
11623 | | <---. | | load address
11624 +-----------+ `--| overlay 3 |
11631 @anchor{A code overlay}A code overlay
11635 The diagram (@pxref{A code overlay}) shows a system with separate data
11636 and instruction address spaces. To map an overlay, the program copies
11637 its code from the larger address space to the instruction address space.
11638 Since the overlays shown here all use the same mapped address, only one
11639 may be mapped at a time. For a system with a single address space for
11640 data and instructions, the diagram would be similar, except that the
11641 program variables and heap would share an address space with the main
11642 program and the overlay area.
11644 An overlay loaded into instruction memory and ready for use is called a
11645 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
11646 instruction memory. An overlay not present (or only partially present)
11647 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
11648 is its address in the larger memory. The mapped address is also called
11649 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
11650 called the @dfn{load memory address}, or @dfn{LMA}.
11652 Unfortunately, overlays are not a completely transparent way to adapt a
11653 program to limited instruction memory. They introduce a new set of
11654 global constraints you must keep in mind as you design your program:
11659 Before calling or returning to a function in an overlay, your program
11660 must make sure that overlay is actually mapped. Otherwise, the call or
11661 return will transfer control to the right address, but in the wrong
11662 overlay, and your program will probably crash.
11665 If the process of mapping an overlay is expensive on your system, you
11666 will need to choose your overlays carefully to minimize their effect on
11667 your program's performance.
11670 The executable file you load onto your system must contain each
11671 overlay's instructions, appearing at the overlay's load address, not its
11672 mapped address. However, each overlay's instructions must be relocated
11673 and its symbols defined as if the overlay were at its mapped address.
11674 You can use GNU linker scripts to specify different load and relocation
11675 addresses for pieces of your program; see @ref{Overlay Description,,,
11676 ld.info, Using ld: the GNU linker}.
11679 The procedure for loading executable files onto your system must be able
11680 to load their contents into the larger address space as well as the
11681 instruction and data spaces.
11685 The overlay system described above is rather simple, and could be
11686 improved in many ways:
11691 If your system has suitable bank switch registers or memory management
11692 hardware, you could use those facilities to make an overlay's load area
11693 contents simply appear at their mapped address in instruction space.
11694 This would probably be faster than copying the overlay to its mapped
11695 area in the usual way.
11698 If your overlays are small enough, you could set aside more than one
11699 overlay area, and have more than one overlay mapped at a time.
11702 You can use overlays to manage data, as well as instructions. In
11703 general, data overlays are even less transparent to your design than
11704 code overlays: whereas code overlays only require care when you call or
11705 return to functions, data overlays require care every time you access
11706 the data. Also, if you change the contents of a data overlay, you
11707 must copy its contents back out to its load address before you can copy a
11708 different data overlay into the same mapped area.
11713 @node Overlay Commands
11714 @section Overlay Commands
11716 To use @value{GDBN}'s overlay support, each overlay in your program must
11717 correspond to a separate section of the executable file. The section's
11718 virtual memory address and load memory address must be the overlay's
11719 mapped and load addresses. Identifying overlays with sections allows
11720 @value{GDBN} to determine the appropriate address of a function or
11721 variable, depending on whether the overlay is mapped or not.
11723 @value{GDBN}'s overlay commands all start with the word @code{overlay};
11724 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
11729 Disable @value{GDBN}'s overlay support. When overlay support is
11730 disabled, @value{GDBN} assumes that all functions and variables are
11731 always present at their mapped addresses. By default, @value{GDBN}'s
11732 overlay support is disabled.
11734 @item overlay manual
11735 @cindex manual overlay debugging
11736 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
11737 relies on you to tell it which overlays are mapped, and which are not,
11738 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
11739 commands described below.
11741 @item overlay map-overlay @var{overlay}
11742 @itemx overlay map @var{overlay}
11743 @cindex map an overlay
11744 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
11745 be the name of the object file section containing the overlay. When an
11746 overlay is mapped, @value{GDBN} assumes it can find the overlay's
11747 functions and variables at their mapped addresses. @value{GDBN} assumes
11748 that any other overlays whose mapped ranges overlap that of
11749 @var{overlay} are now unmapped.
11751 @item overlay unmap-overlay @var{overlay}
11752 @itemx overlay unmap @var{overlay}
11753 @cindex unmap an overlay
11754 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
11755 must be the name of the object file section containing the overlay.
11756 When an overlay is unmapped, @value{GDBN} assumes it can find the
11757 overlay's functions and variables at their load addresses.
11760 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
11761 consults a data structure the overlay manager maintains in the inferior
11762 to see which overlays are mapped. For details, see @ref{Automatic
11763 Overlay Debugging}.
11765 @item overlay load-target
11766 @itemx overlay load
11767 @cindex reloading the overlay table
11768 Re-read the overlay table from the inferior. Normally, @value{GDBN}
11769 re-reads the table @value{GDBN} automatically each time the inferior
11770 stops, so this command should only be necessary if you have changed the
11771 overlay mapping yourself using @value{GDBN}. This command is only
11772 useful when using automatic overlay debugging.
11774 @item overlay list-overlays
11775 @itemx overlay list
11776 @cindex listing mapped overlays
11777 Display a list of the overlays currently mapped, along with their mapped
11778 addresses, load addresses, and sizes.
11782 Normally, when @value{GDBN} prints a code address, it includes the name
11783 of the function the address falls in:
11786 (@value{GDBP}) print main
11787 $3 = @{int ()@} 0x11a0 <main>
11790 When overlay debugging is enabled, @value{GDBN} recognizes code in
11791 unmapped overlays, and prints the names of unmapped functions with
11792 asterisks around them. For example, if @code{foo} is a function in an
11793 unmapped overlay, @value{GDBN} prints it this way:
11796 (@value{GDBP}) overlay list
11797 No sections are mapped.
11798 (@value{GDBP}) print foo
11799 $5 = @{int (int)@} 0x100000 <*foo*>
11802 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
11806 (@value{GDBP}) overlay list
11807 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
11808 mapped at 0x1016 - 0x104a
11809 (@value{GDBP}) print foo
11810 $6 = @{int (int)@} 0x1016 <foo>
11813 When overlay debugging is enabled, @value{GDBN} can find the correct
11814 address for functions and variables in an overlay, whether or not the
11815 overlay is mapped. This allows most @value{GDBN} commands, like
11816 @code{break} and @code{disassemble}, to work normally, even on unmapped
11817 code. However, @value{GDBN}'s breakpoint support has some limitations:
11821 @cindex breakpoints in overlays
11822 @cindex overlays, setting breakpoints in
11823 You can set breakpoints in functions in unmapped overlays, as long as
11824 @value{GDBN} can write to the overlay at its load address.
11826 @value{GDBN} can not set hardware or simulator-based breakpoints in
11827 unmapped overlays. However, if you set a breakpoint at the end of your
11828 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
11829 you are using manual overlay management), @value{GDBN} will re-set its
11830 breakpoints properly.
11834 @node Automatic Overlay Debugging
11835 @section Automatic Overlay Debugging
11836 @cindex automatic overlay debugging
11838 @value{GDBN} can automatically track which overlays are mapped and which
11839 are not, given some simple co-operation from the overlay manager in the
11840 inferior. If you enable automatic overlay debugging with the
11841 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
11842 looks in the inferior's memory for certain variables describing the
11843 current state of the overlays.
11845 Here are the variables your overlay manager must define to support
11846 @value{GDBN}'s automatic overlay debugging:
11850 @item @code{_ovly_table}:
11851 This variable must be an array of the following structures:
11856 /* The overlay's mapped address. */
11859 /* The size of the overlay, in bytes. */
11860 unsigned long size;
11862 /* The overlay's load address. */
11865 /* Non-zero if the overlay is currently mapped;
11867 unsigned long mapped;
11871 @item @code{_novlys}:
11872 This variable must be a four-byte signed integer, holding the total
11873 number of elements in @code{_ovly_table}.
11877 To decide whether a particular overlay is mapped or not, @value{GDBN}
11878 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
11879 @code{lma} members equal the VMA and LMA of the overlay's section in the
11880 executable file. When @value{GDBN} finds a matching entry, it consults
11881 the entry's @code{mapped} member to determine whether the overlay is
11884 In addition, your overlay manager may define a function called
11885 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
11886 will silently set a breakpoint there. If the overlay manager then
11887 calls this function whenever it has changed the overlay table, this
11888 will enable @value{GDBN} to accurately keep track of which overlays
11889 are in program memory, and update any breakpoints that may be set
11890 in overlays. This will allow breakpoints to work even if the
11891 overlays are kept in ROM or other non-writable memory while they
11892 are not being executed.
11894 @node Overlay Sample Program
11895 @section Overlay Sample Program
11896 @cindex overlay example program
11898 When linking a program which uses overlays, you must place the overlays
11899 at their load addresses, while relocating them to run at their mapped
11900 addresses. To do this, you must write a linker script (@pxref{Overlay
11901 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
11902 since linker scripts are specific to a particular host system, target
11903 architecture, and target memory layout, this manual cannot provide
11904 portable sample code demonstrating @value{GDBN}'s overlay support.
11906 However, the @value{GDBN} source distribution does contain an overlaid
11907 program, with linker scripts for a few systems, as part of its test
11908 suite. The program consists of the following files from
11909 @file{gdb/testsuite/gdb.base}:
11913 The main program file.
11915 A simple overlay manager, used by @file{overlays.c}.
11920 Overlay modules, loaded and used by @file{overlays.c}.
11923 Linker scripts for linking the test program on the @code{d10v-elf}
11924 and @code{m32r-elf} targets.
11927 You can build the test program using the @code{d10v-elf} GCC
11928 cross-compiler like this:
11931 $ d10v-elf-gcc -g -c overlays.c
11932 $ d10v-elf-gcc -g -c ovlymgr.c
11933 $ d10v-elf-gcc -g -c foo.c
11934 $ d10v-elf-gcc -g -c bar.c
11935 $ d10v-elf-gcc -g -c baz.c
11936 $ d10v-elf-gcc -g -c grbx.c
11937 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
11938 baz.o grbx.o -Wl,-Td10v.ld -o overlays
11941 The build process is identical for any other architecture, except that
11942 you must substitute the appropriate compiler and linker script for the
11943 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
11947 @chapter Using @value{GDBN} with Different Languages
11950 Although programming languages generally have common aspects, they are
11951 rarely expressed in the same manner. For instance, in ANSI C,
11952 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
11953 Modula-2, it is accomplished by @code{p^}. Values can also be
11954 represented (and displayed) differently. Hex numbers in C appear as
11955 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
11957 @cindex working language
11958 Language-specific information is built into @value{GDBN} for some languages,
11959 allowing you to express operations like the above in your program's
11960 native language, and allowing @value{GDBN} to output values in a manner
11961 consistent with the syntax of your program's native language. The
11962 language you use to build expressions is called the @dfn{working
11966 * Setting:: Switching between source languages
11967 * Show:: Displaying the language
11968 * Checks:: Type and range checks
11969 * Supported Languages:: Supported languages
11970 * Unsupported Languages:: Unsupported languages
11974 @section Switching Between Source Languages
11976 There are two ways to control the working language---either have @value{GDBN}
11977 set it automatically, or select it manually yourself. You can use the
11978 @code{set language} command for either purpose. On startup, @value{GDBN}
11979 defaults to setting the language automatically. The working language is
11980 used to determine how expressions you type are interpreted, how values
11983 In addition to the working language, every source file that
11984 @value{GDBN} knows about has its own working language. For some object
11985 file formats, the compiler might indicate which language a particular
11986 source file is in. However, most of the time @value{GDBN} infers the
11987 language from the name of the file. The language of a source file
11988 controls whether C@t{++} names are demangled---this way @code{backtrace} can
11989 show each frame appropriately for its own language. There is no way to
11990 set the language of a source file from within @value{GDBN}, but you can
11991 set the language associated with a filename extension. @xref{Show, ,
11992 Displaying the Language}.
11994 This is most commonly a problem when you use a program, such
11995 as @code{cfront} or @code{f2c}, that generates C but is written in
11996 another language. In that case, make the
11997 program use @code{#line} directives in its C output; that way
11998 @value{GDBN} will know the correct language of the source code of the original
11999 program, and will display that source code, not the generated C code.
12002 * Filenames:: Filename extensions and languages.
12003 * Manually:: Setting the working language manually
12004 * Automatically:: Having @value{GDBN} infer the source language
12008 @subsection List of Filename Extensions and Languages
12010 If a source file name ends in one of the following extensions, then
12011 @value{GDBN} infers that its language is the one indicated.
12029 C@t{++} source file
12035 Objective-C source file
12039 Fortran source file
12042 Modula-2 source file
12046 Assembler source file. This actually behaves almost like C, but
12047 @value{GDBN} does not skip over function prologues when stepping.
12050 In addition, you may set the language associated with a filename
12051 extension. @xref{Show, , Displaying the Language}.
12054 @subsection Setting the Working Language
12056 If you allow @value{GDBN} to set the language automatically,
12057 expressions are interpreted the same way in your debugging session and
12060 @kindex set language
12061 If you wish, you may set the language manually. To do this, issue the
12062 command @samp{set language @var{lang}}, where @var{lang} is the name of
12063 a language, such as
12064 @code{c} or @code{modula-2}.
12065 For a list of the supported languages, type @samp{set language}.
12067 Setting the language manually prevents @value{GDBN} from updating the working
12068 language automatically. This can lead to confusion if you try
12069 to debug a program when the working language is not the same as the
12070 source language, when an expression is acceptable to both
12071 languages---but means different things. For instance, if the current
12072 source file were written in C, and @value{GDBN} was parsing Modula-2, a
12080 might not have the effect you intended. In C, this means to add
12081 @code{b} and @code{c} and place the result in @code{a}. The result
12082 printed would be the value of @code{a}. In Modula-2, this means to compare
12083 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
12085 @node Automatically
12086 @subsection Having @value{GDBN} Infer the Source Language
12088 To have @value{GDBN} set the working language automatically, use
12089 @samp{set language local} or @samp{set language auto}. @value{GDBN}
12090 then infers the working language. That is, when your program stops in a
12091 frame (usually by encountering a breakpoint), @value{GDBN} sets the
12092 working language to the language recorded for the function in that
12093 frame. If the language for a frame is unknown (that is, if the function
12094 or block corresponding to the frame was defined in a source file that
12095 does not have a recognized extension), the current working language is
12096 not changed, and @value{GDBN} issues a warning.
12098 This may not seem necessary for most programs, which are written
12099 entirely in one source language. However, program modules and libraries
12100 written in one source language can be used by a main program written in
12101 a different source language. Using @samp{set language auto} in this
12102 case frees you from having to set the working language manually.
12105 @section Displaying the Language
12107 The following commands help you find out which language is the
12108 working language, and also what language source files were written in.
12111 @item show language
12112 @kindex show language
12113 Display the current working language. This is the
12114 language you can use with commands such as @code{print} to
12115 build and compute expressions that may involve variables in your program.
12118 @kindex info frame@r{, show the source language}
12119 Display the source language for this frame. This language becomes the
12120 working language if you use an identifier from this frame.
12121 @xref{Frame Info, ,Information about a Frame}, to identify the other
12122 information listed here.
12125 @kindex info source@r{, show the source language}
12126 Display the source language of this source file.
12127 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
12128 information listed here.
12131 In unusual circumstances, you may have source files with extensions
12132 not in the standard list. You can then set the extension associated
12133 with a language explicitly:
12136 @item set extension-language @var{ext} @var{language}
12137 @kindex set extension-language
12138 Tell @value{GDBN} that source files with extension @var{ext} are to be
12139 assumed as written in the source language @var{language}.
12141 @item info extensions
12142 @kindex info extensions
12143 List all the filename extensions and the associated languages.
12147 @section Type and Range Checking
12150 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
12151 checking are included, but they do not yet have any effect. This
12152 section documents the intended facilities.
12154 @c FIXME remove warning when type/range code added
12156 Some languages are designed to guard you against making seemingly common
12157 errors through a series of compile- and run-time checks. These include
12158 checking the type of arguments to functions and operators, and making
12159 sure mathematical overflows are caught at run time. Checks such as
12160 these help to ensure a program's correctness once it has been compiled
12161 by eliminating type mismatches, and providing active checks for range
12162 errors when your program is running.
12164 @value{GDBN} can check for conditions like the above if you wish.
12165 Although @value{GDBN} does not check the statements in your program,
12166 it can check expressions entered directly into @value{GDBN} for
12167 evaluation via the @code{print} command, for example. As with the
12168 working language, @value{GDBN} can also decide whether or not to check
12169 automatically based on your program's source language.
12170 @xref{Supported Languages, ,Supported Languages}, for the default
12171 settings of supported languages.
12174 * Type Checking:: An overview of type checking
12175 * Range Checking:: An overview of range checking
12178 @cindex type checking
12179 @cindex checks, type
12180 @node Type Checking
12181 @subsection An Overview of Type Checking
12183 Some languages, such as Modula-2, are strongly typed, meaning that the
12184 arguments to operators and functions have to be of the correct type,
12185 otherwise an error occurs. These checks prevent type mismatch
12186 errors from ever causing any run-time problems. For example,
12194 The second example fails because the @code{CARDINAL} 1 is not
12195 type-compatible with the @code{REAL} 2.3.
12197 For the expressions you use in @value{GDBN} commands, you can tell the
12198 @value{GDBN} type checker to skip checking;
12199 to treat any mismatches as errors and abandon the expression;
12200 or to only issue warnings when type mismatches occur,
12201 but evaluate the expression anyway. When you choose the last of
12202 these, @value{GDBN} evaluates expressions like the second example above, but
12203 also issues a warning.
12205 Even if you turn type checking off, there may be other reasons
12206 related to type that prevent @value{GDBN} from evaluating an expression.
12207 For instance, @value{GDBN} does not know how to add an @code{int} and
12208 a @code{struct foo}. These particular type errors have nothing to do
12209 with the language in use, and usually arise from expressions, such as
12210 the one described above, which make little sense to evaluate anyway.
12212 Each language defines to what degree it is strict about type. For
12213 instance, both Modula-2 and C require the arguments to arithmetical
12214 operators to be numbers. In C, enumerated types and pointers can be
12215 represented as numbers, so that they are valid arguments to mathematical
12216 operators. @xref{Supported Languages, ,Supported Languages}, for further
12217 details on specific languages.
12219 @value{GDBN} provides some additional commands for controlling the type checker:
12221 @kindex set check type
12222 @kindex show check type
12224 @item set check type auto
12225 Set type checking on or off based on the current working language.
12226 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12229 @item set check type on
12230 @itemx set check type off
12231 Set type checking on or off, overriding the default setting for the
12232 current working language. Issue a warning if the setting does not
12233 match the language default. If any type mismatches occur in
12234 evaluating an expression while type checking is on, @value{GDBN} prints a
12235 message and aborts evaluation of the expression.
12237 @item set check type warn
12238 Cause the type checker to issue warnings, but to always attempt to
12239 evaluate the expression. Evaluating the expression may still
12240 be impossible for other reasons. For example, @value{GDBN} cannot add
12241 numbers and structures.
12244 Show the current setting of the type checker, and whether or not @value{GDBN}
12245 is setting it automatically.
12248 @cindex range checking
12249 @cindex checks, range
12250 @node Range Checking
12251 @subsection An Overview of Range Checking
12253 In some languages (such as Modula-2), it is an error to exceed the
12254 bounds of a type; this is enforced with run-time checks. Such range
12255 checking is meant to ensure program correctness by making sure
12256 computations do not overflow, or indices on an array element access do
12257 not exceed the bounds of the array.
12259 For expressions you use in @value{GDBN} commands, you can tell
12260 @value{GDBN} to treat range errors in one of three ways: ignore them,
12261 always treat them as errors and abandon the expression, or issue
12262 warnings but evaluate the expression anyway.
12264 A range error can result from numerical overflow, from exceeding an
12265 array index bound, or when you type a constant that is not a member
12266 of any type. Some languages, however, do not treat overflows as an
12267 error. In many implementations of C, mathematical overflow causes the
12268 result to ``wrap around'' to lower values---for example, if @var{m} is
12269 the largest integer value, and @var{s} is the smallest, then
12272 @var{m} + 1 @result{} @var{s}
12275 This, too, is specific to individual languages, and in some cases
12276 specific to individual compilers or machines. @xref{Supported Languages, ,
12277 Supported Languages}, for further details on specific languages.
12279 @value{GDBN} provides some additional commands for controlling the range checker:
12281 @kindex set check range
12282 @kindex show check range
12284 @item set check range auto
12285 Set range checking on or off based on the current working language.
12286 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12289 @item set check range on
12290 @itemx set check range off
12291 Set range checking on or off, overriding the default setting for the
12292 current working language. A warning is issued if the setting does not
12293 match the language default. If a range error occurs and range checking is on,
12294 then a message is printed and evaluation of the expression is aborted.
12296 @item set check range warn
12297 Output messages when the @value{GDBN} range checker detects a range error,
12298 but attempt to evaluate the expression anyway. Evaluating the
12299 expression may still be impossible for other reasons, such as accessing
12300 memory that the process does not own (a typical example from many Unix
12304 Show the current setting of the range checker, and whether or not it is
12305 being set automatically by @value{GDBN}.
12308 @node Supported Languages
12309 @section Supported Languages
12311 @value{GDBN} supports C, C@t{++}, D, Objective-C, Fortran, Java, OpenCL C, Pascal,
12312 assembly, Modula-2, and Ada.
12313 @c This is false ...
12314 Some @value{GDBN} features may be used in expressions regardless of the
12315 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
12316 and the @samp{@{type@}addr} construct (@pxref{Expressions,
12317 ,Expressions}) can be used with the constructs of any supported
12320 The following sections detail to what degree each source language is
12321 supported by @value{GDBN}. These sections are not meant to be language
12322 tutorials or references, but serve only as a reference guide to what the
12323 @value{GDBN} expression parser accepts, and what input and output
12324 formats should look like for different languages. There are many good
12325 books written on each of these languages; please look to these for a
12326 language reference or tutorial.
12329 * C:: C and C@t{++}
12331 * Objective-C:: Objective-C
12332 * OpenCL C:: OpenCL C
12333 * Fortran:: Fortran
12335 * Modula-2:: Modula-2
12340 @subsection C and C@t{++}
12342 @cindex C and C@t{++}
12343 @cindex expressions in C or C@t{++}
12345 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
12346 to both languages. Whenever this is the case, we discuss those languages
12350 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
12351 @cindex @sc{gnu} C@t{++}
12352 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
12353 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
12354 effectively, you must compile your C@t{++} programs with a supported
12355 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
12356 compiler (@code{aCC}).
12359 * C Operators:: C and C@t{++} operators
12360 * C Constants:: C and C@t{++} constants
12361 * C Plus Plus Expressions:: C@t{++} expressions
12362 * C Defaults:: Default settings for C and C@t{++}
12363 * C Checks:: C and C@t{++} type and range checks
12364 * Debugging C:: @value{GDBN} and C
12365 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
12366 * Decimal Floating Point:: Numbers in Decimal Floating Point format
12370 @subsubsection C and C@t{++} Operators
12372 @cindex C and C@t{++} operators
12374 Operators must be defined on values of specific types. For instance,
12375 @code{+} is defined on numbers, but not on structures. Operators are
12376 often defined on groups of types.
12378 For the purposes of C and C@t{++}, the following definitions hold:
12383 @emph{Integral types} include @code{int} with any of its storage-class
12384 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
12387 @emph{Floating-point types} include @code{float}, @code{double}, and
12388 @code{long double} (if supported by the target platform).
12391 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
12394 @emph{Scalar types} include all of the above.
12399 The following operators are supported. They are listed here
12400 in order of increasing precedence:
12404 The comma or sequencing operator. Expressions in a comma-separated list
12405 are evaluated from left to right, with the result of the entire
12406 expression being the last expression evaluated.
12409 Assignment. The value of an assignment expression is the value
12410 assigned. Defined on scalar types.
12413 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
12414 and translated to @w{@code{@var{a} = @var{a op b}}}.
12415 @w{@code{@var{op}=}} and @code{=} have the same precedence.
12416 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
12417 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
12420 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
12421 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
12425 Logical @sc{or}. Defined on integral types.
12428 Logical @sc{and}. Defined on integral types.
12431 Bitwise @sc{or}. Defined on integral types.
12434 Bitwise exclusive-@sc{or}. Defined on integral types.
12437 Bitwise @sc{and}. Defined on integral types.
12440 Equality and inequality. Defined on scalar types. The value of these
12441 expressions is 0 for false and non-zero for true.
12443 @item <@r{, }>@r{, }<=@r{, }>=
12444 Less than, greater than, less than or equal, greater than or equal.
12445 Defined on scalar types. The value of these expressions is 0 for false
12446 and non-zero for true.
12449 left shift, and right shift. Defined on integral types.
12452 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12455 Addition and subtraction. Defined on integral types, floating-point types and
12458 @item *@r{, }/@r{, }%
12459 Multiplication, division, and modulus. Multiplication and division are
12460 defined on integral and floating-point types. Modulus is defined on
12464 Increment and decrement. When appearing before a variable, the
12465 operation is performed before the variable is used in an expression;
12466 when appearing after it, the variable's value is used before the
12467 operation takes place.
12470 Pointer dereferencing. Defined on pointer types. Same precedence as
12474 Address operator. Defined on variables. Same precedence as @code{++}.
12476 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
12477 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
12478 to examine the address
12479 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
12483 Negative. Defined on integral and floating-point types. Same
12484 precedence as @code{++}.
12487 Logical negation. Defined on integral types. Same precedence as
12491 Bitwise complement operator. Defined on integral types. Same precedence as
12496 Structure member, and pointer-to-structure member. For convenience,
12497 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
12498 pointer based on the stored type information.
12499 Defined on @code{struct} and @code{union} data.
12502 Dereferences of pointers to members.
12505 Array indexing. @code{@var{a}[@var{i}]} is defined as
12506 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
12509 Function parameter list. Same precedence as @code{->}.
12512 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
12513 and @code{class} types.
12516 Doubled colons also represent the @value{GDBN} scope operator
12517 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
12521 If an operator is redefined in the user code, @value{GDBN} usually
12522 attempts to invoke the redefined version instead of using the operator's
12523 predefined meaning.
12526 @subsubsection C and C@t{++} Constants
12528 @cindex C and C@t{++} constants
12530 @value{GDBN} allows you to express the constants of C and C@t{++} in the
12535 Integer constants are a sequence of digits. Octal constants are
12536 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
12537 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
12538 @samp{l}, specifying that the constant should be treated as a
12542 Floating point constants are a sequence of digits, followed by a decimal
12543 point, followed by a sequence of digits, and optionally followed by an
12544 exponent. An exponent is of the form:
12545 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
12546 sequence of digits. The @samp{+} is optional for positive exponents.
12547 A floating-point constant may also end with a letter @samp{f} or
12548 @samp{F}, specifying that the constant should be treated as being of
12549 the @code{float} (as opposed to the default @code{double}) type; or with
12550 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
12554 Enumerated constants consist of enumerated identifiers, or their
12555 integral equivalents.
12558 Character constants are a single character surrounded by single quotes
12559 (@code{'}), or a number---the ordinal value of the corresponding character
12560 (usually its @sc{ascii} value). Within quotes, the single character may
12561 be represented by a letter or by @dfn{escape sequences}, which are of
12562 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
12563 of the character's ordinal value; or of the form @samp{\@var{x}}, where
12564 @samp{@var{x}} is a predefined special character---for example,
12565 @samp{\n} for newline.
12567 Wide character constants can be written by prefixing a character
12568 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
12569 form of @samp{x}. The target wide character set is used when
12570 computing the value of this constant (@pxref{Character Sets}).
12573 String constants are a sequence of character constants surrounded by
12574 double quotes (@code{"}). Any valid character constant (as described
12575 above) may appear. Double quotes within the string must be preceded by
12576 a backslash, so for instance @samp{"a\"b'c"} is a string of five
12579 Wide string constants can be written by prefixing a string constant
12580 with @samp{L}, as in C. The target wide character set is used when
12581 computing the value of this constant (@pxref{Character Sets}).
12584 Pointer constants are an integral value. You can also write pointers
12585 to constants using the C operator @samp{&}.
12588 Array constants are comma-separated lists surrounded by braces @samp{@{}
12589 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
12590 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
12591 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
12594 @node C Plus Plus Expressions
12595 @subsubsection C@t{++} Expressions
12597 @cindex expressions in C@t{++}
12598 @value{GDBN} expression handling can interpret most C@t{++} expressions.
12600 @cindex debugging C@t{++} programs
12601 @cindex C@t{++} compilers
12602 @cindex debug formats and C@t{++}
12603 @cindex @value{NGCC} and C@t{++}
12605 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
12606 the proper compiler and the proper debug format. Currently,
12607 @value{GDBN} works best when debugging C@t{++} code that is compiled
12608 with the most recent version of @value{NGCC} possible. The DWARF
12609 debugging format is preferred; @value{NGCC} defaults to this on most
12610 popular platforms. Other compilers and/or debug formats are likely to
12611 work badly or not at all when using @value{GDBN} to debug C@t{++}
12612 code. @xref{Compilation}.
12617 @cindex member functions
12619 Member function calls are allowed; you can use expressions like
12622 count = aml->GetOriginal(x, y)
12625 @vindex this@r{, inside C@t{++} member functions}
12626 @cindex namespace in C@t{++}
12628 While a member function is active (in the selected stack frame), your
12629 expressions have the same namespace available as the member function;
12630 that is, @value{GDBN} allows implicit references to the class instance
12631 pointer @code{this} following the same rules as C@t{++}. @code{using}
12632 declarations in the current scope are also respected by @value{GDBN}.
12634 @cindex call overloaded functions
12635 @cindex overloaded functions, calling
12636 @cindex type conversions in C@t{++}
12638 You can call overloaded functions; @value{GDBN} resolves the function
12639 call to the right definition, with some restrictions. @value{GDBN} does not
12640 perform overload resolution involving user-defined type conversions,
12641 calls to constructors, or instantiations of templates that do not exist
12642 in the program. It also cannot handle ellipsis argument lists or
12645 It does perform integral conversions and promotions, floating-point
12646 promotions, arithmetic conversions, pointer conversions, conversions of
12647 class objects to base classes, and standard conversions such as those of
12648 functions or arrays to pointers; it requires an exact match on the
12649 number of function arguments.
12651 Overload resolution is always performed, unless you have specified
12652 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
12653 ,@value{GDBN} Features for C@t{++}}.
12655 You must specify @code{set overload-resolution off} in order to use an
12656 explicit function signature to call an overloaded function, as in
12658 p 'foo(char,int)'('x', 13)
12661 The @value{GDBN} command-completion facility can simplify this;
12662 see @ref{Completion, ,Command Completion}.
12664 @cindex reference declarations
12666 @value{GDBN} understands variables declared as C@t{++} references; you can use
12667 them in expressions just as you do in C@t{++} source---they are automatically
12670 In the parameter list shown when @value{GDBN} displays a frame, the values of
12671 reference variables are not displayed (unlike other variables); this
12672 avoids clutter, since references are often used for large structures.
12673 The @emph{address} of a reference variable is always shown, unless
12674 you have specified @samp{set print address off}.
12677 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
12678 expressions can use it just as expressions in your program do. Since
12679 one scope may be defined in another, you can use @code{::} repeatedly if
12680 necessary, for example in an expression like
12681 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
12682 resolving name scope by reference to source files, in both C and C@t{++}
12683 debugging (@pxref{Variables, ,Program Variables}).
12686 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
12691 @subsubsection C and C@t{++} Defaults
12693 @cindex C and C@t{++} defaults
12695 If you allow @value{GDBN} to set type and range checking automatically, they
12696 both default to @code{off} whenever the working language changes to
12697 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
12698 selects the working language.
12700 If you allow @value{GDBN} to set the language automatically, it
12701 recognizes source files whose names end with @file{.c}, @file{.C}, or
12702 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
12703 these files, it sets the working language to C or C@t{++}.
12704 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
12705 for further details.
12707 @c Type checking is (a) primarily motivated by Modula-2, and (b)
12708 @c unimplemented. If (b) changes, it might make sense to let this node
12709 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
12712 @subsubsection C and C@t{++} Type and Range Checks
12714 @cindex C and C@t{++} checks
12716 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
12717 is not used. However, if you turn type checking on, @value{GDBN}
12718 considers two variables type equivalent if:
12722 The two variables are structured and have the same structure, union, or
12726 The two variables have the same type name, or types that have been
12727 declared equivalent through @code{typedef}.
12730 @c leaving this out because neither J Gilmore nor R Pesch understand it.
12733 The two @code{struct}, @code{union}, or @code{enum} variables are
12734 declared in the same declaration. (Note: this may not be true for all C
12739 Range checking, if turned on, is done on mathematical operations. Array
12740 indices are not checked, since they are often used to index a pointer
12741 that is not itself an array.
12744 @subsubsection @value{GDBN} and C
12746 The @code{set print union} and @code{show print union} commands apply to
12747 the @code{union} type. When set to @samp{on}, any @code{union} that is
12748 inside a @code{struct} or @code{class} is also printed. Otherwise, it
12749 appears as @samp{@{...@}}.
12751 The @code{@@} operator aids in the debugging of dynamic arrays, formed
12752 with pointers and a memory allocation function. @xref{Expressions,
12755 @node Debugging C Plus Plus
12756 @subsubsection @value{GDBN} Features for C@t{++}
12758 @cindex commands for C@t{++}
12760 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
12761 designed specifically for use with C@t{++}. Here is a summary:
12764 @cindex break in overloaded functions
12765 @item @r{breakpoint menus}
12766 When you want a breakpoint in a function whose name is overloaded,
12767 @value{GDBN} has the capability to display a menu of possible breakpoint
12768 locations to help you specify which function definition you want.
12769 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
12771 @cindex overloading in C@t{++}
12772 @item rbreak @var{regex}
12773 Setting breakpoints using regular expressions is helpful for setting
12774 breakpoints on overloaded functions that are not members of any special
12776 @xref{Set Breaks, ,Setting Breakpoints}.
12778 @cindex C@t{++} exception handling
12781 Debug C@t{++} exception handling using these commands. @xref{Set
12782 Catchpoints, , Setting Catchpoints}.
12784 @cindex inheritance
12785 @item ptype @var{typename}
12786 Print inheritance relationships as well as other information for type
12788 @xref{Symbols, ,Examining the Symbol Table}.
12790 @cindex C@t{++} symbol display
12791 @item set print demangle
12792 @itemx show print demangle
12793 @itemx set print asm-demangle
12794 @itemx show print asm-demangle
12795 Control whether C@t{++} symbols display in their source form, both when
12796 displaying code as C@t{++} source and when displaying disassemblies.
12797 @xref{Print Settings, ,Print Settings}.
12799 @item set print object
12800 @itemx show print object
12801 Choose whether to print derived (actual) or declared types of objects.
12802 @xref{Print Settings, ,Print Settings}.
12804 @item set print vtbl
12805 @itemx show print vtbl
12806 Control the format for printing virtual function tables.
12807 @xref{Print Settings, ,Print Settings}.
12808 (The @code{vtbl} commands do not work on programs compiled with the HP
12809 ANSI C@t{++} compiler (@code{aCC}).)
12811 @kindex set overload-resolution
12812 @cindex overloaded functions, overload resolution
12813 @item set overload-resolution on
12814 Enable overload resolution for C@t{++} expression evaluation. The default
12815 is on. For overloaded functions, @value{GDBN} evaluates the arguments
12816 and searches for a function whose signature matches the argument types,
12817 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
12818 Expressions, ,C@t{++} Expressions}, for details).
12819 If it cannot find a match, it emits a message.
12821 @item set overload-resolution off
12822 Disable overload resolution for C@t{++} expression evaluation. For
12823 overloaded functions that are not class member functions, @value{GDBN}
12824 chooses the first function of the specified name that it finds in the
12825 symbol table, whether or not its arguments are of the correct type. For
12826 overloaded functions that are class member functions, @value{GDBN}
12827 searches for a function whose signature @emph{exactly} matches the
12830 @kindex show overload-resolution
12831 @item show overload-resolution
12832 Show the current setting of overload resolution.
12834 @item @r{Overloaded symbol names}
12835 You can specify a particular definition of an overloaded symbol, using
12836 the same notation that is used to declare such symbols in C@t{++}: type
12837 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
12838 also use the @value{GDBN} command-line word completion facilities to list the
12839 available choices, or to finish the type list for you.
12840 @xref{Completion,, Command Completion}, for details on how to do this.
12843 @node Decimal Floating Point
12844 @subsubsection Decimal Floating Point format
12845 @cindex decimal floating point format
12847 @value{GDBN} can examine, set and perform computations with numbers in
12848 decimal floating point format, which in the C language correspond to the
12849 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
12850 specified by the extension to support decimal floating-point arithmetic.
12852 There are two encodings in use, depending on the architecture: BID (Binary
12853 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
12854 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
12857 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
12858 to manipulate decimal floating point numbers, it is not possible to convert
12859 (using a cast, for example) integers wider than 32-bit to decimal float.
12861 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
12862 point computations, error checking in decimal float operations ignores
12863 underflow, overflow and divide by zero exceptions.
12865 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
12866 to inspect @code{_Decimal128} values stored in floating point registers.
12867 See @ref{PowerPC,,PowerPC} for more details.
12873 @value{GDBN} can be used to debug programs written in D and compiled with
12874 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
12875 specific feature --- dynamic arrays.
12878 @subsection Objective-C
12880 @cindex Objective-C
12881 This section provides information about some commands and command
12882 options that are useful for debugging Objective-C code. See also
12883 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
12884 few more commands specific to Objective-C support.
12887 * Method Names in Commands::
12888 * The Print Command with Objective-C::
12891 @node Method Names in Commands
12892 @subsubsection Method Names in Commands
12894 The following commands have been extended to accept Objective-C method
12895 names as line specifications:
12897 @kindex clear@r{, and Objective-C}
12898 @kindex break@r{, and Objective-C}
12899 @kindex info line@r{, and Objective-C}
12900 @kindex jump@r{, and Objective-C}
12901 @kindex list@r{, and Objective-C}
12905 @item @code{info line}
12910 A fully qualified Objective-C method name is specified as
12913 -[@var{Class} @var{methodName}]
12916 where the minus sign is used to indicate an instance method and a
12917 plus sign (not shown) is used to indicate a class method. The class
12918 name @var{Class} and method name @var{methodName} are enclosed in
12919 brackets, similar to the way messages are specified in Objective-C
12920 source code. For example, to set a breakpoint at the @code{create}
12921 instance method of class @code{Fruit} in the program currently being
12925 break -[Fruit create]
12928 To list ten program lines around the @code{initialize} class method,
12932 list +[NSText initialize]
12935 In the current version of @value{GDBN}, the plus or minus sign is
12936 required. In future versions of @value{GDBN}, the plus or minus
12937 sign will be optional, but you can use it to narrow the search. It
12938 is also possible to specify just a method name:
12944 You must specify the complete method name, including any colons. If
12945 your program's source files contain more than one @code{create} method,
12946 you'll be presented with a numbered list of classes that implement that
12947 method. Indicate your choice by number, or type @samp{0} to exit if
12950 As another example, to clear a breakpoint established at the
12951 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
12954 clear -[NSWindow makeKeyAndOrderFront:]
12957 @node The Print Command with Objective-C
12958 @subsubsection The Print Command With Objective-C
12959 @cindex Objective-C, print objects
12960 @kindex print-object
12961 @kindex po @r{(@code{print-object})}
12963 The print command has also been extended to accept methods. For example:
12966 print -[@var{object} hash]
12969 @cindex print an Objective-C object description
12970 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
12972 will tell @value{GDBN} to send the @code{hash} message to @var{object}
12973 and print the result. Also, an additional command has been added,
12974 @code{print-object} or @code{po} for short, which is meant to print
12975 the description of an object. However, this command may only work
12976 with certain Objective-C libraries that have a particular hook
12977 function, @code{_NSPrintForDebugger}, defined.
12980 @subsection OpenCL C
12983 This section provides information about @value{GDBN}s OpenCL C support.
12986 * OpenCL C Datatypes::
12987 * OpenCL C Expressions::
12988 * OpenCL C Operators::
12991 @node OpenCL C Datatypes
12992 @subsubsection OpenCL C Datatypes
12994 @cindex OpenCL C Datatypes
12995 @value{GDBN} supports the builtin scalar and vector datatypes specified
12996 by OpenCL 1.1. In addition the half- and double-precision floating point
12997 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
12998 extensions are also known to @value{GDBN}.
13000 @node OpenCL C Expressions
13001 @subsubsection OpenCL C Expressions
13003 @cindex OpenCL C Expressions
13004 @value{GDBN} supports accesses to vector components including the access as
13005 lvalue where possible. Since OpenCL C is based on C99 most C expressions
13006 supported by @value{GDBN} can be used as well.
13008 @node OpenCL C Operators
13009 @subsubsection OpenCL C Operators
13011 @cindex OpenCL C Operators
13012 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
13016 @subsection Fortran
13017 @cindex Fortran-specific support in @value{GDBN}
13019 @value{GDBN} can be used to debug programs written in Fortran, but it
13020 currently supports only the features of Fortran 77 language.
13022 @cindex trailing underscore, in Fortran symbols
13023 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
13024 among them) append an underscore to the names of variables and
13025 functions. When you debug programs compiled by those compilers, you
13026 will need to refer to variables and functions with a trailing
13030 * Fortran Operators:: Fortran operators and expressions
13031 * Fortran Defaults:: Default settings for Fortran
13032 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
13035 @node Fortran Operators
13036 @subsubsection Fortran Operators and Expressions
13038 @cindex Fortran operators and expressions
13040 Operators must be defined on values of specific types. For instance,
13041 @code{+} is defined on numbers, but not on characters or other non-
13042 arithmetic types. Operators are often defined on groups of types.
13046 The exponentiation operator. It raises the first operand to the power
13050 The range operator. Normally used in the form of array(low:high) to
13051 represent a section of array.
13054 The access component operator. Normally used to access elements in derived
13055 types. Also suitable for unions. As unions aren't part of regular Fortran,
13056 this can only happen when accessing a register that uses a gdbarch-defined
13060 @node Fortran Defaults
13061 @subsubsection Fortran Defaults
13063 @cindex Fortran Defaults
13065 Fortran symbols are usually case-insensitive, so @value{GDBN} by
13066 default uses case-insensitive matches for Fortran symbols. You can
13067 change that with the @samp{set case-insensitive} command, see
13068 @ref{Symbols}, for the details.
13070 @node Special Fortran Commands
13071 @subsubsection Special Fortran Commands
13073 @cindex Special Fortran commands
13075 @value{GDBN} has some commands to support Fortran-specific features,
13076 such as displaying common blocks.
13079 @cindex @code{COMMON} blocks, Fortran
13080 @kindex info common
13081 @item info common @r{[}@var{common-name}@r{]}
13082 This command prints the values contained in the Fortran @code{COMMON}
13083 block whose name is @var{common-name}. With no argument, the names of
13084 all @code{COMMON} blocks visible at the current program location are
13091 @cindex Pascal support in @value{GDBN}, limitations
13092 Debugging Pascal programs which use sets, subranges, file variables, or
13093 nested functions does not currently work. @value{GDBN} does not support
13094 entering expressions, printing values, or similar features using Pascal
13097 The Pascal-specific command @code{set print pascal_static-members}
13098 controls whether static members of Pascal objects are displayed.
13099 @xref{Print Settings, pascal_static-members}.
13102 @subsection Modula-2
13104 @cindex Modula-2, @value{GDBN} support
13106 The extensions made to @value{GDBN} to support Modula-2 only support
13107 output from the @sc{gnu} Modula-2 compiler (which is currently being
13108 developed). Other Modula-2 compilers are not currently supported, and
13109 attempting to debug executables produced by them is most likely
13110 to give an error as @value{GDBN} reads in the executable's symbol
13113 @cindex expressions in Modula-2
13115 * M2 Operators:: Built-in operators
13116 * Built-In Func/Proc:: Built-in functions and procedures
13117 * M2 Constants:: Modula-2 constants
13118 * M2 Types:: Modula-2 types
13119 * M2 Defaults:: Default settings for Modula-2
13120 * Deviations:: Deviations from standard Modula-2
13121 * M2 Checks:: Modula-2 type and range checks
13122 * M2 Scope:: The scope operators @code{::} and @code{.}
13123 * GDB/M2:: @value{GDBN} and Modula-2
13127 @subsubsection Operators
13128 @cindex Modula-2 operators
13130 Operators must be defined on values of specific types. For instance,
13131 @code{+} is defined on numbers, but not on structures. Operators are
13132 often defined on groups of types. For the purposes of Modula-2, the
13133 following definitions hold:
13138 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
13142 @emph{Character types} consist of @code{CHAR} and its subranges.
13145 @emph{Floating-point types} consist of @code{REAL}.
13148 @emph{Pointer types} consist of anything declared as @code{POINTER TO
13152 @emph{Scalar types} consist of all of the above.
13155 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
13158 @emph{Boolean types} consist of @code{BOOLEAN}.
13162 The following operators are supported, and appear in order of
13163 increasing precedence:
13167 Function argument or array index separator.
13170 Assignment. The value of @var{var} @code{:=} @var{value} is
13174 Less than, greater than on integral, floating-point, or enumerated
13178 Less than or equal to, greater than or equal to
13179 on integral, floating-point and enumerated types, or set inclusion on
13180 set types. Same precedence as @code{<}.
13182 @item =@r{, }<>@r{, }#
13183 Equality and two ways of expressing inequality, valid on scalar types.
13184 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
13185 available for inequality, since @code{#} conflicts with the script
13189 Set membership. Defined on set types and the types of their members.
13190 Same precedence as @code{<}.
13193 Boolean disjunction. Defined on boolean types.
13196 Boolean conjunction. Defined on boolean types.
13199 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13202 Addition and subtraction on integral and floating-point types, or union
13203 and difference on set types.
13206 Multiplication on integral and floating-point types, or set intersection
13210 Division on floating-point types, or symmetric set difference on set
13211 types. Same precedence as @code{*}.
13214 Integer division and remainder. Defined on integral types. Same
13215 precedence as @code{*}.
13218 Negative. Defined on @code{INTEGER} and @code{REAL} data.
13221 Pointer dereferencing. Defined on pointer types.
13224 Boolean negation. Defined on boolean types. Same precedence as
13228 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
13229 precedence as @code{^}.
13232 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
13235 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
13239 @value{GDBN} and Modula-2 scope operators.
13243 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
13244 treats the use of the operator @code{IN}, or the use of operators
13245 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
13246 @code{<=}, and @code{>=} on sets as an error.
13250 @node Built-In Func/Proc
13251 @subsubsection Built-in Functions and Procedures
13252 @cindex Modula-2 built-ins
13254 Modula-2 also makes available several built-in procedures and functions.
13255 In describing these, the following metavariables are used:
13260 represents an @code{ARRAY} variable.
13263 represents a @code{CHAR} constant or variable.
13266 represents a variable or constant of integral type.
13269 represents an identifier that belongs to a set. Generally used in the
13270 same function with the metavariable @var{s}. The type of @var{s} should
13271 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
13274 represents a variable or constant of integral or floating-point type.
13277 represents a variable or constant of floating-point type.
13283 represents a variable.
13286 represents a variable or constant of one of many types. See the
13287 explanation of the function for details.
13290 All Modula-2 built-in procedures also return a result, described below.
13294 Returns the absolute value of @var{n}.
13297 If @var{c} is a lower case letter, it returns its upper case
13298 equivalent, otherwise it returns its argument.
13301 Returns the character whose ordinal value is @var{i}.
13304 Decrements the value in the variable @var{v} by one. Returns the new value.
13306 @item DEC(@var{v},@var{i})
13307 Decrements the value in the variable @var{v} by @var{i}. Returns the
13310 @item EXCL(@var{m},@var{s})
13311 Removes the element @var{m} from the set @var{s}. Returns the new
13314 @item FLOAT(@var{i})
13315 Returns the floating point equivalent of the integer @var{i}.
13317 @item HIGH(@var{a})
13318 Returns the index of the last member of @var{a}.
13321 Increments the value in the variable @var{v} by one. Returns the new value.
13323 @item INC(@var{v},@var{i})
13324 Increments the value in the variable @var{v} by @var{i}. Returns the
13327 @item INCL(@var{m},@var{s})
13328 Adds the element @var{m} to the set @var{s} if it is not already
13329 there. Returns the new set.
13332 Returns the maximum value of the type @var{t}.
13335 Returns the minimum value of the type @var{t}.
13338 Returns boolean TRUE if @var{i} is an odd number.
13341 Returns the ordinal value of its argument. For example, the ordinal
13342 value of a character is its @sc{ascii} value (on machines supporting the
13343 @sc{ascii} character set). @var{x} must be of an ordered type, which include
13344 integral, character and enumerated types.
13346 @item SIZE(@var{x})
13347 Returns the size of its argument. @var{x} can be a variable or a type.
13349 @item TRUNC(@var{r})
13350 Returns the integral part of @var{r}.
13352 @item TSIZE(@var{x})
13353 Returns the size of its argument. @var{x} can be a variable or a type.
13355 @item VAL(@var{t},@var{i})
13356 Returns the member of the type @var{t} whose ordinal value is @var{i}.
13360 @emph{Warning:} Sets and their operations are not yet supported, so
13361 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
13365 @cindex Modula-2 constants
13367 @subsubsection Constants
13369 @value{GDBN} allows you to express the constants of Modula-2 in the following
13375 Integer constants are simply a sequence of digits. When used in an
13376 expression, a constant is interpreted to be type-compatible with the
13377 rest of the expression. Hexadecimal integers are specified by a
13378 trailing @samp{H}, and octal integers by a trailing @samp{B}.
13381 Floating point constants appear as a sequence of digits, followed by a
13382 decimal point and another sequence of digits. An optional exponent can
13383 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
13384 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
13385 digits of the floating point constant must be valid decimal (base 10)
13389 Character constants consist of a single character enclosed by a pair of
13390 like quotes, either single (@code{'}) or double (@code{"}). They may
13391 also be expressed by their ordinal value (their @sc{ascii} value, usually)
13392 followed by a @samp{C}.
13395 String constants consist of a sequence of characters enclosed by a
13396 pair of like quotes, either single (@code{'}) or double (@code{"}).
13397 Escape sequences in the style of C are also allowed. @xref{C
13398 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
13402 Enumerated constants consist of an enumerated identifier.
13405 Boolean constants consist of the identifiers @code{TRUE} and
13409 Pointer constants consist of integral values only.
13412 Set constants are not yet supported.
13416 @subsubsection Modula-2 Types
13417 @cindex Modula-2 types
13419 Currently @value{GDBN} can print the following data types in Modula-2
13420 syntax: array types, record types, set types, pointer types, procedure
13421 types, enumerated types, subrange types and base types. You can also
13422 print the contents of variables declared using these type.
13423 This section gives a number of simple source code examples together with
13424 sample @value{GDBN} sessions.
13426 The first example contains the following section of code:
13435 and you can request @value{GDBN} to interrogate the type and value of
13436 @code{r} and @code{s}.
13439 (@value{GDBP}) print s
13441 (@value{GDBP}) ptype s
13443 (@value{GDBP}) print r
13445 (@value{GDBP}) ptype r
13450 Likewise if your source code declares @code{s} as:
13454 s: SET ['A'..'Z'] ;
13458 then you may query the type of @code{s} by:
13461 (@value{GDBP}) ptype s
13462 type = SET ['A'..'Z']
13466 Note that at present you cannot interactively manipulate set
13467 expressions using the debugger.
13469 The following example shows how you might declare an array in Modula-2
13470 and how you can interact with @value{GDBN} to print its type and contents:
13474 s: ARRAY [-10..10] OF CHAR ;
13478 (@value{GDBP}) ptype s
13479 ARRAY [-10..10] OF CHAR
13482 Note that the array handling is not yet complete and although the type
13483 is printed correctly, expression handling still assumes that all
13484 arrays have a lower bound of zero and not @code{-10} as in the example
13487 Here are some more type related Modula-2 examples:
13491 colour = (blue, red, yellow, green) ;
13492 t = [blue..yellow] ;
13500 The @value{GDBN} interaction shows how you can query the data type
13501 and value of a variable.
13504 (@value{GDBP}) print s
13506 (@value{GDBP}) ptype t
13507 type = [blue..yellow]
13511 In this example a Modula-2 array is declared and its contents
13512 displayed. Observe that the contents are written in the same way as
13513 their @code{C} counterparts.
13517 s: ARRAY [1..5] OF CARDINAL ;
13523 (@value{GDBP}) print s
13524 $1 = @{1, 0, 0, 0, 0@}
13525 (@value{GDBP}) ptype s
13526 type = ARRAY [1..5] OF CARDINAL
13529 The Modula-2 language interface to @value{GDBN} also understands
13530 pointer types as shown in this example:
13534 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
13541 and you can request that @value{GDBN} describes the type of @code{s}.
13544 (@value{GDBP}) ptype s
13545 type = POINTER TO ARRAY [1..5] OF CARDINAL
13548 @value{GDBN} handles compound types as we can see in this example.
13549 Here we combine array types, record types, pointer types and subrange
13560 myarray = ARRAY myrange OF CARDINAL ;
13561 myrange = [-2..2] ;
13563 s: POINTER TO ARRAY myrange OF foo ;
13567 and you can ask @value{GDBN} to describe the type of @code{s} as shown
13571 (@value{GDBP}) ptype s
13572 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
13575 f3 : ARRAY [-2..2] OF CARDINAL;
13580 @subsubsection Modula-2 Defaults
13581 @cindex Modula-2 defaults
13583 If type and range checking are set automatically by @value{GDBN}, they
13584 both default to @code{on} whenever the working language changes to
13585 Modula-2. This happens regardless of whether you or @value{GDBN}
13586 selected the working language.
13588 If you allow @value{GDBN} to set the language automatically, then entering
13589 code compiled from a file whose name ends with @file{.mod} sets the
13590 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
13591 Infer the Source Language}, for further details.
13594 @subsubsection Deviations from Standard Modula-2
13595 @cindex Modula-2, deviations from
13597 A few changes have been made to make Modula-2 programs easier to debug.
13598 This is done primarily via loosening its type strictness:
13602 Unlike in standard Modula-2, pointer constants can be formed by
13603 integers. This allows you to modify pointer variables during
13604 debugging. (In standard Modula-2, the actual address contained in a
13605 pointer variable is hidden from you; it can only be modified
13606 through direct assignment to another pointer variable or expression that
13607 returned a pointer.)
13610 C escape sequences can be used in strings and characters to represent
13611 non-printable characters. @value{GDBN} prints out strings with these
13612 escape sequences embedded. Single non-printable characters are
13613 printed using the @samp{CHR(@var{nnn})} format.
13616 The assignment operator (@code{:=}) returns the value of its right-hand
13620 All built-in procedures both modify @emph{and} return their argument.
13624 @subsubsection Modula-2 Type and Range Checks
13625 @cindex Modula-2 checks
13628 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
13631 @c FIXME remove warning when type/range checks added
13633 @value{GDBN} considers two Modula-2 variables type equivalent if:
13637 They are of types that have been declared equivalent via a @code{TYPE
13638 @var{t1} = @var{t2}} statement
13641 They have been declared on the same line. (Note: This is true of the
13642 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
13645 As long as type checking is enabled, any attempt to combine variables
13646 whose types are not equivalent is an error.
13648 Range checking is done on all mathematical operations, assignment, array
13649 index bounds, and all built-in functions and procedures.
13652 @subsubsection The Scope Operators @code{::} and @code{.}
13654 @cindex @code{.}, Modula-2 scope operator
13655 @cindex colon, doubled as scope operator
13657 @vindex colon-colon@r{, in Modula-2}
13658 @c Info cannot handle :: but TeX can.
13661 @vindex ::@r{, in Modula-2}
13664 There are a few subtle differences between the Modula-2 scope operator
13665 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
13670 @var{module} . @var{id}
13671 @var{scope} :: @var{id}
13675 where @var{scope} is the name of a module or a procedure,
13676 @var{module} the name of a module, and @var{id} is any declared
13677 identifier within your program, except another module.
13679 Using the @code{::} operator makes @value{GDBN} search the scope
13680 specified by @var{scope} for the identifier @var{id}. If it is not
13681 found in the specified scope, then @value{GDBN} searches all scopes
13682 enclosing the one specified by @var{scope}.
13684 Using the @code{.} operator makes @value{GDBN} search the current scope for
13685 the identifier specified by @var{id} that was imported from the
13686 definition module specified by @var{module}. With this operator, it is
13687 an error if the identifier @var{id} was not imported from definition
13688 module @var{module}, or if @var{id} is not an identifier in
13692 @subsubsection @value{GDBN} and Modula-2
13694 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
13695 Five subcommands of @code{set print} and @code{show print} apply
13696 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
13697 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
13698 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
13699 analogue in Modula-2.
13701 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
13702 with any language, is not useful with Modula-2. Its
13703 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
13704 created in Modula-2 as they can in C or C@t{++}. However, because an
13705 address can be specified by an integral constant, the construct
13706 @samp{@{@var{type}@}@var{adrexp}} is still useful.
13708 @cindex @code{#} in Modula-2
13709 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
13710 interpreted as the beginning of a comment. Use @code{<>} instead.
13716 The extensions made to @value{GDBN} for Ada only support
13717 output from the @sc{gnu} Ada (GNAT) compiler.
13718 Other Ada compilers are not currently supported, and
13719 attempting to debug executables produced by them is most likely
13723 @cindex expressions in Ada
13725 * Ada Mode Intro:: General remarks on the Ada syntax
13726 and semantics supported by Ada mode
13728 * Omissions from Ada:: Restrictions on the Ada expression syntax.
13729 * Additions to Ada:: Extensions of the Ada expression syntax.
13730 * Stopping Before Main Program:: Debugging the program during elaboration.
13731 * Ada Tasks:: Listing and setting breakpoints in tasks.
13732 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
13733 * Ravenscar Profile:: Tasking Support when using the Ravenscar
13735 * Ada Glitches:: Known peculiarities of Ada mode.
13738 @node Ada Mode Intro
13739 @subsubsection Introduction
13740 @cindex Ada mode, general
13742 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
13743 syntax, with some extensions.
13744 The philosophy behind the design of this subset is
13748 That @value{GDBN} should provide basic literals and access to operations for
13749 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
13750 leaving more sophisticated computations to subprograms written into the
13751 program (which therefore may be called from @value{GDBN}).
13754 That type safety and strict adherence to Ada language restrictions
13755 are not particularly important to the @value{GDBN} user.
13758 That brevity is important to the @value{GDBN} user.
13761 Thus, for brevity, the debugger acts as if all names declared in
13762 user-written packages are directly visible, even if they are not visible
13763 according to Ada rules, thus making it unnecessary to fully qualify most
13764 names with their packages, regardless of context. Where this causes
13765 ambiguity, @value{GDBN} asks the user's intent.
13767 The debugger will start in Ada mode if it detects an Ada main program.
13768 As for other languages, it will enter Ada mode when stopped in a program that
13769 was translated from an Ada source file.
13771 While in Ada mode, you may use `@t{--}' for comments. This is useful
13772 mostly for documenting command files. The standard @value{GDBN} comment
13773 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
13774 middle (to allow based literals).
13776 The debugger supports limited overloading. Given a subprogram call in which
13777 the function symbol has multiple definitions, it will use the number of
13778 actual parameters and some information about their types to attempt to narrow
13779 the set of definitions. It also makes very limited use of context, preferring
13780 procedures to functions in the context of the @code{call} command, and
13781 functions to procedures elsewhere.
13783 @node Omissions from Ada
13784 @subsubsection Omissions from Ada
13785 @cindex Ada, omissions from
13787 Here are the notable omissions from the subset:
13791 Only a subset of the attributes are supported:
13795 @t{'First}, @t{'Last}, and @t{'Length}
13796 on array objects (not on types and subtypes).
13799 @t{'Min} and @t{'Max}.
13802 @t{'Pos} and @t{'Val}.
13808 @t{'Range} on array objects (not subtypes), but only as the right
13809 operand of the membership (@code{in}) operator.
13812 @t{'Access}, @t{'Unchecked_Access}, and
13813 @t{'Unrestricted_Access} (a GNAT extension).
13821 @code{Characters.Latin_1} are not available and
13822 concatenation is not implemented. Thus, escape characters in strings are
13823 not currently available.
13826 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
13827 equality of representations. They will generally work correctly
13828 for strings and arrays whose elements have integer or enumeration types.
13829 They may not work correctly for arrays whose element
13830 types have user-defined equality, for arrays of real values
13831 (in particular, IEEE-conformant floating point, because of negative
13832 zeroes and NaNs), and for arrays whose elements contain unused bits with
13833 indeterminate values.
13836 The other component-by-component array operations (@code{and}, @code{or},
13837 @code{xor}, @code{not}, and relational tests other than equality)
13838 are not implemented.
13841 @cindex array aggregates (Ada)
13842 @cindex record aggregates (Ada)
13843 @cindex aggregates (Ada)
13844 There is limited support for array and record aggregates. They are
13845 permitted only on the right sides of assignments, as in these examples:
13848 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
13849 (@value{GDBP}) set An_Array := (1, others => 0)
13850 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
13851 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
13852 (@value{GDBP}) set A_Record := (1, "Peter", True);
13853 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
13857 discriminant's value by assigning an aggregate has an
13858 undefined effect if that discriminant is used within the record.
13859 However, you can first modify discriminants by directly assigning to
13860 them (which normally would not be allowed in Ada), and then performing an
13861 aggregate assignment. For example, given a variable @code{A_Rec}
13862 declared to have a type such as:
13865 type Rec (Len : Small_Integer := 0) is record
13867 Vals : IntArray (1 .. Len);
13871 you can assign a value with a different size of @code{Vals} with two
13875 (@value{GDBP}) set A_Rec.Len := 4
13876 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
13879 As this example also illustrates, @value{GDBN} is very loose about the usual
13880 rules concerning aggregates. You may leave out some of the
13881 components of an array or record aggregate (such as the @code{Len}
13882 component in the assignment to @code{A_Rec} above); they will retain their
13883 original values upon assignment. You may freely use dynamic values as
13884 indices in component associations. You may even use overlapping or
13885 redundant component associations, although which component values are
13886 assigned in such cases is not defined.
13889 Calls to dispatching subprograms are not implemented.
13892 The overloading algorithm is much more limited (i.e., less selective)
13893 than that of real Ada. It makes only limited use of the context in
13894 which a subexpression appears to resolve its meaning, and it is much
13895 looser in its rules for allowing type matches. As a result, some
13896 function calls will be ambiguous, and the user will be asked to choose
13897 the proper resolution.
13900 The @code{new} operator is not implemented.
13903 Entry calls are not implemented.
13906 Aside from printing, arithmetic operations on the native VAX floating-point
13907 formats are not supported.
13910 It is not possible to slice a packed array.
13913 The names @code{True} and @code{False}, when not part of a qualified name,
13914 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
13916 Should your program
13917 redefine these names in a package or procedure (at best a dubious practice),
13918 you will have to use fully qualified names to access their new definitions.
13921 @node Additions to Ada
13922 @subsubsection Additions to Ada
13923 @cindex Ada, deviations from
13925 As it does for other languages, @value{GDBN} makes certain generic
13926 extensions to Ada (@pxref{Expressions}):
13930 If the expression @var{E} is a variable residing in memory (typically
13931 a local variable or array element) and @var{N} is a positive integer,
13932 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
13933 @var{N}-1 adjacent variables following it in memory as an array. In
13934 Ada, this operator is generally not necessary, since its prime use is
13935 in displaying parts of an array, and slicing will usually do this in
13936 Ada. However, there are occasional uses when debugging programs in
13937 which certain debugging information has been optimized away.
13940 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
13941 appears in function or file @var{B}.'' When @var{B} is a file name,
13942 you must typically surround it in single quotes.
13945 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
13946 @var{type} that appears at address @var{addr}.''
13949 A name starting with @samp{$} is a convenience variable
13950 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
13953 In addition, @value{GDBN} provides a few other shortcuts and outright
13954 additions specific to Ada:
13958 The assignment statement is allowed as an expression, returning
13959 its right-hand operand as its value. Thus, you may enter
13962 (@value{GDBP}) set x := y + 3
13963 (@value{GDBP}) print A(tmp := y + 1)
13967 The semicolon is allowed as an ``operator,'' returning as its value
13968 the value of its right-hand operand.
13969 This allows, for example,
13970 complex conditional breaks:
13973 (@value{GDBP}) break f
13974 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
13978 Rather than use catenation and symbolic character names to introduce special
13979 characters into strings, one may instead use a special bracket notation,
13980 which is also used to print strings. A sequence of characters of the form
13981 @samp{["@var{XX}"]} within a string or character literal denotes the
13982 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
13983 sequence of characters @samp{["""]} also denotes a single quotation mark
13984 in strings. For example,
13986 "One line.["0a"]Next line.["0a"]"
13989 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
13993 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
13994 @t{'Max} is optional (and is ignored in any case). For example, it is valid
13998 (@value{GDBP}) print 'max(x, y)
14002 When printing arrays, @value{GDBN} uses positional notation when the
14003 array has a lower bound of 1, and uses a modified named notation otherwise.
14004 For example, a one-dimensional array of three integers with a lower bound
14005 of 3 might print as
14012 That is, in contrast to valid Ada, only the first component has a @code{=>}
14016 You may abbreviate attributes in expressions with any unique,
14017 multi-character subsequence of
14018 their names (an exact match gets preference).
14019 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
14020 in place of @t{a'length}.
14023 @cindex quoting Ada internal identifiers
14024 Since Ada is case-insensitive, the debugger normally maps identifiers you type
14025 to lower case. The GNAT compiler uses upper-case characters for
14026 some of its internal identifiers, which are normally of no interest to users.
14027 For the rare occasions when you actually have to look at them,
14028 enclose them in angle brackets to avoid the lower-case mapping.
14031 (@value{GDBP}) print <JMPBUF_SAVE>[0]
14035 Printing an object of class-wide type or dereferencing an
14036 access-to-class-wide value will display all the components of the object's
14037 specific type (as indicated by its run-time tag). Likewise, component
14038 selection on such a value will operate on the specific type of the
14043 @node Stopping Before Main Program
14044 @subsubsection Stopping at the Very Beginning
14046 @cindex breakpointing Ada elaboration code
14047 It is sometimes necessary to debug the program during elaboration, and
14048 before reaching the main procedure.
14049 As defined in the Ada Reference
14050 Manual, the elaboration code is invoked from a procedure called
14051 @code{adainit}. To run your program up to the beginning of
14052 elaboration, simply use the following two commands:
14053 @code{tbreak adainit} and @code{run}.
14056 @subsubsection Extensions for Ada Tasks
14057 @cindex Ada, tasking
14059 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
14060 @value{GDBN} provides the following task-related commands:
14065 This command shows a list of current Ada tasks, as in the following example:
14072 (@value{GDBP}) info tasks
14073 ID TID P-ID Pri State Name
14074 1 8088000 0 15 Child Activation Wait main_task
14075 2 80a4000 1 15 Accept Statement b
14076 3 809a800 1 15 Child Activation Wait a
14077 * 4 80ae800 3 15 Runnable c
14082 In this listing, the asterisk before the last task indicates it to be the
14083 task currently being inspected.
14087 Represents @value{GDBN}'s internal task number.
14093 The parent's task ID (@value{GDBN}'s internal task number).
14096 The base priority of the task.
14099 Current state of the task.
14103 The task has been created but has not been activated. It cannot be
14107 The task is not blocked for any reason known to Ada. (It may be waiting
14108 for a mutex, though.) It is conceptually "executing" in normal mode.
14111 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
14112 that were waiting on terminate alternatives have been awakened and have
14113 terminated themselves.
14115 @item Child Activation Wait
14116 The task is waiting for created tasks to complete activation.
14118 @item Accept Statement
14119 The task is waiting on an accept or selective wait statement.
14121 @item Waiting on entry call
14122 The task is waiting on an entry call.
14124 @item Async Select Wait
14125 The task is waiting to start the abortable part of an asynchronous
14129 The task is waiting on a select statement with only a delay
14132 @item Child Termination Wait
14133 The task is sleeping having completed a master within itself, and is
14134 waiting for the tasks dependent on that master to become terminated or
14135 waiting on a terminate Phase.
14137 @item Wait Child in Term Alt
14138 The task is sleeping waiting for tasks on terminate alternatives to
14139 finish terminating.
14141 @item Accepting RV with @var{taskno}
14142 The task is accepting a rendez-vous with the task @var{taskno}.
14146 Name of the task in the program.
14150 @kindex info task @var{taskno}
14151 @item info task @var{taskno}
14152 This command shows detailled informations on the specified task, as in
14153 the following example:
14158 (@value{GDBP}) info tasks
14159 ID TID P-ID Pri State Name
14160 1 8077880 0 15 Child Activation Wait main_task
14161 * 2 807c468 1 15 Runnable task_1
14162 (@value{GDBP}) info task 2
14163 Ada Task: 0x807c468
14166 Parent: 1 (main_task)
14172 @kindex task@r{ (Ada)}
14173 @cindex current Ada task ID
14174 This command prints the ID of the current task.
14180 (@value{GDBP}) info tasks
14181 ID TID P-ID Pri State Name
14182 1 8077870 0 15 Child Activation Wait main_task
14183 * 2 807c458 1 15 Runnable t
14184 (@value{GDBP}) task
14185 [Current task is 2]
14188 @item task @var{taskno}
14189 @cindex Ada task switching
14190 This command is like the @code{thread @var{threadno}}
14191 command (@pxref{Threads}). It switches the context of debugging
14192 from the current task to the given task.
14198 (@value{GDBP}) info tasks
14199 ID TID P-ID Pri State Name
14200 1 8077870 0 15 Child Activation Wait main_task
14201 * 2 807c458 1 15 Runnable t
14202 (@value{GDBP}) task 1
14203 [Switching to task 1]
14204 #0 0x8067726 in pthread_cond_wait ()
14206 #0 0x8067726 in pthread_cond_wait ()
14207 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
14208 #2 0x805cb63 in system.task_primitives.operations.sleep ()
14209 #3 0x806153e in system.tasking.stages.activate_tasks ()
14210 #4 0x804aacc in un () at un.adb:5
14213 @item break @var{linespec} task @var{taskno}
14214 @itemx break @var{linespec} task @var{taskno} if @dots{}
14215 @cindex breakpoints and tasks, in Ada
14216 @cindex task breakpoints, in Ada
14217 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
14218 These commands are like the @code{break @dots{} thread @dots{}}
14219 command (@pxref{Thread Stops}).
14220 @var{linespec} specifies source lines, as described
14221 in @ref{Specify Location}.
14223 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
14224 to specify that you only want @value{GDBN} to stop the program when a
14225 particular Ada task reaches this breakpoint. @var{taskno} is one of the
14226 numeric task identifiers assigned by @value{GDBN}, shown in the first
14227 column of the @samp{info tasks} display.
14229 If you do not specify @samp{task @var{taskno}} when you set a
14230 breakpoint, the breakpoint applies to @emph{all} tasks of your
14233 You can use the @code{task} qualifier on conditional breakpoints as
14234 well; in this case, place @samp{task @var{taskno}} before the
14235 breakpoint condition (before the @code{if}).
14243 (@value{GDBP}) info tasks
14244 ID TID P-ID Pri State Name
14245 1 140022020 0 15 Child Activation Wait main_task
14246 2 140045060 1 15 Accept/Select Wait t2
14247 3 140044840 1 15 Runnable t1
14248 * 4 140056040 1 15 Runnable t3
14249 (@value{GDBP}) b 15 task 2
14250 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
14251 (@value{GDBP}) cont
14256 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
14258 (@value{GDBP}) info tasks
14259 ID TID P-ID Pri State Name
14260 1 140022020 0 15 Child Activation Wait main_task
14261 * 2 140045060 1 15 Runnable t2
14262 3 140044840 1 15 Runnable t1
14263 4 140056040 1 15 Delay Sleep t3
14267 @node Ada Tasks and Core Files
14268 @subsubsection Tasking Support when Debugging Core Files
14269 @cindex Ada tasking and core file debugging
14271 When inspecting a core file, as opposed to debugging a live program,
14272 tasking support may be limited or even unavailable, depending on
14273 the platform being used.
14274 For instance, on x86-linux, the list of tasks is available, but task
14275 switching is not supported. On Tru64, however, task switching will work
14278 On certain platforms, including Tru64, the debugger needs to perform some
14279 memory writes in order to provide Ada tasking support. When inspecting
14280 a core file, this means that the core file must be opened with read-write
14281 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
14282 Under these circumstances, you should make a backup copy of the core
14283 file before inspecting it with @value{GDBN}.
14285 @node Ravenscar Profile
14286 @subsubsection Tasking Support when using the Ravenscar Profile
14287 @cindex Ravenscar Profile
14289 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
14290 specifically designed for systems with safety-critical real-time
14294 @kindex set ravenscar task-switching on
14295 @cindex task switching with program using Ravenscar Profile
14296 @item set ravenscar task-switching on
14297 Allows task switching when debugging a program that uses the Ravenscar
14298 Profile. This is the default.
14300 @kindex set ravenscar task-switching off
14301 @item set ravenscar task-switching off
14302 Turn off task switching when debugging a program that uses the Ravenscar
14303 Profile. This is mostly intended to disable the code that adds support
14304 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
14305 the Ravenscar runtime is preventing @value{GDBN} from working properly.
14306 To be effective, this command should be run before the program is started.
14308 @kindex show ravenscar task-switching
14309 @item show ravenscar task-switching
14310 Show whether it is possible to switch from task to task in a program
14311 using the Ravenscar Profile.
14316 @subsubsection Known Peculiarities of Ada Mode
14317 @cindex Ada, problems
14319 Besides the omissions listed previously (@pxref{Omissions from Ada}),
14320 we know of several problems with and limitations of Ada mode in
14322 some of which will be fixed with planned future releases of the debugger
14323 and the GNU Ada compiler.
14327 Static constants that the compiler chooses not to materialize as objects in
14328 storage are invisible to the debugger.
14331 Named parameter associations in function argument lists are ignored (the
14332 argument lists are treated as positional).
14335 Many useful library packages are currently invisible to the debugger.
14338 Fixed-point arithmetic, conversions, input, and output is carried out using
14339 floating-point arithmetic, and may give results that only approximate those on
14343 The GNAT compiler never generates the prefix @code{Standard} for any of
14344 the standard symbols defined by the Ada language. @value{GDBN} knows about
14345 this: it will strip the prefix from names when you use it, and will never
14346 look for a name you have so qualified among local symbols, nor match against
14347 symbols in other packages or subprograms. If you have
14348 defined entities anywhere in your program other than parameters and
14349 local variables whose simple names match names in @code{Standard},
14350 GNAT's lack of qualification here can cause confusion. When this happens,
14351 you can usually resolve the confusion
14352 by qualifying the problematic names with package
14353 @code{Standard} explicitly.
14356 Older versions of the compiler sometimes generate erroneous debugging
14357 information, resulting in the debugger incorrectly printing the value
14358 of affected entities. In some cases, the debugger is able to work
14359 around an issue automatically. In other cases, the debugger is able
14360 to work around the issue, but the work-around has to be specifically
14363 @kindex set ada trust-PAD-over-XVS
14364 @kindex show ada trust-PAD-over-XVS
14367 @item set ada trust-PAD-over-XVS on
14368 Configure GDB to strictly follow the GNAT encoding when computing the
14369 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
14370 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
14371 a complete description of the encoding used by the GNAT compiler).
14372 This is the default.
14374 @item set ada trust-PAD-over-XVS off
14375 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
14376 sometimes prints the wrong value for certain entities, changing @code{ada
14377 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
14378 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
14379 @code{off}, but this incurs a slight performance penalty, so it is
14380 recommended to leave this setting to @code{on} unless necessary.
14384 @node Unsupported Languages
14385 @section Unsupported Languages
14387 @cindex unsupported languages
14388 @cindex minimal language
14389 In addition to the other fully-supported programming languages,
14390 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
14391 It does not represent a real programming language, but provides a set
14392 of capabilities close to what the C or assembly languages provide.
14393 This should allow most simple operations to be performed while debugging
14394 an application that uses a language currently not supported by @value{GDBN}.
14396 If the language is set to @code{auto}, @value{GDBN} will automatically
14397 select this language if the current frame corresponds to an unsupported
14401 @chapter Examining the Symbol Table
14403 The commands described in this chapter allow you to inquire about the
14404 symbols (names of variables, functions and types) defined in your
14405 program. This information is inherent in the text of your program and
14406 does not change as your program executes. @value{GDBN} finds it in your
14407 program's symbol table, in the file indicated when you started @value{GDBN}
14408 (@pxref{File Options, ,Choosing Files}), or by one of the
14409 file-management commands (@pxref{Files, ,Commands to Specify Files}).
14411 @cindex symbol names
14412 @cindex names of symbols
14413 @cindex quoting names
14414 Occasionally, you may need to refer to symbols that contain unusual
14415 characters, which @value{GDBN} ordinarily treats as word delimiters. The
14416 most frequent case is in referring to static variables in other
14417 source files (@pxref{Variables,,Program Variables}). File names
14418 are recorded in object files as debugging symbols, but @value{GDBN} would
14419 ordinarily parse a typical file name, like @file{foo.c}, as the three words
14420 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
14421 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
14428 looks up the value of @code{x} in the scope of the file @file{foo.c}.
14431 @cindex case-insensitive symbol names
14432 @cindex case sensitivity in symbol names
14433 @kindex set case-sensitive
14434 @item set case-sensitive on
14435 @itemx set case-sensitive off
14436 @itemx set case-sensitive auto
14437 Normally, when @value{GDBN} looks up symbols, it matches their names
14438 with case sensitivity determined by the current source language.
14439 Occasionally, you may wish to control that. The command @code{set
14440 case-sensitive} lets you do that by specifying @code{on} for
14441 case-sensitive matches or @code{off} for case-insensitive ones. If
14442 you specify @code{auto}, case sensitivity is reset to the default
14443 suitable for the source language. The default is case-sensitive
14444 matches for all languages except for Fortran, for which the default is
14445 case-insensitive matches.
14447 @kindex show case-sensitive
14448 @item show case-sensitive
14449 This command shows the current setting of case sensitivity for symbols
14452 @kindex info address
14453 @cindex address of a symbol
14454 @item info address @var{symbol}
14455 Describe where the data for @var{symbol} is stored. For a register
14456 variable, this says which register it is kept in. For a non-register
14457 local variable, this prints the stack-frame offset at which the variable
14460 Note the contrast with @samp{print &@var{symbol}}, which does not work
14461 at all for a register variable, and for a stack local variable prints
14462 the exact address of the current instantiation of the variable.
14464 @kindex info symbol
14465 @cindex symbol from address
14466 @cindex closest symbol and offset for an address
14467 @item info symbol @var{addr}
14468 Print the name of a symbol which is stored at the address @var{addr}.
14469 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
14470 nearest symbol and an offset from it:
14473 (@value{GDBP}) info symbol 0x54320
14474 _initialize_vx + 396 in section .text
14478 This is the opposite of the @code{info address} command. You can use
14479 it to find out the name of a variable or a function given its address.
14481 For dynamically linked executables, the name of executable or shared
14482 library containing the symbol is also printed:
14485 (@value{GDBP}) info symbol 0x400225
14486 _start + 5 in section .text of /tmp/a.out
14487 (@value{GDBP}) info symbol 0x2aaaac2811cf
14488 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
14492 @item whatis [@var{arg}]
14493 Print the data type of @var{arg}, which can be either an expression
14494 or a name of a data type. With no argument, print the data type of
14495 @code{$}, the last value in the value history.
14497 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
14498 is not actually evaluated, and any side-effecting operations (such as
14499 assignments or function calls) inside it do not take place.
14501 If @var{arg} is a variable or an expression, @code{whatis} prints its
14502 literal type as it is used in the source code. If the type was
14503 defined using a @code{typedef}, @code{whatis} will @emph{not} print
14504 the data type underlying the @code{typedef}. If the type of the
14505 variable or the expression is a compound data type, such as
14506 @code{struct} or @code{class}, @code{whatis} never prints their
14507 fields or methods. It just prints the @code{struct}/@code{class}
14508 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
14509 such a compound data type, use @code{ptype}.
14511 If @var{arg} is a type name that was defined using @code{typedef},
14512 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
14513 Unrolling means that @code{whatis} will show the underlying type used
14514 in the @code{typedef} declaration of @var{arg}. However, if that
14515 underlying type is also a @code{typedef}, @code{whatis} will not
14518 For C code, the type names may also have the form @samp{class
14519 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
14520 @var{union-tag}} or @samp{enum @var{enum-tag}}.
14523 @item ptype [@var{arg}]
14524 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
14525 detailed description of the type, instead of just the name of the type.
14526 @xref{Expressions, ,Expressions}.
14528 Contrary to @code{whatis}, @code{ptype} always unrolls any
14529 @code{typedef}s in its argument declaration, whether the argument is
14530 a variable, expression, or a data type. This means that @code{ptype}
14531 of a variable or an expression will not print literally its type as
14532 present in the source code---use @code{whatis} for that. @code{typedef}s at
14533 the pointer or reference targets are also unrolled. Only @code{typedef}s of
14534 fields, methods and inner @code{class typedef}s of @code{struct}s,
14535 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
14537 For example, for this variable declaration:
14540 typedef double real_t;
14541 struct complex @{ real_t real; double imag; @};
14542 typedef struct complex complex_t;
14544 real_t *real_pointer_var;
14548 the two commands give this output:
14552 (@value{GDBP}) whatis var
14554 (@value{GDBP}) ptype var
14555 type = struct complex @{
14559 (@value{GDBP}) whatis complex_t
14560 type = struct complex
14561 (@value{GDBP}) whatis struct complex
14562 type = struct complex
14563 (@value{GDBP}) ptype struct complex
14564 type = struct complex @{
14568 (@value{GDBP}) whatis real_pointer_var
14570 (@value{GDBP}) ptype real_pointer_var
14576 As with @code{whatis}, using @code{ptype} without an argument refers to
14577 the type of @code{$}, the last value in the value history.
14579 @cindex incomplete type
14580 Sometimes, programs use opaque data types or incomplete specifications
14581 of complex data structure. If the debug information included in the
14582 program does not allow @value{GDBN} to display a full declaration of
14583 the data type, it will say @samp{<incomplete type>}. For example,
14584 given these declarations:
14588 struct foo *fooptr;
14592 but no definition for @code{struct foo} itself, @value{GDBN} will say:
14595 (@value{GDBP}) ptype foo
14596 $1 = <incomplete type>
14600 ``Incomplete type'' is C terminology for data types that are not
14601 completely specified.
14604 @item info types @var{regexp}
14606 Print a brief description of all types whose names match the regular
14607 expression @var{regexp} (or all types in your program, if you supply
14608 no argument). Each complete typename is matched as though it were a
14609 complete line; thus, @samp{i type value} gives information on all
14610 types in your program whose names include the string @code{value}, but
14611 @samp{i type ^value$} gives information only on types whose complete
14612 name is @code{value}.
14614 This command differs from @code{ptype} in two ways: first, like
14615 @code{whatis}, it does not print a detailed description; second, it
14616 lists all source files where a type is defined.
14619 @cindex local variables
14620 @item info scope @var{location}
14621 List all the variables local to a particular scope. This command
14622 accepts a @var{location} argument---a function name, a source line, or
14623 an address preceded by a @samp{*}, and prints all the variables local
14624 to the scope defined by that location. (@xref{Specify Location}, for
14625 details about supported forms of @var{location}.) For example:
14628 (@value{GDBP}) @b{info scope command_line_handler}
14629 Scope for command_line_handler:
14630 Symbol rl is an argument at stack/frame offset 8, length 4.
14631 Symbol linebuffer is in static storage at address 0x150a18, length 4.
14632 Symbol linelength is in static storage at address 0x150a1c, length 4.
14633 Symbol p is a local variable in register $esi, length 4.
14634 Symbol p1 is a local variable in register $ebx, length 4.
14635 Symbol nline is a local variable in register $edx, length 4.
14636 Symbol repeat is a local variable at frame offset -8, length 4.
14640 This command is especially useful for determining what data to collect
14641 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
14644 @kindex info source
14646 Show information about the current source file---that is, the source file for
14647 the function containing the current point of execution:
14650 the name of the source file, and the directory containing it,
14652 the directory it was compiled in,
14654 its length, in lines,
14656 which programming language it is written in,
14658 whether the executable includes debugging information for that file, and
14659 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
14661 whether the debugging information includes information about
14662 preprocessor macros.
14666 @kindex info sources
14668 Print the names of all source files in your program for which there is
14669 debugging information, organized into two lists: files whose symbols
14670 have already been read, and files whose symbols will be read when needed.
14672 @kindex info functions
14673 @item info functions
14674 Print the names and data types of all defined functions.
14676 @item info functions @var{regexp}
14677 Print the names and data types of all defined functions
14678 whose names contain a match for regular expression @var{regexp}.
14679 Thus, @samp{info fun step} finds all functions whose names
14680 include @code{step}; @samp{info fun ^step} finds those whose names
14681 start with @code{step}. If a function name contains characters
14682 that conflict with the regular expression language (e.g.@:
14683 @samp{operator*()}), they may be quoted with a backslash.
14685 @kindex info variables
14686 @item info variables
14687 Print the names and data types of all variables that are defined
14688 outside of functions (i.e.@: excluding local variables).
14690 @item info variables @var{regexp}
14691 Print the names and data types of all variables (except for local
14692 variables) whose names contain a match for regular expression
14695 @kindex info classes
14696 @cindex Objective-C, classes and selectors
14698 @itemx info classes @var{regexp}
14699 Display all Objective-C classes in your program, or
14700 (with the @var{regexp} argument) all those matching a particular regular
14703 @kindex info selectors
14704 @item info selectors
14705 @itemx info selectors @var{regexp}
14706 Display all Objective-C selectors in your program, or
14707 (with the @var{regexp} argument) all those matching a particular regular
14711 This was never implemented.
14712 @kindex info methods
14714 @itemx info methods @var{regexp}
14715 The @code{info methods} command permits the user to examine all defined
14716 methods within C@t{++} program, or (with the @var{regexp} argument) a
14717 specific set of methods found in the various C@t{++} classes. Many
14718 C@t{++} classes provide a large number of methods. Thus, the output
14719 from the @code{ptype} command can be overwhelming and hard to use. The
14720 @code{info-methods} command filters the methods, printing only those
14721 which match the regular-expression @var{regexp}.
14724 @cindex reloading symbols
14725 Some systems allow individual object files that make up your program to
14726 be replaced without stopping and restarting your program. For example,
14727 in VxWorks you can simply recompile a defective object file and keep on
14728 running. If you are running on one of these systems, you can allow
14729 @value{GDBN} to reload the symbols for automatically relinked modules:
14732 @kindex set symbol-reloading
14733 @item set symbol-reloading on
14734 Replace symbol definitions for the corresponding source file when an
14735 object file with a particular name is seen again.
14737 @item set symbol-reloading off
14738 Do not replace symbol definitions when encountering object files of the
14739 same name more than once. This is the default state; if you are not
14740 running on a system that permits automatic relinking of modules, you
14741 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
14742 may discard symbols when linking large programs, that may contain
14743 several modules (from different directories or libraries) with the same
14746 @kindex show symbol-reloading
14747 @item show symbol-reloading
14748 Show the current @code{on} or @code{off} setting.
14751 @cindex opaque data types
14752 @kindex set opaque-type-resolution
14753 @item set opaque-type-resolution on
14754 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
14755 declared as a pointer to a @code{struct}, @code{class}, or
14756 @code{union}---for example, @code{struct MyType *}---that is used in one
14757 source file although the full declaration of @code{struct MyType} is in
14758 another source file. The default is on.
14760 A change in the setting of this subcommand will not take effect until
14761 the next time symbols for a file are loaded.
14763 @item set opaque-type-resolution off
14764 Tell @value{GDBN} not to resolve opaque types. In this case, the type
14765 is printed as follows:
14767 @{<no data fields>@}
14770 @kindex show opaque-type-resolution
14771 @item show opaque-type-resolution
14772 Show whether opaque types are resolved or not.
14774 @kindex maint print symbols
14775 @cindex symbol dump
14776 @kindex maint print psymbols
14777 @cindex partial symbol dump
14778 @item maint print symbols @var{filename}
14779 @itemx maint print psymbols @var{filename}
14780 @itemx maint print msymbols @var{filename}
14781 Write a dump of debugging symbol data into the file @var{filename}.
14782 These commands are used to debug the @value{GDBN} symbol-reading code. Only
14783 symbols with debugging data are included. If you use @samp{maint print
14784 symbols}, @value{GDBN} includes all the symbols for which it has already
14785 collected full details: that is, @var{filename} reflects symbols for
14786 only those files whose symbols @value{GDBN} has read. You can use the
14787 command @code{info sources} to find out which files these are. If you
14788 use @samp{maint print psymbols} instead, the dump shows information about
14789 symbols that @value{GDBN} only knows partially---that is, symbols defined in
14790 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
14791 @samp{maint print msymbols} dumps just the minimal symbol information
14792 required for each object file from which @value{GDBN} has read some symbols.
14793 @xref{Files, ,Commands to Specify Files}, for a discussion of how
14794 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
14796 @kindex maint info symtabs
14797 @kindex maint info psymtabs
14798 @cindex listing @value{GDBN}'s internal symbol tables
14799 @cindex symbol tables, listing @value{GDBN}'s internal
14800 @cindex full symbol tables, listing @value{GDBN}'s internal
14801 @cindex partial symbol tables, listing @value{GDBN}'s internal
14802 @item maint info symtabs @r{[} @var{regexp} @r{]}
14803 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
14805 List the @code{struct symtab} or @code{struct partial_symtab}
14806 structures whose names match @var{regexp}. If @var{regexp} is not
14807 given, list them all. The output includes expressions which you can
14808 copy into a @value{GDBN} debugging this one to examine a particular
14809 structure in more detail. For example:
14812 (@value{GDBP}) maint info psymtabs dwarf2read
14813 @{ objfile /home/gnu/build/gdb/gdb
14814 ((struct objfile *) 0x82e69d0)
14815 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
14816 ((struct partial_symtab *) 0x8474b10)
14819 text addresses 0x814d3c8 -- 0x8158074
14820 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
14821 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
14822 dependencies (none)
14825 (@value{GDBP}) maint info symtabs
14829 We see that there is one partial symbol table whose filename contains
14830 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
14831 and we see that @value{GDBN} has not read in any symtabs yet at all.
14832 If we set a breakpoint on a function, that will cause @value{GDBN} to
14833 read the symtab for the compilation unit containing that function:
14836 (@value{GDBP}) break dwarf2_psymtab_to_symtab
14837 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
14839 (@value{GDBP}) maint info symtabs
14840 @{ objfile /home/gnu/build/gdb/gdb
14841 ((struct objfile *) 0x82e69d0)
14842 @{ symtab /home/gnu/src/gdb/dwarf2read.c
14843 ((struct symtab *) 0x86c1f38)
14846 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
14847 linetable ((struct linetable *) 0x8370fa0)
14848 debugformat DWARF 2
14857 @chapter Altering Execution
14859 Once you think you have found an error in your program, you might want to
14860 find out for certain whether correcting the apparent error would lead to
14861 correct results in the rest of the run. You can find the answer by
14862 experiment, using the @value{GDBN} features for altering execution of the
14865 For example, you can store new values into variables or memory
14866 locations, give your program a signal, restart it at a different
14867 address, or even return prematurely from a function.
14870 * Assignment:: Assignment to variables
14871 * Jumping:: Continuing at a different address
14872 * Signaling:: Giving your program a signal
14873 * Returning:: Returning from a function
14874 * Calling:: Calling your program's functions
14875 * Patching:: Patching your program
14879 @section Assignment to Variables
14882 @cindex setting variables
14883 To alter the value of a variable, evaluate an assignment expression.
14884 @xref{Expressions, ,Expressions}. For example,
14891 stores the value 4 into the variable @code{x}, and then prints the
14892 value of the assignment expression (which is 4).
14893 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
14894 information on operators in supported languages.
14896 @kindex set variable
14897 @cindex variables, setting
14898 If you are not interested in seeing the value of the assignment, use the
14899 @code{set} command instead of the @code{print} command. @code{set} is
14900 really the same as @code{print} except that the expression's value is
14901 not printed and is not put in the value history (@pxref{Value History,
14902 ,Value History}). The expression is evaluated only for its effects.
14904 If the beginning of the argument string of the @code{set} command
14905 appears identical to a @code{set} subcommand, use the @code{set
14906 variable} command instead of just @code{set}. This command is identical
14907 to @code{set} except for its lack of subcommands. For example, if your
14908 program has a variable @code{width}, you get an error if you try to set
14909 a new value with just @samp{set width=13}, because @value{GDBN} has the
14910 command @code{set width}:
14913 (@value{GDBP}) whatis width
14915 (@value{GDBP}) p width
14917 (@value{GDBP}) set width=47
14918 Invalid syntax in expression.
14922 The invalid expression, of course, is @samp{=47}. In
14923 order to actually set the program's variable @code{width}, use
14926 (@value{GDBP}) set var width=47
14929 Because the @code{set} command has many subcommands that can conflict
14930 with the names of program variables, it is a good idea to use the
14931 @code{set variable} command instead of just @code{set}. For example, if
14932 your program has a variable @code{g}, you run into problems if you try
14933 to set a new value with just @samp{set g=4}, because @value{GDBN} has
14934 the command @code{set gnutarget}, abbreviated @code{set g}:
14938 (@value{GDBP}) whatis g
14942 (@value{GDBP}) set g=4
14946 The program being debugged has been started already.
14947 Start it from the beginning? (y or n) y
14948 Starting program: /home/smith/cc_progs/a.out
14949 "/home/smith/cc_progs/a.out": can't open to read symbols:
14950 Invalid bfd target.
14951 (@value{GDBP}) show g
14952 The current BFD target is "=4".
14957 The program variable @code{g} did not change, and you silently set the
14958 @code{gnutarget} to an invalid value. In order to set the variable
14962 (@value{GDBP}) set var g=4
14965 @value{GDBN} allows more implicit conversions in assignments than C; you can
14966 freely store an integer value into a pointer variable or vice versa,
14967 and you can convert any structure to any other structure that is the
14968 same length or shorter.
14969 @comment FIXME: how do structs align/pad in these conversions?
14970 @comment /doc@cygnus.com 18dec1990
14972 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
14973 construct to generate a value of specified type at a specified address
14974 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
14975 to memory location @code{0x83040} as an integer (which implies a certain size
14976 and representation in memory), and
14979 set @{int@}0x83040 = 4
14983 stores the value 4 into that memory location.
14986 @section Continuing at a Different Address
14988 Ordinarily, when you continue your program, you do so at the place where
14989 it stopped, with the @code{continue} command. You can instead continue at
14990 an address of your own choosing, with the following commands:
14994 @item jump @var{linespec}
14995 @itemx jump @var{location}
14996 Resume execution at line @var{linespec} or at address given by
14997 @var{location}. Execution stops again immediately if there is a
14998 breakpoint there. @xref{Specify Location}, for a description of the
14999 different forms of @var{linespec} and @var{location}. It is common
15000 practice to use the @code{tbreak} command in conjunction with
15001 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
15003 The @code{jump} command does not change the current stack frame, or
15004 the stack pointer, or the contents of any memory location or any
15005 register other than the program counter. If line @var{linespec} is in
15006 a different function from the one currently executing, the results may
15007 be bizarre if the two functions expect different patterns of arguments or
15008 of local variables. For this reason, the @code{jump} command requests
15009 confirmation if the specified line is not in the function currently
15010 executing. However, even bizarre results are predictable if you are
15011 well acquainted with the machine-language code of your program.
15014 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
15015 On many systems, you can get much the same effect as the @code{jump}
15016 command by storing a new value into the register @code{$pc}. The
15017 difference is that this does not start your program running; it only
15018 changes the address of where it @emph{will} run when you continue. For
15026 makes the next @code{continue} command or stepping command execute at
15027 address @code{0x485}, rather than at the address where your program stopped.
15028 @xref{Continuing and Stepping, ,Continuing and Stepping}.
15030 The most common occasion to use the @code{jump} command is to back
15031 up---perhaps with more breakpoints set---over a portion of a program
15032 that has already executed, in order to examine its execution in more
15037 @section Giving your Program a Signal
15038 @cindex deliver a signal to a program
15042 @item signal @var{signal}
15043 Resume execution where your program stopped, but immediately give it the
15044 signal @var{signal}. @var{signal} can be the name or the number of a
15045 signal. For example, on many systems @code{signal 2} and @code{signal
15046 SIGINT} are both ways of sending an interrupt signal.
15048 Alternatively, if @var{signal} is zero, continue execution without
15049 giving a signal. This is useful when your program stopped on account of
15050 a signal and would ordinary see the signal when resumed with the
15051 @code{continue} command; @samp{signal 0} causes it to resume without a
15054 @code{signal} does not repeat when you press @key{RET} a second time
15055 after executing the command.
15059 Invoking the @code{signal} command is not the same as invoking the
15060 @code{kill} utility from the shell. Sending a signal with @code{kill}
15061 causes @value{GDBN} to decide what to do with the signal depending on
15062 the signal handling tables (@pxref{Signals}). The @code{signal} command
15063 passes the signal directly to your program.
15067 @section Returning from a Function
15070 @cindex returning from a function
15073 @itemx return @var{expression}
15074 You can cancel execution of a function call with the @code{return}
15075 command. If you give an
15076 @var{expression} argument, its value is used as the function's return
15080 When you use @code{return}, @value{GDBN} discards the selected stack frame
15081 (and all frames within it). You can think of this as making the
15082 discarded frame return prematurely. If you wish to specify a value to
15083 be returned, give that value as the argument to @code{return}.
15085 This pops the selected stack frame (@pxref{Selection, ,Selecting a
15086 Frame}), and any other frames inside of it, leaving its caller as the
15087 innermost remaining frame. That frame becomes selected. The
15088 specified value is stored in the registers used for returning values
15091 The @code{return} command does not resume execution; it leaves the
15092 program stopped in the state that would exist if the function had just
15093 returned. In contrast, the @code{finish} command (@pxref{Continuing
15094 and Stepping, ,Continuing and Stepping}) resumes execution until the
15095 selected stack frame returns naturally.
15097 @value{GDBN} needs to know how the @var{expression} argument should be set for
15098 the inferior. The concrete registers assignment depends on the OS ABI and the
15099 type being returned by the selected stack frame. For example it is common for
15100 OS ABI to return floating point values in FPU registers while integer values in
15101 CPU registers. Still some ABIs return even floating point values in CPU
15102 registers. Larger integer widths (such as @code{long long int}) also have
15103 specific placement rules. @value{GDBN} already knows the OS ABI from its
15104 current target so it needs to find out also the type being returned to make the
15105 assignment into the right register(s).
15107 Normally, the selected stack frame has debug info. @value{GDBN} will always
15108 use the debug info instead of the implicit type of @var{expression} when the
15109 debug info is available. For example, if you type @kbd{return -1}, and the
15110 function in the current stack frame is declared to return a @code{long long
15111 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
15112 into a @code{long long int}:
15115 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
15117 (@value{GDBP}) return -1
15118 Make func return now? (y or n) y
15119 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
15120 43 printf ("result=%lld\n", func ());
15124 However, if the selected stack frame does not have a debug info, e.g., if the
15125 function was compiled without debug info, @value{GDBN} has to find out the type
15126 to return from user. Specifying a different type by mistake may set the value
15127 in different inferior registers than the caller code expects. For example,
15128 typing @kbd{return -1} with its implicit type @code{int} would set only a part
15129 of a @code{long long int} result for a debug info less function (on 32-bit
15130 architectures). Therefore the user is required to specify the return type by
15131 an appropriate cast explicitly:
15134 Breakpoint 2, 0x0040050b in func ()
15135 (@value{GDBP}) return -1
15136 Return value type not available for selected stack frame.
15137 Please use an explicit cast of the value to return.
15138 (@value{GDBP}) return (long long int) -1
15139 Make selected stack frame return now? (y or n) y
15140 #0 0x00400526 in main ()
15145 @section Calling Program Functions
15148 @cindex calling functions
15149 @cindex inferior functions, calling
15150 @item print @var{expr}
15151 Evaluate the expression @var{expr} and display the resulting value.
15152 @var{expr} may include calls to functions in the program being
15156 @item call @var{expr}
15157 Evaluate the expression @var{expr} without displaying @code{void}
15160 You can use this variant of the @code{print} command if you want to
15161 execute a function from your program that does not return anything
15162 (a.k.a.@: @dfn{a void function}), but without cluttering the output
15163 with @code{void} returned values that @value{GDBN} will otherwise
15164 print. If the result is not void, it is printed and saved in the
15168 It is possible for the function you call via the @code{print} or
15169 @code{call} command to generate a signal (e.g., if there's a bug in
15170 the function, or if you passed it incorrect arguments). What happens
15171 in that case is controlled by the @code{set unwindonsignal} command.
15173 Similarly, with a C@t{++} program it is possible for the function you
15174 call via the @code{print} or @code{call} command to generate an
15175 exception that is not handled due to the constraints of the dummy
15176 frame. In this case, any exception that is raised in the frame, but has
15177 an out-of-frame exception handler will not be found. GDB builds a
15178 dummy-frame for the inferior function call, and the unwinder cannot
15179 seek for exception handlers outside of this dummy-frame. What happens
15180 in that case is controlled by the
15181 @code{set unwind-on-terminating-exception} command.
15184 @item set unwindonsignal
15185 @kindex set unwindonsignal
15186 @cindex unwind stack in called functions
15187 @cindex call dummy stack unwinding
15188 Set unwinding of the stack if a signal is received while in a function
15189 that @value{GDBN} called in the program being debugged. If set to on,
15190 @value{GDBN} unwinds the stack it created for the call and restores
15191 the context to what it was before the call. If set to off (the
15192 default), @value{GDBN} stops in the frame where the signal was
15195 @item show unwindonsignal
15196 @kindex show unwindonsignal
15197 Show the current setting of stack unwinding in the functions called by
15200 @item set unwind-on-terminating-exception
15201 @kindex set unwind-on-terminating-exception
15202 @cindex unwind stack in called functions with unhandled exceptions
15203 @cindex call dummy stack unwinding on unhandled exception.
15204 Set unwinding of the stack if a C@t{++} exception is raised, but left
15205 unhandled while in a function that @value{GDBN} called in the program being
15206 debugged. If set to on (the default), @value{GDBN} unwinds the stack
15207 it created for the call and restores the context to what it was before
15208 the call. If set to off, @value{GDBN} the exception is delivered to
15209 the default C@t{++} exception handler and the inferior terminated.
15211 @item show unwind-on-terminating-exception
15212 @kindex show unwind-on-terminating-exception
15213 Show the current setting of stack unwinding in the functions called by
15218 @cindex weak alias functions
15219 Sometimes, a function you wish to call is actually a @dfn{weak alias}
15220 for another function. In such case, @value{GDBN} might not pick up
15221 the type information, including the types of the function arguments,
15222 which causes @value{GDBN} to call the inferior function incorrectly.
15223 As a result, the called function will function erroneously and may
15224 even crash. A solution to that is to use the name of the aliased
15228 @section Patching Programs
15230 @cindex patching binaries
15231 @cindex writing into executables
15232 @cindex writing into corefiles
15234 By default, @value{GDBN} opens the file containing your program's
15235 executable code (or the corefile) read-only. This prevents accidental
15236 alterations to machine code; but it also prevents you from intentionally
15237 patching your program's binary.
15239 If you'd like to be able to patch the binary, you can specify that
15240 explicitly with the @code{set write} command. For example, you might
15241 want to turn on internal debugging flags, or even to make emergency
15247 @itemx set write off
15248 If you specify @samp{set write on}, @value{GDBN} opens executable and
15249 core files for both reading and writing; if you specify @kbd{set write
15250 off} (the default), @value{GDBN} opens them read-only.
15252 If you have already loaded a file, you must load it again (using the
15253 @code{exec-file} or @code{core-file} command) after changing @code{set
15254 write}, for your new setting to take effect.
15258 Display whether executable files and core files are opened for writing
15259 as well as reading.
15263 @chapter @value{GDBN} Files
15265 @value{GDBN} needs to know the file name of the program to be debugged,
15266 both in order to read its symbol table and in order to start your
15267 program. To debug a core dump of a previous run, you must also tell
15268 @value{GDBN} the name of the core dump file.
15271 * Files:: Commands to specify files
15272 * Separate Debug Files:: Debugging information in separate files
15273 * Index Files:: Index files speed up GDB
15274 * Symbol Errors:: Errors reading symbol files
15275 * Data Files:: GDB data files
15279 @section Commands to Specify Files
15281 @cindex symbol table
15282 @cindex core dump file
15284 You may want to specify executable and core dump file names. The usual
15285 way to do this is at start-up time, using the arguments to
15286 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
15287 Out of @value{GDBN}}).
15289 Occasionally it is necessary to change to a different file during a
15290 @value{GDBN} session. Or you may run @value{GDBN} and forget to
15291 specify a file you want to use. Or you are debugging a remote target
15292 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
15293 Program}). In these situations the @value{GDBN} commands to specify
15294 new files are useful.
15297 @cindex executable file
15299 @item file @var{filename}
15300 Use @var{filename} as the program to be debugged. It is read for its
15301 symbols and for the contents of pure memory. It is also the program
15302 executed when you use the @code{run} command. If you do not specify a
15303 directory and the file is not found in the @value{GDBN} working directory,
15304 @value{GDBN} uses the environment variable @code{PATH} as a list of
15305 directories to search, just as the shell does when looking for a program
15306 to run. You can change the value of this variable, for both @value{GDBN}
15307 and your program, using the @code{path} command.
15309 @cindex unlinked object files
15310 @cindex patching object files
15311 You can load unlinked object @file{.o} files into @value{GDBN} using
15312 the @code{file} command. You will not be able to ``run'' an object
15313 file, but you can disassemble functions and inspect variables. Also,
15314 if the underlying BFD functionality supports it, you could use
15315 @kbd{gdb -write} to patch object files using this technique. Note
15316 that @value{GDBN} can neither interpret nor modify relocations in this
15317 case, so branches and some initialized variables will appear to go to
15318 the wrong place. But this feature is still handy from time to time.
15321 @code{file} with no argument makes @value{GDBN} discard any information it
15322 has on both executable file and the symbol table.
15325 @item exec-file @r{[} @var{filename} @r{]}
15326 Specify that the program to be run (but not the symbol table) is found
15327 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
15328 if necessary to locate your program. Omitting @var{filename} means to
15329 discard information on the executable file.
15331 @kindex symbol-file
15332 @item symbol-file @r{[} @var{filename} @r{]}
15333 Read symbol table information from file @var{filename}. @code{PATH} is
15334 searched when necessary. Use the @code{file} command to get both symbol
15335 table and program to run from the same file.
15337 @code{symbol-file} with no argument clears out @value{GDBN} information on your
15338 program's symbol table.
15340 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
15341 some breakpoints and auto-display expressions. This is because they may
15342 contain pointers to the internal data recording symbols and data types,
15343 which are part of the old symbol table data being discarded inside
15346 @code{symbol-file} does not repeat if you press @key{RET} again after
15349 When @value{GDBN} is configured for a particular environment, it
15350 understands debugging information in whatever format is the standard
15351 generated for that environment; you may use either a @sc{gnu} compiler, or
15352 other compilers that adhere to the local conventions.
15353 Best results are usually obtained from @sc{gnu} compilers; for example,
15354 using @code{@value{NGCC}} you can generate debugging information for
15357 For most kinds of object files, with the exception of old SVR3 systems
15358 using COFF, the @code{symbol-file} command does not normally read the
15359 symbol table in full right away. Instead, it scans the symbol table
15360 quickly to find which source files and which symbols are present. The
15361 details are read later, one source file at a time, as they are needed.
15363 The purpose of this two-stage reading strategy is to make @value{GDBN}
15364 start up faster. For the most part, it is invisible except for
15365 occasional pauses while the symbol table details for a particular source
15366 file are being read. (The @code{set verbose} command can turn these
15367 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
15368 Warnings and Messages}.)
15370 We have not implemented the two-stage strategy for COFF yet. When the
15371 symbol table is stored in COFF format, @code{symbol-file} reads the
15372 symbol table data in full right away. Note that ``stabs-in-COFF''
15373 still does the two-stage strategy, since the debug info is actually
15377 @cindex reading symbols immediately
15378 @cindex symbols, reading immediately
15379 @item symbol-file @r{[} -readnow @r{]} @var{filename}
15380 @itemx file @r{[} -readnow @r{]} @var{filename}
15381 You can override the @value{GDBN} two-stage strategy for reading symbol
15382 tables by using the @samp{-readnow} option with any of the commands that
15383 load symbol table information, if you want to be sure @value{GDBN} has the
15384 entire symbol table available.
15386 @c FIXME: for now no mention of directories, since this seems to be in
15387 @c flux. 13mar1992 status is that in theory GDB would look either in
15388 @c current dir or in same dir as myprog; but issues like competing
15389 @c GDB's, or clutter in system dirs, mean that in practice right now
15390 @c only current dir is used. FFish says maybe a special GDB hierarchy
15391 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
15395 @item core-file @r{[}@var{filename}@r{]}
15397 Specify the whereabouts of a core dump file to be used as the ``contents
15398 of memory''. Traditionally, core files contain only some parts of the
15399 address space of the process that generated them; @value{GDBN} can access the
15400 executable file itself for other parts.
15402 @code{core-file} with no argument specifies that no core file is
15405 Note that the core file is ignored when your program is actually running
15406 under @value{GDBN}. So, if you have been running your program and you
15407 wish to debug a core file instead, you must kill the subprocess in which
15408 the program is running. To do this, use the @code{kill} command
15409 (@pxref{Kill Process, ,Killing the Child Process}).
15411 @kindex add-symbol-file
15412 @cindex dynamic linking
15413 @item add-symbol-file @var{filename} @var{address}
15414 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
15415 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
15416 The @code{add-symbol-file} command reads additional symbol table
15417 information from the file @var{filename}. You would use this command
15418 when @var{filename} has been dynamically loaded (by some other means)
15419 into the program that is running. @var{address} should be the memory
15420 address at which the file has been loaded; @value{GDBN} cannot figure
15421 this out for itself. You can additionally specify an arbitrary number
15422 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
15423 section name and base address for that section. You can specify any
15424 @var{address} as an expression.
15426 The symbol table of the file @var{filename} is added to the symbol table
15427 originally read with the @code{symbol-file} command. You can use the
15428 @code{add-symbol-file} command any number of times; the new symbol data
15429 thus read keeps adding to the old. To discard all old symbol data
15430 instead, use the @code{symbol-file} command without any arguments.
15432 @cindex relocatable object files, reading symbols from
15433 @cindex object files, relocatable, reading symbols from
15434 @cindex reading symbols from relocatable object files
15435 @cindex symbols, reading from relocatable object files
15436 @cindex @file{.o} files, reading symbols from
15437 Although @var{filename} is typically a shared library file, an
15438 executable file, or some other object file which has been fully
15439 relocated for loading into a process, you can also load symbolic
15440 information from relocatable @file{.o} files, as long as:
15444 the file's symbolic information refers only to linker symbols defined in
15445 that file, not to symbols defined by other object files,
15447 every section the file's symbolic information refers to has actually
15448 been loaded into the inferior, as it appears in the file, and
15450 you can determine the address at which every section was loaded, and
15451 provide these to the @code{add-symbol-file} command.
15455 Some embedded operating systems, like Sun Chorus and VxWorks, can load
15456 relocatable files into an already running program; such systems
15457 typically make the requirements above easy to meet. However, it's
15458 important to recognize that many native systems use complex link
15459 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
15460 assembly, for example) that make the requirements difficult to meet. In
15461 general, one cannot assume that using @code{add-symbol-file} to read a
15462 relocatable object file's symbolic information will have the same effect
15463 as linking the relocatable object file into the program in the normal
15466 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
15468 @kindex add-symbol-file-from-memory
15469 @cindex @code{syscall DSO}
15470 @cindex load symbols from memory
15471 @item add-symbol-file-from-memory @var{address}
15472 Load symbols from the given @var{address} in a dynamically loaded
15473 object file whose image is mapped directly into the inferior's memory.
15474 For example, the Linux kernel maps a @code{syscall DSO} into each
15475 process's address space; this DSO provides kernel-specific code for
15476 some system calls. The argument can be any expression whose
15477 evaluation yields the address of the file's shared object file header.
15478 For this command to work, you must have used @code{symbol-file} or
15479 @code{exec-file} commands in advance.
15481 @kindex add-shared-symbol-files
15483 @item add-shared-symbol-files @var{library-file}
15484 @itemx assf @var{library-file}
15485 The @code{add-shared-symbol-files} command can currently be used only
15486 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
15487 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
15488 @value{GDBN} automatically looks for shared libraries, however if
15489 @value{GDBN} does not find yours, you can invoke
15490 @code{add-shared-symbol-files}. It takes one argument: the shared
15491 library's file name. @code{assf} is a shorthand alias for
15492 @code{add-shared-symbol-files}.
15495 @item section @var{section} @var{addr}
15496 The @code{section} command changes the base address of the named
15497 @var{section} of the exec file to @var{addr}. This can be used if the
15498 exec file does not contain section addresses, (such as in the
15499 @code{a.out} format), or when the addresses specified in the file
15500 itself are wrong. Each section must be changed separately. The
15501 @code{info files} command, described below, lists all the sections and
15505 @kindex info target
15508 @code{info files} and @code{info target} are synonymous; both print the
15509 current target (@pxref{Targets, ,Specifying a Debugging Target}),
15510 including the names of the executable and core dump files currently in
15511 use by @value{GDBN}, and the files from which symbols were loaded. The
15512 command @code{help target} lists all possible targets rather than
15515 @kindex maint info sections
15516 @item maint info sections
15517 Another command that can give you extra information about program sections
15518 is @code{maint info sections}. In addition to the section information
15519 displayed by @code{info files}, this command displays the flags and file
15520 offset of each section in the executable and core dump files. In addition,
15521 @code{maint info sections} provides the following command options (which
15522 may be arbitrarily combined):
15526 Display sections for all loaded object files, including shared libraries.
15527 @item @var{sections}
15528 Display info only for named @var{sections}.
15529 @item @var{section-flags}
15530 Display info only for sections for which @var{section-flags} are true.
15531 The section flags that @value{GDBN} currently knows about are:
15534 Section will have space allocated in the process when loaded.
15535 Set for all sections except those containing debug information.
15537 Section will be loaded from the file into the child process memory.
15538 Set for pre-initialized code and data, clear for @code{.bss} sections.
15540 Section needs to be relocated before loading.
15542 Section cannot be modified by the child process.
15544 Section contains executable code only.
15546 Section contains data only (no executable code).
15548 Section will reside in ROM.
15550 Section contains data for constructor/destructor lists.
15552 Section is not empty.
15554 An instruction to the linker to not output the section.
15555 @item COFF_SHARED_LIBRARY
15556 A notification to the linker that the section contains
15557 COFF shared library information.
15559 Section contains common symbols.
15562 @kindex set trust-readonly-sections
15563 @cindex read-only sections
15564 @item set trust-readonly-sections on
15565 Tell @value{GDBN} that readonly sections in your object file
15566 really are read-only (i.e.@: that their contents will not change).
15567 In that case, @value{GDBN} can fetch values from these sections
15568 out of the object file, rather than from the target program.
15569 For some targets (notably embedded ones), this can be a significant
15570 enhancement to debugging performance.
15572 The default is off.
15574 @item set trust-readonly-sections off
15575 Tell @value{GDBN} not to trust readonly sections. This means that
15576 the contents of the section might change while the program is running,
15577 and must therefore be fetched from the target when needed.
15579 @item show trust-readonly-sections
15580 Show the current setting of trusting readonly sections.
15583 All file-specifying commands allow both absolute and relative file names
15584 as arguments. @value{GDBN} always converts the file name to an absolute file
15585 name and remembers it that way.
15587 @cindex shared libraries
15588 @anchor{Shared Libraries}
15589 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
15590 and IBM RS/6000 AIX shared libraries.
15592 On MS-Windows @value{GDBN} must be linked with the Expat library to support
15593 shared libraries. @xref{Expat}.
15595 @value{GDBN} automatically loads symbol definitions from shared libraries
15596 when you use the @code{run} command, or when you examine a core file.
15597 (Before you issue the @code{run} command, @value{GDBN} does not understand
15598 references to a function in a shared library, however---unless you are
15599 debugging a core file).
15601 On HP-UX, if the program loads a library explicitly, @value{GDBN}
15602 automatically loads the symbols at the time of the @code{shl_load} call.
15604 @c FIXME: some @value{GDBN} release may permit some refs to undef
15605 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
15606 @c FIXME...lib; check this from time to time when updating manual
15608 There are times, however, when you may wish to not automatically load
15609 symbol definitions from shared libraries, such as when they are
15610 particularly large or there are many of them.
15612 To control the automatic loading of shared library symbols, use the
15616 @kindex set auto-solib-add
15617 @item set auto-solib-add @var{mode}
15618 If @var{mode} is @code{on}, symbols from all shared object libraries
15619 will be loaded automatically when the inferior begins execution, you
15620 attach to an independently started inferior, or when the dynamic linker
15621 informs @value{GDBN} that a new library has been loaded. If @var{mode}
15622 is @code{off}, symbols must be loaded manually, using the
15623 @code{sharedlibrary} command. The default value is @code{on}.
15625 @cindex memory used for symbol tables
15626 If your program uses lots of shared libraries with debug info that
15627 takes large amounts of memory, you can decrease the @value{GDBN}
15628 memory footprint by preventing it from automatically loading the
15629 symbols from shared libraries. To that end, type @kbd{set
15630 auto-solib-add off} before running the inferior, then load each
15631 library whose debug symbols you do need with @kbd{sharedlibrary
15632 @var{regexp}}, where @var{regexp} is a regular expression that matches
15633 the libraries whose symbols you want to be loaded.
15635 @kindex show auto-solib-add
15636 @item show auto-solib-add
15637 Display the current autoloading mode.
15640 @cindex load shared library
15641 To explicitly load shared library symbols, use the @code{sharedlibrary}
15645 @kindex info sharedlibrary
15647 @item info share @var{regex}
15648 @itemx info sharedlibrary @var{regex}
15649 Print the names of the shared libraries which are currently loaded
15650 that match @var{regex}. If @var{regex} is omitted then print
15651 all shared libraries that are loaded.
15653 @kindex sharedlibrary
15655 @item sharedlibrary @var{regex}
15656 @itemx share @var{regex}
15657 Load shared object library symbols for files matching a
15658 Unix regular expression.
15659 As with files loaded automatically, it only loads shared libraries
15660 required by your program for a core file or after typing @code{run}. If
15661 @var{regex} is omitted all shared libraries required by your program are
15664 @item nosharedlibrary
15665 @kindex nosharedlibrary
15666 @cindex unload symbols from shared libraries
15667 Unload all shared object library symbols. This discards all symbols
15668 that have been loaded from all shared libraries. Symbols from shared
15669 libraries that were loaded by explicit user requests are not
15673 Sometimes you may wish that @value{GDBN} stops and gives you control
15674 when any of shared library events happen. The best way to do this is
15675 to use @code{catch load} and @code{catch unload} (@pxref{Set
15678 @value{GDBN} also supports the the @code{set stop-on-solib-events}
15679 command for this. This command exists for historical reasons. It is
15680 less useful than setting a catchpoint, because it does not allow for
15681 conditions or commands as a catchpoint does.
15684 @item set stop-on-solib-events
15685 @kindex set stop-on-solib-events
15686 This command controls whether @value{GDBN} should give you control
15687 when the dynamic linker notifies it about some shared library event.
15688 The most common event of interest is loading or unloading of a new
15691 @item show stop-on-solib-events
15692 @kindex show stop-on-solib-events
15693 Show whether @value{GDBN} stops and gives you control when shared
15694 library events happen.
15697 Shared libraries are also supported in many cross or remote debugging
15698 configurations. @value{GDBN} needs to have access to the target's libraries;
15699 this can be accomplished either by providing copies of the libraries
15700 on the host system, or by asking @value{GDBN} to automatically retrieve the
15701 libraries from the target. If copies of the target libraries are
15702 provided, they need to be the same as the target libraries, although the
15703 copies on the target can be stripped as long as the copies on the host are
15706 @cindex where to look for shared libraries
15707 For remote debugging, you need to tell @value{GDBN} where the target
15708 libraries are, so that it can load the correct copies---otherwise, it
15709 may try to load the host's libraries. @value{GDBN} has two variables
15710 to specify the search directories for target libraries.
15713 @cindex prefix for shared library file names
15714 @cindex system root, alternate
15715 @kindex set solib-absolute-prefix
15716 @kindex set sysroot
15717 @item set sysroot @var{path}
15718 Use @var{path} as the system root for the program being debugged. Any
15719 absolute shared library paths will be prefixed with @var{path}; many
15720 runtime loaders store the absolute paths to the shared library in the
15721 target program's memory. If you use @code{set sysroot} to find shared
15722 libraries, they need to be laid out in the same way that they are on
15723 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
15726 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
15727 retrieve the target libraries from the remote system. This is only
15728 supported when using a remote target that supports the @code{remote get}
15729 command (@pxref{File Transfer,,Sending files to a remote system}).
15730 The part of @var{path} following the initial @file{remote:}
15731 (if present) is used as system root prefix on the remote file system.
15732 @footnote{If you want to specify a local system root using a directory
15733 that happens to be named @file{remote:}, you need to use some equivalent
15734 variant of the name like @file{./remote:}.}
15736 For targets with an MS-DOS based filesystem, such as MS-Windows and
15737 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
15738 absolute file name with @var{path}. But first, on Unix hosts,
15739 @value{GDBN} converts all backslash directory separators into forward
15740 slashes, because the backslash is not a directory separator on Unix:
15743 c:\foo\bar.dll @result{} c:/foo/bar.dll
15746 Then, @value{GDBN} attempts prefixing the target file name with
15747 @var{path}, and looks for the resulting file name in the host file
15751 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
15754 If that does not find the shared library, @value{GDBN} tries removing
15755 the @samp{:} character from the drive spec, both for convenience, and,
15756 for the case of the host file system not supporting file names with
15760 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
15763 This makes it possible to have a system root that mirrors a target
15764 with more than one drive. E.g., you may want to setup your local
15765 copies of the target system shared libraries like so (note @samp{c} vs
15769 @file{/path/to/sysroot/c/sys/bin/foo.dll}
15770 @file{/path/to/sysroot/c/sys/bin/bar.dll}
15771 @file{/path/to/sysroot/z/sys/bin/bar.dll}
15775 and point the system root at @file{/path/to/sysroot}, so that
15776 @value{GDBN} can find the correct copies of both
15777 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
15779 If that still does not find the shared library, @value{GDBN} tries
15780 removing the whole drive spec from the target file name:
15783 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
15786 This last lookup makes it possible to not care about the drive name,
15787 if you don't want or need to.
15789 The @code{set solib-absolute-prefix} command is an alias for @code{set
15792 @cindex default system root
15793 @cindex @samp{--with-sysroot}
15794 You can set the default system root by using the configure-time
15795 @samp{--with-sysroot} option. If the system root is inside
15796 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15797 @samp{--exec-prefix}), then the default system root will be updated
15798 automatically if the installed @value{GDBN} is moved to a new
15801 @kindex show sysroot
15803 Display the current shared library prefix.
15805 @kindex set solib-search-path
15806 @item set solib-search-path @var{path}
15807 If this variable is set, @var{path} is a colon-separated list of
15808 directories to search for shared libraries. @samp{solib-search-path}
15809 is used after @samp{sysroot} fails to locate the library, or if the
15810 path to the library is relative instead of absolute. If you want to
15811 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
15812 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
15813 finding your host's libraries. @samp{sysroot} is preferred; setting
15814 it to a nonexistent directory may interfere with automatic loading
15815 of shared library symbols.
15817 @kindex show solib-search-path
15818 @item show solib-search-path
15819 Display the current shared library search path.
15821 @cindex DOS file-name semantics of file names.
15822 @kindex set target-file-system-kind (unix|dos-based|auto)
15823 @kindex show target-file-system-kind
15824 @item set target-file-system-kind @var{kind}
15825 Set assumed file system kind for target reported file names.
15827 Shared library file names as reported by the target system may not
15828 make sense as is on the system @value{GDBN} is running on. For
15829 example, when remote debugging a target that has MS-DOS based file
15830 system semantics, from a Unix host, the target may be reporting to
15831 @value{GDBN} a list of loaded shared libraries with file names such as
15832 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
15833 drive letters, so the @samp{c:\} prefix is not normally understood as
15834 indicating an absolute file name, and neither is the backslash
15835 normally considered a directory separator character. In that case,
15836 the native file system would interpret this whole absolute file name
15837 as a relative file name with no directory components. This would make
15838 it impossible to point @value{GDBN} at a copy of the remote target's
15839 shared libraries on the host using @code{set sysroot}, and impractical
15840 with @code{set solib-search-path}. Setting
15841 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
15842 to interpret such file names similarly to how the target would, and to
15843 map them to file names valid on @value{GDBN}'s native file system
15844 semantics. The value of @var{kind} can be @code{"auto"}, in addition
15845 to one of the supported file system kinds. In that case, @value{GDBN}
15846 tries to determine the appropriate file system variant based on the
15847 current target's operating system (@pxref{ABI, ,Configuring the
15848 Current ABI}). The supported file system settings are:
15852 Instruct @value{GDBN} to assume the target file system is of Unix
15853 kind. Only file names starting the forward slash (@samp{/}) character
15854 are considered absolute, and the directory separator character is also
15858 Instruct @value{GDBN} to assume the target file system is DOS based.
15859 File names starting with either a forward slash, or a drive letter
15860 followed by a colon (e.g., @samp{c:}), are considered absolute, and
15861 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
15862 considered directory separators.
15865 Instruct @value{GDBN} to use the file system kind associated with the
15866 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
15867 This is the default.
15871 @cindex file name canonicalization
15872 @cindex base name differences
15873 When processing file names provided by the user, @value{GDBN}
15874 frequently needs to compare them to the file names recorded in the
15875 program's debug info. Normally, @value{GDBN} compares just the
15876 @dfn{base names} of the files as strings, which is reasonably fast
15877 even for very large programs. (The base name of a file is the last
15878 portion of its name, after stripping all the leading directories.)
15879 This shortcut in comparison is based upon the assumption that files
15880 cannot have more than one base name. This is usually true, but
15881 references to files that use symlinks or similar filesystem
15882 facilities violate that assumption. If your program records files
15883 using such facilities, or if you provide file names to @value{GDBN}
15884 using symlinks etc., you can set @code{basenames-may-differ} to
15885 @code{true} to instruct @value{GDBN} to completely canonicalize each
15886 pair of file names it needs to compare. This will make file-name
15887 comparisons accurate, but at a price of a significant slowdown.
15890 @item set basenames-may-differ
15891 @kindex set basenames-may-differ
15892 Set whether a source file may have multiple base names.
15894 @item show basenames-may-differ
15895 @kindex show basenames-may-differ
15896 Show whether a source file may have multiple base names.
15899 @node Separate Debug Files
15900 @section Debugging Information in Separate Files
15901 @cindex separate debugging information files
15902 @cindex debugging information in separate files
15903 @cindex @file{.debug} subdirectories
15904 @cindex debugging information directory, global
15905 @cindex global debugging information directory
15906 @cindex build ID, and separate debugging files
15907 @cindex @file{.build-id} directory
15909 @value{GDBN} allows you to put a program's debugging information in a
15910 file separate from the executable itself, in a way that allows
15911 @value{GDBN} to find and load the debugging information automatically.
15912 Since debugging information can be very large---sometimes larger
15913 than the executable code itself---some systems distribute debugging
15914 information for their executables in separate files, which users can
15915 install only when they need to debug a problem.
15917 @value{GDBN} supports two ways of specifying the separate debug info
15922 The executable contains a @dfn{debug link} that specifies the name of
15923 the separate debug info file. The separate debug file's name is
15924 usually @file{@var{executable}.debug}, where @var{executable} is the
15925 name of the corresponding executable file without leading directories
15926 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
15927 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
15928 checksum for the debug file, which @value{GDBN} uses to validate that
15929 the executable and the debug file came from the same build.
15932 The executable contains a @dfn{build ID}, a unique bit string that is
15933 also present in the corresponding debug info file. (This is supported
15934 only on some operating systems, notably those which use the ELF format
15935 for binary files and the @sc{gnu} Binutils.) For more details about
15936 this feature, see the description of the @option{--build-id}
15937 command-line option in @ref{Options, , Command Line Options, ld.info,
15938 The GNU Linker}. The debug info file's name is not specified
15939 explicitly by the build ID, but can be computed from the build ID, see
15943 Depending on the way the debug info file is specified, @value{GDBN}
15944 uses two different methods of looking for the debug file:
15948 For the ``debug link'' method, @value{GDBN} looks up the named file in
15949 the directory of the executable file, then in a subdirectory of that
15950 directory named @file{.debug}, and finally under the global debug
15951 directory, in a subdirectory whose name is identical to the leading
15952 directories of the executable's absolute file name.
15955 For the ``build ID'' method, @value{GDBN} looks in the
15956 @file{.build-id} subdirectory of the global debug directory for a file
15957 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
15958 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
15959 are the rest of the bit string. (Real build ID strings are 32 or more
15960 hex characters, not 10.)
15963 So, for example, suppose you ask @value{GDBN} to debug
15964 @file{/usr/bin/ls}, which has a debug link that specifies the
15965 file @file{ls.debug}, and a build ID whose value in hex is
15966 @code{abcdef1234}. If the global debug directory is
15967 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
15968 debug information files, in the indicated order:
15972 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
15974 @file{/usr/bin/ls.debug}
15976 @file{/usr/bin/.debug/ls.debug}
15978 @file{/usr/lib/debug/usr/bin/ls.debug}.
15981 You can set the global debugging info directory's name, and view the
15982 name @value{GDBN} is currently using.
15986 @kindex set debug-file-directory
15987 @item set debug-file-directory @var{directories}
15988 Set the directories which @value{GDBN} searches for separate debugging
15989 information files to @var{directory}. Multiple directory components can be set
15990 concatenating them by a directory separator.
15992 @kindex show debug-file-directory
15993 @item show debug-file-directory
15994 Show the directories @value{GDBN} searches for separate debugging
15999 @cindex @code{.gnu_debuglink} sections
16000 @cindex debug link sections
16001 A debug link is a special section of the executable file named
16002 @code{.gnu_debuglink}. The section must contain:
16006 A filename, with any leading directory components removed, followed by
16009 zero to three bytes of padding, as needed to reach the next four-byte
16010 boundary within the section, and
16012 a four-byte CRC checksum, stored in the same endianness used for the
16013 executable file itself. The checksum is computed on the debugging
16014 information file's full contents by the function given below, passing
16015 zero as the @var{crc} argument.
16018 Any executable file format can carry a debug link, as long as it can
16019 contain a section named @code{.gnu_debuglink} with the contents
16022 @cindex @code{.note.gnu.build-id} sections
16023 @cindex build ID sections
16024 The build ID is a special section in the executable file (and in other
16025 ELF binary files that @value{GDBN} may consider). This section is
16026 often named @code{.note.gnu.build-id}, but that name is not mandatory.
16027 It contains unique identification for the built files---the ID remains
16028 the same across multiple builds of the same build tree. The default
16029 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
16030 content for the build ID string. The same section with an identical
16031 value is present in the original built binary with symbols, in its
16032 stripped variant, and in the separate debugging information file.
16034 The debugging information file itself should be an ordinary
16035 executable, containing a full set of linker symbols, sections, and
16036 debugging information. The sections of the debugging information file
16037 should have the same names, addresses, and sizes as the original file,
16038 but they need not contain any data---much like a @code{.bss} section
16039 in an ordinary executable.
16041 The @sc{gnu} binary utilities (Binutils) package includes the
16042 @samp{objcopy} utility that can produce
16043 the separated executable / debugging information file pairs using the
16044 following commands:
16047 @kbd{objcopy --only-keep-debug foo foo.debug}
16052 These commands remove the debugging
16053 information from the executable file @file{foo} and place it in the file
16054 @file{foo.debug}. You can use the first, second or both methods to link the
16059 The debug link method needs the following additional command to also leave
16060 behind a debug link in @file{foo}:
16063 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
16066 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
16067 a version of the @code{strip} command such that the command @kbd{strip foo -f
16068 foo.debug} has the same functionality as the two @code{objcopy} commands and
16069 the @code{ln -s} command above, together.
16072 Build ID gets embedded into the main executable using @code{ld --build-id} or
16073 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
16074 compatibility fixes for debug files separation are present in @sc{gnu} binary
16075 utilities (Binutils) package since version 2.18.
16080 @cindex CRC algorithm definition
16081 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
16082 IEEE 802.3 using the polynomial:
16084 @c TexInfo requires naked braces for multi-digit exponents for Tex
16085 @c output, but this causes HTML output to barf. HTML has to be set using
16086 @c raw commands. So we end up having to specify this equation in 2
16091 <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>
16092 + <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
16098 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
16099 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
16103 The function is computed byte at a time, taking the least
16104 significant bit of each byte first. The initial pattern
16105 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
16106 the final result is inverted to ensure trailing zeros also affect the
16109 @emph{Note:} This is the same CRC polynomial as used in handling the
16110 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
16111 , @value{GDBN} Remote Serial Protocol}). However in the
16112 case of the Remote Serial Protocol, the CRC is computed @emph{most}
16113 significant bit first, and the result is not inverted, so trailing
16114 zeros have no effect on the CRC value.
16116 To complete the description, we show below the code of the function
16117 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
16118 initially supplied @code{crc} argument means that an initial call to
16119 this function passing in zero will start computing the CRC using
16122 @kindex gnu_debuglink_crc32
16125 gnu_debuglink_crc32 (unsigned long crc,
16126 unsigned char *buf, size_t len)
16128 static const unsigned long crc32_table[256] =
16130 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
16131 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
16132 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
16133 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
16134 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
16135 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
16136 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
16137 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
16138 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
16139 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
16140 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
16141 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
16142 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
16143 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
16144 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
16145 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
16146 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
16147 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
16148 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
16149 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
16150 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
16151 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
16152 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
16153 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
16154 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
16155 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
16156 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
16157 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
16158 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
16159 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
16160 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
16161 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
16162 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
16163 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
16164 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
16165 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
16166 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
16167 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
16168 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
16169 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
16170 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
16171 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
16172 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
16173 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
16174 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
16175 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
16176 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
16177 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
16178 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
16179 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
16180 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
16183 unsigned char *end;
16185 crc = ~crc & 0xffffffff;
16186 for (end = buf + len; buf < end; ++buf)
16187 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
16188 return ~crc & 0xffffffff;
16193 This computation does not apply to the ``build ID'' method.
16197 @section Index Files Speed Up @value{GDBN}
16198 @cindex index files
16199 @cindex @samp{.gdb_index} section
16201 When @value{GDBN} finds a symbol file, it scans the symbols in the
16202 file in order to construct an internal symbol table. This lets most
16203 @value{GDBN} operations work quickly---at the cost of a delay early
16204 on. For large programs, this delay can be quite lengthy, so
16205 @value{GDBN} provides a way to build an index, which speeds up
16208 The index is stored as a section in the symbol file. @value{GDBN} can
16209 write the index to a file, then you can put it into the symbol file
16210 using @command{objcopy}.
16212 To create an index file, use the @code{save gdb-index} command:
16215 @item save gdb-index @var{directory}
16216 @kindex save gdb-index
16217 Create an index file for each symbol file currently known by
16218 @value{GDBN}. Each file is named after its corresponding symbol file,
16219 with @samp{.gdb-index} appended, and is written into the given
16223 Once you have created an index file you can merge it into your symbol
16224 file, here named @file{symfile}, using @command{objcopy}:
16227 $ objcopy --add-section .gdb_index=symfile.gdb-index \
16228 --set-section-flags .gdb_index=readonly symfile symfile
16231 There are currently some limitation on indices. They only work when
16232 for DWARF debugging information, not stabs. And, they do not
16233 currently work for programs using Ada.
16235 @node Symbol Errors
16236 @section Errors Reading Symbol Files
16238 While reading a symbol file, @value{GDBN} occasionally encounters problems,
16239 such as symbol types it does not recognize, or known bugs in compiler
16240 output. By default, @value{GDBN} does not notify you of such problems, since
16241 they are relatively common and primarily of interest to people
16242 debugging compilers. If you are interested in seeing information
16243 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
16244 only one message about each such type of problem, no matter how many
16245 times the problem occurs; or you can ask @value{GDBN} to print more messages,
16246 to see how many times the problems occur, with the @code{set
16247 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
16250 The messages currently printed, and their meanings, include:
16253 @item inner block not inside outer block in @var{symbol}
16255 The symbol information shows where symbol scopes begin and end
16256 (such as at the start of a function or a block of statements). This
16257 error indicates that an inner scope block is not fully contained
16258 in its outer scope blocks.
16260 @value{GDBN} circumvents the problem by treating the inner block as if it had
16261 the same scope as the outer block. In the error message, @var{symbol}
16262 may be shown as ``@code{(don't know)}'' if the outer block is not a
16265 @item block at @var{address} out of order
16267 The symbol information for symbol scope blocks should occur in
16268 order of increasing addresses. This error indicates that it does not
16271 @value{GDBN} does not circumvent this problem, and has trouble
16272 locating symbols in the source file whose symbols it is reading. (You
16273 can often determine what source file is affected by specifying
16274 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
16277 @item bad block start address patched
16279 The symbol information for a symbol scope block has a start address
16280 smaller than the address of the preceding source line. This is known
16281 to occur in the SunOS 4.1.1 (and earlier) C compiler.
16283 @value{GDBN} circumvents the problem by treating the symbol scope block as
16284 starting on the previous source line.
16286 @item bad string table offset in symbol @var{n}
16289 Symbol number @var{n} contains a pointer into the string table which is
16290 larger than the size of the string table.
16292 @value{GDBN} circumvents the problem by considering the symbol to have the
16293 name @code{foo}, which may cause other problems if many symbols end up
16296 @item unknown symbol type @code{0x@var{nn}}
16298 The symbol information contains new data types that @value{GDBN} does
16299 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
16300 uncomprehended information, in hexadecimal.
16302 @value{GDBN} circumvents the error by ignoring this symbol information.
16303 This usually allows you to debug your program, though certain symbols
16304 are not accessible. If you encounter such a problem and feel like
16305 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
16306 on @code{complain}, then go up to the function @code{read_dbx_symtab}
16307 and examine @code{*bufp} to see the symbol.
16309 @item stub type has NULL name
16311 @value{GDBN} could not find the full definition for a struct or class.
16313 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
16314 The symbol information for a C@t{++} member function is missing some
16315 information that recent versions of the compiler should have output for
16318 @item info mismatch between compiler and debugger
16320 @value{GDBN} could not parse a type specification output by the compiler.
16325 @section GDB Data Files
16327 @cindex prefix for data files
16328 @value{GDBN} will sometimes read an auxiliary data file. These files
16329 are kept in a directory known as the @dfn{data directory}.
16331 You can set the data directory's name, and view the name @value{GDBN}
16332 is currently using.
16335 @kindex set data-directory
16336 @item set data-directory @var{directory}
16337 Set the directory which @value{GDBN} searches for auxiliary data files
16338 to @var{directory}.
16340 @kindex show data-directory
16341 @item show data-directory
16342 Show the directory @value{GDBN} searches for auxiliary data files.
16345 @cindex default data directory
16346 @cindex @samp{--with-gdb-datadir}
16347 You can set the default data directory by using the configure-time
16348 @samp{--with-gdb-datadir} option. If the data directory is inside
16349 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
16350 @samp{--exec-prefix}), then the default data directory will be updated
16351 automatically if the installed @value{GDBN} is moved to a new
16354 The data directory may also be specified with the
16355 @code{--data-directory} command line option.
16356 @xref{Mode Options}.
16359 @chapter Specifying a Debugging Target
16361 @cindex debugging target
16362 A @dfn{target} is the execution environment occupied by your program.
16364 Often, @value{GDBN} runs in the same host environment as your program;
16365 in that case, the debugging target is specified as a side effect when
16366 you use the @code{file} or @code{core} commands. When you need more
16367 flexibility---for example, running @value{GDBN} on a physically separate
16368 host, or controlling a standalone system over a serial port or a
16369 realtime system over a TCP/IP connection---you can use the @code{target}
16370 command to specify one of the target types configured for @value{GDBN}
16371 (@pxref{Target Commands, ,Commands for Managing Targets}).
16373 @cindex target architecture
16374 It is possible to build @value{GDBN} for several different @dfn{target
16375 architectures}. When @value{GDBN} is built like that, you can choose
16376 one of the available architectures with the @kbd{set architecture}
16380 @kindex set architecture
16381 @kindex show architecture
16382 @item set architecture @var{arch}
16383 This command sets the current target architecture to @var{arch}. The
16384 value of @var{arch} can be @code{"auto"}, in addition to one of the
16385 supported architectures.
16387 @item show architecture
16388 Show the current target architecture.
16390 @item set processor
16392 @kindex set processor
16393 @kindex show processor
16394 These are alias commands for, respectively, @code{set architecture}
16395 and @code{show architecture}.
16399 * Active Targets:: Active targets
16400 * Target Commands:: Commands for managing targets
16401 * Byte Order:: Choosing target byte order
16404 @node Active Targets
16405 @section Active Targets
16407 @cindex stacking targets
16408 @cindex active targets
16409 @cindex multiple targets
16411 There are multiple classes of targets such as: processes, executable files or
16412 recording sessions. Core files belong to the process class, making core file
16413 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
16414 on multiple active targets, one in each class. This allows you to (for
16415 example) start a process and inspect its activity, while still having access to
16416 the executable file after the process finishes. Or if you start process
16417 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
16418 presented a virtual layer of the recording target, while the process target
16419 remains stopped at the chronologically last point of the process execution.
16421 Use the @code{core-file} and @code{exec-file} commands to select a new core
16422 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
16423 specify as a target a process that is already running, use the @code{attach}
16424 command (@pxref{Attach, ,Debugging an Already-running Process}).
16426 @node Target Commands
16427 @section Commands for Managing Targets
16430 @item target @var{type} @var{parameters}
16431 Connects the @value{GDBN} host environment to a target machine or
16432 process. A target is typically a protocol for talking to debugging
16433 facilities. You use the argument @var{type} to specify the type or
16434 protocol of the target machine.
16436 Further @var{parameters} are interpreted by the target protocol, but
16437 typically include things like device names or host names to connect
16438 with, process numbers, and baud rates.
16440 The @code{target} command does not repeat if you press @key{RET} again
16441 after executing the command.
16443 @kindex help target
16445 Displays the names of all targets available. To display targets
16446 currently selected, use either @code{info target} or @code{info files}
16447 (@pxref{Files, ,Commands to Specify Files}).
16449 @item help target @var{name}
16450 Describe a particular target, including any parameters necessary to
16453 @kindex set gnutarget
16454 @item set gnutarget @var{args}
16455 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
16456 knows whether it is reading an @dfn{executable},
16457 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
16458 with the @code{set gnutarget} command. Unlike most @code{target} commands,
16459 with @code{gnutarget} the @code{target} refers to a program, not a machine.
16462 @emph{Warning:} To specify a file format with @code{set gnutarget},
16463 you must know the actual BFD name.
16467 @xref{Files, , Commands to Specify Files}.
16469 @kindex show gnutarget
16470 @item show gnutarget
16471 Use the @code{show gnutarget} command to display what file format
16472 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
16473 @value{GDBN} will determine the file format for each file automatically,
16474 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
16477 @cindex common targets
16478 Here are some common targets (available, or not, depending on the GDB
16483 @item target exec @var{program}
16484 @cindex executable file target
16485 An executable file. @samp{target exec @var{program}} is the same as
16486 @samp{exec-file @var{program}}.
16488 @item target core @var{filename}
16489 @cindex core dump file target
16490 A core dump file. @samp{target core @var{filename}} is the same as
16491 @samp{core-file @var{filename}}.
16493 @item target remote @var{medium}
16494 @cindex remote target
16495 A remote system connected to @value{GDBN} via a serial line or network
16496 connection. This command tells @value{GDBN} to use its own remote
16497 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
16499 For example, if you have a board connected to @file{/dev/ttya} on the
16500 machine running @value{GDBN}, you could say:
16503 target remote /dev/ttya
16506 @code{target remote} supports the @code{load} command. This is only
16507 useful if you have some other way of getting the stub to the target
16508 system, and you can put it somewhere in memory where it won't get
16509 clobbered by the download.
16511 @item target sim @r{[}@var{simargs}@r{]} @dots{}
16512 @cindex built-in simulator target
16513 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
16521 works; however, you cannot assume that a specific memory map, device
16522 drivers, or even basic I/O is available, although some simulators do
16523 provide these. For info about any processor-specific simulator details,
16524 see the appropriate section in @ref{Embedded Processors, ,Embedded
16529 Some configurations may include these targets as well:
16533 @item target nrom @var{dev}
16534 @cindex NetROM ROM emulator target
16535 NetROM ROM emulator. This target only supports downloading.
16539 Different targets are available on different configurations of @value{GDBN};
16540 your configuration may have more or fewer targets.
16542 Many remote targets require you to download the executable's code once
16543 you've successfully established a connection. You may wish to control
16544 various aspects of this process.
16549 @kindex set hash@r{, for remote monitors}
16550 @cindex hash mark while downloading
16551 This command controls whether a hash mark @samp{#} is displayed while
16552 downloading a file to the remote monitor. If on, a hash mark is
16553 displayed after each S-record is successfully downloaded to the
16557 @kindex show hash@r{, for remote monitors}
16558 Show the current status of displaying the hash mark.
16560 @item set debug monitor
16561 @kindex set debug monitor
16562 @cindex display remote monitor communications
16563 Enable or disable display of communications messages between
16564 @value{GDBN} and the remote monitor.
16566 @item show debug monitor
16567 @kindex show debug monitor
16568 Show the current status of displaying communications between
16569 @value{GDBN} and the remote monitor.
16574 @kindex load @var{filename}
16575 @item load @var{filename}
16577 Depending on what remote debugging facilities are configured into
16578 @value{GDBN}, the @code{load} command may be available. Where it exists, it
16579 is meant to make @var{filename} (an executable) available for debugging
16580 on the remote system---by downloading, or dynamic linking, for example.
16581 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
16582 the @code{add-symbol-file} command.
16584 If your @value{GDBN} does not have a @code{load} command, attempting to
16585 execute it gets the error message ``@code{You can't do that when your
16586 target is @dots{}}''
16588 The file is loaded at whatever address is specified in the executable.
16589 For some object file formats, you can specify the load address when you
16590 link the program; for other formats, like a.out, the object file format
16591 specifies a fixed address.
16592 @c FIXME! This would be a good place for an xref to the GNU linker doc.
16594 Depending on the remote side capabilities, @value{GDBN} may be able to
16595 load programs into flash memory.
16597 @code{load} does not repeat if you press @key{RET} again after using it.
16601 @section Choosing Target Byte Order
16603 @cindex choosing target byte order
16604 @cindex target byte order
16606 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
16607 offer the ability to run either big-endian or little-endian byte
16608 orders. Usually the executable or symbol will include a bit to
16609 designate the endian-ness, and you will not need to worry about
16610 which to use. However, you may still find it useful to adjust
16611 @value{GDBN}'s idea of processor endian-ness manually.
16615 @item set endian big
16616 Instruct @value{GDBN} to assume the target is big-endian.
16618 @item set endian little
16619 Instruct @value{GDBN} to assume the target is little-endian.
16621 @item set endian auto
16622 Instruct @value{GDBN} to use the byte order associated with the
16626 Display @value{GDBN}'s current idea of the target byte order.
16630 Note that these commands merely adjust interpretation of symbolic
16631 data on the host, and that they have absolutely no effect on the
16635 @node Remote Debugging
16636 @chapter Debugging Remote Programs
16637 @cindex remote debugging
16639 If you are trying to debug a program running on a machine that cannot run
16640 @value{GDBN} in the usual way, it is often useful to use remote debugging.
16641 For example, you might use remote debugging on an operating system kernel,
16642 or on a small system which does not have a general purpose operating system
16643 powerful enough to run a full-featured debugger.
16645 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
16646 to make this work with particular debugging targets. In addition,
16647 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
16648 but not specific to any particular target system) which you can use if you
16649 write the remote stubs---the code that runs on the remote system to
16650 communicate with @value{GDBN}.
16652 Other remote targets may be available in your
16653 configuration of @value{GDBN}; use @code{help target} to list them.
16656 * Connecting:: Connecting to a remote target
16657 * File Transfer:: Sending files to a remote system
16658 * Server:: Using the gdbserver program
16659 * Remote Configuration:: Remote configuration
16660 * Remote Stub:: Implementing a remote stub
16664 @section Connecting to a Remote Target
16666 On the @value{GDBN} host machine, you will need an unstripped copy of
16667 your program, since @value{GDBN} needs symbol and debugging information.
16668 Start up @value{GDBN} as usual, using the name of the local copy of your
16669 program as the first argument.
16671 @cindex @code{target remote}
16672 @value{GDBN} can communicate with the target over a serial line, or
16673 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
16674 each case, @value{GDBN} uses the same protocol for debugging your
16675 program; only the medium carrying the debugging packets varies. The
16676 @code{target remote} command establishes a connection to the target.
16677 Its arguments indicate which medium to use:
16681 @item target remote @var{serial-device}
16682 @cindex serial line, @code{target remote}
16683 Use @var{serial-device} to communicate with the target. For example,
16684 to use a serial line connected to the device named @file{/dev/ttyb}:
16687 target remote /dev/ttyb
16690 If you're using a serial line, you may want to give @value{GDBN} the
16691 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
16692 (@pxref{Remote Configuration, set remotebaud}) before the
16693 @code{target} command.
16695 @item target remote @code{@var{host}:@var{port}}
16696 @itemx target remote @code{tcp:@var{host}:@var{port}}
16697 @cindex @acronym{TCP} port, @code{target remote}
16698 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
16699 The @var{host} may be either a host name or a numeric @acronym{IP}
16700 address; @var{port} must be a decimal number. The @var{host} could be
16701 the target machine itself, if it is directly connected to the net, or
16702 it might be a terminal server which in turn has a serial line to the
16705 For example, to connect to port 2828 on a terminal server named
16709 target remote manyfarms:2828
16712 If your remote target is actually running on the same machine as your
16713 debugger session (e.g.@: a simulator for your target running on the
16714 same host), you can omit the hostname. For example, to connect to
16715 port 1234 on your local machine:
16718 target remote :1234
16722 Note that the colon is still required here.
16724 @item target remote @code{udp:@var{host}:@var{port}}
16725 @cindex @acronym{UDP} port, @code{target remote}
16726 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
16727 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
16730 target remote udp:manyfarms:2828
16733 When using a @acronym{UDP} connection for remote debugging, you should
16734 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
16735 can silently drop packets on busy or unreliable networks, which will
16736 cause havoc with your debugging session.
16738 @item target remote | @var{command}
16739 @cindex pipe, @code{target remote} to
16740 Run @var{command} in the background and communicate with it using a
16741 pipe. The @var{command} is a shell command, to be parsed and expanded
16742 by the system's command shell, @code{/bin/sh}; it should expect remote
16743 protocol packets on its standard input, and send replies on its
16744 standard output. You could use this to run a stand-alone simulator
16745 that speaks the remote debugging protocol, to make net connections
16746 using programs like @code{ssh}, or for other similar tricks.
16748 If @var{command} closes its standard output (perhaps by exiting),
16749 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
16750 program has already exited, this will have no effect.)
16754 Once the connection has been established, you can use all the usual
16755 commands to examine and change data. The remote program is already
16756 running; you can use @kbd{step} and @kbd{continue}, and you do not
16757 need to use @kbd{run}.
16759 @cindex interrupting remote programs
16760 @cindex remote programs, interrupting
16761 Whenever @value{GDBN} is waiting for the remote program, if you type the
16762 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
16763 program. This may or may not succeed, depending in part on the hardware
16764 and the serial drivers the remote system uses. If you type the
16765 interrupt character once again, @value{GDBN} displays this prompt:
16768 Interrupted while waiting for the program.
16769 Give up (and stop debugging it)? (y or n)
16772 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
16773 (If you decide you want to try again later, you can use @samp{target
16774 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
16775 goes back to waiting.
16778 @kindex detach (remote)
16780 When you have finished debugging the remote program, you can use the
16781 @code{detach} command to release it from @value{GDBN} control.
16782 Detaching from the target normally resumes its execution, but the results
16783 will depend on your particular remote stub. After the @code{detach}
16784 command, @value{GDBN} is free to connect to another target.
16788 The @code{disconnect} command behaves like @code{detach}, except that
16789 the target is generally not resumed. It will wait for @value{GDBN}
16790 (this instance or another one) to connect and continue debugging. After
16791 the @code{disconnect} command, @value{GDBN} is again free to connect to
16794 @cindex send command to remote monitor
16795 @cindex extend @value{GDBN} for remote targets
16796 @cindex add new commands for external monitor
16798 @item monitor @var{cmd}
16799 This command allows you to send arbitrary commands directly to the
16800 remote monitor. Since @value{GDBN} doesn't care about the commands it
16801 sends like this, this command is the way to extend @value{GDBN}---you
16802 can add new commands that only the external monitor will understand
16806 @node File Transfer
16807 @section Sending files to a remote system
16808 @cindex remote target, file transfer
16809 @cindex file transfer
16810 @cindex sending files to remote systems
16812 Some remote targets offer the ability to transfer files over the same
16813 connection used to communicate with @value{GDBN}. This is convenient
16814 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
16815 running @code{gdbserver} over a network interface. For other targets,
16816 e.g.@: embedded devices with only a single serial port, this may be
16817 the only way to upload or download files.
16819 Not all remote targets support these commands.
16823 @item remote put @var{hostfile} @var{targetfile}
16824 Copy file @var{hostfile} from the host system (the machine running
16825 @value{GDBN}) to @var{targetfile} on the target system.
16828 @item remote get @var{targetfile} @var{hostfile}
16829 Copy file @var{targetfile} from the target system to @var{hostfile}
16830 on the host system.
16832 @kindex remote delete
16833 @item remote delete @var{targetfile}
16834 Delete @var{targetfile} from the target system.
16839 @section Using the @code{gdbserver} Program
16842 @cindex remote connection without stubs
16843 @code{gdbserver} is a control program for Unix-like systems, which
16844 allows you to connect your program with a remote @value{GDBN} via
16845 @code{target remote}---but without linking in the usual debugging stub.
16847 @code{gdbserver} is not a complete replacement for the debugging stubs,
16848 because it requires essentially the same operating-system facilities
16849 that @value{GDBN} itself does. In fact, a system that can run
16850 @code{gdbserver} to connect to a remote @value{GDBN} could also run
16851 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
16852 because it is a much smaller program than @value{GDBN} itself. It is
16853 also easier to port than all of @value{GDBN}, so you may be able to get
16854 started more quickly on a new system by using @code{gdbserver}.
16855 Finally, if you develop code for real-time systems, you may find that
16856 the tradeoffs involved in real-time operation make it more convenient to
16857 do as much development work as possible on another system, for example
16858 by cross-compiling. You can use @code{gdbserver} to make a similar
16859 choice for debugging.
16861 @value{GDBN} and @code{gdbserver} communicate via either a serial line
16862 or a TCP connection, using the standard @value{GDBN} remote serial
16866 @emph{Warning:} @code{gdbserver} does not have any built-in security.
16867 Do not run @code{gdbserver} connected to any public network; a
16868 @value{GDBN} connection to @code{gdbserver} provides access to the
16869 target system with the same privileges as the user running
16873 @subsection Running @code{gdbserver}
16874 @cindex arguments, to @code{gdbserver}
16875 @cindex @code{gdbserver}, command-line arguments
16877 Run @code{gdbserver} on the target system. You need a copy of the
16878 program you want to debug, including any libraries it requires.
16879 @code{gdbserver} does not need your program's symbol table, so you can
16880 strip the program if necessary to save space. @value{GDBN} on the host
16881 system does all the symbol handling.
16883 To use the server, you must tell it how to communicate with @value{GDBN};
16884 the name of your program; and the arguments for your program. The usual
16888 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
16891 @var{comm} is either a device name (to use a serial line), or a TCP
16892 hostname and portnumber, or @code{-} or @code{stdio} to use
16893 stdin/stdout of @code{gdbserver}.
16894 For example, to debug Emacs with the argument
16895 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
16899 target> gdbserver /dev/com1 emacs foo.txt
16902 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
16905 To use a TCP connection instead of a serial line:
16908 target> gdbserver host:2345 emacs foo.txt
16911 The only difference from the previous example is the first argument,
16912 specifying that you are communicating with the host @value{GDBN} via
16913 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
16914 expect a TCP connection from machine @samp{host} to local TCP port 2345.
16915 (Currently, the @samp{host} part is ignored.) You can choose any number
16916 you want for the port number as long as it does not conflict with any
16917 TCP ports already in use on the target system (for example, @code{23} is
16918 reserved for @code{telnet}).@footnote{If you choose a port number that
16919 conflicts with another service, @code{gdbserver} prints an error message
16920 and exits.} You must use the same port number with the host @value{GDBN}
16921 @code{target remote} command.
16923 The @code{stdio} connection is useful when starting @code{gdbserver}
16927 (gdb) target remote | ssh -T hostname gdbserver - hello
16930 The @samp{-T} option to ssh is provided because we don't need a remote pty,
16931 and we don't want escape-character handling. Ssh does this by default when
16932 a command is provided, the flag is provided to make it explicit.
16933 You could elide it if you want to.
16935 Programs started with stdio-connected gdbserver have @file{/dev/null} for
16936 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
16937 display through a pipe connected to gdbserver.
16938 Both @code{stdout} and @code{stderr} use the same pipe.
16940 @subsubsection Attaching to a Running Program
16941 @cindex attach to a program, @code{gdbserver}
16942 @cindex @option{--attach}, @code{gdbserver} option
16944 On some targets, @code{gdbserver} can also attach to running programs.
16945 This is accomplished via the @code{--attach} argument. The syntax is:
16948 target> gdbserver --attach @var{comm} @var{pid}
16951 @var{pid} is the process ID of a currently running process. It isn't necessary
16952 to point @code{gdbserver} at a binary for the running process.
16955 You can debug processes by name instead of process ID if your target has the
16956 @code{pidof} utility:
16959 target> gdbserver --attach @var{comm} `pidof @var{program}`
16962 In case more than one copy of @var{program} is running, or @var{program}
16963 has multiple threads, most versions of @code{pidof} support the
16964 @code{-s} option to only return the first process ID.
16966 @subsubsection Multi-Process Mode for @code{gdbserver}
16967 @cindex @code{gdbserver}, multiple processes
16968 @cindex multiple processes with @code{gdbserver}
16970 When you connect to @code{gdbserver} using @code{target remote},
16971 @code{gdbserver} debugs the specified program only once. When the
16972 program exits, or you detach from it, @value{GDBN} closes the connection
16973 and @code{gdbserver} exits.
16975 If you connect using @kbd{target extended-remote}, @code{gdbserver}
16976 enters multi-process mode. When the debugged program exits, or you
16977 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
16978 though no program is running. The @code{run} and @code{attach}
16979 commands instruct @code{gdbserver} to run or attach to a new program.
16980 The @code{run} command uses @code{set remote exec-file} (@pxref{set
16981 remote exec-file}) to select the program to run. Command line
16982 arguments are supported, except for wildcard expansion and I/O
16983 redirection (@pxref{Arguments}).
16985 @cindex @option{--multi}, @code{gdbserver} option
16986 To start @code{gdbserver} without supplying an initial command to run
16987 or process ID to attach, use the @option{--multi} command line option.
16988 Then you can connect using @kbd{target extended-remote} and start
16989 the program you want to debug.
16991 In multi-process mode @code{gdbserver} does not automatically exit unless you
16992 use the option @option{--once}. You can terminate it by using
16993 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
16994 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
16995 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
16996 @option{--multi} option to @code{gdbserver} has no influence on that.
16998 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
17000 This section applies only when @code{gdbserver} is run to listen on a TCP port.
17002 @code{gdbserver} normally terminates after all of its debugged processes have
17003 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
17004 extended-remote}, @code{gdbserver} stays running even with no processes left.
17005 @value{GDBN} normally terminates the spawned debugged process on its exit,
17006 which normally also terminates @code{gdbserver} in the @kbd{target remote}
17007 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
17008 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
17009 stays running even in the @kbd{target remote} mode.
17011 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
17012 Such reconnecting is useful for features like @ref{disconnected tracing}. For
17013 completeness, at most one @value{GDBN} can be connected at a time.
17015 @cindex @option{--once}, @code{gdbserver} option
17016 By default, @code{gdbserver} keeps the listening TCP port open, so that
17017 additional connections are possible. However, if you start @code{gdbserver}
17018 with the @option{--once} option, it will stop listening for any further
17019 connection attempts after connecting to the first @value{GDBN} session. This
17020 means no further connections to @code{gdbserver} will be possible after the
17021 first one. It also means @code{gdbserver} will terminate after the first
17022 connection with remote @value{GDBN} has closed, even for unexpectedly closed
17023 connections and even in the @kbd{target extended-remote} mode. The
17024 @option{--once} option allows reusing the same port number for connecting to
17025 multiple instances of @code{gdbserver} running on the same host, since each
17026 instance closes its port after the first connection.
17028 @subsubsection Other Command-Line Arguments for @code{gdbserver}
17030 @cindex @option{--debug}, @code{gdbserver} option
17031 The @option{--debug} option tells @code{gdbserver} to display extra
17032 status information about the debugging process.
17033 @cindex @option{--remote-debug}, @code{gdbserver} option
17034 The @option{--remote-debug} option tells @code{gdbserver} to display
17035 remote protocol debug output. These options are intended for
17036 @code{gdbserver} development and for bug reports to the developers.
17038 @cindex @option{--wrapper}, @code{gdbserver} option
17039 The @option{--wrapper} option specifies a wrapper to launch programs
17040 for debugging. The option should be followed by the name of the
17041 wrapper, then any command-line arguments to pass to the wrapper, then
17042 @kbd{--} indicating the end of the wrapper arguments.
17044 @code{gdbserver} runs the specified wrapper program with a combined
17045 command line including the wrapper arguments, then the name of the
17046 program to debug, then any arguments to the program. The wrapper
17047 runs until it executes your program, and then @value{GDBN} gains control.
17049 You can use any program that eventually calls @code{execve} with
17050 its arguments as a wrapper. Several standard Unix utilities do
17051 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
17052 with @code{exec "$@@"} will also work.
17054 For example, you can use @code{env} to pass an environment variable to
17055 the debugged program, without setting the variable in @code{gdbserver}'s
17059 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
17062 @subsection Connecting to @code{gdbserver}
17064 Run @value{GDBN} on the host system.
17066 First make sure you have the necessary symbol files. Load symbols for
17067 your application using the @code{file} command before you connect. Use
17068 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
17069 was compiled with the correct sysroot using @code{--with-sysroot}).
17071 The symbol file and target libraries must exactly match the executable
17072 and libraries on the target, with one exception: the files on the host
17073 system should not be stripped, even if the files on the target system
17074 are. Mismatched or missing files will lead to confusing results
17075 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
17076 files may also prevent @code{gdbserver} from debugging multi-threaded
17079 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
17080 For TCP connections, you must start up @code{gdbserver} prior to using
17081 the @code{target remote} command. Otherwise you may get an error whose
17082 text depends on the host system, but which usually looks something like
17083 @samp{Connection refused}. Don't use the @code{load}
17084 command in @value{GDBN} when using @code{gdbserver}, since the program is
17085 already on the target.
17087 @subsection Monitor Commands for @code{gdbserver}
17088 @cindex monitor commands, for @code{gdbserver}
17089 @anchor{Monitor Commands for gdbserver}
17091 During a @value{GDBN} session using @code{gdbserver}, you can use the
17092 @code{monitor} command to send special requests to @code{gdbserver}.
17093 Here are the available commands.
17097 List the available monitor commands.
17099 @item monitor set debug 0
17100 @itemx monitor set debug 1
17101 Disable or enable general debugging messages.
17103 @item monitor set remote-debug 0
17104 @itemx monitor set remote-debug 1
17105 Disable or enable specific debugging messages associated with the remote
17106 protocol (@pxref{Remote Protocol}).
17108 @item monitor set libthread-db-search-path [PATH]
17109 @cindex gdbserver, search path for @code{libthread_db}
17110 When this command is issued, @var{path} is a colon-separated list of
17111 directories to search for @code{libthread_db} (@pxref{Threads,,set
17112 libthread-db-search-path}). If you omit @var{path},
17113 @samp{libthread-db-search-path} will be reset to its default value.
17115 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
17116 not supported in @code{gdbserver}.
17119 Tell gdbserver to exit immediately. This command should be followed by
17120 @code{disconnect} to close the debugging session. @code{gdbserver} will
17121 detach from any attached processes and kill any processes it created.
17122 Use @code{monitor exit} to terminate @code{gdbserver} at the end
17123 of a multi-process mode debug session.
17127 @subsection Tracepoints support in @code{gdbserver}
17128 @cindex tracepoints support in @code{gdbserver}
17130 On some targets, @code{gdbserver} supports tracepoints, fast
17131 tracepoints and static tracepoints.
17133 For fast or static tracepoints to work, a special library called the
17134 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
17135 This library is built and distributed as an integral part of
17136 @code{gdbserver}. In addition, support for static tracepoints
17137 requires building the in-process agent library with static tracepoints
17138 support. At present, the UST (LTTng Userspace Tracer,
17139 @url{http://lttng.org/ust}) tracing engine is supported. This support
17140 is automatically available if UST development headers are found in the
17141 standard include path when @code{gdbserver} is built, or if
17142 @code{gdbserver} was explicitly configured using @option{--with-ust}
17143 to point at such headers. You can explicitly disable the support
17144 using @option{--with-ust=no}.
17146 There are several ways to load the in-process agent in your program:
17149 @item Specifying it as dependency at link time
17151 You can link your program dynamically with the in-process agent
17152 library. On most systems, this is accomplished by adding
17153 @code{-linproctrace} to the link command.
17155 @item Using the system's preloading mechanisms
17157 You can force loading the in-process agent at startup time by using
17158 your system's support for preloading shared libraries. Many Unixes
17159 support the concept of preloading user defined libraries. In most
17160 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
17161 in the environment. See also the description of @code{gdbserver}'s
17162 @option{--wrapper} command line option.
17164 @item Using @value{GDBN} to force loading the agent at run time
17166 On some systems, you can force the inferior to load a shared library,
17167 by calling a dynamic loader function in the inferior that takes care
17168 of dynamically looking up and loading a shared library. On most Unix
17169 systems, the function is @code{dlopen}. You'll use the @code{call}
17170 command for that. For example:
17173 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
17176 Note that on most Unix systems, for the @code{dlopen} function to be
17177 available, the program needs to be linked with @code{-ldl}.
17180 On systems that have a userspace dynamic loader, like most Unix
17181 systems, when you connect to @code{gdbserver} using @code{target
17182 remote}, you'll find that the program is stopped at the dynamic
17183 loader's entry point, and no shared library has been loaded in the
17184 program's address space yet, including the in-process agent. In that
17185 case, before being able to use any of the fast or static tracepoints
17186 features, you need to let the loader run and load the shared
17187 libraries. The simplest way to do that is to run the program to the
17188 main procedure. E.g., if debugging a C or C@t{++} program, start
17189 @code{gdbserver} like so:
17192 $ gdbserver :9999 myprogram
17195 Start GDB and connect to @code{gdbserver} like so, and run to main:
17199 (@value{GDBP}) target remote myhost:9999
17200 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
17201 (@value{GDBP}) b main
17202 (@value{GDBP}) continue
17205 The in-process tracing agent library should now be loaded into the
17206 process; you can confirm it with the @code{info sharedlibrary}
17207 command, which will list @file{libinproctrace.so} as loaded in the
17208 process. You are now ready to install fast tracepoints, list static
17209 tracepoint markers, probe static tracepoints markers, and start
17212 @node Remote Configuration
17213 @section Remote Configuration
17216 @kindex show remote
17217 This section documents the configuration options available when
17218 debugging remote programs. For the options related to the File I/O
17219 extensions of the remote protocol, see @ref{system,
17220 system-call-allowed}.
17223 @item set remoteaddresssize @var{bits}
17224 @cindex address size for remote targets
17225 @cindex bits in remote address
17226 Set the maximum size of address in a memory packet to the specified
17227 number of bits. @value{GDBN} will mask off the address bits above
17228 that number, when it passes addresses to the remote target. The
17229 default value is the number of bits in the target's address.
17231 @item show remoteaddresssize
17232 Show the current value of remote address size in bits.
17234 @item set remotebaud @var{n}
17235 @cindex baud rate for remote targets
17236 Set the baud rate for the remote serial I/O to @var{n} baud. The
17237 value is used to set the speed of the serial port used for debugging
17240 @item show remotebaud
17241 Show the current speed of the remote connection.
17243 @item set remotebreak
17244 @cindex interrupt remote programs
17245 @cindex BREAK signal instead of Ctrl-C
17246 @anchor{set remotebreak}
17247 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
17248 when you type @kbd{Ctrl-c} to interrupt the program running
17249 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
17250 character instead. The default is off, since most remote systems
17251 expect to see @samp{Ctrl-C} as the interrupt signal.
17253 @item show remotebreak
17254 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
17255 interrupt the remote program.
17257 @item set remoteflow on
17258 @itemx set remoteflow off
17259 @kindex set remoteflow
17260 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
17261 on the serial port used to communicate to the remote target.
17263 @item show remoteflow
17264 @kindex show remoteflow
17265 Show the current setting of hardware flow control.
17267 @item set remotelogbase @var{base}
17268 Set the base (a.k.a.@: radix) of logging serial protocol
17269 communications to @var{base}. Supported values of @var{base} are:
17270 @code{ascii}, @code{octal}, and @code{hex}. The default is
17273 @item show remotelogbase
17274 Show the current setting of the radix for logging remote serial
17277 @item set remotelogfile @var{file}
17278 @cindex record serial communications on file
17279 Record remote serial communications on the named @var{file}. The
17280 default is not to record at all.
17282 @item show remotelogfile.
17283 Show the current setting of the file name on which to record the
17284 serial communications.
17286 @item set remotetimeout @var{num}
17287 @cindex timeout for serial communications
17288 @cindex remote timeout
17289 Set the timeout limit to wait for the remote target to respond to
17290 @var{num} seconds. The default is 2 seconds.
17292 @item show remotetimeout
17293 Show the current number of seconds to wait for the remote target
17296 @cindex limit hardware breakpoints and watchpoints
17297 @cindex remote target, limit break- and watchpoints
17298 @anchor{set remote hardware-watchpoint-limit}
17299 @anchor{set remote hardware-breakpoint-limit}
17300 @item set remote hardware-watchpoint-limit @var{limit}
17301 @itemx set remote hardware-breakpoint-limit @var{limit}
17302 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
17303 watchpoints. A limit of -1, the default, is treated as unlimited.
17305 @cindex limit hardware watchpoints length
17306 @cindex remote target, limit watchpoints length
17307 @anchor{set remote hardware-watchpoint-length-limit}
17308 @item set remote hardware-watchpoint-length-limit @var{limit}
17309 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
17310 a remote hardware watchpoint. A limit of -1, the default, is treated
17313 @item show remote hardware-watchpoint-length-limit
17314 Show the current limit (in bytes) of the maximum length of
17315 a remote hardware watchpoint.
17317 @item set remote exec-file @var{filename}
17318 @itemx show remote exec-file
17319 @anchor{set remote exec-file}
17320 @cindex executable file, for remote target
17321 Select the file used for @code{run} with @code{target
17322 extended-remote}. This should be set to a filename valid on the
17323 target system. If it is not set, the target will use a default
17324 filename (e.g.@: the last program run).
17326 @item set remote interrupt-sequence
17327 @cindex interrupt remote programs
17328 @cindex select Ctrl-C, BREAK or BREAK-g
17329 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
17330 @samp{BREAK-g} as the
17331 sequence to the remote target in order to interrupt the execution.
17332 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
17333 is high level of serial line for some certain time.
17334 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
17335 It is @code{BREAK} signal followed by character @code{g}.
17337 @item show interrupt-sequence
17338 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
17339 is sent by @value{GDBN} to interrupt the remote program.
17340 @code{BREAK-g} is BREAK signal followed by @code{g} and
17341 also known as Magic SysRq g.
17343 @item set remote interrupt-on-connect
17344 @cindex send interrupt-sequence on start
17345 Specify whether interrupt-sequence is sent to remote target when
17346 @value{GDBN} connects to it. This is mostly needed when you debug
17347 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
17348 which is known as Magic SysRq g in order to connect @value{GDBN}.
17350 @item show interrupt-on-connect
17351 Show whether interrupt-sequence is sent
17352 to remote target when @value{GDBN} connects to it.
17356 @item set tcp auto-retry on
17357 @cindex auto-retry, for remote TCP target
17358 Enable auto-retry for remote TCP connections. This is useful if the remote
17359 debugging agent is launched in parallel with @value{GDBN}; there is a race
17360 condition because the agent may not become ready to accept the connection
17361 before @value{GDBN} attempts to connect. When auto-retry is
17362 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
17363 to establish the connection using the timeout specified by
17364 @code{set tcp connect-timeout}.
17366 @item set tcp auto-retry off
17367 Do not auto-retry failed TCP connections.
17369 @item show tcp auto-retry
17370 Show the current auto-retry setting.
17372 @item set tcp connect-timeout @var{seconds}
17373 @cindex connection timeout, for remote TCP target
17374 @cindex timeout, for remote target connection
17375 Set the timeout for establishing a TCP connection to the remote target to
17376 @var{seconds}. The timeout affects both polling to retry failed connections
17377 (enabled by @code{set tcp auto-retry on}) and waiting for connections
17378 that are merely slow to complete, and represents an approximate cumulative
17381 @item show tcp connect-timeout
17382 Show the current connection timeout setting.
17385 @cindex remote packets, enabling and disabling
17386 The @value{GDBN} remote protocol autodetects the packets supported by
17387 your debugging stub. If you need to override the autodetection, you
17388 can use these commands to enable or disable individual packets. Each
17389 packet can be set to @samp{on} (the remote target supports this
17390 packet), @samp{off} (the remote target does not support this packet),
17391 or @samp{auto} (detect remote target support for this packet). They
17392 all default to @samp{auto}. For more information about each packet,
17393 see @ref{Remote Protocol}.
17395 During normal use, you should not have to use any of these commands.
17396 If you do, that may be a bug in your remote debugging stub, or a bug
17397 in @value{GDBN}. You may want to report the problem to the
17398 @value{GDBN} developers.
17400 For each packet @var{name}, the command to enable or disable the
17401 packet is @code{set remote @var{name}-packet}. The available settings
17404 @multitable @columnfractions 0.28 0.32 0.25
17407 @tab Related Features
17409 @item @code{fetch-register}
17411 @tab @code{info registers}
17413 @item @code{set-register}
17417 @item @code{binary-download}
17419 @tab @code{load}, @code{set}
17421 @item @code{read-aux-vector}
17422 @tab @code{qXfer:auxv:read}
17423 @tab @code{info auxv}
17425 @item @code{symbol-lookup}
17426 @tab @code{qSymbol}
17427 @tab Detecting multiple threads
17429 @item @code{attach}
17430 @tab @code{vAttach}
17433 @item @code{verbose-resume}
17435 @tab Stepping or resuming multiple threads
17441 @item @code{software-breakpoint}
17445 @item @code{hardware-breakpoint}
17449 @item @code{write-watchpoint}
17453 @item @code{read-watchpoint}
17457 @item @code{access-watchpoint}
17461 @item @code{target-features}
17462 @tab @code{qXfer:features:read}
17463 @tab @code{set architecture}
17465 @item @code{library-info}
17466 @tab @code{qXfer:libraries:read}
17467 @tab @code{info sharedlibrary}
17469 @item @code{memory-map}
17470 @tab @code{qXfer:memory-map:read}
17471 @tab @code{info mem}
17473 @item @code{read-sdata-object}
17474 @tab @code{qXfer:sdata:read}
17475 @tab @code{print $_sdata}
17477 @item @code{read-spu-object}
17478 @tab @code{qXfer:spu:read}
17479 @tab @code{info spu}
17481 @item @code{write-spu-object}
17482 @tab @code{qXfer:spu:write}
17483 @tab @code{info spu}
17485 @item @code{read-siginfo-object}
17486 @tab @code{qXfer:siginfo:read}
17487 @tab @code{print $_siginfo}
17489 @item @code{write-siginfo-object}
17490 @tab @code{qXfer:siginfo:write}
17491 @tab @code{set $_siginfo}
17493 @item @code{threads}
17494 @tab @code{qXfer:threads:read}
17495 @tab @code{info threads}
17497 @item @code{get-thread-local-@*storage-address}
17498 @tab @code{qGetTLSAddr}
17499 @tab Displaying @code{__thread} variables
17501 @item @code{get-thread-information-block-address}
17502 @tab @code{qGetTIBAddr}
17503 @tab Display MS-Windows Thread Information Block.
17505 @item @code{search-memory}
17506 @tab @code{qSearch:memory}
17509 @item @code{supported-packets}
17510 @tab @code{qSupported}
17511 @tab Remote communications parameters
17513 @item @code{pass-signals}
17514 @tab @code{QPassSignals}
17515 @tab @code{handle @var{signal}}
17517 @item @code{program-signals}
17518 @tab @code{QProgramSignals}
17519 @tab @code{handle @var{signal}}
17521 @item @code{hostio-close-packet}
17522 @tab @code{vFile:close}
17523 @tab @code{remote get}, @code{remote put}
17525 @item @code{hostio-open-packet}
17526 @tab @code{vFile:open}
17527 @tab @code{remote get}, @code{remote put}
17529 @item @code{hostio-pread-packet}
17530 @tab @code{vFile:pread}
17531 @tab @code{remote get}, @code{remote put}
17533 @item @code{hostio-pwrite-packet}
17534 @tab @code{vFile:pwrite}
17535 @tab @code{remote get}, @code{remote put}
17537 @item @code{hostio-unlink-packet}
17538 @tab @code{vFile:unlink}
17539 @tab @code{remote delete}
17541 @item @code{hostio-readlink-packet}
17542 @tab @code{vFile:readlink}
17545 @item @code{noack-packet}
17546 @tab @code{QStartNoAckMode}
17547 @tab Packet acknowledgment
17549 @item @code{osdata}
17550 @tab @code{qXfer:osdata:read}
17551 @tab @code{info os}
17553 @item @code{query-attached}
17554 @tab @code{qAttached}
17555 @tab Querying remote process attach state.
17557 @item @code{traceframe-info}
17558 @tab @code{qXfer:traceframe-info:read}
17559 @tab Traceframe info
17561 @item @code{install-in-trace}
17562 @tab @code{InstallInTrace}
17563 @tab Install tracepoint in tracing
17565 @item @code{disable-randomization}
17566 @tab @code{QDisableRandomization}
17567 @tab @code{set disable-randomization}
17569 @item @code{conditional-breakpoints-packet}
17570 @tab @code{Z0 and Z1}
17571 @tab @code{Support for target-side breakpoint condition evaluation}
17575 @section Implementing a Remote Stub
17577 @cindex debugging stub, example
17578 @cindex remote stub, example
17579 @cindex stub example, remote debugging
17580 The stub files provided with @value{GDBN} implement the target side of the
17581 communication protocol, and the @value{GDBN} side is implemented in the
17582 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
17583 these subroutines to communicate, and ignore the details. (If you're
17584 implementing your own stub file, you can still ignore the details: start
17585 with one of the existing stub files. @file{sparc-stub.c} is the best
17586 organized, and therefore the easiest to read.)
17588 @cindex remote serial debugging, overview
17589 To debug a program running on another machine (the debugging
17590 @dfn{target} machine), you must first arrange for all the usual
17591 prerequisites for the program to run by itself. For example, for a C
17596 A startup routine to set up the C runtime environment; these usually
17597 have a name like @file{crt0}. The startup routine may be supplied by
17598 your hardware supplier, or you may have to write your own.
17601 A C subroutine library to support your program's
17602 subroutine calls, notably managing input and output.
17605 A way of getting your program to the other machine---for example, a
17606 download program. These are often supplied by the hardware
17607 manufacturer, but you may have to write your own from hardware
17611 The next step is to arrange for your program to use a serial port to
17612 communicate with the machine where @value{GDBN} is running (the @dfn{host}
17613 machine). In general terms, the scheme looks like this:
17617 @value{GDBN} already understands how to use this protocol; when everything
17618 else is set up, you can simply use the @samp{target remote} command
17619 (@pxref{Targets,,Specifying a Debugging Target}).
17621 @item On the target,
17622 you must link with your program a few special-purpose subroutines that
17623 implement the @value{GDBN} remote serial protocol. The file containing these
17624 subroutines is called a @dfn{debugging stub}.
17626 On certain remote targets, you can use an auxiliary program
17627 @code{gdbserver} instead of linking a stub into your program.
17628 @xref{Server,,Using the @code{gdbserver} Program}, for details.
17631 The debugging stub is specific to the architecture of the remote
17632 machine; for example, use @file{sparc-stub.c} to debug programs on
17635 @cindex remote serial stub list
17636 These working remote stubs are distributed with @value{GDBN}:
17641 @cindex @file{i386-stub.c}
17644 For Intel 386 and compatible architectures.
17647 @cindex @file{m68k-stub.c}
17648 @cindex Motorola 680x0
17650 For Motorola 680x0 architectures.
17653 @cindex @file{sh-stub.c}
17656 For Renesas SH architectures.
17659 @cindex @file{sparc-stub.c}
17661 For @sc{sparc} architectures.
17663 @item sparcl-stub.c
17664 @cindex @file{sparcl-stub.c}
17667 For Fujitsu @sc{sparclite} architectures.
17671 The @file{README} file in the @value{GDBN} distribution may list other
17672 recently added stubs.
17675 * Stub Contents:: What the stub can do for you
17676 * Bootstrapping:: What you must do for the stub
17677 * Debug Session:: Putting it all together
17680 @node Stub Contents
17681 @subsection What the Stub Can Do for You
17683 @cindex remote serial stub
17684 The debugging stub for your architecture supplies these three
17688 @item set_debug_traps
17689 @findex set_debug_traps
17690 @cindex remote serial stub, initialization
17691 This routine arranges for @code{handle_exception} to run when your
17692 program stops. You must call this subroutine explicitly in your
17693 program's startup code.
17695 @item handle_exception
17696 @findex handle_exception
17697 @cindex remote serial stub, main routine
17698 This is the central workhorse, but your program never calls it
17699 explicitly---the setup code arranges for @code{handle_exception} to
17700 run when a trap is triggered.
17702 @code{handle_exception} takes control when your program stops during
17703 execution (for example, on a breakpoint), and mediates communications
17704 with @value{GDBN} on the host machine. This is where the communications
17705 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
17706 representative on the target machine. It begins by sending summary
17707 information on the state of your program, then continues to execute,
17708 retrieving and transmitting any information @value{GDBN} needs, until you
17709 execute a @value{GDBN} command that makes your program resume; at that point,
17710 @code{handle_exception} returns control to your own code on the target
17714 @cindex @code{breakpoint} subroutine, remote
17715 Use this auxiliary subroutine to make your program contain a
17716 breakpoint. Depending on the particular situation, this may be the only
17717 way for @value{GDBN} to get control. For instance, if your target
17718 machine has some sort of interrupt button, you won't need to call this;
17719 pressing the interrupt button transfers control to
17720 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
17721 simply receiving characters on the serial port may also trigger a trap;
17722 again, in that situation, you don't need to call @code{breakpoint} from
17723 your own program---simply running @samp{target remote} from the host
17724 @value{GDBN} session gets control.
17726 Call @code{breakpoint} if none of these is true, or if you simply want
17727 to make certain your program stops at a predetermined point for the
17728 start of your debugging session.
17731 @node Bootstrapping
17732 @subsection What You Must Do for the Stub
17734 @cindex remote stub, support routines
17735 The debugging stubs that come with @value{GDBN} are set up for a particular
17736 chip architecture, but they have no information about the rest of your
17737 debugging target machine.
17739 First of all you need to tell the stub how to communicate with the
17743 @item int getDebugChar()
17744 @findex getDebugChar
17745 Write this subroutine to read a single character from the serial port.
17746 It may be identical to @code{getchar} for your target system; a
17747 different name is used to allow you to distinguish the two if you wish.
17749 @item void putDebugChar(int)
17750 @findex putDebugChar
17751 Write this subroutine to write a single character to the serial port.
17752 It may be identical to @code{putchar} for your target system; a
17753 different name is used to allow you to distinguish the two if you wish.
17756 @cindex control C, and remote debugging
17757 @cindex interrupting remote targets
17758 If you want @value{GDBN} to be able to stop your program while it is
17759 running, you need to use an interrupt-driven serial driver, and arrange
17760 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
17761 character). That is the character which @value{GDBN} uses to tell the
17762 remote system to stop.
17764 Getting the debugging target to return the proper status to @value{GDBN}
17765 probably requires changes to the standard stub; one quick and dirty way
17766 is to just execute a breakpoint instruction (the ``dirty'' part is that
17767 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
17769 Other routines you need to supply are:
17772 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
17773 @findex exceptionHandler
17774 Write this function to install @var{exception_address} in the exception
17775 handling tables. You need to do this because the stub does not have any
17776 way of knowing what the exception handling tables on your target system
17777 are like (for example, the processor's table might be in @sc{rom},
17778 containing entries which point to a table in @sc{ram}).
17779 @var{exception_number} is the exception number which should be changed;
17780 its meaning is architecture-dependent (for example, different numbers
17781 might represent divide by zero, misaligned access, etc). When this
17782 exception occurs, control should be transferred directly to
17783 @var{exception_address}, and the processor state (stack, registers,
17784 and so on) should be just as it is when a processor exception occurs. So if
17785 you want to use a jump instruction to reach @var{exception_address}, it
17786 should be a simple jump, not a jump to subroutine.
17788 For the 386, @var{exception_address} should be installed as an interrupt
17789 gate so that interrupts are masked while the handler runs. The gate
17790 should be at privilege level 0 (the most privileged level). The
17791 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
17792 help from @code{exceptionHandler}.
17794 @item void flush_i_cache()
17795 @findex flush_i_cache
17796 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
17797 instruction cache, if any, on your target machine. If there is no
17798 instruction cache, this subroutine may be a no-op.
17800 On target machines that have instruction caches, @value{GDBN} requires this
17801 function to make certain that the state of your program is stable.
17805 You must also make sure this library routine is available:
17808 @item void *memset(void *, int, int)
17810 This is the standard library function @code{memset} that sets an area of
17811 memory to a known value. If you have one of the free versions of
17812 @code{libc.a}, @code{memset} can be found there; otherwise, you must
17813 either obtain it from your hardware manufacturer, or write your own.
17816 If you do not use the GNU C compiler, you may need other standard
17817 library subroutines as well; this varies from one stub to another,
17818 but in general the stubs are likely to use any of the common library
17819 subroutines which @code{@value{NGCC}} generates as inline code.
17822 @node Debug Session
17823 @subsection Putting it All Together
17825 @cindex remote serial debugging summary
17826 In summary, when your program is ready to debug, you must follow these
17831 Make sure you have defined the supporting low-level routines
17832 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
17834 @code{getDebugChar}, @code{putDebugChar},
17835 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
17839 Insert these lines in your program's startup code, before the main
17840 procedure is called:
17847 On some machines, when a breakpoint trap is raised, the hardware
17848 automatically makes the PC point to the instruction after the
17849 breakpoint. If your machine doesn't do that, you may need to adjust
17850 @code{handle_exception} to arrange for it to return to the instruction
17851 after the breakpoint on this first invocation, so that your program
17852 doesn't keep hitting the initial breakpoint instead of making
17856 For the 680x0 stub only, you need to provide a variable called
17857 @code{exceptionHook}. Normally you just use:
17860 void (*exceptionHook)() = 0;
17864 but if before calling @code{set_debug_traps}, you set it to point to a
17865 function in your program, that function is called when
17866 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
17867 error). The function indicated by @code{exceptionHook} is called with
17868 one parameter: an @code{int} which is the exception number.
17871 Compile and link together: your program, the @value{GDBN} debugging stub for
17872 your target architecture, and the supporting subroutines.
17875 Make sure you have a serial connection between your target machine and
17876 the @value{GDBN} host, and identify the serial port on the host.
17879 @c The "remote" target now provides a `load' command, so we should
17880 @c document that. FIXME.
17881 Download your program to your target machine (or get it there by
17882 whatever means the manufacturer provides), and start it.
17885 Start @value{GDBN} on the host, and connect to the target
17886 (@pxref{Connecting,,Connecting to a Remote Target}).
17890 @node Configurations
17891 @chapter Configuration-Specific Information
17893 While nearly all @value{GDBN} commands are available for all native and
17894 cross versions of the debugger, there are some exceptions. This chapter
17895 describes things that are only available in certain configurations.
17897 There are three major categories of configurations: native
17898 configurations, where the host and target are the same, embedded
17899 operating system configurations, which are usually the same for several
17900 different processor architectures, and bare embedded processors, which
17901 are quite different from each other.
17906 * Embedded Processors::
17913 This section describes details specific to particular native
17918 * BSD libkvm Interface:: Debugging BSD kernel memory images
17919 * SVR4 Process Information:: SVR4 process information
17920 * DJGPP Native:: Features specific to the DJGPP port
17921 * Cygwin Native:: Features specific to the Cygwin port
17922 * Hurd Native:: Features specific to @sc{gnu} Hurd
17923 * Neutrino:: Features specific to QNX Neutrino
17924 * Darwin:: Features specific to Darwin
17930 On HP-UX systems, if you refer to a function or variable name that
17931 begins with a dollar sign, @value{GDBN} searches for a user or system
17932 name first, before it searches for a convenience variable.
17935 @node BSD libkvm Interface
17936 @subsection BSD libkvm Interface
17939 @cindex kernel memory image
17940 @cindex kernel crash dump
17942 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
17943 interface that provides a uniform interface for accessing kernel virtual
17944 memory images, including live systems and crash dumps. @value{GDBN}
17945 uses this interface to allow you to debug live kernels and kernel crash
17946 dumps on many native BSD configurations. This is implemented as a
17947 special @code{kvm} debugging target. For debugging a live system, load
17948 the currently running kernel into @value{GDBN} and connect to the
17952 (@value{GDBP}) @b{target kvm}
17955 For debugging crash dumps, provide the file name of the crash dump as an
17959 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
17962 Once connected to the @code{kvm} target, the following commands are
17968 Set current context from the @dfn{Process Control Block} (PCB) address.
17971 Set current context from proc address. This command isn't available on
17972 modern FreeBSD systems.
17975 @node SVR4 Process Information
17976 @subsection SVR4 Process Information
17978 @cindex examine process image
17979 @cindex process info via @file{/proc}
17981 Many versions of SVR4 and compatible systems provide a facility called
17982 @samp{/proc} that can be used to examine the image of a running
17983 process using file-system subroutines. If @value{GDBN} is configured
17984 for an operating system with this facility, the command @code{info
17985 proc} is available to report information about the process running
17986 your program, or about any process running on your system. @code{info
17987 proc} works only on SVR4 systems that include the @code{procfs} code.
17988 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
17989 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
17995 @itemx info proc @var{process-id}
17996 Summarize available information about any running process. If a
17997 process ID is specified by @var{process-id}, display information about
17998 that process; otherwise display information about the program being
17999 debugged. The summary includes the debugged process ID, the command
18000 line used to invoke it, its current working directory, and its
18001 executable file's absolute file name.
18003 On some systems, @var{process-id} can be of the form
18004 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
18005 within a process. If the optional @var{pid} part is missing, it means
18006 a thread from the process being debugged (the leading @samp{/} still
18007 needs to be present, or else @value{GDBN} will interpret the number as
18008 a process ID rather than a thread ID).
18010 @item info proc mappings
18011 @cindex memory address space mappings
18012 Report the memory address space ranges accessible in the program, with
18013 information on whether the process has read, write, or execute access
18014 rights to each range. On @sc{gnu}/Linux systems, each memory range
18015 includes the object file which is mapped to that range, instead of the
18016 memory access rights to that range.
18018 @item info proc stat
18019 @itemx info proc status
18020 @cindex process detailed status information
18021 These subcommands are specific to @sc{gnu}/Linux systems. They show
18022 the process-related information, including the user ID and group ID;
18023 how many threads are there in the process; its virtual memory usage;
18024 the signals that are pending, blocked, and ignored; its TTY; its
18025 consumption of system and user time; its stack size; its @samp{nice}
18026 value; etc. For more information, see the @samp{proc} man page
18027 (type @kbd{man 5 proc} from your shell prompt).
18029 @item info proc all
18030 Show all the information about the process described under all of the
18031 above @code{info proc} subcommands.
18034 @comment These sub-options of 'info proc' were not included when
18035 @comment procfs.c was re-written. Keep their descriptions around
18036 @comment against the day when someone finds the time to put them back in.
18037 @kindex info proc times
18038 @item info proc times
18039 Starting time, user CPU time, and system CPU time for your program and
18042 @kindex info proc id
18044 Report on the process IDs related to your program: its own process ID,
18045 the ID of its parent, the process group ID, and the session ID.
18048 @item set procfs-trace
18049 @kindex set procfs-trace
18050 @cindex @code{procfs} API calls
18051 This command enables and disables tracing of @code{procfs} API calls.
18053 @item show procfs-trace
18054 @kindex show procfs-trace
18055 Show the current state of @code{procfs} API call tracing.
18057 @item set procfs-file @var{file}
18058 @kindex set procfs-file
18059 Tell @value{GDBN} to write @code{procfs} API trace to the named
18060 @var{file}. @value{GDBN} appends the trace info to the previous
18061 contents of the file. The default is to display the trace on the
18064 @item show procfs-file
18065 @kindex show procfs-file
18066 Show the file to which @code{procfs} API trace is written.
18068 @item proc-trace-entry
18069 @itemx proc-trace-exit
18070 @itemx proc-untrace-entry
18071 @itemx proc-untrace-exit
18072 @kindex proc-trace-entry
18073 @kindex proc-trace-exit
18074 @kindex proc-untrace-entry
18075 @kindex proc-untrace-exit
18076 These commands enable and disable tracing of entries into and exits
18077 from the @code{syscall} interface.
18080 @kindex info pidlist
18081 @cindex process list, QNX Neutrino
18082 For QNX Neutrino only, this command displays the list of all the
18083 processes and all the threads within each process.
18086 @kindex info meminfo
18087 @cindex mapinfo list, QNX Neutrino
18088 For QNX Neutrino only, this command displays the list of all mapinfos.
18092 @subsection Features for Debugging @sc{djgpp} Programs
18093 @cindex @sc{djgpp} debugging
18094 @cindex native @sc{djgpp} debugging
18095 @cindex MS-DOS-specific commands
18098 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
18099 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
18100 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
18101 top of real-mode DOS systems and their emulations.
18103 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
18104 defines a few commands specific to the @sc{djgpp} port. This
18105 subsection describes those commands.
18110 This is a prefix of @sc{djgpp}-specific commands which print
18111 information about the target system and important OS structures.
18114 @cindex MS-DOS system info
18115 @cindex free memory information (MS-DOS)
18116 @item info dos sysinfo
18117 This command displays assorted information about the underlying
18118 platform: the CPU type and features, the OS version and flavor, the
18119 DPMI version, and the available conventional and DPMI memory.
18124 @cindex segment descriptor tables
18125 @cindex descriptor tables display
18127 @itemx info dos ldt
18128 @itemx info dos idt
18129 These 3 commands display entries from, respectively, Global, Local,
18130 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
18131 tables are data structures which store a descriptor for each segment
18132 that is currently in use. The segment's selector is an index into a
18133 descriptor table; the table entry for that index holds the
18134 descriptor's base address and limit, and its attributes and access
18137 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
18138 segment (used for both data and the stack), and a DOS segment (which
18139 allows access to DOS/BIOS data structures and absolute addresses in
18140 conventional memory). However, the DPMI host will usually define
18141 additional segments in order to support the DPMI environment.
18143 @cindex garbled pointers
18144 These commands allow to display entries from the descriptor tables.
18145 Without an argument, all entries from the specified table are
18146 displayed. An argument, which should be an integer expression, means
18147 display a single entry whose index is given by the argument. For
18148 example, here's a convenient way to display information about the
18149 debugged program's data segment:
18152 @exdent @code{(@value{GDBP}) info dos ldt $ds}
18153 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
18157 This comes in handy when you want to see whether a pointer is outside
18158 the data segment's limit (i.e.@: @dfn{garbled}).
18160 @cindex page tables display (MS-DOS)
18162 @itemx info dos pte
18163 These two commands display entries from, respectively, the Page
18164 Directory and the Page Tables. Page Directories and Page Tables are
18165 data structures which control how virtual memory addresses are mapped
18166 into physical addresses. A Page Table includes an entry for every
18167 page of memory that is mapped into the program's address space; there
18168 may be several Page Tables, each one holding up to 4096 entries. A
18169 Page Directory has up to 4096 entries, one each for every Page Table
18170 that is currently in use.
18172 Without an argument, @kbd{info dos pde} displays the entire Page
18173 Directory, and @kbd{info dos pte} displays all the entries in all of
18174 the Page Tables. An argument, an integer expression, given to the
18175 @kbd{info dos pde} command means display only that entry from the Page
18176 Directory table. An argument given to the @kbd{info dos pte} command
18177 means display entries from a single Page Table, the one pointed to by
18178 the specified entry in the Page Directory.
18180 @cindex direct memory access (DMA) on MS-DOS
18181 These commands are useful when your program uses @dfn{DMA} (Direct
18182 Memory Access), which needs physical addresses to program the DMA
18185 These commands are supported only with some DPMI servers.
18187 @cindex physical address from linear address
18188 @item info dos address-pte @var{addr}
18189 This command displays the Page Table entry for a specified linear
18190 address. The argument @var{addr} is a linear address which should
18191 already have the appropriate segment's base address added to it,
18192 because this command accepts addresses which may belong to @emph{any}
18193 segment. For example, here's how to display the Page Table entry for
18194 the page where a variable @code{i} is stored:
18197 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
18198 @exdent @code{Page Table entry for address 0x11a00d30:}
18199 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
18203 This says that @code{i} is stored at offset @code{0xd30} from the page
18204 whose physical base address is @code{0x02698000}, and shows all the
18205 attributes of that page.
18207 Note that you must cast the addresses of variables to a @code{char *},
18208 since otherwise the value of @code{__djgpp_base_address}, the base
18209 address of all variables and functions in a @sc{djgpp} program, will
18210 be added using the rules of C pointer arithmetics: if @code{i} is
18211 declared an @code{int}, @value{GDBN} will add 4 times the value of
18212 @code{__djgpp_base_address} to the address of @code{i}.
18214 Here's another example, it displays the Page Table entry for the
18218 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
18219 @exdent @code{Page Table entry for address 0x29110:}
18220 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
18224 (The @code{+ 3} offset is because the transfer buffer's address is the
18225 3rd member of the @code{_go32_info_block} structure.) The output
18226 clearly shows that this DPMI server maps the addresses in conventional
18227 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
18228 linear (@code{0x29110}) addresses are identical.
18230 This command is supported only with some DPMI servers.
18233 @cindex DOS serial data link, remote debugging
18234 In addition to native debugging, the DJGPP port supports remote
18235 debugging via a serial data link. The following commands are specific
18236 to remote serial debugging in the DJGPP port of @value{GDBN}.
18239 @kindex set com1base
18240 @kindex set com1irq
18241 @kindex set com2base
18242 @kindex set com2irq
18243 @kindex set com3base
18244 @kindex set com3irq
18245 @kindex set com4base
18246 @kindex set com4irq
18247 @item set com1base @var{addr}
18248 This command sets the base I/O port address of the @file{COM1} serial
18251 @item set com1irq @var{irq}
18252 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
18253 for the @file{COM1} serial port.
18255 There are similar commands @samp{set com2base}, @samp{set com3irq},
18256 etc.@: for setting the port address and the @code{IRQ} lines for the
18259 @kindex show com1base
18260 @kindex show com1irq
18261 @kindex show com2base
18262 @kindex show com2irq
18263 @kindex show com3base
18264 @kindex show com3irq
18265 @kindex show com4base
18266 @kindex show com4irq
18267 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
18268 display the current settings of the base address and the @code{IRQ}
18269 lines used by the COM ports.
18272 @kindex info serial
18273 @cindex DOS serial port status
18274 This command prints the status of the 4 DOS serial ports. For each
18275 port, it prints whether it's active or not, its I/O base address and
18276 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
18277 counts of various errors encountered so far.
18281 @node Cygwin Native
18282 @subsection Features for Debugging MS Windows PE Executables
18283 @cindex MS Windows debugging
18284 @cindex native Cygwin debugging
18285 @cindex Cygwin-specific commands
18287 @value{GDBN} supports native debugging of MS Windows programs, including
18288 DLLs with and without symbolic debugging information.
18290 @cindex Ctrl-BREAK, MS-Windows
18291 @cindex interrupt debuggee on MS-Windows
18292 MS-Windows programs that call @code{SetConsoleMode} to switch off the
18293 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
18294 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
18295 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
18296 sequence, which can be used to interrupt the debuggee even if it
18299 There are various additional Cygwin-specific commands, described in
18300 this section. Working with DLLs that have no debugging symbols is
18301 described in @ref{Non-debug DLL Symbols}.
18306 This is a prefix of MS Windows-specific commands which print
18307 information about the target system and important OS structures.
18309 @item info w32 selector
18310 This command displays information returned by
18311 the Win32 API @code{GetThreadSelectorEntry} function.
18312 It takes an optional argument that is evaluated to
18313 a long value to give the information about this given selector.
18314 Without argument, this command displays information
18315 about the six segment registers.
18317 @item info w32 thread-information-block
18318 This command displays thread specific information stored in the
18319 Thread Information Block (readable on the X86 CPU family using @code{$fs}
18320 selector for 32-bit programs and @code{$gs} for 64-bit programs).
18324 This is a Cygwin-specific alias of @code{info shared}.
18326 @kindex dll-symbols
18328 This command loads symbols from a dll similarly to
18329 add-sym command but without the need to specify a base address.
18331 @kindex set cygwin-exceptions
18332 @cindex debugging the Cygwin DLL
18333 @cindex Cygwin DLL, debugging
18334 @item set cygwin-exceptions @var{mode}
18335 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
18336 happen inside the Cygwin DLL. If @var{mode} is @code{off},
18337 @value{GDBN} will delay recognition of exceptions, and may ignore some
18338 exceptions which seem to be caused by internal Cygwin DLL
18339 ``bookkeeping''. This option is meant primarily for debugging the
18340 Cygwin DLL itself; the default value is @code{off} to avoid annoying
18341 @value{GDBN} users with false @code{SIGSEGV} signals.
18343 @kindex show cygwin-exceptions
18344 @item show cygwin-exceptions
18345 Displays whether @value{GDBN} will break on exceptions that happen
18346 inside the Cygwin DLL itself.
18348 @kindex set new-console
18349 @item set new-console @var{mode}
18350 If @var{mode} is @code{on} the debuggee will
18351 be started in a new console on next start.
18352 If @var{mode} is @code{off}, the debuggee will
18353 be started in the same console as the debugger.
18355 @kindex show new-console
18356 @item show new-console
18357 Displays whether a new console is used
18358 when the debuggee is started.
18360 @kindex set new-group
18361 @item set new-group @var{mode}
18362 This boolean value controls whether the debuggee should
18363 start a new group or stay in the same group as the debugger.
18364 This affects the way the Windows OS handles
18367 @kindex show new-group
18368 @item show new-group
18369 Displays current value of new-group boolean.
18371 @kindex set debugevents
18372 @item set debugevents
18373 This boolean value adds debug output concerning kernel events related
18374 to the debuggee seen by the debugger. This includes events that
18375 signal thread and process creation and exit, DLL loading and
18376 unloading, console interrupts, and debugging messages produced by the
18377 Windows @code{OutputDebugString} API call.
18379 @kindex set debugexec
18380 @item set debugexec
18381 This boolean value adds debug output concerning execute events
18382 (such as resume thread) seen by the debugger.
18384 @kindex set debugexceptions
18385 @item set debugexceptions
18386 This boolean value adds debug output concerning exceptions in the
18387 debuggee seen by the debugger.
18389 @kindex set debugmemory
18390 @item set debugmemory
18391 This boolean value adds debug output concerning debuggee memory reads
18392 and writes by the debugger.
18396 This boolean values specifies whether the debuggee is called
18397 via a shell or directly (default value is on).
18401 Displays if the debuggee will be started with a shell.
18406 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
18409 @node Non-debug DLL Symbols
18410 @subsubsection Support for DLLs without Debugging Symbols
18411 @cindex DLLs with no debugging symbols
18412 @cindex Minimal symbols and DLLs
18414 Very often on windows, some of the DLLs that your program relies on do
18415 not include symbolic debugging information (for example,
18416 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
18417 symbols in a DLL, it relies on the minimal amount of symbolic
18418 information contained in the DLL's export table. This section
18419 describes working with such symbols, known internally to @value{GDBN} as
18420 ``minimal symbols''.
18422 Note that before the debugged program has started execution, no DLLs
18423 will have been loaded. The easiest way around this problem is simply to
18424 start the program --- either by setting a breakpoint or letting the
18425 program run once to completion. It is also possible to force
18426 @value{GDBN} to load a particular DLL before starting the executable ---
18427 see the shared library information in @ref{Files}, or the
18428 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
18429 explicitly loading symbols from a DLL with no debugging information will
18430 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
18431 which may adversely affect symbol lookup performance.
18433 @subsubsection DLL Name Prefixes
18435 In keeping with the naming conventions used by the Microsoft debugging
18436 tools, DLL export symbols are made available with a prefix based on the
18437 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
18438 also entered into the symbol table, so @code{CreateFileA} is often
18439 sufficient. In some cases there will be name clashes within a program
18440 (particularly if the executable itself includes full debugging symbols)
18441 necessitating the use of the fully qualified name when referring to the
18442 contents of the DLL. Use single-quotes around the name to avoid the
18443 exclamation mark (``!'') being interpreted as a language operator.
18445 Note that the internal name of the DLL may be all upper-case, even
18446 though the file name of the DLL is lower-case, or vice-versa. Since
18447 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
18448 some confusion. If in doubt, try the @code{info functions} and
18449 @code{info variables} commands or even @code{maint print msymbols}
18450 (@pxref{Symbols}). Here's an example:
18453 (@value{GDBP}) info function CreateFileA
18454 All functions matching regular expression "CreateFileA":
18456 Non-debugging symbols:
18457 0x77e885f4 CreateFileA
18458 0x77e885f4 KERNEL32!CreateFileA
18462 (@value{GDBP}) info function !
18463 All functions matching regular expression "!":
18465 Non-debugging symbols:
18466 0x6100114c cygwin1!__assert
18467 0x61004034 cygwin1!_dll_crt0@@0
18468 0x61004240 cygwin1!dll_crt0(per_process *)
18472 @subsubsection Working with Minimal Symbols
18474 Symbols extracted from a DLL's export table do not contain very much
18475 type information. All that @value{GDBN} can do is guess whether a symbol
18476 refers to a function or variable depending on the linker section that
18477 contains the symbol. Also note that the actual contents of the memory
18478 contained in a DLL are not available unless the program is running. This
18479 means that you cannot examine the contents of a variable or disassemble
18480 a function within a DLL without a running program.
18482 Variables are generally treated as pointers and dereferenced
18483 automatically. For this reason, it is often necessary to prefix a
18484 variable name with the address-of operator (``&'') and provide explicit
18485 type information in the command. Here's an example of the type of
18489 (@value{GDBP}) print 'cygwin1!__argv'
18494 (@value{GDBP}) x 'cygwin1!__argv'
18495 0x10021610: "\230y\""
18498 And two possible solutions:
18501 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
18502 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
18506 (@value{GDBP}) x/2x &'cygwin1!__argv'
18507 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
18508 (@value{GDBP}) x/x 0x10021608
18509 0x10021608: 0x0022fd98
18510 (@value{GDBP}) x/s 0x0022fd98
18511 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
18514 Setting a break point within a DLL is possible even before the program
18515 starts execution. However, under these circumstances, @value{GDBN} can't
18516 examine the initial instructions of the function in order to skip the
18517 function's frame set-up code. You can work around this by using ``*&''
18518 to set the breakpoint at a raw memory address:
18521 (@value{GDBP}) break *&'python22!PyOS_Readline'
18522 Breakpoint 1 at 0x1e04eff0
18525 The author of these extensions is not entirely convinced that setting a
18526 break point within a shared DLL like @file{kernel32.dll} is completely
18530 @subsection Commands Specific to @sc{gnu} Hurd Systems
18531 @cindex @sc{gnu} Hurd debugging
18533 This subsection describes @value{GDBN} commands specific to the
18534 @sc{gnu} Hurd native debugging.
18539 @kindex set signals@r{, Hurd command}
18540 @kindex set sigs@r{, Hurd command}
18541 This command toggles the state of inferior signal interception by
18542 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
18543 affected by this command. @code{sigs} is a shorthand alias for
18548 @kindex show signals@r{, Hurd command}
18549 @kindex show sigs@r{, Hurd command}
18550 Show the current state of intercepting inferior's signals.
18552 @item set signal-thread
18553 @itemx set sigthread
18554 @kindex set signal-thread
18555 @kindex set sigthread
18556 This command tells @value{GDBN} which thread is the @code{libc} signal
18557 thread. That thread is run when a signal is delivered to a running
18558 process. @code{set sigthread} is the shorthand alias of @code{set
18561 @item show signal-thread
18562 @itemx show sigthread
18563 @kindex show signal-thread
18564 @kindex show sigthread
18565 These two commands show which thread will run when the inferior is
18566 delivered a signal.
18569 @kindex set stopped@r{, Hurd command}
18570 This commands tells @value{GDBN} that the inferior process is stopped,
18571 as with the @code{SIGSTOP} signal. The stopped process can be
18572 continued by delivering a signal to it.
18575 @kindex show stopped@r{, Hurd command}
18576 This command shows whether @value{GDBN} thinks the debuggee is
18579 @item set exceptions
18580 @kindex set exceptions@r{, Hurd command}
18581 Use this command to turn off trapping of exceptions in the inferior.
18582 When exception trapping is off, neither breakpoints nor
18583 single-stepping will work. To restore the default, set exception
18586 @item show exceptions
18587 @kindex show exceptions@r{, Hurd command}
18588 Show the current state of trapping exceptions in the inferior.
18590 @item set task pause
18591 @kindex set task@r{, Hurd commands}
18592 @cindex task attributes (@sc{gnu} Hurd)
18593 @cindex pause current task (@sc{gnu} Hurd)
18594 This command toggles task suspension when @value{GDBN} has control.
18595 Setting it to on takes effect immediately, and the task is suspended
18596 whenever @value{GDBN} gets control. Setting it to off will take
18597 effect the next time the inferior is continued. If this option is set
18598 to off, you can use @code{set thread default pause on} or @code{set
18599 thread pause on} (see below) to pause individual threads.
18601 @item show task pause
18602 @kindex show task@r{, Hurd commands}
18603 Show the current state of task suspension.
18605 @item set task detach-suspend-count
18606 @cindex task suspend count
18607 @cindex detach from task, @sc{gnu} Hurd
18608 This command sets the suspend count the task will be left with when
18609 @value{GDBN} detaches from it.
18611 @item show task detach-suspend-count
18612 Show the suspend count the task will be left with when detaching.
18614 @item set task exception-port
18615 @itemx set task excp
18616 @cindex task exception port, @sc{gnu} Hurd
18617 This command sets the task exception port to which @value{GDBN} will
18618 forward exceptions. The argument should be the value of the @dfn{send
18619 rights} of the task. @code{set task excp} is a shorthand alias.
18621 @item set noninvasive
18622 @cindex noninvasive task options
18623 This command switches @value{GDBN} to a mode that is the least
18624 invasive as far as interfering with the inferior is concerned. This
18625 is the same as using @code{set task pause}, @code{set exceptions}, and
18626 @code{set signals} to values opposite to the defaults.
18628 @item info send-rights
18629 @itemx info receive-rights
18630 @itemx info port-rights
18631 @itemx info port-sets
18632 @itemx info dead-names
18635 @cindex send rights, @sc{gnu} Hurd
18636 @cindex receive rights, @sc{gnu} Hurd
18637 @cindex port rights, @sc{gnu} Hurd
18638 @cindex port sets, @sc{gnu} Hurd
18639 @cindex dead names, @sc{gnu} Hurd
18640 These commands display information about, respectively, send rights,
18641 receive rights, port rights, port sets, and dead names of a task.
18642 There are also shorthand aliases: @code{info ports} for @code{info
18643 port-rights} and @code{info psets} for @code{info port-sets}.
18645 @item set thread pause
18646 @kindex set thread@r{, Hurd command}
18647 @cindex thread properties, @sc{gnu} Hurd
18648 @cindex pause current thread (@sc{gnu} Hurd)
18649 This command toggles current thread suspension when @value{GDBN} has
18650 control. Setting it to on takes effect immediately, and the current
18651 thread is suspended whenever @value{GDBN} gets control. Setting it to
18652 off will take effect the next time the inferior is continued.
18653 Normally, this command has no effect, since when @value{GDBN} has
18654 control, the whole task is suspended. However, if you used @code{set
18655 task pause off} (see above), this command comes in handy to suspend
18656 only the current thread.
18658 @item show thread pause
18659 @kindex show thread@r{, Hurd command}
18660 This command shows the state of current thread suspension.
18662 @item set thread run
18663 This command sets whether the current thread is allowed to run.
18665 @item show thread run
18666 Show whether the current thread is allowed to run.
18668 @item set thread detach-suspend-count
18669 @cindex thread suspend count, @sc{gnu} Hurd
18670 @cindex detach from thread, @sc{gnu} Hurd
18671 This command sets the suspend count @value{GDBN} will leave on a
18672 thread when detaching. This number is relative to the suspend count
18673 found by @value{GDBN} when it notices the thread; use @code{set thread
18674 takeover-suspend-count} to force it to an absolute value.
18676 @item show thread detach-suspend-count
18677 Show the suspend count @value{GDBN} will leave on the thread when
18680 @item set thread exception-port
18681 @itemx set thread excp
18682 Set the thread exception port to which to forward exceptions. This
18683 overrides the port set by @code{set task exception-port} (see above).
18684 @code{set thread excp} is the shorthand alias.
18686 @item set thread takeover-suspend-count
18687 Normally, @value{GDBN}'s thread suspend counts are relative to the
18688 value @value{GDBN} finds when it notices each thread. This command
18689 changes the suspend counts to be absolute instead.
18691 @item set thread default
18692 @itemx show thread default
18693 @cindex thread default settings, @sc{gnu} Hurd
18694 Each of the above @code{set thread} commands has a @code{set thread
18695 default} counterpart (e.g., @code{set thread default pause}, @code{set
18696 thread default exception-port}, etc.). The @code{thread default}
18697 variety of commands sets the default thread properties for all
18698 threads; you can then change the properties of individual threads with
18699 the non-default commands.
18704 @subsection QNX Neutrino
18705 @cindex QNX Neutrino
18707 @value{GDBN} provides the following commands specific to the QNX
18711 @item set debug nto-debug
18712 @kindex set debug nto-debug
18713 When set to on, enables debugging messages specific to the QNX
18716 @item show debug nto-debug
18717 @kindex show debug nto-debug
18718 Show the current state of QNX Neutrino messages.
18725 @value{GDBN} provides the following commands specific to the Darwin target:
18728 @item set debug darwin @var{num}
18729 @kindex set debug darwin
18730 When set to a non zero value, enables debugging messages specific to
18731 the Darwin support. Higher values produce more verbose output.
18733 @item show debug darwin
18734 @kindex show debug darwin
18735 Show the current state of Darwin messages.
18737 @item set debug mach-o @var{num}
18738 @kindex set debug mach-o
18739 When set to a non zero value, enables debugging messages while
18740 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
18741 file format used on Darwin for object and executable files.) Higher
18742 values produce more verbose output. This is a command to diagnose
18743 problems internal to @value{GDBN} and should not be needed in normal
18746 @item show debug mach-o
18747 @kindex show debug mach-o
18748 Show the current state of Mach-O file messages.
18750 @item set mach-exceptions on
18751 @itemx set mach-exceptions off
18752 @kindex set mach-exceptions
18753 On Darwin, faults are first reported as a Mach exception and are then
18754 mapped to a Posix signal. Use this command to turn on trapping of
18755 Mach exceptions in the inferior. This might be sometimes useful to
18756 better understand the cause of a fault. The default is off.
18758 @item show mach-exceptions
18759 @kindex show mach-exceptions
18760 Show the current state of exceptions trapping.
18765 @section Embedded Operating Systems
18767 This section describes configurations involving the debugging of
18768 embedded operating systems that are available for several different
18772 * VxWorks:: Using @value{GDBN} with VxWorks
18775 @value{GDBN} includes the ability to debug programs running on
18776 various real-time operating systems.
18779 @subsection Using @value{GDBN} with VxWorks
18785 @kindex target vxworks
18786 @item target vxworks @var{machinename}
18787 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
18788 is the target system's machine name or IP address.
18792 On VxWorks, @code{load} links @var{filename} dynamically on the
18793 current target system as well as adding its symbols in @value{GDBN}.
18795 @value{GDBN} enables developers to spawn and debug tasks running on networked
18796 VxWorks targets from a Unix host. Already-running tasks spawned from
18797 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
18798 both the Unix host and on the VxWorks target. The program
18799 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
18800 installed with the name @code{vxgdb}, to distinguish it from a
18801 @value{GDBN} for debugging programs on the host itself.)
18804 @item VxWorks-timeout @var{args}
18805 @kindex vxworks-timeout
18806 All VxWorks-based targets now support the option @code{vxworks-timeout}.
18807 This option is set by the user, and @var{args} represents the number of
18808 seconds @value{GDBN} waits for responses to rpc's. You might use this if
18809 your VxWorks target is a slow software simulator or is on the far side
18810 of a thin network line.
18813 The following information on connecting to VxWorks was current when
18814 this manual was produced; newer releases of VxWorks may use revised
18817 @findex INCLUDE_RDB
18818 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
18819 to include the remote debugging interface routines in the VxWorks
18820 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
18821 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
18822 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
18823 source debugging task @code{tRdbTask} when VxWorks is booted. For more
18824 information on configuring and remaking VxWorks, see the manufacturer's
18826 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
18828 Once you have included @file{rdb.a} in your VxWorks system image and set
18829 your Unix execution search path to find @value{GDBN}, you are ready to
18830 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
18831 @code{vxgdb}, depending on your installation).
18833 @value{GDBN} comes up showing the prompt:
18840 * VxWorks Connection:: Connecting to VxWorks
18841 * VxWorks Download:: VxWorks download
18842 * VxWorks Attach:: Running tasks
18845 @node VxWorks Connection
18846 @subsubsection Connecting to VxWorks
18848 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
18849 network. To connect to a target whose host name is ``@code{tt}'', type:
18852 (vxgdb) target vxworks tt
18856 @value{GDBN} displays messages like these:
18859 Attaching remote machine across net...
18864 @value{GDBN} then attempts to read the symbol tables of any object modules
18865 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
18866 these files by searching the directories listed in the command search
18867 path (@pxref{Environment, ,Your Program's Environment}); if it fails
18868 to find an object file, it displays a message such as:
18871 prog.o: No such file or directory.
18874 When this happens, add the appropriate directory to the search path with
18875 the @value{GDBN} command @code{path}, and execute the @code{target}
18878 @node VxWorks Download
18879 @subsubsection VxWorks Download
18881 @cindex download to VxWorks
18882 If you have connected to the VxWorks target and you want to debug an
18883 object that has not yet been loaded, you can use the @value{GDBN}
18884 @code{load} command to download a file from Unix to VxWorks
18885 incrementally. The object file given as an argument to the @code{load}
18886 command is actually opened twice: first by the VxWorks target in order
18887 to download the code, then by @value{GDBN} in order to read the symbol
18888 table. This can lead to problems if the current working directories on
18889 the two systems differ. If both systems have NFS mounted the same
18890 filesystems, you can avoid these problems by using absolute paths.
18891 Otherwise, it is simplest to set the working directory on both systems
18892 to the directory in which the object file resides, and then to reference
18893 the file by its name, without any path. For instance, a program
18894 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
18895 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
18896 program, type this on VxWorks:
18899 -> cd "@var{vxpath}/vw/demo/rdb"
18903 Then, in @value{GDBN}, type:
18906 (vxgdb) cd @var{hostpath}/vw/demo/rdb
18907 (vxgdb) load prog.o
18910 @value{GDBN} displays a response similar to this:
18913 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
18916 You can also use the @code{load} command to reload an object module
18917 after editing and recompiling the corresponding source file. Note that
18918 this makes @value{GDBN} delete all currently-defined breakpoints,
18919 auto-displays, and convenience variables, and to clear the value
18920 history. (This is necessary in order to preserve the integrity of
18921 debugger's data structures that reference the target system's symbol
18924 @node VxWorks Attach
18925 @subsubsection Running Tasks
18927 @cindex running VxWorks tasks
18928 You can also attach to an existing task using the @code{attach} command as
18932 (vxgdb) attach @var{task}
18936 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
18937 or suspended when you attach to it. Running tasks are suspended at
18938 the time of attachment.
18940 @node Embedded Processors
18941 @section Embedded Processors
18943 This section goes into details specific to particular embedded
18946 @cindex send command to simulator
18947 Whenever a specific embedded processor has a simulator, @value{GDBN}
18948 allows to send an arbitrary command to the simulator.
18951 @item sim @var{command}
18952 @kindex sim@r{, a command}
18953 Send an arbitrary @var{command} string to the simulator. Consult the
18954 documentation for the specific simulator in use for information about
18955 acceptable commands.
18961 * M32R/D:: Renesas M32R/D
18962 * M68K:: Motorola M68K
18963 * MicroBlaze:: Xilinx MicroBlaze
18964 * MIPS Embedded:: MIPS Embedded
18965 * OpenRISC 1000:: OpenRisc 1000
18966 * PA:: HP PA Embedded
18967 * PowerPC Embedded:: PowerPC Embedded
18968 * Sparclet:: Tsqware Sparclet
18969 * Sparclite:: Fujitsu Sparclite
18970 * Z8000:: Zilog Z8000
18973 * Super-H:: Renesas Super-H
18982 @item target rdi @var{dev}
18983 ARM Angel monitor, via RDI library interface to ADP protocol. You may
18984 use this target to communicate with both boards running the Angel
18985 monitor, or with the EmbeddedICE JTAG debug device.
18988 @item target rdp @var{dev}
18993 @value{GDBN} provides the following ARM-specific commands:
18996 @item set arm disassembler
18998 This commands selects from a list of disassembly styles. The
18999 @code{"std"} style is the standard style.
19001 @item show arm disassembler
19003 Show the current disassembly style.
19005 @item set arm apcs32
19006 @cindex ARM 32-bit mode
19007 This command toggles ARM operation mode between 32-bit and 26-bit.
19009 @item show arm apcs32
19010 Display the current usage of the ARM 32-bit mode.
19012 @item set arm fpu @var{fputype}
19013 This command sets the ARM floating-point unit (FPU) type. The
19014 argument @var{fputype} can be one of these:
19018 Determine the FPU type by querying the OS ABI.
19020 Software FPU, with mixed-endian doubles on little-endian ARM
19023 GCC-compiled FPA co-processor.
19025 Software FPU with pure-endian doubles.
19031 Show the current type of the FPU.
19034 This command forces @value{GDBN} to use the specified ABI.
19037 Show the currently used ABI.
19039 @item set arm fallback-mode (arm|thumb|auto)
19040 @value{GDBN} uses the symbol table, when available, to determine
19041 whether instructions are ARM or Thumb. This command controls
19042 @value{GDBN}'s default behavior when the symbol table is not
19043 available. The default is @samp{auto}, which causes @value{GDBN} to
19044 use the current execution mode (from the @code{T} bit in the @code{CPSR}
19047 @item show arm fallback-mode
19048 Show the current fallback instruction mode.
19050 @item set arm force-mode (arm|thumb|auto)
19051 This command overrides use of the symbol table to determine whether
19052 instructions are ARM or Thumb. The default is @samp{auto}, which
19053 causes @value{GDBN} to use the symbol table and then the setting
19054 of @samp{set arm fallback-mode}.
19056 @item show arm force-mode
19057 Show the current forced instruction mode.
19059 @item set debug arm
19060 Toggle whether to display ARM-specific debugging messages from the ARM
19061 target support subsystem.
19063 @item show debug arm
19064 Show whether ARM-specific debugging messages are enabled.
19067 The following commands are available when an ARM target is debugged
19068 using the RDI interface:
19071 @item rdilogfile @r{[}@var{file}@r{]}
19073 @cindex ADP (Angel Debugger Protocol) logging
19074 Set the filename for the ADP (Angel Debugger Protocol) packet log.
19075 With an argument, sets the log file to the specified @var{file}. With
19076 no argument, show the current log file name. The default log file is
19079 @item rdilogenable @r{[}@var{arg}@r{]}
19080 @kindex rdilogenable
19081 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
19082 enables logging, with an argument 0 or @code{"no"} disables it. With
19083 no arguments displays the current setting. When logging is enabled,
19084 ADP packets exchanged between @value{GDBN} and the RDI target device
19085 are logged to a file.
19087 @item set rdiromatzero
19088 @kindex set rdiromatzero
19089 @cindex ROM at zero address, RDI
19090 Tell @value{GDBN} whether the target has ROM at address 0. If on,
19091 vector catching is disabled, so that zero address can be used. If off
19092 (the default), vector catching is enabled. For this command to take
19093 effect, it needs to be invoked prior to the @code{target rdi} command.
19095 @item show rdiromatzero
19096 @kindex show rdiromatzero
19097 Show the current setting of ROM at zero address.
19099 @item set rdiheartbeat
19100 @kindex set rdiheartbeat
19101 @cindex RDI heartbeat
19102 Enable or disable RDI heartbeat packets. It is not recommended to
19103 turn on this option, since it confuses ARM and EPI JTAG interface, as
19104 well as the Angel monitor.
19106 @item show rdiheartbeat
19107 @kindex show rdiheartbeat
19108 Show the setting of RDI heartbeat packets.
19112 @item target sim @r{[}@var{simargs}@r{]} @dots{}
19113 The @value{GDBN} ARM simulator accepts the following optional arguments.
19116 @item --swi-support=@var{type}
19117 Tell the simulator which SWI interfaces to support.
19118 @var{type} may be a comma separated list of the following values.
19119 The default value is @code{all}.
19132 @subsection Renesas M32R/D and M32R/SDI
19135 @kindex target m32r
19136 @item target m32r @var{dev}
19137 Renesas M32R/D ROM monitor.
19139 @kindex target m32rsdi
19140 @item target m32rsdi @var{dev}
19141 Renesas M32R SDI server, connected via parallel port to the board.
19144 The following @value{GDBN} commands are specific to the M32R monitor:
19147 @item set download-path @var{path}
19148 @kindex set download-path
19149 @cindex find downloadable @sc{srec} files (M32R)
19150 Set the default path for finding downloadable @sc{srec} files.
19152 @item show download-path
19153 @kindex show download-path
19154 Show the default path for downloadable @sc{srec} files.
19156 @item set board-address @var{addr}
19157 @kindex set board-address
19158 @cindex M32-EVA target board address
19159 Set the IP address for the M32R-EVA target board.
19161 @item show board-address
19162 @kindex show board-address
19163 Show the current IP address of the target board.
19165 @item set server-address @var{addr}
19166 @kindex set server-address
19167 @cindex download server address (M32R)
19168 Set the IP address for the download server, which is the @value{GDBN}'s
19171 @item show server-address
19172 @kindex show server-address
19173 Display the IP address of the download server.
19175 @item upload @r{[}@var{file}@r{]}
19176 @kindex upload@r{, M32R}
19177 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
19178 upload capability. If no @var{file} argument is given, the current
19179 executable file is uploaded.
19181 @item tload @r{[}@var{file}@r{]}
19182 @kindex tload@r{, M32R}
19183 Test the @code{upload} command.
19186 The following commands are available for M32R/SDI:
19191 @cindex reset SDI connection, M32R
19192 This command resets the SDI connection.
19196 This command shows the SDI connection status.
19199 @kindex debug_chaos
19200 @cindex M32R/Chaos debugging
19201 Instructs the remote that M32R/Chaos debugging is to be used.
19203 @item use_debug_dma
19204 @kindex use_debug_dma
19205 Instructs the remote to use the DEBUG_DMA method of accessing memory.
19208 @kindex use_mon_code
19209 Instructs the remote to use the MON_CODE method of accessing memory.
19212 @kindex use_ib_break
19213 Instructs the remote to set breakpoints by IB break.
19215 @item use_dbt_break
19216 @kindex use_dbt_break
19217 Instructs the remote to set breakpoints by DBT.
19223 The Motorola m68k configuration includes ColdFire support, and a
19224 target command for the following ROM monitor.
19228 @kindex target dbug
19229 @item target dbug @var{dev}
19230 dBUG ROM monitor for Motorola ColdFire.
19235 @subsection MicroBlaze
19236 @cindex Xilinx MicroBlaze
19237 @cindex XMD, Xilinx Microprocessor Debugger
19239 The MicroBlaze is a soft-core processor supported on various Xilinx
19240 FPGAs, such as Spartan or Virtex series. Boards with these processors
19241 usually have JTAG ports which connect to a host system running the Xilinx
19242 Embedded Development Kit (EDK) or Software Development Kit (SDK).
19243 This host system is used to download the configuration bitstream to
19244 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
19245 communicates with the target board using the JTAG interface and
19246 presents a @code{gdbserver} interface to the board. By default
19247 @code{xmd} uses port @code{1234}. (While it is possible to change
19248 this default port, it requires the use of undocumented @code{xmd}
19249 commands. Contact Xilinx support if you need to do this.)
19251 Use these GDB commands to connect to the MicroBlaze target processor.
19254 @item target remote :1234
19255 Use this command to connect to the target if you are running @value{GDBN}
19256 on the same system as @code{xmd}.
19258 @item target remote @var{xmd-host}:1234
19259 Use this command to connect to the target if it is connected to @code{xmd}
19260 running on a different system named @var{xmd-host}.
19263 Use this command to download a program to the MicroBlaze target.
19265 @item set debug microblaze @var{n}
19266 Enable MicroBlaze-specific debugging messages if non-zero.
19268 @item show debug microblaze @var{n}
19269 Show MicroBlaze-specific debugging level.
19272 @node MIPS Embedded
19273 @subsection MIPS Embedded
19275 @cindex MIPS boards
19276 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
19277 MIPS board attached to a serial line. This is available when
19278 you configure @value{GDBN} with @samp{--target=mips-elf}.
19281 Use these @value{GDBN} commands to specify the connection to your target board:
19284 @item target mips @var{port}
19285 @kindex target mips @var{port}
19286 To run a program on the board, start up @code{@value{GDBP}} with the
19287 name of your program as the argument. To connect to the board, use the
19288 command @samp{target mips @var{port}}, where @var{port} is the name of
19289 the serial port connected to the board. If the program has not already
19290 been downloaded to the board, you may use the @code{load} command to
19291 download it. You can then use all the usual @value{GDBN} commands.
19293 For example, this sequence connects to the target board through a serial
19294 port, and loads and runs a program called @var{prog} through the
19298 host$ @value{GDBP} @var{prog}
19299 @value{GDBN} is free software and @dots{}
19300 (@value{GDBP}) target mips /dev/ttyb
19301 (@value{GDBP}) load @var{prog}
19305 @item target mips @var{hostname}:@var{portnumber}
19306 On some @value{GDBN} host configurations, you can specify a TCP
19307 connection (for instance, to a serial line managed by a terminal
19308 concentrator) instead of a serial port, using the syntax
19309 @samp{@var{hostname}:@var{portnumber}}.
19311 @item target pmon @var{port}
19312 @kindex target pmon @var{port}
19315 @item target ddb @var{port}
19316 @kindex target ddb @var{port}
19317 NEC's DDB variant of PMON for Vr4300.
19319 @item target lsi @var{port}
19320 @kindex target lsi @var{port}
19321 LSI variant of PMON.
19323 @kindex target r3900
19324 @item target r3900 @var{dev}
19325 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
19327 @kindex target array
19328 @item target array @var{dev}
19329 Array Tech LSI33K RAID controller board.
19335 @value{GDBN} also supports these special commands for MIPS targets:
19338 @item set mipsfpu double
19339 @itemx set mipsfpu single
19340 @itemx set mipsfpu none
19341 @itemx set mipsfpu auto
19342 @itemx show mipsfpu
19343 @kindex set mipsfpu
19344 @kindex show mipsfpu
19345 @cindex MIPS remote floating point
19346 @cindex floating point, MIPS remote
19347 If your target board does not support the MIPS floating point
19348 coprocessor, you should use the command @samp{set mipsfpu none} (if you
19349 need this, you may wish to put the command in your @value{GDBN} init
19350 file). This tells @value{GDBN} how to find the return value of
19351 functions which return floating point values. It also allows
19352 @value{GDBN} to avoid saving the floating point registers when calling
19353 functions on the board. If you are using a floating point coprocessor
19354 with only single precision floating point support, as on the @sc{r4650}
19355 processor, use the command @samp{set mipsfpu single}. The default
19356 double precision floating point coprocessor may be selected using
19357 @samp{set mipsfpu double}.
19359 In previous versions the only choices were double precision or no
19360 floating point, so @samp{set mipsfpu on} will select double precision
19361 and @samp{set mipsfpu off} will select no floating point.
19363 As usual, you can inquire about the @code{mipsfpu} variable with
19364 @samp{show mipsfpu}.
19366 @item set timeout @var{seconds}
19367 @itemx set retransmit-timeout @var{seconds}
19368 @itemx show timeout
19369 @itemx show retransmit-timeout
19370 @cindex @code{timeout}, MIPS protocol
19371 @cindex @code{retransmit-timeout}, MIPS protocol
19372 @kindex set timeout
19373 @kindex show timeout
19374 @kindex set retransmit-timeout
19375 @kindex show retransmit-timeout
19376 You can control the timeout used while waiting for a packet, in the MIPS
19377 remote protocol, with the @code{set timeout @var{seconds}} command. The
19378 default is 5 seconds. Similarly, you can control the timeout used while
19379 waiting for an acknowledgment of a packet with the @code{set
19380 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
19381 You can inspect both values with @code{show timeout} and @code{show
19382 retransmit-timeout}. (These commands are @emph{only} available when
19383 @value{GDBN} is configured for @samp{--target=mips-elf}.)
19385 The timeout set by @code{set timeout} does not apply when @value{GDBN}
19386 is waiting for your program to stop. In that case, @value{GDBN} waits
19387 forever because it has no way of knowing how long the program is going
19388 to run before stopping.
19390 @item set syn-garbage-limit @var{num}
19391 @kindex set syn-garbage-limit@r{, MIPS remote}
19392 @cindex synchronize with remote MIPS target
19393 Limit the maximum number of characters @value{GDBN} should ignore when
19394 it tries to synchronize with the remote target. The default is 10
19395 characters. Setting the limit to -1 means there's no limit.
19397 @item show syn-garbage-limit
19398 @kindex show syn-garbage-limit@r{, MIPS remote}
19399 Show the current limit on the number of characters to ignore when
19400 trying to synchronize with the remote system.
19402 @item set monitor-prompt @var{prompt}
19403 @kindex set monitor-prompt@r{, MIPS remote}
19404 @cindex remote monitor prompt
19405 Tell @value{GDBN} to expect the specified @var{prompt} string from the
19406 remote monitor. The default depends on the target:
19416 @item show monitor-prompt
19417 @kindex show monitor-prompt@r{, MIPS remote}
19418 Show the current strings @value{GDBN} expects as the prompt from the
19421 @item set monitor-warnings
19422 @kindex set monitor-warnings@r{, MIPS remote}
19423 Enable or disable monitor warnings about hardware breakpoints. This
19424 has effect only for the @code{lsi} target. When on, @value{GDBN} will
19425 display warning messages whose codes are returned by the @code{lsi}
19426 PMON monitor for breakpoint commands.
19428 @item show monitor-warnings
19429 @kindex show monitor-warnings@r{, MIPS remote}
19430 Show the current setting of printing monitor warnings.
19432 @item pmon @var{command}
19433 @kindex pmon@r{, MIPS remote}
19434 @cindex send PMON command
19435 This command allows sending an arbitrary @var{command} string to the
19436 monitor. The monitor must be in debug mode for this to work.
19439 @node OpenRISC 1000
19440 @subsection OpenRISC 1000
19441 @cindex OpenRISC 1000
19443 @cindex or1k boards
19444 See OR1k Architecture document (@uref{www.opencores.org}) for more information
19445 about platform and commands.
19449 @kindex target jtag
19450 @item target jtag jtag://@var{host}:@var{port}
19452 Connects to remote JTAG server.
19453 JTAG remote server can be either an or1ksim or JTAG server,
19454 connected via parallel port to the board.
19456 Example: @code{target jtag jtag://localhost:9999}
19459 @item or1ksim @var{command}
19460 If connected to @code{or1ksim} OpenRISC 1000 Architectural
19461 Simulator, proprietary commands can be executed.
19463 @kindex info or1k spr
19464 @item info or1k spr
19465 Displays spr groups.
19467 @item info or1k spr @var{group}
19468 @itemx info or1k spr @var{groupno}
19469 Displays register names in selected group.
19471 @item info or1k spr @var{group} @var{register}
19472 @itemx info or1k spr @var{register}
19473 @itemx info or1k spr @var{groupno} @var{registerno}
19474 @itemx info or1k spr @var{registerno}
19475 Shows information about specified spr register.
19478 @item spr @var{group} @var{register} @var{value}
19479 @itemx spr @var{register @var{value}}
19480 @itemx spr @var{groupno} @var{registerno @var{value}}
19481 @itemx spr @var{registerno @var{value}}
19482 Writes @var{value} to specified spr register.
19485 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
19486 It is very similar to @value{GDBN} trace, except it does not interfere with normal
19487 program execution and is thus much faster. Hardware breakpoints/watchpoint
19488 triggers can be set using:
19491 Load effective address/data
19493 Store effective address/data
19495 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
19500 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
19501 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
19503 @code{htrace} commands:
19504 @cindex OpenRISC 1000 htrace
19507 @item hwatch @var{conditional}
19508 Set hardware watchpoint on combination of Load/Store Effective Address(es)
19509 or Data. For example:
19511 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
19513 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
19517 Display information about current HW trace configuration.
19519 @item htrace trigger @var{conditional}
19520 Set starting criteria for HW trace.
19522 @item htrace qualifier @var{conditional}
19523 Set acquisition qualifier for HW trace.
19525 @item htrace stop @var{conditional}
19526 Set HW trace stopping criteria.
19528 @item htrace record [@var{data}]*
19529 Selects the data to be recorded, when qualifier is met and HW trace was
19532 @item htrace enable
19533 @itemx htrace disable
19534 Enables/disables the HW trace.
19536 @item htrace rewind [@var{filename}]
19537 Clears currently recorded trace data.
19539 If filename is specified, new trace file is made and any newly collected data
19540 will be written there.
19542 @item htrace print [@var{start} [@var{len}]]
19543 Prints trace buffer, using current record configuration.
19545 @item htrace mode continuous
19546 Set continuous trace mode.
19548 @item htrace mode suspend
19549 Set suspend trace mode.
19553 @node PowerPC Embedded
19554 @subsection PowerPC Embedded
19556 @cindex DVC register
19557 @value{GDBN} supports using the DVC (Data Value Compare) register to
19558 implement in hardware simple hardware watchpoint conditions of the form:
19561 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
19562 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
19565 The DVC register will be automatically used when @value{GDBN} detects
19566 such pattern in a condition expression, and the created watchpoint uses one
19567 debug register (either the @code{exact-watchpoints} option is on and the
19568 variable is scalar, or the variable has a length of one byte). This feature
19569 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
19572 When running on PowerPC embedded processors, @value{GDBN} automatically uses
19573 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
19574 in which case watchpoints using only one debug register are created when
19575 watching variables of scalar types.
19577 You can create an artificial array to watch an arbitrary memory
19578 region using one of the following commands (@pxref{Expressions}):
19581 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
19582 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
19585 PowerPC embedded processors support masked watchpoints. See the discussion
19586 about the @code{mask} argument in @ref{Set Watchpoints}.
19588 @cindex ranged breakpoint
19589 PowerPC embedded processors support hardware accelerated
19590 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
19591 the inferior whenever it executes an instruction at any address within
19592 the range it specifies. To set a ranged breakpoint in @value{GDBN},
19593 use the @code{break-range} command.
19595 @value{GDBN} provides the following PowerPC-specific commands:
19598 @kindex break-range
19599 @item break-range @var{start-location}, @var{end-location}
19600 Set a breakpoint for an address range.
19601 @var{start-location} and @var{end-location} can specify a function name,
19602 a line number, an offset of lines from the current line or from the start
19603 location, or an address of an instruction (see @ref{Specify Location},
19604 for a list of all the possible ways to specify a @var{location}.)
19605 The breakpoint will stop execution of the inferior whenever it
19606 executes an instruction at any address within the specified range,
19607 (including @var{start-location} and @var{end-location}.)
19609 @kindex set powerpc
19610 @item set powerpc soft-float
19611 @itemx show powerpc soft-float
19612 Force @value{GDBN} to use (or not use) a software floating point calling
19613 convention. By default, @value{GDBN} selects the calling convention based
19614 on the selected architecture and the provided executable file.
19616 @item set powerpc vector-abi
19617 @itemx show powerpc vector-abi
19618 Force @value{GDBN} to use the specified calling convention for vector
19619 arguments and return values. The valid options are @samp{auto};
19620 @samp{generic}, to avoid vector registers even if they are present;
19621 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
19622 registers. By default, @value{GDBN} selects the calling convention
19623 based on the selected architecture and the provided executable file.
19625 @item set powerpc exact-watchpoints
19626 @itemx show powerpc exact-watchpoints
19627 Allow @value{GDBN} to use only one debug register when watching a variable
19628 of scalar type, thus assuming that the variable is accessed through the
19629 address of its first byte.
19631 @kindex target dink32
19632 @item target dink32 @var{dev}
19633 DINK32 ROM monitor.
19635 @kindex target ppcbug
19636 @item target ppcbug @var{dev}
19637 @kindex target ppcbug1
19638 @item target ppcbug1 @var{dev}
19639 PPCBUG ROM monitor for PowerPC.
19642 @item target sds @var{dev}
19643 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
19646 @cindex SDS protocol
19647 The following commands specific to the SDS protocol are supported
19651 @item set sdstimeout @var{nsec}
19652 @kindex set sdstimeout
19653 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
19654 default is 2 seconds.
19656 @item show sdstimeout
19657 @kindex show sdstimeout
19658 Show the current value of the SDS timeout.
19660 @item sds @var{command}
19661 @kindex sds@r{, a command}
19662 Send the specified @var{command} string to the SDS monitor.
19667 @subsection HP PA Embedded
19671 @kindex target op50n
19672 @item target op50n @var{dev}
19673 OP50N monitor, running on an OKI HPPA board.
19675 @kindex target w89k
19676 @item target w89k @var{dev}
19677 W89K monitor, running on a Winbond HPPA board.
19682 @subsection Tsqware Sparclet
19686 @value{GDBN} enables developers to debug tasks running on
19687 Sparclet targets from a Unix host.
19688 @value{GDBN} uses code that runs on
19689 both the Unix host and on the Sparclet target. The program
19690 @code{@value{GDBP}} is installed and executed on the Unix host.
19693 @item remotetimeout @var{args}
19694 @kindex remotetimeout
19695 @value{GDBN} supports the option @code{remotetimeout}.
19696 This option is set by the user, and @var{args} represents the number of
19697 seconds @value{GDBN} waits for responses.
19700 @cindex compiling, on Sparclet
19701 When compiling for debugging, include the options @samp{-g} to get debug
19702 information and @samp{-Ttext} to relocate the program to where you wish to
19703 load it on the target. You may also want to add the options @samp{-n} or
19704 @samp{-N} in order to reduce the size of the sections. Example:
19707 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
19710 You can use @code{objdump} to verify that the addresses are what you intended:
19713 sparclet-aout-objdump --headers --syms prog
19716 @cindex running, on Sparclet
19718 your Unix execution search path to find @value{GDBN}, you are ready to
19719 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
19720 (or @code{sparclet-aout-gdb}, depending on your installation).
19722 @value{GDBN} comes up showing the prompt:
19729 * Sparclet File:: Setting the file to debug
19730 * Sparclet Connection:: Connecting to Sparclet
19731 * Sparclet Download:: Sparclet download
19732 * Sparclet Execution:: Running and debugging
19735 @node Sparclet File
19736 @subsubsection Setting File to Debug
19738 The @value{GDBN} command @code{file} lets you choose with program to debug.
19741 (gdbslet) file prog
19745 @value{GDBN} then attempts to read the symbol table of @file{prog}.
19746 @value{GDBN} locates
19747 the file by searching the directories listed in the command search
19749 If the file was compiled with debug information (option @samp{-g}), source
19750 files will be searched as well.
19751 @value{GDBN} locates
19752 the source files by searching the directories listed in the directory search
19753 path (@pxref{Environment, ,Your Program's Environment}).
19755 to find a file, it displays a message such as:
19758 prog: No such file or directory.
19761 When this happens, add the appropriate directories to the search paths with
19762 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
19763 @code{target} command again.
19765 @node Sparclet Connection
19766 @subsubsection Connecting to Sparclet
19768 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
19769 To connect to a target on serial port ``@code{ttya}'', type:
19772 (gdbslet) target sparclet /dev/ttya
19773 Remote target sparclet connected to /dev/ttya
19774 main () at ../prog.c:3
19778 @value{GDBN} displays messages like these:
19784 @node Sparclet Download
19785 @subsubsection Sparclet Download
19787 @cindex download to Sparclet
19788 Once connected to the Sparclet target,
19789 you can use the @value{GDBN}
19790 @code{load} command to download the file from the host to the target.
19791 The file name and load offset should be given as arguments to the @code{load}
19793 Since the file format is aout, the program must be loaded to the starting
19794 address. You can use @code{objdump} to find out what this value is. The load
19795 offset is an offset which is added to the VMA (virtual memory address)
19796 of each of the file's sections.
19797 For instance, if the program
19798 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
19799 and bss at 0x12010170, in @value{GDBN}, type:
19802 (gdbslet) load prog 0x12010000
19803 Loading section .text, size 0xdb0 vma 0x12010000
19806 If the code is loaded at a different address then what the program was linked
19807 to, you may need to use the @code{section} and @code{add-symbol-file} commands
19808 to tell @value{GDBN} where to map the symbol table.
19810 @node Sparclet Execution
19811 @subsubsection Running and Debugging
19813 @cindex running and debugging Sparclet programs
19814 You can now begin debugging the task using @value{GDBN}'s execution control
19815 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
19816 manual for the list of commands.
19820 Breakpoint 1 at 0x12010000: file prog.c, line 3.
19822 Starting program: prog
19823 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
19824 3 char *symarg = 0;
19826 4 char *execarg = "hello!";
19831 @subsection Fujitsu Sparclite
19835 @kindex target sparclite
19836 @item target sparclite @var{dev}
19837 Fujitsu sparclite boards, used only for the purpose of loading.
19838 You must use an additional command to debug the program.
19839 For example: target remote @var{dev} using @value{GDBN} standard
19845 @subsection Zilog Z8000
19848 @cindex simulator, Z8000
19849 @cindex Zilog Z8000 simulator
19851 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
19854 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
19855 unsegmented variant of the Z8000 architecture) or the Z8001 (the
19856 segmented variant). The simulator recognizes which architecture is
19857 appropriate by inspecting the object code.
19860 @item target sim @var{args}
19862 @kindex target sim@r{, with Z8000}
19863 Debug programs on a simulated CPU. If the simulator supports setup
19864 options, specify them via @var{args}.
19868 After specifying this target, you can debug programs for the simulated
19869 CPU in the same style as programs for your host computer; use the
19870 @code{file} command to load a new program image, the @code{run} command
19871 to run your program, and so on.
19873 As well as making available all the usual machine registers
19874 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
19875 additional items of information as specially named registers:
19880 Counts clock-ticks in the simulator.
19883 Counts instructions run in the simulator.
19886 Execution time in 60ths of a second.
19890 You can refer to these values in @value{GDBN} expressions with the usual
19891 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
19892 conditional breakpoint that suspends only after at least 5000
19893 simulated clock ticks.
19896 @subsection Atmel AVR
19899 When configured for debugging the Atmel AVR, @value{GDBN} supports the
19900 following AVR-specific commands:
19903 @item info io_registers
19904 @kindex info io_registers@r{, AVR}
19905 @cindex I/O registers (Atmel AVR)
19906 This command displays information about the AVR I/O registers. For
19907 each register, @value{GDBN} prints its number and value.
19914 When configured for debugging CRIS, @value{GDBN} provides the
19915 following CRIS-specific commands:
19918 @item set cris-version @var{ver}
19919 @cindex CRIS version
19920 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
19921 The CRIS version affects register names and sizes. This command is useful in
19922 case autodetection of the CRIS version fails.
19924 @item show cris-version
19925 Show the current CRIS version.
19927 @item set cris-dwarf2-cfi
19928 @cindex DWARF-2 CFI and CRIS
19929 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
19930 Change to @samp{off} when using @code{gcc-cris} whose version is below
19933 @item show cris-dwarf2-cfi
19934 Show the current state of using DWARF-2 CFI.
19936 @item set cris-mode @var{mode}
19938 Set the current CRIS mode to @var{mode}. It should only be changed when
19939 debugging in guru mode, in which case it should be set to
19940 @samp{guru} (the default is @samp{normal}).
19942 @item show cris-mode
19943 Show the current CRIS mode.
19947 @subsection Renesas Super-H
19950 For the Renesas Super-H processor, @value{GDBN} provides these
19955 @kindex regs@r{, Super-H}
19956 Show the values of all Super-H registers.
19958 @item set sh calling-convention @var{convention}
19959 @kindex set sh calling-convention
19960 Set the calling-convention used when calling functions from @value{GDBN}.
19961 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
19962 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
19963 convention. If the DWARF-2 information of the called function specifies
19964 that the function follows the Renesas calling convention, the function
19965 is called using the Renesas calling convention. If the calling convention
19966 is set to @samp{renesas}, the Renesas calling convention is always used,
19967 regardless of the DWARF-2 information. This can be used to override the
19968 default of @samp{gcc} if debug information is missing, or the compiler
19969 does not emit the DWARF-2 calling convention entry for a function.
19971 @item show sh calling-convention
19972 @kindex show sh calling-convention
19973 Show the current calling convention setting.
19978 @node Architectures
19979 @section Architectures
19981 This section describes characteristics of architectures that affect
19982 all uses of @value{GDBN} with the architecture, both native and cross.
19989 * HPPA:: HP PA architecture
19990 * SPU:: Cell Broadband Engine SPU architecture
19995 @subsection x86 Architecture-specific Issues
19998 @item set struct-convention @var{mode}
19999 @kindex set struct-convention
20000 @cindex struct return convention
20001 @cindex struct/union returned in registers
20002 Set the convention used by the inferior to return @code{struct}s and
20003 @code{union}s from functions to @var{mode}. Possible values of
20004 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
20005 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
20006 are returned on the stack, while @code{"reg"} means that a
20007 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
20008 be returned in a register.
20010 @item show struct-convention
20011 @kindex show struct-convention
20012 Show the current setting of the convention to return @code{struct}s
20021 @kindex set rstack_high_address
20022 @cindex AMD 29K register stack
20023 @cindex register stack, AMD29K
20024 @item set rstack_high_address @var{address}
20025 On AMD 29000 family processors, registers are saved in a separate
20026 @dfn{register stack}. There is no way for @value{GDBN} to determine the
20027 extent of this stack. Normally, @value{GDBN} just assumes that the
20028 stack is ``large enough''. This may result in @value{GDBN} referencing
20029 memory locations that do not exist. If necessary, you can get around
20030 this problem by specifying the ending address of the register stack with
20031 the @code{set rstack_high_address} command. The argument should be an
20032 address, which you probably want to precede with @samp{0x} to specify in
20035 @kindex show rstack_high_address
20036 @item show rstack_high_address
20037 Display the current limit of the register stack, on AMD 29000 family
20045 See the following section.
20050 @cindex stack on Alpha
20051 @cindex stack on MIPS
20052 @cindex Alpha stack
20054 Alpha- and MIPS-based computers use an unusual stack frame, which
20055 sometimes requires @value{GDBN} to search backward in the object code to
20056 find the beginning of a function.
20058 @cindex response time, MIPS debugging
20059 To improve response time (especially for embedded applications, where
20060 @value{GDBN} may be restricted to a slow serial line for this search)
20061 you may want to limit the size of this search, using one of these
20065 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
20066 @item set heuristic-fence-post @var{limit}
20067 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
20068 search for the beginning of a function. A value of @var{0} (the
20069 default) means there is no limit. However, except for @var{0}, the
20070 larger the limit the more bytes @code{heuristic-fence-post} must search
20071 and therefore the longer it takes to run. You should only need to use
20072 this command when debugging a stripped executable.
20074 @item show heuristic-fence-post
20075 Display the current limit.
20079 These commands are available @emph{only} when @value{GDBN} is configured
20080 for debugging programs on Alpha or MIPS processors.
20082 Several MIPS-specific commands are available when debugging MIPS
20086 @item set mips abi @var{arg}
20087 @kindex set mips abi
20088 @cindex set ABI for MIPS
20089 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
20090 values of @var{arg} are:
20094 The default ABI associated with the current binary (this is the
20104 @item show mips abi
20105 @kindex show mips abi
20106 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
20109 @itemx show mipsfpu
20110 @xref{MIPS Embedded, set mipsfpu}.
20112 @item set mips mask-address @var{arg}
20113 @kindex set mips mask-address
20114 @cindex MIPS addresses, masking
20115 This command determines whether the most-significant 32 bits of 64-bit
20116 MIPS addresses are masked off. The argument @var{arg} can be
20117 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
20118 setting, which lets @value{GDBN} determine the correct value.
20120 @item show mips mask-address
20121 @kindex show mips mask-address
20122 Show whether the upper 32 bits of MIPS addresses are masked off or
20125 @item set remote-mips64-transfers-32bit-regs
20126 @kindex set remote-mips64-transfers-32bit-regs
20127 This command controls compatibility with 64-bit MIPS targets that
20128 transfer data in 32-bit quantities. If you have an old MIPS 64 target
20129 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
20130 and 64 bits for other registers, set this option to @samp{on}.
20132 @item show remote-mips64-transfers-32bit-regs
20133 @kindex show remote-mips64-transfers-32bit-regs
20134 Show the current setting of compatibility with older MIPS 64 targets.
20136 @item set debug mips
20137 @kindex set debug mips
20138 This command turns on and off debugging messages for the MIPS-specific
20139 target code in @value{GDBN}.
20141 @item show debug mips
20142 @kindex show debug mips
20143 Show the current setting of MIPS debugging messages.
20149 @cindex HPPA support
20151 When @value{GDBN} is debugging the HP PA architecture, it provides the
20152 following special commands:
20155 @item set debug hppa
20156 @kindex set debug hppa
20157 This command determines whether HPPA architecture-specific debugging
20158 messages are to be displayed.
20160 @item show debug hppa
20161 Show whether HPPA debugging messages are displayed.
20163 @item maint print unwind @var{address}
20164 @kindex maint print unwind@r{, HPPA}
20165 This command displays the contents of the unwind table entry at the
20166 given @var{address}.
20172 @subsection Cell Broadband Engine SPU architecture
20173 @cindex Cell Broadband Engine
20176 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
20177 it provides the following special commands:
20180 @item info spu event
20182 Display SPU event facility status. Shows current event mask
20183 and pending event status.
20185 @item info spu signal
20186 Display SPU signal notification facility status. Shows pending
20187 signal-control word and signal notification mode of both signal
20188 notification channels.
20190 @item info spu mailbox
20191 Display SPU mailbox facility status. Shows all pending entries,
20192 in order of processing, in each of the SPU Write Outbound,
20193 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
20196 Display MFC DMA status. Shows all pending commands in the MFC
20197 DMA queue. For each entry, opcode, tag, class IDs, effective
20198 and local store addresses and transfer size are shown.
20200 @item info spu proxydma
20201 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
20202 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
20203 and local store addresses and transfer size are shown.
20207 When @value{GDBN} is debugging a combined PowerPC/SPU application
20208 on the Cell Broadband Engine, it provides in addition the following
20212 @item set spu stop-on-load @var{arg}
20214 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
20215 will give control to the user when a new SPE thread enters its @code{main}
20216 function. The default is @code{off}.
20218 @item show spu stop-on-load
20220 Show whether to stop for new SPE threads.
20222 @item set spu auto-flush-cache @var{arg}
20223 Set whether to automatically flush the software-managed cache. When set to
20224 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
20225 cache to be flushed whenever SPE execution stops. This provides a consistent
20226 view of PowerPC memory that is accessed via the cache. If an application
20227 does not use the software-managed cache, this option has no effect.
20229 @item show spu auto-flush-cache
20230 Show whether to automatically flush the software-managed cache.
20235 @subsection PowerPC
20236 @cindex PowerPC architecture
20238 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
20239 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
20240 numbers stored in the floating point registers. These values must be stored
20241 in two consecutive registers, always starting at an even register like
20242 @code{f0} or @code{f2}.
20244 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
20245 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
20246 @code{f2} and @code{f3} for @code{$dl1} and so on.
20248 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
20249 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
20252 @node Controlling GDB
20253 @chapter Controlling @value{GDBN}
20255 You can alter the way @value{GDBN} interacts with you by using the
20256 @code{set} command. For commands controlling how @value{GDBN} displays
20257 data, see @ref{Print Settings, ,Print Settings}. Other settings are
20262 * Editing:: Command editing
20263 * Command History:: Command history
20264 * Screen Size:: Screen size
20265 * Numbers:: Numbers
20266 * ABI:: Configuring the current ABI
20267 * Messages/Warnings:: Optional warnings and messages
20268 * Debugging Output:: Optional messages about internal happenings
20269 * Other Misc Settings:: Other Miscellaneous Settings
20277 @value{GDBN} indicates its readiness to read a command by printing a string
20278 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
20279 can change the prompt string with the @code{set prompt} command. For
20280 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
20281 the prompt in one of the @value{GDBN} sessions so that you can always tell
20282 which one you are talking to.
20284 @emph{Note:} @code{set prompt} does not add a space for you after the
20285 prompt you set. This allows you to set a prompt which ends in a space
20286 or a prompt that does not.
20290 @item set prompt @var{newprompt}
20291 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
20293 @kindex show prompt
20295 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
20298 Versions of @value{GDBN} that ship with Python scripting enabled have
20299 prompt extensions. The commands for interacting with these extensions
20303 @kindex set extended-prompt
20304 @item set extended-prompt @var{prompt}
20305 Set an extended prompt that allows for substitutions.
20306 @xref{gdb.prompt}, for a list of escape sequences that can be used for
20307 substitution. Any escape sequences specified as part of the prompt
20308 string are replaced with the corresponding strings each time the prompt
20314 set extended-prompt Current working directory: \w (gdb)
20317 Note that when an extended-prompt is set, it takes control of the
20318 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
20320 @kindex show extended-prompt
20321 @item show extended-prompt
20322 Prints the extended prompt. Any escape sequences specified as part of
20323 the prompt string with @code{set extended-prompt}, are replaced with the
20324 corresponding strings each time the prompt is displayed.
20328 @section Command Editing
20330 @cindex command line editing
20332 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
20333 @sc{gnu} library provides consistent behavior for programs which provide a
20334 command line interface to the user. Advantages are @sc{gnu} Emacs-style
20335 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
20336 substitution, and a storage and recall of command history across
20337 debugging sessions.
20339 You may control the behavior of command line editing in @value{GDBN} with the
20340 command @code{set}.
20343 @kindex set editing
20346 @itemx set editing on
20347 Enable command line editing (enabled by default).
20349 @item set editing off
20350 Disable command line editing.
20352 @kindex show editing
20354 Show whether command line editing is enabled.
20357 @ifset SYSTEM_READLINE
20358 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
20360 @ifclear SYSTEM_READLINE
20361 @xref{Command Line Editing},
20363 for more details about the Readline
20364 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
20365 encouraged to read that chapter.
20367 @node Command History
20368 @section Command History
20369 @cindex command history
20371 @value{GDBN} can keep track of the commands you type during your
20372 debugging sessions, so that you can be certain of precisely what
20373 happened. Use these commands to manage the @value{GDBN} command
20376 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
20377 package, to provide the history facility.
20378 @ifset SYSTEM_READLINE
20379 @xref{Using History Interactively, , , history, GNU History Library},
20381 @ifclear SYSTEM_READLINE
20382 @xref{Using History Interactively},
20384 for the detailed description of the History library.
20386 To issue a command to @value{GDBN} without affecting certain aspects of
20387 the state which is seen by users, prefix it with @samp{server }
20388 (@pxref{Server Prefix}). This
20389 means that this command will not affect the command history, nor will it
20390 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
20391 pressed on a line by itself.
20393 @cindex @code{server}, command prefix
20394 The server prefix does not affect the recording of values into the value
20395 history; to print a value without recording it into the value history,
20396 use the @code{output} command instead of the @code{print} command.
20398 Here is the description of @value{GDBN} commands related to command
20402 @cindex history substitution
20403 @cindex history file
20404 @kindex set history filename
20405 @cindex @env{GDBHISTFILE}, environment variable
20406 @item set history filename @var{fname}
20407 Set the name of the @value{GDBN} command history file to @var{fname}.
20408 This is the file where @value{GDBN} reads an initial command history
20409 list, and where it writes the command history from this session when it
20410 exits. You can access this list through history expansion or through
20411 the history command editing characters listed below. This file defaults
20412 to the value of the environment variable @code{GDBHISTFILE}, or to
20413 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
20416 @cindex save command history
20417 @kindex set history save
20418 @item set history save
20419 @itemx set history save on
20420 Record command history in a file, whose name may be specified with the
20421 @code{set history filename} command. By default, this option is disabled.
20423 @item set history save off
20424 Stop recording command history in a file.
20426 @cindex history size
20427 @kindex set history size
20428 @cindex @env{HISTSIZE}, environment variable
20429 @item set history size @var{size}
20430 Set the number of commands which @value{GDBN} keeps in its history list.
20431 This defaults to the value of the environment variable
20432 @code{HISTSIZE}, or to 256 if this variable is not set.
20435 History expansion assigns special meaning to the character @kbd{!}.
20436 @ifset SYSTEM_READLINE
20437 @xref{Event Designators, , , history, GNU History Library},
20439 @ifclear SYSTEM_READLINE
20440 @xref{Event Designators},
20444 @cindex history expansion, turn on/off
20445 Since @kbd{!} is also the logical not operator in C, history expansion
20446 is off by default. If you decide to enable history expansion with the
20447 @code{set history expansion on} command, you may sometimes need to
20448 follow @kbd{!} (when it is used as logical not, in an expression) with
20449 a space or a tab to prevent it from being expanded. The readline
20450 history facilities do not attempt substitution on the strings
20451 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
20453 The commands to control history expansion are:
20456 @item set history expansion on
20457 @itemx set history expansion
20458 @kindex set history expansion
20459 Enable history expansion. History expansion is off by default.
20461 @item set history expansion off
20462 Disable history expansion.
20465 @kindex show history
20467 @itemx show history filename
20468 @itemx show history save
20469 @itemx show history size
20470 @itemx show history expansion
20471 These commands display the state of the @value{GDBN} history parameters.
20472 @code{show history} by itself displays all four states.
20477 @kindex show commands
20478 @cindex show last commands
20479 @cindex display command history
20480 @item show commands
20481 Display the last ten commands in the command history.
20483 @item show commands @var{n}
20484 Print ten commands centered on command number @var{n}.
20486 @item show commands +
20487 Print ten commands just after the commands last printed.
20491 @section Screen Size
20492 @cindex size of screen
20493 @cindex pauses in output
20495 Certain commands to @value{GDBN} may produce large amounts of
20496 information output to the screen. To help you read all of it,
20497 @value{GDBN} pauses and asks you for input at the end of each page of
20498 output. Type @key{RET} when you want to continue the output, or @kbd{q}
20499 to discard the remaining output. Also, the screen width setting
20500 determines when to wrap lines of output. Depending on what is being
20501 printed, @value{GDBN} tries to break the line at a readable place,
20502 rather than simply letting it overflow onto the following line.
20504 Normally @value{GDBN} knows the size of the screen from the terminal
20505 driver software. For example, on Unix @value{GDBN} uses the termcap data base
20506 together with the value of the @code{TERM} environment variable and the
20507 @code{stty rows} and @code{stty cols} settings. If this is not correct,
20508 you can override it with the @code{set height} and @code{set
20515 @kindex show height
20516 @item set height @var{lpp}
20518 @itemx set width @var{cpl}
20520 These @code{set} commands specify a screen height of @var{lpp} lines and
20521 a screen width of @var{cpl} characters. The associated @code{show}
20522 commands display the current settings.
20524 If you specify a height of zero lines, @value{GDBN} does not pause during
20525 output no matter how long the output is. This is useful if output is to a
20526 file or to an editor buffer.
20528 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
20529 from wrapping its output.
20531 @item set pagination on
20532 @itemx set pagination off
20533 @kindex set pagination
20534 Turn the output pagination on or off; the default is on. Turning
20535 pagination off is the alternative to @code{set height 0}. Note that
20536 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
20537 Options, -batch}) also automatically disables pagination.
20539 @item show pagination
20540 @kindex show pagination
20541 Show the current pagination mode.
20546 @cindex number representation
20547 @cindex entering numbers
20549 You can always enter numbers in octal, decimal, or hexadecimal in
20550 @value{GDBN} by the usual conventions: octal numbers begin with
20551 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
20552 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
20553 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
20554 10; likewise, the default display for numbers---when no particular
20555 format is specified---is base 10. You can change the default base for
20556 both input and output with the commands described below.
20559 @kindex set input-radix
20560 @item set input-radix @var{base}
20561 Set the default base for numeric input. Supported choices
20562 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
20563 specified either unambiguously or using the current input radix; for
20567 set input-radix 012
20568 set input-radix 10.
20569 set input-radix 0xa
20573 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
20574 leaves the input radix unchanged, no matter what it was, since
20575 @samp{10}, being without any leading or trailing signs of its base, is
20576 interpreted in the current radix. Thus, if the current radix is 16,
20577 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
20580 @kindex set output-radix
20581 @item set output-radix @var{base}
20582 Set the default base for numeric display. Supported choices
20583 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
20584 specified either unambiguously or using the current input radix.
20586 @kindex show input-radix
20587 @item show input-radix
20588 Display the current default base for numeric input.
20590 @kindex show output-radix
20591 @item show output-radix
20592 Display the current default base for numeric display.
20594 @item set radix @r{[}@var{base}@r{]}
20598 These commands set and show the default base for both input and output
20599 of numbers. @code{set radix} sets the radix of input and output to
20600 the same base; without an argument, it resets the radix back to its
20601 default value of 10.
20606 @section Configuring the Current ABI
20608 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
20609 application automatically. However, sometimes you need to override its
20610 conclusions. Use these commands to manage @value{GDBN}'s view of the
20617 One @value{GDBN} configuration can debug binaries for multiple operating
20618 system targets, either via remote debugging or native emulation.
20619 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
20620 but you can override its conclusion using the @code{set osabi} command.
20621 One example where this is useful is in debugging of binaries which use
20622 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
20623 not have the same identifying marks that the standard C library for your
20628 Show the OS ABI currently in use.
20631 With no argument, show the list of registered available OS ABI's.
20633 @item set osabi @var{abi}
20634 Set the current OS ABI to @var{abi}.
20637 @cindex float promotion
20639 Generally, the way that an argument of type @code{float} is passed to a
20640 function depends on whether the function is prototyped. For a prototyped
20641 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
20642 according to the architecture's convention for @code{float}. For unprototyped
20643 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
20644 @code{double} and then passed.
20646 Unfortunately, some forms of debug information do not reliably indicate whether
20647 a function is prototyped. If @value{GDBN} calls a function that is not marked
20648 as prototyped, it consults @kbd{set coerce-float-to-double}.
20651 @kindex set coerce-float-to-double
20652 @item set coerce-float-to-double
20653 @itemx set coerce-float-to-double on
20654 Arguments of type @code{float} will be promoted to @code{double} when passed
20655 to an unprototyped function. This is the default setting.
20657 @item set coerce-float-to-double off
20658 Arguments of type @code{float} will be passed directly to unprototyped
20661 @kindex show coerce-float-to-double
20662 @item show coerce-float-to-double
20663 Show the current setting of promoting @code{float} to @code{double}.
20667 @kindex show cp-abi
20668 @value{GDBN} needs to know the ABI used for your program's C@t{++}
20669 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
20670 used to build your application. @value{GDBN} only fully supports
20671 programs with a single C@t{++} ABI; if your program contains code using
20672 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
20673 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
20674 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
20675 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
20676 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
20677 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
20682 Show the C@t{++} ABI currently in use.
20685 With no argument, show the list of supported C@t{++} ABI's.
20687 @item set cp-abi @var{abi}
20688 @itemx set cp-abi auto
20689 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
20692 @node Messages/Warnings
20693 @section Optional Warnings and Messages
20695 @cindex verbose operation
20696 @cindex optional warnings
20697 By default, @value{GDBN} is silent about its inner workings. If you are
20698 running on a slow machine, you may want to use the @code{set verbose}
20699 command. This makes @value{GDBN} tell you when it does a lengthy
20700 internal operation, so you will not think it has crashed.
20702 Currently, the messages controlled by @code{set verbose} are those
20703 which announce that the symbol table for a source file is being read;
20704 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
20707 @kindex set verbose
20708 @item set verbose on
20709 Enables @value{GDBN} output of certain informational messages.
20711 @item set verbose off
20712 Disables @value{GDBN} output of certain informational messages.
20714 @kindex show verbose
20716 Displays whether @code{set verbose} is on or off.
20719 By default, if @value{GDBN} encounters bugs in the symbol table of an
20720 object file, it is silent; but if you are debugging a compiler, you may
20721 find this information useful (@pxref{Symbol Errors, ,Errors Reading
20726 @kindex set complaints
20727 @item set complaints @var{limit}
20728 Permits @value{GDBN} to output @var{limit} complaints about each type of
20729 unusual symbols before becoming silent about the problem. Set
20730 @var{limit} to zero to suppress all complaints; set it to a large number
20731 to prevent complaints from being suppressed.
20733 @kindex show complaints
20734 @item show complaints
20735 Displays how many symbol complaints @value{GDBN} is permitted to produce.
20739 @anchor{confirmation requests}
20740 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
20741 lot of stupid questions to confirm certain commands. For example, if
20742 you try to run a program which is already running:
20746 The program being debugged has been started already.
20747 Start it from the beginning? (y or n)
20750 If you are willing to unflinchingly face the consequences of your own
20751 commands, you can disable this ``feature'':
20755 @kindex set confirm
20757 @cindex confirmation
20758 @cindex stupid questions
20759 @item set confirm off
20760 Disables confirmation requests. Note that running @value{GDBN} with
20761 the @option{--batch} option (@pxref{Mode Options, -batch}) also
20762 automatically disables confirmation requests.
20764 @item set confirm on
20765 Enables confirmation requests (the default).
20767 @kindex show confirm
20769 Displays state of confirmation requests.
20773 @cindex command tracing
20774 If you need to debug user-defined commands or sourced files you may find it
20775 useful to enable @dfn{command tracing}. In this mode each command will be
20776 printed as it is executed, prefixed with one or more @samp{+} symbols, the
20777 quantity denoting the call depth of each command.
20780 @kindex set trace-commands
20781 @cindex command scripts, debugging
20782 @item set trace-commands on
20783 Enable command tracing.
20784 @item set trace-commands off
20785 Disable command tracing.
20786 @item show trace-commands
20787 Display the current state of command tracing.
20790 @node Debugging Output
20791 @section Optional Messages about Internal Happenings
20792 @cindex optional debugging messages
20794 @value{GDBN} has commands that enable optional debugging messages from
20795 various @value{GDBN} subsystems; normally these commands are of
20796 interest to @value{GDBN} maintainers, or when reporting a bug. This
20797 section documents those commands.
20800 @kindex set exec-done-display
20801 @item set exec-done-display
20802 Turns on or off the notification of asynchronous commands'
20803 completion. When on, @value{GDBN} will print a message when an
20804 asynchronous command finishes its execution. The default is off.
20805 @kindex show exec-done-display
20806 @item show exec-done-display
20807 Displays the current setting of asynchronous command completion
20810 @cindex gdbarch debugging info
20811 @cindex architecture debugging info
20812 @item set debug arch
20813 Turns on or off display of gdbarch debugging info. The default is off
20815 @item show debug arch
20816 Displays the current state of displaying gdbarch debugging info.
20817 @item set debug aix-thread
20818 @cindex AIX threads
20819 Display debugging messages about inner workings of the AIX thread
20821 @item show debug aix-thread
20822 Show the current state of AIX thread debugging info display.
20823 @item set debug check-physname
20825 Check the results of the ``physname'' computation. When reading DWARF
20826 debugging information for C@t{++}, @value{GDBN} attempts to compute
20827 each entity's name. @value{GDBN} can do this computation in two
20828 different ways, depending on exactly what information is present.
20829 When enabled, this setting causes @value{GDBN} to compute the names
20830 both ways and display any discrepancies.
20831 @item show debug check-physname
20832 Show the current state of ``physname'' checking.
20833 @item set debug dwarf2-die
20834 @cindex DWARF2 DIEs
20835 Dump DWARF2 DIEs after they are read in.
20836 The value is the number of nesting levels to print.
20837 A value of zero turns off the display.
20838 @item show debug dwarf2-die
20839 Show the current state of DWARF2 DIE debugging.
20840 @item set debug displaced
20841 @cindex displaced stepping debugging info
20842 Turns on or off display of @value{GDBN} debugging info for the
20843 displaced stepping support. The default is off.
20844 @item show debug displaced
20845 Displays the current state of displaying @value{GDBN} debugging info
20846 related to displaced stepping.
20847 @item set debug event
20848 @cindex event debugging info
20849 Turns on or off display of @value{GDBN} event debugging info. The
20851 @item show debug event
20852 Displays the current state of displaying @value{GDBN} event debugging
20854 @item set debug expression
20855 @cindex expression debugging info
20856 Turns on or off display of debugging info about @value{GDBN}
20857 expression parsing. The default is off.
20858 @item show debug expression
20859 Displays the current state of displaying debugging info about
20860 @value{GDBN} expression parsing.
20861 @item set debug frame
20862 @cindex frame debugging info
20863 Turns on or off display of @value{GDBN} frame debugging info. The
20865 @item show debug frame
20866 Displays the current state of displaying @value{GDBN} frame debugging
20868 @item set debug gnu-nat
20869 @cindex @sc{gnu}/Hurd debug messages
20870 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
20871 @item show debug gnu-nat
20872 Show the current state of @sc{gnu}/Hurd debugging messages.
20873 @item set debug infrun
20874 @cindex inferior debugging info
20875 Turns on or off display of @value{GDBN} debugging info for running the inferior.
20876 The default is off. @file{infrun.c} contains GDB's runtime state machine used
20877 for implementing operations such as single-stepping the inferior.
20878 @item show debug infrun
20879 Displays the current state of @value{GDBN} inferior debugging.
20880 @item set debug jit
20881 @cindex just-in-time compilation, debugging messages
20882 Turns on or off debugging messages from JIT debug support.
20883 @item show debug jit
20884 Displays the current state of @value{GDBN} JIT debugging.
20885 @item set debug lin-lwp
20886 @cindex @sc{gnu}/Linux LWP debug messages
20887 @cindex Linux lightweight processes
20888 Turns on or off debugging messages from the Linux LWP debug support.
20889 @item show debug lin-lwp
20890 Show the current state of Linux LWP debugging messages.
20891 @item set debug observer
20892 @cindex observer debugging info
20893 Turns on or off display of @value{GDBN} observer debugging. This
20894 includes info such as the notification of observable events.
20895 @item show debug observer
20896 Displays the current state of observer debugging.
20897 @item set debug overload
20898 @cindex C@t{++} overload debugging info
20899 Turns on or off display of @value{GDBN} C@t{++} overload debugging
20900 info. This includes info such as ranking of functions, etc. The default
20902 @item show debug overload
20903 Displays the current state of displaying @value{GDBN} C@t{++} overload
20905 @cindex expression parser, debugging info
20906 @cindex debug expression parser
20907 @item set debug parser
20908 Turns on or off the display of expression parser debugging output.
20909 Internally, this sets the @code{yydebug} variable in the expression
20910 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
20911 details. The default is off.
20912 @item show debug parser
20913 Show the current state of expression parser debugging.
20914 @cindex packets, reporting on stdout
20915 @cindex serial connections, debugging
20916 @cindex debug remote protocol
20917 @cindex remote protocol debugging
20918 @cindex display remote packets
20919 @item set debug remote
20920 Turns on or off display of reports on all packets sent back and forth across
20921 the serial line to the remote machine. The info is printed on the
20922 @value{GDBN} standard output stream. The default is off.
20923 @item show debug remote
20924 Displays the state of display of remote packets.
20925 @item set debug serial
20926 Turns on or off display of @value{GDBN} serial debugging info. The
20928 @item show debug serial
20929 Displays the current state of displaying @value{GDBN} serial debugging
20931 @item set debug solib-frv
20932 @cindex FR-V shared-library debugging
20933 Turns on or off debugging messages for FR-V shared-library code.
20934 @item show debug solib-frv
20935 Display the current state of FR-V shared-library code debugging
20937 @item set debug target
20938 @cindex target debugging info
20939 Turns on or off display of @value{GDBN} target debugging info. This info
20940 includes what is going on at the target level of GDB, as it happens. The
20941 default is 0. Set it to 1 to track events, and to 2 to also track the
20942 value of large memory transfers. Changes to this flag do not take effect
20943 until the next time you connect to a target or use the @code{run} command.
20944 @item show debug target
20945 Displays the current state of displaying @value{GDBN} target debugging
20947 @item set debug timestamp
20948 @cindex timestampping debugging info
20949 Turns on or off display of timestamps with @value{GDBN} debugging info.
20950 When enabled, seconds and microseconds are displayed before each debugging
20952 @item show debug timestamp
20953 Displays the current state of displaying timestamps with @value{GDBN}
20955 @item set debugvarobj
20956 @cindex variable object debugging info
20957 Turns on or off display of @value{GDBN} variable object debugging
20958 info. The default is off.
20959 @item show debugvarobj
20960 Displays the current state of displaying @value{GDBN} variable object
20962 @item set debug xml
20963 @cindex XML parser debugging
20964 Turns on or off debugging messages for built-in XML parsers.
20965 @item show debug xml
20966 Displays the current state of XML debugging messages.
20969 @node Other Misc Settings
20970 @section Other Miscellaneous Settings
20971 @cindex miscellaneous settings
20974 @kindex set interactive-mode
20975 @item set interactive-mode
20976 If @code{on}, forces @value{GDBN} to assume that GDB was started
20977 in a terminal. In practice, this means that @value{GDBN} should wait
20978 for the user to answer queries generated by commands entered at
20979 the command prompt. If @code{off}, forces @value{GDBN} to operate
20980 in the opposite mode, and it uses the default answers to all queries.
20981 If @code{auto} (the default), @value{GDBN} tries to determine whether
20982 its standard input is a terminal, and works in interactive-mode if it
20983 is, non-interactively otherwise.
20985 In the vast majority of cases, the debugger should be able to guess
20986 correctly which mode should be used. But this setting can be useful
20987 in certain specific cases, such as running a MinGW @value{GDBN}
20988 inside a cygwin window.
20990 @kindex show interactive-mode
20991 @item show interactive-mode
20992 Displays whether the debugger is operating in interactive mode or not.
20995 @node Extending GDB
20996 @chapter Extending @value{GDBN}
20997 @cindex extending GDB
20999 @value{GDBN} provides three mechanisms for extension. The first is based
21000 on composition of @value{GDBN} commands, the second is based on the
21001 Python scripting language, and the third is for defining new aliases of
21004 To facilitate the use of the first two extensions, @value{GDBN} is capable
21005 of evaluating the contents of a file. When doing so, @value{GDBN}
21006 can recognize which scripting language is being used by looking at
21007 the filename extension. Files with an unrecognized filename extension
21008 are always treated as a @value{GDBN} Command Files.
21009 @xref{Command Files,, Command files}.
21011 You can control how @value{GDBN} evaluates these files with the following
21015 @kindex set script-extension
21016 @kindex show script-extension
21017 @item set script-extension off
21018 All scripts are always evaluated as @value{GDBN} Command Files.
21020 @item set script-extension soft
21021 The debugger determines the scripting language based on filename
21022 extension. If this scripting language is supported, @value{GDBN}
21023 evaluates the script using that language. Otherwise, it evaluates
21024 the file as a @value{GDBN} Command File.
21026 @item set script-extension strict
21027 The debugger determines the scripting language based on filename
21028 extension, and evaluates the script using that language. If the
21029 language is not supported, then the evaluation fails.
21031 @item show script-extension
21032 Display the current value of the @code{script-extension} option.
21037 * Sequences:: Canned Sequences of Commands
21038 * Python:: Scripting @value{GDBN} using Python
21039 * Aliases:: Creating new spellings of existing commands
21043 @section Canned Sequences of Commands
21045 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
21046 Command Lists}), @value{GDBN} provides two ways to store sequences of
21047 commands for execution as a unit: user-defined commands and command
21051 * Define:: How to define your own commands
21052 * Hooks:: Hooks for user-defined commands
21053 * Command Files:: How to write scripts of commands to be stored in a file
21054 * Output:: Commands for controlled output
21058 @subsection User-defined Commands
21060 @cindex user-defined command
21061 @cindex arguments, to user-defined commands
21062 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
21063 which you assign a new name as a command. This is done with the
21064 @code{define} command. User commands may accept up to 10 arguments
21065 separated by whitespace. Arguments are accessed within the user command
21066 via @code{$arg0@dots{}$arg9}. A trivial example:
21070 print $arg0 + $arg1 + $arg2
21075 To execute the command use:
21082 This defines the command @code{adder}, which prints the sum of
21083 its three arguments. Note the arguments are text substitutions, so they may
21084 reference variables, use complex expressions, or even perform inferior
21087 @cindex argument count in user-defined commands
21088 @cindex how many arguments (user-defined commands)
21089 In addition, @code{$argc} may be used to find out how many arguments have
21090 been passed. This expands to a number in the range 0@dots{}10.
21095 print $arg0 + $arg1
21098 print $arg0 + $arg1 + $arg2
21106 @item define @var{commandname}
21107 Define a command named @var{commandname}. If there is already a command
21108 by that name, you are asked to confirm that you want to redefine it.
21109 @var{commandname} may be a bare command name consisting of letters,
21110 numbers, dashes, and underscores. It may also start with any predefined
21111 prefix command. For example, @samp{define target my-target} creates
21112 a user-defined @samp{target my-target} command.
21114 The definition of the command is made up of other @value{GDBN} command lines,
21115 which are given following the @code{define} command. The end of these
21116 commands is marked by a line containing @code{end}.
21119 @kindex end@r{ (user-defined commands)}
21120 @item document @var{commandname}
21121 Document the user-defined command @var{commandname}, so that it can be
21122 accessed by @code{help}. The command @var{commandname} must already be
21123 defined. This command reads lines of documentation just as @code{define}
21124 reads the lines of the command definition, ending with @code{end}.
21125 After the @code{document} command is finished, @code{help} on command
21126 @var{commandname} displays the documentation you have written.
21128 You may use the @code{document} command again to change the
21129 documentation of a command. Redefining the command with @code{define}
21130 does not change the documentation.
21132 @kindex dont-repeat
21133 @cindex don't repeat command
21135 Used inside a user-defined command, this tells @value{GDBN} that this
21136 command should not be repeated when the user hits @key{RET}
21137 (@pxref{Command Syntax, repeat last command}).
21139 @kindex help user-defined
21140 @item help user-defined
21141 List all user-defined commands and all python commands defined in class
21142 COMAND_USER. The first line of the documentation or docstring is
21147 @itemx show user @var{commandname}
21148 Display the @value{GDBN} commands used to define @var{commandname} (but
21149 not its documentation). If no @var{commandname} is given, display the
21150 definitions for all user-defined commands.
21151 This does not work for user-defined python commands.
21153 @cindex infinite recursion in user-defined commands
21154 @kindex show max-user-call-depth
21155 @kindex set max-user-call-depth
21156 @item show max-user-call-depth
21157 @itemx set max-user-call-depth
21158 The value of @code{max-user-call-depth} controls how many recursion
21159 levels are allowed in user-defined commands before @value{GDBN} suspects an
21160 infinite recursion and aborts the command.
21161 This does not apply to user-defined python commands.
21164 In addition to the above commands, user-defined commands frequently
21165 use control flow commands, described in @ref{Command Files}.
21167 When user-defined commands are executed, the
21168 commands of the definition are not printed. An error in any command
21169 stops execution of the user-defined command.
21171 If used interactively, commands that would ask for confirmation proceed
21172 without asking when used inside a user-defined command. Many @value{GDBN}
21173 commands that normally print messages to say what they are doing omit the
21174 messages when used in a user-defined command.
21177 @subsection User-defined Command Hooks
21178 @cindex command hooks
21179 @cindex hooks, for commands
21180 @cindex hooks, pre-command
21183 You may define @dfn{hooks}, which are a special kind of user-defined
21184 command. Whenever you run the command @samp{foo}, if the user-defined
21185 command @samp{hook-foo} exists, it is executed (with no arguments)
21186 before that command.
21188 @cindex hooks, post-command
21190 A hook may also be defined which is run after the command you executed.
21191 Whenever you run the command @samp{foo}, if the user-defined command
21192 @samp{hookpost-foo} exists, it is executed (with no arguments) after
21193 that command. Post-execution hooks may exist simultaneously with
21194 pre-execution hooks, for the same command.
21196 It is valid for a hook to call the command which it hooks. If this
21197 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
21199 @c It would be nice if hookpost could be passed a parameter indicating
21200 @c if the command it hooks executed properly or not. FIXME!
21202 @kindex stop@r{, a pseudo-command}
21203 In addition, a pseudo-command, @samp{stop} exists. Defining
21204 (@samp{hook-stop}) makes the associated commands execute every time
21205 execution stops in your program: before breakpoint commands are run,
21206 displays are printed, or the stack frame is printed.
21208 For example, to ignore @code{SIGALRM} signals while
21209 single-stepping, but treat them normally during normal execution,
21214 handle SIGALRM nopass
21218 handle SIGALRM pass
21221 define hook-continue
21222 handle SIGALRM pass
21226 As a further example, to hook at the beginning and end of the @code{echo}
21227 command, and to add extra text to the beginning and end of the message,
21235 define hookpost-echo
21239 (@value{GDBP}) echo Hello World
21240 <<<---Hello World--->>>
21245 You can define a hook for any single-word command in @value{GDBN}, but
21246 not for command aliases; you should define a hook for the basic command
21247 name, e.g.@: @code{backtrace} rather than @code{bt}.
21248 @c FIXME! So how does Joe User discover whether a command is an alias
21250 You can hook a multi-word command by adding @code{hook-} or
21251 @code{hookpost-} to the last word of the command, e.g.@:
21252 @samp{define target hook-remote} to add a hook to @samp{target remote}.
21254 If an error occurs during the execution of your hook, execution of
21255 @value{GDBN} commands stops and @value{GDBN} issues a prompt
21256 (before the command that you actually typed had a chance to run).
21258 If you try to define a hook which does not match any known command, you
21259 get a warning from the @code{define} command.
21261 @node Command Files
21262 @subsection Command Files
21264 @cindex command files
21265 @cindex scripting commands
21266 A command file for @value{GDBN} is a text file made of lines that are
21267 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
21268 also be included. An empty line in a command file does nothing; it
21269 does not mean to repeat the last command, as it would from the
21272 You can request the execution of a command file with the @code{source}
21273 command. Note that the @code{source} command is also used to evaluate
21274 scripts that are not Command Files. The exact behavior can be configured
21275 using the @code{script-extension} setting.
21276 @xref{Extending GDB,, Extending GDB}.
21280 @cindex execute commands from a file
21281 @item source [-s] [-v] @var{filename}
21282 Execute the command file @var{filename}.
21285 The lines in a command file are generally executed sequentially,
21286 unless the order of execution is changed by one of the
21287 @emph{flow-control commands} described below. The commands are not
21288 printed as they are executed. An error in any command terminates
21289 execution of the command file and control is returned to the console.
21291 @value{GDBN} first searches for @var{filename} in the current directory.
21292 If the file is not found there, and @var{filename} does not specify a
21293 directory, then @value{GDBN} also looks for the file on the source search path
21294 (specified with the @samp{directory} command);
21295 except that @file{$cdir} is not searched because the compilation directory
21296 is not relevant to scripts.
21298 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
21299 on the search path even if @var{filename} specifies a directory.
21300 The search is done by appending @var{filename} to each element of the
21301 search path. So, for example, if @var{filename} is @file{mylib/myscript}
21302 and the search path contains @file{/home/user} then @value{GDBN} will
21303 look for the script @file{/home/user/mylib/myscript}.
21304 The search is also done if @var{filename} is an absolute path.
21305 For example, if @var{filename} is @file{/tmp/myscript} and
21306 the search path contains @file{/home/user} then @value{GDBN} will
21307 look for the script @file{/home/user/tmp/myscript}.
21308 For DOS-like systems, if @var{filename} contains a drive specification,
21309 it is stripped before concatenation. For example, if @var{filename} is
21310 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
21311 will look for the script @file{c:/tmp/myscript}.
21313 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
21314 each command as it is executed. The option must be given before
21315 @var{filename}, and is interpreted as part of the filename anywhere else.
21317 Commands that would ask for confirmation if used interactively proceed
21318 without asking when used in a command file. Many @value{GDBN} commands that
21319 normally print messages to say what they are doing omit the messages
21320 when called from command files.
21322 @value{GDBN} also accepts command input from standard input. In this
21323 mode, normal output goes to standard output and error output goes to
21324 standard error. Errors in a command file supplied on standard input do
21325 not terminate execution of the command file---execution continues with
21329 gdb < cmds > log 2>&1
21332 (The syntax above will vary depending on the shell used.) This example
21333 will execute commands from the file @file{cmds}. All output and errors
21334 would be directed to @file{log}.
21336 Since commands stored on command files tend to be more general than
21337 commands typed interactively, they frequently need to deal with
21338 complicated situations, such as different or unexpected values of
21339 variables and symbols, changes in how the program being debugged is
21340 built, etc. @value{GDBN} provides a set of flow-control commands to
21341 deal with these complexities. Using these commands, you can write
21342 complex scripts that loop over data structures, execute commands
21343 conditionally, etc.
21350 This command allows to include in your script conditionally executed
21351 commands. The @code{if} command takes a single argument, which is an
21352 expression to evaluate. It is followed by a series of commands that
21353 are executed only if the expression is true (its value is nonzero).
21354 There can then optionally be an @code{else} line, followed by a series
21355 of commands that are only executed if the expression was false. The
21356 end of the list is marked by a line containing @code{end}.
21360 This command allows to write loops. Its syntax is similar to
21361 @code{if}: the command takes a single argument, which is an expression
21362 to evaluate, and must be followed by the commands to execute, one per
21363 line, terminated by an @code{end}. These commands are called the
21364 @dfn{body} of the loop. The commands in the body of @code{while} are
21365 executed repeatedly as long as the expression evaluates to true.
21369 This command exits the @code{while} loop in whose body it is included.
21370 Execution of the script continues after that @code{while}s @code{end}
21373 @kindex loop_continue
21374 @item loop_continue
21375 This command skips the execution of the rest of the body of commands
21376 in the @code{while} loop in whose body it is included. Execution
21377 branches to the beginning of the @code{while} loop, where it evaluates
21378 the controlling expression.
21380 @kindex end@r{ (if/else/while commands)}
21382 Terminate the block of commands that are the body of @code{if},
21383 @code{else}, or @code{while} flow-control commands.
21388 @subsection Commands for Controlled Output
21390 During the execution of a command file or a user-defined command, normal
21391 @value{GDBN} output is suppressed; the only output that appears is what is
21392 explicitly printed by the commands in the definition. This section
21393 describes three commands useful for generating exactly the output you
21398 @item echo @var{text}
21399 @c I do not consider backslash-space a standard C escape sequence
21400 @c because it is not in ANSI.
21401 Print @var{text}. Nonprinting characters can be included in
21402 @var{text} using C escape sequences, such as @samp{\n} to print a
21403 newline. @strong{No newline is printed unless you specify one.}
21404 In addition to the standard C escape sequences, a backslash followed
21405 by a space stands for a space. This is useful for displaying a
21406 string with spaces at the beginning or the end, since leading and
21407 trailing spaces are otherwise trimmed from all arguments.
21408 To print @samp{@w{ }and foo =@w{ }}, use the command
21409 @samp{echo \@w{ }and foo = \@w{ }}.
21411 A backslash at the end of @var{text} can be used, as in C, to continue
21412 the command onto subsequent lines. For example,
21415 echo This is some text\n\
21416 which is continued\n\
21417 onto several lines.\n
21420 produces the same output as
21423 echo This is some text\n
21424 echo which is continued\n
21425 echo onto several lines.\n
21429 @item output @var{expression}
21430 Print the value of @var{expression} and nothing but that value: no
21431 newlines, no @samp{$@var{nn} = }. The value is not entered in the
21432 value history either. @xref{Expressions, ,Expressions}, for more information
21435 @item output/@var{fmt} @var{expression}
21436 Print the value of @var{expression} in format @var{fmt}. You can use
21437 the same formats as for @code{print}. @xref{Output Formats,,Output
21438 Formats}, for more information.
21441 @item printf @var{template}, @var{expressions}@dots{}
21442 Print the values of one or more @var{expressions} under the control of
21443 the string @var{template}. To print several values, make
21444 @var{expressions} be a comma-separated list of individual expressions,
21445 which may be either numbers or pointers. Their values are printed as
21446 specified by @var{template}, exactly as a C program would do by
21447 executing the code below:
21450 printf (@var{template}, @var{expressions}@dots{});
21453 As in @code{C} @code{printf}, ordinary characters in @var{template}
21454 are printed verbatim, while @dfn{conversion specification} introduced
21455 by the @samp{%} character cause subsequent @var{expressions} to be
21456 evaluated, their values converted and formatted according to type and
21457 style information encoded in the conversion specifications, and then
21460 For example, you can print two values in hex like this:
21463 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
21466 @code{printf} supports all the standard @code{C} conversion
21467 specifications, including the flags and modifiers between the @samp{%}
21468 character and the conversion letter, with the following exceptions:
21472 The argument-ordering modifiers, such as @samp{2$}, are not supported.
21475 The modifier @samp{*} is not supported for specifying precision or
21479 The @samp{'} flag (for separation of digits into groups according to
21480 @code{LC_NUMERIC'}) is not supported.
21483 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
21487 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
21490 The conversion letters @samp{a} and @samp{A} are not supported.
21494 Note that the @samp{ll} type modifier is supported only if the
21495 underlying @code{C} implementation used to build @value{GDBN} supports
21496 the @code{long long int} type, and the @samp{L} type modifier is
21497 supported only if @code{long double} type is available.
21499 As in @code{C}, @code{printf} supports simple backslash-escape
21500 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
21501 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
21502 single character. Octal and hexadecimal escape sequences are not
21505 Additionally, @code{printf} supports conversion specifications for DFP
21506 (@dfn{Decimal Floating Point}) types using the following length modifiers
21507 together with a floating point specifier.
21512 @samp{H} for printing @code{Decimal32} types.
21515 @samp{D} for printing @code{Decimal64} types.
21518 @samp{DD} for printing @code{Decimal128} types.
21521 If the underlying @code{C} implementation used to build @value{GDBN} has
21522 support for the three length modifiers for DFP types, other modifiers
21523 such as width and precision will also be available for @value{GDBN} to use.
21525 In case there is no such @code{C} support, no additional modifiers will be
21526 available and the value will be printed in the standard way.
21528 Here's an example of printing DFP types using the above conversion letters:
21530 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
21534 @item eval @var{template}, @var{expressions}@dots{}
21535 Convert the values of one or more @var{expressions} under the control of
21536 the string @var{template} to a command line, and call it.
21541 @section Scripting @value{GDBN} using Python
21542 @cindex python scripting
21543 @cindex scripting with python
21545 You can script @value{GDBN} using the @uref{http://www.python.org/,
21546 Python programming language}. This feature is available only if
21547 @value{GDBN} was configured using @option{--with-python}.
21549 @cindex python directory
21550 Python scripts used by @value{GDBN} should be installed in
21551 @file{@var{data-directory}/python}, where @var{data-directory} is
21552 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
21553 This directory, known as the @dfn{python directory},
21554 is automatically added to the Python Search Path in order to allow
21555 the Python interpreter to locate all scripts installed at this location.
21557 Additionally, @value{GDBN} commands and convenience functions which
21558 are written in Python and are located in the
21559 @file{@var{data-directory}/python/gdb/command} or
21560 @file{@var{data-directory}/python/gdb/function} directories are
21561 automatically imported when @value{GDBN} starts.
21564 * Python Commands:: Accessing Python from @value{GDBN}.
21565 * Python API:: Accessing @value{GDBN} from Python.
21566 * Auto-loading:: Automatically loading Python code.
21567 * Python modules:: Python modules provided by @value{GDBN}.
21570 @node Python Commands
21571 @subsection Python Commands
21572 @cindex python commands
21573 @cindex commands to access python
21575 @value{GDBN} provides one command for accessing the Python interpreter,
21576 and one related setting:
21580 @item python @r{[}@var{code}@r{]}
21581 The @code{python} command can be used to evaluate Python code.
21583 If given an argument, the @code{python} command will evaluate the
21584 argument as a Python command. For example:
21587 (@value{GDBP}) python print 23
21591 If you do not provide an argument to @code{python}, it will act as a
21592 multi-line command, like @code{define}. In this case, the Python
21593 script is made up of subsequent command lines, given after the
21594 @code{python} command. This command list is terminated using a line
21595 containing @code{end}. For example:
21598 (@value{GDBP}) python
21600 End with a line saying just "end".
21606 @kindex set python print-stack
21607 @item set python print-stack
21608 By default, @value{GDBN} will print only the message component of a
21609 Python exception when an error occurs in a Python script. This can be
21610 controlled using @code{set python print-stack}: if @code{full}, then
21611 full Python stack printing is enabled; if @code{none}, then Python stack
21612 and message printing is disabled; if @code{message}, the default, only
21613 the message component of the error is printed.
21616 It is also possible to execute a Python script from the @value{GDBN}
21620 @item source @file{script-name}
21621 The script name must end with @samp{.py} and @value{GDBN} must be configured
21622 to recognize the script language based on filename extension using
21623 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
21625 @item python execfile ("script-name")
21626 This method is based on the @code{execfile} Python built-in function,
21627 and thus is always available.
21631 @subsection Python API
21633 @cindex programming in python
21635 @cindex python stdout
21636 @cindex python pagination
21637 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
21638 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
21639 A Python program which outputs to one of these streams may have its
21640 output interrupted by the user (@pxref{Screen Size}). In this
21641 situation, a Python @code{KeyboardInterrupt} exception is thrown.
21644 * Basic Python:: Basic Python Functions.
21645 * Exception Handling:: How Python exceptions are translated.
21646 * Values From Inferior:: Python representation of values.
21647 * Types In Python:: Python representation of types.
21648 * Pretty Printing API:: Pretty-printing values.
21649 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
21650 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
21651 * Inferiors In Python:: Python representation of inferiors (processes)
21652 * Events In Python:: Listening for events from @value{GDBN}.
21653 * Threads In Python:: Accessing inferior threads from Python.
21654 * Commands In Python:: Implementing new commands in Python.
21655 * Parameters In Python:: Adding new @value{GDBN} parameters.
21656 * Functions In Python:: Writing new convenience functions.
21657 * Progspaces In Python:: Program spaces.
21658 * Objfiles In Python:: Object files.
21659 * Frames In Python:: Accessing inferior stack frames from Python.
21660 * Blocks In Python:: Accessing frame blocks from Python.
21661 * Symbols In Python:: Python representation of symbols.
21662 * Symbol Tables In Python:: Python representation of symbol tables.
21663 * Lazy Strings In Python:: Python representation of lazy strings.
21664 * Breakpoints In Python:: Manipulating breakpoints using Python.
21665 * Finish Breakpoints in Python:: Setting Breakpoints on function return
21670 @subsubsection Basic Python
21672 @cindex python functions
21673 @cindex python module
21675 @value{GDBN} introduces a new Python module, named @code{gdb}. All
21676 methods and classes added by @value{GDBN} are placed in this module.
21677 @value{GDBN} automatically @code{import}s the @code{gdb} module for
21678 use in all scripts evaluated by the @code{python} command.
21680 @findex gdb.PYTHONDIR
21681 @defvar gdb.PYTHONDIR
21682 A string containing the python directory (@pxref{Python}).
21685 @findex gdb.execute
21686 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
21687 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
21688 If a GDB exception happens while @var{command} runs, it is
21689 translated as described in @ref{Exception Handling,,Exception Handling}.
21691 @var{from_tty} specifies whether @value{GDBN} ought to consider this
21692 command as having originated from the user invoking it interactively.
21693 It must be a boolean value. If omitted, it defaults to @code{False}.
21695 By default, any output produced by @var{command} is sent to
21696 @value{GDBN}'s standard output. If the @var{to_string} parameter is
21697 @code{True}, then output will be collected by @code{gdb.execute} and
21698 returned as a string. The default is @code{False}, in which case the
21699 return value is @code{None}. If @var{to_string} is @code{True}, the
21700 @value{GDBN} virtual terminal will be temporarily set to unlimited width
21701 and height, and its pagination will be disabled; @pxref{Screen Size}.
21704 @findex gdb.breakpoints
21705 @defun gdb.breakpoints ()
21706 Return a sequence holding all of @value{GDBN}'s breakpoints.
21707 @xref{Breakpoints In Python}, for more information.
21710 @findex gdb.parameter
21711 @defun gdb.parameter (parameter)
21712 Return the value of a @value{GDBN} parameter. @var{parameter} is a
21713 string naming the parameter to look up; @var{parameter} may contain
21714 spaces if the parameter has a multi-part name. For example,
21715 @samp{print object} is a valid parameter name.
21717 If the named parameter does not exist, this function throws a
21718 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
21719 parameter's value is converted to a Python value of the appropriate
21720 type, and returned.
21723 @findex gdb.history
21724 @defun gdb.history (number)
21725 Return a value from @value{GDBN}'s value history (@pxref{Value
21726 History}). @var{number} indicates which history element to return.
21727 If @var{number} is negative, then @value{GDBN} will take its absolute value
21728 and count backward from the last element (i.e., the most recent element) to
21729 find the value to return. If @var{number} is zero, then @value{GDBN} will
21730 return the most recent element. If the element specified by @var{number}
21731 doesn't exist in the value history, a @code{gdb.error} exception will be
21734 If no exception is raised, the return value is always an instance of
21735 @code{gdb.Value} (@pxref{Values From Inferior}).
21738 @findex gdb.parse_and_eval
21739 @defun gdb.parse_and_eval (expression)
21740 Parse @var{expression} as an expression in the current language,
21741 evaluate it, and return the result as a @code{gdb.Value}.
21742 @var{expression} must be a string.
21744 This function can be useful when implementing a new command
21745 (@pxref{Commands In Python}), as it provides a way to parse the
21746 command's argument as an expression. It is also useful simply to
21747 compute values, for example, it is the only way to get the value of a
21748 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
21751 @findex gdb.post_event
21752 @defun gdb.post_event (event)
21753 Put @var{event}, a callable object taking no arguments, into
21754 @value{GDBN}'s internal event queue. This callable will be invoked at
21755 some later point, during @value{GDBN}'s event processing. Events
21756 posted using @code{post_event} will be run in the order in which they
21757 were posted; however, there is no way to know when they will be
21758 processed relative to other events inside @value{GDBN}.
21760 @value{GDBN} is not thread-safe. If your Python program uses multiple
21761 threads, you must be careful to only call @value{GDBN}-specific
21762 functions in the main @value{GDBN} thread. @code{post_event} ensures
21766 (@value{GDBP}) python
21770 > def __init__(self, message):
21771 > self.message = message;
21772 > def __call__(self):
21773 > gdb.write(self.message)
21775 >class MyThread1 (threading.Thread):
21777 > gdb.post_event(Writer("Hello "))
21779 >class MyThread2 (threading.Thread):
21781 > gdb.post_event(Writer("World\n"))
21783 >MyThread1().start()
21784 >MyThread2().start()
21786 (@value{GDBP}) Hello World
21791 @defun gdb.write (string @r{[}, stream{]})
21792 Print a string to @value{GDBN}'s paginated output stream. The
21793 optional @var{stream} determines the stream to print to. The default
21794 stream is @value{GDBN}'s standard output stream. Possible stream
21801 @value{GDBN}'s standard output stream.
21806 @value{GDBN}'s standard error stream.
21811 @value{GDBN}'s log stream (@pxref{Logging Output}).
21814 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
21815 call this function and will automatically direct the output to the
21820 @defun gdb.flush ()
21821 Flush the buffer of a @value{GDBN} paginated stream so that the
21822 contents are displayed immediately. @value{GDBN} will flush the
21823 contents of a stream automatically when it encounters a newline in the
21824 buffer. The optional @var{stream} determines the stream to flush. The
21825 default stream is @value{GDBN}'s standard output stream. Possible
21832 @value{GDBN}'s standard output stream.
21837 @value{GDBN}'s standard error stream.
21842 @value{GDBN}'s log stream (@pxref{Logging Output}).
21846 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
21847 call this function for the relevant stream.
21850 @findex gdb.target_charset
21851 @defun gdb.target_charset ()
21852 Return the name of the current target character set (@pxref{Character
21853 Sets}). This differs from @code{gdb.parameter('target-charset')} in
21854 that @samp{auto} is never returned.
21857 @findex gdb.target_wide_charset
21858 @defun gdb.target_wide_charset ()
21859 Return the name of the current target wide character set
21860 (@pxref{Character Sets}). This differs from
21861 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
21865 @findex gdb.solib_name
21866 @defun gdb.solib_name (address)
21867 Return the name of the shared library holding the given @var{address}
21868 as a string, or @code{None}.
21871 @findex gdb.decode_line
21872 @defun gdb.decode_line @r{[}expression@r{]}
21873 Return locations of the line specified by @var{expression}, or of the
21874 current line if no argument was given. This function returns a Python
21875 tuple containing two elements. The first element contains a string
21876 holding any unparsed section of @var{expression} (or @code{None} if
21877 the expression has been fully parsed). The second element contains
21878 either @code{None} or another tuple that contains all the locations
21879 that match the expression represented as @code{gdb.Symtab_and_line}
21880 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
21881 provided, it is decoded the way that @value{GDBN}'s inbuilt
21882 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
21885 @defun gdb.prompt_hook (current_prompt)
21886 @anchor{prompt_hook}
21888 If @var{prompt_hook} is callable, @value{GDBN} will call the method
21889 assigned to this operation before a prompt is displayed by
21892 The parameter @code{current_prompt} contains the current @value{GDBN}
21893 prompt. This method must return a Python string, or @code{None}. If
21894 a string is returned, the @value{GDBN} prompt will be set to that
21895 string. If @code{None} is returned, @value{GDBN} will continue to use
21896 the current prompt.
21898 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
21899 such as those used by readline for command input, and annotation
21900 related prompts are prohibited from being changed.
21903 @node Exception Handling
21904 @subsubsection Exception Handling
21905 @cindex python exceptions
21906 @cindex exceptions, python
21908 When executing the @code{python} command, Python exceptions
21909 uncaught within the Python code are translated to calls to
21910 @value{GDBN} error-reporting mechanism. If the command that called
21911 @code{python} does not handle the error, @value{GDBN} will
21912 terminate it and print an error message containing the Python
21913 exception name, the associated value, and the Python call stack
21914 backtrace at the point where the exception was raised. Example:
21917 (@value{GDBP}) python print foo
21918 Traceback (most recent call last):
21919 File "<string>", line 1, in <module>
21920 NameError: name 'foo' is not defined
21923 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
21924 Python code are converted to Python exceptions. The type of the
21925 Python exception depends on the error.
21929 This is the base class for most exceptions generated by @value{GDBN}.
21930 It is derived from @code{RuntimeError}, for compatibility with earlier
21931 versions of @value{GDBN}.
21933 If an error occurring in @value{GDBN} does not fit into some more
21934 specific category, then the generated exception will have this type.
21936 @item gdb.MemoryError
21937 This is a subclass of @code{gdb.error} which is thrown when an
21938 operation tried to access invalid memory in the inferior.
21940 @item KeyboardInterrupt
21941 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
21942 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
21945 In all cases, your exception handler will see the @value{GDBN} error
21946 message as its value and the Python call stack backtrace at the Python
21947 statement closest to where the @value{GDBN} error occured as the
21950 @findex gdb.GdbError
21951 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
21952 it is useful to be able to throw an exception that doesn't cause a
21953 traceback to be printed. For example, the user may have invoked the
21954 command incorrectly. Use the @code{gdb.GdbError} exception
21955 to handle this case. Example:
21959 >class HelloWorld (gdb.Command):
21960 > """Greet the whole world."""
21961 > def __init__ (self):
21962 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
21963 > def invoke (self, args, from_tty):
21964 > argv = gdb.string_to_argv (args)
21965 > if len (argv) != 0:
21966 > raise gdb.GdbError ("hello-world takes no arguments")
21967 > print "Hello, World!"
21970 (gdb) hello-world 42
21971 hello-world takes no arguments
21974 @node Values From Inferior
21975 @subsubsection Values From Inferior
21976 @cindex values from inferior, with Python
21977 @cindex python, working with values from inferior
21979 @cindex @code{gdb.Value}
21980 @value{GDBN} provides values it obtains from the inferior program in
21981 an object of type @code{gdb.Value}. @value{GDBN} uses this object
21982 for its internal bookkeeping of the inferior's values, and for
21983 fetching values when necessary.
21985 Inferior values that are simple scalars can be used directly in
21986 Python expressions that are valid for the value's data type. Here's
21987 an example for an integer or floating-point value @code{some_val}:
21994 As result of this, @code{bar} will also be a @code{gdb.Value} object
21995 whose values are of the same type as those of @code{some_val}.
21997 Inferior values that are structures or instances of some class can
21998 be accessed using the Python @dfn{dictionary syntax}. For example, if
21999 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
22000 can access its @code{foo} element with:
22003 bar = some_val['foo']
22006 Again, @code{bar} will also be a @code{gdb.Value} object.
22008 A @code{gdb.Value} that represents a function can be executed via
22009 inferior function call. Any arguments provided to the call must match
22010 the function's prototype, and must be provided in the order specified
22013 For example, @code{some_val} is a @code{gdb.Value} instance
22014 representing a function that takes two integers as arguments. To
22015 execute this function, call it like so:
22018 result = some_val (10,20)
22021 Any values returned from a function call will be stored as a
22024 The following attributes are provided:
22027 @defvar Value.address
22028 If this object is addressable, this read-only attribute holds a
22029 @code{gdb.Value} object representing the address. Otherwise,
22030 this attribute holds @code{None}.
22033 @cindex optimized out value in Python
22034 @defvar Value.is_optimized_out
22035 This read-only boolean attribute is true if the compiler optimized out
22036 this value, thus it is not available for fetching from the inferior.
22040 The type of this @code{gdb.Value}. The value of this attribute is a
22041 @code{gdb.Type} object (@pxref{Types In Python}).
22044 @defvar Value.dynamic_type
22045 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
22046 type information (@acronym{RTTI}) to determine the dynamic type of the
22047 value. If this value is of class type, it will return the class in
22048 which the value is embedded, if any. If this value is of pointer or
22049 reference to a class type, it will compute the dynamic type of the
22050 referenced object, and return a pointer or reference to that type,
22051 respectively. In all other cases, it will return the value's static
22054 Note that this feature will only work when debugging a C@t{++} program
22055 that includes @acronym{RTTI} for the object in question. Otherwise,
22056 it will just return the static type of the value as in @kbd{ptype foo}
22057 (@pxref{Symbols, ptype}).
22060 @defvar Value.is_lazy
22061 The value of this read-only boolean attribute is @code{True} if this
22062 @code{gdb.Value} has not yet been fetched from the inferior.
22063 @value{GDBN} does not fetch values until necessary, for efficiency.
22067 myval = gdb.parse_and_eval ('somevar')
22070 The value of @code{somevar} is not fetched at this time. It will be
22071 fetched when the value is needed, or when the @code{fetch_lazy}
22076 The following methods are provided:
22079 @defun Value.__init__ (@var{val})
22080 Many Python values can be converted directly to a @code{gdb.Value} via
22081 this object initializer. Specifically:
22084 @item Python boolean
22085 A Python boolean is converted to the boolean type from the current
22088 @item Python integer
22089 A Python integer is converted to the C @code{long} type for the
22090 current architecture.
22093 A Python long is converted to the C @code{long long} type for the
22094 current architecture.
22097 A Python float is converted to the C @code{double} type for the
22098 current architecture.
22100 @item Python string
22101 A Python string is converted to a target string, using the current
22104 @item @code{gdb.Value}
22105 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
22107 @item @code{gdb.LazyString}
22108 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
22109 Python}), then the lazy string's @code{value} method is called, and
22110 its result is used.
22114 @defun Value.cast (type)
22115 Return a new instance of @code{gdb.Value} that is the result of
22116 casting this instance to the type described by @var{type}, which must
22117 be a @code{gdb.Type} object. If the cast cannot be performed for some
22118 reason, this method throws an exception.
22121 @defun Value.dereference ()
22122 For pointer data types, this method returns a new @code{gdb.Value} object
22123 whose contents is the object pointed to by the pointer. For example, if
22124 @code{foo} is a C pointer to an @code{int}, declared in your C program as
22131 then you can use the corresponding @code{gdb.Value} to access what
22132 @code{foo} points to like this:
22135 bar = foo.dereference ()
22138 The result @code{bar} will be a @code{gdb.Value} object holding the
22139 value pointed to by @code{foo}.
22142 @defun Value.dynamic_cast (type)
22143 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
22144 operator were used. Consult a C@t{++} reference for details.
22147 @defun Value.reinterpret_cast (type)
22148 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
22149 operator were used. Consult a C@t{++} reference for details.
22152 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
22153 If this @code{gdb.Value} represents a string, then this method
22154 converts the contents to a Python string. Otherwise, this method will
22155 throw an exception.
22157 Strings are recognized in a language-specific way; whether a given
22158 @code{gdb.Value} represents a string is determined by the current
22161 For C-like languages, a value is a string if it is a pointer to or an
22162 array of characters or ints. The string is assumed to be terminated
22163 by a zero of the appropriate width. However if the optional length
22164 argument is given, the string will be converted to that given length,
22165 ignoring any embedded zeros that the string may contain.
22167 If the optional @var{encoding} argument is given, it must be a string
22168 naming the encoding of the string in the @code{gdb.Value}, such as
22169 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
22170 the same encodings as the corresponding argument to Python's
22171 @code{string.decode} method, and the Python codec machinery will be used
22172 to convert the string. If @var{encoding} is not given, or if
22173 @var{encoding} is the empty string, then either the @code{target-charset}
22174 (@pxref{Character Sets}) will be used, or a language-specific encoding
22175 will be used, if the current language is able to supply one.
22177 The optional @var{errors} argument is the same as the corresponding
22178 argument to Python's @code{string.decode} method.
22180 If the optional @var{length} argument is given, the string will be
22181 fetched and converted to the given length.
22184 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
22185 If this @code{gdb.Value} represents a string, then this method
22186 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
22187 In Python}). Otherwise, this method will throw an exception.
22189 If the optional @var{encoding} argument is given, it must be a string
22190 naming the encoding of the @code{gdb.LazyString}. Some examples are:
22191 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
22192 @var{encoding} argument is an encoding that @value{GDBN} does
22193 recognize, @value{GDBN} will raise an error.
22195 When a lazy string is printed, the @value{GDBN} encoding machinery is
22196 used to convert the string during printing. If the optional
22197 @var{encoding} argument is not provided, or is an empty string,
22198 @value{GDBN} will automatically select the encoding most suitable for
22199 the string type. For further information on encoding in @value{GDBN}
22200 please see @ref{Character Sets}.
22202 If the optional @var{length} argument is given, the string will be
22203 fetched and encoded to the length of characters specified. If
22204 the @var{length} argument is not provided, the string will be fetched
22205 and encoded until a null of appropriate width is found.
22208 @defun Value.fetch_lazy ()
22209 If the @code{gdb.Value} object is currently a lazy value
22210 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
22211 fetched from the inferior. Any errors that occur in the process
22212 will produce a Python exception.
22214 If the @code{gdb.Value} object is not a lazy value, this method
22217 This method does not return a value.
22222 @node Types In Python
22223 @subsubsection Types In Python
22224 @cindex types in Python
22225 @cindex Python, working with types
22228 @value{GDBN} represents types from the inferior using the class
22231 The following type-related functions are available in the @code{gdb}
22234 @findex gdb.lookup_type
22235 @defun gdb.lookup_type (name @r{[}, block@r{]})
22236 This function looks up a type by name. @var{name} is the name of the
22237 type to look up. It must be a string.
22239 If @var{block} is given, then @var{name} is looked up in that scope.
22240 Otherwise, it is searched for globally.
22242 Ordinarily, this function will return an instance of @code{gdb.Type}.
22243 If the named type cannot be found, it will throw an exception.
22246 If the type is a structure or class type, or an enum type, the fields
22247 of that type can be accessed using the Python @dfn{dictionary syntax}.
22248 For example, if @code{some_type} is a @code{gdb.Type} instance holding
22249 a structure type, you can access its @code{foo} field with:
22252 bar = some_type['foo']
22255 @code{bar} will be a @code{gdb.Field} object; see below under the
22256 description of the @code{Type.fields} method for a description of the
22257 @code{gdb.Field} class.
22259 An instance of @code{Type} has the following attributes:
22263 The type code for this type. The type code will be one of the
22264 @code{TYPE_CODE_} constants defined below.
22267 @defvar Type.sizeof
22268 The size of this type, in target @code{char} units. Usually, a
22269 target's @code{char} type will be an 8-bit byte. However, on some
22270 unusual platforms, this type may have a different size.
22274 The tag name for this type. The tag name is the name after
22275 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
22276 languages have this concept. If this type has no tag name, then
22277 @code{None} is returned.
22281 The following methods are provided:
22284 @defun Type.fields ()
22285 For structure and union types, this method returns the fields. Range
22286 types have two fields, the minimum and maximum values. Enum types
22287 have one field per enum constant. Function and method types have one
22288 field per parameter. The base types of C@t{++} classes are also
22289 represented as fields. If the type has no fields, or does not fit
22290 into one of these categories, an empty sequence will be returned.
22292 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
22295 This attribute is not available for @code{static} fields (as in
22296 C@t{++} or Java). For non-@code{static} fields, the value is the bit
22297 position of the field. For @code{enum} fields, the value is the
22298 enumeration member's integer representation.
22301 The name of the field, or @code{None} for anonymous fields.
22304 This is @code{True} if the field is artificial, usually meaning that
22305 it was provided by the compiler and not the user. This attribute is
22306 always provided, and is @code{False} if the field is not artificial.
22308 @item is_base_class
22309 This is @code{True} if the field represents a base class of a C@t{++}
22310 structure. This attribute is always provided, and is @code{False}
22311 if the field is not a base class of the type that is the argument of
22312 @code{fields}, or if that type was not a C@t{++} class.
22315 If the field is packed, or is a bitfield, then this will have a
22316 non-zero value, which is the size of the field in bits. Otherwise,
22317 this will be zero; in this case the field's size is given by its type.
22320 The type of the field. This is usually an instance of @code{Type},
22321 but it can be @code{None} in some situations.
22325 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
22326 Return a new @code{gdb.Type} object which represents an array of this
22327 type. If one argument is given, it is the inclusive upper bound of
22328 the array; in this case the lower bound is zero. If two arguments are
22329 given, the first argument is the lower bound of the array, and the
22330 second argument is the upper bound of the array. An array's length
22331 must not be negative, but the bounds can be.
22334 @defun Type.const ()
22335 Return a new @code{gdb.Type} object which represents a
22336 @code{const}-qualified variant of this type.
22339 @defun Type.volatile ()
22340 Return a new @code{gdb.Type} object which represents a
22341 @code{volatile}-qualified variant of this type.
22344 @defun Type.unqualified ()
22345 Return a new @code{gdb.Type} object which represents an unqualified
22346 variant of this type. That is, the result is neither @code{const} nor
22350 @defun Type.range ()
22351 Return a Python @code{Tuple} object that contains two elements: the
22352 low bound of the argument type and the high bound of that type. If
22353 the type does not have a range, @value{GDBN} will raise a
22354 @code{gdb.error} exception (@pxref{Exception Handling}).
22357 @defun Type.reference ()
22358 Return a new @code{gdb.Type} object which represents a reference to this
22362 @defun Type.pointer ()
22363 Return a new @code{gdb.Type} object which represents a pointer to this
22367 @defun Type.strip_typedefs ()
22368 Return a new @code{gdb.Type} that represents the real type,
22369 after removing all layers of typedefs.
22372 @defun Type.target ()
22373 Return a new @code{gdb.Type} object which represents the target type
22376 For a pointer type, the target type is the type of the pointed-to
22377 object. For an array type (meaning C-like arrays), the target type is
22378 the type of the elements of the array. For a function or method type,
22379 the target type is the type of the return value. For a complex type,
22380 the target type is the type of the elements. For a typedef, the
22381 target type is the aliased type.
22383 If the type does not have a target, this method will throw an
22387 @defun Type.template_argument (n @r{[}, block@r{]})
22388 If this @code{gdb.Type} is an instantiation of a template, this will
22389 return a new @code{gdb.Type} which represents the type of the
22390 @var{n}th template argument.
22392 If this @code{gdb.Type} is not a template type, this will throw an
22393 exception. Ordinarily, only C@t{++} code will have template types.
22395 If @var{block} is given, then @var{name} is looked up in that scope.
22396 Otherwise, it is searched for globally.
22401 Each type has a code, which indicates what category this type falls
22402 into. The available type categories are represented by constants
22403 defined in the @code{gdb} module:
22406 @findex TYPE_CODE_PTR
22407 @findex gdb.TYPE_CODE_PTR
22408 @item gdb.TYPE_CODE_PTR
22409 The type is a pointer.
22411 @findex TYPE_CODE_ARRAY
22412 @findex gdb.TYPE_CODE_ARRAY
22413 @item gdb.TYPE_CODE_ARRAY
22414 The type is an array.
22416 @findex TYPE_CODE_STRUCT
22417 @findex gdb.TYPE_CODE_STRUCT
22418 @item gdb.TYPE_CODE_STRUCT
22419 The type is a structure.
22421 @findex TYPE_CODE_UNION
22422 @findex gdb.TYPE_CODE_UNION
22423 @item gdb.TYPE_CODE_UNION
22424 The type is a union.
22426 @findex TYPE_CODE_ENUM
22427 @findex gdb.TYPE_CODE_ENUM
22428 @item gdb.TYPE_CODE_ENUM
22429 The type is an enum.
22431 @findex TYPE_CODE_FLAGS
22432 @findex gdb.TYPE_CODE_FLAGS
22433 @item gdb.TYPE_CODE_FLAGS
22434 A bit flags type, used for things such as status registers.
22436 @findex TYPE_CODE_FUNC
22437 @findex gdb.TYPE_CODE_FUNC
22438 @item gdb.TYPE_CODE_FUNC
22439 The type is a function.
22441 @findex TYPE_CODE_INT
22442 @findex gdb.TYPE_CODE_INT
22443 @item gdb.TYPE_CODE_INT
22444 The type is an integer type.
22446 @findex TYPE_CODE_FLT
22447 @findex gdb.TYPE_CODE_FLT
22448 @item gdb.TYPE_CODE_FLT
22449 A floating point type.
22451 @findex TYPE_CODE_VOID
22452 @findex gdb.TYPE_CODE_VOID
22453 @item gdb.TYPE_CODE_VOID
22454 The special type @code{void}.
22456 @findex TYPE_CODE_SET
22457 @findex gdb.TYPE_CODE_SET
22458 @item gdb.TYPE_CODE_SET
22461 @findex TYPE_CODE_RANGE
22462 @findex gdb.TYPE_CODE_RANGE
22463 @item gdb.TYPE_CODE_RANGE
22464 A range type, that is, an integer type with bounds.
22466 @findex TYPE_CODE_STRING
22467 @findex gdb.TYPE_CODE_STRING
22468 @item gdb.TYPE_CODE_STRING
22469 A string type. Note that this is only used for certain languages with
22470 language-defined string types; C strings are not represented this way.
22472 @findex TYPE_CODE_BITSTRING
22473 @findex gdb.TYPE_CODE_BITSTRING
22474 @item gdb.TYPE_CODE_BITSTRING
22477 @findex TYPE_CODE_ERROR
22478 @findex gdb.TYPE_CODE_ERROR
22479 @item gdb.TYPE_CODE_ERROR
22480 An unknown or erroneous type.
22482 @findex TYPE_CODE_METHOD
22483 @findex gdb.TYPE_CODE_METHOD
22484 @item gdb.TYPE_CODE_METHOD
22485 A method type, as found in C@t{++} or Java.
22487 @findex TYPE_CODE_METHODPTR
22488 @findex gdb.TYPE_CODE_METHODPTR
22489 @item gdb.TYPE_CODE_METHODPTR
22490 A pointer-to-member-function.
22492 @findex TYPE_CODE_MEMBERPTR
22493 @findex gdb.TYPE_CODE_MEMBERPTR
22494 @item gdb.TYPE_CODE_MEMBERPTR
22495 A pointer-to-member.
22497 @findex TYPE_CODE_REF
22498 @findex gdb.TYPE_CODE_REF
22499 @item gdb.TYPE_CODE_REF
22502 @findex TYPE_CODE_CHAR
22503 @findex gdb.TYPE_CODE_CHAR
22504 @item gdb.TYPE_CODE_CHAR
22507 @findex TYPE_CODE_BOOL
22508 @findex gdb.TYPE_CODE_BOOL
22509 @item gdb.TYPE_CODE_BOOL
22512 @findex TYPE_CODE_COMPLEX
22513 @findex gdb.TYPE_CODE_COMPLEX
22514 @item gdb.TYPE_CODE_COMPLEX
22515 A complex float type.
22517 @findex TYPE_CODE_TYPEDEF
22518 @findex gdb.TYPE_CODE_TYPEDEF
22519 @item gdb.TYPE_CODE_TYPEDEF
22520 A typedef to some other type.
22522 @findex TYPE_CODE_NAMESPACE
22523 @findex gdb.TYPE_CODE_NAMESPACE
22524 @item gdb.TYPE_CODE_NAMESPACE
22525 A C@t{++} namespace.
22527 @findex TYPE_CODE_DECFLOAT
22528 @findex gdb.TYPE_CODE_DECFLOAT
22529 @item gdb.TYPE_CODE_DECFLOAT
22530 A decimal floating point type.
22532 @findex TYPE_CODE_INTERNAL_FUNCTION
22533 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
22534 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
22535 A function internal to @value{GDBN}. This is the type used to represent
22536 convenience functions.
22539 Further support for types is provided in the @code{gdb.types}
22540 Python module (@pxref{gdb.types}).
22542 @node Pretty Printing API
22543 @subsubsection Pretty Printing API
22545 An example output is provided (@pxref{Pretty Printing}).
22547 A pretty-printer is just an object that holds a value and implements a
22548 specific interface, defined here.
22550 @defun pretty_printer.children (self)
22551 @value{GDBN} will call this method on a pretty-printer to compute the
22552 children of the pretty-printer's value.
22554 This method must return an object conforming to the Python iterator
22555 protocol. Each item returned by the iterator must be a tuple holding
22556 two elements. The first element is the ``name'' of the child; the
22557 second element is the child's value. The value can be any Python
22558 object which is convertible to a @value{GDBN} value.
22560 This method is optional. If it does not exist, @value{GDBN} will act
22561 as though the value has no children.
22564 @defun pretty_printer.display_hint (self)
22565 The CLI may call this method and use its result to change the
22566 formatting of a value. The result will also be supplied to an MI
22567 consumer as a @samp{displayhint} attribute of the variable being
22570 This method is optional. If it does exist, this method must return a
22573 Some display hints are predefined by @value{GDBN}:
22577 Indicate that the object being printed is ``array-like''. The CLI
22578 uses this to respect parameters such as @code{set print elements} and
22579 @code{set print array}.
22582 Indicate that the object being printed is ``map-like'', and that the
22583 children of this value can be assumed to alternate between keys and
22587 Indicate that the object being printed is ``string-like''. If the
22588 printer's @code{to_string} method returns a Python string of some
22589 kind, then @value{GDBN} will call its internal language-specific
22590 string-printing function to format the string. For the CLI this means
22591 adding quotation marks, possibly escaping some characters, respecting
22592 @code{set print elements}, and the like.
22596 @defun pretty_printer.to_string (self)
22597 @value{GDBN} will call this method to display the string
22598 representation of the value passed to the object's constructor.
22600 When printing from the CLI, if the @code{to_string} method exists,
22601 then @value{GDBN} will prepend its result to the values returned by
22602 @code{children}. Exactly how this formatting is done is dependent on
22603 the display hint, and may change as more hints are added. Also,
22604 depending on the print settings (@pxref{Print Settings}), the CLI may
22605 print just the result of @code{to_string} in a stack trace, omitting
22606 the result of @code{children}.
22608 If this method returns a string, it is printed verbatim.
22610 Otherwise, if this method returns an instance of @code{gdb.Value},
22611 then @value{GDBN} prints this value. This may result in a call to
22612 another pretty-printer.
22614 If instead the method returns a Python value which is convertible to a
22615 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
22616 the resulting value. Again, this may result in a call to another
22617 pretty-printer. Python scalars (integers, floats, and booleans) and
22618 strings are convertible to @code{gdb.Value}; other types are not.
22620 Finally, if this method returns @code{None} then no further operations
22621 are peformed in this method and nothing is printed.
22623 If the result is not one of these types, an exception is raised.
22626 @value{GDBN} provides a function which can be used to look up the
22627 default pretty-printer for a @code{gdb.Value}:
22629 @findex gdb.default_visualizer
22630 @defun gdb.default_visualizer (value)
22631 This function takes a @code{gdb.Value} object as an argument. If a
22632 pretty-printer for this value exists, then it is returned. If no such
22633 printer exists, then this returns @code{None}.
22636 @node Selecting Pretty-Printers
22637 @subsubsection Selecting Pretty-Printers
22639 The Python list @code{gdb.pretty_printers} contains an array of
22640 functions or callable objects that have been registered via addition
22641 as a pretty-printer. Printers in this list are called @code{global}
22642 printers, they're available when debugging all inferiors.
22643 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
22644 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
22647 Each function on these lists is passed a single @code{gdb.Value}
22648 argument and should return a pretty-printer object conforming to the
22649 interface definition above (@pxref{Pretty Printing API}). If a function
22650 cannot create a pretty-printer for the value, it should return
22653 @value{GDBN} first checks the @code{pretty_printers} attribute of each
22654 @code{gdb.Objfile} in the current program space and iteratively calls
22655 each enabled lookup routine in the list for that @code{gdb.Objfile}
22656 until it receives a pretty-printer object.
22657 If no pretty-printer is found in the objfile lists, @value{GDBN} then
22658 searches the pretty-printer list of the current program space,
22659 calling each enabled function until an object is returned.
22660 After these lists have been exhausted, it tries the global
22661 @code{gdb.pretty_printers} list, again calling each enabled function until an
22662 object is returned.
22664 The order in which the objfiles are searched is not specified. For a
22665 given list, functions are always invoked from the head of the list,
22666 and iterated over sequentially until the end of the list, or a printer
22667 object is returned.
22669 For various reasons a pretty-printer may not work.
22670 For example, the underlying data structure may have changed and
22671 the pretty-printer is out of date.
22673 The consequences of a broken pretty-printer are severe enough that
22674 @value{GDBN} provides support for enabling and disabling individual
22675 printers. For example, if @code{print frame-arguments} is on,
22676 a backtrace can become highly illegible if any argument is printed
22677 with a broken printer.
22679 Pretty-printers are enabled and disabled by attaching an @code{enabled}
22680 attribute to the registered function or callable object. If this attribute
22681 is present and its value is @code{False}, the printer is disabled, otherwise
22682 the printer is enabled.
22684 @node Writing a Pretty-Printer
22685 @subsubsection Writing a Pretty-Printer
22686 @cindex writing a pretty-printer
22688 A pretty-printer consists of two parts: a lookup function to detect
22689 if the type is supported, and the printer itself.
22691 Here is an example showing how a @code{std::string} printer might be
22692 written. @xref{Pretty Printing API}, for details on the API this class
22696 class StdStringPrinter(object):
22697 "Print a std::string"
22699 def __init__(self, val):
22702 def to_string(self):
22703 return self.val['_M_dataplus']['_M_p']
22705 def display_hint(self):
22709 And here is an example showing how a lookup function for the printer
22710 example above might be written.
22713 def str_lookup_function(val):
22714 lookup_tag = val.type.tag
22715 if lookup_tag == None:
22717 regex = re.compile("^std::basic_string<char,.*>$")
22718 if regex.match(lookup_tag):
22719 return StdStringPrinter(val)
22723 The example lookup function extracts the value's type, and attempts to
22724 match it to a type that it can pretty-print. If it is a type the
22725 printer can pretty-print, it will return a printer object. If not, it
22726 returns @code{None}.
22728 We recommend that you put your core pretty-printers into a Python
22729 package. If your pretty-printers are for use with a library, we
22730 further recommend embedding a version number into the package name.
22731 This practice will enable @value{GDBN} to load multiple versions of
22732 your pretty-printers at the same time, because they will have
22735 You should write auto-loaded code (@pxref{Auto-loading}) such that it
22736 can be evaluated multiple times without changing its meaning. An
22737 ideal auto-load file will consist solely of @code{import}s of your
22738 printer modules, followed by a call to a register pretty-printers with
22739 the current objfile.
22741 Taken as a whole, this approach will scale nicely to multiple
22742 inferiors, each potentially using a different library version.
22743 Embedding a version number in the Python package name will ensure that
22744 @value{GDBN} is able to load both sets of printers simultaneously.
22745 Then, because the search for pretty-printers is done by objfile, and
22746 because your auto-loaded code took care to register your library's
22747 printers with a specific objfile, @value{GDBN} will find the correct
22748 printers for the specific version of the library used by each
22751 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
22752 this code might appear in @code{gdb.libstdcxx.v6}:
22755 def register_printers(objfile):
22756 objfile.pretty_printers.append(str_lookup_function)
22760 And then the corresponding contents of the auto-load file would be:
22763 import gdb.libstdcxx.v6
22764 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
22767 The previous example illustrates a basic pretty-printer.
22768 There are a few things that can be improved on.
22769 The printer doesn't have a name, making it hard to identify in a
22770 list of installed printers. The lookup function has a name, but
22771 lookup functions can have arbitrary, even identical, names.
22773 Second, the printer only handles one type, whereas a library typically has
22774 several types. One could install a lookup function for each desired type
22775 in the library, but one could also have a single lookup function recognize
22776 several types. The latter is the conventional way this is handled.
22777 If a pretty-printer can handle multiple data types, then its
22778 @dfn{subprinters} are the printers for the individual data types.
22780 The @code{gdb.printing} module provides a formal way of solving these
22781 problems (@pxref{gdb.printing}).
22782 Here is another example that handles multiple types.
22784 These are the types we are going to pretty-print:
22787 struct foo @{ int a, b; @};
22788 struct bar @{ struct foo x, y; @};
22791 Here are the printers:
22795 """Print a foo object."""
22797 def __init__(self, val):
22800 def to_string(self):
22801 return ("a=<" + str(self.val["a"]) +
22802 "> b=<" + str(self.val["b"]) + ">")
22805 """Print a bar object."""
22807 def __init__(self, val):
22810 def to_string(self):
22811 return ("x=<" + str(self.val["x"]) +
22812 "> y=<" + str(self.val["y"]) + ">")
22815 This example doesn't need a lookup function, that is handled by the
22816 @code{gdb.printing} module. Instead a function is provided to build up
22817 the object that handles the lookup.
22820 import gdb.printing
22822 def build_pretty_printer():
22823 pp = gdb.printing.RegexpCollectionPrettyPrinter(
22825 pp.add_printer('foo', '^foo$', fooPrinter)
22826 pp.add_printer('bar', '^bar$', barPrinter)
22830 And here is the autoload support:
22833 import gdb.printing
22835 gdb.printing.register_pretty_printer(
22836 gdb.current_objfile(),
22837 my_library.build_pretty_printer())
22840 Finally, when this printer is loaded into @value{GDBN}, here is the
22841 corresponding output of @samp{info pretty-printer}:
22844 (gdb) info pretty-printer
22851 @node Inferiors In Python
22852 @subsubsection Inferiors In Python
22853 @cindex inferiors in Python
22855 @findex gdb.Inferior
22856 Programs which are being run under @value{GDBN} are called inferiors
22857 (@pxref{Inferiors and Programs}). Python scripts can access
22858 information about and manipulate inferiors controlled by @value{GDBN}
22859 via objects of the @code{gdb.Inferior} class.
22861 The following inferior-related functions are available in the @code{gdb}
22864 @defun gdb.inferiors ()
22865 Return a tuple containing all inferior objects.
22868 @defun gdb.selected_inferior ()
22869 Return an object representing the current inferior.
22872 A @code{gdb.Inferior} object has the following attributes:
22875 @defvar Inferior.num
22876 ID of inferior, as assigned by GDB.
22879 @defvar Inferior.pid
22880 Process ID of the inferior, as assigned by the underlying operating
22884 @defvar Inferior.was_attached
22885 Boolean signaling whether the inferior was created using `attach', or
22886 started by @value{GDBN} itself.
22890 A @code{gdb.Inferior} object has the following methods:
22893 @defun Inferior.is_valid ()
22894 Returns @code{True} if the @code{gdb.Inferior} object is valid,
22895 @code{False} if not. A @code{gdb.Inferior} object will become invalid
22896 if the inferior no longer exists within @value{GDBN}. All other
22897 @code{gdb.Inferior} methods will throw an exception if it is invalid
22898 at the time the method is called.
22901 @defun Inferior.threads ()
22902 This method returns a tuple holding all the threads which are valid
22903 when it is called. If there are no valid threads, the method will
22904 return an empty tuple.
22907 @findex gdb.read_memory
22908 @defun Inferior.read_memory (address, length)
22909 Read @var{length} bytes of memory from the inferior, starting at
22910 @var{address}. Returns a buffer object, which behaves much like an array
22911 or a string. It can be modified and given to the @code{gdb.write_memory}
22915 @findex gdb.write_memory
22916 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
22917 Write the contents of @var{buffer} to the inferior, starting at
22918 @var{address}. The @var{buffer} parameter must be a Python object
22919 which supports the buffer protocol, i.e., a string, an array or the
22920 object returned from @code{gdb.read_memory}. If given, @var{length}
22921 determines the number of bytes from @var{buffer} to be written.
22924 @findex gdb.search_memory
22925 @defun Inferior.search_memory (address, length, pattern)
22926 Search a region of the inferior memory starting at @var{address} with
22927 the given @var{length} using the search pattern supplied in
22928 @var{pattern}. The @var{pattern} parameter must be a Python object
22929 which supports the buffer protocol, i.e., a string, an array or the
22930 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
22931 containing the address where the pattern was found, or @code{None} if
22932 the pattern could not be found.
22936 @node Events In Python
22937 @subsubsection Events In Python
22938 @cindex inferior events in Python
22940 @value{GDBN} provides a general event facility so that Python code can be
22941 notified of various state changes, particularly changes that occur in
22944 An @dfn{event} is just an object that describes some state change. The
22945 type of the object and its attributes will vary depending on the details
22946 of the change. All the existing events are described below.
22948 In order to be notified of an event, you must register an event handler
22949 with an @dfn{event registry}. An event registry is an object in the
22950 @code{gdb.events} module which dispatches particular events. A registry
22951 provides methods to register and unregister event handlers:
22954 @defun EventRegistry.connect (object)
22955 Add the given callable @var{object} to the registry. This object will be
22956 called when an event corresponding to this registry occurs.
22959 @defun EventRegistry.disconnect (object)
22960 Remove the given @var{object} from the registry. Once removed, the object
22961 will no longer receive notifications of events.
22965 Here is an example:
22968 def exit_handler (event):
22969 print "event type: exit"
22970 print "exit code: %d" % (event.exit_code)
22972 gdb.events.exited.connect (exit_handler)
22975 In the above example we connect our handler @code{exit_handler} to the
22976 registry @code{events.exited}. Once connected, @code{exit_handler} gets
22977 called when the inferior exits. The argument @dfn{event} in this example is
22978 of type @code{gdb.ExitedEvent}. As you can see in the example the
22979 @code{ExitedEvent} object has an attribute which indicates the exit code of
22982 The following is a listing of the event registries that are available and
22983 details of the events they emit:
22988 Emits @code{gdb.ThreadEvent}.
22990 Some events can be thread specific when @value{GDBN} is running in non-stop
22991 mode. When represented in Python, these events all extend
22992 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
22993 events which are emitted by this or other modules might extend this event.
22994 Examples of these events are @code{gdb.BreakpointEvent} and
22995 @code{gdb.ContinueEvent}.
22998 @defvar ThreadEvent.inferior_thread
22999 In non-stop mode this attribute will be set to the specific thread which was
23000 involved in the emitted event. Otherwise, it will be set to @code{None}.
23004 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
23006 This event indicates that the inferior has been continued after a stop. For
23007 inherited attribute refer to @code{gdb.ThreadEvent} above.
23009 @item events.exited
23010 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
23011 @code{events.ExitedEvent} has two attributes:
23013 @defvar ExitedEvent.exit_code
23014 An integer representing the exit code, if available, which the inferior
23015 has returned. (The exit code could be unavailable if, for example,
23016 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
23017 the attribute does not exist.
23019 @defvar ExitedEvent inferior
23020 A reference to the inferior which triggered the @code{exited} event.
23025 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
23027 Indicates that the inferior has stopped. All events emitted by this registry
23028 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
23029 will indicate the stopped thread when @value{GDBN} is running in non-stop
23030 mode. Refer to @code{gdb.ThreadEvent} above for more details.
23032 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
23034 This event indicates that the inferior or one of its threads has received as
23035 signal. @code{gdb.SignalEvent} has the following attributes:
23038 @defvar SignalEvent.stop_signal
23039 A string representing the signal received by the inferior. A list of possible
23040 signal values can be obtained by running the command @code{info signals} in
23041 the @value{GDBN} command prompt.
23045 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
23047 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
23048 been hit, and has the following attributes:
23051 @defvar BreakpointEvent.breakpoints
23052 A sequence containing references to all the breakpoints (type
23053 @code{gdb.Breakpoint}) that were hit.
23054 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
23056 @defvar BreakpointEvent.breakpoint
23057 A reference to the first breakpoint that was hit.
23058 This function is maintained for backward compatibility and is now deprecated
23059 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
23063 @item events.new_objfile
23064 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
23065 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
23068 @defvar NewObjFileEvent.new_objfile
23069 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
23070 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
23076 @node Threads In Python
23077 @subsubsection Threads In Python
23078 @cindex threads in python
23080 @findex gdb.InferiorThread
23081 Python scripts can access information about, and manipulate inferior threads
23082 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
23084 The following thread-related functions are available in the @code{gdb}
23087 @findex gdb.selected_thread
23088 @defun gdb.selected_thread ()
23089 This function returns the thread object for the selected thread. If there
23090 is no selected thread, this will return @code{None}.
23093 A @code{gdb.InferiorThread} object has the following attributes:
23096 @defvar InferiorThread.name
23097 The name of the thread. If the user specified a name using
23098 @code{thread name}, then this returns that name. Otherwise, if an
23099 OS-supplied name is available, then it is returned. Otherwise, this
23100 returns @code{None}.
23102 This attribute can be assigned to. The new value must be a string
23103 object, which sets the new name, or @code{None}, which removes any
23104 user-specified thread name.
23107 @defvar InferiorThread.num
23108 ID of the thread, as assigned by GDB.
23111 @defvar InferiorThread.ptid
23112 ID of the thread, as assigned by the operating system. This attribute is a
23113 tuple containing three integers. The first is the Process ID (PID); the second
23114 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
23115 Either the LWPID or TID may be 0, which indicates that the operating system
23116 does not use that identifier.
23120 A @code{gdb.InferiorThread} object has the following methods:
23123 @defun InferiorThread.is_valid ()
23124 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
23125 @code{False} if not. A @code{gdb.InferiorThread} object will become
23126 invalid if the thread exits, or the inferior that the thread belongs
23127 is deleted. All other @code{gdb.InferiorThread} methods will throw an
23128 exception if it is invalid at the time the method is called.
23131 @defun InferiorThread.switch ()
23132 This changes @value{GDBN}'s currently selected thread to the one represented
23136 @defun InferiorThread.is_stopped ()
23137 Return a Boolean indicating whether the thread is stopped.
23140 @defun InferiorThread.is_running ()
23141 Return a Boolean indicating whether the thread is running.
23144 @defun InferiorThread.is_exited ()
23145 Return a Boolean indicating whether the thread is exited.
23149 @node Commands In Python
23150 @subsubsection Commands In Python
23152 @cindex commands in python
23153 @cindex python commands
23154 You can implement new @value{GDBN} CLI commands in Python. A CLI
23155 command is implemented using an instance of the @code{gdb.Command}
23156 class, most commonly using a subclass.
23158 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
23159 The object initializer for @code{Command} registers the new command
23160 with @value{GDBN}. This initializer is normally invoked from the
23161 subclass' own @code{__init__} method.
23163 @var{name} is the name of the command. If @var{name} consists of
23164 multiple words, then the initial words are looked for as prefix
23165 commands. In this case, if one of the prefix commands does not exist,
23166 an exception is raised.
23168 There is no support for multi-line commands.
23170 @var{command_class} should be one of the @samp{COMMAND_} constants
23171 defined below. This argument tells @value{GDBN} how to categorize the
23172 new command in the help system.
23174 @var{completer_class} is an optional argument. If given, it should be
23175 one of the @samp{COMPLETE_} constants defined below. This argument
23176 tells @value{GDBN} how to perform completion for this command. If not
23177 given, @value{GDBN} will attempt to complete using the object's
23178 @code{complete} method (see below); if no such method is found, an
23179 error will occur when completion is attempted.
23181 @var{prefix} is an optional argument. If @code{True}, then the new
23182 command is a prefix command; sub-commands of this command may be
23185 The help text for the new command is taken from the Python
23186 documentation string for the command's class, if there is one. If no
23187 documentation string is provided, the default value ``This command is
23188 not documented.'' is used.
23191 @cindex don't repeat Python command
23192 @defun Command.dont_repeat ()
23193 By default, a @value{GDBN} command is repeated when the user enters a
23194 blank line at the command prompt. A command can suppress this
23195 behavior by invoking the @code{dont_repeat} method. This is similar
23196 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
23199 @defun Command.invoke (argument, from_tty)
23200 This method is called by @value{GDBN} when this command is invoked.
23202 @var{argument} is a string. It is the argument to the command, after
23203 leading and trailing whitespace has been stripped.
23205 @var{from_tty} is a boolean argument. When true, this means that the
23206 command was entered by the user at the terminal; when false it means
23207 that the command came from elsewhere.
23209 If this method throws an exception, it is turned into a @value{GDBN}
23210 @code{error} call. Otherwise, the return value is ignored.
23212 @findex gdb.string_to_argv
23213 To break @var{argument} up into an argv-like string use
23214 @code{gdb.string_to_argv}. This function behaves identically to
23215 @value{GDBN}'s internal argument lexer @code{buildargv}.
23216 It is recommended to use this for consistency.
23217 Arguments are separated by spaces and may be quoted.
23221 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
23222 ['1', '2 "3', '4 "5', "6 '7"]
23227 @cindex completion of Python commands
23228 @defun Command.complete (text, word)
23229 This method is called by @value{GDBN} when the user attempts
23230 completion on this command. All forms of completion are handled by
23231 this method, that is, the @key{TAB} and @key{M-?} key bindings
23232 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
23235 The arguments @var{text} and @var{word} are both strings. @var{text}
23236 holds the complete command line up to the cursor's location.
23237 @var{word} holds the last word of the command line; this is computed
23238 using a word-breaking heuristic.
23240 The @code{complete} method can return several values:
23243 If the return value is a sequence, the contents of the sequence are
23244 used as the completions. It is up to @code{complete} to ensure that the
23245 contents actually do complete the word. A zero-length sequence is
23246 allowed, it means that there were no completions available. Only
23247 string elements of the sequence are used; other elements in the
23248 sequence are ignored.
23251 If the return value is one of the @samp{COMPLETE_} constants defined
23252 below, then the corresponding @value{GDBN}-internal completion
23253 function is invoked, and its result is used.
23256 All other results are treated as though there were no available
23261 When a new command is registered, it must be declared as a member of
23262 some general class of commands. This is used to classify top-level
23263 commands in the on-line help system; note that prefix commands are not
23264 listed under their own category but rather that of their top-level
23265 command. The available classifications are represented by constants
23266 defined in the @code{gdb} module:
23269 @findex COMMAND_NONE
23270 @findex gdb.COMMAND_NONE
23271 @item gdb.COMMAND_NONE
23272 The command does not belong to any particular class. A command in
23273 this category will not be displayed in any of the help categories.
23275 @findex COMMAND_RUNNING
23276 @findex gdb.COMMAND_RUNNING
23277 @item gdb.COMMAND_RUNNING
23278 The command is related to running the inferior. For example,
23279 @code{start}, @code{step}, and @code{continue} are in this category.
23280 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
23281 commands in this category.
23283 @findex COMMAND_DATA
23284 @findex gdb.COMMAND_DATA
23285 @item gdb.COMMAND_DATA
23286 The command is related to data or variables. For example,
23287 @code{call}, @code{find}, and @code{print} are in this category. Type
23288 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
23291 @findex COMMAND_STACK
23292 @findex gdb.COMMAND_STACK
23293 @item gdb.COMMAND_STACK
23294 The command has to do with manipulation of the stack. For example,
23295 @code{backtrace}, @code{frame}, and @code{return} are in this
23296 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
23297 list of commands in this category.
23299 @findex COMMAND_FILES
23300 @findex gdb.COMMAND_FILES
23301 @item gdb.COMMAND_FILES
23302 This class is used for file-related commands. For example,
23303 @code{file}, @code{list} and @code{section} are in this category.
23304 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
23305 commands in this category.
23307 @findex COMMAND_SUPPORT
23308 @findex gdb.COMMAND_SUPPORT
23309 @item gdb.COMMAND_SUPPORT
23310 This should be used for ``support facilities'', generally meaning
23311 things that are useful to the user when interacting with @value{GDBN},
23312 but not related to the state of the inferior. For example,
23313 @code{help}, @code{make}, and @code{shell} are in this category. Type
23314 @kbd{help support} at the @value{GDBN} prompt to see a list of
23315 commands in this category.
23317 @findex COMMAND_STATUS
23318 @findex gdb.COMMAND_STATUS
23319 @item gdb.COMMAND_STATUS
23320 The command is an @samp{info}-related command, that is, related to the
23321 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
23322 and @code{show} are in this category. Type @kbd{help status} at the
23323 @value{GDBN} prompt to see a list of commands in this category.
23325 @findex COMMAND_BREAKPOINTS
23326 @findex gdb.COMMAND_BREAKPOINTS
23327 @item gdb.COMMAND_BREAKPOINTS
23328 The command has to do with breakpoints. For example, @code{break},
23329 @code{clear}, and @code{delete} are in this category. Type @kbd{help
23330 breakpoints} at the @value{GDBN} prompt to see a list of commands in
23333 @findex COMMAND_TRACEPOINTS
23334 @findex gdb.COMMAND_TRACEPOINTS
23335 @item gdb.COMMAND_TRACEPOINTS
23336 The command has to do with tracepoints. For example, @code{trace},
23337 @code{actions}, and @code{tfind} are in this category. Type
23338 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
23339 commands in this category.
23341 @findex COMMAND_USER
23342 @findex gdb.COMMAND_USER
23343 @item gdb.COMMAND_USER
23344 The command is a general purpose command for the user, and typically
23345 does not fit in one of the other categories.
23346 Type @kbd{help user-defined} at the @value{GDBN} prompt to see
23347 a list of commands in this category, as well as the list of gdb macros
23348 (@pxref{Sequences}).
23350 @findex COMMAND_OBSCURE
23351 @findex gdb.COMMAND_OBSCURE
23352 @item gdb.COMMAND_OBSCURE
23353 The command is only used in unusual circumstances, or is not of
23354 general interest to users. For example, @code{checkpoint},
23355 @code{fork}, and @code{stop} are in this category. Type @kbd{help
23356 obscure} at the @value{GDBN} prompt to see a list of commands in this
23359 @findex COMMAND_MAINTENANCE
23360 @findex gdb.COMMAND_MAINTENANCE
23361 @item gdb.COMMAND_MAINTENANCE
23362 The command is only useful to @value{GDBN} maintainers. The
23363 @code{maintenance} and @code{flushregs} commands are in this category.
23364 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
23365 commands in this category.
23368 A new command can use a predefined completion function, either by
23369 specifying it via an argument at initialization, or by returning it
23370 from the @code{complete} method. These predefined completion
23371 constants are all defined in the @code{gdb} module:
23374 @findex COMPLETE_NONE
23375 @findex gdb.COMPLETE_NONE
23376 @item gdb.COMPLETE_NONE
23377 This constant means that no completion should be done.
23379 @findex COMPLETE_FILENAME
23380 @findex gdb.COMPLETE_FILENAME
23381 @item gdb.COMPLETE_FILENAME
23382 This constant means that filename completion should be performed.
23384 @findex COMPLETE_LOCATION
23385 @findex gdb.COMPLETE_LOCATION
23386 @item gdb.COMPLETE_LOCATION
23387 This constant means that location completion should be done.
23388 @xref{Specify Location}.
23390 @findex COMPLETE_COMMAND
23391 @findex gdb.COMPLETE_COMMAND
23392 @item gdb.COMPLETE_COMMAND
23393 This constant means that completion should examine @value{GDBN}
23396 @findex COMPLETE_SYMBOL
23397 @findex gdb.COMPLETE_SYMBOL
23398 @item gdb.COMPLETE_SYMBOL
23399 This constant means that completion should be done using symbol names
23403 The following code snippet shows how a trivial CLI command can be
23404 implemented in Python:
23407 class HelloWorld (gdb.Command):
23408 """Greet the whole world."""
23410 def __init__ (self):
23411 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
23413 def invoke (self, arg, from_tty):
23414 print "Hello, World!"
23419 The last line instantiates the class, and is necessary to trigger the
23420 registration of the command with @value{GDBN}. Depending on how the
23421 Python code is read into @value{GDBN}, you may need to import the
23422 @code{gdb} module explicitly.
23424 @node Parameters In Python
23425 @subsubsection Parameters In Python
23427 @cindex parameters in python
23428 @cindex python parameters
23429 @tindex gdb.Parameter
23431 You can implement new @value{GDBN} parameters using Python. A new
23432 parameter is implemented as an instance of the @code{gdb.Parameter}
23435 Parameters are exposed to the user via the @code{set} and
23436 @code{show} commands. @xref{Help}.
23438 There are many parameters that already exist and can be set in
23439 @value{GDBN}. Two examples are: @code{set follow fork} and
23440 @code{set charset}. Setting these parameters influences certain
23441 behavior in @value{GDBN}. Similarly, you can define parameters that
23442 can be used to influence behavior in custom Python scripts and commands.
23444 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
23445 The object initializer for @code{Parameter} registers the new
23446 parameter with @value{GDBN}. This initializer is normally invoked
23447 from the subclass' own @code{__init__} method.
23449 @var{name} is the name of the new parameter. If @var{name} consists
23450 of multiple words, then the initial words are looked for as prefix
23451 parameters. An example of this can be illustrated with the
23452 @code{set print} set of parameters. If @var{name} is
23453 @code{print foo}, then @code{print} will be searched as the prefix
23454 parameter. In this case the parameter can subsequently be accessed in
23455 @value{GDBN} as @code{set print foo}.
23457 If @var{name} consists of multiple words, and no prefix parameter group
23458 can be found, an exception is raised.
23460 @var{command-class} should be one of the @samp{COMMAND_} constants
23461 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
23462 categorize the new parameter in the help system.
23464 @var{parameter-class} should be one of the @samp{PARAM_} constants
23465 defined below. This argument tells @value{GDBN} the type of the new
23466 parameter; this information is used for input validation and
23469 If @var{parameter-class} is @code{PARAM_ENUM}, then
23470 @var{enum-sequence} must be a sequence of strings. These strings
23471 represent the possible values for the parameter.
23473 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
23474 of a fourth argument will cause an exception to be thrown.
23476 The help text for the new parameter is taken from the Python
23477 documentation string for the parameter's class, if there is one. If
23478 there is no documentation string, a default value is used.
23481 @defvar Parameter.set_doc
23482 If this attribute exists, and is a string, then its value is used as
23483 the help text for this parameter's @code{set} command. The value is
23484 examined when @code{Parameter.__init__} is invoked; subsequent changes
23488 @defvar Parameter.show_doc
23489 If this attribute exists, and is a string, then its value is used as
23490 the help text for this parameter's @code{show} command. The value is
23491 examined when @code{Parameter.__init__} is invoked; subsequent changes
23495 @defvar Parameter.value
23496 The @code{value} attribute holds the underlying value of the
23497 parameter. It can be read and assigned to just as any other
23498 attribute. @value{GDBN} does validation when assignments are made.
23501 There are two methods that should be implemented in any
23502 @code{Parameter} class. These are:
23504 @defun Parameter.get_set_string (self)
23505 @value{GDBN} will call this method when a @var{parameter}'s value has
23506 been changed via the @code{set} API (for example, @kbd{set foo off}).
23507 The @code{value} attribute has already been populated with the new
23508 value and may be used in output. This method must return a string.
23511 @defun Parameter.get_show_string (self, svalue)
23512 @value{GDBN} will call this method when a @var{parameter}'s
23513 @code{show} API has been invoked (for example, @kbd{show foo}). The
23514 argument @code{svalue} receives the string representation of the
23515 current value. This method must return a string.
23518 When a new parameter is defined, its type must be specified. The
23519 available types are represented by constants defined in the @code{gdb}
23523 @findex PARAM_BOOLEAN
23524 @findex gdb.PARAM_BOOLEAN
23525 @item gdb.PARAM_BOOLEAN
23526 The value is a plain boolean. The Python boolean values, @code{True}
23527 and @code{False} are the only valid values.
23529 @findex PARAM_AUTO_BOOLEAN
23530 @findex gdb.PARAM_AUTO_BOOLEAN
23531 @item gdb.PARAM_AUTO_BOOLEAN
23532 The value has three possible states: true, false, and @samp{auto}. In
23533 Python, true and false are represented using boolean constants, and
23534 @samp{auto} is represented using @code{None}.
23536 @findex PARAM_UINTEGER
23537 @findex gdb.PARAM_UINTEGER
23538 @item gdb.PARAM_UINTEGER
23539 The value is an unsigned integer. The value of 0 should be
23540 interpreted to mean ``unlimited''.
23542 @findex PARAM_INTEGER
23543 @findex gdb.PARAM_INTEGER
23544 @item gdb.PARAM_INTEGER
23545 The value is a signed integer. The value of 0 should be interpreted
23546 to mean ``unlimited''.
23548 @findex PARAM_STRING
23549 @findex gdb.PARAM_STRING
23550 @item gdb.PARAM_STRING
23551 The value is a string. When the user modifies the string, any escape
23552 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
23553 translated into corresponding characters and encoded into the current
23556 @findex PARAM_STRING_NOESCAPE
23557 @findex gdb.PARAM_STRING_NOESCAPE
23558 @item gdb.PARAM_STRING_NOESCAPE
23559 The value is a string. When the user modifies the string, escapes are
23560 passed through untranslated.
23562 @findex PARAM_OPTIONAL_FILENAME
23563 @findex gdb.PARAM_OPTIONAL_FILENAME
23564 @item gdb.PARAM_OPTIONAL_FILENAME
23565 The value is a either a filename (a string), or @code{None}.
23567 @findex PARAM_FILENAME
23568 @findex gdb.PARAM_FILENAME
23569 @item gdb.PARAM_FILENAME
23570 The value is a filename. This is just like
23571 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
23573 @findex PARAM_ZINTEGER
23574 @findex gdb.PARAM_ZINTEGER
23575 @item gdb.PARAM_ZINTEGER
23576 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
23577 is interpreted as itself.
23580 @findex gdb.PARAM_ENUM
23581 @item gdb.PARAM_ENUM
23582 The value is a string, which must be one of a collection string
23583 constants provided when the parameter is created.
23586 @node Functions In Python
23587 @subsubsection Writing new convenience functions
23589 @cindex writing convenience functions
23590 @cindex convenience functions in python
23591 @cindex python convenience functions
23592 @tindex gdb.Function
23594 You can implement new convenience functions (@pxref{Convenience Vars})
23595 in Python. A convenience function is an instance of a subclass of the
23596 class @code{gdb.Function}.
23598 @defun Function.__init__ (name)
23599 The initializer for @code{Function} registers the new function with
23600 @value{GDBN}. The argument @var{name} is the name of the function,
23601 a string. The function will be visible to the user as a convenience
23602 variable of type @code{internal function}, whose name is the same as
23603 the given @var{name}.
23605 The documentation for the new function is taken from the documentation
23606 string for the new class.
23609 @defun Function.invoke (@var{*args})
23610 When a convenience function is evaluated, its arguments are converted
23611 to instances of @code{gdb.Value}, and then the function's
23612 @code{invoke} method is called. Note that @value{GDBN} does not
23613 predetermine the arity of convenience functions. Instead, all
23614 available arguments are passed to @code{invoke}, following the
23615 standard Python calling convention. In particular, a convenience
23616 function can have default values for parameters without ill effect.
23618 The return value of this method is used as its value in the enclosing
23619 expression. If an ordinary Python value is returned, it is converted
23620 to a @code{gdb.Value} following the usual rules.
23623 The following code snippet shows how a trivial convenience function can
23624 be implemented in Python:
23627 class Greet (gdb.Function):
23628 """Return string to greet someone.
23629 Takes a name as argument."""
23631 def __init__ (self):
23632 super (Greet, self).__init__ ("greet")
23634 def invoke (self, name):
23635 return "Hello, %s!" % name.string ()
23640 The last line instantiates the class, and is necessary to trigger the
23641 registration of the function with @value{GDBN}. Depending on how the
23642 Python code is read into @value{GDBN}, you may need to import the
23643 @code{gdb} module explicitly.
23645 @node Progspaces In Python
23646 @subsubsection Program Spaces In Python
23648 @cindex progspaces in python
23649 @tindex gdb.Progspace
23651 A program space, or @dfn{progspace}, represents a symbolic view
23652 of an address space.
23653 It consists of all of the objfiles of the program.
23654 @xref{Objfiles In Python}.
23655 @xref{Inferiors and Programs, program spaces}, for more details
23656 about program spaces.
23658 The following progspace-related functions are available in the
23661 @findex gdb.current_progspace
23662 @defun gdb.current_progspace ()
23663 This function returns the program space of the currently selected inferior.
23664 @xref{Inferiors and Programs}.
23667 @findex gdb.progspaces
23668 @defun gdb.progspaces ()
23669 Return a sequence of all the progspaces currently known to @value{GDBN}.
23672 Each progspace is represented by an instance of the @code{gdb.Progspace}
23675 @defvar Progspace.filename
23676 The file name of the progspace as a string.
23679 @defvar Progspace.pretty_printers
23680 The @code{pretty_printers} attribute is a list of functions. It is
23681 used to look up pretty-printers. A @code{Value} is passed to each
23682 function in order; if the function returns @code{None}, then the
23683 search continues. Otherwise, the return value should be an object
23684 which is used to format the value. @xref{Pretty Printing API}, for more
23688 @node Objfiles In Python
23689 @subsubsection Objfiles In Python
23691 @cindex objfiles in python
23692 @tindex gdb.Objfile
23694 @value{GDBN} loads symbols for an inferior from various
23695 symbol-containing files (@pxref{Files}). These include the primary
23696 executable file, any shared libraries used by the inferior, and any
23697 separate debug info files (@pxref{Separate Debug Files}).
23698 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
23700 The following objfile-related functions are available in the
23703 @findex gdb.current_objfile
23704 @defun gdb.current_objfile ()
23705 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
23706 sets the ``current objfile'' to the corresponding objfile. This
23707 function returns the current objfile. If there is no current objfile,
23708 this function returns @code{None}.
23711 @findex gdb.objfiles
23712 @defun gdb.objfiles ()
23713 Return a sequence of all the objfiles current known to @value{GDBN}.
23714 @xref{Objfiles In Python}.
23717 Each objfile is represented by an instance of the @code{gdb.Objfile}
23720 @defvar Objfile.filename
23721 The file name of the objfile as a string.
23724 @defvar Objfile.pretty_printers
23725 The @code{pretty_printers} attribute is a list of functions. It is
23726 used to look up pretty-printers. A @code{Value} is passed to each
23727 function in order; if the function returns @code{None}, then the
23728 search continues. Otherwise, the return value should be an object
23729 which is used to format the value. @xref{Pretty Printing API}, for more
23733 A @code{gdb.Objfile} object has the following methods:
23735 @defun Objfile.is_valid ()
23736 Returns @code{True} if the @code{gdb.Objfile} object is valid,
23737 @code{False} if not. A @code{gdb.Objfile} object can become invalid
23738 if the object file it refers to is not loaded in @value{GDBN} any
23739 longer. All other @code{gdb.Objfile} methods will throw an exception
23740 if it is invalid at the time the method is called.
23743 @node Frames In Python
23744 @subsubsection Accessing inferior stack frames from Python.
23746 @cindex frames in python
23747 When the debugged program stops, @value{GDBN} is able to analyze its call
23748 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
23749 represents a frame in the stack. A @code{gdb.Frame} object is only valid
23750 while its corresponding frame exists in the inferior's stack. If you try
23751 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
23752 exception (@pxref{Exception Handling}).
23754 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
23758 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
23762 The following frame-related functions are available in the @code{gdb} module:
23764 @findex gdb.selected_frame
23765 @defun gdb.selected_frame ()
23766 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
23769 @findex gdb.newest_frame
23770 @defun gdb.newest_frame ()
23771 Return the newest frame object for the selected thread.
23774 @defun gdb.frame_stop_reason_string (reason)
23775 Return a string explaining the reason why @value{GDBN} stopped unwinding
23776 frames, as expressed by the given @var{reason} code (an integer, see the
23777 @code{unwind_stop_reason} method further down in this section).
23780 A @code{gdb.Frame} object has the following methods:
23783 @defun Frame.is_valid ()
23784 Returns true if the @code{gdb.Frame} object is valid, false if not.
23785 A frame object can become invalid if the frame it refers to doesn't
23786 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
23787 an exception if it is invalid at the time the method is called.
23790 @defun Frame.name ()
23791 Returns the function name of the frame, or @code{None} if it can't be
23795 @defun Frame.type ()
23796 Returns the type of the frame. The value can be one of:
23798 @item gdb.NORMAL_FRAME
23799 An ordinary stack frame.
23801 @item gdb.DUMMY_FRAME
23802 A fake stack frame that was created by @value{GDBN} when performing an
23803 inferior function call.
23805 @item gdb.INLINE_FRAME
23806 A frame representing an inlined function. The function was inlined
23807 into a @code{gdb.NORMAL_FRAME} that is older than this one.
23809 @item gdb.TAILCALL_FRAME
23810 A frame representing a tail call. @xref{Tail Call Frames}.
23812 @item gdb.SIGTRAMP_FRAME
23813 A signal trampoline frame. This is the frame created by the OS when
23814 it calls into a signal handler.
23816 @item gdb.ARCH_FRAME
23817 A fake stack frame representing a cross-architecture call.
23819 @item gdb.SENTINEL_FRAME
23820 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
23825 @defun Frame.unwind_stop_reason ()
23826 Return an integer representing the reason why it's not possible to find
23827 more frames toward the outermost frame. Use
23828 @code{gdb.frame_stop_reason_string} to convert the value returned by this
23829 function to a string. The value can be one of:
23832 @item gdb.FRAME_UNWIND_NO_REASON
23833 No particular reason (older frames should be available).
23835 @item gdb.FRAME_UNWIND_NULL_ID
23836 The previous frame's analyzer returns an invalid result.
23838 @item gdb.FRAME_UNWIND_OUTERMOST
23839 This frame is the outermost.
23841 @item gdb.FRAME_UNWIND_UNAVAILABLE
23842 Cannot unwind further, because that would require knowing the
23843 values of registers or memory that have not been collected.
23845 @item gdb.FRAME_UNWIND_INNER_ID
23846 This frame ID looks like it ought to belong to a NEXT frame,
23847 but we got it for a PREV frame. Normally, this is a sign of
23848 unwinder failure. It could also indicate stack corruption.
23850 @item gdb.FRAME_UNWIND_SAME_ID
23851 This frame has the same ID as the previous one. That means
23852 that unwinding further would almost certainly give us another
23853 frame with exactly the same ID, so break the chain. Normally,
23854 this is a sign of unwinder failure. It could also indicate
23857 @item gdb.FRAME_UNWIND_NO_SAVED_PC
23858 The frame unwinder did not find any saved PC, but we needed
23859 one to unwind further.
23861 @item gdb.FRAME_UNWIND_FIRST_ERROR
23862 Any stop reason greater or equal to this value indicates some kind
23863 of error. This special value facilitates writing code that tests
23864 for errors in unwinding in a way that will work correctly even if
23865 the list of the other values is modified in future @value{GDBN}
23866 versions. Using it, you could write:
23868 reason = gdb.selected_frame().unwind_stop_reason ()
23869 reason_str = gdb.frame_stop_reason_string (reason)
23870 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
23871 print "An error occured: %s" % reason_str
23878 Returns the frame's resume address.
23881 @defun Frame.block ()
23882 Return the frame's code block. @xref{Blocks In Python}.
23885 @defun Frame.function ()
23886 Return the symbol for the function corresponding to this frame.
23887 @xref{Symbols In Python}.
23890 @defun Frame.older ()
23891 Return the frame that called this frame.
23894 @defun Frame.newer ()
23895 Return the frame called by this frame.
23898 @defun Frame.find_sal ()
23899 Return the frame's symtab and line object.
23900 @xref{Symbol Tables In Python}.
23903 @defun Frame.read_var (variable @r{[}, block@r{]})
23904 Return the value of @var{variable} in this frame. If the optional
23905 argument @var{block} is provided, search for the variable from that
23906 block; otherwise start at the frame's current block (which is
23907 determined by the frame's current program counter). @var{variable}
23908 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
23909 @code{gdb.Block} object.
23912 @defun Frame.select ()
23913 Set this frame to be the selected frame. @xref{Stack, ,Examining the
23918 @node Blocks In Python
23919 @subsubsection Accessing frame blocks from Python.
23921 @cindex blocks in python
23924 Within each frame, @value{GDBN} maintains information on each block
23925 stored in that frame. These blocks are organized hierarchically, and
23926 are represented individually in Python as a @code{gdb.Block}.
23927 Please see @ref{Frames In Python}, for a more in-depth discussion on
23928 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
23929 detailed technical information on @value{GDBN}'s book-keeping of the
23932 A @code{gdb.Block} is iterable. The iterator returns the symbols
23933 (@pxref{Symbols In Python}) local to the block.
23935 The following block-related functions are available in the @code{gdb}
23938 @findex gdb.block_for_pc
23939 @defun gdb.block_for_pc (pc)
23940 Return the @code{gdb.Block} containing the given @var{pc} value. If the
23941 block cannot be found for the @var{pc} value specified, the function
23942 will return @code{None}.
23945 A @code{gdb.Block} object has the following methods:
23948 @defun Block.is_valid ()
23949 Returns @code{True} if the @code{gdb.Block} object is valid,
23950 @code{False} if not. A block object can become invalid if the block it
23951 refers to doesn't exist anymore in the inferior. All other
23952 @code{gdb.Block} methods will throw an exception if it is invalid at
23953 the time the method is called. The block's validity is also checked
23954 during iteration over symbols of the block.
23958 A @code{gdb.Block} object has the following attributes:
23961 @defvar Block.start
23962 The start address of the block. This attribute is not writable.
23966 The end address of the block. This attribute is not writable.
23969 @defvar Block.function
23970 The name of the block represented as a @code{gdb.Symbol}. If the
23971 block is not named, then this attribute holds @code{None}. This
23972 attribute is not writable.
23975 @defvar Block.superblock
23976 The block containing this block. If this parent block does not exist,
23977 this attribute holds @code{None}. This attribute is not writable.
23980 @defvar Block.global_block
23981 The global block associated with this block. This attribute is not
23985 @defvar Block.static_block
23986 The static block associated with this block. This attribute is not
23990 @defvar Block.is_global
23991 @code{True} if the @code{gdb.Block} object is a global block,
23992 @code{False} if not. This attribute is not
23996 @defvar Block.is_static
23997 @code{True} if the @code{gdb.Block} object is a static block,
23998 @code{False} if not. This attribute is not writable.
24002 @node Symbols In Python
24003 @subsubsection Python representation of Symbols.
24005 @cindex symbols in python
24008 @value{GDBN} represents every variable, function and type as an
24009 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
24010 Similarly, Python represents these symbols in @value{GDBN} with the
24011 @code{gdb.Symbol} object.
24013 The following symbol-related functions are available in the @code{gdb}
24016 @findex gdb.lookup_symbol
24017 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
24018 This function searches for a symbol by name. The search scope can be
24019 restricted to the parameters defined in the optional domain and block
24022 @var{name} is the name of the symbol. It must be a string. The
24023 optional @var{block} argument restricts the search to symbols visible
24024 in that @var{block}. The @var{block} argument must be a
24025 @code{gdb.Block} object. If omitted, the block for the current frame
24026 is used. The optional @var{domain} argument restricts
24027 the search to the domain type. The @var{domain} argument must be a
24028 domain constant defined in the @code{gdb} module and described later
24031 The result is a tuple of two elements.
24032 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
24034 If the symbol is found, the second element is @code{True} if the symbol
24035 is a field of a method's object (e.g., @code{this} in C@t{++}),
24036 otherwise it is @code{False}.
24037 If the symbol is not found, the second element is @code{False}.
24040 @findex gdb.lookup_global_symbol
24041 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
24042 This function searches for a global symbol by name.
24043 The search scope can be restricted to by the domain argument.
24045 @var{name} is the name of the symbol. It must be a string.
24046 The optional @var{domain} argument restricts the search to the domain type.
24047 The @var{domain} argument must be a domain constant defined in the @code{gdb}
24048 module and described later in this chapter.
24050 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
24054 A @code{gdb.Symbol} object has the following attributes:
24057 @defvar Symbol.type
24058 The type of the symbol or @code{None} if no type is recorded.
24059 This attribute is represented as a @code{gdb.Type} object.
24060 @xref{Types In Python}. This attribute is not writable.
24063 @defvar Symbol.symtab
24064 The symbol table in which the symbol appears. This attribute is
24065 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
24066 Python}. This attribute is not writable.
24069 @defvar Symbol.line
24070 The line number in the source code at which the symbol was defined.
24071 This is an integer.
24074 @defvar Symbol.name
24075 The name of the symbol as a string. This attribute is not writable.
24078 @defvar Symbol.linkage_name
24079 The name of the symbol, as used by the linker (i.e., may be mangled).
24080 This attribute is not writable.
24083 @defvar Symbol.print_name
24084 The name of the symbol in a form suitable for output. This is either
24085 @code{name} or @code{linkage_name}, depending on whether the user
24086 asked @value{GDBN} to display demangled or mangled names.
24089 @defvar Symbol.addr_class
24090 The address class of the symbol. This classifies how to find the value
24091 of a symbol. Each address class is a constant defined in the
24092 @code{gdb} module and described later in this chapter.
24095 @defvar Symbol.needs_frame
24096 This is @code{True} if evaluating this symbol's value requires a frame
24097 (@pxref{Frames In Python}) and @code{False} otherwise. Typically,
24098 local variables will require a frame, but other symbols will not.
24101 @defvar Symbol.is_argument
24102 @code{True} if the symbol is an argument of a function.
24105 @defvar Symbol.is_constant
24106 @code{True} if the symbol is a constant.
24109 @defvar Symbol.is_function
24110 @code{True} if the symbol is a function or a method.
24113 @defvar Symbol.is_variable
24114 @code{True} if the symbol is a variable.
24118 A @code{gdb.Symbol} object has the following methods:
24121 @defun Symbol.is_valid ()
24122 Returns @code{True} if the @code{gdb.Symbol} object is valid,
24123 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
24124 the symbol it refers to does not exist in @value{GDBN} any longer.
24125 All other @code{gdb.Symbol} methods will throw an exception if it is
24126 invalid at the time the method is called.
24129 @defun Symbol.value (@r{[}frame@r{]})
24130 Compute the value of the symbol, as a @code{gdb.Value}. For
24131 functions, this computes the address of the function, cast to the
24132 appropriate type. If the symbol requires a frame in order to compute
24133 its value, then @var{frame} must be given. If @var{frame} is not
24134 given, or if @var{frame} is invalid, then this method will throw an
24139 The available domain categories in @code{gdb.Symbol} are represented
24140 as constants in the @code{gdb} module:
24143 @findex SYMBOL_UNDEF_DOMAIN
24144 @findex gdb.SYMBOL_UNDEF_DOMAIN
24145 @item gdb.SYMBOL_UNDEF_DOMAIN
24146 This is used when a domain has not been discovered or none of the
24147 following domains apply. This usually indicates an error either
24148 in the symbol information or in @value{GDBN}'s handling of symbols.
24149 @findex SYMBOL_VAR_DOMAIN
24150 @findex gdb.SYMBOL_VAR_DOMAIN
24151 @item gdb.SYMBOL_VAR_DOMAIN
24152 This domain contains variables, function names, typedef names and enum
24154 @findex SYMBOL_STRUCT_DOMAIN
24155 @findex gdb.SYMBOL_STRUCT_DOMAIN
24156 @item gdb.SYMBOL_STRUCT_DOMAIN
24157 This domain holds struct, union and enum type names.
24158 @findex SYMBOL_LABEL_DOMAIN
24159 @findex gdb.SYMBOL_LABEL_DOMAIN
24160 @item gdb.SYMBOL_LABEL_DOMAIN
24161 This domain contains names of labels (for gotos).
24162 @findex SYMBOL_VARIABLES_DOMAIN
24163 @findex gdb.SYMBOL_VARIABLES_DOMAIN
24164 @item gdb.SYMBOL_VARIABLES_DOMAIN
24165 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
24166 contains everything minus functions and types.
24167 @findex SYMBOL_FUNCTIONS_DOMAIN
24168 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
24169 @item gdb.SYMBOL_FUNCTION_DOMAIN
24170 This domain contains all functions.
24171 @findex SYMBOL_TYPES_DOMAIN
24172 @findex gdb.SYMBOL_TYPES_DOMAIN
24173 @item gdb.SYMBOL_TYPES_DOMAIN
24174 This domain contains all types.
24177 The available address class categories in @code{gdb.Symbol} are represented
24178 as constants in the @code{gdb} module:
24181 @findex SYMBOL_LOC_UNDEF
24182 @findex gdb.SYMBOL_LOC_UNDEF
24183 @item gdb.SYMBOL_LOC_UNDEF
24184 If this is returned by address class, it indicates an error either in
24185 the symbol information or in @value{GDBN}'s handling of symbols.
24186 @findex SYMBOL_LOC_CONST
24187 @findex gdb.SYMBOL_LOC_CONST
24188 @item gdb.SYMBOL_LOC_CONST
24189 Value is constant int.
24190 @findex SYMBOL_LOC_STATIC
24191 @findex gdb.SYMBOL_LOC_STATIC
24192 @item gdb.SYMBOL_LOC_STATIC
24193 Value is at a fixed address.
24194 @findex SYMBOL_LOC_REGISTER
24195 @findex gdb.SYMBOL_LOC_REGISTER
24196 @item gdb.SYMBOL_LOC_REGISTER
24197 Value is in a register.
24198 @findex SYMBOL_LOC_ARG
24199 @findex gdb.SYMBOL_LOC_ARG
24200 @item gdb.SYMBOL_LOC_ARG
24201 Value is an argument. This value is at the offset stored within the
24202 symbol inside the frame's argument list.
24203 @findex SYMBOL_LOC_REF_ARG
24204 @findex gdb.SYMBOL_LOC_REF_ARG
24205 @item gdb.SYMBOL_LOC_REF_ARG
24206 Value address is stored in the frame's argument list. Just like
24207 @code{LOC_ARG} except that the value's address is stored at the
24208 offset, not the value itself.
24209 @findex SYMBOL_LOC_REGPARM_ADDR
24210 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
24211 @item gdb.SYMBOL_LOC_REGPARM_ADDR
24212 Value is a specified register. Just like @code{LOC_REGISTER} except
24213 the register holds the address of the argument instead of the argument
24215 @findex SYMBOL_LOC_LOCAL
24216 @findex gdb.SYMBOL_LOC_LOCAL
24217 @item gdb.SYMBOL_LOC_LOCAL
24218 Value is a local variable.
24219 @findex SYMBOL_LOC_TYPEDEF
24220 @findex gdb.SYMBOL_LOC_TYPEDEF
24221 @item gdb.SYMBOL_LOC_TYPEDEF
24222 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
24224 @findex SYMBOL_LOC_BLOCK
24225 @findex gdb.SYMBOL_LOC_BLOCK
24226 @item gdb.SYMBOL_LOC_BLOCK
24228 @findex SYMBOL_LOC_CONST_BYTES
24229 @findex gdb.SYMBOL_LOC_CONST_BYTES
24230 @item gdb.SYMBOL_LOC_CONST_BYTES
24231 Value is a byte-sequence.
24232 @findex SYMBOL_LOC_UNRESOLVED
24233 @findex gdb.SYMBOL_LOC_UNRESOLVED
24234 @item gdb.SYMBOL_LOC_UNRESOLVED
24235 Value is at a fixed address, but the address of the variable has to be
24236 determined from the minimal symbol table whenever the variable is
24238 @findex SYMBOL_LOC_OPTIMIZED_OUT
24239 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
24240 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
24241 The value does not actually exist in the program.
24242 @findex SYMBOL_LOC_COMPUTED
24243 @findex gdb.SYMBOL_LOC_COMPUTED
24244 @item gdb.SYMBOL_LOC_COMPUTED
24245 The value's address is a computed location.
24248 @node Symbol Tables In Python
24249 @subsubsection Symbol table representation in Python.
24251 @cindex symbol tables in python
24253 @tindex gdb.Symtab_and_line
24255 Access to symbol table data maintained by @value{GDBN} on the inferior
24256 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
24257 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
24258 from the @code{find_sal} method in @code{gdb.Frame} object.
24259 @xref{Frames In Python}.
24261 For more information on @value{GDBN}'s symbol table management, see
24262 @ref{Symbols, ,Examining the Symbol Table}, for more information.
24264 A @code{gdb.Symtab_and_line} object has the following attributes:
24267 @defvar Symtab_and_line.symtab
24268 The symbol table object (@code{gdb.Symtab}) for this frame.
24269 This attribute is not writable.
24272 @defvar Symtab_and_line.pc
24273 Indicates the current program counter address. This attribute is not
24277 @defvar Symtab_and_line.line
24278 Indicates the current line number for this object. This
24279 attribute is not writable.
24283 A @code{gdb.Symtab_and_line} object has the following methods:
24286 @defun Symtab_and_line.is_valid ()
24287 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
24288 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
24289 invalid if the Symbol table and line object it refers to does not
24290 exist in @value{GDBN} any longer. All other
24291 @code{gdb.Symtab_and_line} methods will throw an exception if it is
24292 invalid at the time the method is called.
24296 A @code{gdb.Symtab} object has the following attributes:
24299 @defvar Symtab.filename
24300 The symbol table's source filename. This attribute is not writable.
24303 @defvar Symtab.objfile
24304 The symbol table's backing object file. @xref{Objfiles In Python}.
24305 This attribute is not writable.
24309 A @code{gdb.Symtab} object has the following methods:
24312 @defun Symtab.is_valid ()
24313 Returns @code{True} if the @code{gdb.Symtab} object is valid,
24314 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
24315 the symbol table it refers to does not exist in @value{GDBN} any
24316 longer. All other @code{gdb.Symtab} methods will throw an exception
24317 if it is invalid at the time the method is called.
24320 @defun Symtab.fullname ()
24321 Return the symbol table's source absolute file name.
24325 @node Breakpoints In Python
24326 @subsubsection Manipulating breakpoints using Python
24328 @cindex breakpoints in python
24329 @tindex gdb.Breakpoint
24331 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
24334 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal@r{]]]})
24335 Create a new breakpoint. @var{spec} is a string naming the
24336 location of the breakpoint, or an expression that defines a
24337 watchpoint. The contents can be any location recognized by the
24338 @code{break} command, or in the case of a watchpoint, by the @code{watch}
24339 command. The optional @var{type} denotes the breakpoint to create
24340 from the types defined later in this chapter. This argument can be
24341 either: @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
24342 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} argument
24343 allows the breakpoint to become invisible to the user. The breakpoint
24344 will neither be reported when created, nor will it be listed in the
24345 output from @code{info breakpoints} (but will be listed with the
24346 @code{maint info breakpoints} command). The optional @var{wp_class}
24347 argument defines the class of watchpoint to create, if @var{type} is
24348 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it is
24349 assumed to be a @code{gdb.WP_WRITE} class.
24352 @defun Breakpoint.stop (self)
24353 The @code{gdb.Breakpoint} class can be sub-classed and, in
24354 particular, you may choose to implement the @code{stop} method.
24355 If this method is defined as a sub-class of @code{gdb.Breakpoint},
24356 it will be called when the inferior reaches any location of a
24357 breakpoint which instantiates that sub-class. If the method returns
24358 @code{True}, the inferior will be stopped at the location of the
24359 breakpoint, otherwise the inferior will continue.
24361 If there are multiple breakpoints at the same location with a
24362 @code{stop} method, each one will be called regardless of the
24363 return status of the previous. This ensures that all @code{stop}
24364 methods have a chance to execute at that location. In this scenario
24365 if one of the methods returns @code{True} but the others return
24366 @code{False}, the inferior will still be stopped.
24368 You should not alter the execution state of the inferior (i.e.@:, step,
24369 next, etc.), alter the current frame context (i.e.@:, change the current
24370 active frame), or alter, add or delete any breakpoint. As a general
24371 rule, you should not alter any data within @value{GDBN} or the inferior
24374 Example @code{stop} implementation:
24377 class MyBreakpoint (gdb.Breakpoint):
24379 inf_val = gdb.parse_and_eval("foo")
24386 The available watchpoint types represented by constants are defined in the
24391 @findex gdb.WP_READ
24393 Read only watchpoint.
24396 @findex gdb.WP_WRITE
24398 Write only watchpoint.
24401 @findex gdb.WP_ACCESS
24402 @item gdb.WP_ACCESS
24403 Read/Write watchpoint.
24406 @defun Breakpoint.is_valid ()
24407 Return @code{True} if this @code{Breakpoint} object is valid,
24408 @code{False} otherwise. A @code{Breakpoint} object can become invalid
24409 if the user deletes the breakpoint. In this case, the object still
24410 exists, but the underlying breakpoint does not. In the cases of
24411 watchpoint scope, the watchpoint remains valid even if execution of the
24412 inferior leaves the scope of that watchpoint.
24415 @defun Breakpoint.delete
24416 Permanently deletes the @value{GDBN} breakpoint. This also
24417 invalidates the Python @code{Breakpoint} object. Any further access
24418 to this object's attributes or methods will raise an error.
24421 @defvar Breakpoint.enabled
24422 This attribute is @code{True} if the breakpoint is enabled, and
24423 @code{False} otherwise. This attribute is writable.
24426 @defvar Breakpoint.silent
24427 This attribute is @code{True} if the breakpoint is silent, and
24428 @code{False} otherwise. This attribute is writable.
24430 Note that a breakpoint can also be silent if it has commands and the
24431 first command is @code{silent}. This is not reported by the
24432 @code{silent} attribute.
24435 @defvar Breakpoint.thread
24436 If the breakpoint is thread-specific, this attribute holds the thread
24437 id. If the breakpoint is not thread-specific, this attribute is
24438 @code{None}. This attribute is writable.
24441 @defvar Breakpoint.task
24442 If the breakpoint is Ada task-specific, this attribute holds the Ada task
24443 id. If the breakpoint is not task-specific (or the underlying
24444 language is not Ada), this attribute is @code{None}. This attribute
24448 @defvar Breakpoint.ignore_count
24449 This attribute holds the ignore count for the breakpoint, an integer.
24450 This attribute is writable.
24453 @defvar Breakpoint.number
24454 This attribute holds the breakpoint's number --- the identifier used by
24455 the user to manipulate the breakpoint. This attribute is not writable.
24458 @defvar Breakpoint.type
24459 This attribute holds the breakpoint's type --- the identifier used to
24460 determine the actual breakpoint type or use-case. This attribute is not
24464 @defvar Breakpoint.visible
24465 This attribute tells whether the breakpoint is visible to the user
24466 when set, or when the @samp{info breakpoints} command is run. This
24467 attribute is not writable.
24470 The available types are represented by constants defined in the @code{gdb}
24474 @findex BP_BREAKPOINT
24475 @findex gdb.BP_BREAKPOINT
24476 @item gdb.BP_BREAKPOINT
24477 Normal code breakpoint.
24479 @findex BP_WATCHPOINT
24480 @findex gdb.BP_WATCHPOINT
24481 @item gdb.BP_WATCHPOINT
24482 Watchpoint breakpoint.
24484 @findex BP_HARDWARE_WATCHPOINT
24485 @findex gdb.BP_HARDWARE_WATCHPOINT
24486 @item gdb.BP_HARDWARE_WATCHPOINT
24487 Hardware assisted watchpoint.
24489 @findex BP_READ_WATCHPOINT
24490 @findex gdb.BP_READ_WATCHPOINT
24491 @item gdb.BP_READ_WATCHPOINT
24492 Hardware assisted read watchpoint.
24494 @findex BP_ACCESS_WATCHPOINT
24495 @findex gdb.BP_ACCESS_WATCHPOINT
24496 @item gdb.BP_ACCESS_WATCHPOINT
24497 Hardware assisted access watchpoint.
24500 @defvar Breakpoint.hit_count
24501 This attribute holds the hit count for the breakpoint, an integer.
24502 This attribute is writable, but currently it can only be set to zero.
24505 @defvar Breakpoint.location
24506 This attribute holds the location of the breakpoint, as specified by
24507 the user. It is a string. If the breakpoint does not have a location
24508 (that is, it is a watchpoint) the attribute's value is @code{None}. This
24509 attribute is not writable.
24512 @defvar Breakpoint.expression
24513 This attribute holds a breakpoint expression, as specified by
24514 the user. It is a string. If the breakpoint does not have an
24515 expression (the breakpoint is not a watchpoint) the attribute's value
24516 is @code{None}. This attribute is not writable.
24519 @defvar Breakpoint.condition
24520 This attribute holds the condition of the breakpoint, as specified by
24521 the user. It is a string. If there is no condition, this attribute's
24522 value is @code{None}. This attribute is writable.
24525 @defvar Breakpoint.commands
24526 This attribute holds the commands attached to the breakpoint. If
24527 there are commands, this attribute's value is a string holding all the
24528 commands, separated by newlines. If there are no commands, this
24529 attribute is @code{None}. This attribute is not writable.
24532 @node Finish Breakpoints in Python
24533 @subsubsection Finish Breakpoints
24535 @cindex python finish breakpoints
24536 @tindex gdb.FinishBreakpoint
24538 A finish breakpoint is a temporary breakpoint set at the return address of
24539 a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint}
24540 extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled
24541 and deleted when the execution will run out of the breakpoint scope (i.e.@:
24542 @code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered).
24543 Finish breakpoints are thread specific and must be create with the right
24546 @defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]})
24547 Create a finish breakpoint at the return address of the @code{gdb.Frame}
24548 object @var{frame}. If @var{frame} is not provided, this defaults to the
24549 newest frame. The optional @var{internal} argument allows the breakpoint to
24550 become invisible to the user. @xref{Breakpoints In Python}, for further
24551 details about this argument.
24554 @defun FinishBreakpoint.out_of_scope (self)
24555 In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN}
24556 @code{return} command, @dots{}), a function may not properly terminate, and
24557 thus never hit the finish breakpoint. When @value{GDBN} notices such a
24558 situation, the @code{out_of_scope} callback will be triggered.
24560 You may want to sub-class @code{gdb.FinishBreakpoint} and override this
24564 class MyFinishBreakpoint (gdb.FinishBreakpoint)
24566 print "normal finish"
24569 def out_of_scope ():
24570 print "abnormal finish"
24574 @defvar FinishBreakpoint.return_value
24575 When @value{GDBN} is stopped at a finish breakpoint and the frame
24576 used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this
24577 attribute will contain a @code{gdb.Value} object corresponding to the return
24578 value of the function. The value will be @code{None} if the function return
24579 type is @code{void} or if the return value was not computable. This attribute
24583 @node Lazy Strings In Python
24584 @subsubsection Python representation of lazy strings.
24586 @cindex lazy strings in python
24587 @tindex gdb.LazyString
24589 A @dfn{lazy string} is a string whose contents is not retrieved or
24590 encoded until it is needed.
24592 A @code{gdb.LazyString} is represented in @value{GDBN} as an
24593 @code{address} that points to a region of memory, an @code{encoding}
24594 that will be used to encode that region of memory, and a @code{length}
24595 to delimit the region of memory that represents the string. The
24596 difference between a @code{gdb.LazyString} and a string wrapped within
24597 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
24598 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
24599 retrieved and encoded during printing, while a @code{gdb.Value}
24600 wrapping a string is immediately retrieved and encoded on creation.
24602 A @code{gdb.LazyString} object has the following functions:
24604 @defun LazyString.value ()
24605 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
24606 will point to the string in memory, but will lose all the delayed
24607 retrieval, encoding and handling that @value{GDBN} applies to a
24608 @code{gdb.LazyString}.
24611 @defvar LazyString.address
24612 This attribute holds the address of the string. This attribute is not
24616 @defvar LazyString.length
24617 This attribute holds the length of the string in characters. If the
24618 length is -1, then the string will be fetched and encoded up to the
24619 first null of appropriate width. This attribute is not writable.
24622 @defvar LazyString.encoding
24623 This attribute holds the encoding that will be applied to the string
24624 when the string is printed by @value{GDBN}. If the encoding is not
24625 set, or contains an empty string, then @value{GDBN} will select the
24626 most appropriate encoding when the string is printed. This attribute
24630 @defvar LazyString.type
24631 This attribute holds the type that is represented by the lazy string's
24632 type. For a lazy string this will always be a pointer type. To
24633 resolve this to the lazy string's character type, use the type's
24634 @code{target} method. @xref{Types In Python}. This attribute is not
24639 @subsection Auto-loading
24640 @cindex auto-loading, Python
24642 When a new object file is read (for example, due to the @code{file}
24643 command, or because the inferior has loaded a shared library),
24644 @value{GDBN} will look for Python support scripts in several ways:
24645 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
24648 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
24649 * .debug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
24650 * Which flavor to choose?::
24653 The auto-loading feature is useful for supplying application-specific
24654 debugging commands and scripts.
24656 Auto-loading can be enabled or disabled,
24657 and the list of auto-loaded scripts can be printed.
24660 @kindex set auto-load-scripts
24661 @item set auto-load-scripts [yes|no]
24662 Enable or disable the auto-loading of Python scripts.
24664 @kindex show auto-load-scripts
24665 @item show auto-load-scripts
24666 Show whether auto-loading of Python scripts is enabled or disabled.
24668 @kindex info auto-load-scripts
24669 @cindex print list of auto-loaded scripts
24670 @item info auto-load-scripts [@var{regexp}]
24671 Print the list of all scripts that @value{GDBN} auto-loaded.
24673 Also printed is the list of scripts that were mentioned in
24674 the @code{.debug_gdb_scripts} section and were not found
24675 (@pxref{.debug_gdb_scripts section}).
24676 This is useful because their names are not printed when @value{GDBN}
24677 tries to load them and fails. There may be many of them, and printing
24678 an error message for each one is problematic.
24680 If @var{regexp} is supplied only scripts with matching names are printed.
24685 (gdb) info auto-load-scripts
24687 Yes py-section-script.py
24688 full name: /tmp/py-section-script.py
24689 Missing my-foo-pretty-printers.py
24693 When reading an auto-loaded file, @value{GDBN} sets the
24694 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
24695 function (@pxref{Objfiles In Python}). This can be useful for
24696 registering objfile-specific pretty-printers.
24698 @node objfile-gdb.py file
24699 @subsubsection The @file{@var{objfile}-gdb.py} file
24700 @cindex @file{@var{objfile}-gdb.py}
24702 When a new object file is read, @value{GDBN} looks for
24703 a file named @file{@var{objfile}-gdb.py},
24704 where @var{objfile} is the object file's real name, formed by ensuring
24705 that the file name is absolute, following all symlinks, and resolving
24706 @code{.} and @code{..} components. If this file exists and is
24707 readable, @value{GDBN} will evaluate it as a Python script.
24709 If this file does not exist, and if the parameter
24710 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
24711 then @value{GDBN} will look for @var{real-name} in all of the
24712 directories mentioned in the value of @code{debug-file-directory}.
24714 Finally, if this file does not exist, then @value{GDBN} will look for
24715 a file named @file{@var{data-directory}/auto-load/@var{real-name}}, where
24716 @var{data-directory} is @value{GDBN}'s data directory (available via
24717 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
24718 is the object file's real name, as described above.
24720 @value{GDBN} does not track which files it has already auto-loaded this way.
24721 @value{GDBN} will load the associated script every time the corresponding
24722 @var{objfile} is opened.
24723 So your @file{-gdb.py} file should be careful to avoid errors if it
24724 is evaluated more than once.
24726 @node .debug_gdb_scripts section
24727 @subsubsection The @code{.debug_gdb_scripts} section
24728 @cindex @code{.debug_gdb_scripts} section
24730 For systems using file formats like ELF and COFF,
24731 when @value{GDBN} loads a new object file
24732 it will look for a special section named @samp{.debug_gdb_scripts}.
24733 If this section exists, its contents is a list of names of scripts to load.
24735 @value{GDBN} will look for each specified script file first in the
24736 current directory and then along the source search path
24737 (@pxref{Source Path, ,Specifying Source Directories}),
24738 except that @file{$cdir} is not searched, since the compilation
24739 directory is not relevant to scripts.
24741 Entries can be placed in section @code{.debug_gdb_scripts} with,
24742 for example, this GCC macro:
24745 /* Note: The "MS" section flags are to remove duplicates. */
24746 #define DEFINE_GDB_SCRIPT(script_name) \
24748 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
24750 .asciz \"" script_name "\"\n\
24756 Then one can reference the macro in a header or source file like this:
24759 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
24762 The script name may include directories if desired.
24764 If the macro is put in a header, any application or library
24765 using this header will get a reference to the specified script.
24767 @node Which flavor to choose?
24768 @subsubsection Which flavor to choose?
24770 Given the multiple ways of auto-loading Python scripts, it might not always
24771 be clear which one to choose. This section provides some guidance.
24773 Benefits of the @file{-gdb.py} way:
24777 Can be used with file formats that don't support multiple sections.
24780 Ease of finding scripts for public libraries.
24782 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
24783 in the source search path.
24784 For publicly installed libraries, e.g., @file{libstdc++}, there typically
24785 isn't a source directory in which to find the script.
24788 Doesn't require source code additions.
24791 Benefits of the @code{.debug_gdb_scripts} way:
24795 Works with static linking.
24797 Scripts for libraries done the @file{-gdb.py} way require an objfile to
24798 trigger their loading. When an application is statically linked the only
24799 objfile available is the executable, and it is cumbersome to attach all the
24800 scripts from all the input libraries to the executable's @file{-gdb.py} script.
24803 Works with classes that are entirely inlined.
24805 Some classes can be entirely inlined, and thus there may not be an associated
24806 shared library to attach a @file{-gdb.py} script to.
24809 Scripts needn't be copied out of the source tree.
24811 In some circumstances, apps can be built out of large collections of internal
24812 libraries, and the build infrastructure necessary to install the
24813 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
24814 cumbersome. It may be easier to specify the scripts in the
24815 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
24816 top of the source tree to the source search path.
24819 @node Python modules
24820 @subsection Python modules
24821 @cindex python modules
24823 @value{GDBN} comes with several modules to assist writing Python code.
24826 * gdb.printing:: Building and registering pretty-printers.
24827 * gdb.types:: Utilities for working with types.
24828 * gdb.prompt:: Utilities for prompt value substitution.
24832 @subsubsection gdb.printing
24833 @cindex gdb.printing
24835 This module provides a collection of utilities for working with
24839 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
24840 This class specifies the API that makes @samp{info pretty-printer},
24841 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
24842 Pretty-printers should generally inherit from this class.
24844 @item SubPrettyPrinter (@var{name})
24845 For printers that handle multiple types, this class specifies the
24846 corresponding API for the subprinters.
24848 @item RegexpCollectionPrettyPrinter (@var{name})
24849 Utility class for handling multiple printers, all recognized via
24850 regular expressions.
24851 @xref{Writing a Pretty-Printer}, for an example.
24853 @item FlagEnumerationPrinter (@var{name})
24854 A pretty-printer which handles printing of @code{enum} values. Unlike
24855 @value{GDBN}'s built-in @code{enum} printing, this printer attempts to
24856 work properly when there is some overlap between the enumeration
24857 constants. @var{name} is the name of the printer and also the name of
24858 the @code{enum} type to look up.
24860 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
24861 Register @var{printer} with the pretty-printer list of @var{obj}.
24862 If @var{replace} is @code{True} then any existing copy of the printer
24863 is replaced. Otherwise a @code{RuntimeError} exception is raised
24864 if a printer with the same name already exists.
24868 @subsubsection gdb.types
24871 This module provides a collection of utilities for working with
24872 @code{gdb.Types} objects.
24875 @item get_basic_type (@var{type})
24876 Return @var{type} with const and volatile qualifiers stripped,
24877 and with typedefs and C@t{++} references converted to the underlying type.
24882 typedef const int const_int;
24884 const_int& foo_ref (foo);
24885 int main () @{ return 0; @}
24892 (gdb) python import gdb.types
24893 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
24894 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
24898 @item has_field (@var{type}, @var{field})
24899 Return @code{True} if @var{type}, assumed to be a type with fields
24900 (e.g., a structure or union), has field @var{field}.
24902 @item make_enum_dict (@var{enum_type})
24903 Return a Python @code{dictionary} type produced from @var{enum_type}.
24905 @item deep_items (@var{type})
24906 Returns a Python iterator similar to the standard
24907 @code{gdb.Type.iteritems} method, except that the iterator returned
24908 by @code{deep_items} will recursively traverse anonymous struct or
24909 union fields. For example:
24923 Then in @value{GDBN}:
24925 (@value{GDBP}) python import gdb.types
24926 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
24927 (@value{GDBP}) python print struct_a.keys ()
24929 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
24930 @{['a', 'b0', 'b1']@}
24936 @subsubsection gdb.prompt
24939 This module provides a method for prompt value-substitution.
24942 @item substitute_prompt (@var{string})
24943 Return @var{string} with escape sequences substituted by values. Some
24944 escape sequences take arguments. You can specify arguments inside
24945 ``@{@}'' immediately following the escape sequence.
24947 The escape sequences you can pass to this function are:
24951 Substitute a backslash.
24953 Substitute an ESC character.
24955 Substitute the selected frame; an argument names a frame parameter.
24957 Substitute a newline.
24959 Substitute a parameter's value; the argument names the parameter.
24961 Substitute a carriage return.
24963 Substitute the selected thread; an argument names a thread parameter.
24965 Substitute the version of GDB.
24967 Substitute the current working directory.
24969 Begin a sequence of non-printing characters. These sequences are
24970 typically used with the ESC character, and are not counted in the string
24971 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
24972 blue-colored ``(gdb)'' prompt where the length is five.
24974 End a sequence of non-printing characters.
24980 substitute_prompt (``frame: \f,
24981 print arguments: \p@{print frame-arguments@}'')
24984 @exdent will return the string:
24987 "frame: main, print arguments: scalars"
24992 @section Creating new spellings of existing commands
24993 @cindex aliases for commands
24995 It is often useful to define alternate spellings of existing commands.
24996 For example, if a new @value{GDBN} command defined in Python has
24997 a long name to type, it is handy to have an abbreviated version of it
24998 that involves less typing.
25000 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
25001 of the @samp{step} command even though it is otherwise an ambiguous
25002 abbreviation of other commands like @samp{set} and @samp{show}.
25004 Aliases are also used to provide shortened or more common versions
25005 of multi-word commands. For example, @value{GDBN} provides the
25006 @samp{tty} alias of the @samp{set inferior-tty} command.
25008 You can define a new alias with the @samp{alias} command.
25013 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
25017 @var{ALIAS} specifies the name of the new alias.
25018 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
25021 @var{COMMAND} specifies the name of an existing command
25022 that is being aliased.
25024 The @samp{-a} option specifies that the new alias is an abbreviation
25025 of the command. Abbreviations are not shown in command
25026 lists displayed by the @samp{help} command.
25028 The @samp{--} option specifies the end of options,
25029 and is useful when @var{ALIAS} begins with a dash.
25031 Here is a simple example showing how to make an abbreviation
25032 of a command so that there is less to type.
25033 Suppose you were tired of typing @samp{disas}, the current
25034 shortest unambiguous abbreviation of the @samp{disassemble} command
25035 and you wanted an even shorter version named @samp{di}.
25036 The following will accomplish this.
25039 (gdb) alias -a di = disas
25042 Note that aliases are different from user-defined commands.
25043 With a user-defined command, you also need to write documentation
25044 for it with the @samp{document} command.
25045 An alias automatically picks up the documentation of the existing command.
25047 Here is an example where we make @samp{elms} an abbreviation of
25048 @samp{elements} in the @samp{set print elements} command.
25049 This is to show that you can make an abbreviation of any part
25053 (gdb) alias -a set print elms = set print elements
25054 (gdb) alias -a show print elms = show print elements
25055 (gdb) set p elms 20
25057 Limit on string chars or array elements to print is 200.
25060 Note that if you are defining an alias of a @samp{set} command,
25061 and you want to have an alias for the corresponding @samp{show}
25062 command, then you need to define the latter separately.
25064 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
25065 @var{ALIAS}, just as they are normally.
25068 (gdb) alias -a set pr elms = set p ele
25071 Finally, here is an example showing the creation of a one word
25072 alias for a more complex command.
25073 This creates alias @samp{spe} of the command @samp{set print elements}.
25076 (gdb) alias spe = set print elements
25081 @chapter Command Interpreters
25082 @cindex command interpreters
25084 @value{GDBN} supports multiple command interpreters, and some command
25085 infrastructure to allow users or user interface writers to switch
25086 between interpreters or run commands in other interpreters.
25088 @value{GDBN} currently supports two command interpreters, the console
25089 interpreter (sometimes called the command-line interpreter or @sc{cli})
25090 and the machine interface interpreter (or @sc{gdb/mi}). This manual
25091 describes both of these interfaces in great detail.
25093 By default, @value{GDBN} will start with the console interpreter.
25094 However, the user may choose to start @value{GDBN} with another
25095 interpreter by specifying the @option{-i} or @option{--interpreter}
25096 startup options. Defined interpreters include:
25100 @cindex console interpreter
25101 The traditional console or command-line interpreter. This is the most often
25102 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
25103 @value{GDBN} will use this interpreter.
25106 @cindex mi interpreter
25107 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
25108 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
25109 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
25113 @cindex mi2 interpreter
25114 The current @sc{gdb/mi} interface.
25117 @cindex mi1 interpreter
25118 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
25122 @cindex invoke another interpreter
25123 The interpreter being used by @value{GDBN} may not be dynamically
25124 switched at runtime. Although possible, this could lead to a very
25125 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
25126 enters the command "interpreter-set console" in a console view,
25127 @value{GDBN} would switch to using the console interpreter, rendering
25128 the IDE inoperable!
25130 @kindex interpreter-exec
25131 Although you may only choose a single interpreter at startup, you may execute
25132 commands in any interpreter from the current interpreter using the appropriate
25133 command. If you are running the console interpreter, simply use the
25134 @code{interpreter-exec} command:
25137 interpreter-exec mi "-data-list-register-names"
25140 @sc{gdb/mi} has a similar command, although it is only available in versions of
25141 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
25144 @chapter @value{GDBN} Text User Interface
25146 @cindex Text User Interface
25149 * TUI Overview:: TUI overview
25150 * TUI Keys:: TUI key bindings
25151 * TUI Single Key Mode:: TUI single key mode
25152 * TUI Commands:: TUI-specific commands
25153 * TUI Configuration:: TUI configuration variables
25156 The @value{GDBN} Text User Interface (TUI) is a terminal
25157 interface which uses the @code{curses} library to show the source
25158 file, the assembly output, the program registers and @value{GDBN}
25159 commands in separate text windows. The TUI mode is supported only
25160 on platforms where a suitable version of the @code{curses} library
25163 The TUI mode is enabled by default when you invoke @value{GDBN} as
25164 @samp{@value{GDBP} -tui}.
25165 You can also switch in and out of TUI mode while @value{GDBN} runs by
25166 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
25167 @xref{TUI Keys, ,TUI Key Bindings}.
25170 @section TUI Overview
25172 In TUI mode, @value{GDBN} can display several text windows:
25176 This window is the @value{GDBN} command window with the @value{GDBN}
25177 prompt and the @value{GDBN} output. The @value{GDBN} input is still
25178 managed using readline.
25181 The source window shows the source file of the program. The current
25182 line and active breakpoints are displayed in this window.
25185 The assembly window shows the disassembly output of the program.
25188 This window shows the processor registers. Registers are highlighted
25189 when their values change.
25192 The source and assembly windows show the current program position
25193 by highlighting the current line and marking it with a @samp{>} marker.
25194 Breakpoints are indicated with two markers. The first marker
25195 indicates the breakpoint type:
25199 Breakpoint which was hit at least once.
25202 Breakpoint which was never hit.
25205 Hardware breakpoint which was hit at least once.
25208 Hardware breakpoint which was never hit.
25211 The second marker indicates whether the breakpoint is enabled or not:
25215 Breakpoint is enabled.
25218 Breakpoint is disabled.
25221 The source, assembly and register windows are updated when the current
25222 thread changes, when the frame changes, or when the program counter
25225 These windows are not all visible at the same time. The command
25226 window is always visible. The others can be arranged in several
25237 source and assembly,
25240 source and registers, or
25243 assembly and registers.
25246 A status line above the command window shows the following information:
25250 Indicates the current @value{GDBN} target.
25251 (@pxref{Targets, ,Specifying a Debugging Target}).
25254 Gives the current process or thread number.
25255 When no process is being debugged, this field is set to @code{No process}.
25258 Gives the current function name for the selected frame.
25259 The name is demangled if demangling is turned on (@pxref{Print Settings}).
25260 When there is no symbol corresponding to the current program counter,
25261 the string @code{??} is displayed.
25264 Indicates the current line number for the selected frame.
25265 When the current line number is not known, the string @code{??} is displayed.
25268 Indicates the current program counter address.
25272 @section TUI Key Bindings
25273 @cindex TUI key bindings
25275 The TUI installs several key bindings in the readline keymaps
25276 @ifset SYSTEM_READLINE
25277 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
25279 @ifclear SYSTEM_READLINE
25280 (@pxref{Command Line Editing}).
25282 The following key bindings are installed for both TUI mode and the
25283 @value{GDBN} standard mode.
25292 Enter or leave the TUI mode. When leaving the TUI mode,
25293 the curses window management stops and @value{GDBN} operates using
25294 its standard mode, writing on the terminal directly. When reentering
25295 the TUI mode, control is given back to the curses windows.
25296 The screen is then refreshed.
25300 Use a TUI layout with only one window. The layout will
25301 either be @samp{source} or @samp{assembly}. When the TUI mode
25302 is not active, it will switch to the TUI mode.
25304 Think of this key binding as the Emacs @kbd{C-x 1} binding.
25308 Use a TUI layout with at least two windows. When the current
25309 layout already has two windows, the next layout with two windows is used.
25310 When a new layout is chosen, one window will always be common to the
25311 previous layout and the new one.
25313 Think of it as the Emacs @kbd{C-x 2} binding.
25317 Change the active window. The TUI associates several key bindings
25318 (like scrolling and arrow keys) with the active window. This command
25319 gives the focus to the next TUI window.
25321 Think of it as the Emacs @kbd{C-x o} binding.
25325 Switch in and out of the TUI SingleKey mode that binds single
25326 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
25329 The following key bindings only work in the TUI mode:
25334 Scroll the active window one page up.
25338 Scroll the active window one page down.
25342 Scroll the active window one line up.
25346 Scroll the active window one line down.
25350 Scroll the active window one column left.
25354 Scroll the active window one column right.
25358 Refresh the screen.
25361 Because the arrow keys scroll the active window in the TUI mode, they
25362 are not available for their normal use by readline unless the command
25363 window has the focus. When another window is active, you must use
25364 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
25365 and @kbd{C-f} to control the command window.
25367 @node TUI Single Key Mode
25368 @section TUI Single Key Mode
25369 @cindex TUI single key mode
25371 The TUI also provides a @dfn{SingleKey} mode, which binds several
25372 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
25373 switch into this mode, where the following key bindings are used:
25376 @kindex c @r{(SingleKey TUI key)}
25380 @kindex d @r{(SingleKey TUI key)}
25384 @kindex f @r{(SingleKey TUI key)}
25388 @kindex n @r{(SingleKey TUI key)}
25392 @kindex q @r{(SingleKey TUI key)}
25394 exit the SingleKey mode.
25396 @kindex r @r{(SingleKey TUI key)}
25400 @kindex s @r{(SingleKey TUI key)}
25404 @kindex u @r{(SingleKey TUI key)}
25408 @kindex v @r{(SingleKey TUI key)}
25412 @kindex w @r{(SingleKey TUI key)}
25417 Other keys temporarily switch to the @value{GDBN} command prompt.
25418 The key that was pressed is inserted in the editing buffer so that
25419 it is possible to type most @value{GDBN} commands without interaction
25420 with the TUI SingleKey mode. Once the command is entered the TUI
25421 SingleKey mode is restored. The only way to permanently leave
25422 this mode is by typing @kbd{q} or @kbd{C-x s}.
25426 @section TUI-specific Commands
25427 @cindex TUI commands
25429 The TUI has specific commands to control the text windows.
25430 These commands are always available, even when @value{GDBN} is not in
25431 the TUI mode. When @value{GDBN} is in the standard mode, most
25432 of these commands will automatically switch to the TUI mode.
25434 Note that if @value{GDBN}'s @code{stdout} is not connected to a
25435 terminal, or @value{GDBN} has been started with the machine interface
25436 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
25437 these commands will fail with an error, because it would not be
25438 possible or desirable to enable curses window management.
25443 List and give the size of all displayed windows.
25447 Display the next layout.
25450 Display the previous layout.
25453 Display the source window only.
25456 Display the assembly window only.
25459 Display the source and assembly window.
25462 Display the register window together with the source or assembly window.
25466 Make the next window active for scrolling.
25469 Make the previous window active for scrolling.
25472 Make the source window active for scrolling.
25475 Make the assembly window active for scrolling.
25478 Make the register window active for scrolling.
25481 Make the command window active for scrolling.
25485 Refresh the screen. This is similar to typing @kbd{C-L}.
25487 @item tui reg float
25489 Show the floating point registers in the register window.
25491 @item tui reg general
25492 Show the general registers in the register window.
25495 Show the next register group. The list of register groups as well as
25496 their order is target specific. The predefined register groups are the
25497 following: @code{general}, @code{float}, @code{system}, @code{vector},
25498 @code{all}, @code{save}, @code{restore}.
25500 @item tui reg system
25501 Show the system registers in the register window.
25505 Update the source window and the current execution point.
25507 @item winheight @var{name} +@var{count}
25508 @itemx winheight @var{name} -@var{count}
25510 Change the height of the window @var{name} by @var{count}
25511 lines. Positive counts increase the height, while negative counts
25514 @item tabset @var{nchars}
25516 Set the width of tab stops to be @var{nchars} characters.
25519 @node TUI Configuration
25520 @section TUI Configuration Variables
25521 @cindex TUI configuration variables
25523 Several configuration variables control the appearance of TUI windows.
25526 @item set tui border-kind @var{kind}
25527 @kindex set tui border-kind
25528 Select the border appearance for the source, assembly and register windows.
25529 The possible values are the following:
25532 Use a space character to draw the border.
25535 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
25538 Use the Alternate Character Set to draw the border. The border is
25539 drawn using character line graphics if the terminal supports them.
25542 @item set tui border-mode @var{mode}
25543 @kindex set tui border-mode
25544 @itemx set tui active-border-mode @var{mode}
25545 @kindex set tui active-border-mode
25546 Select the display attributes for the borders of the inactive windows
25547 or the active window. The @var{mode} can be one of the following:
25550 Use normal attributes to display the border.
25556 Use reverse video mode.
25559 Use half bright mode.
25561 @item half-standout
25562 Use half bright and standout mode.
25565 Use extra bright or bold mode.
25567 @item bold-standout
25568 Use extra bright or bold and standout mode.
25573 @chapter Using @value{GDBN} under @sc{gnu} Emacs
25576 @cindex @sc{gnu} Emacs
25577 A special interface allows you to use @sc{gnu} Emacs to view (and
25578 edit) the source files for the program you are debugging with
25581 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
25582 executable file you want to debug as an argument. This command starts
25583 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
25584 created Emacs buffer.
25585 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
25587 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
25592 All ``terminal'' input and output goes through an Emacs buffer, called
25595 This applies both to @value{GDBN} commands and their output, and to the input
25596 and output done by the program you are debugging.
25598 This is useful because it means that you can copy the text of previous
25599 commands and input them again; you can even use parts of the output
25602 All the facilities of Emacs' Shell mode are available for interacting
25603 with your program. In particular, you can send signals the usual
25604 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
25608 @value{GDBN} displays source code through Emacs.
25610 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
25611 source file for that frame and puts an arrow (@samp{=>}) at the
25612 left margin of the current line. Emacs uses a separate buffer for
25613 source display, and splits the screen to show both your @value{GDBN} session
25616 Explicit @value{GDBN} @code{list} or search commands still produce output as
25617 usual, but you probably have no reason to use them from Emacs.
25620 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
25621 a graphical mode, enabled by default, which provides further buffers
25622 that can control the execution and describe the state of your program.
25623 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
25625 If you specify an absolute file name when prompted for the @kbd{M-x
25626 gdb} argument, then Emacs sets your current working directory to where
25627 your program resides. If you only specify the file name, then Emacs
25628 sets your current working directory to the directory associated
25629 with the previous buffer. In this case, @value{GDBN} may find your
25630 program by searching your environment's @code{PATH} variable, but on
25631 some operating systems it might not find the source. So, although the
25632 @value{GDBN} input and output session proceeds normally, the auxiliary
25633 buffer does not display the current source and line of execution.
25635 The initial working directory of @value{GDBN} is printed on the top
25636 line of the GUD buffer and this serves as a default for the commands
25637 that specify files for @value{GDBN} to operate on. @xref{Files,
25638 ,Commands to Specify Files}.
25640 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
25641 need to call @value{GDBN} by a different name (for example, if you
25642 keep several configurations around, with different names) you can
25643 customize the Emacs variable @code{gud-gdb-command-name} to run the
25646 In the GUD buffer, you can use these special Emacs commands in
25647 addition to the standard Shell mode commands:
25651 Describe the features of Emacs' GUD Mode.
25654 Execute to another source line, like the @value{GDBN} @code{step} command; also
25655 update the display window to show the current file and location.
25658 Execute to next source line in this function, skipping all function
25659 calls, like the @value{GDBN} @code{next} command. Then update the display window
25660 to show the current file and location.
25663 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
25664 display window accordingly.
25667 Execute until exit from the selected stack frame, like the @value{GDBN}
25668 @code{finish} command.
25671 Continue execution of your program, like the @value{GDBN} @code{continue}
25675 Go up the number of frames indicated by the numeric argument
25676 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
25677 like the @value{GDBN} @code{up} command.
25680 Go down the number of frames indicated by the numeric argument, like the
25681 @value{GDBN} @code{down} command.
25684 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
25685 tells @value{GDBN} to set a breakpoint on the source line point is on.
25687 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
25688 separate frame which shows a backtrace when the GUD buffer is current.
25689 Move point to any frame in the stack and type @key{RET} to make it
25690 become the current frame and display the associated source in the
25691 source buffer. Alternatively, click @kbd{Mouse-2} to make the
25692 selected frame become the current one. In graphical mode, the
25693 speedbar displays watch expressions.
25695 If you accidentally delete the source-display buffer, an easy way to get
25696 it back is to type the command @code{f} in the @value{GDBN} buffer, to
25697 request a frame display; when you run under Emacs, this recreates
25698 the source buffer if necessary to show you the context of the current
25701 The source files displayed in Emacs are in ordinary Emacs buffers
25702 which are visiting the source files in the usual way. You can edit
25703 the files with these buffers if you wish; but keep in mind that @value{GDBN}
25704 communicates with Emacs in terms of line numbers. If you add or
25705 delete lines from the text, the line numbers that @value{GDBN} knows cease
25706 to correspond properly with the code.
25708 A more detailed description of Emacs' interaction with @value{GDBN} is
25709 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
25712 @c The following dropped because Epoch is nonstandard. Reactivate
25713 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
25715 @kindex Emacs Epoch environment
25719 Version 18 of @sc{gnu} Emacs has a built-in window system
25720 called the @code{epoch}
25721 environment. Users of this environment can use a new command,
25722 @code{inspect} which performs identically to @code{print} except that
25723 each value is printed in its own window.
25728 @chapter The @sc{gdb/mi} Interface
25730 @unnumberedsec Function and Purpose
25732 @cindex @sc{gdb/mi}, its purpose
25733 @sc{gdb/mi} is a line based machine oriented text interface to
25734 @value{GDBN} and is activated by specifying using the
25735 @option{--interpreter} command line option (@pxref{Mode Options}). It
25736 is specifically intended to support the development of systems which
25737 use the debugger as just one small component of a larger system.
25739 This chapter is a specification of the @sc{gdb/mi} interface. It is written
25740 in the form of a reference manual.
25742 Note that @sc{gdb/mi} is still under construction, so some of the
25743 features described below are incomplete and subject to change
25744 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
25746 @unnumberedsec Notation and Terminology
25748 @cindex notational conventions, for @sc{gdb/mi}
25749 This chapter uses the following notation:
25753 @code{|} separates two alternatives.
25756 @code{[ @var{something} ]} indicates that @var{something} is optional:
25757 it may or may not be given.
25760 @code{( @var{group} )*} means that @var{group} inside the parentheses
25761 may repeat zero or more times.
25764 @code{( @var{group} )+} means that @var{group} inside the parentheses
25765 may repeat one or more times.
25768 @code{"@var{string}"} means a literal @var{string}.
25772 @heading Dependencies
25776 * GDB/MI General Design::
25777 * GDB/MI Command Syntax::
25778 * GDB/MI Compatibility with CLI::
25779 * GDB/MI Development and Front Ends::
25780 * GDB/MI Output Records::
25781 * GDB/MI Simple Examples::
25782 * GDB/MI Command Description Format::
25783 * GDB/MI Breakpoint Commands::
25784 * GDB/MI Program Context::
25785 * GDB/MI Thread Commands::
25786 * GDB/MI Ada Tasking Commands::
25787 * GDB/MI Program Execution::
25788 * GDB/MI Stack Manipulation::
25789 * GDB/MI Variable Objects::
25790 * GDB/MI Data Manipulation::
25791 * GDB/MI Tracepoint Commands::
25792 * GDB/MI Symbol Query::
25793 * GDB/MI File Commands::
25795 * GDB/MI Kod Commands::
25796 * GDB/MI Memory Overlay Commands::
25797 * GDB/MI Signal Handling Commands::
25799 * GDB/MI Target Manipulation::
25800 * GDB/MI File Transfer Commands::
25801 * GDB/MI Miscellaneous Commands::
25804 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25805 @node GDB/MI General Design
25806 @section @sc{gdb/mi} General Design
25807 @cindex GDB/MI General Design
25809 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
25810 parts---commands sent to @value{GDBN}, responses to those commands
25811 and notifications. Each command results in exactly one response,
25812 indicating either successful completion of the command, or an error.
25813 For the commands that do not resume the target, the response contains the
25814 requested information. For the commands that resume the target, the
25815 response only indicates whether the target was successfully resumed.
25816 Notifications is the mechanism for reporting changes in the state of the
25817 target, or in @value{GDBN} state, that cannot conveniently be associated with
25818 a command and reported as part of that command response.
25820 The important examples of notifications are:
25824 Exec notifications. These are used to report changes in
25825 target state---when a target is resumed, or stopped. It would not
25826 be feasible to include this information in response of resuming
25827 commands, because one resume commands can result in multiple events in
25828 different threads. Also, quite some time may pass before any event
25829 happens in the target, while a frontend needs to know whether the resuming
25830 command itself was successfully executed.
25833 Console output, and status notifications. Console output
25834 notifications are used to report output of CLI commands, as well as
25835 diagnostics for other commands. Status notifications are used to
25836 report the progress of a long-running operation. Naturally, including
25837 this information in command response would mean no output is produced
25838 until the command is finished, which is undesirable.
25841 General notifications. Commands may have various side effects on
25842 the @value{GDBN} or target state beyond their official purpose. For example,
25843 a command may change the selected thread. Although such changes can
25844 be included in command response, using notification allows for more
25845 orthogonal frontend design.
25849 There's no guarantee that whenever an MI command reports an error,
25850 @value{GDBN} or the target are in any specific state, and especially,
25851 the state is not reverted to the state before the MI command was
25852 processed. Therefore, whenever an MI command results in an error,
25853 we recommend that the frontend refreshes all the information shown in
25854 the user interface.
25858 * Context management::
25859 * Asynchronous and non-stop modes::
25863 @node Context management
25864 @subsection Context management
25866 In most cases when @value{GDBN} accesses the target, this access is
25867 done in context of a specific thread and frame (@pxref{Frames}).
25868 Often, even when accessing global data, the target requires that a thread
25869 be specified. The CLI interface maintains the selected thread and frame,
25870 and supplies them to target on each command. This is convenient,
25871 because a command line user would not want to specify that information
25872 explicitly on each command, and because user interacts with
25873 @value{GDBN} via a single terminal, so no confusion is possible as
25874 to what thread and frame are the current ones.
25876 In the case of MI, the concept of selected thread and frame is less
25877 useful. First, a frontend can easily remember this information
25878 itself. Second, a graphical frontend can have more than one window,
25879 each one used for debugging a different thread, and the frontend might
25880 want to access additional threads for internal purposes. This
25881 increases the risk that by relying on implicitly selected thread, the
25882 frontend may be operating on a wrong one. Therefore, each MI command
25883 should explicitly specify which thread and frame to operate on. To
25884 make it possible, each MI command accepts the @samp{--thread} and
25885 @samp{--frame} options, the value to each is @value{GDBN} identifier
25886 for thread and frame to operate on.
25888 Usually, each top-level window in a frontend allows the user to select
25889 a thread and a frame, and remembers the user selection for further
25890 operations. However, in some cases @value{GDBN} may suggest that the
25891 current thread be changed. For example, when stopping on a breakpoint
25892 it is reasonable to switch to the thread where breakpoint is hit. For
25893 another example, if the user issues the CLI @samp{thread} command via
25894 the frontend, it is desirable to change the frontend's selected thread to the
25895 one specified by user. @value{GDBN} communicates the suggestion to
25896 change current thread using the @samp{=thread-selected} notification.
25897 No such notification is available for the selected frame at the moment.
25899 Note that historically, MI shares the selected thread with CLI, so
25900 frontends used the @code{-thread-select} to execute commands in the
25901 right context. However, getting this to work right is cumbersome. The
25902 simplest way is for frontend to emit @code{-thread-select} command
25903 before every command. This doubles the number of commands that need
25904 to be sent. The alternative approach is to suppress @code{-thread-select}
25905 if the selected thread in @value{GDBN} is supposed to be identical to the
25906 thread the frontend wants to operate on. However, getting this
25907 optimization right can be tricky. In particular, if the frontend
25908 sends several commands to @value{GDBN}, and one of the commands changes the
25909 selected thread, then the behaviour of subsequent commands will
25910 change. So, a frontend should either wait for response from such
25911 problematic commands, or explicitly add @code{-thread-select} for
25912 all subsequent commands. No frontend is known to do this exactly
25913 right, so it is suggested to just always pass the @samp{--thread} and
25914 @samp{--frame} options.
25916 @node Asynchronous and non-stop modes
25917 @subsection Asynchronous command execution and non-stop mode
25919 On some targets, @value{GDBN} is capable of processing MI commands
25920 even while the target is running. This is called @dfn{asynchronous
25921 command execution} (@pxref{Background Execution}). The frontend may
25922 specify a preferrence for asynchronous execution using the
25923 @code{-gdb-set target-async 1} command, which should be emitted before
25924 either running the executable or attaching to the target. After the
25925 frontend has started the executable or attached to the target, it can
25926 find if asynchronous execution is enabled using the
25927 @code{-list-target-features} command.
25929 Even if @value{GDBN} can accept a command while target is running,
25930 many commands that access the target do not work when the target is
25931 running. Therefore, asynchronous command execution is most useful
25932 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
25933 it is possible to examine the state of one thread, while other threads
25936 When a given thread is running, MI commands that try to access the
25937 target in the context of that thread may not work, or may work only on
25938 some targets. In particular, commands that try to operate on thread's
25939 stack will not work, on any target. Commands that read memory, or
25940 modify breakpoints, may work or not work, depending on the target. Note
25941 that even commands that operate on global state, such as @code{print},
25942 @code{set}, and breakpoint commands, still access the target in the
25943 context of a specific thread, so frontend should try to find a
25944 stopped thread and perform the operation on that thread (using the
25945 @samp{--thread} option).
25947 Which commands will work in the context of a running thread is
25948 highly target dependent. However, the two commands
25949 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
25950 to find the state of a thread, will always work.
25952 @node Thread groups
25953 @subsection Thread groups
25954 @value{GDBN} may be used to debug several processes at the same time.
25955 On some platfroms, @value{GDBN} may support debugging of several
25956 hardware systems, each one having several cores with several different
25957 processes running on each core. This section describes the MI
25958 mechanism to support such debugging scenarios.
25960 The key observation is that regardless of the structure of the
25961 target, MI can have a global list of threads, because most commands that
25962 accept the @samp{--thread} option do not need to know what process that
25963 thread belongs to. Therefore, it is not necessary to introduce
25964 neither additional @samp{--process} option, nor an notion of the
25965 current process in the MI interface. The only strictly new feature
25966 that is required is the ability to find how the threads are grouped
25969 To allow the user to discover such grouping, and to support arbitrary
25970 hierarchy of machines/cores/processes, MI introduces the concept of a
25971 @dfn{thread group}. Thread group is a collection of threads and other
25972 thread groups. A thread group always has a string identifier, a type,
25973 and may have additional attributes specific to the type. A new
25974 command, @code{-list-thread-groups}, returns the list of top-level
25975 thread groups, which correspond to processes that @value{GDBN} is
25976 debugging at the moment. By passing an identifier of a thread group
25977 to the @code{-list-thread-groups} command, it is possible to obtain
25978 the members of specific thread group.
25980 To allow the user to easily discover processes, and other objects, he
25981 wishes to debug, a concept of @dfn{available thread group} is
25982 introduced. Available thread group is an thread group that
25983 @value{GDBN} is not debugging, but that can be attached to, using the
25984 @code{-target-attach} command. The list of available top-level thread
25985 groups can be obtained using @samp{-list-thread-groups --available}.
25986 In general, the content of a thread group may be only retrieved only
25987 after attaching to that thread group.
25989 Thread groups are related to inferiors (@pxref{Inferiors and
25990 Programs}). Each inferior corresponds to a thread group of a special
25991 type @samp{process}, and some additional operations are permitted on
25992 such thread groups.
25994 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25995 @node GDB/MI Command Syntax
25996 @section @sc{gdb/mi} Command Syntax
25999 * GDB/MI Input Syntax::
26000 * GDB/MI Output Syntax::
26003 @node GDB/MI Input Syntax
26004 @subsection @sc{gdb/mi} Input Syntax
26006 @cindex input syntax for @sc{gdb/mi}
26007 @cindex @sc{gdb/mi}, input syntax
26009 @item @var{command} @expansion{}
26010 @code{@var{cli-command} | @var{mi-command}}
26012 @item @var{cli-command} @expansion{}
26013 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
26014 @var{cli-command} is any existing @value{GDBN} CLI command.
26016 @item @var{mi-command} @expansion{}
26017 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
26018 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
26020 @item @var{token} @expansion{}
26021 "any sequence of digits"
26023 @item @var{option} @expansion{}
26024 @code{"-" @var{parameter} [ " " @var{parameter} ]}
26026 @item @var{parameter} @expansion{}
26027 @code{@var{non-blank-sequence} | @var{c-string}}
26029 @item @var{operation} @expansion{}
26030 @emph{any of the operations described in this chapter}
26032 @item @var{non-blank-sequence} @expansion{}
26033 @emph{anything, provided it doesn't contain special characters such as
26034 "-", @var{nl}, """ and of course " "}
26036 @item @var{c-string} @expansion{}
26037 @code{""" @var{seven-bit-iso-c-string-content} """}
26039 @item @var{nl} @expansion{}
26048 The CLI commands are still handled by the @sc{mi} interpreter; their
26049 output is described below.
26052 The @code{@var{token}}, when present, is passed back when the command
26056 Some @sc{mi} commands accept optional arguments as part of the parameter
26057 list. Each option is identified by a leading @samp{-} (dash) and may be
26058 followed by an optional argument parameter. Options occur first in the
26059 parameter list and can be delimited from normal parameters using
26060 @samp{--} (this is useful when some parameters begin with a dash).
26067 We want easy access to the existing CLI syntax (for debugging).
26070 We want it to be easy to spot a @sc{mi} operation.
26073 @node GDB/MI Output Syntax
26074 @subsection @sc{gdb/mi} Output Syntax
26076 @cindex output syntax of @sc{gdb/mi}
26077 @cindex @sc{gdb/mi}, output syntax
26078 The output from @sc{gdb/mi} consists of zero or more out-of-band records
26079 followed, optionally, by a single result record. This result record
26080 is for the most recent command. The sequence of output records is
26081 terminated by @samp{(gdb)}.
26083 If an input command was prefixed with a @code{@var{token}} then the
26084 corresponding output for that command will also be prefixed by that same
26088 @item @var{output} @expansion{}
26089 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
26091 @item @var{result-record} @expansion{}
26092 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
26094 @item @var{out-of-band-record} @expansion{}
26095 @code{@var{async-record} | @var{stream-record}}
26097 @item @var{async-record} @expansion{}
26098 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
26100 @item @var{exec-async-output} @expansion{}
26101 @code{[ @var{token} ] "*" @var{async-output}}
26103 @item @var{status-async-output} @expansion{}
26104 @code{[ @var{token} ] "+" @var{async-output}}
26106 @item @var{notify-async-output} @expansion{}
26107 @code{[ @var{token} ] "=" @var{async-output}}
26109 @item @var{async-output} @expansion{}
26110 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
26112 @item @var{result-class} @expansion{}
26113 @code{"done" | "running" | "connected" | "error" | "exit"}
26115 @item @var{async-class} @expansion{}
26116 @code{"stopped" | @var{others}} (where @var{others} will be added
26117 depending on the needs---this is still in development).
26119 @item @var{result} @expansion{}
26120 @code{ @var{variable} "=" @var{value}}
26122 @item @var{variable} @expansion{}
26123 @code{ @var{string} }
26125 @item @var{value} @expansion{}
26126 @code{ @var{const} | @var{tuple} | @var{list} }
26128 @item @var{const} @expansion{}
26129 @code{@var{c-string}}
26131 @item @var{tuple} @expansion{}
26132 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
26134 @item @var{list} @expansion{}
26135 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
26136 @var{result} ( "," @var{result} )* "]" }
26138 @item @var{stream-record} @expansion{}
26139 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
26141 @item @var{console-stream-output} @expansion{}
26142 @code{"~" @var{c-string}}
26144 @item @var{target-stream-output} @expansion{}
26145 @code{"@@" @var{c-string}}
26147 @item @var{log-stream-output} @expansion{}
26148 @code{"&" @var{c-string}}
26150 @item @var{nl} @expansion{}
26153 @item @var{token} @expansion{}
26154 @emph{any sequence of digits}.
26162 All output sequences end in a single line containing a period.
26165 The @code{@var{token}} is from the corresponding request. Note that
26166 for all async output, while the token is allowed by the grammar and
26167 may be output by future versions of @value{GDBN} for select async
26168 output messages, it is generally omitted. Frontends should treat
26169 all async output as reporting general changes in the state of the
26170 target and there should be no need to associate async output to any
26174 @cindex status output in @sc{gdb/mi}
26175 @var{status-async-output} contains on-going status information about the
26176 progress of a slow operation. It can be discarded. All status output is
26177 prefixed by @samp{+}.
26180 @cindex async output in @sc{gdb/mi}
26181 @var{exec-async-output} contains asynchronous state change on the target
26182 (stopped, started, disappeared). All async output is prefixed by
26186 @cindex notify output in @sc{gdb/mi}
26187 @var{notify-async-output} contains supplementary information that the
26188 client should handle (e.g., a new breakpoint information). All notify
26189 output is prefixed by @samp{=}.
26192 @cindex console output in @sc{gdb/mi}
26193 @var{console-stream-output} is output that should be displayed as is in the
26194 console. It is the textual response to a CLI command. All the console
26195 output is prefixed by @samp{~}.
26198 @cindex target output in @sc{gdb/mi}
26199 @var{target-stream-output} is the output produced by the target program.
26200 All the target output is prefixed by @samp{@@}.
26203 @cindex log output in @sc{gdb/mi}
26204 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
26205 instance messages that should be displayed as part of an error log. All
26206 the log output is prefixed by @samp{&}.
26209 @cindex list output in @sc{gdb/mi}
26210 New @sc{gdb/mi} commands should only output @var{lists} containing
26216 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
26217 details about the various output records.
26219 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26220 @node GDB/MI Compatibility with CLI
26221 @section @sc{gdb/mi} Compatibility with CLI
26223 @cindex compatibility, @sc{gdb/mi} and CLI
26224 @cindex @sc{gdb/mi}, compatibility with CLI
26226 For the developers convenience CLI commands can be entered directly,
26227 but there may be some unexpected behaviour. For example, commands
26228 that query the user will behave as if the user replied yes, breakpoint
26229 command lists are not executed and some CLI commands, such as
26230 @code{if}, @code{when} and @code{define}, prompt for further input with
26231 @samp{>}, which is not valid MI output.
26233 This feature may be removed at some stage in the future and it is
26234 recommended that front ends use the @code{-interpreter-exec} command
26235 (@pxref{-interpreter-exec}).
26237 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26238 @node GDB/MI Development and Front Ends
26239 @section @sc{gdb/mi} Development and Front Ends
26240 @cindex @sc{gdb/mi} development
26242 The application which takes the MI output and presents the state of the
26243 program being debugged to the user is called a @dfn{front end}.
26245 Although @sc{gdb/mi} is still incomplete, it is currently being used
26246 by a variety of front ends to @value{GDBN}. This makes it difficult
26247 to introduce new functionality without breaking existing usage. This
26248 section tries to minimize the problems by describing how the protocol
26251 Some changes in MI need not break a carefully designed front end, and
26252 for these the MI version will remain unchanged. The following is a
26253 list of changes that may occur within one level, so front ends should
26254 parse MI output in a way that can handle them:
26258 New MI commands may be added.
26261 New fields may be added to the output of any MI command.
26264 The range of values for fields with specified values, e.g.,
26265 @code{in_scope} (@pxref{-var-update}) may be extended.
26267 @c The format of field's content e.g type prefix, may change so parse it
26268 @c at your own risk. Yes, in general?
26270 @c The order of fields may change? Shouldn't really matter but it might
26271 @c resolve inconsistencies.
26274 If the changes are likely to break front ends, the MI version level
26275 will be increased by one. This will allow the front end to parse the
26276 output according to the MI version. Apart from mi0, new versions of
26277 @value{GDBN} will not support old versions of MI and it will be the
26278 responsibility of the front end to work with the new one.
26280 @c Starting with mi3, add a new command -mi-version that prints the MI
26283 The best way to avoid unexpected changes in MI that might break your front
26284 end is to make your project known to @value{GDBN} developers and
26285 follow development on @email{gdb@@sourceware.org} and
26286 @email{gdb-patches@@sourceware.org}.
26287 @cindex mailing lists
26289 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26290 @node GDB/MI Output Records
26291 @section @sc{gdb/mi} Output Records
26294 * GDB/MI Result Records::
26295 * GDB/MI Stream Records::
26296 * GDB/MI Async Records::
26297 * GDB/MI Frame Information::
26298 * GDB/MI Thread Information::
26299 * GDB/MI Ada Exception Information::
26302 @node GDB/MI Result Records
26303 @subsection @sc{gdb/mi} Result Records
26305 @cindex result records in @sc{gdb/mi}
26306 @cindex @sc{gdb/mi}, result records
26307 In addition to a number of out-of-band notifications, the response to a
26308 @sc{gdb/mi} command includes one of the following result indications:
26312 @item "^done" [ "," @var{results} ]
26313 The synchronous operation was successful, @code{@var{results}} are the return
26318 This result record is equivalent to @samp{^done}. Historically, it
26319 was output instead of @samp{^done} if the command has resumed the
26320 target. This behaviour is maintained for backward compatibility, but
26321 all frontends should treat @samp{^done} and @samp{^running}
26322 identically and rely on the @samp{*running} output record to determine
26323 which threads are resumed.
26327 @value{GDBN} has connected to a remote target.
26329 @item "^error" "," @var{c-string}
26331 The operation failed. The @code{@var{c-string}} contains the corresponding
26336 @value{GDBN} has terminated.
26340 @node GDB/MI Stream Records
26341 @subsection @sc{gdb/mi} Stream Records
26343 @cindex @sc{gdb/mi}, stream records
26344 @cindex stream records in @sc{gdb/mi}
26345 @value{GDBN} internally maintains a number of output streams: the console, the
26346 target, and the log. The output intended for each of these streams is
26347 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
26349 Each stream record begins with a unique @dfn{prefix character} which
26350 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
26351 Syntax}). In addition to the prefix, each stream record contains a
26352 @code{@var{string-output}}. This is either raw text (with an implicit new
26353 line) or a quoted C string (which does not contain an implicit newline).
26356 @item "~" @var{string-output}
26357 The console output stream contains text that should be displayed in the
26358 CLI console window. It contains the textual responses to CLI commands.
26360 @item "@@" @var{string-output}
26361 The target output stream contains any textual output from the running
26362 target. This is only present when GDB's event loop is truly
26363 asynchronous, which is currently only the case for remote targets.
26365 @item "&" @var{string-output}
26366 The log stream contains debugging messages being produced by @value{GDBN}'s
26370 @node GDB/MI Async Records
26371 @subsection @sc{gdb/mi} Async Records
26373 @cindex async records in @sc{gdb/mi}
26374 @cindex @sc{gdb/mi}, async records
26375 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
26376 additional changes that have occurred. Those changes can either be a
26377 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
26378 target activity (e.g., target stopped).
26380 The following is the list of possible async records:
26384 @item *running,thread-id="@var{thread}"
26385 The target is now running. The @var{thread} field tells which
26386 specific thread is now running, and can be @samp{all} if all threads
26387 are running. The frontend should assume that no interaction with a
26388 running thread is possible after this notification is produced.
26389 The frontend should not assume that this notification is output
26390 only once for any command. @value{GDBN} may emit this notification
26391 several times, either for different threads, because it cannot resume
26392 all threads together, or even for a single thread, if the thread must
26393 be stepped though some code before letting it run freely.
26395 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
26396 The target has stopped. The @var{reason} field can have one of the
26400 @item breakpoint-hit
26401 A breakpoint was reached.
26402 @item watchpoint-trigger
26403 A watchpoint was triggered.
26404 @item read-watchpoint-trigger
26405 A read watchpoint was triggered.
26406 @item access-watchpoint-trigger
26407 An access watchpoint was triggered.
26408 @item function-finished
26409 An -exec-finish or similar CLI command was accomplished.
26410 @item location-reached
26411 An -exec-until or similar CLI command was accomplished.
26412 @item watchpoint-scope
26413 A watchpoint has gone out of scope.
26414 @item end-stepping-range
26415 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
26416 similar CLI command was accomplished.
26417 @item exited-signalled
26418 The inferior exited because of a signal.
26420 The inferior exited.
26421 @item exited-normally
26422 The inferior exited normally.
26423 @item signal-received
26424 A signal was received by the inferior.
26426 The inferior has stopped due to a library being loaded or unloaded.
26427 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
26428 set or when a @code{catch load} or @code{catch unload} catchpoint is
26429 in use (@pxref{Set Catchpoints}).
26431 The inferior has forked. This is reported when @code{catch fork}
26432 (@pxref{Set Catchpoints}) has been used.
26434 The inferior has vforked. This is reported in when @code{catch vfork}
26435 (@pxref{Set Catchpoints}) has been used.
26436 @item syscall-entry
26437 The inferior entered a system call. This is reported when @code{catch
26438 syscall} (@pxref{Set Catchpoints}) has been used.
26439 @item syscall-entry
26440 The inferior returned from a system call. This is reported when
26441 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
26443 The inferior called @code{exec}. This is reported when @code{catch exec}
26444 (@pxref{Set Catchpoints}) has been used.
26447 The @var{id} field identifies the thread that directly caused the stop
26448 -- for example by hitting a breakpoint. Depending on whether all-stop
26449 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
26450 stop all threads, or only the thread that directly triggered the stop.
26451 If all threads are stopped, the @var{stopped} field will have the
26452 value of @code{"all"}. Otherwise, the value of the @var{stopped}
26453 field will be a list of thread identifiers. Presently, this list will
26454 always include a single thread, but frontend should be prepared to see
26455 several threads in the list. The @var{core} field reports the
26456 processor core on which the stop event has happened. This field may be absent
26457 if such information is not available.
26459 @item =thread-group-added,id="@var{id}"
26460 @itemx =thread-group-removed,id="@var{id}"
26461 A thread group was either added or removed. The @var{id} field
26462 contains the @value{GDBN} identifier of the thread group. When a thread
26463 group is added, it generally might not be associated with a running
26464 process. When a thread group is removed, its id becomes invalid and
26465 cannot be used in any way.
26467 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
26468 A thread group became associated with a running program,
26469 either because the program was just started or the thread group
26470 was attached to a program. The @var{id} field contains the
26471 @value{GDBN} identifier of the thread group. The @var{pid} field
26472 contains process identifier, specific to the operating system.
26474 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
26475 A thread group is no longer associated with a running program,
26476 either because the program has exited, or because it was detached
26477 from. The @var{id} field contains the @value{GDBN} identifier of the
26478 thread group. @var{code} is the exit code of the inferior; it exists
26479 only when the inferior exited with some code.
26481 @item =thread-created,id="@var{id}",group-id="@var{gid}"
26482 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
26483 A thread either was created, or has exited. The @var{id} field
26484 contains the @value{GDBN} identifier of the thread. The @var{gid}
26485 field identifies the thread group this thread belongs to.
26487 @item =thread-selected,id="@var{id}"
26488 Informs that the selected thread was changed as result of the last
26489 command. This notification is not emitted as result of @code{-thread-select}
26490 command but is emitted whenever an MI command that is not documented
26491 to change the selected thread actually changes it. In particular,
26492 invoking, directly or indirectly (via user-defined command), the CLI
26493 @code{thread} command, will generate this notification.
26495 We suggest that in response to this notification, front ends
26496 highlight the selected thread and cause subsequent commands to apply to
26499 @item =library-loaded,...
26500 Reports that a new library file was loaded by the program. This
26501 notification has 4 fields---@var{id}, @var{target-name},
26502 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
26503 opaque identifier of the library. For remote debugging case,
26504 @var{target-name} and @var{host-name} fields give the name of the
26505 library file on the target, and on the host respectively. For native
26506 debugging, both those fields have the same value. The
26507 @var{symbols-loaded} field is emitted only for backward compatibility
26508 and should not be relied on to convey any useful information. The
26509 @var{thread-group} field, if present, specifies the id of the thread
26510 group in whose context the library was loaded. If the field is
26511 absent, it means the library was loaded in the context of all present
26514 @item =library-unloaded,...
26515 Reports that a library was unloaded by the program. This notification
26516 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
26517 the same meaning as for the @code{=library-loaded} notification.
26518 The @var{thread-group} field, if present, specifies the id of the
26519 thread group in whose context the library was unloaded. If the field is
26520 absent, it means the library was unloaded in the context of all present
26523 @item =breakpoint-created,bkpt=@{...@}
26524 @itemx =breakpoint-modified,bkpt=@{...@}
26525 @itemx =breakpoint-deleted,bkpt=@{...@}
26526 Reports that a breakpoint was created, modified, or deleted,
26527 respectively. Only user-visible breakpoints are reported to the MI
26530 The @var{bkpt} argument is of the same form as returned by the various
26531 breakpoint commands; @xref{GDB/MI Breakpoint Commands}.
26533 Note that if a breakpoint is emitted in the result record of a
26534 command, then it will not also be emitted in an async record.
26538 @node GDB/MI Frame Information
26539 @subsection @sc{gdb/mi} Frame Information
26541 Response from many MI commands includes an information about stack
26542 frame. This information is a tuple that may have the following
26547 The level of the stack frame. The innermost frame has the level of
26548 zero. This field is always present.
26551 The name of the function corresponding to the frame. This field may
26552 be absent if @value{GDBN} is unable to determine the function name.
26555 The code address for the frame. This field is always present.
26558 The name of the source files that correspond to the frame's code
26559 address. This field may be absent.
26562 The source line corresponding to the frames' code address. This field
26566 The name of the binary file (either executable or shared library) the
26567 corresponds to the frame's code address. This field may be absent.
26571 @node GDB/MI Thread Information
26572 @subsection @sc{gdb/mi} Thread Information
26574 Whenever @value{GDBN} has to report an information about a thread, it
26575 uses a tuple with the following fields:
26579 The numeric id assigned to the thread by @value{GDBN}. This field is
26583 Target-specific string identifying the thread. This field is always present.
26586 Additional information about the thread provided by the target.
26587 It is supposed to be human-readable and not interpreted by the
26588 frontend. This field is optional.
26591 Either @samp{stopped} or @samp{running}, depending on whether the
26592 thread is presently running. This field is always present.
26595 The value of this field is an integer number of the processor core the
26596 thread was last seen on. This field is optional.
26599 @node GDB/MI Ada Exception Information
26600 @subsection @sc{gdb/mi} Ada Exception Information
26602 Whenever a @code{*stopped} record is emitted because the program
26603 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
26604 @value{GDBN} provides the name of the exception that was raised via
26605 the @code{exception-name} field.
26607 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26608 @node GDB/MI Simple Examples
26609 @section Simple Examples of @sc{gdb/mi} Interaction
26610 @cindex @sc{gdb/mi}, simple examples
26612 This subsection presents several simple examples of interaction using
26613 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
26614 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
26615 the output received from @sc{gdb/mi}.
26617 Note the line breaks shown in the examples are here only for
26618 readability, they don't appear in the real output.
26620 @subheading Setting a Breakpoint
26622 Setting a breakpoint generates synchronous output which contains detailed
26623 information of the breakpoint.
26626 -> -break-insert main
26627 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26628 enabled="y",addr="0x08048564",func="main",file="myprog.c",
26629 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
26633 @subheading Program Execution
26635 Program execution generates asynchronous records and MI gives the
26636 reason that execution stopped.
26642 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
26643 frame=@{addr="0x08048564",func="main",
26644 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
26645 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
26650 <- *stopped,reason="exited-normally"
26654 @subheading Quitting @value{GDBN}
26656 Quitting @value{GDBN} just prints the result class @samp{^exit}.
26664 Please note that @samp{^exit} is printed immediately, but it might
26665 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
26666 performs necessary cleanups, including killing programs being debugged
26667 or disconnecting from debug hardware, so the frontend should wait till
26668 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
26669 fails to exit in reasonable time.
26671 @subheading A Bad Command
26673 Here's what happens if you pass a non-existent command:
26677 <- ^error,msg="Undefined MI command: rubbish"
26682 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26683 @node GDB/MI Command Description Format
26684 @section @sc{gdb/mi} Command Description Format
26686 The remaining sections describe blocks of commands. Each block of
26687 commands is laid out in a fashion similar to this section.
26689 @subheading Motivation
26691 The motivation for this collection of commands.
26693 @subheading Introduction
26695 A brief introduction to this collection of commands as a whole.
26697 @subheading Commands
26699 For each command in the block, the following is described:
26701 @subsubheading Synopsis
26704 -command @var{args}@dots{}
26707 @subsubheading Result
26709 @subsubheading @value{GDBN} Command
26711 The corresponding @value{GDBN} CLI command(s), if any.
26713 @subsubheading Example
26715 Example(s) formatted for readability. Some of the described commands have
26716 not been implemented yet and these are labeled N.A.@: (not available).
26719 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26720 @node GDB/MI Breakpoint Commands
26721 @section @sc{gdb/mi} Breakpoint Commands
26723 @cindex breakpoint commands for @sc{gdb/mi}
26724 @cindex @sc{gdb/mi}, breakpoint commands
26725 This section documents @sc{gdb/mi} commands for manipulating
26728 @subheading The @code{-break-after} Command
26729 @findex -break-after
26731 @subsubheading Synopsis
26734 -break-after @var{number} @var{count}
26737 The breakpoint number @var{number} is not in effect until it has been
26738 hit @var{count} times. To see how this is reflected in the output of
26739 the @samp{-break-list} command, see the description of the
26740 @samp{-break-list} command below.
26742 @subsubheading @value{GDBN} Command
26744 The corresponding @value{GDBN} command is @samp{ignore}.
26746 @subsubheading Example
26751 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26752 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26753 fullname="/home/foo/hello.c",line="5",times="0"@}
26760 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26761 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26762 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26763 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26764 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26765 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26766 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26767 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26768 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26769 line="5",times="0",ignore="3"@}]@}
26774 @subheading The @code{-break-catch} Command
26775 @findex -break-catch
26778 @subheading The @code{-break-commands} Command
26779 @findex -break-commands
26781 @subsubheading Synopsis
26784 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
26787 Specifies the CLI commands that should be executed when breakpoint
26788 @var{number} is hit. The parameters @var{command1} to @var{commandN}
26789 are the commands. If no command is specified, any previously-set
26790 commands are cleared. @xref{Break Commands}. Typical use of this
26791 functionality is tracing a program, that is, printing of values of
26792 some variables whenever breakpoint is hit and then continuing.
26794 @subsubheading @value{GDBN} Command
26796 The corresponding @value{GDBN} command is @samp{commands}.
26798 @subsubheading Example
26803 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
26804 enabled="y",addr="0x000100d0",func="main",file="hello.c",
26805 fullname="/home/foo/hello.c",line="5",times="0"@}
26807 -break-commands 1 "print v" "continue"
26812 @subheading The @code{-break-condition} Command
26813 @findex -break-condition
26815 @subsubheading Synopsis
26818 -break-condition @var{number} @var{expr}
26821 Breakpoint @var{number} will stop the program only if the condition in
26822 @var{expr} is true. The condition becomes part of the
26823 @samp{-break-list} output (see the description of the @samp{-break-list}
26826 @subsubheading @value{GDBN} Command
26828 The corresponding @value{GDBN} command is @samp{condition}.
26830 @subsubheading Example
26834 -break-condition 1 1
26838 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26839 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26840 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26841 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26842 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26843 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26844 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26845 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
26846 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26847 line="5",cond="1",times="0",ignore="3"@}]@}
26851 @subheading The @code{-break-delete} Command
26852 @findex -break-delete
26854 @subsubheading Synopsis
26857 -break-delete ( @var{breakpoint} )+
26860 Delete the breakpoint(s) whose number(s) are specified in the argument
26861 list. This is obviously reflected in the breakpoint list.
26863 @subsubheading @value{GDBN} Command
26865 The corresponding @value{GDBN} command is @samp{delete}.
26867 @subsubheading Example
26875 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
26876 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26877 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26878 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26879 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26880 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26881 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26886 @subheading The @code{-break-disable} Command
26887 @findex -break-disable
26889 @subsubheading Synopsis
26892 -break-disable ( @var{breakpoint} )+
26895 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
26896 break list is now set to @samp{n} for the named @var{breakpoint}(s).
26898 @subsubheading @value{GDBN} Command
26900 The corresponding @value{GDBN} command is @samp{disable}.
26902 @subsubheading Example
26910 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26911 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26912 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26913 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26914 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26915 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26916 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26917 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
26918 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26919 line="5",times="0"@}]@}
26923 @subheading The @code{-break-enable} Command
26924 @findex -break-enable
26926 @subsubheading Synopsis
26929 -break-enable ( @var{breakpoint} )+
26932 Enable (previously disabled) @var{breakpoint}(s).
26934 @subsubheading @value{GDBN} Command
26936 The corresponding @value{GDBN} command is @samp{enable}.
26938 @subsubheading Example
26946 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
26947 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
26948 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
26949 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
26950 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
26951 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
26952 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
26953 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
26954 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
26955 line="5",times="0"@}]@}
26959 @subheading The @code{-break-info} Command
26960 @findex -break-info
26962 @subsubheading Synopsis
26965 -break-info @var{breakpoint}
26969 Get information about a single breakpoint.
26971 @subsubheading @value{GDBN} Command
26973 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
26975 @subsubheading Example
26978 @subheading The @code{-break-insert} Command
26979 @findex -break-insert
26981 @subsubheading Synopsis
26984 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
26985 [ -c @var{condition} ] [ -i @var{ignore-count} ]
26986 [ -p @var{thread} ] [ @var{location} ]
26990 If specified, @var{location}, can be one of:
26997 @item filename:linenum
26998 @item filename:function
27002 The possible optional parameters of this command are:
27006 Insert a temporary breakpoint.
27008 Insert a hardware breakpoint.
27009 @item -c @var{condition}
27010 Make the breakpoint conditional on @var{condition}.
27011 @item -i @var{ignore-count}
27012 Initialize the @var{ignore-count}.
27014 If @var{location} cannot be parsed (for example if it
27015 refers to unknown files or functions), create a pending
27016 breakpoint. Without this flag, @value{GDBN} will report
27017 an error, and won't create a breakpoint, if @var{location}
27020 Create a disabled breakpoint.
27022 Create a tracepoint. @xref{Tracepoints}. When this parameter
27023 is used together with @samp{-h}, a fast tracepoint is created.
27026 @subsubheading Result
27028 The result is in the form:
27031 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
27032 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
27033 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
27034 times="@var{times}"@}
27038 where @var{number} is the @value{GDBN} number for this breakpoint,
27039 @var{funcname} is the name of the function where the breakpoint was
27040 inserted, @var{filename} is the name of the source file which contains
27041 this function, @var{lineno} is the source line number within that file
27042 and @var{times} the number of times that the breakpoint has been hit
27043 (always 0 for -break-insert but may be greater for -break-info or -break-list
27044 which use the same output).
27046 Note: this format is open to change.
27047 @c An out-of-band breakpoint instead of part of the result?
27049 @subsubheading @value{GDBN} Command
27051 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
27052 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
27054 @subsubheading Example
27059 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
27060 fullname="/home/foo/recursive2.c,line="4",times="0"@}
27062 -break-insert -t foo
27063 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
27064 fullname="/home/foo/recursive2.c,line="11",times="0"@}
27067 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27068 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27069 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27070 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27071 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27072 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27073 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27074 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27075 addr="0x0001072c", func="main",file="recursive2.c",
27076 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
27077 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
27078 addr="0x00010774",func="foo",file="recursive2.c",
27079 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
27081 -break-insert -r foo.*
27082 ~int foo(int, int);
27083 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
27084 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
27088 @subheading The @code{-break-list} Command
27089 @findex -break-list
27091 @subsubheading Synopsis
27097 Displays the list of inserted breakpoints, showing the following fields:
27101 number of the breakpoint
27103 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
27105 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
27108 is the breakpoint enabled or no: @samp{y} or @samp{n}
27110 memory location at which the breakpoint is set
27112 logical location of the breakpoint, expressed by function name, file
27115 number of times the breakpoint has been hit
27118 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
27119 @code{body} field is an empty list.
27121 @subsubheading @value{GDBN} Command
27123 The corresponding @value{GDBN} command is @samp{info break}.
27125 @subsubheading Example
27130 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27131 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27132 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27133 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27134 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27135 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27136 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27137 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27138 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
27139 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
27140 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
27141 line="13",times="0"@}]@}
27145 Here's an example of the result when there are no breakpoints:
27150 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
27151 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27152 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27153 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27154 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27155 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27156 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27161 @subheading The @code{-break-passcount} Command
27162 @findex -break-passcount
27164 @subsubheading Synopsis
27167 -break-passcount @var{tracepoint-number} @var{passcount}
27170 Set the passcount for tracepoint @var{tracepoint-number} to
27171 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
27172 is not a tracepoint, error is emitted. This corresponds to CLI
27173 command @samp{passcount}.
27175 @subheading The @code{-break-watch} Command
27176 @findex -break-watch
27178 @subsubheading Synopsis
27181 -break-watch [ -a | -r ]
27184 Create a watchpoint. With the @samp{-a} option it will create an
27185 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
27186 read from or on a write to the memory location. With the @samp{-r}
27187 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
27188 trigger only when the memory location is accessed for reading. Without
27189 either of the options, the watchpoint created is a regular watchpoint,
27190 i.e., it will trigger when the memory location is accessed for writing.
27191 @xref{Set Watchpoints, , Setting Watchpoints}.
27193 Note that @samp{-break-list} will report a single list of watchpoints and
27194 breakpoints inserted.
27196 @subsubheading @value{GDBN} Command
27198 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
27201 @subsubheading Example
27203 Setting a watchpoint on a variable in the @code{main} function:
27208 ^done,wpt=@{number="2",exp="x"@}
27213 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
27214 value=@{old="-268439212",new="55"@},
27215 frame=@{func="main",args=[],file="recursive2.c",
27216 fullname="/home/foo/bar/recursive2.c",line="5"@}
27220 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
27221 the program execution twice: first for the variable changing value, then
27222 for the watchpoint going out of scope.
27227 ^done,wpt=@{number="5",exp="C"@}
27232 *stopped,reason="watchpoint-trigger",
27233 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
27234 frame=@{func="callee4",args=[],
27235 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27236 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27241 *stopped,reason="watchpoint-scope",wpnum="5",
27242 frame=@{func="callee3",args=[@{name="strarg",
27243 value="0x11940 \"A string argument.\""@}],
27244 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27245 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27249 Listing breakpoints and watchpoints, at different points in the program
27250 execution. Note that once the watchpoint goes out of scope, it is
27256 ^done,wpt=@{number="2",exp="C"@}
27259 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27260 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27261 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27262 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27263 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27264 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27265 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27266 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27267 addr="0x00010734",func="callee4",
27268 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27269 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
27270 bkpt=@{number="2",type="watchpoint",disp="keep",
27271 enabled="y",addr="",what="C",times="0"@}]@}
27276 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
27277 value=@{old="-276895068",new="3"@},
27278 frame=@{func="callee4",args=[],
27279 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27280 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
27283 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
27284 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27285 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27286 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27287 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27288 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27289 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27290 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27291 addr="0x00010734",func="callee4",
27292 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27293 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
27294 bkpt=@{number="2",type="watchpoint",disp="keep",
27295 enabled="y",addr="",what="C",times="-5"@}]@}
27299 ^done,reason="watchpoint-scope",wpnum="2",
27300 frame=@{func="callee3",args=[@{name="strarg",
27301 value="0x11940 \"A string argument.\""@}],
27302 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27303 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
27306 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
27307 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
27308 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
27309 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
27310 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
27311 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
27312 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
27313 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
27314 addr="0x00010734",func="callee4",
27315 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
27316 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
27321 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27322 @node GDB/MI Program Context
27323 @section @sc{gdb/mi} Program Context
27325 @subheading The @code{-exec-arguments} Command
27326 @findex -exec-arguments
27329 @subsubheading Synopsis
27332 -exec-arguments @var{args}
27335 Set the inferior program arguments, to be used in the next
27338 @subsubheading @value{GDBN} Command
27340 The corresponding @value{GDBN} command is @samp{set args}.
27342 @subsubheading Example
27346 -exec-arguments -v word
27353 @subheading The @code{-exec-show-arguments} Command
27354 @findex -exec-show-arguments
27356 @subsubheading Synopsis
27359 -exec-show-arguments
27362 Print the arguments of the program.
27364 @subsubheading @value{GDBN} Command
27366 The corresponding @value{GDBN} command is @samp{show args}.
27368 @subsubheading Example
27373 @subheading The @code{-environment-cd} Command
27374 @findex -environment-cd
27376 @subsubheading Synopsis
27379 -environment-cd @var{pathdir}
27382 Set @value{GDBN}'s working directory.
27384 @subsubheading @value{GDBN} Command
27386 The corresponding @value{GDBN} command is @samp{cd}.
27388 @subsubheading Example
27392 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27398 @subheading The @code{-environment-directory} Command
27399 @findex -environment-directory
27401 @subsubheading Synopsis
27404 -environment-directory [ -r ] [ @var{pathdir} ]+
27407 Add directories @var{pathdir} to beginning of search path for source files.
27408 If the @samp{-r} option is used, the search path is reset to the default
27409 search path. If directories @var{pathdir} are supplied in addition to the
27410 @samp{-r} option, the search path is first reset and then addition
27412 Multiple directories may be specified, separated by blanks. Specifying
27413 multiple directories in a single command
27414 results in the directories added to the beginning of the
27415 search path in the same order they were presented in the command.
27416 If blanks are needed as
27417 part of a directory name, double-quotes should be used around
27418 the name. In the command output, the path will show up separated
27419 by the system directory-separator character. The directory-separator
27420 character must not be used
27421 in any directory name.
27422 If no directories are specified, the current search path is displayed.
27424 @subsubheading @value{GDBN} Command
27426 The corresponding @value{GDBN} command is @samp{dir}.
27428 @subsubheading Example
27432 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
27433 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27435 -environment-directory ""
27436 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
27438 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
27439 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
27441 -environment-directory -r
27442 ^done,source-path="$cdir:$cwd"
27447 @subheading The @code{-environment-path} Command
27448 @findex -environment-path
27450 @subsubheading Synopsis
27453 -environment-path [ -r ] [ @var{pathdir} ]+
27456 Add directories @var{pathdir} to beginning of search path for object files.
27457 If the @samp{-r} option is used, the search path is reset to the original
27458 search path that existed at gdb start-up. If directories @var{pathdir} are
27459 supplied in addition to the
27460 @samp{-r} option, the search path is first reset and then addition
27462 Multiple directories may be specified, separated by blanks. Specifying
27463 multiple directories in a single command
27464 results in the directories added to the beginning of the
27465 search path in the same order they were presented in the command.
27466 If blanks are needed as
27467 part of a directory name, double-quotes should be used around
27468 the name. In the command output, the path will show up separated
27469 by the system directory-separator character. The directory-separator
27470 character must not be used
27471 in any directory name.
27472 If no directories are specified, the current path is displayed.
27475 @subsubheading @value{GDBN} Command
27477 The corresponding @value{GDBN} command is @samp{path}.
27479 @subsubheading Example
27484 ^done,path="/usr/bin"
27486 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
27487 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
27489 -environment-path -r /usr/local/bin
27490 ^done,path="/usr/local/bin:/usr/bin"
27495 @subheading The @code{-environment-pwd} Command
27496 @findex -environment-pwd
27498 @subsubheading Synopsis
27504 Show the current working directory.
27506 @subsubheading @value{GDBN} Command
27508 The corresponding @value{GDBN} command is @samp{pwd}.
27510 @subsubheading Example
27515 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
27519 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27520 @node GDB/MI Thread Commands
27521 @section @sc{gdb/mi} Thread Commands
27524 @subheading The @code{-thread-info} Command
27525 @findex -thread-info
27527 @subsubheading Synopsis
27530 -thread-info [ @var{thread-id} ]
27533 Reports information about either a specific thread, if
27534 the @var{thread-id} parameter is present, or about all
27535 threads. When printing information about all threads,
27536 also reports the current thread.
27538 @subsubheading @value{GDBN} Command
27540 The @samp{info thread} command prints the same information
27543 @subsubheading Result
27545 The result is a list of threads. The following attributes are
27546 defined for a given thread:
27550 This field exists only for the current thread. It has the value @samp{*}.
27553 The identifier that @value{GDBN} uses to refer to the thread.
27556 The identifier that the target uses to refer to the thread.
27559 Extra information about the thread, in a target-specific format. This
27563 The name of the thread. If the user specified a name using the
27564 @code{thread name} command, then this name is given. Otherwise, if
27565 @value{GDBN} can extract the thread name from the target, then that
27566 name is given. If @value{GDBN} cannot find the thread name, then this
27570 The stack frame currently executing in the thread.
27573 The thread's state. The @samp{state} field may have the following
27578 The thread is stopped. Frame information is available for stopped
27582 The thread is running. There's no frame information for running
27588 If @value{GDBN} can find the CPU core on which this thread is running,
27589 then this field is the core identifier. This field is optional.
27593 @subsubheading Example
27598 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
27599 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
27600 args=[]@},state="running"@},
27601 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
27602 frame=@{level="0",addr="0x0804891f",func="foo",
27603 args=[@{name="i",value="10"@}],
27604 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
27605 state="running"@}],
27606 current-thread-id="1"
27610 @subheading The @code{-thread-list-ids} Command
27611 @findex -thread-list-ids
27613 @subsubheading Synopsis
27619 Produces a list of the currently known @value{GDBN} thread ids. At the
27620 end of the list it also prints the total number of such threads.
27622 This command is retained for historical reasons, the
27623 @code{-thread-info} command should be used instead.
27625 @subsubheading @value{GDBN} Command
27627 Part of @samp{info threads} supplies the same information.
27629 @subsubheading Example
27634 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27635 current-thread-id="1",number-of-threads="3"
27640 @subheading The @code{-thread-select} Command
27641 @findex -thread-select
27643 @subsubheading Synopsis
27646 -thread-select @var{threadnum}
27649 Make @var{threadnum} the current thread. It prints the number of the new
27650 current thread, and the topmost frame for that thread.
27652 This command is deprecated in favor of explicitly using the
27653 @samp{--thread} option to each command.
27655 @subsubheading @value{GDBN} Command
27657 The corresponding @value{GDBN} command is @samp{thread}.
27659 @subsubheading Example
27666 *stopped,reason="end-stepping-range",thread-id="2",line="187",
27667 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
27671 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
27672 number-of-threads="3"
27675 ^done,new-thread-id="3",
27676 frame=@{level="0",func="vprintf",
27677 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
27678 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
27682 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27683 @node GDB/MI Ada Tasking Commands
27684 @section @sc{gdb/mi} Ada Tasking Commands
27686 @subheading The @code{-ada-task-info} Command
27687 @findex -ada-task-info
27689 @subsubheading Synopsis
27692 -ada-task-info [ @var{task-id} ]
27695 Reports information about either a specific Ada task, if the
27696 @var{task-id} parameter is present, or about all Ada tasks.
27698 @subsubheading @value{GDBN} Command
27700 The @samp{info tasks} command prints the same information
27701 about all Ada tasks (@pxref{Ada Tasks}).
27703 @subsubheading Result
27705 The result is a table of Ada tasks. The following columns are
27706 defined for each Ada task:
27710 This field exists only for the current thread. It has the value @samp{*}.
27713 The identifier that @value{GDBN} uses to refer to the Ada task.
27716 The identifier that the target uses to refer to the Ada task.
27719 The identifier of the thread corresponding to the Ada task.
27721 This field should always exist, as Ada tasks are always implemented
27722 on top of a thread. But if @value{GDBN} cannot find this corresponding
27723 thread for any reason, the field is omitted.
27726 This field exists only when the task was created by another task.
27727 In this case, it provides the ID of the parent task.
27730 The base priority of the task.
27733 The current state of the task. For a detailed description of the
27734 possible states, see @ref{Ada Tasks}.
27737 The name of the task.
27741 @subsubheading Example
27745 ^done,tasks=@{nr_rows="3",nr_cols="8",
27746 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
27747 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
27748 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
27749 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
27750 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
27751 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
27752 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
27753 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
27754 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
27755 state="Child Termination Wait",name="main_task"@}]@}
27759 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27760 @node GDB/MI Program Execution
27761 @section @sc{gdb/mi} Program Execution
27763 These are the asynchronous commands which generate the out-of-band
27764 record @samp{*stopped}. Currently @value{GDBN} only really executes
27765 asynchronously with remote targets and this interaction is mimicked in
27768 @subheading The @code{-exec-continue} Command
27769 @findex -exec-continue
27771 @subsubheading Synopsis
27774 -exec-continue [--reverse] [--all|--thread-group N]
27777 Resumes the execution of the inferior program, which will continue
27778 to execute until it reaches a debugger stop event. If the
27779 @samp{--reverse} option is specified, execution resumes in reverse until
27780 it reaches a stop event. Stop events may include
27783 breakpoints or watchpoints
27785 signals or exceptions
27787 the end of the process (or its beginning under @samp{--reverse})
27789 the end or beginning of a replay log if one is being used.
27791 In all-stop mode (@pxref{All-Stop
27792 Mode}), may resume only one thread, or all threads, depending on the
27793 value of the @samp{scheduler-locking} variable. If @samp{--all} is
27794 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
27795 ignored in all-stop mode. If the @samp{--thread-group} options is
27796 specified, then all threads in that thread group are resumed.
27798 @subsubheading @value{GDBN} Command
27800 The corresponding @value{GDBN} corresponding is @samp{continue}.
27802 @subsubheading Example
27809 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
27810 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
27816 @subheading The @code{-exec-finish} Command
27817 @findex -exec-finish
27819 @subsubheading Synopsis
27822 -exec-finish [--reverse]
27825 Resumes the execution of the inferior program until the current
27826 function is exited. Displays the results returned by the function.
27827 If the @samp{--reverse} option is specified, resumes the reverse
27828 execution of the inferior program until the point where current
27829 function was called.
27831 @subsubheading @value{GDBN} Command
27833 The corresponding @value{GDBN} command is @samp{finish}.
27835 @subsubheading Example
27837 Function returning @code{void}.
27844 *stopped,reason="function-finished",frame=@{func="main",args=[],
27845 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
27849 Function returning other than @code{void}. The name of the internal
27850 @value{GDBN} variable storing the result is printed, together with the
27857 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
27858 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
27859 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
27860 gdb-result-var="$1",return-value="0"
27865 @subheading The @code{-exec-interrupt} Command
27866 @findex -exec-interrupt
27868 @subsubheading Synopsis
27871 -exec-interrupt [--all|--thread-group N]
27874 Interrupts the background execution of the target. Note how the token
27875 associated with the stop message is the one for the execution command
27876 that has been interrupted. The token for the interrupt itself only
27877 appears in the @samp{^done} output. If the user is trying to
27878 interrupt a non-running program, an error message will be printed.
27880 Note that when asynchronous execution is enabled, this command is
27881 asynchronous just like other execution commands. That is, first the
27882 @samp{^done} response will be printed, and the target stop will be
27883 reported after that using the @samp{*stopped} notification.
27885 In non-stop mode, only the context thread is interrupted by default.
27886 All threads (in all inferiors) will be interrupted if the
27887 @samp{--all} option is specified. If the @samp{--thread-group}
27888 option is specified, all threads in that group will be interrupted.
27890 @subsubheading @value{GDBN} Command
27892 The corresponding @value{GDBN} command is @samp{interrupt}.
27894 @subsubheading Example
27905 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
27906 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
27907 fullname="/home/foo/bar/try.c",line="13"@}
27912 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
27916 @subheading The @code{-exec-jump} Command
27919 @subsubheading Synopsis
27922 -exec-jump @var{location}
27925 Resumes execution of the inferior program at the location specified by
27926 parameter. @xref{Specify Location}, for a description of the
27927 different forms of @var{location}.
27929 @subsubheading @value{GDBN} Command
27931 The corresponding @value{GDBN} command is @samp{jump}.
27933 @subsubheading Example
27936 -exec-jump foo.c:10
27937 *running,thread-id="all"
27942 @subheading The @code{-exec-next} Command
27945 @subsubheading Synopsis
27948 -exec-next [--reverse]
27951 Resumes execution of the inferior program, stopping when the beginning
27952 of the next source line is reached.
27954 If the @samp{--reverse} option is specified, resumes reverse execution
27955 of the inferior program, stopping at the beginning of the previous
27956 source line. If you issue this command on the first line of a
27957 function, it will take you back to the caller of that function, to the
27958 source line where the function was called.
27961 @subsubheading @value{GDBN} Command
27963 The corresponding @value{GDBN} command is @samp{next}.
27965 @subsubheading Example
27971 *stopped,reason="end-stepping-range",line="8",file="hello.c"
27976 @subheading The @code{-exec-next-instruction} Command
27977 @findex -exec-next-instruction
27979 @subsubheading Synopsis
27982 -exec-next-instruction [--reverse]
27985 Executes one machine instruction. If the instruction is a function
27986 call, continues until the function returns. If the program stops at an
27987 instruction in the middle of a source line, the address will be
27990 If the @samp{--reverse} option is specified, resumes reverse execution
27991 of the inferior program, stopping at the previous instruction. If the
27992 previously executed instruction was a return from another function,
27993 it will continue to execute in reverse until the call to that function
27994 (from the current stack frame) is reached.
27996 @subsubheading @value{GDBN} Command
27998 The corresponding @value{GDBN} command is @samp{nexti}.
28000 @subsubheading Example
28004 -exec-next-instruction
28008 *stopped,reason="end-stepping-range",
28009 addr="0x000100d4",line="5",file="hello.c"
28014 @subheading The @code{-exec-return} Command
28015 @findex -exec-return
28017 @subsubheading Synopsis
28023 Makes current function return immediately. Doesn't execute the inferior.
28024 Displays the new current frame.
28026 @subsubheading @value{GDBN} Command
28028 The corresponding @value{GDBN} command is @samp{return}.
28030 @subsubheading Example
28034 200-break-insert callee4
28035 200^done,bkpt=@{number="1",addr="0x00010734",
28036 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28041 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28042 frame=@{func="callee4",args=[],
28043 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28044 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
28050 111^done,frame=@{level="0",func="callee3",
28051 args=[@{name="strarg",
28052 value="0x11940 \"A string argument.\""@}],
28053 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28054 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28059 @subheading The @code{-exec-run} Command
28062 @subsubheading Synopsis
28065 -exec-run [--all | --thread-group N]
28068 Starts execution of the inferior from the beginning. The inferior
28069 executes until either a breakpoint is encountered or the program
28070 exits. In the latter case the output will include an exit code, if
28071 the program has exited exceptionally.
28073 When no option is specified, the current inferior is started. If the
28074 @samp{--thread-group} option is specified, it should refer to a thread
28075 group of type @samp{process}, and that thread group will be started.
28076 If the @samp{--all} option is specified, then all inferiors will be started.
28078 @subsubheading @value{GDBN} Command
28080 The corresponding @value{GDBN} command is @samp{run}.
28082 @subsubheading Examples
28087 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
28092 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
28093 frame=@{func="main",args=[],file="recursive2.c",
28094 fullname="/home/foo/bar/recursive2.c",line="4"@}
28099 Program exited normally:
28107 *stopped,reason="exited-normally"
28112 Program exited exceptionally:
28120 *stopped,reason="exited",exit-code="01"
28124 Another way the program can terminate is if it receives a signal such as
28125 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
28129 *stopped,reason="exited-signalled",signal-name="SIGINT",
28130 signal-meaning="Interrupt"
28134 @c @subheading -exec-signal
28137 @subheading The @code{-exec-step} Command
28140 @subsubheading Synopsis
28143 -exec-step [--reverse]
28146 Resumes execution of the inferior program, stopping when the beginning
28147 of the next source line is reached, if the next source line is not a
28148 function call. If it is, stop at the first instruction of the called
28149 function. If the @samp{--reverse} option is specified, resumes reverse
28150 execution of the inferior program, stopping at the beginning of the
28151 previously executed source line.
28153 @subsubheading @value{GDBN} Command
28155 The corresponding @value{GDBN} command is @samp{step}.
28157 @subsubheading Example
28159 Stepping into a function:
28165 *stopped,reason="end-stepping-range",
28166 frame=@{func="foo",args=[@{name="a",value="10"@},
28167 @{name="b",value="0"@}],file="recursive2.c",
28168 fullname="/home/foo/bar/recursive2.c",line="11"@}
28178 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
28183 @subheading The @code{-exec-step-instruction} Command
28184 @findex -exec-step-instruction
28186 @subsubheading Synopsis
28189 -exec-step-instruction [--reverse]
28192 Resumes the inferior which executes one machine instruction. If the
28193 @samp{--reverse} option is specified, resumes reverse execution of the
28194 inferior program, stopping at the previously executed instruction.
28195 The output, once @value{GDBN} has stopped, will vary depending on
28196 whether we have stopped in the middle of a source line or not. In the
28197 former case, the address at which the program stopped will be printed
28200 @subsubheading @value{GDBN} Command
28202 The corresponding @value{GDBN} command is @samp{stepi}.
28204 @subsubheading Example
28208 -exec-step-instruction
28212 *stopped,reason="end-stepping-range",
28213 frame=@{func="foo",args=[],file="try.c",
28214 fullname="/home/foo/bar/try.c",line="10"@}
28216 -exec-step-instruction
28220 *stopped,reason="end-stepping-range",
28221 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
28222 fullname="/home/foo/bar/try.c",line="10"@}
28227 @subheading The @code{-exec-until} Command
28228 @findex -exec-until
28230 @subsubheading Synopsis
28233 -exec-until [ @var{location} ]
28236 Executes the inferior until the @var{location} specified in the
28237 argument is reached. If there is no argument, the inferior executes
28238 until a source line greater than the current one is reached. The
28239 reason for stopping in this case will be @samp{location-reached}.
28241 @subsubheading @value{GDBN} Command
28243 The corresponding @value{GDBN} command is @samp{until}.
28245 @subsubheading Example
28249 -exec-until recursive2.c:6
28253 *stopped,reason="location-reached",frame=@{func="main",args=[],
28254 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
28259 @subheading -file-clear
28260 Is this going away????
28263 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28264 @node GDB/MI Stack Manipulation
28265 @section @sc{gdb/mi} Stack Manipulation Commands
28268 @subheading The @code{-stack-info-frame} Command
28269 @findex -stack-info-frame
28271 @subsubheading Synopsis
28277 Get info on the selected frame.
28279 @subsubheading @value{GDBN} Command
28281 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
28282 (without arguments).
28284 @subsubheading Example
28289 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
28290 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28291 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
28295 @subheading The @code{-stack-info-depth} Command
28296 @findex -stack-info-depth
28298 @subsubheading Synopsis
28301 -stack-info-depth [ @var{max-depth} ]
28304 Return the depth of the stack. If the integer argument @var{max-depth}
28305 is specified, do not count beyond @var{max-depth} frames.
28307 @subsubheading @value{GDBN} Command
28309 There's no equivalent @value{GDBN} command.
28311 @subsubheading Example
28313 For a stack with frame levels 0 through 11:
28320 -stack-info-depth 4
28323 -stack-info-depth 12
28326 -stack-info-depth 11
28329 -stack-info-depth 13
28334 @subheading The @code{-stack-list-arguments} Command
28335 @findex -stack-list-arguments
28337 @subsubheading Synopsis
28340 -stack-list-arguments @var{print-values}
28341 [ @var{low-frame} @var{high-frame} ]
28344 Display a list of the arguments for the frames between @var{low-frame}
28345 and @var{high-frame} (inclusive). If @var{low-frame} and
28346 @var{high-frame} are not provided, list the arguments for the whole
28347 call stack. If the two arguments are equal, show the single frame
28348 at the corresponding level. It is an error if @var{low-frame} is
28349 larger than the actual number of frames. On the other hand,
28350 @var{high-frame} may be larger than the actual number of frames, in
28351 which case only existing frames will be returned.
28353 If @var{print-values} is 0 or @code{--no-values}, print only the names of
28354 the variables; if it is 1 or @code{--all-values}, print also their
28355 values; and if it is 2 or @code{--simple-values}, print the name,
28356 type and value for simple data types, and the name and type for arrays,
28357 structures and unions.
28359 Use of this command to obtain arguments in a single frame is
28360 deprecated in favor of the @samp{-stack-list-variables} command.
28362 @subsubheading @value{GDBN} Command
28364 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
28365 @samp{gdb_get_args} command which partially overlaps with the
28366 functionality of @samp{-stack-list-arguments}.
28368 @subsubheading Example
28375 frame=@{level="0",addr="0x00010734",func="callee4",
28376 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28377 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
28378 frame=@{level="1",addr="0x0001076c",func="callee3",
28379 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28380 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
28381 frame=@{level="2",addr="0x0001078c",func="callee2",
28382 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28383 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
28384 frame=@{level="3",addr="0x000107b4",func="callee1",
28385 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28386 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
28387 frame=@{level="4",addr="0x000107e0",func="main",
28388 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28389 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
28391 -stack-list-arguments 0
28394 frame=@{level="0",args=[]@},
28395 frame=@{level="1",args=[name="strarg"]@},
28396 frame=@{level="2",args=[name="intarg",name="strarg"]@},
28397 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
28398 frame=@{level="4",args=[]@}]
28400 -stack-list-arguments 1
28403 frame=@{level="0",args=[]@},
28405 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28406 frame=@{level="2",args=[
28407 @{name="intarg",value="2"@},
28408 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
28409 @{frame=@{level="3",args=[
28410 @{name="intarg",value="2"@},
28411 @{name="strarg",value="0x11940 \"A string argument.\""@},
28412 @{name="fltarg",value="3.5"@}]@},
28413 frame=@{level="4",args=[]@}]
28415 -stack-list-arguments 0 2 2
28416 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
28418 -stack-list-arguments 1 2 2
28419 ^done,stack-args=[frame=@{level="2",
28420 args=[@{name="intarg",value="2"@},
28421 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
28425 @c @subheading -stack-list-exception-handlers
28428 @subheading The @code{-stack-list-frames} Command
28429 @findex -stack-list-frames
28431 @subsubheading Synopsis
28434 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
28437 List the frames currently on the stack. For each frame it displays the
28442 The frame number, 0 being the topmost frame, i.e., the innermost function.
28444 The @code{$pc} value for that frame.
28448 File name of the source file where the function lives.
28449 @item @var{fullname}
28450 The full file name of the source file where the function lives.
28452 Line number corresponding to the @code{$pc}.
28454 The shared library where this function is defined. This is only given
28455 if the frame's function is not known.
28458 If invoked without arguments, this command prints a backtrace for the
28459 whole stack. If given two integer arguments, it shows the frames whose
28460 levels are between the two arguments (inclusive). If the two arguments
28461 are equal, it shows the single frame at the corresponding level. It is
28462 an error if @var{low-frame} is larger than the actual number of
28463 frames. On the other hand, @var{high-frame} may be larger than the
28464 actual number of frames, in which case only existing frames will be returned.
28466 @subsubheading @value{GDBN} Command
28468 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
28470 @subsubheading Example
28472 Full stack backtrace:
28478 [frame=@{level="0",addr="0x0001076c",func="foo",
28479 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
28480 frame=@{level="1",addr="0x000107a4",func="foo",
28481 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28482 frame=@{level="2",addr="0x000107a4",func="foo",
28483 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28484 frame=@{level="3",addr="0x000107a4",func="foo",
28485 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28486 frame=@{level="4",addr="0x000107a4",func="foo",
28487 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28488 frame=@{level="5",addr="0x000107a4",func="foo",
28489 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28490 frame=@{level="6",addr="0x000107a4",func="foo",
28491 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28492 frame=@{level="7",addr="0x000107a4",func="foo",
28493 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28494 frame=@{level="8",addr="0x000107a4",func="foo",
28495 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28496 frame=@{level="9",addr="0x000107a4",func="foo",
28497 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28498 frame=@{level="10",addr="0x000107a4",func="foo",
28499 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28500 frame=@{level="11",addr="0x00010738",func="main",
28501 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
28505 Show frames between @var{low_frame} and @var{high_frame}:
28509 -stack-list-frames 3 5
28511 [frame=@{level="3",addr="0x000107a4",func="foo",
28512 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28513 frame=@{level="4",addr="0x000107a4",func="foo",
28514 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
28515 frame=@{level="5",addr="0x000107a4",func="foo",
28516 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28520 Show a single frame:
28524 -stack-list-frames 3 3
28526 [frame=@{level="3",addr="0x000107a4",func="foo",
28527 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
28532 @subheading The @code{-stack-list-locals} Command
28533 @findex -stack-list-locals
28535 @subsubheading Synopsis
28538 -stack-list-locals @var{print-values}
28541 Display the local variable names for the selected frame. If
28542 @var{print-values} is 0 or @code{--no-values}, print only the names of
28543 the variables; if it is 1 or @code{--all-values}, print also their
28544 values; and if it is 2 or @code{--simple-values}, print the name,
28545 type and value for simple data types, and the name and type for arrays,
28546 structures and unions. In this last case, a frontend can immediately
28547 display the value of simple data types and create variable objects for
28548 other data types when the user wishes to explore their values in
28551 This command is deprecated in favor of the
28552 @samp{-stack-list-variables} command.
28554 @subsubheading @value{GDBN} Command
28556 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
28558 @subsubheading Example
28562 -stack-list-locals 0
28563 ^done,locals=[name="A",name="B",name="C"]
28565 -stack-list-locals --all-values
28566 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
28567 @{name="C",value="@{1, 2, 3@}"@}]
28568 -stack-list-locals --simple-values
28569 ^done,locals=[@{name="A",type="int",value="1"@},
28570 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
28574 @subheading The @code{-stack-list-variables} Command
28575 @findex -stack-list-variables
28577 @subsubheading Synopsis
28580 -stack-list-variables @var{print-values}
28583 Display the names of local variables and function arguments for the selected frame. If
28584 @var{print-values} is 0 or @code{--no-values}, print only the names of
28585 the variables; if it is 1 or @code{--all-values}, print also their
28586 values; and if it is 2 or @code{--simple-values}, print the name,
28587 type and value for simple data types, and the name and type for arrays,
28588 structures and unions.
28590 @subsubheading Example
28594 -stack-list-variables --thread 1 --frame 0 --all-values
28595 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
28600 @subheading The @code{-stack-select-frame} Command
28601 @findex -stack-select-frame
28603 @subsubheading Synopsis
28606 -stack-select-frame @var{framenum}
28609 Change the selected frame. Select a different frame @var{framenum} on
28612 This command in deprecated in favor of passing the @samp{--frame}
28613 option to every command.
28615 @subsubheading @value{GDBN} Command
28617 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
28618 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
28620 @subsubheading Example
28624 -stack-select-frame 2
28629 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28630 @node GDB/MI Variable Objects
28631 @section @sc{gdb/mi} Variable Objects
28635 @subheading Motivation for Variable Objects in @sc{gdb/mi}
28637 For the implementation of a variable debugger window (locals, watched
28638 expressions, etc.), we are proposing the adaptation of the existing code
28639 used by @code{Insight}.
28641 The two main reasons for that are:
28645 It has been proven in practice (it is already on its second generation).
28648 It will shorten development time (needless to say how important it is
28652 The original interface was designed to be used by Tcl code, so it was
28653 slightly changed so it could be used through @sc{gdb/mi}. This section
28654 describes the @sc{gdb/mi} operations that will be available and gives some
28655 hints about their use.
28657 @emph{Note}: In addition to the set of operations described here, we
28658 expect the @sc{gui} implementation of a variable window to require, at
28659 least, the following operations:
28662 @item @code{-gdb-show} @code{output-radix}
28663 @item @code{-stack-list-arguments}
28664 @item @code{-stack-list-locals}
28665 @item @code{-stack-select-frame}
28670 @subheading Introduction to Variable Objects
28672 @cindex variable objects in @sc{gdb/mi}
28674 Variable objects are "object-oriented" MI interface for examining and
28675 changing values of expressions. Unlike some other MI interfaces that
28676 work with expressions, variable objects are specifically designed for
28677 simple and efficient presentation in the frontend. A variable object
28678 is identified by string name. When a variable object is created, the
28679 frontend specifies the expression for that variable object. The
28680 expression can be a simple variable, or it can be an arbitrary complex
28681 expression, and can even involve CPU registers. After creating a
28682 variable object, the frontend can invoke other variable object
28683 operations---for example to obtain or change the value of a variable
28684 object, or to change display format.
28686 Variable objects have hierarchical tree structure. Any variable object
28687 that corresponds to a composite type, such as structure in C, has
28688 a number of child variable objects, for example corresponding to each
28689 element of a structure. A child variable object can itself have
28690 children, recursively. Recursion ends when we reach
28691 leaf variable objects, which always have built-in types. Child variable
28692 objects are created only by explicit request, so if a frontend
28693 is not interested in the children of a particular variable object, no
28694 child will be created.
28696 For a leaf variable object it is possible to obtain its value as a
28697 string, or set the value from a string. String value can be also
28698 obtained for a non-leaf variable object, but it's generally a string
28699 that only indicates the type of the object, and does not list its
28700 contents. Assignment to a non-leaf variable object is not allowed.
28702 A frontend does not need to read the values of all variable objects each time
28703 the program stops. Instead, MI provides an update command that lists all
28704 variable objects whose values has changed since the last update
28705 operation. This considerably reduces the amount of data that must
28706 be transferred to the frontend. As noted above, children variable
28707 objects are created on demand, and only leaf variable objects have a
28708 real value. As result, gdb will read target memory only for leaf
28709 variables that frontend has created.
28711 The automatic update is not always desirable. For example, a frontend
28712 might want to keep a value of some expression for future reference,
28713 and never update it. For another example, fetching memory is
28714 relatively slow for embedded targets, so a frontend might want
28715 to disable automatic update for the variables that are either not
28716 visible on the screen, or ``closed''. This is possible using so
28717 called ``frozen variable objects''. Such variable objects are never
28718 implicitly updated.
28720 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
28721 fixed variable object, the expression is parsed when the variable
28722 object is created, including associating identifiers to specific
28723 variables. The meaning of expression never changes. For a floating
28724 variable object the values of variables whose names appear in the
28725 expressions are re-evaluated every time in the context of the current
28726 frame. Consider this example:
28731 struct work_state state;
28738 If a fixed variable object for the @code{state} variable is created in
28739 this function, and we enter the recursive call, the variable
28740 object will report the value of @code{state} in the top-level
28741 @code{do_work} invocation. On the other hand, a floating variable
28742 object will report the value of @code{state} in the current frame.
28744 If an expression specified when creating a fixed variable object
28745 refers to a local variable, the variable object becomes bound to the
28746 thread and frame in which the variable object is created. When such
28747 variable object is updated, @value{GDBN} makes sure that the
28748 thread/frame combination the variable object is bound to still exists,
28749 and re-evaluates the variable object in context of that thread/frame.
28751 The following is the complete set of @sc{gdb/mi} operations defined to
28752 access this functionality:
28754 @multitable @columnfractions .4 .6
28755 @item @strong{Operation}
28756 @tab @strong{Description}
28758 @item @code{-enable-pretty-printing}
28759 @tab enable Python-based pretty-printing
28760 @item @code{-var-create}
28761 @tab create a variable object
28762 @item @code{-var-delete}
28763 @tab delete the variable object and/or its children
28764 @item @code{-var-set-format}
28765 @tab set the display format of this variable
28766 @item @code{-var-show-format}
28767 @tab show the display format of this variable
28768 @item @code{-var-info-num-children}
28769 @tab tells how many children this object has
28770 @item @code{-var-list-children}
28771 @tab return a list of the object's children
28772 @item @code{-var-info-type}
28773 @tab show the type of this variable object
28774 @item @code{-var-info-expression}
28775 @tab print parent-relative expression that this variable object represents
28776 @item @code{-var-info-path-expression}
28777 @tab print full expression that this variable object represents
28778 @item @code{-var-show-attributes}
28779 @tab is this variable editable? does it exist here?
28780 @item @code{-var-evaluate-expression}
28781 @tab get the value of this variable
28782 @item @code{-var-assign}
28783 @tab set the value of this variable
28784 @item @code{-var-update}
28785 @tab update the variable and its children
28786 @item @code{-var-set-frozen}
28787 @tab set frozeness attribute
28788 @item @code{-var-set-update-range}
28789 @tab set range of children to display on update
28792 In the next subsection we describe each operation in detail and suggest
28793 how it can be used.
28795 @subheading Description And Use of Operations on Variable Objects
28797 @subheading The @code{-enable-pretty-printing} Command
28798 @findex -enable-pretty-printing
28801 -enable-pretty-printing
28804 @value{GDBN} allows Python-based visualizers to affect the output of the
28805 MI variable object commands. However, because there was no way to
28806 implement this in a fully backward-compatible way, a front end must
28807 request that this functionality be enabled.
28809 Once enabled, this feature cannot be disabled.
28811 Note that if Python support has not been compiled into @value{GDBN},
28812 this command will still succeed (and do nothing).
28814 This feature is currently (as of @value{GDBN} 7.0) experimental, and
28815 may work differently in future versions of @value{GDBN}.
28817 @subheading The @code{-var-create} Command
28818 @findex -var-create
28820 @subsubheading Synopsis
28823 -var-create @{@var{name} | "-"@}
28824 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
28827 This operation creates a variable object, which allows the monitoring of
28828 a variable, the result of an expression, a memory cell or a CPU
28831 The @var{name} parameter is the string by which the object can be
28832 referenced. It must be unique. If @samp{-} is specified, the varobj
28833 system will generate a string ``varNNNNNN'' automatically. It will be
28834 unique provided that one does not specify @var{name} of that format.
28835 The command fails if a duplicate name is found.
28837 The frame under which the expression should be evaluated can be
28838 specified by @var{frame-addr}. A @samp{*} indicates that the current
28839 frame should be used. A @samp{@@} indicates that a floating variable
28840 object must be created.
28842 @var{expression} is any expression valid on the current language set (must not
28843 begin with a @samp{*}), or one of the following:
28847 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
28850 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
28853 @samp{$@var{regname}} --- a CPU register name
28856 @cindex dynamic varobj
28857 A varobj's contents may be provided by a Python-based pretty-printer. In this
28858 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
28859 have slightly different semantics in some cases. If the
28860 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
28861 will never create a dynamic varobj. This ensures backward
28862 compatibility for existing clients.
28864 @subsubheading Result
28866 This operation returns attributes of the newly-created varobj. These
28871 The name of the varobj.
28874 The number of children of the varobj. This number is not necessarily
28875 reliable for a dynamic varobj. Instead, you must examine the
28876 @samp{has_more} attribute.
28879 The varobj's scalar value. For a varobj whose type is some sort of
28880 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
28881 will not be interesting.
28884 The varobj's type. This is a string representation of the type, as
28885 would be printed by the @value{GDBN} CLI.
28888 If a variable object is bound to a specific thread, then this is the
28889 thread's identifier.
28892 For a dynamic varobj, this indicates whether there appear to be any
28893 children available. For a non-dynamic varobj, this will be 0.
28896 This attribute will be present and have the value @samp{1} if the
28897 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
28898 then this attribute will not be present.
28901 A dynamic varobj can supply a display hint to the front end. The
28902 value comes directly from the Python pretty-printer object's
28903 @code{display_hint} method. @xref{Pretty Printing API}.
28906 Typical output will look like this:
28909 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
28910 has_more="@var{has_more}"
28914 @subheading The @code{-var-delete} Command
28915 @findex -var-delete
28917 @subsubheading Synopsis
28920 -var-delete [ -c ] @var{name}
28923 Deletes a previously created variable object and all of its children.
28924 With the @samp{-c} option, just deletes the children.
28926 Returns an error if the object @var{name} is not found.
28929 @subheading The @code{-var-set-format} Command
28930 @findex -var-set-format
28932 @subsubheading Synopsis
28935 -var-set-format @var{name} @var{format-spec}
28938 Sets the output format for the value of the object @var{name} to be
28941 @anchor{-var-set-format}
28942 The syntax for the @var{format-spec} is as follows:
28945 @var{format-spec} @expansion{}
28946 @{binary | decimal | hexadecimal | octal | natural@}
28949 The natural format is the default format choosen automatically
28950 based on the variable type (like decimal for an @code{int}, hex
28951 for pointers, etc.).
28953 For a variable with children, the format is set only on the
28954 variable itself, and the children are not affected.
28956 @subheading The @code{-var-show-format} Command
28957 @findex -var-show-format
28959 @subsubheading Synopsis
28962 -var-show-format @var{name}
28965 Returns the format used to display the value of the object @var{name}.
28968 @var{format} @expansion{}
28973 @subheading The @code{-var-info-num-children} Command
28974 @findex -var-info-num-children
28976 @subsubheading Synopsis
28979 -var-info-num-children @var{name}
28982 Returns the number of children of a variable object @var{name}:
28988 Note that this number is not completely reliable for a dynamic varobj.
28989 It will return the current number of children, but more children may
28993 @subheading The @code{-var-list-children} Command
28994 @findex -var-list-children
28996 @subsubheading Synopsis
28999 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
29001 @anchor{-var-list-children}
29003 Return a list of the children of the specified variable object and
29004 create variable objects for them, if they do not already exist. With
29005 a single argument or if @var{print-values} has a value of 0 or
29006 @code{--no-values}, print only the names of the variables; if
29007 @var{print-values} is 1 or @code{--all-values}, also print their
29008 values; and if it is 2 or @code{--simple-values} print the name and
29009 value for simple data types and just the name for arrays, structures
29012 @var{from} and @var{to}, if specified, indicate the range of children
29013 to report. If @var{from} or @var{to} is less than zero, the range is
29014 reset and all children will be reported. Otherwise, children starting
29015 at @var{from} (zero-based) and up to and excluding @var{to} will be
29018 If a child range is requested, it will only affect the current call to
29019 @code{-var-list-children}, but not future calls to @code{-var-update}.
29020 For this, you must instead use @code{-var-set-update-range}. The
29021 intent of this approach is to enable a front end to implement any
29022 update approach it likes; for example, scrolling a view may cause the
29023 front end to request more children with @code{-var-list-children}, and
29024 then the front end could call @code{-var-set-update-range} with a
29025 different range to ensure that future updates are restricted to just
29028 For each child the following results are returned:
29033 Name of the variable object created for this child.
29036 The expression to be shown to the user by the front end to designate this child.
29037 For example this may be the name of a structure member.
29039 For a dynamic varobj, this value cannot be used to form an
29040 expression. There is no way to do this at all with a dynamic varobj.
29042 For C/C@t{++} structures there are several pseudo children returned to
29043 designate access qualifiers. For these pseudo children @var{exp} is
29044 @samp{public}, @samp{private}, or @samp{protected}. In this case the
29045 type and value are not present.
29047 A dynamic varobj will not report the access qualifying
29048 pseudo-children, regardless of the language. This information is not
29049 available at all with a dynamic varobj.
29052 Number of children this child has. For a dynamic varobj, this will be
29056 The type of the child.
29059 If values were requested, this is the value.
29062 If this variable object is associated with a thread, this is the thread id.
29063 Otherwise this result is not present.
29066 If the variable object is frozen, this variable will be present with a value of 1.
29069 The result may have its own attributes:
29073 A dynamic varobj can supply a display hint to the front end. The
29074 value comes directly from the Python pretty-printer object's
29075 @code{display_hint} method. @xref{Pretty Printing API}.
29078 This is an integer attribute which is nonzero if there are children
29079 remaining after the end of the selected range.
29082 @subsubheading Example
29086 -var-list-children n
29087 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29088 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
29090 -var-list-children --all-values n
29091 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
29092 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
29096 @subheading The @code{-var-info-type} Command
29097 @findex -var-info-type
29099 @subsubheading Synopsis
29102 -var-info-type @var{name}
29105 Returns the type of the specified variable @var{name}. The type is
29106 returned as a string in the same format as it is output by the
29110 type=@var{typename}
29114 @subheading The @code{-var-info-expression} Command
29115 @findex -var-info-expression
29117 @subsubheading Synopsis
29120 -var-info-expression @var{name}
29123 Returns a string that is suitable for presenting this
29124 variable object in user interface. The string is generally
29125 not valid expression in the current language, and cannot be evaluated.
29127 For example, if @code{a} is an array, and variable object
29128 @code{A} was created for @code{a}, then we'll get this output:
29131 (gdb) -var-info-expression A.1
29132 ^done,lang="C",exp="1"
29136 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
29138 Note that the output of the @code{-var-list-children} command also
29139 includes those expressions, so the @code{-var-info-expression} command
29142 @subheading The @code{-var-info-path-expression} Command
29143 @findex -var-info-path-expression
29145 @subsubheading Synopsis
29148 -var-info-path-expression @var{name}
29151 Returns an expression that can be evaluated in the current
29152 context and will yield the same value that a variable object has.
29153 Compare this with the @code{-var-info-expression} command, which
29154 result can be used only for UI presentation. Typical use of
29155 the @code{-var-info-path-expression} command is creating a
29156 watchpoint from a variable object.
29158 This command is currently not valid for children of a dynamic varobj,
29159 and will give an error when invoked on one.
29161 For example, suppose @code{C} is a C@t{++} class, derived from class
29162 @code{Base}, and that the @code{Base} class has a member called
29163 @code{m_size}. Assume a variable @code{c} is has the type of
29164 @code{C} and a variable object @code{C} was created for variable
29165 @code{c}. Then, we'll get this output:
29167 (gdb) -var-info-path-expression C.Base.public.m_size
29168 ^done,path_expr=((Base)c).m_size)
29171 @subheading The @code{-var-show-attributes} Command
29172 @findex -var-show-attributes
29174 @subsubheading Synopsis
29177 -var-show-attributes @var{name}
29180 List attributes of the specified variable object @var{name}:
29183 status=@var{attr} [ ( ,@var{attr} )* ]
29187 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
29189 @subheading The @code{-var-evaluate-expression} Command
29190 @findex -var-evaluate-expression
29192 @subsubheading Synopsis
29195 -var-evaluate-expression [-f @var{format-spec}] @var{name}
29198 Evaluates the expression that is represented by the specified variable
29199 object and returns its value as a string. The format of the string
29200 can be specified with the @samp{-f} option. The possible values of
29201 this option are the same as for @code{-var-set-format}
29202 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
29203 the current display format will be used. The current display format
29204 can be changed using the @code{-var-set-format} command.
29210 Note that one must invoke @code{-var-list-children} for a variable
29211 before the value of a child variable can be evaluated.
29213 @subheading The @code{-var-assign} Command
29214 @findex -var-assign
29216 @subsubheading Synopsis
29219 -var-assign @var{name} @var{expression}
29222 Assigns the value of @var{expression} to the variable object specified
29223 by @var{name}. The object must be @samp{editable}. If the variable's
29224 value is altered by the assign, the variable will show up in any
29225 subsequent @code{-var-update} list.
29227 @subsubheading Example
29235 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
29239 @subheading The @code{-var-update} Command
29240 @findex -var-update
29242 @subsubheading Synopsis
29245 -var-update [@var{print-values}] @{@var{name} | "*"@}
29248 Reevaluate the expressions corresponding to the variable object
29249 @var{name} and all its direct and indirect children, and return the
29250 list of variable objects whose values have changed; @var{name} must
29251 be a root variable object. Here, ``changed'' means that the result of
29252 @code{-var-evaluate-expression} before and after the
29253 @code{-var-update} is different. If @samp{*} is used as the variable
29254 object names, all existing variable objects are updated, except
29255 for frozen ones (@pxref{-var-set-frozen}). The option
29256 @var{print-values} determines whether both names and values, or just
29257 names are printed. The possible values of this option are the same
29258 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
29259 recommended to use the @samp{--all-values} option, to reduce the
29260 number of MI commands needed on each program stop.
29262 With the @samp{*} parameter, if a variable object is bound to a
29263 currently running thread, it will not be updated, without any
29266 If @code{-var-set-update-range} was previously used on a varobj, then
29267 only the selected range of children will be reported.
29269 @code{-var-update} reports all the changed varobjs in a tuple named
29272 Each item in the change list is itself a tuple holding:
29276 The name of the varobj.
29279 If values were requested for this update, then this field will be
29280 present and will hold the value of the varobj.
29283 @anchor{-var-update}
29284 This field is a string which may take one of three values:
29288 The variable object's current value is valid.
29291 The variable object does not currently hold a valid value but it may
29292 hold one in the future if its associated expression comes back into
29296 The variable object no longer holds a valid value.
29297 This can occur when the executable file being debugged has changed,
29298 either through recompilation or by using the @value{GDBN} @code{file}
29299 command. The front end should normally choose to delete these variable
29303 In the future new values may be added to this list so the front should
29304 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
29307 This is only present if the varobj is still valid. If the type
29308 changed, then this will be the string @samp{true}; otherwise it will
29312 If the varobj's type changed, then this field will be present and will
29315 @item new_num_children
29316 For a dynamic varobj, if the number of children changed, or if the
29317 type changed, this will be the new number of children.
29319 The @samp{numchild} field in other varobj responses is generally not
29320 valid for a dynamic varobj -- it will show the number of children that
29321 @value{GDBN} knows about, but because dynamic varobjs lazily
29322 instantiate their children, this will not reflect the number of
29323 children which may be available.
29325 The @samp{new_num_children} attribute only reports changes to the
29326 number of children known by @value{GDBN}. This is the only way to
29327 detect whether an update has removed children (which necessarily can
29328 only happen at the end of the update range).
29331 The display hint, if any.
29334 This is an integer value, which will be 1 if there are more children
29335 available outside the varobj's update range.
29338 This attribute will be present and have the value @samp{1} if the
29339 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
29340 then this attribute will not be present.
29343 If new children were added to a dynamic varobj within the selected
29344 update range (as set by @code{-var-set-update-range}), then they will
29345 be listed in this attribute.
29348 @subsubheading Example
29355 -var-update --all-values var1
29356 ^done,changelist=[@{name="var1",value="3",in_scope="true",
29357 type_changed="false"@}]
29361 @subheading The @code{-var-set-frozen} Command
29362 @findex -var-set-frozen
29363 @anchor{-var-set-frozen}
29365 @subsubheading Synopsis
29368 -var-set-frozen @var{name} @var{flag}
29371 Set the frozenness flag on the variable object @var{name}. The
29372 @var{flag} parameter should be either @samp{1} to make the variable
29373 frozen or @samp{0} to make it unfrozen. If a variable object is
29374 frozen, then neither itself, nor any of its children, are
29375 implicitly updated by @code{-var-update} of
29376 a parent variable or by @code{-var-update *}. Only
29377 @code{-var-update} of the variable itself will update its value and
29378 values of its children. After a variable object is unfrozen, it is
29379 implicitly updated by all subsequent @code{-var-update} operations.
29380 Unfreezing a variable does not update it, only subsequent
29381 @code{-var-update} does.
29383 @subsubheading Example
29387 -var-set-frozen V 1
29392 @subheading The @code{-var-set-update-range} command
29393 @findex -var-set-update-range
29394 @anchor{-var-set-update-range}
29396 @subsubheading Synopsis
29399 -var-set-update-range @var{name} @var{from} @var{to}
29402 Set the range of children to be returned by future invocations of
29403 @code{-var-update}.
29405 @var{from} and @var{to} indicate the range of children to report. If
29406 @var{from} or @var{to} is less than zero, the range is reset and all
29407 children will be reported. Otherwise, children starting at @var{from}
29408 (zero-based) and up to and excluding @var{to} will be reported.
29410 @subsubheading Example
29414 -var-set-update-range V 1 2
29418 @subheading The @code{-var-set-visualizer} command
29419 @findex -var-set-visualizer
29420 @anchor{-var-set-visualizer}
29422 @subsubheading Synopsis
29425 -var-set-visualizer @var{name} @var{visualizer}
29428 Set a visualizer for the variable object @var{name}.
29430 @var{visualizer} is the visualizer to use. The special value
29431 @samp{None} means to disable any visualizer in use.
29433 If not @samp{None}, @var{visualizer} must be a Python expression.
29434 This expression must evaluate to a callable object which accepts a
29435 single argument. @value{GDBN} will call this object with the value of
29436 the varobj @var{name} as an argument (this is done so that the same
29437 Python pretty-printing code can be used for both the CLI and MI).
29438 When called, this object must return an object which conforms to the
29439 pretty-printing interface (@pxref{Pretty Printing API}).
29441 The pre-defined function @code{gdb.default_visualizer} may be used to
29442 select a visualizer by following the built-in process
29443 (@pxref{Selecting Pretty-Printers}). This is done automatically when
29444 a varobj is created, and so ordinarily is not needed.
29446 This feature is only available if Python support is enabled. The MI
29447 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
29448 can be used to check this.
29450 @subsubheading Example
29452 Resetting the visualizer:
29456 -var-set-visualizer V None
29460 Reselecting the default (type-based) visualizer:
29464 -var-set-visualizer V gdb.default_visualizer
29468 Suppose @code{SomeClass} is a visualizer class. A lambda expression
29469 can be used to instantiate this class for a varobj:
29473 -var-set-visualizer V "lambda val: SomeClass()"
29477 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29478 @node GDB/MI Data Manipulation
29479 @section @sc{gdb/mi} Data Manipulation
29481 @cindex data manipulation, in @sc{gdb/mi}
29482 @cindex @sc{gdb/mi}, data manipulation
29483 This section describes the @sc{gdb/mi} commands that manipulate data:
29484 examine memory and registers, evaluate expressions, etc.
29486 @c REMOVED FROM THE INTERFACE.
29487 @c @subheading -data-assign
29488 @c Change the value of a program variable. Plenty of side effects.
29489 @c @subsubheading GDB Command
29491 @c @subsubheading Example
29494 @subheading The @code{-data-disassemble} Command
29495 @findex -data-disassemble
29497 @subsubheading Synopsis
29501 [ -s @var{start-addr} -e @var{end-addr} ]
29502 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
29510 @item @var{start-addr}
29511 is the beginning address (or @code{$pc})
29512 @item @var{end-addr}
29514 @item @var{filename}
29515 is the name of the file to disassemble
29516 @item @var{linenum}
29517 is the line number to disassemble around
29519 is the number of disassembly lines to be produced. If it is -1,
29520 the whole function will be disassembled, in case no @var{end-addr} is
29521 specified. If @var{end-addr} is specified as a non-zero value, and
29522 @var{lines} is lower than the number of disassembly lines between
29523 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
29524 displayed; if @var{lines} is higher than the number of lines between
29525 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
29528 is either 0 (meaning only disassembly), 1 (meaning mixed source and
29529 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
29530 mixed source and disassembly with raw opcodes).
29533 @subsubheading Result
29535 The output for each instruction is composed of four fields:
29544 Note that whatever included in the instruction field, is not manipulated
29545 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
29547 @subsubheading @value{GDBN} Command
29549 There's no direct mapping from this command to the CLI.
29551 @subsubheading Example
29553 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
29557 -data-disassemble -s $pc -e "$pc + 20" -- 0
29560 @{address="0x000107c0",func-name="main",offset="4",
29561 inst="mov 2, %o0"@},
29562 @{address="0x000107c4",func-name="main",offset="8",
29563 inst="sethi %hi(0x11800), %o2"@},
29564 @{address="0x000107c8",func-name="main",offset="12",
29565 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
29566 @{address="0x000107cc",func-name="main",offset="16",
29567 inst="sethi %hi(0x11800), %o2"@},
29568 @{address="0x000107d0",func-name="main",offset="20",
29569 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
29573 Disassemble the whole @code{main} function. Line 32 is part of
29577 -data-disassemble -f basics.c -l 32 -- 0
29579 @{address="0x000107bc",func-name="main",offset="0",
29580 inst="save %sp, -112, %sp"@},
29581 @{address="0x000107c0",func-name="main",offset="4",
29582 inst="mov 2, %o0"@},
29583 @{address="0x000107c4",func-name="main",offset="8",
29584 inst="sethi %hi(0x11800), %o2"@},
29586 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
29587 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
29591 Disassemble 3 instructions from the start of @code{main}:
29595 -data-disassemble -f basics.c -l 32 -n 3 -- 0
29597 @{address="0x000107bc",func-name="main",offset="0",
29598 inst="save %sp, -112, %sp"@},
29599 @{address="0x000107c0",func-name="main",offset="4",
29600 inst="mov 2, %o0"@},
29601 @{address="0x000107c4",func-name="main",offset="8",
29602 inst="sethi %hi(0x11800), %o2"@}]
29606 Disassemble 3 instructions from the start of @code{main} in mixed mode:
29610 -data-disassemble -f basics.c -l 32 -n 3 -- 1
29612 src_and_asm_line=@{line="31",
29613 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
29614 testsuite/gdb.mi/basics.c",line_asm_insn=[
29615 @{address="0x000107bc",func-name="main",offset="0",
29616 inst="save %sp, -112, %sp"@}]@},
29617 src_and_asm_line=@{line="32",
29618 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
29619 testsuite/gdb.mi/basics.c",line_asm_insn=[
29620 @{address="0x000107c0",func-name="main",offset="4",
29621 inst="mov 2, %o0"@},
29622 @{address="0x000107c4",func-name="main",offset="8",
29623 inst="sethi %hi(0x11800), %o2"@}]@}]
29628 @subheading The @code{-data-evaluate-expression} Command
29629 @findex -data-evaluate-expression
29631 @subsubheading Synopsis
29634 -data-evaluate-expression @var{expr}
29637 Evaluate @var{expr} as an expression. The expression could contain an
29638 inferior function call. The function call will execute synchronously.
29639 If the expression contains spaces, it must be enclosed in double quotes.
29641 @subsubheading @value{GDBN} Command
29643 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
29644 @samp{call}. In @code{gdbtk} only, there's a corresponding
29645 @samp{gdb_eval} command.
29647 @subsubheading Example
29649 In the following example, the numbers that precede the commands are the
29650 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
29651 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
29655 211-data-evaluate-expression A
29658 311-data-evaluate-expression &A
29659 311^done,value="0xefffeb7c"
29661 411-data-evaluate-expression A+3
29664 511-data-evaluate-expression "A + 3"
29670 @subheading The @code{-data-list-changed-registers} Command
29671 @findex -data-list-changed-registers
29673 @subsubheading Synopsis
29676 -data-list-changed-registers
29679 Display a list of the registers that have changed.
29681 @subsubheading @value{GDBN} Command
29683 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
29684 has the corresponding command @samp{gdb_changed_register_list}.
29686 @subsubheading Example
29688 On a PPC MBX board:
29696 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
29697 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
29700 -data-list-changed-registers
29701 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
29702 "10","11","13","14","15","16","17","18","19","20","21","22","23",
29703 "24","25","26","27","28","30","31","64","65","66","67","69"]
29708 @subheading The @code{-data-list-register-names} Command
29709 @findex -data-list-register-names
29711 @subsubheading Synopsis
29714 -data-list-register-names [ ( @var{regno} )+ ]
29717 Show a list of register names for the current target. If no arguments
29718 are given, it shows a list of the names of all the registers. If
29719 integer numbers are given as arguments, it will print a list of the
29720 names of the registers corresponding to the arguments. To ensure
29721 consistency between a register name and its number, the output list may
29722 include empty register names.
29724 @subsubheading @value{GDBN} Command
29726 @value{GDBN} does not have a command which corresponds to
29727 @samp{-data-list-register-names}. In @code{gdbtk} there is a
29728 corresponding command @samp{gdb_regnames}.
29730 @subsubheading Example
29732 For the PPC MBX board:
29735 -data-list-register-names
29736 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
29737 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
29738 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
29739 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
29740 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
29741 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
29742 "", "pc","ps","cr","lr","ctr","xer"]
29744 -data-list-register-names 1 2 3
29745 ^done,register-names=["r1","r2","r3"]
29749 @subheading The @code{-data-list-register-values} Command
29750 @findex -data-list-register-values
29752 @subsubheading Synopsis
29755 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
29758 Display the registers' contents. @var{fmt} is the format according to
29759 which the registers' contents are to be returned, followed by an optional
29760 list of numbers specifying the registers to display. A missing list of
29761 numbers indicates that the contents of all the registers must be returned.
29763 Allowed formats for @var{fmt} are:
29780 @subsubheading @value{GDBN} Command
29782 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
29783 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
29785 @subsubheading Example
29787 For a PPC MBX board (note: line breaks are for readability only, they
29788 don't appear in the actual output):
29792 -data-list-register-values r 64 65
29793 ^done,register-values=[@{number="64",value="0xfe00a300"@},
29794 @{number="65",value="0x00029002"@}]
29796 -data-list-register-values x
29797 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
29798 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
29799 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
29800 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
29801 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
29802 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
29803 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
29804 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
29805 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
29806 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
29807 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
29808 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
29809 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
29810 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
29811 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
29812 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
29813 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
29814 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
29815 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
29816 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
29817 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
29818 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
29819 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
29820 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
29821 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
29822 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
29823 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
29824 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
29825 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
29826 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
29827 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
29828 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
29829 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
29830 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
29831 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
29832 @{number="69",value="0x20002b03"@}]
29837 @subheading The @code{-data-read-memory} Command
29838 @findex -data-read-memory
29840 This command is deprecated, use @code{-data-read-memory-bytes} instead.
29842 @subsubheading Synopsis
29845 -data-read-memory [ -o @var{byte-offset} ]
29846 @var{address} @var{word-format} @var{word-size}
29847 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
29854 @item @var{address}
29855 An expression specifying the address of the first memory word to be
29856 read. Complex expressions containing embedded white space should be
29857 quoted using the C convention.
29859 @item @var{word-format}
29860 The format to be used to print the memory words. The notation is the
29861 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
29864 @item @var{word-size}
29865 The size of each memory word in bytes.
29867 @item @var{nr-rows}
29868 The number of rows in the output table.
29870 @item @var{nr-cols}
29871 The number of columns in the output table.
29874 If present, indicates that each row should include an @sc{ascii} dump. The
29875 value of @var{aschar} is used as a padding character when a byte is not a
29876 member of the printable @sc{ascii} character set (printable @sc{ascii}
29877 characters are those whose code is between 32 and 126, inclusively).
29879 @item @var{byte-offset}
29880 An offset to add to the @var{address} before fetching memory.
29883 This command displays memory contents as a table of @var{nr-rows} by
29884 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
29885 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
29886 (returned as @samp{total-bytes}). Should less than the requested number
29887 of bytes be returned by the target, the missing words are identified
29888 using @samp{N/A}. The number of bytes read from the target is returned
29889 in @samp{nr-bytes} and the starting address used to read memory in
29892 The address of the next/previous row or page is available in
29893 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
29896 @subsubheading @value{GDBN} Command
29898 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
29899 @samp{gdb_get_mem} memory read command.
29901 @subsubheading Example
29903 Read six bytes of memory starting at @code{bytes+6} but then offset by
29904 @code{-6} bytes. Format as three rows of two columns. One byte per
29905 word. Display each word in hex.
29909 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
29910 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
29911 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
29912 prev-page="0x0000138a",memory=[
29913 @{addr="0x00001390",data=["0x00","0x01"]@},
29914 @{addr="0x00001392",data=["0x02","0x03"]@},
29915 @{addr="0x00001394",data=["0x04","0x05"]@}]
29919 Read two bytes of memory starting at address @code{shorts + 64} and
29920 display as a single word formatted in decimal.
29924 5-data-read-memory shorts+64 d 2 1 1
29925 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
29926 next-row="0x00001512",prev-row="0x0000150e",
29927 next-page="0x00001512",prev-page="0x0000150e",memory=[
29928 @{addr="0x00001510",data=["128"]@}]
29932 Read thirty two bytes of memory starting at @code{bytes+16} and format
29933 as eight rows of four columns. Include a string encoding with @samp{x}
29934 used as the non-printable character.
29938 4-data-read-memory bytes+16 x 1 8 4 x
29939 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
29940 next-row="0x000013c0",prev-row="0x0000139c",
29941 next-page="0x000013c0",prev-page="0x00001380",memory=[
29942 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
29943 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
29944 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
29945 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
29946 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
29947 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
29948 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
29949 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
29953 @subheading The @code{-data-read-memory-bytes} Command
29954 @findex -data-read-memory-bytes
29956 @subsubheading Synopsis
29959 -data-read-memory-bytes [ -o @var{byte-offset} ]
29960 @var{address} @var{count}
29967 @item @var{address}
29968 An expression specifying the address of the first memory word to be
29969 read. Complex expressions containing embedded white space should be
29970 quoted using the C convention.
29973 The number of bytes to read. This should be an integer literal.
29975 @item @var{byte-offset}
29976 The offsets in bytes relative to @var{address} at which to start
29977 reading. This should be an integer literal. This option is provided
29978 so that a frontend is not required to first evaluate address and then
29979 perform address arithmetics itself.
29983 This command attempts to read all accessible memory regions in the
29984 specified range. First, all regions marked as unreadable in the memory
29985 map (if one is defined) will be skipped. @xref{Memory Region
29986 Attributes}. Second, @value{GDBN} will attempt to read the remaining
29987 regions. For each one, if reading full region results in an errors,
29988 @value{GDBN} will try to read a subset of the region.
29990 In general, every single byte in the region may be readable or not,
29991 and the only way to read every readable byte is to try a read at
29992 every address, which is not practical. Therefore, @value{GDBN} will
29993 attempt to read all accessible bytes at either beginning or the end
29994 of the region, using a binary division scheme. This heuristic works
29995 well for reading accross a memory map boundary. Note that if a region
29996 has a readable range that is neither at the beginning or the end,
29997 @value{GDBN} will not read it.
29999 The result record (@pxref{GDB/MI Result Records}) that is output of
30000 the command includes a field named @samp{memory} whose content is a
30001 list of tuples. Each tuple represent a successfully read memory block
30002 and has the following fields:
30006 The start address of the memory block, as hexadecimal literal.
30009 The end address of the memory block, as hexadecimal literal.
30012 The offset of the memory block, as hexadecimal literal, relative to
30013 the start address passed to @code{-data-read-memory-bytes}.
30016 The contents of the memory block, in hex.
30022 @subsubheading @value{GDBN} Command
30024 The corresponding @value{GDBN} command is @samp{x}.
30026 @subsubheading Example
30030 -data-read-memory-bytes &a 10
30031 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
30033 contents="01000000020000000300"@}]
30038 @subheading The @code{-data-write-memory-bytes} Command
30039 @findex -data-write-memory-bytes
30041 @subsubheading Synopsis
30044 -data-write-memory-bytes @var{address} @var{contents}
30051 @item @var{address}
30052 An expression specifying the address of the first memory word to be
30053 read. Complex expressions containing embedded white space should be
30054 quoted using the C convention.
30056 @item @var{contents}
30057 The hex-encoded bytes to write.
30061 @subsubheading @value{GDBN} Command
30063 There's no corresponding @value{GDBN} command.
30065 @subsubheading Example
30069 -data-write-memory-bytes &a "aabbccdd"
30075 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30076 @node GDB/MI Tracepoint Commands
30077 @section @sc{gdb/mi} Tracepoint Commands
30079 The commands defined in this section implement MI support for
30080 tracepoints. For detailed introduction, see @ref{Tracepoints}.
30082 @subheading The @code{-trace-find} Command
30083 @findex -trace-find
30085 @subsubheading Synopsis
30088 -trace-find @var{mode} [@var{parameters}@dots{}]
30091 Find a trace frame using criteria defined by @var{mode} and
30092 @var{parameters}. The following table lists permissible
30093 modes and their parameters. For details of operation, see @ref{tfind}.
30098 No parameters are required. Stops examining trace frames.
30101 An integer is required as parameter. Selects tracepoint frame with
30104 @item tracepoint-number
30105 An integer is required as parameter. Finds next
30106 trace frame that corresponds to tracepoint with the specified number.
30109 An address is required as parameter. Finds
30110 next trace frame that corresponds to any tracepoint at the specified
30113 @item pc-inside-range
30114 Two addresses are required as parameters. Finds next trace
30115 frame that corresponds to a tracepoint at an address inside the
30116 specified range. Both bounds are considered to be inside the range.
30118 @item pc-outside-range
30119 Two addresses are required as parameters. Finds
30120 next trace frame that corresponds to a tracepoint at an address outside
30121 the specified range. Both bounds are considered to be inside the range.
30124 Line specification is required as parameter. @xref{Specify Location}.
30125 Finds next trace frame that corresponds to a tracepoint at
30126 the specified location.
30130 If @samp{none} was passed as @var{mode}, the response does not
30131 have fields. Otherwise, the response may have the following fields:
30135 This field has either @samp{0} or @samp{1} as the value, depending
30136 on whether a matching tracepoint was found.
30139 The index of the found traceframe. This field is present iff
30140 the @samp{found} field has value of @samp{1}.
30143 The index of the found tracepoint. This field is present iff
30144 the @samp{found} field has value of @samp{1}.
30147 The information about the frame corresponding to the found trace
30148 frame. This field is present only if a trace frame was found.
30149 @xref{GDB/MI Frame Information}, for description of this field.
30153 @subsubheading @value{GDBN} Command
30155 The corresponding @value{GDBN} command is @samp{tfind}.
30157 @subheading -trace-define-variable
30158 @findex -trace-define-variable
30160 @subsubheading Synopsis
30163 -trace-define-variable @var{name} [ @var{value} ]
30166 Create trace variable @var{name} if it does not exist. If
30167 @var{value} is specified, sets the initial value of the specified
30168 trace variable to that value. Note that the @var{name} should start
30169 with the @samp{$} character.
30171 @subsubheading @value{GDBN} Command
30173 The corresponding @value{GDBN} command is @samp{tvariable}.
30175 @subheading -trace-list-variables
30176 @findex -trace-list-variables
30178 @subsubheading Synopsis
30181 -trace-list-variables
30184 Return a table of all defined trace variables. Each element of the
30185 table has the following fields:
30189 The name of the trace variable. This field is always present.
30192 The initial value. This is a 64-bit signed integer. This
30193 field is always present.
30196 The value the trace variable has at the moment. This is a 64-bit
30197 signed integer. This field is absent iff current value is
30198 not defined, for example if the trace was never run, or is
30203 @subsubheading @value{GDBN} Command
30205 The corresponding @value{GDBN} command is @samp{tvariables}.
30207 @subsubheading Example
30211 -trace-list-variables
30212 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
30213 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
30214 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
30215 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
30216 body=[variable=@{name="$trace_timestamp",initial="0"@}
30217 variable=@{name="$foo",initial="10",current="15"@}]@}
30221 @subheading -trace-save
30222 @findex -trace-save
30224 @subsubheading Synopsis
30227 -trace-save [-r ] @var{filename}
30230 Saves the collected trace data to @var{filename}. Without the
30231 @samp{-r} option, the data is downloaded from the target and saved
30232 in a local file. With the @samp{-r} option the target is asked
30233 to perform the save.
30235 @subsubheading @value{GDBN} Command
30237 The corresponding @value{GDBN} command is @samp{tsave}.
30240 @subheading -trace-start
30241 @findex -trace-start
30243 @subsubheading Synopsis
30249 Starts a tracing experiments. The result of this command does not
30252 @subsubheading @value{GDBN} Command
30254 The corresponding @value{GDBN} command is @samp{tstart}.
30256 @subheading -trace-status
30257 @findex -trace-status
30259 @subsubheading Synopsis
30265 Obtains the status of a tracing experiment. The result may include
30266 the following fields:
30271 May have a value of either @samp{0}, when no tracing operations are
30272 supported, @samp{1}, when all tracing operations are supported, or
30273 @samp{file} when examining trace file. In the latter case, examining
30274 of trace frame is possible but new tracing experiement cannot be
30275 started. This field is always present.
30278 May have a value of either @samp{0} or @samp{1} depending on whether
30279 tracing experiement is in progress on target. This field is present
30280 if @samp{supported} field is not @samp{0}.
30283 Report the reason why the tracing was stopped last time. This field
30284 may be absent iff tracing was never stopped on target yet. The
30285 value of @samp{request} means the tracing was stopped as result of
30286 the @code{-trace-stop} command. The value of @samp{overflow} means
30287 the tracing buffer is full. The value of @samp{disconnection} means
30288 tracing was automatically stopped when @value{GDBN} has disconnected.
30289 The value of @samp{passcount} means tracing was stopped when a
30290 tracepoint was passed a maximal number of times for that tracepoint.
30291 This field is present if @samp{supported} field is not @samp{0}.
30293 @item stopping-tracepoint
30294 The number of tracepoint whose passcount as exceeded. This field is
30295 present iff the @samp{stop-reason} field has the value of
30299 @itemx frames-created
30300 The @samp{frames} field is a count of the total number of trace frames
30301 in the trace buffer, while @samp{frames-created} is the total created
30302 during the run, including ones that were discarded, such as when a
30303 circular trace buffer filled up. Both fields are optional.
30307 These fields tell the current size of the tracing buffer and the
30308 remaining space. These fields are optional.
30311 The value of the circular trace buffer flag. @code{1} means that the
30312 trace buffer is circular and old trace frames will be discarded if
30313 necessary to make room, @code{0} means that the trace buffer is linear
30317 The value of the disconnected tracing flag. @code{1} means that
30318 tracing will continue after @value{GDBN} disconnects, @code{0} means
30319 that the trace run will stop.
30323 @subsubheading @value{GDBN} Command
30325 The corresponding @value{GDBN} command is @samp{tstatus}.
30327 @subheading -trace-stop
30328 @findex -trace-stop
30330 @subsubheading Synopsis
30336 Stops a tracing experiment. The result of this command has the same
30337 fields as @code{-trace-status}, except that the @samp{supported} and
30338 @samp{running} fields are not output.
30340 @subsubheading @value{GDBN} Command
30342 The corresponding @value{GDBN} command is @samp{tstop}.
30345 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30346 @node GDB/MI Symbol Query
30347 @section @sc{gdb/mi} Symbol Query Commands
30351 @subheading The @code{-symbol-info-address} Command
30352 @findex -symbol-info-address
30354 @subsubheading Synopsis
30357 -symbol-info-address @var{symbol}
30360 Describe where @var{symbol} is stored.
30362 @subsubheading @value{GDBN} Command
30364 The corresponding @value{GDBN} command is @samp{info address}.
30366 @subsubheading Example
30370 @subheading The @code{-symbol-info-file} Command
30371 @findex -symbol-info-file
30373 @subsubheading Synopsis
30379 Show the file for the symbol.
30381 @subsubheading @value{GDBN} Command
30383 There's no equivalent @value{GDBN} command. @code{gdbtk} has
30384 @samp{gdb_find_file}.
30386 @subsubheading Example
30390 @subheading The @code{-symbol-info-function} Command
30391 @findex -symbol-info-function
30393 @subsubheading Synopsis
30396 -symbol-info-function
30399 Show which function the symbol lives in.
30401 @subsubheading @value{GDBN} Command
30403 @samp{gdb_get_function} in @code{gdbtk}.
30405 @subsubheading Example
30409 @subheading The @code{-symbol-info-line} Command
30410 @findex -symbol-info-line
30412 @subsubheading Synopsis
30418 Show the core addresses of the code for a source line.
30420 @subsubheading @value{GDBN} Command
30422 The corresponding @value{GDBN} command is @samp{info line}.
30423 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
30425 @subsubheading Example
30429 @subheading The @code{-symbol-info-symbol} Command
30430 @findex -symbol-info-symbol
30432 @subsubheading Synopsis
30435 -symbol-info-symbol @var{addr}
30438 Describe what symbol is at location @var{addr}.
30440 @subsubheading @value{GDBN} Command
30442 The corresponding @value{GDBN} command is @samp{info symbol}.
30444 @subsubheading Example
30448 @subheading The @code{-symbol-list-functions} Command
30449 @findex -symbol-list-functions
30451 @subsubheading Synopsis
30454 -symbol-list-functions
30457 List the functions in the executable.
30459 @subsubheading @value{GDBN} Command
30461 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
30462 @samp{gdb_search} in @code{gdbtk}.
30464 @subsubheading Example
30469 @subheading The @code{-symbol-list-lines} Command
30470 @findex -symbol-list-lines
30472 @subsubheading Synopsis
30475 -symbol-list-lines @var{filename}
30478 Print the list of lines that contain code and their associated program
30479 addresses for the given source filename. The entries are sorted in
30480 ascending PC order.
30482 @subsubheading @value{GDBN} Command
30484 There is no corresponding @value{GDBN} command.
30486 @subsubheading Example
30489 -symbol-list-lines basics.c
30490 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
30496 @subheading The @code{-symbol-list-types} Command
30497 @findex -symbol-list-types
30499 @subsubheading Synopsis
30505 List all the type names.
30507 @subsubheading @value{GDBN} Command
30509 The corresponding commands are @samp{info types} in @value{GDBN},
30510 @samp{gdb_search} in @code{gdbtk}.
30512 @subsubheading Example
30516 @subheading The @code{-symbol-list-variables} Command
30517 @findex -symbol-list-variables
30519 @subsubheading Synopsis
30522 -symbol-list-variables
30525 List all the global and static variable names.
30527 @subsubheading @value{GDBN} Command
30529 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
30531 @subsubheading Example
30535 @subheading The @code{-symbol-locate} Command
30536 @findex -symbol-locate
30538 @subsubheading Synopsis
30544 @subsubheading @value{GDBN} Command
30546 @samp{gdb_loc} in @code{gdbtk}.
30548 @subsubheading Example
30552 @subheading The @code{-symbol-type} Command
30553 @findex -symbol-type
30555 @subsubheading Synopsis
30558 -symbol-type @var{variable}
30561 Show type of @var{variable}.
30563 @subsubheading @value{GDBN} Command
30565 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
30566 @samp{gdb_obj_variable}.
30568 @subsubheading Example
30573 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30574 @node GDB/MI File Commands
30575 @section @sc{gdb/mi} File Commands
30577 This section describes the GDB/MI commands to specify executable file names
30578 and to read in and obtain symbol table information.
30580 @subheading The @code{-file-exec-and-symbols} Command
30581 @findex -file-exec-and-symbols
30583 @subsubheading Synopsis
30586 -file-exec-and-symbols @var{file}
30589 Specify the executable file to be debugged. This file is the one from
30590 which the symbol table is also read. If no file is specified, the
30591 command clears the executable and symbol information. If breakpoints
30592 are set when using this command with no arguments, @value{GDBN} will produce
30593 error messages. Otherwise, no output is produced, except a completion
30596 @subsubheading @value{GDBN} Command
30598 The corresponding @value{GDBN} command is @samp{file}.
30600 @subsubheading Example
30604 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30610 @subheading The @code{-file-exec-file} Command
30611 @findex -file-exec-file
30613 @subsubheading Synopsis
30616 -file-exec-file @var{file}
30619 Specify the executable file to be debugged. Unlike
30620 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
30621 from this file. If used without argument, @value{GDBN} clears the information
30622 about the executable file. No output is produced, except a completion
30625 @subsubheading @value{GDBN} Command
30627 The corresponding @value{GDBN} command is @samp{exec-file}.
30629 @subsubheading Example
30633 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30640 @subheading The @code{-file-list-exec-sections} Command
30641 @findex -file-list-exec-sections
30643 @subsubheading Synopsis
30646 -file-list-exec-sections
30649 List the sections of the current executable file.
30651 @subsubheading @value{GDBN} Command
30653 The @value{GDBN} command @samp{info file} shows, among the rest, the same
30654 information as this command. @code{gdbtk} has a corresponding command
30655 @samp{gdb_load_info}.
30657 @subsubheading Example
30662 @subheading The @code{-file-list-exec-source-file} Command
30663 @findex -file-list-exec-source-file
30665 @subsubheading Synopsis
30668 -file-list-exec-source-file
30671 List the line number, the current source file, and the absolute path
30672 to the current source file for the current executable. The macro
30673 information field has a value of @samp{1} or @samp{0} depending on
30674 whether or not the file includes preprocessor macro information.
30676 @subsubheading @value{GDBN} Command
30678 The @value{GDBN} equivalent is @samp{info source}
30680 @subsubheading Example
30684 123-file-list-exec-source-file
30685 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
30690 @subheading The @code{-file-list-exec-source-files} Command
30691 @findex -file-list-exec-source-files
30693 @subsubheading Synopsis
30696 -file-list-exec-source-files
30699 List the source files for the current executable.
30701 It will always output the filename, but only when @value{GDBN} can find
30702 the absolute file name of a source file, will it output the fullname.
30704 @subsubheading @value{GDBN} Command
30706 The @value{GDBN} equivalent is @samp{info sources}.
30707 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
30709 @subsubheading Example
30712 -file-list-exec-source-files
30714 @{file=foo.c,fullname=/home/foo.c@},
30715 @{file=/home/bar.c,fullname=/home/bar.c@},
30716 @{file=gdb_could_not_find_fullpath.c@}]
30721 @subheading The @code{-file-list-shared-libraries} Command
30722 @findex -file-list-shared-libraries
30724 @subsubheading Synopsis
30727 -file-list-shared-libraries
30730 List the shared libraries in the program.
30732 @subsubheading @value{GDBN} Command
30734 The corresponding @value{GDBN} command is @samp{info shared}.
30736 @subsubheading Example
30740 @subheading The @code{-file-list-symbol-files} Command
30741 @findex -file-list-symbol-files
30743 @subsubheading Synopsis
30746 -file-list-symbol-files
30751 @subsubheading @value{GDBN} Command
30753 The corresponding @value{GDBN} command is @samp{info file} (part of it).
30755 @subsubheading Example
30760 @subheading The @code{-file-symbol-file} Command
30761 @findex -file-symbol-file
30763 @subsubheading Synopsis
30766 -file-symbol-file @var{file}
30769 Read symbol table info from the specified @var{file} argument. When
30770 used without arguments, clears @value{GDBN}'s symbol table info. No output is
30771 produced, except for a completion notification.
30773 @subsubheading @value{GDBN} Command
30775 The corresponding @value{GDBN} command is @samp{symbol-file}.
30777 @subsubheading Example
30781 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
30787 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30788 @node GDB/MI Memory Overlay Commands
30789 @section @sc{gdb/mi} Memory Overlay Commands
30791 The memory overlay commands are not implemented.
30793 @c @subheading -overlay-auto
30795 @c @subheading -overlay-list-mapping-state
30797 @c @subheading -overlay-list-overlays
30799 @c @subheading -overlay-map
30801 @c @subheading -overlay-off
30803 @c @subheading -overlay-on
30805 @c @subheading -overlay-unmap
30807 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30808 @node GDB/MI Signal Handling Commands
30809 @section @sc{gdb/mi} Signal Handling Commands
30811 Signal handling commands are not implemented.
30813 @c @subheading -signal-handle
30815 @c @subheading -signal-list-handle-actions
30817 @c @subheading -signal-list-signal-types
30821 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30822 @node GDB/MI Target Manipulation
30823 @section @sc{gdb/mi} Target Manipulation Commands
30826 @subheading The @code{-target-attach} Command
30827 @findex -target-attach
30829 @subsubheading Synopsis
30832 -target-attach @var{pid} | @var{gid} | @var{file}
30835 Attach to a process @var{pid} or a file @var{file} outside of
30836 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
30837 group, the id previously returned by
30838 @samp{-list-thread-groups --available} must be used.
30840 @subsubheading @value{GDBN} Command
30842 The corresponding @value{GDBN} command is @samp{attach}.
30844 @subsubheading Example
30848 =thread-created,id="1"
30849 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
30855 @subheading The @code{-target-compare-sections} Command
30856 @findex -target-compare-sections
30858 @subsubheading Synopsis
30861 -target-compare-sections [ @var{section} ]
30864 Compare data of section @var{section} on target to the exec file.
30865 Without the argument, all sections are compared.
30867 @subsubheading @value{GDBN} Command
30869 The @value{GDBN} equivalent is @samp{compare-sections}.
30871 @subsubheading Example
30876 @subheading The @code{-target-detach} Command
30877 @findex -target-detach
30879 @subsubheading Synopsis
30882 -target-detach [ @var{pid} | @var{gid} ]
30885 Detach from the remote target which normally resumes its execution.
30886 If either @var{pid} or @var{gid} is specified, detaches from either
30887 the specified process, or specified thread group. There's no output.
30889 @subsubheading @value{GDBN} Command
30891 The corresponding @value{GDBN} command is @samp{detach}.
30893 @subsubheading Example
30903 @subheading The @code{-target-disconnect} Command
30904 @findex -target-disconnect
30906 @subsubheading Synopsis
30912 Disconnect from the remote target. There's no output and the target is
30913 generally not resumed.
30915 @subsubheading @value{GDBN} Command
30917 The corresponding @value{GDBN} command is @samp{disconnect}.
30919 @subsubheading Example
30929 @subheading The @code{-target-download} Command
30930 @findex -target-download
30932 @subsubheading Synopsis
30938 Loads the executable onto the remote target.
30939 It prints out an update message every half second, which includes the fields:
30943 The name of the section.
30945 The size of what has been sent so far for that section.
30947 The size of the section.
30949 The total size of what was sent so far (the current and the previous sections).
30951 The size of the overall executable to download.
30955 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
30956 @sc{gdb/mi} Output Syntax}).
30958 In addition, it prints the name and size of the sections, as they are
30959 downloaded. These messages include the following fields:
30963 The name of the section.
30965 The size of the section.
30967 The size of the overall executable to download.
30971 At the end, a summary is printed.
30973 @subsubheading @value{GDBN} Command
30975 The corresponding @value{GDBN} command is @samp{load}.
30977 @subsubheading Example
30979 Note: each status message appears on a single line. Here the messages
30980 have been broken down so that they can fit onto a page.
30985 +download,@{section=".text",section-size="6668",total-size="9880"@}
30986 +download,@{section=".text",section-sent="512",section-size="6668",
30987 total-sent="512",total-size="9880"@}
30988 +download,@{section=".text",section-sent="1024",section-size="6668",
30989 total-sent="1024",total-size="9880"@}
30990 +download,@{section=".text",section-sent="1536",section-size="6668",
30991 total-sent="1536",total-size="9880"@}
30992 +download,@{section=".text",section-sent="2048",section-size="6668",
30993 total-sent="2048",total-size="9880"@}
30994 +download,@{section=".text",section-sent="2560",section-size="6668",
30995 total-sent="2560",total-size="9880"@}
30996 +download,@{section=".text",section-sent="3072",section-size="6668",
30997 total-sent="3072",total-size="9880"@}
30998 +download,@{section=".text",section-sent="3584",section-size="6668",
30999 total-sent="3584",total-size="9880"@}
31000 +download,@{section=".text",section-sent="4096",section-size="6668",
31001 total-sent="4096",total-size="9880"@}
31002 +download,@{section=".text",section-sent="4608",section-size="6668",
31003 total-sent="4608",total-size="9880"@}
31004 +download,@{section=".text",section-sent="5120",section-size="6668",
31005 total-sent="5120",total-size="9880"@}
31006 +download,@{section=".text",section-sent="5632",section-size="6668",
31007 total-sent="5632",total-size="9880"@}
31008 +download,@{section=".text",section-sent="6144",section-size="6668",
31009 total-sent="6144",total-size="9880"@}
31010 +download,@{section=".text",section-sent="6656",section-size="6668",
31011 total-sent="6656",total-size="9880"@}
31012 +download,@{section=".init",section-size="28",total-size="9880"@}
31013 +download,@{section=".fini",section-size="28",total-size="9880"@}
31014 +download,@{section=".data",section-size="3156",total-size="9880"@}
31015 +download,@{section=".data",section-sent="512",section-size="3156",
31016 total-sent="7236",total-size="9880"@}
31017 +download,@{section=".data",section-sent="1024",section-size="3156",
31018 total-sent="7748",total-size="9880"@}
31019 +download,@{section=".data",section-sent="1536",section-size="3156",
31020 total-sent="8260",total-size="9880"@}
31021 +download,@{section=".data",section-sent="2048",section-size="3156",
31022 total-sent="8772",total-size="9880"@}
31023 +download,@{section=".data",section-sent="2560",section-size="3156",
31024 total-sent="9284",total-size="9880"@}
31025 +download,@{section=".data",section-sent="3072",section-size="3156",
31026 total-sent="9796",total-size="9880"@}
31027 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
31034 @subheading The @code{-target-exec-status} Command
31035 @findex -target-exec-status
31037 @subsubheading Synopsis
31040 -target-exec-status
31043 Provide information on the state of the target (whether it is running or
31044 not, for instance).
31046 @subsubheading @value{GDBN} Command
31048 There's no equivalent @value{GDBN} command.
31050 @subsubheading Example
31054 @subheading The @code{-target-list-available-targets} Command
31055 @findex -target-list-available-targets
31057 @subsubheading Synopsis
31060 -target-list-available-targets
31063 List the possible targets to connect to.
31065 @subsubheading @value{GDBN} Command
31067 The corresponding @value{GDBN} command is @samp{help target}.
31069 @subsubheading Example
31073 @subheading The @code{-target-list-current-targets} Command
31074 @findex -target-list-current-targets
31076 @subsubheading Synopsis
31079 -target-list-current-targets
31082 Describe the current target.
31084 @subsubheading @value{GDBN} Command
31086 The corresponding information is printed by @samp{info file} (among
31089 @subsubheading Example
31093 @subheading The @code{-target-list-parameters} Command
31094 @findex -target-list-parameters
31096 @subsubheading Synopsis
31099 -target-list-parameters
31105 @subsubheading @value{GDBN} Command
31109 @subsubheading Example
31113 @subheading The @code{-target-select} Command
31114 @findex -target-select
31116 @subsubheading Synopsis
31119 -target-select @var{type} @var{parameters @dots{}}
31122 Connect @value{GDBN} to the remote target. This command takes two args:
31126 The type of target, for instance @samp{remote}, etc.
31127 @item @var{parameters}
31128 Device names, host names and the like. @xref{Target Commands, ,
31129 Commands for Managing Targets}, for more details.
31132 The output is a connection notification, followed by the address at
31133 which the target program is, in the following form:
31136 ^connected,addr="@var{address}",func="@var{function name}",
31137 args=[@var{arg list}]
31140 @subsubheading @value{GDBN} Command
31142 The corresponding @value{GDBN} command is @samp{target}.
31144 @subsubheading Example
31148 -target-select remote /dev/ttya
31149 ^connected,addr="0xfe00a300",func="??",args=[]
31153 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31154 @node GDB/MI File Transfer Commands
31155 @section @sc{gdb/mi} File Transfer Commands
31158 @subheading The @code{-target-file-put} Command
31159 @findex -target-file-put
31161 @subsubheading Synopsis
31164 -target-file-put @var{hostfile} @var{targetfile}
31167 Copy file @var{hostfile} from the host system (the machine running
31168 @value{GDBN}) to @var{targetfile} on the target system.
31170 @subsubheading @value{GDBN} Command
31172 The corresponding @value{GDBN} command is @samp{remote put}.
31174 @subsubheading Example
31178 -target-file-put localfile remotefile
31184 @subheading The @code{-target-file-get} Command
31185 @findex -target-file-get
31187 @subsubheading Synopsis
31190 -target-file-get @var{targetfile} @var{hostfile}
31193 Copy file @var{targetfile} from the target system to @var{hostfile}
31194 on the host system.
31196 @subsubheading @value{GDBN} Command
31198 The corresponding @value{GDBN} command is @samp{remote get}.
31200 @subsubheading Example
31204 -target-file-get remotefile localfile
31210 @subheading The @code{-target-file-delete} Command
31211 @findex -target-file-delete
31213 @subsubheading Synopsis
31216 -target-file-delete @var{targetfile}
31219 Delete @var{targetfile} from the target system.
31221 @subsubheading @value{GDBN} Command
31223 The corresponding @value{GDBN} command is @samp{remote delete}.
31225 @subsubheading Example
31229 -target-file-delete remotefile
31235 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31236 @node GDB/MI Miscellaneous Commands
31237 @section Miscellaneous @sc{gdb/mi} Commands
31239 @c @subheading -gdb-complete
31241 @subheading The @code{-gdb-exit} Command
31244 @subsubheading Synopsis
31250 Exit @value{GDBN} immediately.
31252 @subsubheading @value{GDBN} Command
31254 Approximately corresponds to @samp{quit}.
31256 @subsubheading Example
31266 @subheading The @code{-exec-abort} Command
31267 @findex -exec-abort
31269 @subsubheading Synopsis
31275 Kill the inferior running program.
31277 @subsubheading @value{GDBN} Command
31279 The corresponding @value{GDBN} command is @samp{kill}.
31281 @subsubheading Example
31286 @subheading The @code{-gdb-set} Command
31289 @subsubheading Synopsis
31295 Set an internal @value{GDBN} variable.
31296 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
31298 @subsubheading @value{GDBN} Command
31300 The corresponding @value{GDBN} command is @samp{set}.
31302 @subsubheading Example
31312 @subheading The @code{-gdb-show} Command
31315 @subsubheading Synopsis
31321 Show the current value of a @value{GDBN} variable.
31323 @subsubheading @value{GDBN} Command
31325 The corresponding @value{GDBN} command is @samp{show}.
31327 @subsubheading Example
31336 @c @subheading -gdb-source
31339 @subheading The @code{-gdb-version} Command
31340 @findex -gdb-version
31342 @subsubheading Synopsis
31348 Show version information for @value{GDBN}. Used mostly in testing.
31350 @subsubheading @value{GDBN} Command
31352 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
31353 default shows this information when you start an interactive session.
31355 @subsubheading Example
31357 @c This example modifies the actual output from GDB to avoid overfull
31363 ~Copyright 2000 Free Software Foundation, Inc.
31364 ~GDB is free software, covered by the GNU General Public License, and
31365 ~you are welcome to change it and/or distribute copies of it under
31366 ~ certain conditions.
31367 ~Type "show copying" to see the conditions.
31368 ~There is absolutely no warranty for GDB. Type "show warranty" for
31370 ~This GDB was configured as
31371 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
31376 @subheading The @code{-list-features} Command
31377 @findex -list-features
31379 Returns a list of particular features of the MI protocol that
31380 this version of gdb implements. A feature can be a command,
31381 or a new field in an output of some command, or even an
31382 important bugfix. While a frontend can sometimes detect presence
31383 of a feature at runtime, it is easier to perform detection at debugger
31386 The command returns a list of strings, with each string naming an
31387 available feature. Each returned string is just a name, it does not
31388 have any internal structure. The list of possible feature names
31394 (gdb) -list-features
31395 ^done,result=["feature1","feature2"]
31398 The current list of features is:
31401 @item frozen-varobjs
31402 Indicates support for the @code{-var-set-frozen} command, as well
31403 as possible presense of the @code{frozen} field in the output
31404 of @code{-varobj-create}.
31405 @item pending-breakpoints
31406 Indicates support for the @option{-f} option to the @code{-break-insert}
31409 Indicates Python scripting support, Python-based
31410 pretty-printing commands, and possible presence of the
31411 @samp{display_hint} field in the output of @code{-var-list-children}
31413 Indicates support for the @code{-thread-info} command.
31414 @item data-read-memory-bytes
31415 Indicates support for the @code{-data-read-memory-bytes} and the
31416 @code{-data-write-memory-bytes} commands.
31417 @item breakpoint-notifications
31418 Indicates that changes to breakpoints and breakpoints created via the
31419 CLI will be announced via async records.
31420 @item ada-task-info
31421 Indicates support for the @code{-ada-task-info} command.
31424 @subheading The @code{-list-target-features} Command
31425 @findex -list-target-features
31427 Returns a list of particular features that are supported by the
31428 target. Those features affect the permitted MI commands, but
31429 unlike the features reported by the @code{-list-features} command, the
31430 features depend on which target GDB is using at the moment. Whenever
31431 a target can change, due to commands such as @code{-target-select},
31432 @code{-target-attach} or @code{-exec-run}, the list of target features
31433 may change, and the frontend should obtain it again.
31437 (gdb) -list-features
31438 ^done,result=["async"]
31441 The current list of features is:
31445 Indicates that the target is capable of asynchronous command
31446 execution, which means that @value{GDBN} will accept further commands
31447 while the target is running.
31450 Indicates that the target is capable of reverse execution.
31451 @xref{Reverse Execution}, for more information.
31455 @subheading The @code{-list-thread-groups} Command
31456 @findex -list-thread-groups
31458 @subheading Synopsis
31461 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
31464 Lists thread groups (@pxref{Thread groups}). When a single thread
31465 group is passed as the argument, lists the children of that group.
31466 When several thread group are passed, lists information about those
31467 thread groups. Without any parameters, lists information about all
31468 top-level thread groups.
31470 Normally, thread groups that are being debugged are reported.
31471 With the @samp{--available} option, @value{GDBN} reports thread groups
31472 available on the target.
31474 The output of this command may have either a @samp{threads} result or
31475 a @samp{groups} result. The @samp{thread} result has a list of tuples
31476 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
31477 Information}). The @samp{groups} result has a list of tuples as value,
31478 each tuple describing a thread group. If top-level groups are
31479 requested (that is, no parameter is passed), or when several groups
31480 are passed, the output always has a @samp{groups} result. The format
31481 of the @samp{group} result is described below.
31483 To reduce the number of roundtrips it's possible to list thread groups
31484 together with their children, by passing the @samp{--recurse} option
31485 and the recursion depth. Presently, only recursion depth of 1 is
31486 permitted. If this option is present, then every reported thread group
31487 will also include its children, either as @samp{group} or
31488 @samp{threads} field.
31490 In general, any combination of option and parameters is permitted, with
31491 the following caveats:
31495 When a single thread group is passed, the output will typically
31496 be the @samp{threads} result. Because threads may not contain
31497 anything, the @samp{recurse} option will be ignored.
31500 When the @samp{--available} option is passed, limited information may
31501 be available. In particular, the list of threads of a process might
31502 be inaccessible. Further, specifying specific thread groups might
31503 not give any performance advantage over listing all thread groups.
31504 The frontend should assume that @samp{-list-thread-groups --available}
31505 is always an expensive operation and cache the results.
31509 The @samp{groups} result is a list of tuples, where each tuple may
31510 have the following fields:
31514 Identifier of the thread group. This field is always present.
31515 The identifier is an opaque string; frontends should not try to
31516 convert it to an integer, even though it might look like one.
31519 The type of the thread group. At present, only @samp{process} is a
31523 The target-specific process identifier. This field is only present
31524 for thread groups of type @samp{process} and only if the process exists.
31527 The number of children this thread group has. This field may be
31528 absent for an available thread group.
31531 This field has a list of tuples as value, each tuple describing a
31532 thread. It may be present if the @samp{--recurse} option is
31533 specified, and it's actually possible to obtain the threads.
31536 This field is a list of integers, each identifying a core that one
31537 thread of the group is running on. This field may be absent if
31538 such information is not available.
31541 The name of the executable file that corresponds to this thread group.
31542 The field is only present for thread groups of type @samp{process},
31543 and only if there is a corresponding executable file.
31547 @subheading Example
31551 -list-thread-groups
31552 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
31553 -list-thread-groups 17
31554 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
31555 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
31556 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
31557 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
31558 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
31559 -list-thread-groups --available
31560 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
31561 -list-thread-groups --available --recurse 1
31562 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31563 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31564 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
31565 -list-thread-groups --available --recurse 1 17 18
31566 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
31567 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
31568 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
31572 @subheading The @code{-add-inferior} Command
31573 @findex -add-inferior
31575 @subheading Synopsis
31581 Creates a new inferior (@pxref{Inferiors and Programs}). The created
31582 inferior is not associated with any executable. Such association may
31583 be established with the @samp{-file-exec-and-symbols} command
31584 (@pxref{GDB/MI File Commands}). The command response has a single
31585 field, @samp{thread-group}, whose value is the identifier of the
31586 thread group corresponding to the new inferior.
31588 @subheading Example
31593 ^done,thread-group="i3"
31596 @subheading The @code{-interpreter-exec} Command
31597 @findex -interpreter-exec
31599 @subheading Synopsis
31602 -interpreter-exec @var{interpreter} @var{command}
31604 @anchor{-interpreter-exec}
31606 Execute the specified @var{command} in the given @var{interpreter}.
31608 @subheading @value{GDBN} Command
31610 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
31612 @subheading Example
31616 -interpreter-exec console "break main"
31617 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
31618 &"During symbol reading, bad structure-type format.\n"
31619 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
31624 @subheading The @code{-inferior-tty-set} Command
31625 @findex -inferior-tty-set
31627 @subheading Synopsis
31630 -inferior-tty-set /dev/pts/1
31633 Set terminal for future runs of the program being debugged.
31635 @subheading @value{GDBN} Command
31637 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
31639 @subheading Example
31643 -inferior-tty-set /dev/pts/1
31648 @subheading The @code{-inferior-tty-show} Command
31649 @findex -inferior-tty-show
31651 @subheading Synopsis
31657 Show terminal for future runs of program being debugged.
31659 @subheading @value{GDBN} Command
31661 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
31663 @subheading Example
31667 -inferior-tty-set /dev/pts/1
31671 ^done,inferior_tty_terminal="/dev/pts/1"
31675 @subheading The @code{-enable-timings} Command
31676 @findex -enable-timings
31678 @subheading Synopsis
31681 -enable-timings [yes | no]
31684 Toggle the printing of the wallclock, user and system times for an MI
31685 command as a field in its output. This command is to help frontend
31686 developers optimize the performance of their code. No argument is
31687 equivalent to @samp{yes}.
31689 @subheading @value{GDBN} Command
31693 @subheading Example
31701 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
31702 addr="0x080484ed",func="main",file="myprog.c",
31703 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
31704 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
31712 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
31713 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
31714 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
31715 fullname="/home/nickrob/myprog.c",line="73"@}
31720 @chapter @value{GDBN} Annotations
31722 This chapter describes annotations in @value{GDBN}. Annotations were
31723 designed to interface @value{GDBN} to graphical user interfaces or other
31724 similar programs which want to interact with @value{GDBN} at a
31725 relatively high level.
31727 The annotation mechanism has largely been superseded by @sc{gdb/mi}
31731 This is Edition @value{EDITION}, @value{DATE}.
31735 * Annotations Overview:: What annotations are; the general syntax.
31736 * Server Prefix:: Issuing a command without affecting user state.
31737 * Prompting:: Annotations marking @value{GDBN}'s need for input.
31738 * Errors:: Annotations for error messages.
31739 * Invalidation:: Some annotations describe things now invalid.
31740 * Annotations for Running::
31741 Whether the program is running, how it stopped, etc.
31742 * Source Annotations:: Annotations describing source code.
31745 @node Annotations Overview
31746 @section What is an Annotation?
31747 @cindex annotations
31749 Annotations start with a newline character, two @samp{control-z}
31750 characters, and the name of the annotation. If there is no additional
31751 information associated with this annotation, the name of the annotation
31752 is followed immediately by a newline. If there is additional
31753 information, the name of the annotation is followed by a space, the
31754 additional information, and a newline. The additional information
31755 cannot contain newline characters.
31757 Any output not beginning with a newline and two @samp{control-z}
31758 characters denotes literal output from @value{GDBN}. Currently there is
31759 no need for @value{GDBN} to output a newline followed by two
31760 @samp{control-z} characters, but if there was such a need, the
31761 annotations could be extended with an @samp{escape} annotation which
31762 means those three characters as output.
31764 The annotation @var{level}, which is specified using the
31765 @option{--annotate} command line option (@pxref{Mode Options}), controls
31766 how much information @value{GDBN} prints together with its prompt,
31767 values of expressions, source lines, and other types of output. Level 0
31768 is for no annotations, level 1 is for use when @value{GDBN} is run as a
31769 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
31770 for programs that control @value{GDBN}, and level 2 annotations have
31771 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
31772 Interface, annotate, GDB's Obsolete Annotations}).
31775 @kindex set annotate
31776 @item set annotate @var{level}
31777 The @value{GDBN} command @code{set annotate} sets the level of
31778 annotations to the specified @var{level}.
31780 @item show annotate
31781 @kindex show annotate
31782 Show the current annotation level.
31785 This chapter describes level 3 annotations.
31787 A simple example of starting up @value{GDBN} with annotations is:
31790 $ @kbd{gdb --annotate=3}
31792 Copyright 2003 Free Software Foundation, Inc.
31793 GDB is free software, covered by the GNU General Public License,
31794 and you are welcome to change it and/or distribute copies of it
31795 under certain conditions.
31796 Type "show copying" to see the conditions.
31797 There is absolutely no warranty for GDB. Type "show warranty"
31799 This GDB was configured as "i386-pc-linux-gnu"
31810 Here @samp{quit} is input to @value{GDBN}; the rest is output from
31811 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
31812 denotes a @samp{control-z} character) are annotations; the rest is
31813 output from @value{GDBN}.
31815 @node Server Prefix
31816 @section The Server Prefix
31817 @cindex server prefix
31819 If you prefix a command with @samp{server } then it will not affect
31820 the command history, nor will it affect @value{GDBN}'s notion of which
31821 command to repeat if @key{RET} is pressed on a line by itself. This
31822 means that commands can be run behind a user's back by a front-end in
31823 a transparent manner.
31825 The @code{server } prefix does not affect the recording of values into
31826 the value history; to print a value without recording it into the
31827 value history, use the @code{output} command instead of the
31828 @code{print} command.
31830 Using this prefix also disables confirmation requests
31831 (@pxref{confirmation requests}).
31834 @section Annotation for @value{GDBN} Input
31836 @cindex annotations for prompts
31837 When @value{GDBN} prompts for input, it annotates this fact so it is possible
31838 to know when to send output, when the output from a given command is
31841 Different kinds of input each have a different @dfn{input type}. Each
31842 input type has three annotations: a @code{pre-} annotation, which
31843 denotes the beginning of any prompt which is being output, a plain
31844 annotation, which denotes the end of the prompt, and then a @code{post-}
31845 annotation which denotes the end of any echo which may (or may not) be
31846 associated with the input. For example, the @code{prompt} input type
31847 features the following annotations:
31855 The input types are
31858 @findex pre-prompt annotation
31859 @findex prompt annotation
31860 @findex post-prompt annotation
31862 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
31864 @findex pre-commands annotation
31865 @findex commands annotation
31866 @findex post-commands annotation
31868 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
31869 command. The annotations are repeated for each command which is input.
31871 @findex pre-overload-choice annotation
31872 @findex overload-choice annotation
31873 @findex post-overload-choice annotation
31874 @item overload-choice
31875 When @value{GDBN} wants the user to select between various overloaded functions.
31877 @findex pre-query annotation
31878 @findex query annotation
31879 @findex post-query annotation
31881 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
31883 @findex pre-prompt-for-continue annotation
31884 @findex prompt-for-continue annotation
31885 @findex post-prompt-for-continue annotation
31886 @item prompt-for-continue
31887 When @value{GDBN} is asking the user to press return to continue. Note: Don't
31888 expect this to work well; instead use @code{set height 0} to disable
31889 prompting. This is because the counting of lines is buggy in the
31890 presence of annotations.
31895 @cindex annotations for errors, warnings and interrupts
31897 @findex quit annotation
31902 This annotation occurs right before @value{GDBN} responds to an interrupt.
31904 @findex error annotation
31909 This annotation occurs right before @value{GDBN} responds to an error.
31911 Quit and error annotations indicate that any annotations which @value{GDBN} was
31912 in the middle of may end abruptly. For example, if a
31913 @code{value-history-begin} annotation is followed by a @code{error}, one
31914 cannot expect to receive the matching @code{value-history-end}. One
31915 cannot expect not to receive it either, however; an error annotation
31916 does not necessarily mean that @value{GDBN} is immediately returning all the way
31919 @findex error-begin annotation
31920 A quit or error annotation may be preceded by
31926 Any output between that and the quit or error annotation is the error
31929 Warning messages are not yet annotated.
31930 @c If we want to change that, need to fix warning(), type_error(),
31931 @c range_error(), and possibly other places.
31934 @section Invalidation Notices
31936 @cindex annotations for invalidation messages
31937 The following annotations say that certain pieces of state may have
31941 @findex frames-invalid annotation
31942 @item ^Z^Zframes-invalid
31944 The frames (for example, output from the @code{backtrace} command) may
31947 @findex breakpoints-invalid annotation
31948 @item ^Z^Zbreakpoints-invalid
31950 The breakpoints may have changed. For example, the user just added or
31951 deleted a breakpoint.
31954 @node Annotations for Running
31955 @section Running the Program
31956 @cindex annotations for running programs
31958 @findex starting annotation
31959 @findex stopping annotation
31960 When the program starts executing due to a @value{GDBN} command such as
31961 @code{step} or @code{continue},
31967 is output. When the program stops,
31973 is output. Before the @code{stopped} annotation, a variety of
31974 annotations describe how the program stopped.
31977 @findex exited annotation
31978 @item ^Z^Zexited @var{exit-status}
31979 The program exited, and @var{exit-status} is the exit status (zero for
31980 successful exit, otherwise nonzero).
31982 @findex signalled annotation
31983 @findex signal-name annotation
31984 @findex signal-name-end annotation
31985 @findex signal-string annotation
31986 @findex signal-string-end annotation
31987 @item ^Z^Zsignalled
31988 The program exited with a signal. After the @code{^Z^Zsignalled}, the
31989 annotation continues:
31995 ^Z^Zsignal-name-end
31999 ^Z^Zsignal-string-end
32004 where @var{name} is the name of the signal, such as @code{SIGILL} or
32005 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
32006 as @code{Illegal Instruction} or @code{Segmentation fault}.
32007 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
32008 user's benefit and have no particular format.
32010 @findex signal annotation
32012 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
32013 just saying that the program received the signal, not that it was
32014 terminated with it.
32016 @findex breakpoint annotation
32017 @item ^Z^Zbreakpoint @var{number}
32018 The program hit breakpoint number @var{number}.
32020 @findex watchpoint annotation
32021 @item ^Z^Zwatchpoint @var{number}
32022 The program hit watchpoint number @var{number}.
32025 @node Source Annotations
32026 @section Displaying Source
32027 @cindex annotations for source display
32029 @findex source annotation
32030 The following annotation is used instead of displaying source code:
32033 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
32036 where @var{filename} is an absolute file name indicating which source
32037 file, @var{line} is the line number within that file (where 1 is the
32038 first line in the file), @var{character} is the character position
32039 within the file (where 0 is the first character in the file) (for most
32040 debug formats this will necessarily point to the beginning of a line),
32041 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
32042 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
32043 @var{addr} is the address in the target program associated with the
32044 source which is being displayed. @var{addr} is in the form @samp{0x}
32045 followed by one or more lowercase hex digits (note that this does not
32046 depend on the language).
32048 @node JIT Interface
32049 @chapter JIT Compilation Interface
32050 @cindex just-in-time compilation
32051 @cindex JIT compilation interface
32053 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
32054 interface. A JIT compiler is a program or library that generates native
32055 executable code at runtime and executes it, usually in order to achieve good
32056 performance while maintaining platform independence.
32058 Programs that use JIT compilation are normally difficult to debug because
32059 portions of their code are generated at runtime, instead of being loaded from
32060 object files, which is where @value{GDBN} normally finds the program's symbols
32061 and debug information. In order to debug programs that use JIT compilation,
32062 @value{GDBN} has an interface that allows the program to register in-memory
32063 symbol files with @value{GDBN} at runtime.
32065 If you are using @value{GDBN} to debug a program that uses this interface, then
32066 it should work transparently so long as you have not stripped the binary. If
32067 you are developing a JIT compiler, then the interface is documented in the rest
32068 of this chapter. At this time, the only known client of this interface is the
32071 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
32072 JIT compiler communicates with @value{GDBN} by writing data into a global
32073 variable and calling a fuction at a well-known symbol. When @value{GDBN}
32074 attaches, it reads a linked list of symbol files from the global variable to
32075 find existing code, and puts a breakpoint in the function so that it can find
32076 out about additional code.
32079 * Declarations:: Relevant C struct declarations
32080 * Registering Code:: Steps to register code
32081 * Unregistering Code:: Steps to unregister code
32082 * Custom Debug Info:: Emit debug information in a custom format
32086 @section JIT Declarations
32088 These are the relevant struct declarations that a C program should include to
32089 implement the interface:
32099 struct jit_code_entry
32101 struct jit_code_entry *next_entry;
32102 struct jit_code_entry *prev_entry;
32103 const char *symfile_addr;
32104 uint64_t symfile_size;
32107 struct jit_descriptor
32110 /* This type should be jit_actions_t, but we use uint32_t
32111 to be explicit about the bitwidth. */
32112 uint32_t action_flag;
32113 struct jit_code_entry *relevant_entry;
32114 struct jit_code_entry *first_entry;
32117 /* GDB puts a breakpoint in this function. */
32118 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
32120 /* Make sure to specify the version statically, because the
32121 debugger may check the version before we can set it. */
32122 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
32125 If the JIT is multi-threaded, then it is important that the JIT synchronize any
32126 modifications to this global data properly, which can easily be done by putting
32127 a global mutex around modifications to these structures.
32129 @node Registering Code
32130 @section Registering Code
32132 To register code with @value{GDBN}, the JIT should follow this protocol:
32136 Generate an object file in memory with symbols and other desired debug
32137 information. The file must include the virtual addresses of the sections.
32140 Create a code entry for the file, which gives the start and size of the symbol
32144 Add it to the linked list in the JIT descriptor.
32147 Point the relevant_entry field of the descriptor at the entry.
32150 Set @code{action_flag} to @code{JIT_REGISTER} and call
32151 @code{__jit_debug_register_code}.
32154 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
32155 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
32156 new code. However, the linked list must still be maintained in order to allow
32157 @value{GDBN} to attach to a running process and still find the symbol files.
32159 @node Unregistering Code
32160 @section Unregistering Code
32162 If code is freed, then the JIT should use the following protocol:
32166 Remove the code entry corresponding to the code from the linked list.
32169 Point the @code{relevant_entry} field of the descriptor at the code entry.
32172 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
32173 @code{__jit_debug_register_code}.
32176 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
32177 and the JIT will leak the memory used for the associated symbol files.
32179 @node Custom Debug Info
32180 @section Custom Debug Info
32181 @cindex custom JIT debug info
32182 @cindex JIT debug info reader
32184 Generating debug information in platform-native file formats (like ELF
32185 or COFF) may be an overkill for JIT compilers; especially if all the
32186 debug info is used for is displaying a meaningful backtrace. The
32187 issue can be resolved by having the JIT writers decide on a debug info
32188 format and also provide a reader that parses the debug info generated
32189 by the JIT compiler. This section gives a brief overview on writing
32190 such a parser. More specific details can be found in the source file
32191 @file{gdb/jit-reader.in}, which is also installed as a header at
32192 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
32194 The reader is implemented as a shared object (so this functionality is
32195 not available on platforms which don't allow loading shared objects at
32196 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
32197 @code{jit-reader-unload} are provided, to be used to load and unload
32198 the readers from a preconfigured directory. Once loaded, the shared
32199 object is used the parse the debug information emitted by the JIT
32203 * Using JIT Debug Info Readers:: How to use supplied readers correctly
32204 * Writing JIT Debug Info Readers:: Creating a debug-info reader
32207 @node Using JIT Debug Info Readers
32208 @subsection Using JIT Debug Info Readers
32209 @kindex jit-reader-load
32210 @kindex jit-reader-unload
32212 Readers can be loaded and unloaded using the @code{jit-reader-load}
32213 and @code{jit-reader-unload} commands.
32216 @item jit-reader-load @var{reader-name}
32217 Load the JIT reader named @var{reader-name}. On a UNIX system, this
32218 will usually load @file{@var{libdir}/gdb/@var{reader-name}}, where
32219 @var{libdir} is the system library directory, usually
32220 @file{/usr/local/lib}. Only one reader can be active at a time;
32221 trying to load a second reader when one is already loaded will result
32222 in @value{GDBN} reporting an error. A new JIT reader can be loaded by
32223 first unloading the current one using @code{jit-reader-load} and then
32224 invoking @code{jit-reader-load}.
32226 @item jit-reader-unload
32227 Unload the currently loaded JIT reader.
32231 @node Writing JIT Debug Info Readers
32232 @subsection Writing JIT Debug Info Readers
32233 @cindex writing JIT debug info readers
32235 As mentioned, a reader is essentially a shared object conforming to a
32236 certain ABI. This ABI is described in @file{jit-reader.h}.
32238 @file{jit-reader.h} defines the structures, macros and functions
32239 required to write a reader. It is installed (along with
32240 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
32241 the system include directory.
32243 Readers need to be released under a GPL compatible license. A reader
32244 can be declared as released under such a license by placing the macro
32245 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
32247 The entry point for readers is the symbol @code{gdb_init_reader},
32248 which is expected to be a function with the prototype
32250 @findex gdb_init_reader
32252 extern struct gdb_reader_funcs *gdb_init_reader (void);
32255 @cindex @code{struct gdb_reader_funcs}
32257 @code{struct gdb_reader_funcs} contains a set of pointers to callback
32258 functions. These functions are executed to read the debug info
32259 generated by the JIT compiler (@code{read}), to unwind stack frames
32260 (@code{unwind}) and to create canonical frame IDs
32261 (@code{get_Frame_id}). It also has a callback that is called when the
32262 reader is being unloaded (@code{destroy}). The struct looks like this
32265 struct gdb_reader_funcs
32267 /* Must be set to GDB_READER_INTERFACE_VERSION. */
32268 int reader_version;
32270 /* For use by the reader. */
32273 gdb_read_debug_info *read;
32274 gdb_unwind_frame *unwind;
32275 gdb_get_frame_id *get_frame_id;
32276 gdb_destroy_reader *destroy;
32280 @cindex @code{struct gdb_symbol_callbacks}
32281 @cindex @code{struct gdb_unwind_callbacks}
32283 The callbacks are provided with another set of callbacks by
32284 @value{GDBN} to do their job. For @code{read}, these callbacks are
32285 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
32286 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
32287 @code{struct gdb_symbol_callbacks} has callbacks to create new object
32288 files and new symbol tables inside those object files. @code{struct
32289 gdb_unwind_callbacks} has callbacks to read registers off the current
32290 frame and to write out the values of the registers in the previous
32291 frame. Both have a callback (@code{target_read}) to read bytes off the
32292 target's address space.
32294 @node In-Process Agent
32295 @chapter In-Process Agent
32296 @cindex debugging agent
32297 The traditional debugging model is conceptually low-speed, but works fine,
32298 because most bugs can be reproduced in debugging-mode execution. However,
32299 as multi-core or many-core processors are becoming mainstream, and
32300 multi-threaded programs become more and more popular, there should be more
32301 and more bugs that only manifest themselves at normal-mode execution, for
32302 example, thread races, because debugger's interference with the program's
32303 timing may conceal the bugs. On the other hand, in some applications,
32304 it is not feasible for the debugger to interrupt the program's execution
32305 long enough for the developer to learn anything helpful about its behavior.
32306 If the program's correctness depends on its real-time behavior, delays
32307 introduced by a debugger might cause the program to fail, even when the
32308 code itself is correct. It is useful to be able to observe the program's
32309 behavior without interrupting it.
32311 Therefore, traditional debugging model is too intrusive to reproduce
32312 some bugs. In order to reduce the interference with the program, we can
32313 reduce the number of operations performed by debugger. The
32314 @dfn{In-Process Agent}, a shared library, is running within the same
32315 process with inferior, and is able to perform some debugging operations
32316 itself. As a result, debugger is only involved when necessary, and
32317 performance of debugging can be improved accordingly. Note that
32318 interference with program can be reduced but can't be removed completely,
32319 because the in-process agent will still stop or slow down the program.
32321 The in-process agent can interpret and execute Agent Expressions
32322 (@pxref{Agent Expressions}) during performing debugging operations. The
32323 agent expressions can be used for different purposes, such as collecting
32324 data in tracepoints, and condition evaluation in breakpoints.
32326 @anchor{Control Agent}
32327 You can control whether the in-process agent is used as an aid for
32328 debugging with the following commands:
32331 @kindex set agent on
32333 Causes the in-process agent to perform some operations on behalf of the
32334 debugger. Just which operations requested by the user will be done
32335 by the in-process agent depends on the its capabilities. For example,
32336 if you request to evaluate breakpoint conditions in the in-process agent,
32337 and the in-process agent has such capability as well, then breakpoint
32338 conditions will be evaluated in the in-process agent.
32340 @kindex set agent off
32341 @item set agent off
32342 Disables execution of debugging operations by the in-process agent. All
32343 of the operations will be performed by @value{GDBN}.
32347 Display the current setting of execution of debugging operations by
32348 the in-process agent.
32352 @chapter Reporting Bugs in @value{GDBN}
32353 @cindex bugs in @value{GDBN}
32354 @cindex reporting bugs in @value{GDBN}
32356 Your bug reports play an essential role in making @value{GDBN} reliable.
32358 Reporting a bug may help you by bringing a solution to your problem, or it
32359 may not. But in any case the principal function of a bug report is to help
32360 the entire community by making the next version of @value{GDBN} work better. Bug
32361 reports are your contribution to the maintenance of @value{GDBN}.
32363 In order for a bug report to serve its purpose, you must include the
32364 information that enables us to fix the bug.
32367 * Bug Criteria:: Have you found a bug?
32368 * Bug Reporting:: How to report bugs
32372 @section Have You Found a Bug?
32373 @cindex bug criteria
32375 If you are not sure whether you have found a bug, here are some guidelines:
32378 @cindex fatal signal
32379 @cindex debugger crash
32380 @cindex crash of debugger
32382 If the debugger gets a fatal signal, for any input whatever, that is a
32383 @value{GDBN} bug. Reliable debuggers never crash.
32385 @cindex error on valid input
32387 If @value{GDBN} produces an error message for valid input, that is a
32388 bug. (Note that if you're cross debugging, the problem may also be
32389 somewhere in the connection to the target.)
32391 @cindex invalid input
32393 If @value{GDBN} does not produce an error message for invalid input,
32394 that is a bug. However, you should note that your idea of
32395 ``invalid input'' might be our idea of ``an extension'' or ``support
32396 for traditional practice''.
32399 If you are an experienced user of debugging tools, your suggestions
32400 for improvement of @value{GDBN} are welcome in any case.
32403 @node Bug Reporting
32404 @section How to Report Bugs
32405 @cindex bug reports
32406 @cindex @value{GDBN} bugs, reporting
32408 A number of companies and individuals offer support for @sc{gnu} products.
32409 If you obtained @value{GDBN} from a support organization, we recommend you
32410 contact that organization first.
32412 You can find contact information for many support companies and
32413 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
32415 @c should add a web page ref...
32418 @ifset BUGURL_DEFAULT
32419 In any event, we also recommend that you submit bug reports for
32420 @value{GDBN}. The preferred method is to submit them directly using
32421 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
32422 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
32425 @strong{Do not send bug reports to @samp{info-gdb}, or to
32426 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
32427 not want to receive bug reports. Those that do have arranged to receive
32430 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
32431 serves as a repeater. The mailing list and the newsgroup carry exactly
32432 the same messages. Often people think of posting bug reports to the
32433 newsgroup instead of mailing them. This appears to work, but it has one
32434 problem which can be crucial: a newsgroup posting often lacks a mail
32435 path back to the sender. Thus, if we need to ask for more information,
32436 we may be unable to reach you. For this reason, it is better to send
32437 bug reports to the mailing list.
32439 @ifclear BUGURL_DEFAULT
32440 In any event, we also recommend that you submit bug reports for
32441 @value{GDBN} to @value{BUGURL}.
32445 The fundamental principle of reporting bugs usefully is this:
32446 @strong{report all the facts}. If you are not sure whether to state a
32447 fact or leave it out, state it!
32449 Often people omit facts because they think they know what causes the
32450 problem and assume that some details do not matter. Thus, you might
32451 assume that the name of the variable you use in an example does not matter.
32452 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
32453 stray memory reference which happens to fetch from the location where that
32454 name is stored in memory; perhaps, if the name were different, the contents
32455 of that location would fool the debugger into doing the right thing despite
32456 the bug. Play it safe and give a specific, complete example. That is the
32457 easiest thing for you to do, and the most helpful.
32459 Keep in mind that the purpose of a bug report is to enable us to fix the
32460 bug. It may be that the bug has been reported previously, but neither
32461 you nor we can know that unless your bug report is complete and
32464 Sometimes people give a few sketchy facts and ask, ``Does this ring a
32465 bell?'' Those bug reports are useless, and we urge everyone to
32466 @emph{refuse to respond to them} except to chide the sender to report
32469 To enable us to fix the bug, you should include all these things:
32473 The version of @value{GDBN}. @value{GDBN} announces it if you start
32474 with no arguments; you can also print it at any time using @code{show
32477 Without this, we will not know whether there is any point in looking for
32478 the bug in the current version of @value{GDBN}.
32481 The type of machine you are using, and the operating system name and
32485 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
32486 ``@value{GCC}--2.8.1''.
32489 What compiler (and its version) was used to compile the program you are
32490 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
32491 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
32492 to get this information; for other compilers, see the documentation for
32496 The command arguments you gave the compiler to compile your example and
32497 observe the bug. For example, did you use @samp{-O}? To guarantee
32498 you will not omit something important, list them all. A copy of the
32499 Makefile (or the output from make) is sufficient.
32501 If we were to try to guess the arguments, we would probably guess wrong
32502 and then we might not encounter the bug.
32505 A complete input script, and all necessary source files, that will
32509 A description of what behavior you observe that you believe is
32510 incorrect. For example, ``It gets a fatal signal.''
32512 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
32513 will certainly notice it. But if the bug is incorrect output, we might
32514 not notice unless it is glaringly wrong. You might as well not give us
32515 a chance to make a mistake.
32517 Even if the problem you experience is a fatal signal, you should still
32518 say so explicitly. Suppose something strange is going on, such as, your
32519 copy of @value{GDBN} is out of synch, or you have encountered a bug in
32520 the C library on your system. (This has happened!) Your copy might
32521 crash and ours would not. If you told us to expect a crash, then when
32522 ours fails to crash, we would know that the bug was not happening for
32523 us. If you had not told us to expect a crash, then we would not be able
32524 to draw any conclusion from our observations.
32527 @cindex recording a session script
32528 To collect all this information, you can use a session recording program
32529 such as @command{script}, which is available on many Unix systems.
32530 Just run your @value{GDBN} session inside @command{script} and then
32531 include the @file{typescript} file with your bug report.
32533 Another way to record a @value{GDBN} session is to run @value{GDBN}
32534 inside Emacs and then save the entire buffer to a file.
32537 If you wish to suggest changes to the @value{GDBN} source, send us context
32538 diffs. If you even discuss something in the @value{GDBN} source, refer to
32539 it by context, not by line number.
32541 The line numbers in our development sources will not match those in your
32542 sources. Your line numbers would convey no useful information to us.
32546 Here are some things that are not necessary:
32550 A description of the envelope of the bug.
32552 Often people who encounter a bug spend a lot of time investigating
32553 which changes to the input file will make the bug go away and which
32554 changes will not affect it.
32556 This is often time consuming and not very useful, because the way we
32557 will find the bug is by running a single example under the debugger
32558 with breakpoints, not by pure deduction from a series of examples.
32559 We recommend that you save your time for something else.
32561 Of course, if you can find a simpler example to report @emph{instead}
32562 of the original one, that is a convenience for us. Errors in the
32563 output will be easier to spot, running under the debugger will take
32564 less time, and so on.
32566 However, simplification is not vital; if you do not want to do this,
32567 report the bug anyway and send us the entire test case you used.
32570 A patch for the bug.
32572 A patch for the bug does help us if it is a good one. But do not omit
32573 the necessary information, such as the test case, on the assumption that
32574 a patch is all we need. We might see problems with your patch and decide
32575 to fix the problem another way, or we might not understand it at all.
32577 Sometimes with a program as complicated as @value{GDBN} it is very hard to
32578 construct an example that will make the program follow a certain path
32579 through the code. If you do not send us the example, we will not be able
32580 to construct one, so we will not be able to verify that the bug is fixed.
32582 And if we cannot understand what bug you are trying to fix, or why your
32583 patch should be an improvement, we will not install it. A test case will
32584 help us to understand.
32587 A guess about what the bug is or what it depends on.
32589 Such guesses are usually wrong. Even we cannot guess right about such
32590 things without first using the debugger to find the facts.
32593 @c The readline documentation is distributed with the readline code
32594 @c and consists of the two following files:
32597 @c Use -I with makeinfo to point to the appropriate directory,
32598 @c environment var TEXINPUTS with TeX.
32599 @ifclear SYSTEM_READLINE
32600 @include rluser.texi
32601 @include hsuser.texi
32605 @appendix In Memoriam
32607 The @value{GDBN} project mourns the loss of the following long-time
32612 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
32613 to Free Software in general. Outside of @value{GDBN}, he was known in
32614 the Amiga world for his series of Fish Disks, and the GeekGadget project.
32616 @item Michael Snyder
32617 Michael was one of the Global Maintainers of the @value{GDBN} project,
32618 with contributions recorded as early as 1996, until 2011. In addition
32619 to his day to day participation, he was a large driving force behind
32620 adding Reverse Debugging to @value{GDBN}.
32623 Beyond their technical contributions to the project, they were also
32624 enjoyable members of the Free Software Community. We will miss them.
32626 @node Formatting Documentation
32627 @appendix Formatting Documentation
32629 @cindex @value{GDBN} reference card
32630 @cindex reference card
32631 The @value{GDBN} 4 release includes an already-formatted reference card, ready
32632 for printing with PostScript or Ghostscript, in the @file{gdb}
32633 subdirectory of the main source directory@footnote{In
32634 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
32635 release.}. If you can use PostScript or Ghostscript with your printer,
32636 you can print the reference card immediately with @file{refcard.ps}.
32638 The release also includes the source for the reference card. You
32639 can format it, using @TeX{}, by typing:
32645 The @value{GDBN} reference card is designed to print in @dfn{landscape}
32646 mode on US ``letter'' size paper;
32647 that is, on a sheet 11 inches wide by 8.5 inches
32648 high. You will need to specify this form of printing as an option to
32649 your @sc{dvi} output program.
32651 @cindex documentation
32653 All the documentation for @value{GDBN} comes as part of the machine-readable
32654 distribution. The documentation is written in Texinfo format, which is
32655 a documentation system that uses a single source file to produce both
32656 on-line information and a printed manual. You can use one of the Info
32657 formatting commands to create the on-line version of the documentation
32658 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
32660 @value{GDBN} includes an already formatted copy of the on-line Info
32661 version of this manual in the @file{gdb} subdirectory. The main Info
32662 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
32663 subordinate files matching @samp{gdb.info*} in the same directory. If
32664 necessary, you can print out these files, or read them with any editor;
32665 but they are easier to read using the @code{info} subsystem in @sc{gnu}
32666 Emacs or the standalone @code{info} program, available as part of the
32667 @sc{gnu} Texinfo distribution.
32669 If you want to format these Info files yourself, you need one of the
32670 Info formatting programs, such as @code{texinfo-format-buffer} or
32673 If you have @code{makeinfo} installed, and are in the top level
32674 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
32675 version @value{GDBVN}), you can make the Info file by typing:
32682 If you want to typeset and print copies of this manual, you need @TeX{},
32683 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
32684 Texinfo definitions file.
32686 @TeX{} is a typesetting program; it does not print files directly, but
32687 produces output files called @sc{dvi} files. To print a typeset
32688 document, you need a program to print @sc{dvi} files. If your system
32689 has @TeX{} installed, chances are it has such a program. The precise
32690 command to use depends on your system; @kbd{lpr -d} is common; another
32691 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
32692 require a file name without any extension or a @samp{.dvi} extension.
32694 @TeX{} also requires a macro definitions file called
32695 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
32696 written in Texinfo format. On its own, @TeX{} cannot either read or
32697 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
32698 and is located in the @file{gdb-@var{version-number}/texinfo}
32701 If you have @TeX{} and a @sc{dvi} printer program installed, you can
32702 typeset and print this manual. First switch to the @file{gdb}
32703 subdirectory of the main source directory (for example, to
32704 @file{gdb-@value{GDBVN}/gdb}) and type:
32710 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
32712 @node Installing GDB
32713 @appendix Installing @value{GDBN}
32714 @cindex installation
32717 * Requirements:: Requirements for building @value{GDBN}
32718 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
32719 * Separate Objdir:: Compiling @value{GDBN} in another directory
32720 * Config Names:: Specifying names for hosts and targets
32721 * Configure Options:: Summary of options for configure
32722 * System-wide configuration:: Having a system-wide init file
32726 @section Requirements for Building @value{GDBN}
32727 @cindex building @value{GDBN}, requirements for
32729 Building @value{GDBN} requires various tools and packages to be available.
32730 Other packages will be used only if they are found.
32732 @heading Tools/Packages Necessary for Building @value{GDBN}
32734 @item ISO C90 compiler
32735 @value{GDBN} is written in ISO C90. It should be buildable with any
32736 working C90 compiler, e.g.@: GCC.
32740 @heading Tools/Packages Optional for Building @value{GDBN}
32744 @value{GDBN} can use the Expat XML parsing library. This library may be
32745 included with your operating system distribution; if it is not, you
32746 can get the latest version from @url{http://expat.sourceforge.net}.
32747 The @file{configure} script will search for this library in several
32748 standard locations; if it is installed in an unusual path, you can
32749 use the @option{--with-libexpat-prefix} option to specify its location.
32755 Remote protocol memory maps (@pxref{Memory Map Format})
32757 Target descriptions (@pxref{Target Descriptions})
32759 Remote shared library lists (@xref{Library List Format},
32760 or alternatively @pxref{Library List Format for SVR4 Targets})
32762 MS-Windows shared libraries (@pxref{Shared Libraries})
32764 Traceframe info (@pxref{Traceframe Info Format})
32768 @cindex compressed debug sections
32769 @value{GDBN} will use the @samp{zlib} library, if available, to read
32770 compressed debug sections. Some linkers, such as GNU gold, are capable
32771 of producing binaries with compressed debug sections. If @value{GDBN}
32772 is compiled with @samp{zlib}, it will be able to read the debug
32773 information in such binaries.
32775 The @samp{zlib} library is likely included with your operating system
32776 distribution; if it is not, you can get the latest version from
32777 @url{http://zlib.net}.
32780 @value{GDBN}'s features related to character sets (@pxref{Character
32781 Sets}) require a functioning @code{iconv} implementation. If you are
32782 on a GNU system, then this is provided by the GNU C Library. Some
32783 other systems also provide a working @code{iconv}.
32785 If @value{GDBN} is using the @code{iconv} program which is installed
32786 in a non-standard place, you will need to tell @value{GDBN} where to find it.
32787 This is done with @option{--with-iconv-bin} which specifies the
32788 directory that contains the @code{iconv} program.
32790 On systems without @code{iconv}, you can install GNU Libiconv. If you
32791 have previously installed Libiconv, you can use the
32792 @option{--with-libiconv-prefix} option to configure.
32794 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
32795 arrange to build Libiconv if a directory named @file{libiconv} appears
32796 in the top-most source directory. If Libiconv is built this way, and
32797 if the operating system does not provide a suitable @code{iconv}
32798 implementation, then the just-built library will automatically be used
32799 by @value{GDBN}. One easy way to set this up is to download GNU
32800 Libiconv, unpack it, and then rename the directory holding the
32801 Libiconv source code to @samp{libiconv}.
32804 @node Running Configure
32805 @section Invoking the @value{GDBN} @file{configure} Script
32806 @cindex configuring @value{GDBN}
32807 @value{GDBN} comes with a @file{configure} script that automates the process
32808 of preparing @value{GDBN} for installation; you can then use @code{make} to
32809 build the @code{gdb} program.
32811 @c irrelevant in info file; it's as current as the code it lives with.
32812 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
32813 look at the @file{README} file in the sources; we may have improved the
32814 installation procedures since publishing this manual.}
32817 The @value{GDBN} distribution includes all the source code you need for
32818 @value{GDBN} in a single directory, whose name is usually composed by
32819 appending the version number to @samp{gdb}.
32821 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
32822 @file{gdb-@value{GDBVN}} directory. That directory contains:
32825 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
32826 script for configuring @value{GDBN} and all its supporting libraries
32828 @item gdb-@value{GDBVN}/gdb
32829 the source specific to @value{GDBN} itself
32831 @item gdb-@value{GDBVN}/bfd
32832 source for the Binary File Descriptor library
32834 @item gdb-@value{GDBVN}/include
32835 @sc{gnu} include files
32837 @item gdb-@value{GDBVN}/libiberty
32838 source for the @samp{-liberty} free software library
32840 @item gdb-@value{GDBVN}/opcodes
32841 source for the library of opcode tables and disassemblers
32843 @item gdb-@value{GDBVN}/readline
32844 source for the @sc{gnu} command-line interface
32846 @item gdb-@value{GDBVN}/glob
32847 source for the @sc{gnu} filename pattern-matching subroutine
32849 @item gdb-@value{GDBVN}/mmalloc
32850 source for the @sc{gnu} memory-mapped malloc package
32853 The simplest way to configure and build @value{GDBN} is to run @file{configure}
32854 from the @file{gdb-@var{version-number}} source directory, which in
32855 this example is the @file{gdb-@value{GDBVN}} directory.
32857 First switch to the @file{gdb-@var{version-number}} source directory
32858 if you are not already in it; then run @file{configure}. Pass the
32859 identifier for the platform on which @value{GDBN} will run as an
32865 cd gdb-@value{GDBVN}
32866 ./configure @var{host}
32871 where @var{host} is an identifier such as @samp{sun4} or
32872 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
32873 (You can often leave off @var{host}; @file{configure} tries to guess the
32874 correct value by examining your system.)
32876 Running @samp{configure @var{host}} and then running @code{make} builds the
32877 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
32878 libraries, then @code{gdb} itself. The configured source files, and the
32879 binaries, are left in the corresponding source directories.
32882 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
32883 system does not recognize this automatically when you run a different
32884 shell, you may need to run @code{sh} on it explicitly:
32887 sh configure @var{host}
32890 If you run @file{configure} from a directory that contains source
32891 directories for multiple libraries or programs, such as the
32892 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
32894 creates configuration files for every directory level underneath (unless
32895 you tell it not to, with the @samp{--norecursion} option).
32897 You should run the @file{configure} script from the top directory in the
32898 source tree, the @file{gdb-@var{version-number}} directory. If you run
32899 @file{configure} from one of the subdirectories, you will configure only
32900 that subdirectory. That is usually not what you want. In particular,
32901 if you run the first @file{configure} from the @file{gdb} subdirectory
32902 of the @file{gdb-@var{version-number}} directory, you will omit the
32903 configuration of @file{bfd}, @file{readline}, and other sibling
32904 directories of the @file{gdb} subdirectory. This leads to build errors
32905 about missing include files such as @file{bfd/bfd.h}.
32907 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
32908 However, you should make sure that the shell on your path (named by
32909 the @samp{SHELL} environment variable) is publicly readable. Remember
32910 that @value{GDBN} uses the shell to start your program---some systems refuse to
32911 let @value{GDBN} debug child processes whose programs are not readable.
32913 @node Separate Objdir
32914 @section Compiling @value{GDBN} in Another Directory
32916 If you want to run @value{GDBN} versions for several host or target machines,
32917 you need a different @code{gdb} compiled for each combination of
32918 host and target. @file{configure} is designed to make this easy by
32919 allowing you to generate each configuration in a separate subdirectory,
32920 rather than in the source directory. If your @code{make} program
32921 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
32922 @code{make} in each of these directories builds the @code{gdb}
32923 program specified there.
32925 To build @code{gdb} in a separate directory, run @file{configure}
32926 with the @samp{--srcdir} option to specify where to find the source.
32927 (You also need to specify a path to find @file{configure}
32928 itself from your working directory. If the path to @file{configure}
32929 would be the same as the argument to @samp{--srcdir}, you can leave out
32930 the @samp{--srcdir} option; it is assumed.)
32932 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
32933 separate directory for a Sun 4 like this:
32937 cd gdb-@value{GDBVN}
32940 ../gdb-@value{GDBVN}/configure sun4
32945 When @file{configure} builds a configuration using a remote source
32946 directory, it creates a tree for the binaries with the same structure
32947 (and using the same names) as the tree under the source directory. In
32948 the example, you'd find the Sun 4 library @file{libiberty.a} in the
32949 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
32950 @file{gdb-sun4/gdb}.
32952 Make sure that your path to the @file{configure} script has just one
32953 instance of @file{gdb} in it. If your path to @file{configure} looks
32954 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
32955 one subdirectory of @value{GDBN}, not the whole package. This leads to
32956 build errors about missing include files such as @file{bfd/bfd.h}.
32958 One popular reason to build several @value{GDBN} configurations in separate
32959 directories is to configure @value{GDBN} for cross-compiling (where
32960 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
32961 programs that run on another machine---the @dfn{target}).
32962 You specify a cross-debugging target by
32963 giving the @samp{--target=@var{target}} option to @file{configure}.
32965 When you run @code{make} to build a program or library, you must run
32966 it in a configured directory---whatever directory you were in when you
32967 called @file{configure} (or one of its subdirectories).
32969 The @code{Makefile} that @file{configure} generates in each source
32970 directory also runs recursively. If you type @code{make} in a source
32971 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
32972 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
32973 will build all the required libraries, and then build GDB.
32975 When you have multiple hosts or targets configured in separate
32976 directories, you can run @code{make} on them in parallel (for example,
32977 if they are NFS-mounted on each of the hosts); they will not interfere
32981 @section Specifying Names for Hosts and Targets
32983 The specifications used for hosts and targets in the @file{configure}
32984 script are based on a three-part naming scheme, but some short predefined
32985 aliases are also supported. The full naming scheme encodes three pieces
32986 of information in the following pattern:
32989 @var{architecture}-@var{vendor}-@var{os}
32992 For example, you can use the alias @code{sun4} as a @var{host} argument,
32993 or as the value for @var{target} in a @code{--target=@var{target}}
32994 option. The equivalent full name is @samp{sparc-sun-sunos4}.
32996 The @file{configure} script accompanying @value{GDBN} does not provide
32997 any query facility to list all supported host and target names or
32998 aliases. @file{configure} calls the Bourne shell script
32999 @code{config.sub} to map abbreviations to full names; you can read the
33000 script, if you wish, or you can use it to test your guesses on
33001 abbreviations---for example:
33004 % sh config.sub i386-linux
33006 % sh config.sub alpha-linux
33007 alpha-unknown-linux-gnu
33008 % sh config.sub hp9k700
33010 % sh config.sub sun4
33011 sparc-sun-sunos4.1.1
33012 % sh config.sub sun3
33013 m68k-sun-sunos4.1.1
33014 % sh config.sub i986v
33015 Invalid configuration `i986v': machine `i986v' not recognized
33019 @code{config.sub} is also distributed in the @value{GDBN} source
33020 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
33022 @node Configure Options
33023 @section @file{configure} Options
33025 Here is a summary of the @file{configure} options and arguments that
33026 are most often useful for building @value{GDBN}. @file{configure} also has
33027 several other options not listed here. @inforef{What Configure
33028 Does,,configure.info}, for a full explanation of @file{configure}.
33031 configure @r{[}--help@r{]}
33032 @r{[}--prefix=@var{dir}@r{]}
33033 @r{[}--exec-prefix=@var{dir}@r{]}
33034 @r{[}--srcdir=@var{dirname}@r{]}
33035 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
33036 @r{[}--target=@var{target}@r{]}
33041 You may introduce options with a single @samp{-} rather than
33042 @samp{--} if you prefer; but you may abbreviate option names if you use
33047 Display a quick summary of how to invoke @file{configure}.
33049 @item --prefix=@var{dir}
33050 Configure the source to install programs and files under directory
33053 @item --exec-prefix=@var{dir}
33054 Configure the source to install programs under directory
33057 @c avoid splitting the warning from the explanation:
33059 @item --srcdir=@var{dirname}
33060 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
33061 @code{make} that implements the @code{VPATH} feature.}@*
33062 Use this option to make configurations in directories separate from the
33063 @value{GDBN} source directories. Among other things, you can use this to
33064 build (or maintain) several configurations simultaneously, in separate
33065 directories. @file{configure} writes configuration-specific files in
33066 the current directory, but arranges for them to use the source in the
33067 directory @var{dirname}. @file{configure} creates directories under
33068 the working directory in parallel to the source directories below
33071 @item --norecursion
33072 Configure only the directory level where @file{configure} is executed; do not
33073 propagate configuration to subdirectories.
33075 @item --target=@var{target}
33076 Configure @value{GDBN} for cross-debugging programs running on the specified
33077 @var{target}. Without this option, @value{GDBN} is configured to debug
33078 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
33080 There is no convenient way to generate a list of all available targets.
33082 @item @var{host} @dots{}
33083 Configure @value{GDBN} to run on the specified @var{host}.
33085 There is no convenient way to generate a list of all available hosts.
33088 There are many other options available as well, but they are generally
33089 needed for special purposes only.
33091 @node System-wide configuration
33092 @section System-wide configuration and settings
33093 @cindex system-wide init file
33095 @value{GDBN} can be configured to have a system-wide init file;
33096 this file will be read and executed at startup (@pxref{Startup, , What
33097 @value{GDBN} does during startup}).
33099 Here is the corresponding configure option:
33102 @item --with-system-gdbinit=@var{file}
33103 Specify that the default location of the system-wide init file is
33107 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
33108 it may be subject to relocation. Two possible cases:
33112 If the default location of this init file contains @file{$prefix},
33113 it will be subject to relocation. Suppose that the configure options
33114 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
33115 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
33116 init file is looked for as @file{$install/etc/gdbinit} instead of
33117 @file{$prefix/etc/gdbinit}.
33120 By contrast, if the default location does not contain the prefix,
33121 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
33122 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
33123 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
33124 wherever @value{GDBN} is installed.
33127 @node Maintenance Commands
33128 @appendix Maintenance Commands
33129 @cindex maintenance commands
33130 @cindex internal commands
33132 In addition to commands intended for @value{GDBN} users, @value{GDBN}
33133 includes a number of commands intended for @value{GDBN} developers,
33134 that are not documented elsewhere in this manual. These commands are
33135 provided here for reference. (For commands that turn on debugging
33136 messages, see @ref{Debugging Output}.)
33139 @kindex maint agent
33140 @kindex maint agent-eval
33141 @item maint agent @var{expression}
33142 @itemx maint agent-eval @var{expression}
33143 Translate the given @var{expression} into remote agent bytecodes.
33144 This command is useful for debugging the Agent Expression mechanism
33145 (@pxref{Agent Expressions}). The @samp{agent} version produces an
33146 expression useful for data collection, such as by tracepoints, while
33147 @samp{maint agent-eval} produces an expression that evaluates directly
33148 to a result. For instance, a collection expression for @code{globa +
33149 globb} will include bytecodes to record four bytes of memory at each
33150 of the addresses of @code{globa} and @code{globb}, while discarding
33151 the result of the addition, while an evaluation expression will do the
33152 addition and return the sum.
33154 @kindex maint info breakpoints
33155 @item @anchor{maint info breakpoints}maint info breakpoints
33156 Using the same format as @samp{info breakpoints}, display both the
33157 breakpoints you've set explicitly, and those @value{GDBN} is using for
33158 internal purposes. Internal breakpoints are shown with negative
33159 breakpoint numbers. The type column identifies what kind of breakpoint
33164 Normal, explicitly set breakpoint.
33167 Normal, explicitly set watchpoint.
33170 Internal breakpoint, used to handle correctly stepping through
33171 @code{longjmp} calls.
33173 @item longjmp resume
33174 Internal breakpoint at the target of a @code{longjmp}.
33177 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
33180 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
33183 Shared library events.
33187 @kindex set displaced-stepping
33188 @kindex show displaced-stepping
33189 @cindex displaced stepping support
33190 @cindex out-of-line single-stepping
33191 @item set displaced-stepping
33192 @itemx show displaced-stepping
33193 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
33194 if the target supports it. Displaced stepping is a way to single-step
33195 over breakpoints without removing them from the inferior, by executing
33196 an out-of-line copy of the instruction that was originally at the
33197 breakpoint location. It is also known as out-of-line single-stepping.
33200 @item set displaced-stepping on
33201 If the target architecture supports it, @value{GDBN} will use
33202 displaced stepping to step over breakpoints.
33204 @item set displaced-stepping off
33205 @value{GDBN} will not use displaced stepping to step over breakpoints,
33206 even if such is supported by the target architecture.
33208 @cindex non-stop mode, and @samp{set displaced-stepping}
33209 @item set displaced-stepping auto
33210 This is the default mode. @value{GDBN} will use displaced stepping
33211 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
33212 architecture supports displaced stepping.
33215 @kindex maint check-symtabs
33216 @item maint check-symtabs
33217 Check the consistency of psymtabs and symtabs.
33219 @kindex maint cplus first_component
33220 @item maint cplus first_component @var{name}
33221 Print the first C@t{++} class/namespace component of @var{name}.
33223 @kindex maint cplus namespace
33224 @item maint cplus namespace
33225 Print the list of possible C@t{++} namespaces.
33227 @kindex maint demangle
33228 @item maint demangle @var{name}
33229 Demangle a C@t{++} or Objective-C mangled @var{name}.
33231 @kindex maint deprecate
33232 @kindex maint undeprecate
33233 @cindex deprecated commands
33234 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
33235 @itemx maint undeprecate @var{command}
33236 Deprecate or undeprecate the named @var{command}. Deprecated commands
33237 cause @value{GDBN} to issue a warning when you use them. The optional
33238 argument @var{replacement} says which newer command should be used in
33239 favor of the deprecated one; if it is given, @value{GDBN} will mention
33240 the replacement as part of the warning.
33242 @kindex maint dump-me
33243 @item maint dump-me
33244 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
33245 Cause a fatal signal in the debugger and force it to dump its core.
33246 This is supported only on systems which support aborting a program
33247 with the @code{SIGQUIT} signal.
33249 @kindex maint internal-error
33250 @kindex maint internal-warning
33251 @item maint internal-error @r{[}@var{message-text}@r{]}
33252 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
33253 Cause @value{GDBN} to call the internal function @code{internal_error}
33254 or @code{internal_warning} and hence behave as though an internal error
33255 or internal warning has been detected. In addition to reporting the
33256 internal problem, these functions give the user the opportunity to
33257 either quit @value{GDBN} or create a core file of the current
33258 @value{GDBN} session.
33260 These commands take an optional parameter @var{message-text} that is
33261 used as the text of the error or warning message.
33263 Here's an example of using @code{internal-error}:
33266 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
33267 @dots{}/maint.c:121: internal-error: testing, 1, 2
33268 A problem internal to GDB has been detected. Further
33269 debugging may prove unreliable.
33270 Quit this debugging session? (y or n) @kbd{n}
33271 Create a core file? (y or n) @kbd{n}
33275 @cindex @value{GDBN} internal error
33276 @cindex internal errors, control of @value{GDBN} behavior
33278 @kindex maint set internal-error
33279 @kindex maint show internal-error
33280 @kindex maint set internal-warning
33281 @kindex maint show internal-warning
33282 @item maint set internal-error @var{action} [ask|yes|no]
33283 @itemx maint show internal-error @var{action}
33284 @itemx maint set internal-warning @var{action} [ask|yes|no]
33285 @itemx maint show internal-warning @var{action}
33286 When @value{GDBN} reports an internal problem (error or warning) it
33287 gives the user the opportunity to both quit @value{GDBN} and create a
33288 core file of the current @value{GDBN} session. These commands let you
33289 override the default behaviour for each particular @var{action},
33290 described in the table below.
33294 You can specify that @value{GDBN} should always (yes) or never (no)
33295 quit. The default is to ask the user what to do.
33298 You can specify that @value{GDBN} should always (yes) or never (no)
33299 create a core file. The default is to ask the user what to do.
33302 @kindex maint packet
33303 @item maint packet @var{text}
33304 If @value{GDBN} is talking to an inferior via the serial protocol,
33305 then this command sends the string @var{text} to the inferior, and
33306 displays the response packet. @value{GDBN} supplies the initial
33307 @samp{$} character, the terminating @samp{#} character, and the
33310 @kindex maint print architecture
33311 @item maint print architecture @r{[}@var{file}@r{]}
33312 Print the entire architecture configuration. The optional argument
33313 @var{file} names the file where the output goes.
33315 @kindex maint print c-tdesc
33316 @item maint print c-tdesc
33317 Print the current target description (@pxref{Target Descriptions}) as
33318 a C source file. The created source file can be used in @value{GDBN}
33319 when an XML parser is not available to parse the description.
33321 @kindex maint print dummy-frames
33322 @item maint print dummy-frames
33323 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
33326 (@value{GDBP}) @kbd{b add}
33328 (@value{GDBP}) @kbd{print add(2,3)}
33329 Breakpoint 2, add (a=2, b=3) at @dots{}
33331 The program being debugged stopped while in a function called from GDB.
33333 (@value{GDBP}) @kbd{maint print dummy-frames}
33334 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
33335 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
33336 call_lo=0x01014000 call_hi=0x01014001
33340 Takes an optional file parameter.
33342 @kindex maint print registers
33343 @kindex maint print raw-registers
33344 @kindex maint print cooked-registers
33345 @kindex maint print register-groups
33346 @kindex maint print remote-registers
33347 @item maint print registers @r{[}@var{file}@r{]}
33348 @itemx maint print raw-registers @r{[}@var{file}@r{]}
33349 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
33350 @itemx maint print register-groups @r{[}@var{file}@r{]}
33351 @itemx maint print remote-registers @r{[}@var{file}@r{]}
33352 Print @value{GDBN}'s internal register data structures.
33354 The command @code{maint print raw-registers} includes the contents of
33355 the raw register cache; the command @code{maint print
33356 cooked-registers} includes the (cooked) value of all registers,
33357 including registers which aren't available on the target nor visible
33358 to user; the command @code{maint print register-groups} includes the
33359 groups that each register is a member of; and the command @code{maint
33360 print remote-registers} includes the remote target's register numbers
33361 and offsets in the `G' packets. @xref{Registers,, Registers, gdbint,
33362 @value{GDBN} Internals}.
33364 These commands take an optional parameter, a file name to which to
33365 write the information.
33367 @kindex maint print reggroups
33368 @item maint print reggroups @r{[}@var{file}@r{]}
33369 Print @value{GDBN}'s internal register group data structures. The
33370 optional argument @var{file} tells to what file to write the
33373 The register groups info looks like this:
33376 (@value{GDBP}) @kbd{maint print reggroups}
33389 This command forces @value{GDBN} to flush its internal register cache.
33391 @kindex maint print objfiles
33392 @cindex info for known object files
33393 @item maint print objfiles
33394 Print a dump of all known object files. For each object file, this
33395 command prints its name, address in memory, and all of its psymtabs
33398 @kindex maint print section-scripts
33399 @cindex info for known .debug_gdb_scripts-loaded scripts
33400 @item maint print section-scripts [@var{regexp}]
33401 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
33402 If @var{regexp} is specified, only print scripts loaded by object files
33403 matching @var{regexp}.
33404 For each script, this command prints its name as specified in the objfile,
33405 and the full path if known.
33406 @xref{.debug_gdb_scripts section}.
33408 @kindex maint print statistics
33409 @cindex bcache statistics
33410 @item maint print statistics
33411 This command prints, for each object file in the program, various data
33412 about that object file followed by the byte cache (@dfn{bcache})
33413 statistics for the object file. The objfile data includes the number
33414 of minimal, partial, full, and stabs symbols, the number of types
33415 defined by the objfile, the number of as yet unexpanded psym tables,
33416 the number of line tables and string tables, and the amount of memory
33417 used by the various tables. The bcache statistics include the counts,
33418 sizes, and counts of duplicates of all and unique objects, max,
33419 average, and median entry size, total memory used and its overhead and
33420 savings, and various measures of the hash table size and chain
33423 @kindex maint print target-stack
33424 @cindex target stack description
33425 @item maint print target-stack
33426 A @dfn{target} is an interface between the debugger and a particular
33427 kind of file or process. Targets can be stacked in @dfn{strata},
33428 so that more than one target can potentially respond to a request.
33429 In particular, memory accesses will walk down the stack of targets
33430 until they find a target that is interested in handling that particular
33433 This command prints a short description of each layer that was pushed on
33434 the @dfn{target stack}, starting from the top layer down to the bottom one.
33436 @kindex maint print type
33437 @cindex type chain of a data type
33438 @item maint print type @var{expr}
33439 Print the type chain for a type specified by @var{expr}. The argument
33440 can be either a type name or a symbol. If it is a symbol, the type of
33441 that symbol is described. The type chain produced by this command is
33442 a recursive definition of the data type as stored in @value{GDBN}'s
33443 data structures, including its flags and contained types.
33445 @kindex maint set dwarf2 always-disassemble
33446 @kindex maint show dwarf2 always-disassemble
33447 @item maint set dwarf2 always-disassemble
33448 @item maint show dwarf2 always-disassemble
33449 Control the behavior of @code{info address} when using DWARF debugging
33452 The default is @code{off}, which means that @value{GDBN} should try to
33453 describe a variable's location in an easily readable format. When
33454 @code{on}, @value{GDBN} will instead display the DWARF location
33455 expression in an assembly-like format. Note that some locations are
33456 too complex for @value{GDBN} to describe simply; in this case you will
33457 always see the disassembly form.
33459 Here is an example of the resulting disassembly:
33462 (gdb) info addr argc
33463 Symbol "argc" is a complex DWARF expression:
33467 For more information on these expressions, see
33468 @uref{http://www.dwarfstd.org/, the DWARF standard}.
33470 @kindex maint set dwarf2 max-cache-age
33471 @kindex maint show dwarf2 max-cache-age
33472 @item maint set dwarf2 max-cache-age
33473 @itemx maint show dwarf2 max-cache-age
33474 Control the DWARF 2 compilation unit cache.
33476 @cindex DWARF 2 compilation units cache
33477 In object files with inter-compilation-unit references, such as those
33478 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
33479 reader needs to frequently refer to previously read compilation units.
33480 This setting controls how long a compilation unit will remain in the
33481 cache if it is not referenced. A higher limit means that cached
33482 compilation units will be stored in memory longer, and more total
33483 memory will be used. Setting it to zero disables caching, which will
33484 slow down @value{GDBN} startup, but reduce memory consumption.
33486 @kindex maint set profile
33487 @kindex maint show profile
33488 @cindex profiling GDB
33489 @item maint set profile
33490 @itemx maint show profile
33491 Control profiling of @value{GDBN}.
33493 Profiling will be disabled until you use the @samp{maint set profile}
33494 command to enable it. When you enable profiling, the system will begin
33495 collecting timing and execution count data; when you disable profiling or
33496 exit @value{GDBN}, the results will be written to a log file. Remember that
33497 if you use profiling, @value{GDBN} will overwrite the profiling log file
33498 (often called @file{gmon.out}). If you have a record of important profiling
33499 data in a @file{gmon.out} file, be sure to move it to a safe location.
33501 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
33502 compiled with the @samp{-pg} compiler option.
33504 @kindex maint set show-debug-regs
33505 @kindex maint show show-debug-regs
33506 @cindex hardware debug registers
33507 @item maint set show-debug-regs
33508 @itemx maint show show-debug-regs
33509 Control whether to show variables that mirror the hardware debug
33510 registers. Use @code{ON} to enable, @code{OFF} to disable. If
33511 enabled, the debug registers values are shown when @value{GDBN} inserts or
33512 removes a hardware breakpoint or watchpoint, and when the inferior
33513 triggers a hardware-assisted breakpoint or watchpoint.
33515 @kindex maint set show-all-tib
33516 @kindex maint show show-all-tib
33517 @item maint set show-all-tib
33518 @itemx maint show show-all-tib
33519 Control whether to show all non zero areas within a 1k block starting
33520 at thread local base, when using the @samp{info w32 thread-information-block}
33523 @kindex maint space
33524 @cindex memory used by commands
33526 Control whether to display memory usage for each command. If set to a
33527 nonzero value, @value{GDBN} will display how much memory each command
33528 took, following the command's own output. This can also be requested
33529 by invoking @value{GDBN} with the @option{--statistics} command-line
33530 switch (@pxref{Mode Options}).
33533 @cindex time of command execution
33535 Control whether to display the execution time of @value{GDBN} for each command.
33536 If set to a nonzero value, @value{GDBN} will display how much time it
33537 took to execute each command, following the command's own output.
33538 Both CPU time and wallclock time are printed.
33539 Printing both is useful when trying to determine whether the cost is
33540 CPU or, e.g., disk/network, latency.
33541 Note that the CPU time printed is for @value{GDBN} only, it does not include
33542 the execution time of the inferior because there's no mechanism currently
33543 to compute how much time was spent by @value{GDBN} and how much time was
33544 spent by the program been debugged.
33545 This can also be requested by invoking @value{GDBN} with the
33546 @option{--statistics} command-line switch (@pxref{Mode Options}).
33548 @kindex maint translate-address
33549 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
33550 Find the symbol stored at the location specified by the address
33551 @var{addr} and an optional section name @var{section}. If found,
33552 @value{GDBN} prints the name of the closest symbol and an offset from
33553 the symbol's location to the specified address. This is similar to
33554 the @code{info address} command (@pxref{Symbols}), except that this
33555 command also allows to find symbols in other sections.
33557 If section was not specified, the section in which the symbol was found
33558 is also printed. For dynamically linked executables, the name of
33559 executable or shared library containing the symbol is printed as well.
33563 The following command is useful for non-interactive invocations of
33564 @value{GDBN}, such as in the test suite.
33567 @item set watchdog @var{nsec}
33568 @kindex set watchdog
33569 @cindex watchdog timer
33570 @cindex timeout for commands
33571 Set the maximum number of seconds @value{GDBN} will wait for the
33572 target operation to finish. If this time expires, @value{GDBN}
33573 reports and error and the command is aborted.
33575 @item show watchdog
33576 Show the current setting of the target wait timeout.
33579 @node Remote Protocol
33580 @appendix @value{GDBN} Remote Serial Protocol
33585 * Stop Reply Packets::
33586 * General Query Packets::
33587 * Architecture-Specific Protocol Details::
33588 * Tracepoint Packets::
33589 * Host I/O Packets::
33591 * Notification Packets::
33592 * Remote Non-Stop::
33593 * Packet Acknowledgment::
33595 * File-I/O Remote Protocol Extension::
33596 * Library List Format::
33597 * Library List Format for SVR4 Targets::
33598 * Memory Map Format::
33599 * Thread List Format::
33600 * Traceframe Info Format::
33606 There may be occasions when you need to know something about the
33607 protocol---for example, if there is only one serial port to your target
33608 machine, you might want your program to do something special if it
33609 recognizes a packet meant for @value{GDBN}.
33611 In the examples below, @samp{->} and @samp{<-} are used to indicate
33612 transmitted and received data, respectively.
33614 @cindex protocol, @value{GDBN} remote serial
33615 @cindex serial protocol, @value{GDBN} remote
33616 @cindex remote serial protocol
33617 All @value{GDBN} commands and responses (other than acknowledgments
33618 and notifications, see @ref{Notification Packets}) are sent as a
33619 @var{packet}. A @var{packet} is introduced with the character
33620 @samp{$}, the actual @var{packet-data}, and the terminating character
33621 @samp{#} followed by a two-digit @var{checksum}:
33624 @code{$}@var{packet-data}@code{#}@var{checksum}
33628 @cindex checksum, for @value{GDBN} remote
33630 The two-digit @var{checksum} is computed as the modulo 256 sum of all
33631 characters between the leading @samp{$} and the trailing @samp{#} (an
33632 eight bit unsigned checksum).
33634 Implementors should note that prior to @value{GDBN} 5.0 the protocol
33635 specification also included an optional two-digit @var{sequence-id}:
33638 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
33641 @cindex sequence-id, for @value{GDBN} remote
33643 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
33644 has never output @var{sequence-id}s. Stubs that handle packets added
33645 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
33647 When either the host or the target machine receives a packet, the first
33648 response expected is an acknowledgment: either @samp{+} (to indicate
33649 the package was received correctly) or @samp{-} (to request
33653 -> @code{$}@var{packet-data}@code{#}@var{checksum}
33658 The @samp{+}/@samp{-} acknowledgments can be disabled
33659 once a connection is established.
33660 @xref{Packet Acknowledgment}, for details.
33662 The host (@value{GDBN}) sends @var{command}s, and the target (the
33663 debugging stub incorporated in your program) sends a @var{response}. In
33664 the case of step and continue @var{command}s, the response is only sent
33665 when the operation has completed, and the target has again stopped all
33666 threads in all attached processes. This is the default all-stop mode
33667 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
33668 execution mode; see @ref{Remote Non-Stop}, for details.
33670 @var{packet-data} consists of a sequence of characters with the
33671 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
33674 @cindex remote protocol, field separator
33675 Fields within the packet should be separated using @samp{,} @samp{;} or
33676 @samp{:}. Except where otherwise noted all numbers are represented in
33677 @sc{hex} with leading zeros suppressed.
33679 Implementors should note that prior to @value{GDBN} 5.0, the character
33680 @samp{:} could not appear as the third character in a packet (as it
33681 would potentially conflict with the @var{sequence-id}).
33683 @cindex remote protocol, binary data
33684 @anchor{Binary Data}
33685 Binary data in most packets is encoded either as two hexadecimal
33686 digits per byte of binary data. This allowed the traditional remote
33687 protocol to work over connections which were only seven-bit clean.
33688 Some packets designed more recently assume an eight-bit clean
33689 connection, and use a more efficient encoding to send and receive
33692 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
33693 as an escape character. Any escaped byte is transmitted as the escape
33694 character followed by the original character XORed with @code{0x20}.
33695 For example, the byte @code{0x7d} would be transmitted as the two
33696 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
33697 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
33698 @samp{@}}) must always be escaped. Responses sent by the stub
33699 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
33700 is not interpreted as the start of a run-length encoded sequence
33703 Response @var{data} can be run-length encoded to save space.
33704 Run-length encoding replaces runs of identical characters with one
33705 instance of the repeated character, followed by a @samp{*} and a
33706 repeat count. The repeat count is itself sent encoded, to avoid
33707 binary characters in @var{data}: a value of @var{n} is sent as
33708 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
33709 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
33710 code 32) for a repeat count of 3. (This is because run-length
33711 encoding starts to win for counts 3 or more.) Thus, for example,
33712 @samp{0* } is a run-length encoding of ``0000'': the space character
33713 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
33716 The printable characters @samp{#} and @samp{$} or with a numeric value
33717 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
33718 seven repeats (@samp{$}) can be expanded using a repeat count of only
33719 five (@samp{"}). For example, @samp{00000000} can be encoded as
33722 The error response returned for some packets includes a two character
33723 error number. That number is not well defined.
33725 @cindex empty response, for unsupported packets
33726 For any @var{command} not supported by the stub, an empty response
33727 (@samp{$#00}) should be returned. That way it is possible to extend the
33728 protocol. A newer @value{GDBN} can tell if a packet is supported based
33731 At a minimum, a stub is required to support the @samp{g} and @samp{G}
33732 commands for register access, and the @samp{m} and @samp{M} commands
33733 for memory access. Stubs that only control single-threaded targets
33734 can implement run control with the @samp{c} (continue), and @samp{s}
33735 (step) commands. Stubs that support multi-threading targets should
33736 support the @samp{vCont} command. All other commands are optional.
33741 The following table provides a complete list of all currently defined
33742 @var{command}s and their corresponding response @var{data}.
33743 @xref{File-I/O Remote Protocol Extension}, for details about the File
33744 I/O extension of the remote protocol.
33746 Each packet's description has a template showing the packet's overall
33747 syntax, followed by an explanation of the packet's meaning. We
33748 include spaces in some of the templates for clarity; these are not
33749 part of the packet's syntax. No @value{GDBN} packet uses spaces to
33750 separate its components. For example, a template like @samp{foo
33751 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
33752 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
33753 @var{baz}. @value{GDBN} does not transmit a space character between the
33754 @samp{foo} and the @var{bar}, or between the @var{bar} and the
33757 @cindex @var{thread-id}, in remote protocol
33758 @anchor{thread-id syntax}
33759 Several packets and replies include a @var{thread-id} field to identify
33760 a thread. Normally these are positive numbers with a target-specific
33761 interpretation, formatted as big-endian hex strings. A @var{thread-id}
33762 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
33765 In addition, the remote protocol supports a multiprocess feature in
33766 which the @var{thread-id} syntax is extended to optionally include both
33767 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
33768 The @var{pid} (process) and @var{tid} (thread) components each have the
33769 format described above: a positive number with target-specific
33770 interpretation formatted as a big-endian hex string, literal @samp{-1}
33771 to indicate all processes or threads (respectively), or @samp{0} to
33772 indicate an arbitrary process or thread. Specifying just a process, as
33773 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
33774 error to specify all processes but a specific thread, such as
33775 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
33776 for those packets and replies explicitly documented to include a process
33777 ID, rather than a @var{thread-id}.
33779 The multiprocess @var{thread-id} syntax extensions are only used if both
33780 @value{GDBN} and the stub report support for the @samp{multiprocess}
33781 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
33784 Note that all packet forms beginning with an upper- or lower-case
33785 letter, other than those described here, are reserved for future use.
33787 Here are the packet descriptions.
33792 @cindex @samp{!} packet
33793 @anchor{extended mode}
33794 Enable extended mode. In extended mode, the remote server is made
33795 persistent. The @samp{R} packet is used to restart the program being
33801 The remote target both supports and has enabled extended mode.
33805 @cindex @samp{?} packet
33806 Indicate the reason the target halted. The reply is the same as for
33807 step and continue. This packet has a special interpretation when the
33808 target is in non-stop mode; see @ref{Remote Non-Stop}.
33811 @xref{Stop Reply Packets}, for the reply specifications.
33813 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
33814 @cindex @samp{A} packet
33815 Initialized @code{argv[]} array passed into program. @var{arglen}
33816 specifies the number of bytes in the hex encoded byte stream
33817 @var{arg}. See @code{gdbserver} for more details.
33822 The arguments were set.
33828 @cindex @samp{b} packet
33829 (Don't use this packet; its behavior is not well-defined.)
33830 Change the serial line speed to @var{baud}.
33832 JTC: @emph{When does the transport layer state change? When it's
33833 received, or after the ACK is transmitted. In either case, there are
33834 problems if the command or the acknowledgment packet is dropped.}
33836 Stan: @emph{If people really wanted to add something like this, and get
33837 it working for the first time, they ought to modify ser-unix.c to send
33838 some kind of out-of-band message to a specially-setup stub and have the
33839 switch happen "in between" packets, so that from remote protocol's point
33840 of view, nothing actually happened.}
33842 @item B @var{addr},@var{mode}
33843 @cindex @samp{B} packet
33844 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
33845 breakpoint at @var{addr}.
33847 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
33848 (@pxref{insert breakpoint or watchpoint packet}).
33850 @cindex @samp{bc} packet
33853 Backward continue. Execute the target system in reverse. No parameter.
33854 @xref{Reverse Execution}, for more information.
33857 @xref{Stop Reply Packets}, for the reply specifications.
33859 @cindex @samp{bs} packet
33862 Backward single step. Execute one instruction in reverse. No parameter.
33863 @xref{Reverse Execution}, for more information.
33866 @xref{Stop Reply Packets}, for the reply specifications.
33868 @item c @r{[}@var{addr}@r{]}
33869 @cindex @samp{c} packet
33870 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
33871 resume at current address.
33873 This packet is deprecated for multi-threading support. @xref{vCont
33877 @xref{Stop Reply Packets}, for the reply specifications.
33879 @item C @var{sig}@r{[};@var{addr}@r{]}
33880 @cindex @samp{C} packet
33881 Continue with signal @var{sig} (hex signal number). If
33882 @samp{;@var{addr}} is omitted, resume at same address.
33884 This packet is deprecated for multi-threading support. @xref{vCont
33888 @xref{Stop Reply Packets}, for the reply specifications.
33891 @cindex @samp{d} packet
33894 Don't use this packet; instead, define a general set packet
33895 (@pxref{General Query Packets}).
33899 @cindex @samp{D} packet
33900 The first form of the packet is used to detach @value{GDBN} from the
33901 remote system. It is sent to the remote target
33902 before @value{GDBN} disconnects via the @code{detach} command.
33904 The second form, including a process ID, is used when multiprocess
33905 protocol extensions are enabled (@pxref{multiprocess extensions}), to
33906 detach only a specific process. The @var{pid} is specified as a
33907 big-endian hex string.
33917 @item F @var{RC},@var{EE},@var{CF};@var{XX}
33918 @cindex @samp{F} packet
33919 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
33920 This is part of the File-I/O protocol extension. @xref{File-I/O
33921 Remote Protocol Extension}, for the specification.
33924 @anchor{read registers packet}
33925 @cindex @samp{g} packet
33926 Read general registers.
33930 @item @var{XX@dots{}}
33931 Each byte of register data is described by two hex digits. The bytes
33932 with the register are transmitted in target byte order. The size of
33933 each register and their position within the @samp{g} packet are
33934 determined by the @value{GDBN} internal gdbarch functions
33935 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
33936 specification of several standard @samp{g} packets is specified below.
33938 When reading registers from a trace frame (@pxref{Analyze Collected
33939 Data,,Using the Collected Data}), the stub may also return a string of
33940 literal @samp{x}'s in place of the register data digits, to indicate
33941 that the corresponding register has not been collected, thus its value
33942 is unavailable. For example, for an architecture with 4 registers of
33943 4 bytes each, the following reply indicates to @value{GDBN} that
33944 registers 0 and 2 have not been collected, while registers 1 and 3
33945 have been collected, and both have zero value:
33949 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
33956 @item G @var{XX@dots{}}
33957 @cindex @samp{G} packet
33958 Write general registers. @xref{read registers packet}, for a
33959 description of the @var{XX@dots{}} data.
33969 @item H @var{op} @var{thread-id}
33970 @cindex @samp{H} packet
33971 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
33972 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
33973 it should be @samp{c} for step and continue operations (note that this
33974 is deprecated, supporting the @samp{vCont} command is a better
33975 option), @samp{g} for other operations. The thread designator
33976 @var{thread-id} has the format and interpretation described in
33977 @ref{thread-id syntax}.
33988 @c 'H': How restrictive (or permissive) is the thread model. If a
33989 @c thread is selected and stopped, are other threads allowed
33990 @c to continue to execute? As I mentioned above, I think the
33991 @c semantics of each command when a thread is selected must be
33992 @c described. For example:
33994 @c 'g': If the stub supports threads and a specific thread is
33995 @c selected, returns the register block from that thread;
33996 @c otherwise returns current registers.
33998 @c 'G' If the stub supports threads and a specific thread is
33999 @c selected, sets the registers of the register block of
34000 @c that thread; otherwise sets current registers.
34002 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
34003 @anchor{cycle step packet}
34004 @cindex @samp{i} packet
34005 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
34006 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
34007 step starting at that address.
34010 @cindex @samp{I} packet
34011 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
34015 @cindex @samp{k} packet
34018 FIXME: @emph{There is no description of how to operate when a specific
34019 thread context has been selected (i.e.@: does 'k' kill only that
34022 @item m @var{addr},@var{length}
34023 @cindex @samp{m} packet
34024 Read @var{length} bytes of memory starting at address @var{addr}.
34025 Note that @var{addr} may not be aligned to any particular boundary.
34027 The stub need not use any particular size or alignment when gathering
34028 data from memory for the response; even if @var{addr} is word-aligned
34029 and @var{length} is a multiple of the word size, the stub is free to
34030 use byte accesses, or not. For this reason, this packet may not be
34031 suitable for accessing memory-mapped I/O devices.
34032 @cindex alignment of remote memory accesses
34033 @cindex size of remote memory accesses
34034 @cindex memory, alignment and size of remote accesses
34038 @item @var{XX@dots{}}
34039 Memory contents; each byte is transmitted as a two-digit hexadecimal
34040 number. The reply may contain fewer bytes than requested if the
34041 server was able to read only part of the region of memory.
34046 @item M @var{addr},@var{length}:@var{XX@dots{}}
34047 @cindex @samp{M} packet
34048 Write @var{length} bytes of memory starting at address @var{addr}.
34049 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
34050 hexadecimal number.
34057 for an error (this includes the case where only part of the data was
34062 @cindex @samp{p} packet
34063 Read the value of register @var{n}; @var{n} is in hex.
34064 @xref{read registers packet}, for a description of how the returned
34065 register value is encoded.
34069 @item @var{XX@dots{}}
34070 the register's value
34074 Indicating an unrecognized @var{query}.
34077 @item P @var{n@dots{}}=@var{r@dots{}}
34078 @anchor{write register packet}
34079 @cindex @samp{P} packet
34080 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
34081 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
34082 digits for each byte in the register (target byte order).
34092 @item q @var{name} @var{params}@dots{}
34093 @itemx Q @var{name} @var{params}@dots{}
34094 @cindex @samp{q} packet
34095 @cindex @samp{Q} packet
34096 General query (@samp{q}) and set (@samp{Q}). These packets are
34097 described fully in @ref{General Query Packets}.
34100 @cindex @samp{r} packet
34101 Reset the entire system.
34103 Don't use this packet; use the @samp{R} packet instead.
34106 @cindex @samp{R} packet
34107 Restart the program being debugged. @var{XX}, while needed, is ignored.
34108 This packet is only available in extended mode (@pxref{extended mode}).
34110 The @samp{R} packet has no reply.
34112 @item s @r{[}@var{addr}@r{]}
34113 @cindex @samp{s} packet
34114 Single step. @var{addr} is the address at which to resume. If
34115 @var{addr} is omitted, resume at same address.
34117 This packet is deprecated for multi-threading support. @xref{vCont
34121 @xref{Stop Reply Packets}, for the reply specifications.
34123 @item S @var{sig}@r{[};@var{addr}@r{]}
34124 @anchor{step with signal packet}
34125 @cindex @samp{S} packet
34126 Step with signal. This is analogous to the @samp{C} packet, but
34127 requests a single-step, rather than a normal resumption of execution.
34129 This packet is deprecated for multi-threading support. @xref{vCont
34133 @xref{Stop Reply Packets}, for the reply specifications.
34135 @item t @var{addr}:@var{PP},@var{MM}
34136 @cindex @samp{t} packet
34137 Search backwards starting at address @var{addr} for a match with pattern
34138 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
34139 @var{addr} must be at least 3 digits.
34141 @item T @var{thread-id}
34142 @cindex @samp{T} packet
34143 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
34148 thread is still alive
34154 Packets starting with @samp{v} are identified by a multi-letter name,
34155 up to the first @samp{;} or @samp{?} (or the end of the packet).
34157 @item vAttach;@var{pid}
34158 @cindex @samp{vAttach} packet
34159 Attach to a new process with the specified process ID @var{pid}.
34160 The process ID is a
34161 hexadecimal integer identifying the process. In all-stop mode, all
34162 threads in the attached process are stopped; in non-stop mode, it may be
34163 attached without being stopped if that is supported by the target.
34165 @c In non-stop mode, on a successful vAttach, the stub should set the
34166 @c current thread to a thread of the newly-attached process. After
34167 @c attaching, GDB queries for the attached process's thread ID with qC.
34168 @c Also note that, from a user perspective, whether or not the
34169 @c target is stopped on attach in non-stop mode depends on whether you
34170 @c use the foreground or background version of the attach command, not
34171 @c on what vAttach does; GDB does the right thing with respect to either
34172 @c stopping or restarting threads.
34174 This packet is only available in extended mode (@pxref{extended mode}).
34180 @item @r{Any stop packet}
34181 for success in all-stop mode (@pxref{Stop Reply Packets})
34183 for success in non-stop mode (@pxref{Remote Non-Stop})
34186 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
34187 @cindex @samp{vCont} packet
34188 @anchor{vCont packet}
34189 Resume the inferior, specifying different actions for each thread.
34190 If an action is specified with no @var{thread-id}, then it is applied to any
34191 threads that don't have a specific action specified; if no default action is
34192 specified then other threads should remain stopped in all-stop mode and
34193 in their current state in non-stop mode.
34194 Specifying multiple
34195 default actions is an error; specifying no actions is also an error.
34196 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
34198 Currently supported actions are:
34204 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
34208 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
34213 The optional argument @var{addr} normally associated with the
34214 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
34215 not supported in @samp{vCont}.
34217 The @samp{t} action is only relevant in non-stop mode
34218 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
34219 A stop reply should be generated for any affected thread not already stopped.
34220 When a thread is stopped by means of a @samp{t} action,
34221 the corresponding stop reply should indicate that the thread has stopped with
34222 signal @samp{0}, regardless of whether the target uses some other signal
34223 as an implementation detail.
34225 The stub must support @samp{vCont} if it reports support for
34226 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
34227 this case @samp{vCont} actions can be specified to apply to all threads
34228 in a process by using the @samp{p@var{pid}.-1} form of the
34232 @xref{Stop Reply Packets}, for the reply specifications.
34235 @cindex @samp{vCont?} packet
34236 Request a list of actions supported by the @samp{vCont} packet.
34240 @item vCont@r{[};@var{action}@dots{}@r{]}
34241 The @samp{vCont} packet is supported. Each @var{action} is a supported
34242 command in the @samp{vCont} packet.
34244 The @samp{vCont} packet is not supported.
34247 @item vFile:@var{operation}:@var{parameter}@dots{}
34248 @cindex @samp{vFile} packet
34249 Perform a file operation on the target system. For details,
34250 see @ref{Host I/O Packets}.
34252 @item vFlashErase:@var{addr},@var{length}
34253 @cindex @samp{vFlashErase} packet
34254 Direct the stub to erase @var{length} bytes of flash starting at
34255 @var{addr}. The region may enclose any number of flash blocks, but
34256 its start and end must fall on block boundaries, as indicated by the
34257 flash block size appearing in the memory map (@pxref{Memory Map
34258 Format}). @value{GDBN} groups flash memory programming operations
34259 together, and sends a @samp{vFlashDone} request after each group; the
34260 stub is allowed to delay erase operation until the @samp{vFlashDone}
34261 packet is received.
34271 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
34272 @cindex @samp{vFlashWrite} packet
34273 Direct the stub to write data to flash address @var{addr}. The data
34274 is passed in binary form using the same encoding as for the @samp{X}
34275 packet (@pxref{Binary Data}). The memory ranges specified by
34276 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
34277 not overlap, and must appear in order of increasing addresses
34278 (although @samp{vFlashErase} packets for higher addresses may already
34279 have been received; the ordering is guaranteed only between
34280 @samp{vFlashWrite} packets). If a packet writes to an address that was
34281 neither erased by a preceding @samp{vFlashErase} packet nor by some other
34282 target-specific method, the results are unpredictable.
34290 for vFlashWrite addressing non-flash memory
34296 @cindex @samp{vFlashDone} packet
34297 Indicate to the stub that flash programming operation is finished.
34298 The stub is permitted to delay or batch the effects of a group of
34299 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
34300 @samp{vFlashDone} packet is received. The contents of the affected
34301 regions of flash memory are unpredictable until the @samp{vFlashDone}
34302 request is completed.
34304 @item vKill;@var{pid}
34305 @cindex @samp{vKill} packet
34306 Kill the process with the specified process ID. @var{pid} is a
34307 hexadecimal integer identifying the process. This packet is used in
34308 preference to @samp{k} when multiprocess protocol extensions are
34309 supported; see @ref{multiprocess extensions}.
34319 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
34320 @cindex @samp{vRun} packet
34321 Run the program @var{filename}, passing it each @var{argument} on its
34322 command line. The file and arguments are hex-encoded strings. If
34323 @var{filename} is an empty string, the stub may use a default program
34324 (e.g.@: the last program run). The program is created in the stopped
34327 @c FIXME: What about non-stop mode?
34329 This packet is only available in extended mode (@pxref{extended mode}).
34335 @item @r{Any stop packet}
34336 for success (@pxref{Stop Reply Packets})
34340 @anchor{vStopped packet}
34341 @cindex @samp{vStopped} packet
34343 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
34344 reply and prompt for the stub to report another one.
34348 @item @r{Any stop packet}
34349 if there is another unreported stop event (@pxref{Stop Reply Packets})
34351 if there are no unreported stop events
34354 @item X @var{addr},@var{length}:@var{XX@dots{}}
34356 @cindex @samp{X} packet
34357 Write data to memory, where the data is transmitted in binary.
34358 @var{addr} is address, @var{length} is number of bytes,
34359 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
34369 @item z @var{type},@var{addr},@var{kind}
34370 @itemx Z @var{type},@var{addr},@var{kind}
34371 @anchor{insert breakpoint or watchpoint packet}
34372 @cindex @samp{z} packet
34373 @cindex @samp{Z} packets
34374 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
34375 watchpoint starting at address @var{address} of kind @var{kind}.
34377 Each breakpoint and watchpoint packet @var{type} is documented
34380 @emph{Implementation notes: A remote target shall return an empty string
34381 for an unrecognized breakpoint or watchpoint packet @var{type}. A
34382 remote target shall support either both or neither of a given
34383 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
34384 avoid potential problems with duplicate packets, the operations should
34385 be implemented in an idempotent way.}
34387 @item z0,@var{addr},@var{kind}
34388 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
34389 @cindex @samp{z0} packet
34390 @cindex @samp{Z0} packet
34391 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
34392 @var{addr} of type @var{kind}.
34394 A memory breakpoint is implemented by replacing the instruction at
34395 @var{addr} with a software breakpoint or trap instruction. The
34396 @var{kind} is target-specific and typically indicates the size of
34397 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
34398 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
34399 architectures have additional meanings for @var{kind};
34400 @var{cond_list} is an optional list of conditional expressions in bytecode
34401 form that should be evaluated on the target's side. These are the
34402 conditions that should be taken into consideration when deciding if
34403 the breakpoint trigger should be reported back to @var{GDBN}.
34405 The @var{cond_list} parameter is comprised of a series of expressions,
34406 concatenated without separators. Each expression has the following form:
34410 @item X @var{len},@var{expr}
34411 @var{len} is the length of the bytecode expression and @var{expr} is the
34412 actual conditional expression in bytecode form.
34416 see @ref{Architecture-Specific Protocol Details}.
34418 @emph{Implementation note: It is possible for a target to copy or move
34419 code that contains memory breakpoints (e.g., when implementing
34420 overlays). The behavior of this packet, in the presence of such a
34421 target, is not defined.}
34433 @item z1,@var{addr},@var{kind}
34434 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
34435 @cindex @samp{z1} packet
34436 @cindex @samp{Z1} packet
34437 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
34438 address @var{addr}.
34440 A hardware breakpoint is implemented using a mechanism that is not
34441 dependant on being able to modify the target's memory. @var{kind}
34442 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
34444 @emph{Implementation note: A hardware breakpoint is not affected by code
34457 @item z2,@var{addr},@var{kind}
34458 @itemx Z2,@var{addr},@var{kind}
34459 @cindex @samp{z2} packet
34460 @cindex @samp{Z2} packet
34461 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
34462 @var{kind} is interpreted as the number of bytes to watch.
34474 @item z3,@var{addr},@var{kind}
34475 @itemx Z3,@var{addr},@var{kind}
34476 @cindex @samp{z3} packet
34477 @cindex @samp{Z3} packet
34478 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
34479 @var{kind} is interpreted as the number of bytes to watch.
34491 @item z4,@var{addr},@var{kind}
34492 @itemx Z4,@var{addr},@var{kind}
34493 @cindex @samp{z4} packet
34494 @cindex @samp{Z4} packet
34495 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
34496 @var{kind} is interpreted as the number of bytes to watch.
34510 @node Stop Reply Packets
34511 @section Stop Reply Packets
34512 @cindex stop reply packets
34514 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
34515 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
34516 receive any of the below as a reply. Except for @samp{?}
34517 and @samp{vStopped}, that reply is only returned
34518 when the target halts. In the below the exact meaning of @dfn{signal
34519 number} is defined by the header @file{include/gdb/signals.h} in the
34520 @value{GDBN} source code.
34522 As in the description of request packets, we include spaces in the
34523 reply templates for clarity; these are not part of the reply packet's
34524 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
34530 The program received signal number @var{AA} (a two-digit hexadecimal
34531 number). This is equivalent to a @samp{T} response with no
34532 @var{n}:@var{r} pairs.
34534 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
34535 @cindex @samp{T} packet reply
34536 The program received signal number @var{AA} (a two-digit hexadecimal
34537 number). This is equivalent to an @samp{S} response, except that the
34538 @samp{@var{n}:@var{r}} pairs can carry values of important registers
34539 and other information directly in the stop reply packet, reducing
34540 round-trip latency. Single-step and breakpoint traps are reported
34541 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
34545 If @var{n} is a hexadecimal number, it is a register number, and the
34546 corresponding @var{r} gives that register's value. @var{r} is a
34547 series of bytes in target byte order, with each byte given by a
34548 two-digit hex number.
34551 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
34552 the stopped thread, as specified in @ref{thread-id syntax}.
34555 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
34556 the core on which the stop event was detected.
34559 If @var{n} is a recognized @dfn{stop reason}, it describes a more
34560 specific event that stopped the target. The currently defined stop
34561 reasons are listed below. @var{aa} should be @samp{05}, the trap
34562 signal. At most one stop reason should be present.
34565 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
34566 and go on to the next; this allows us to extend the protocol in the
34570 The currently defined stop reasons are:
34576 The packet indicates a watchpoint hit, and @var{r} is the data address, in
34579 @cindex shared library events, remote reply
34581 The packet indicates that the loaded libraries have changed.
34582 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
34583 list of loaded libraries. @var{r} is ignored.
34585 @cindex replay log events, remote reply
34587 The packet indicates that the target cannot continue replaying
34588 logged execution events, because it has reached the end (or the
34589 beginning when executing backward) of the log. The value of @var{r}
34590 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
34591 for more information.
34595 @itemx W @var{AA} ; process:@var{pid}
34596 The process exited, and @var{AA} is the exit status. This is only
34597 applicable to certain targets.
34599 The second form of the response, including the process ID of the exited
34600 process, can be used only when @value{GDBN} has reported support for
34601 multiprocess protocol extensions; see @ref{multiprocess extensions}.
34602 The @var{pid} is formatted as a big-endian hex string.
34605 @itemx X @var{AA} ; process:@var{pid}
34606 The process terminated with signal @var{AA}.
34608 The second form of the response, including the process ID of the
34609 terminated process, can be used only when @value{GDBN} has reported
34610 support for multiprocess protocol extensions; see @ref{multiprocess
34611 extensions}. The @var{pid} is formatted as a big-endian hex string.
34613 @item O @var{XX}@dots{}
34614 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
34615 written as the program's console output. This can happen at any time
34616 while the program is running and the debugger should continue to wait
34617 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
34619 @item F @var{call-id},@var{parameter}@dots{}
34620 @var{call-id} is the identifier which says which host system call should
34621 be called. This is just the name of the function. Translation into the
34622 correct system call is only applicable as it's defined in @value{GDBN}.
34623 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
34626 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
34627 this very system call.
34629 The target replies with this packet when it expects @value{GDBN} to
34630 call a host system call on behalf of the target. @value{GDBN} replies
34631 with an appropriate @samp{F} packet and keeps up waiting for the next
34632 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
34633 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
34634 Protocol Extension}, for more details.
34638 @node General Query Packets
34639 @section General Query Packets
34640 @cindex remote query requests
34642 Packets starting with @samp{q} are @dfn{general query packets};
34643 packets starting with @samp{Q} are @dfn{general set packets}. General
34644 query and set packets are a semi-unified form for retrieving and
34645 sending information to and from the stub.
34647 The initial letter of a query or set packet is followed by a name
34648 indicating what sort of thing the packet applies to. For example,
34649 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
34650 definitions with the stub. These packet names follow some
34655 The name must not contain commas, colons or semicolons.
34657 Most @value{GDBN} query and set packets have a leading upper case
34660 The names of custom vendor packets should use a company prefix, in
34661 lower case, followed by a period. For example, packets designed at
34662 the Acme Corporation might begin with @samp{qacme.foo} (for querying
34663 foos) or @samp{Qacme.bar} (for setting bars).
34666 The name of a query or set packet should be separated from any
34667 parameters by a @samp{:}; the parameters themselves should be
34668 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
34669 full packet name, and check for a separator or the end of the packet,
34670 in case two packet names share a common prefix. New packets should not begin
34671 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
34672 packets predate these conventions, and have arguments without any terminator
34673 for the packet name; we suspect they are in widespread use in places that
34674 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
34675 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
34678 Like the descriptions of the other packets, each description here
34679 has a template showing the packet's overall syntax, followed by an
34680 explanation of the packet's meaning. We include spaces in some of the
34681 templates for clarity; these are not part of the packet's syntax. No
34682 @value{GDBN} packet uses spaces to separate its components.
34684 Here are the currently defined query and set packets:
34690 Turn on or off the agent as a helper to perform some debugging operations
34691 delegated from @value{GDBN} (@pxref{Control Agent}).
34693 @item QAllow:@var{op}:@var{val}@dots{}
34694 @cindex @samp{QAllow} packet
34695 Specify which operations @value{GDBN} expects to request of the
34696 target, as a semicolon-separated list of operation name and value
34697 pairs. Possible values for @var{op} include @samp{WriteReg},
34698 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
34699 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
34700 indicating that @value{GDBN} will not request the operation, or 1,
34701 indicating that it may. (The target can then use this to set up its
34702 own internals optimally, for instance if the debugger never expects to
34703 insert breakpoints, it may not need to install its own trap handler.)
34706 @cindex current thread, remote request
34707 @cindex @samp{qC} packet
34708 Return the current thread ID.
34712 @item QC @var{thread-id}
34713 Where @var{thread-id} is a thread ID as documented in
34714 @ref{thread-id syntax}.
34715 @item @r{(anything else)}
34716 Any other reply implies the old thread ID.
34719 @item qCRC:@var{addr},@var{length}
34720 @cindex CRC of memory block, remote request
34721 @cindex @samp{qCRC} packet
34722 Compute the CRC checksum of a block of memory using CRC-32 defined in
34723 IEEE 802.3. The CRC is computed byte at a time, taking the most
34724 significant bit of each byte first. The initial pattern code
34725 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
34727 @emph{Note:} This is the same CRC used in validating separate debug
34728 files (@pxref{Separate Debug Files, , Debugging Information in Separate
34729 Files}). However the algorithm is slightly different. When validating
34730 separate debug files, the CRC is computed taking the @emph{least}
34731 significant bit of each byte first, and the final result is inverted to
34732 detect trailing zeros.
34737 An error (such as memory fault)
34738 @item C @var{crc32}
34739 The specified memory region's checksum is @var{crc32}.
34742 @item QDisableRandomization:@var{value}
34743 @cindex disable address space randomization, remote request
34744 @cindex @samp{QDisableRandomization} packet
34745 Some target operating systems will randomize the virtual address space
34746 of the inferior process as a security feature, but provide a feature
34747 to disable such randomization, e.g.@: to allow for a more deterministic
34748 debugging experience. On such systems, this packet with a @var{value}
34749 of 1 directs the target to disable address space randomization for
34750 processes subsequently started via @samp{vRun} packets, while a packet
34751 with a @var{value} of 0 tells the target to enable address space
34754 This packet is only available in extended mode (@pxref{extended mode}).
34759 The request succeeded.
34762 An error occurred. @var{nn} are hex digits.
34765 An empty reply indicates that @samp{QDisableRandomization} is not supported
34769 This packet is not probed by default; the remote stub must request it,
34770 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34771 This should only be done on targets that actually support disabling
34772 address space randomization.
34775 @itemx qsThreadInfo
34776 @cindex list active threads, remote request
34777 @cindex @samp{qfThreadInfo} packet
34778 @cindex @samp{qsThreadInfo} packet
34779 Obtain a list of all active thread IDs from the target (OS). Since there
34780 may be too many active threads to fit into one reply packet, this query
34781 works iteratively: it may require more than one query/reply sequence to
34782 obtain the entire list of threads. The first query of the sequence will
34783 be the @samp{qfThreadInfo} query; subsequent queries in the
34784 sequence will be the @samp{qsThreadInfo} query.
34786 NOTE: This packet replaces the @samp{qL} query (see below).
34790 @item m @var{thread-id}
34792 @item m @var{thread-id},@var{thread-id}@dots{}
34793 a comma-separated list of thread IDs
34795 (lower case letter @samp{L}) denotes end of list.
34798 In response to each query, the target will reply with a list of one or
34799 more thread IDs, separated by commas.
34800 @value{GDBN} will respond to each reply with a request for more thread
34801 ids (using the @samp{qs} form of the query), until the target responds
34802 with @samp{l} (lower-case ell, for @dfn{last}).
34803 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
34806 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
34807 @cindex get thread-local storage address, remote request
34808 @cindex @samp{qGetTLSAddr} packet
34809 Fetch the address associated with thread local storage specified
34810 by @var{thread-id}, @var{offset}, and @var{lm}.
34812 @var{thread-id} is the thread ID associated with the
34813 thread for which to fetch the TLS address. @xref{thread-id syntax}.
34815 @var{offset} is the (big endian, hex encoded) offset associated with the
34816 thread local variable. (This offset is obtained from the debug
34817 information associated with the variable.)
34819 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
34820 load module associated with the thread local storage. For example,
34821 a @sc{gnu}/Linux system will pass the link map address of the shared
34822 object associated with the thread local storage under consideration.
34823 Other operating environments may choose to represent the load module
34824 differently, so the precise meaning of this parameter will vary.
34828 @item @var{XX}@dots{}
34829 Hex encoded (big endian) bytes representing the address of the thread
34830 local storage requested.
34833 An error occurred. @var{nn} are hex digits.
34836 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
34839 @item qGetTIBAddr:@var{thread-id}
34840 @cindex get thread information block address
34841 @cindex @samp{qGetTIBAddr} packet
34842 Fetch address of the Windows OS specific Thread Information Block.
34844 @var{thread-id} is the thread ID associated with the thread.
34848 @item @var{XX}@dots{}
34849 Hex encoded (big endian) bytes representing the linear address of the
34850 thread information block.
34853 An error occured. This means that either the thread was not found, or the
34854 address could not be retrieved.
34857 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
34860 @item qL @var{startflag} @var{threadcount} @var{nextthread}
34861 Obtain thread information from RTOS. Where: @var{startflag} (one hex
34862 digit) is one to indicate the first query and zero to indicate a
34863 subsequent query; @var{threadcount} (two hex digits) is the maximum
34864 number of threads the response packet can contain; and @var{nextthread}
34865 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
34866 returned in the response as @var{argthread}.
34868 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
34872 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
34873 Where: @var{count} (two hex digits) is the number of threads being
34874 returned; @var{done} (one hex digit) is zero to indicate more threads
34875 and one indicates no further threads; @var{argthreadid} (eight hex
34876 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
34877 is a sequence of thread IDs from the target. @var{threadid} (eight hex
34878 digits). See @code{remote.c:parse_threadlist_response()}.
34882 @cindex section offsets, remote request
34883 @cindex @samp{qOffsets} packet
34884 Get section offsets that the target used when relocating the downloaded
34889 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
34890 Relocate the @code{Text} section by @var{xxx} from its original address.
34891 Relocate the @code{Data} section by @var{yyy} from its original address.
34892 If the object file format provides segment information (e.g.@: @sc{elf}
34893 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
34894 segments by the supplied offsets.
34896 @emph{Note: while a @code{Bss} offset may be included in the response,
34897 @value{GDBN} ignores this and instead applies the @code{Data} offset
34898 to the @code{Bss} section.}
34900 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
34901 Relocate the first segment of the object file, which conventionally
34902 contains program code, to a starting address of @var{xxx}. If
34903 @samp{DataSeg} is specified, relocate the second segment, which
34904 conventionally contains modifiable data, to a starting address of
34905 @var{yyy}. @value{GDBN} will report an error if the object file
34906 does not contain segment information, or does not contain at least
34907 as many segments as mentioned in the reply. Extra segments are
34908 kept at fixed offsets relative to the last relocated segment.
34911 @item qP @var{mode} @var{thread-id}
34912 @cindex thread information, remote request
34913 @cindex @samp{qP} packet
34914 Returns information on @var{thread-id}. Where: @var{mode} is a hex
34915 encoded 32 bit mode; @var{thread-id} is a thread ID
34916 (@pxref{thread-id syntax}).
34918 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
34921 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
34925 @cindex non-stop mode, remote request
34926 @cindex @samp{QNonStop} packet
34928 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
34929 @xref{Remote Non-Stop}, for more information.
34934 The request succeeded.
34937 An error occurred. @var{nn} are hex digits.
34940 An empty reply indicates that @samp{QNonStop} is not supported by
34944 This packet is not probed by default; the remote stub must request it,
34945 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34946 Use of this packet is controlled by the @code{set non-stop} command;
34947 @pxref{Non-Stop Mode}.
34949 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
34950 @cindex pass signals to inferior, remote request
34951 @cindex @samp{QPassSignals} packet
34952 @anchor{QPassSignals}
34953 Each listed @var{signal} should be passed directly to the inferior process.
34954 Signals are numbered identically to continue packets and stop replies
34955 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
34956 strictly greater than the previous item. These signals do not need to stop
34957 the inferior, or be reported to @value{GDBN}. All other signals should be
34958 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
34959 combine; any earlier @samp{QPassSignals} list is completely replaced by the
34960 new list. This packet improves performance when using @samp{handle
34961 @var{signal} nostop noprint pass}.
34966 The request succeeded.
34969 An error occurred. @var{nn} are hex digits.
34972 An empty reply indicates that @samp{QPassSignals} is not supported by
34976 Use of this packet is controlled by the @code{set remote pass-signals}
34977 command (@pxref{Remote Configuration, set remote pass-signals}).
34978 This packet is not probed by default; the remote stub must request it,
34979 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
34981 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
34982 @cindex signals the inferior may see, remote request
34983 @cindex @samp{QProgramSignals} packet
34984 @anchor{QProgramSignals}
34985 Each listed @var{signal} may be delivered to the inferior process.
34986 Others should be silently discarded.
34988 In some cases, the remote stub may need to decide whether to deliver a
34989 signal to the program or not without @value{GDBN} involvement. One
34990 example of that is while detaching --- the program's threads may have
34991 stopped for signals that haven't yet had a chance of being reported to
34992 @value{GDBN}, and so the remote stub can use the signal list specified
34993 by this packet to know whether to deliver or ignore those pending
34996 This does not influence whether to deliver a signal as requested by a
34997 resumption packet (@pxref{vCont packet}).
34999 Signals are numbered identically to continue packets and stop replies
35000 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
35001 strictly greater than the previous item. Multiple
35002 @samp{QProgramSignals} packets do not combine; any earlier
35003 @samp{QProgramSignals} list is completely replaced by the new list.
35008 The request succeeded.
35011 An error occurred. @var{nn} are hex digits.
35014 An empty reply indicates that @samp{QProgramSignals} is not supported
35018 Use of this packet is controlled by the @code{set remote program-signals}
35019 command (@pxref{Remote Configuration, set remote program-signals}).
35020 This packet is not probed by default; the remote stub must request it,
35021 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35023 @item qRcmd,@var{command}
35024 @cindex execute remote command, remote request
35025 @cindex @samp{qRcmd} packet
35026 @var{command} (hex encoded) is passed to the local interpreter for
35027 execution. Invalid commands should be reported using the output
35028 string. Before the final result packet, the target may also respond
35029 with a number of intermediate @samp{O@var{output}} console output
35030 packets. @emph{Implementors should note that providing access to a
35031 stubs's interpreter may have security implications}.
35036 A command response with no output.
35038 A command response with the hex encoded output string @var{OUTPUT}.
35040 Indicate a badly formed request.
35042 An empty reply indicates that @samp{qRcmd} is not recognized.
35045 (Note that the @code{qRcmd} packet's name is separated from the
35046 command by a @samp{,}, not a @samp{:}, contrary to the naming
35047 conventions above. Please don't use this packet as a model for new
35050 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
35051 @cindex searching memory, in remote debugging
35052 @cindex @samp{qSearch:memory} packet
35053 @anchor{qSearch memory}
35054 Search @var{length} bytes at @var{address} for @var{search-pattern}.
35055 @var{address} and @var{length} are encoded in hex.
35056 @var{search-pattern} is a sequence of bytes, hex encoded.
35061 The pattern was not found.
35063 The pattern was found at @var{address}.
35065 A badly formed request or an error was encountered while searching memory.
35067 An empty reply indicates that @samp{qSearch:memory} is not recognized.
35070 @item QStartNoAckMode
35071 @cindex @samp{QStartNoAckMode} packet
35072 @anchor{QStartNoAckMode}
35073 Request that the remote stub disable the normal @samp{+}/@samp{-}
35074 protocol acknowledgments (@pxref{Packet Acknowledgment}).
35079 The stub has switched to no-acknowledgment mode.
35080 @value{GDBN} acknowledges this reponse,
35081 but neither the stub nor @value{GDBN} shall send or expect further
35082 @samp{+}/@samp{-} acknowledgments in the current connection.
35084 An empty reply indicates that the stub does not support no-acknowledgment mode.
35087 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
35088 @cindex supported packets, remote query
35089 @cindex features of the remote protocol
35090 @cindex @samp{qSupported} packet
35091 @anchor{qSupported}
35092 Tell the remote stub about features supported by @value{GDBN}, and
35093 query the stub for features it supports. This packet allows
35094 @value{GDBN} and the remote stub to take advantage of each others'
35095 features. @samp{qSupported} also consolidates multiple feature probes
35096 at startup, to improve @value{GDBN} performance---a single larger
35097 packet performs better than multiple smaller probe packets on
35098 high-latency links. Some features may enable behavior which must not
35099 be on by default, e.g.@: because it would confuse older clients or
35100 stubs. Other features may describe packets which could be
35101 automatically probed for, but are not. These features must be
35102 reported before @value{GDBN} will use them. This ``default
35103 unsupported'' behavior is not appropriate for all packets, but it
35104 helps to keep the initial connection time under control with new
35105 versions of @value{GDBN} which support increasing numbers of packets.
35109 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
35110 The stub supports or does not support each returned @var{stubfeature},
35111 depending on the form of each @var{stubfeature} (see below for the
35114 An empty reply indicates that @samp{qSupported} is not recognized,
35115 or that no features needed to be reported to @value{GDBN}.
35118 The allowed forms for each feature (either a @var{gdbfeature} in the
35119 @samp{qSupported} packet, or a @var{stubfeature} in the response)
35123 @item @var{name}=@var{value}
35124 The remote protocol feature @var{name} is supported, and associated
35125 with the specified @var{value}. The format of @var{value} depends
35126 on the feature, but it must not include a semicolon.
35128 The remote protocol feature @var{name} is supported, and does not
35129 need an associated value.
35131 The remote protocol feature @var{name} is not supported.
35133 The remote protocol feature @var{name} may be supported, and
35134 @value{GDBN} should auto-detect support in some other way when it is
35135 needed. This form will not be used for @var{gdbfeature} notifications,
35136 but may be used for @var{stubfeature} responses.
35139 Whenever the stub receives a @samp{qSupported} request, the
35140 supplied set of @value{GDBN} features should override any previous
35141 request. This allows @value{GDBN} to put the stub in a known
35142 state, even if the stub had previously been communicating with
35143 a different version of @value{GDBN}.
35145 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
35150 This feature indicates whether @value{GDBN} supports multiprocess
35151 extensions to the remote protocol. @value{GDBN} does not use such
35152 extensions unless the stub also reports that it supports them by
35153 including @samp{multiprocess+} in its @samp{qSupported} reply.
35154 @xref{multiprocess extensions}, for details.
35157 This feature indicates that @value{GDBN} supports the XML target
35158 description. If the stub sees @samp{xmlRegisters=} with target
35159 specific strings separated by a comma, it will report register
35163 This feature indicates whether @value{GDBN} supports the
35164 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
35165 instruction reply packet}).
35168 Stubs should ignore any unknown values for
35169 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
35170 packet supports receiving packets of unlimited length (earlier
35171 versions of @value{GDBN} may reject overly long responses). Additional values
35172 for @var{gdbfeature} may be defined in the future to let the stub take
35173 advantage of new features in @value{GDBN}, e.g.@: incompatible
35174 improvements in the remote protocol---the @samp{multiprocess} feature is
35175 an example of such a feature. The stub's reply should be independent
35176 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
35177 describes all the features it supports, and then the stub replies with
35178 all the features it supports.
35180 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
35181 responses, as long as each response uses one of the standard forms.
35183 Some features are flags. A stub which supports a flag feature
35184 should respond with a @samp{+} form response. Other features
35185 require values, and the stub should respond with an @samp{=}
35188 Each feature has a default value, which @value{GDBN} will use if
35189 @samp{qSupported} is not available or if the feature is not mentioned
35190 in the @samp{qSupported} response. The default values are fixed; a
35191 stub is free to omit any feature responses that match the defaults.
35193 Not all features can be probed, but for those which can, the probing
35194 mechanism is useful: in some cases, a stub's internal
35195 architecture may not allow the protocol layer to know some information
35196 about the underlying target in advance. This is especially common in
35197 stubs which may be configured for multiple targets.
35199 These are the currently defined stub features and their properties:
35201 @multitable @columnfractions 0.35 0.2 0.12 0.2
35202 @c NOTE: The first row should be @headitem, but we do not yet require
35203 @c a new enough version of Texinfo (4.7) to use @headitem.
35205 @tab Value Required
35209 @item @samp{PacketSize}
35214 @item @samp{qXfer:auxv:read}
35219 @item @samp{qXfer:features:read}
35224 @item @samp{qXfer:libraries:read}
35229 @item @samp{qXfer:memory-map:read}
35234 @item @samp{qXfer:sdata:read}
35239 @item @samp{qXfer:spu:read}
35244 @item @samp{qXfer:spu:write}
35249 @item @samp{qXfer:siginfo:read}
35254 @item @samp{qXfer:siginfo:write}
35259 @item @samp{qXfer:threads:read}
35264 @item @samp{qXfer:traceframe-info:read}
35269 @item @samp{qXfer:uib:read}
35274 @item @samp{qXfer:fdpic:read}
35279 @item @samp{QNonStop}
35284 @item @samp{QPassSignals}
35289 @item @samp{QStartNoAckMode}
35294 @item @samp{multiprocess}
35299 @item @samp{ConditionalBreakpoints}
35304 @item @samp{ConditionalTracepoints}
35309 @item @samp{ReverseContinue}
35314 @item @samp{ReverseStep}
35319 @item @samp{TracepointSource}
35324 @item @samp{QAgent}
35329 @item @samp{QAllow}
35334 @item @samp{QDisableRandomization}
35339 @item @samp{EnableDisableTracepoints}
35344 @item @samp{tracenz}
35351 These are the currently defined stub features, in more detail:
35354 @cindex packet size, remote protocol
35355 @item PacketSize=@var{bytes}
35356 The remote stub can accept packets up to at least @var{bytes} in
35357 length. @value{GDBN} will send packets up to this size for bulk
35358 transfers, and will never send larger packets. This is a limit on the
35359 data characters in the packet, including the frame and checksum.
35360 There is no trailing NUL byte in a remote protocol packet; if the stub
35361 stores packets in a NUL-terminated format, it should allow an extra
35362 byte in its buffer for the NUL. If this stub feature is not supported,
35363 @value{GDBN} guesses based on the size of the @samp{g} packet response.
35365 @item qXfer:auxv:read
35366 The remote stub understands the @samp{qXfer:auxv:read} packet
35367 (@pxref{qXfer auxiliary vector read}).
35369 @item qXfer:features:read
35370 The remote stub understands the @samp{qXfer:features:read} packet
35371 (@pxref{qXfer target description read}).
35373 @item qXfer:libraries:read
35374 The remote stub understands the @samp{qXfer:libraries:read} packet
35375 (@pxref{qXfer library list read}).
35377 @item qXfer:libraries-svr4:read
35378 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
35379 (@pxref{qXfer svr4 library list read}).
35381 @item qXfer:memory-map:read
35382 The remote stub understands the @samp{qXfer:memory-map:read} packet
35383 (@pxref{qXfer memory map read}).
35385 @item qXfer:sdata:read
35386 The remote stub understands the @samp{qXfer:sdata:read} packet
35387 (@pxref{qXfer sdata read}).
35389 @item qXfer:spu:read
35390 The remote stub understands the @samp{qXfer:spu:read} packet
35391 (@pxref{qXfer spu read}).
35393 @item qXfer:spu:write
35394 The remote stub understands the @samp{qXfer:spu:write} packet
35395 (@pxref{qXfer spu write}).
35397 @item qXfer:siginfo:read
35398 The remote stub understands the @samp{qXfer:siginfo:read} packet
35399 (@pxref{qXfer siginfo read}).
35401 @item qXfer:siginfo:write
35402 The remote stub understands the @samp{qXfer:siginfo:write} packet
35403 (@pxref{qXfer siginfo write}).
35405 @item qXfer:threads:read
35406 The remote stub understands the @samp{qXfer:threads:read} packet
35407 (@pxref{qXfer threads read}).
35409 @item qXfer:traceframe-info:read
35410 The remote stub understands the @samp{qXfer:traceframe-info:read}
35411 packet (@pxref{qXfer traceframe info read}).
35413 @item qXfer:uib:read
35414 The remote stub understands the @samp{qXfer:uib:read}
35415 packet (@pxref{qXfer unwind info block}).
35417 @item qXfer:fdpic:read
35418 The remote stub understands the @samp{qXfer:fdpic:read}
35419 packet (@pxref{qXfer fdpic loadmap read}).
35422 The remote stub understands the @samp{QNonStop} packet
35423 (@pxref{QNonStop}).
35426 The remote stub understands the @samp{QPassSignals} packet
35427 (@pxref{QPassSignals}).
35429 @item QStartNoAckMode
35430 The remote stub understands the @samp{QStartNoAckMode} packet and
35431 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
35434 @anchor{multiprocess extensions}
35435 @cindex multiprocess extensions, in remote protocol
35436 The remote stub understands the multiprocess extensions to the remote
35437 protocol syntax. The multiprocess extensions affect the syntax of
35438 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
35439 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
35440 replies. Note that reporting this feature indicates support for the
35441 syntactic extensions only, not that the stub necessarily supports
35442 debugging of more than one process at a time. The stub must not use
35443 multiprocess extensions in packet replies unless @value{GDBN} has also
35444 indicated it supports them in its @samp{qSupported} request.
35446 @item qXfer:osdata:read
35447 The remote stub understands the @samp{qXfer:osdata:read} packet
35448 ((@pxref{qXfer osdata read}).
35450 @item ConditionalBreakpoints
35451 The target accepts and implements evaluation of conditional expressions
35452 defined for breakpoints. The target will only report breakpoint triggers
35453 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
35455 @item ConditionalTracepoints
35456 The remote stub accepts and implements conditional expressions defined
35457 for tracepoints (@pxref{Tracepoint Conditions}).
35459 @item ReverseContinue
35460 The remote stub accepts and implements the reverse continue packet
35464 The remote stub accepts and implements the reverse step packet
35467 @item TracepointSource
35468 The remote stub understands the @samp{QTDPsrc} packet that supplies
35469 the source form of tracepoint definitions.
35472 The remote stub understands the @samp{QAgent} packet.
35475 The remote stub understands the @samp{QAllow} packet.
35477 @item QDisableRandomization
35478 The remote stub understands the @samp{QDisableRandomization} packet.
35480 @item StaticTracepoint
35481 @cindex static tracepoints, in remote protocol
35482 The remote stub supports static tracepoints.
35484 @item InstallInTrace
35485 @anchor{install tracepoint in tracing}
35486 The remote stub supports installing tracepoint in tracing.
35488 @item EnableDisableTracepoints
35489 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
35490 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
35491 to be enabled and disabled while a trace experiment is running.
35494 @cindex string tracing, in remote protocol
35495 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
35496 See @ref{Bytecode Descriptions} for details about the bytecode.
35501 @cindex symbol lookup, remote request
35502 @cindex @samp{qSymbol} packet
35503 Notify the target that @value{GDBN} is prepared to serve symbol lookup
35504 requests. Accept requests from the target for the values of symbols.
35509 The target does not need to look up any (more) symbols.
35510 @item qSymbol:@var{sym_name}
35511 The target requests the value of symbol @var{sym_name} (hex encoded).
35512 @value{GDBN} may provide the value by using the
35513 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
35517 @item qSymbol:@var{sym_value}:@var{sym_name}
35518 Set the value of @var{sym_name} to @var{sym_value}.
35520 @var{sym_name} (hex encoded) is the name of a symbol whose value the
35521 target has previously requested.
35523 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
35524 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
35530 The target does not need to look up any (more) symbols.
35531 @item qSymbol:@var{sym_name}
35532 The target requests the value of a new symbol @var{sym_name} (hex
35533 encoded). @value{GDBN} will continue to supply the values of symbols
35534 (if available), until the target ceases to request them.
35539 @item QTDisconnected
35546 @itemx qTMinFTPILen
35548 @xref{Tracepoint Packets}.
35550 @item qThreadExtraInfo,@var{thread-id}
35551 @cindex thread attributes info, remote request
35552 @cindex @samp{qThreadExtraInfo} packet
35553 Obtain a printable string description of a thread's attributes from
35554 the target OS. @var{thread-id} is a thread ID;
35555 see @ref{thread-id syntax}. This
35556 string may contain anything that the target OS thinks is interesting
35557 for @value{GDBN} to tell the user about the thread. The string is
35558 displayed in @value{GDBN}'s @code{info threads} display. Some
35559 examples of possible thread extra info strings are @samp{Runnable}, or
35560 @samp{Blocked on Mutex}.
35564 @item @var{XX}@dots{}
35565 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
35566 comprising the printable string containing the extra information about
35567 the thread's attributes.
35570 (Note that the @code{qThreadExtraInfo} packet's name is separated from
35571 the command by a @samp{,}, not a @samp{:}, contrary to the naming
35572 conventions above. Please don't use this packet as a model for new
35591 @xref{Tracepoint Packets}.
35593 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
35594 @cindex read special object, remote request
35595 @cindex @samp{qXfer} packet
35596 @anchor{qXfer read}
35597 Read uninterpreted bytes from the target's special data area
35598 identified by the keyword @var{object}. Request @var{length} bytes
35599 starting at @var{offset} bytes into the data. The content and
35600 encoding of @var{annex} is specific to @var{object}; it can supply
35601 additional details about what data to access.
35603 Here are the specific requests of this form defined so far. All
35604 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
35605 formats, listed below.
35608 @item qXfer:auxv:read::@var{offset},@var{length}
35609 @anchor{qXfer auxiliary vector read}
35610 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
35611 auxiliary vector}. Note @var{annex} must be empty.
35613 This packet is not probed by default; the remote stub must request it,
35614 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35616 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
35617 @anchor{qXfer target description read}
35618 Access the @dfn{target description}. @xref{Target Descriptions}. The
35619 annex specifies which XML document to access. The main description is
35620 always loaded from the @samp{target.xml} annex.
35622 This packet is not probed by default; the remote stub must request it,
35623 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35625 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
35626 @anchor{qXfer library list read}
35627 Access the target's list of loaded libraries. @xref{Library List Format}.
35628 The annex part of the generic @samp{qXfer} packet must be empty
35629 (@pxref{qXfer read}).
35631 Targets which maintain a list of libraries in the program's memory do
35632 not need to implement this packet; it is designed for platforms where
35633 the operating system manages the list of loaded libraries.
35635 This packet is not probed by default; the remote stub must request it,
35636 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35638 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
35639 @anchor{qXfer svr4 library list read}
35640 Access the target's list of loaded libraries when the target is an SVR4
35641 platform. @xref{Library List Format for SVR4 Targets}. The annex part
35642 of the generic @samp{qXfer} packet must be empty (@pxref{qXfer read}).
35644 This packet is optional for better performance on SVR4 targets.
35645 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
35647 This packet is not probed by default; the remote stub must request it,
35648 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35650 @item qXfer:memory-map:read::@var{offset},@var{length}
35651 @anchor{qXfer memory map read}
35652 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
35653 annex part of the generic @samp{qXfer} packet must be empty
35654 (@pxref{qXfer read}).
35656 This packet is not probed by default; the remote stub must request it,
35657 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35659 @item qXfer:sdata:read::@var{offset},@var{length}
35660 @anchor{qXfer sdata read}
35662 Read contents of the extra collected static tracepoint marker
35663 information. The annex part of the generic @samp{qXfer} packet must
35664 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
35667 This packet is not probed by default; the remote stub must request it,
35668 by supplying an appropriate @samp{qSupported} response
35669 (@pxref{qSupported}).
35671 @item qXfer:siginfo:read::@var{offset},@var{length}
35672 @anchor{qXfer siginfo read}
35673 Read contents of the extra signal information on the target
35674 system. The annex part of the generic @samp{qXfer} packet must be
35675 empty (@pxref{qXfer read}).
35677 This packet is not probed by default; the remote stub must request it,
35678 by supplying an appropriate @samp{qSupported} response
35679 (@pxref{qSupported}).
35681 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
35682 @anchor{qXfer spu read}
35683 Read contents of an @code{spufs} file on the target system. The
35684 annex specifies which file to read; it must be of the form
35685 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
35686 in the target process, and @var{name} identifes the @code{spufs} file
35687 in that context to be accessed.
35689 This packet is not probed by default; the remote stub must request it,
35690 by supplying an appropriate @samp{qSupported} response
35691 (@pxref{qSupported}).
35693 @item qXfer:threads:read::@var{offset},@var{length}
35694 @anchor{qXfer threads read}
35695 Access the list of threads on target. @xref{Thread List Format}. The
35696 annex part of the generic @samp{qXfer} packet must be empty
35697 (@pxref{qXfer read}).
35699 This packet is not probed by default; the remote stub must request it,
35700 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35702 @item qXfer:traceframe-info:read::@var{offset},@var{length}
35703 @anchor{qXfer traceframe info read}
35705 Return a description of the current traceframe's contents.
35706 @xref{Traceframe Info Format}. The annex part of the generic
35707 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
35709 This packet is not probed by default; the remote stub must request it,
35710 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35712 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
35713 @anchor{qXfer unwind info block}
35715 Return the unwind information block for @var{pc}. This packet is used
35716 on OpenVMS/ia64 to ask the kernel unwind information.
35718 This packet is not probed by default.
35720 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
35721 @anchor{qXfer fdpic loadmap read}
35722 Read contents of @code{loadmap}s on the target system. The
35723 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
35724 executable @code{loadmap} or interpreter @code{loadmap} to read.
35726 This packet is not probed by default; the remote stub must request it,
35727 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35729 @item qXfer:osdata:read::@var{offset},@var{length}
35730 @anchor{qXfer osdata read}
35731 Access the target's @dfn{operating system information}.
35732 @xref{Operating System Information}.
35739 Data @var{data} (@pxref{Binary Data}) has been read from the
35740 target. There may be more data at a higher address (although
35741 it is permitted to return @samp{m} even for the last valid
35742 block of data, as long as at least one byte of data was read).
35743 @var{data} may have fewer bytes than the @var{length} in the
35747 Data @var{data} (@pxref{Binary Data}) has been read from the target.
35748 There is no more data to be read. @var{data} may have fewer bytes
35749 than the @var{length} in the request.
35752 The @var{offset} in the request is at the end of the data.
35753 There is no more data to be read.
35756 The request was malformed, or @var{annex} was invalid.
35759 The offset was invalid, or there was an error encountered reading the data.
35760 @var{nn} is a hex-encoded @code{errno} value.
35763 An empty reply indicates the @var{object} string was not recognized by
35764 the stub, or that the object does not support reading.
35767 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
35768 @cindex write data into object, remote request
35769 @anchor{qXfer write}
35770 Write uninterpreted bytes into the target's special data area
35771 identified by the keyword @var{object}, starting at @var{offset} bytes
35772 into the data. @var{data}@dots{} is the binary-encoded data
35773 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
35774 is specific to @var{object}; it can supply additional details about what data
35777 Here are the specific requests of this form defined so far. All
35778 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
35779 formats, listed below.
35782 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
35783 @anchor{qXfer siginfo write}
35784 Write @var{data} to the extra signal information on the target system.
35785 The annex part of the generic @samp{qXfer} packet must be
35786 empty (@pxref{qXfer write}).
35788 This packet is not probed by default; the remote stub must request it,
35789 by supplying an appropriate @samp{qSupported} response
35790 (@pxref{qSupported}).
35792 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
35793 @anchor{qXfer spu write}
35794 Write @var{data} to an @code{spufs} file on the target system. The
35795 annex specifies which file to write; it must be of the form
35796 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
35797 in the target process, and @var{name} identifes the @code{spufs} file
35798 in that context to be accessed.
35800 This packet is not probed by default; the remote stub must request it,
35801 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
35807 @var{nn} (hex encoded) is the number of bytes written.
35808 This may be fewer bytes than supplied in the request.
35811 The request was malformed, or @var{annex} was invalid.
35814 The offset was invalid, or there was an error encountered writing the data.
35815 @var{nn} is a hex-encoded @code{errno} value.
35818 An empty reply indicates the @var{object} string was not
35819 recognized by the stub, or that the object does not support writing.
35822 @item qXfer:@var{object}:@var{operation}:@dots{}
35823 Requests of this form may be added in the future. When a stub does
35824 not recognize the @var{object} keyword, or its support for
35825 @var{object} does not recognize the @var{operation} keyword, the stub
35826 must respond with an empty packet.
35828 @item qAttached:@var{pid}
35829 @cindex query attached, remote request
35830 @cindex @samp{qAttached} packet
35831 Return an indication of whether the remote server attached to an
35832 existing process or created a new process. When the multiprocess
35833 protocol extensions are supported (@pxref{multiprocess extensions}),
35834 @var{pid} is an integer in hexadecimal format identifying the target
35835 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
35836 the query packet will be simplified as @samp{qAttached}.
35838 This query is used, for example, to know whether the remote process
35839 should be detached or killed when a @value{GDBN} session is ended with
35840 the @code{quit} command.
35845 The remote server attached to an existing process.
35847 The remote server created a new process.
35849 A badly formed request or an error was encountered.
35854 @node Architecture-Specific Protocol Details
35855 @section Architecture-Specific Protocol Details
35857 This section describes how the remote protocol is applied to specific
35858 target architectures. Also see @ref{Standard Target Features}, for
35859 details of XML target descriptions for each architecture.
35863 @subsubsection Breakpoint Kinds
35865 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
35870 16-bit Thumb mode breakpoint.
35873 32-bit Thumb mode (Thumb-2) breakpoint.
35876 32-bit ARM mode breakpoint.
35882 @subsubsection Register Packet Format
35884 The following @code{g}/@code{G} packets have previously been defined.
35885 In the below, some thirty-two bit registers are transferred as
35886 sixty-four bits. Those registers should be zero/sign extended (which?)
35887 to fill the space allocated. Register bytes are transferred in target
35888 byte order. The two nibbles within a register byte are transferred
35889 most-significant - least-significant.
35895 All registers are transferred as thirty-two bit quantities in the order:
35896 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
35897 registers; fsr; fir; fp.
35901 All registers are transferred as sixty-four bit quantities (including
35902 thirty-two bit registers such as @code{sr}). The ordering is the same
35907 @node Tracepoint Packets
35908 @section Tracepoint Packets
35909 @cindex tracepoint packets
35910 @cindex packets, tracepoint
35912 Here we describe the packets @value{GDBN} uses to implement
35913 tracepoints (@pxref{Tracepoints}).
35917 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
35918 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
35919 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
35920 the tracepoint is disabled. @var{step} is the tracepoint's step
35921 count, and @var{pass} is its pass count. If an @samp{F} is present,
35922 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
35923 the number of bytes that the target should copy elsewhere to make room
35924 for the tracepoint. If an @samp{X} is present, it introduces a
35925 tracepoint condition, which consists of a hexadecimal length, followed
35926 by a comma and hex-encoded bytes, in a manner similar to action
35927 encodings as described below. If the trailing @samp{-} is present,
35928 further @samp{QTDP} packets will follow to specify this tracepoint's
35934 The packet was understood and carried out.
35936 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
35938 The packet was not recognized.
35941 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
35942 Define actions to be taken when a tracepoint is hit. @var{n} and
35943 @var{addr} must be the same as in the initial @samp{QTDP} packet for
35944 this tracepoint. This packet may only be sent immediately after
35945 another @samp{QTDP} packet that ended with a @samp{-}. If the
35946 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
35947 specifying more actions for this tracepoint.
35949 In the series of action packets for a given tracepoint, at most one
35950 can have an @samp{S} before its first @var{action}. If such a packet
35951 is sent, it and the following packets define ``while-stepping''
35952 actions. Any prior packets define ordinary actions --- that is, those
35953 taken when the tracepoint is first hit. If no action packet has an
35954 @samp{S}, then all the packets in the series specify ordinary
35955 tracepoint actions.
35957 The @samp{@var{action}@dots{}} portion of the packet is a series of
35958 actions, concatenated without separators. Each action has one of the
35964 Collect the registers whose bits are set in @var{mask}. @var{mask} is
35965 a hexadecimal number whose @var{i}'th bit is set if register number
35966 @var{i} should be collected. (The least significant bit is numbered
35967 zero.) Note that @var{mask} may be any number of digits long; it may
35968 not fit in a 32-bit word.
35970 @item M @var{basereg},@var{offset},@var{len}
35971 Collect @var{len} bytes of memory starting at the address in register
35972 number @var{basereg}, plus @var{offset}. If @var{basereg} is
35973 @samp{-1}, then the range has a fixed address: @var{offset} is the
35974 address of the lowest byte to collect. The @var{basereg},
35975 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
35976 values (the @samp{-1} value for @var{basereg} is a special case).
35978 @item X @var{len},@var{expr}
35979 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
35980 it directs. @var{expr} is an agent expression, as described in
35981 @ref{Agent Expressions}. Each byte of the expression is encoded as a
35982 two-digit hex number in the packet; @var{len} is the number of bytes
35983 in the expression (and thus one-half the number of hex digits in the
35988 Any number of actions may be packed together in a single @samp{QTDP}
35989 packet, as long as the packet does not exceed the maximum packet
35990 length (400 bytes, for many stubs). There may be only one @samp{R}
35991 action per tracepoint, and it must precede any @samp{M} or @samp{X}
35992 actions. Any registers referred to by @samp{M} and @samp{X} actions
35993 must be collected by a preceding @samp{R} action. (The
35994 ``while-stepping'' actions are treated as if they were attached to a
35995 separate tracepoint, as far as these restrictions are concerned.)
36000 The packet was understood and carried out.
36002 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
36004 The packet was not recognized.
36007 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
36008 @cindex @samp{QTDPsrc} packet
36009 Specify a source string of tracepoint @var{n} at address @var{addr}.
36010 This is useful to get accurate reproduction of the tracepoints
36011 originally downloaded at the beginning of the trace run. @var{type}
36012 is the name of the tracepoint part, such as @samp{cond} for the
36013 tracepoint's conditional expression (see below for a list of types), while
36014 @var{bytes} is the string, encoded in hexadecimal.
36016 @var{start} is the offset of the @var{bytes} within the overall source
36017 string, while @var{slen} is the total length of the source string.
36018 This is intended for handling source strings that are longer than will
36019 fit in a single packet.
36020 @c Add detailed example when this info is moved into a dedicated
36021 @c tracepoint descriptions section.
36023 The available string types are @samp{at} for the location,
36024 @samp{cond} for the conditional, and @samp{cmd} for an action command.
36025 @value{GDBN} sends a separate packet for each command in the action
36026 list, in the same order in which the commands are stored in the list.
36028 The target does not need to do anything with source strings except
36029 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
36032 Although this packet is optional, and @value{GDBN} will only send it
36033 if the target replies with @samp{TracepointSource} @xref{General
36034 Query Packets}, it makes both disconnected tracing and trace files
36035 much easier to use. Otherwise the user must be careful that the
36036 tracepoints in effect while looking at trace frames are identical to
36037 the ones in effect during the trace run; even a small discrepancy
36038 could cause @samp{tdump} not to work, or a particular trace frame not
36041 @item QTDV:@var{n}:@var{value}
36042 @cindex define trace state variable, remote request
36043 @cindex @samp{QTDV} packet
36044 Create a new trace state variable, number @var{n}, with an initial
36045 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
36046 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
36047 the option of not using this packet for initial values of zero; the
36048 target should simply create the trace state variables as they are
36049 mentioned in expressions.
36051 @item QTFrame:@var{n}
36052 Select the @var{n}'th tracepoint frame from the buffer, and use the
36053 register and memory contents recorded there to answer subsequent
36054 request packets from @value{GDBN}.
36056 A successful reply from the stub indicates that the stub has found the
36057 requested frame. The response is a series of parts, concatenated
36058 without separators, describing the frame we selected. Each part has
36059 one of the following forms:
36063 The selected frame is number @var{n} in the trace frame buffer;
36064 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
36065 was no frame matching the criteria in the request packet.
36068 The selected trace frame records a hit of tracepoint number @var{t};
36069 @var{t} is a hexadecimal number.
36073 @item QTFrame:pc:@var{addr}
36074 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36075 currently selected frame whose PC is @var{addr};
36076 @var{addr} is a hexadecimal number.
36078 @item QTFrame:tdp:@var{t}
36079 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36080 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
36081 is a hexadecimal number.
36083 @item QTFrame:range:@var{start}:@var{end}
36084 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
36085 currently selected frame whose PC is between @var{start} (inclusive)
36086 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
36089 @item QTFrame:outside:@var{start}:@var{end}
36090 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
36091 frame @emph{outside} the given range of addresses (exclusive).
36094 This packet requests the minimum length of instruction at which a fast
36095 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
36096 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
36097 it depends on the target system being able to create trampolines in
36098 the first 64K of memory, which might or might not be possible for that
36099 system. So the reply to this packet will be 4 if it is able to
36106 The minimum instruction length is currently unknown.
36108 The minimum instruction length is @var{length}, where @var{length} is greater
36109 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
36110 that a fast tracepoint may be placed on any instruction regardless of size.
36112 An error has occurred.
36114 An empty reply indicates that the request is not supported by the stub.
36118 Begin the tracepoint experiment. Begin collecting data from
36119 tracepoint hits in the trace frame buffer. This packet supports the
36120 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
36121 instruction reply packet}).
36124 End the tracepoint experiment. Stop collecting trace frames.
36126 @item QTEnable:@var{n}:@var{addr}
36128 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
36129 experiment. If the tracepoint was previously disabled, then collection
36130 of data from it will resume.
36132 @item QTDisable:@var{n}:@var{addr}
36134 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
36135 experiment. No more data will be collected from the tracepoint unless
36136 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
36139 Clear the table of tracepoints, and empty the trace frame buffer.
36141 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
36142 Establish the given ranges of memory as ``transparent''. The stub
36143 will answer requests for these ranges from memory's current contents,
36144 if they were not collected as part of the tracepoint hit.
36146 @value{GDBN} uses this to mark read-only regions of memory, like those
36147 containing program code. Since these areas never change, they should
36148 still have the same contents they did when the tracepoint was hit, so
36149 there's no reason for the stub to refuse to provide their contents.
36151 @item QTDisconnected:@var{value}
36152 Set the choice to what to do with the tracing run when @value{GDBN}
36153 disconnects from the target. A @var{value} of 1 directs the target to
36154 continue the tracing run, while 0 tells the target to stop tracing if
36155 @value{GDBN} is no longer in the picture.
36158 Ask the stub if there is a trace experiment running right now.
36160 The reply has the form:
36164 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
36165 @var{running} is a single digit @code{1} if the trace is presently
36166 running, or @code{0} if not. It is followed by semicolon-separated
36167 optional fields that an agent may use to report additional status.
36171 If the trace is not running, the agent may report any of several
36172 explanations as one of the optional fields:
36177 No trace has been run yet.
36179 @item tstop[:@var{text}]:0
36180 The trace was stopped by a user-originated stop command. The optional
36181 @var{text} field is a user-supplied string supplied as part of the
36182 stop command (for instance, an explanation of why the trace was
36183 stopped manually). It is hex-encoded.
36186 The trace stopped because the trace buffer filled up.
36188 @item tdisconnected:0
36189 The trace stopped because @value{GDBN} disconnected from the target.
36191 @item tpasscount:@var{tpnum}
36192 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
36194 @item terror:@var{text}:@var{tpnum}
36195 The trace stopped because tracepoint @var{tpnum} had an error. The
36196 string @var{text} is available to describe the nature of the error
36197 (for instance, a divide by zero in the condition expression).
36198 @var{text} is hex encoded.
36201 The trace stopped for some other reason.
36205 Additional optional fields supply statistical and other information.
36206 Although not required, they are extremely useful for users monitoring
36207 the progress of a trace run. If a trace has stopped, and these
36208 numbers are reported, they must reflect the state of the just-stopped
36213 @item tframes:@var{n}
36214 The number of trace frames in the buffer.
36216 @item tcreated:@var{n}
36217 The total number of trace frames created during the run. This may
36218 be larger than the trace frame count, if the buffer is circular.
36220 @item tsize:@var{n}
36221 The total size of the trace buffer, in bytes.
36223 @item tfree:@var{n}
36224 The number of bytes still unused in the buffer.
36226 @item circular:@var{n}
36227 The value of the circular trace buffer flag. @code{1} means that the
36228 trace buffer is circular and old trace frames will be discarded if
36229 necessary to make room, @code{0} means that the trace buffer is linear
36232 @item disconn:@var{n}
36233 The value of the disconnected tracing flag. @code{1} means that
36234 tracing will continue after @value{GDBN} disconnects, @code{0} means
36235 that the trace run will stop.
36239 @item qTP:@var{tp}:@var{addr}
36240 @cindex tracepoint status, remote request
36241 @cindex @samp{qTP} packet
36242 Ask the stub for the current state of tracepoint number @var{tp} at
36243 address @var{addr}.
36247 @item V@var{hits}:@var{usage}
36248 The tracepoint has been hit @var{hits} times so far during the trace
36249 run, and accounts for @var{usage} in the trace buffer. Note that
36250 @code{while-stepping} steps are not counted as separate hits, but the
36251 steps' space consumption is added into the usage number.
36255 @item qTV:@var{var}
36256 @cindex trace state variable value, remote request
36257 @cindex @samp{qTV} packet
36258 Ask the stub for the value of the trace state variable number @var{var}.
36263 The value of the variable is @var{value}. This will be the current
36264 value of the variable if the user is examining a running target, or a
36265 saved value if the variable was collected in the trace frame that the
36266 user is looking at. Note that multiple requests may result in
36267 different reply values, such as when requesting values while the
36268 program is running.
36271 The value of the variable is unknown. This would occur, for example,
36272 if the user is examining a trace frame in which the requested variable
36278 These packets request data about tracepoints that are being used by
36279 the target. @value{GDBN} sends @code{qTfP} to get the first piece
36280 of data, and multiple @code{qTsP} to get additional pieces. Replies
36281 to these packets generally take the form of the @code{QTDP} packets
36282 that define tracepoints. (FIXME add detailed syntax)
36286 These packets request data about trace state variables that are on the
36287 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
36288 and multiple @code{qTsV} to get additional variables. Replies to
36289 these packets follow the syntax of the @code{QTDV} packets that define
36290 trace state variables.
36294 These packets request data about static tracepoint markers that exist
36295 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
36296 first piece of data, and multiple @code{qTsSTM} to get additional
36297 pieces. Replies to these packets take the following form:
36301 @item m @var{address}:@var{id}:@var{extra}
36303 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
36304 a comma-separated list of markers
36306 (lower case letter @samp{L}) denotes end of list.
36308 An error occurred. @var{nn} are hex digits.
36310 An empty reply indicates that the request is not supported by the
36314 @var{address} is encoded in hex.
36315 @var{id} and @var{extra} are strings encoded in hex.
36317 In response to each query, the target will reply with a list of one or
36318 more markers, separated by commas. @value{GDBN} will respond to each
36319 reply with a request for more markers (using the @samp{qs} form of the
36320 query), until the target responds with @samp{l} (lower-case ell, for
36323 @item qTSTMat:@var{address}
36324 This packets requests data about static tracepoint markers in the
36325 target program at @var{address}. Replies to this packet follow the
36326 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
36327 tracepoint markers.
36329 @item QTSave:@var{filename}
36330 This packet directs the target to save trace data to the file name
36331 @var{filename} in the target's filesystem. @var{filename} is encoded
36332 as a hex string; the interpretation of the file name (relative vs
36333 absolute, wild cards, etc) is up to the target.
36335 @item qTBuffer:@var{offset},@var{len}
36336 Return up to @var{len} bytes of the current contents of trace buffer,
36337 starting at @var{offset}. The trace buffer is treated as if it were
36338 a contiguous collection of traceframes, as per the trace file format.
36339 The reply consists as many hex-encoded bytes as the target can deliver
36340 in a packet; it is not an error to return fewer than were asked for.
36341 A reply consisting of just @code{l} indicates that no bytes are
36344 @item QTBuffer:circular:@var{value}
36345 This packet directs the target to use a circular trace buffer if
36346 @var{value} is 1, or a linear buffer if the value is 0.
36348 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
36349 This packet adds optional textual notes to the trace run. Allowable
36350 types include @code{user}, @code{notes}, and @code{tstop}, the
36351 @var{text} fields are arbitrary strings, hex-encoded.
36355 @subsection Relocate instruction reply packet
36356 When installing fast tracepoints in memory, the target may need to
36357 relocate the instruction currently at the tracepoint address to a
36358 different address in memory. For most instructions, a simple copy is
36359 enough, but, for example, call instructions that implicitly push the
36360 return address on the stack, and relative branches or other
36361 PC-relative instructions require offset adjustment, so that the effect
36362 of executing the instruction at a different address is the same as if
36363 it had executed in the original location.
36365 In response to several of the tracepoint packets, the target may also
36366 respond with a number of intermediate @samp{qRelocInsn} request
36367 packets before the final result packet, to have @value{GDBN} handle
36368 this relocation operation. If a packet supports this mechanism, its
36369 documentation will explicitly say so. See for example the above
36370 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
36371 format of the request is:
36374 @item qRelocInsn:@var{from};@var{to}
36376 This requests @value{GDBN} to copy instruction at address @var{from}
36377 to address @var{to}, possibly adjusted so that executing the
36378 instruction at @var{to} has the same effect as executing it at
36379 @var{from}. @value{GDBN} writes the adjusted instruction to target
36380 memory starting at @var{to}.
36385 @item qRelocInsn:@var{adjusted_size}
36386 Informs the stub the relocation is complete. @var{adjusted_size} is
36387 the length in bytes of resulting relocated instruction sequence.
36389 A badly formed request was detected, or an error was encountered while
36390 relocating the instruction.
36393 @node Host I/O Packets
36394 @section Host I/O Packets
36395 @cindex Host I/O, remote protocol
36396 @cindex file transfer, remote protocol
36398 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
36399 operations on the far side of a remote link. For example, Host I/O is
36400 used to upload and download files to a remote target with its own
36401 filesystem. Host I/O uses the same constant values and data structure
36402 layout as the target-initiated File-I/O protocol. However, the
36403 Host I/O packets are structured differently. The target-initiated
36404 protocol relies on target memory to store parameters and buffers.
36405 Host I/O requests are initiated by @value{GDBN}, and the
36406 target's memory is not involved. @xref{File-I/O Remote Protocol
36407 Extension}, for more details on the target-initiated protocol.
36409 The Host I/O request packets all encode a single operation along with
36410 its arguments. They have this format:
36414 @item vFile:@var{operation}: @var{parameter}@dots{}
36415 @var{operation} is the name of the particular request; the target
36416 should compare the entire packet name up to the second colon when checking
36417 for a supported operation. The format of @var{parameter} depends on
36418 the operation. Numbers are always passed in hexadecimal. Negative
36419 numbers have an explicit minus sign (i.e.@: two's complement is not
36420 used). Strings (e.g.@: filenames) are encoded as a series of
36421 hexadecimal bytes. The last argument to a system call may be a
36422 buffer of escaped binary data (@pxref{Binary Data}).
36426 The valid responses to Host I/O packets are:
36430 @item F @var{result} [, @var{errno}] [; @var{attachment}]
36431 @var{result} is the integer value returned by this operation, usually
36432 non-negative for success and -1 for errors. If an error has occured,
36433 @var{errno} will be included in the result. @var{errno} will have a
36434 value defined by the File-I/O protocol (@pxref{Errno Values}). For
36435 operations which return data, @var{attachment} supplies the data as a
36436 binary buffer. Binary buffers in response packets are escaped in the
36437 normal way (@pxref{Binary Data}). See the individual packet
36438 documentation for the interpretation of @var{result} and
36442 An empty response indicates that this operation is not recognized.
36446 These are the supported Host I/O operations:
36449 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
36450 Open a file at @var{pathname} and return a file descriptor for it, or
36451 return -1 if an error occurs. @var{pathname} is a string,
36452 @var{flags} is an integer indicating a mask of open flags
36453 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
36454 of mode bits to use if the file is created (@pxref{mode_t Values}).
36455 @xref{open}, for details of the open flags and mode values.
36457 @item vFile:close: @var{fd}
36458 Close the open file corresponding to @var{fd} and return 0, or
36459 -1 if an error occurs.
36461 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
36462 Read data from the open file corresponding to @var{fd}. Up to
36463 @var{count} bytes will be read from the file, starting at @var{offset}
36464 relative to the start of the file. The target may read fewer bytes;
36465 common reasons include packet size limits and an end-of-file
36466 condition. The number of bytes read is returned. Zero should only be
36467 returned for a successful read at the end of the file, or if
36468 @var{count} was zero.
36470 The data read should be returned as a binary attachment on success.
36471 If zero bytes were read, the response should include an empty binary
36472 attachment (i.e.@: a trailing semicolon). The return value is the
36473 number of target bytes read; the binary attachment may be longer if
36474 some characters were escaped.
36476 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
36477 Write @var{data} (a binary buffer) to the open file corresponding
36478 to @var{fd}. Start the write at @var{offset} from the start of the
36479 file. Unlike many @code{write} system calls, there is no
36480 separate @var{count} argument; the length of @var{data} in the
36481 packet is used. @samp{vFile:write} returns the number of bytes written,
36482 which may be shorter than the length of @var{data}, or -1 if an
36485 @item vFile:unlink: @var{pathname}
36486 Delete the file at @var{pathname} on the target. Return 0,
36487 or -1 if an error occurs. @var{pathname} is a string.
36489 @item vFile:readlink: @var{filename}
36490 Read value of symbolic link @var{filename} on the target. Return
36491 the number of bytes read, or -1 if an error occurs.
36493 The data read should be returned as a binary attachment on success.
36494 If zero bytes were read, the response should include an empty binary
36495 attachment (i.e.@: a trailing semicolon). The return value is the
36496 number of target bytes read; the binary attachment may be longer if
36497 some characters were escaped.
36502 @section Interrupts
36503 @cindex interrupts (remote protocol)
36505 When a program on the remote target is running, @value{GDBN} may
36506 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
36507 a @code{BREAK} followed by @code{g},
36508 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
36510 The precise meaning of @code{BREAK} is defined by the transport
36511 mechanism and may, in fact, be undefined. @value{GDBN} does not
36512 currently define a @code{BREAK} mechanism for any of the network
36513 interfaces except for TCP, in which case @value{GDBN} sends the
36514 @code{telnet} BREAK sequence.
36516 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
36517 transport mechanisms. It is represented by sending the single byte
36518 @code{0x03} without any of the usual packet overhead described in
36519 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
36520 transmitted as part of a packet, it is considered to be packet data
36521 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
36522 (@pxref{X packet}), used for binary downloads, may include an unescaped
36523 @code{0x03} as part of its packet.
36525 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
36526 When Linux kernel receives this sequence from serial port,
36527 it stops execution and connects to gdb.
36529 Stubs are not required to recognize these interrupt mechanisms and the
36530 precise meaning associated with receipt of the interrupt is
36531 implementation defined. If the target supports debugging of multiple
36532 threads and/or processes, it should attempt to interrupt all
36533 currently-executing threads and processes.
36534 If the stub is successful at interrupting the
36535 running program, it should send one of the stop
36536 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
36537 of successfully stopping the program in all-stop mode, and a stop reply
36538 for each stopped thread in non-stop mode.
36539 Interrupts received while the
36540 program is stopped are discarded.
36542 @node Notification Packets
36543 @section Notification Packets
36544 @cindex notification packets
36545 @cindex packets, notification
36547 The @value{GDBN} remote serial protocol includes @dfn{notifications},
36548 packets that require no acknowledgment. Both the GDB and the stub
36549 may send notifications (although the only notifications defined at
36550 present are sent by the stub). Notifications carry information
36551 without incurring the round-trip latency of an acknowledgment, and so
36552 are useful for low-impact communications where occasional packet loss
36555 A notification packet has the form @samp{% @var{data} #
36556 @var{checksum}}, where @var{data} is the content of the notification,
36557 and @var{checksum} is a checksum of @var{data}, computed and formatted
36558 as for ordinary @value{GDBN} packets. A notification's @var{data}
36559 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
36560 receiving a notification, the recipient sends no @samp{+} or @samp{-}
36561 to acknowledge the notification's receipt or to report its corruption.
36563 Every notification's @var{data} begins with a name, which contains no
36564 colon characters, followed by a colon character.
36566 Recipients should silently ignore corrupted notifications and
36567 notifications they do not understand. Recipients should restart
36568 timeout periods on receipt of a well-formed notification, whether or
36569 not they understand it.
36571 Senders should only send the notifications described here when this
36572 protocol description specifies that they are permitted. In the
36573 future, we may extend the protocol to permit existing notifications in
36574 new contexts; this rule helps older senders avoid confusing newer
36577 (Older versions of @value{GDBN} ignore bytes received until they see
36578 the @samp{$} byte that begins an ordinary packet, so new stubs may
36579 transmit notifications without fear of confusing older clients. There
36580 are no notifications defined for @value{GDBN} to send at the moment, but we
36581 assume that most older stubs would ignore them, as well.)
36583 The following notification packets from the stub to @value{GDBN} are
36587 @item Stop: @var{reply}
36588 Report an asynchronous stop event in non-stop mode.
36589 The @var{reply} has the form of a stop reply, as
36590 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
36591 for information on how these notifications are acknowledged by
36595 @node Remote Non-Stop
36596 @section Remote Protocol Support for Non-Stop Mode
36598 @value{GDBN}'s remote protocol supports non-stop debugging of
36599 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
36600 supports non-stop mode, it should report that to @value{GDBN} by including
36601 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
36603 @value{GDBN} typically sends a @samp{QNonStop} packet only when
36604 establishing a new connection with the stub. Entering non-stop mode
36605 does not alter the state of any currently-running threads, but targets
36606 must stop all threads in any already-attached processes when entering
36607 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
36608 probe the target state after a mode change.
36610 In non-stop mode, when an attached process encounters an event that
36611 would otherwise be reported with a stop reply, it uses the
36612 asynchronous notification mechanism (@pxref{Notification Packets}) to
36613 inform @value{GDBN}. In contrast to all-stop mode, where all threads
36614 in all processes are stopped when a stop reply is sent, in non-stop
36615 mode only the thread reporting the stop event is stopped. That is,
36616 when reporting a @samp{S} or @samp{T} response to indicate completion
36617 of a step operation, hitting a breakpoint, or a fault, only the
36618 affected thread is stopped; any other still-running threads continue
36619 to run. When reporting a @samp{W} or @samp{X} response, all running
36620 threads belonging to other attached processes continue to run.
36622 Only one stop reply notification at a time may be pending; if
36623 additional stop events occur before @value{GDBN} has acknowledged the
36624 previous notification, they must be queued by the stub for later
36625 synchronous transmission in response to @samp{vStopped} packets from
36626 @value{GDBN}. Because the notification mechanism is unreliable,
36627 the stub is permitted to resend a stop reply notification
36628 if it believes @value{GDBN} may not have received it. @value{GDBN}
36629 ignores additional stop reply notifications received before it has
36630 finished processing a previous notification and the stub has completed
36631 sending any queued stop events.
36633 Otherwise, @value{GDBN} must be prepared to receive a stop reply
36634 notification at any time. Specifically, they may appear when
36635 @value{GDBN} is not otherwise reading input from the stub, or when
36636 @value{GDBN} is expecting to read a normal synchronous response or a
36637 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
36638 Notification packets are distinct from any other communication from
36639 the stub so there is no ambiguity.
36641 After receiving a stop reply notification, @value{GDBN} shall
36642 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
36643 as a regular, synchronous request to the stub. Such acknowledgment
36644 is not required to happen immediately, as @value{GDBN} is permitted to
36645 send other, unrelated packets to the stub first, which the stub should
36648 Upon receiving a @samp{vStopped} packet, if the stub has other queued
36649 stop events to report to @value{GDBN}, it shall respond by sending a
36650 normal stop reply response. @value{GDBN} shall then send another
36651 @samp{vStopped} packet to solicit further responses; again, it is
36652 permitted to send other, unrelated packets as well which the stub
36653 should process normally.
36655 If the stub receives a @samp{vStopped} packet and there are no
36656 additional stop events to report, the stub shall return an @samp{OK}
36657 response. At this point, if further stop events occur, the stub shall
36658 send a new stop reply notification, @value{GDBN} shall accept the
36659 notification, and the process shall be repeated.
36661 In non-stop mode, the target shall respond to the @samp{?} packet as
36662 follows. First, any incomplete stop reply notification/@samp{vStopped}
36663 sequence in progress is abandoned. The target must begin a new
36664 sequence reporting stop events for all stopped threads, whether or not
36665 it has previously reported those events to @value{GDBN}. The first
36666 stop reply is sent as a synchronous reply to the @samp{?} packet, and
36667 subsequent stop replies are sent as responses to @samp{vStopped} packets
36668 using the mechanism described above. The target must not send
36669 asynchronous stop reply notifications until the sequence is complete.
36670 If all threads are running when the target receives the @samp{?} packet,
36671 or if the target is not attached to any process, it shall respond
36674 @node Packet Acknowledgment
36675 @section Packet Acknowledgment
36677 @cindex acknowledgment, for @value{GDBN} remote
36678 @cindex packet acknowledgment, for @value{GDBN} remote
36679 By default, when either the host or the target machine receives a packet,
36680 the first response expected is an acknowledgment: either @samp{+} (to indicate
36681 the package was received correctly) or @samp{-} (to request retransmission).
36682 This mechanism allows the @value{GDBN} remote protocol to operate over
36683 unreliable transport mechanisms, such as a serial line.
36685 In cases where the transport mechanism is itself reliable (such as a pipe or
36686 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
36687 It may be desirable to disable them in that case to reduce communication
36688 overhead, or for other reasons. This can be accomplished by means of the
36689 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
36691 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
36692 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
36693 and response format still includes the normal checksum, as described in
36694 @ref{Overview}, but the checksum may be ignored by the receiver.
36696 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
36697 no-acknowledgment mode, it should report that to @value{GDBN}
36698 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
36699 @pxref{qSupported}.
36700 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
36701 disabled via the @code{set remote noack-packet off} command
36702 (@pxref{Remote Configuration}),
36703 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
36704 Only then may the stub actually turn off packet acknowledgments.
36705 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
36706 response, which can be safely ignored by the stub.
36708 Note that @code{set remote noack-packet} command only affects negotiation
36709 between @value{GDBN} and the stub when subsequent connections are made;
36710 it does not affect the protocol acknowledgment state for any current
36712 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
36713 new connection is established,
36714 there is also no protocol request to re-enable the acknowledgments
36715 for the current connection, once disabled.
36720 Example sequence of a target being re-started. Notice how the restart
36721 does not get any direct output:
36726 @emph{target restarts}
36729 <- @code{T001:1234123412341234}
36733 Example sequence of a target being stepped by a single instruction:
36736 -> @code{G1445@dots{}}
36741 <- @code{T001:1234123412341234}
36745 <- @code{1455@dots{}}
36749 @node File-I/O Remote Protocol Extension
36750 @section File-I/O Remote Protocol Extension
36751 @cindex File-I/O remote protocol extension
36754 * File-I/O Overview::
36755 * Protocol Basics::
36756 * The F Request Packet::
36757 * The F Reply Packet::
36758 * The Ctrl-C Message::
36760 * List of Supported Calls::
36761 * Protocol-specific Representation of Datatypes::
36763 * File-I/O Examples::
36766 @node File-I/O Overview
36767 @subsection File-I/O Overview
36768 @cindex file-i/o overview
36770 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
36771 target to use the host's file system and console I/O to perform various
36772 system calls. System calls on the target system are translated into a
36773 remote protocol packet to the host system, which then performs the needed
36774 actions and returns a response packet to the target system.
36775 This simulates file system operations even on targets that lack file systems.
36777 The protocol is defined to be independent of both the host and target systems.
36778 It uses its own internal representation of datatypes and values. Both
36779 @value{GDBN} and the target's @value{GDBN} stub are responsible for
36780 translating the system-dependent value representations into the internal
36781 protocol representations when data is transmitted.
36783 The communication is synchronous. A system call is possible only when
36784 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
36785 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
36786 the target is stopped to allow deterministic access to the target's
36787 memory. Therefore File-I/O is not interruptible by target signals. On
36788 the other hand, it is possible to interrupt File-I/O by a user interrupt
36789 (@samp{Ctrl-C}) within @value{GDBN}.
36791 The target's request to perform a host system call does not finish
36792 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
36793 after finishing the system call, the target returns to continuing the
36794 previous activity (continue, step). No additional continue or step
36795 request from @value{GDBN} is required.
36798 (@value{GDBP}) continue
36799 <- target requests 'system call X'
36800 target is stopped, @value{GDBN} executes system call
36801 -> @value{GDBN} returns result
36802 ... target continues, @value{GDBN} returns to wait for the target
36803 <- target hits breakpoint and sends a Txx packet
36806 The protocol only supports I/O on the console and to regular files on
36807 the host file system. Character or block special devices, pipes,
36808 named pipes, sockets or any other communication method on the host
36809 system are not supported by this protocol.
36811 File I/O is not supported in non-stop mode.
36813 @node Protocol Basics
36814 @subsection Protocol Basics
36815 @cindex protocol basics, file-i/o
36817 The File-I/O protocol uses the @code{F} packet as the request as well
36818 as reply packet. Since a File-I/O system call can only occur when
36819 @value{GDBN} is waiting for a response from the continuing or stepping target,
36820 the File-I/O request is a reply that @value{GDBN} has to expect as a result
36821 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
36822 This @code{F} packet contains all information needed to allow @value{GDBN}
36823 to call the appropriate host system call:
36827 A unique identifier for the requested system call.
36830 All parameters to the system call. Pointers are given as addresses
36831 in the target memory address space. Pointers to strings are given as
36832 pointer/length pair. Numerical values are given as they are.
36833 Numerical control flags are given in a protocol-specific representation.
36837 At this point, @value{GDBN} has to perform the following actions.
36841 If the parameters include pointer values to data needed as input to a
36842 system call, @value{GDBN} requests this data from the target with a
36843 standard @code{m} packet request. This additional communication has to be
36844 expected by the target implementation and is handled as any other @code{m}
36848 @value{GDBN} translates all value from protocol representation to host
36849 representation as needed. Datatypes are coerced into the host types.
36852 @value{GDBN} calls the system call.
36855 It then coerces datatypes back to protocol representation.
36858 If the system call is expected to return data in buffer space specified
36859 by pointer parameters to the call, the data is transmitted to the
36860 target using a @code{M} or @code{X} packet. This packet has to be expected
36861 by the target implementation and is handled as any other @code{M} or @code{X}
36866 Eventually @value{GDBN} replies with another @code{F} packet which contains all
36867 necessary information for the target to continue. This at least contains
36874 @code{errno}, if has been changed by the system call.
36881 After having done the needed type and value coercion, the target continues
36882 the latest continue or step action.
36884 @node The F Request Packet
36885 @subsection The @code{F} Request Packet
36886 @cindex file-i/o request packet
36887 @cindex @code{F} request packet
36889 The @code{F} request packet has the following format:
36892 @item F@var{call-id},@var{parameter@dots{}}
36894 @var{call-id} is the identifier to indicate the host system call to be called.
36895 This is just the name of the function.
36897 @var{parameter@dots{}} are the parameters to the system call.
36898 Parameters are hexadecimal integer values, either the actual values in case
36899 of scalar datatypes, pointers to target buffer space in case of compound
36900 datatypes and unspecified memory areas, or pointer/length pairs in case
36901 of string parameters. These are appended to the @var{call-id} as a
36902 comma-delimited list. All values are transmitted in ASCII
36903 string representation, pointer/length pairs separated by a slash.
36909 @node The F Reply Packet
36910 @subsection The @code{F} Reply Packet
36911 @cindex file-i/o reply packet
36912 @cindex @code{F} reply packet
36914 The @code{F} reply packet has the following format:
36918 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
36920 @var{retcode} is the return code of the system call as hexadecimal value.
36922 @var{errno} is the @code{errno} set by the call, in protocol-specific
36924 This parameter can be omitted if the call was successful.
36926 @var{Ctrl-C flag} is only sent if the user requested a break. In this
36927 case, @var{errno} must be sent as well, even if the call was successful.
36928 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
36935 or, if the call was interrupted before the host call has been performed:
36942 assuming 4 is the protocol-specific representation of @code{EINTR}.
36947 @node The Ctrl-C Message
36948 @subsection The @samp{Ctrl-C} Message
36949 @cindex ctrl-c message, in file-i/o protocol
36951 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
36952 reply packet (@pxref{The F Reply Packet}),
36953 the target should behave as if it had
36954 gotten a break message. The meaning for the target is ``system call
36955 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
36956 (as with a break message) and return to @value{GDBN} with a @code{T02}
36959 It's important for the target to know in which
36960 state the system call was interrupted. There are two possible cases:
36964 The system call hasn't been performed on the host yet.
36967 The system call on the host has been finished.
36971 These two states can be distinguished by the target by the value of the
36972 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
36973 call hasn't been performed. This is equivalent to the @code{EINTR} handling
36974 on POSIX systems. In any other case, the target may presume that the
36975 system call has been finished --- successfully or not --- and should behave
36976 as if the break message arrived right after the system call.
36978 @value{GDBN} must behave reliably. If the system call has not been called
36979 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
36980 @code{errno} in the packet. If the system call on the host has been finished
36981 before the user requests a break, the full action must be finished by
36982 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
36983 The @code{F} packet may only be sent when either nothing has happened
36984 or the full action has been completed.
36987 @subsection Console I/O
36988 @cindex console i/o as part of file-i/o
36990 By default and if not explicitly closed by the target system, the file
36991 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
36992 on the @value{GDBN} console is handled as any other file output operation
36993 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
36994 by @value{GDBN} so that after the target read request from file descriptor
36995 0 all following typing is buffered until either one of the following
37000 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
37002 system call is treated as finished.
37005 The user presses @key{RET}. This is treated as end of input with a trailing
37009 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
37010 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
37014 If the user has typed more characters than fit in the buffer given to
37015 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
37016 either another @code{read(0, @dots{})} is requested by the target, or debugging
37017 is stopped at the user's request.
37020 @node List of Supported Calls
37021 @subsection List of Supported Calls
37022 @cindex list of supported file-i/o calls
37039 @unnumberedsubsubsec open
37040 @cindex open, file-i/o system call
37045 int open(const char *pathname, int flags);
37046 int open(const char *pathname, int flags, mode_t mode);
37050 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
37053 @var{flags} is the bitwise @code{OR} of the following values:
37057 If the file does not exist it will be created. The host
37058 rules apply as far as file ownership and time stamps
37062 When used with @code{O_CREAT}, if the file already exists it is
37063 an error and open() fails.
37066 If the file already exists and the open mode allows
37067 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
37068 truncated to zero length.
37071 The file is opened in append mode.
37074 The file is opened for reading only.
37077 The file is opened for writing only.
37080 The file is opened for reading and writing.
37084 Other bits are silently ignored.
37088 @var{mode} is the bitwise @code{OR} of the following values:
37092 User has read permission.
37095 User has write permission.
37098 Group has read permission.
37101 Group has write permission.
37104 Others have read permission.
37107 Others have write permission.
37111 Other bits are silently ignored.
37114 @item Return value:
37115 @code{open} returns the new file descriptor or -1 if an error
37122 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
37125 @var{pathname} refers to a directory.
37128 The requested access is not allowed.
37131 @var{pathname} was too long.
37134 A directory component in @var{pathname} does not exist.
37137 @var{pathname} refers to a device, pipe, named pipe or socket.
37140 @var{pathname} refers to a file on a read-only filesystem and
37141 write access was requested.
37144 @var{pathname} is an invalid pointer value.
37147 No space on device to create the file.
37150 The process already has the maximum number of files open.
37153 The limit on the total number of files open on the system
37157 The call was interrupted by the user.
37163 @unnumberedsubsubsec close
37164 @cindex close, file-i/o system call
37173 @samp{Fclose,@var{fd}}
37175 @item Return value:
37176 @code{close} returns zero on success, or -1 if an error occurred.
37182 @var{fd} isn't a valid open file descriptor.
37185 The call was interrupted by the user.
37191 @unnumberedsubsubsec read
37192 @cindex read, file-i/o system call
37197 int read(int fd, void *buf, unsigned int count);
37201 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
37203 @item Return value:
37204 On success, the number of bytes read is returned.
37205 Zero indicates end of file. If count is zero, read
37206 returns zero as well. On error, -1 is returned.
37212 @var{fd} is not a valid file descriptor or is not open for
37216 @var{bufptr} is an invalid pointer value.
37219 The call was interrupted by the user.
37225 @unnumberedsubsubsec write
37226 @cindex write, file-i/o system call
37231 int write(int fd, const void *buf, unsigned int count);
37235 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
37237 @item Return value:
37238 On success, the number of bytes written are returned.
37239 Zero indicates nothing was written. On error, -1
37246 @var{fd} is not a valid file descriptor or is not open for
37250 @var{bufptr} is an invalid pointer value.
37253 An attempt was made to write a file that exceeds the
37254 host-specific maximum file size allowed.
37257 No space on device to write the data.
37260 The call was interrupted by the user.
37266 @unnumberedsubsubsec lseek
37267 @cindex lseek, file-i/o system call
37272 long lseek (int fd, long offset, int flag);
37276 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
37278 @var{flag} is one of:
37282 The offset is set to @var{offset} bytes.
37285 The offset is set to its current location plus @var{offset}
37289 The offset is set to the size of the file plus @var{offset}
37293 @item Return value:
37294 On success, the resulting unsigned offset in bytes from
37295 the beginning of the file is returned. Otherwise, a
37296 value of -1 is returned.
37302 @var{fd} is not a valid open file descriptor.
37305 @var{fd} is associated with the @value{GDBN} console.
37308 @var{flag} is not a proper value.
37311 The call was interrupted by the user.
37317 @unnumberedsubsubsec rename
37318 @cindex rename, file-i/o system call
37323 int rename(const char *oldpath, const char *newpath);
37327 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
37329 @item Return value:
37330 On success, zero is returned. On error, -1 is returned.
37336 @var{newpath} is an existing directory, but @var{oldpath} is not a
37340 @var{newpath} is a non-empty directory.
37343 @var{oldpath} or @var{newpath} is a directory that is in use by some
37347 An attempt was made to make a directory a subdirectory
37351 A component used as a directory in @var{oldpath} or new
37352 path is not a directory. Or @var{oldpath} is a directory
37353 and @var{newpath} exists but is not a directory.
37356 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
37359 No access to the file or the path of the file.
37363 @var{oldpath} or @var{newpath} was too long.
37366 A directory component in @var{oldpath} or @var{newpath} does not exist.
37369 The file is on a read-only filesystem.
37372 The device containing the file has no room for the new
37376 The call was interrupted by the user.
37382 @unnumberedsubsubsec unlink
37383 @cindex unlink, file-i/o system call
37388 int unlink(const char *pathname);
37392 @samp{Funlink,@var{pathnameptr}/@var{len}}
37394 @item Return value:
37395 On success, zero is returned. On error, -1 is returned.
37401 No access to the file or the path of the file.
37404 The system does not allow unlinking of directories.
37407 The file @var{pathname} cannot be unlinked because it's
37408 being used by another process.
37411 @var{pathnameptr} is an invalid pointer value.
37414 @var{pathname} was too long.
37417 A directory component in @var{pathname} does not exist.
37420 A component of the path is not a directory.
37423 The file is on a read-only filesystem.
37426 The call was interrupted by the user.
37432 @unnumberedsubsubsec stat/fstat
37433 @cindex fstat, file-i/o system call
37434 @cindex stat, file-i/o system call
37439 int stat(const char *pathname, struct stat *buf);
37440 int fstat(int fd, struct stat *buf);
37444 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
37445 @samp{Ffstat,@var{fd},@var{bufptr}}
37447 @item Return value:
37448 On success, zero is returned. On error, -1 is returned.
37454 @var{fd} is not a valid open file.
37457 A directory component in @var{pathname} does not exist or the
37458 path is an empty string.
37461 A component of the path is not a directory.
37464 @var{pathnameptr} is an invalid pointer value.
37467 No access to the file or the path of the file.
37470 @var{pathname} was too long.
37473 The call was interrupted by the user.
37479 @unnumberedsubsubsec gettimeofday
37480 @cindex gettimeofday, file-i/o system call
37485 int gettimeofday(struct timeval *tv, void *tz);
37489 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
37491 @item Return value:
37492 On success, 0 is returned, -1 otherwise.
37498 @var{tz} is a non-NULL pointer.
37501 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
37507 @unnumberedsubsubsec isatty
37508 @cindex isatty, file-i/o system call
37513 int isatty(int fd);
37517 @samp{Fisatty,@var{fd}}
37519 @item Return value:
37520 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
37526 The call was interrupted by the user.
37531 Note that the @code{isatty} call is treated as a special case: it returns
37532 1 to the target if the file descriptor is attached
37533 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
37534 would require implementing @code{ioctl} and would be more complex than
37539 @unnumberedsubsubsec system
37540 @cindex system, file-i/o system call
37545 int system(const char *command);
37549 @samp{Fsystem,@var{commandptr}/@var{len}}
37551 @item Return value:
37552 If @var{len} is zero, the return value indicates whether a shell is
37553 available. A zero return value indicates a shell is not available.
37554 For non-zero @var{len}, the value returned is -1 on error and the
37555 return status of the command otherwise. Only the exit status of the
37556 command is returned, which is extracted from the host's @code{system}
37557 return value by calling @code{WEXITSTATUS(retval)}. In case
37558 @file{/bin/sh} could not be executed, 127 is returned.
37564 The call was interrupted by the user.
37569 @value{GDBN} takes over the full task of calling the necessary host calls
37570 to perform the @code{system} call. The return value of @code{system} on
37571 the host is simplified before it's returned
37572 to the target. Any termination signal information from the child process
37573 is discarded, and the return value consists
37574 entirely of the exit status of the called command.
37576 Due to security concerns, the @code{system} call is by default refused
37577 by @value{GDBN}. The user has to allow this call explicitly with the
37578 @code{set remote system-call-allowed 1} command.
37581 @item set remote system-call-allowed
37582 @kindex set remote system-call-allowed
37583 Control whether to allow the @code{system} calls in the File I/O
37584 protocol for the remote target. The default is zero (disabled).
37586 @item show remote system-call-allowed
37587 @kindex show remote system-call-allowed
37588 Show whether the @code{system} calls are allowed in the File I/O
37592 @node Protocol-specific Representation of Datatypes
37593 @subsection Protocol-specific Representation of Datatypes
37594 @cindex protocol-specific representation of datatypes, in file-i/o protocol
37597 * Integral Datatypes::
37599 * Memory Transfer::
37604 @node Integral Datatypes
37605 @unnumberedsubsubsec Integral Datatypes
37606 @cindex integral datatypes, in file-i/o protocol
37608 The integral datatypes used in the system calls are @code{int},
37609 @code{unsigned int}, @code{long}, @code{unsigned long},
37610 @code{mode_t}, and @code{time_t}.
37612 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
37613 implemented as 32 bit values in this protocol.
37615 @code{long} and @code{unsigned long} are implemented as 64 bit types.
37617 @xref{Limits}, for corresponding MIN and MAX values (similar to those
37618 in @file{limits.h}) to allow range checking on host and target.
37620 @code{time_t} datatypes are defined as seconds since the Epoch.
37622 All integral datatypes transferred as part of a memory read or write of a
37623 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
37626 @node Pointer Values
37627 @unnumberedsubsubsec Pointer Values
37628 @cindex pointer values, in file-i/o protocol
37630 Pointers to target data are transmitted as they are. An exception
37631 is made for pointers to buffers for which the length isn't
37632 transmitted as part of the function call, namely strings. Strings
37633 are transmitted as a pointer/length pair, both as hex values, e.g.@:
37640 which is a pointer to data of length 18 bytes at position 0x1aaf.
37641 The length is defined as the full string length in bytes, including
37642 the trailing null byte. For example, the string @code{"hello world"}
37643 at address 0x123456 is transmitted as
37649 @node Memory Transfer
37650 @unnumberedsubsubsec Memory Transfer
37651 @cindex memory transfer, in file-i/o protocol
37653 Structured data which is transferred using a memory read or write (for
37654 example, a @code{struct stat}) is expected to be in a protocol-specific format
37655 with all scalar multibyte datatypes being big endian. Translation to
37656 this representation needs to be done both by the target before the @code{F}
37657 packet is sent, and by @value{GDBN} before
37658 it transfers memory to the target. Transferred pointers to structured
37659 data should point to the already-coerced data at any time.
37663 @unnumberedsubsubsec struct stat
37664 @cindex struct stat, in file-i/o protocol
37666 The buffer of type @code{struct stat} used by the target and @value{GDBN}
37667 is defined as follows:
37671 unsigned int st_dev; /* device */
37672 unsigned int st_ino; /* inode */
37673 mode_t st_mode; /* protection */
37674 unsigned int st_nlink; /* number of hard links */
37675 unsigned int st_uid; /* user ID of owner */
37676 unsigned int st_gid; /* group ID of owner */
37677 unsigned int st_rdev; /* device type (if inode device) */
37678 unsigned long st_size; /* total size, in bytes */
37679 unsigned long st_blksize; /* blocksize for filesystem I/O */
37680 unsigned long st_blocks; /* number of blocks allocated */
37681 time_t st_atime; /* time of last access */
37682 time_t st_mtime; /* time of last modification */
37683 time_t st_ctime; /* time of last change */
37687 The integral datatypes conform to the definitions given in the
37688 appropriate section (see @ref{Integral Datatypes}, for details) so this
37689 structure is of size 64 bytes.
37691 The values of several fields have a restricted meaning and/or
37697 A value of 0 represents a file, 1 the console.
37700 No valid meaning for the target. Transmitted unchanged.
37703 Valid mode bits are described in @ref{Constants}. Any other
37704 bits have currently no meaning for the target.
37709 No valid meaning for the target. Transmitted unchanged.
37714 These values have a host and file system dependent
37715 accuracy. Especially on Windows hosts, the file system may not
37716 support exact timing values.
37719 The target gets a @code{struct stat} of the above representation and is
37720 responsible for coercing it to the target representation before
37723 Note that due to size differences between the host, target, and protocol
37724 representations of @code{struct stat} members, these members could eventually
37725 get truncated on the target.
37727 @node struct timeval
37728 @unnumberedsubsubsec struct timeval
37729 @cindex struct timeval, in file-i/o protocol
37731 The buffer of type @code{struct timeval} used by the File-I/O protocol
37732 is defined as follows:
37736 time_t tv_sec; /* second */
37737 long tv_usec; /* microsecond */
37741 The integral datatypes conform to the definitions given in the
37742 appropriate section (see @ref{Integral Datatypes}, for details) so this
37743 structure is of size 8 bytes.
37746 @subsection Constants
37747 @cindex constants, in file-i/o protocol
37749 The following values are used for the constants inside of the
37750 protocol. @value{GDBN} and target are responsible for translating these
37751 values before and after the call as needed.
37762 @unnumberedsubsubsec Open Flags
37763 @cindex open flags, in file-i/o protocol
37765 All values are given in hexadecimal representation.
37777 @node mode_t Values
37778 @unnumberedsubsubsec mode_t Values
37779 @cindex mode_t values, in file-i/o protocol
37781 All values are given in octal representation.
37798 @unnumberedsubsubsec Errno Values
37799 @cindex errno values, in file-i/o protocol
37801 All values are given in decimal representation.
37826 @code{EUNKNOWN} is used as a fallback error value if a host system returns
37827 any error value not in the list of supported error numbers.
37830 @unnumberedsubsubsec Lseek Flags
37831 @cindex lseek flags, in file-i/o protocol
37840 @unnumberedsubsubsec Limits
37841 @cindex limits, in file-i/o protocol
37843 All values are given in decimal representation.
37846 INT_MIN -2147483648
37848 UINT_MAX 4294967295
37849 LONG_MIN -9223372036854775808
37850 LONG_MAX 9223372036854775807
37851 ULONG_MAX 18446744073709551615
37854 @node File-I/O Examples
37855 @subsection File-I/O Examples
37856 @cindex file-i/o examples
37858 Example sequence of a write call, file descriptor 3, buffer is at target
37859 address 0x1234, 6 bytes should be written:
37862 <- @code{Fwrite,3,1234,6}
37863 @emph{request memory read from target}
37866 @emph{return "6 bytes written"}
37870 Example sequence of a read call, file descriptor 3, buffer is at target
37871 address 0x1234, 6 bytes should be read:
37874 <- @code{Fread,3,1234,6}
37875 @emph{request memory write to target}
37876 -> @code{X1234,6:XXXXXX}
37877 @emph{return "6 bytes read"}
37881 Example sequence of a read call, call fails on the host due to invalid
37882 file descriptor (@code{EBADF}):
37885 <- @code{Fread,3,1234,6}
37889 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
37893 <- @code{Fread,3,1234,6}
37898 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
37902 <- @code{Fread,3,1234,6}
37903 -> @code{X1234,6:XXXXXX}
37907 @node Library List Format
37908 @section Library List Format
37909 @cindex library list format, remote protocol
37911 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
37912 same process as your application to manage libraries. In this case,
37913 @value{GDBN} can use the loader's symbol table and normal memory
37914 operations to maintain a list of shared libraries. On other
37915 platforms, the operating system manages loaded libraries.
37916 @value{GDBN} can not retrieve the list of currently loaded libraries
37917 through memory operations, so it uses the @samp{qXfer:libraries:read}
37918 packet (@pxref{qXfer library list read}) instead. The remote stub
37919 queries the target's operating system and reports which libraries
37922 The @samp{qXfer:libraries:read} packet returns an XML document which
37923 lists loaded libraries and their offsets. Each library has an
37924 associated name and one or more segment or section base addresses,
37925 which report where the library was loaded in memory.
37927 For the common case of libraries that are fully linked binaries, the
37928 library should have a list of segments. If the target supports
37929 dynamic linking of a relocatable object file, its library XML element
37930 should instead include a list of allocated sections. The segment or
37931 section bases are start addresses, not relocation offsets; they do not
37932 depend on the library's link-time base addresses.
37934 @value{GDBN} must be linked with the Expat library to support XML
37935 library lists. @xref{Expat}.
37937 A simple memory map, with one loaded library relocated by a single
37938 offset, looks like this:
37942 <library name="/lib/libc.so.6">
37943 <segment address="0x10000000"/>
37948 Another simple memory map, with one loaded library with three
37949 allocated sections (.text, .data, .bss), looks like this:
37953 <library name="sharedlib.o">
37954 <section address="0x10000000"/>
37955 <section address="0x20000000"/>
37956 <section address="0x30000000"/>
37961 The format of a library list is described by this DTD:
37964 <!-- library-list: Root element with versioning -->
37965 <!ELEMENT library-list (library)*>
37966 <!ATTLIST library-list version CDATA #FIXED "1.0">
37967 <!ELEMENT library (segment*, section*)>
37968 <!ATTLIST library name CDATA #REQUIRED>
37969 <!ELEMENT segment EMPTY>
37970 <!ATTLIST segment address CDATA #REQUIRED>
37971 <!ELEMENT section EMPTY>
37972 <!ATTLIST section address CDATA #REQUIRED>
37975 In addition, segments and section descriptors cannot be mixed within a
37976 single library element, and you must supply at least one segment or
37977 section for each library.
37979 @node Library List Format for SVR4 Targets
37980 @section Library List Format for SVR4 Targets
37981 @cindex library list format, remote protocol
37983 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
37984 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
37985 shared libraries. Still a special library list provided by this packet is
37986 more efficient for the @value{GDBN} remote protocol.
37988 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
37989 loaded libraries and their SVR4 linker parameters. For each library on SVR4
37990 target, the following parameters are reported:
37994 @code{name}, the absolute file name from the @code{l_name} field of
37995 @code{struct link_map}.
37997 @code{lm} with address of @code{struct link_map} used for TLS
37998 (Thread Local Storage) access.
38000 @code{l_addr}, the displacement as read from the field @code{l_addr} of
38001 @code{struct link_map}. For prelinked libraries this is not an absolute
38002 memory address. It is a displacement of absolute memory address against
38003 address the file was prelinked to during the library load.
38005 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
38008 Additionally the single @code{main-lm} attribute specifies address of
38009 @code{struct link_map} used for the main executable. This parameter is used
38010 for TLS access and its presence is optional.
38012 @value{GDBN} must be linked with the Expat library to support XML
38013 SVR4 library lists. @xref{Expat}.
38015 A simple memory map, with two loaded libraries (which do not use prelink),
38019 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
38020 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
38022 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
38024 </library-list-svr>
38027 The format of an SVR4 library list is described by this DTD:
38030 <!-- library-list-svr4: Root element with versioning -->
38031 <!ELEMENT library-list-svr4 (library)*>
38032 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
38033 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
38034 <!ELEMENT library EMPTY>
38035 <!ATTLIST library name CDATA #REQUIRED>
38036 <!ATTLIST library lm CDATA #REQUIRED>
38037 <!ATTLIST library l_addr CDATA #REQUIRED>
38038 <!ATTLIST library l_ld CDATA #REQUIRED>
38041 @node Memory Map Format
38042 @section Memory Map Format
38043 @cindex memory map format
38045 To be able to write into flash memory, @value{GDBN} needs to obtain a
38046 memory map from the target. This section describes the format of the
38049 The memory map is obtained using the @samp{qXfer:memory-map:read}
38050 (@pxref{qXfer memory map read}) packet and is an XML document that
38051 lists memory regions.
38053 @value{GDBN} must be linked with the Expat library to support XML
38054 memory maps. @xref{Expat}.
38056 The top-level structure of the document is shown below:
38059 <?xml version="1.0"?>
38060 <!DOCTYPE memory-map
38061 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
38062 "http://sourceware.org/gdb/gdb-memory-map.dtd">
38068 Each region can be either:
38073 A region of RAM starting at @var{addr} and extending for @var{length}
38077 <memory type="ram" start="@var{addr}" length="@var{length}"/>
38082 A region of read-only memory:
38085 <memory type="rom" start="@var{addr}" length="@var{length}"/>
38090 A region of flash memory, with erasure blocks @var{blocksize}
38094 <memory type="flash" start="@var{addr}" length="@var{length}">
38095 <property name="blocksize">@var{blocksize}</property>
38101 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
38102 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
38103 packets to write to addresses in such ranges.
38105 The formal DTD for memory map format is given below:
38108 <!-- ................................................... -->
38109 <!-- Memory Map XML DTD ................................ -->
38110 <!-- File: memory-map.dtd .............................. -->
38111 <!-- .................................... .............. -->
38112 <!-- memory-map.dtd -->
38113 <!-- memory-map: Root element with versioning -->
38114 <!ELEMENT memory-map (memory | property)>
38115 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
38116 <!ELEMENT memory (property)>
38117 <!-- memory: Specifies a memory region,
38118 and its type, or device. -->
38119 <!ATTLIST memory type CDATA #REQUIRED
38120 start CDATA #REQUIRED
38121 length CDATA #REQUIRED
38122 device CDATA #IMPLIED>
38123 <!-- property: Generic attribute tag -->
38124 <!ELEMENT property (#PCDATA | property)*>
38125 <!ATTLIST property name CDATA #REQUIRED>
38128 @node Thread List Format
38129 @section Thread List Format
38130 @cindex thread list format
38132 To efficiently update the list of threads and their attributes,
38133 @value{GDBN} issues the @samp{qXfer:threads:read} packet
38134 (@pxref{qXfer threads read}) and obtains the XML document with
38135 the following structure:
38138 <?xml version="1.0"?>
38140 <thread id="id" core="0">
38141 ... description ...
38146 Each @samp{thread} element must have the @samp{id} attribute that
38147 identifies the thread (@pxref{thread-id syntax}). The
38148 @samp{core} attribute, if present, specifies which processor core
38149 the thread was last executing on. The content of the of @samp{thread}
38150 element is interpreted as human-readable auxilliary information.
38152 @node Traceframe Info Format
38153 @section Traceframe Info Format
38154 @cindex traceframe info format
38156 To be able to know which objects in the inferior can be examined when
38157 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
38158 memory ranges, registers and trace state variables that have been
38159 collected in a traceframe.
38161 This list is obtained using the @samp{qXfer:traceframe-info:read}
38162 (@pxref{qXfer traceframe info read}) packet and is an XML document.
38164 @value{GDBN} must be linked with the Expat library to support XML
38165 traceframe info discovery. @xref{Expat}.
38167 The top-level structure of the document is shown below:
38170 <?xml version="1.0"?>
38171 <!DOCTYPE traceframe-info
38172 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
38173 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
38179 Each traceframe block can be either:
38184 A region of collected memory starting at @var{addr} and extending for
38185 @var{length} bytes from there:
38188 <memory start="@var{addr}" length="@var{length}"/>
38193 The formal DTD for the traceframe info format is given below:
38196 <!ELEMENT traceframe-info (memory)* >
38197 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
38199 <!ELEMENT memory EMPTY>
38200 <!ATTLIST memory start CDATA #REQUIRED
38201 length CDATA #REQUIRED>
38204 @include agentexpr.texi
38206 @node Target Descriptions
38207 @appendix Target Descriptions
38208 @cindex target descriptions
38210 One of the challenges of using @value{GDBN} to debug embedded systems
38211 is that there are so many minor variants of each processor
38212 architecture in use. It is common practice for vendors to start with
38213 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
38214 and then make changes to adapt it to a particular market niche. Some
38215 architectures have hundreds of variants, available from dozens of
38216 vendors. This leads to a number of problems:
38220 With so many different customized processors, it is difficult for
38221 the @value{GDBN} maintainers to keep up with the changes.
38223 Since individual variants may have short lifetimes or limited
38224 audiences, it may not be worthwhile to carry information about every
38225 variant in the @value{GDBN} source tree.
38227 When @value{GDBN} does support the architecture of the embedded system
38228 at hand, the task of finding the correct architecture name to give the
38229 @command{set architecture} command can be error-prone.
38232 To address these problems, the @value{GDBN} remote protocol allows a
38233 target system to not only identify itself to @value{GDBN}, but to
38234 actually describe its own features. This lets @value{GDBN} support
38235 processor variants it has never seen before --- to the extent that the
38236 descriptions are accurate, and that @value{GDBN} understands them.
38238 @value{GDBN} must be linked with the Expat library to support XML
38239 target descriptions. @xref{Expat}.
38242 * Retrieving Descriptions:: How descriptions are fetched from a target.
38243 * Target Description Format:: The contents of a target description.
38244 * Predefined Target Types:: Standard types available for target
38246 * Standard Target Features:: Features @value{GDBN} knows about.
38249 @node Retrieving Descriptions
38250 @section Retrieving Descriptions
38252 Target descriptions can be read from the target automatically, or
38253 specified by the user manually. The default behavior is to read the
38254 description from the target. @value{GDBN} retrieves it via the remote
38255 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
38256 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
38257 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
38258 XML document, of the form described in @ref{Target Description
38261 Alternatively, you can specify a file to read for the target description.
38262 If a file is set, the target will not be queried. The commands to
38263 specify a file are:
38266 @cindex set tdesc filename
38267 @item set tdesc filename @var{path}
38268 Read the target description from @var{path}.
38270 @cindex unset tdesc filename
38271 @item unset tdesc filename
38272 Do not read the XML target description from a file. @value{GDBN}
38273 will use the description supplied by the current target.
38275 @cindex show tdesc filename
38276 @item show tdesc filename
38277 Show the filename to read for a target description, if any.
38281 @node Target Description Format
38282 @section Target Description Format
38283 @cindex target descriptions, XML format
38285 A target description annex is an @uref{http://www.w3.org/XML/, XML}
38286 document which complies with the Document Type Definition provided in
38287 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
38288 means you can use generally available tools like @command{xmllint} to
38289 check that your feature descriptions are well-formed and valid.
38290 However, to help people unfamiliar with XML write descriptions for
38291 their targets, we also describe the grammar here.
38293 Target descriptions can identify the architecture of the remote target
38294 and (for some architectures) provide information about custom register
38295 sets. They can also identify the OS ABI of the remote target.
38296 @value{GDBN} can use this information to autoconfigure for your
38297 target, or to warn you if you connect to an unsupported target.
38299 Here is a simple target description:
38302 <target version="1.0">
38303 <architecture>i386:x86-64</architecture>
38308 This minimal description only says that the target uses
38309 the x86-64 architecture.
38311 A target description has the following overall form, with [ ] marking
38312 optional elements and @dots{} marking repeatable elements. The elements
38313 are explained further below.
38316 <?xml version="1.0"?>
38317 <!DOCTYPE target SYSTEM "gdb-target.dtd">
38318 <target version="1.0">
38319 @r{[}@var{architecture}@r{]}
38320 @r{[}@var{osabi}@r{]}
38321 @r{[}@var{compatible}@r{]}
38322 @r{[}@var{feature}@dots{}@r{]}
38327 The description is generally insensitive to whitespace and line
38328 breaks, under the usual common-sense rules. The XML version
38329 declaration and document type declaration can generally be omitted
38330 (@value{GDBN} does not require them), but specifying them may be
38331 useful for XML validation tools. The @samp{version} attribute for
38332 @samp{<target>} may also be omitted, but we recommend
38333 including it; if future versions of @value{GDBN} use an incompatible
38334 revision of @file{gdb-target.dtd}, they will detect and report
38335 the version mismatch.
38337 @subsection Inclusion
38338 @cindex target descriptions, inclusion
38341 @cindex <xi:include>
38344 It can sometimes be valuable to split a target description up into
38345 several different annexes, either for organizational purposes, or to
38346 share files between different possible target descriptions. You can
38347 divide a description into multiple files by replacing any element of
38348 the target description with an inclusion directive of the form:
38351 <xi:include href="@var{document}"/>
38355 When @value{GDBN} encounters an element of this form, it will retrieve
38356 the named XML @var{document}, and replace the inclusion directive with
38357 the contents of that document. If the current description was read
38358 using @samp{qXfer}, then so will be the included document;
38359 @var{document} will be interpreted as the name of an annex. If the
38360 current description was read from a file, @value{GDBN} will look for
38361 @var{document} as a file in the same directory where it found the
38362 original description.
38364 @subsection Architecture
38365 @cindex <architecture>
38367 An @samp{<architecture>} element has this form:
38370 <architecture>@var{arch}</architecture>
38373 @var{arch} is one of the architectures from the set accepted by
38374 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
38377 @cindex @code{<osabi>}
38379 This optional field was introduced in @value{GDBN} version 7.0.
38380 Previous versions of @value{GDBN} ignore it.
38382 An @samp{<osabi>} element has this form:
38385 <osabi>@var{abi-name}</osabi>
38388 @var{abi-name} is an OS ABI name from the same selection accepted by
38389 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
38391 @subsection Compatible Architecture
38392 @cindex @code{<compatible>}
38394 This optional field was introduced in @value{GDBN} version 7.0.
38395 Previous versions of @value{GDBN} ignore it.
38397 A @samp{<compatible>} element has this form:
38400 <compatible>@var{arch}</compatible>
38403 @var{arch} is one of the architectures from the set accepted by
38404 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
38406 A @samp{<compatible>} element is used to specify that the target
38407 is able to run binaries in some other than the main target architecture
38408 given by the @samp{<architecture>} element. For example, on the
38409 Cell Broadband Engine, the main architecture is @code{powerpc:common}
38410 or @code{powerpc:common64}, but the system is able to run binaries
38411 in the @code{spu} architecture as well. The way to describe this
38412 capability with @samp{<compatible>} is as follows:
38415 <architecture>powerpc:common</architecture>
38416 <compatible>spu</compatible>
38419 @subsection Features
38422 Each @samp{<feature>} describes some logical portion of the target
38423 system. Features are currently used to describe available CPU
38424 registers and the types of their contents. A @samp{<feature>} element
38428 <feature name="@var{name}">
38429 @r{[}@var{type}@dots{}@r{]}
38435 Each feature's name should be unique within the description. The name
38436 of a feature does not matter unless @value{GDBN} has some special
38437 knowledge of the contents of that feature; if it does, the feature
38438 should have its standard name. @xref{Standard Target Features}.
38442 Any register's value is a collection of bits which @value{GDBN} must
38443 interpret. The default interpretation is a two's complement integer,
38444 but other types can be requested by name in the register description.
38445 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
38446 Target Types}), and the description can define additional composite types.
38448 Each type element must have an @samp{id} attribute, which gives
38449 a unique (within the containing @samp{<feature>}) name to the type.
38450 Types must be defined before they are used.
38453 Some targets offer vector registers, which can be treated as arrays
38454 of scalar elements. These types are written as @samp{<vector>} elements,
38455 specifying the array element type, @var{type}, and the number of elements,
38459 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
38463 If a register's value is usefully viewed in multiple ways, define it
38464 with a union type containing the useful representations. The
38465 @samp{<union>} element contains one or more @samp{<field>} elements,
38466 each of which has a @var{name} and a @var{type}:
38469 <union id="@var{id}">
38470 <field name="@var{name}" type="@var{type}"/>
38476 If a register's value is composed from several separate values, define
38477 it with a structure type. There are two forms of the @samp{<struct>}
38478 element; a @samp{<struct>} element must either contain only bitfields
38479 or contain no bitfields. If the structure contains only bitfields,
38480 its total size in bytes must be specified, each bitfield must have an
38481 explicit start and end, and bitfields are automatically assigned an
38482 integer type. The field's @var{start} should be less than or
38483 equal to its @var{end}, and zero represents the least significant bit.
38486 <struct id="@var{id}" size="@var{size}">
38487 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
38492 If the structure contains no bitfields, then each field has an
38493 explicit type, and no implicit padding is added.
38496 <struct id="@var{id}">
38497 <field name="@var{name}" type="@var{type}"/>
38503 If a register's value is a series of single-bit flags, define it with
38504 a flags type. The @samp{<flags>} element has an explicit @var{size}
38505 and contains one or more @samp{<field>} elements. Each field has a
38506 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
38510 <flags id="@var{id}" size="@var{size}">
38511 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
38516 @subsection Registers
38519 Each register is represented as an element with this form:
38522 <reg name="@var{name}"
38523 bitsize="@var{size}"
38524 @r{[}regnum="@var{num}"@r{]}
38525 @r{[}save-restore="@var{save-restore}"@r{]}
38526 @r{[}type="@var{type}"@r{]}
38527 @r{[}group="@var{group}"@r{]}/>
38531 The components are as follows:
38536 The register's name; it must be unique within the target description.
38539 The register's size, in bits.
38542 The register's number. If omitted, a register's number is one greater
38543 than that of the previous register (either in the current feature or in
38544 a preceding feature); the first register in the target description
38545 defaults to zero. This register number is used to read or write
38546 the register; e.g.@: it is used in the remote @code{p} and @code{P}
38547 packets, and registers appear in the @code{g} and @code{G} packets
38548 in order of increasing register number.
38551 Whether the register should be preserved across inferior function
38552 calls; this must be either @code{yes} or @code{no}. The default is
38553 @code{yes}, which is appropriate for most registers except for
38554 some system control registers; this is not related to the target's
38558 The type of the register. @var{type} may be a predefined type, a type
38559 defined in the current feature, or one of the special types @code{int}
38560 and @code{float}. @code{int} is an integer type of the correct size
38561 for @var{bitsize}, and @code{float} is a floating point type (in the
38562 architecture's normal floating point format) of the correct size for
38563 @var{bitsize}. The default is @code{int}.
38566 The register group to which this register belongs. @var{group} must
38567 be either @code{general}, @code{float}, or @code{vector}. If no
38568 @var{group} is specified, @value{GDBN} will not display the register
38569 in @code{info registers}.
38573 @node Predefined Target Types
38574 @section Predefined Target Types
38575 @cindex target descriptions, predefined types
38577 Type definitions in the self-description can build up composite types
38578 from basic building blocks, but can not define fundamental types. Instead,
38579 standard identifiers are provided by @value{GDBN} for the fundamental
38580 types. The currently supported types are:
38589 Signed integer types holding the specified number of bits.
38596 Unsigned integer types holding the specified number of bits.
38600 Pointers to unspecified code and data. The program counter and
38601 any dedicated return address register may be marked as code
38602 pointers; printing a code pointer converts it into a symbolic
38603 address. The stack pointer and any dedicated address registers
38604 may be marked as data pointers.
38607 Single precision IEEE floating point.
38610 Double precision IEEE floating point.
38613 The 12-byte extended precision format used by ARM FPA registers.
38616 The 10-byte extended precision format used by x87 registers.
38619 32bit @sc{eflags} register used by x86.
38622 32bit @sc{mxcsr} register used by x86.
38626 @node Standard Target Features
38627 @section Standard Target Features
38628 @cindex target descriptions, standard features
38630 A target description must contain either no registers or all the
38631 target's registers. If the description contains no registers, then
38632 @value{GDBN} will assume a default register layout, selected based on
38633 the architecture. If the description contains any registers, the
38634 default layout will not be used; the standard registers must be
38635 described in the target description, in such a way that @value{GDBN}
38636 can recognize them.
38638 This is accomplished by giving specific names to feature elements
38639 which contain standard registers. @value{GDBN} will look for features
38640 with those names and verify that they contain the expected registers;
38641 if any known feature is missing required registers, or if any required
38642 feature is missing, @value{GDBN} will reject the target
38643 description. You can add additional registers to any of the
38644 standard features --- @value{GDBN} will display them just as if
38645 they were added to an unrecognized feature.
38647 This section lists the known features and their expected contents.
38648 Sample XML documents for these features are included in the
38649 @value{GDBN} source tree, in the directory @file{gdb/features}.
38651 Names recognized by @value{GDBN} should include the name of the
38652 company or organization which selected the name, and the overall
38653 architecture to which the feature applies; so e.g.@: the feature
38654 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
38656 The names of registers are not case sensitive for the purpose
38657 of recognizing standard features, but @value{GDBN} will only display
38658 registers using the capitalization used in the description.
38665 * PowerPC Features::
38671 @subsection ARM Features
38672 @cindex target descriptions, ARM features
38674 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
38676 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
38677 @samp{lr}, @samp{pc}, and @samp{cpsr}.
38679 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
38680 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
38681 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
38684 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
38685 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
38687 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
38688 it should contain at least registers @samp{wR0} through @samp{wR15} and
38689 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
38690 @samp{wCSSF}, and @samp{wCASF} registers are optional.
38692 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
38693 should contain at least registers @samp{d0} through @samp{d15}. If
38694 they are present, @samp{d16} through @samp{d31} should also be included.
38695 @value{GDBN} will synthesize the single-precision registers from
38696 halves of the double-precision registers.
38698 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
38699 need to contain registers; it instructs @value{GDBN} to display the
38700 VFP double-precision registers as vectors and to synthesize the
38701 quad-precision registers from pairs of double-precision registers.
38702 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
38703 be present and include 32 double-precision registers.
38705 @node i386 Features
38706 @subsection i386 Features
38707 @cindex target descriptions, i386 features
38709 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
38710 targets. It should describe the following registers:
38714 @samp{eax} through @samp{edi} plus @samp{eip} for i386
38716 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
38718 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
38719 @samp{fs}, @samp{gs}
38721 @samp{st0} through @samp{st7}
38723 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
38724 @samp{foseg}, @samp{fooff} and @samp{fop}
38727 The register sets may be different, depending on the target.
38729 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
38730 describe registers:
38734 @samp{xmm0} through @samp{xmm7} for i386
38736 @samp{xmm0} through @samp{xmm15} for amd64
38741 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
38742 @samp{org.gnu.gdb.i386.sse} feature. It should
38743 describe the upper 128 bits of @sc{ymm} registers:
38747 @samp{ymm0h} through @samp{ymm7h} for i386
38749 @samp{ymm0h} through @samp{ymm15h} for amd64
38752 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
38753 describe a single register, @samp{orig_eax}.
38755 @node MIPS Features
38756 @subsection MIPS Features
38757 @cindex target descriptions, MIPS features
38759 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
38760 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
38761 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
38764 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
38765 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
38766 registers. They may be 32-bit or 64-bit depending on the target.
38768 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
38769 it may be optional in a future version of @value{GDBN}. It should
38770 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
38771 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
38773 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
38774 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
38775 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
38776 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
38778 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
38779 contain a single register, @samp{restart}, which is used by the
38780 Linux kernel to control restartable syscalls.
38782 @node M68K Features
38783 @subsection M68K Features
38784 @cindex target descriptions, M68K features
38787 @item @samp{org.gnu.gdb.m68k.core}
38788 @itemx @samp{org.gnu.gdb.coldfire.core}
38789 @itemx @samp{org.gnu.gdb.fido.core}
38790 One of those features must be always present.
38791 The feature that is present determines which flavor of m68k is
38792 used. The feature that is present should contain registers
38793 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
38794 @samp{sp}, @samp{ps} and @samp{pc}.
38796 @item @samp{org.gnu.gdb.coldfire.fp}
38797 This feature is optional. If present, it should contain registers
38798 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
38802 @node PowerPC Features
38803 @subsection PowerPC Features
38804 @cindex target descriptions, PowerPC features
38806 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
38807 targets. It should contain registers @samp{r0} through @samp{r31},
38808 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
38809 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
38811 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
38812 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
38814 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
38815 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
38818 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
38819 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
38820 will combine these registers with the floating point registers
38821 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
38822 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
38823 through @samp{vs63}, the set of vector registers for POWER7.
38825 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
38826 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
38827 @samp{spefscr}. SPE targets should provide 32-bit registers in
38828 @samp{org.gnu.gdb.power.core} and provide the upper halves in
38829 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
38830 these to present registers @samp{ev0} through @samp{ev31} to the
38833 @node TIC6x Features
38834 @subsection TMS320C6x Features
38835 @cindex target descriptions, TIC6x features
38836 @cindex target descriptions, TMS320C6x features
38837 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
38838 targets. It should contain registers @samp{A0} through @samp{A15},
38839 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
38841 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
38842 contain registers @samp{A16} through @samp{A31} and @samp{B16}
38843 through @samp{B31}.
38845 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
38846 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
38848 @node Operating System Information
38849 @appendix Operating System Information
38850 @cindex operating system information
38856 Users of @value{GDBN} often wish to obtain information about the state of
38857 the operating system running on the target---for example the list of
38858 processes, or the list of open files. This section describes the
38859 mechanism that makes it possible. This mechanism is similar to the
38860 target features mechanism (@pxref{Target Descriptions}), but focuses
38861 on a different aspect of target.
38863 Operating system information is retrived from the target via the
38864 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
38865 read}). The object name in the request should be @samp{osdata}, and
38866 the @var{annex} identifies the data to be fetched.
38869 @appendixsection Process list
38870 @cindex operating system information, process list
38872 When requesting the process list, the @var{annex} field in the
38873 @samp{qXfer} request should be @samp{processes}. The returned data is
38874 an XML document. The formal syntax of this document is defined in
38875 @file{gdb/features/osdata.dtd}.
38877 An example document is:
38880 <?xml version="1.0"?>
38881 <!DOCTYPE target SYSTEM "osdata.dtd">
38882 <osdata type="processes">
38884 <column name="pid">1</column>
38885 <column name="user">root</column>
38886 <column name="command">/sbin/init</column>
38887 <column name="cores">1,2,3</column>
38892 Each item should include a column whose name is @samp{pid}. The value
38893 of that column should identify the process on the target. The
38894 @samp{user} and @samp{command} columns are optional, and will be
38895 displayed by @value{GDBN}. The @samp{cores} column, if present,
38896 should contain a comma-separated list of cores that this process
38897 is running on. Target may provide additional columns,
38898 which @value{GDBN} currently ignores.
38900 @node Trace File Format
38901 @appendix Trace File Format
38902 @cindex trace file format
38904 The trace file comes in three parts: a header, a textual description
38905 section, and a trace frame section with binary data.
38907 The header has the form @code{\x7fTRACE0\n}. The first byte is
38908 @code{0x7f} so as to indicate that the file contains binary data,
38909 while the @code{0} is a version number that may have different values
38912 The description section consists of multiple lines of @sc{ascii} text
38913 separated by newline characters (@code{0xa}). The lines may include a
38914 variety of optional descriptive or context-setting information, such
38915 as tracepoint definitions or register set size. @value{GDBN} will
38916 ignore any line that it does not recognize. An empty line marks the end
38919 @c FIXME add some specific types of data
38921 The trace frame section consists of a number of consecutive frames.
38922 Each frame begins with a two-byte tracepoint number, followed by a
38923 four-byte size giving the amount of data in the frame. The data in
38924 the frame consists of a number of blocks, each introduced by a
38925 character indicating its type (at least register, memory, and trace
38926 state variable). The data in this section is raw binary, not a
38927 hexadecimal or other encoding; its endianness matches the target's
38930 @c FIXME bi-arch may require endianness/arch info in description section
38933 @item R @var{bytes}
38934 Register block. The number and ordering of bytes matches that of a
38935 @code{g} packet in the remote protocol. Note that these are the
38936 actual bytes, in target order and @value{GDBN} register order, not a
38937 hexadecimal encoding.
38939 @item M @var{address} @var{length} @var{bytes}...
38940 Memory block. This is a contiguous block of memory, at the 8-byte
38941 address @var{address}, with a 2-byte length @var{length}, followed by
38942 @var{length} bytes.
38944 @item V @var{number} @var{value}
38945 Trace state variable block. This records the 8-byte signed value
38946 @var{value} of trace state variable numbered @var{number}.
38950 Future enhancements of the trace file format may include additional types
38953 @node Index Section Format
38954 @appendix @code{.gdb_index} section format
38955 @cindex .gdb_index section format
38956 @cindex index section format
38958 This section documents the index section that is created by @code{save
38959 gdb-index} (@pxref{Index Files}). The index section is
38960 DWARF-specific; some knowledge of DWARF is assumed in this
38963 The mapped index file format is designed to be directly
38964 @code{mmap}able on any architecture. In most cases, a datum is
38965 represented using a little-endian 32-bit integer value, called an
38966 @code{offset_type}. Big endian machines must byte-swap the values
38967 before using them. Exceptions to this rule are noted. The data is
38968 laid out such that alignment is always respected.
38970 A mapped index consists of several areas, laid out in order.
38974 The file header. This is a sequence of values, of @code{offset_type}
38975 unless otherwise noted:
38979 The version number, currently 5. Versions 1, 2 and 3 are obsolete.
38980 Version 4 differs by its hashing function.
38983 The offset, from the start of the file, of the CU list.
38986 The offset, from the start of the file, of the types CU list. Note
38987 that this area can be empty, in which case this offset will be equal
38988 to the next offset.
38991 The offset, from the start of the file, of the address area.
38994 The offset, from the start of the file, of the symbol table.
38997 The offset, from the start of the file, of the constant pool.
39001 The CU list. This is a sequence of pairs of 64-bit little-endian
39002 values, sorted by the CU offset. The first element in each pair is
39003 the offset of a CU in the @code{.debug_info} section. The second
39004 element in each pair is the length of that CU. References to a CU
39005 elsewhere in the map are done using a CU index, which is just the
39006 0-based index into this table. Note that if there are type CUs, then
39007 conceptually CUs and type CUs form a single list for the purposes of
39011 The types CU list. This is a sequence of triplets of 64-bit
39012 little-endian values. In a triplet, the first value is the CU offset,
39013 the second value is the type offset in the CU, and the third value is
39014 the type signature. The types CU list is not sorted.
39017 The address area. The address area consists of a sequence of address
39018 entries. Each address entry has three elements:
39022 The low address. This is a 64-bit little-endian value.
39025 The high address. This is a 64-bit little-endian value. Like
39026 @code{DW_AT_high_pc}, the value is one byte beyond the end.
39029 The CU index. This is an @code{offset_type} value.
39033 The symbol table. This is an open-addressed hash table. The size of
39034 the hash table is always a power of 2.
39036 Each slot in the hash table consists of a pair of @code{offset_type}
39037 values. The first value is the offset of the symbol's name in the
39038 constant pool. The second value is the offset of the CU vector in the
39041 If both values are 0, then this slot in the hash table is empty. This
39042 is ok because while 0 is a valid constant pool index, it cannot be a
39043 valid index for both a string and a CU vector.
39045 The hash value for a table entry is computed by applying an
39046 iterative hash function to the symbol's name. Starting with an
39047 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
39048 the string is incorporated into the hash using the formula depending on the
39053 The formula is @code{r = r * 67 + c - 113}.
39056 The formula is @code{r = r * 67 + tolower (c) - 113}.
39059 The terminating @samp{\0} is not incorporated into the hash.
39061 The step size used in the hash table is computed via
39062 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
39063 value, and @samp{size} is the size of the hash table. The step size
39064 is used to find the next candidate slot when handling a hash
39067 The names of C@t{++} symbols in the hash table are canonicalized. We
39068 don't currently have a simple description of the canonicalization
39069 algorithm; if you intend to create new index sections, you must read
39073 The constant pool. This is simply a bunch of bytes. It is organized
39074 so that alignment is correct: CU vectors are stored first, followed by
39077 A CU vector in the constant pool is a sequence of @code{offset_type}
39078 values. The first value is the number of CU indices in the vector.
39079 Each subsequent value is the index of a CU in the CU list. This
39080 element in the hash table is used to indicate which CUs define the
39083 A string in the constant pool is zero-terminated.
39088 @node GNU Free Documentation License
39089 @appendix GNU Free Documentation License
39098 % I think something like @colophon should be in texinfo. In the
39100 \long\def\colophon{\hbox to0pt{}\vfill
39101 \centerline{The body of this manual is set in}
39102 \centerline{\fontname\tenrm,}
39103 \centerline{with headings in {\bf\fontname\tenbf}}
39104 \centerline{and examples in {\tt\fontname\tentt}.}
39105 \centerline{{\it\fontname\tenit\/},}
39106 \centerline{{\bf\fontname\tenbf}, and}
39107 \centerline{{\sl\fontname\tensl\/}}
39108 \centerline{are used for emphasis.}\vfill}
39110 % Blame: doc@cygnus.com, 1991.