1 \input texinfo @c -*-texinfo-*-
2 @c Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,
3 @c 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
4 @c Free Software Foundation, Inc.
7 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
8 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
26 @c readline appendices use @vindex, @findex and @ftable,
27 @c annotate.texi and gdbmi use @findex.
31 @c !!set GDB manual's edition---not the same as GDB version!
32 @c This is updated by GNU Press.
35 @c !!set GDB edit command default editor
38 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
40 @c This is a dir.info fragment to support semi-automated addition of
41 @c manuals to an info tree.
42 @dircategory Software development
44 * Gdb: (gdb). The GNU debugger.
48 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
49 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
50 Free Software Foundation, Inc.
52 Permission is granted to copy, distribute and/or modify this document
53 under the terms of the GNU Free Documentation License, Version 1.3 or
54 any later version published by the Free Software Foundation; with the
55 Invariant Sections being ``Free Software'' and ``Free Software Needs
56 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
57 and with the Back-Cover Texts as in (a) below.
59 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
60 this GNU Manual. Buying copies from GNU Press supports the FSF in
61 developing GNU and promoting software freedom.''
65 This file documents the @sc{gnu} debugger @value{GDBN}.
67 This is the @value{EDITION} Edition, of @cite{Debugging with
68 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
69 @ifset VERSION_PACKAGE
70 @value{VERSION_PACKAGE}
72 Version @value{GDBVN}.
78 @title Debugging with @value{GDBN}
79 @subtitle The @sc{gnu} Source-Level Debugger
81 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
82 @ifset VERSION_PACKAGE
84 @subtitle @value{VERSION_PACKAGE}
86 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
90 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
91 \hfill {\it Debugging with @value{GDBN}}\par
92 \hfill \TeX{}info \texinfoversion\par
96 @vskip 0pt plus 1filll
97 Published by the Free Software Foundation @*
98 51 Franklin Street, Fifth Floor,
99 Boston, MA 02110-1301, USA@*
100 ISBN 1-882114-77-9 @*
104 This edition of the GDB manual is dedicated to the memory of Fred
105 Fish. Fred was a long-standing contributor to GDB and to Free
106 software in general. We will miss him.
111 @node Top, Summary, (dir), (dir)
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN}
118 @ifset VERSION_PACKAGE
119 @value{VERSION_PACKAGE}
121 Version @value{GDBVN}.
123 Copyright (C) 1988-2010 Free Software Foundation, Inc.
125 This edition of the GDB manual is dedicated to the memory of Fred
126 Fish. Fred was a long-standing contributor to GDB and to Free
127 software in general. We will miss him.
130 * Summary:: Summary of @value{GDBN}
131 * Sample Session:: A sample @value{GDBN} session
133 * Invocation:: Getting in and out of @value{GDBN}
134 * Commands:: @value{GDBN} commands
135 * Running:: Running programs under @value{GDBN}
136 * Stopping:: Stopping and continuing
137 * Reverse Execution:: Running programs backward
138 * Process Record and Replay:: Recording inferior's execution and replaying it
139 * Stack:: Examining the stack
140 * Source:: Examining source files
141 * Data:: Examining data
142 * Optimized Code:: Debugging optimized code
143 * Macros:: Preprocessor Macros
144 * Tracepoints:: Debugging remote targets non-intrusively
145 * Overlays:: Debugging programs that use overlays
147 * Languages:: Using @value{GDBN} with different languages
149 * Symbols:: Examining the symbol table
150 * Altering:: Altering execution
151 * GDB Files:: @value{GDBN} files
152 * Targets:: Specifying a debugging target
153 * Remote Debugging:: Debugging remote programs
154 * Configurations:: Configuration-specific information
155 * Controlling GDB:: Controlling @value{GDBN}
156 * Extending GDB:: Extending @value{GDBN}
157 * Interpreters:: Command Interpreters
158 * TUI:: @value{GDBN} Text User Interface
159 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
160 * GDB/MI:: @value{GDBN}'s Machine Interface.
161 * Annotations:: @value{GDBN}'s annotation interface.
162 * JIT Interface:: Using the JIT debugging interface.
164 * GDB Bugs:: Reporting bugs in @value{GDBN}
166 @ifset SYSTEM_READLINE
167 * Command Line Editing: (rluserman). Command Line Editing
168 * Using History Interactively: (history). Using History Interactively
170 @ifclear SYSTEM_READLINE
171 * Command Line Editing:: Command Line Editing
172 * Using History Interactively:: Using History Interactively
174 * Formatting Documentation:: How to format and print @value{GDBN} documentation
175 * Installing GDB:: Installing GDB
176 * Maintenance Commands:: Maintenance Commands
177 * Remote Protocol:: GDB Remote Serial Protocol
178 * Agent Expressions:: The GDB Agent Expression Mechanism
179 * Target Descriptions:: How targets can describe themselves to
181 * Operating System Information:: Getting additional information from
183 * Trace File Format:: GDB trace file format
184 * Copying:: GNU General Public License says
185 how you can copy and share GDB
186 * GNU Free Documentation License:: The license for this documentation
195 @unnumbered Summary of @value{GDBN}
197 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
198 going on ``inside'' another program while it executes---or what another
199 program was doing at the moment it crashed.
201 @value{GDBN} can do four main kinds of things (plus other things in support of
202 these) to help you catch bugs in the act:
206 Start your program, specifying anything that might affect its behavior.
209 Make your program stop on specified conditions.
212 Examine what has happened, when your program has stopped.
215 Change things in your program, so you can experiment with correcting the
216 effects of one bug and go on to learn about another.
219 You can use @value{GDBN} to debug programs written in C and C@t{++}.
220 For more information, see @ref{Supported Languages,,Supported Languages}.
221 For more information, see @ref{C,,C and C++}.
223 Support for D is partial. For information on D, see
227 Support for Modula-2 is partial. For information on Modula-2, see
228 @ref{Modula-2,,Modula-2}.
230 Support for OpenCL C is partial. For information on OpenCL C, see
231 @ref{OpenCL C,,OpenCL C}.
234 Debugging Pascal programs which use sets, subranges, file variables, or
235 nested functions does not currently work. @value{GDBN} does not support
236 entering expressions, printing values, or similar features using Pascal
240 @value{GDBN} can be used to debug programs written in Fortran, although
241 it may be necessary to refer to some variables with a trailing
244 @value{GDBN} can be used to debug programs written in Objective-C,
245 using either the Apple/NeXT or the GNU Objective-C runtime.
248 * Free Software:: Freely redistributable software
249 * Contributors:: Contributors to GDB
253 @unnumberedsec Free Software
255 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
256 General Public License
257 (GPL). The GPL gives you the freedom to copy or adapt a licensed
258 program---but every person getting a copy also gets with it the
259 freedom to modify that copy (which means that they must get access to
260 the source code), and the freedom to distribute further copies.
261 Typical software companies use copyrights to limit your freedoms; the
262 Free Software Foundation uses the GPL to preserve these freedoms.
264 Fundamentally, the General Public License is a license which says that
265 you have these freedoms and that you cannot take these freedoms away
268 @unnumberedsec Free Software Needs Free Documentation
270 The biggest deficiency in the free software community today is not in
271 the software---it is the lack of good free documentation that we can
272 include with the free software. Many of our most important
273 programs do not come with free reference manuals and free introductory
274 texts. Documentation is an essential part of any software package;
275 when an important free software package does not come with a free
276 manual and a free tutorial, that is a major gap. We have many such
279 Consider Perl, for instance. The tutorial manuals that people
280 normally use are non-free. How did this come about? Because the
281 authors of those manuals published them with restrictive terms---no
282 copying, no modification, source files not available---which exclude
283 them from the free software world.
285 That wasn't the first time this sort of thing happened, and it was far
286 from the last. Many times we have heard a GNU user eagerly describe a
287 manual that he is writing, his intended contribution to the community,
288 only to learn that he had ruined everything by signing a publication
289 contract to make it non-free.
291 Free documentation, like free software, is a matter of freedom, not
292 price. The problem with the non-free manual is not that publishers
293 charge a price for printed copies---that in itself is fine. (The Free
294 Software Foundation sells printed copies of manuals, too.) The
295 problem is the restrictions on the use of the manual. Free manuals
296 are available in source code form, and give you permission to copy and
297 modify. Non-free manuals do not allow this.
299 The criteria of freedom for a free manual are roughly the same as for
300 free software. Redistribution (including the normal kinds of
301 commercial redistribution) must be permitted, so that the manual can
302 accompany every copy of the program, both on-line and on paper.
304 Permission for modification of the technical content is crucial too.
305 When people modify the software, adding or changing features, if they
306 are conscientious they will change the manual too---so they can
307 provide accurate and clear documentation for the modified program. A
308 manual that leaves you no choice but to write a new manual to document
309 a changed version of the program is not really available to our
312 Some kinds of limits on the way modification is handled are
313 acceptable. For example, requirements to preserve the original
314 author's copyright notice, the distribution terms, or the list of
315 authors, are ok. It is also no problem to require modified versions
316 to include notice that they were modified. Even entire sections that
317 may not be deleted or changed are acceptable, as long as they deal
318 with nontechnical topics (like this one). These kinds of restrictions
319 are acceptable because they don't obstruct the community's normal use
322 However, it must be possible to modify all the @emph{technical}
323 content of the manual, and then distribute the result in all the usual
324 media, through all the usual channels. Otherwise, the restrictions
325 obstruct the use of the manual, it is not free, and we need another
326 manual to replace it.
328 Please spread the word about this issue. Our community continues to
329 lose manuals to proprietary publishing. If we spread the word that
330 free software needs free reference manuals and free tutorials, perhaps
331 the next person who wants to contribute by writing documentation will
332 realize, before it is too late, that only free manuals contribute to
333 the free software community.
335 If you are writing documentation, please insist on publishing it under
336 the GNU Free Documentation License or another free documentation
337 license. Remember that this decision requires your approval---you
338 don't have to let the publisher decide. Some commercial publishers
339 will use a free license if you insist, but they will not propose the
340 option; it is up to you to raise the issue and say firmly that this is
341 what you want. If the publisher you are dealing with refuses, please
342 try other publishers. If you're not sure whether a proposed license
343 is free, write to @email{licensing@@gnu.org}.
345 You can encourage commercial publishers to sell more free, copylefted
346 manuals and tutorials by buying them, and particularly by buying
347 copies from the publishers that paid for their writing or for major
348 improvements. Meanwhile, try to avoid buying non-free documentation
349 at all. Check the distribution terms of a manual before you buy it,
350 and insist that whoever seeks your business must respect your freedom.
351 Check the history of the book, and try to reward the publishers that
352 have paid or pay the authors to work on it.
354 The Free Software Foundation maintains a list of free documentation
355 published by other publishers, at
356 @url{http://www.fsf.org/doc/other-free-books.html}.
359 @unnumberedsec Contributors to @value{GDBN}
361 Richard Stallman was the original author of @value{GDBN}, and of many
362 other @sc{gnu} programs. Many others have contributed to its
363 development. This section attempts to credit major contributors. One
364 of the virtues of free software is that everyone is free to contribute
365 to it; with regret, we cannot actually acknowledge everyone here. The
366 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
367 blow-by-blow account.
369 Changes much prior to version 2.0 are lost in the mists of time.
372 @emph{Plea:} Additions to this section are particularly welcome. If you
373 or your friends (or enemies, to be evenhanded) have been unfairly
374 omitted from this list, we would like to add your names!
377 So that they may not regard their many labors as thankless, we
378 particularly thank those who shepherded @value{GDBN} through major
380 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
381 Jim Blandy (release 4.18);
382 Jason Molenda (release 4.17);
383 Stan Shebs (release 4.14);
384 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
385 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
386 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
387 Jim Kingdon (releases 3.5, 3.4, and 3.3);
388 and Randy Smith (releases 3.2, 3.1, and 3.0).
390 Richard Stallman, assisted at various times by Peter TerMaat, Chris
391 Hanson, and Richard Mlynarik, handled releases through 2.8.
393 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
394 in @value{GDBN}, with significant additional contributions from Per
395 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
396 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
397 much general update work leading to release 3.0).
399 @value{GDBN} uses the BFD subroutine library to examine multiple
400 object-file formats; BFD was a joint project of David V.
401 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
403 David Johnson wrote the original COFF support; Pace Willison did
404 the original support for encapsulated COFF.
406 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
408 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
409 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
411 Jean-Daniel Fekete contributed Sun 386i support.
412 Chris Hanson improved the HP9000 support.
413 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
414 David Johnson contributed Encore Umax support.
415 Jyrki Kuoppala contributed Altos 3068 support.
416 Jeff Law contributed HP PA and SOM support.
417 Keith Packard contributed NS32K support.
418 Doug Rabson contributed Acorn Risc Machine support.
419 Bob Rusk contributed Harris Nighthawk CX-UX support.
420 Chris Smith contributed Convex support (and Fortran debugging).
421 Jonathan Stone contributed Pyramid support.
422 Michael Tiemann contributed SPARC support.
423 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
424 Pace Willison contributed Intel 386 support.
425 Jay Vosburgh contributed Symmetry support.
426 Marko Mlinar contributed OpenRISC 1000 support.
428 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
430 Rich Schaefer and Peter Schauer helped with support of SunOS shared
433 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
434 about several machine instruction sets.
436 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
437 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
438 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
439 and RDI targets, respectively.
441 Brian Fox is the author of the readline libraries providing
442 command-line editing and command history.
444 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
445 Modula-2 support, and contributed the Languages chapter of this manual.
447 Fred Fish wrote most of the support for Unix System Vr4.
448 He also enhanced the command-completion support to cover C@t{++} overloaded
451 Hitachi America (now Renesas America), Ltd. sponsored the support for
452 H8/300, H8/500, and Super-H processors.
454 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
456 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
459 Toshiba sponsored the support for the TX39 Mips processor.
461 Matsushita sponsored the support for the MN10200 and MN10300 processors.
463 Fujitsu sponsored the support for SPARClite and FR30 processors.
465 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
468 Michael Snyder added support for tracepoints.
470 Stu Grossman wrote gdbserver.
472 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
473 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
475 The following people at the Hewlett-Packard Company contributed
476 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
477 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
478 compiler, and the Text User Interface (nee Terminal User Interface):
479 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
480 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
481 provided HP-specific information in this manual.
483 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
484 Robert Hoehne made significant contributions to the DJGPP port.
486 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
487 development since 1991. Cygnus engineers who have worked on @value{GDBN}
488 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
489 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
490 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
491 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
492 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
493 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
494 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
495 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
496 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
497 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
498 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
499 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
500 Zuhn have made contributions both large and small.
502 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
503 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
505 Jim Blandy added support for preprocessor macros, while working for Red
508 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
509 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
510 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
511 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
512 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
513 with the migration of old architectures to this new framework.
515 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
516 unwinder framework, this consisting of a fresh new design featuring
517 frame IDs, independent frame sniffers, and the sentinel frame. Mark
518 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
519 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
520 trad unwinders. The architecture-specific changes, each involving a
521 complete rewrite of the architecture's frame code, were carried out by
522 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
523 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
524 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
525 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
528 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
529 Tensilica, Inc.@: contributed support for Xtensa processors. Others
530 who have worked on the Xtensa port of @value{GDBN} in the past include
531 Steve Tjiang, John Newlin, and Scott Foehner.
533 Michael Eager and staff of Xilinx, Inc., contributed support for the
534 Xilinx MicroBlaze architecture.
537 @chapter A Sample @value{GDBN} Session
539 You can use this manual at your leisure to read all about @value{GDBN}.
540 However, a handful of commands are enough to get started using the
541 debugger. This chapter illustrates those commands.
544 In this sample session, we emphasize user input like this: @b{input},
545 to make it easier to pick out from the surrounding output.
548 @c FIXME: this example may not be appropriate for some configs, where
549 @c FIXME...primary interest is in remote use.
551 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
552 processor) exhibits the following bug: sometimes, when we change its
553 quote strings from the default, the commands used to capture one macro
554 definition within another stop working. In the following short @code{m4}
555 session, we define a macro @code{foo} which expands to @code{0000}; we
556 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
557 same thing. However, when we change the open quote string to
558 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
559 procedure fails to define a new synonym @code{baz}:
568 @b{define(bar,defn(`foo'))}
572 @b{changequote(<QUOTE>,<UNQUOTE>)}
574 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
577 m4: End of input: 0: fatal error: EOF in string
581 Let us use @value{GDBN} to try to see what is going on.
584 $ @b{@value{GDBP} m4}
585 @c FIXME: this falsifies the exact text played out, to permit smallbook
586 @c FIXME... format to come out better.
587 @value{GDBN} is free software and you are welcome to distribute copies
588 of it under certain conditions; type "show copying" to see
590 There is absolutely no warranty for @value{GDBN}; type "show warranty"
593 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
598 @value{GDBN} reads only enough symbol data to know where to find the
599 rest when needed; as a result, the first prompt comes up very quickly.
600 We now tell @value{GDBN} to use a narrower display width than usual, so
601 that examples fit in this manual.
604 (@value{GDBP}) @b{set width 70}
608 We need to see how the @code{m4} built-in @code{changequote} works.
609 Having looked at the source, we know the relevant subroutine is
610 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
611 @code{break} command.
614 (@value{GDBP}) @b{break m4_changequote}
615 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
619 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
620 control; as long as control does not reach the @code{m4_changequote}
621 subroutine, the program runs as usual:
624 (@value{GDBP}) @b{run}
625 Starting program: /work/Editorial/gdb/gnu/m4/m4
633 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
634 suspends execution of @code{m4}, displaying information about the
635 context where it stops.
638 @b{changequote(<QUOTE>,<UNQUOTE>)}
640 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
642 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
646 Now we use the command @code{n} (@code{next}) to advance execution to
647 the next line of the current function.
651 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
656 @code{set_quotes} looks like a promising subroutine. We can go into it
657 by using the command @code{s} (@code{step}) instead of @code{next}.
658 @code{step} goes to the next line to be executed in @emph{any}
659 subroutine, so it steps into @code{set_quotes}.
663 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
665 530 if (lquote != def_lquote)
669 The display that shows the subroutine where @code{m4} is now
670 suspended (and its arguments) is called a stack frame display. It
671 shows a summary of the stack. We can use the @code{backtrace}
672 command (which can also be spelled @code{bt}), to see where we are
673 in the stack as a whole: the @code{backtrace} command displays a
674 stack frame for each active subroutine.
677 (@value{GDBP}) @b{bt}
678 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
680 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
682 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
683 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
685 #4 0x79dc in expand_input () at macro.c:40
686 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
690 We step through a few more lines to see what happens. The first two
691 times, we can use @samp{s}; the next two times we use @code{n} to avoid
692 falling into the @code{xstrdup} subroutine.
696 0x3b5c 532 if (rquote != def_rquote)
698 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
699 def_lquote : xstrdup(lq);
701 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
704 538 len_lquote = strlen(rquote);
708 The last line displayed looks a little odd; we can examine the variables
709 @code{lquote} and @code{rquote} to see if they are in fact the new left
710 and right quotes we specified. We use the command @code{p}
711 (@code{print}) to see their values.
714 (@value{GDBP}) @b{p lquote}
715 $1 = 0x35d40 "<QUOTE>"
716 (@value{GDBP}) @b{p rquote}
717 $2 = 0x35d50 "<UNQUOTE>"
721 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
722 To look at some context, we can display ten lines of source
723 surrounding the current line with the @code{l} (@code{list}) command.
729 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
731 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
734 538 len_lquote = strlen(rquote);
735 539 len_rquote = strlen(lquote);
742 Let us step past the two lines that set @code{len_lquote} and
743 @code{len_rquote}, and then examine the values of those variables.
747 539 len_rquote = strlen(lquote);
750 (@value{GDBP}) @b{p len_lquote}
752 (@value{GDBP}) @b{p len_rquote}
757 That certainly looks wrong, assuming @code{len_lquote} and
758 @code{len_rquote} are meant to be the lengths of @code{lquote} and
759 @code{rquote} respectively. We can set them to better values using
760 the @code{p} command, since it can print the value of
761 any expression---and that expression can include subroutine calls and
765 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
767 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
772 Is that enough to fix the problem of using the new quotes with the
773 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
774 executing with the @code{c} (@code{continue}) command, and then try the
775 example that caused trouble initially:
781 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
788 Success! The new quotes now work just as well as the default ones. The
789 problem seems to have been just the two typos defining the wrong
790 lengths. We allow @code{m4} exit by giving it an EOF as input:
794 Program exited normally.
798 The message @samp{Program exited normally.} is from @value{GDBN}; it
799 indicates @code{m4} has finished executing. We can end our @value{GDBN}
800 session with the @value{GDBN} @code{quit} command.
803 (@value{GDBP}) @b{quit}
807 @chapter Getting In and Out of @value{GDBN}
809 This chapter discusses how to start @value{GDBN}, and how to get out of it.
813 type @samp{@value{GDBP}} to start @value{GDBN}.
815 type @kbd{quit} or @kbd{Ctrl-d} to exit.
819 * Invoking GDB:: How to start @value{GDBN}
820 * Quitting GDB:: How to quit @value{GDBN}
821 * Shell Commands:: How to use shell commands inside @value{GDBN}
822 * Logging Output:: How to log @value{GDBN}'s output to a file
826 @section Invoking @value{GDBN}
828 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
829 @value{GDBN} reads commands from the terminal until you tell it to exit.
831 You can also run @code{@value{GDBP}} with a variety of arguments and options,
832 to specify more of your debugging environment at the outset.
834 The command-line options described here are designed
835 to cover a variety of situations; in some environments, some of these
836 options may effectively be unavailable.
838 The most usual way to start @value{GDBN} is with one argument,
839 specifying an executable program:
842 @value{GDBP} @var{program}
846 You can also start with both an executable program and a core file
850 @value{GDBP} @var{program} @var{core}
853 You can, instead, specify a process ID as a second argument, if you want
854 to debug a running process:
857 @value{GDBP} @var{program} 1234
861 would attach @value{GDBN} to process @code{1234} (unless you also have a file
862 named @file{1234}; @value{GDBN} does check for a core file first).
864 Taking advantage of the second command-line argument requires a fairly
865 complete operating system; when you use @value{GDBN} as a remote
866 debugger attached to a bare board, there may not be any notion of
867 ``process'', and there is often no way to get a core dump. @value{GDBN}
868 will warn you if it is unable to attach or to read core dumps.
870 You can optionally have @code{@value{GDBP}} pass any arguments after the
871 executable file to the inferior using @code{--args}. This option stops
874 @value{GDBP} --args gcc -O2 -c foo.c
876 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
877 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
879 You can run @code{@value{GDBP}} without printing the front material, which describes
880 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
887 You can further control how @value{GDBN} starts up by using command-line
888 options. @value{GDBN} itself can remind you of the options available.
898 to display all available options and briefly describe their use
899 (@samp{@value{GDBP} -h} is a shorter equivalent).
901 All options and command line arguments you give are processed
902 in sequential order. The order makes a difference when the
903 @samp{-x} option is used.
907 * File Options:: Choosing files
908 * Mode Options:: Choosing modes
909 * Startup:: What @value{GDBN} does during startup
913 @subsection Choosing Files
915 When @value{GDBN} starts, it reads any arguments other than options as
916 specifying an executable file and core file (or process ID). This is
917 the same as if the arguments were specified by the @samp{-se} and
918 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
919 first argument that does not have an associated option flag as
920 equivalent to the @samp{-se} option followed by that argument; and the
921 second argument that does not have an associated option flag, if any, as
922 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
923 If the second argument begins with a decimal digit, @value{GDBN} will
924 first attempt to attach to it as a process, and if that fails, attempt
925 to open it as a corefile. If you have a corefile whose name begins with
926 a digit, you can prevent @value{GDBN} from treating it as a pid by
927 prefixing it with @file{./}, e.g.@: @file{./12345}.
929 If @value{GDBN} has not been configured to included core file support,
930 such as for most embedded targets, then it will complain about a second
931 argument and ignore it.
933 Many options have both long and short forms; both are shown in the
934 following list. @value{GDBN} also recognizes the long forms if you truncate
935 them, so long as enough of the option is present to be unambiguous.
936 (If you prefer, you can flag option arguments with @samp{--} rather
937 than @samp{-}, though we illustrate the more usual convention.)
939 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
940 @c way, both those who look for -foo and --foo in the index, will find
944 @item -symbols @var{file}
946 @cindex @code{--symbols}
948 Read symbol table from file @var{file}.
950 @item -exec @var{file}
952 @cindex @code{--exec}
954 Use file @var{file} as the executable file to execute when appropriate,
955 and for examining pure data in conjunction with a core dump.
959 Read symbol table from file @var{file} and use it as the executable
962 @item -core @var{file}
964 @cindex @code{--core}
966 Use file @var{file} as a core dump to examine.
968 @item -pid @var{number}
969 @itemx -p @var{number}
972 Connect to process ID @var{number}, as with the @code{attach} command.
974 @item -command @var{file}
976 @cindex @code{--command}
978 Execute commands from file @var{file}. The contents of this file is
979 evaluated exactly as the @code{source} command would.
980 @xref{Command Files,, Command files}.
982 @item -eval-command @var{command}
983 @itemx -ex @var{command}
984 @cindex @code{--eval-command}
986 Execute a single @value{GDBN} command.
988 This option may be used multiple times to call multiple commands. It may
989 also be interleaved with @samp{-command} as required.
992 @value{GDBP} -ex 'target sim' -ex 'load' \
993 -x setbreakpoints -ex 'run' a.out
996 @item -directory @var{directory}
997 @itemx -d @var{directory}
998 @cindex @code{--directory}
1000 Add @var{directory} to the path to search for source and script files.
1004 @cindex @code{--readnow}
1006 Read each symbol file's entire symbol table immediately, rather than
1007 the default, which is to read it incrementally as it is needed.
1008 This makes startup slower, but makes future operations faster.
1013 @subsection Choosing Modes
1015 You can run @value{GDBN} in various alternative modes---for example, in
1016 batch mode or quiet mode.
1023 Do not execute commands found in any initialization files. Normally,
1024 @value{GDBN} executes the commands in these files after all the command
1025 options and arguments have been processed. @xref{Command Files,,Command
1031 @cindex @code{--quiet}
1032 @cindex @code{--silent}
1034 ``Quiet''. Do not print the introductory and copyright messages. These
1035 messages are also suppressed in batch mode.
1038 @cindex @code{--batch}
1039 Run in batch mode. Exit with status @code{0} after processing all the
1040 command files specified with @samp{-x} (and all commands from
1041 initialization files, if not inhibited with @samp{-n}). Exit with
1042 nonzero status if an error occurs in executing the @value{GDBN} commands
1043 in the command files. Batch mode also disables pagination, sets unlimited
1044 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1045 off} were in effect (@pxref{Messages/Warnings}).
1047 Batch mode may be useful for running @value{GDBN} as a filter, for
1048 example to download and run a program on another computer; in order to
1049 make this more useful, the message
1052 Program exited normally.
1056 (which is ordinarily issued whenever a program running under
1057 @value{GDBN} control terminates) is not issued when running in batch
1061 @cindex @code{--batch-silent}
1062 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1063 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1064 unaffected). This is much quieter than @samp{-silent} and would be useless
1065 for an interactive session.
1067 This is particularly useful when using targets that give @samp{Loading section}
1068 messages, for example.
1070 Note that targets that give their output via @value{GDBN}, as opposed to
1071 writing directly to @code{stdout}, will also be made silent.
1073 @item -return-child-result
1074 @cindex @code{--return-child-result}
1075 The return code from @value{GDBN} will be the return code from the child
1076 process (the process being debugged), with the following exceptions:
1080 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1081 internal error. In this case the exit code is the same as it would have been
1082 without @samp{-return-child-result}.
1084 The user quits with an explicit value. E.g., @samp{quit 1}.
1086 The child process never runs, or is not allowed to terminate, in which case
1087 the exit code will be -1.
1090 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1091 when @value{GDBN} is being used as a remote program loader or simulator
1096 @cindex @code{--nowindows}
1098 ``No windows''. If @value{GDBN} comes with a graphical user interface
1099 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1100 interface. If no GUI is available, this option has no effect.
1104 @cindex @code{--windows}
1106 If @value{GDBN} includes a GUI, then this option requires it to be
1109 @item -cd @var{directory}
1111 Run @value{GDBN} using @var{directory} as its working directory,
1112 instead of the current directory.
1114 @item -data-directory @var{directory}
1115 @cindex @code{--data-directory}
1116 Run @value{GDBN} using @var{directory} as its data directory.
1117 The data directory is where @value{GDBN} searches for its
1118 auxiliary files. @xref{Data Files}.
1122 @cindex @code{--fullname}
1124 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1125 subprocess. It tells @value{GDBN} to output the full file name and line
1126 number in a standard, recognizable fashion each time a stack frame is
1127 displayed (which includes each time your program stops). This
1128 recognizable format looks like two @samp{\032} characters, followed by
1129 the file name, line number and character position separated by colons,
1130 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1131 @samp{\032} characters as a signal to display the source code for the
1135 @cindex @code{--epoch}
1136 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1137 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1138 routines so as to allow Epoch to display values of expressions in a
1141 @item -annotate @var{level}
1142 @cindex @code{--annotate}
1143 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1144 effect is identical to using @samp{set annotate @var{level}}
1145 (@pxref{Annotations}). The annotation @var{level} controls how much
1146 information @value{GDBN} prints together with its prompt, values of
1147 expressions, source lines, and other types of output. Level 0 is the
1148 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1149 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1150 that control @value{GDBN}, and level 2 has been deprecated.
1152 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1156 @cindex @code{--args}
1157 Change interpretation of command line so that arguments following the
1158 executable file are passed as command line arguments to the inferior.
1159 This option stops option processing.
1161 @item -baud @var{bps}
1163 @cindex @code{--baud}
1165 Set the line speed (baud rate or bits per second) of any serial
1166 interface used by @value{GDBN} for remote debugging.
1168 @item -l @var{timeout}
1170 Set the timeout (in seconds) of any communication used by @value{GDBN}
1171 for remote debugging.
1173 @item -tty @var{device}
1174 @itemx -t @var{device}
1175 @cindex @code{--tty}
1177 Run using @var{device} for your program's standard input and output.
1178 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1180 @c resolve the situation of these eventually
1182 @cindex @code{--tui}
1183 Activate the @dfn{Text User Interface} when starting. The Text User
1184 Interface manages several text windows on the terminal, showing
1185 source, assembly, registers and @value{GDBN} command outputs
1186 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1187 Text User Interface can be enabled by invoking the program
1188 @samp{@value{GDBTUI}}. Do not use this option if you run @value{GDBN} from
1189 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1192 @c @cindex @code{--xdb}
1193 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1194 @c For information, see the file @file{xdb_trans.html}, which is usually
1195 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1198 @item -interpreter @var{interp}
1199 @cindex @code{--interpreter}
1200 Use the interpreter @var{interp} for interface with the controlling
1201 program or device. This option is meant to be set by programs which
1202 communicate with @value{GDBN} using it as a back end.
1203 @xref{Interpreters, , Command Interpreters}.
1205 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1206 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1207 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1208 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1209 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1210 @sc{gdb/mi} interfaces are no longer supported.
1213 @cindex @code{--write}
1214 Open the executable and core files for both reading and writing. This
1215 is equivalent to the @samp{set write on} command inside @value{GDBN}
1219 @cindex @code{--statistics}
1220 This option causes @value{GDBN} to print statistics about time and
1221 memory usage after it completes each command and returns to the prompt.
1224 @cindex @code{--version}
1225 This option causes @value{GDBN} to print its version number and
1226 no-warranty blurb, and exit.
1231 @subsection What @value{GDBN} Does During Startup
1232 @cindex @value{GDBN} startup
1234 Here's the description of what @value{GDBN} does during session startup:
1238 Sets up the command interpreter as specified by the command line
1239 (@pxref{Mode Options, interpreter}).
1243 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1244 used when building @value{GDBN}; @pxref{System-wide configuration,
1245 ,System-wide configuration and settings}) and executes all the commands in
1249 Reads the init file (if any) in your home directory@footnote{On
1250 DOS/Windows systems, the home directory is the one pointed to by the
1251 @code{HOME} environment variable.} and executes all the commands in
1255 Processes command line options and operands.
1258 Reads and executes the commands from init file (if any) in the current
1259 working directory. This is only done if the current directory is
1260 different from your home directory. Thus, you can have more than one
1261 init file, one generic in your home directory, and another, specific
1262 to the program you are debugging, in the directory where you invoke
1266 If the command line specified a program to debug, or a process to
1267 attach to, or a core file, @value{GDBN} loads any auto-loaded
1268 scripts provided for the program or for its loaded shared libraries.
1269 @xref{Auto-loading}.
1271 If you wish to disable the auto-loading during startup,
1272 you must do something like the following:
1275 $ gdb -ex "set auto-load-scripts off" -ex "file myprogram"
1278 The following does not work because the auto-loading is turned off too late:
1281 $ gdb -ex "set auto-load-scripts off" myprogram
1285 Reads command files specified by the @samp{-x} option. @xref{Command
1286 Files}, for more details about @value{GDBN} command files.
1289 Reads the command history recorded in the @dfn{history file}.
1290 @xref{Command History}, for more details about the command history and the
1291 files where @value{GDBN} records it.
1294 Init files use the same syntax as @dfn{command files} (@pxref{Command
1295 Files}) and are processed by @value{GDBN} in the same way. The init
1296 file in your home directory can set options (such as @samp{set
1297 complaints}) that affect subsequent processing of command line options
1298 and operands. Init files are not executed if you use the @samp{-nx}
1299 option (@pxref{Mode Options, ,Choosing Modes}).
1301 To display the list of init files loaded by gdb at startup, you
1302 can use @kbd{gdb --help}.
1304 @cindex init file name
1305 @cindex @file{.gdbinit}
1306 @cindex @file{gdb.ini}
1307 The @value{GDBN} init files are normally called @file{.gdbinit}.
1308 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1309 the limitations of file names imposed by DOS filesystems. The Windows
1310 ports of @value{GDBN} use the standard name, but if they find a
1311 @file{gdb.ini} file, they warn you about that and suggest to rename
1312 the file to the standard name.
1316 @section Quitting @value{GDBN}
1317 @cindex exiting @value{GDBN}
1318 @cindex leaving @value{GDBN}
1321 @kindex quit @r{[}@var{expression}@r{]}
1322 @kindex q @r{(@code{quit})}
1323 @item quit @r{[}@var{expression}@r{]}
1325 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1326 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1327 do not supply @var{expression}, @value{GDBN} will terminate normally;
1328 otherwise it will terminate using the result of @var{expression} as the
1333 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1334 terminates the action of any @value{GDBN} command that is in progress and
1335 returns to @value{GDBN} command level. It is safe to type the interrupt
1336 character at any time because @value{GDBN} does not allow it to take effect
1337 until a time when it is safe.
1339 If you have been using @value{GDBN} to control an attached process or
1340 device, you can release it with the @code{detach} command
1341 (@pxref{Attach, ,Debugging an Already-running Process}).
1343 @node Shell Commands
1344 @section Shell Commands
1346 If you need to execute occasional shell commands during your
1347 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1348 just use the @code{shell} command.
1352 @cindex shell escape
1353 @item shell @var{command string}
1354 Invoke a standard shell to execute @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_delete to_fputs to_put to_rewind
1598 to_data to_flush to_isatty to_read to_write
1602 This is because the @code{gdb_stdout} is a variable of the type
1603 @code{struct ui_file} that is defined in @value{GDBN} sources as
1610 ui_file_flush_ftype *to_flush;
1611 ui_file_write_ftype *to_write;
1612 ui_file_fputs_ftype *to_fputs;
1613 ui_file_read_ftype *to_read;
1614 ui_file_delete_ftype *to_delete;
1615 ui_file_isatty_ftype *to_isatty;
1616 ui_file_rewind_ftype *to_rewind;
1617 ui_file_put_ftype *to_put;
1624 @section Getting Help
1625 @cindex online documentation
1628 You can always ask @value{GDBN} itself for information on its commands,
1629 using the command @code{help}.
1632 @kindex h @r{(@code{help})}
1635 You can use @code{help} (abbreviated @code{h}) with no arguments to
1636 display a short list of named classes of commands:
1640 List of classes of commands:
1642 aliases -- Aliases of other commands
1643 breakpoints -- Making program stop at certain points
1644 data -- Examining data
1645 files -- Specifying and examining files
1646 internals -- Maintenance commands
1647 obscure -- Obscure features
1648 running -- Running the program
1649 stack -- Examining the stack
1650 status -- Status inquiries
1651 support -- Support facilities
1652 tracepoints -- Tracing of program execution without
1653 stopping the program
1654 user-defined -- User-defined commands
1656 Type "help" followed by a class name for a list of
1657 commands in that class.
1658 Type "help" followed by command name for full
1660 Command name abbreviations are allowed if unambiguous.
1663 @c the above line break eliminates huge line overfull...
1665 @item help @var{class}
1666 Using one of the general help classes as an argument, you can get a
1667 list of the individual commands in that class. For example, here is the
1668 help display for the class @code{status}:
1671 (@value{GDBP}) help status
1676 @c Line break in "show" line falsifies real output, but needed
1677 @c to fit in smallbook page size.
1678 info -- Generic command for showing things
1679 about the program being debugged
1680 show -- Generic command for showing things
1683 Type "help" followed by command name for full
1685 Command name abbreviations are allowed if unambiguous.
1689 @item help @var{command}
1690 With a command name as @code{help} argument, @value{GDBN} displays a
1691 short paragraph on how to use that command.
1694 @item apropos @var{args}
1695 The @code{apropos} command searches through all of the @value{GDBN}
1696 commands, and their documentation, for the regular expression specified in
1697 @var{args}. It prints out all matches found. For example:
1708 set symbol-reloading -- Set dynamic symbol table reloading
1709 multiple times in one run
1710 show symbol-reloading -- Show dynamic symbol table reloading
1711 multiple times in one run
1716 @item complete @var{args}
1717 The @code{complete @var{args}} command lists all the possible completions
1718 for the beginning of a command. Use @var{args} to specify the beginning of the
1719 command you want completed. For example:
1725 @noindent results in:
1736 @noindent This is intended for use by @sc{gnu} Emacs.
1739 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1740 and @code{show} to inquire about the state of your program, or the state
1741 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1742 manual introduces each of them in the appropriate context. The listings
1743 under @code{info} and under @code{show} in the Index point to
1744 all the sub-commands. @xref{Index}.
1749 @kindex i @r{(@code{info})}
1751 This command (abbreviated @code{i}) is for describing the state of your
1752 program. For example, you can show the arguments passed to a function
1753 with @code{info args}, list the registers currently in use with @code{info
1754 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1755 You can get a complete list of the @code{info} sub-commands with
1756 @w{@code{help info}}.
1760 You can assign the result of an expression to an environment variable with
1761 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1762 @code{set prompt $}.
1766 In contrast to @code{info}, @code{show} is for describing the state of
1767 @value{GDBN} itself.
1768 You can change most of the things you can @code{show}, by using the
1769 related command @code{set}; for example, you can control what number
1770 system is used for displays with @code{set radix}, or simply inquire
1771 which is currently in use with @code{show radix}.
1774 To display all the settable parameters and their current
1775 values, you can use @code{show} with no arguments; you may also use
1776 @code{info set}. Both commands produce the same display.
1777 @c FIXME: "info set" violates the rule that "info" is for state of
1778 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1779 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1783 Here are three miscellaneous @code{show} subcommands, all of which are
1784 exceptional in lacking corresponding @code{set} commands:
1787 @kindex show version
1788 @cindex @value{GDBN} version number
1790 Show what version of @value{GDBN} is running. You should include this
1791 information in @value{GDBN} bug-reports. If multiple versions of
1792 @value{GDBN} are in use at your site, you may need to determine which
1793 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1794 commands are introduced, and old ones may wither away. Also, many
1795 system vendors ship variant versions of @value{GDBN}, and there are
1796 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1797 The version number is the same as the one announced when you start
1800 @kindex show copying
1801 @kindex info copying
1802 @cindex display @value{GDBN} copyright
1805 Display information about permission for copying @value{GDBN}.
1807 @kindex show warranty
1808 @kindex info warranty
1810 @itemx info warranty
1811 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1812 if your version of @value{GDBN} comes with one.
1817 @chapter Running Programs Under @value{GDBN}
1819 When you run a program under @value{GDBN}, you must first generate
1820 debugging information when you compile it.
1822 You may start @value{GDBN} with its arguments, if any, in an environment
1823 of your choice. If you are doing native debugging, you may redirect
1824 your program's input and output, debug an already running process, or
1825 kill a child process.
1828 * Compilation:: Compiling for debugging
1829 * Starting:: Starting your program
1830 * Arguments:: Your program's arguments
1831 * Environment:: Your program's environment
1833 * Working Directory:: Your program's working directory
1834 * Input/Output:: Your program's input and output
1835 * Attach:: Debugging an already-running process
1836 * Kill Process:: Killing the child process
1838 * Inferiors and Programs:: Debugging multiple inferiors and programs
1839 * Threads:: Debugging programs with multiple threads
1840 * Forks:: Debugging forks
1841 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1845 @section Compiling for Debugging
1847 In order to debug a program effectively, you need to generate
1848 debugging information when you compile it. This debugging information
1849 is stored in the object file; it describes the data type of each
1850 variable or function and the correspondence between source line numbers
1851 and addresses in the executable code.
1853 To request debugging information, specify the @samp{-g} option when you run
1856 Programs that are to be shipped to your customers are compiled with
1857 optimizations, using the @samp{-O} compiler option. However, some
1858 compilers are unable to handle the @samp{-g} and @samp{-O} options
1859 together. Using those compilers, you cannot generate optimized
1860 executables containing debugging information.
1862 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1863 without @samp{-O}, making it possible to debug optimized code. We
1864 recommend that you @emph{always} use @samp{-g} whenever you compile a
1865 program. You may think your program is correct, but there is no sense
1866 in pushing your luck. For more information, see @ref{Optimized Code}.
1868 Older versions of the @sc{gnu} C compiler permitted a variant option
1869 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1870 format; if your @sc{gnu} C compiler has this option, do not use it.
1872 @value{GDBN} knows about preprocessor macros and can show you their
1873 expansion (@pxref{Macros}). Most compilers do not include information
1874 about preprocessor macros in the debugging information if you specify
1875 the @option{-g} flag alone, because this information is rather large.
1876 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1877 provides macro information if you specify the options
1878 @option{-gdwarf-2} and @option{-g3}; the former option requests
1879 debugging information in the Dwarf 2 format, and the latter requests
1880 ``extra information''. In the future, we hope to find more compact
1881 ways to represent macro information, so that it can be included with
1886 @section Starting your Program
1892 @kindex r @r{(@code{run})}
1895 Use the @code{run} command to start your program under @value{GDBN}.
1896 You must first specify the program name (except on VxWorks) with an
1897 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1898 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1899 (@pxref{Files, ,Commands to Specify Files}).
1903 If you are running your program in an execution environment that
1904 supports processes, @code{run} creates an inferior process and makes
1905 that process run your program. In some environments without processes,
1906 @code{run} jumps to the start of your program. Other targets,
1907 like @samp{remote}, are always running. If you get an error
1908 message like this one:
1911 The "remote" target does not support "run".
1912 Try "help target" or "continue".
1916 then use @code{continue} to run your program. You may need @code{load}
1917 first (@pxref{load}).
1919 The execution of a program is affected by certain information it
1920 receives from its superior. @value{GDBN} provides ways to specify this
1921 information, which you must do @emph{before} starting your program. (You
1922 can change it after starting your program, but such changes only affect
1923 your program the next time you start it.) This information may be
1924 divided into four categories:
1927 @item The @emph{arguments.}
1928 Specify the arguments to give your program as the arguments of the
1929 @code{run} command. If a shell is available on your target, the shell
1930 is used to pass the arguments, so that you may use normal conventions
1931 (such as wildcard expansion or variable substitution) in describing
1933 In Unix systems, you can control which shell is used with the
1934 @code{SHELL} environment variable.
1935 @xref{Arguments, ,Your Program's Arguments}.
1937 @item The @emph{environment.}
1938 Your program normally inherits its environment from @value{GDBN}, but you can
1939 use the @value{GDBN} commands @code{set environment} and @code{unset
1940 environment} to change parts of the environment that affect
1941 your program. @xref{Environment, ,Your Program's Environment}.
1943 @item The @emph{working directory.}
1944 Your program inherits its working directory from @value{GDBN}. You can set
1945 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1946 @xref{Working Directory, ,Your Program's Working Directory}.
1948 @item The @emph{standard input and output.}
1949 Your program normally uses the same device for standard input and
1950 standard output as @value{GDBN} is using. You can redirect input and output
1951 in the @code{run} command line, or you can use the @code{tty} command to
1952 set a different device for your program.
1953 @xref{Input/Output, ,Your Program's Input and Output}.
1956 @emph{Warning:} While input and output redirection work, you cannot use
1957 pipes to pass the output of the program you are debugging to another
1958 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1962 When you issue the @code{run} command, your program begins to execute
1963 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1964 of how to arrange for your program to stop. Once your program has
1965 stopped, you may call functions in your program, using the @code{print}
1966 or @code{call} commands. @xref{Data, ,Examining Data}.
1968 If the modification time of your symbol file has changed since the last
1969 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1970 table, and reads it again. When it does this, @value{GDBN} tries to retain
1971 your current breakpoints.
1976 @cindex run to main procedure
1977 The name of the main procedure can vary from language to language.
1978 With C or C@t{++}, the main procedure name is always @code{main}, but
1979 other languages such as Ada do not require a specific name for their
1980 main procedure. The debugger provides a convenient way to start the
1981 execution of the program and to stop at the beginning of the main
1982 procedure, depending on the language used.
1984 The @samp{start} command does the equivalent of setting a temporary
1985 breakpoint at the beginning of the main procedure and then invoking
1986 the @samp{run} command.
1988 @cindex elaboration phase
1989 Some programs contain an @dfn{elaboration} phase where some startup code is
1990 executed before the main procedure is called. This depends on the
1991 languages used to write your program. In C@t{++}, for instance,
1992 constructors for static and global objects are executed before
1993 @code{main} is called. It is therefore possible that the debugger stops
1994 before reaching the main procedure. However, the temporary breakpoint
1995 will remain to halt execution.
1997 Specify the arguments to give to your program as arguments to the
1998 @samp{start} command. These arguments will be given verbatim to the
1999 underlying @samp{run} command. Note that the same arguments will be
2000 reused if no argument is provided during subsequent calls to
2001 @samp{start} or @samp{run}.
2003 It is sometimes necessary to debug the program during elaboration. In
2004 these cases, using the @code{start} command would stop the execution of
2005 your program too late, as the program would have already completed the
2006 elaboration phase. Under these circumstances, insert breakpoints in your
2007 elaboration code before running your program.
2009 @kindex set exec-wrapper
2010 @item set exec-wrapper @var{wrapper}
2011 @itemx show exec-wrapper
2012 @itemx unset exec-wrapper
2013 When @samp{exec-wrapper} is set, the specified wrapper is used to
2014 launch programs for debugging. @value{GDBN} starts your program
2015 with a shell command of the form @kbd{exec @var{wrapper}
2016 @var{program}}. Quoting is added to @var{program} and its
2017 arguments, but not to @var{wrapper}, so you should add quotes if
2018 appropriate for your shell. The wrapper runs until it executes
2019 your program, and then @value{GDBN} takes control.
2021 You can use any program that eventually calls @code{execve} with
2022 its arguments as a wrapper. Several standard Unix utilities do
2023 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2024 with @code{exec "$@@"} will also work.
2026 For example, you can use @code{env} to pass an environment variable to
2027 the debugged program, without setting the variable in your shell's
2031 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2035 This command is available when debugging locally on most targets, excluding
2036 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2038 @kindex set disable-randomization
2039 @item set disable-randomization
2040 @itemx set disable-randomization on
2041 This option (enabled by default in @value{GDBN}) will turn off the native
2042 randomization of the virtual address space of the started program. This option
2043 is useful for multiple debugging sessions to make the execution better
2044 reproducible and memory addresses reusable across debugging sessions.
2046 This feature is implemented only on @sc{gnu}/Linux. You can get the same
2050 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2053 @item set disable-randomization off
2054 Leave the behavior of the started executable unchanged. Some bugs rear their
2055 ugly heads only when the program is loaded at certain addresses. If your bug
2056 disappears when you run the program under @value{GDBN}, that might be because
2057 @value{GDBN} by default disables the address randomization on platforms, such
2058 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2059 disable-randomization off} to try to reproduce such elusive bugs.
2061 The virtual address space randomization is implemented only on @sc{gnu}/Linux.
2062 It protects the programs against some kinds of security attacks. In these
2063 cases the attacker needs to know the exact location of a concrete executable
2064 code. Randomizing its location makes it impossible to inject jumps misusing
2065 a code at its expected addresses.
2067 Prelinking shared libraries provides a startup performance advantage but it
2068 makes addresses in these libraries predictable for privileged processes by
2069 having just unprivileged access at the target system. Reading the shared
2070 library binary gives enough information for assembling the malicious code
2071 misusing it. Still even a prelinked shared library can get loaded at a new
2072 random address just requiring the regular relocation process during the
2073 startup. Shared libraries not already prelinked are always loaded at
2074 a randomly chosen address.
2076 Position independent executables (PIE) contain position independent code
2077 similar to the shared libraries and therefore such executables get loaded at
2078 a randomly chosen address upon startup. PIE executables always load even
2079 already prelinked shared libraries at a random address. You can build such
2080 executable using @command{gcc -fPIE -pie}.
2082 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2083 (as long as the randomization is enabled).
2085 @item show disable-randomization
2086 Show the current setting of the explicit disable of the native randomization of
2087 the virtual address space of the started program.
2092 @section Your Program's Arguments
2094 @cindex arguments (to your program)
2095 The arguments to your program can be specified by the arguments of the
2097 They are passed to a shell, which expands wildcard characters and
2098 performs redirection of I/O, and thence to your program. Your
2099 @code{SHELL} environment variable (if it exists) specifies what shell
2100 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2101 the default shell (@file{/bin/sh} on Unix).
2103 On non-Unix systems, the program is usually invoked directly by
2104 @value{GDBN}, which emulates I/O redirection via the appropriate system
2105 calls, and the wildcard characters are expanded by the startup code of
2106 the program, not by the shell.
2108 @code{run} with no arguments uses the same arguments used by the previous
2109 @code{run}, or those set by the @code{set args} command.
2114 Specify the arguments to be used the next time your program is run. If
2115 @code{set args} has no arguments, @code{run} executes your program
2116 with no arguments. Once you have run your program with arguments,
2117 using @code{set args} before the next @code{run} is the only way to run
2118 it again without arguments.
2122 Show the arguments to give your program when it is started.
2126 @section Your Program's Environment
2128 @cindex environment (of your program)
2129 The @dfn{environment} consists of a set of environment variables and
2130 their values. Environment variables conventionally record such things as
2131 your user name, your home directory, your terminal type, and your search
2132 path for programs to run. Usually you set up environment variables with
2133 the shell and they are inherited by all the other programs you run. When
2134 debugging, it can be useful to try running your program with a modified
2135 environment without having to start @value{GDBN} over again.
2139 @item path @var{directory}
2140 Add @var{directory} to the front of the @code{PATH} environment variable
2141 (the search path for executables) that will be passed to your program.
2142 The value of @code{PATH} used by @value{GDBN} does not change.
2143 You may specify several directory names, separated by whitespace or by a
2144 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2145 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2146 is moved to the front, so it is searched sooner.
2148 You can use the string @samp{$cwd} to refer to whatever is the current
2149 working directory at the time @value{GDBN} searches the path. If you
2150 use @samp{.} instead, it refers to the directory where you executed the
2151 @code{path} command. @value{GDBN} replaces @samp{.} in the
2152 @var{directory} argument (with the current path) before adding
2153 @var{directory} to the search path.
2154 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2155 @c document that, since repeating it would be a no-op.
2159 Display the list of search paths for executables (the @code{PATH}
2160 environment variable).
2162 @kindex show environment
2163 @item show environment @r{[}@var{varname}@r{]}
2164 Print the value of environment variable @var{varname} to be given to
2165 your program when it starts. If you do not supply @var{varname},
2166 print the names and values of all environment variables to be given to
2167 your program. You can abbreviate @code{environment} as @code{env}.
2169 @kindex set environment
2170 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2171 Set environment variable @var{varname} to @var{value}. The value
2172 changes for your program only, not for @value{GDBN} itself. @var{value} may
2173 be any string; the values of environment variables are just strings, and
2174 any interpretation is supplied by your program itself. The @var{value}
2175 parameter is optional; if it is eliminated, the variable is set to a
2177 @c "any string" here does not include leading, trailing
2178 @c blanks. Gnu asks: does anyone care?
2180 For example, this command:
2187 tells the debugged program, when subsequently run, that its user is named
2188 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2189 are not actually required.)
2191 @kindex unset environment
2192 @item unset environment @var{varname}
2193 Remove variable @var{varname} from the environment to be passed to your
2194 program. This is different from @samp{set env @var{varname} =};
2195 @code{unset environment} removes the variable from the environment,
2196 rather than assigning it an empty value.
2199 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2201 by your @code{SHELL} environment variable if it exists (or
2202 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2203 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2204 @file{.bashrc} for BASH---any variables you set in that file affect
2205 your program. You may wish to move setting of environment variables to
2206 files that are only run when you sign on, such as @file{.login} or
2209 @node Working Directory
2210 @section Your Program's Working Directory
2212 @cindex working directory (of your program)
2213 Each time you start your program with @code{run}, it inherits its
2214 working directory from the current working directory of @value{GDBN}.
2215 The @value{GDBN} working directory is initially whatever it inherited
2216 from its parent process (typically the shell), but you can specify a new
2217 working directory in @value{GDBN} with the @code{cd} command.
2219 The @value{GDBN} working directory also serves as a default for the commands
2220 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2225 @cindex change working directory
2226 @item cd @var{directory}
2227 Set the @value{GDBN} working directory to @var{directory}.
2231 Print the @value{GDBN} working directory.
2234 It is generally impossible to find the current working directory of
2235 the process being debugged (since a program can change its directory
2236 during its run). If you work on a system where @value{GDBN} is
2237 configured with the @file{/proc} support, you can use the @code{info
2238 proc} command (@pxref{SVR4 Process Information}) to find out the
2239 current working directory of the debuggee.
2242 @section Your Program's Input and Output
2247 By default, the program you run under @value{GDBN} does input and output to
2248 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2249 to its own terminal modes to interact with you, but it records the terminal
2250 modes your program was using and switches back to them when you continue
2251 running your program.
2254 @kindex info terminal
2256 Displays information recorded by @value{GDBN} about the terminal modes your
2260 You can redirect your program's input and/or output using shell
2261 redirection with the @code{run} command. For example,
2268 starts your program, diverting its output to the file @file{outfile}.
2271 @cindex controlling terminal
2272 Another way to specify where your program should do input and output is
2273 with the @code{tty} command. This command accepts a file name as
2274 argument, and causes this file to be the default for future @code{run}
2275 commands. It also resets the controlling terminal for the child
2276 process, for future @code{run} commands. For example,
2283 directs that processes started with subsequent @code{run} commands
2284 default to do input and output on the terminal @file{/dev/ttyb} and have
2285 that as their controlling terminal.
2287 An explicit redirection in @code{run} overrides the @code{tty} command's
2288 effect on the input/output device, but not its effect on the controlling
2291 When you use the @code{tty} command or redirect input in the @code{run}
2292 command, only the input @emph{for your program} is affected. The input
2293 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2294 for @code{set inferior-tty}.
2296 @cindex inferior tty
2297 @cindex set inferior controlling terminal
2298 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2299 display the name of the terminal that will be used for future runs of your
2303 @item set inferior-tty /dev/ttyb
2304 @kindex set inferior-tty
2305 Set the tty for the program being debugged to /dev/ttyb.
2307 @item show inferior-tty
2308 @kindex show inferior-tty
2309 Show the current tty for the program being debugged.
2313 @section Debugging an Already-running Process
2318 @item attach @var{process-id}
2319 This command attaches to a running process---one that was started
2320 outside @value{GDBN}. (@code{info files} shows your active
2321 targets.) The command takes as argument a process ID. The usual way to
2322 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2323 or with the @samp{jobs -l} shell command.
2325 @code{attach} does not repeat if you press @key{RET} a second time after
2326 executing the command.
2329 To use @code{attach}, your program must be running in an environment
2330 which supports processes; for example, @code{attach} does not work for
2331 programs on bare-board targets that lack an operating system. You must
2332 also have permission to send the process a signal.
2334 When you use @code{attach}, the debugger finds the program running in
2335 the process first by looking in the current working directory, then (if
2336 the program is not found) by using the source file search path
2337 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2338 the @code{file} command to load the program. @xref{Files, ,Commands to
2341 The first thing @value{GDBN} does after arranging to debug the specified
2342 process is to stop it. You can examine and modify an attached process
2343 with all the @value{GDBN} commands that are ordinarily available when
2344 you start processes with @code{run}. You can insert breakpoints; you
2345 can step and continue; you can modify storage. If you would rather the
2346 process continue running, you may use the @code{continue} command after
2347 attaching @value{GDBN} to the process.
2352 When you have finished debugging the attached process, you can use the
2353 @code{detach} command to release it from @value{GDBN} control. Detaching
2354 the process continues its execution. After the @code{detach} command,
2355 that process and @value{GDBN} become completely independent once more, and you
2356 are ready to @code{attach} another process or start one with @code{run}.
2357 @code{detach} does not repeat if you press @key{RET} again after
2358 executing the command.
2361 If you exit @value{GDBN} while you have an attached process, you detach
2362 that process. If you use the @code{run} command, you kill that process.
2363 By default, @value{GDBN} asks for confirmation if you try to do either of these
2364 things; you can control whether or not you need to confirm by using the
2365 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2369 @section Killing the Child Process
2374 Kill the child process in which your program is running under @value{GDBN}.
2377 This command is useful if you wish to debug a core dump instead of a
2378 running process. @value{GDBN} ignores any core dump file while your program
2381 On some operating systems, a program cannot be executed outside @value{GDBN}
2382 while you have breakpoints set on it inside @value{GDBN}. You can use the
2383 @code{kill} command in this situation to permit running your program
2384 outside the debugger.
2386 The @code{kill} command is also useful if you wish to recompile and
2387 relink your program, since on many systems it is impossible to modify an
2388 executable file while it is running in a process. In this case, when you
2389 next type @code{run}, @value{GDBN} notices that the file has changed, and
2390 reads the symbol table again (while trying to preserve your current
2391 breakpoint settings).
2393 @node Inferiors and Programs
2394 @section Debugging Multiple Inferiors and Programs
2396 @value{GDBN} lets you run and debug multiple programs in a single
2397 session. In addition, @value{GDBN} on some systems may let you run
2398 several programs simultaneously (otherwise you have to exit from one
2399 before starting another). In the most general case, you can have
2400 multiple threads of execution in each of multiple processes, launched
2401 from multiple executables.
2404 @value{GDBN} represents the state of each program execution with an
2405 object called an @dfn{inferior}. An inferior typically corresponds to
2406 a process, but is more general and applies also to targets that do not
2407 have processes. Inferiors may be created before a process runs, and
2408 may be retained after a process exits. Inferiors have unique
2409 identifiers that are different from process ids. Usually each
2410 inferior will also have its own distinct address space, although some
2411 embedded targets may have several inferiors running in different parts
2412 of a single address space. Each inferior may in turn have multiple
2413 threads running in it.
2415 To find out what inferiors exist at any moment, use @w{@code{info
2419 @kindex info inferiors
2420 @item info inferiors
2421 Print a list of all inferiors currently being managed by @value{GDBN}.
2423 @value{GDBN} displays for each inferior (in this order):
2427 the inferior number assigned by @value{GDBN}
2430 the target system's inferior identifier
2433 the name of the executable the inferior is running.
2438 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2439 indicates the current inferior.
2443 @c end table here to get a little more width for example
2446 (@value{GDBP}) info inferiors
2447 Num Description Executable
2448 2 process 2307 hello
2449 * 1 process 3401 goodbye
2452 To switch focus between inferiors, use the @code{inferior} command:
2455 @kindex inferior @var{infno}
2456 @item inferior @var{infno}
2457 Make inferior number @var{infno} the current inferior. The argument
2458 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2459 in the first field of the @samp{info inferiors} display.
2463 You can get multiple executables into a debugging session via the
2464 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2465 systems @value{GDBN} can add inferiors to the debug session
2466 automatically by following calls to @code{fork} and @code{exec}. To
2467 remove inferiors from the debugging session use the
2468 @w{@code{remove-inferior}} command.
2471 @kindex add-inferior
2472 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2473 Adds @var{n} inferiors to be run using @var{executable} as the
2474 executable. @var{n} defaults to 1. If no executable is specified,
2475 the inferiors begins empty, with no program. You can still assign or
2476 change the program assigned to the inferior at any time by using the
2477 @code{file} command with the executable name as its argument.
2479 @kindex clone-inferior
2480 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2481 Adds @var{n} inferiors ready to execute the same program as inferior
2482 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2483 number of the current inferior. This is a convenient command when you
2484 want to run another instance of the inferior you are debugging.
2487 (@value{GDBP}) info inferiors
2488 Num Description Executable
2489 * 1 process 29964 helloworld
2490 (@value{GDBP}) clone-inferior
2493 (@value{GDBP}) info inferiors
2494 Num Description Executable
2496 * 1 process 29964 helloworld
2499 You can now simply switch focus to inferior 2 and run it.
2501 @kindex remove-inferior
2502 @item remove-inferior @var{infno}
2503 Removes the inferior @var{infno}. It is not possible to remove an
2504 inferior that is running with this command. For those, use the
2505 @code{kill} or @code{detach} command first.
2509 To quit debugging one of the running inferiors that is not the current
2510 inferior, you can either detach from it by using the @w{@code{detach
2511 inferior}} command (allowing it to run independently), or kill it
2512 using the @w{@code{kill inferior}} command:
2515 @kindex detach inferior @var{infno}
2516 @item detach inferior @var{infno}
2517 Detach from the inferior identified by @value{GDBN} inferior number
2518 @var{infno}. Note that the inferior's entry still stays on the list
2519 of inferiors shown by @code{info inferiors}, but its Description will
2522 @kindex kill inferior @var{infno}
2523 @item kill inferior @var{infno}
2524 Kill the inferior identified by @value{GDBN} inferior number
2525 @var{infno}. Note that the inferior's entry still stays on the list
2526 of inferiors shown by @code{info inferiors}, but its Description will
2530 After the successful completion of a command such as @code{detach},
2531 @code{detach inferior}, @code{kill} or @code{kill inferior}, or after
2532 a normal process exit, the inferior is still valid and listed with
2533 @code{info inferiors}, ready to be restarted.
2536 To be notified when inferiors are started or exit under @value{GDBN}'s
2537 control use @w{@code{set print inferior-events}}:
2540 @kindex set print inferior-events
2541 @cindex print messages on inferior start and exit
2542 @item set print inferior-events
2543 @itemx set print inferior-events on
2544 @itemx set print inferior-events off
2545 The @code{set print inferior-events} command allows you to enable or
2546 disable printing of messages when @value{GDBN} notices that new
2547 inferiors have started or that inferiors have exited or have been
2548 detached. By default, these messages will not be printed.
2550 @kindex show print inferior-events
2551 @item show print inferior-events
2552 Show whether messages will be printed when @value{GDBN} detects that
2553 inferiors have started, exited or have been detached.
2556 Many commands will work the same with multiple programs as with a
2557 single program: e.g., @code{print myglobal} will simply display the
2558 value of @code{myglobal} in the current inferior.
2561 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2562 get more info about the relationship of inferiors, programs, address
2563 spaces in a debug session. You can do that with the @w{@code{maint
2564 info program-spaces}} command.
2567 @kindex maint info program-spaces
2568 @item maint info program-spaces
2569 Print a list of all program spaces currently being managed by
2572 @value{GDBN} displays for each program space (in this order):
2576 the program space number assigned by @value{GDBN}
2579 the name of the executable loaded into the program space, with e.g.,
2580 the @code{file} command.
2585 An asterisk @samp{*} preceding the @value{GDBN} program space number
2586 indicates the current program space.
2588 In addition, below each program space line, @value{GDBN} prints extra
2589 information that isn't suitable to display in tabular form. For
2590 example, the list of inferiors bound to the program space.
2593 (@value{GDBP}) maint info program-spaces
2596 Bound inferiors: ID 1 (process 21561)
2600 Here we can see that no inferior is running the program @code{hello},
2601 while @code{process 21561} is running the program @code{goodbye}. On
2602 some targets, it is possible that multiple inferiors are bound to the
2603 same program space. The most common example is that of debugging both
2604 the parent and child processes of a @code{vfork} call. For example,
2607 (@value{GDBP}) maint info program-spaces
2610 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2613 Here, both inferior 2 and inferior 1 are running in the same program
2614 space as a result of inferior 1 having executed a @code{vfork} call.
2618 @section Debugging Programs with Multiple Threads
2620 @cindex threads of execution
2621 @cindex multiple threads
2622 @cindex switching threads
2623 In some operating systems, such as HP-UX and Solaris, a single program
2624 may have more than one @dfn{thread} of execution. The precise semantics
2625 of threads differ from one operating system to another, but in general
2626 the threads of a single program are akin to multiple processes---except
2627 that they share one address space (that is, they can all examine and
2628 modify the same variables). On the other hand, each thread has its own
2629 registers and execution stack, and perhaps private memory.
2631 @value{GDBN} provides these facilities for debugging multi-thread
2635 @item automatic notification of new threads
2636 @item @samp{thread @var{threadno}}, a command to switch among threads
2637 @item @samp{info threads}, a command to inquire about existing threads
2638 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2639 a command to apply a command to a list of threads
2640 @item thread-specific breakpoints
2641 @item @samp{set print thread-events}, which controls printing of
2642 messages on thread start and exit.
2643 @item @samp{set libthread-db-search-path @var{path}}, which lets
2644 the user specify which @code{libthread_db} to use if the default choice
2645 isn't compatible with the program.
2649 @emph{Warning:} These facilities are not yet available on every
2650 @value{GDBN} configuration where the operating system supports threads.
2651 If your @value{GDBN} does not support threads, these commands have no
2652 effect. For example, a system without thread support shows no output
2653 from @samp{info threads}, and always rejects the @code{thread} command,
2657 (@value{GDBP}) info threads
2658 (@value{GDBP}) thread 1
2659 Thread ID 1 not known. Use the "info threads" command to
2660 see the IDs of currently known threads.
2662 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2663 @c doesn't support threads"?
2666 @cindex focus of debugging
2667 @cindex current thread
2668 The @value{GDBN} thread debugging facility allows you to observe all
2669 threads while your program runs---but whenever @value{GDBN} takes
2670 control, one thread in particular is always the focus of debugging.
2671 This thread is called the @dfn{current thread}. Debugging commands show
2672 program information from the perspective of the current thread.
2674 @cindex @code{New} @var{systag} message
2675 @cindex thread identifier (system)
2676 @c FIXME-implementors!! It would be more helpful if the [New...] message
2677 @c included GDB's numeric thread handle, so you could just go to that
2678 @c thread without first checking `info threads'.
2679 Whenever @value{GDBN} detects a new thread in your program, it displays
2680 the target system's identification for the thread with a message in the
2681 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2682 whose form varies depending on the particular system. For example, on
2683 @sc{gnu}/Linux, you might see
2686 [New Thread 46912507313328 (LWP 25582)]
2690 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2691 the @var{systag} is simply something like @samp{process 368}, with no
2694 @c FIXME!! (1) Does the [New...] message appear even for the very first
2695 @c thread of a program, or does it only appear for the
2696 @c second---i.e.@: when it becomes obvious we have a multithread
2698 @c (2) *Is* there necessarily a first thread always? Or do some
2699 @c multithread systems permit starting a program with multiple
2700 @c threads ab initio?
2702 @cindex thread number
2703 @cindex thread identifier (GDB)
2704 For debugging purposes, @value{GDBN} associates its own thread
2705 number---always a single integer---with each thread in your program.
2708 @kindex info threads
2710 Display a summary of all threads currently in your
2711 program. @value{GDBN} displays for each thread (in this order):
2715 the thread number assigned by @value{GDBN}
2718 the target system's thread identifier (@var{systag})
2721 the current stack frame summary for that thread
2725 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2726 indicates the current thread.
2730 @c end table here to get a little more width for example
2733 (@value{GDBP}) info threads
2734 3 process 35 thread 27 0x34e5 in sigpause ()
2735 2 process 35 thread 23 0x34e5 in sigpause ()
2736 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2742 @cindex debugging multithreaded programs (on HP-UX)
2743 @cindex thread identifier (GDB), on HP-UX
2744 For debugging purposes, @value{GDBN} associates its own thread
2745 number---a small integer assigned in thread-creation order---with each
2746 thread in your program.
2748 @cindex @code{New} @var{systag} message, on HP-UX
2749 @cindex thread identifier (system), on HP-UX
2750 @c FIXME-implementors!! It would be more helpful if the [New...] message
2751 @c included GDB's numeric thread handle, so you could just go to that
2752 @c thread without first checking `info threads'.
2753 Whenever @value{GDBN} detects a new thread in your program, it displays
2754 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2755 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2756 whose form varies depending on the particular system. For example, on
2760 [New thread 2 (system thread 26594)]
2764 when @value{GDBN} notices a new thread.
2767 @kindex info threads (HP-UX)
2769 Display a summary of all threads currently in your
2770 program. @value{GDBN} displays for each thread (in this order):
2773 @item the thread number assigned by @value{GDBN}
2775 @item the target system's thread identifier (@var{systag})
2777 @item the current stack frame summary for that thread
2781 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2782 indicates the current thread.
2786 @c end table here to get a little more width for example
2789 (@value{GDBP}) info threads
2790 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2792 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2793 from /usr/lib/libc.2
2794 1 system thread 27905 0x7b003498 in _brk () \@*
2795 from /usr/lib/libc.2
2798 On Solaris, you can display more information about user threads with a
2799 Solaris-specific command:
2802 @item maint info sol-threads
2803 @kindex maint info sol-threads
2804 @cindex thread info (Solaris)
2805 Display info on Solaris user threads.
2809 @kindex thread @var{threadno}
2810 @item thread @var{threadno}
2811 Make thread number @var{threadno} the current thread. The command
2812 argument @var{threadno} is the internal @value{GDBN} thread number, as
2813 shown in the first field of the @samp{info threads} display.
2814 @value{GDBN} responds by displaying the system identifier of the thread
2815 you selected, and its current stack frame summary:
2818 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2819 (@value{GDBP}) thread 2
2820 [Switching to process 35 thread 23]
2821 0x34e5 in sigpause ()
2825 As with the @samp{[New @dots{}]} message, the form of the text after
2826 @samp{Switching to} depends on your system's conventions for identifying
2829 @vindex $_thread@r{, convenience variable}
2830 The debugger convenience variable @samp{$_thread} contains the number
2831 of the current thread. You may find this useful in writing breakpoint
2832 conditional expressions, command scripts, and so forth. See
2833 @xref{Convenience Vars,, Convenience Variables}, for general
2834 information on convenience variables.
2836 @kindex thread apply
2837 @cindex apply command to several threads
2838 @item thread apply [@var{threadno}] [@var{all}] @var{command}
2839 The @code{thread apply} command allows you to apply the named
2840 @var{command} to one or more threads. Specify the numbers of the
2841 threads that you want affected with the command argument
2842 @var{threadno}. It can be a single thread number, one of the numbers
2843 shown in the first field of the @samp{info threads} display; or it
2844 could be a range of thread numbers, as in @code{2-4}. To apply a
2845 command to all threads, type @kbd{thread apply all @var{command}}.
2847 @kindex set print thread-events
2848 @cindex print messages on thread start and exit
2849 @item set print thread-events
2850 @itemx set print thread-events on
2851 @itemx set print thread-events off
2852 The @code{set print thread-events} command allows you to enable or
2853 disable printing of messages when @value{GDBN} notices that new threads have
2854 started or that threads have exited. By default, these messages will
2855 be printed if detection of these events is supported by the target.
2856 Note that these messages cannot be disabled on all targets.
2858 @kindex show print thread-events
2859 @item show print thread-events
2860 Show whether messages will be printed when @value{GDBN} detects that threads
2861 have started and exited.
2864 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2865 more information about how @value{GDBN} behaves when you stop and start
2866 programs with multiple threads.
2868 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2869 watchpoints in programs with multiple threads.
2872 @kindex set libthread-db-search-path
2873 @cindex search path for @code{libthread_db}
2874 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2875 If this variable is set, @var{path} is a colon-separated list of
2876 directories @value{GDBN} will use to search for @code{libthread_db}.
2877 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2880 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2881 @code{libthread_db} library to obtain information about threads in the
2882 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2883 to find @code{libthread_db}. If that fails, @value{GDBN} will continue
2884 with default system shared library directories, and finally the directory
2885 from which @code{libpthread} was loaded in the inferior process.
2887 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2888 @value{GDBN} attempts to initialize it with the current inferior process.
2889 If this initialization fails (which could happen because of a version
2890 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2891 will unload @code{libthread_db}, and continue with the next directory.
2892 If none of @code{libthread_db} libraries initialize successfully,
2893 @value{GDBN} will issue a warning and thread debugging will be disabled.
2895 Setting @code{libthread-db-search-path} is currently implemented
2896 only on some platforms.
2898 @kindex show libthread-db-search-path
2899 @item show libthread-db-search-path
2900 Display current libthread_db search path.
2902 @kindex set debug libthread-db
2903 @kindex show debug libthread-db
2904 @cindex debugging @code{libthread_db}
2905 @item set debug libthread-db
2906 @itemx show debug libthread-db
2907 Turns on or off display of @code{libthread_db}-related events.
2908 Use @code{1} to enable, @code{0} to disable.
2912 @section Debugging Forks
2914 @cindex fork, debugging programs which call
2915 @cindex multiple processes
2916 @cindex processes, multiple
2917 On most systems, @value{GDBN} has no special support for debugging
2918 programs which create additional processes using the @code{fork}
2919 function. When a program forks, @value{GDBN} will continue to debug the
2920 parent process and the child process will run unimpeded. If you have
2921 set a breakpoint in any code which the child then executes, the child
2922 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2923 will cause it to terminate.
2925 However, if you want to debug the child process there is a workaround
2926 which isn't too painful. Put a call to @code{sleep} in the code which
2927 the child process executes after the fork. It may be useful to sleep
2928 only if a certain environment variable is set, or a certain file exists,
2929 so that the delay need not occur when you don't want to run @value{GDBN}
2930 on the child. While the child is sleeping, use the @code{ps} program to
2931 get its process ID. Then tell @value{GDBN} (a new invocation of
2932 @value{GDBN} if you are also debugging the parent process) to attach to
2933 the child process (@pxref{Attach}). From that point on you can debug
2934 the child process just like any other process which you attached to.
2936 On some systems, @value{GDBN} provides support for debugging programs that
2937 create additional processes using the @code{fork} or @code{vfork} functions.
2938 Currently, the only platforms with this feature are HP-UX (11.x and later
2939 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2941 By default, when a program forks, @value{GDBN} will continue to debug
2942 the parent process and the child process will run unimpeded.
2944 If you want to follow the child process instead of the parent process,
2945 use the command @w{@code{set follow-fork-mode}}.
2948 @kindex set follow-fork-mode
2949 @item set follow-fork-mode @var{mode}
2950 Set the debugger response to a program call of @code{fork} or
2951 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2952 process. The @var{mode} argument can be:
2956 The original process is debugged after a fork. The child process runs
2957 unimpeded. This is the default.
2960 The new process is debugged after a fork. The parent process runs
2965 @kindex show follow-fork-mode
2966 @item show follow-fork-mode
2967 Display the current debugger response to a @code{fork} or @code{vfork} call.
2970 @cindex debugging multiple processes
2971 On Linux, if you want to debug both the parent and child processes, use the
2972 command @w{@code{set detach-on-fork}}.
2975 @kindex set detach-on-fork
2976 @item set detach-on-fork @var{mode}
2977 Tells gdb whether to detach one of the processes after a fork, or
2978 retain debugger control over them both.
2982 The child process (or parent process, depending on the value of
2983 @code{follow-fork-mode}) will be detached and allowed to run
2984 independently. This is the default.
2987 Both processes will be held under the control of @value{GDBN}.
2988 One process (child or parent, depending on the value of
2989 @code{follow-fork-mode}) is debugged as usual, while the other
2994 @kindex show detach-on-fork
2995 @item show detach-on-fork
2996 Show whether detach-on-fork mode is on/off.
2999 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3000 will retain control of all forked processes (including nested forks).
3001 You can list the forked processes under the control of @value{GDBN} by
3002 using the @w{@code{info inferiors}} command, and switch from one fork
3003 to another by using the @code{inferior} command (@pxref{Inferiors and
3004 Programs, ,Debugging Multiple Inferiors and Programs}).
3006 To quit debugging one of the forked processes, you can either detach
3007 from it by using the @w{@code{detach inferior}} command (allowing it
3008 to run independently), or kill it using the @w{@code{kill inferior}}
3009 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3012 If you ask to debug a child process and a @code{vfork} is followed by an
3013 @code{exec}, @value{GDBN} executes the new target up to the first
3014 breakpoint in the new target. If you have a breakpoint set on
3015 @code{main} in your original program, the breakpoint will also be set on
3016 the child process's @code{main}.
3018 On some systems, when a child process is spawned by @code{vfork}, you
3019 cannot debug the child or parent until an @code{exec} call completes.
3021 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3022 call executes, the new target restarts. To restart the parent
3023 process, use the @code{file} command with the parent executable name
3024 as its argument. By default, after an @code{exec} call executes,
3025 @value{GDBN} discards the symbols of the previous executable image.
3026 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3030 @kindex set follow-exec-mode
3031 @item set follow-exec-mode @var{mode}
3033 Set debugger response to a program call of @code{exec}. An
3034 @code{exec} call replaces the program image of a process.
3036 @code{follow-exec-mode} can be:
3040 @value{GDBN} creates a new inferior and rebinds the process to this
3041 new inferior. The program the process was running before the
3042 @code{exec} call can be restarted afterwards by restarting the
3048 (@value{GDBP}) info inferiors
3050 Id Description Executable
3053 process 12020 is executing new program: prog2
3054 Program exited normally.
3055 (@value{GDBP}) info inferiors
3056 Id Description Executable
3062 @value{GDBN} keeps the process bound to the same inferior. The new
3063 executable image replaces the previous executable loaded in the
3064 inferior. Restarting the inferior after the @code{exec} call, with
3065 e.g., the @code{run} command, restarts the executable the process was
3066 running after the @code{exec} call. This is the default mode.
3071 (@value{GDBP}) info inferiors
3072 Id Description Executable
3075 process 12020 is executing new program: prog2
3076 Program exited normally.
3077 (@value{GDBP}) info inferiors
3078 Id Description Executable
3085 You can use the @code{catch} command to make @value{GDBN} stop whenever
3086 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3087 Catchpoints, ,Setting Catchpoints}.
3089 @node Checkpoint/Restart
3090 @section Setting a @emph{Bookmark} to Return to Later
3095 @cindex snapshot of a process
3096 @cindex rewind program state
3098 On certain operating systems@footnote{Currently, only
3099 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3100 program's state, called a @dfn{checkpoint}, and come back to it
3103 Returning to a checkpoint effectively undoes everything that has
3104 happened in the program since the @code{checkpoint} was saved. This
3105 includes changes in memory, registers, and even (within some limits)
3106 system state. Effectively, it is like going back in time to the
3107 moment when the checkpoint was saved.
3109 Thus, if you're stepping thru a program and you think you're
3110 getting close to the point where things go wrong, you can save
3111 a checkpoint. Then, if you accidentally go too far and miss
3112 the critical statement, instead of having to restart your program
3113 from the beginning, you can just go back to the checkpoint and
3114 start again from there.
3116 This can be especially useful if it takes a lot of time or
3117 steps to reach the point where you think the bug occurs.
3119 To use the @code{checkpoint}/@code{restart} method of debugging:
3124 Save a snapshot of the debugged program's current execution state.
3125 The @code{checkpoint} command takes no arguments, but each checkpoint
3126 is assigned a small integer id, similar to a breakpoint id.
3128 @kindex info checkpoints
3129 @item info checkpoints
3130 List the checkpoints that have been saved in the current debugging
3131 session. For each checkpoint, the following information will be
3138 @item Source line, or label
3141 @kindex restart @var{checkpoint-id}
3142 @item restart @var{checkpoint-id}
3143 Restore the program state that was saved as checkpoint number
3144 @var{checkpoint-id}. All program variables, registers, stack frames
3145 etc.@: will be returned to the values that they had when the checkpoint
3146 was saved. In essence, gdb will ``wind back the clock'' to the point
3147 in time when the checkpoint was saved.
3149 Note that breakpoints, @value{GDBN} variables, command history etc.
3150 are not affected by restoring a checkpoint. In general, a checkpoint
3151 only restores things that reside in the program being debugged, not in
3154 @kindex delete checkpoint @var{checkpoint-id}
3155 @item delete checkpoint @var{checkpoint-id}
3156 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3160 Returning to a previously saved checkpoint will restore the user state
3161 of the program being debugged, plus a significant subset of the system
3162 (OS) state, including file pointers. It won't ``un-write'' data from
3163 a file, but it will rewind the file pointer to the previous location,
3164 so that the previously written data can be overwritten. For files
3165 opened in read mode, the pointer will also be restored so that the
3166 previously read data can be read again.
3168 Of course, characters that have been sent to a printer (or other
3169 external device) cannot be ``snatched back'', and characters received
3170 from eg.@: a serial device can be removed from internal program buffers,
3171 but they cannot be ``pushed back'' into the serial pipeline, ready to
3172 be received again. Similarly, the actual contents of files that have
3173 been changed cannot be restored (at this time).
3175 However, within those constraints, you actually can ``rewind'' your
3176 program to a previously saved point in time, and begin debugging it
3177 again --- and you can change the course of events so as to debug a
3178 different execution path this time.
3180 @cindex checkpoints and process id
3181 Finally, there is one bit of internal program state that will be
3182 different when you return to a checkpoint --- the program's process
3183 id. Each checkpoint will have a unique process id (or @var{pid}),
3184 and each will be different from the program's original @var{pid}.
3185 If your program has saved a local copy of its process id, this could
3186 potentially pose a problem.
3188 @subsection A Non-obvious Benefit of Using Checkpoints
3190 On some systems such as @sc{gnu}/Linux, address space randomization
3191 is performed on new processes for security reasons. This makes it
3192 difficult or impossible to set a breakpoint, or watchpoint, on an
3193 absolute address if you have to restart the program, since the
3194 absolute location of a symbol will change from one execution to the
3197 A checkpoint, however, is an @emph{identical} copy of a process.
3198 Therefore if you create a checkpoint at (eg.@:) the start of main,
3199 and simply return to that checkpoint instead of restarting the
3200 process, you can avoid the effects of address randomization and
3201 your symbols will all stay in the same place.
3204 @chapter Stopping and Continuing
3206 The principal purposes of using a debugger are so that you can stop your
3207 program before it terminates; or so that, if your program runs into
3208 trouble, you can investigate and find out why.
3210 Inside @value{GDBN}, your program may stop for any of several reasons,
3211 such as a signal, a breakpoint, or reaching a new line after a
3212 @value{GDBN} command such as @code{step}. You may then examine and
3213 change variables, set new breakpoints or remove old ones, and then
3214 continue execution. Usually, the messages shown by @value{GDBN} provide
3215 ample explanation of the status of your program---but you can also
3216 explicitly request this information at any time.
3219 @kindex info program
3221 Display information about the status of your program: whether it is
3222 running or not, what process it is, and why it stopped.
3226 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3227 * Continuing and Stepping:: Resuming execution
3229 * Thread Stops:: Stopping and starting multi-thread programs
3233 @section Breakpoints, Watchpoints, and Catchpoints
3236 A @dfn{breakpoint} makes your program stop whenever a certain point in
3237 the program is reached. For each breakpoint, you can add conditions to
3238 control in finer detail whether your program stops. You can set
3239 breakpoints with the @code{break} command and its variants (@pxref{Set
3240 Breaks, ,Setting Breakpoints}), to specify the place where your program
3241 should stop by line number, function name or exact address in the
3244 On some systems, you can set breakpoints in shared libraries before
3245 the executable is run. There is a minor limitation on HP-UX systems:
3246 you must wait until the executable is run in order to set breakpoints
3247 in shared library routines that are not called directly by the program
3248 (for example, routines that are arguments in a @code{pthread_create}
3252 @cindex data breakpoints
3253 @cindex memory tracing
3254 @cindex breakpoint on memory address
3255 @cindex breakpoint on variable modification
3256 A @dfn{watchpoint} is a special breakpoint that stops your program
3257 when the value of an expression changes. The expression may be a value
3258 of a variable, or it could involve values of one or more variables
3259 combined by operators, such as @samp{a + b}. This is sometimes called
3260 @dfn{data breakpoints}. You must use a different command to set
3261 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3262 from that, you can manage a watchpoint like any other breakpoint: you
3263 enable, disable, and delete both breakpoints and watchpoints using the
3266 You can arrange to have values from your program displayed automatically
3267 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3271 @cindex breakpoint on events
3272 A @dfn{catchpoint} is another special breakpoint that stops your program
3273 when a certain kind of event occurs, such as the throwing of a C@t{++}
3274 exception or the loading of a library. As with watchpoints, you use a
3275 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3276 Catchpoints}), but aside from that, you can manage a catchpoint like any
3277 other breakpoint. (To stop when your program receives a signal, use the
3278 @code{handle} command; see @ref{Signals, ,Signals}.)
3280 @cindex breakpoint numbers
3281 @cindex numbers for breakpoints
3282 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3283 catchpoint when you create it; these numbers are successive integers
3284 starting with one. In many of the commands for controlling various
3285 features of breakpoints you use the breakpoint number to say which
3286 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3287 @dfn{disabled}; if disabled, it has no effect on your program until you
3290 @cindex breakpoint ranges
3291 @cindex ranges of breakpoints
3292 Some @value{GDBN} commands accept a range of breakpoints on which to
3293 operate. A breakpoint range is either a single breakpoint number, like
3294 @samp{5}, or two such numbers, in increasing order, separated by a
3295 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3296 all breakpoints in that range are operated on.
3299 * Set Breaks:: Setting breakpoints
3300 * Set Watchpoints:: Setting watchpoints
3301 * Set Catchpoints:: Setting catchpoints
3302 * Delete Breaks:: Deleting breakpoints
3303 * Disabling:: Disabling breakpoints
3304 * Conditions:: Break conditions
3305 * Break Commands:: Breakpoint command lists
3306 * Save Breakpoints:: How to save breakpoints in a file
3307 * Error in Breakpoints:: ``Cannot insert breakpoints''
3308 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3312 @subsection Setting Breakpoints
3314 @c FIXME LMB what does GDB do if no code on line of breakpt?
3315 @c consider in particular declaration with/without initialization.
3317 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3320 @kindex b @r{(@code{break})}
3321 @vindex $bpnum@r{, convenience variable}
3322 @cindex latest breakpoint
3323 Breakpoints are set with the @code{break} command (abbreviated
3324 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3325 number of the breakpoint you've set most recently; see @ref{Convenience
3326 Vars,, Convenience Variables}, for a discussion of what you can do with
3327 convenience variables.
3330 @item break @var{location}
3331 Set a breakpoint at the given @var{location}, which can specify a
3332 function name, a line number, or an address of an instruction.
3333 (@xref{Specify Location}, for a list of all the possible ways to
3334 specify a @var{location}.) The breakpoint will stop your program just
3335 before it executes any of the code in the specified @var{location}.
3337 When using source languages that permit overloading of symbols, such as
3338 C@t{++}, a function name may refer to more than one possible place to break.
3339 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3342 It is also possible to insert a breakpoint that will stop the program
3343 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3344 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3347 When called without any arguments, @code{break} sets a breakpoint at
3348 the next instruction to be executed in the selected stack frame
3349 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3350 innermost, this makes your program stop as soon as control
3351 returns to that frame. This is similar to the effect of a
3352 @code{finish} command in the frame inside the selected frame---except
3353 that @code{finish} does not leave an active breakpoint. If you use
3354 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3355 the next time it reaches the current location; this may be useful
3358 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3359 least one instruction has been executed. If it did not do this, you
3360 would be unable to proceed past a breakpoint without first disabling the
3361 breakpoint. This rule applies whether or not the breakpoint already
3362 existed when your program stopped.
3364 @item break @dots{} if @var{cond}
3365 Set a breakpoint with condition @var{cond}; evaluate the expression
3366 @var{cond} each time the breakpoint is reached, and stop only if the
3367 value is nonzero---that is, if @var{cond} evaluates as true.
3368 @samp{@dots{}} stands for one of the possible arguments described
3369 above (or no argument) specifying where to break. @xref{Conditions,
3370 ,Break Conditions}, for more information on breakpoint conditions.
3373 @item tbreak @var{args}
3374 Set a breakpoint enabled only for one stop. @var{args} are the
3375 same as for the @code{break} command, and the breakpoint is set in the same
3376 way, but the breakpoint is automatically deleted after the first time your
3377 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3380 @cindex hardware breakpoints
3381 @item hbreak @var{args}
3382 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3383 @code{break} command and the breakpoint is set in the same way, but the
3384 breakpoint requires hardware support and some target hardware may not
3385 have this support. The main purpose of this is EPROM/ROM code
3386 debugging, so you can set a breakpoint at an instruction without
3387 changing the instruction. This can be used with the new trap-generation
3388 provided by SPARClite DSU and most x86-based targets. These targets
3389 will generate traps when a program accesses some data or instruction
3390 address that is assigned to the debug registers. However the hardware
3391 breakpoint registers can take a limited number of breakpoints. For
3392 example, on the DSU, only two data breakpoints can be set at a time, and
3393 @value{GDBN} will reject this command if more than two are used. Delete
3394 or disable unused hardware breakpoints before setting new ones
3395 (@pxref{Disabling, ,Disabling Breakpoints}).
3396 @xref{Conditions, ,Break Conditions}.
3397 For remote targets, you can restrict the number of hardware
3398 breakpoints @value{GDBN} will use, see @ref{set remote
3399 hardware-breakpoint-limit}.
3402 @item thbreak @var{args}
3403 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3404 are the same as for the @code{hbreak} command and the breakpoint is set in
3405 the same way. However, like the @code{tbreak} command,
3406 the breakpoint is automatically deleted after the
3407 first time your program stops there. Also, like the @code{hbreak}
3408 command, the breakpoint requires hardware support and some target hardware
3409 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3410 See also @ref{Conditions, ,Break Conditions}.
3413 @cindex regular expression
3414 @cindex breakpoints at functions matching a regexp
3415 @cindex set breakpoints in many functions
3416 @item rbreak @var{regex}
3417 Set breakpoints on all functions matching the regular expression
3418 @var{regex}. This command sets an unconditional breakpoint on all
3419 matches, printing a list of all breakpoints it set. Once these
3420 breakpoints are set, they are treated just like the breakpoints set with
3421 the @code{break} command. You can delete them, disable them, or make
3422 them conditional the same way as any other breakpoint.
3424 The syntax of the regular expression is the standard one used with tools
3425 like @file{grep}. Note that this is different from the syntax used by
3426 shells, so for instance @code{foo*} matches all functions that include
3427 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3428 @code{.*} leading and trailing the regular expression you supply, so to
3429 match only functions that begin with @code{foo}, use @code{^foo}.
3431 @cindex non-member C@t{++} functions, set breakpoint in
3432 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3433 breakpoints on overloaded functions that are not members of any special
3436 @cindex set breakpoints on all functions
3437 The @code{rbreak} command can be used to set breakpoints in
3438 @strong{all} the functions in a program, like this:
3441 (@value{GDBP}) rbreak .
3444 @item rbreak @var{file}:@var{regex}
3445 If @code{rbreak} is called with a filename qualification, it limits
3446 the search for functions matching the given regular expression to the
3447 specified @var{file}. This can be used, for example, to set breakpoints on
3448 every function in a given file:
3451 (@value{GDBP}) rbreak file.c:.
3454 The colon separating the filename qualifier from the regex may
3455 optionally be surrounded by spaces.
3457 @kindex info breakpoints
3458 @cindex @code{$_} and @code{info breakpoints}
3459 @item info breakpoints @r{[}@var{n}@r{]}
3460 @itemx info break @r{[}@var{n}@r{]}
3461 Print a table of all breakpoints, watchpoints, and catchpoints set and
3462 not deleted. Optional argument @var{n} means print information only
3463 about the specified breakpoint (or watchpoint or catchpoint). For
3464 each breakpoint, following columns are printed:
3467 @item Breakpoint Numbers
3469 Breakpoint, watchpoint, or catchpoint.
3471 Whether the breakpoint is marked to be disabled or deleted when hit.
3472 @item Enabled or Disabled
3473 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3474 that are not enabled.
3476 Where the breakpoint is in your program, as a memory address. For a
3477 pending breakpoint whose address is not yet known, this field will
3478 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3479 library that has the symbol or line referred by breakpoint is loaded.
3480 See below for details. A breakpoint with several locations will
3481 have @samp{<MULTIPLE>} in this field---see below for details.
3483 Where the breakpoint is in the source for your program, as a file and
3484 line number. For a pending breakpoint, the original string passed to
3485 the breakpoint command will be listed as it cannot be resolved until
3486 the appropriate shared library is loaded in the future.
3490 If a breakpoint is conditional, @code{info break} shows the condition on
3491 the line following the affected breakpoint; breakpoint commands, if any,
3492 are listed after that. A pending breakpoint is allowed to have a condition
3493 specified for it. The condition is not parsed for validity until a shared
3494 library is loaded that allows the pending breakpoint to resolve to a
3498 @code{info break} with a breakpoint
3499 number @var{n} as argument lists only that breakpoint. The
3500 convenience variable @code{$_} and the default examining-address for
3501 the @code{x} command are set to the address of the last breakpoint
3502 listed (@pxref{Memory, ,Examining Memory}).
3505 @code{info break} displays a count of the number of times the breakpoint
3506 has been hit. This is especially useful in conjunction with the
3507 @code{ignore} command. You can ignore a large number of breakpoint
3508 hits, look at the breakpoint info to see how many times the breakpoint
3509 was hit, and then run again, ignoring one less than that number. This
3510 will get you quickly to the last hit of that breakpoint.
3513 @value{GDBN} allows you to set any number of breakpoints at the same place in
3514 your program. There is nothing silly or meaningless about this. When
3515 the breakpoints are conditional, this is even useful
3516 (@pxref{Conditions, ,Break Conditions}).
3518 @cindex multiple locations, breakpoints
3519 @cindex breakpoints, multiple locations
3520 It is possible that a breakpoint corresponds to several locations
3521 in your program. Examples of this situation are:
3525 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3526 instances of the function body, used in different cases.
3529 For a C@t{++} template function, a given line in the function can
3530 correspond to any number of instantiations.
3533 For an inlined function, a given source line can correspond to
3534 several places where that function is inlined.
3537 In all those cases, @value{GDBN} will insert a breakpoint at all
3538 the relevant locations@footnote{
3539 As of this writing, multiple-location breakpoints work only if there's
3540 line number information for all the locations. This means that they
3541 will generally not work in system libraries, unless you have debug
3542 info with line numbers for them.}.
3544 A breakpoint with multiple locations is displayed in the breakpoint
3545 table using several rows---one header row, followed by one row for
3546 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3547 address column. The rows for individual locations contain the actual
3548 addresses for locations, and show the functions to which those
3549 locations belong. The number column for a location is of the form
3550 @var{breakpoint-number}.@var{location-number}.
3555 Num Type Disp Enb Address What
3556 1 breakpoint keep y <MULTIPLE>
3558 breakpoint already hit 1 time
3559 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3560 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3563 Each location can be individually enabled or disabled by passing
3564 @var{breakpoint-number}.@var{location-number} as argument to the
3565 @code{enable} and @code{disable} commands. Note that you cannot
3566 delete the individual locations from the list, you can only delete the
3567 entire list of locations that belong to their parent breakpoint (with
3568 the @kbd{delete @var{num}} command, where @var{num} is the number of
3569 the parent breakpoint, 1 in the above example). Disabling or enabling
3570 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3571 that belong to that breakpoint.
3573 @cindex pending breakpoints
3574 It's quite common to have a breakpoint inside a shared library.
3575 Shared libraries can be loaded and unloaded explicitly,
3576 and possibly repeatedly, as the program is executed. To support
3577 this use case, @value{GDBN} updates breakpoint locations whenever
3578 any shared library is loaded or unloaded. Typically, you would
3579 set a breakpoint in a shared library at the beginning of your
3580 debugging session, when the library is not loaded, and when the
3581 symbols from the library are not available. When you try to set
3582 breakpoint, @value{GDBN} will ask you if you want to set
3583 a so called @dfn{pending breakpoint}---breakpoint whose address
3584 is not yet resolved.
3586 After the program is run, whenever a new shared library is loaded,
3587 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3588 shared library contains the symbol or line referred to by some
3589 pending breakpoint, that breakpoint is resolved and becomes an
3590 ordinary breakpoint. When a library is unloaded, all breakpoints
3591 that refer to its symbols or source lines become pending again.
3593 This logic works for breakpoints with multiple locations, too. For
3594 example, if you have a breakpoint in a C@t{++} template function, and
3595 a newly loaded shared library has an instantiation of that template,
3596 a new location is added to the list of locations for the breakpoint.
3598 Except for having unresolved address, pending breakpoints do not
3599 differ from regular breakpoints. You can set conditions or commands,
3600 enable and disable them and perform other breakpoint operations.
3602 @value{GDBN} provides some additional commands for controlling what
3603 happens when the @samp{break} command cannot resolve breakpoint
3604 address specification to an address:
3606 @kindex set breakpoint pending
3607 @kindex show breakpoint pending
3609 @item set breakpoint pending auto
3610 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3611 location, it queries you whether a pending breakpoint should be created.
3613 @item set breakpoint pending on
3614 This indicates that an unrecognized breakpoint location should automatically
3615 result in a pending breakpoint being created.
3617 @item set breakpoint pending off
3618 This indicates that pending breakpoints are not to be created. Any
3619 unrecognized breakpoint location results in an error. This setting does
3620 not affect any pending breakpoints previously created.
3622 @item show breakpoint pending
3623 Show the current behavior setting for creating pending breakpoints.
3626 The settings above only affect the @code{break} command and its
3627 variants. Once breakpoint is set, it will be automatically updated
3628 as shared libraries are loaded and unloaded.
3630 @cindex automatic hardware breakpoints
3631 For some targets, @value{GDBN} can automatically decide if hardware or
3632 software breakpoints should be used, depending on whether the
3633 breakpoint address is read-only or read-write. This applies to
3634 breakpoints set with the @code{break} command as well as to internal
3635 breakpoints set by commands like @code{next} and @code{finish}. For
3636 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3639 You can control this automatic behaviour with the following commands::
3641 @kindex set breakpoint auto-hw
3642 @kindex show breakpoint auto-hw
3644 @item set breakpoint auto-hw on
3645 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3646 will try to use the target memory map to decide if software or hardware
3647 breakpoint must be used.
3649 @item set breakpoint auto-hw off
3650 This indicates @value{GDBN} should not automatically select breakpoint
3651 type. If the target provides a memory map, @value{GDBN} will warn when
3652 trying to set software breakpoint at a read-only address.
3655 @value{GDBN} normally implements breakpoints by replacing the program code
3656 at the breakpoint address with a special instruction, which, when
3657 executed, given control to the debugger. By default, the program
3658 code is so modified only when the program is resumed. As soon as
3659 the program stops, @value{GDBN} restores the original instructions. This
3660 behaviour guards against leaving breakpoints inserted in the
3661 target should gdb abrubptly disconnect. However, with slow remote
3662 targets, inserting and removing breakpoint can reduce the performance.
3663 This behavior can be controlled with the following commands::
3665 @kindex set breakpoint always-inserted
3666 @kindex show breakpoint always-inserted
3668 @item set breakpoint always-inserted off
3669 All breakpoints, including newly added by the user, are inserted in
3670 the target only when the target is resumed. All breakpoints are
3671 removed from the target when it stops.
3673 @item set breakpoint always-inserted on
3674 Causes all breakpoints to be inserted in the target at all times. If
3675 the user adds a new breakpoint, or changes an existing breakpoint, the
3676 breakpoints in the target are updated immediately. A breakpoint is
3677 removed from the target only when breakpoint itself is removed.
3679 @cindex non-stop mode, and @code{breakpoint always-inserted}
3680 @item set breakpoint always-inserted auto
3681 This is the default mode. If @value{GDBN} is controlling the inferior
3682 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3683 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3684 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3685 @code{breakpoint always-inserted} mode is off.
3688 @cindex negative breakpoint numbers
3689 @cindex internal @value{GDBN} breakpoints
3690 @value{GDBN} itself sometimes sets breakpoints in your program for
3691 special purposes, such as proper handling of @code{longjmp} (in C
3692 programs). These internal breakpoints are assigned negative numbers,
3693 starting with @code{-1}; @samp{info breakpoints} does not display them.
3694 You can see these breakpoints with the @value{GDBN} maintenance command
3695 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3698 @node Set Watchpoints
3699 @subsection Setting Watchpoints
3701 @cindex setting watchpoints
3702 You can use a watchpoint to stop execution whenever the value of an
3703 expression changes, without having to predict a particular place where
3704 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3705 The expression may be as simple as the value of a single variable, or
3706 as complex as many variables combined by operators. Examples include:
3710 A reference to the value of a single variable.
3713 An address cast to an appropriate data type. For example,
3714 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3715 address (assuming an @code{int} occupies 4 bytes).
3718 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3719 expression can use any operators valid in the program's native
3720 language (@pxref{Languages}).
3723 You can set a watchpoint on an expression even if the expression can
3724 not be evaluated yet. For instance, you can set a watchpoint on
3725 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3726 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3727 the expression produces a valid value. If the expression becomes
3728 valid in some other way than changing a variable (e.g.@: if the memory
3729 pointed to by @samp{*global_ptr} becomes readable as the result of a
3730 @code{malloc} call), @value{GDBN} may not stop until the next time
3731 the expression changes.
3733 @cindex software watchpoints
3734 @cindex hardware watchpoints
3735 Depending on your system, watchpoints may be implemented in software or
3736 hardware. @value{GDBN} does software watchpointing by single-stepping your
3737 program and testing the variable's value each time, which is hundreds of
3738 times slower than normal execution. (But this may still be worth it, to
3739 catch errors where you have no clue what part of your program is the
3742 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3743 x86-based targets, @value{GDBN} includes support for hardware
3744 watchpoints, which do not slow down the running of your program.
3748 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]}
3749 Set a watchpoint for an expression. @value{GDBN} will break when the
3750 expression @var{expr} is written into by the program and its value
3751 changes. The simplest (and the most popular) use of this command is
3752 to watch the value of a single variable:
3755 (@value{GDBP}) watch foo
3758 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3759 clause, @value{GDBN} breaks only when the thread identified by
3760 @var{threadnum} changes the value of @var{expr}. If any other threads
3761 change the value of @var{expr}, @value{GDBN} will not break. Note
3762 that watchpoints restricted to a single thread in this way only work
3763 with Hardware Watchpoints.
3765 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3766 (see below). The @code{-location} argument tells @value{GDBN} to
3767 instead watch the memory referred to by @var{expr}. In this case,
3768 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3769 and watch the memory at that address. The type of the result is used
3770 to determine the size of the watched memory. If the expression's
3771 result does not have an address, then @value{GDBN} will print an
3775 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]}
3776 Set a watchpoint that will break when the value of @var{expr} is read
3780 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]}
3781 Set a watchpoint that will break when @var{expr} is either read from
3782 or written into by the program.
3784 @kindex info watchpoints @r{[}@var{n}@r{]}
3785 @item info watchpoints
3786 This command prints a list of watchpoints, using the same format as
3787 @code{info break} (@pxref{Set Breaks}).
3790 If you watch for a change in a numerically entered address you need to
3791 dereference it, as the address itself is just a constant number which will
3792 never change. @value{GDBN} refuses to create a watchpoint that watches
3793 a never-changing value:
3796 (@value{GDBP}) watch 0x600850
3797 Cannot watch constant value 0x600850.
3798 (@value{GDBP}) watch *(int *) 0x600850
3799 Watchpoint 1: *(int *) 6293584
3802 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3803 watchpoints execute very quickly, and the debugger reports a change in
3804 value at the exact instruction where the change occurs. If @value{GDBN}
3805 cannot set a hardware watchpoint, it sets a software watchpoint, which
3806 executes more slowly and reports the change in value at the next
3807 @emph{statement}, not the instruction, after the change occurs.
3809 @cindex use only software watchpoints
3810 You can force @value{GDBN} to use only software watchpoints with the
3811 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3812 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3813 the underlying system supports them. (Note that hardware-assisted
3814 watchpoints that were set @emph{before} setting
3815 @code{can-use-hw-watchpoints} to zero will still use the hardware
3816 mechanism of watching expression values.)
3819 @item set can-use-hw-watchpoints
3820 @kindex set can-use-hw-watchpoints
3821 Set whether or not to use hardware watchpoints.
3823 @item show can-use-hw-watchpoints
3824 @kindex show can-use-hw-watchpoints
3825 Show the current mode of using hardware watchpoints.
3828 For remote targets, you can restrict the number of hardware
3829 watchpoints @value{GDBN} will use, see @ref{set remote
3830 hardware-breakpoint-limit}.
3832 When you issue the @code{watch} command, @value{GDBN} reports
3835 Hardware watchpoint @var{num}: @var{expr}
3839 if it was able to set a hardware watchpoint.
3841 Currently, the @code{awatch} and @code{rwatch} commands can only set
3842 hardware watchpoints, because accesses to data that don't change the
3843 value of the watched expression cannot be detected without examining
3844 every instruction as it is being executed, and @value{GDBN} does not do
3845 that currently. If @value{GDBN} finds that it is unable to set a
3846 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3847 will print a message like this:
3850 Expression cannot be implemented with read/access watchpoint.
3853 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3854 data type of the watched expression is wider than what a hardware
3855 watchpoint on the target machine can handle. For example, some systems
3856 can only watch regions that are up to 4 bytes wide; on such systems you
3857 cannot set hardware watchpoints for an expression that yields a
3858 double-precision floating-point number (which is typically 8 bytes
3859 wide). As a work-around, it might be possible to break the large region
3860 into a series of smaller ones and watch them with separate watchpoints.
3862 If you set too many hardware watchpoints, @value{GDBN} might be unable
3863 to insert all of them when you resume the execution of your program.
3864 Since the precise number of active watchpoints is unknown until such
3865 time as the program is about to be resumed, @value{GDBN} might not be
3866 able to warn you about this when you set the watchpoints, and the
3867 warning will be printed only when the program is resumed:
3870 Hardware watchpoint @var{num}: Could not insert watchpoint
3874 If this happens, delete or disable some of the watchpoints.
3876 Watching complex expressions that reference many variables can also
3877 exhaust the resources available for hardware-assisted watchpoints.
3878 That's because @value{GDBN} needs to watch every variable in the
3879 expression with separately allocated resources.
3881 If you call a function interactively using @code{print} or @code{call},
3882 any watchpoints you have set will be inactive until @value{GDBN} reaches another
3883 kind of breakpoint or the call completes.
3885 @value{GDBN} automatically deletes watchpoints that watch local
3886 (automatic) variables, or expressions that involve such variables, when
3887 they go out of scope, that is, when the execution leaves the block in
3888 which these variables were defined. In particular, when the program
3889 being debugged terminates, @emph{all} local variables go out of scope,
3890 and so only watchpoints that watch global variables remain set. If you
3891 rerun the program, you will need to set all such watchpoints again. One
3892 way of doing that would be to set a code breakpoint at the entry to the
3893 @code{main} function and when it breaks, set all the watchpoints.
3895 @cindex watchpoints and threads
3896 @cindex threads and watchpoints
3897 In multi-threaded programs, watchpoints will detect changes to the
3898 watched expression from every thread.
3901 @emph{Warning:} In multi-threaded programs, software watchpoints
3902 have only limited usefulness. If @value{GDBN} creates a software
3903 watchpoint, it can only watch the value of an expression @emph{in a
3904 single thread}. If you are confident that the expression can only
3905 change due to the current thread's activity (and if you are also
3906 confident that no other thread can become current), then you can use
3907 software watchpoints as usual. However, @value{GDBN} may not notice
3908 when a non-current thread's activity changes the expression. (Hardware
3909 watchpoints, in contrast, watch an expression in all threads.)
3912 @xref{set remote hardware-watchpoint-limit}.
3914 @node Set Catchpoints
3915 @subsection Setting Catchpoints
3916 @cindex catchpoints, setting
3917 @cindex exception handlers
3918 @cindex event handling
3920 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3921 kinds of program events, such as C@t{++} exceptions or the loading of a
3922 shared library. Use the @code{catch} command to set a catchpoint.
3926 @item catch @var{event}
3927 Stop when @var{event} occurs. @var{event} can be any of the following:
3930 @cindex stop on C@t{++} exceptions
3931 The throwing of a C@t{++} exception.
3934 The catching of a C@t{++} exception.
3937 @cindex Ada exception catching
3938 @cindex catch Ada exceptions
3939 An Ada exception being raised. If an exception name is specified
3940 at the end of the command (eg @code{catch exception Program_Error}),
3941 the debugger will stop only when this specific exception is raised.
3942 Otherwise, the debugger stops execution when any Ada exception is raised.
3944 When inserting an exception catchpoint on a user-defined exception whose
3945 name is identical to one of the exceptions defined by the language, the
3946 fully qualified name must be used as the exception name. Otherwise,
3947 @value{GDBN} will assume that it should stop on the pre-defined exception
3948 rather than the user-defined one. For instance, assuming an exception
3949 called @code{Constraint_Error} is defined in package @code{Pck}, then
3950 the command to use to catch such exceptions is @kbd{catch exception
3951 Pck.Constraint_Error}.
3953 @item exception unhandled
3954 An exception that was raised but is not handled by the program.
3957 A failed Ada assertion.
3960 @cindex break on fork/exec
3961 A call to @code{exec}. This is currently only available for HP-UX
3965 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
3966 @cindex break on a system call.
3967 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
3968 syscall is a mechanism for application programs to request a service
3969 from the operating system (OS) or one of the OS system services.
3970 @value{GDBN} can catch some or all of the syscalls issued by the
3971 debuggee, and show the related information for each syscall. If no
3972 argument is specified, calls to and returns from all system calls
3975 @var{name} can be any system call name that is valid for the
3976 underlying OS. Just what syscalls are valid depends on the OS. On
3977 GNU and Unix systems, you can find the full list of valid syscall
3978 names on @file{/usr/include/asm/unistd.h}.
3980 @c For MS-Windows, the syscall names and the corresponding numbers
3981 @c can be found, e.g., on this URL:
3982 @c http://www.metasploit.com/users/opcode/syscalls.html
3983 @c but we don't support Windows syscalls yet.
3985 Normally, @value{GDBN} knows in advance which syscalls are valid for
3986 each OS, so you can use the @value{GDBN} command-line completion
3987 facilities (@pxref{Completion,, command completion}) to list the
3990 You may also specify the system call numerically. A syscall's
3991 number is the value passed to the OS's syscall dispatcher to
3992 identify the requested service. When you specify the syscall by its
3993 name, @value{GDBN} uses its database of syscalls to convert the name
3994 into the corresponding numeric code, but using the number directly
3995 may be useful if @value{GDBN}'s database does not have the complete
3996 list of syscalls on your system (e.g., because @value{GDBN} lags
3997 behind the OS upgrades).
3999 The example below illustrates how this command works if you don't provide
4003 (@value{GDBP}) catch syscall
4004 Catchpoint 1 (syscall)
4006 Starting program: /tmp/catch-syscall
4008 Catchpoint 1 (call to syscall 'close'), \
4009 0xffffe424 in __kernel_vsyscall ()
4013 Catchpoint 1 (returned from syscall 'close'), \
4014 0xffffe424 in __kernel_vsyscall ()
4018 Here is an example of catching a system call by name:
4021 (@value{GDBP}) catch syscall chroot
4022 Catchpoint 1 (syscall 'chroot' [61])
4024 Starting program: /tmp/catch-syscall
4026 Catchpoint 1 (call to syscall 'chroot'), \
4027 0xffffe424 in __kernel_vsyscall ()
4031 Catchpoint 1 (returned from syscall 'chroot'), \
4032 0xffffe424 in __kernel_vsyscall ()
4036 An example of specifying a system call numerically. In the case
4037 below, the syscall number has a corresponding entry in the XML
4038 file, so @value{GDBN} finds its name and prints it:
4041 (@value{GDBP}) catch syscall 252
4042 Catchpoint 1 (syscall(s) 'exit_group')
4044 Starting program: /tmp/catch-syscall
4046 Catchpoint 1 (call to syscall 'exit_group'), \
4047 0xffffe424 in __kernel_vsyscall ()
4051 Program exited normally.
4055 However, there can be situations when there is no corresponding name
4056 in XML file for that syscall number. In this case, @value{GDBN} prints
4057 a warning message saying that it was not able to find the syscall name,
4058 but the catchpoint will be set anyway. See the example below:
4061 (@value{GDBP}) catch syscall 764
4062 warning: The number '764' does not represent a known syscall.
4063 Catchpoint 2 (syscall 764)
4067 If you configure @value{GDBN} using the @samp{--without-expat} option,
4068 it will not be able to display syscall names. Also, if your
4069 architecture does not have an XML file describing its system calls,
4070 you will not be able to see the syscall names. It is important to
4071 notice that these two features are used for accessing the syscall
4072 name database. In either case, you will see a warning like this:
4075 (@value{GDBP}) catch syscall
4076 warning: Could not open "syscalls/i386-linux.xml"
4077 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4078 GDB will not be able to display syscall names.
4079 Catchpoint 1 (syscall)
4083 Of course, the file name will change depending on your architecture and system.
4085 Still using the example above, you can also try to catch a syscall by its
4086 number. In this case, you would see something like:
4089 (@value{GDBP}) catch syscall 252
4090 Catchpoint 1 (syscall(s) 252)
4093 Again, in this case @value{GDBN} would not be able to display syscall's names.
4096 A call to @code{fork}. This is currently only available for HP-UX
4100 A call to @code{vfork}. This is currently only available for HP-UX
4105 @item tcatch @var{event}
4106 Set a catchpoint that is enabled only for one stop. The catchpoint is
4107 automatically deleted after the first time the event is caught.
4111 Use the @code{info break} command to list the current catchpoints.
4113 There are currently some limitations to C@t{++} exception handling
4114 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4118 If you call a function interactively, @value{GDBN} normally returns
4119 control to you when the function has finished executing. If the call
4120 raises an exception, however, the call may bypass the mechanism that
4121 returns control to you and cause your program either to abort or to
4122 simply continue running until it hits a breakpoint, catches a signal
4123 that @value{GDBN} is listening for, or exits. This is the case even if
4124 you set a catchpoint for the exception; catchpoints on exceptions are
4125 disabled within interactive calls.
4128 You cannot raise an exception interactively.
4131 You cannot install an exception handler interactively.
4134 @cindex raise exceptions
4135 Sometimes @code{catch} is not the best way to debug exception handling:
4136 if you need to know exactly where an exception is raised, it is better to
4137 stop @emph{before} the exception handler is called, since that way you
4138 can see the stack before any unwinding takes place. If you set a
4139 breakpoint in an exception handler instead, it may not be easy to find
4140 out where the exception was raised.
4142 To stop just before an exception handler is called, you need some
4143 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4144 raised by calling a library function named @code{__raise_exception}
4145 which has the following ANSI C interface:
4148 /* @var{addr} is where the exception identifier is stored.
4149 @var{id} is the exception identifier. */
4150 void __raise_exception (void **addr, void *id);
4154 To make the debugger catch all exceptions before any stack
4155 unwinding takes place, set a breakpoint on @code{__raise_exception}
4156 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4158 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4159 that depends on the value of @var{id}, you can stop your program when
4160 a specific exception is raised. You can use multiple conditional
4161 breakpoints to stop your program when any of a number of exceptions are
4166 @subsection Deleting Breakpoints
4168 @cindex clearing breakpoints, watchpoints, catchpoints
4169 @cindex deleting breakpoints, watchpoints, catchpoints
4170 It is often necessary to eliminate a breakpoint, watchpoint, or
4171 catchpoint once it has done its job and you no longer want your program
4172 to stop there. This is called @dfn{deleting} the breakpoint. A
4173 breakpoint that has been deleted no longer exists; it is forgotten.
4175 With the @code{clear} command you can delete breakpoints according to
4176 where they are in your program. With the @code{delete} command you can
4177 delete individual breakpoints, watchpoints, or catchpoints by specifying
4178 their breakpoint numbers.
4180 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4181 automatically ignores breakpoints on the first instruction to be executed
4182 when you continue execution without changing the execution address.
4187 Delete any breakpoints at the next instruction to be executed in the
4188 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4189 the innermost frame is selected, this is a good way to delete a
4190 breakpoint where your program just stopped.
4192 @item clear @var{location}
4193 Delete any breakpoints set at the specified @var{location}.
4194 @xref{Specify Location}, for the various forms of @var{location}; the
4195 most useful ones are listed below:
4198 @item clear @var{function}
4199 @itemx clear @var{filename}:@var{function}
4200 Delete any breakpoints set at entry to the named @var{function}.
4202 @item clear @var{linenum}
4203 @itemx clear @var{filename}:@var{linenum}
4204 Delete any breakpoints set at or within the code of the specified
4205 @var{linenum} of the specified @var{filename}.
4208 @cindex delete breakpoints
4210 @kindex d @r{(@code{delete})}
4211 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4212 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4213 ranges specified as arguments. If no argument is specified, delete all
4214 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4215 confirm off}). You can abbreviate this command as @code{d}.
4219 @subsection Disabling Breakpoints
4221 @cindex enable/disable a breakpoint
4222 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4223 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4224 it had been deleted, but remembers the information on the breakpoint so
4225 that you can @dfn{enable} it again later.
4227 You disable and enable breakpoints, watchpoints, and catchpoints with
4228 the @code{enable} and @code{disable} commands, optionally specifying
4229 one or more breakpoint numbers as arguments. Use @code{info break} to
4230 print a list of all breakpoints, watchpoints, and catchpoints if you
4231 do not know which numbers to use.
4233 Disabling and enabling a breakpoint that has multiple locations
4234 affects all of its locations.
4236 A breakpoint, watchpoint, or catchpoint can have any of four different
4237 states of enablement:
4241 Enabled. The breakpoint stops your program. A breakpoint set
4242 with the @code{break} command starts out in this state.
4244 Disabled. The breakpoint has no effect on your program.
4246 Enabled once. The breakpoint stops your program, but then becomes
4249 Enabled for deletion. The breakpoint stops your program, but
4250 immediately after it does so it is deleted permanently. A breakpoint
4251 set with the @code{tbreak} command starts out in this state.
4254 You can use the following commands to enable or disable breakpoints,
4255 watchpoints, and catchpoints:
4259 @kindex dis @r{(@code{disable})}
4260 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4261 Disable the specified breakpoints---or all breakpoints, if none are
4262 listed. A disabled breakpoint has no effect but is not forgotten. All
4263 options such as ignore-counts, conditions and commands are remembered in
4264 case the breakpoint is enabled again later. You may abbreviate
4265 @code{disable} as @code{dis}.
4268 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4269 Enable the specified breakpoints (or all defined breakpoints). They
4270 become effective once again in stopping your program.
4272 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4273 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4274 of these breakpoints immediately after stopping your program.
4276 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4277 Enable the specified breakpoints to work once, then die. @value{GDBN}
4278 deletes any of these breakpoints as soon as your program stops there.
4279 Breakpoints set by the @code{tbreak} command start out in this state.
4282 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4283 @c confusing: tbreak is also initially enabled.
4284 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4285 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4286 subsequently, they become disabled or enabled only when you use one of
4287 the commands above. (The command @code{until} can set and delete a
4288 breakpoint of its own, but it does not change the state of your other
4289 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4293 @subsection Break Conditions
4294 @cindex conditional breakpoints
4295 @cindex breakpoint conditions
4297 @c FIXME what is scope of break condition expr? Context where wanted?
4298 @c in particular for a watchpoint?
4299 The simplest sort of breakpoint breaks every time your program reaches a
4300 specified place. You can also specify a @dfn{condition} for a
4301 breakpoint. A condition is just a Boolean expression in your
4302 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4303 a condition evaluates the expression each time your program reaches it,
4304 and your program stops only if the condition is @emph{true}.
4306 This is the converse of using assertions for program validation; in that
4307 situation, you want to stop when the assertion is violated---that is,
4308 when the condition is false. In C, if you want to test an assertion expressed
4309 by the condition @var{assert}, you should set the condition
4310 @samp{! @var{assert}} on the appropriate breakpoint.
4312 Conditions are also accepted for watchpoints; you may not need them,
4313 since a watchpoint is inspecting the value of an expression anyhow---but
4314 it might be simpler, say, to just set a watchpoint on a variable name,
4315 and specify a condition that tests whether the new value is an interesting
4318 Break conditions can have side effects, and may even call functions in
4319 your program. This can be useful, for example, to activate functions
4320 that log program progress, or to use your own print functions to
4321 format special data structures. The effects are completely predictable
4322 unless there is another enabled breakpoint at the same address. (In
4323 that case, @value{GDBN} might see the other breakpoint first and stop your
4324 program without checking the condition of this one.) Note that
4325 breakpoint commands are usually more convenient and flexible than break
4327 purpose of performing side effects when a breakpoint is reached
4328 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4330 Break conditions can be specified when a breakpoint is set, by using
4331 @samp{if} in the arguments to the @code{break} command. @xref{Set
4332 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4333 with the @code{condition} command.
4335 You can also use the @code{if} keyword with the @code{watch} command.
4336 The @code{catch} command does not recognize the @code{if} keyword;
4337 @code{condition} is the only way to impose a further condition on a
4342 @item condition @var{bnum} @var{expression}
4343 Specify @var{expression} as the break condition for breakpoint,
4344 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4345 breakpoint @var{bnum} stops your program only if the value of
4346 @var{expression} is true (nonzero, in C). When you use
4347 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4348 syntactic correctness, and to determine whether symbols in it have
4349 referents in the context of your breakpoint. If @var{expression} uses
4350 symbols not referenced in the context of the breakpoint, @value{GDBN}
4351 prints an error message:
4354 No symbol "foo" in current context.
4359 not actually evaluate @var{expression} at the time the @code{condition}
4360 command (or a command that sets a breakpoint with a condition, like
4361 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4363 @item condition @var{bnum}
4364 Remove the condition from breakpoint number @var{bnum}. It becomes
4365 an ordinary unconditional breakpoint.
4368 @cindex ignore count (of breakpoint)
4369 A special case of a breakpoint condition is to stop only when the
4370 breakpoint has been reached a certain number of times. This is so
4371 useful that there is a special way to do it, using the @dfn{ignore
4372 count} of the breakpoint. Every breakpoint has an ignore count, which
4373 is an integer. Most of the time, the ignore count is zero, and
4374 therefore has no effect. But if your program reaches a breakpoint whose
4375 ignore count is positive, then instead of stopping, it just decrements
4376 the ignore count by one and continues. As a result, if the ignore count
4377 value is @var{n}, the breakpoint does not stop the next @var{n} times
4378 your program reaches it.
4382 @item ignore @var{bnum} @var{count}
4383 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4384 The next @var{count} times the breakpoint is reached, your program's
4385 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4388 To make the breakpoint stop the next time it is reached, specify
4391 When you use @code{continue} to resume execution of your program from a
4392 breakpoint, you can specify an ignore count directly as an argument to
4393 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4394 Stepping,,Continuing and Stepping}.
4396 If a breakpoint has a positive ignore count and a condition, the
4397 condition is not checked. Once the ignore count reaches zero,
4398 @value{GDBN} resumes checking the condition.
4400 You could achieve the effect of the ignore count with a condition such
4401 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4402 is decremented each time. @xref{Convenience Vars, ,Convenience
4406 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4409 @node Break Commands
4410 @subsection Breakpoint Command Lists
4412 @cindex breakpoint commands
4413 You can give any breakpoint (or watchpoint or catchpoint) a series of
4414 commands to execute when your program stops due to that breakpoint. For
4415 example, you might want to print the values of certain expressions, or
4416 enable other breakpoints.
4420 @kindex end@r{ (breakpoint commands)}
4421 @item commands @r{[}@var{range}@dots{}@r{]}
4422 @itemx @dots{} @var{command-list} @dots{}
4424 Specify a list of commands for the given breakpoints. The commands
4425 themselves appear on the following lines. Type a line containing just
4426 @code{end} to terminate the commands.
4428 To remove all commands from a breakpoint, type @code{commands} and
4429 follow it immediately with @code{end}; that is, give no commands.
4431 With no argument, @code{commands} refers to the last breakpoint,
4432 watchpoint, or catchpoint set (not to the breakpoint most recently
4433 encountered). If the most recent breakpoints were set with a single
4434 command, then the @code{commands} will apply to all the breakpoints
4435 set by that command. This applies to breakpoints set by
4436 @code{rbreak}, and also applies when a single @code{break} command
4437 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4441 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4442 disabled within a @var{command-list}.
4444 You can use breakpoint commands to start your program up again. Simply
4445 use the @code{continue} command, or @code{step}, or any other command
4446 that resumes execution.
4448 Any other commands in the command list, after a command that resumes
4449 execution, are ignored. This is because any time you resume execution
4450 (even with a simple @code{next} or @code{step}), you may encounter
4451 another breakpoint---which could have its own command list, leading to
4452 ambiguities about which list to execute.
4455 If the first command you specify in a command list is @code{silent}, the
4456 usual message about stopping at a breakpoint is not printed. This may
4457 be desirable for breakpoints that are to print a specific message and
4458 then continue. If none of the remaining commands print anything, you
4459 see no sign that the breakpoint was reached. @code{silent} is
4460 meaningful only at the beginning of a breakpoint command list.
4462 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4463 print precisely controlled output, and are often useful in silent
4464 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4466 For example, here is how you could use breakpoint commands to print the
4467 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4473 printf "x is %d\n",x
4478 One application for breakpoint commands is to compensate for one bug so
4479 you can test for another. Put a breakpoint just after the erroneous line
4480 of code, give it a condition to detect the case in which something
4481 erroneous has been done, and give it commands to assign correct values
4482 to any variables that need them. End with the @code{continue} command
4483 so that your program does not stop, and start with the @code{silent}
4484 command so that no output is produced. Here is an example:
4495 @node Save Breakpoints
4496 @subsection How to save breakpoints to a file
4498 To save breakpoint definitions to a file use the @w{@code{save
4499 breakpoints}} command.
4502 @kindex save breakpoints
4503 @cindex save breakpoints to a file for future sessions
4504 @item save breakpoints [@var{filename}]
4505 This command saves all current breakpoint definitions together with
4506 their commands and ignore counts, into a file @file{@var{filename}}
4507 suitable for use in a later debugging session. This includes all
4508 types of breakpoints (breakpoints, watchpoints, catchpoints,
4509 tracepoints). To read the saved breakpoint definitions, use the
4510 @code{source} command (@pxref{Command Files}). Note that watchpoints
4511 with expressions involving local variables may fail to be recreated
4512 because it may not be possible to access the context where the
4513 watchpoint is valid anymore. Because the saved breakpoint definitions
4514 are simply a sequence of @value{GDBN} commands that recreate the
4515 breakpoints, you can edit the file in your favorite editing program,
4516 and remove the breakpoint definitions you're not interested in, or
4517 that can no longer be recreated.
4520 @c @ifclear BARETARGET
4521 @node Error in Breakpoints
4522 @subsection ``Cannot insert breakpoints''
4524 If you request too many active hardware-assisted breakpoints and
4525 watchpoints, you will see this error message:
4527 @c FIXME: the precise wording of this message may change; the relevant
4528 @c source change is not committed yet (Sep 3, 1999).
4530 Stopped; cannot insert breakpoints.
4531 You may have requested too many hardware breakpoints and watchpoints.
4535 This message is printed when you attempt to resume the program, since
4536 only then @value{GDBN} knows exactly how many hardware breakpoints and
4537 watchpoints it needs to insert.
4539 When this message is printed, you need to disable or remove some of the
4540 hardware-assisted breakpoints and watchpoints, and then continue.
4542 @node Breakpoint-related Warnings
4543 @subsection ``Breakpoint address adjusted...''
4544 @cindex breakpoint address adjusted
4546 Some processor architectures place constraints on the addresses at
4547 which breakpoints may be placed. For architectures thus constrained,
4548 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4549 with the constraints dictated by the architecture.
4551 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4552 a VLIW architecture in which a number of RISC-like instructions may be
4553 bundled together for parallel execution. The FR-V architecture
4554 constrains the location of a breakpoint instruction within such a
4555 bundle to the instruction with the lowest address. @value{GDBN}
4556 honors this constraint by adjusting a breakpoint's address to the
4557 first in the bundle.
4559 It is not uncommon for optimized code to have bundles which contain
4560 instructions from different source statements, thus it may happen that
4561 a breakpoint's address will be adjusted from one source statement to
4562 another. Since this adjustment may significantly alter @value{GDBN}'s
4563 breakpoint related behavior from what the user expects, a warning is
4564 printed when the breakpoint is first set and also when the breakpoint
4567 A warning like the one below is printed when setting a breakpoint
4568 that's been subject to address adjustment:
4571 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4574 Such warnings are printed both for user settable and @value{GDBN}'s
4575 internal breakpoints. If you see one of these warnings, you should
4576 verify that a breakpoint set at the adjusted address will have the
4577 desired affect. If not, the breakpoint in question may be removed and
4578 other breakpoints may be set which will have the desired behavior.
4579 E.g., it may be sufficient to place the breakpoint at a later
4580 instruction. A conditional breakpoint may also be useful in some
4581 cases to prevent the breakpoint from triggering too often.
4583 @value{GDBN} will also issue a warning when stopping at one of these
4584 adjusted breakpoints:
4587 warning: Breakpoint 1 address previously adjusted from 0x00010414
4591 When this warning is encountered, it may be too late to take remedial
4592 action except in cases where the breakpoint is hit earlier or more
4593 frequently than expected.
4595 @node Continuing and Stepping
4596 @section Continuing and Stepping
4600 @cindex resuming execution
4601 @dfn{Continuing} means resuming program execution until your program
4602 completes normally. In contrast, @dfn{stepping} means executing just
4603 one more ``step'' of your program, where ``step'' may mean either one
4604 line of source code, or one machine instruction (depending on what
4605 particular command you use). Either when continuing or when stepping,
4606 your program may stop even sooner, due to a breakpoint or a signal. (If
4607 it stops due to a signal, you may want to use @code{handle}, or use
4608 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4612 @kindex c @r{(@code{continue})}
4613 @kindex fg @r{(resume foreground execution)}
4614 @item continue @r{[}@var{ignore-count}@r{]}
4615 @itemx c @r{[}@var{ignore-count}@r{]}
4616 @itemx fg @r{[}@var{ignore-count}@r{]}
4617 Resume program execution, at the address where your program last stopped;
4618 any breakpoints set at that address are bypassed. The optional argument
4619 @var{ignore-count} allows you to specify a further number of times to
4620 ignore a breakpoint at this location; its effect is like that of
4621 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4623 The argument @var{ignore-count} is meaningful only when your program
4624 stopped due to a breakpoint. At other times, the argument to
4625 @code{continue} is ignored.
4627 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4628 debugged program is deemed to be the foreground program) are provided
4629 purely for convenience, and have exactly the same behavior as
4633 To resume execution at a different place, you can use @code{return}
4634 (@pxref{Returning, ,Returning from a Function}) to go back to the
4635 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4636 Different Address}) to go to an arbitrary location in your program.
4638 A typical technique for using stepping is to set a breakpoint
4639 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4640 beginning of the function or the section of your program where a problem
4641 is believed to lie, run your program until it stops at that breakpoint,
4642 and then step through the suspect area, examining the variables that are
4643 interesting, until you see the problem happen.
4647 @kindex s @r{(@code{step})}
4649 Continue running your program until control reaches a different source
4650 line, then stop it and return control to @value{GDBN}. This command is
4651 abbreviated @code{s}.
4654 @c "without debugging information" is imprecise; actually "without line
4655 @c numbers in the debugging information". (gcc -g1 has debugging info but
4656 @c not line numbers). But it seems complex to try to make that
4657 @c distinction here.
4658 @emph{Warning:} If you use the @code{step} command while control is
4659 within a function that was compiled without debugging information,
4660 execution proceeds until control reaches a function that does have
4661 debugging information. Likewise, it will not step into a function which
4662 is compiled without debugging information. To step through functions
4663 without debugging information, use the @code{stepi} command, described
4667 The @code{step} command only stops at the first instruction of a source
4668 line. This prevents the multiple stops that could otherwise occur in
4669 @code{switch} statements, @code{for} loops, etc. @code{step} continues
4670 to stop if a function that has debugging information is called within
4671 the line. In other words, @code{step} @emph{steps inside} any functions
4672 called within the line.
4674 Also, the @code{step} command only enters a function if there is line
4675 number information for the function. Otherwise it acts like the
4676 @code{next} command. This avoids problems when using @code{cc -gl}
4677 on MIPS machines. Previously, @code{step} entered subroutines if there
4678 was any debugging information about the routine.
4680 @item step @var{count}
4681 Continue running as in @code{step}, but do so @var{count} times. If a
4682 breakpoint is reached, or a signal not related to stepping occurs before
4683 @var{count} steps, stepping stops right away.
4686 @kindex n @r{(@code{next})}
4687 @item next @r{[}@var{count}@r{]}
4688 Continue to the next source line in the current (innermost) stack frame.
4689 This is similar to @code{step}, but function calls that appear within
4690 the line of code are executed without stopping. Execution stops when
4691 control reaches a different line of code at the original stack level
4692 that was executing when you gave the @code{next} command. This command
4693 is abbreviated @code{n}.
4695 An argument @var{count} is a repeat count, as for @code{step}.
4698 @c FIX ME!! Do we delete this, or is there a way it fits in with
4699 @c the following paragraph? --- Vctoria
4701 @c @code{next} within a function that lacks debugging information acts like
4702 @c @code{step}, but any function calls appearing within the code of the
4703 @c function are executed without stopping.
4705 The @code{next} command only stops at the first instruction of a
4706 source line. This prevents multiple stops that could otherwise occur in
4707 @code{switch} statements, @code{for} loops, etc.
4709 @kindex set step-mode
4711 @cindex functions without line info, and stepping
4712 @cindex stepping into functions with no line info
4713 @itemx set step-mode on
4714 The @code{set step-mode on} command causes the @code{step} command to
4715 stop at the first instruction of a function which contains no debug line
4716 information rather than stepping over it.
4718 This is useful in cases where you may be interested in inspecting the
4719 machine instructions of a function which has no symbolic info and do not
4720 want @value{GDBN} to automatically skip over this function.
4722 @item set step-mode off
4723 Causes the @code{step} command to step over any functions which contains no
4724 debug information. This is the default.
4726 @item show step-mode
4727 Show whether @value{GDBN} will stop in or step over functions without
4728 source line debug information.
4731 @kindex fin @r{(@code{finish})}
4733 Continue running until just after function in the selected stack frame
4734 returns. Print the returned value (if any). This command can be
4735 abbreviated as @code{fin}.
4737 Contrast this with the @code{return} command (@pxref{Returning,
4738 ,Returning from a Function}).
4741 @kindex u @r{(@code{until})}
4742 @cindex run until specified location
4745 Continue running until a source line past the current line, in the
4746 current stack frame, is reached. This command is used to avoid single
4747 stepping through a loop more than once. It is like the @code{next}
4748 command, except that when @code{until} encounters a jump, it
4749 automatically continues execution until the program counter is greater
4750 than the address of the jump.
4752 This means that when you reach the end of a loop after single stepping
4753 though it, @code{until} makes your program continue execution until it
4754 exits the loop. In contrast, a @code{next} command at the end of a loop
4755 simply steps back to the beginning of the loop, which forces you to step
4756 through the next iteration.
4758 @code{until} always stops your program if it attempts to exit the current
4761 @code{until} may produce somewhat counterintuitive results if the order
4762 of machine code does not match the order of the source lines. For
4763 example, in the following excerpt from a debugging session, the @code{f}
4764 (@code{frame}) command shows that execution is stopped at line
4765 @code{206}; yet when we use @code{until}, we get to line @code{195}:
4769 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
4771 (@value{GDBP}) until
4772 195 for ( ; argc > 0; NEXTARG) @{
4775 This happened because, for execution efficiency, the compiler had
4776 generated code for the loop closure test at the end, rather than the
4777 start, of the loop---even though the test in a C @code{for}-loop is
4778 written before the body of the loop. The @code{until} command appeared
4779 to step back to the beginning of the loop when it advanced to this
4780 expression; however, it has not really gone to an earlier
4781 statement---not in terms of the actual machine code.
4783 @code{until} with no argument works by means of single
4784 instruction stepping, and hence is slower than @code{until} with an
4787 @item until @var{location}
4788 @itemx u @var{location}
4789 Continue running your program until either the specified location is
4790 reached, or the current stack frame returns. @var{location} is any of
4791 the forms described in @ref{Specify Location}.
4792 This form of the command uses temporary breakpoints, and
4793 hence is quicker than @code{until} without an argument. The specified
4794 location is actually reached only if it is in the current frame. This
4795 implies that @code{until} can be used to skip over recursive function
4796 invocations. For instance in the code below, if the current location is
4797 line @code{96}, issuing @code{until 99} will execute the program up to
4798 line @code{99} in the same invocation of factorial, i.e., after the inner
4799 invocations have returned.
4802 94 int factorial (int value)
4804 96 if (value > 1) @{
4805 97 value *= factorial (value - 1);
4812 @kindex advance @var{location}
4813 @itemx advance @var{location}
4814 Continue running the program up to the given @var{location}. An argument is
4815 required, which should be of one of the forms described in
4816 @ref{Specify Location}.
4817 Execution will also stop upon exit from the current stack
4818 frame. This command is similar to @code{until}, but @code{advance} will
4819 not skip over recursive function calls, and the target location doesn't
4820 have to be in the same frame as the current one.
4824 @kindex si @r{(@code{stepi})}
4826 @itemx stepi @var{arg}
4828 Execute one machine instruction, then stop and return to the debugger.
4830 It is often useful to do @samp{display/i $pc} when stepping by machine
4831 instructions. This makes @value{GDBN} automatically display the next
4832 instruction to be executed, each time your program stops. @xref{Auto
4833 Display,, Automatic Display}.
4835 An argument is a repeat count, as in @code{step}.
4839 @kindex ni @r{(@code{nexti})}
4841 @itemx nexti @var{arg}
4843 Execute one machine instruction, but if it is a function call,
4844 proceed until the function returns.
4846 An argument is a repeat count, as in @code{next}.
4853 A signal is an asynchronous event that can happen in a program. The
4854 operating system defines the possible kinds of signals, and gives each
4855 kind a name and a number. For example, in Unix @code{SIGINT} is the
4856 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
4857 @code{SIGSEGV} is the signal a program gets from referencing a place in
4858 memory far away from all the areas in use; @code{SIGALRM} occurs when
4859 the alarm clock timer goes off (which happens only if your program has
4860 requested an alarm).
4862 @cindex fatal signals
4863 Some signals, including @code{SIGALRM}, are a normal part of the
4864 functioning of your program. Others, such as @code{SIGSEGV}, indicate
4865 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
4866 program has not specified in advance some other way to handle the signal.
4867 @code{SIGINT} does not indicate an error in your program, but it is normally
4868 fatal so it can carry out the purpose of the interrupt: to kill the program.
4870 @value{GDBN} has the ability to detect any occurrence of a signal in your
4871 program. You can tell @value{GDBN} in advance what to do for each kind of
4874 @cindex handling signals
4875 Normally, @value{GDBN} is set up to let the non-erroneous signals like
4876 @code{SIGALRM} be silently passed to your program
4877 (so as not to interfere with their role in the program's functioning)
4878 but to stop your program immediately whenever an error signal happens.
4879 You can change these settings with the @code{handle} command.
4882 @kindex info signals
4886 Print a table of all the kinds of signals and how @value{GDBN} has been told to
4887 handle each one. You can use this to see the signal numbers of all
4888 the defined types of signals.
4890 @item info signals @var{sig}
4891 Similar, but print information only about the specified signal number.
4893 @code{info handle} is an alias for @code{info signals}.
4896 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
4897 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
4898 can be the number of a signal or its name (with or without the
4899 @samp{SIG} at the beginning); a list of signal numbers of the form
4900 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
4901 known signals. Optional arguments @var{keywords}, described below,
4902 say what change to make.
4906 The keywords allowed by the @code{handle} command can be abbreviated.
4907 Their full names are:
4911 @value{GDBN} should not stop your program when this signal happens. It may
4912 still print a message telling you that the signal has come in.
4915 @value{GDBN} should stop your program when this signal happens. This implies
4916 the @code{print} keyword as well.
4919 @value{GDBN} should print a message when this signal happens.
4922 @value{GDBN} should not mention the occurrence of the signal at all. This
4923 implies the @code{nostop} keyword as well.
4927 @value{GDBN} should allow your program to see this signal; your program
4928 can handle the signal, or else it may terminate if the signal is fatal
4929 and not handled. @code{pass} and @code{noignore} are synonyms.
4933 @value{GDBN} should not allow your program to see this signal.
4934 @code{nopass} and @code{ignore} are synonyms.
4938 When a signal stops your program, the signal is not visible to the
4940 continue. Your program sees the signal then, if @code{pass} is in
4941 effect for the signal in question @emph{at that time}. In other words,
4942 after @value{GDBN} reports a signal, you can use the @code{handle}
4943 command with @code{pass} or @code{nopass} to control whether your
4944 program sees that signal when you continue.
4946 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
4947 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
4948 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
4951 You can also use the @code{signal} command to prevent your program from
4952 seeing a signal, or cause it to see a signal it normally would not see,
4953 or to give it any signal at any time. For example, if your program stopped
4954 due to some sort of memory reference error, you might store correct
4955 values into the erroneous variables and continue, hoping to see more
4956 execution; but your program would probably terminate immediately as
4957 a result of the fatal signal once it saw the signal. To prevent this,
4958 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
4961 @cindex extra signal information
4962 @anchor{extra signal information}
4964 On some targets, @value{GDBN} can inspect extra signal information
4965 associated with the intercepted signal, before it is actually
4966 delivered to the program being debugged. This information is exported
4967 by the convenience variable @code{$_siginfo}, and consists of data
4968 that is passed by the kernel to the signal handler at the time of the
4969 receipt of a signal. The data type of the information itself is
4970 target dependent. You can see the data type using the @code{ptype
4971 $_siginfo} command. On Unix systems, it typically corresponds to the
4972 standard @code{siginfo_t} type, as defined in the @file{signal.h}
4975 Here's an example, on a @sc{gnu}/Linux system, printing the stray
4976 referenced address that raised a segmentation fault.
4980 (@value{GDBP}) continue
4981 Program received signal SIGSEGV, Segmentation fault.
4982 0x0000000000400766 in main ()
4984 (@value{GDBP}) ptype $_siginfo
4991 struct @{...@} _kill;
4992 struct @{...@} _timer;
4994 struct @{...@} _sigchld;
4995 struct @{...@} _sigfault;
4996 struct @{...@} _sigpoll;
4999 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5003 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5004 $1 = (void *) 0x7ffff7ff7000
5008 Depending on target support, @code{$_siginfo} may also be writable.
5011 @section Stopping and Starting Multi-thread Programs
5013 @cindex stopped threads
5014 @cindex threads, stopped
5016 @cindex continuing threads
5017 @cindex threads, continuing
5019 @value{GDBN} supports debugging programs with multiple threads
5020 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5021 are two modes of controlling execution of your program within the
5022 debugger. In the default mode, referred to as @dfn{all-stop mode},
5023 when any thread in your program stops (for example, at a breakpoint
5024 or while being stepped), all other threads in the program are also stopped by
5025 @value{GDBN}. On some targets, @value{GDBN} also supports
5026 @dfn{non-stop mode}, in which other threads can continue to run freely while
5027 you examine the stopped thread in the debugger.
5030 * All-Stop Mode:: All threads stop when GDB takes control
5031 * Non-Stop Mode:: Other threads continue to execute
5032 * Background Execution:: Running your program asynchronously
5033 * Thread-Specific Breakpoints:: Controlling breakpoints
5034 * Interrupted System Calls:: GDB may interfere with system calls
5035 * Observer Mode:: GDB does not alter program behavior
5039 @subsection All-Stop Mode
5041 @cindex all-stop mode
5043 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5044 @emph{all} threads of execution stop, not just the current thread. This
5045 allows you to examine the overall state of the program, including
5046 switching between threads, without worrying that things may change
5049 Conversely, whenever you restart the program, @emph{all} threads start
5050 executing. @emph{This is true even when single-stepping} with commands
5051 like @code{step} or @code{next}.
5053 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5054 Since thread scheduling is up to your debugging target's operating
5055 system (not controlled by @value{GDBN}), other threads may
5056 execute more than one statement while the current thread completes a
5057 single step. Moreover, in general other threads stop in the middle of a
5058 statement, rather than at a clean statement boundary, when the program
5061 You might even find your program stopped in another thread after
5062 continuing or even single-stepping. This happens whenever some other
5063 thread runs into a breakpoint, a signal, or an exception before the
5064 first thread completes whatever you requested.
5066 @cindex automatic thread selection
5067 @cindex switching threads automatically
5068 @cindex threads, automatic switching
5069 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5070 signal, it automatically selects the thread where that breakpoint or
5071 signal happened. @value{GDBN} alerts you to the context switch with a
5072 message such as @samp{[Switching to Thread @var{n}]} to identify the
5075 On some OSes, you can modify @value{GDBN}'s default behavior by
5076 locking the OS scheduler to allow only a single thread to run.
5079 @item set scheduler-locking @var{mode}
5080 @cindex scheduler locking mode
5081 @cindex lock scheduler
5082 Set the scheduler locking mode. If it is @code{off}, then there is no
5083 locking and any thread may run at any time. If @code{on}, then only the
5084 current thread may run when the inferior is resumed. The @code{step}
5085 mode optimizes for single-stepping; it prevents other threads
5086 from preempting the current thread while you are stepping, so that
5087 the focus of debugging does not change unexpectedly.
5088 Other threads only rarely (or never) get a chance to run
5089 when you step. They are more likely to run when you @samp{next} over a
5090 function call, and they are completely free to run when you use commands
5091 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5092 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5093 the current thread away from the thread that you are debugging.
5095 @item show scheduler-locking
5096 Display the current scheduler locking mode.
5099 @cindex resume threads of multiple processes simultaneously
5100 By default, when you issue one of the execution commands such as
5101 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5102 threads of the current inferior to run. For example, if @value{GDBN}
5103 is attached to two inferiors, each with two threads, the
5104 @code{continue} command resumes only the two threads of the current
5105 inferior. This is useful, for example, when you debug a program that
5106 forks and you want to hold the parent stopped (so that, for instance,
5107 it doesn't run to exit), while you debug the child. In other
5108 situations, you may not be interested in inspecting the current state
5109 of any of the processes @value{GDBN} is attached to, and you may want
5110 to resume them all until some breakpoint is hit. In the latter case,
5111 you can instruct @value{GDBN} to allow all threads of all the
5112 inferiors to run with the @w{@code{set schedule-multiple}} command.
5115 @kindex set schedule-multiple
5116 @item set schedule-multiple
5117 Set the mode for allowing threads of multiple processes to be resumed
5118 when an execution command is issued. When @code{on}, all threads of
5119 all processes are allowed to run. When @code{off}, only the threads
5120 of the current process are resumed. The default is @code{off}. The
5121 @code{scheduler-locking} mode takes precedence when set to @code{on},
5122 or while you are stepping and set to @code{step}.
5124 @item show schedule-multiple
5125 Display the current mode for resuming the execution of threads of
5130 @subsection Non-Stop Mode
5132 @cindex non-stop mode
5134 @c This section is really only a place-holder, and needs to be expanded
5135 @c with more details.
5137 For some multi-threaded targets, @value{GDBN} supports an optional
5138 mode of operation in which you can examine stopped program threads in
5139 the debugger while other threads continue to execute freely. This
5140 minimizes intrusion when debugging live systems, such as programs
5141 where some threads have real-time constraints or must continue to
5142 respond to external events. This is referred to as @dfn{non-stop} mode.
5144 In non-stop mode, when a thread stops to report a debugging event,
5145 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5146 threads as well, in contrast to the all-stop mode behavior. Additionally,
5147 execution commands such as @code{continue} and @code{step} apply by default
5148 only to the current thread in non-stop mode, rather than all threads as
5149 in all-stop mode. This allows you to control threads explicitly in
5150 ways that are not possible in all-stop mode --- for example, stepping
5151 one thread while allowing others to run freely, stepping
5152 one thread while holding all others stopped, or stepping several threads
5153 independently and simultaneously.
5155 To enter non-stop mode, use this sequence of commands before you run
5156 or attach to your program:
5159 # Enable the async interface.
5162 # If using the CLI, pagination breaks non-stop.
5165 # Finally, turn it on!
5169 You can use these commands to manipulate the non-stop mode setting:
5172 @kindex set non-stop
5173 @item set non-stop on
5174 Enable selection of non-stop mode.
5175 @item set non-stop off
5176 Disable selection of non-stop mode.
5177 @kindex show non-stop
5179 Show the current non-stop enablement setting.
5182 Note these commands only reflect whether non-stop mode is enabled,
5183 not whether the currently-executing program is being run in non-stop mode.
5184 In particular, the @code{set non-stop} preference is only consulted when
5185 @value{GDBN} starts or connects to the target program, and it is generally
5186 not possible to switch modes once debugging has started. Furthermore,
5187 since not all targets support non-stop mode, even when you have enabled
5188 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5191 In non-stop mode, all execution commands apply only to the current thread
5192 by default. That is, @code{continue} only continues one thread.
5193 To continue all threads, issue @code{continue -a} or @code{c -a}.
5195 You can use @value{GDBN}'s background execution commands
5196 (@pxref{Background Execution}) to run some threads in the background
5197 while you continue to examine or step others from @value{GDBN}.
5198 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5199 always executed asynchronously in non-stop mode.
5201 Suspending execution is done with the @code{interrupt} command when
5202 running in the background, or @kbd{Ctrl-c} during foreground execution.
5203 In all-stop mode, this stops the whole process;
5204 but in non-stop mode the interrupt applies only to the current thread.
5205 To stop the whole program, use @code{interrupt -a}.
5207 Other execution commands do not currently support the @code{-a} option.
5209 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5210 that thread current, as it does in all-stop mode. This is because the
5211 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5212 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5213 changed to a different thread just as you entered a command to operate on the
5214 previously current thread.
5216 @node Background Execution
5217 @subsection Background Execution
5219 @cindex foreground execution
5220 @cindex background execution
5221 @cindex asynchronous execution
5222 @cindex execution, foreground, background and asynchronous
5224 @value{GDBN}'s execution commands have two variants: the normal
5225 foreground (synchronous) behavior, and a background
5226 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5227 the program to report that some thread has stopped before prompting for
5228 another command. In background execution, @value{GDBN} immediately gives
5229 a command prompt so that you can issue other commands while your program runs.
5231 You need to explicitly enable asynchronous mode before you can use
5232 background execution commands. You can use these commands to
5233 manipulate the asynchronous mode setting:
5236 @kindex set target-async
5237 @item set target-async on
5238 Enable asynchronous mode.
5239 @item set target-async off
5240 Disable asynchronous mode.
5241 @kindex show target-async
5242 @item show target-async
5243 Show the current target-async setting.
5246 If the target doesn't support async mode, @value{GDBN} issues an error
5247 message if you attempt to use the background execution commands.
5249 To specify background execution, add a @code{&} to the command. For example,
5250 the background form of the @code{continue} command is @code{continue&}, or
5251 just @code{c&}. The execution commands that accept background execution
5257 @xref{Starting, , Starting your Program}.
5261 @xref{Attach, , Debugging an Already-running Process}.
5265 @xref{Continuing and Stepping, step}.
5269 @xref{Continuing and Stepping, stepi}.
5273 @xref{Continuing and Stepping, next}.
5277 @xref{Continuing and Stepping, nexti}.
5281 @xref{Continuing and Stepping, continue}.
5285 @xref{Continuing and Stepping, finish}.
5289 @xref{Continuing and Stepping, until}.
5293 Background execution is especially useful in conjunction with non-stop
5294 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5295 However, you can also use these commands in the normal all-stop mode with
5296 the restriction that you cannot issue another execution command until the
5297 previous one finishes. Examples of commands that are valid in all-stop
5298 mode while the program is running include @code{help} and @code{info break}.
5300 You can interrupt your program while it is running in the background by
5301 using the @code{interrupt} command.
5308 Suspend execution of the running program. In all-stop mode,
5309 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5310 only the current thread. To stop the whole program in non-stop mode,
5311 use @code{interrupt -a}.
5314 @node Thread-Specific Breakpoints
5315 @subsection Thread-Specific Breakpoints
5317 When your program has multiple threads (@pxref{Threads,, Debugging
5318 Programs with Multiple Threads}), you can choose whether to set
5319 breakpoints on all threads, or on a particular thread.
5322 @cindex breakpoints and threads
5323 @cindex thread breakpoints
5324 @kindex break @dots{} thread @var{threadno}
5325 @item break @var{linespec} thread @var{threadno}
5326 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5327 @var{linespec} specifies source lines; there are several ways of
5328 writing them (@pxref{Specify Location}), but the effect is always to
5329 specify some source line.
5331 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5332 to specify that you only want @value{GDBN} to stop the program when a
5333 particular thread reaches this breakpoint. @var{threadno} is one of the
5334 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5335 column of the @samp{info threads} display.
5337 If you do not specify @samp{thread @var{threadno}} when you set a
5338 breakpoint, the breakpoint applies to @emph{all} threads of your
5341 You can use the @code{thread} qualifier on conditional breakpoints as
5342 well; in this case, place @samp{thread @var{threadno}} before or
5343 after the breakpoint condition, like this:
5346 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5351 @node Interrupted System Calls
5352 @subsection Interrupted System Calls
5354 @cindex thread breakpoints and system calls
5355 @cindex system calls and thread breakpoints
5356 @cindex premature return from system calls
5357 There is an unfortunate side effect when using @value{GDBN} to debug
5358 multi-threaded programs. If one thread stops for a
5359 breakpoint, or for some other reason, and another thread is blocked in a
5360 system call, then the system call may return prematurely. This is a
5361 consequence of the interaction between multiple threads and the signals
5362 that @value{GDBN} uses to implement breakpoints and other events that
5365 To handle this problem, your program should check the return value of
5366 each system call and react appropriately. This is good programming
5369 For example, do not write code like this:
5375 The call to @code{sleep} will return early if a different thread stops
5376 at a breakpoint or for some other reason.
5378 Instead, write this:
5383 unslept = sleep (unslept);
5386 A system call is allowed to return early, so the system is still
5387 conforming to its specification. But @value{GDBN} does cause your
5388 multi-threaded program to behave differently than it would without
5391 Also, @value{GDBN} uses internal breakpoints in the thread library to
5392 monitor certain events such as thread creation and thread destruction.
5393 When such an event happens, a system call in another thread may return
5394 prematurely, even though your program does not appear to stop.
5397 @subsection Observer Mode
5399 If you want to build on non-stop mode and observe program behavior
5400 without any chance of disruption by @value{GDBN}, you can set
5401 variables to disable all of the debugger's attempts to modify state,
5402 whether by writing memory, inserting breakpoints, etc. These operate
5403 at a low level, intercepting operations from all commands.
5405 When all of these are set to @code{off}, then @value{GDBN} is said to
5406 be @dfn{observer mode}. As a convenience, the variable
5407 @code{observer} can be set to disable these, plus enable non-stop
5410 Note that @value{GDBN} will not prevent you from making nonsensical
5411 combinations of these settings. For instance, if you have enabled
5412 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5413 then breakpoints that work by writing trap instructions into the code
5414 stream will still not be able to be placed.
5419 @item set observer on
5420 @itemx set observer off
5421 When set to @code{on}, this disables all the permission variables
5422 below (except for @code{insert-fast-tracepoints}), plus enables
5423 non-stop debugging. Setting this to @code{off} switches back to
5424 normal debugging, though remaining in non-stop mode.
5427 Show whether observer mode is on or off.
5429 @kindex may-write-registers
5430 @item set may-write-registers on
5431 @itemx set may-write-registers off
5432 This controls whether @value{GDBN} will attempt to alter the values of
5433 registers, such as with assignment expressions in @code{print}, or the
5434 @code{jump} command. It defaults to @code{on}.
5436 @item show may-write-registers
5437 Show the current permission to write registers.
5439 @kindex may-write-memory
5440 @item set may-write-memory on
5441 @itemx set may-write-memory off
5442 This controls whether @value{GDBN} will attempt to alter the contents
5443 of memory, such as with assignment expressions in @code{print}. It
5444 defaults to @code{on}.
5446 @item show may-write-memory
5447 Show the current permission to write memory.
5449 @kindex may-insert-breakpoints
5450 @item set may-insert-breakpoints on
5451 @itemx set may-insert-breakpoints off
5452 This controls whether @value{GDBN} will attempt to insert breakpoints.
5453 This affects all breakpoints, including internal breakpoints defined
5454 by @value{GDBN}. It defaults to @code{on}.
5456 @item show may-insert-breakpoints
5457 Show the current permission to insert breakpoints.
5459 @kindex may-insert-tracepoints
5460 @item set may-insert-tracepoints on
5461 @itemx set may-insert-tracepoints off
5462 This controls whether @value{GDBN} will attempt to insert (regular)
5463 tracepoints at the beginning of a tracing experiment. It affects only
5464 non-fast tracepoints, fast tracepoints being under the control of
5465 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5467 @item show may-insert-tracepoints
5468 Show the current permission to insert tracepoints.
5470 @kindex may-insert-fast-tracepoints
5471 @item set may-insert-fast-tracepoints on
5472 @itemx set may-insert-fast-tracepoints off
5473 This controls whether @value{GDBN} will attempt to insert fast
5474 tracepoints at the beginning of a tracing experiment. It affects only
5475 fast tracepoints, regular (non-fast) tracepoints being under the
5476 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5478 @item show may-insert-fast-tracepoints
5479 Show the current permission to insert fast tracepoints.
5481 @kindex may-interrupt
5482 @item set may-interrupt on
5483 @itemx set may-interrupt off
5484 This controls whether @value{GDBN} will attempt to interrupt or stop
5485 program execution. When this variable is @code{off}, the
5486 @code{interrupt} command will have no effect, nor will
5487 @kbd{Ctrl-c}. It defaults to @code{on}.
5489 @item show may-interrupt
5490 Show the current permission to interrupt or stop the program.
5494 @node Reverse Execution
5495 @chapter Running programs backward
5496 @cindex reverse execution
5497 @cindex running programs backward
5499 When you are debugging a program, it is not unusual to realize that
5500 you have gone too far, and some event of interest has already happened.
5501 If the target environment supports it, @value{GDBN} can allow you to
5502 ``rewind'' the program by running it backward.
5504 A target environment that supports reverse execution should be able
5505 to ``undo'' the changes in machine state that have taken place as the
5506 program was executing normally. Variables, registers etc.@: should
5507 revert to their previous values. Obviously this requires a great
5508 deal of sophistication on the part of the target environment; not
5509 all target environments can support reverse execution.
5511 When a program is executed in reverse, the instructions that
5512 have most recently been executed are ``un-executed'', in reverse
5513 order. The program counter runs backward, following the previous
5514 thread of execution in reverse. As each instruction is ``un-executed'',
5515 the values of memory and/or registers that were changed by that
5516 instruction are reverted to their previous states. After executing
5517 a piece of source code in reverse, all side effects of that code
5518 should be ``undone'', and all variables should be returned to their
5519 prior values@footnote{
5520 Note that some side effects are easier to undo than others. For instance,
5521 memory and registers are relatively easy, but device I/O is hard. Some
5522 targets may be able undo things like device I/O, and some may not.
5524 The contract between @value{GDBN} and the reverse executing target
5525 requires only that the target do something reasonable when
5526 @value{GDBN} tells it to execute backwards, and then report the
5527 results back to @value{GDBN}. Whatever the target reports back to
5528 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5529 assumes that the memory and registers that the target reports are in a
5530 consistant state, but @value{GDBN} accepts whatever it is given.
5533 If you are debugging in a target environment that supports
5534 reverse execution, @value{GDBN} provides the following commands.
5537 @kindex reverse-continue
5538 @kindex rc @r{(@code{reverse-continue})}
5539 @item reverse-continue @r{[}@var{ignore-count}@r{]}
5540 @itemx rc @r{[}@var{ignore-count}@r{]}
5541 Beginning at the point where your program last stopped, start executing
5542 in reverse. Reverse execution will stop for breakpoints and synchronous
5543 exceptions (signals), just like normal execution. Behavior of
5544 asynchronous signals depends on the target environment.
5546 @kindex reverse-step
5547 @kindex rs @r{(@code{step})}
5548 @item reverse-step @r{[}@var{count}@r{]}
5549 Run the program backward until control reaches the start of a
5550 different source line; then stop it, and return control to @value{GDBN}.
5552 Like the @code{step} command, @code{reverse-step} will only stop
5553 at the beginning of a source line. It ``un-executes'' the previously
5554 executed source line. If the previous source line included calls to
5555 debuggable functions, @code{reverse-step} will step (backward) into
5556 the called function, stopping at the beginning of the @emph{last}
5557 statement in the called function (typically a return statement).
5559 Also, as with the @code{step} command, if non-debuggable functions are
5560 called, @code{reverse-step} will run thru them backward without stopping.
5562 @kindex reverse-stepi
5563 @kindex rsi @r{(@code{reverse-stepi})}
5564 @item reverse-stepi @r{[}@var{count}@r{]}
5565 Reverse-execute one machine instruction. Note that the instruction
5566 to be reverse-executed is @emph{not} the one pointed to by the program
5567 counter, but the instruction executed prior to that one. For instance,
5568 if the last instruction was a jump, @code{reverse-stepi} will take you
5569 back from the destination of the jump to the jump instruction itself.
5571 @kindex reverse-next
5572 @kindex rn @r{(@code{reverse-next})}
5573 @item reverse-next @r{[}@var{count}@r{]}
5574 Run backward to the beginning of the previous line executed in
5575 the current (innermost) stack frame. If the line contains function
5576 calls, they will be ``un-executed'' without stopping. Starting from
5577 the first line of a function, @code{reverse-next} will take you back
5578 to the caller of that function, @emph{before} the function was called,
5579 just as the normal @code{next} command would take you from the last
5580 line of a function back to its return to its caller
5581 @footnote{Unless the code is too heavily optimized.}.
5583 @kindex reverse-nexti
5584 @kindex rni @r{(@code{reverse-nexti})}
5585 @item reverse-nexti @r{[}@var{count}@r{]}
5586 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
5587 in reverse, except that called functions are ``un-executed'' atomically.
5588 That is, if the previously executed instruction was a return from
5589 another function, @code{reverse-nexti} will continue to execute
5590 in reverse until the call to that function (from the current stack
5593 @kindex reverse-finish
5594 @item reverse-finish
5595 Just as the @code{finish} command takes you to the point where the
5596 current function returns, @code{reverse-finish} takes you to the point
5597 where it was called. Instead of ending up at the end of the current
5598 function invocation, you end up at the beginning.
5600 @kindex set exec-direction
5601 @item set exec-direction
5602 Set the direction of target execution.
5603 @itemx set exec-direction reverse
5604 @cindex execute forward or backward in time
5605 @value{GDBN} will perform all execution commands in reverse, until the
5606 exec-direction mode is changed to ``forward''. Affected commands include
5607 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
5608 command cannot be used in reverse mode.
5609 @item set exec-direction forward
5610 @value{GDBN} will perform all execution commands in the normal fashion.
5611 This is the default.
5615 @node Process Record and Replay
5616 @chapter Recording Inferior's Execution and Replaying It
5617 @cindex process record and replay
5618 @cindex recording inferior's execution and replaying it
5620 On some platforms, @value{GDBN} provides a special @dfn{process record
5621 and replay} target that can record a log of the process execution, and
5622 replay it later with both forward and reverse execution commands.
5625 When this target is in use, if the execution log includes the record
5626 for the next instruction, @value{GDBN} will debug in @dfn{replay
5627 mode}. In the replay mode, the inferior does not really execute code
5628 instructions. Instead, all the events that normally happen during
5629 code execution are taken from the execution log. While code is not
5630 really executed in replay mode, the values of registers (including the
5631 program counter register) and the memory of the inferior are still
5632 changed as they normally would. Their contents are taken from the
5636 If the record for the next instruction is not in the execution log,
5637 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
5638 inferior executes normally, and @value{GDBN} records the execution log
5641 The process record and replay target supports reverse execution
5642 (@pxref{Reverse Execution}), even if the platform on which the
5643 inferior runs does not. However, the reverse execution is limited in
5644 this case by the range of the instructions recorded in the execution
5645 log. In other words, reverse execution on platforms that don't
5646 support it directly can only be done in the replay mode.
5648 When debugging in the reverse direction, @value{GDBN} will work in
5649 replay mode as long as the execution log includes the record for the
5650 previous instruction; otherwise, it will work in record mode, if the
5651 platform supports reverse execution, or stop if not.
5653 For architecture environments that support process record and replay,
5654 @value{GDBN} provides the following commands:
5657 @kindex target record
5661 This command starts the process record and replay target. The process
5662 record and replay target can only debug a process that is already
5663 running. Therefore, you need first to start the process with the
5664 @kbd{run} or @kbd{start} commands, and then start the recording with
5665 the @kbd{target record} command.
5667 Both @code{record} and @code{rec} are aliases of @code{target record}.
5669 @cindex displaced stepping, and process record and replay
5670 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
5671 will be automatically disabled when process record and replay target
5672 is started. That's because the process record and replay target
5673 doesn't support displaced stepping.
5675 @cindex non-stop mode, and process record and replay
5676 @cindex asynchronous execution, and process record and replay
5677 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
5678 the asynchronous execution mode (@pxref{Background Execution}), the
5679 process record and replay target cannot be started because it doesn't
5680 support these two modes.
5685 Stop the process record and replay target. When process record and
5686 replay target stops, the entire execution log will be deleted and the
5687 inferior will either be terminated, or will remain in its final state.
5689 When you stop the process record and replay target in record mode (at
5690 the end of the execution log), the inferior will be stopped at the
5691 next instruction that would have been recorded. In other words, if
5692 you record for a while and then stop recording, the inferior process
5693 will be left in the same state as if the recording never happened.
5695 On the other hand, if the process record and replay target is stopped
5696 while in replay mode (that is, not at the end of the execution log,
5697 but at some earlier point), the inferior process will become ``live''
5698 at that earlier state, and it will then be possible to continue the
5699 usual ``live'' debugging of the process from that state.
5701 When the inferior process exits, or @value{GDBN} detaches from it,
5702 process record and replay target will automatically stop itself.
5705 @item record save @var{filename}
5706 Save the execution log to a file @file{@var{filename}}.
5707 Default filename is @file{gdb_record.@var{process_id}}, where
5708 @var{process_id} is the process ID of the inferior.
5710 @kindex record restore
5711 @item record restore @var{filename}
5712 Restore the execution log from a file @file{@var{filename}}.
5713 File must have been created with @code{record save}.
5715 @kindex set record insn-number-max
5716 @item set record insn-number-max @var{limit}
5717 Set the limit of instructions to be recorded. Default value is 200000.
5719 If @var{limit} is a positive number, then @value{GDBN} will start
5720 deleting instructions from the log once the number of the record
5721 instructions becomes greater than @var{limit}. For every new recorded
5722 instruction, @value{GDBN} will delete the earliest recorded
5723 instruction to keep the number of recorded instructions at the limit.
5724 (Since deleting recorded instructions loses information, @value{GDBN}
5725 lets you control what happens when the limit is reached, by means of
5726 the @code{stop-at-limit} option, described below.)
5728 If @var{limit} is zero, @value{GDBN} will never delete recorded
5729 instructions from the execution log. The number of recorded
5730 instructions is unlimited in this case.
5732 @kindex show record insn-number-max
5733 @item show record insn-number-max
5734 Show the limit of instructions to be recorded.
5736 @kindex set record stop-at-limit
5737 @item set record stop-at-limit
5738 Control the behavior when the number of recorded instructions reaches
5739 the limit. If ON (the default), @value{GDBN} will stop when the limit
5740 is reached for the first time and ask you whether you want to stop the
5741 inferior or continue running it and recording the execution log. If
5742 you decide to continue recording, each new recorded instruction will
5743 cause the oldest one to be deleted.
5745 If this option is OFF, @value{GDBN} will automatically delete the
5746 oldest record to make room for each new one, without asking.
5748 @kindex show record stop-at-limit
5749 @item show record stop-at-limit
5750 Show the current setting of @code{stop-at-limit}.
5752 @kindex set record memory-query
5753 @item set record memory-query
5754 Control the behavior when @value{GDBN} is unable to record memory
5755 changes caused by an instruction. If ON, @value{GDBN} will query
5756 whether to stop the inferior in that case.
5758 If this option is OFF (the default), @value{GDBN} will automatically
5759 ignore the effect of such instructions on memory. Later, when
5760 @value{GDBN} replays this execution log, it will mark the log of this
5761 instruction as not accessible, and it will not affect the replay
5764 @kindex show record memory-query
5765 @item show record memory-query
5766 Show the current setting of @code{memory-query}.
5770 Show various statistics about the state of process record and its
5771 in-memory execution log buffer, including:
5775 Whether in record mode or replay mode.
5777 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
5779 Highest recorded instruction number.
5781 Current instruction about to be replayed (if in replay mode).
5783 Number of instructions contained in the execution log.
5785 Maximum number of instructions that may be contained in the execution log.
5788 @kindex record delete
5791 When record target runs in replay mode (``in the past''), delete the
5792 subsequent execution log and begin to record a new execution log starting
5793 from the current address. This means you will abandon the previously
5794 recorded ``future'' and begin recording a new ``future''.
5799 @chapter Examining the Stack
5801 When your program has stopped, the first thing you need to know is where it
5802 stopped and how it got there.
5805 Each time your program performs a function call, information about the call
5807 That information includes the location of the call in your program,
5808 the arguments of the call,
5809 and the local variables of the function being called.
5810 The information is saved in a block of data called a @dfn{stack frame}.
5811 The stack frames are allocated in a region of memory called the @dfn{call
5814 When your program stops, the @value{GDBN} commands for examining the
5815 stack allow you to see all of this information.
5817 @cindex selected frame
5818 One of the stack frames is @dfn{selected} by @value{GDBN} and many
5819 @value{GDBN} commands refer implicitly to the selected frame. In
5820 particular, whenever you ask @value{GDBN} for the value of a variable in
5821 your program, the value is found in the selected frame. There are
5822 special @value{GDBN} commands to select whichever frame you are
5823 interested in. @xref{Selection, ,Selecting a Frame}.
5825 When your program stops, @value{GDBN} automatically selects the
5826 currently executing frame and describes it briefly, similar to the
5827 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
5830 * Frames:: Stack frames
5831 * Backtrace:: Backtraces
5832 * Selection:: Selecting a frame
5833 * Frame Info:: Information on a frame
5838 @section Stack Frames
5840 @cindex frame, definition
5842 The call stack is divided up into contiguous pieces called @dfn{stack
5843 frames}, or @dfn{frames} for short; each frame is the data associated
5844 with one call to one function. The frame contains the arguments given
5845 to the function, the function's local variables, and the address at
5846 which the function is executing.
5848 @cindex initial frame
5849 @cindex outermost frame
5850 @cindex innermost frame
5851 When your program is started, the stack has only one frame, that of the
5852 function @code{main}. This is called the @dfn{initial} frame or the
5853 @dfn{outermost} frame. Each time a function is called, a new frame is
5854 made. Each time a function returns, the frame for that function invocation
5855 is eliminated. If a function is recursive, there can be many frames for
5856 the same function. The frame for the function in which execution is
5857 actually occurring is called the @dfn{innermost} frame. This is the most
5858 recently created of all the stack frames that still exist.
5860 @cindex frame pointer
5861 Inside your program, stack frames are identified by their addresses. A
5862 stack frame consists of many bytes, each of which has its own address; each
5863 kind of computer has a convention for choosing one byte whose
5864 address serves as the address of the frame. Usually this address is kept
5865 in a register called the @dfn{frame pointer register}
5866 (@pxref{Registers, $fp}) while execution is going on in that frame.
5868 @cindex frame number
5869 @value{GDBN} assigns numbers to all existing stack frames, starting with
5870 zero for the innermost frame, one for the frame that called it,
5871 and so on upward. These numbers do not really exist in your program;
5872 they are assigned by @value{GDBN} to give you a way of designating stack
5873 frames in @value{GDBN} commands.
5875 @c The -fomit-frame-pointer below perennially causes hbox overflow
5876 @c underflow problems.
5877 @cindex frameless execution
5878 Some compilers provide a way to compile functions so that they operate
5879 without stack frames. (For example, the @value{NGCC} option
5881 @samp{-fomit-frame-pointer}
5883 generates functions without a frame.)
5884 This is occasionally done with heavily used library functions to save
5885 the frame setup time. @value{GDBN} has limited facilities for dealing
5886 with these function invocations. If the innermost function invocation
5887 has no stack frame, @value{GDBN} nevertheless regards it as though
5888 it had a separate frame, which is numbered zero as usual, allowing
5889 correct tracing of the function call chain. However, @value{GDBN} has
5890 no provision for frameless functions elsewhere in the stack.
5893 @kindex frame@r{, command}
5894 @cindex current stack frame
5895 @item frame @var{args}
5896 The @code{frame} command allows you to move from one stack frame to another,
5897 and to print the stack frame you select. @var{args} may be either the
5898 address of the frame or the stack frame number. Without an argument,
5899 @code{frame} prints the current stack frame.
5901 @kindex select-frame
5902 @cindex selecting frame silently
5904 The @code{select-frame} command allows you to move from one stack frame
5905 to another without printing the frame. This is the silent version of
5913 @cindex call stack traces
5914 A backtrace is a summary of how your program got where it is. It shows one
5915 line per frame, for many frames, starting with the currently executing
5916 frame (frame zero), followed by its caller (frame one), and on up the
5921 @kindex bt @r{(@code{backtrace})}
5924 Print a backtrace of the entire stack: one line per frame for all
5925 frames in the stack.
5927 You can stop the backtrace at any time by typing the system interrupt
5928 character, normally @kbd{Ctrl-c}.
5930 @item backtrace @var{n}
5932 Similar, but print only the innermost @var{n} frames.
5934 @item backtrace -@var{n}
5936 Similar, but print only the outermost @var{n} frames.
5938 @item backtrace full
5940 @itemx bt full @var{n}
5941 @itemx bt full -@var{n}
5942 Print the values of the local variables also. @var{n} specifies the
5943 number of frames to print, as described above.
5948 The names @code{where} and @code{info stack} (abbreviated @code{info s})
5949 are additional aliases for @code{backtrace}.
5951 @cindex multiple threads, backtrace
5952 In a multi-threaded program, @value{GDBN} by default shows the
5953 backtrace only for the current thread. To display the backtrace for
5954 several or all of the threads, use the command @code{thread apply}
5955 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
5956 apply all backtrace}, @value{GDBN} will display the backtrace for all
5957 the threads; this is handy when you debug a core dump of a
5958 multi-threaded program.
5960 Each line in the backtrace shows the frame number and the function name.
5961 The program counter value is also shown---unless you use @code{set
5962 print address off}. The backtrace also shows the source file name and
5963 line number, as well as the arguments to the function. The program
5964 counter value is omitted if it is at the beginning of the code for that
5967 Here is an example of a backtrace. It was made with the command
5968 @samp{bt 3}, so it shows the innermost three frames.
5972 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
5974 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
5975 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
5977 (More stack frames follow...)
5982 The display for frame zero does not begin with a program counter
5983 value, indicating that your program has stopped at the beginning of the
5984 code for line @code{993} of @code{builtin.c}.
5987 The value of parameter @code{data} in frame 1 has been replaced by
5988 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
5989 only if it is a scalar (integer, pointer, enumeration, etc). See command
5990 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
5991 on how to configure the way function parameter values are printed.
5993 @cindex value optimized out, in backtrace
5994 @cindex function call arguments, optimized out
5995 If your program was compiled with optimizations, some compilers will
5996 optimize away arguments passed to functions if those arguments are
5997 never used after the call. Such optimizations generate code that
5998 passes arguments through registers, but doesn't store those arguments
5999 in the stack frame. @value{GDBN} has no way of displaying such
6000 arguments in stack frames other than the innermost one. Here's what
6001 such a backtrace might look like:
6005 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6007 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
6008 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
6010 (More stack frames follow...)
6015 The values of arguments that were not saved in their stack frames are
6016 shown as @samp{<value optimized out>}.
6018 If you need to display the values of such optimized-out arguments,
6019 either deduce that from other variables whose values depend on the one
6020 you are interested in, or recompile without optimizations.
6022 @cindex backtrace beyond @code{main} function
6023 @cindex program entry point
6024 @cindex startup code, and backtrace
6025 Most programs have a standard user entry point---a place where system
6026 libraries and startup code transition into user code. For C this is
6027 @code{main}@footnote{
6028 Note that embedded programs (the so-called ``free-standing''
6029 environment) are not required to have a @code{main} function as the
6030 entry point. They could even have multiple entry points.}.
6031 When @value{GDBN} finds the entry function in a backtrace
6032 it will terminate the backtrace, to avoid tracing into highly
6033 system-specific (and generally uninteresting) code.
6035 If you need to examine the startup code, or limit the number of levels
6036 in a backtrace, you can change this behavior:
6039 @item set backtrace past-main
6040 @itemx set backtrace past-main on
6041 @kindex set backtrace
6042 Backtraces will continue past the user entry point.
6044 @item set backtrace past-main off
6045 Backtraces will stop when they encounter the user entry point. This is the
6048 @item show backtrace past-main
6049 @kindex show backtrace
6050 Display the current user entry point backtrace policy.
6052 @item set backtrace past-entry
6053 @itemx set backtrace past-entry on
6054 Backtraces will continue past the internal entry point of an application.
6055 This entry point is encoded by the linker when the application is built,
6056 and is likely before the user entry point @code{main} (or equivalent) is called.
6058 @item set backtrace past-entry off
6059 Backtraces will stop when they encounter the internal entry point of an
6060 application. This is the default.
6062 @item show backtrace past-entry
6063 Display the current internal entry point backtrace policy.
6065 @item set backtrace limit @var{n}
6066 @itemx set backtrace limit 0
6067 @cindex backtrace limit
6068 Limit the backtrace to @var{n} levels. A value of zero means
6071 @item show backtrace limit
6072 Display the current limit on backtrace levels.
6076 @section Selecting a Frame
6078 Most commands for examining the stack and other data in your program work on
6079 whichever stack frame is selected at the moment. Here are the commands for
6080 selecting a stack frame; all of them finish by printing a brief description
6081 of the stack frame just selected.
6084 @kindex frame@r{, selecting}
6085 @kindex f @r{(@code{frame})}
6088 Select frame number @var{n}. Recall that frame zero is the innermost
6089 (currently executing) frame, frame one is the frame that called the
6090 innermost one, and so on. The highest-numbered frame is the one for
6093 @item frame @var{addr}
6095 Select the frame at address @var{addr}. This is useful mainly if the
6096 chaining of stack frames has been damaged by a bug, making it
6097 impossible for @value{GDBN} to assign numbers properly to all frames. In
6098 addition, this can be useful when your program has multiple stacks and
6099 switches between them.
6101 On the SPARC architecture, @code{frame} needs two addresses to
6102 select an arbitrary frame: a frame pointer and a stack pointer.
6104 On the MIPS and Alpha architecture, it needs two addresses: a stack
6105 pointer and a program counter.
6107 On the 29k architecture, it needs three addresses: a register stack
6108 pointer, a program counter, and a memory stack pointer.
6112 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6113 advances toward the outermost frame, to higher frame numbers, to frames
6114 that have existed longer. @var{n} defaults to one.
6117 @kindex do @r{(@code{down})}
6119 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6120 advances toward the innermost frame, to lower frame numbers, to frames
6121 that were created more recently. @var{n} defaults to one. You may
6122 abbreviate @code{down} as @code{do}.
6125 All of these commands end by printing two lines of output describing the
6126 frame. The first line shows the frame number, the function name, the
6127 arguments, and the source file and line number of execution in that
6128 frame. The second line shows the text of that source line.
6136 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6138 10 read_input_file (argv[i]);
6142 After such a printout, the @code{list} command with no arguments
6143 prints ten lines centered on the point of execution in the frame.
6144 You can also edit the program at the point of execution with your favorite
6145 editing program by typing @code{edit}.
6146 @xref{List, ,Printing Source Lines},
6150 @kindex down-silently
6152 @item up-silently @var{n}
6153 @itemx down-silently @var{n}
6154 These two commands are variants of @code{up} and @code{down},
6155 respectively; they differ in that they do their work silently, without
6156 causing display of the new frame. They are intended primarily for use
6157 in @value{GDBN} command scripts, where the output might be unnecessary and
6162 @section Information About a Frame
6164 There are several other commands to print information about the selected
6170 When used without any argument, this command does not change which
6171 frame is selected, but prints a brief description of the currently
6172 selected stack frame. It can be abbreviated @code{f}. With an
6173 argument, this command is used to select a stack frame.
6174 @xref{Selection, ,Selecting a Frame}.
6177 @kindex info f @r{(@code{info frame})}
6180 This command prints a verbose description of the selected stack frame,
6185 the address of the frame
6187 the address of the next frame down (called by this frame)
6189 the address of the next frame up (caller of this frame)
6191 the language in which the source code corresponding to this frame is written
6193 the address of the frame's arguments
6195 the address of the frame's local variables
6197 the program counter saved in it (the address of execution in the caller frame)
6199 which registers were saved in the frame
6202 @noindent The verbose description is useful when
6203 something has gone wrong that has made the stack format fail to fit
6204 the usual conventions.
6206 @item info frame @var{addr}
6207 @itemx info f @var{addr}
6208 Print a verbose description of the frame at address @var{addr}, without
6209 selecting that frame. The selected frame remains unchanged by this
6210 command. This requires the same kind of address (more than one for some
6211 architectures) that you specify in the @code{frame} command.
6212 @xref{Selection, ,Selecting a Frame}.
6216 Print the arguments of the selected frame, each on a separate line.
6220 Print the local variables of the selected frame, each on a separate
6221 line. These are all variables (declared either static or automatic)
6222 accessible at the point of execution of the selected frame.
6225 @cindex catch exceptions, list active handlers
6226 @cindex exception handlers, how to list
6228 Print a list of all the exception handlers that are active in the
6229 current stack frame at the current point of execution. To see other
6230 exception handlers, visit the associated frame (using the @code{up},
6231 @code{down}, or @code{frame} commands); then type @code{info catch}.
6232 @xref{Set Catchpoints, , Setting Catchpoints}.
6238 @chapter Examining Source Files
6240 @value{GDBN} can print parts of your program's source, since the debugging
6241 information recorded in the program tells @value{GDBN} what source files were
6242 used to build it. When your program stops, @value{GDBN} spontaneously prints
6243 the line where it stopped. Likewise, when you select a stack frame
6244 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6245 execution in that frame has stopped. You can print other portions of
6246 source files by explicit command.
6248 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6249 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6250 @value{GDBN} under @sc{gnu} Emacs}.
6253 * List:: Printing source lines
6254 * Specify Location:: How to specify code locations
6255 * Edit:: Editing source files
6256 * Search:: Searching source files
6257 * Source Path:: Specifying source directories
6258 * Machine Code:: Source and machine code
6262 @section Printing Source Lines
6265 @kindex l @r{(@code{list})}
6266 To print lines from a source file, use the @code{list} command
6267 (abbreviated @code{l}). By default, ten lines are printed.
6268 There are several ways to specify what part of the file you want to
6269 print; see @ref{Specify Location}, for the full list.
6271 Here are the forms of the @code{list} command most commonly used:
6274 @item list @var{linenum}
6275 Print lines centered around line number @var{linenum} in the
6276 current source file.
6278 @item list @var{function}
6279 Print lines centered around the beginning of function
6283 Print more lines. If the last lines printed were printed with a
6284 @code{list} command, this prints lines following the last lines
6285 printed; however, if the last line printed was a solitary line printed
6286 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6287 Stack}), this prints lines centered around that line.
6290 Print lines just before the lines last printed.
6293 @cindex @code{list}, how many lines to display
6294 By default, @value{GDBN} prints ten source lines with any of these forms of
6295 the @code{list} command. You can change this using @code{set listsize}:
6298 @kindex set listsize
6299 @item set listsize @var{count}
6300 Make the @code{list} command display @var{count} source lines (unless
6301 the @code{list} argument explicitly specifies some other number).
6303 @kindex show listsize
6305 Display the number of lines that @code{list} prints.
6308 Repeating a @code{list} command with @key{RET} discards the argument,
6309 so it is equivalent to typing just @code{list}. This is more useful
6310 than listing the same lines again. An exception is made for an
6311 argument of @samp{-}; that argument is preserved in repetition so that
6312 each repetition moves up in the source file.
6314 In general, the @code{list} command expects you to supply zero, one or two
6315 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6316 of writing them (@pxref{Specify Location}), but the effect is always
6317 to specify some source line.
6319 Here is a complete description of the possible arguments for @code{list}:
6322 @item list @var{linespec}
6323 Print lines centered around the line specified by @var{linespec}.
6325 @item list @var{first},@var{last}
6326 Print lines from @var{first} to @var{last}. Both arguments are
6327 linespecs. When a @code{list} command has two linespecs, and the
6328 source file of the second linespec is omitted, this refers to
6329 the same source file as the first linespec.
6331 @item list ,@var{last}
6332 Print lines ending with @var{last}.
6334 @item list @var{first},
6335 Print lines starting with @var{first}.
6338 Print lines just after the lines last printed.
6341 Print lines just before the lines last printed.
6344 As described in the preceding table.
6347 @node Specify Location
6348 @section Specifying a Location
6349 @cindex specifying location
6352 Several @value{GDBN} commands accept arguments that specify a location
6353 of your program's code. Since @value{GDBN} is a source-level
6354 debugger, a location usually specifies some line in the source code;
6355 for that reason, locations are also known as @dfn{linespecs}.
6357 Here are all the different ways of specifying a code location that
6358 @value{GDBN} understands:
6362 Specifies the line number @var{linenum} of the current source file.
6365 @itemx +@var{offset}
6366 Specifies the line @var{offset} lines before or after the @dfn{current
6367 line}. For the @code{list} command, the current line is the last one
6368 printed; for the breakpoint commands, this is the line at which
6369 execution stopped in the currently selected @dfn{stack frame}
6370 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6371 used as the second of the two linespecs in a @code{list} command,
6372 this specifies the line @var{offset} lines up or down from the first
6375 @item @var{filename}:@var{linenum}
6376 Specifies the line @var{linenum} in the source file @var{filename}.
6378 @item @var{function}
6379 Specifies the line that begins the body of the function @var{function}.
6380 For example, in C, this is the line with the open brace.
6382 @item @var{filename}:@var{function}
6383 Specifies the line that begins the body of the function @var{function}
6384 in the file @var{filename}. You only need the file name with a
6385 function name to avoid ambiguity when there are identically named
6386 functions in different source files.
6389 Specifies the line at which the label named @var{label} appears.
6390 @value{GDBN} searches for the label in the function corresponding to
6391 the currently selected stack frame. If there is no current selected
6392 stack frame (for instance, if the inferior is not running), then
6393 @value{GDBN} will not search for a label.
6395 @item *@var{address}
6396 Specifies the program address @var{address}. For line-oriented
6397 commands, such as @code{list} and @code{edit}, this specifies a source
6398 line that contains @var{address}. For @code{break} and other
6399 breakpoint oriented commands, this can be used to set breakpoints in
6400 parts of your program which do not have debugging information or
6403 Here @var{address} may be any expression valid in the current working
6404 language (@pxref{Languages, working language}) that specifies a code
6405 address. In addition, as a convenience, @value{GDBN} extends the
6406 semantics of expressions used in locations to cover the situations
6407 that frequently happen during debugging. Here are the various forms
6411 @item @var{expression}
6412 Any expression valid in the current working language.
6414 @item @var{funcaddr}
6415 An address of a function or procedure derived from its name. In C,
6416 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6417 simply the function's name @var{function} (and actually a special case
6418 of a valid expression). In Pascal and Modula-2, this is
6419 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6420 (although the Pascal form also works).
6422 This form specifies the address of the function's first instruction,
6423 before the stack frame and arguments have been set up.
6425 @item '@var{filename}'::@var{funcaddr}
6426 Like @var{funcaddr} above, but also specifies the name of the source
6427 file explicitly. This is useful if the name of the function does not
6428 specify the function unambiguously, e.g., if there are several
6429 functions with identical names in different source files.
6436 @section Editing Source Files
6437 @cindex editing source files
6440 @kindex e @r{(@code{edit})}
6441 To edit the lines in a source file, use the @code{edit} command.
6442 The editing program of your choice
6443 is invoked with the current line set to
6444 the active line in the program.
6445 Alternatively, there are several ways to specify what part of the file you
6446 want to print if you want to see other parts of the program:
6449 @item edit @var{location}
6450 Edit the source file specified by @code{location}. Editing starts at
6451 that @var{location}, e.g., at the specified source line of the
6452 specified file. @xref{Specify Location}, for all the possible forms
6453 of the @var{location} argument; here are the forms of the @code{edit}
6454 command most commonly used:
6457 @item edit @var{number}
6458 Edit the current source file with @var{number} as the active line number.
6460 @item edit @var{function}
6461 Edit the file containing @var{function} at the beginning of its definition.
6466 @subsection Choosing your Editor
6467 You can customize @value{GDBN} to use any editor you want
6469 The only restriction is that your editor (say @code{ex}), recognizes the
6470 following command-line syntax:
6472 ex +@var{number} file
6474 The optional numeric value +@var{number} specifies the number of the line in
6475 the file where to start editing.}.
6476 By default, it is @file{@value{EDITOR}}, but you can change this
6477 by setting the environment variable @code{EDITOR} before using
6478 @value{GDBN}. For example, to configure @value{GDBN} to use the
6479 @code{vi} editor, you could use these commands with the @code{sh} shell:
6485 or in the @code{csh} shell,
6487 setenv EDITOR /usr/bin/vi
6492 @section Searching Source Files
6493 @cindex searching source files
6495 There are two commands for searching through the current source file for a
6500 @kindex forward-search
6501 @item forward-search @var{regexp}
6502 @itemx search @var{regexp}
6503 The command @samp{forward-search @var{regexp}} checks each line,
6504 starting with the one following the last line listed, for a match for
6505 @var{regexp}. It lists the line that is found. You can use the
6506 synonym @samp{search @var{regexp}} or abbreviate the command name as
6509 @kindex reverse-search
6510 @item reverse-search @var{regexp}
6511 The command @samp{reverse-search @var{regexp}} checks each line, starting
6512 with the one before the last line listed and going backward, for a match
6513 for @var{regexp}. It lists the line that is found. You can abbreviate
6514 this command as @code{rev}.
6518 @section Specifying Source Directories
6521 @cindex directories for source files
6522 Executable programs sometimes do not record the directories of the source
6523 files from which they were compiled, just the names. Even when they do,
6524 the directories could be moved between the compilation and your debugging
6525 session. @value{GDBN} has a list of directories to search for source files;
6526 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
6527 it tries all the directories in the list, in the order they are present
6528 in the list, until it finds a file with the desired name.
6530 For example, suppose an executable references the file
6531 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
6532 @file{/mnt/cross}. The file is first looked up literally; if this
6533 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
6534 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
6535 message is printed. @value{GDBN} does not look up the parts of the
6536 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
6537 Likewise, the subdirectories of the source path are not searched: if
6538 the source path is @file{/mnt/cross}, and the binary refers to
6539 @file{foo.c}, @value{GDBN} would not find it under
6540 @file{/mnt/cross/usr/src/foo-1.0/lib}.
6542 Plain file names, relative file names with leading directories, file
6543 names containing dots, etc.@: are all treated as described above; for
6544 instance, if the source path is @file{/mnt/cross}, and the source file
6545 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
6546 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
6547 that---@file{/mnt/cross/foo.c}.
6549 Note that the executable search path is @emph{not} used to locate the
6552 Whenever you reset or rearrange the source path, @value{GDBN} clears out
6553 any information it has cached about where source files are found and where
6554 each line is in the file.
6558 When you start @value{GDBN}, its source path includes only @samp{cdir}
6559 and @samp{cwd}, in that order.
6560 To add other directories, use the @code{directory} command.
6562 The search path is used to find both program source files and @value{GDBN}
6563 script files (read using the @samp{-command} option and @samp{source} command).
6565 In addition to the source path, @value{GDBN} provides a set of commands
6566 that manage a list of source path substitution rules. A @dfn{substitution
6567 rule} specifies how to rewrite source directories stored in the program's
6568 debug information in case the sources were moved to a different
6569 directory between compilation and debugging. A rule is made of
6570 two strings, the first specifying what needs to be rewritten in
6571 the path, and the second specifying how it should be rewritten.
6572 In @ref{set substitute-path}, we name these two parts @var{from} and
6573 @var{to} respectively. @value{GDBN} does a simple string replacement
6574 of @var{from} with @var{to} at the start of the directory part of the
6575 source file name, and uses that result instead of the original file
6576 name to look up the sources.
6578 Using the previous example, suppose the @file{foo-1.0} tree has been
6579 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
6580 @value{GDBN} to replace @file{/usr/src} in all source path names with
6581 @file{/mnt/cross}. The first lookup will then be
6582 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
6583 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
6584 substitution rule, use the @code{set substitute-path} command
6585 (@pxref{set substitute-path}).
6587 To avoid unexpected substitution results, a rule is applied only if the
6588 @var{from} part of the directory name ends at a directory separator.
6589 For instance, a rule substituting @file{/usr/source} into
6590 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
6591 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
6592 is applied only at the beginning of the directory name, this rule will
6593 not be applied to @file{/root/usr/source/baz.c} either.
6595 In many cases, you can achieve the same result using the @code{directory}
6596 command. However, @code{set substitute-path} can be more efficient in
6597 the case where the sources are organized in a complex tree with multiple
6598 subdirectories. With the @code{directory} command, you need to add each
6599 subdirectory of your project. If you moved the entire tree while
6600 preserving its internal organization, then @code{set substitute-path}
6601 allows you to direct the debugger to all the sources with one single
6604 @code{set substitute-path} is also more than just a shortcut command.
6605 The source path is only used if the file at the original location no
6606 longer exists. On the other hand, @code{set substitute-path} modifies
6607 the debugger behavior to look at the rewritten location instead. So, if
6608 for any reason a source file that is not relevant to your executable is
6609 located at the original location, a substitution rule is the only
6610 method available to point @value{GDBN} at the new location.
6612 @cindex @samp{--with-relocated-sources}
6613 @cindex default source path substitution
6614 You can configure a default source path substitution rule by
6615 configuring @value{GDBN} with the
6616 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
6617 should be the name of a directory under @value{GDBN}'s configured
6618 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
6619 directory names in debug information under @var{dir} will be adjusted
6620 automatically if the installed @value{GDBN} is moved to a new
6621 location. This is useful if @value{GDBN}, libraries or executables
6622 with debug information and corresponding source code are being moved
6626 @item directory @var{dirname} @dots{}
6627 @item dir @var{dirname} @dots{}
6628 Add directory @var{dirname} to the front of the source path. Several
6629 directory names may be given to this command, separated by @samp{:}
6630 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
6631 part of absolute file names) or
6632 whitespace. You may specify a directory that is already in the source
6633 path; this moves it forward, so @value{GDBN} searches it sooner.
6637 @vindex $cdir@r{, convenience variable}
6638 @vindex $cwd@r{, convenience variable}
6639 @cindex compilation directory
6640 @cindex current directory
6641 @cindex working directory
6642 @cindex directory, current
6643 @cindex directory, compilation
6644 You can use the string @samp{$cdir} to refer to the compilation
6645 directory (if one is recorded), and @samp{$cwd} to refer to the current
6646 working directory. @samp{$cwd} is not the same as @samp{.}---the former
6647 tracks the current working directory as it changes during your @value{GDBN}
6648 session, while the latter is immediately expanded to the current
6649 directory at the time you add an entry to the source path.
6652 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
6654 @c RET-repeat for @code{directory} is explicitly disabled, but since
6655 @c repeating it would be a no-op we do not say that. (thanks to RMS)
6657 @item set directories @var{path-list}
6658 @kindex set directories
6659 Set the source path to @var{path-list}.
6660 @samp{$cdir:$cwd} are added if missing.
6662 @item show directories
6663 @kindex show directories
6664 Print the source path: show which directories it contains.
6666 @anchor{set substitute-path}
6667 @item set substitute-path @var{from} @var{to}
6668 @kindex set substitute-path
6669 Define a source path substitution rule, and add it at the end of the
6670 current list of existing substitution rules. If a rule with the same
6671 @var{from} was already defined, then the old rule is also deleted.
6673 For example, if the file @file{/foo/bar/baz.c} was moved to
6674 @file{/mnt/cross/baz.c}, then the command
6677 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
6681 will tell @value{GDBN} to replace @samp{/usr/src} with
6682 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
6683 @file{baz.c} even though it was moved.
6685 In the case when more than one substitution rule have been defined,
6686 the rules are evaluated one by one in the order where they have been
6687 defined. The first one matching, if any, is selected to perform
6690 For instance, if we had entered the following commands:
6693 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
6694 (@value{GDBP}) set substitute-path /usr/src /mnt/src
6698 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
6699 @file{/mnt/include/defs.h} by using the first rule. However, it would
6700 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
6701 @file{/mnt/src/lib/foo.c}.
6704 @item unset substitute-path [path]
6705 @kindex unset substitute-path
6706 If a path is specified, search the current list of substitution rules
6707 for a rule that would rewrite that path. Delete that rule if found.
6708 A warning is emitted by the debugger if no rule could be found.
6710 If no path is specified, then all substitution rules are deleted.
6712 @item show substitute-path [path]
6713 @kindex show substitute-path
6714 If a path is specified, then print the source path substitution rule
6715 which would rewrite that path, if any.
6717 If no path is specified, then print all existing source path substitution
6722 If your source path is cluttered with directories that are no longer of
6723 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
6724 versions of source. You can correct the situation as follows:
6728 Use @code{directory} with no argument to reset the source path to its default value.
6731 Use @code{directory} with suitable arguments to reinstall the
6732 directories you want in the source path. You can add all the
6733 directories in one command.
6737 @section Source and Machine Code
6738 @cindex source line and its code address
6740 You can use the command @code{info line} to map source lines to program
6741 addresses (and vice versa), and the command @code{disassemble} to display
6742 a range of addresses as machine instructions. You can use the command
6743 @code{set disassemble-next-line} to set whether to disassemble next
6744 source line when execution stops. When run under @sc{gnu} Emacs
6745 mode, the @code{info line} command causes the arrow to point to the
6746 line specified. Also, @code{info line} prints addresses in symbolic form as
6751 @item info line @var{linespec}
6752 Print the starting and ending addresses of the compiled code for
6753 source line @var{linespec}. You can specify source lines in any of
6754 the ways documented in @ref{Specify Location}.
6757 For example, we can use @code{info line} to discover the location of
6758 the object code for the first line of function
6759 @code{m4_changequote}:
6761 @c FIXME: I think this example should also show the addresses in
6762 @c symbolic form, as they usually would be displayed.
6764 (@value{GDBP}) info line m4_changequote
6765 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
6769 @cindex code address and its source line
6770 We can also inquire (using @code{*@var{addr}} as the form for
6771 @var{linespec}) what source line covers a particular address:
6773 (@value{GDBP}) info line *0x63ff
6774 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
6777 @cindex @code{$_} and @code{info line}
6778 @cindex @code{x} command, default address
6779 @kindex x@r{(examine), and} info line
6780 After @code{info line}, the default address for the @code{x} command
6781 is changed to the starting address of the line, so that @samp{x/i} is
6782 sufficient to begin examining the machine code (@pxref{Memory,
6783 ,Examining Memory}). Also, this address is saved as the value of the
6784 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
6789 @cindex assembly instructions
6790 @cindex instructions, assembly
6791 @cindex machine instructions
6792 @cindex listing machine instructions
6794 @itemx disassemble /m
6795 @itemx disassemble /r
6796 This specialized command dumps a range of memory as machine
6797 instructions. It can also print mixed source+disassembly by specifying
6798 the @code{/m} modifier and print the raw instructions in hex as well as
6799 in symbolic form by specifying the @code{/r}.
6800 The default memory range is the function surrounding the
6801 program counter of the selected frame. A single argument to this
6802 command is a program counter value; @value{GDBN} dumps the function
6803 surrounding this value. When two arguments are given, they should
6804 be separated by a comma, possibly surrounded by whitespace. The
6805 arguments specify a range of addresses to dump, in one of two forms:
6808 @item @var{start},@var{end}
6809 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
6810 @item @var{start},+@var{length}
6811 the addresses from @var{start} (inclusive) to
6812 @code{@var{start}+@var{length}} (exclusive).
6816 When 2 arguments are specified, the name of the function is also
6817 printed (since there could be several functions in the given range).
6819 The argument(s) can be any expression yielding a numeric value, such as
6820 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
6822 If the range of memory being disassembled contains current program counter,
6823 the instruction at that location is shown with a @code{=>} marker.
6826 The following example shows the disassembly of a range of addresses of
6827 HP PA-RISC 2.0 code:
6830 (@value{GDBP}) disas 0x32c4, 0x32e4
6831 Dump of assembler code from 0x32c4 to 0x32e4:
6832 0x32c4 <main+204>: addil 0,dp
6833 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
6834 0x32cc <main+212>: ldil 0x3000,r31
6835 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
6836 0x32d4 <main+220>: ldo 0(r31),rp
6837 0x32d8 <main+224>: addil -0x800,dp
6838 0x32dc <main+228>: ldo 0x588(r1),r26
6839 0x32e0 <main+232>: ldil 0x3000,r31
6840 End of assembler dump.
6843 Here is an example showing mixed source+assembly for Intel x86, when the
6844 program is stopped just after function prologue:
6847 (@value{GDBP}) disas /m main
6848 Dump of assembler code for function main:
6850 0x08048330 <+0>: push %ebp
6851 0x08048331 <+1>: mov %esp,%ebp
6852 0x08048333 <+3>: sub $0x8,%esp
6853 0x08048336 <+6>: and $0xfffffff0,%esp
6854 0x08048339 <+9>: sub $0x10,%esp
6856 6 printf ("Hello.\n");
6857 => 0x0804833c <+12>: movl $0x8048440,(%esp)
6858 0x08048343 <+19>: call 0x8048284 <puts@@plt>
6862 0x08048348 <+24>: mov $0x0,%eax
6863 0x0804834d <+29>: leave
6864 0x0804834e <+30>: ret
6866 End of assembler dump.
6869 Here is another example showing raw instructions in hex for AMD x86-64,
6872 (gdb) disas /r 0x400281,+10
6873 Dump of assembler code from 0x400281 to 0x40028b:
6874 0x0000000000400281: 38 36 cmp %dh,(%rsi)
6875 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
6876 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
6877 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
6878 End of assembler dump.
6881 Some architectures have more than one commonly-used set of instruction
6882 mnemonics or other syntax.
6884 For programs that were dynamically linked and use shared libraries,
6885 instructions that call functions or branch to locations in the shared
6886 libraries might show a seemingly bogus location---it's actually a
6887 location of the relocation table. On some architectures, @value{GDBN}
6888 might be able to resolve these to actual function names.
6891 @kindex set disassembly-flavor
6892 @cindex Intel disassembly flavor
6893 @cindex AT&T disassembly flavor
6894 @item set disassembly-flavor @var{instruction-set}
6895 Select the instruction set to use when disassembling the
6896 program via the @code{disassemble} or @code{x/i} commands.
6898 Currently this command is only defined for the Intel x86 family. You
6899 can set @var{instruction-set} to either @code{intel} or @code{att}.
6900 The default is @code{att}, the AT&T flavor used by default by Unix
6901 assemblers for x86-based targets.
6903 @kindex show disassembly-flavor
6904 @item show disassembly-flavor
6905 Show the current setting of the disassembly flavor.
6909 @kindex set disassemble-next-line
6910 @kindex show disassemble-next-line
6911 @item set disassemble-next-line
6912 @itemx show disassemble-next-line
6913 Control whether or not @value{GDBN} will disassemble the next source
6914 line or instruction when execution stops. If ON, @value{GDBN} will
6915 display disassembly of the next source line when execution of the
6916 program being debugged stops. This is @emph{in addition} to
6917 displaying the source line itself, which @value{GDBN} always does if
6918 possible. If the next source line cannot be displayed for some reason
6919 (e.g., if @value{GDBN} cannot find the source file, or there's no line
6920 info in the debug info), @value{GDBN} will display disassembly of the
6921 next @emph{instruction} instead of showing the next source line. If
6922 AUTO, @value{GDBN} will display disassembly of next instruction only
6923 if the source line cannot be displayed. This setting causes
6924 @value{GDBN} to display some feedback when you step through a function
6925 with no line info or whose source file is unavailable. The default is
6926 OFF, which means never display the disassembly of the next line or
6932 @chapter Examining Data
6934 @cindex printing data
6935 @cindex examining data
6938 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
6939 @c document because it is nonstandard... Under Epoch it displays in a
6940 @c different window or something like that.
6941 The usual way to examine data in your program is with the @code{print}
6942 command (abbreviated @code{p}), or its synonym @code{inspect}. It
6943 evaluates and prints the value of an expression of the language your
6944 program is written in (@pxref{Languages, ,Using @value{GDBN} with
6945 Different Languages}). It may also print the expression using a
6946 Python-based pretty-printer (@pxref{Pretty Printing}).
6949 @item print @var{expr}
6950 @itemx print /@var{f} @var{expr}
6951 @var{expr} is an expression (in the source language). By default the
6952 value of @var{expr} is printed in a format appropriate to its data type;
6953 you can choose a different format by specifying @samp{/@var{f}}, where
6954 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
6958 @itemx print /@var{f}
6959 @cindex reprint the last value
6960 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
6961 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
6962 conveniently inspect the same value in an alternative format.
6965 A more low-level way of examining data is with the @code{x} command.
6966 It examines data in memory at a specified address and prints it in a
6967 specified format. @xref{Memory, ,Examining Memory}.
6969 If you are interested in information about types, or about how the
6970 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
6971 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
6975 * Expressions:: Expressions
6976 * Ambiguous Expressions:: Ambiguous Expressions
6977 * Variables:: Program variables
6978 * Arrays:: Artificial arrays
6979 * Output Formats:: Output formats
6980 * Memory:: Examining memory
6981 * Auto Display:: Automatic display
6982 * Print Settings:: Print settings
6983 * Pretty Printing:: Python pretty printing
6984 * Value History:: Value history
6985 * Convenience Vars:: Convenience variables
6986 * Registers:: Registers
6987 * Floating Point Hardware:: Floating point hardware
6988 * Vector Unit:: Vector Unit
6989 * OS Information:: Auxiliary data provided by operating system
6990 * Memory Region Attributes:: Memory region attributes
6991 * Dump/Restore Files:: Copy between memory and a file
6992 * Core File Generation:: Cause a program dump its core
6993 * Character Sets:: Debugging programs that use a different
6994 character set than GDB does
6995 * Caching Remote Data:: Data caching for remote targets
6996 * Searching Memory:: Searching memory for a sequence of bytes
7000 @section Expressions
7003 @code{print} and many other @value{GDBN} commands accept an expression and
7004 compute its value. Any kind of constant, variable or operator defined
7005 by the programming language you are using is valid in an expression in
7006 @value{GDBN}. This includes conditional expressions, function calls,
7007 casts, and string constants. It also includes preprocessor macros, if
7008 you compiled your program to include this information; see
7011 @cindex arrays in expressions
7012 @value{GDBN} supports array constants in expressions input by
7013 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
7014 you can use the command @code{print @{1, 2, 3@}} to create an array
7015 of three integers. If you pass an array to a function or assign it
7016 to a program variable, @value{GDBN} copies the array to memory that
7017 is @code{malloc}ed in the target program.
7019 Because C is so widespread, most of the expressions shown in examples in
7020 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
7021 Languages}, for information on how to use expressions in other
7024 In this section, we discuss operators that you can use in @value{GDBN}
7025 expressions regardless of your programming language.
7027 @cindex casts, in expressions
7028 Casts are supported in all languages, not just in C, because it is so
7029 useful to cast a number into a pointer in order to examine a structure
7030 at that address in memory.
7031 @c FIXME: casts supported---Mod2 true?
7033 @value{GDBN} supports these operators, in addition to those common
7034 to programming languages:
7038 @samp{@@} is a binary operator for treating parts of memory as arrays.
7039 @xref{Arrays, ,Artificial Arrays}, for more information.
7042 @samp{::} allows you to specify a variable in terms of the file or
7043 function where it is defined. @xref{Variables, ,Program Variables}.
7045 @cindex @{@var{type}@}
7046 @cindex type casting memory
7047 @cindex memory, viewing as typed object
7048 @cindex casts, to view memory
7049 @item @{@var{type}@} @var{addr}
7050 Refers to an object of type @var{type} stored at address @var{addr} in
7051 memory. @var{addr} may be any expression whose value is an integer or
7052 pointer (but parentheses are required around binary operators, just as in
7053 a cast). This construct is allowed regardless of what kind of data is
7054 normally supposed to reside at @var{addr}.
7057 @node Ambiguous Expressions
7058 @section Ambiguous Expressions
7059 @cindex ambiguous expressions
7061 Expressions can sometimes contain some ambiguous elements. For instance,
7062 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7063 a single function name to be defined several times, for application in
7064 different contexts. This is called @dfn{overloading}. Another example
7065 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7066 templates and is typically instantiated several times, resulting in
7067 the same function name being defined in different contexts.
7069 In some cases and depending on the language, it is possible to adjust
7070 the expression to remove the ambiguity. For instance in C@t{++}, you
7071 can specify the signature of the function you want to break on, as in
7072 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7073 qualified name of your function often makes the expression unambiguous
7076 When an ambiguity that needs to be resolved is detected, the debugger
7077 has the capability to display a menu of numbered choices for each
7078 possibility, and then waits for the selection with the prompt @samp{>}.
7079 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7080 aborts the current command. If the command in which the expression was
7081 used allows more than one choice to be selected, the next option in the
7082 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7085 For example, the following session excerpt shows an attempt to set a
7086 breakpoint at the overloaded symbol @code{String::after}.
7087 We choose three particular definitions of that function name:
7089 @c FIXME! This is likely to change to show arg type lists, at least
7092 (@value{GDBP}) b String::after
7095 [2] file:String.cc; line number:867
7096 [3] file:String.cc; line number:860
7097 [4] file:String.cc; line number:875
7098 [5] file:String.cc; line number:853
7099 [6] file:String.cc; line number:846
7100 [7] file:String.cc; line number:735
7102 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7103 Breakpoint 2 at 0xb344: file String.cc, line 875.
7104 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7105 Multiple breakpoints were set.
7106 Use the "delete" command to delete unwanted
7113 @kindex set multiple-symbols
7114 @item set multiple-symbols @var{mode}
7115 @cindex multiple-symbols menu
7117 This option allows you to adjust the debugger behavior when an expression
7120 By default, @var{mode} is set to @code{all}. If the command with which
7121 the expression is used allows more than one choice, then @value{GDBN}
7122 automatically selects all possible choices. For instance, inserting
7123 a breakpoint on a function using an ambiguous name results in a breakpoint
7124 inserted on each possible match. However, if a unique choice must be made,
7125 then @value{GDBN} uses the menu to help you disambiguate the expression.
7126 For instance, printing the address of an overloaded function will result
7127 in the use of the menu.
7129 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7130 when an ambiguity is detected.
7132 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7133 an error due to the ambiguity and the command is aborted.
7135 @kindex show multiple-symbols
7136 @item show multiple-symbols
7137 Show the current value of the @code{multiple-symbols} setting.
7141 @section Program Variables
7143 The most common kind of expression to use is the name of a variable
7146 Variables in expressions are understood in the selected stack frame
7147 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7151 global (or file-static)
7158 visible according to the scope rules of the
7159 programming language from the point of execution in that frame
7162 @noindent This means that in the function
7177 you can examine and use the variable @code{a} whenever your program is
7178 executing within the function @code{foo}, but you can only use or
7179 examine the variable @code{b} while your program is executing inside
7180 the block where @code{b} is declared.
7182 @cindex variable name conflict
7183 There is an exception: you can refer to a variable or function whose
7184 scope is a single source file even if the current execution point is not
7185 in this file. But it is possible to have more than one such variable or
7186 function with the same name (in different source files). If that
7187 happens, referring to that name has unpredictable effects. If you wish,
7188 you can specify a static variable in a particular function or file,
7189 using the colon-colon (@code{::}) notation:
7191 @cindex colon-colon, context for variables/functions
7193 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7194 @cindex @code{::}, context for variables/functions
7197 @var{file}::@var{variable}
7198 @var{function}::@var{variable}
7202 Here @var{file} or @var{function} is the name of the context for the
7203 static @var{variable}. In the case of file names, you can use quotes to
7204 make sure @value{GDBN} parses the file name as a single word---for example,
7205 to print a global value of @code{x} defined in @file{f2.c}:
7208 (@value{GDBP}) p 'f2.c'::x
7211 @cindex C@t{++} scope resolution
7212 This use of @samp{::} is very rarely in conflict with the very similar
7213 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7214 scope resolution operator in @value{GDBN} expressions.
7215 @c FIXME: Um, so what happens in one of those rare cases where it's in
7218 @cindex wrong values
7219 @cindex variable values, wrong
7220 @cindex function entry/exit, wrong values of variables
7221 @cindex optimized code, wrong values of variables
7223 @emph{Warning:} Occasionally, a local variable may appear to have the
7224 wrong value at certain points in a function---just after entry to a new
7225 scope, and just before exit.
7227 You may see this problem when you are stepping by machine instructions.
7228 This is because, on most machines, it takes more than one instruction to
7229 set up a stack frame (including local variable definitions); if you are
7230 stepping by machine instructions, variables may appear to have the wrong
7231 values until the stack frame is completely built. On exit, it usually
7232 also takes more than one machine instruction to destroy a stack frame;
7233 after you begin stepping through that group of instructions, local
7234 variable definitions may be gone.
7236 This may also happen when the compiler does significant optimizations.
7237 To be sure of always seeing accurate values, turn off all optimization
7240 @cindex ``No symbol "foo" in current context''
7241 Another possible effect of compiler optimizations is to optimize
7242 unused variables out of existence, or assign variables to registers (as
7243 opposed to memory addresses). Depending on the support for such cases
7244 offered by the debug info format used by the compiler, @value{GDBN}
7245 might not be able to display values for such local variables. If that
7246 happens, @value{GDBN} will print a message like this:
7249 No symbol "foo" in current context.
7252 To solve such problems, either recompile without optimizations, or use a
7253 different debug info format, if the compiler supports several such
7254 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
7255 usually supports the @option{-gstabs+} option. @option{-gstabs+}
7256 produces debug info in a format that is superior to formats such as
7257 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
7258 an effective form for debug info. @xref{Debugging Options,,Options
7259 for Debugging Your Program or GCC, gcc.info, Using the @sc{gnu}
7260 Compiler Collection (GCC)}.
7261 @xref{C, ,C and C@t{++}}, for more information about debug info formats
7262 that are best suited to C@t{++} programs.
7264 If you ask to print an object whose contents are unknown to
7265 @value{GDBN}, e.g., because its data type is not completely specified
7266 by the debug information, @value{GDBN} will say @samp{<incomplete
7267 type>}. @xref{Symbols, incomplete type}, for more about this.
7269 Strings are identified as arrays of @code{char} values without specified
7270 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7271 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7272 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7273 defines literal string type @code{"char"} as @code{char} without a sign.
7278 signed char var1[] = "A";
7281 You get during debugging
7286 $2 = @{65 'A', 0 '\0'@}
7290 @section Artificial Arrays
7292 @cindex artificial array
7294 @kindex @@@r{, referencing memory as an array}
7295 It is often useful to print out several successive objects of the
7296 same type in memory; a section of an array, or an array of
7297 dynamically determined size for which only a pointer exists in the
7300 You can do this by referring to a contiguous span of memory as an
7301 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7302 operand of @samp{@@} should be the first element of the desired array
7303 and be an individual object. The right operand should be the desired length
7304 of the array. The result is an array value whose elements are all of
7305 the type of the left argument. The first element is actually the left
7306 argument; the second element comes from bytes of memory immediately
7307 following those that hold the first element, and so on. Here is an
7308 example. If a program says
7311 int *array = (int *) malloc (len * sizeof (int));
7315 you can print the contents of @code{array} with
7321 The left operand of @samp{@@} must reside in memory. Array values made
7322 with @samp{@@} in this way behave just like other arrays in terms of
7323 subscripting, and are coerced to pointers when used in expressions.
7324 Artificial arrays most often appear in expressions via the value history
7325 (@pxref{Value History, ,Value History}), after printing one out.
7327 Another way to create an artificial array is to use a cast.
7328 This re-interprets a value as if it were an array.
7329 The value need not be in memory:
7331 (@value{GDBP}) p/x (short[2])0x12345678
7332 $1 = @{0x1234, 0x5678@}
7335 As a convenience, if you leave the array length out (as in
7336 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
7337 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
7339 (@value{GDBP}) p/x (short[])0x12345678
7340 $2 = @{0x1234, 0x5678@}
7343 Sometimes the artificial array mechanism is not quite enough; in
7344 moderately complex data structures, the elements of interest may not
7345 actually be adjacent---for example, if you are interested in the values
7346 of pointers in an array. One useful work-around in this situation is
7347 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
7348 Variables}) as a counter in an expression that prints the first
7349 interesting value, and then repeat that expression via @key{RET}. For
7350 instance, suppose you have an array @code{dtab} of pointers to
7351 structures, and you are interested in the values of a field @code{fv}
7352 in each structure. Here is an example of what you might type:
7362 @node Output Formats
7363 @section Output Formats
7365 @cindex formatted output
7366 @cindex output formats
7367 By default, @value{GDBN} prints a value according to its data type. Sometimes
7368 this is not what you want. For example, you might want to print a number
7369 in hex, or a pointer in decimal. Or you might want to view data in memory
7370 at a certain address as a character string or as an instruction. To do
7371 these things, specify an @dfn{output format} when you print a value.
7373 The simplest use of output formats is to say how to print a value
7374 already computed. This is done by starting the arguments of the
7375 @code{print} command with a slash and a format letter. The format
7376 letters supported are:
7380 Regard the bits of the value as an integer, and print the integer in
7384 Print as integer in signed decimal.
7387 Print as integer in unsigned decimal.
7390 Print as integer in octal.
7393 Print as integer in binary. The letter @samp{t} stands for ``two''.
7394 @footnote{@samp{b} cannot be used because these format letters are also
7395 used with the @code{x} command, where @samp{b} stands for ``byte'';
7396 see @ref{Memory,,Examining Memory}.}
7399 @cindex unknown address, locating
7400 @cindex locate address
7401 Print as an address, both absolute in hexadecimal and as an offset from
7402 the nearest preceding symbol. You can use this format used to discover
7403 where (in what function) an unknown address is located:
7406 (@value{GDBP}) p/a 0x54320
7407 $3 = 0x54320 <_initialize_vx+396>
7411 The command @code{info symbol 0x54320} yields similar results.
7412 @xref{Symbols, info symbol}.
7415 Regard as an integer and print it as a character constant. This
7416 prints both the numerical value and its character representation. The
7417 character representation is replaced with the octal escape @samp{\nnn}
7418 for characters outside the 7-bit @sc{ascii} range.
7420 Without this format, @value{GDBN} displays @code{char},
7421 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
7422 constants. Single-byte members of vectors are displayed as integer
7426 Regard the bits of the value as a floating point number and print
7427 using typical floating point syntax.
7430 @cindex printing strings
7431 @cindex printing byte arrays
7432 Regard as a string, if possible. With this format, pointers to single-byte
7433 data are displayed as null-terminated strings and arrays of single-byte data
7434 are displayed as fixed-length strings. Other values are displayed in their
7437 Without this format, @value{GDBN} displays pointers to and arrays of
7438 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
7439 strings. Single-byte members of a vector are displayed as an integer
7443 @cindex raw printing
7444 Print using the @samp{raw} formatting. By default, @value{GDBN} will
7445 use a Python-based pretty-printer, if one is available (@pxref{Pretty
7446 Printing}). This typically results in a higher-level display of the
7447 value's contents. The @samp{r} format bypasses any Python
7448 pretty-printer which might exist.
7451 For example, to print the program counter in hex (@pxref{Registers}), type
7458 Note that no space is required before the slash; this is because command
7459 names in @value{GDBN} cannot contain a slash.
7461 To reprint the last value in the value history with a different format,
7462 you can use the @code{print} command with just a format and no
7463 expression. For example, @samp{p/x} reprints the last value in hex.
7466 @section Examining Memory
7468 You can use the command @code{x} (for ``examine'') to examine memory in
7469 any of several formats, independently of your program's data types.
7471 @cindex examining memory
7473 @kindex x @r{(examine memory)}
7474 @item x/@var{nfu} @var{addr}
7477 Use the @code{x} command to examine memory.
7480 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
7481 much memory to display and how to format it; @var{addr} is an
7482 expression giving the address where you want to start displaying memory.
7483 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
7484 Several commands set convenient defaults for @var{addr}.
7487 @item @var{n}, the repeat count
7488 The repeat count is a decimal integer; the default is 1. It specifies
7489 how much memory (counting by units @var{u}) to display.
7490 @c This really is **decimal**; unaffected by 'set radix' as of GDB
7493 @item @var{f}, the display format
7494 The display format is one of the formats used by @code{print}
7495 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
7496 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
7497 The default is @samp{x} (hexadecimal) initially. The default changes
7498 each time you use either @code{x} or @code{print}.
7500 @item @var{u}, the unit size
7501 The unit size is any of
7507 Halfwords (two bytes).
7509 Words (four bytes). This is the initial default.
7511 Giant words (eight bytes).
7514 Each time you specify a unit size with @code{x}, that size becomes the
7515 default unit the next time you use @code{x}. For the @samp{i} format,
7516 the unit size is ignored and is normally not written. For the @samp{s} format,
7517 the unit size defaults to @samp{b}, unless it is explicitly given.
7518 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
7519 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
7520 Note that the results depend on the programming language of the
7521 current compilation unit. If the language is C, the @samp{s}
7522 modifier will use the UTF-16 encoding while @samp{w} will use
7523 UTF-32. The encoding is set by the programming language and cannot
7526 @item @var{addr}, starting display address
7527 @var{addr} is the address where you want @value{GDBN} to begin displaying
7528 memory. The expression need not have a pointer value (though it may);
7529 it is always interpreted as an integer address of a byte of memory.
7530 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
7531 @var{addr} is usually just after the last address examined---but several
7532 other commands also set the default address: @code{info breakpoints} (to
7533 the address of the last breakpoint listed), @code{info line} (to the
7534 starting address of a line), and @code{print} (if you use it to display
7535 a value from memory).
7538 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
7539 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
7540 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
7541 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
7542 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
7544 Since the letters indicating unit sizes are all distinct from the
7545 letters specifying output formats, you do not have to remember whether
7546 unit size or format comes first; either order works. The output
7547 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
7548 (However, the count @var{n} must come first; @samp{wx4} does not work.)
7550 Even though the unit size @var{u} is ignored for the formats @samp{s}
7551 and @samp{i}, you might still want to use a count @var{n}; for example,
7552 @samp{3i} specifies that you want to see three machine instructions,
7553 including any operands. For convenience, especially when used with
7554 the @code{display} command, the @samp{i} format also prints branch delay
7555 slot instructions, if any, beyond the count specified, which immediately
7556 follow the last instruction that is within the count. The command
7557 @code{disassemble} gives an alternative way of inspecting machine
7558 instructions; see @ref{Machine Code,,Source and Machine Code}.
7560 All the defaults for the arguments to @code{x} are designed to make it
7561 easy to continue scanning memory with minimal specifications each time
7562 you use @code{x}. For example, after you have inspected three machine
7563 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
7564 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
7565 the repeat count @var{n} is used again; the other arguments default as
7566 for successive uses of @code{x}.
7568 When examining machine instructions, the instruction at current program
7569 counter is shown with a @code{=>} marker. For example:
7572 (@value{GDBP}) x/5i $pc-6
7573 0x804837f <main+11>: mov %esp,%ebp
7574 0x8048381 <main+13>: push %ecx
7575 0x8048382 <main+14>: sub $0x4,%esp
7576 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
7577 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
7580 @cindex @code{$_}, @code{$__}, and value history
7581 The addresses and contents printed by the @code{x} command are not saved
7582 in the value history because there is often too much of them and they
7583 would get in the way. Instead, @value{GDBN} makes these values available for
7584 subsequent use in expressions as values of the convenience variables
7585 @code{$_} and @code{$__}. After an @code{x} command, the last address
7586 examined is available for use in expressions in the convenience variable
7587 @code{$_}. The contents of that address, as examined, are available in
7588 the convenience variable @code{$__}.
7590 If the @code{x} command has a repeat count, the address and contents saved
7591 are from the last memory unit printed; this is not the same as the last
7592 address printed if several units were printed on the last line of output.
7594 @cindex remote memory comparison
7595 @cindex verify remote memory image
7596 When you are debugging a program running on a remote target machine
7597 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
7598 remote machine's memory against the executable file you downloaded to
7599 the target. The @code{compare-sections} command is provided for such
7603 @kindex compare-sections
7604 @item compare-sections @r{[}@var{section-name}@r{]}
7605 Compare the data of a loadable section @var{section-name} in the
7606 executable file of the program being debugged with the same section in
7607 the remote machine's memory, and report any mismatches. With no
7608 arguments, compares all loadable sections. This command's
7609 availability depends on the target's support for the @code{"qCRC"}
7614 @section Automatic Display
7615 @cindex automatic display
7616 @cindex display of expressions
7618 If you find that you want to print the value of an expression frequently
7619 (to see how it changes), you might want to add it to the @dfn{automatic
7620 display list} so that @value{GDBN} prints its value each time your program stops.
7621 Each expression added to the list is given a number to identify it;
7622 to remove an expression from the list, you specify that number.
7623 The automatic display looks like this:
7627 3: bar[5] = (struct hack *) 0x3804
7631 This display shows item numbers, expressions and their current values. As with
7632 displays you request manually using @code{x} or @code{print}, you can
7633 specify the output format you prefer; in fact, @code{display} decides
7634 whether to use @code{print} or @code{x} depending your format
7635 specification---it uses @code{x} if you specify either the @samp{i}
7636 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
7640 @item display @var{expr}
7641 Add the expression @var{expr} to the list of expressions to display
7642 each time your program stops. @xref{Expressions, ,Expressions}.
7644 @code{display} does not repeat if you press @key{RET} again after using it.
7646 @item display/@var{fmt} @var{expr}
7647 For @var{fmt} specifying only a display format and not a size or
7648 count, add the expression @var{expr} to the auto-display list but
7649 arrange to display it each time in the specified format @var{fmt}.
7650 @xref{Output Formats,,Output Formats}.
7652 @item display/@var{fmt} @var{addr}
7653 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
7654 number of units, add the expression @var{addr} as a memory address to
7655 be examined each time your program stops. Examining means in effect
7656 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
7659 For example, @samp{display/i $pc} can be helpful, to see the machine
7660 instruction about to be executed each time execution stops (@samp{$pc}
7661 is a common name for the program counter; @pxref{Registers, ,Registers}).
7664 @kindex delete display
7666 @item undisplay @var{dnums}@dots{}
7667 @itemx delete display @var{dnums}@dots{}
7668 Remove item numbers @var{dnums} from the list of expressions to display.
7670 @code{undisplay} does not repeat if you press @key{RET} after using it.
7671 (Otherwise you would just get the error @samp{No display number @dots{}}.)
7673 @kindex disable display
7674 @item disable display @var{dnums}@dots{}
7675 Disable the display of item numbers @var{dnums}. A disabled display
7676 item is not printed automatically, but is not forgotten. It may be
7677 enabled again later.
7679 @kindex enable display
7680 @item enable display @var{dnums}@dots{}
7681 Enable display of item numbers @var{dnums}. It becomes effective once
7682 again in auto display of its expression, until you specify otherwise.
7685 Display the current values of the expressions on the list, just as is
7686 done when your program stops.
7688 @kindex info display
7690 Print the list of expressions previously set up to display
7691 automatically, each one with its item number, but without showing the
7692 values. This includes disabled expressions, which are marked as such.
7693 It also includes expressions which would not be displayed right now
7694 because they refer to automatic variables not currently available.
7697 @cindex display disabled out of scope
7698 If a display expression refers to local variables, then it does not make
7699 sense outside the lexical context for which it was set up. Such an
7700 expression is disabled when execution enters a context where one of its
7701 variables is not defined. For example, if you give the command
7702 @code{display last_char} while inside a function with an argument
7703 @code{last_char}, @value{GDBN} displays this argument while your program
7704 continues to stop inside that function. When it stops elsewhere---where
7705 there is no variable @code{last_char}---the display is disabled
7706 automatically. The next time your program stops where @code{last_char}
7707 is meaningful, you can enable the display expression once again.
7709 @node Print Settings
7710 @section Print Settings
7712 @cindex format options
7713 @cindex print settings
7714 @value{GDBN} provides the following ways to control how arrays, structures,
7715 and symbols are printed.
7718 These settings are useful for debugging programs in any language:
7722 @item set print address
7723 @itemx set print address on
7724 @cindex print/don't print memory addresses
7725 @value{GDBN} prints memory addresses showing the location of stack
7726 traces, structure values, pointer values, breakpoints, and so forth,
7727 even when it also displays the contents of those addresses. The default
7728 is @code{on}. For example, this is what a stack frame display looks like with
7729 @code{set print address on}:
7734 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
7736 530 if (lquote != def_lquote)
7740 @item set print address off
7741 Do not print addresses when displaying their contents. For example,
7742 this is the same stack frame displayed with @code{set print address off}:
7746 (@value{GDBP}) set print addr off
7748 #0 set_quotes (lq="<<", rq=">>") at input.c:530
7749 530 if (lquote != def_lquote)
7753 You can use @samp{set print address off} to eliminate all machine
7754 dependent displays from the @value{GDBN} interface. For example, with
7755 @code{print address off}, you should get the same text for backtraces on
7756 all machines---whether or not they involve pointer arguments.
7759 @item show print address
7760 Show whether or not addresses are to be printed.
7763 When @value{GDBN} prints a symbolic address, it normally prints the
7764 closest earlier symbol plus an offset. If that symbol does not uniquely
7765 identify the address (for example, it is a name whose scope is a single
7766 source file), you may need to clarify. One way to do this is with
7767 @code{info line}, for example @samp{info line *0x4537}. Alternately,
7768 you can set @value{GDBN} to print the source file and line number when
7769 it prints a symbolic address:
7772 @item set print symbol-filename on
7773 @cindex source file and line of a symbol
7774 @cindex symbol, source file and line
7775 Tell @value{GDBN} to print the source file name and line number of a
7776 symbol in the symbolic form of an address.
7778 @item set print symbol-filename off
7779 Do not print source file name and line number of a symbol. This is the
7782 @item show print symbol-filename
7783 Show whether or not @value{GDBN} will print the source file name and
7784 line number of a symbol in the symbolic form of an address.
7787 Another situation where it is helpful to show symbol filenames and line
7788 numbers is when disassembling code; @value{GDBN} shows you the line
7789 number and source file that corresponds to each instruction.
7791 Also, you may wish to see the symbolic form only if the address being
7792 printed is reasonably close to the closest earlier symbol:
7795 @item set print max-symbolic-offset @var{max-offset}
7796 @cindex maximum value for offset of closest symbol
7797 Tell @value{GDBN} to only display the symbolic form of an address if the
7798 offset between the closest earlier symbol and the address is less than
7799 @var{max-offset}. The default is 0, which tells @value{GDBN}
7800 to always print the symbolic form of an address if any symbol precedes it.
7802 @item show print max-symbolic-offset
7803 Ask how large the maximum offset is that @value{GDBN} prints in a
7807 @cindex wild pointer, interpreting
7808 @cindex pointer, finding referent
7809 If you have a pointer and you are not sure where it points, try
7810 @samp{set print symbol-filename on}. Then you can determine the name
7811 and source file location of the variable where it points, using
7812 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
7813 For example, here @value{GDBN} shows that a variable @code{ptt} points
7814 at another variable @code{t}, defined in @file{hi2.c}:
7817 (@value{GDBP}) set print symbol-filename on
7818 (@value{GDBP}) p/a ptt
7819 $4 = 0xe008 <t in hi2.c>
7823 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
7824 does not show the symbol name and filename of the referent, even with
7825 the appropriate @code{set print} options turned on.
7828 Other settings control how different kinds of objects are printed:
7831 @item set print array
7832 @itemx set print array on
7833 @cindex pretty print arrays
7834 Pretty print arrays. This format is more convenient to read,
7835 but uses more space. The default is off.
7837 @item set print array off
7838 Return to compressed format for arrays.
7840 @item show print array
7841 Show whether compressed or pretty format is selected for displaying
7844 @cindex print array indexes
7845 @item set print array-indexes
7846 @itemx set print array-indexes on
7847 Print the index of each element when displaying arrays. May be more
7848 convenient to locate a given element in the array or quickly find the
7849 index of a given element in that printed array. The default is off.
7851 @item set print array-indexes off
7852 Stop printing element indexes when displaying arrays.
7854 @item show print array-indexes
7855 Show whether the index of each element is printed when displaying
7858 @item set print elements @var{number-of-elements}
7859 @cindex number of array elements to print
7860 @cindex limit on number of printed array elements
7861 Set a limit on how many elements of an array @value{GDBN} will print.
7862 If @value{GDBN} is printing a large array, it stops printing after it has
7863 printed the number of elements set by the @code{set print elements} command.
7864 This limit also applies to the display of strings.
7865 When @value{GDBN} starts, this limit is set to 200.
7866 Setting @var{number-of-elements} to zero means that the printing is unlimited.
7868 @item show print elements
7869 Display the number of elements of a large array that @value{GDBN} will print.
7870 If the number is 0, then the printing is unlimited.
7872 @item set print frame-arguments @var{value}
7873 @kindex set print frame-arguments
7874 @cindex printing frame argument values
7875 @cindex print all frame argument values
7876 @cindex print frame argument values for scalars only
7877 @cindex do not print frame argument values
7878 This command allows to control how the values of arguments are printed
7879 when the debugger prints a frame (@pxref{Frames}). The possible
7884 The values of all arguments are printed.
7887 Print the value of an argument only if it is a scalar. The value of more
7888 complex arguments such as arrays, structures, unions, etc, is replaced
7889 by @code{@dots{}}. This is the default. Here is an example where
7890 only scalar arguments are shown:
7893 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
7898 None of the argument values are printed. Instead, the value of each argument
7899 is replaced by @code{@dots{}}. In this case, the example above now becomes:
7902 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
7907 By default, only scalar arguments are printed. This command can be used
7908 to configure the debugger to print the value of all arguments, regardless
7909 of their type. However, it is often advantageous to not print the value
7910 of more complex parameters. For instance, it reduces the amount of
7911 information printed in each frame, making the backtrace more readable.
7912 Also, it improves performance when displaying Ada frames, because
7913 the computation of large arguments can sometimes be CPU-intensive,
7914 especially in large applications. Setting @code{print frame-arguments}
7915 to @code{scalars} (the default) or @code{none} avoids this computation,
7916 thus speeding up the display of each Ada frame.
7918 @item show print frame-arguments
7919 Show how the value of arguments should be displayed when printing a frame.
7921 @item set print repeats
7922 @cindex repeated array elements
7923 Set the threshold for suppressing display of repeated array
7924 elements. When the number of consecutive identical elements of an
7925 array exceeds the threshold, @value{GDBN} prints the string
7926 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
7927 identical repetitions, instead of displaying the identical elements
7928 themselves. Setting the threshold to zero will cause all elements to
7929 be individually printed. The default threshold is 10.
7931 @item show print repeats
7932 Display the current threshold for printing repeated identical
7935 @item set print null-stop
7936 @cindex @sc{null} elements in arrays
7937 Cause @value{GDBN} to stop printing the characters of an array when the first
7938 @sc{null} is encountered. This is useful when large arrays actually
7939 contain only short strings.
7942 @item show print null-stop
7943 Show whether @value{GDBN} stops printing an array on the first
7944 @sc{null} character.
7946 @item set print pretty on
7947 @cindex print structures in indented form
7948 @cindex indentation in structure display
7949 Cause @value{GDBN} to print structures in an indented format with one member
7950 per line, like this:
7965 @item set print pretty off
7966 Cause @value{GDBN} to print structures in a compact format, like this:
7970 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
7971 meat = 0x54 "Pork"@}
7976 This is the default format.
7978 @item show print pretty
7979 Show which format @value{GDBN} is using to print structures.
7981 @item set print sevenbit-strings on
7982 @cindex eight-bit characters in strings
7983 @cindex octal escapes in strings
7984 Print using only seven-bit characters; if this option is set,
7985 @value{GDBN} displays any eight-bit characters (in strings or
7986 character values) using the notation @code{\}@var{nnn}. This setting is
7987 best if you are working in English (@sc{ascii}) and you use the
7988 high-order bit of characters as a marker or ``meta'' bit.
7990 @item set print sevenbit-strings off
7991 Print full eight-bit characters. This allows the use of more
7992 international character sets, and is the default.
7994 @item show print sevenbit-strings
7995 Show whether or not @value{GDBN} is printing only seven-bit characters.
7997 @item set print union on
7998 @cindex unions in structures, printing
7999 Tell @value{GDBN} to print unions which are contained in structures
8000 and other unions. This is the default setting.
8002 @item set print union off
8003 Tell @value{GDBN} not to print unions which are contained in
8004 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
8007 @item show print union
8008 Ask @value{GDBN} whether or not it will print unions which are contained in
8009 structures and other unions.
8011 For example, given the declarations
8014 typedef enum @{Tree, Bug@} Species;
8015 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
8016 typedef enum @{Caterpillar, Cocoon, Butterfly@}
8027 struct thing foo = @{Tree, @{Acorn@}@};
8031 with @code{set print union on} in effect @samp{p foo} would print
8034 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
8038 and with @code{set print union off} in effect it would print
8041 $1 = @{it = Tree, form = @{...@}@}
8045 @code{set print union} affects programs written in C-like languages
8051 These settings are of interest when debugging C@t{++} programs:
8054 @cindex demangling C@t{++} names
8055 @item set print demangle
8056 @itemx set print demangle on
8057 Print C@t{++} names in their source form rather than in the encoded
8058 (``mangled'') form passed to the assembler and linker for type-safe
8059 linkage. The default is on.
8061 @item show print demangle
8062 Show whether C@t{++} names are printed in mangled or demangled form.
8064 @item set print asm-demangle
8065 @itemx set print asm-demangle on
8066 Print C@t{++} names in their source form rather than their mangled form, even
8067 in assembler code printouts such as instruction disassemblies.
8070 @item show print asm-demangle
8071 Show whether C@t{++} names in assembly listings are printed in mangled
8074 @cindex C@t{++} symbol decoding style
8075 @cindex symbol decoding style, C@t{++}
8076 @kindex set demangle-style
8077 @item set demangle-style @var{style}
8078 Choose among several encoding schemes used by different compilers to
8079 represent C@t{++} names. The choices for @var{style} are currently:
8083 Allow @value{GDBN} to choose a decoding style by inspecting your program.
8086 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
8087 This is the default.
8090 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
8093 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
8096 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
8097 @strong{Warning:} this setting alone is not sufficient to allow
8098 debugging @code{cfront}-generated executables. @value{GDBN} would
8099 require further enhancement to permit that.
8102 If you omit @var{style}, you will see a list of possible formats.
8104 @item show demangle-style
8105 Display the encoding style currently in use for decoding C@t{++} symbols.
8107 @item set print object
8108 @itemx set print object on
8109 @cindex derived type of an object, printing
8110 @cindex display derived types
8111 When displaying a pointer to an object, identify the @emph{actual}
8112 (derived) type of the object rather than the @emph{declared} type, using
8113 the virtual function table.
8115 @item set print object off
8116 Display only the declared type of objects, without reference to the
8117 virtual function table. This is the default setting.
8119 @item show print object
8120 Show whether actual, or declared, object types are displayed.
8122 @item set print static-members
8123 @itemx set print static-members on
8124 @cindex static members of C@t{++} objects
8125 Print static members when displaying a C@t{++} object. The default is on.
8127 @item set print static-members off
8128 Do not print static members when displaying a C@t{++} object.
8130 @item show print static-members
8131 Show whether C@t{++} static members are printed or not.
8133 @item set print pascal_static-members
8134 @itemx set print pascal_static-members on
8135 @cindex static members of Pascal objects
8136 @cindex Pascal objects, static members display
8137 Print static members when displaying a Pascal object. The default is on.
8139 @item set print pascal_static-members off
8140 Do not print static members when displaying a Pascal object.
8142 @item show print pascal_static-members
8143 Show whether Pascal static members are printed or not.
8145 @c These don't work with HP ANSI C++ yet.
8146 @item set print vtbl
8147 @itemx set print vtbl on
8148 @cindex pretty print C@t{++} virtual function tables
8149 @cindex virtual functions (C@t{++}) display
8150 @cindex VTBL display
8151 Pretty print C@t{++} virtual function tables. The default is off.
8152 (The @code{vtbl} commands do not work on programs compiled with the HP
8153 ANSI C@t{++} compiler (@code{aCC}).)
8155 @item set print vtbl off
8156 Do not pretty print C@t{++} virtual function tables.
8158 @item show print vtbl
8159 Show whether C@t{++} virtual function tables are pretty printed, or not.
8162 @node Pretty Printing
8163 @section Pretty Printing
8165 @value{GDBN} provides a mechanism to allow pretty-printing of values using
8166 Python code. It greatly simplifies the display of complex objects. This
8167 mechanism works for both MI and the CLI.
8170 * Pretty-Printer Introduction:: Introduction to pretty-printers
8171 * Pretty-Printer Example:: An example pretty-printer
8172 * Pretty-Printer Commands:: Pretty-printer commands
8175 @node Pretty-Printer Introduction
8176 @subsection Pretty-Printer Introduction
8178 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
8179 registered for the value. If there is then @value{GDBN} invokes the
8180 pretty-printer to print the value. Otherwise the value is printed normally.
8182 Pretty-printers are normally named. This makes them easy to manage.
8183 The @samp{info pretty-printer} command will list all the installed
8184 pretty-printers with their names.
8185 If a pretty-printer can handle multiple data types, then its
8186 @dfn{subprinters} are the printers for the individual data types.
8187 Each such subprinter has its own name.
8188 The format of the name is @var{printer-name};@var{subprinter-name}.
8190 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
8191 Typically they are automatically loaded and registered when the corresponding
8192 debug information is loaded, thus making them available without having to
8193 do anything special.
8195 There are three places where a pretty-printer can be registered.
8199 Pretty-printers registered globally are available when debugging
8203 Pretty-printers registered with a program space are available only
8204 when debugging that program.
8205 @xref{Progspaces In Python}, for more details on program spaces in Python.
8208 Pretty-printers registered with an objfile are loaded and unloaded
8209 with the corresponding objfile (e.g., shared library).
8210 @xref{Objfiles In Python}, for more details on objfiles in Python.
8213 @xref{Selecting Pretty-Printers}, for further information on how
8214 pretty-printers are selected,
8216 @xref{Writing a Pretty-Printer}, for implementing pretty printers
8219 @node Pretty-Printer Example
8220 @subsection Pretty-Printer Example
8222 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
8225 (@value{GDBP}) print s
8227 static npos = 4294967295,
8229 <std::allocator<char>> = @{
8230 <__gnu_cxx::new_allocator<char>> = @{
8231 <No data fields>@}, <No data fields>
8233 members of std::basic_string<char, std::char_traits<char>,
8234 std::allocator<char> >::_Alloc_hider:
8235 _M_p = 0x804a014 "abcd"
8240 With a pretty-printer for @code{std::string} only the contents are printed:
8243 (@value{GDBP}) print s
8247 @node Pretty-Printer Commands
8248 @subsection Pretty-Printer Commands
8249 @cindex pretty-printer commands
8252 @kindex info pretty-printer
8253 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8254 Print the list of installed pretty-printers.
8255 This includes disabled pretty-printers, which are marked as such.
8257 @var{object-regexp} is a regular expression matching the objects
8258 whose pretty-printers to list.
8259 Objects can be @code{global}, the program space's file
8260 (@pxref{Progspaces In Python}),
8261 and the object files within that program space (@pxref{Objfiles In Python}).
8262 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
8263 looks up a printer from these three objects.
8265 @var{name-regexp} is a regular expression matching the name of the printers
8268 @kindex disable pretty-printer
8269 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8270 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8271 A disabled pretty-printer is not forgotten, it may be enabled again later.
8273 @kindex enable pretty-printer
8274 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
8275 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
8280 Suppose we have three pretty-printers installed: one from library1.so
8281 named @code{foo} that prints objects of type @code{foo}, and
8282 another from library2.so named @code{bar} that prints two types of objects,
8283 @code{bar1} and @code{bar2}.
8286 (gdb) info pretty-printer
8293 (gdb) info pretty-printer library2
8298 (gdb) disable pretty-printer library1
8300 2 of 3 printers enabled
8301 (gdb) info pretty-printer
8308 (gdb) disable pretty-printer library2 bar:bar1
8310 1 of 3 printers enabled
8311 (gdb) info pretty-printer library2
8318 (gdb) disable pretty-printer library2 bar
8320 0 of 3 printers enabled
8321 (gdb) info pretty-printer library2
8330 Note that for @code{bar} the entire printer can be disabled,
8331 as can each individual subprinter.
8334 @section Value History
8336 @cindex value history
8337 @cindex history of values printed by @value{GDBN}
8338 Values printed by the @code{print} command are saved in the @value{GDBN}
8339 @dfn{value history}. This allows you to refer to them in other expressions.
8340 Values are kept until the symbol table is re-read or discarded
8341 (for example with the @code{file} or @code{symbol-file} commands).
8342 When the symbol table changes, the value history is discarded,
8343 since the values may contain pointers back to the types defined in the
8348 @cindex history number
8349 The values printed are given @dfn{history numbers} by which you can
8350 refer to them. These are successive integers starting with one.
8351 @code{print} shows you the history number assigned to a value by
8352 printing @samp{$@var{num} = } before the value; here @var{num} is the
8355 To refer to any previous value, use @samp{$} followed by the value's
8356 history number. The way @code{print} labels its output is designed to
8357 remind you of this. Just @code{$} refers to the most recent value in
8358 the history, and @code{$$} refers to the value before that.
8359 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
8360 is the value just prior to @code{$$}, @code{$$1} is equivalent to
8361 @code{$$}, and @code{$$0} is equivalent to @code{$}.
8363 For example, suppose you have just printed a pointer to a structure and
8364 want to see the contents of the structure. It suffices to type
8370 If you have a chain of structures where the component @code{next} points
8371 to the next one, you can print the contents of the next one with this:
8378 You can print successive links in the chain by repeating this
8379 command---which you can do by just typing @key{RET}.
8381 Note that the history records values, not expressions. If the value of
8382 @code{x} is 4 and you type these commands:
8390 then the value recorded in the value history by the @code{print} command
8391 remains 4 even though the value of @code{x} has changed.
8396 Print the last ten values in the value history, with their item numbers.
8397 This is like @samp{p@ $$9} repeated ten times, except that @code{show
8398 values} does not change the history.
8400 @item show values @var{n}
8401 Print ten history values centered on history item number @var{n}.
8404 Print ten history values just after the values last printed. If no more
8405 values are available, @code{show values +} produces no display.
8408 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
8409 same effect as @samp{show values +}.
8411 @node Convenience Vars
8412 @section Convenience Variables
8414 @cindex convenience variables
8415 @cindex user-defined variables
8416 @value{GDBN} provides @dfn{convenience variables} that you can use within
8417 @value{GDBN} to hold on to a value and refer to it later. These variables
8418 exist entirely within @value{GDBN}; they are not part of your program, and
8419 setting a convenience variable has no direct effect on further execution
8420 of your program. That is why you can use them freely.
8422 Convenience variables are prefixed with @samp{$}. Any name preceded by
8423 @samp{$} can be used for a convenience variable, unless it is one of
8424 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
8425 (Value history references, in contrast, are @emph{numbers} preceded
8426 by @samp{$}. @xref{Value History, ,Value History}.)
8428 You can save a value in a convenience variable with an assignment
8429 expression, just as you would set a variable in your program.
8433 set $foo = *object_ptr
8437 would save in @code{$foo} the value contained in the object pointed to by
8440 Using a convenience variable for the first time creates it, but its
8441 value is @code{void} until you assign a new value. You can alter the
8442 value with another assignment at any time.
8444 Convenience variables have no fixed types. You can assign a convenience
8445 variable any type of value, including structures and arrays, even if
8446 that variable already has a value of a different type. The convenience
8447 variable, when used as an expression, has the type of its current value.
8450 @kindex show convenience
8451 @cindex show all user variables
8452 @item show convenience
8453 Print a list of convenience variables used so far, and their values.
8454 Abbreviated @code{show conv}.
8456 @kindex init-if-undefined
8457 @cindex convenience variables, initializing
8458 @item init-if-undefined $@var{variable} = @var{expression}
8459 Set a convenience variable if it has not already been set. This is useful
8460 for user-defined commands that keep some state. It is similar, in concept,
8461 to using local static variables with initializers in C (except that
8462 convenience variables are global). It can also be used to allow users to
8463 override default values used in a command script.
8465 If the variable is already defined then the expression is not evaluated so
8466 any side-effects do not occur.
8469 One of the ways to use a convenience variable is as a counter to be
8470 incremented or a pointer to be advanced. For example, to print
8471 a field from successive elements of an array of structures:
8475 print bar[$i++]->contents
8479 Repeat that command by typing @key{RET}.
8481 Some convenience variables are created automatically by @value{GDBN} and given
8482 values likely to be useful.
8485 @vindex $_@r{, convenience variable}
8487 The variable @code{$_} is automatically set by the @code{x} command to
8488 the last address examined (@pxref{Memory, ,Examining Memory}). Other
8489 commands which provide a default address for @code{x} to examine also
8490 set @code{$_} to that address; these commands include @code{info line}
8491 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
8492 except when set by the @code{x} command, in which case it is a pointer
8493 to the type of @code{$__}.
8495 @vindex $__@r{, convenience variable}
8497 The variable @code{$__} is automatically set by the @code{x} command
8498 to the value found in the last address examined. Its type is chosen
8499 to match the format in which the data was printed.
8502 @vindex $_exitcode@r{, convenience variable}
8503 The variable @code{$_exitcode} is automatically set to the exit code when
8504 the program being debugged terminates.
8507 @vindex $_sdata@r{, inspect, convenience variable}
8508 The variable @code{$_sdata} contains extra collected static tracepoint
8509 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
8510 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
8511 if extra static tracepoint data has not been collected.
8514 @vindex $_siginfo@r{, convenience variable}
8515 The variable @code{$_siginfo} contains extra signal information
8516 (@pxref{extra signal information}). Note that @code{$_siginfo}
8517 could be empty, if the application has not yet received any signals.
8518 For example, it will be empty before you execute the @code{run} command.
8521 @vindex $_tlb@r{, convenience variable}
8522 The variable @code{$_tlb} is automatically set when debugging
8523 applications running on MS-Windows in native mode or connected to
8524 gdbserver that supports the @code{qGetTIBAddr} request.
8525 @xref{General Query Packets}.
8526 This variable contains the address of the thread information block.
8530 On HP-UX systems, if you refer to a function or variable name that
8531 begins with a dollar sign, @value{GDBN} searches for a user or system
8532 name first, before it searches for a convenience variable.
8534 @cindex convenience functions
8535 @value{GDBN} also supplies some @dfn{convenience functions}. These
8536 have a syntax similar to convenience variables. A convenience
8537 function can be used in an expression just like an ordinary function;
8538 however, a convenience function is implemented internally to
8543 @kindex help function
8544 @cindex show all convenience functions
8545 Print a list of all convenience functions.
8552 You can refer to machine register contents, in expressions, as variables
8553 with names starting with @samp{$}. The names of registers are different
8554 for each machine; use @code{info registers} to see the names used on
8558 @kindex info registers
8559 @item info registers
8560 Print the names and values of all registers except floating-point
8561 and vector registers (in the selected stack frame).
8563 @kindex info all-registers
8564 @cindex floating point registers
8565 @item info all-registers
8566 Print the names and values of all registers, including floating-point
8567 and vector registers (in the selected stack frame).
8569 @item info registers @var{regname} @dots{}
8570 Print the @dfn{relativized} value of each specified register @var{regname}.
8571 As discussed in detail below, register values are normally relative to
8572 the selected stack frame. @var{regname} may be any register name valid on
8573 the machine you are using, with or without the initial @samp{$}.
8576 @cindex stack pointer register
8577 @cindex program counter register
8578 @cindex process status register
8579 @cindex frame pointer register
8580 @cindex standard registers
8581 @value{GDBN} has four ``standard'' register names that are available (in
8582 expressions) on most machines---whenever they do not conflict with an
8583 architecture's canonical mnemonics for registers. The register names
8584 @code{$pc} and @code{$sp} are used for the program counter register and
8585 the stack pointer. @code{$fp} is used for a register that contains a
8586 pointer to the current stack frame, and @code{$ps} is used for a
8587 register that contains the processor status. For example,
8588 you could print the program counter in hex with
8595 or print the instruction to be executed next with
8602 or add four to the stack pointer@footnote{This is a way of removing
8603 one word from the stack, on machines where stacks grow downward in
8604 memory (most machines, nowadays). This assumes that the innermost
8605 stack frame is selected; setting @code{$sp} is not allowed when other
8606 stack frames are selected. To pop entire frames off the stack,
8607 regardless of machine architecture, use @code{return};
8608 see @ref{Returning, ,Returning from a Function}.} with
8614 Whenever possible, these four standard register names are available on
8615 your machine even though the machine has different canonical mnemonics,
8616 so long as there is no conflict. The @code{info registers} command
8617 shows the canonical names. For example, on the SPARC, @code{info
8618 registers} displays the processor status register as @code{$psr} but you
8619 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
8620 is an alias for the @sc{eflags} register.
8622 @value{GDBN} always considers the contents of an ordinary register as an
8623 integer when the register is examined in this way. Some machines have
8624 special registers which can hold nothing but floating point; these
8625 registers are considered to have floating point values. There is no way
8626 to refer to the contents of an ordinary register as floating point value
8627 (although you can @emph{print} it as a floating point value with
8628 @samp{print/f $@var{regname}}).
8630 Some registers have distinct ``raw'' and ``virtual'' data formats. This
8631 means that the data format in which the register contents are saved by
8632 the operating system is not the same one that your program normally
8633 sees. For example, the registers of the 68881 floating point
8634 coprocessor are always saved in ``extended'' (raw) format, but all C
8635 programs expect to work with ``double'' (virtual) format. In such
8636 cases, @value{GDBN} normally works with the virtual format only (the format
8637 that makes sense for your program), but the @code{info registers} command
8638 prints the data in both formats.
8640 @cindex SSE registers (x86)
8641 @cindex MMX registers (x86)
8642 Some machines have special registers whose contents can be interpreted
8643 in several different ways. For example, modern x86-based machines
8644 have SSE and MMX registers that can hold several values packed
8645 together in several different formats. @value{GDBN} refers to such
8646 registers in @code{struct} notation:
8649 (@value{GDBP}) print $xmm1
8651 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
8652 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
8653 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
8654 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
8655 v4_int32 = @{0, 20657912, 11, 13@},
8656 v2_int64 = @{88725056443645952, 55834574859@},
8657 uint128 = 0x0000000d0000000b013b36f800000000
8662 To set values of such registers, you need to tell @value{GDBN} which
8663 view of the register you wish to change, as if you were assigning
8664 value to a @code{struct} member:
8667 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
8670 Normally, register values are relative to the selected stack frame
8671 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
8672 value that the register would contain if all stack frames farther in
8673 were exited and their saved registers restored. In order to see the
8674 true contents of hardware registers, you must select the innermost
8675 frame (with @samp{frame 0}).
8677 However, @value{GDBN} must deduce where registers are saved, from the machine
8678 code generated by your compiler. If some registers are not saved, or if
8679 @value{GDBN} is unable to locate the saved registers, the selected stack
8680 frame makes no difference.
8682 @node Floating Point Hardware
8683 @section Floating Point Hardware
8684 @cindex floating point
8686 Depending on the configuration, @value{GDBN} may be able to give
8687 you more information about the status of the floating point hardware.
8692 Display hardware-dependent information about the floating
8693 point unit. The exact contents and layout vary depending on the
8694 floating point chip. Currently, @samp{info float} is supported on
8695 the ARM and x86 machines.
8699 @section Vector Unit
8702 Depending on the configuration, @value{GDBN} may be able to give you
8703 more information about the status of the vector unit.
8708 Display information about the vector unit. The exact contents and
8709 layout vary depending on the hardware.
8712 @node OS Information
8713 @section Operating System Auxiliary Information
8714 @cindex OS information
8716 @value{GDBN} provides interfaces to useful OS facilities that can help
8717 you debug your program.
8719 @cindex @code{ptrace} system call
8720 @cindex @code{struct user} contents
8721 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
8722 machines), it interfaces with the inferior via the @code{ptrace}
8723 system call. The operating system creates a special sata structure,
8724 called @code{struct user}, for this interface. You can use the
8725 command @code{info udot} to display the contents of this data
8731 Display the contents of the @code{struct user} maintained by the OS
8732 kernel for the program being debugged. @value{GDBN} displays the
8733 contents of @code{struct user} as a list of hex numbers, similar to
8734 the @code{examine} command.
8737 @cindex auxiliary vector
8738 @cindex vector, auxiliary
8739 Some operating systems supply an @dfn{auxiliary vector} to programs at
8740 startup. This is akin to the arguments and environment that you
8741 specify for a program, but contains a system-dependent variety of
8742 binary values that tell system libraries important details about the
8743 hardware, operating system, and process. Each value's purpose is
8744 identified by an integer tag; the meanings are well-known but system-specific.
8745 Depending on the configuration and operating system facilities,
8746 @value{GDBN} may be able to show you this information. For remote
8747 targets, this functionality may further depend on the remote stub's
8748 support of the @samp{qXfer:auxv:read} packet, see
8749 @ref{qXfer auxiliary vector read}.
8754 Display the auxiliary vector of the inferior, which can be either a
8755 live process or a core dump file. @value{GDBN} prints each tag value
8756 numerically, and also shows names and text descriptions for recognized
8757 tags. Some values in the vector are numbers, some bit masks, and some
8758 pointers to strings or other data. @value{GDBN} displays each value in the
8759 most appropriate form for a recognized tag, and in hexadecimal for
8760 an unrecognized tag.
8763 On some targets, @value{GDBN} can access operating-system-specific information
8764 and display it to user, without interpretation. For remote targets,
8765 this functionality depends on the remote stub's support of the
8766 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
8771 List the types of OS information available for the target. If the
8772 target does not return a list of possible types, this command will
8775 @kindex info os processes
8776 @item info os processes
8777 Display the list of processes on the target. For each process,
8778 @value{GDBN} prints the process identifier, the name of the user, and
8779 the command corresponding to the process.
8782 @node Memory Region Attributes
8783 @section Memory Region Attributes
8784 @cindex memory region attributes
8786 @dfn{Memory region attributes} allow you to describe special handling
8787 required by regions of your target's memory. @value{GDBN} uses
8788 attributes to determine whether to allow certain types of memory
8789 accesses; whether to use specific width accesses; and whether to cache
8790 target memory. By default the description of memory regions is
8791 fetched from the target (if the current target supports this), but the
8792 user can override the fetched regions.
8794 Defined memory regions can be individually enabled and disabled. When a
8795 memory region is disabled, @value{GDBN} uses the default attributes when
8796 accessing memory in that region. Similarly, if no memory regions have
8797 been defined, @value{GDBN} uses the default attributes when accessing
8800 When a memory region is defined, it is given a number to identify it;
8801 to enable, disable, or remove a memory region, you specify that number.
8805 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
8806 Define a memory region bounded by @var{lower} and @var{upper} with
8807 attributes @var{attributes}@dots{}, and add it to the list of regions
8808 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
8809 case: it is treated as the target's maximum memory address.
8810 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
8813 Discard any user changes to the memory regions and use target-supplied
8814 regions, if available, or no regions if the target does not support.
8817 @item delete mem @var{nums}@dots{}
8818 Remove memory regions @var{nums}@dots{} from the list of regions
8819 monitored by @value{GDBN}.
8822 @item disable mem @var{nums}@dots{}
8823 Disable monitoring of memory regions @var{nums}@dots{}.
8824 A disabled memory region is not forgotten.
8825 It may be enabled again later.
8828 @item enable mem @var{nums}@dots{}
8829 Enable monitoring of memory regions @var{nums}@dots{}.
8833 Print a table of all defined memory regions, with the following columns
8837 @item Memory Region Number
8838 @item Enabled or Disabled.
8839 Enabled memory regions are marked with @samp{y}.
8840 Disabled memory regions are marked with @samp{n}.
8843 The address defining the inclusive lower bound of the memory region.
8846 The address defining the exclusive upper bound of the memory region.
8849 The list of attributes set for this memory region.
8854 @subsection Attributes
8856 @subsubsection Memory Access Mode
8857 The access mode attributes set whether @value{GDBN} may make read or
8858 write accesses to a memory region.
8860 While these attributes prevent @value{GDBN} from performing invalid
8861 memory accesses, they do nothing to prevent the target system, I/O DMA,
8862 etc.@: from accessing memory.
8866 Memory is read only.
8868 Memory is write only.
8870 Memory is read/write. This is the default.
8873 @subsubsection Memory Access Size
8874 The access size attribute tells @value{GDBN} to use specific sized
8875 accesses in the memory region. Often memory mapped device registers
8876 require specific sized accesses. If no access size attribute is
8877 specified, @value{GDBN} may use accesses of any size.
8881 Use 8 bit memory accesses.
8883 Use 16 bit memory accesses.
8885 Use 32 bit memory accesses.
8887 Use 64 bit memory accesses.
8890 @c @subsubsection Hardware/Software Breakpoints
8891 @c The hardware/software breakpoint attributes set whether @value{GDBN}
8892 @c will use hardware or software breakpoints for the internal breakpoints
8893 @c used by the step, next, finish, until, etc. commands.
8897 @c Always use hardware breakpoints
8898 @c @item swbreak (default)
8901 @subsubsection Data Cache
8902 The data cache attributes set whether @value{GDBN} will cache target
8903 memory. While this generally improves performance by reducing debug
8904 protocol overhead, it can lead to incorrect results because @value{GDBN}
8905 does not know about volatile variables or memory mapped device
8910 Enable @value{GDBN} to cache target memory.
8912 Disable @value{GDBN} from caching target memory. This is the default.
8915 @subsection Memory Access Checking
8916 @value{GDBN} can be instructed to refuse accesses to memory that is
8917 not explicitly described. This can be useful if accessing such
8918 regions has undesired effects for a specific target, or to provide
8919 better error checking. The following commands control this behaviour.
8922 @kindex set mem inaccessible-by-default
8923 @item set mem inaccessible-by-default [on|off]
8924 If @code{on} is specified, make @value{GDBN} treat memory not
8925 explicitly described by the memory ranges as non-existent and refuse accesses
8926 to such memory. The checks are only performed if there's at least one
8927 memory range defined. If @code{off} is specified, make @value{GDBN}
8928 treat the memory not explicitly described by the memory ranges as RAM.
8929 The default value is @code{on}.
8930 @kindex show mem inaccessible-by-default
8931 @item show mem inaccessible-by-default
8932 Show the current handling of accesses to unknown memory.
8936 @c @subsubsection Memory Write Verification
8937 @c The memory write verification attributes set whether @value{GDBN}
8938 @c will re-reads data after each write to verify the write was successful.
8942 @c @item noverify (default)
8945 @node Dump/Restore Files
8946 @section Copy Between Memory and a File
8947 @cindex dump/restore files
8948 @cindex append data to a file
8949 @cindex dump data to a file
8950 @cindex restore data from a file
8952 You can use the commands @code{dump}, @code{append}, and
8953 @code{restore} to copy data between target memory and a file. The
8954 @code{dump} and @code{append} commands write data to a file, and the
8955 @code{restore} command reads data from a file back into the inferior's
8956 memory. Files may be in binary, Motorola S-record, Intel hex, or
8957 Tektronix Hex format; however, @value{GDBN} can only append to binary
8963 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8964 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
8965 Dump the contents of memory from @var{start_addr} to @var{end_addr},
8966 or the value of @var{expr}, to @var{filename} in the given format.
8968 The @var{format} parameter may be any one of:
8975 Motorola S-record format.
8977 Tektronix Hex format.
8980 @value{GDBN} uses the same definitions of these formats as the
8981 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
8982 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
8986 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
8987 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
8988 Append the contents of memory from @var{start_addr} to @var{end_addr},
8989 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
8990 (@value{GDBN} can only append data to files in raw binary form.)
8993 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
8994 Restore the contents of file @var{filename} into memory. The
8995 @code{restore} command can automatically recognize any known @sc{bfd}
8996 file format, except for raw binary. To restore a raw binary file you
8997 must specify the optional keyword @code{binary} after the filename.
8999 If @var{bias} is non-zero, its value will be added to the addresses
9000 contained in the file. Binary files always start at address zero, so
9001 they will be restored at address @var{bias}. Other bfd files have
9002 a built-in location; they will be restored at offset @var{bias}
9005 If @var{start} and/or @var{end} are non-zero, then only data between
9006 file offset @var{start} and file offset @var{end} will be restored.
9007 These offsets are relative to the addresses in the file, before
9008 the @var{bias} argument is applied.
9012 @node Core File Generation
9013 @section How to Produce a Core File from Your Program
9014 @cindex dump core from inferior
9016 A @dfn{core file} or @dfn{core dump} is a file that records the memory
9017 image of a running process and its process status (register values
9018 etc.). Its primary use is post-mortem debugging of a program that
9019 crashed while it ran outside a debugger. A program that crashes
9020 automatically produces a core file, unless this feature is disabled by
9021 the user. @xref{Files}, for information on invoking @value{GDBN} in
9022 the post-mortem debugging mode.
9024 Occasionally, you may wish to produce a core file of the program you
9025 are debugging in order to preserve a snapshot of its state.
9026 @value{GDBN} has a special command for that.
9030 @kindex generate-core-file
9031 @item generate-core-file [@var{file}]
9032 @itemx gcore [@var{file}]
9033 Produce a core dump of the inferior process. The optional argument
9034 @var{file} specifies the file name where to put the core dump. If not
9035 specified, the file name defaults to @file{core.@var{pid}}, where
9036 @var{pid} is the inferior process ID.
9038 Note that this command is implemented only for some systems (as of
9039 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
9042 @node Character Sets
9043 @section Character Sets
9044 @cindex character sets
9046 @cindex translating between character sets
9047 @cindex host character set
9048 @cindex target character set
9050 If the program you are debugging uses a different character set to
9051 represent characters and strings than the one @value{GDBN} uses itself,
9052 @value{GDBN} can automatically translate between the character sets for
9053 you. The character set @value{GDBN} uses we call the @dfn{host
9054 character set}; the one the inferior program uses we call the
9055 @dfn{target character set}.
9057 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
9058 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
9059 remote protocol (@pxref{Remote Debugging}) to debug a program
9060 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
9061 then the host character set is Latin-1, and the target character set is
9062 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
9063 target-charset EBCDIC-US}, then @value{GDBN} translates between
9064 @sc{ebcdic} and Latin 1 as you print character or string values, or use
9065 character and string literals in expressions.
9067 @value{GDBN} has no way to automatically recognize which character set
9068 the inferior program uses; you must tell it, using the @code{set
9069 target-charset} command, described below.
9071 Here are the commands for controlling @value{GDBN}'s character set
9075 @item set target-charset @var{charset}
9076 @kindex set target-charset
9077 Set the current target character set to @var{charset}. To display the
9078 list of supported target character sets, type
9079 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
9081 @item set host-charset @var{charset}
9082 @kindex set host-charset
9083 Set the current host character set to @var{charset}.
9085 By default, @value{GDBN} uses a host character set appropriate to the
9086 system it is running on; you can override that default using the
9087 @code{set host-charset} command. On some systems, @value{GDBN} cannot
9088 automatically determine the appropriate host character set. In this
9089 case, @value{GDBN} uses @samp{UTF-8}.
9091 @value{GDBN} can only use certain character sets as its host character
9092 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
9093 @value{GDBN} will list the host character sets it supports.
9095 @item set charset @var{charset}
9097 Set the current host and target character sets to @var{charset}. As
9098 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
9099 @value{GDBN} will list the names of the character sets that can be used
9100 for both host and target.
9103 @kindex show charset
9104 Show the names of the current host and target character sets.
9106 @item show host-charset
9107 @kindex show host-charset
9108 Show the name of the current host character set.
9110 @item show target-charset
9111 @kindex show target-charset
9112 Show the name of the current target character set.
9114 @item set target-wide-charset @var{charset}
9115 @kindex set target-wide-charset
9116 Set the current target's wide character set to @var{charset}. This is
9117 the character set used by the target's @code{wchar_t} type. To
9118 display the list of supported wide character sets, type
9119 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
9121 @item show target-wide-charset
9122 @kindex show target-wide-charset
9123 Show the name of the current target's wide character set.
9126 Here is an example of @value{GDBN}'s character set support in action.
9127 Assume that the following source code has been placed in the file
9128 @file{charset-test.c}:
9134 = @{72, 101, 108, 108, 111, 44, 32, 119,
9135 111, 114, 108, 100, 33, 10, 0@};
9136 char ibm1047_hello[]
9137 = @{200, 133, 147, 147, 150, 107, 64, 166,
9138 150, 153, 147, 132, 90, 37, 0@};
9142 printf ("Hello, world!\n");
9146 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
9147 containing the string @samp{Hello, world!} followed by a newline,
9148 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
9150 We compile the program, and invoke the debugger on it:
9153 $ gcc -g charset-test.c -o charset-test
9154 $ gdb -nw charset-test
9155 GNU gdb 2001-12-19-cvs
9156 Copyright 2001 Free Software Foundation, Inc.
9161 We can use the @code{show charset} command to see what character sets
9162 @value{GDBN} is currently using to interpret and display characters and
9166 (@value{GDBP}) show charset
9167 The current host and target character set is `ISO-8859-1'.
9171 For the sake of printing this manual, let's use @sc{ascii} as our
9172 initial character set:
9174 (@value{GDBP}) set charset ASCII
9175 (@value{GDBP}) show charset
9176 The current host and target character set is `ASCII'.
9180 Let's assume that @sc{ascii} is indeed the correct character set for our
9181 host system --- in other words, let's assume that if @value{GDBN} prints
9182 characters using the @sc{ascii} character set, our terminal will display
9183 them properly. Since our current target character set is also
9184 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
9187 (@value{GDBP}) print ascii_hello
9188 $1 = 0x401698 "Hello, world!\n"
9189 (@value{GDBP}) print ascii_hello[0]
9194 @value{GDBN} uses the target character set for character and string
9195 literals you use in expressions:
9198 (@value{GDBP}) print '+'
9203 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
9206 @value{GDBN} relies on the user to tell it which character set the
9207 target program uses. If we print @code{ibm1047_hello} while our target
9208 character set is still @sc{ascii}, we get jibberish:
9211 (@value{GDBP}) print ibm1047_hello
9212 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
9213 (@value{GDBP}) print ibm1047_hello[0]
9218 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
9219 @value{GDBN} tells us the character sets it supports:
9222 (@value{GDBP}) set target-charset
9223 ASCII EBCDIC-US IBM1047 ISO-8859-1
9224 (@value{GDBP}) set target-charset
9227 We can select @sc{ibm1047} as our target character set, and examine the
9228 program's strings again. Now the @sc{ascii} string is wrong, but
9229 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
9230 target character set, @sc{ibm1047}, to the host character set,
9231 @sc{ascii}, and they display correctly:
9234 (@value{GDBP}) set target-charset IBM1047
9235 (@value{GDBP}) show charset
9236 The current host character set is `ASCII'.
9237 The current target character set is `IBM1047'.
9238 (@value{GDBP}) print ascii_hello
9239 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
9240 (@value{GDBP}) print ascii_hello[0]
9242 (@value{GDBP}) print ibm1047_hello
9243 $8 = 0x4016a8 "Hello, world!\n"
9244 (@value{GDBP}) print ibm1047_hello[0]
9249 As above, @value{GDBN} uses the target character set for character and
9250 string literals you use in expressions:
9253 (@value{GDBP}) print '+'
9258 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
9261 @node Caching Remote Data
9262 @section Caching Data of Remote Targets
9263 @cindex caching data of remote targets
9265 @value{GDBN} caches data exchanged between the debugger and a
9266 remote target (@pxref{Remote Debugging}). Such caching generally improves
9267 performance, because it reduces the overhead of the remote protocol by
9268 bundling memory reads and writes into large chunks. Unfortunately, simply
9269 caching everything would lead to incorrect results, since @value{GDBN}
9270 does not necessarily know anything about volatile values, memory-mapped I/O
9271 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
9272 memory can be changed @emph{while} a gdb command is executing.
9273 Therefore, by default, @value{GDBN} only caches data
9274 known to be on the stack@footnote{In non-stop mode, it is moderately
9275 rare for a running thread to modify the stack of a stopped thread
9276 in a way that would interfere with a backtrace, and caching of
9277 stack reads provides a significant speed up of remote backtraces.}.
9278 Other regions of memory can be explicitly marked as
9279 cacheable; see @pxref{Memory Region Attributes}.
9282 @kindex set remotecache
9283 @item set remotecache on
9284 @itemx set remotecache off
9285 This option no longer does anything; it exists for compatibility
9288 @kindex show remotecache
9289 @item show remotecache
9290 Show the current state of the obsolete remotecache flag.
9292 @kindex set stack-cache
9293 @item set stack-cache on
9294 @itemx set stack-cache off
9295 Enable or disable caching of stack accesses. When @code{ON}, use
9296 caching. By default, this option is @code{ON}.
9298 @kindex show stack-cache
9299 @item show stack-cache
9300 Show the current state of data caching for memory accesses.
9303 @item info dcache @r{[}line@r{]}
9304 Print the information about the data cache performance. The
9305 information displayed includes the dcache width and depth, and for
9306 each cache line, its number, address, and how many times it was
9307 referenced. This command is useful for debugging the data cache
9310 If a line number is specified, the contents of that line will be
9314 @node Searching Memory
9315 @section Search Memory
9316 @cindex searching memory
9318 Memory can be searched for a particular sequence of bytes with the
9319 @code{find} command.
9323 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9324 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
9325 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
9326 etc. The search begins at address @var{start_addr} and continues for either
9327 @var{len} bytes or through to @var{end_addr} inclusive.
9330 @var{s} and @var{n} are optional parameters.
9331 They may be specified in either order, apart or together.
9334 @item @var{s}, search query size
9335 The size of each search query value.
9341 halfwords (two bytes)
9345 giant words (eight bytes)
9348 All values are interpreted in the current language.
9349 This means, for example, that if the current source language is C/C@t{++}
9350 then searching for the string ``hello'' includes the trailing '\0'.
9352 If the value size is not specified, it is taken from the
9353 value's type in the current language.
9354 This is useful when one wants to specify the search
9355 pattern as a mixture of types.
9356 Note that this means, for example, that in the case of C-like languages
9357 a search for an untyped 0x42 will search for @samp{(int) 0x42}
9358 which is typically four bytes.
9360 @item @var{n}, maximum number of finds
9361 The maximum number of matches to print. The default is to print all finds.
9364 You can use strings as search values. Quote them with double-quotes
9366 The string value is copied into the search pattern byte by byte,
9367 regardless of the endianness of the target and the size specification.
9369 The address of each match found is printed as well as a count of the
9370 number of matches found.
9372 The address of the last value found is stored in convenience variable
9374 A count of the number of matches is stored in @samp{$numfound}.
9376 For example, if stopped at the @code{printf} in this function:
9382 static char hello[] = "hello-hello";
9383 static struct @{ char c; short s; int i; @}
9384 __attribute__ ((packed)) mixed
9385 = @{ 'c', 0x1234, 0x87654321 @};
9386 printf ("%s\n", hello);
9391 you get during debugging:
9394 (gdb) find &hello[0], +sizeof(hello), "hello"
9395 0x804956d <hello.1620+6>
9397 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
9398 0x8049567 <hello.1620>
9399 0x804956d <hello.1620+6>
9401 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
9402 0x8049567 <hello.1620>
9404 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
9405 0x8049560 <mixed.1625>
9407 (gdb) print $numfound
9410 $2 = (void *) 0x8049560
9413 @node Optimized Code
9414 @chapter Debugging Optimized Code
9415 @cindex optimized code, debugging
9416 @cindex debugging optimized code
9418 Almost all compilers support optimization. With optimization
9419 disabled, the compiler generates assembly code that corresponds
9420 directly to your source code, in a simplistic way. As the compiler
9421 applies more powerful optimizations, the generated assembly code
9422 diverges from your original source code. With help from debugging
9423 information generated by the compiler, @value{GDBN} can map from
9424 the running program back to constructs from your original source.
9426 @value{GDBN} is more accurate with optimization disabled. If you
9427 can recompile without optimization, it is easier to follow the
9428 progress of your program during debugging. But, there are many cases
9429 where you may need to debug an optimized version.
9431 When you debug a program compiled with @samp{-g -O}, remember that the
9432 optimizer has rearranged your code; the debugger shows you what is
9433 really there. Do not be too surprised when the execution path does not
9434 exactly match your source file! An extreme example: if you define a
9435 variable, but never use it, @value{GDBN} never sees that
9436 variable---because the compiler optimizes it out of existence.
9438 Some things do not work as well with @samp{-g -O} as with just
9439 @samp{-g}, particularly on machines with instruction scheduling. If in
9440 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
9441 please report it to us as a bug (including a test case!).
9442 @xref{Variables}, for more information about debugging optimized code.
9445 * Inline Functions:: How @value{GDBN} presents inlining
9448 @node Inline Functions
9449 @section Inline Functions
9450 @cindex inline functions, debugging
9452 @dfn{Inlining} is an optimization that inserts a copy of the function
9453 body directly at each call site, instead of jumping to a shared
9454 routine. @value{GDBN} displays inlined functions just like
9455 non-inlined functions. They appear in backtraces. You can view their
9456 arguments and local variables, step into them with @code{step}, skip
9457 them with @code{next}, and escape from them with @code{finish}.
9458 You can check whether a function was inlined by using the
9459 @code{info frame} command.
9461 For @value{GDBN} to support inlined functions, the compiler must
9462 record information about inlining in the debug information ---
9463 @value{NGCC} using the @sc{dwarf 2} format does this, and several
9464 other compilers do also. @value{GDBN} only supports inlined functions
9465 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
9466 do not emit two required attributes (@samp{DW_AT_call_file} and
9467 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
9468 function calls with earlier versions of @value{NGCC}. It instead
9469 displays the arguments and local variables of inlined functions as
9470 local variables in the caller.
9472 The body of an inlined function is directly included at its call site;
9473 unlike a non-inlined function, there are no instructions devoted to
9474 the call. @value{GDBN} still pretends that the call site and the
9475 start of the inlined function are different instructions. Stepping to
9476 the call site shows the call site, and then stepping again shows
9477 the first line of the inlined function, even though no additional
9478 instructions are executed.
9480 This makes source-level debugging much clearer; you can see both the
9481 context of the call and then the effect of the call. Only stepping by
9482 a single instruction using @code{stepi} or @code{nexti} does not do
9483 this; single instruction steps always show the inlined body.
9485 There are some ways that @value{GDBN} does not pretend that inlined
9486 function calls are the same as normal calls:
9490 You cannot set breakpoints on inlined functions. @value{GDBN}
9491 either reports that there is no symbol with that name, or else sets the
9492 breakpoint only on non-inlined copies of the function. This limitation
9493 will be removed in a future version of @value{GDBN}; until then,
9494 set a breakpoint by line number on the first line of the inlined
9498 Setting breakpoints at the call site of an inlined function may not
9499 work, because the call site does not contain any code. @value{GDBN}
9500 may incorrectly move the breakpoint to the next line of the enclosing
9501 function, after the call. This limitation will be removed in a future
9502 version of @value{GDBN}; until then, set a breakpoint on an earlier line
9503 or inside the inlined function instead.
9506 @value{GDBN} cannot locate the return value of inlined calls after
9507 using the @code{finish} command. This is a limitation of compiler-generated
9508 debugging information; after @code{finish}, you can step to the next line
9509 and print a variable where your program stored the return value.
9515 @chapter C Preprocessor Macros
9517 Some languages, such as C and C@t{++}, provide a way to define and invoke
9518 ``preprocessor macros'' which expand into strings of tokens.
9519 @value{GDBN} can evaluate expressions containing macro invocations, show
9520 the result of macro expansion, and show a macro's definition, including
9521 where it was defined.
9523 You may need to compile your program specially to provide @value{GDBN}
9524 with information about preprocessor macros. Most compilers do not
9525 include macros in their debugging information, even when you compile
9526 with the @option{-g} flag. @xref{Compilation}.
9528 A program may define a macro at one point, remove that definition later,
9529 and then provide a different definition after that. Thus, at different
9530 points in the program, a macro may have different definitions, or have
9531 no definition at all. If there is a current stack frame, @value{GDBN}
9532 uses the macros in scope at that frame's source code line. Otherwise,
9533 @value{GDBN} uses the macros in scope at the current listing location;
9536 Whenever @value{GDBN} evaluates an expression, it always expands any
9537 macro invocations present in the expression. @value{GDBN} also provides
9538 the following commands for working with macros explicitly.
9542 @kindex macro expand
9543 @cindex macro expansion, showing the results of preprocessor
9544 @cindex preprocessor macro expansion, showing the results of
9545 @cindex expanding preprocessor macros
9546 @item macro expand @var{expression}
9547 @itemx macro exp @var{expression}
9548 Show the results of expanding all preprocessor macro invocations in
9549 @var{expression}. Since @value{GDBN} simply expands macros, but does
9550 not parse the result, @var{expression} need not be a valid expression;
9551 it can be any string of tokens.
9554 @item macro expand-once @var{expression}
9555 @itemx macro exp1 @var{expression}
9556 @cindex expand macro once
9557 @i{(This command is not yet implemented.)} Show the results of
9558 expanding those preprocessor macro invocations that appear explicitly in
9559 @var{expression}. Macro invocations appearing in that expansion are
9560 left unchanged. This command allows you to see the effect of a
9561 particular macro more clearly, without being confused by further
9562 expansions. Since @value{GDBN} simply expands macros, but does not
9563 parse the result, @var{expression} need not be a valid expression; it
9564 can be any string of tokens.
9567 @cindex macro definition, showing
9568 @cindex definition, showing a macro's
9569 @item info macro @var{macro}
9570 Show the definition of the macro named @var{macro}, and describe the
9571 source location or compiler command-line where that definition was established.
9573 @kindex macro define
9574 @cindex user-defined macros
9575 @cindex defining macros interactively
9576 @cindex macros, user-defined
9577 @item macro define @var{macro} @var{replacement-list}
9578 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
9579 Introduce a definition for a preprocessor macro named @var{macro},
9580 invocations of which are replaced by the tokens given in
9581 @var{replacement-list}. The first form of this command defines an
9582 ``object-like'' macro, which takes no arguments; the second form
9583 defines a ``function-like'' macro, which takes the arguments given in
9586 A definition introduced by this command is in scope in every
9587 expression evaluated in @value{GDBN}, until it is removed with the
9588 @code{macro undef} command, described below. The definition overrides
9589 all definitions for @var{macro} present in the program being debugged,
9590 as well as any previous user-supplied definition.
9593 @item macro undef @var{macro}
9594 Remove any user-supplied definition for the macro named @var{macro}.
9595 This command only affects definitions provided with the @code{macro
9596 define} command, described above; it cannot remove definitions present
9597 in the program being debugged.
9601 List all the macros defined using the @code{macro define} command.
9604 @cindex macros, example of debugging with
9605 Here is a transcript showing the above commands in action. First, we
9606 show our source files:
9614 #define ADD(x) (M + x)
9619 printf ("Hello, world!\n");
9621 printf ("We're so creative.\n");
9623 printf ("Goodbye, world!\n");
9630 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
9631 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
9632 compiler includes information about preprocessor macros in the debugging
9636 $ gcc -gdwarf-2 -g3 sample.c -o sample
9640 Now, we start @value{GDBN} on our sample program:
9644 GNU gdb 2002-05-06-cvs
9645 Copyright 2002 Free Software Foundation, Inc.
9646 GDB is free software, @dots{}
9650 We can expand macros and examine their definitions, even when the
9651 program is not running. @value{GDBN} uses the current listing position
9652 to decide which macro definitions are in scope:
9655 (@value{GDBP}) list main
9658 5 #define ADD(x) (M + x)
9663 10 printf ("Hello, world!\n");
9665 12 printf ("We're so creative.\n");
9666 (@value{GDBP}) info macro ADD
9667 Defined at /home/jimb/gdb/macros/play/sample.c:5
9668 #define ADD(x) (M + x)
9669 (@value{GDBP}) info macro Q
9670 Defined at /home/jimb/gdb/macros/play/sample.h:1
9671 included at /home/jimb/gdb/macros/play/sample.c:2
9673 (@value{GDBP}) macro expand ADD(1)
9674 expands to: (42 + 1)
9675 (@value{GDBP}) macro expand-once ADD(1)
9676 expands to: once (M + 1)
9680 In the example above, note that @code{macro expand-once} expands only
9681 the macro invocation explicit in the original text --- the invocation of
9682 @code{ADD} --- but does not expand the invocation of the macro @code{M},
9683 which was introduced by @code{ADD}.
9685 Once the program is running, @value{GDBN} uses the macro definitions in
9686 force at the source line of the current stack frame:
9689 (@value{GDBP}) break main
9690 Breakpoint 1 at 0x8048370: file sample.c, line 10.
9692 Starting program: /home/jimb/gdb/macros/play/sample
9694 Breakpoint 1, main () at sample.c:10
9695 10 printf ("Hello, world!\n");
9699 At line 10, the definition of the macro @code{N} at line 9 is in force:
9702 (@value{GDBP}) info macro N
9703 Defined at /home/jimb/gdb/macros/play/sample.c:9
9705 (@value{GDBP}) macro expand N Q M
9707 (@value{GDBP}) print N Q M
9712 As we step over directives that remove @code{N}'s definition, and then
9713 give it a new definition, @value{GDBN} finds the definition (or lack
9714 thereof) in force at each point:
9719 12 printf ("We're so creative.\n");
9720 (@value{GDBP}) info macro N
9721 The symbol `N' has no definition as a C/C++ preprocessor macro
9722 at /home/jimb/gdb/macros/play/sample.c:12
9725 14 printf ("Goodbye, world!\n");
9726 (@value{GDBP}) info macro N
9727 Defined at /home/jimb/gdb/macros/play/sample.c:13
9729 (@value{GDBP}) macro expand N Q M
9730 expands to: 1729 < 42
9731 (@value{GDBP}) print N Q M
9736 In addition to source files, macros can be defined on the compilation command
9737 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
9738 such a way, @value{GDBN} displays the location of their definition as line zero
9739 of the source file submitted to the compiler.
9742 (@value{GDBP}) info macro __STDC__
9743 Defined at /home/jimb/gdb/macros/play/sample.c:0
9750 @chapter Tracepoints
9751 @c This chapter is based on the documentation written by Michael
9752 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
9755 In some applications, it is not feasible for the debugger to interrupt
9756 the program's execution long enough for the developer to learn
9757 anything helpful about its behavior. If the program's correctness
9758 depends on its real-time behavior, delays introduced by a debugger
9759 might cause the program to change its behavior drastically, or perhaps
9760 fail, even when the code itself is correct. It is useful to be able
9761 to observe the program's behavior without interrupting it.
9763 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
9764 specify locations in the program, called @dfn{tracepoints}, and
9765 arbitrary expressions to evaluate when those tracepoints are reached.
9766 Later, using the @code{tfind} command, you can examine the values
9767 those expressions had when the program hit the tracepoints. The
9768 expressions may also denote objects in memory---structures or arrays,
9769 for example---whose values @value{GDBN} should record; while visiting
9770 a particular tracepoint, you may inspect those objects as if they were
9771 in memory at that moment. However, because @value{GDBN} records these
9772 values without interacting with you, it can do so quickly and
9773 unobtrusively, hopefully not disturbing the program's behavior.
9775 The tracepoint facility is currently available only for remote
9776 targets. @xref{Targets}. In addition, your remote target must know
9777 how to collect trace data. This functionality is implemented in the
9778 remote stub; however, none of the stubs distributed with @value{GDBN}
9779 support tracepoints as of this writing. The format of the remote
9780 packets used to implement tracepoints are described in @ref{Tracepoint
9783 It is also possible to get trace data from a file, in a manner reminiscent
9784 of corefiles; you specify the filename, and use @code{tfind} to search
9785 through the file. @xref{Trace Files}, for more details.
9787 This chapter describes the tracepoint commands and features.
9791 * Analyze Collected Data::
9792 * Tracepoint Variables::
9796 @node Set Tracepoints
9797 @section Commands to Set Tracepoints
9799 Before running such a @dfn{trace experiment}, an arbitrary number of
9800 tracepoints can be set. A tracepoint is actually a special type of
9801 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
9802 standard breakpoint commands. For instance, as with breakpoints,
9803 tracepoint numbers are successive integers starting from one, and many
9804 of the commands associated with tracepoints take the tracepoint number
9805 as their argument, to identify which tracepoint to work on.
9807 For each tracepoint, you can specify, in advance, some arbitrary set
9808 of data that you want the target to collect in the trace buffer when
9809 it hits that tracepoint. The collected data can include registers,
9810 local variables, or global data. Later, you can use @value{GDBN}
9811 commands to examine the values these data had at the time the
9814 Tracepoints do not support every breakpoint feature. Ignore counts on
9815 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
9816 commands when they are hit. Tracepoints may not be thread-specific
9819 @cindex fast tracepoints
9820 Some targets may support @dfn{fast tracepoints}, which are inserted in
9821 a different way (such as with a jump instead of a trap), that is
9822 faster but possibly restricted in where they may be installed.
9824 @cindex static tracepoints
9825 @cindex markers, static tracepoints
9826 @cindex probing markers, static tracepoints
9827 Regular and fast tracepoints are dynamic tracing facilities, meaning
9828 that they can be used to insert tracepoints at (almost) any location
9829 in the target. Some targets may also support controlling @dfn{static
9830 tracepoints} from @value{GDBN}. With static tracing, a set of
9831 instrumentation points, also known as @dfn{markers}, are embedded in
9832 the target program, and can be activated or deactivated by name or
9833 address. These are usually placed at locations which facilitate
9834 investigating what the target is actually doing. @value{GDBN}'s
9835 support for static tracing includes being able to list instrumentation
9836 points, and attach them with @value{GDBN} defined high level
9837 tracepoints that expose the whole range of convenience of
9838 @value{GDBN}'s tracepoints support. Namelly, support for collecting
9839 registers values and values of global or local (to the instrumentation
9840 point) variables; tracepoint conditions and trace state variables.
9841 The act of installing a @value{GDBN} static tracepoint on an
9842 instrumentation point, or marker, is referred to as @dfn{probing} a
9843 static tracepoint marker.
9845 @code{gdbserver} supports tracepoints on some target systems.
9846 @xref{Server,,Tracepoints support in @code{gdbserver}}.
9848 This section describes commands to set tracepoints and associated
9849 conditions and actions.
9852 * Create and Delete Tracepoints::
9853 * Enable and Disable Tracepoints::
9854 * Tracepoint Passcounts::
9855 * Tracepoint Conditions::
9856 * Trace State Variables::
9857 * Tracepoint Actions::
9858 * Listing Tracepoints::
9859 * Listing Static Tracepoint Markers::
9860 * Starting and Stopping Trace Experiments::
9861 * Tracepoint Restrictions::
9864 @node Create and Delete Tracepoints
9865 @subsection Create and Delete Tracepoints
9868 @cindex set tracepoint
9870 @item trace @var{location}
9871 The @code{trace} command is very similar to the @code{break} command.
9872 Its argument @var{location} can be a source line, a function name, or
9873 an address in the target program. @xref{Specify Location}. The
9874 @code{trace} command defines a tracepoint, which is a point in the
9875 target program where the debugger will briefly stop, collect some
9876 data, and then allow the program to continue. Setting a tracepoint or
9877 changing its actions doesn't take effect until the next @code{tstart}
9878 command, and once a trace experiment is running, further changes will
9879 not have any effect until the next trace experiment starts.
9881 Here are some examples of using the @code{trace} command:
9884 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
9886 (@value{GDBP}) @b{trace +2} // 2 lines forward
9888 (@value{GDBP}) @b{trace my_function} // first source line of function
9890 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
9892 (@value{GDBP}) @b{trace *0x2117c4} // an address
9896 You can abbreviate @code{trace} as @code{tr}.
9898 @item trace @var{location} if @var{cond}
9899 Set a tracepoint with condition @var{cond}; evaluate the expression
9900 @var{cond} each time the tracepoint is reached, and collect data only
9901 if the value is nonzero---that is, if @var{cond} evaluates as true.
9902 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
9903 information on tracepoint conditions.
9905 @item ftrace @var{location} [ if @var{cond} ]
9906 @cindex set fast tracepoint
9907 @cindex fast tracepoints, setting
9909 The @code{ftrace} command sets a fast tracepoint. For targets that
9910 support them, fast tracepoints will use a more efficient but possibly
9911 less general technique to trigger data collection, such as a jump
9912 instruction instead of a trap, or some sort of hardware support. It
9913 may not be possible to create a fast tracepoint at the desired
9914 location, in which case the command will exit with an explanatory
9917 @value{GDBN} handles arguments to @code{ftrace} exactly as for
9920 @item strace @var{location} [ if @var{cond} ]
9921 @cindex set static tracepoint
9922 @cindex static tracepoints, setting
9923 @cindex probe static tracepoint marker
9925 The @code{strace} command sets a static tracepoint. For targets that
9926 support it, setting a static tracepoint probes a static
9927 instrumentation point, or marker, found at @var{location}. It may not
9928 be possible to set a static tracepoint at the desired location, in
9929 which case the command will exit with an explanatory message.
9931 @value{GDBN} handles arguments to @code{strace} exactly as for
9932 @code{trace}, with the addition that the user can also specify
9933 @code{-m @var{marker}} as @var{location}. This probes the marker
9934 identified by the @var{marker} string identifier. This identifier
9935 depends on the static tracepoint backend library your program is
9936 using. You can find all the marker identifiers in the @samp{ID} field
9937 of the @code{info static-tracepoint-markers} command output.
9938 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
9939 Markers}. For example, in the following small program using the UST
9945 trace_mark(ust, bar33, "str %s", "FOOBAZ");
9950 the marker id is composed of joining the first two arguments to the
9951 @code{trace_mark} call with a slash, which translates to:
9954 (@value{GDBP}) info static-tracepoint-markers
9955 Cnt Enb ID Address What
9956 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
9962 so you may probe the marker above with:
9965 (@value{GDBP}) strace -m ust/bar33
9968 Static tracepoints accept an extra collect action --- @code{collect
9969 $_sdata}. This collects arbitrary user data passed in the probe point
9970 call to the tracing library. In the UST example above, you'll see
9971 that the third argument to @code{trace_mark} is a printf-like format
9972 string. The user data is then the result of running that formating
9973 string against the following arguments. Note that @code{info
9974 static-tracepoint-markers} command output lists that format string in
9975 the @samp{Data:} field.
9977 You can inspect this data when analyzing the trace buffer, by printing
9978 the $_sdata variable like any other variable available to
9979 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
9982 @cindex last tracepoint number
9983 @cindex recent tracepoint number
9984 @cindex tracepoint number
9985 The convenience variable @code{$tpnum} records the tracepoint number
9986 of the most recently set tracepoint.
9988 @kindex delete tracepoint
9989 @cindex tracepoint deletion
9990 @item delete tracepoint @r{[}@var{num}@r{]}
9991 Permanently delete one or more tracepoints. With no argument, the
9992 default is to delete all tracepoints. Note that the regular
9993 @code{delete} command can remove tracepoints also.
9998 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
10000 (@value{GDBP}) @b{delete trace} // remove all tracepoints
10004 You can abbreviate this command as @code{del tr}.
10007 @node Enable and Disable Tracepoints
10008 @subsection Enable and Disable Tracepoints
10010 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
10013 @kindex disable tracepoint
10014 @item disable tracepoint @r{[}@var{num}@r{]}
10015 Disable tracepoint @var{num}, or all tracepoints if no argument
10016 @var{num} is given. A disabled tracepoint will have no effect during
10017 the next trace experiment, but it is not forgotten. You can re-enable
10018 a disabled tracepoint using the @code{enable tracepoint} command.
10020 @kindex enable tracepoint
10021 @item enable tracepoint @r{[}@var{num}@r{]}
10022 Enable tracepoint @var{num}, or all tracepoints. The enabled
10023 tracepoints will become effective the next time a trace experiment is
10027 @node Tracepoint Passcounts
10028 @subsection Tracepoint Passcounts
10032 @cindex tracepoint pass count
10033 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
10034 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
10035 automatically stop a trace experiment. If a tracepoint's passcount is
10036 @var{n}, then the trace experiment will be automatically stopped on
10037 the @var{n}'th time that tracepoint is hit. If the tracepoint number
10038 @var{num} is not specified, the @code{passcount} command sets the
10039 passcount of the most recently defined tracepoint. If no passcount is
10040 given, the trace experiment will run until stopped explicitly by the
10046 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
10047 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
10049 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
10050 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
10051 (@value{GDBP}) @b{trace foo}
10052 (@value{GDBP}) @b{pass 3}
10053 (@value{GDBP}) @b{trace bar}
10054 (@value{GDBP}) @b{pass 2}
10055 (@value{GDBP}) @b{trace baz}
10056 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
10057 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
10058 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
10059 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
10063 @node Tracepoint Conditions
10064 @subsection Tracepoint Conditions
10065 @cindex conditional tracepoints
10066 @cindex tracepoint conditions
10068 The simplest sort of tracepoint collects data every time your program
10069 reaches a specified place. You can also specify a @dfn{condition} for
10070 a tracepoint. A condition is just a Boolean expression in your
10071 programming language (@pxref{Expressions, ,Expressions}). A
10072 tracepoint with a condition evaluates the expression each time your
10073 program reaches it, and data collection happens only if the condition
10076 Tracepoint conditions can be specified when a tracepoint is set, by
10077 using @samp{if} in the arguments to the @code{trace} command.
10078 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
10079 also be set or changed at any time with the @code{condition} command,
10080 just as with breakpoints.
10082 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
10083 the conditional expression itself. Instead, @value{GDBN} encodes the
10084 expression into an agent expression (@pxref{Agent Expressions}
10085 suitable for execution on the target, independently of @value{GDBN}.
10086 Global variables become raw memory locations, locals become stack
10087 accesses, and so forth.
10089 For instance, suppose you have a function that is usually called
10090 frequently, but should not be called after an error has occurred. You
10091 could use the following tracepoint command to collect data about calls
10092 of that function that happen while the error code is propagating
10093 through the program; an unconditional tracepoint could end up
10094 collecting thousands of useless trace frames that you would have to
10098 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
10101 @node Trace State Variables
10102 @subsection Trace State Variables
10103 @cindex trace state variables
10105 A @dfn{trace state variable} is a special type of variable that is
10106 created and managed by target-side code. The syntax is the same as
10107 that for GDB's convenience variables (a string prefixed with ``$''),
10108 but they are stored on the target. They must be created explicitly,
10109 using a @code{tvariable} command. They are always 64-bit signed
10112 Trace state variables are remembered by @value{GDBN}, and downloaded
10113 to the target along with tracepoint information when the trace
10114 experiment starts. There are no intrinsic limits on the number of
10115 trace state variables, beyond memory limitations of the target.
10117 @cindex convenience variables, and trace state variables
10118 Although trace state variables are managed by the target, you can use
10119 them in print commands and expressions as if they were convenience
10120 variables; @value{GDBN} will get the current value from the target
10121 while the trace experiment is running. Trace state variables share
10122 the same namespace as other ``$'' variables, which means that you
10123 cannot have trace state variables with names like @code{$23} or
10124 @code{$pc}, nor can you have a trace state variable and a convenience
10125 variable with the same name.
10129 @item tvariable $@var{name} [ = @var{expression} ]
10131 The @code{tvariable} command creates a new trace state variable named
10132 @code{$@var{name}}, and optionally gives it an initial value of
10133 @var{expression}. @var{expression} is evaluated when this command is
10134 entered; the result will be converted to an integer if possible,
10135 otherwise @value{GDBN} will report an error. A subsequent
10136 @code{tvariable} command specifying the same name does not create a
10137 variable, but instead assigns the supplied initial value to the
10138 existing variable of that name, overwriting any previous initial
10139 value. The default initial value is 0.
10141 @item info tvariables
10142 @kindex info tvariables
10143 List all the trace state variables along with their initial values.
10144 Their current values may also be displayed, if the trace experiment is
10147 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
10148 @kindex delete tvariable
10149 Delete the given trace state variables, or all of them if no arguments
10154 @node Tracepoint Actions
10155 @subsection Tracepoint Action Lists
10159 @cindex tracepoint actions
10160 @item actions @r{[}@var{num}@r{]}
10161 This command will prompt for a list of actions to be taken when the
10162 tracepoint is hit. If the tracepoint number @var{num} is not
10163 specified, this command sets the actions for the one that was most
10164 recently defined (so that you can define a tracepoint and then say
10165 @code{actions} without bothering about its number). You specify the
10166 actions themselves on the following lines, one action at a time, and
10167 terminate the actions list with a line containing just @code{end}. So
10168 far, the only defined actions are @code{collect}, @code{teval}, and
10169 @code{while-stepping}.
10171 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
10172 Commands, ,Breakpoint Command Lists}), except that only the defined
10173 actions are allowed; any other @value{GDBN} command is rejected.
10175 @cindex remove actions from a tracepoint
10176 To remove all actions from a tracepoint, type @samp{actions @var{num}}
10177 and follow it immediately with @samp{end}.
10180 (@value{GDBP}) @b{collect @var{data}} // collect some data
10182 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
10184 (@value{GDBP}) @b{end} // signals the end of actions.
10187 In the following example, the action list begins with @code{collect}
10188 commands indicating the things to be collected when the tracepoint is
10189 hit. Then, in order to single-step and collect additional data
10190 following the tracepoint, a @code{while-stepping} command is used,
10191 followed by the list of things to be collected after each step in a
10192 sequence of single steps. The @code{while-stepping} command is
10193 terminated by its own separate @code{end} command. Lastly, the action
10194 list is terminated by an @code{end} command.
10197 (@value{GDBP}) @b{trace foo}
10198 (@value{GDBP}) @b{actions}
10199 Enter actions for tracepoint 1, one per line:
10202 > while-stepping 12
10203 > collect $pc, arr[i]
10208 @kindex collect @r{(tracepoints)}
10209 @item collect @var{expr1}, @var{expr2}, @dots{}
10210 Collect values of the given expressions when the tracepoint is hit.
10211 This command accepts a comma-separated list of any valid expressions.
10212 In addition to global, static, or local variables, the following
10213 special arguments are supported:
10217 Collect all registers.
10220 Collect all function arguments.
10223 Collect all local variables.
10226 @vindex $_sdata@r{, collect}
10227 Collect static tracepoint marker specific data. Only available for
10228 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
10229 Lists}. On the UST static tracepoints library backend, an
10230 instrumentation point resembles a @code{printf} function call. The
10231 tracing library is able to collect user specified data formatted to a
10232 character string using the format provided by the programmer that
10233 instrumented the program. Other backends have similar mechanisms.
10234 Here's an example of a UST marker call:
10237 const char master_name[] = "$your_name";
10238 trace_mark(channel1, marker1, "hello %s", master_name)
10241 In this case, collecting @code{$_sdata} collects the string
10242 @samp{hello $yourname}. When analyzing the trace buffer, you can
10243 inspect @samp{$_sdata} like any other variable available to
10247 You can give several consecutive @code{collect} commands, each one
10248 with a single argument, or one @code{collect} command with several
10249 arguments separated by commas; the effect is the same.
10251 The command @code{info scope} (@pxref{Symbols, info scope}) is
10252 particularly useful for figuring out what data to collect.
10254 @kindex teval @r{(tracepoints)}
10255 @item teval @var{expr1}, @var{expr2}, @dots{}
10256 Evaluate the given expressions when the tracepoint is hit. This
10257 command accepts a comma-separated list of expressions. The results
10258 are discarded, so this is mainly useful for assigning values to trace
10259 state variables (@pxref{Trace State Variables}) without adding those
10260 values to the trace buffer, as would be the case if the @code{collect}
10263 @kindex while-stepping @r{(tracepoints)}
10264 @item while-stepping @var{n}
10265 Perform @var{n} single-step instruction traces after the tracepoint,
10266 collecting new data after each step. The @code{while-stepping}
10267 command is followed by the list of what to collect while stepping
10268 (followed by its own @code{end} command):
10271 > while-stepping 12
10272 > collect $regs, myglobal
10278 Note that @code{$pc} is not automatically collected by
10279 @code{while-stepping}; you need to explicitly collect that register if
10280 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
10283 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
10284 @kindex set default-collect
10285 @cindex default collection action
10286 This variable is a list of expressions to collect at each tracepoint
10287 hit. It is effectively an additional @code{collect} action prepended
10288 to every tracepoint action list. The expressions are parsed
10289 individually for each tracepoint, so for instance a variable named
10290 @code{xyz} may be interpreted as a global for one tracepoint, and a
10291 local for another, as appropriate to the tracepoint's location.
10293 @item show default-collect
10294 @kindex show default-collect
10295 Show the list of expressions that are collected by default at each
10300 @node Listing Tracepoints
10301 @subsection Listing Tracepoints
10304 @kindex info tracepoints
10306 @cindex information about tracepoints
10307 @item info tracepoints @r{[}@var{num}@r{]}
10308 Display information about the tracepoint @var{num}. If you don't
10309 specify a tracepoint number, displays information about all the
10310 tracepoints defined so far. The format is similar to that used for
10311 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
10312 command, simply restricting itself to tracepoints.
10314 A tracepoint's listing may include additional information specific to
10319 its passcount as given by the @code{passcount @var{n}} command
10323 (@value{GDBP}) @b{info trace}
10324 Num Type Disp Enb Address What
10325 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
10327 collect globfoo, $regs
10336 This command can be abbreviated @code{info tp}.
10339 @node Listing Static Tracepoint Markers
10340 @subsection Listing Static Tracepoint Markers
10343 @kindex info static-tracepoint-markers
10344 @cindex information about static tracepoint markers
10345 @item info static-tracepoint-markers
10346 Display information about all static tracepoint markers defined in the
10349 For each marker, the following columns are printed:
10353 An incrementing counter, output to help readability. This is not a
10356 The marker ID, as reported by the target.
10357 @item Enabled or Disabled
10358 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
10359 that are not enabled.
10361 Where the marker is in your program, as a memory address.
10363 Where the marker is in the source for your program, as a file and line
10364 number. If the debug information included in the program does not
10365 allow @value{GDBN} to locate the source of the marker, this column
10366 will be left blank.
10370 In addition, the following information may be printed for each marker:
10374 User data passed to the tracing library by the marker call. In the
10375 UST backend, this is the format string passed as argument to the
10377 @item Static tracepoints probing the marker
10378 The list of static tracepoints attached to the marker.
10382 (@value{GDBP}) info static-tracepoint-markers
10383 Cnt ID Enb Address What
10384 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
10385 Data: number1 %d number2 %d
10386 Probed by static tracepoints: #2
10387 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
10393 @node Starting and Stopping Trace Experiments
10394 @subsection Starting and Stopping Trace Experiments
10398 @cindex start a new trace experiment
10399 @cindex collected data discarded
10401 This command takes no arguments. It starts the trace experiment, and
10402 begins collecting data. This has the side effect of discarding all
10403 the data collected in the trace buffer during the previous trace
10407 @cindex stop a running trace experiment
10409 This command takes no arguments. It ends the trace experiment, and
10410 stops collecting data.
10412 @strong{Note}: a trace experiment and data collection may stop
10413 automatically if any tracepoint's passcount is reached
10414 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
10417 @cindex status of trace data collection
10418 @cindex trace experiment, status of
10420 This command displays the status of the current trace data
10424 Here is an example of the commands we described so far:
10427 (@value{GDBP}) @b{trace gdb_c_test}
10428 (@value{GDBP}) @b{actions}
10429 Enter actions for tracepoint #1, one per line.
10430 > collect $regs,$locals,$args
10431 > while-stepping 11
10435 (@value{GDBP}) @b{tstart}
10436 [time passes @dots{}]
10437 (@value{GDBP}) @b{tstop}
10440 @cindex disconnected tracing
10441 You can choose to continue running the trace experiment even if
10442 @value{GDBN} disconnects from the target, voluntarily or
10443 involuntarily. For commands such as @code{detach}, the debugger will
10444 ask what you want to do with the trace. But for unexpected
10445 terminations (@value{GDBN} crash, network outage), it would be
10446 unfortunate to lose hard-won trace data, so the variable
10447 @code{disconnected-tracing} lets you decide whether the trace should
10448 continue running without @value{GDBN}.
10451 @item set disconnected-tracing on
10452 @itemx set disconnected-tracing off
10453 @kindex set disconnected-tracing
10454 Choose whether a tracing run should continue to run if @value{GDBN}
10455 has disconnected from the target. Note that @code{detach} or
10456 @code{quit} will ask you directly what to do about a running trace no
10457 matter what this variable's setting, so the variable is mainly useful
10458 for handling unexpected situations, such as loss of the network.
10460 @item show disconnected-tracing
10461 @kindex show disconnected-tracing
10462 Show the current choice for disconnected tracing.
10466 When you reconnect to the target, the trace experiment may or may not
10467 still be running; it might have filled the trace buffer in the
10468 meantime, or stopped for one of the other reasons. If it is running,
10469 it will continue after reconnection.
10471 Upon reconnection, the target will upload information about the
10472 tracepoints in effect. @value{GDBN} will then compare that
10473 information to the set of tracepoints currently defined, and attempt
10474 to match them up, allowing for the possibility that the numbers may
10475 have changed due to creation and deletion in the meantime. If one of
10476 the target's tracepoints does not match any in @value{GDBN}, the
10477 debugger will create a new tracepoint, so that you have a number with
10478 which to specify that tracepoint. This matching-up process is
10479 necessarily heuristic, and it may result in useless tracepoints being
10480 created; you may simply delete them if they are of no use.
10482 @cindex circular trace buffer
10483 If your target agent supports a @dfn{circular trace buffer}, then you
10484 can run a trace experiment indefinitely without filling the trace
10485 buffer; when space runs out, the agent deletes already-collected trace
10486 frames, oldest first, until there is enough room to continue
10487 collecting. This is especially useful if your tracepoints are being
10488 hit too often, and your trace gets terminated prematurely because the
10489 buffer is full. To ask for a circular trace buffer, simply set
10490 @samp{circular_trace_buffer} to on. You can set this at any time,
10491 including during tracing; if the agent can do it, it will change
10492 buffer handling on the fly, otherwise it will not take effect until
10496 @item set circular-trace-buffer on
10497 @itemx set circular-trace-buffer off
10498 @kindex set circular-trace-buffer
10499 Choose whether a tracing run should use a linear or circular buffer
10500 for trace data. A linear buffer will not lose any trace data, but may
10501 fill up prematurely, while a circular buffer will discard old trace
10502 data, but it will have always room for the latest tracepoint hits.
10504 @item show circular-trace-buffer
10505 @kindex show circular-trace-buffer
10506 Show the current choice for the trace buffer. Note that this may not
10507 match the agent's current buffer handling, nor is it guaranteed to
10508 match the setting that might have been in effect during a past run,
10509 for instance if you are looking at frames from a trace file.
10513 @node Tracepoint Restrictions
10514 @subsection Tracepoint Restrictions
10516 @cindex tracepoint restrictions
10517 There are a number of restrictions on the use of tracepoints. As
10518 described above, tracepoint data gathering occurs on the target
10519 without interaction from @value{GDBN}. Thus the full capabilities of
10520 the debugger are not available during data gathering, and then at data
10521 examination time, you will be limited by only having what was
10522 collected. The following items describe some common problems, but it
10523 is not exhaustive, and you may run into additional difficulties not
10529 Tracepoint expressions are intended to gather objects (lvalues). Thus
10530 the full flexibility of GDB's expression evaluator is not available.
10531 You cannot call functions, cast objects to aggregate types, access
10532 convenience variables or modify values (except by assignment to trace
10533 state variables). Some language features may implicitly call
10534 functions (for instance Objective-C fields with accessors), and therefore
10535 cannot be collected either.
10538 Collection of local variables, either individually or in bulk with
10539 @code{$locals} or @code{$args}, during @code{while-stepping} may
10540 behave erratically. The stepping action may enter a new scope (for
10541 instance by stepping into a function), or the location of the variable
10542 may change (for instance it is loaded into a register). The
10543 tracepoint data recorded uses the location information for the
10544 variables that is correct for the tracepoint location. When the
10545 tracepoint is created, it is not possible, in general, to determine
10546 where the steps of a @code{while-stepping} sequence will advance the
10547 program---particularly if a conditional branch is stepped.
10550 Collection of an incompletely-initialized or partially-destroyed object
10551 may result in something that @value{GDBN} cannot display, or displays
10552 in a misleading way.
10555 When @value{GDBN} displays a pointer to character it automatically
10556 dereferences the pointer to also display characters of the string
10557 being pointed to. However, collecting the pointer during tracing does
10558 not automatically collect the string. You need to explicitly
10559 dereference the pointer and provide size information if you want to
10560 collect not only the pointer, but the memory pointed to. For example,
10561 @code{*ptr@@50} can be used to collect the 50 element array pointed to
10565 It is not possible to collect a complete stack backtrace at a
10566 tracepoint. Instead, you may collect the registers and a few hundred
10567 bytes from the stack pointer with something like @code{*$esp@@300}
10568 (adjust to use the name of the actual stack pointer register on your
10569 target architecture, and the amount of stack you wish to capture).
10570 Then the @code{backtrace} command will show a partial backtrace when
10571 using a trace frame. The number of stack frames that can be examined
10572 depends on the sizes of the frames in the collected stack. Note that
10573 if you ask for a block so large that it goes past the bottom of the
10574 stack, the target agent may report an error trying to read from an
10578 If you do not collect registers at a tracepoint, @value{GDBN} can
10579 infer that the value of @code{$pc} must be the same as the address of
10580 the tracepoint and use that when you are looking at a trace frame
10581 for that tracepoint. However, this cannot work if the tracepoint has
10582 multiple locations (for instance if it was set in a function that was
10583 inlined), or if it has a @code{while-stepping} loop. In those cases
10584 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
10589 @node Analyze Collected Data
10590 @section Using the Collected Data
10592 After the tracepoint experiment ends, you use @value{GDBN} commands
10593 for examining the trace data. The basic idea is that each tracepoint
10594 collects a trace @dfn{snapshot} every time it is hit and another
10595 snapshot every time it single-steps. All these snapshots are
10596 consecutively numbered from zero and go into a buffer, and you can
10597 examine them later. The way you examine them is to @dfn{focus} on a
10598 specific trace snapshot. When the remote stub is focused on a trace
10599 snapshot, it will respond to all @value{GDBN} requests for memory and
10600 registers by reading from the buffer which belongs to that snapshot,
10601 rather than from @emph{real} memory or registers of the program being
10602 debugged. This means that @strong{all} @value{GDBN} commands
10603 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
10604 behave as if we were currently debugging the program state as it was
10605 when the tracepoint occurred. Any requests for data that are not in
10606 the buffer will fail.
10609 * tfind:: How to select a trace snapshot
10610 * tdump:: How to display all data for a snapshot
10611 * save tracepoints:: How to save tracepoints for a future run
10615 @subsection @code{tfind @var{n}}
10618 @cindex select trace snapshot
10619 @cindex find trace snapshot
10620 The basic command for selecting a trace snapshot from the buffer is
10621 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
10622 counting from zero. If no argument @var{n} is given, the next
10623 snapshot is selected.
10625 Here are the various forms of using the @code{tfind} command.
10629 Find the first snapshot in the buffer. This is a synonym for
10630 @code{tfind 0} (since 0 is the number of the first snapshot).
10633 Stop debugging trace snapshots, resume @emph{live} debugging.
10636 Same as @samp{tfind none}.
10639 No argument means find the next trace snapshot.
10642 Find the previous trace snapshot before the current one. This permits
10643 retracing earlier steps.
10645 @item tfind tracepoint @var{num}
10646 Find the next snapshot associated with tracepoint @var{num}. Search
10647 proceeds forward from the last examined trace snapshot. If no
10648 argument @var{num} is given, it means find the next snapshot collected
10649 for the same tracepoint as the current snapshot.
10651 @item tfind pc @var{addr}
10652 Find the next snapshot associated with the value @var{addr} of the
10653 program counter. Search proceeds forward from the last examined trace
10654 snapshot. If no argument @var{addr} is given, it means find the next
10655 snapshot with the same value of PC as the current snapshot.
10657 @item tfind outside @var{addr1}, @var{addr2}
10658 Find the next snapshot whose PC is outside the given range of
10659 addresses (exclusive).
10661 @item tfind range @var{addr1}, @var{addr2}
10662 Find the next snapshot whose PC is between @var{addr1} and
10663 @var{addr2} (inclusive).
10665 @item tfind line @r{[}@var{file}:@r{]}@var{n}
10666 Find the next snapshot associated with the source line @var{n}. If
10667 the optional argument @var{file} is given, refer to line @var{n} in
10668 that source file. Search proceeds forward from the last examined
10669 trace snapshot. If no argument @var{n} is given, it means find the
10670 next line other than the one currently being examined; thus saying
10671 @code{tfind line} repeatedly can appear to have the same effect as
10672 stepping from line to line in a @emph{live} debugging session.
10675 The default arguments for the @code{tfind} commands are specifically
10676 designed to make it easy to scan through the trace buffer. For
10677 instance, @code{tfind} with no argument selects the next trace
10678 snapshot, and @code{tfind -} with no argument selects the previous
10679 trace snapshot. So, by giving one @code{tfind} command, and then
10680 simply hitting @key{RET} repeatedly you can examine all the trace
10681 snapshots in order. Or, by saying @code{tfind -} and then hitting
10682 @key{RET} repeatedly you can examine the snapshots in reverse order.
10683 The @code{tfind line} command with no argument selects the snapshot
10684 for the next source line executed. The @code{tfind pc} command with
10685 no argument selects the next snapshot with the same program counter
10686 (PC) as the current frame. The @code{tfind tracepoint} command with
10687 no argument selects the next trace snapshot collected by the same
10688 tracepoint as the current one.
10690 In addition to letting you scan through the trace buffer manually,
10691 these commands make it easy to construct @value{GDBN} scripts that
10692 scan through the trace buffer and print out whatever collected data
10693 you are interested in. Thus, if we want to examine the PC, FP, and SP
10694 registers from each trace frame in the buffer, we can say this:
10697 (@value{GDBP}) @b{tfind start}
10698 (@value{GDBP}) @b{while ($trace_frame != -1)}
10699 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
10700 $trace_frame, $pc, $sp, $fp
10704 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
10705 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
10706 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
10707 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
10708 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
10709 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
10710 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
10711 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
10712 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
10713 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
10714 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
10717 Or, if we want to examine the variable @code{X} at each source line in
10721 (@value{GDBP}) @b{tfind start}
10722 (@value{GDBP}) @b{while ($trace_frame != -1)}
10723 > printf "Frame %d, X == %d\n", $trace_frame, X
10733 @subsection @code{tdump}
10735 @cindex dump all data collected at tracepoint
10736 @cindex tracepoint data, display
10738 This command takes no arguments. It prints all the data collected at
10739 the current trace snapshot.
10742 (@value{GDBP}) @b{trace 444}
10743 (@value{GDBP}) @b{actions}
10744 Enter actions for tracepoint #2, one per line:
10745 > collect $regs, $locals, $args, gdb_long_test
10748 (@value{GDBP}) @b{tstart}
10750 (@value{GDBP}) @b{tfind line 444}
10751 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
10753 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
10755 (@value{GDBP}) @b{tdump}
10756 Data collected at tracepoint 2, trace frame 1:
10757 d0 0xc4aa0085 -995491707
10761 d4 0x71aea3d 119204413
10764 d7 0x380035 3670069
10765 a0 0x19e24a 1696330
10766 a1 0x3000668 50333288
10768 a3 0x322000 3284992
10769 a4 0x3000698 50333336
10770 a5 0x1ad3cc 1758156
10771 fp 0x30bf3c 0x30bf3c
10772 sp 0x30bf34 0x30bf34
10774 pc 0x20b2c8 0x20b2c8
10778 p = 0x20e5b4 "gdb-test"
10785 gdb_long_test = 17 '\021'
10790 @code{tdump} works by scanning the tracepoint's current collection
10791 actions and printing the value of each expression listed. So
10792 @code{tdump} can fail, if after a run, you change the tracepoint's
10793 actions to mention variables that were not collected during the run.
10795 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
10796 uses the collected value of @code{$pc} to distinguish between trace
10797 frames that were collected at the tracepoint hit, and frames that were
10798 collected while stepping. This allows it to correctly choose whether
10799 to display the basic list of collections, or the collections from the
10800 body of the while-stepping loop. However, if @code{$pc} was not collected,
10801 then @code{tdump} will always attempt to dump using the basic collection
10802 list, and may fail if a while-stepping frame does not include all the
10803 same data that is collected at the tracepoint hit.
10804 @c This is getting pretty arcane, example would be good.
10806 @node save tracepoints
10807 @subsection @code{save tracepoints @var{filename}}
10808 @kindex save tracepoints
10809 @kindex save-tracepoints
10810 @cindex save tracepoints for future sessions
10812 This command saves all current tracepoint definitions together with
10813 their actions and passcounts, into a file @file{@var{filename}}
10814 suitable for use in a later debugging session. To read the saved
10815 tracepoint definitions, use the @code{source} command (@pxref{Command
10816 Files}). The @w{@code{save-tracepoints}} command is a deprecated
10817 alias for @w{@code{save tracepoints}}
10819 @node Tracepoint Variables
10820 @section Convenience Variables for Tracepoints
10821 @cindex tracepoint variables
10822 @cindex convenience variables for tracepoints
10825 @vindex $trace_frame
10826 @item (int) $trace_frame
10827 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
10828 snapshot is selected.
10830 @vindex $tracepoint
10831 @item (int) $tracepoint
10832 The tracepoint for the current trace snapshot.
10834 @vindex $trace_line
10835 @item (int) $trace_line
10836 The line number for the current trace snapshot.
10838 @vindex $trace_file
10839 @item (char []) $trace_file
10840 The source file for the current trace snapshot.
10842 @vindex $trace_func
10843 @item (char []) $trace_func
10844 The name of the function containing @code{$tracepoint}.
10847 Note: @code{$trace_file} is not suitable for use in @code{printf},
10848 use @code{output} instead.
10850 Here's a simple example of using these convenience variables for
10851 stepping through all the trace snapshots and printing some of their
10852 data. Note that these are not the same as trace state variables,
10853 which are managed by the target.
10856 (@value{GDBP}) @b{tfind start}
10858 (@value{GDBP}) @b{while $trace_frame != -1}
10859 > output $trace_file
10860 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
10866 @section Using Trace Files
10867 @cindex trace files
10869 In some situations, the target running a trace experiment may no
10870 longer be available; perhaps it crashed, or the hardware was needed
10871 for a different activity. To handle these cases, you can arrange to
10872 dump the trace data into a file, and later use that file as a source
10873 of trace data, via the @code{target tfile} command.
10878 @item tsave [ -r ] @var{filename}
10879 Save the trace data to @var{filename}. By default, this command
10880 assumes that @var{filename} refers to the host filesystem, so if
10881 necessary @value{GDBN} will copy raw trace data up from the target and
10882 then save it. If the target supports it, you can also supply the
10883 optional argument @code{-r} (``remote'') to direct the target to save
10884 the data directly into @var{filename} in its own filesystem, which may be
10885 more efficient if the trace buffer is very large. (Note, however, that
10886 @code{target tfile} can only read from files accessible to the host.)
10888 @kindex target tfile
10890 @item target tfile @var{filename}
10891 Use the file named @var{filename} as a source of trace data. Commands
10892 that examine data work as they do with a live target, but it is not
10893 possible to run any new trace experiments. @code{tstatus} will report
10894 the state of the trace run at the moment the data was saved, as well
10895 as the current trace frame you are examining. @var{filename} must be
10896 on a filesystem accessible to the host.
10901 @chapter Debugging Programs That Use Overlays
10904 If your program is too large to fit completely in your target system's
10905 memory, you can sometimes use @dfn{overlays} to work around this
10906 problem. @value{GDBN} provides some support for debugging programs that
10910 * How Overlays Work:: A general explanation of overlays.
10911 * Overlay Commands:: Managing overlays in @value{GDBN}.
10912 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
10913 mapped by asking the inferior.
10914 * Overlay Sample Program:: A sample program using overlays.
10917 @node How Overlays Work
10918 @section How Overlays Work
10919 @cindex mapped overlays
10920 @cindex unmapped overlays
10921 @cindex load address, overlay's
10922 @cindex mapped address
10923 @cindex overlay area
10925 Suppose you have a computer whose instruction address space is only 64
10926 kilobytes long, but which has much more memory which can be accessed by
10927 other means: special instructions, segment registers, or memory
10928 management hardware, for example. Suppose further that you want to
10929 adapt a program which is larger than 64 kilobytes to run on this system.
10931 One solution is to identify modules of your program which are relatively
10932 independent, and need not call each other directly; call these modules
10933 @dfn{overlays}. Separate the overlays from the main program, and place
10934 their machine code in the larger memory. Place your main program in
10935 instruction memory, but leave at least enough space there to hold the
10936 largest overlay as well.
10938 Now, to call a function located in an overlay, you must first copy that
10939 overlay's machine code from the large memory into the space set aside
10940 for it in the instruction memory, and then jump to its entry point
10943 @c NB: In the below the mapped area's size is greater or equal to the
10944 @c size of all overlays. This is intentional to remind the developer
10945 @c that overlays don't necessarily need to be the same size.
10949 Data Instruction Larger
10950 Address Space Address Space Address Space
10951 +-----------+ +-----------+ +-----------+
10953 +-----------+ +-----------+ +-----------+<-- overlay 1
10954 | program | | main | .----| overlay 1 | load address
10955 | variables | | program | | +-----------+
10956 | and heap | | | | | |
10957 +-----------+ | | | +-----------+<-- overlay 2
10958 | | +-----------+ | | | load address
10959 +-----------+ | | | .-| overlay 2 |
10961 mapped --->+-----------+ | | +-----------+
10962 address | | | | | |
10963 | overlay | <-' | | |
10964 | area | <---' +-----------+<-- overlay 3
10965 | | <---. | | load address
10966 +-----------+ `--| overlay 3 |
10973 @anchor{A code overlay}A code overlay
10977 The diagram (@pxref{A code overlay}) shows a system with separate data
10978 and instruction address spaces. To map an overlay, the program copies
10979 its code from the larger address space to the instruction address space.
10980 Since the overlays shown here all use the same mapped address, only one
10981 may be mapped at a time. For a system with a single address space for
10982 data and instructions, the diagram would be similar, except that the
10983 program variables and heap would share an address space with the main
10984 program and the overlay area.
10986 An overlay loaded into instruction memory and ready for use is called a
10987 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
10988 instruction memory. An overlay not present (or only partially present)
10989 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
10990 is its address in the larger memory. The mapped address is also called
10991 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
10992 called the @dfn{load memory address}, or @dfn{LMA}.
10994 Unfortunately, overlays are not a completely transparent way to adapt a
10995 program to limited instruction memory. They introduce a new set of
10996 global constraints you must keep in mind as you design your program:
11001 Before calling or returning to a function in an overlay, your program
11002 must make sure that overlay is actually mapped. Otherwise, the call or
11003 return will transfer control to the right address, but in the wrong
11004 overlay, and your program will probably crash.
11007 If the process of mapping an overlay is expensive on your system, you
11008 will need to choose your overlays carefully to minimize their effect on
11009 your program's performance.
11012 The executable file you load onto your system must contain each
11013 overlay's instructions, appearing at the overlay's load address, not its
11014 mapped address. However, each overlay's instructions must be relocated
11015 and its symbols defined as if the overlay were at its mapped address.
11016 You can use GNU linker scripts to specify different load and relocation
11017 addresses for pieces of your program; see @ref{Overlay Description,,,
11018 ld.info, Using ld: the GNU linker}.
11021 The procedure for loading executable files onto your system must be able
11022 to load their contents into the larger address space as well as the
11023 instruction and data spaces.
11027 The overlay system described above is rather simple, and could be
11028 improved in many ways:
11033 If your system has suitable bank switch registers or memory management
11034 hardware, you could use those facilities to make an overlay's load area
11035 contents simply appear at their mapped address in instruction space.
11036 This would probably be faster than copying the overlay to its mapped
11037 area in the usual way.
11040 If your overlays are small enough, you could set aside more than one
11041 overlay area, and have more than one overlay mapped at a time.
11044 You can use overlays to manage data, as well as instructions. In
11045 general, data overlays are even less transparent to your design than
11046 code overlays: whereas code overlays only require care when you call or
11047 return to functions, data overlays require care every time you access
11048 the data. Also, if you change the contents of a data overlay, you
11049 must copy its contents back out to its load address before you can copy a
11050 different data overlay into the same mapped area.
11055 @node Overlay Commands
11056 @section Overlay Commands
11058 To use @value{GDBN}'s overlay support, each overlay in your program must
11059 correspond to a separate section of the executable file. The section's
11060 virtual memory address and load memory address must be the overlay's
11061 mapped and load addresses. Identifying overlays with sections allows
11062 @value{GDBN} to determine the appropriate address of a function or
11063 variable, depending on whether the overlay is mapped or not.
11065 @value{GDBN}'s overlay commands all start with the word @code{overlay};
11066 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
11071 Disable @value{GDBN}'s overlay support. When overlay support is
11072 disabled, @value{GDBN} assumes that all functions and variables are
11073 always present at their mapped addresses. By default, @value{GDBN}'s
11074 overlay support is disabled.
11076 @item overlay manual
11077 @cindex manual overlay debugging
11078 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
11079 relies on you to tell it which overlays are mapped, and which are not,
11080 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
11081 commands described below.
11083 @item overlay map-overlay @var{overlay}
11084 @itemx overlay map @var{overlay}
11085 @cindex map an overlay
11086 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
11087 be the name of the object file section containing the overlay. When an
11088 overlay is mapped, @value{GDBN} assumes it can find the overlay's
11089 functions and variables at their mapped addresses. @value{GDBN} assumes
11090 that any other overlays whose mapped ranges overlap that of
11091 @var{overlay} are now unmapped.
11093 @item overlay unmap-overlay @var{overlay}
11094 @itemx overlay unmap @var{overlay}
11095 @cindex unmap an overlay
11096 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
11097 must be the name of the object file section containing the overlay.
11098 When an overlay is unmapped, @value{GDBN} assumes it can find the
11099 overlay's functions and variables at their load addresses.
11102 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
11103 consults a data structure the overlay manager maintains in the inferior
11104 to see which overlays are mapped. For details, see @ref{Automatic
11105 Overlay Debugging}.
11107 @item overlay load-target
11108 @itemx overlay load
11109 @cindex reloading the overlay table
11110 Re-read the overlay table from the inferior. Normally, @value{GDBN}
11111 re-reads the table @value{GDBN} automatically each time the inferior
11112 stops, so this command should only be necessary if you have changed the
11113 overlay mapping yourself using @value{GDBN}. This command is only
11114 useful when using automatic overlay debugging.
11116 @item overlay list-overlays
11117 @itemx overlay list
11118 @cindex listing mapped overlays
11119 Display a list of the overlays currently mapped, along with their mapped
11120 addresses, load addresses, and sizes.
11124 Normally, when @value{GDBN} prints a code address, it includes the name
11125 of the function the address falls in:
11128 (@value{GDBP}) print main
11129 $3 = @{int ()@} 0x11a0 <main>
11132 When overlay debugging is enabled, @value{GDBN} recognizes code in
11133 unmapped overlays, and prints the names of unmapped functions with
11134 asterisks around them. For example, if @code{foo} is a function in an
11135 unmapped overlay, @value{GDBN} prints it this way:
11138 (@value{GDBP}) overlay list
11139 No sections are mapped.
11140 (@value{GDBP}) print foo
11141 $5 = @{int (int)@} 0x100000 <*foo*>
11144 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
11148 (@value{GDBP}) overlay list
11149 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
11150 mapped at 0x1016 - 0x104a
11151 (@value{GDBP}) print foo
11152 $6 = @{int (int)@} 0x1016 <foo>
11155 When overlay debugging is enabled, @value{GDBN} can find the correct
11156 address for functions and variables in an overlay, whether or not the
11157 overlay is mapped. This allows most @value{GDBN} commands, like
11158 @code{break} and @code{disassemble}, to work normally, even on unmapped
11159 code. However, @value{GDBN}'s breakpoint support has some limitations:
11163 @cindex breakpoints in overlays
11164 @cindex overlays, setting breakpoints in
11165 You can set breakpoints in functions in unmapped overlays, as long as
11166 @value{GDBN} can write to the overlay at its load address.
11168 @value{GDBN} can not set hardware or simulator-based breakpoints in
11169 unmapped overlays. However, if you set a breakpoint at the end of your
11170 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
11171 you are using manual overlay management), @value{GDBN} will re-set its
11172 breakpoints properly.
11176 @node Automatic Overlay Debugging
11177 @section Automatic Overlay Debugging
11178 @cindex automatic overlay debugging
11180 @value{GDBN} can automatically track which overlays are mapped and which
11181 are not, given some simple co-operation from the overlay manager in the
11182 inferior. If you enable automatic overlay debugging with the
11183 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
11184 looks in the inferior's memory for certain variables describing the
11185 current state of the overlays.
11187 Here are the variables your overlay manager must define to support
11188 @value{GDBN}'s automatic overlay debugging:
11192 @item @code{_ovly_table}:
11193 This variable must be an array of the following structures:
11198 /* The overlay's mapped address. */
11201 /* The size of the overlay, in bytes. */
11202 unsigned long size;
11204 /* The overlay's load address. */
11207 /* Non-zero if the overlay is currently mapped;
11209 unsigned long mapped;
11213 @item @code{_novlys}:
11214 This variable must be a four-byte signed integer, holding the total
11215 number of elements in @code{_ovly_table}.
11219 To decide whether a particular overlay is mapped or not, @value{GDBN}
11220 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
11221 @code{lma} members equal the VMA and LMA of the overlay's section in the
11222 executable file. When @value{GDBN} finds a matching entry, it consults
11223 the entry's @code{mapped} member to determine whether the overlay is
11226 In addition, your overlay manager may define a function called
11227 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
11228 will silently set a breakpoint there. If the overlay manager then
11229 calls this function whenever it has changed the overlay table, this
11230 will enable @value{GDBN} to accurately keep track of which overlays
11231 are in program memory, and update any breakpoints that may be set
11232 in overlays. This will allow breakpoints to work even if the
11233 overlays are kept in ROM or other non-writable memory while they
11234 are not being executed.
11236 @node Overlay Sample Program
11237 @section Overlay Sample Program
11238 @cindex overlay example program
11240 When linking a program which uses overlays, you must place the overlays
11241 at their load addresses, while relocating them to run at their mapped
11242 addresses. To do this, you must write a linker script (@pxref{Overlay
11243 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
11244 since linker scripts are specific to a particular host system, target
11245 architecture, and target memory layout, this manual cannot provide
11246 portable sample code demonstrating @value{GDBN}'s overlay support.
11248 However, the @value{GDBN} source distribution does contain an overlaid
11249 program, with linker scripts for a few systems, as part of its test
11250 suite. The program consists of the following files from
11251 @file{gdb/testsuite/gdb.base}:
11255 The main program file.
11257 A simple overlay manager, used by @file{overlays.c}.
11262 Overlay modules, loaded and used by @file{overlays.c}.
11265 Linker scripts for linking the test program on the @code{d10v-elf}
11266 and @code{m32r-elf} targets.
11269 You can build the test program using the @code{d10v-elf} GCC
11270 cross-compiler like this:
11273 $ d10v-elf-gcc -g -c overlays.c
11274 $ d10v-elf-gcc -g -c ovlymgr.c
11275 $ d10v-elf-gcc -g -c foo.c
11276 $ d10v-elf-gcc -g -c bar.c
11277 $ d10v-elf-gcc -g -c baz.c
11278 $ d10v-elf-gcc -g -c grbx.c
11279 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
11280 baz.o grbx.o -Wl,-Td10v.ld -o overlays
11283 The build process is identical for any other architecture, except that
11284 you must substitute the appropriate compiler and linker script for the
11285 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
11289 @chapter Using @value{GDBN} with Different Languages
11292 Although programming languages generally have common aspects, they are
11293 rarely expressed in the same manner. For instance, in ANSI C,
11294 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
11295 Modula-2, it is accomplished by @code{p^}. Values can also be
11296 represented (and displayed) differently. Hex numbers in C appear as
11297 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
11299 @cindex working language
11300 Language-specific information is built into @value{GDBN} for some languages,
11301 allowing you to express operations like the above in your program's
11302 native language, and allowing @value{GDBN} to output values in a manner
11303 consistent with the syntax of your program's native language. The
11304 language you use to build expressions is called the @dfn{working
11308 * Setting:: Switching between source languages
11309 * Show:: Displaying the language
11310 * Checks:: Type and range checks
11311 * Supported Languages:: Supported languages
11312 * Unsupported Languages:: Unsupported languages
11316 @section Switching Between Source Languages
11318 There are two ways to control the working language---either have @value{GDBN}
11319 set it automatically, or select it manually yourself. You can use the
11320 @code{set language} command for either purpose. On startup, @value{GDBN}
11321 defaults to setting the language automatically. The working language is
11322 used to determine how expressions you type are interpreted, how values
11325 In addition to the working language, every source file that
11326 @value{GDBN} knows about has its own working language. For some object
11327 file formats, the compiler might indicate which language a particular
11328 source file is in. However, most of the time @value{GDBN} infers the
11329 language from the name of the file. The language of a source file
11330 controls whether C@t{++} names are demangled---this way @code{backtrace} can
11331 show each frame appropriately for its own language. There is no way to
11332 set the language of a source file from within @value{GDBN}, but you can
11333 set the language associated with a filename extension. @xref{Show, ,
11334 Displaying the Language}.
11336 This is most commonly a problem when you use a program, such
11337 as @code{cfront} or @code{f2c}, that generates C but is written in
11338 another language. In that case, make the
11339 program use @code{#line} directives in its C output; that way
11340 @value{GDBN} will know the correct language of the source code of the original
11341 program, and will display that source code, not the generated C code.
11344 * Filenames:: Filename extensions and languages.
11345 * Manually:: Setting the working language manually
11346 * Automatically:: Having @value{GDBN} infer the source language
11350 @subsection List of Filename Extensions and Languages
11352 If a source file name ends in one of the following extensions, then
11353 @value{GDBN} infers that its language is the one indicated.
11371 C@t{++} source file
11377 Objective-C source file
11381 Fortran source file
11384 Modula-2 source file
11388 Assembler source file. This actually behaves almost like C, but
11389 @value{GDBN} does not skip over function prologues when stepping.
11392 In addition, you may set the language associated with a filename
11393 extension. @xref{Show, , Displaying the Language}.
11396 @subsection Setting the Working Language
11398 If you allow @value{GDBN} to set the language automatically,
11399 expressions are interpreted the same way in your debugging session and
11402 @kindex set language
11403 If you wish, you may set the language manually. To do this, issue the
11404 command @samp{set language @var{lang}}, where @var{lang} is the name of
11405 a language, such as
11406 @code{c} or @code{modula-2}.
11407 For a list of the supported languages, type @samp{set language}.
11409 Setting the language manually prevents @value{GDBN} from updating the working
11410 language automatically. This can lead to confusion if you try
11411 to debug a program when the working language is not the same as the
11412 source language, when an expression is acceptable to both
11413 languages---but means different things. For instance, if the current
11414 source file were written in C, and @value{GDBN} was parsing Modula-2, a
11422 might not have the effect you intended. In C, this means to add
11423 @code{b} and @code{c} and place the result in @code{a}. The result
11424 printed would be the value of @code{a}. In Modula-2, this means to compare
11425 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
11427 @node Automatically
11428 @subsection Having @value{GDBN} Infer the Source Language
11430 To have @value{GDBN} set the working language automatically, use
11431 @samp{set language local} or @samp{set language auto}. @value{GDBN}
11432 then infers the working language. That is, when your program stops in a
11433 frame (usually by encountering a breakpoint), @value{GDBN} sets the
11434 working language to the language recorded for the function in that
11435 frame. If the language for a frame is unknown (that is, if the function
11436 or block corresponding to the frame was defined in a source file that
11437 does not have a recognized extension), the current working language is
11438 not changed, and @value{GDBN} issues a warning.
11440 This may not seem necessary for most programs, which are written
11441 entirely in one source language. However, program modules and libraries
11442 written in one source language can be used by a main program written in
11443 a different source language. Using @samp{set language auto} in this
11444 case frees you from having to set the working language manually.
11447 @section Displaying the Language
11449 The following commands help you find out which language is the
11450 working language, and also what language source files were written in.
11453 @item show language
11454 @kindex show language
11455 Display the current working language. This is the
11456 language you can use with commands such as @code{print} to
11457 build and compute expressions that may involve variables in your program.
11460 @kindex info frame@r{, show the source language}
11461 Display the source language for this frame. This language becomes the
11462 working language if you use an identifier from this frame.
11463 @xref{Frame Info, ,Information about a Frame}, to identify the other
11464 information listed here.
11467 @kindex info source@r{, show the source language}
11468 Display the source language of this source file.
11469 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
11470 information listed here.
11473 In unusual circumstances, you may have source files with extensions
11474 not in the standard list. You can then set the extension associated
11475 with a language explicitly:
11478 @item set extension-language @var{ext} @var{language}
11479 @kindex set extension-language
11480 Tell @value{GDBN} that source files with extension @var{ext} are to be
11481 assumed as written in the source language @var{language}.
11483 @item info extensions
11484 @kindex info extensions
11485 List all the filename extensions and the associated languages.
11489 @section Type and Range Checking
11492 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
11493 checking are included, but they do not yet have any effect. This
11494 section documents the intended facilities.
11496 @c FIXME remove warning when type/range code added
11498 Some languages are designed to guard you against making seemingly common
11499 errors through a series of compile- and run-time checks. These include
11500 checking the type of arguments to functions and operators, and making
11501 sure mathematical overflows are caught at run time. Checks such as
11502 these help to ensure a program's correctness once it has been compiled
11503 by eliminating type mismatches, and providing active checks for range
11504 errors when your program is running.
11506 @value{GDBN} can check for conditions like the above if you wish.
11507 Although @value{GDBN} does not check the statements in your program,
11508 it can check expressions entered directly into @value{GDBN} for
11509 evaluation via the @code{print} command, for example. As with the
11510 working language, @value{GDBN} can also decide whether or not to check
11511 automatically based on your program's source language.
11512 @xref{Supported Languages, ,Supported Languages}, for the default
11513 settings of supported languages.
11516 * Type Checking:: An overview of type checking
11517 * Range Checking:: An overview of range checking
11520 @cindex type checking
11521 @cindex checks, type
11522 @node Type Checking
11523 @subsection An Overview of Type Checking
11525 Some languages, such as Modula-2, are strongly typed, meaning that the
11526 arguments to operators and functions have to be of the correct type,
11527 otherwise an error occurs. These checks prevent type mismatch
11528 errors from ever causing any run-time problems. For example,
11536 The second example fails because the @code{CARDINAL} 1 is not
11537 type-compatible with the @code{REAL} 2.3.
11539 For the expressions you use in @value{GDBN} commands, you can tell the
11540 @value{GDBN} type checker to skip checking;
11541 to treat any mismatches as errors and abandon the expression;
11542 or to only issue warnings when type mismatches occur,
11543 but evaluate the expression anyway. When you choose the last of
11544 these, @value{GDBN} evaluates expressions like the second example above, but
11545 also issues a warning.
11547 Even if you turn type checking off, there may be other reasons
11548 related to type that prevent @value{GDBN} from evaluating an expression.
11549 For instance, @value{GDBN} does not know how to add an @code{int} and
11550 a @code{struct foo}. These particular type errors have nothing to do
11551 with the language in use, and usually arise from expressions, such as
11552 the one described above, which make little sense to evaluate anyway.
11554 Each language defines to what degree it is strict about type. For
11555 instance, both Modula-2 and C require the arguments to arithmetical
11556 operators to be numbers. In C, enumerated types and pointers can be
11557 represented as numbers, so that they are valid arguments to mathematical
11558 operators. @xref{Supported Languages, ,Supported Languages}, for further
11559 details on specific languages.
11561 @value{GDBN} provides some additional commands for controlling the type checker:
11563 @kindex set check type
11564 @kindex show check type
11566 @item set check type auto
11567 Set type checking on or off based on the current working language.
11568 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11571 @item set check type on
11572 @itemx set check type off
11573 Set type checking on or off, overriding the default setting for the
11574 current working language. Issue a warning if the setting does not
11575 match the language default. If any type mismatches occur in
11576 evaluating an expression while type checking is on, @value{GDBN} prints a
11577 message and aborts evaluation of the expression.
11579 @item set check type warn
11580 Cause the type checker to issue warnings, but to always attempt to
11581 evaluate the expression. Evaluating the expression may still
11582 be impossible for other reasons. For example, @value{GDBN} cannot add
11583 numbers and structures.
11586 Show the current setting of the type checker, and whether or not @value{GDBN}
11587 is setting it automatically.
11590 @cindex range checking
11591 @cindex checks, range
11592 @node Range Checking
11593 @subsection An Overview of Range Checking
11595 In some languages (such as Modula-2), it is an error to exceed the
11596 bounds of a type; this is enforced with run-time checks. Such range
11597 checking is meant to ensure program correctness by making sure
11598 computations do not overflow, or indices on an array element access do
11599 not exceed the bounds of the array.
11601 For expressions you use in @value{GDBN} commands, you can tell
11602 @value{GDBN} to treat range errors in one of three ways: ignore them,
11603 always treat them as errors and abandon the expression, or issue
11604 warnings but evaluate the expression anyway.
11606 A range error can result from numerical overflow, from exceeding an
11607 array index bound, or when you type a constant that is not a member
11608 of any type. Some languages, however, do not treat overflows as an
11609 error. In many implementations of C, mathematical overflow causes the
11610 result to ``wrap around'' to lower values---for example, if @var{m} is
11611 the largest integer value, and @var{s} is the smallest, then
11614 @var{m} + 1 @result{} @var{s}
11617 This, too, is specific to individual languages, and in some cases
11618 specific to individual compilers or machines. @xref{Supported Languages, ,
11619 Supported Languages}, for further details on specific languages.
11621 @value{GDBN} provides some additional commands for controlling the range checker:
11623 @kindex set check range
11624 @kindex show check range
11626 @item set check range auto
11627 Set range checking on or off based on the current working language.
11628 @xref{Supported Languages, ,Supported Languages}, for the default settings for
11631 @item set check range on
11632 @itemx set check range off
11633 Set range checking on or off, overriding the default setting for the
11634 current working language. A warning is issued if the setting does not
11635 match the language default. If a range error occurs and range checking is on,
11636 then a message is printed and evaluation of the expression is aborted.
11638 @item set check range warn
11639 Output messages when the @value{GDBN} range checker detects a range error,
11640 but attempt to evaluate the expression anyway. Evaluating the
11641 expression may still be impossible for other reasons, such as accessing
11642 memory that the process does not own (a typical example from many Unix
11646 Show the current setting of the range checker, and whether or not it is
11647 being set automatically by @value{GDBN}.
11650 @node Supported Languages
11651 @section Supported Languages
11653 @value{GDBN} supports C, C@t{++}, D, Objective-C, Fortran, Java, OpenCL C, Pascal,
11654 assembly, Modula-2, and Ada.
11655 @c This is false ...
11656 Some @value{GDBN} features may be used in expressions regardless of the
11657 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
11658 and the @samp{@{type@}addr} construct (@pxref{Expressions,
11659 ,Expressions}) can be used with the constructs of any supported
11662 The following sections detail to what degree each source language is
11663 supported by @value{GDBN}. These sections are not meant to be language
11664 tutorials or references, but serve only as a reference guide to what the
11665 @value{GDBN} expression parser accepts, and what input and output
11666 formats should look like for different languages. There are many good
11667 books written on each of these languages; please look to these for a
11668 language reference or tutorial.
11671 * C:: C and C@t{++}
11673 * Objective-C:: Objective-C
11674 * OpenCL C:: OpenCL C
11675 * Fortran:: Fortran
11677 * Modula-2:: Modula-2
11682 @subsection C and C@t{++}
11684 @cindex C and C@t{++}
11685 @cindex expressions in C or C@t{++}
11687 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
11688 to both languages. Whenever this is the case, we discuss those languages
11692 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
11693 @cindex @sc{gnu} C@t{++}
11694 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
11695 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
11696 effectively, you must compile your C@t{++} programs with a supported
11697 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
11698 compiler (@code{aCC}).
11700 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
11701 format; if it doesn't work on your system, try the stabs+ debugging
11702 format. You can select those formats explicitly with the @code{g++}
11703 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
11704 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
11705 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}.
11708 * C Operators:: C and C@t{++} operators
11709 * C Constants:: C and C@t{++} constants
11710 * C Plus Plus Expressions:: C@t{++} expressions
11711 * C Defaults:: Default settings for C and C@t{++}
11712 * C Checks:: C and C@t{++} type and range checks
11713 * Debugging C:: @value{GDBN} and C
11714 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
11715 * Decimal Floating Point:: Numbers in Decimal Floating Point format
11719 @subsubsection C and C@t{++} Operators
11721 @cindex C and C@t{++} operators
11723 Operators must be defined on values of specific types. For instance,
11724 @code{+} is defined on numbers, but not on structures. Operators are
11725 often defined on groups of types.
11727 For the purposes of C and C@t{++}, the following definitions hold:
11732 @emph{Integral types} include @code{int} with any of its storage-class
11733 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
11736 @emph{Floating-point types} include @code{float}, @code{double}, and
11737 @code{long double} (if supported by the target platform).
11740 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
11743 @emph{Scalar types} include all of the above.
11748 The following operators are supported. They are listed here
11749 in order of increasing precedence:
11753 The comma or sequencing operator. Expressions in a comma-separated list
11754 are evaluated from left to right, with the result of the entire
11755 expression being the last expression evaluated.
11758 Assignment. The value of an assignment expression is the value
11759 assigned. Defined on scalar types.
11762 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
11763 and translated to @w{@code{@var{a} = @var{a op b}}}.
11764 @w{@code{@var{op}=}} and @code{=} have the same precedence.
11765 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
11766 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
11769 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
11770 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
11774 Logical @sc{or}. Defined on integral types.
11777 Logical @sc{and}. Defined on integral types.
11780 Bitwise @sc{or}. Defined on integral types.
11783 Bitwise exclusive-@sc{or}. Defined on integral types.
11786 Bitwise @sc{and}. Defined on integral types.
11789 Equality and inequality. Defined on scalar types. The value of these
11790 expressions is 0 for false and non-zero for true.
11792 @item <@r{, }>@r{, }<=@r{, }>=
11793 Less than, greater than, less than or equal, greater than or equal.
11794 Defined on scalar types. The value of these expressions is 0 for false
11795 and non-zero for true.
11798 left shift, and right shift. Defined on integral types.
11801 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
11804 Addition and subtraction. Defined on integral types, floating-point types and
11807 @item *@r{, }/@r{, }%
11808 Multiplication, division, and modulus. Multiplication and division are
11809 defined on integral and floating-point types. Modulus is defined on
11813 Increment and decrement. When appearing before a variable, the
11814 operation is performed before the variable is used in an expression;
11815 when appearing after it, the variable's value is used before the
11816 operation takes place.
11819 Pointer dereferencing. Defined on pointer types. Same precedence as
11823 Address operator. Defined on variables. Same precedence as @code{++}.
11825 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
11826 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
11827 to examine the address
11828 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
11832 Negative. Defined on integral and floating-point types. Same
11833 precedence as @code{++}.
11836 Logical negation. Defined on integral types. Same precedence as
11840 Bitwise complement operator. Defined on integral types. Same precedence as
11845 Structure member, and pointer-to-structure member. For convenience,
11846 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
11847 pointer based on the stored type information.
11848 Defined on @code{struct} and @code{union} data.
11851 Dereferences of pointers to members.
11854 Array indexing. @code{@var{a}[@var{i}]} is defined as
11855 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
11858 Function parameter list. Same precedence as @code{->}.
11861 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
11862 and @code{class} types.
11865 Doubled colons also represent the @value{GDBN} scope operator
11866 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
11870 If an operator is redefined in the user code, @value{GDBN} usually
11871 attempts to invoke the redefined version instead of using the operator's
11872 predefined meaning.
11875 @subsubsection C and C@t{++} Constants
11877 @cindex C and C@t{++} constants
11879 @value{GDBN} allows you to express the constants of C and C@t{++} in the
11884 Integer constants are a sequence of digits. Octal constants are
11885 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
11886 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
11887 @samp{l}, specifying that the constant should be treated as a
11891 Floating point constants are a sequence of digits, followed by a decimal
11892 point, followed by a sequence of digits, and optionally followed by an
11893 exponent. An exponent is of the form:
11894 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
11895 sequence of digits. The @samp{+} is optional for positive exponents.
11896 A floating-point constant may also end with a letter @samp{f} or
11897 @samp{F}, specifying that the constant should be treated as being of
11898 the @code{float} (as opposed to the default @code{double}) type; or with
11899 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
11903 Enumerated constants consist of enumerated identifiers, or their
11904 integral equivalents.
11907 Character constants are a single character surrounded by single quotes
11908 (@code{'}), or a number---the ordinal value of the corresponding character
11909 (usually its @sc{ascii} value). Within quotes, the single character may
11910 be represented by a letter or by @dfn{escape sequences}, which are of
11911 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
11912 of the character's ordinal value; or of the form @samp{\@var{x}}, where
11913 @samp{@var{x}} is a predefined special character---for example,
11914 @samp{\n} for newline.
11917 String constants are a sequence of character constants surrounded by
11918 double quotes (@code{"}). Any valid character constant (as described
11919 above) may appear. Double quotes within the string must be preceded by
11920 a backslash, so for instance @samp{"a\"b'c"} is a string of five
11924 Pointer constants are an integral value. You can also write pointers
11925 to constants using the C operator @samp{&}.
11928 Array constants are comma-separated lists surrounded by braces @samp{@{}
11929 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
11930 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
11931 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
11934 @node C Plus Plus Expressions
11935 @subsubsection C@t{++} Expressions
11937 @cindex expressions in C@t{++}
11938 @value{GDBN} expression handling can interpret most C@t{++} expressions.
11940 @cindex debugging C@t{++} programs
11941 @cindex C@t{++} compilers
11942 @cindex debug formats and C@t{++}
11943 @cindex @value{NGCC} and C@t{++}
11945 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
11946 proper compiler and the proper debug format. Currently, @value{GDBN}
11947 works best when debugging C@t{++} code that is compiled with
11948 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
11949 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
11950 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
11951 stabs+ as their default debug format, so you usually don't need to
11952 specify a debug format explicitly. Other compilers and/or debug formats
11953 are likely to work badly or not at all when using @value{GDBN} to debug
11959 @cindex member functions
11961 Member function calls are allowed; you can use expressions like
11964 count = aml->GetOriginal(x, y)
11967 @vindex this@r{, inside C@t{++} member functions}
11968 @cindex namespace in C@t{++}
11970 While a member function is active (in the selected stack frame), your
11971 expressions have the same namespace available as the member function;
11972 that is, @value{GDBN} allows implicit references to the class instance
11973 pointer @code{this} following the same rules as C@t{++}.
11975 @cindex call overloaded functions
11976 @cindex overloaded functions, calling
11977 @cindex type conversions in C@t{++}
11979 You can call overloaded functions; @value{GDBN} resolves the function
11980 call to the right definition, with some restrictions. @value{GDBN} does not
11981 perform overload resolution involving user-defined type conversions,
11982 calls to constructors, or instantiations of templates that do not exist
11983 in the program. It also cannot handle ellipsis argument lists or
11986 It does perform integral conversions and promotions, floating-point
11987 promotions, arithmetic conversions, pointer conversions, conversions of
11988 class objects to base classes, and standard conversions such as those of
11989 functions or arrays to pointers; it requires an exact match on the
11990 number of function arguments.
11992 Overload resolution is always performed, unless you have specified
11993 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
11994 ,@value{GDBN} Features for C@t{++}}.
11996 You must specify @code{set overload-resolution off} in order to use an
11997 explicit function signature to call an overloaded function, as in
11999 p 'foo(char,int)'('x', 13)
12002 The @value{GDBN} command-completion facility can simplify this;
12003 see @ref{Completion, ,Command Completion}.
12005 @cindex reference declarations
12007 @value{GDBN} understands variables declared as C@t{++} references; you can use
12008 them in expressions just as you do in C@t{++} source---they are automatically
12011 In the parameter list shown when @value{GDBN} displays a frame, the values of
12012 reference variables are not displayed (unlike other variables); this
12013 avoids clutter, since references are often used for large structures.
12014 The @emph{address} of a reference variable is always shown, unless
12015 you have specified @samp{set print address off}.
12018 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
12019 expressions can use it just as expressions in your program do. Since
12020 one scope may be defined in another, you can use @code{::} repeatedly if
12021 necessary, for example in an expression like
12022 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
12023 resolving name scope by reference to source files, in both C and C@t{++}
12024 debugging (@pxref{Variables, ,Program Variables}).
12027 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
12028 calling virtual functions correctly, printing out virtual bases of
12029 objects, calling functions in a base subobject, casting objects, and
12030 invoking user-defined operators.
12033 @subsubsection C and C@t{++} Defaults
12035 @cindex C and C@t{++} defaults
12037 If you allow @value{GDBN} to set type and range checking automatically, they
12038 both default to @code{off} whenever the working language changes to
12039 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
12040 selects the working language.
12042 If you allow @value{GDBN} to set the language automatically, it
12043 recognizes source files whose names end with @file{.c}, @file{.C}, or
12044 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
12045 these files, it sets the working language to C or C@t{++}.
12046 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
12047 for further details.
12049 @c Type checking is (a) primarily motivated by Modula-2, and (b)
12050 @c unimplemented. If (b) changes, it might make sense to let this node
12051 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
12054 @subsubsection C and C@t{++} Type and Range Checks
12056 @cindex C and C@t{++} checks
12058 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
12059 is not used. However, if you turn type checking on, @value{GDBN}
12060 considers two variables type equivalent if:
12064 The two variables are structured and have the same structure, union, or
12068 The two variables have the same type name, or types that have been
12069 declared equivalent through @code{typedef}.
12072 @c leaving this out because neither J Gilmore nor R Pesch understand it.
12075 The two @code{struct}, @code{union}, or @code{enum} variables are
12076 declared in the same declaration. (Note: this may not be true for all C
12081 Range checking, if turned on, is done on mathematical operations. Array
12082 indices are not checked, since they are often used to index a pointer
12083 that is not itself an array.
12086 @subsubsection @value{GDBN} and C
12088 The @code{set print union} and @code{show print union} commands apply to
12089 the @code{union} type. When set to @samp{on}, any @code{union} that is
12090 inside a @code{struct} or @code{class} is also printed. Otherwise, it
12091 appears as @samp{@{...@}}.
12093 The @code{@@} operator aids in the debugging of dynamic arrays, formed
12094 with pointers and a memory allocation function. @xref{Expressions,
12097 @node Debugging C Plus Plus
12098 @subsubsection @value{GDBN} Features for C@t{++}
12100 @cindex commands for C@t{++}
12102 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
12103 designed specifically for use with C@t{++}. Here is a summary:
12106 @cindex break in overloaded functions
12107 @item @r{breakpoint menus}
12108 When you want a breakpoint in a function whose name is overloaded,
12109 @value{GDBN} has the capability to display a menu of possible breakpoint
12110 locations to help you specify which function definition you want.
12111 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
12113 @cindex overloading in C@t{++}
12114 @item rbreak @var{regex}
12115 Setting breakpoints using regular expressions is helpful for setting
12116 breakpoints on overloaded functions that are not members of any special
12118 @xref{Set Breaks, ,Setting Breakpoints}.
12120 @cindex C@t{++} exception handling
12123 Debug C@t{++} exception handling using these commands. @xref{Set
12124 Catchpoints, , Setting Catchpoints}.
12126 @cindex inheritance
12127 @item ptype @var{typename}
12128 Print inheritance relationships as well as other information for type
12130 @xref{Symbols, ,Examining the Symbol Table}.
12132 @cindex C@t{++} symbol display
12133 @item set print demangle
12134 @itemx show print demangle
12135 @itemx set print asm-demangle
12136 @itemx show print asm-demangle
12137 Control whether C@t{++} symbols display in their source form, both when
12138 displaying code as C@t{++} source and when displaying disassemblies.
12139 @xref{Print Settings, ,Print Settings}.
12141 @item set print object
12142 @itemx show print object
12143 Choose whether to print derived (actual) or declared types of objects.
12144 @xref{Print Settings, ,Print Settings}.
12146 @item set print vtbl
12147 @itemx show print vtbl
12148 Control the format for printing virtual function tables.
12149 @xref{Print Settings, ,Print Settings}.
12150 (The @code{vtbl} commands do not work on programs compiled with the HP
12151 ANSI C@t{++} compiler (@code{aCC}).)
12153 @kindex set overload-resolution
12154 @cindex overloaded functions, overload resolution
12155 @item set overload-resolution on
12156 Enable overload resolution for C@t{++} expression evaluation. The default
12157 is on. For overloaded functions, @value{GDBN} evaluates the arguments
12158 and searches for a function whose signature matches the argument types,
12159 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
12160 Expressions, ,C@t{++} Expressions}, for details).
12161 If it cannot find a match, it emits a message.
12163 @item set overload-resolution off
12164 Disable overload resolution for C@t{++} expression evaluation. For
12165 overloaded functions that are not class member functions, @value{GDBN}
12166 chooses the first function of the specified name that it finds in the
12167 symbol table, whether or not its arguments are of the correct type. For
12168 overloaded functions that are class member functions, @value{GDBN}
12169 searches for a function whose signature @emph{exactly} matches the
12172 @kindex show overload-resolution
12173 @item show overload-resolution
12174 Show the current setting of overload resolution.
12176 @item @r{Overloaded symbol names}
12177 You can specify a particular definition of an overloaded symbol, using
12178 the same notation that is used to declare such symbols in C@t{++}: type
12179 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
12180 also use the @value{GDBN} command-line word completion facilities to list the
12181 available choices, or to finish the type list for you.
12182 @xref{Completion,, Command Completion}, for details on how to do this.
12185 @node Decimal Floating Point
12186 @subsubsection Decimal Floating Point format
12187 @cindex decimal floating point format
12189 @value{GDBN} can examine, set and perform computations with numbers in
12190 decimal floating point format, which in the C language correspond to the
12191 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
12192 specified by the extension to support decimal floating-point arithmetic.
12194 There are two encodings in use, depending on the architecture: BID (Binary
12195 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
12196 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
12199 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
12200 to manipulate decimal floating point numbers, it is not possible to convert
12201 (using a cast, for example) integers wider than 32-bit to decimal float.
12203 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
12204 point computations, error checking in decimal float operations ignores
12205 underflow, overflow and divide by zero exceptions.
12207 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
12208 to inspect @code{_Decimal128} values stored in floating point registers.
12209 See @ref{PowerPC,,PowerPC} for more details.
12215 @value{GDBN} can be used to debug programs written in D and compiled with
12216 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
12217 specific feature --- dynamic arrays.
12220 @subsection Objective-C
12222 @cindex Objective-C
12223 This section provides information about some commands and command
12224 options that are useful for debugging Objective-C code. See also
12225 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
12226 few more commands specific to Objective-C support.
12229 * Method Names in Commands::
12230 * The Print Command with Objective-C::
12233 @node Method Names in Commands
12234 @subsubsection Method Names in Commands
12236 The following commands have been extended to accept Objective-C method
12237 names as line specifications:
12239 @kindex clear@r{, and Objective-C}
12240 @kindex break@r{, and Objective-C}
12241 @kindex info line@r{, and Objective-C}
12242 @kindex jump@r{, and Objective-C}
12243 @kindex list@r{, and Objective-C}
12247 @item @code{info line}
12252 A fully qualified Objective-C method name is specified as
12255 -[@var{Class} @var{methodName}]
12258 where the minus sign is used to indicate an instance method and a
12259 plus sign (not shown) is used to indicate a class method. The class
12260 name @var{Class} and method name @var{methodName} are enclosed in
12261 brackets, similar to the way messages are specified in Objective-C
12262 source code. For example, to set a breakpoint at the @code{create}
12263 instance method of class @code{Fruit} in the program currently being
12267 break -[Fruit create]
12270 To list ten program lines around the @code{initialize} class method,
12274 list +[NSText initialize]
12277 In the current version of @value{GDBN}, the plus or minus sign is
12278 required. In future versions of @value{GDBN}, the plus or minus
12279 sign will be optional, but you can use it to narrow the search. It
12280 is also possible to specify just a method name:
12286 You must specify the complete method name, including any colons. If
12287 your program's source files contain more than one @code{create} method,
12288 you'll be presented with a numbered list of classes that implement that
12289 method. Indicate your choice by number, or type @samp{0} to exit if
12292 As another example, to clear a breakpoint established at the
12293 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
12296 clear -[NSWindow makeKeyAndOrderFront:]
12299 @node The Print Command with Objective-C
12300 @subsubsection The Print Command With Objective-C
12301 @cindex Objective-C, print objects
12302 @kindex print-object
12303 @kindex po @r{(@code{print-object})}
12305 The print command has also been extended to accept methods. For example:
12308 print -[@var{object} hash]
12311 @cindex print an Objective-C object description
12312 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
12314 will tell @value{GDBN} to send the @code{hash} message to @var{object}
12315 and print the result. Also, an additional command has been added,
12316 @code{print-object} or @code{po} for short, which is meant to print
12317 the description of an object. However, this command may only work
12318 with certain Objective-C libraries that have a particular hook
12319 function, @code{_NSPrintForDebugger}, defined.
12322 @subsection OpenCL C
12325 This section provides information about @value{GDBN}s OpenCL C support.
12328 * OpenCL C Datatypes::
12329 * OpenCL C Expressions::
12330 * OpenCL C Operators::
12333 @node OpenCL C Datatypes
12334 @subsubsection OpenCL C Datatypes
12336 @cindex OpenCL C Datatypes
12337 @value{GDBN} supports the builtin scalar and vector datatypes specified
12338 by OpenCL 1.1. In addition the half- and double-precision floating point
12339 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
12340 extensions are also known to @value{GDBN}.
12342 @node OpenCL C Expressions
12343 @subsubsection OpenCL C Expressions
12345 @cindex OpenCL C Expressions
12346 @value{GDBN} supports accesses to vector components including the access as
12347 lvalue where possible. Since OpenCL C is based on C99 most C expressions
12348 supported by @value{GDBN} can be used as well.
12350 @node OpenCL C Operators
12351 @subsubsection OpenCL C Operators
12353 @cindex OpenCL C Operators
12354 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
12358 @subsection Fortran
12359 @cindex Fortran-specific support in @value{GDBN}
12361 @value{GDBN} can be used to debug programs written in Fortran, but it
12362 currently supports only the features of Fortran 77 language.
12364 @cindex trailing underscore, in Fortran symbols
12365 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
12366 among them) append an underscore to the names of variables and
12367 functions. When you debug programs compiled by those compilers, you
12368 will need to refer to variables and functions with a trailing
12372 * Fortran Operators:: Fortran operators and expressions
12373 * Fortran Defaults:: Default settings for Fortran
12374 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
12377 @node Fortran Operators
12378 @subsubsection Fortran Operators and Expressions
12380 @cindex Fortran operators and expressions
12382 Operators must be defined on values of specific types. For instance,
12383 @code{+} is defined on numbers, but not on characters or other non-
12384 arithmetic types. Operators are often defined on groups of types.
12388 The exponentiation operator. It raises the first operand to the power
12392 The range operator. Normally used in the form of array(low:high) to
12393 represent a section of array.
12396 The access component operator. Normally used to access elements in derived
12397 types. Also suitable for unions. As unions aren't part of regular Fortran,
12398 this can only happen when accessing a register that uses a gdbarch-defined
12402 @node Fortran Defaults
12403 @subsubsection Fortran Defaults
12405 @cindex Fortran Defaults
12407 Fortran symbols are usually case-insensitive, so @value{GDBN} by
12408 default uses case-insensitive matches for Fortran symbols. You can
12409 change that with the @samp{set case-insensitive} command, see
12410 @ref{Symbols}, for the details.
12412 @node Special Fortran Commands
12413 @subsubsection Special Fortran Commands
12415 @cindex Special Fortran commands
12417 @value{GDBN} has some commands to support Fortran-specific features,
12418 such as displaying common blocks.
12421 @cindex @code{COMMON} blocks, Fortran
12422 @kindex info common
12423 @item info common @r{[}@var{common-name}@r{]}
12424 This command prints the values contained in the Fortran @code{COMMON}
12425 block whose name is @var{common-name}. With no argument, the names of
12426 all @code{COMMON} blocks visible at the current program location are
12433 @cindex Pascal support in @value{GDBN}, limitations
12434 Debugging Pascal programs which use sets, subranges, file variables, or
12435 nested functions does not currently work. @value{GDBN} does not support
12436 entering expressions, printing values, or similar features using Pascal
12439 The Pascal-specific command @code{set print pascal_static-members}
12440 controls whether static members of Pascal objects are displayed.
12441 @xref{Print Settings, pascal_static-members}.
12444 @subsection Modula-2
12446 @cindex Modula-2, @value{GDBN} support
12448 The extensions made to @value{GDBN} to support Modula-2 only support
12449 output from the @sc{gnu} Modula-2 compiler (which is currently being
12450 developed). Other Modula-2 compilers are not currently supported, and
12451 attempting to debug executables produced by them is most likely
12452 to give an error as @value{GDBN} reads in the executable's symbol
12455 @cindex expressions in Modula-2
12457 * M2 Operators:: Built-in operators
12458 * Built-In Func/Proc:: Built-in functions and procedures
12459 * M2 Constants:: Modula-2 constants
12460 * M2 Types:: Modula-2 types
12461 * M2 Defaults:: Default settings for Modula-2
12462 * Deviations:: Deviations from standard Modula-2
12463 * M2 Checks:: Modula-2 type and range checks
12464 * M2 Scope:: The scope operators @code{::} and @code{.}
12465 * GDB/M2:: @value{GDBN} and Modula-2
12469 @subsubsection Operators
12470 @cindex Modula-2 operators
12472 Operators must be defined on values of specific types. For instance,
12473 @code{+} is defined on numbers, but not on structures. Operators are
12474 often defined on groups of types. For the purposes of Modula-2, the
12475 following definitions hold:
12480 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
12484 @emph{Character types} consist of @code{CHAR} and its subranges.
12487 @emph{Floating-point types} consist of @code{REAL}.
12490 @emph{Pointer types} consist of anything declared as @code{POINTER TO
12494 @emph{Scalar types} consist of all of the above.
12497 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
12500 @emph{Boolean types} consist of @code{BOOLEAN}.
12504 The following operators are supported, and appear in order of
12505 increasing precedence:
12509 Function argument or array index separator.
12512 Assignment. The value of @var{var} @code{:=} @var{value} is
12516 Less than, greater than on integral, floating-point, or enumerated
12520 Less than or equal to, greater than or equal to
12521 on integral, floating-point and enumerated types, or set inclusion on
12522 set types. Same precedence as @code{<}.
12524 @item =@r{, }<>@r{, }#
12525 Equality and two ways of expressing inequality, valid on scalar types.
12526 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
12527 available for inequality, since @code{#} conflicts with the script
12531 Set membership. Defined on set types and the types of their members.
12532 Same precedence as @code{<}.
12535 Boolean disjunction. Defined on boolean types.
12538 Boolean conjunction. Defined on boolean types.
12541 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
12544 Addition and subtraction on integral and floating-point types, or union
12545 and difference on set types.
12548 Multiplication on integral and floating-point types, or set intersection
12552 Division on floating-point types, or symmetric set difference on set
12553 types. Same precedence as @code{*}.
12556 Integer division and remainder. Defined on integral types. Same
12557 precedence as @code{*}.
12560 Negative. Defined on @code{INTEGER} and @code{REAL} data.
12563 Pointer dereferencing. Defined on pointer types.
12566 Boolean negation. Defined on boolean types. Same precedence as
12570 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
12571 precedence as @code{^}.
12574 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
12577 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
12581 @value{GDBN} and Modula-2 scope operators.
12585 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
12586 treats the use of the operator @code{IN}, or the use of operators
12587 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
12588 @code{<=}, and @code{>=} on sets as an error.
12592 @node Built-In Func/Proc
12593 @subsubsection Built-in Functions and Procedures
12594 @cindex Modula-2 built-ins
12596 Modula-2 also makes available several built-in procedures and functions.
12597 In describing these, the following metavariables are used:
12602 represents an @code{ARRAY} variable.
12605 represents a @code{CHAR} constant or variable.
12608 represents a variable or constant of integral type.
12611 represents an identifier that belongs to a set. Generally used in the
12612 same function with the metavariable @var{s}. The type of @var{s} should
12613 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
12616 represents a variable or constant of integral or floating-point type.
12619 represents a variable or constant of floating-point type.
12625 represents a variable.
12628 represents a variable or constant of one of many types. See the
12629 explanation of the function for details.
12632 All Modula-2 built-in procedures also return a result, described below.
12636 Returns the absolute value of @var{n}.
12639 If @var{c} is a lower case letter, it returns its upper case
12640 equivalent, otherwise it returns its argument.
12643 Returns the character whose ordinal value is @var{i}.
12646 Decrements the value in the variable @var{v} by one. Returns the new value.
12648 @item DEC(@var{v},@var{i})
12649 Decrements the value in the variable @var{v} by @var{i}. Returns the
12652 @item EXCL(@var{m},@var{s})
12653 Removes the element @var{m} from the set @var{s}. Returns the new
12656 @item FLOAT(@var{i})
12657 Returns the floating point equivalent of the integer @var{i}.
12659 @item HIGH(@var{a})
12660 Returns the index of the last member of @var{a}.
12663 Increments the value in the variable @var{v} by one. Returns the new value.
12665 @item INC(@var{v},@var{i})
12666 Increments the value in the variable @var{v} by @var{i}. Returns the
12669 @item INCL(@var{m},@var{s})
12670 Adds the element @var{m} to the set @var{s} if it is not already
12671 there. Returns the new set.
12674 Returns the maximum value of the type @var{t}.
12677 Returns the minimum value of the type @var{t}.
12680 Returns boolean TRUE if @var{i} is an odd number.
12683 Returns the ordinal value of its argument. For example, the ordinal
12684 value of a character is its @sc{ascii} value (on machines supporting the
12685 @sc{ascii} character set). @var{x} must be of an ordered type, which include
12686 integral, character and enumerated types.
12688 @item SIZE(@var{x})
12689 Returns the size of its argument. @var{x} can be a variable or a type.
12691 @item TRUNC(@var{r})
12692 Returns the integral part of @var{r}.
12694 @item TSIZE(@var{x})
12695 Returns the size of its argument. @var{x} can be a variable or a type.
12697 @item VAL(@var{t},@var{i})
12698 Returns the member of the type @var{t} whose ordinal value is @var{i}.
12702 @emph{Warning:} Sets and their operations are not yet supported, so
12703 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
12707 @cindex Modula-2 constants
12709 @subsubsection Constants
12711 @value{GDBN} allows you to express the constants of Modula-2 in the following
12717 Integer constants are simply a sequence of digits. When used in an
12718 expression, a constant is interpreted to be type-compatible with the
12719 rest of the expression. Hexadecimal integers are specified by a
12720 trailing @samp{H}, and octal integers by a trailing @samp{B}.
12723 Floating point constants appear as a sequence of digits, followed by a
12724 decimal point and another sequence of digits. An optional exponent can
12725 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
12726 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
12727 digits of the floating point constant must be valid decimal (base 10)
12731 Character constants consist of a single character enclosed by a pair of
12732 like quotes, either single (@code{'}) or double (@code{"}). They may
12733 also be expressed by their ordinal value (their @sc{ascii} value, usually)
12734 followed by a @samp{C}.
12737 String constants consist of a sequence of characters enclosed by a
12738 pair of like quotes, either single (@code{'}) or double (@code{"}).
12739 Escape sequences in the style of C are also allowed. @xref{C
12740 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
12744 Enumerated constants consist of an enumerated identifier.
12747 Boolean constants consist of the identifiers @code{TRUE} and
12751 Pointer constants consist of integral values only.
12754 Set constants are not yet supported.
12758 @subsubsection Modula-2 Types
12759 @cindex Modula-2 types
12761 Currently @value{GDBN} can print the following data types in Modula-2
12762 syntax: array types, record types, set types, pointer types, procedure
12763 types, enumerated types, subrange types and base types. You can also
12764 print the contents of variables declared using these type.
12765 This section gives a number of simple source code examples together with
12766 sample @value{GDBN} sessions.
12768 The first example contains the following section of code:
12777 and you can request @value{GDBN} to interrogate the type and value of
12778 @code{r} and @code{s}.
12781 (@value{GDBP}) print s
12783 (@value{GDBP}) ptype s
12785 (@value{GDBP}) print r
12787 (@value{GDBP}) ptype r
12792 Likewise if your source code declares @code{s} as:
12796 s: SET ['A'..'Z'] ;
12800 then you may query the type of @code{s} by:
12803 (@value{GDBP}) ptype s
12804 type = SET ['A'..'Z']
12808 Note that at present you cannot interactively manipulate set
12809 expressions using the debugger.
12811 The following example shows how you might declare an array in Modula-2
12812 and how you can interact with @value{GDBN} to print its type and contents:
12816 s: ARRAY [-10..10] OF CHAR ;
12820 (@value{GDBP}) ptype s
12821 ARRAY [-10..10] OF CHAR
12824 Note that the array handling is not yet complete and although the type
12825 is printed correctly, expression handling still assumes that all
12826 arrays have a lower bound of zero and not @code{-10} as in the example
12829 Here are some more type related Modula-2 examples:
12833 colour = (blue, red, yellow, green) ;
12834 t = [blue..yellow] ;
12842 The @value{GDBN} interaction shows how you can query the data type
12843 and value of a variable.
12846 (@value{GDBP}) print s
12848 (@value{GDBP}) ptype t
12849 type = [blue..yellow]
12853 In this example a Modula-2 array is declared and its contents
12854 displayed. Observe that the contents are written in the same way as
12855 their @code{C} counterparts.
12859 s: ARRAY [1..5] OF CARDINAL ;
12865 (@value{GDBP}) print s
12866 $1 = @{1, 0, 0, 0, 0@}
12867 (@value{GDBP}) ptype s
12868 type = ARRAY [1..5] OF CARDINAL
12871 The Modula-2 language interface to @value{GDBN} also understands
12872 pointer types as shown in this example:
12876 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
12883 and you can request that @value{GDBN} describes the type of @code{s}.
12886 (@value{GDBP}) ptype s
12887 type = POINTER TO ARRAY [1..5] OF CARDINAL
12890 @value{GDBN} handles compound types as we can see in this example.
12891 Here we combine array types, record types, pointer types and subrange
12902 myarray = ARRAY myrange OF CARDINAL ;
12903 myrange = [-2..2] ;
12905 s: POINTER TO ARRAY myrange OF foo ;
12909 and you can ask @value{GDBN} to describe the type of @code{s} as shown
12913 (@value{GDBP}) ptype s
12914 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
12917 f3 : ARRAY [-2..2] OF CARDINAL;
12922 @subsubsection Modula-2 Defaults
12923 @cindex Modula-2 defaults
12925 If type and range checking are set automatically by @value{GDBN}, they
12926 both default to @code{on} whenever the working language changes to
12927 Modula-2. This happens regardless of whether you or @value{GDBN}
12928 selected the working language.
12930 If you allow @value{GDBN} to set the language automatically, then entering
12931 code compiled from a file whose name ends with @file{.mod} sets the
12932 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
12933 Infer the Source Language}, for further details.
12936 @subsubsection Deviations from Standard Modula-2
12937 @cindex Modula-2, deviations from
12939 A few changes have been made to make Modula-2 programs easier to debug.
12940 This is done primarily via loosening its type strictness:
12944 Unlike in standard Modula-2, pointer constants can be formed by
12945 integers. This allows you to modify pointer variables during
12946 debugging. (In standard Modula-2, the actual address contained in a
12947 pointer variable is hidden from you; it can only be modified
12948 through direct assignment to another pointer variable or expression that
12949 returned a pointer.)
12952 C escape sequences can be used in strings and characters to represent
12953 non-printable characters. @value{GDBN} prints out strings with these
12954 escape sequences embedded. Single non-printable characters are
12955 printed using the @samp{CHR(@var{nnn})} format.
12958 The assignment operator (@code{:=}) returns the value of its right-hand
12962 All built-in procedures both modify @emph{and} return their argument.
12966 @subsubsection Modula-2 Type and Range Checks
12967 @cindex Modula-2 checks
12970 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
12973 @c FIXME remove warning when type/range checks added
12975 @value{GDBN} considers two Modula-2 variables type equivalent if:
12979 They are of types that have been declared equivalent via a @code{TYPE
12980 @var{t1} = @var{t2}} statement
12983 They have been declared on the same line. (Note: This is true of the
12984 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
12987 As long as type checking is enabled, any attempt to combine variables
12988 whose types are not equivalent is an error.
12990 Range checking is done on all mathematical operations, assignment, array
12991 index bounds, and all built-in functions and procedures.
12994 @subsubsection The Scope Operators @code{::} and @code{.}
12996 @cindex @code{.}, Modula-2 scope operator
12997 @cindex colon, doubled as scope operator
12999 @vindex colon-colon@r{, in Modula-2}
13000 @c Info cannot handle :: but TeX can.
13003 @vindex ::@r{, in Modula-2}
13006 There are a few subtle differences between the Modula-2 scope operator
13007 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
13012 @var{module} . @var{id}
13013 @var{scope} :: @var{id}
13017 where @var{scope} is the name of a module or a procedure,
13018 @var{module} the name of a module, and @var{id} is any declared
13019 identifier within your program, except another module.
13021 Using the @code{::} operator makes @value{GDBN} search the scope
13022 specified by @var{scope} for the identifier @var{id}. If it is not
13023 found in the specified scope, then @value{GDBN} searches all scopes
13024 enclosing the one specified by @var{scope}.
13026 Using the @code{.} operator makes @value{GDBN} search the current scope for
13027 the identifier specified by @var{id} that was imported from the
13028 definition module specified by @var{module}. With this operator, it is
13029 an error if the identifier @var{id} was not imported from definition
13030 module @var{module}, or if @var{id} is not an identifier in
13034 @subsubsection @value{GDBN} and Modula-2
13036 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
13037 Five subcommands of @code{set print} and @code{show print} apply
13038 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
13039 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
13040 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
13041 analogue in Modula-2.
13043 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
13044 with any language, is not useful with Modula-2. Its
13045 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
13046 created in Modula-2 as they can in C or C@t{++}. However, because an
13047 address can be specified by an integral constant, the construct
13048 @samp{@{@var{type}@}@var{adrexp}} is still useful.
13050 @cindex @code{#} in Modula-2
13051 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
13052 interpreted as the beginning of a comment. Use @code{<>} instead.
13058 The extensions made to @value{GDBN} for Ada only support
13059 output from the @sc{gnu} Ada (GNAT) compiler.
13060 Other Ada compilers are not currently supported, and
13061 attempting to debug executables produced by them is most likely
13065 @cindex expressions in Ada
13067 * Ada Mode Intro:: General remarks on the Ada syntax
13068 and semantics supported by Ada mode
13070 * Omissions from Ada:: Restrictions on the Ada expression syntax.
13071 * Additions to Ada:: Extensions of the Ada expression syntax.
13072 * Stopping Before Main Program:: Debugging the program during elaboration.
13073 * Ada Tasks:: Listing and setting breakpoints in tasks.
13074 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
13075 * Ravenscar Profile:: Tasking Support when using the Ravenscar
13077 * Ada Glitches:: Known peculiarities of Ada mode.
13080 @node Ada Mode Intro
13081 @subsubsection Introduction
13082 @cindex Ada mode, general
13084 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
13085 syntax, with some extensions.
13086 The philosophy behind the design of this subset is
13090 That @value{GDBN} should provide basic literals and access to operations for
13091 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
13092 leaving more sophisticated computations to subprograms written into the
13093 program (which therefore may be called from @value{GDBN}).
13096 That type safety and strict adherence to Ada language restrictions
13097 are not particularly important to the @value{GDBN} user.
13100 That brevity is important to the @value{GDBN} user.
13103 Thus, for brevity, the debugger acts as if all names declared in
13104 user-written packages are directly visible, even if they are not visible
13105 according to Ada rules, thus making it unnecessary to fully qualify most
13106 names with their packages, regardless of context. Where this causes
13107 ambiguity, @value{GDBN} asks the user's intent.
13109 The debugger will start in Ada mode if it detects an Ada main program.
13110 As for other languages, it will enter Ada mode when stopped in a program that
13111 was translated from an Ada source file.
13113 While in Ada mode, you may use `@t{--}' for comments. This is useful
13114 mostly for documenting command files. The standard @value{GDBN} comment
13115 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
13116 middle (to allow based literals).
13118 The debugger supports limited overloading. Given a subprogram call in which
13119 the function symbol has multiple definitions, it will use the number of
13120 actual parameters and some information about their types to attempt to narrow
13121 the set of definitions. It also makes very limited use of context, preferring
13122 procedures to functions in the context of the @code{call} command, and
13123 functions to procedures elsewhere.
13125 @node Omissions from Ada
13126 @subsubsection Omissions from Ada
13127 @cindex Ada, omissions from
13129 Here are the notable omissions from the subset:
13133 Only a subset of the attributes are supported:
13137 @t{'First}, @t{'Last}, and @t{'Length}
13138 on array objects (not on types and subtypes).
13141 @t{'Min} and @t{'Max}.
13144 @t{'Pos} and @t{'Val}.
13150 @t{'Range} on array objects (not subtypes), but only as the right
13151 operand of the membership (@code{in}) operator.
13154 @t{'Access}, @t{'Unchecked_Access}, and
13155 @t{'Unrestricted_Access} (a GNAT extension).
13163 @code{Characters.Latin_1} are not available and
13164 concatenation is not implemented. Thus, escape characters in strings are
13165 not currently available.
13168 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
13169 equality of representations. They will generally work correctly
13170 for strings and arrays whose elements have integer or enumeration types.
13171 They may not work correctly for arrays whose element
13172 types have user-defined equality, for arrays of real values
13173 (in particular, IEEE-conformant floating point, because of negative
13174 zeroes and NaNs), and for arrays whose elements contain unused bits with
13175 indeterminate values.
13178 The other component-by-component array operations (@code{and}, @code{or},
13179 @code{xor}, @code{not}, and relational tests other than equality)
13180 are not implemented.
13183 @cindex array aggregates (Ada)
13184 @cindex record aggregates (Ada)
13185 @cindex aggregates (Ada)
13186 There is limited support for array and record aggregates. They are
13187 permitted only on the right sides of assignments, as in these examples:
13190 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
13191 (@value{GDBP}) set An_Array := (1, others => 0)
13192 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
13193 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
13194 (@value{GDBP}) set A_Record := (1, "Peter", True);
13195 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
13199 discriminant's value by assigning an aggregate has an
13200 undefined effect if that discriminant is used within the record.
13201 However, you can first modify discriminants by directly assigning to
13202 them (which normally would not be allowed in Ada), and then performing an
13203 aggregate assignment. For example, given a variable @code{A_Rec}
13204 declared to have a type such as:
13207 type Rec (Len : Small_Integer := 0) is record
13209 Vals : IntArray (1 .. Len);
13213 you can assign a value with a different size of @code{Vals} with two
13217 (@value{GDBP}) set A_Rec.Len := 4
13218 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
13221 As this example also illustrates, @value{GDBN} is very loose about the usual
13222 rules concerning aggregates. You may leave out some of the
13223 components of an array or record aggregate (such as the @code{Len}
13224 component in the assignment to @code{A_Rec} above); they will retain their
13225 original values upon assignment. You may freely use dynamic values as
13226 indices in component associations. You may even use overlapping or
13227 redundant component associations, although which component values are
13228 assigned in such cases is not defined.
13231 Calls to dispatching subprograms are not implemented.
13234 The overloading algorithm is much more limited (i.e., less selective)
13235 than that of real Ada. It makes only limited use of the context in
13236 which a subexpression appears to resolve its meaning, and it is much
13237 looser in its rules for allowing type matches. As a result, some
13238 function calls will be ambiguous, and the user will be asked to choose
13239 the proper resolution.
13242 The @code{new} operator is not implemented.
13245 Entry calls are not implemented.
13248 Aside from printing, arithmetic operations on the native VAX floating-point
13249 formats are not supported.
13252 It is not possible to slice a packed array.
13255 The names @code{True} and @code{False}, when not part of a qualified name,
13256 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
13258 Should your program
13259 redefine these names in a package or procedure (at best a dubious practice),
13260 you will have to use fully qualified names to access their new definitions.
13263 @node Additions to Ada
13264 @subsubsection Additions to Ada
13265 @cindex Ada, deviations from
13267 As it does for other languages, @value{GDBN} makes certain generic
13268 extensions to Ada (@pxref{Expressions}):
13272 If the expression @var{E} is a variable residing in memory (typically
13273 a local variable or array element) and @var{N} is a positive integer,
13274 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
13275 @var{N}-1 adjacent variables following it in memory as an array. In
13276 Ada, this operator is generally not necessary, since its prime use is
13277 in displaying parts of an array, and slicing will usually do this in
13278 Ada. However, there are occasional uses when debugging programs in
13279 which certain debugging information has been optimized away.
13282 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
13283 appears in function or file @var{B}.'' When @var{B} is a file name,
13284 you must typically surround it in single quotes.
13287 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
13288 @var{type} that appears at address @var{addr}.''
13291 A name starting with @samp{$} is a convenience variable
13292 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
13295 In addition, @value{GDBN} provides a few other shortcuts and outright
13296 additions specific to Ada:
13300 The assignment statement is allowed as an expression, returning
13301 its right-hand operand as its value. Thus, you may enter
13304 (@value{GDBP}) set x := y + 3
13305 (@value{GDBP}) print A(tmp := y + 1)
13309 The semicolon is allowed as an ``operator,'' returning as its value
13310 the value of its right-hand operand.
13311 This allows, for example,
13312 complex conditional breaks:
13315 (@value{GDBP}) break f
13316 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
13320 Rather than use catenation and symbolic character names to introduce special
13321 characters into strings, one may instead use a special bracket notation,
13322 which is also used to print strings. A sequence of characters of the form
13323 @samp{["@var{XX}"]} within a string or character literal denotes the
13324 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
13325 sequence of characters @samp{["""]} also denotes a single quotation mark
13326 in strings. For example,
13328 "One line.["0a"]Next line.["0a"]"
13331 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
13335 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
13336 @t{'Max} is optional (and is ignored in any case). For example, it is valid
13340 (@value{GDBP}) print 'max(x, y)
13344 When printing arrays, @value{GDBN} uses positional notation when the
13345 array has a lower bound of 1, and uses a modified named notation otherwise.
13346 For example, a one-dimensional array of three integers with a lower bound
13347 of 3 might print as
13354 That is, in contrast to valid Ada, only the first component has a @code{=>}
13358 You may abbreviate attributes in expressions with any unique,
13359 multi-character subsequence of
13360 their names (an exact match gets preference).
13361 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
13362 in place of @t{a'length}.
13365 @cindex quoting Ada internal identifiers
13366 Since Ada is case-insensitive, the debugger normally maps identifiers you type
13367 to lower case. The GNAT compiler uses upper-case characters for
13368 some of its internal identifiers, which are normally of no interest to users.
13369 For the rare occasions when you actually have to look at them,
13370 enclose them in angle brackets to avoid the lower-case mapping.
13373 (@value{GDBP}) print <JMPBUF_SAVE>[0]
13377 Printing an object of class-wide type or dereferencing an
13378 access-to-class-wide value will display all the components of the object's
13379 specific type (as indicated by its run-time tag). Likewise, component
13380 selection on such a value will operate on the specific type of the
13385 @node Stopping Before Main Program
13386 @subsubsection Stopping at the Very Beginning
13388 @cindex breakpointing Ada elaboration code
13389 It is sometimes necessary to debug the program during elaboration, and
13390 before reaching the main procedure.
13391 As defined in the Ada Reference
13392 Manual, the elaboration code is invoked from a procedure called
13393 @code{adainit}. To run your program up to the beginning of
13394 elaboration, simply use the following two commands:
13395 @code{tbreak adainit} and @code{run}.
13398 @subsubsection Extensions for Ada Tasks
13399 @cindex Ada, tasking
13401 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
13402 @value{GDBN} provides the following task-related commands:
13407 This command shows a list of current Ada tasks, as in the following example:
13414 (@value{GDBP}) info tasks
13415 ID TID P-ID Pri State Name
13416 1 8088000 0 15 Child Activation Wait main_task
13417 2 80a4000 1 15 Accept Statement b
13418 3 809a800 1 15 Child Activation Wait a
13419 * 4 80ae800 3 15 Runnable c
13424 In this listing, the asterisk before the last task indicates it to be the
13425 task currently being inspected.
13429 Represents @value{GDBN}'s internal task number.
13435 The parent's task ID (@value{GDBN}'s internal task number).
13438 The base priority of the task.
13441 Current state of the task.
13445 The task has been created but has not been activated. It cannot be
13449 The task is not blocked for any reason known to Ada. (It may be waiting
13450 for a mutex, though.) It is conceptually "executing" in normal mode.
13453 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
13454 that were waiting on terminate alternatives have been awakened and have
13455 terminated themselves.
13457 @item Child Activation Wait
13458 The task is waiting for created tasks to complete activation.
13460 @item Accept Statement
13461 The task is waiting on an accept or selective wait statement.
13463 @item Waiting on entry call
13464 The task is waiting on an entry call.
13466 @item Async Select Wait
13467 The task is waiting to start the abortable part of an asynchronous
13471 The task is waiting on a select statement with only a delay
13474 @item Child Termination Wait
13475 The task is sleeping having completed a master within itself, and is
13476 waiting for the tasks dependent on that master to become terminated or
13477 waiting on a terminate Phase.
13479 @item Wait Child in Term Alt
13480 The task is sleeping waiting for tasks on terminate alternatives to
13481 finish terminating.
13483 @item Accepting RV with @var{taskno}
13484 The task is accepting a rendez-vous with the task @var{taskno}.
13488 Name of the task in the program.
13492 @kindex info task @var{taskno}
13493 @item info task @var{taskno}
13494 This command shows detailled informations on the specified task, as in
13495 the following example:
13500 (@value{GDBP}) info tasks
13501 ID TID P-ID Pri State Name
13502 1 8077880 0 15 Child Activation Wait main_task
13503 * 2 807c468 1 15 Runnable task_1
13504 (@value{GDBP}) info task 2
13505 Ada Task: 0x807c468
13508 Parent: 1 (main_task)
13514 @kindex task@r{ (Ada)}
13515 @cindex current Ada task ID
13516 This command prints the ID of the current task.
13522 (@value{GDBP}) info tasks
13523 ID TID P-ID Pri State Name
13524 1 8077870 0 15 Child Activation Wait main_task
13525 * 2 807c458 1 15 Runnable t
13526 (@value{GDBP}) task
13527 [Current task is 2]
13530 @item task @var{taskno}
13531 @cindex Ada task switching
13532 This command is like the @code{thread @var{threadno}}
13533 command (@pxref{Threads}). It switches the context of debugging
13534 from the current task to the given task.
13540 (@value{GDBP}) info tasks
13541 ID TID P-ID Pri State Name
13542 1 8077870 0 15 Child Activation Wait main_task
13543 * 2 807c458 1 15 Runnable t
13544 (@value{GDBP}) task 1
13545 [Switching to task 1]
13546 #0 0x8067726 in pthread_cond_wait ()
13548 #0 0x8067726 in pthread_cond_wait ()
13549 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
13550 #2 0x805cb63 in system.task_primitives.operations.sleep ()
13551 #3 0x806153e in system.tasking.stages.activate_tasks ()
13552 #4 0x804aacc in un () at un.adb:5
13555 @item break @var{linespec} task @var{taskno}
13556 @itemx break @var{linespec} task @var{taskno} if @dots{}
13557 @cindex breakpoints and tasks, in Ada
13558 @cindex task breakpoints, in Ada
13559 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
13560 These commands are like the @code{break @dots{} thread @dots{}}
13561 command (@pxref{Thread Stops}).
13562 @var{linespec} specifies source lines, as described
13563 in @ref{Specify Location}.
13565 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
13566 to specify that you only want @value{GDBN} to stop the program when a
13567 particular Ada task reaches this breakpoint. @var{taskno} is one of the
13568 numeric task identifiers assigned by @value{GDBN}, shown in the first
13569 column of the @samp{info tasks} display.
13571 If you do not specify @samp{task @var{taskno}} when you set a
13572 breakpoint, the breakpoint applies to @emph{all} tasks of your
13575 You can use the @code{task} qualifier on conditional breakpoints as
13576 well; in this case, place @samp{task @var{taskno}} before the
13577 breakpoint condition (before the @code{if}).
13585 (@value{GDBP}) info tasks
13586 ID TID P-ID Pri State Name
13587 1 140022020 0 15 Child Activation Wait main_task
13588 2 140045060 1 15 Accept/Select Wait t2
13589 3 140044840 1 15 Runnable t1
13590 * 4 140056040 1 15 Runnable t3
13591 (@value{GDBP}) b 15 task 2
13592 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
13593 (@value{GDBP}) cont
13598 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
13600 (@value{GDBP}) info tasks
13601 ID TID P-ID Pri State Name
13602 1 140022020 0 15 Child Activation Wait main_task
13603 * 2 140045060 1 15 Runnable t2
13604 3 140044840 1 15 Runnable t1
13605 4 140056040 1 15 Delay Sleep t3
13609 @node Ada Tasks and Core Files
13610 @subsubsection Tasking Support when Debugging Core Files
13611 @cindex Ada tasking and core file debugging
13613 When inspecting a core file, as opposed to debugging a live program,
13614 tasking support may be limited or even unavailable, depending on
13615 the platform being used.
13616 For instance, on x86-linux, the list of tasks is available, but task
13617 switching is not supported. On Tru64, however, task switching will work
13620 On certain platforms, including Tru64, the debugger needs to perform some
13621 memory writes in order to provide Ada tasking support. When inspecting
13622 a core file, this means that the core file must be opened with read-write
13623 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
13624 Under these circumstances, you should make a backup copy of the core
13625 file before inspecting it with @value{GDBN}.
13627 @node Ravenscar Profile
13628 @subsubsection Tasking Support when using the Ravenscar Profile
13629 @cindex Ravenscar Profile
13631 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
13632 specifically designed for systems with safety-critical real-time
13636 @kindex set ravenscar task-switching on
13637 @cindex task switching with program using Ravenscar Profile
13638 @item set ravenscar task-switching on
13639 Allows task switching when debugging a program that uses the Ravenscar
13640 Profile. This is the default.
13642 @kindex set ravenscar task-switching off
13643 @item set ravenscar task-switching off
13644 Turn off task switching when debugging a program that uses the Ravenscar
13645 Profile. This is mostly intended to disable the code that adds support
13646 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
13647 the Ravenscar runtime is preventing @value{GDBN} from working properly.
13648 To be effective, this command should be run before the program is started.
13650 @kindex show ravenscar task-switching
13651 @item show ravenscar task-switching
13652 Show whether it is possible to switch from task to task in a program
13653 using the Ravenscar Profile.
13658 @subsubsection Known Peculiarities of Ada Mode
13659 @cindex Ada, problems
13661 Besides the omissions listed previously (@pxref{Omissions from Ada}),
13662 we know of several problems with and limitations of Ada mode in
13664 some of which will be fixed with planned future releases of the debugger
13665 and the GNU Ada compiler.
13669 Currently, the debugger
13670 has insufficient information to determine whether certain pointers represent
13671 pointers to objects or the objects themselves.
13672 Thus, the user may have to tack an extra @code{.all} after an expression
13673 to get it printed properly.
13676 Static constants that the compiler chooses not to materialize as objects in
13677 storage are invisible to the debugger.
13680 Named parameter associations in function argument lists are ignored (the
13681 argument lists are treated as positional).
13684 Many useful library packages are currently invisible to the debugger.
13687 Fixed-point arithmetic, conversions, input, and output is carried out using
13688 floating-point arithmetic, and may give results that only approximate those on
13692 The GNAT compiler never generates the prefix @code{Standard} for any of
13693 the standard symbols defined by the Ada language. @value{GDBN} knows about
13694 this: it will strip the prefix from names when you use it, and will never
13695 look for a name you have so qualified among local symbols, nor match against
13696 symbols in other packages or subprograms. If you have
13697 defined entities anywhere in your program other than parameters and
13698 local variables whose simple names match names in @code{Standard},
13699 GNAT's lack of qualification here can cause confusion. When this happens,
13700 you can usually resolve the confusion
13701 by qualifying the problematic names with package
13702 @code{Standard} explicitly.
13705 Older versions of the compiler sometimes generate erroneous debugging
13706 information, resulting in the debugger incorrectly printing the value
13707 of affected entities. In some cases, the debugger is able to work
13708 around an issue automatically. In other cases, the debugger is able
13709 to work around the issue, but the work-around has to be specifically
13712 @kindex set ada trust-PAD-over-XVS
13713 @kindex show ada trust-PAD-over-XVS
13716 @item set ada trust-PAD-over-XVS on
13717 Configure GDB to strictly follow the GNAT encoding when computing the
13718 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
13719 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
13720 a complete description of the encoding used by the GNAT compiler).
13721 This is the default.
13723 @item set ada trust-PAD-over-XVS off
13724 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
13725 sometimes prints the wrong value for certain entities, changing @code{ada
13726 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
13727 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
13728 @code{off}, but this incurs a slight performance penalty, so it is
13729 recommended to leave this setting to @code{on} unless necessary.
13733 @node Unsupported Languages
13734 @section Unsupported Languages
13736 @cindex unsupported languages
13737 @cindex minimal language
13738 In addition to the other fully-supported programming languages,
13739 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
13740 It does not represent a real programming language, but provides a set
13741 of capabilities close to what the C or assembly languages provide.
13742 This should allow most simple operations to be performed while debugging
13743 an application that uses a language currently not supported by @value{GDBN}.
13745 If the language is set to @code{auto}, @value{GDBN} will automatically
13746 select this language if the current frame corresponds to an unsupported
13750 @chapter Examining the Symbol Table
13752 The commands described in this chapter allow you to inquire about the
13753 symbols (names of variables, functions and types) defined in your
13754 program. This information is inherent in the text of your program and
13755 does not change as your program executes. @value{GDBN} finds it in your
13756 program's symbol table, in the file indicated when you started @value{GDBN}
13757 (@pxref{File Options, ,Choosing Files}), or by one of the
13758 file-management commands (@pxref{Files, ,Commands to Specify Files}).
13760 @cindex symbol names
13761 @cindex names of symbols
13762 @cindex quoting names
13763 Occasionally, you may need to refer to symbols that contain unusual
13764 characters, which @value{GDBN} ordinarily treats as word delimiters. The
13765 most frequent case is in referring to static variables in other
13766 source files (@pxref{Variables,,Program Variables}). File names
13767 are recorded in object files as debugging symbols, but @value{GDBN} would
13768 ordinarily parse a typical file name, like @file{foo.c}, as the three words
13769 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
13770 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
13777 looks up the value of @code{x} in the scope of the file @file{foo.c}.
13780 @cindex case-insensitive symbol names
13781 @cindex case sensitivity in symbol names
13782 @kindex set case-sensitive
13783 @item set case-sensitive on
13784 @itemx set case-sensitive off
13785 @itemx set case-sensitive auto
13786 Normally, when @value{GDBN} looks up symbols, it matches their names
13787 with case sensitivity determined by the current source language.
13788 Occasionally, you may wish to control that. The command @code{set
13789 case-sensitive} lets you do that by specifying @code{on} for
13790 case-sensitive matches or @code{off} for case-insensitive ones. If
13791 you specify @code{auto}, case sensitivity is reset to the default
13792 suitable for the source language. The default is case-sensitive
13793 matches for all languages except for Fortran, for which the default is
13794 case-insensitive matches.
13796 @kindex show case-sensitive
13797 @item show case-sensitive
13798 This command shows the current setting of case sensitivity for symbols
13801 @kindex info address
13802 @cindex address of a symbol
13803 @item info address @var{symbol}
13804 Describe where the data for @var{symbol} is stored. For a register
13805 variable, this says which register it is kept in. For a non-register
13806 local variable, this prints the stack-frame offset at which the variable
13809 Note the contrast with @samp{print &@var{symbol}}, which does not work
13810 at all for a register variable, and for a stack local variable prints
13811 the exact address of the current instantiation of the variable.
13813 @kindex info symbol
13814 @cindex symbol from address
13815 @cindex closest symbol and offset for an address
13816 @item info symbol @var{addr}
13817 Print the name of a symbol which is stored at the address @var{addr}.
13818 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
13819 nearest symbol and an offset from it:
13822 (@value{GDBP}) info symbol 0x54320
13823 _initialize_vx + 396 in section .text
13827 This is the opposite of the @code{info address} command. You can use
13828 it to find out the name of a variable or a function given its address.
13830 For dynamically linked executables, the name of executable or shared
13831 library containing the symbol is also printed:
13834 (@value{GDBP}) info symbol 0x400225
13835 _start + 5 in section .text of /tmp/a.out
13836 (@value{GDBP}) info symbol 0x2aaaac2811cf
13837 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
13841 @item whatis [@var{arg}]
13842 Print the data type of @var{arg}, which can be either an expression or
13843 a data type. With no argument, print the data type of @code{$}, the
13844 last value in the value history. If @var{arg} is an expression, it is
13845 not actually evaluated, and any side-effecting operations (such as
13846 assignments or function calls) inside it do not take place. If
13847 @var{arg} is a type name, it may be the name of a type or typedef, or
13848 for C code it may have the form @samp{class @var{class-name}},
13849 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
13850 @samp{enum @var{enum-tag}}.
13851 @xref{Expressions, ,Expressions}.
13854 @item ptype [@var{arg}]
13855 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
13856 detailed description of the type, instead of just the name of the type.
13857 @xref{Expressions, ,Expressions}.
13859 For example, for this variable declaration:
13862 struct complex @{double real; double imag;@} v;
13866 the two commands give this output:
13870 (@value{GDBP}) whatis v
13871 type = struct complex
13872 (@value{GDBP}) ptype v
13873 type = struct complex @{
13881 As with @code{whatis}, using @code{ptype} without an argument refers to
13882 the type of @code{$}, the last value in the value history.
13884 @cindex incomplete type
13885 Sometimes, programs use opaque data types or incomplete specifications
13886 of complex data structure. If the debug information included in the
13887 program does not allow @value{GDBN} to display a full declaration of
13888 the data type, it will say @samp{<incomplete type>}. For example,
13889 given these declarations:
13893 struct foo *fooptr;
13897 but no definition for @code{struct foo} itself, @value{GDBN} will say:
13900 (@value{GDBP}) ptype foo
13901 $1 = <incomplete type>
13905 ``Incomplete type'' is C terminology for data types that are not
13906 completely specified.
13909 @item info types @var{regexp}
13911 Print a brief description of all types whose names match the regular
13912 expression @var{regexp} (or all types in your program, if you supply
13913 no argument). Each complete typename is matched as though it were a
13914 complete line; thus, @samp{i type value} gives information on all
13915 types in your program whose names include the string @code{value}, but
13916 @samp{i type ^value$} gives information only on types whose complete
13917 name is @code{value}.
13919 This command differs from @code{ptype} in two ways: first, like
13920 @code{whatis}, it does not print a detailed description; second, it
13921 lists all source files where a type is defined.
13924 @cindex local variables
13925 @item info scope @var{location}
13926 List all the variables local to a particular scope. This command
13927 accepts a @var{location} argument---a function name, a source line, or
13928 an address preceded by a @samp{*}, and prints all the variables local
13929 to the scope defined by that location. (@xref{Specify Location}, for
13930 details about supported forms of @var{location}.) For example:
13933 (@value{GDBP}) @b{info scope command_line_handler}
13934 Scope for command_line_handler:
13935 Symbol rl is an argument at stack/frame offset 8, length 4.
13936 Symbol linebuffer is in static storage at address 0x150a18, length 4.
13937 Symbol linelength is in static storage at address 0x150a1c, length 4.
13938 Symbol p is a local variable in register $esi, length 4.
13939 Symbol p1 is a local variable in register $ebx, length 4.
13940 Symbol nline is a local variable in register $edx, length 4.
13941 Symbol repeat is a local variable at frame offset -8, length 4.
13945 This command is especially useful for determining what data to collect
13946 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
13949 @kindex info source
13951 Show information about the current source file---that is, the source file for
13952 the function containing the current point of execution:
13955 the name of the source file, and the directory containing it,
13957 the directory it was compiled in,
13959 its length, in lines,
13961 which programming language it is written in,
13963 whether the executable includes debugging information for that file, and
13964 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
13966 whether the debugging information includes information about
13967 preprocessor macros.
13971 @kindex info sources
13973 Print the names of all source files in your program for which there is
13974 debugging information, organized into two lists: files whose symbols
13975 have already been read, and files whose symbols will be read when needed.
13977 @kindex info functions
13978 @item info functions
13979 Print the names and data types of all defined functions.
13981 @item info functions @var{regexp}
13982 Print the names and data types of all defined functions
13983 whose names contain a match for regular expression @var{regexp}.
13984 Thus, @samp{info fun step} finds all functions whose names
13985 include @code{step}; @samp{info fun ^step} finds those whose names
13986 start with @code{step}. If a function name contains characters
13987 that conflict with the regular expression language (e.g.@:
13988 @samp{operator*()}), they may be quoted with a backslash.
13990 @kindex info variables
13991 @item info variables
13992 Print the names and data types of all variables that are defined
13993 outside of functions (i.e.@: excluding local variables).
13995 @item info variables @var{regexp}
13996 Print the names and data types of all variables (except for local
13997 variables) whose names contain a match for regular expression
14000 @kindex info classes
14001 @cindex Objective-C, classes and selectors
14003 @itemx info classes @var{regexp}
14004 Display all Objective-C classes in your program, or
14005 (with the @var{regexp} argument) all those matching a particular regular
14008 @kindex info selectors
14009 @item info selectors
14010 @itemx info selectors @var{regexp}
14011 Display all Objective-C selectors in your program, or
14012 (with the @var{regexp} argument) all those matching a particular regular
14016 This was never implemented.
14017 @kindex info methods
14019 @itemx info methods @var{regexp}
14020 The @code{info methods} command permits the user to examine all defined
14021 methods within C@t{++} program, or (with the @var{regexp} argument) a
14022 specific set of methods found in the various C@t{++} classes. Many
14023 C@t{++} classes provide a large number of methods. Thus, the output
14024 from the @code{ptype} command can be overwhelming and hard to use. The
14025 @code{info-methods} command filters the methods, printing only those
14026 which match the regular-expression @var{regexp}.
14029 @cindex reloading symbols
14030 Some systems allow individual object files that make up your program to
14031 be replaced without stopping and restarting your program. For example,
14032 in VxWorks you can simply recompile a defective object file and keep on
14033 running. If you are running on one of these systems, you can allow
14034 @value{GDBN} to reload the symbols for automatically relinked modules:
14037 @kindex set symbol-reloading
14038 @item set symbol-reloading on
14039 Replace symbol definitions for the corresponding source file when an
14040 object file with a particular name is seen again.
14042 @item set symbol-reloading off
14043 Do not replace symbol definitions when encountering object files of the
14044 same name more than once. This is the default state; if you are not
14045 running on a system that permits automatic relinking of modules, you
14046 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
14047 may discard symbols when linking large programs, that may contain
14048 several modules (from different directories or libraries) with the same
14051 @kindex show symbol-reloading
14052 @item show symbol-reloading
14053 Show the current @code{on} or @code{off} setting.
14056 @cindex opaque data types
14057 @kindex set opaque-type-resolution
14058 @item set opaque-type-resolution on
14059 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
14060 declared as a pointer to a @code{struct}, @code{class}, or
14061 @code{union}---for example, @code{struct MyType *}---that is used in one
14062 source file although the full declaration of @code{struct MyType} is in
14063 another source file. The default is on.
14065 A change in the setting of this subcommand will not take effect until
14066 the next time symbols for a file are loaded.
14068 @item set opaque-type-resolution off
14069 Tell @value{GDBN} not to resolve opaque types. In this case, the type
14070 is printed as follows:
14072 @{<no data fields>@}
14075 @kindex show opaque-type-resolution
14076 @item show opaque-type-resolution
14077 Show whether opaque types are resolved or not.
14079 @kindex maint print symbols
14080 @cindex symbol dump
14081 @kindex maint print psymbols
14082 @cindex partial symbol dump
14083 @item maint print symbols @var{filename}
14084 @itemx maint print psymbols @var{filename}
14085 @itemx maint print msymbols @var{filename}
14086 Write a dump of debugging symbol data into the file @var{filename}.
14087 These commands are used to debug the @value{GDBN} symbol-reading code. Only
14088 symbols with debugging data are included. If you use @samp{maint print
14089 symbols}, @value{GDBN} includes all the symbols for which it has already
14090 collected full details: that is, @var{filename} reflects symbols for
14091 only those files whose symbols @value{GDBN} has read. You can use the
14092 command @code{info sources} to find out which files these are. If you
14093 use @samp{maint print psymbols} instead, the dump shows information about
14094 symbols that @value{GDBN} only knows partially---that is, symbols defined in
14095 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
14096 @samp{maint print msymbols} dumps just the minimal symbol information
14097 required for each object file from which @value{GDBN} has read some symbols.
14098 @xref{Files, ,Commands to Specify Files}, for a discussion of how
14099 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
14101 @kindex maint info symtabs
14102 @kindex maint info psymtabs
14103 @cindex listing @value{GDBN}'s internal symbol tables
14104 @cindex symbol tables, listing @value{GDBN}'s internal
14105 @cindex full symbol tables, listing @value{GDBN}'s internal
14106 @cindex partial symbol tables, listing @value{GDBN}'s internal
14107 @item maint info symtabs @r{[} @var{regexp} @r{]}
14108 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
14110 List the @code{struct symtab} or @code{struct partial_symtab}
14111 structures whose names match @var{regexp}. If @var{regexp} is not
14112 given, list them all. The output includes expressions which you can
14113 copy into a @value{GDBN} debugging this one to examine a particular
14114 structure in more detail. For example:
14117 (@value{GDBP}) maint info psymtabs dwarf2read
14118 @{ objfile /home/gnu/build/gdb/gdb
14119 ((struct objfile *) 0x82e69d0)
14120 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
14121 ((struct partial_symtab *) 0x8474b10)
14124 text addresses 0x814d3c8 -- 0x8158074
14125 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
14126 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
14127 dependencies (none)
14130 (@value{GDBP}) maint info symtabs
14134 We see that there is one partial symbol table whose filename contains
14135 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
14136 and we see that @value{GDBN} has not read in any symtabs yet at all.
14137 If we set a breakpoint on a function, that will cause @value{GDBN} to
14138 read the symtab for the compilation unit containing that function:
14141 (@value{GDBP}) break dwarf2_psymtab_to_symtab
14142 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
14144 (@value{GDBP}) maint info symtabs
14145 @{ objfile /home/gnu/build/gdb/gdb
14146 ((struct objfile *) 0x82e69d0)
14147 @{ symtab /home/gnu/src/gdb/dwarf2read.c
14148 ((struct symtab *) 0x86c1f38)
14151 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
14152 linetable ((struct linetable *) 0x8370fa0)
14153 debugformat DWARF 2
14162 @chapter Altering Execution
14164 Once you think you have found an error in your program, you might want to
14165 find out for certain whether correcting the apparent error would lead to
14166 correct results in the rest of the run. You can find the answer by
14167 experiment, using the @value{GDBN} features for altering execution of the
14170 For example, you can store new values into variables or memory
14171 locations, give your program a signal, restart it at a different
14172 address, or even return prematurely from a function.
14175 * Assignment:: Assignment to variables
14176 * Jumping:: Continuing at a different address
14177 * Signaling:: Giving your program a signal
14178 * Returning:: Returning from a function
14179 * Calling:: Calling your program's functions
14180 * Patching:: Patching your program
14184 @section Assignment to Variables
14187 @cindex setting variables
14188 To alter the value of a variable, evaluate an assignment expression.
14189 @xref{Expressions, ,Expressions}. For example,
14196 stores the value 4 into the variable @code{x}, and then prints the
14197 value of the assignment expression (which is 4).
14198 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
14199 information on operators in supported languages.
14201 @kindex set variable
14202 @cindex variables, setting
14203 If you are not interested in seeing the value of the assignment, use the
14204 @code{set} command instead of the @code{print} command. @code{set} is
14205 really the same as @code{print} except that the expression's value is
14206 not printed and is not put in the value history (@pxref{Value History,
14207 ,Value History}). The expression is evaluated only for its effects.
14209 If the beginning of the argument string of the @code{set} command
14210 appears identical to a @code{set} subcommand, use the @code{set
14211 variable} command instead of just @code{set}. This command is identical
14212 to @code{set} except for its lack of subcommands. For example, if your
14213 program has a variable @code{width}, you get an error if you try to set
14214 a new value with just @samp{set width=13}, because @value{GDBN} has the
14215 command @code{set width}:
14218 (@value{GDBP}) whatis width
14220 (@value{GDBP}) p width
14222 (@value{GDBP}) set width=47
14223 Invalid syntax in expression.
14227 The invalid expression, of course, is @samp{=47}. In
14228 order to actually set the program's variable @code{width}, use
14231 (@value{GDBP}) set var width=47
14234 Because the @code{set} command has many subcommands that can conflict
14235 with the names of program variables, it is a good idea to use the
14236 @code{set variable} command instead of just @code{set}. For example, if
14237 your program has a variable @code{g}, you run into problems if you try
14238 to set a new value with just @samp{set g=4}, because @value{GDBN} has
14239 the command @code{set gnutarget}, abbreviated @code{set g}:
14243 (@value{GDBP}) whatis g
14247 (@value{GDBP}) set g=4
14251 The program being debugged has been started already.
14252 Start it from the beginning? (y or n) y
14253 Starting program: /home/smith/cc_progs/a.out
14254 "/home/smith/cc_progs/a.out": can't open to read symbols:
14255 Invalid bfd target.
14256 (@value{GDBP}) show g
14257 The current BFD target is "=4".
14262 The program variable @code{g} did not change, and you silently set the
14263 @code{gnutarget} to an invalid value. In order to set the variable
14267 (@value{GDBP}) set var g=4
14270 @value{GDBN} allows more implicit conversions in assignments than C; you can
14271 freely store an integer value into a pointer variable or vice versa,
14272 and you can convert any structure to any other structure that is the
14273 same length or shorter.
14274 @comment FIXME: how do structs align/pad in these conversions?
14275 @comment /doc@cygnus.com 18dec1990
14277 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
14278 construct to generate a value of specified type at a specified address
14279 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
14280 to memory location @code{0x83040} as an integer (which implies a certain size
14281 and representation in memory), and
14284 set @{int@}0x83040 = 4
14288 stores the value 4 into that memory location.
14291 @section Continuing at a Different Address
14293 Ordinarily, when you continue your program, you do so at the place where
14294 it stopped, with the @code{continue} command. You can instead continue at
14295 an address of your own choosing, with the following commands:
14299 @item jump @var{linespec}
14300 @itemx jump @var{location}
14301 Resume execution at line @var{linespec} or at address given by
14302 @var{location}. Execution stops again immediately if there is a
14303 breakpoint there. @xref{Specify Location}, for a description of the
14304 different forms of @var{linespec} and @var{location}. It is common
14305 practice to use the @code{tbreak} command in conjunction with
14306 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
14308 The @code{jump} command does not change the current stack frame, or
14309 the stack pointer, or the contents of any memory location or any
14310 register other than the program counter. If line @var{linespec} is in
14311 a different function from the one currently executing, the results may
14312 be bizarre if the two functions expect different patterns of arguments or
14313 of local variables. For this reason, the @code{jump} command requests
14314 confirmation if the specified line is not in the function currently
14315 executing. However, even bizarre results are predictable if you are
14316 well acquainted with the machine-language code of your program.
14319 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
14320 On many systems, you can get much the same effect as the @code{jump}
14321 command by storing a new value into the register @code{$pc}. The
14322 difference is that this does not start your program running; it only
14323 changes the address of where it @emph{will} run when you continue. For
14331 makes the next @code{continue} command or stepping command execute at
14332 address @code{0x485}, rather than at the address where your program stopped.
14333 @xref{Continuing and Stepping, ,Continuing and Stepping}.
14335 The most common occasion to use the @code{jump} command is to back
14336 up---perhaps with more breakpoints set---over a portion of a program
14337 that has already executed, in order to examine its execution in more
14342 @section Giving your Program a Signal
14343 @cindex deliver a signal to a program
14347 @item signal @var{signal}
14348 Resume execution where your program stopped, but immediately give it the
14349 signal @var{signal}. @var{signal} can be the name or the number of a
14350 signal. For example, on many systems @code{signal 2} and @code{signal
14351 SIGINT} are both ways of sending an interrupt signal.
14353 Alternatively, if @var{signal} is zero, continue execution without
14354 giving a signal. This is useful when your program stopped on account of
14355 a signal and would ordinary see the signal when resumed with the
14356 @code{continue} command; @samp{signal 0} causes it to resume without a
14359 @code{signal} does not repeat when you press @key{RET} a second time
14360 after executing the command.
14364 Invoking the @code{signal} command is not the same as invoking the
14365 @code{kill} utility from the shell. Sending a signal with @code{kill}
14366 causes @value{GDBN} to decide what to do with the signal depending on
14367 the signal handling tables (@pxref{Signals}). The @code{signal} command
14368 passes the signal directly to your program.
14372 @section Returning from a Function
14375 @cindex returning from a function
14378 @itemx return @var{expression}
14379 You can cancel execution of a function call with the @code{return}
14380 command. If you give an
14381 @var{expression} argument, its value is used as the function's return
14385 When you use @code{return}, @value{GDBN} discards the selected stack frame
14386 (and all frames within it). You can think of this as making the
14387 discarded frame return prematurely. If you wish to specify a value to
14388 be returned, give that value as the argument to @code{return}.
14390 This pops the selected stack frame (@pxref{Selection, ,Selecting a
14391 Frame}), and any other frames inside of it, leaving its caller as the
14392 innermost remaining frame. That frame becomes selected. The
14393 specified value is stored in the registers used for returning values
14396 The @code{return} command does not resume execution; it leaves the
14397 program stopped in the state that would exist if the function had just
14398 returned. In contrast, the @code{finish} command (@pxref{Continuing
14399 and Stepping, ,Continuing and Stepping}) resumes execution until the
14400 selected stack frame returns naturally.
14402 @value{GDBN} needs to know how the @var{expression} argument should be set for
14403 the inferior. The concrete registers assignment depends on the OS ABI and the
14404 type being returned by the selected stack frame. For example it is common for
14405 OS ABI to return floating point values in FPU registers while integer values in
14406 CPU registers. Still some ABIs return even floating point values in CPU
14407 registers. Larger integer widths (such as @code{long long int}) also have
14408 specific placement rules. @value{GDBN} already knows the OS ABI from its
14409 current target so it needs to find out also the type being returned to make the
14410 assignment into the right register(s).
14412 Normally, the selected stack frame has debug info. @value{GDBN} will always
14413 use the debug info instead of the implicit type of @var{expression} when the
14414 debug info is available. For example, if you type @kbd{return -1}, and the
14415 function in the current stack frame is declared to return a @code{long long
14416 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
14417 into a @code{long long int}:
14420 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
14422 (@value{GDBP}) return -1
14423 Make func return now? (y or n) y
14424 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
14425 43 printf ("result=%lld\n", func ());
14429 However, if the selected stack frame does not have a debug info, e.g., if the
14430 function was compiled without debug info, @value{GDBN} has to find out the type
14431 to return from user. Specifying a different type by mistake may set the value
14432 in different inferior registers than the caller code expects. For example,
14433 typing @kbd{return -1} with its implicit type @code{int} would set only a part
14434 of a @code{long long int} result for a debug info less function (on 32-bit
14435 architectures). Therefore the user is required to specify the return type by
14436 an appropriate cast explicitly:
14439 Breakpoint 2, 0x0040050b in func ()
14440 (@value{GDBP}) return -1
14441 Return value type not available for selected stack frame.
14442 Please use an explicit cast of the value to return.
14443 (@value{GDBP}) return (long long int) -1
14444 Make selected stack frame return now? (y or n) y
14445 #0 0x00400526 in main ()
14450 @section Calling Program Functions
14453 @cindex calling functions
14454 @cindex inferior functions, calling
14455 @item print @var{expr}
14456 Evaluate the expression @var{expr} and display the resulting value.
14457 @var{expr} may include calls to functions in the program being
14461 @item call @var{expr}
14462 Evaluate the expression @var{expr} without displaying @code{void}
14465 You can use this variant of the @code{print} command if you want to
14466 execute a function from your program that does not return anything
14467 (a.k.a.@: @dfn{a void function}), but without cluttering the output
14468 with @code{void} returned values that @value{GDBN} will otherwise
14469 print. If the result is not void, it is printed and saved in the
14473 It is possible for the function you call via the @code{print} or
14474 @code{call} command to generate a signal (e.g., if there's a bug in
14475 the function, or if you passed it incorrect arguments). What happens
14476 in that case is controlled by the @code{set unwindonsignal} command.
14478 Similarly, with a C@t{++} program it is possible for the function you
14479 call via the @code{print} or @code{call} command to generate an
14480 exception that is not handled due to the constraints of the dummy
14481 frame. In this case, any exception that is raised in the frame, but has
14482 an out-of-frame exception handler will not be found. GDB builds a
14483 dummy-frame for the inferior function call, and the unwinder cannot
14484 seek for exception handlers outside of this dummy-frame. What happens
14485 in that case is controlled by the
14486 @code{set unwind-on-terminating-exception} command.
14489 @item set unwindonsignal
14490 @kindex set unwindonsignal
14491 @cindex unwind stack in called functions
14492 @cindex call dummy stack unwinding
14493 Set unwinding of the stack if a signal is received while in a function
14494 that @value{GDBN} called in the program being debugged. If set to on,
14495 @value{GDBN} unwinds the stack it created for the call and restores
14496 the context to what it was before the call. If set to off (the
14497 default), @value{GDBN} stops in the frame where the signal was
14500 @item show unwindonsignal
14501 @kindex show unwindonsignal
14502 Show the current setting of stack unwinding in the functions called by
14505 @item set unwind-on-terminating-exception
14506 @kindex set unwind-on-terminating-exception
14507 @cindex unwind stack in called functions with unhandled exceptions
14508 @cindex call dummy stack unwinding on unhandled exception.
14509 Set unwinding of the stack if a C@t{++} exception is raised, but left
14510 unhandled while in a function that @value{GDBN} called in the program being
14511 debugged. If set to on (the default), @value{GDBN} unwinds the stack
14512 it created for the call and restores the context to what it was before
14513 the call. If set to off, @value{GDBN} the exception is delivered to
14514 the default C@t{++} exception handler and the inferior terminated.
14516 @item show unwind-on-terminating-exception
14517 @kindex show unwind-on-terminating-exception
14518 Show the current setting of stack unwinding in the functions called by
14523 @cindex weak alias functions
14524 Sometimes, a function you wish to call is actually a @dfn{weak alias}
14525 for another function. In such case, @value{GDBN} might not pick up
14526 the type information, including the types of the function arguments,
14527 which causes @value{GDBN} to call the inferior function incorrectly.
14528 As a result, the called function will function erroneously and may
14529 even crash. A solution to that is to use the name of the aliased
14533 @section Patching Programs
14535 @cindex patching binaries
14536 @cindex writing into executables
14537 @cindex writing into corefiles
14539 By default, @value{GDBN} opens the file containing your program's
14540 executable code (or the corefile) read-only. This prevents accidental
14541 alterations to machine code; but it also prevents you from intentionally
14542 patching your program's binary.
14544 If you'd like to be able to patch the binary, you can specify that
14545 explicitly with the @code{set write} command. For example, you might
14546 want to turn on internal debugging flags, or even to make emergency
14552 @itemx set write off
14553 If you specify @samp{set write on}, @value{GDBN} opens executable and
14554 core files for both reading and writing; if you specify @kbd{set write
14555 off} (the default), @value{GDBN} opens them read-only.
14557 If you have already loaded a file, you must load it again (using the
14558 @code{exec-file} or @code{core-file} command) after changing @code{set
14559 write}, for your new setting to take effect.
14563 Display whether executable files and core files are opened for writing
14564 as well as reading.
14568 @chapter @value{GDBN} Files
14570 @value{GDBN} needs to know the file name of the program to be debugged,
14571 both in order to read its symbol table and in order to start your
14572 program. To debug a core dump of a previous run, you must also tell
14573 @value{GDBN} the name of the core dump file.
14576 * Files:: Commands to specify files
14577 * Separate Debug Files:: Debugging information in separate files
14578 * Index Files:: Index files speed up GDB
14579 * Symbol Errors:: Errors reading symbol files
14580 * Data Files:: GDB data files
14584 @section Commands to Specify Files
14586 @cindex symbol table
14587 @cindex core dump file
14589 You may want to specify executable and core dump file names. The usual
14590 way to do this is at start-up time, using the arguments to
14591 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
14592 Out of @value{GDBN}}).
14594 Occasionally it is necessary to change to a different file during a
14595 @value{GDBN} session. Or you may run @value{GDBN} and forget to
14596 specify a file you want to use. Or you are debugging a remote target
14597 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
14598 Program}). In these situations the @value{GDBN} commands to specify
14599 new files are useful.
14602 @cindex executable file
14604 @item file @var{filename}
14605 Use @var{filename} as the program to be debugged. It is read for its
14606 symbols and for the contents of pure memory. It is also the program
14607 executed when you use the @code{run} command. If you do not specify a
14608 directory and the file is not found in the @value{GDBN} working directory,
14609 @value{GDBN} uses the environment variable @code{PATH} as a list of
14610 directories to search, just as the shell does when looking for a program
14611 to run. You can change the value of this variable, for both @value{GDBN}
14612 and your program, using the @code{path} command.
14614 @cindex unlinked object files
14615 @cindex patching object files
14616 You can load unlinked object @file{.o} files into @value{GDBN} using
14617 the @code{file} command. You will not be able to ``run'' an object
14618 file, but you can disassemble functions and inspect variables. Also,
14619 if the underlying BFD functionality supports it, you could use
14620 @kbd{gdb -write} to patch object files using this technique. Note
14621 that @value{GDBN} can neither interpret nor modify relocations in this
14622 case, so branches and some initialized variables will appear to go to
14623 the wrong place. But this feature is still handy from time to time.
14626 @code{file} with no argument makes @value{GDBN} discard any information it
14627 has on both executable file and the symbol table.
14630 @item exec-file @r{[} @var{filename} @r{]}
14631 Specify that the program to be run (but not the symbol table) is found
14632 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
14633 if necessary to locate your program. Omitting @var{filename} means to
14634 discard information on the executable file.
14636 @kindex symbol-file
14637 @item symbol-file @r{[} @var{filename} @r{]}
14638 Read symbol table information from file @var{filename}. @code{PATH} is
14639 searched when necessary. Use the @code{file} command to get both symbol
14640 table and program to run from the same file.
14642 @code{symbol-file} with no argument clears out @value{GDBN} information on your
14643 program's symbol table.
14645 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
14646 some breakpoints and auto-display expressions. This is because they may
14647 contain pointers to the internal data recording symbols and data types,
14648 which are part of the old symbol table data being discarded inside
14651 @code{symbol-file} does not repeat if you press @key{RET} again after
14654 When @value{GDBN} is configured for a particular environment, it
14655 understands debugging information in whatever format is the standard
14656 generated for that environment; you may use either a @sc{gnu} compiler, or
14657 other compilers that adhere to the local conventions.
14658 Best results are usually obtained from @sc{gnu} compilers; for example,
14659 using @code{@value{NGCC}} you can generate debugging information for
14662 For most kinds of object files, with the exception of old SVR3 systems
14663 using COFF, the @code{symbol-file} command does not normally read the
14664 symbol table in full right away. Instead, it scans the symbol table
14665 quickly to find which source files and which symbols are present. The
14666 details are read later, one source file at a time, as they are needed.
14668 The purpose of this two-stage reading strategy is to make @value{GDBN}
14669 start up faster. For the most part, it is invisible except for
14670 occasional pauses while the symbol table details for a particular source
14671 file are being read. (The @code{set verbose} command can turn these
14672 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
14673 Warnings and Messages}.)
14675 We have not implemented the two-stage strategy for COFF yet. When the
14676 symbol table is stored in COFF format, @code{symbol-file} reads the
14677 symbol table data in full right away. Note that ``stabs-in-COFF''
14678 still does the two-stage strategy, since the debug info is actually
14682 @cindex reading symbols immediately
14683 @cindex symbols, reading immediately
14684 @item symbol-file @r{[} -readnow @r{]} @var{filename}
14685 @itemx file @r{[} -readnow @r{]} @var{filename}
14686 You can override the @value{GDBN} two-stage strategy for reading symbol
14687 tables by using the @samp{-readnow} option with any of the commands that
14688 load symbol table information, if you want to be sure @value{GDBN} has the
14689 entire symbol table available.
14691 @c FIXME: for now no mention of directories, since this seems to be in
14692 @c flux. 13mar1992 status is that in theory GDB would look either in
14693 @c current dir or in same dir as myprog; but issues like competing
14694 @c GDB's, or clutter in system dirs, mean that in practice right now
14695 @c only current dir is used. FFish says maybe a special GDB hierarchy
14696 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
14700 @item core-file @r{[}@var{filename}@r{]}
14702 Specify the whereabouts of a core dump file to be used as the ``contents
14703 of memory''. Traditionally, core files contain only some parts of the
14704 address space of the process that generated them; @value{GDBN} can access the
14705 executable file itself for other parts.
14707 @code{core-file} with no argument specifies that no core file is
14710 Note that the core file is ignored when your program is actually running
14711 under @value{GDBN}. So, if you have been running your program and you
14712 wish to debug a core file instead, you must kill the subprocess in which
14713 the program is running. To do this, use the @code{kill} command
14714 (@pxref{Kill Process, ,Killing the Child Process}).
14716 @kindex add-symbol-file
14717 @cindex dynamic linking
14718 @item add-symbol-file @var{filename} @var{address}
14719 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
14720 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
14721 The @code{add-symbol-file} command reads additional symbol table
14722 information from the file @var{filename}. You would use this command
14723 when @var{filename} has been dynamically loaded (by some other means)
14724 into the program that is running. @var{address} should be the memory
14725 address at which the file has been loaded; @value{GDBN} cannot figure
14726 this out for itself. You can additionally specify an arbitrary number
14727 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
14728 section name and base address for that section. You can specify any
14729 @var{address} as an expression.
14731 The symbol table of the file @var{filename} is added to the symbol table
14732 originally read with the @code{symbol-file} command. You can use the
14733 @code{add-symbol-file} command any number of times; the new symbol data
14734 thus read keeps adding to the old. To discard all old symbol data
14735 instead, use the @code{symbol-file} command without any arguments.
14737 @cindex relocatable object files, reading symbols from
14738 @cindex object files, relocatable, reading symbols from
14739 @cindex reading symbols from relocatable object files
14740 @cindex symbols, reading from relocatable object files
14741 @cindex @file{.o} files, reading symbols from
14742 Although @var{filename} is typically a shared library file, an
14743 executable file, or some other object file which has been fully
14744 relocated for loading into a process, you can also load symbolic
14745 information from relocatable @file{.o} files, as long as:
14749 the file's symbolic information refers only to linker symbols defined in
14750 that file, not to symbols defined by other object files,
14752 every section the file's symbolic information refers to has actually
14753 been loaded into the inferior, as it appears in the file, and
14755 you can determine the address at which every section was loaded, and
14756 provide these to the @code{add-symbol-file} command.
14760 Some embedded operating systems, like Sun Chorus and VxWorks, can load
14761 relocatable files into an already running program; such systems
14762 typically make the requirements above easy to meet. However, it's
14763 important to recognize that many native systems use complex link
14764 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
14765 assembly, for example) that make the requirements difficult to meet. In
14766 general, one cannot assume that using @code{add-symbol-file} to read a
14767 relocatable object file's symbolic information will have the same effect
14768 as linking the relocatable object file into the program in the normal
14771 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
14773 @kindex add-symbol-file-from-memory
14774 @cindex @code{syscall DSO}
14775 @cindex load symbols from memory
14776 @item add-symbol-file-from-memory @var{address}
14777 Load symbols from the given @var{address} in a dynamically loaded
14778 object file whose image is mapped directly into the inferior's memory.
14779 For example, the Linux kernel maps a @code{syscall DSO} into each
14780 process's address space; this DSO provides kernel-specific code for
14781 some system calls. The argument can be any expression whose
14782 evaluation yields the address of the file's shared object file header.
14783 For this command to work, you must have used @code{symbol-file} or
14784 @code{exec-file} commands in advance.
14786 @kindex add-shared-symbol-files
14788 @item add-shared-symbol-files @var{library-file}
14789 @itemx assf @var{library-file}
14790 The @code{add-shared-symbol-files} command can currently be used only
14791 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
14792 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
14793 @value{GDBN} automatically looks for shared libraries, however if
14794 @value{GDBN} does not find yours, you can invoke
14795 @code{add-shared-symbol-files}. It takes one argument: the shared
14796 library's file name. @code{assf} is a shorthand alias for
14797 @code{add-shared-symbol-files}.
14800 @item section @var{section} @var{addr}
14801 The @code{section} command changes the base address of the named
14802 @var{section} of the exec file to @var{addr}. This can be used if the
14803 exec file does not contain section addresses, (such as in the
14804 @code{a.out} format), or when the addresses specified in the file
14805 itself are wrong. Each section must be changed separately. The
14806 @code{info files} command, described below, lists all the sections and
14810 @kindex info target
14813 @code{info files} and @code{info target} are synonymous; both print the
14814 current target (@pxref{Targets, ,Specifying a Debugging Target}),
14815 including the names of the executable and core dump files currently in
14816 use by @value{GDBN}, and the files from which symbols were loaded. The
14817 command @code{help target} lists all possible targets rather than
14820 @kindex maint info sections
14821 @item maint info sections
14822 Another command that can give you extra information about program sections
14823 is @code{maint info sections}. In addition to the section information
14824 displayed by @code{info files}, this command displays the flags and file
14825 offset of each section in the executable and core dump files. In addition,
14826 @code{maint info sections} provides the following command options (which
14827 may be arbitrarily combined):
14831 Display sections for all loaded object files, including shared libraries.
14832 @item @var{sections}
14833 Display info only for named @var{sections}.
14834 @item @var{section-flags}
14835 Display info only for sections for which @var{section-flags} are true.
14836 The section flags that @value{GDBN} currently knows about are:
14839 Section will have space allocated in the process when loaded.
14840 Set for all sections except those containing debug information.
14842 Section will be loaded from the file into the child process memory.
14843 Set for pre-initialized code and data, clear for @code{.bss} sections.
14845 Section needs to be relocated before loading.
14847 Section cannot be modified by the child process.
14849 Section contains executable code only.
14851 Section contains data only (no executable code).
14853 Section will reside in ROM.
14855 Section contains data for constructor/destructor lists.
14857 Section is not empty.
14859 An instruction to the linker to not output the section.
14860 @item COFF_SHARED_LIBRARY
14861 A notification to the linker that the section contains
14862 COFF shared library information.
14864 Section contains common symbols.
14867 @kindex set trust-readonly-sections
14868 @cindex read-only sections
14869 @item set trust-readonly-sections on
14870 Tell @value{GDBN} that readonly sections in your object file
14871 really are read-only (i.e.@: that their contents will not change).
14872 In that case, @value{GDBN} can fetch values from these sections
14873 out of the object file, rather than from the target program.
14874 For some targets (notably embedded ones), this can be a significant
14875 enhancement to debugging performance.
14877 The default is off.
14879 @item set trust-readonly-sections off
14880 Tell @value{GDBN} not to trust readonly sections. This means that
14881 the contents of the section might change while the program is running,
14882 and must therefore be fetched from the target when needed.
14884 @item show trust-readonly-sections
14885 Show the current setting of trusting readonly sections.
14888 All file-specifying commands allow both absolute and relative file names
14889 as arguments. @value{GDBN} always converts the file name to an absolute file
14890 name and remembers it that way.
14892 @cindex shared libraries
14893 @anchor{Shared Libraries}
14894 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
14895 and IBM RS/6000 AIX shared libraries.
14897 On MS-Windows @value{GDBN} must be linked with the Expat library to support
14898 shared libraries. @xref{Expat}.
14900 @value{GDBN} automatically loads symbol definitions from shared libraries
14901 when you use the @code{run} command, or when you examine a core file.
14902 (Before you issue the @code{run} command, @value{GDBN} does not understand
14903 references to a function in a shared library, however---unless you are
14904 debugging a core file).
14906 On HP-UX, if the program loads a library explicitly, @value{GDBN}
14907 automatically loads the symbols at the time of the @code{shl_load} call.
14909 @c FIXME: some @value{GDBN} release may permit some refs to undef
14910 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
14911 @c FIXME...lib; check this from time to time when updating manual
14913 There are times, however, when you may wish to not automatically load
14914 symbol definitions from shared libraries, such as when they are
14915 particularly large or there are many of them.
14917 To control the automatic loading of shared library symbols, use the
14921 @kindex set auto-solib-add
14922 @item set auto-solib-add @var{mode}
14923 If @var{mode} is @code{on}, symbols from all shared object libraries
14924 will be loaded automatically when the inferior begins execution, you
14925 attach to an independently started inferior, or when the dynamic linker
14926 informs @value{GDBN} that a new library has been loaded. If @var{mode}
14927 is @code{off}, symbols must be loaded manually, using the
14928 @code{sharedlibrary} command. The default value is @code{on}.
14930 @cindex memory used for symbol tables
14931 If your program uses lots of shared libraries with debug info that
14932 takes large amounts of memory, you can decrease the @value{GDBN}
14933 memory footprint by preventing it from automatically loading the
14934 symbols from shared libraries. To that end, type @kbd{set
14935 auto-solib-add off} before running the inferior, then load each
14936 library whose debug symbols you do need with @kbd{sharedlibrary
14937 @var{regexp}}, where @var{regexp} is a regular expression that matches
14938 the libraries whose symbols you want to be loaded.
14940 @kindex show auto-solib-add
14941 @item show auto-solib-add
14942 Display the current autoloading mode.
14945 @cindex load shared library
14946 To explicitly load shared library symbols, use the @code{sharedlibrary}
14950 @kindex info sharedlibrary
14952 @item info share @var{regex}
14953 @itemx info sharedlibrary @var{regex}
14954 Print the names of the shared libraries which are currently loaded
14955 that match @var{regex}. If @var{regex} is omitted then print
14956 all shared libraries that are loaded.
14958 @kindex sharedlibrary
14960 @item sharedlibrary @var{regex}
14961 @itemx share @var{regex}
14962 Load shared object library symbols for files matching a
14963 Unix regular expression.
14964 As with files loaded automatically, it only loads shared libraries
14965 required by your program for a core file or after typing @code{run}. If
14966 @var{regex} is omitted all shared libraries required by your program are
14969 @item nosharedlibrary
14970 @kindex nosharedlibrary
14971 @cindex unload symbols from shared libraries
14972 Unload all shared object library symbols. This discards all symbols
14973 that have been loaded from all shared libraries. Symbols from shared
14974 libraries that were loaded by explicit user requests are not
14978 Sometimes you may wish that @value{GDBN} stops and gives you control
14979 when any of shared library events happen. Use the @code{set
14980 stop-on-solib-events} command for this:
14983 @item set stop-on-solib-events
14984 @kindex set stop-on-solib-events
14985 This command controls whether @value{GDBN} should give you control
14986 when the dynamic linker notifies it about some shared library event.
14987 The most common event of interest is loading or unloading of a new
14990 @item show stop-on-solib-events
14991 @kindex show stop-on-solib-events
14992 Show whether @value{GDBN} stops and gives you control when shared
14993 library events happen.
14996 Shared libraries are also supported in many cross or remote debugging
14997 configurations. @value{GDBN} needs to have access to the target's libraries;
14998 this can be accomplished either by providing copies of the libraries
14999 on the host system, or by asking @value{GDBN} to automatically retrieve the
15000 libraries from the target. If copies of the target libraries are
15001 provided, they need to be the same as the target libraries, although the
15002 copies on the target can be stripped as long as the copies on the host are
15005 @cindex where to look for shared libraries
15006 For remote debugging, you need to tell @value{GDBN} where the target
15007 libraries are, so that it can load the correct copies---otherwise, it
15008 may try to load the host's libraries. @value{GDBN} has two variables
15009 to specify the search directories for target libraries.
15012 @cindex prefix for shared library file names
15013 @cindex system root, alternate
15014 @kindex set solib-absolute-prefix
15015 @kindex set sysroot
15016 @item set sysroot @var{path}
15017 Use @var{path} as the system root for the program being debugged. Any
15018 absolute shared library paths will be prefixed with @var{path}; many
15019 runtime loaders store the absolute paths to the shared library in the
15020 target program's memory. If you use @code{set sysroot} to find shared
15021 libraries, they need to be laid out in the same way that they are on
15022 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
15025 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
15026 retrieve the target libraries from the remote system. This is only
15027 supported when using a remote target that supports the @code{remote get}
15028 command (@pxref{File Transfer,,Sending files to a remote system}).
15029 The part of @var{path} following the initial @file{remote:}
15030 (if present) is used as system root prefix on the remote file system.
15031 @footnote{If you want to specify a local system root using a directory
15032 that happens to be named @file{remote:}, you need to use some equivalent
15033 variant of the name like @file{./remote:}.}
15035 For targets with an MS-DOS based filesystem, such as MS-Windows and
15036 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
15037 absolute file name with @var{path}. But first, on Unix hosts,
15038 @value{GDBN} converts all backslash directory separators into forward
15039 slashes, because the backslash is not a directory separator on Unix:
15042 c:\foo\bar.dll @result{} c:/foo/bar.dll
15045 Then, @value{GDBN} attempts prefixing the target file name with
15046 @var{path}, and looks for the resulting file name in the host file
15050 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
15053 If that does not find the shared library, @value{GDBN} tries removing
15054 the @samp{:} character from the drive spec, both for convenience, and,
15055 for the case of the host file system not supporting file names with
15059 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
15062 This makes it possible to have a system root that mirrors a target
15063 with more than one drive. E.g., you may want to setup your local
15064 copies of the target system shared libraries like so (note @samp{c} vs
15068 @file{/path/to/sysroot/c/sys/bin/foo.dll}
15069 @file{/path/to/sysroot/c/sys/bin/bar.dll}
15070 @file{/path/to/sysroot/z/sys/bin/bar.dll}
15074 and point the system root at @file{/path/to/sysroot}, so that
15075 @value{GDBN} can find the correct copies of both
15076 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
15078 If that still does not find the shared library, @value{GDBN} tries
15079 removing the whole drive spec from the target file name:
15082 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
15085 This last lookup makes it possible to not care about the drive name,
15086 if you don't want or need to.
15088 The @code{set solib-absolute-prefix} command is an alias for @code{set
15091 @cindex default system root
15092 @cindex @samp{--with-sysroot}
15093 You can set the default system root by using the configure-time
15094 @samp{--with-sysroot} option. If the system root is inside
15095 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15096 @samp{--exec-prefix}), then the default system root will be updated
15097 automatically if the installed @value{GDBN} is moved to a new
15100 @kindex show sysroot
15102 Display the current shared library prefix.
15104 @kindex set solib-search-path
15105 @item set solib-search-path @var{path}
15106 If this variable is set, @var{path} is a colon-separated list of
15107 directories to search for shared libraries. @samp{solib-search-path}
15108 is used after @samp{sysroot} fails to locate the library, or if the
15109 path to the library is relative instead of absolute. If you want to
15110 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
15111 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
15112 finding your host's libraries. @samp{sysroot} is preferred; setting
15113 it to a nonexistent directory may interfere with automatic loading
15114 of shared library symbols.
15116 @kindex show solib-search-path
15117 @item show solib-search-path
15118 Display the current shared library search path.
15120 @cindex DOS file-name semantics of file names.
15121 @kindex set target-file-system-kind (unix|dos-based|auto)
15122 @kindex show target-file-system-kind
15123 @item set target-file-system-kind @var{kind}
15124 Set assumed file system kind for target reported file names.
15126 Shared library file names as reported by the target system may not
15127 make sense as is on the system @value{GDBN} is running on. For
15128 example, when remote debugging a target that has MS-DOS based file
15129 system semantics, from a Unix host, the target may be reporting to
15130 @value{GDBN} a list of loaded shared libraries with file names such as
15131 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
15132 drive letters, so the @samp{c:\} prefix is not normally understood as
15133 indicating an absolute file name, and neither is the backslash
15134 normally considered a directory separator character. In that case,
15135 the native file system would interpret this whole absolute file name
15136 as a relative file name with no directory components. This would make
15137 it impossible to point @value{GDBN} at a copy of the remote target's
15138 shared libraries on the host using @code{set sysroot}, and impractical
15139 with @code{set solib-search-path}. Setting
15140 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
15141 to interpret such file names similarly to how the target would, and to
15142 map them to file names valid on @value{GDBN}'s native file system
15143 semantics. The value of @var{kind} can be @code{"auto"}, in addition
15144 to one of the supported file system kinds. In that case, @value{GDBN}
15145 tries to determine the appropriate file system variant based on the
15146 current target's operating system (@pxref{ABI, ,Configuring the
15147 Current ABI}). The supported file system settings are:
15151 Instruct @value{GDBN} to assume the target file system is of Unix
15152 kind. Only file names starting the forward slash (@samp{/}) character
15153 are considered absolute, and the directory separator character is also
15157 Instruct @value{GDBN} to assume the target file system is DOS based.
15158 File names starting with either a forward slash, or a drive letter
15159 followed by a colon (e.g., @samp{c:}), are considered absolute, and
15160 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
15161 considered directory separators.
15164 Instruct @value{GDBN} to use the file system kind associated with the
15165 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
15166 This is the default.
15171 @node Separate Debug Files
15172 @section Debugging Information in Separate Files
15173 @cindex separate debugging information files
15174 @cindex debugging information in separate files
15175 @cindex @file{.debug} subdirectories
15176 @cindex debugging information directory, global
15177 @cindex global debugging information directory
15178 @cindex build ID, and separate debugging files
15179 @cindex @file{.build-id} directory
15181 @value{GDBN} allows you to put a program's debugging information in a
15182 file separate from the executable itself, in a way that allows
15183 @value{GDBN} to find and load the debugging information automatically.
15184 Since debugging information can be very large---sometimes larger
15185 than the executable code itself---some systems distribute debugging
15186 information for their executables in separate files, which users can
15187 install only when they need to debug a problem.
15189 @value{GDBN} supports two ways of specifying the separate debug info
15194 The executable contains a @dfn{debug link} that specifies the name of
15195 the separate debug info file. The separate debug file's name is
15196 usually @file{@var{executable}.debug}, where @var{executable} is the
15197 name of the corresponding executable file without leading directories
15198 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
15199 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
15200 checksum for the debug file, which @value{GDBN} uses to validate that
15201 the executable and the debug file came from the same build.
15204 The executable contains a @dfn{build ID}, a unique bit string that is
15205 also present in the corresponding debug info file. (This is supported
15206 only on some operating systems, notably those which use the ELF format
15207 for binary files and the @sc{gnu} Binutils.) For more details about
15208 this feature, see the description of the @option{--build-id}
15209 command-line option in @ref{Options, , Command Line Options, ld.info,
15210 The GNU Linker}. The debug info file's name is not specified
15211 explicitly by the build ID, but can be computed from the build ID, see
15215 Depending on the way the debug info file is specified, @value{GDBN}
15216 uses two different methods of looking for the debug file:
15220 For the ``debug link'' method, @value{GDBN} looks up the named file in
15221 the directory of the executable file, then in a subdirectory of that
15222 directory named @file{.debug}, and finally under the global debug
15223 directory, in a subdirectory whose name is identical to the leading
15224 directories of the executable's absolute file name.
15227 For the ``build ID'' method, @value{GDBN} looks in the
15228 @file{.build-id} subdirectory of the global debug directory for a file
15229 named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
15230 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
15231 are the rest of the bit string. (Real build ID strings are 32 or more
15232 hex characters, not 10.)
15235 So, for example, suppose you ask @value{GDBN} to debug
15236 @file{/usr/bin/ls}, which has a debug link that specifies the
15237 file @file{ls.debug}, and a build ID whose value in hex is
15238 @code{abcdef1234}. If the global debug directory is
15239 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
15240 debug information files, in the indicated order:
15244 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
15246 @file{/usr/bin/ls.debug}
15248 @file{/usr/bin/.debug/ls.debug}
15250 @file{/usr/lib/debug/usr/bin/ls.debug}.
15253 You can set the global debugging info directory's name, and view the
15254 name @value{GDBN} is currently using.
15258 @kindex set debug-file-directory
15259 @item set debug-file-directory @var{directories}
15260 Set the directories which @value{GDBN} searches for separate debugging
15261 information files to @var{directory}. Multiple directory components can be set
15262 concatenating them by a directory separator.
15264 @kindex show debug-file-directory
15265 @item show debug-file-directory
15266 Show the directories @value{GDBN} searches for separate debugging
15271 @cindex @code{.gnu_debuglink} sections
15272 @cindex debug link sections
15273 A debug link is a special section of the executable file named
15274 @code{.gnu_debuglink}. The section must contain:
15278 A filename, with any leading directory components removed, followed by
15281 zero to three bytes of padding, as needed to reach the next four-byte
15282 boundary within the section, and
15284 a four-byte CRC checksum, stored in the same endianness used for the
15285 executable file itself. The checksum is computed on the debugging
15286 information file's full contents by the function given below, passing
15287 zero as the @var{crc} argument.
15290 Any executable file format can carry a debug link, as long as it can
15291 contain a section named @code{.gnu_debuglink} with the contents
15294 @cindex @code{.note.gnu.build-id} sections
15295 @cindex build ID sections
15296 The build ID is a special section in the executable file (and in other
15297 ELF binary files that @value{GDBN} may consider). This section is
15298 often named @code{.note.gnu.build-id}, but that name is not mandatory.
15299 It contains unique identification for the built files---the ID remains
15300 the same across multiple builds of the same build tree. The default
15301 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
15302 content for the build ID string. The same section with an identical
15303 value is present in the original built binary with symbols, in its
15304 stripped variant, and in the separate debugging information file.
15306 The debugging information file itself should be an ordinary
15307 executable, containing a full set of linker symbols, sections, and
15308 debugging information. The sections of the debugging information file
15309 should have the same names, addresses, and sizes as the original file,
15310 but they need not contain any data---much like a @code{.bss} section
15311 in an ordinary executable.
15313 The @sc{gnu} binary utilities (Binutils) package includes the
15314 @samp{objcopy} utility that can produce
15315 the separated executable / debugging information file pairs using the
15316 following commands:
15319 @kbd{objcopy --only-keep-debug foo foo.debug}
15324 These commands remove the debugging
15325 information from the executable file @file{foo} and place it in the file
15326 @file{foo.debug}. You can use the first, second or both methods to link the
15331 The debug link method needs the following additional command to also leave
15332 behind a debug link in @file{foo}:
15335 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
15338 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
15339 a version of the @code{strip} command such that the command @kbd{strip foo -f
15340 foo.debug} has the same functionality as the two @code{objcopy} commands and
15341 the @code{ln -s} command above, together.
15344 Build ID gets embedded into the main executable using @code{ld --build-id} or
15345 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
15346 compatibility fixes for debug files separation are present in @sc{gnu} binary
15347 utilities (Binutils) package since version 2.18.
15352 @cindex CRC algorithm definition
15353 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
15354 IEEE 802.3 using the polynomial:
15356 @c TexInfo requires naked braces for multi-digit exponents for Tex
15357 @c output, but this causes HTML output to barf. HTML has to be set using
15358 @c raw commands. So we end up having to specify this equation in 2
15363 <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>
15364 + <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
15370 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
15371 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
15375 The function is computed byte at a time, taking the least
15376 significant bit of each byte first. The initial pattern
15377 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
15378 the final result is inverted to ensure trailing zeros also affect the
15381 @emph{Note:} This is the same CRC polynomial as used in handling the
15382 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
15383 , @value{GDBN} Remote Serial Protocol}). However in the
15384 case of the Remote Serial Protocol, the CRC is computed @emph{most}
15385 significant bit first, and the result is not inverted, so trailing
15386 zeros have no effect on the CRC value.
15388 To complete the description, we show below the code of the function
15389 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
15390 initially supplied @code{crc} argument means that an initial call to
15391 this function passing in zero will start computing the CRC using
15394 @kindex gnu_debuglink_crc32
15397 gnu_debuglink_crc32 (unsigned long crc,
15398 unsigned char *buf, size_t len)
15400 static const unsigned long crc32_table[256] =
15402 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
15403 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
15404 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
15405 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
15406 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
15407 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
15408 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
15409 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
15410 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
15411 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
15412 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
15413 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
15414 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
15415 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
15416 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
15417 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
15418 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
15419 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
15420 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
15421 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
15422 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
15423 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
15424 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
15425 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
15426 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
15427 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
15428 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
15429 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
15430 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
15431 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
15432 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
15433 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
15434 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
15435 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
15436 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
15437 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
15438 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
15439 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
15440 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
15441 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
15442 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
15443 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
15444 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
15445 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
15446 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
15447 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
15448 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
15449 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
15450 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
15451 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
15452 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
15455 unsigned char *end;
15457 crc = ~crc & 0xffffffff;
15458 for (end = buf + len; buf < end; ++buf)
15459 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
15460 return ~crc & 0xffffffff;
15465 This computation does not apply to the ``build ID'' method.
15469 @section Index Files Speed Up @value{GDBN}
15470 @cindex index files
15471 @cindex @samp{.gdb_index} section
15473 When @value{GDBN} finds a symbol file, it scans the symbols in the
15474 file in order to construct an internal symbol table. This lets most
15475 @value{GDBN} operations work quickly---at the cost of a delay early
15476 on. For large programs, this delay can be quite lengthy, so
15477 @value{GDBN} provides a way to build an index, which speeds up
15480 The index is stored as a section in the symbol file. @value{GDBN} can
15481 write the index to a file, then you can put it into the symbol file
15482 using @command{objcopy}.
15484 To create an index file, use the @code{save gdb-index} command:
15487 @item save gdb-index @var{directory}
15488 @kindex save gdb-index
15489 Create an index file for each symbol file currently known by
15490 @value{GDBN}. Each file is named after its corresponding symbol file,
15491 with @samp{.gdb-index} appended, and is written into the given
15495 Once you have created an index file you can merge it into your symbol
15496 file, here named @file{symfile}, using @command{objcopy}:
15499 $ objcopy --add-section .gdb_index=symfile.gdb-index \
15500 --set-section-flags .gdb_index=readonly symfile symfile
15503 There are currently some limitation on indices. They only work when
15504 for DWARF debugging information, not stabs. And, they do not
15505 currently work for programs using Ada.
15507 @node Symbol Errors
15508 @section Errors Reading Symbol Files
15510 While reading a symbol file, @value{GDBN} occasionally encounters problems,
15511 such as symbol types it does not recognize, or known bugs in compiler
15512 output. By default, @value{GDBN} does not notify you of such problems, since
15513 they are relatively common and primarily of interest to people
15514 debugging compilers. If you are interested in seeing information
15515 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
15516 only one message about each such type of problem, no matter how many
15517 times the problem occurs; or you can ask @value{GDBN} to print more messages,
15518 to see how many times the problems occur, with the @code{set
15519 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
15522 The messages currently printed, and their meanings, include:
15525 @item inner block not inside outer block in @var{symbol}
15527 The symbol information shows where symbol scopes begin and end
15528 (such as at the start of a function or a block of statements). This
15529 error indicates that an inner scope block is not fully contained
15530 in its outer scope blocks.
15532 @value{GDBN} circumvents the problem by treating the inner block as if it had
15533 the same scope as the outer block. In the error message, @var{symbol}
15534 may be shown as ``@code{(don't know)}'' if the outer block is not a
15537 @item block at @var{address} out of order
15539 The symbol information for symbol scope blocks should occur in
15540 order of increasing addresses. This error indicates that it does not
15543 @value{GDBN} does not circumvent this problem, and has trouble
15544 locating symbols in the source file whose symbols it is reading. (You
15545 can often determine what source file is affected by specifying
15546 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
15549 @item bad block start address patched
15551 The symbol information for a symbol scope block has a start address
15552 smaller than the address of the preceding source line. This is known
15553 to occur in the SunOS 4.1.1 (and earlier) C compiler.
15555 @value{GDBN} circumvents the problem by treating the symbol scope block as
15556 starting on the previous source line.
15558 @item bad string table offset in symbol @var{n}
15561 Symbol number @var{n} contains a pointer into the string table which is
15562 larger than the size of the string table.
15564 @value{GDBN} circumvents the problem by considering the symbol to have the
15565 name @code{foo}, which may cause other problems if many symbols end up
15568 @item unknown symbol type @code{0x@var{nn}}
15570 The symbol information contains new data types that @value{GDBN} does
15571 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
15572 uncomprehended information, in hexadecimal.
15574 @value{GDBN} circumvents the error by ignoring this symbol information.
15575 This usually allows you to debug your program, though certain symbols
15576 are not accessible. If you encounter such a problem and feel like
15577 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
15578 on @code{complain}, then go up to the function @code{read_dbx_symtab}
15579 and examine @code{*bufp} to see the symbol.
15581 @item stub type has NULL name
15583 @value{GDBN} could not find the full definition for a struct or class.
15585 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
15586 The symbol information for a C@t{++} member function is missing some
15587 information that recent versions of the compiler should have output for
15590 @item info mismatch between compiler and debugger
15592 @value{GDBN} could not parse a type specification output by the compiler.
15597 @section GDB Data Files
15599 @cindex prefix for data files
15600 @value{GDBN} will sometimes read an auxiliary data file. These files
15601 are kept in a directory known as the @dfn{data directory}.
15603 You can set the data directory's name, and view the name @value{GDBN}
15604 is currently using.
15607 @kindex set data-directory
15608 @item set data-directory @var{directory}
15609 Set the directory which @value{GDBN} searches for auxiliary data files
15610 to @var{directory}.
15612 @kindex show data-directory
15613 @item show data-directory
15614 Show the directory @value{GDBN} searches for auxiliary data files.
15617 @cindex default data directory
15618 @cindex @samp{--with-gdb-datadir}
15619 You can set the default data directory by using the configure-time
15620 @samp{--with-gdb-datadir} option. If the data directory is inside
15621 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
15622 @samp{--exec-prefix}), then the default data directory will be updated
15623 automatically if the installed @value{GDBN} is moved to a new
15626 The data directory may also be specified with the
15627 @code{--data-directory} command line option.
15628 @xref{Mode Options}.
15631 @chapter Specifying a Debugging Target
15633 @cindex debugging target
15634 A @dfn{target} is the execution environment occupied by your program.
15636 Often, @value{GDBN} runs in the same host environment as your program;
15637 in that case, the debugging target is specified as a side effect when
15638 you use the @code{file} or @code{core} commands. When you need more
15639 flexibility---for example, running @value{GDBN} on a physically separate
15640 host, or controlling a standalone system over a serial port or a
15641 realtime system over a TCP/IP connection---you can use the @code{target}
15642 command to specify one of the target types configured for @value{GDBN}
15643 (@pxref{Target Commands, ,Commands for Managing Targets}).
15645 @cindex target architecture
15646 It is possible to build @value{GDBN} for several different @dfn{target
15647 architectures}. When @value{GDBN} is built like that, you can choose
15648 one of the available architectures with the @kbd{set architecture}
15652 @kindex set architecture
15653 @kindex show architecture
15654 @item set architecture @var{arch}
15655 This command sets the current target architecture to @var{arch}. The
15656 value of @var{arch} can be @code{"auto"}, in addition to one of the
15657 supported architectures.
15659 @item show architecture
15660 Show the current target architecture.
15662 @item set processor
15664 @kindex set processor
15665 @kindex show processor
15666 These are alias commands for, respectively, @code{set architecture}
15667 and @code{show architecture}.
15671 * Active Targets:: Active targets
15672 * Target Commands:: Commands for managing targets
15673 * Byte Order:: Choosing target byte order
15676 @node Active Targets
15677 @section Active Targets
15679 @cindex stacking targets
15680 @cindex active targets
15681 @cindex multiple targets
15683 There are multiple classes of targets such as: processes, executable files or
15684 recording sessions. Core files belong to the process class, making core file
15685 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
15686 on multiple active targets, one in each class. This allows you to (for
15687 example) start a process and inspect its activity, while still having access to
15688 the executable file after the process finishes. Or if you start process
15689 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
15690 presented a virtual layer of the recording target, while the process target
15691 remains stopped at the chronologically last point of the process execution.
15693 Use the @code{core-file} and @code{exec-file} commands to select a new core
15694 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
15695 specify as a target a process that is already running, use the @code{attach}
15696 command (@pxref{Attach, ,Debugging an Already-running Process}).
15698 @node Target Commands
15699 @section Commands for Managing Targets
15702 @item target @var{type} @var{parameters}
15703 Connects the @value{GDBN} host environment to a target machine or
15704 process. A target is typically a protocol for talking to debugging
15705 facilities. You use the argument @var{type} to specify the type or
15706 protocol of the target machine.
15708 Further @var{parameters} are interpreted by the target protocol, but
15709 typically include things like device names or host names to connect
15710 with, process numbers, and baud rates.
15712 The @code{target} command does not repeat if you press @key{RET} again
15713 after executing the command.
15715 @kindex help target
15717 Displays the names of all targets available. To display targets
15718 currently selected, use either @code{info target} or @code{info files}
15719 (@pxref{Files, ,Commands to Specify Files}).
15721 @item help target @var{name}
15722 Describe a particular target, including any parameters necessary to
15725 @kindex set gnutarget
15726 @item set gnutarget @var{args}
15727 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
15728 knows whether it is reading an @dfn{executable},
15729 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
15730 with the @code{set gnutarget} command. Unlike most @code{target} commands,
15731 with @code{gnutarget} the @code{target} refers to a program, not a machine.
15734 @emph{Warning:} To specify a file format with @code{set gnutarget},
15735 you must know the actual BFD name.
15739 @xref{Files, , Commands to Specify Files}.
15741 @kindex show gnutarget
15742 @item show gnutarget
15743 Use the @code{show gnutarget} command to display what file format
15744 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
15745 @value{GDBN} will determine the file format for each file automatically,
15746 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
15749 @cindex common targets
15750 Here are some common targets (available, or not, depending on the GDB
15755 @item target exec @var{program}
15756 @cindex executable file target
15757 An executable file. @samp{target exec @var{program}} is the same as
15758 @samp{exec-file @var{program}}.
15760 @item target core @var{filename}
15761 @cindex core dump file target
15762 A core dump file. @samp{target core @var{filename}} is the same as
15763 @samp{core-file @var{filename}}.
15765 @item target remote @var{medium}
15766 @cindex remote target
15767 A remote system connected to @value{GDBN} via a serial line or network
15768 connection. This command tells @value{GDBN} to use its own remote
15769 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
15771 For example, if you have a board connected to @file{/dev/ttya} on the
15772 machine running @value{GDBN}, you could say:
15775 target remote /dev/ttya
15778 @code{target remote} supports the @code{load} command. This is only
15779 useful if you have some other way of getting the stub to the target
15780 system, and you can put it somewhere in memory where it won't get
15781 clobbered by the download.
15783 @item target sim @r{[}@var{simargs}@r{]} @dots{}
15784 @cindex built-in simulator target
15785 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
15793 works; however, you cannot assume that a specific memory map, device
15794 drivers, or even basic I/O is available, although some simulators do
15795 provide these. For info about any processor-specific simulator details,
15796 see the appropriate section in @ref{Embedded Processors, ,Embedded
15801 Some configurations may include these targets as well:
15805 @item target nrom @var{dev}
15806 @cindex NetROM ROM emulator target
15807 NetROM ROM emulator. This target only supports downloading.
15811 Different targets are available on different configurations of @value{GDBN};
15812 your configuration may have more or fewer targets.
15814 Many remote targets require you to download the executable's code once
15815 you've successfully established a connection. You may wish to control
15816 various aspects of this process.
15821 @kindex set hash@r{, for remote monitors}
15822 @cindex hash mark while downloading
15823 This command controls whether a hash mark @samp{#} is displayed while
15824 downloading a file to the remote monitor. If on, a hash mark is
15825 displayed after each S-record is successfully downloaded to the
15829 @kindex show hash@r{, for remote monitors}
15830 Show the current status of displaying the hash mark.
15832 @item set debug monitor
15833 @kindex set debug monitor
15834 @cindex display remote monitor communications
15835 Enable or disable display of communications messages between
15836 @value{GDBN} and the remote monitor.
15838 @item show debug monitor
15839 @kindex show debug monitor
15840 Show the current status of displaying communications between
15841 @value{GDBN} and the remote monitor.
15846 @kindex load @var{filename}
15847 @item load @var{filename}
15849 Depending on what remote debugging facilities are configured into
15850 @value{GDBN}, the @code{load} command may be available. Where it exists, it
15851 is meant to make @var{filename} (an executable) available for debugging
15852 on the remote system---by downloading, or dynamic linking, for example.
15853 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
15854 the @code{add-symbol-file} command.
15856 If your @value{GDBN} does not have a @code{load} command, attempting to
15857 execute it gets the error message ``@code{You can't do that when your
15858 target is @dots{}}''
15860 The file is loaded at whatever address is specified in the executable.
15861 For some object file formats, you can specify the load address when you
15862 link the program; for other formats, like a.out, the object file format
15863 specifies a fixed address.
15864 @c FIXME! This would be a good place for an xref to the GNU linker doc.
15866 Depending on the remote side capabilities, @value{GDBN} may be able to
15867 load programs into flash memory.
15869 @code{load} does not repeat if you press @key{RET} again after using it.
15873 @section Choosing Target Byte Order
15875 @cindex choosing target byte order
15876 @cindex target byte order
15878 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
15879 offer the ability to run either big-endian or little-endian byte
15880 orders. Usually the executable or symbol will include a bit to
15881 designate the endian-ness, and you will not need to worry about
15882 which to use. However, you may still find it useful to adjust
15883 @value{GDBN}'s idea of processor endian-ness manually.
15887 @item set endian big
15888 Instruct @value{GDBN} to assume the target is big-endian.
15890 @item set endian little
15891 Instruct @value{GDBN} to assume the target is little-endian.
15893 @item set endian auto
15894 Instruct @value{GDBN} to use the byte order associated with the
15898 Display @value{GDBN}'s current idea of the target byte order.
15902 Note that these commands merely adjust interpretation of symbolic
15903 data on the host, and that they have absolutely no effect on the
15907 @node Remote Debugging
15908 @chapter Debugging Remote Programs
15909 @cindex remote debugging
15911 If you are trying to debug a program running on a machine that cannot run
15912 @value{GDBN} in the usual way, it is often useful to use remote debugging.
15913 For example, you might use remote debugging on an operating system kernel,
15914 or on a small system which does not have a general purpose operating system
15915 powerful enough to run a full-featured debugger.
15917 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
15918 to make this work with particular debugging targets. In addition,
15919 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
15920 but not specific to any particular target system) which you can use if you
15921 write the remote stubs---the code that runs on the remote system to
15922 communicate with @value{GDBN}.
15924 Other remote targets may be available in your
15925 configuration of @value{GDBN}; use @code{help target} to list them.
15928 * Connecting:: Connecting to a remote target
15929 * File Transfer:: Sending files to a remote system
15930 * Server:: Using the gdbserver program
15931 * Remote Configuration:: Remote configuration
15932 * Remote Stub:: Implementing a remote stub
15936 @section Connecting to a Remote Target
15938 On the @value{GDBN} host machine, you will need an unstripped copy of
15939 your program, since @value{GDBN} needs symbol and debugging information.
15940 Start up @value{GDBN} as usual, using the name of the local copy of your
15941 program as the first argument.
15943 @cindex @code{target remote}
15944 @value{GDBN} can communicate with the target over a serial line, or
15945 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
15946 each case, @value{GDBN} uses the same protocol for debugging your
15947 program; only the medium carrying the debugging packets varies. The
15948 @code{target remote} command establishes a connection to the target.
15949 Its arguments indicate which medium to use:
15953 @item target remote @var{serial-device}
15954 @cindex serial line, @code{target remote}
15955 Use @var{serial-device} to communicate with the target. For example,
15956 to use a serial line connected to the device named @file{/dev/ttyb}:
15959 target remote /dev/ttyb
15962 If you're using a serial line, you may want to give @value{GDBN} the
15963 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
15964 (@pxref{Remote Configuration, set remotebaud}) before the
15965 @code{target} command.
15967 @item target remote @code{@var{host}:@var{port}}
15968 @itemx target remote @code{tcp:@var{host}:@var{port}}
15969 @cindex @acronym{TCP} port, @code{target remote}
15970 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
15971 The @var{host} may be either a host name or a numeric @acronym{IP}
15972 address; @var{port} must be a decimal number. The @var{host} could be
15973 the target machine itself, if it is directly connected to the net, or
15974 it might be a terminal server which in turn has a serial line to the
15977 For example, to connect to port 2828 on a terminal server named
15981 target remote manyfarms:2828
15984 If your remote target is actually running on the same machine as your
15985 debugger session (e.g.@: a simulator for your target running on the
15986 same host), you can omit the hostname. For example, to connect to
15987 port 1234 on your local machine:
15990 target remote :1234
15994 Note that the colon is still required here.
15996 @item target remote @code{udp:@var{host}:@var{port}}
15997 @cindex @acronym{UDP} port, @code{target remote}
15998 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
15999 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
16002 target remote udp:manyfarms:2828
16005 When using a @acronym{UDP} connection for remote debugging, you should
16006 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
16007 can silently drop packets on busy or unreliable networks, which will
16008 cause havoc with your debugging session.
16010 @item target remote | @var{command}
16011 @cindex pipe, @code{target remote} to
16012 Run @var{command} in the background and communicate with it using a
16013 pipe. The @var{command} is a shell command, to be parsed and expanded
16014 by the system's command shell, @code{/bin/sh}; it should expect remote
16015 protocol packets on its standard input, and send replies on its
16016 standard output. You could use this to run a stand-alone simulator
16017 that speaks the remote debugging protocol, to make net connections
16018 using programs like @code{ssh}, or for other similar tricks.
16020 If @var{command} closes its standard output (perhaps by exiting),
16021 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
16022 program has already exited, this will have no effect.)
16026 Once the connection has been established, you can use all the usual
16027 commands to examine and change data. The remote program is already
16028 running; you can use @kbd{step} and @kbd{continue}, and you do not
16029 need to use @kbd{run}.
16031 @cindex interrupting remote programs
16032 @cindex remote programs, interrupting
16033 Whenever @value{GDBN} is waiting for the remote program, if you type the
16034 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
16035 program. This may or may not succeed, depending in part on the hardware
16036 and the serial drivers the remote system uses. If you type the
16037 interrupt character once again, @value{GDBN} displays this prompt:
16040 Interrupted while waiting for the program.
16041 Give up (and stop debugging it)? (y or n)
16044 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
16045 (If you decide you want to try again later, you can use @samp{target
16046 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
16047 goes back to waiting.
16050 @kindex detach (remote)
16052 When you have finished debugging the remote program, you can use the
16053 @code{detach} command to release it from @value{GDBN} control.
16054 Detaching from the target normally resumes its execution, but the results
16055 will depend on your particular remote stub. After the @code{detach}
16056 command, @value{GDBN} is free to connect to another target.
16060 The @code{disconnect} command behaves like @code{detach}, except that
16061 the target is generally not resumed. It will wait for @value{GDBN}
16062 (this instance or another one) to connect and continue debugging. After
16063 the @code{disconnect} command, @value{GDBN} is again free to connect to
16066 @cindex send command to remote monitor
16067 @cindex extend @value{GDBN} for remote targets
16068 @cindex add new commands for external monitor
16070 @item monitor @var{cmd}
16071 This command allows you to send arbitrary commands directly to the
16072 remote monitor. Since @value{GDBN} doesn't care about the commands it
16073 sends like this, this command is the way to extend @value{GDBN}---you
16074 can add new commands that only the external monitor will understand
16078 @node File Transfer
16079 @section Sending files to a remote system
16080 @cindex remote target, file transfer
16081 @cindex file transfer
16082 @cindex sending files to remote systems
16084 Some remote targets offer the ability to transfer files over the same
16085 connection used to communicate with @value{GDBN}. This is convenient
16086 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
16087 running @code{gdbserver} over a network interface. For other targets,
16088 e.g.@: embedded devices with only a single serial port, this may be
16089 the only way to upload or download files.
16091 Not all remote targets support these commands.
16095 @item remote put @var{hostfile} @var{targetfile}
16096 Copy file @var{hostfile} from the host system (the machine running
16097 @value{GDBN}) to @var{targetfile} on the target system.
16100 @item remote get @var{targetfile} @var{hostfile}
16101 Copy file @var{targetfile} from the target system to @var{hostfile}
16102 on the host system.
16104 @kindex remote delete
16105 @item remote delete @var{targetfile}
16106 Delete @var{targetfile} from the target system.
16111 @section Using the @code{gdbserver} Program
16114 @cindex remote connection without stubs
16115 @code{gdbserver} is a control program for Unix-like systems, which
16116 allows you to connect your program with a remote @value{GDBN} via
16117 @code{target remote}---but without linking in the usual debugging stub.
16119 @code{gdbserver} is not a complete replacement for the debugging stubs,
16120 because it requires essentially the same operating-system facilities
16121 that @value{GDBN} itself does. In fact, a system that can run
16122 @code{gdbserver} to connect to a remote @value{GDBN} could also run
16123 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
16124 because it is a much smaller program than @value{GDBN} itself. It is
16125 also easier to port than all of @value{GDBN}, so you may be able to get
16126 started more quickly on a new system by using @code{gdbserver}.
16127 Finally, if you develop code for real-time systems, you may find that
16128 the tradeoffs involved in real-time operation make it more convenient to
16129 do as much development work as possible on another system, for example
16130 by cross-compiling. You can use @code{gdbserver} to make a similar
16131 choice for debugging.
16133 @value{GDBN} and @code{gdbserver} communicate via either a serial line
16134 or a TCP connection, using the standard @value{GDBN} remote serial
16138 @emph{Warning:} @code{gdbserver} does not have any built-in security.
16139 Do not run @code{gdbserver} connected to any public network; a
16140 @value{GDBN} connection to @code{gdbserver} provides access to the
16141 target system with the same privileges as the user running
16145 @subsection Running @code{gdbserver}
16146 @cindex arguments, to @code{gdbserver}
16148 Run @code{gdbserver} on the target system. You need a copy of the
16149 program you want to debug, including any libraries it requires.
16150 @code{gdbserver} does not need your program's symbol table, so you can
16151 strip the program if necessary to save space. @value{GDBN} on the host
16152 system does all the symbol handling.
16154 To use the server, you must tell it how to communicate with @value{GDBN};
16155 the name of your program; and the arguments for your program. The usual
16159 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
16162 @var{comm} is either a device name (to use a serial line) or a TCP
16163 hostname and portnumber. For example, to debug Emacs with the argument
16164 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
16168 target> gdbserver /dev/com1 emacs foo.txt
16171 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
16174 To use a TCP connection instead of a serial line:
16177 target> gdbserver host:2345 emacs foo.txt
16180 The only difference from the previous example is the first argument,
16181 specifying that you are communicating with the host @value{GDBN} via
16182 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
16183 expect a TCP connection from machine @samp{host} to local TCP port 2345.
16184 (Currently, the @samp{host} part is ignored.) You can choose any number
16185 you want for the port number as long as it does not conflict with any
16186 TCP ports already in use on the target system (for example, @code{23} is
16187 reserved for @code{telnet}).@footnote{If you choose a port number that
16188 conflicts with another service, @code{gdbserver} prints an error message
16189 and exits.} You must use the same port number with the host @value{GDBN}
16190 @code{target remote} command.
16192 @subsubsection Attaching to a Running Program
16194 On some targets, @code{gdbserver} can also attach to running programs.
16195 This is accomplished via the @code{--attach} argument. The syntax is:
16198 target> gdbserver --attach @var{comm} @var{pid}
16201 @var{pid} is the process ID of a currently running process. It isn't necessary
16202 to point @code{gdbserver} at a binary for the running process.
16205 @cindex attach to a program by name
16206 You can debug processes by name instead of process ID if your target has the
16207 @code{pidof} utility:
16210 target> gdbserver --attach @var{comm} `pidof @var{program}`
16213 In case more than one copy of @var{program} is running, or @var{program}
16214 has multiple threads, most versions of @code{pidof} support the
16215 @code{-s} option to only return the first process ID.
16217 @subsubsection Multi-Process Mode for @code{gdbserver}
16218 @cindex gdbserver, multiple processes
16219 @cindex multiple processes with gdbserver
16221 When you connect to @code{gdbserver} using @code{target remote},
16222 @code{gdbserver} debugs the specified program only once. When the
16223 program exits, or you detach from it, @value{GDBN} closes the connection
16224 and @code{gdbserver} exits.
16226 If you connect using @kbd{target extended-remote}, @code{gdbserver}
16227 enters multi-process mode. When the debugged program exits, or you
16228 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
16229 though no program is running. The @code{run} and @code{attach}
16230 commands instruct @code{gdbserver} to run or attach to a new program.
16231 The @code{run} command uses @code{set remote exec-file} (@pxref{set
16232 remote exec-file}) to select the program to run. Command line
16233 arguments are supported, except for wildcard expansion and I/O
16234 redirection (@pxref{Arguments}).
16236 To start @code{gdbserver} without supplying an initial command to run
16237 or process ID to attach, use the @option{--multi} command line option.
16238 Then you can connect using @kbd{target extended-remote} and start
16239 the program you want to debug.
16241 @code{gdbserver} does not automatically exit in multi-process mode.
16242 You can terminate it by using @code{monitor exit}
16243 (@pxref{Monitor Commands for gdbserver}).
16245 @subsubsection Other Command-Line Arguments for @code{gdbserver}
16247 The @option{--debug} option tells @code{gdbserver} to display extra
16248 status information about the debugging process. The
16249 @option{--remote-debug} option tells @code{gdbserver} to display
16250 remote protocol debug output. These options are intended for
16251 @code{gdbserver} development and for bug reports to the developers.
16253 The @option{--wrapper} option specifies a wrapper to launch programs
16254 for debugging. The option should be followed by the name of the
16255 wrapper, then any command-line arguments to pass to the wrapper, then
16256 @kbd{--} indicating the end of the wrapper arguments.
16258 @code{gdbserver} runs the specified wrapper program with a combined
16259 command line including the wrapper arguments, then the name of the
16260 program to debug, then any arguments to the program. The wrapper
16261 runs until it executes your program, and then @value{GDBN} gains control.
16263 You can use any program that eventually calls @code{execve} with
16264 its arguments as a wrapper. Several standard Unix utilities do
16265 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
16266 with @code{exec "$@@"} will also work.
16268 For example, you can use @code{env} to pass an environment variable to
16269 the debugged program, without setting the variable in @code{gdbserver}'s
16273 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
16276 @subsection Connecting to @code{gdbserver}
16278 Run @value{GDBN} on the host system.
16280 First make sure you have the necessary symbol files. Load symbols for
16281 your application using the @code{file} command before you connect. Use
16282 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
16283 was compiled with the correct sysroot using @code{--with-sysroot}).
16285 The symbol file and target libraries must exactly match the executable
16286 and libraries on the target, with one exception: the files on the host
16287 system should not be stripped, even if the files on the target system
16288 are. Mismatched or missing files will lead to confusing results
16289 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
16290 files may also prevent @code{gdbserver} from debugging multi-threaded
16293 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
16294 For TCP connections, you must start up @code{gdbserver} prior to using
16295 the @code{target remote} command. Otherwise you may get an error whose
16296 text depends on the host system, but which usually looks something like
16297 @samp{Connection refused}. Don't use the @code{load}
16298 command in @value{GDBN} when using @code{gdbserver}, since the program is
16299 already on the target.
16301 @subsection Monitor Commands for @code{gdbserver}
16302 @cindex monitor commands, for @code{gdbserver}
16303 @anchor{Monitor Commands for gdbserver}
16305 During a @value{GDBN} session using @code{gdbserver}, you can use the
16306 @code{monitor} command to send special requests to @code{gdbserver}.
16307 Here are the available commands.
16311 List the available monitor commands.
16313 @item monitor set debug 0
16314 @itemx monitor set debug 1
16315 Disable or enable general debugging messages.
16317 @item monitor set remote-debug 0
16318 @itemx monitor set remote-debug 1
16319 Disable or enable specific debugging messages associated with the remote
16320 protocol (@pxref{Remote Protocol}).
16322 @item monitor set libthread-db-search-path [PATH]
16323 @cindex gdbserver, search path for @code{libthread_db}
16324 When this command is issued, @var{path} is a colon-separated list of
16325 directories to search for @code{libthread_db} (@pxref{Threads,,set
16326 libthread-db-search-path}). If you omit @var{path},
16327 @samp{libthread-db-search-path} will be reset to an empty list.
16330 Tell gdbserver to exit immediately. This command should be followed by
16331 @code{disconnect} to close the debugging session. @code{gdbserver} will
16332 detach from any attached processes and kill any processes it created.
16333 Use @code{monitor exit} to terminate @code{gdbserver} at the end
16334 of a multi-process mode debug session.
16338 @subsection Tracepoints support in @code{gdbserver}
16339 @cindex tracepoints support in @code{gdbserver}
16341 On some targets, @code{gdbserver} supports tracepoints, fast
16342 tracepoints and static tracepoints.
16344 For fast or static tracepoints to work, a special library called the
16345 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
16346 This library is built and distributed as an integral part of
16347 @code{gdbserver}. In addition, support for static tracepoints
16348 requires building the in-process agent library with static tracepoints
16349 support. At present, the UST (LTTng Userspace Tracer,
16350 @url{http://lttng.org/ust}) tracing engine is supported. This support
16351 is automatically available if UST development headers are found in the
16352 standard include path when @code{gdbserver} is built, or if
16353 @code{gdbserver} was explicitly configured using @option{--with-ust}
16354 to point at such headers. You can explicitly disable the support
16355 using @option{--with-ust=no}.
16357 There are several ways to load the in-process agent in your program:
16360 @item Specifying it as dependency at link time
16362 You can link your program dynamically with the in-process agent
16363 library. On most systems, this is accomplished by adding
16364 @code{-linproctrace} to the link command.
16366 @item Using the system's preloading mechanisms
16368 You can force loading the in-process agent at startup time by using
16369 your system's support for preloading shared libraries. Many Unixes
16370 support the concept of preloading user defined libraries. In most
16371 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
16372 in the environment. See also the description of @code{gdbserver}'s
16373 @option{--wrapper} command line option.
16375 @item Using @value{GDBN} to force loading the agent at run time
16377 On some systems, you can force the inferior to load a shared library,
16378 by calling a dynamic loader function in the inferior that takes care
16379 of dynamically looking up and loading a shared library. On most Unix
16380 systems, the function is @code{dlopen}. You'll use the @code{call}
16381 command for that. For example:
16384 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
16387 Note that on most Unix systems, for the @code{dlopen} function to be
16388 available, the program needs to be linked with @code{-ldl}.
16391 On systems that have a userspace dynamic loader, like most Unix
16392 systems, when you connect to @code{gdbserver} using @code{target
16393 remote}, you'll find that the program is stopped at the dynamic
16394 loader's entry point, and no shared library has been loaded in the
16395 program's address space yet, including the in-process agent. In that
16396 case, before being able to use any of the fast or static tracepoints
16397 features, you need to let the loader run and load the shared
16398 libraries. The simplest way to do that is to run the program to the
16399 main procedure. E.g., if debugging a C or C@t{++} program, start
16400 @code{gdbserver} like so:
16403 $ gdbserver :9999 myprogram
16406 Start GDB and connect to @code{gdbserver} like so, and run to main:
16410 (@value{GDBP}) target remote myhost:9999
16411 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
16412 (@value{GDBP}) b main
16413 (@value{GDBP}) continue
16416 The in-process tracing agent library should now be loaded into the
16417 process; you can confirm it with the @code{info sharedlibrary}
16418 command, which will list @file{libinproctrace.so} as loaded in the
16419 process. You are now ready to install fast tracepoints, list static
16420 tracepoint markers, probe static tracepoints markers, and start
16423 @node Remote Configuration
16424 @section Remote Configuration
16427 @kindex show remote
16428 This section documents the configuration options available when
16429 debugging remote programs. For the options related to the File I/O
16430 extensions of the remote protocol, see @ref{system,
16431 system-call-allowed}.
16434 @item set remoteaddresssize @var{bits}
16435 @cindex address size for remote targets
16436 @cindex bits in remote address
16437 Set the maximum size of address in a memory packet to the specified
16438 number of bits. @value{GDBN} will mask off the address bits above
16439 that number, when it passes addresses to the remote target. The
16440 default value is the number of bits in the target's address.
16442 @item show remoteaddresssize
16443 Show the current value of remote address size in bits.
16445 @item set remotebaud @var{n}
16446 @cindex baud rate for remote targets
16447 Set the baud rate for the remote serial I/O to @var{n} baud. The
16448 value is used to set the speed of the serial port used for debugging
16451 @item show remotebaud
16452 Show the current speed of the remote connection.
16454 @item set remotebreak
16455 @cindex interrupt remote programs
16456 @cindex BREAK signal instead of Ctrl-C
16457 @anchor{set remotebreak}
16458 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
16459 when you type @kbd{Ctrl-c} to interrupt the program running
16460 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
16461 character instead. The default is off, since most remote systems
16462 expect to see @samp{Ctrl-C} as the interrupt signal.
16464 @item show remotebreak
16465 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
16466 interrupt the remote program.
16468 @item set remoteflow on
16469 @itemx set remoteflow off
16470 @kindex set remoteflow
16471 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
16472 on the serial port used to communicate to the remote target.
16474 @item show remoteflow
16475 @kindex show remoteflow
16476 Show the current setting of hardware flow control.
16478 @item set remotelogbase @var{base}
16479 Set the base (a.k.a.@: radix) of logging serial protocol
16480 communications to @var{base}. Supported values of @var{base} are:
16481 @code{ascii}, @code{octal}, and @code{hex}. The default is
16484 @item show remotelogbase
16485 Show the current setting of the radix for logging remote serial
16488 @item set remotelogfile @var{file}
16489 @cindex record serial communications on file
16490 Record remote serial communications on the named @var{file}. The
16491 default is not to record at all.
16493 @item show remotelogfile.
16494 Show the current setting of the file name on which to record the
16495 serial communications.
16497 @item set remotetimeout @var{num}
16498 @cindex timeout for serial communications
16499 @cindex remote timeout
16500 Set the timeout limit to wait for the remote target to respond to
16501 @var{num} seconds. The default is 2 seconds.
16503 @item show remotetimeout
16504 Show the current number of seconds to wait for the remote target
16507 @cindex limit hardware breakpoints and watchpoints
16508 @cindex remote target, limit break- and watchpoints
16509 @anchor{set remote hardware-watchpoint-limit}
16510 @anchor{set remote hardware-breakpoint-limit}
16511 @item set remote hardware-watchpoint-limit @var{limit}
16512 @itemx set remote hardware-breakpoint-limit @var{limit}
16513 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
16514 watchpoints. A limit of -1, the default, is treated as unlimited.
16516 @item set remote exec-file @var{filename}
16517 @itemx show remote exec-file
16518 @anchor{set remote exec-file}
16519 @cindex executable file, for remote target
16520 Select the file used for @code{run} with @code{target
16521 extended-remote}. This should be set to a filename valid on the
16522 target system. If it is not set, the target will use a default
16523 filename (e.g.@: the last program run).
16525 @item set remote interrupt-sequence
16526 @cindex interrupt remote programs
16527 @cindex select Ctrl-C, BREAK or BREAK-g
16528 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
16529 @samp{BREAK-g} as the
16530 sequence to the remote target in order to interrupt the execution.
16531 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
16532 is high level of serial line for some certain time.
16533 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
16534 It is @code{BREAK} signal followed by character @code{g}.
16536 @item show interrupt-sequence
16537 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
16538 is sent by @value{GDBN} to interrupt the remote program.
16539 @code{BREAK-g} is BREAK signal followed by @code{g} and
16540 also known as Magic SysRq g.
16542 @item set remote interrupt-on-connect
16543 @cindex send interrupt-sequence on start
16544 Specify whether interrupt-sequence is sent to remote target when
16545 @value{GDBN} connects to it. This is mostly needed when you debug
16546 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
16547 which is known as Magic SysRq g in order to connect @value{GDBN}.
16549 @item show interrupt-on-connect
16550 Show whether interrupt-sequence is sent
16551 to remote target when @value{GDBN} connects to it.
16555 @item set tcp auto-retry on
16556 @cindex auto-retry, for remote TCP target
16557 Enable auto-retry for remote TCP connections. This is useful if the remote
16558 debugging agent is launched in parallel with @value{GDBN}; there is a race
16559 condition because the agent may not become ready to accept the connection
16560 before @value{GDBN} attempts to connect. When auto-retry is
16561 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
16562 to establish the connection using the timeout specified by
16563 @code{set tcp connect-timeout}.
16565 @item set tcp auto-retry off
16566 Do not auto-retry failed TCP connections.
16568 @item show tcp auto-retry
16569 Show the current auto-retry setting.
16571 @item set tcp connect-timeout @var{seconds}
16572 @cindex connection timeout, for remote TCP target
16573 @cindex timeout, for remote target connection
16574 Set the timeout for establishing a TCP connection to the remote target to
16575 @var{seconds}. The timeout affects both polling to retry failed connections
16576 (enabled by @code{set tcp auto-retry on}) and waiting for connections
16577 that are merely slow to complete, and represents an approximate cumulative
16580 @item show tcp connect-timeout
16581 Show the current connection timeout setting.
16584 @cindex remote packets, enabling and disabling
16585 The @value{GDBN} remote protocol autodetects the packets supported by
16586 your debugging stub. If you need to override the autodetection, you
16587 can use these commands to enable or disable individual packets. Each
16588 packet can be set to @samp{on} (the remote target supports this
16589 packet), @samp{off} (the remote target does not support this packet),
16590 or @samp{auto} (detect remote target support for this packet). They
16591 all default to @samp{auto}. For more information about each packet,
16592 see @ref{Remote Protocol}.
16594 During normal use, you should not have to use any of these commands.
16595 If you do, that may be a bug in your remote debugging stub, or a bug
16596 in @value{GDBN}. You may want to report the problem to the
16597 @value{GDBN} developers.
16599 For each packet @var{name}, the command to enable or disable the
16600 packet is @code{set remote @var{name}-packet}. The available settings
16603 @multitable @columnfractions 0.28 0.32 0.25
16606 @tab Related Features
16608 @item @code{fetch-register}
16610 @tab @code{info registers}
16612 @item @code{set-register}
16616 @item @code{binary-download}
16618 @tab @code{load}, @code{set}
16620 @item @code{read-aux-vector}
16621 @tab @code{qXfer:auxv:read}
16622 @tab @code{info auxv}
16624 @item @code{symbol-lookup}
16625 @tab @code{qSymbol}
16626 @tab Detecting multiple threads
16628 @item @code{attach}
16629 @tab @code{vAttach}
16632 @item @code{verbose-resume}
16634 @tab Stepping or resuming multiple threads
16640 @item @code{software-breakpoint}
16644 @item @code{hardware-breakpoint}
16648 @item @code{write-watchpoint}
16652 @item @code{read-watchpoint}
16656 @item @code{access-watchpoint}
16660 @item @code{target-features}
16661 @tab @code{qXfer:features:read}
16662 @tab @code{set architecture}
16664 @item @code{library-info}
16665 @tab @code{qXfer:libraries:read}
16666 @tab @code{info sharedlibrary}
16668 @item @code{memory-map}
16669 @tab @code{qXfer:memory-map:read}
16670 @tab @code{info mem}
16672 @item @code{read-sdata-object}
16673 @tab @code{qXfer:sdata:read}
16674 @tab @code{print $_sdata}
16676 @item @code{read-spu-object}
16677 @tab @code{qXfer:spu:read}
16678 @tab @code{info spu}
16680 @item @code{write-spu-object}
16681 @tab @code{qXfer:spu:write}
16682 @tab @code{info spu}
16684 @item @code{read-siginfo-object}
16685 @tab @code{qXfer:siginfo:read}
16686 @tab @code{print $_siginfo}
16688 @item @code{write-siginfo-object}
16689 @tab @code{qXfer:siginfo:write}
16690 @tab @code{set $_siginfo}
16692 @item @code{threads}
16693 @tab @code{qXfer:threads:read}
16694 @tab @code{info threads}
16696 @item @code{get-thread-local-@*storage-address}
16697 @tab @code{qGetTLSAddr}
16698 @tab Displaying @code{__thread} variables
16700 @item @code{get-thread-information-block-address}
16701 @tab @code{qGetTIBAddr}
16702 @tab Display MS-Windows Thread Information Block.
16704 @item @code{search-memory}
16705 @tab @code{qSearch:memory}
16708 @item @code{supported-packets}
16709 @tab @code{qSupported}
16710 @tab Remote communications parameters
16712 @item @code{pass-signals}
16713 @tab @code{QPassSignals}
16714 @tab @code{handle @var{signal}}
16716 @item @code{hostio-close-packet}
16717 @tab @code{vFile:close}
16718 @tab @code{remote get}, @code{remote put}
16720 @item @code{hostio-open-packet}
16721 @tab @code{vFile:open}
16722 @tab @code{remote get}, @code{remote put}
16724 @item @code{hostio-pread-packet}
16725 @tab @code{vFile:pread}
16726 @tab @code{remote get}, @code{remote put}
16728 @item @code{hostio-pwrite-packet}
16729 @tab @code{vFile:pwrite}
16730 @tab @code{remote get}, @code{remote put}
16732 @item @code{hostio-unlink-packet}
16733 @tab @code{vFile:unlink}
16734 @tab @code{remote delete}
16736 @item @code{noack-packet}
16737 @tab @code{QStartNoAckMode}
16738 @tab Packet acknowledgment
16740 @item @code{osdata}
16741 @tab @code{qXfer:osdata:read}
16742 @tab @code{info os}
16744 @item @code{query-attached}
16745 @tab @code{qAttached}
16746 @tab Querying remote process attach state.
16750 @section Implementing a Remote Stub
16752 @cindex debugging stub, example
16753 @cindex remote stub, example
16754 @cindex stub example, remote debugging
16755 The stub files provided with @value{GDBN} implement the target side of the
16756 communication protocol, and the @value{GDBN} side is implemented in the
16757 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
16758 these subroutines to communicate, and ignore the details. (If you're
16759 implementing your own stub file, you can still ignore the details: start
16760 with one of the existing stub files. @file{sparc-stub.c} is the best
16761 organized, and therefore the easiest to read.)
16763 @cindex remote serial debugging, overview
16764 To debug a program running on another machine (the debugging
16765 @dfn{target} machine), you must first arrange for all the usual
16766 prerequisites for the program to run by itself. For example, for a C
16771 A startup routine to set up the C runtime environment; these usually
16772 have a name like @file{crt0}. The startup routine may be supplied by
16773 your hardware supplier, or you may have to write your own.
16776 A C subroutine library to support your program's
16777 subroutine calls, notably managing input and output.
16780 A way of getting your program to the other machine---for example, a
16781 download program. These are often supplied by the hardware
16782 manufacturer, but you may have to write your own from hardware
16786 The next step is to arrange for your program to use a serial port to
16787 communicate with the machine where @value{GDBN} is running (the @dfn{host}
16788 machine). In general terms, the scheme looks like this:
16792 @value{GDBN} already understands how to use this protocol; when everything
16793 else is set up, you can simply use the @samp{target remote} command
16794 (@pxref{Targets,,Specifying a Debugging Target}).
16796 @item On the target,
16797 you must link with your program a few special-purpose subroutines that
16798 implement the @value{GDBN} remote serial protocol. The file containing these
16799 subroutines is called a @dfn{debugging stub}.
16801 On certain remote targets, you can use an auxiliary program
16802 @code{gdbserver} instead of linking a stub into your program.
16803 @xref{Server,,Using the @code{gdbserver} Program}, for details.
16806 The debugging stub is specific to the architecture of the remote
16807 machine; for example, use @file{sparc-stub.c} to debug programs on
16810 @cindex remote serial stub list
16811 These working remote stubs are distributed with @value{GDBN}:
16816 @cindex @file{i386-stub.c}
16819 For Intel 386 and compatible architectures.
16822 @cindex @file{m68k-stub.c}
16823 @cindex Motorola 680x0
16825 For Motorola 680x0 architectures.
16828 @cindex @file{sh-stub.c}
16831 For Renesas SH architectures.
16834 @cindex @file{sparc-stub.c}
16836 For @sc{sparc} architectures.
16838 @item sparcl-stub.c
16839 @cindex @file{sparcl-stub.c}
16842 For Fujitsu @sc{sparclite} architectures.
16846 The @file{README} file in the @value{GDBN} distribution may list other
16847 recently added stubs.
16850 * Stub Contents:: What the stub can do for you
16851 * Bootstrapping:: What you must do for the stub
16852 * Debug Session:: Putting it all together
16855 @node Stub Contents
16856 @subsection What the Stub Can Do for You
16858 @cindex remote serial stub
16859 The debugging stub for your architecture supplies these three
16863 @item set_debug_traps
16864 @findex set_debug_traps
16865 @cindex remote serial stub, initialization
16866 This routine arranges for @code{handle_exception} to run when your
16867 program stops. You must call this subroutine explicitly near the
16868 beginning of your program.
16870 @item handle_exception
16871 @findex handle_exception
16872 @cindex remote serial stub, main routine
16873 This is the central workhorse, but your program never calls it
16874 explicitly---the setup code arranges for @code{handle_exception} to
16875 run when a trap is triggered.
16877 @code{handle_exception} takes control when your program stops during
16878 execution (for example, on a breakpoint), and mediates communications
16879 with @value{GDBN} on the host machine. This is where the communications
16880 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
16881 representative on the target machine. It begins by sending summary
16882 information on the state of your program, then continues to execute,
16883 retrieving and transmitting any information @value{GDBN} needs, until you
16884 execute a @value{GDBN} command that makes your program resume; at that point,
16885 @code{handle_exception} returns control to your own code on the target
16889 @cindex @code{breakpoint} subroutine, remote
16890 Use this auxiliary subroutine to make your program contain a
16891 breakpoint. Depending on the particular situation, this may be the only
16892 way for @value{GDBN} to get control. For instance, if your target
16893 machine has some sort of interrupt button, you won't need to call this;
16894 pressing the interrupt button transfers control to
16895 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
16896 simply receiving characters on the serial port may also trigger a trap;
16897 again, in that situation, you don't need to call @code{breakpoint} from
16898 your own program---simply running @samp{target remote} from the host
16899 @value{GDBN} session gets control.
16901 Call @code{breakpoint} if none of these is true, or if you simply want
16902 to make certain your program stops at a predetermined point for the
16903 start of your debugging session.
16906 @node Bootstrapping
16907 @subsection What You Must Do for the Stub
16909 @cindex remote stub, support routines
16910 The debugging stubs that come with @value{GDBN} are set up for a particular
16911 chip architecture, but they have no information about the rest of your
16912 debugging target machine.
16914 First of all you need to tell the stub how to communicate with the
16918 @item int getDebugChar()
16919 @findex getDebugChar
16920 Write this subroutine to read a single character from the serial port.
16921 It may be identical to @code{getchar} for your target system; a
16922 different name is used to allow you to distinguish the two if you wish.
16924 @item void putDebugChar(int)
16925 @findex putDebugChar
16926 Write this subroutine to write a single character to the serial port.
16927 It may be identical to @code{putchar} for your target system; a
16928 different name is used to allow you to distinguish the two if you wish.
16931 @cindex control C, and remote debugging
16932 @cindex interrupting remote targets
16933 If you want @value{GDBN} to be able to stop your program while it is
16934 running, you need to use an interrupt-driven serial driver, and arrange
16935 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
16936 character). That is the character which @value{GDBN} uses to tell the
16937 remote system to stop.
16939 Getting the debugging target to return the proper status to @value{GDBN}
16940 probably requires changes to the standard stub; one quick and dirty way
16941 is to just execute a breakpoint instruction (the ``dirty'' part is that
16942 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
16944 Other routines you need to supply are:
16947 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
16948 @findex exceptionHandler
16949 Write this function to install @var{exception_address} in the exception
16950 handling tables. You need to do this because the stub does not have any
16951 way of knowing what the exception handling tables on your target system
16952 are like (for example, the processor's table might be in @sc{rom},
16953 containing entries which point to a table in @sc{ram}).
16954 @var{exception_number} is the exception number which should be changed;
16955 its meaning is architecture-dependent (for example, different numbers
16956 might represent divide by zero, misaligned access, etc). When this
16957 exception occurs, control should be transferred directly to
16958 @var{exception_address}, and the processor state (stack, registers,
16959 and so on) should be just as it is when a processor exception occurs. So if
16960 you want to use a jump instruction to reach @var{exception_address}, it
16961 should be a simple jump, not a jump to subroutine.
16963 For the 386, @var{exception_address} should be installed as an interrupt
16964 gate so that interrupts are masked while the handler runs. The gate
16965 should be at privilege level 0 (the most privileged level). The
16966 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
16967 help from @code{exceptionHandler}.
16969 @item void flush_i_cache()
16970 @findex flush_i_cache
16971 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
16972 instruction cache, if any, on your target machine. If there is no
16973 instruction cache, this subroutine may be a no-op.
16975 On target machines that have instruction caches, @value{GDBN} requires this
16976 function to make certain that the state of your program is stable.
16980 You must also make sure this library routine is available:
16983 @item void *memset(void *, int, int)
16985 This is the standard library function @code{memset} that sets an area of
16986 memory to a known value. If you have one of the free versions of
16987 @code{libc.a}, @code{memset} can be found there; otherwise, you must
16988 either obtain it from your hardware manufacturer, or write your own.
16991 If you do not use the GNU C compiler, you may need other standard
16992 library subroutines as well; this varies from one stub to another,
16993 but in general the stubs are likely to use any of the common library
16994 subroutines which @code{@value{NGCC}} generates as inline code.
16997 @node Debug Session
16998 @subsection Putting it All Together
17000 @cindex remote serial debugging summary
17001 In summary, when your program is ready to debug, you must follow these
17006 Make sure you have defined the supporting low-level routines
17007 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
17009 @code{getDebugChar}, @code{putDebugChar},
17010 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
17014 Insert these lines near the top of your program:
17022 For the 680x0 stub only, you need to provide a variable called
17023 @code{exceptionHook}. Normally you just use:
17026 void (*exceptionHook)() = 0;
17030 but if before calling @code{set_debug_traps}, you set it to point to a
17031 function in your program, that function is called when
17032 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
17033 error). The function indicated by @code{exceptionHook} is called with
17034 one parameter: an @code{int} which is the exception number.
17037 Compile and link together: your program, the @value{GDBN} debugging stub for
17038 your target architecture, and the supporting subroutines.
17041 Make sure you have a serial connection between your target machine and
17042 the @value{GDBN} host, and identify the serial port on the host.
17045 @c The "remote" target now provides a `load' command, so we should
17046 @c document that. FIXME.
17047 Download your program to your target machine (or get it there by
17048 whatever means the manufacturer provides), and start it.
17051 Start @value{GDBN} on the host, and connect to the target
17052 (@pxref{Connecting,,Connecting to a Remote Target}).
17056 @node Configurations
17057 @chapter Configuration-Specific Information
17059 While nearly all @value{GDBN} commands are available for all native and
17060 cross versions of the debugger, there are some exceptions. This chapter
17061 describes things that are only available in certain configurations.
17063 There are three major categories of configurations: native
17064 configurations, where the host and target are the same, embedded
17065 operating system configurations, which are usually the same for several
17066 different processor architectures, and bare embedded processors, which
17067 are quite different from each other.
17072 * Embedded Processors::
17079 This section describes details specific to particular native
17084 * BSD libkvm Interface:: Debugging BSD kernel memory images
17085 * SVR4 Process Information:: SVR4 process information
17086 * DJGPP Native:: Features specific to the DJGPP port
17087 * Cygwin Native:: Features specific to the Cygwin port
17088 * Hurd Native:: Features specific to @sc{gnu} Hurd
17089 * Neutrino:: Features specific to QNX Neutrino
17090 * Darwin:: Features specific to Darwin
17096 On HP-UX systems, if you refer to a function or variable name that
17097 begins with a dollar sign, @value{GDBN} searches for a user or system
17098 name first, before it searches for a convenience variable.
17101 @node BSD libkvm Interface
17102 @subsection BSD libkvm Interface
17105 @cindex kernel memory image
17106 @cindex kernel crash dump
17108 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
17109 interface that provides a uniform interface for accessing kernel virtual
17110 memory images, including live systems and crash dumps. @value{GDBN}
17111 uses this interface to allow you to debug live kernels and kernel crash
17112 dumps on many native BSD configurations. This is implemented as a
17113 special @code{kvm} debugging target. For debugging a live system, load
17114 the currently running kernel into @value{GDBN} and connect to the
17118 (@value{GDBP}) @b{target kvm}
17121 For debugging crash dumps, provide the file name of the crash dump as an
17125 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
17128 Once connected to the @code{kvm} target, the following commands are
17134 Set current context from the @dfn{Process Control Block} (PCB) address.
17137 Set current context from proc address. This command isn't available on
17138 modern FreeBSD systems.
17141 @node SVR4 Process Information
17142 @subsection SVR4 Process Information
17144 @cindex examine process image
17145 @cindex process info via @file{/proc}
17147 Many versions of SVR4 and compatible systems provide a facility called
17148 @samp{/proc} that can be used to examine the image of a running
17149 process using file-system subroutines. If @value{GDBN} is configured
17150 for an operating system with this facility, the command @code{info
17151 proc} is available to report information about the process running
17152 your program, or about any process running on your system. @code{info
17153 proc} works only on SVR4 systems that include the @code{procfs} code.
17154 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
17155 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
17161 @itemx info proc @var{process-id}
17162 Summarize available information about any running process. If a
17163 process ID is specified by @var{process-id}, display information about
17164 that process; otherwise display information about the program being
17165 debugged. The summary includes the debugged process ID, the command
17166 line used to invoke it, its current working directory, and its
17167 executable file's absolute file name.
17169 On some systems, @var{process-id} can be of the form
17170 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
17171 within a process. If the optional @var{pid} part is missing, it means
17172 a thread from the process being debugged (the leading @samp{/} still
17173 needs to be present, or else @value{GDBN} will interpret the number as
17174 a process ID rather than a thread ID).
17176 @item info proc mappings
17177 @cindex memory address space mappings
17178 Report the memory address space ranges accessible in the program, with
17179 information on whether the process has read, write, or execute access
17180 rights to each range. On @sc{gnu}/Linux systems, each memory range
17181 includes the object file which is mapped to that range, instead of the
17182 memory access rights to that range.
17184 @item info proc stat
17185 @itemx info proc status
17186 @cindex process detailed status information
17187 These subcommands are specific to @sc{gnu}/Linux systems. They show
17188 the process-related information, including the user ID and group ID;
17189 how many threads are there in the process; its virtual memory usage;
17190 the signals that are pending, blocked, and ignored; its TTY; its
17191 consumption of system and user time; its stack size; its @samp{nice}
17192 value; etc. For more information, see the @samp{proc} man page
17193 (type @kbd{man 5 proc} from your shell prompt).
17195 @item info proc all
17196 Show all the information about the process described under all of the
17197 above @code{info proc} subcommands.
17200 @comment These sub-options of 'info proc' were not included when
17201 @comment procfs.c was re-written. Keep their descriptions around
17202 @comment against the day when someone finds the time to put them back in.
17203 @kindex info proc times
17204 @item info proc times
17205 Starting time, user CPU time, and system CPU time for your program and
17208 @kindex info proc id
17210 Report on the process IDs related to your program: its own process ID,
17211 the ID of its parent, the process group ID, and the session ID.
17214 @item set procfs-trace
17215 @kindex set procfs-trace
17216 @cindex @code{procfs} API calls
17217 This command enables and disables tracing of @code{procfs} API calls.
17219 @item show procfs-trace
17220 @kindex show procfs-trace
17221 Show the current state of @code{procfs} API call tracing.
17223 @item set procfs-file @var{file}
17224 @kindex set procfs-file
17225 Tell @value{GDBN} to write @code{procfs} API trace to the named
17226 @var{file}. @value{GDBN} appends the trace info to the previous
17227 contents of the file. The default is to display the trace on the
17230 @item show procfs-file
17231 @kindex show procfs-file
17232 Show the file to which @code{procfs} API trace is written.
17234 @item proc-trace-entry
17235 @itemx proc-trace-exit
17236 @itemx proc-untrace-entry
17237 @itemx proc-untrace-exit
17238 @kindex proc-trace-entry
17239 @kindex proc-trace-exit
17240 @kindex proc-untrace-entry
17241 @kindex proc-untrace-exit
17242 These commands enable and disable tracing of entries into and exits
17243 from the @code{syscall} interface.
17246 @kindex info pidlist
17247 @cindex process list, QNX Neutrino
17248 For QNX Neutrino only, this command displays the list of all the
17249 processes and all the threads within each process.
17252 @kindex info meminfo
17253 @cindex mapinfo list, QNX Neutrino
17254 For QNX Neutrino only, this command displays the list of all mapinfos.
17258 @subsection Features for Debugging @sc{djgpp} Programs
17259 @cindex @sc{djgpp} debugging
17260 @cindex native @sc{djgpp} debugging
17261 @cindex MS-DOS-specific commands
17264 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
17265 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
17266 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
17267 top of real-mode DOS systems and their emulations.
17269 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
17270 defines a few commands specific to the @sc{djgpp} port. This
17271 subsection describes those commands.
17276 This is a prefix of @sc{djgpp}-specific commands which print
17277 information about the target system and important OS structures.
17280 @cindex MS-DOS system info
17281 @cindex free memory information (MS-DOS)
17282 @item info dos sysinfo
17283 This command displays assorted information about the underlying
17284 platform: the CPU type and features, the OS version and flavor, the
17285 DPMI version, and the available conventional and DPMI memory.
17290 @cindex segment descriptor tables
17291 @cindex descriptor tables display
17293 @itemx info dos ldt
17294 @itemx info dos idt
17295 These 3 commands display entries from, respectively, Global, Local,
17296 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
17297 tables are data structures which store a descriptor for each segment
17298 that is currently in use. The segment's selector is an index into a
17299 descriptor table; the table entry for that index holds the
17300 descriptor's base address and limit, and its attributes and access
17303 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
17304 segment (used for both data and the stack), and a DOS segment (which
17305 allows access to DOS/BIOS data structures and absolute addresses in
17306 conventional memory). However, the DPMI host will usually define
17307 additional segments in order to support the DPMI environment.
17309 @cindex garbled pointers
17310 These commands allow to display entries from the descriptor tables.
17311 Without an argument, all entries from the specified table are
17312 displayed. An argument, which should be an integer expression, means
17313 display a single entry whose index is given by the argument. For
17314 example, here's a convenient way to display information about the
17315 debugged program's data segment:
17318 @exdent @code{(@value{GDBP}) info dos ldt $ds}
17319 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
17323 This comes in handy when you want to see whether a pointer is outside
17324 the data segment's limit (i.e.@: @dfn{garbled}).
17326 @cindex page tables display (MS-DOS)
17328 @itemx info dos pte
17329 These two commands display entries from, respectively, the Page
17330 Directory and the Page Tables. Page Directories and Page Tables are
17331 data structures which control how virtual memory addresses are mapped
17332 into physical addresses. A Page Table includes an entry for every
17333 page of memory that is mapped into the program's address space; there
17334 may be several Page Tables, each one holding up to 4096 entries. A
17335 Page Directory has up to 4096 entries, one each for every Page Table
17336 that is currently in use.
17338 Without an argument, @kbd{info dos pde} displays the entire Page
17339 Directory, and @kbd{info dos pte} displays all the entries in all of
17340 the Page Tables. An argument, an integer expression, given to the
17341 @kbd{info dos pde} command means display only that entry from the Page
17342 Directory table. An argument given to the @kbd{info dos pte} command
17343 means display entries from a single Page Table, the one pointed to by
17344 the specified entry in the Page Directory.
17346 @cindex direct memory access (DMA) on MS-DOS
17347 These commands are useful when your program uses @dfn{DMA} (Direct
17348 Memory Access), which needs physical addresses to program the DMA
17351 These commands are supported only with some DPMI servers.
17353 @cindex physical address from linear address
17354 @item info dos address-pte @var{addr}
17355 This command displays the Page Table entry for a specified linear
17356 address. The argument @var{addr} is a linear address which should
17357 already have the appropriate segment's base address added to it,
17358 because this command accepts addresses which may belong to @emph{any}
17359 segment. For example, here's how to display the Page Table entry for
17360 the page where a variable @code{i} is stored:
17363 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
17364 @exdent @code{Page Table entry for address 0x11a00d30:}
17365 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
17369 This says that @code{i} is stored at offset @code{0xd30} from the page
17370 whose physical base address is @code{0x02698000}, and shows all the
17371 attributes of that page.
17373 Note that you must cast the addresses of variables to a @code{char *},
17374 since otherwise the value of @code{__djgpp_base_address}, the base
17375 address of all variables and functions in a @sc{djgpp} program, will
17376 be added using the rules of C pointer arithmetics: if @code{i} is
17377 declared an @code{int}, @value{GDBN} will add 4 times the value of
17378 @code{__djgpp_base_address} to the address of @code{i}.
17380 Here's another example, it displays the Page Table entry for the
17384 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
17385 @exdent @code{Page Table entry for address 0x29110:}
17386 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
17390 (The @code{+ 3} offset is because the transfer buffer's address is the
17391 3rd member of the @code{_go32_info_block} structure.) The output
17392 clearly shows that this DPMI server maps the addresses in conventional
17393 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
17394 linear (@code{0x29110}) addresses are identical.
17396 This command is supported only with some DPMI servers.
17399 @cindex DOS serial data link, remote debugging
17400 In addition to native debugging, the DJGPP port supports remote
17401 debugging via a serial data link. The following commands are specific
17402 to remote serial debugging in the DJGPP port of @value{GDBN}.
17405 @kindex set com1base
17406 @kindex set com1irq
17407 @kindex set com2base
17408 @kindex set com2irq
17409 @kindex set com3base
17410 @kindex set com3irq
17411 @kindex set com4base
17412 @kindex set com4irq
17413 @item set com1base @var{addr}
17414 This command sets the base I/O port address of the @file{COM1} serial
17417 @item set com1irq @var{irq}
17418 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
17419 for the @file{COM1} serial port.
17421 There are similar commands @samp{set com2base}, @samp{set com3irq},
17422 etc.@: for setting the port address and the @code{IRQ} lines for the
17425 @kindex show com1base
17426 @kindex show com1irq
17427 @kindex show com2base
17428 @kindex show com2irq
17429 @kindex show com3base
17430 @kindex show com3irq
17431 @kindex show com4base
17432 @kindex show com4irq
17433 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
17434 display the current settings of the base address and the @code{IRQ}
17435 lines used by the COM ports.
17438 @kindex info serial
17439 @cindex DOS serial port status
17440 This command prints the status of the 4 DOS serial ports. For each
17441 port, it prints whether it's active or not, its I/O base address and
17442 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
17443 counts of various errors encountered so far.
17447 @node Cygwin Native
17448 @subsection Features for Debugging MS Windows PE Executables
17449 @cindex MS Windows debugging
17450 @cindex native Cygwin debugging
17451 @cindex Cygwin-specific commands
17453 @value{GDBN} supports native debugging of MS Windows programs, including
17454 DLLs with and without symbolic debugging information.
17456 @cindex Ctrl-BREAK, MS-Windows
17457 @cindex interrupt debuggee on MS-Windows
17458 MS-Windows programs that call @code{SetConsoleMode} to switch off the
17459 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
17460 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
17461 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
17462 sequence, which can be used to interrupt the debuggee even if it
17465 There are various additional Cygwin-specific commands, described in
17466 this section. Working with DLLs that have no debugging symbols is
17467 described in @ref{Non-debug DLL Symbols}.
17472 This is a prefix of MS Windows-specific commands which print
17473 information about the target system and important OS structures.
17475 @item info w32 selector
17476 This command displays information returned by
17477 the Win32 API @code{GetThreadSelectorEntry} function.
17478 It takes an optional argument that is evaluated to
17479 a long value to give the information about this given selector.
17480 Without argument, this command displays information
17481 about the six segment registers.
17483 @item info w32 thread-information-block
17484 This command displays thread specific information stored in the
17485 Thread Information Block (readable on the X86 CPU family using @code{$fs}
17486 selector for 32-bit programs and @code{$gs} for 64-bit programs).
17490 This is a Cygwin-specific alias of @code{info shared}.
17492 @kindex dll-symbols
17494 This command loads symbols from a dll similarly to
17495 add-sym command but without the need to specify a base address.
17497 @kindex set cygwin-exceptions
17498 @cindex debugging the Cygwin DLL
17499 @cindex Cygwin DLL, debugging
17500 @item set cygwin-exceptions @var{mode}
17501 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
17502 happen inside the Cygwin DLL. If @var{mode} is @code{off},
17503 @value{GDBN} will delay recognition of exceptions, and may ignore some
17504 exceptions which seem to be caused by internal Cygwin DLL
17505 ``bookkeeping''. This option is meant primarily for debugging the
17506 Cygwin DLL itself; the default value is @code{off} to avoid annoying
17507 @value{GDBN} users with false @code{SIGSEGV} signals.
17509 @kindex show cygwin-exceptions
17510 @item show cygwin-exceptions
17511 Displays whether @value{GDBN} will break on exceptions that happen
17512 inside the Cygwin DLL itself.
17514 @kindex set new-console
17515 @item set new-console @var{mode}
17516 If @var{mode} is @code{on} the debuggee will
17517 be started in a new console on next start.
17518 If @var{mode} is @code{off}, the debuggee will
17519 be started in the same console as the debugger.
17521 @kindex show new-console
17522 @item show new-console
17523 Displays whether a new console is used
17524 when the debuggee is started.
17526 @kindex set new-group
17527 @item set new-group @var{mode}
17528 This boolean value controls whether the debuggee should
17529 start a new group or stay in the same group as the debugger.
17530 This affects the way the Windows OS handles
17533 @kindex show new-group
17534 @item show new-group
17535 Displays current value of new-group boolean.
17537 @kindex set debugevents
17538 @item set debugevents
17539 This boolean value adds debug output concerning kernel events related
17540 to the debuggee seen by the debugger. This includes events that
17541 signal thread and process creation and exit, DLL loading and
17542 unloading, console interrupts, and debugging messages produced by the
17543 Windows @code{OutputDebugString} API call.
17545 @kindex set debugexec
17546 @item set debugexec
17547 This boolean value adds debug output concerning execute events
17548 (such as resume thread) seen by the debugger.
17550 @kindex set debugexceptions
17551 @item set debugexceptions
17552 This boolean value adds debug output concerning exceptions in the
17553 debuggee seen by the debugger.
17555 @kindex set debugmemory
17556 @item set debugmemory
17557 This boolean value adds debug output concerning debuggee memory reads
17558 and writes by the debugger.
17562 This boolean values specifies whether the debuggee is called
17563 via a shell or directly (default value is on).
17567 Displays if the debuggee will be started with a shell.
17572 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
17575 @node Non-debug DLL Symbols
17576 @subsubsection Support for DLLs without Debugging Symbols
17577 @cindex DLLs with no debugging symbols
17578 @cindex Minimal symbols and DLLs
17580 Very often on windows, some of the DLLs that your program relies on do
17581 not include symbolic debugging information (for example,
17582 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
17583 symbols in a DLL, it relies on the minimal amount of symbolic
17584 information contained in the DLL's export table. This section
17585 describes working with such symbols, known internally to @value{GDBN} as
17586 ``minimal symbols''.
17588 Note that before the debugged program has started execution, no DLLs
17589 will have been loaded. The easiest way around this problem is simply to
17590 start the program --- either by setting a breakpoint or letting the
17591 program run once to completion. It is also possible to force
17592 @value{GDBN} to load a particular DLL before starting the executable ---
17593 see the shared library information in @ref{Files}, or the
17594 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
17595 explicitly loading symbols from a DLL with no debugging information will
17596 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
17597 which may adversely affect symbol lookup performance.
17599 @subsubsection DLL Name Prefixes
17601 In keeping with the naming conventions used by the Microsoft debugging
17602 tools, DLL export symbols are made available with a prefix based on the
17603 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
17604 also entered into the symbol table, so @code{CreateFileA} is often
17605 sufficient. In some cases there will be name clashes within a program
17606 (particularly if the executable itself includes full debugging symbols)
17607 necessitating the use of the fully qualified name when referring to the
17608 contents of the DLL. Use single-quotes around the name to avoid the
17609 exclamation mark (``!'') being interpreted as a language operator.
17611 Note that the internal name of the DLL may be all upper-case, even
17612 though the file name of the DLL is lower-case, or vice-versa. Since
17613 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
17614 some confusion. If in doubt, try the @code{info functions} and
17615 @code{info variables} commands or even @code{maint print msymbols}
17616 (@pxref{Symbols}). Here's an example:
17619 (@value{GDBP}) info function CreateFileA
17620 All functions matching regular expression "CreateFileA":
17622 Non-debugging symbols:
17623 0x77e885f4 CreateFileA
17624 0x77e885f4 KERNEL32!CreateFileA
17628 (@value{GDBP}) info function !
17629 All functions matching regular expression "!":
17631 Non-debugging symbols:
17632 0x6100114c cygwin1!__assert
17633 0x61004034 cygwin1!_dll_crt0@@0
17634 0x61004240 cygwin1!dll_crt0(per_process *)
17638 @subsubsection Working with Minimal Symbols
17640 Symbols extracted from a DLL's export table do not contain very much
17641 type information. All that @value{GDBN} can do is guess whether a symbol
17642 refers to a function or variable depending on the linker section that
17643 contains the symbol. Also note that the actual contents of the memory
17644 contained in a DLL are not available unless the program is running. This
17645 means that you cannot examine the contents of a variable or disassemble
17646 a function within a DLL without a running program.
17648 Variables are generally treated as pointers and dereferenced
17649 automatically. For this reason, it is often necessary to prefix a
17650 variable name with the address-of operator (``&'') and provide explicit
17651 type information in the command. Here's an example of the type of
17655 (@value{GDBP}) print 'cygwin1!__argv'
17660 (@value{GDBP}) x 'cygwin1!__argv'
17661 0x10021610: "\230y\""
17664 And two possible solutions:
17667 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
17668 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
17672 (@value{GDBP}) x/2x &'cygwin1!__argv'
17673 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
17674 (@value{GDBP}) x/x 0x10021608
17675 0x10021608: 0x0022fd98
17676 (@value{GDBP}) x/s 0x0022fd98
17677 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
17680 Setting a break point within a DLL is possible even before the program
17681 starts execution. However, under these circumstances, @value{GDBN} can't
17682 examine the initial instructions of the function in order to skip the
17683 function's frame set-up code. You can work around this by using ``*&''
17684 to set the breakpoint at a raw memory address:
17687 (@value{GDBP}) break *&'python22!PyOS_Readline'
17688 Breakpoint 1 at 0x1e04eff0
17691 The author of these extensions is not entirely convinced that setting a
17692 break point within a shared DLL like @file{kernel32.dll} is completely
17696 @subsection Commands Specific to @sc{gnu} Hurd Systems
17697 @cindex @sc{gnu} Hurd debugging
17699 This subsection describes @value{GDBN} commands specific to the
17700 @sc{gnu} Hurd native debugging.
17705 @kindex set signals@r{, Hurd command}
17706 @kindex set sigs@r{, Hurd command}
17707 This command toggles the state of inferior signal interception by
17708 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
17709 affected by this command. @code{sigs} is a shorthand alias for
17714 @kindex show signals@r{, Hurd command}
17715 @kindex show sigs@r{, Hurd command}
17716 Show the current state of intercepting inferior's signals.
17718 @item set signal-thread
17719 @itemx set sigthread
17720 @kindex set signal-thread
17721 @kindex set sigthread
17722 This command tells @value{GDBN} which thread is the @code{libc} signal
17723 thread. That thread is run when a signal is delivered to a running
17724 process. @code{set sigthread} is the shorthand alias of @code{set
17727 @item show signal-thread
17728 @itemx show sigthread
17729 @kindex show signal-thread
17730 @kindex show sigthread
17731 These two commands show which thread will run when the inferior is
17732 delivered a signal.
17735 @kindex set stopped@r{, Hurd command}
17736 This commands tells @value{GDBN} that the inferior process is stopped,
17737 as with the @code{SIGSTOP} signal. The stopped process can be
17738 continued by delivering a signal to it.
17741 @kindex show stopped@r{, Hurd command}
17742 This command shows whether @value{GDBN} thinks the debuggee is
17745 @item set exceptions
17746 @kindex set exceptions@r{, Hurd command}
17747 Use this command to turn off trapping of exceptions in the inferior.
17748 When exception trapping is off, neither breakpoints nor
17749 single-stepping will work. To restore the default, set exception
17752 @item show exceptions
17753 @kindex show exceptions@r{, Hurd command}
17754 Show the current state of trapping exceptions in the inferior.
17756 @item set task pause
17757 @kindex set task@r{, Hurd commands}
17758 @cindex task attributes (@sc{gnu} Hurd)
17759 @cindex pause current task (@sc{gnu} Hurd)
17760 This command toggles task suspension when @value{GDBN} has control.
17761 Setting it to on takes effect immediately, and the task is suspended
17762 whenever @value{GDBN} gets control. Setting it to off will take
17763 effect the next time the inferior is continued. If this option is set
17764 to off, you can use @code{set thread default pause on} or @code{set
17765 thread pause on} (see below) to pause individual threads.
17767 @item show task pause
17768 @kindex show task@r{, Hurd commands}
17769 Show the current state of task suspension.
17771 @item set task detach-suspend-count
17772 @cindex task suspend count
17773 @cindex detach from task, @sc{gnu} Hurd
17774 This command sets the suspend count the task will be left with when
17775 @value{GDBN} detaches from it.
17777 @item show task detach-suspend-count
17778 Show the suspend count the task will be left with when detaching.
17780 @item set task exception-port
17781 @itemx set task excp
17782 @cindex task exception port, @sc{gnu} Hurd
17783 This command sets the task exception port to which @value{GDBN} will
17784 forward exceptions. The argument should be the value of the @dfn{send
17785 rights} of the task. @code{set task excp} is a shorthand alias.
17787 @item set noninvasive
17788 @cindex noninvasive task options
17789 This command switches @value{GDBN} to a mode that is the least
17790 invasive as far as interfering with the inferior is concerned. This
17791 is the same as using @code{set task pause}, @code{set exceptions}, and
17792 @code{set signals} to values opposite to the defaults.
17794 @item info send-rights
17795 @itemx info receive-rights
17796 @itemx info port-rights
17797 @itemx info port-sets
17798 @itemx info dead-names
17801 @cindex send rights, @sc{gnu} Hurd
17802 @cindex receive rights, @sc{gnu} Hurd
17803 @cindex port rights, @sc{gnu} Hurd
17804 @cindex port sets, @sc{gnu} Hurd
17805 @cindex dead names, @sc{gnu} Hurd
17806 These commands display information about, respectively, send rights,
17807 receive rights, port rights, port sets, and dead names of a task.
17808 There are also shorthand aliases: @code{info ports} for @code{info
17809 port-rights} and @code{info psets} for @code{info port-sets}.
17811 @item set thread pause
17812 @kindex set thread@r{, Hurd command}
17813 @cindex thread properties, @sc{gnu} Hurd
17814 @cindex pause current thread (@sc{gnu} Hurd)
17815 This command toggles current thread suspension when @value{GDBN} has
17816 control. Setting it to on takes effect immediately, and the current
17817 thread is suspended whenever @value{GDBN} gets control. Setting it to
17818 off will take effect the next time the inferior is continued.
17819 Normally, this command has no effect, since when @value{GDBN} has
17820 control, the whole task is suspended. However, if you used @code{set
17821 task pause off} (see above), this command comes in handy to suspend
17822 only the current thread.
17824 @item show thread pause
17825 @kindex show thread@r{, Hurd command}
17826 This command shows the state of current thread suspension.
17828 @item set thread run
17829 This command sets whether the current thread is allowed to run.
17831 @item show thread run
17832 Show whether the current thread is allowed to run.
17834 @item set thread detach-suspend-count
17835 @cindex thread suspend count, @sc{gnu} Hurd
17836 @cindex detach from thread, @sc{gnu} Hurd
17837 This command sets the suspend count @value{GDBN} will leave on a
17838 thread when detaching. This number is relative to the suspend count
17839 found by @value{GDBN} when it notices the thread; use @code{set thread
17840 takeover-suspend-count} to force it to an absolute value.
17842 @item show thread detach-suspend-count
17843 Show the suspend count @value{GDBN} will leave on the thread when
17846 @item set thread exception-port
17847 @itemx set thread excp
17848 Set the thread exception port to which to forward exceptions. This
17849 overrides the port set by @code{set task exception-port} (see above).
17850 @code{set thread excp} is the shorthand alias.
17852 @item set thread takeover-suspend-count
17853 Normally, @value{GDBN}'s thread suspend counts are relative to the
17854 value @value{GDBN} finds when it notices each thread. This command
17855 changes the suspend counts to be absolute instead.
17857 @item set thread default
17858 @itemx show thread default
17859 @cindex thread default settings, @sc{gnu} Hurd
17860 Each of the above @code{set thread} commands has a @code{set thread
17861 default} counterpart (e.g., @code{set thread default pause}, @code{set
17862 thread default exception-port}, etc.). The @code{thread default}
17863 variety of commands sets the default thread properties for all
17864 threads; you can then change the properties of individual threads with
17865 the non-default commands.
17870 @subsection QNX Neutrino
17871 @cindex QNX Neutrino
17873 @value{GDBN} provides the following commands specific to the QNX
17877 @item set debug nto-debug
17878 @kindex set debug nto-debug
17879 When set to on, enables debugging messages specific to the QNX
17882 @item show debug nto-debug
17883 @kindex show debug nto-debug
17884 Show the current state of QNX Neutrino messages.
17891 @value{GDBN} provides the following commands specific to the Darwin target:
17894 @item set debug darwin @var{num}
17895 @kindex set debug darwin
17896 When set to a non zero value, enables debugging messages specific to
17897 the Darwin support. Higher values produce more verbose output.
17899 @item show debug darwin
17900 @kindex show debug darwin
17901 Show the current state of Darwin messages.
17903 @item set debug mach-o @var{num}
17904 @kindex set debug mach-o
17905 When set to a non zero value, enables debugging messages while
17906 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
17907 file format used on Darwin for object and executable files.) Higher
17908 values produce more verbose output. This is a command to diagnose
17909 problems internal to @value{GDBN} and should not be needed in normal
17912 @item show debug mach-o
17913 @kindex show debug mach-o
17914 Show the current state of Mach-O file messages.
17916 @item set mach-exceptions on
17917 @itemx set mach-exceptions off
17918 @kindex set mach-exceptions
17919 On Darwin, faults are first reported as a Mach exception and are then
17920 mapped to a Posix signal. Use this command to turn on trapping of
17921 Mach exceptions in the inferior. This might be sometimes useful to
17922 better understand the cause of a fault. The default is off.
17924 @item show mach-exceptions
17925 @kindex show mach-exceptions
17926 Show the current state of exceptions trapping.
17931 @section Embedded Operating Systems
17933 This section describes configurations involving the debugging of
17934 embedded operating systems that are available for several different
17938 * VxWorks:: Using @value{GDBN} with VxWorks
17941 @value{GDBN} includes the ability to debug programs running on
17942 various real-time operating systems.
17945 @subsection Using @value{GDBN} with VxWorks
17951 @kindex target vxworks
17952 @item target vxworks @var{machinename}
17953 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
17954 is the target system's machine name or IP address.
17958 On VxWorks, @code{load} links @var{filename} dynamically on the
17959 current target system as well as adding its symbols in @value{GDBN}.
17961 @value{GDBN} enables developers to spawn and debug tasks running on networked
17962 VxWorks targets from a Unix host. Already-running tasks spawned from
17963 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
17964 both the Unix host and on the VxWorks target. The program
17965 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
17966 installed with the name @code{vxgdb}, to distinguish it from a
17967 @value{GDBN} for debugging programs on the host itself.)
17970 @item VxWorks-timeout @var{args}
17971 @kindex vxworks-timeout
17972 All VxWorks-based targets now support the option @code{vxworks-timeout}.
17973 This option is set by the user, and @var{args} represents the number of
17974 seconds @value{GDBN} waits for responses to rpc's. You might use this if
17975 your VxWorks target is a slow software simulator or is on the far side
17976 of a thin network line.
17979 The following information on connecting to VxWorks was current when
17980 this manual was produced; newer releases of VxWorks may use revised
17983 @findex INCLUDE_RDB
17984 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
17985 to include the remote debugging interface routines in the VxWorks
17986 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
17987 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
17988 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
17989 source debugging task @code{tRdbTask} when VxWorks is booted. For more
17990 information on configuring and remaking VxWorks, see the manufacturer's
17992 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
17994 Once you have included @file{rdb.a} in your VxWorks system image and set
17995 your Unix execution search path to find @value{GDBN}, you are ready to
17996 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
17997 @code{vxgdb}, depending on your installation).
17999 @value{GDBN} comes up showing the prompt:
18006 * VxWorks Connection:: Connecting to VxWorks
18007 * VxWorks Download:: VxWorks download
18008 * VxWorks Attach:: Running tasks
18011 @node VxWorks Connection
18012 @subsubsection Connecting to VxWorks
18014 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
18015 network. To connect to a target whose host name is ``@code{tt}'', type:
18018 (vxgdb) target vxworks tt
18022 @value{GDBN} displays messages like these:
18025 Attaching remote machine across net...
18030 @value{GDBN} then attempts to read the symbol tables of any object modules
18031 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
18032 these files by searching the directories listed in the command search
18033 path (@pxref{Environment, ,Your Program's Environment}); if it fails
18034 to find an object file, it displays a message such as:
18037 prog.o: No such file or directory.
18040 When this happens, add the appropriate directory to the search path with
18041 the @value{GDBN} command @code{path}, and execute the @code{target}
18044 @node VxWorks Download
18045 @subsubsection VxWorks Download
18047 @cindex download to VxWorks
18048 If you have connected to the VxWorks target and you want to debug an
18049 object that has not yet been loaded, you can use the @value{GDBN}
18050 @code{load} command to download a file from Unix to VxWorks
18051 incrementally. The object file given as an argument to the @code{load}
18052 command is actually opened twice: first by the VxWorks target in order
18053 to download the code, then by @value{GDBN} in order to read the symbol
18054 table. This can lead to problems if the current working directories on
18055 the two systems differ. If both systems have NFS mounted the same
18056 filesystems, you can avoid these problems by using absolute paths.
18057 Otherwise, it is simplest to set the working directory on both systems
18058 to the directory in which the object file resides, and then to reference
18059 the file by its name, without any path. For instance, a program
18060 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
18061 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
18062 program, type this on VxWorks:
18065 -> cd "@var{vxpath}/vw/demo/rdb"
18069 Then, in @value{GDBN}, type:
18072 (vxgdb) cd @var{hostpath}/vw/demo/rdb
18073 (vxgdb) load prog.o
18076 @value{GDBN} displays a response similar to this:
18079 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
18082 You can also use the @code{load} command to reload an object module
18083 after editing and recompiling the corresponding source file. Note that
18084 this makes @value{GDBN} delete all currently-defined breakpoints,
18085 auto-displays, and convenience variables, and to clear the value
18086 history. (This is necessary in order to preserve the integrity of
18087 debugger's data structures that reference the target system's symbol
18090 @node VxWorks Attach
18091 @subsubsection Running Tasks
18093 @cindex running VxWorks tasks
18094 You can also attach to an existing task using the @code{attach} command as
18098 (vxgdb) attach @var{task}
18102 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
18103 or suspended when you attach to it. Running tasks are suspended at
18104 the time of attachment.
18106 @node Embedded Processors
18107 @section Embedded Processors
18109 This section goes into details specific to particular embedded
18112 @cindex send command to simulator
18113 Whenever a specific embedded processor has a simulator, @value{GDBN}
18114 allows to send an arbitrary command to the simulator.
18117 @item sim @var{command}
18118 @kindex sim@r{, a command}
18119 Send an arbitrary @var{command} string to the simulator. Consult the
18120 documentation for the specific simulator in use for information about
18121 acceptable commands.
18127 * M32R/D:: Renesas M32R/D
18128 * M68K:: Motorola M68K
18129 * MicroBlaze:: Xilinx MicroBlaze
18130 * MIPS Embedded:: MIPS Embedded
18131 * OpenRISC 1000:: OpenRisc 1000
18132 * PA:: HP PA Embedded
18133 * PowerPC Embedded:: PowerPC Embedded
18134 * Sparclet:: Tsqware Sparclet
18135 * Sparclite:: Fujitsu Sparclite
18136 * Z8000:: Zilog Z8000
18139 * Super-H:: Renesas Super-H
18148 @item target rdi @var{dev}
18149 ARM Angel monitor, via RDI library interface to ADP protocol. You may
18150 use this target to communicate with both boards running the Angel
18151 monitor, or with the EmbeddedICE JTAG debug device.
18154 @item target rdp @var{dev}
18159 @value{GDBN} provides the following ARM-specific commands:
18162 @item set arm disassembler
18164 This commands selects from a list of disassembly styles. The
18165 @code{"std"} style is the standard style.
18167 @item show arm disassembler
18169 Show the current disassembly style.
18171 @item set arm apcs32
18172 @cindex ARM 32-bit mode
18173 This command toggles ARM operation mode between 32-bit and 26-bit.
18175 @item show arm apcs32
18176 Display the current usage of the ARM 32-bit mode.
18178 @item set arm fpu @var{fputype}
18179 This command sets the ARM floating-point unit (FPU) type. The
18180 argument @var{fputype} can be one of these:
18184 Determine the FPU type by querying the OS ABI.
18186 Software FPU, with mixed-endian doubles on little-endian ARM
18189 GCC-compiled FPA co-processor.
18191 Software FPU with pure-endian doubles.
18197 Show the current type of the FPU.
18200 This command forces @value{GDBN} to use the specified ABI.
18203 Show the currently used ABI.
18205 @item set arm fallback-mode (arm|thumb|auto)
18206 @value{GDBN} uses the symbol table, when available, to determine
18207 whether instructions are ARM or Thumb. This command controls
18208 @value{GDBN}'s default behavior when the symbol table is not
18209 available. The default is @samp{auto}, which causes @value{GDBN} to
18210 use the current execution mode (from the @code{T} bit in the @code{CPSR}
18213 @item show arm fallback-mode
18214 Show the current fallback instruction mode.
18216 @item set arm force-mode (arm|thumb|auto)
18217 This command overrides use of the symbol table to determine whether
18218 instructions are ARM or Thumb. The default is @samp{auto}, which
18219 causes @value{GDBN} to use the symbol table and then the setting
18220 of @samp{set arm fallback-mode}.
18222 @item show arm force-mode
18223 Show the current forced instruction mode.
18225 @item set debug arm
18226 Toggle whether to display ARM-specific debugging messages from the ARM
18227 target support subsystem.
18229 @item show debug arm
18230 Show whether ARM-specific debugging messages are enabled.
18233 The following commands are available when an ARM target is debugged
18234 using the RDI interface:
18237 @item rdilogfile @r{[}@var{file}@r{]}
18239 @cindex ADP (Angel Debugger Protocol) logging
18240 Set the filename for the ADP (Angel Debugger Protocol) packet log.
18241 With an argument, sets the log file to the specified @var{file}. With
18242 no argument, show the current log file name. The default log file is
18245 @item rdilogenable @r{[}@var{arg}@r{]}
18246 @kindex rdilogenable
18247 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
18248 enables logging, with an argument 0 or @code{"no"} disables it. With
18249 no arguments displays the current setting. When logging is enabled,
18250 ADP packets exchanged between @value{GDBN} and the RDI target device
18251 are logged to a file.
18253 @item set rdiromatzero
18254 @kindex set rdiromatzero
18255 @cindex ROM at zero address, RDI
18256 Tell @value{GDBN} whether the target has ROM at address 0. If on,
18257 vector catching is disabled, so that zero address can be used. If off
18258 (the default), vector catching is enabled. For this command to take
18259 effect, it needs to be invoked prior to the @code{target rdi} command.
18261 @item show rdiromatzero
18262 @kindex show rdiromatzero
18263 Show the current setting of ROM at zero address.
18265 @item set rdiheartbeat
18266 @kindex set rdiheartbeat
18267 @cindex RDI heartbeat
18268 Enable or disable RDI heartbeat packets. It is not recommended to
18269 turn on this option, since it confuses ARM and EPI JTAG interface, as
18270 well as the Angel monitor.
18272 @item show rdiheartbeat
18273 @kindex show rdiheartbeat
18274 Show the setting of RDI heartbeat packets.
18278 @item target sim @r{[}@var{simargs}@r{]} @dots{}
18279 The @value{GDBN} ARM simulator accepts the following optional arguments.
18282 @item --swi-support=@var{type}
18283 Tell the simulator which SWI interfaces to support.
18284 @var{type} may be a comma separated list of the following values.
18285 The default value is @code{all}.
18298 @subsection Renesas M32R/D and M32R/SDI
18301 @kindex target m32r
18302 @item target m32r @var{dev}
18303 Renesas M32R/D ROM monitor.
18305 @kindex target m32rsdi
18306 @item target m32rsdi @var{dev}
18307 Renesas M32R SDI server, connected via parallel port to the board.
18310 The following @value{GDBN} commands are specific to the M32R monitor:
18313 @item set download-path @var{path}
18314 @kindex set download-path
18315 @cindex find downloadable @sc{srec} files (M32R)
18316 Set the default path for finding downloadable @sc{srec} files.
18318 @item show download-path
18319 @kindex show download-path
18320 Show the default path for downloadable @sc{srec} files.
18322 @item set board-address @var{addr}
18323 @kindex set board-address
18324 @cindex M32-EVA target board address
18325 Set the IP address for the M32R-EVA target board.
18327 @item show board-address
18328 @kindex show board-address
18329 Show the current IP address of the target board.
18331 @item set server-address @var{addr}
18332 @kindex set server-address
18333 @cindex download server address (M32R)
18334 Set the IP address for the download server, which is the @value{GDBN}'s
18337 @item show server-address
18338 @kindex show server-address
18339 Display the IP address of the download server.
18341 @item upload @r{[}@var{file}@r{]}
18342 @kindex upload@r{, M32R}
18343 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
18344 upload capability. If no @var{file} argument is given, the current
18345 executable file is uploaded.
18347 @item tload @r{[}@var{file}@r{]}
18348 @kindex tload@r{, M32R}
18349 Test the @code{upload} command.
18352 The following commands are available for M32R/SDI:
18357 @cindex reset SDI connection, M32R
18358 This command resets the SDI connection.
18362 This command shows the SDI connection status.
18365 @kindex debug_chaos
18366 @cindex M32R/Chaos debugging
18367 Instructs the remote that M32R/Chaos debugging is to be used.
18369 @item use_debug_dma
18370 @kindex use_debug_dma
18371 Instructs the remote to use the DEBUG_DMA method of accessing memory.
18374 @kindex use_mon_code
18375 Instructs the remote to use the MON_CODE method of accessing memory.
18378 @kindex use_ib_break
18379 Instructs the remote to set breakpoints by IB break.
18381 @item use_dbt_break
18382 @kindex use_dbt_break
18383 Instructs the remote to set breakpoints by DBT.
18389 The Motorola m68k configuration includes ColdFire support, and a
18390 target command for the following ROM monitor.
18394 @kindex target dbug
18395 @item target dbug @var{dev}
18396 dBUG ROM monitor for Motorola ColdFire.
18401 @subsection MicroBlaze
18402 @cindex Xilinx MicroBlaze
18403 @cindex XMD, Xilinx Microprocessor Debugger
18405 The MicroBlaze is a soft-core processor supported on various Xilinx
18406 FPGAs, such as Spartan or Virtex series. Boards with these processors
18407 usually have JTAG ports which connect to a host system running the Xilinx
18408 Embedded Development Kit (EDK) or Software Development Kit (SDK).
18409 This host system is used to download the configuration bitstream to
18410 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
18411 communicates with the target board using the JTAG interface and
18412 presents a @code{gdbserver} interface to the board. By default
18413 @code{xmd} uses port @code{1234}. (While it is possible to change
18414 this default port, it requires the use of undocumented @code{xmd}
18415 commands. Contact Xilinx support if you need to do this.)
18417 Use these GDB commands to connect to the MicroBlaze target processor.
18420 @item target remote :1234
18421 Use this command to connect to the target if you are running @value{GDBN}
18422 on the same system as @code{xmd}.
18424 @item target remote @var{xmd-host}:1234
18425 Use this command to connect to the target if it is connected to @code{xmd}
18426 running on a different system named @var{xmd-host}.
18429 Use this command to download a program to the MicroBlaze target.
18431 @item set debug microblaze @var{n}
18432 Enable MicroBlaze-specific debugging messages if non-zero.
18434 @item show debug microblaze @var{n}
18435 Show MicroBlaze-specific debugging level.
18438 @node MIPS Embedded
18439 @subsection MIPS Embedded
18441 @cindex MIPS boards
18442 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
18443 MIPS board attached to a serial line. This is available when
18444 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
18447 Use these @value{GDBN} commands to specify the connection to your target board:
18450 @item target mips @var{port}
18451 @kindex target mips @var{port}
18452 To run a program on the board, start up @code{@value{GDBP}} with the
18453 name of your program as the argument. To connect to the board, use the
18454 command @samp{target mips @var{port}}, where @var{port} is the name of
18455 the serial port connected to the board. If the program has not already
18456 been downloaded to the board, you may use the @code{load} command to
18457 download it. You can then use all the usual @value{GDBN} commands.
18459 For example, this sequence connects to the target board through a serial
18460 port, and loads and runs a program called @var{prog} through the
18464 host$ @value{GDBP} @var{prog}
18465 @value{GDBN} is free software and @dots{}
18466 (@value{GDBP}) target mips /dev/ttyb
18467 (@value{GDBP}) load @var{prog}
18471 @item target mips @var{hostname}:@var{portnumber}
18472 On some @value{GDBN} host configurations, you can specify a TCP
18473 connection (for instance, to a serial line managed by a terminal
18474 concentrator) instead of a serial port, using the syntax
18475 @samp{@var{hostname}:@var{portnumber}}.
18477 @item target pmon @var{port}
18478 @kindex target pmon @var{port}
18481 @item target ddb @var{port}
18482 @kindex target ddb @var{port}
18483 NEC's DDB variant of PMON for Vr4300.
18485 @item target lsi @var{port}
18486 @kindex target lsi @var{port}
18487 LSI variant of PMON.
18489 @kindex target r3900
18490 @item target r3900 @var{dev}
18491 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
18493 @kindex target array
18494 @item target array @var{dev}
18495 Array Tech LSI33K RAID controller board.
18501 @value{GDBN} also supports these special commands for MIPS targets:
18504 @item set mipsfpu double
18505 @itemx set mipsfpu single
18506 @itemx set mipsfpu none
18507 @itemx set mipsfpu auto
18508 @itemx show mipsfpu
18509 @kindex set mipsfpu
18510 @kindex show mipsfpu
18511 @cindex MIPS remote floating point
18512 @cindex floating point, MIPS remote
18513 If your target board does not support the MIPS floating point
18514 coprocessor, you should use the command @samp{set mipsfpu none} (if you
18515 need this, you may wish to put the command in your @value{GDBN} init
18516 file). This tells @value{GDBN} how to find the return value of
18517 functions which return floating point values. It also allows
18518 @value{GDBN} to avoid saving the floating point registers when calling
18519 functions on the board. If you are using a floating point coprocessor
18520 with only single precision floating point support, as on the @sc{r4650}
18521 processor, use the command @samp{set mipsfpu single}. The default
18522 double precision floating point coprocessor may be selected using
18523 @samp{set mipsfpu double}.
18525 In previous versions the only choices were double precision or no
18526 floating point, so @samp{set mipsfpu on} will select double precision
18527 and @samp{set mipsfpu off} will select no floating point.
18529 As usual, you can inquire about the @code{mipsfpu} variable with
18530 @samp{show mipsfpu}.
18532 @item set timeout @var{seconds}
18533 @itemx set retransmit-timeout @var{seconds}
18534 @itemx show timeout
18535 @itemx show retransmit-timeout
18536 @cindex @code{timeout}, MIPS protocol
18537 @cindex @code{retransmit-timeout}, MIPS protocol
18538 @kindex set timeout
18539 @kindex show timeout
18540 @kindex set retransmit-timeout
18541 @kindex show retransmit-timeout
18542 You can control the timeout used while waiting for a packet, in the MIPS
18543 remote protocol, with the @code{set timeout @var{seconds}} command. The
18544 default is 5 seconds. Similarly, you can control the timeout used while
18545 waiting for an acknowledgment of a packet with the @code{set
18546 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
18547 You can inspect both values with @code{show timeout} and @code{show
18548 retransmit-timeout}. (These commands are @emph{only} available when
18549 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
18551 The timeout set by @code{set timeout} does not apply when @value{GDBN}
18552 is waiting for your program to stop. In that case, @value{GDBN} waits
18553 forever because it has no way of knowing how long the program is going
18554 to run before stopping.
18556 @item set syn-garbage-limit @var{num}
18557 @kindex set syn-garbage-limit@r{, MIPS remote}
18558 @cindex synchronize with remote MIPS target
18559 Limit the maximum number of characters @value{GDBN} should ignore when
18560 it tries to synchronize with the remote target. The default is 10
18561 characters. Setting the limit to -1 means there's no limit.
18563 @item show syn-garbage-limit
18564 @kindex show syn-garbage-limit@r{, MIPS remote}
18565 Show the current limit on the number of characters to ignore when
18566 trying to synchronize with the remote system.
18568 @item set monitor-prompt @var{prompt}
18569 @kindex set monitor-prompt@r{, MIPS remote}
18570 @cindex remote monitor prompt
18571 Tell @value{GDBN} to expect the specified @var{prompt} string from the
18572 remote monitor. The default depends on the target:
18582 @item show monitor-prompt
18583 @kindex show monitor-prompt@r{, MIPS remote}
18584 Show the current strings @value{GDBN} expects as the prompt from the
18587 @item set monitor-warnings
18588 @kindex set monitor-warnings@r{, MIPS remote}
18589 Enable or disable monitor warnings about hardware breakpoints. This
18590 has effect only for the @code{lsi} target. When on, @value{GDBN} will
18591 display warning messages whose codes are returned by the @code{lsi}
18592 PMON monitor for breakpoint commands.
18594 @item show monitor-warnings
18595 @kindex show monitor-warnings@r{, MIPS remote}
18596 Show the current setting of printing monitor warnings.
18598 @item pmon @var{command}
18599 @kindex pmon@r{, MIPS remote}
18600 @cindex send PMON command
18601 This command allows sending an arbitrary @var{command} string to the
18602 monitor. The monitor must be in debug mode for this to work.
18605 @node OpenRISC 1000
18606 @subsection OpenRISC 1000
18607 @cindex OpenRISC 1000
18609 @cindex or1k boards
18610 See OR1k Architecture document (@uref{www.opencores.org}) for more information
18611 about platform and commands.
18615 @kindex target jtag
18616 @item target jtag jtag://@var{host}:@var{port}
18618 Connects to remote JTAG server.
18619 JTAG remote server can be either an or1ksim or JTAG server,
18620 connected via parallel port to the board.
18622 Example: @code{target jtag jtag://localhost:9999}
18625 @item or1ksim @var{command}
18626 If connected to @code{or1ksim} OpenRISC 1000 Architectural
18627 Simulator, proprietary commands can be executed.
18629 @kindex info or1k spr
18630 @item info or1k spr
18631 Displays spr groups.
18633 @item info or1k spr @var{group}
18634 @itemx info or1k spr @var{groupno}
18635 Displays register names in selected group.
18637 @item info or1k spr @var{group} @var{register}
18638 @itemx info or1k spr @var{register}
18639 @itemx info or1k spr @var{groupno} @var{registerno}
18640 @itemx info or1k spr @var{registerno}
18641 Shows information about specified spr register.
18644 @item spr @var{group} @var{register} @var{value}
18645 @itemx spr @var{register @var{value}}
18646 @itemx spr @var{groupno} @var{registerno @var{value}}
18647 @itemx spr @var{registerno @var{value}}
18648 Writes @var{value} to specified spr register.
18651 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
18652 It is very similar to @value{GDBN} trace, except it does not interfere with normal
18653 program execution and is thus much faster. Hardware breakpoints/watchpoint
18654 triggers can be set using:
18657 Load effective address/data
18659 Store effective address/data
18661 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
18666 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
18667 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
18669 @code{htrace} commands:
18670 @cindex OpenRISC 1000 htrace
18673 @item hwatch @var{conditional}
18674 Set hardware watchpoint on combination of Load/Store Effective Address(es)
18675 or Data. For example:
18677 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
18679 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
18683 Display information about current HW trace configuration.
18685 @item htrace trigger @var{conditional}
18686 Set starting criteria for HW trace.
18688 @item htrace qualifier @var{conditional}
18689 Set acquisition qualifier for HW trace.
18691 @item htrace stop @var{conditional}
18692 Set HW trace stopping criteria.
18694 @item htrace record [@var{data}]*
18695 Selects the data to be recorded, when qualifier is met and HW trace was
18698 @item htrace enable
18699 @itemx htrace disable
18700 Enables/disables the HW trace.
18702 @item htrace rewind [@var{filename}]
18703 Clears currently recorded trace data.
18705 If filename is specified, new trace file is made and any newly collected data
18706 will be written there.
18708 @item htrace print [@var{start} [@var{len}]]
18709 Prints trace buffer, using current record configuration.
18711 @item htrace mode continuous
18712 Set continuous trace mode.
18714 @item htrace mode suspend
18715 Set suspend trace mode.
18719 @node PowerPC Embedded
18720 @subsection PowerPC Embedded
18722 @cindex DVC register
18723 @value{GDBN} supports using the DVC (Data Value Compare) register to
18724 implement in hardware simple hardware watchpoint conditions of the form:
18727 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
18728 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
18731 The DVC register will be automatically used whenever @value{GDBN} detects
18732 such pattern in a condition expression. This feature is available in native
18733 @value{GDBN} running on a Linux kernel version 2.6.34 or newer.
18735 @value{GDBN} provides the following PowerPC-specific commands:
18738 @kindex set powerpc
18739 @item set powerpc soft-float
18740 @itemx show powerpc soft-float
18741 Force @value{GDBN} to use (or not use) a software floating point calling
18742 convention. By default, @value{GDBN} selects the calling convention based
18743 on the selected architecture and the provided executable file.
18745 @item set powerpc vector-abi
18746 @itemx show powerpc vector-abi
18747 Force @value{GDBN} to use the specified calling convention for vector
18748 arguments and return values. The valid options are @samp{auto};
18749 @samp{generic}, to avoid vector registers even if they are present;
18750 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
18751 registers. By default, @value{GDBN} selects the calling convention
18752 based on the selected architecture and the provided executable file.
18754 @kindex target dink32
18755 @item target dink32 @var{dev}
18756 DINK32 ROM monitor.
18758 @kindex target ppcbug
18759 @item target ppcbug @var{dev}
18760 @kindex target ppcbug1
18761 @item target ppcbug1 @var{dev}
18762 PPCBUG ROM monitor for PowerPC.
18765 @item target sds @var{dev}
18766 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
18769 @cindex SDS protocol
18770 The following commands specific to the SDS protocol are supported
18774 @item set sdstimeout @var{nsec}
18775 @kindex set sdstimeout
18776 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
18777 default is 2 seconds.
18779 @item show sdstimeout
18780 @kindex show sdstimeout
18781 Show the current value of the SDS timeout.
18783 @item sds @var{command}
18784 @kindex sds@r{, a command}
18785 Send the specified @var{command} string to the SDS monitor.
18790 @subsection HP PA Embedded
18794 @kindex target op50n
18795 @item target op50n @var{dev}
18796 OP50N monitor, running on an OKI HPPA board.
18798 @kindex target w89k
18799 @item target w89k @var{dev}
18800 W89K monitor, running on a Winbond HPPA board.
18805 @subsection Tsqware Sparclet
18809 @value{GDBN} enables developers to debug tasks running on
18810 Sparclet targets from a Unix host.
18811 @value{GDBN} uses code that runs on
18812 both the Unix host and on the Sparclet target. The program
18813 @code{@value{GDBP}} is installed and executed on the Unix host.
18816 @item remotetimeout @var{args}
18817 @kindex remotetimeout
18818 @value{GDBN} supports the option @code{remotetimeout}.
18819 This option is set by the user, and @var{args} represents the number of
18820 seconds @value{GDBN} waits for responses.
18823 @cindex compiling, on Sparclet
18824 When compiling for debugging, include the options @samp{-g} to get debug
18825 information and @samp{-Ttext} to relocate the program to where you wish to
18826 load it on the target. You may also want to add the options @samp{-n} or
18827 @samp{-N} in order to reduce the size of the sections. Example:
18830 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
18833 You can use @code{objdump} to verify that the addresses are what you intended:
18836 sparclet-aout-objdump --headers --syms prog
18839 @cindex running, on Sparclet
18841 your Unix execution search path to find @value{GDBN}, you are ready to
18842 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
18843 (or @code{sparclet-aout-gdb}, depending on your installation).
18845 @value{GDBN} comes up showing the prompt:
18852 * Sparclet File:: Setting the file to debug
18853 * Sparclet Connection:: Connecting to Sparclet
18854 * Sparclet Download:: Sparclet download
18855 * Sparclet Execution:: Running and debugging
18858 @node Sparclet File
18859 @subsubsection Setting File to Debug
18861 The @value{GDBN} command @code{file} lets you choose with program to debug.
18864 (gdbslet) file prog
18868 @value{GDBN} then attempts to read the symbol table of @file{prog}.
18869 @value{GDBN} locates
18870 the file by searching the directories listed in the command search
18872 If the file was compiled with debug information (option @samp{-g}), source
18873 files will be searched as well.
18874 @value{GDBN} locates
18875 the source files by searching the directories listed in the directory search
18876 path (@pxref{Environment, ,Your Program's Environment}).
18878 to find a file, it displays a message such as:
18881 prog: No such file or directory.
18884 When this happens, add the appropriate directories to the search paths with
18885 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
18886 @code{target} command again.
18888 @node Sparclet Connection
18889 @subsubsection Connecting to Sparclet
18891 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
18892 To connect to a target on serial port ``@code{ttya}'', type:
18895 (gdbslet) target sparclet /dev/ttya
18896 Remote target sparclet connected to /dev/ttya
18897 main () at ../prog.c:3
18901 @value{GDBN} displays messages like these:
18907 @node Sparclet Download
18908 @subsubsection Sparclet Download
18910 @cindex download to Sparclet
18911 Once connected to the Sparclet target,
18912 you can use the @value{GDBN}
18913 @code{load} command to download the file from the host to the target.
18914 The file name and load offset should be given as arguments to the @code{load}
18916 Since the file format is aout, the program must be loaded to the starting
18917 address. You can use @code{objdump} to find out what this value is. The load
18918 offset is an offset which is added to the VMA (virtual memory address)
18919 of each of the file's sections.
18920 For instance, if the program
18921 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
18922 and bss at 0x12010170, in @value{GDBN}, type:
18925 (gdbslet) load prog 0x12010000
18926 Loading section .text, size 0xdb0 vma 0x12010000
18929 If the code is loaded at a different address then what the program was linked
18930 to, you may need to use the @code{section} and @code{add-symbol-file} commands
18931 to tell @value{GDBN} where to map the symbol table.
18933 @node Sparclet Execution
18934 @subsubsection Running and Debugging
18936 @cindex running and debugging Sparclet programs
18937 You can now begin debugging the task using @value{GDBN}'s execution control
18938 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
18939 manual for the list of commands.
18943 Breakpoint 1 at 0x12010000: file prog.c, line 3.
18945 Starting program: prog
18946 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
18947 3 char *symarg = 0;
18949 4 char *execarg = "hello!";
18954 @subsection Fujitsu Sparclite
18958 @kindex target sparclite
18959 @item target sparclite @var{dev}
18960 Fujitsu sparclite boards, used only for the purpose of loading.
18961 You must use an additional command to debug the program.
18962 For example: target remote @var{dev} using @value{GDBN} standard
18968 @subsection Zilog Z8000
18971 @cindex simulator, Z8000
18972 @cindex Zilog Z8000 simulator
18974 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
18977 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
18978 unsegmented variant of the Z8000 architecture) or the Z8001 (the
18979 segmented variant). The simulator recognizes which architecture is
18980 appropriate by inspecting the object code.
18983 @item target sim @var{args}
18985 @kindex target sim@r{, with Z8000}
18986 Debug programs on a simulated CPU. If the simulator supports setup
18987 options, specify them via @var{args}.
18991 After specifying this target, you can debug programs for the simulated
18992 CPU in the same style as programs for your host computer; use the
18993 @code{file} command to load a new program image, the @code{run} command
18994 to run your program, and so on.
18996 As well as making available all the usual machine registers
18997 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
18998 additional items of information as specially named registers:
19003 Counts clock-ticks in the simulator.
19006 Counts instructions run in the simulator.
19009 Execution time in 60ths of a second.
19013 You can refer to these values in @value{GDBN} expressions with the usual
19014 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
19015 conditional breakpoint that suspends only after at least 5000
19016 simulated clock ticks.
19019 @subsection Atmel AVR
19022 When configured for debugging the Atmel AVR, @value{GDBN} supports the
19023 following AVR-specific commands:
19026 @item info io_registers
19027 @kindex info io_registers@r{, AVR}
19028 @cindex I/O registers (Atmel AVR)
19029 This command displays information about the AVR I/O registers. For
19030 each register, @value{GDBN} prints its number and value.
19037 When configured for debugging CRIS, @value{GDBN} provides the
19038 following CRIS-specific commands:
19041 @item set cris-version @var{ver}
19042 @cindex CRIS version
19043 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
19044 The CRIS version affects register names and sizes. This command is useful in
19045 case autodetection of the CRIS version fails.
19047 @item show cris-version
19048 Show the current CRIS version.
19050 @item set cris-dwarf2-cfi
19051 @cindex DWARF-2 CFI and CRIS
19052 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
19053 Change to @samp{off} when using @code{gcc-cris} whose version is below
19056 @item show cris-dwarf2-cfi
19057 Show the current state of using DWARF-2 CFI.
19059 @item set cris-mode @var{mode}
19061 Set the current CRIS mode to @var{mode}. It should only be changed when
19062 debugging in guru mode, in which case it should be set to
19063 @samp{guru} (the default is @samp{normal}).
19065 @item show cris-mode
19066 Show the current CRIS mode.
19070 @subsection Renesas Super-H
19073 For the Renesas Super-H processor, @value{GDBN} provides these
19078 @kindex regs@r{, Super-H}
19079 Show the values of all Super-H registers.
19081 @item set sh calling-convention @var{convention}
19082 @kindex set sh calling-convention
19083 Set the calling-convention used when calling functions from @value{GDBN}.
19084 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
19085 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
19086 convention. If the DWARF-2 information of the called function specifies
19087 that the function follows the Renesas calling convention, the function
19088 is called using the Renesas calling convention. If the calling convention
19089 is set to @samp{renesas}, the Renesas calling convention is always used,
19090 regardless of the DWARF-2 information. This can be used to override the
19091 default of @samp{gcc} if debug information is missing, or the compiler
19092 does not emit the DWARF-2 calling convention entry for a function.
19094 @item show sh calling-convention
19095 @kindex show sh calling-convention
19096 Show the current calling convention setting.
19101 @node Architectures
19102 @section Architectures
19104 This section describes characteristics of architectures that affect
19105 all uses of @value{GDBN} with the architecture, both native and cross.
19112 * HPPA:: HP PA architecture
19113 * SPU:: Cell Broadband Engine SPU architecture
19118 @subsection x86 Architecture-specific Issues
19121 @item set struct-convention @var{mode}
19122 @kindex set struct-convention
19123 @cindex struct return convention
19124 @cindex struct/union returned in registers
19125 Set the convention used by the inferior to return @code{struct}s and
19126 @code{union}s from functions to @var{mode}. Possible values of
19127 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
19128 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
19129 are returned on the stack, while @code{"reg"} means that a
19130 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
19131 be returned in a register.
19133 @item show struct-convention
19134 @kindex show struct-convention
19135 Show the current setting of the convention to return @code{struct}s
19144 @kindex set rstack_high_address
19145 @cindex AMD 29K register stack
19146 @cindex register stack, AMD29K
19147 @item set rstack_high_address @var{address}
19148 On AMD 29000 family processors, registers are saved in a separate
19149 @dfn{register stack}. There is no way for @value{GDBN} to determine the
19150 extent of this stack. Normally, @value{GDBN} just assumes that the
19151 stack is ``large enough''. This may result in @value{GDBN} referencing
19152 memory locations that do not exist. If necessary, you can get around
19153 this problem by specifying the ending address of the register stack with
19154 the @code{set rstack_high_address} command. The argument should be an
19155 address, which you probably want to precede with @samp{0x} to specify in
19158 @kindex show rstack_high_address
19159 @item show rstack_high_address
19160 Display the current limit of the register stack, on AMD 29000 family
19168 See the following section.
19173 @cindex stack on Alpha
19174 @cindex stack on MIPS
19175 @cindex Alpha stack
19177 Alpha- and MIPS-based computers use an unusual stack frame, which
19178 sometimes requires @value{GDBN} to search backward in the object code to
19179 find the beginning of a function.
19181 @cindex response time, MIPS debugging
19182 To improve response time (especially for embedded applications, where
19183 @value{GDBN} may be restricted to a slow serial line for this search)
19184 you may want to limit the size of this search, using one of these
19188 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
19189 @item set heuristic-fence-post @var{limit}
19190 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
19191 search for the beginning of a function. A value of @var{0} (the
19192 default) means there is no limit. However, except for @var{0}, the
19193 larger the limit the more bytes @code{heuristic-fence-post} must search
19194 and therefore the longer it takes to run. You should only need to use
19195 this command when debugging a stripped executable.
19197 @item show heuristic-fence-post
19198 Display the current limit.
19202 These commands are available @emph{only} when @value{GDBN} is configured
19203 for debugging programs on Alpha or MIPS processors.
19205 Several MIPS-specific commands are available when debugging MIPS
19209 @item set mips abi @var{arg}
19210 @kindex set mips abi
19211 @cindex set ABI for MIPS
19212 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
19213 values of @var{arg} are:
19217 The default ABI associated with the current binary (this is the
19228 @item show mips abi
19229 @kindex show mips abi
19230 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
19233 @itemx show mipsfpu
19234 @xref{MIPS Embedded, set mipsfpu}.
19236 @item set mips mask-address @var{arg}
19237 @kindex set mips mask-address
19238 @cindex MIPS addresses, masking
19239 This command determines whether the most-significant 32 bits of 64-bit
19240 MIPS addresses are masked off. The argument @var{arg} can be
19241 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
19242 setting, which lets @value{GDBN} determine the correct value.
19244 @item show mips mask-address
19245 @kindex show mips mask-address
19246 Show whether the upper 32 bits of MIPS addresses are masked off or
19249 @item set remote-mips64-transfers-32bit-regs
19250 @kindex set remote-mips64-transfers-32bit-regs
19251 This command controls compatibility with 64-bit MIPS targets that
19252 transfer data in 32-bit quantities. If you have an old MIPS 64 target
19253 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
19254 and 64 bits for other registers, set this option to @samp{on}.
19256 @item show remote-mips64-transfers-32bit-regs
19257 @kindex show remote-mips64-transfers-32bit-regs
19258 Show the current setting of compatibility with older MIPS 64 targets.
19260 @item set debug mips
19261 @kindex set debug mips
19262 This command turns on and off debugging messages for the MIPS-specific
19263 target code in @value{GDBN}.
19265 @item show debug mips
19266 @kindex show debug mips
19267 Show the current setting of MIPS debugging messages.
19273 @cindex HPPA support
19275 When @value{GDBN} is debugging the HP PA architecture, it provides the
19276 following special commands:
19279 @item set debug hppa
19280 @kindex set debug hppa
19281 This command determines whether HPPA architecture-specific debugging
19282 messages are to be displayed.
19284 @item show debug hppa
19285 Show whether HPPA debugging messages are displayed.
19287 @item maint print unwind @var{address}
19288 @kindex maint print unwind@r{, HPPA}
19289 This command displays the contents of the unwind table entry at the
19290 given @var{address}.
19296 @subsection Cell Broadband Engine SPU architecture
19297 @cindex Cell Broadband Engine
19300 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
19301 it provides the following special commands:
19304 @item info spu event
19306 Display SPU event facility status. Shows current event mask
19307 and pending event status.
19309 @item info spu signal
19310 Display SPU signal notification facility status. Shows pending
19311 signal-control word and signal notification mode of both signal
19312 notification channels.
19314 @item info spu mailbox
19315 Display SPU mailbox facility status. Shows all pending entries,
19316 in order of processing, in each of the SPU Write Outbound,
19317 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
19320 Display MFC DMA status. Shows all pending commands in the MFC
19321 DMA queue. For each entry, opcode, tag, class IDs, effective
19322 and local store addresses and transfer size are shown.
19324 @item info spu proxydma
19325 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
19326 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
19327 and local store addresses and transfer size are shown.
19331 When @value{GDBN} is debugging a combined PowerPC/SPU application
19332 on the Cell Broadband Engine, it provides in addition the following
19336 @item set spu stop-on-load @var{arg}
19338 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
19339 will give control to the user when a new SPE thread enters its @code{main}
19340 function. The default is @code{off}.
19342 @item show spu stop-on-load
19344 Show whether to stop for new SPE threads.
19346 @item set spu auto-flush-cache @var{arg}
19347 Set whether to automatically flush the software-managed cache. When set to
19348 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
19349 cache to be flushed whenever SPE execution stops. This provides a consistent
19350 view of PowerPC memory that is accessed via the cache. If an application
19351 does not use the software-managed cache, this option has no effect.
19353 @item show spu auto-flush-cache
19354 Show whether to automatically flush the software-managed cache.
19359 @subsection PowerPC
19360 @cindex PowerPC architecture
19362 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
19363 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
19364 numbers stored in the floating point registers. These values must be stored
19365 in two consecutive registers, always starting at an even register like
19366 @code{f0} or @code{f2}.
19368 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
19369 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
19370 @code{f2} and @code{f3} for @code{$dl1} and so on.
19372 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
19373 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
19376 @node Controlling GDB
19377 @chapter Controlling @value{GDBN}
19379 You can alter the way @value{GDBN} interacts with you by using the
19380 @code{set} command. For commands controlling how @value{GDBN} displays
19381 data, see @ref{Print Settings, ,Print Settings}. Other settings are
19386 * Editing:: Command editing
19387 * Command History:: Command history
19388 * Screen Size:: Screen size
19389 * Numbers:: Numbers
19390 * ABI:: Configuring the current ABI
19391 * Messages/Warnings:: Optional warnings and messages
19392 * Debugging Output:: Optional messages about internal happenings
19393 * Other Misc Settings:: Other Miscellaneous Settings
19401 @value{GDBN} indicates its readiness to read a command by printing a string
19402 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
19403 can change the prompt string with the @code{set prompt} command. For
19404 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
19405 the prompt in one of the @value{GDBN} sessions so that you can always tell
19406 which one you are talking to.
19408 @emph{Note:} @code{set prompt} does not add a space for you after the
19409 prompt you set. This allows you to set a prompt which ends in a space
19410 or a prompt that does not.
19414 @item set prompt @var{newprompt}
19415 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
19417 @kindex show prompt
19419 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
19423 @section Command Editing
19425 @cindex command line editing
19427 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
19428 @sc{gnu} library provides consistent behavior for programs which provide a
19429 command line interface to the user. Advantages are @sc{gnu} Emacs-style
19430 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
19431 substitution, and a storage and recall of command history across
19432 debugging sessions.
19434 You may control the behavior of command line editing in @value{GDBN} with the
19435 command @code{set}.
19438 @kindex set editing
19441 @itemx set editing on
19442 Enable command line editing (enabled by default).
19444 @item set editing off
19445 Disable command line editing.
19447 @kindex show editing
19449 Show whether command line editing is enabled.
19452 @ifset SYSTEM_READLINE
19453 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
19455 @ifclear SYSTEM_READLINE
19456 @xref{Command Line Editing},
19458 for more details about the Readline
19459 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
19460 encouraged to read that chapter.
19462 @node Command History
19463 @section Command History
19464 @cindex command history
19466 @value{GDBN} can keep track of the commands you type during your
19467 debugging sessions, so that you can be certain of precisely what
19468 happened. Use these commands to manage the @value{GDBN} command
19471 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
19472 package, to provide the history facility.
19473 @ifset SYSTEM_READLINE
19474 @xref{Using History Interactively, , , history, GNU History Library},
19476 @ifclear SYSTEM_READLINE
19477 @xref{Using History Interactively},
19479 for the detailed description of the History library.
19481 To issue a command to @value{GDBN} without affecting certain aspects of
19482 the state which is seen by users, prefix it with @samp{server }
19483 (@pxref{Server Prefix}). This
19484 means that this command will not affect the command history, nor will it
19485 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
19486 pressed on a line by itself.
19488 @cindex @code{server}, command prefix
19489 The server prefix does not affect the recording of values into the value
19490 history; to print a value without recording it into the value history,
19491 use the @code{output} command instead of the @code{print} command.
19493 Here is the description of @value{GDBN} commands related to command
19497 @cindex history substitution
19498 @cindex history file
19499 @kindex set history filename
19500 @cindex @env{GDBHISTFILE}, environment variable
19501 @item set history filename @var{fname}
19502 Set the name of the @value{GDBN} command history file to @var{fname}.
19503 This is the file where @value{GDBN} reads an initial command history
19504 list, and where it writes the command history from this session when it
19505 exits. You can access this list through history expansion or through
19506 the history command editing characters listed below. This file defaults
19507 to the value of the environment variable @code{GDBHISTFILE}, or to
19508 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
19511 @cindex save command history
19512 @kindex set history save
19513 @item set history save
19514 @itemx set history save on
19515 Record command history in a file, whose name may be specified with the
19516 @code{set history filename} command. By default, this option is disabled.
19518 @item set history save off
19519 Stop recording command history in a file.
19521 @cindex history size
19522 @kindex set history size
19523 @cindex @env{HISTSIZE}, environment variable
19524 @item set history size @var{size}
19525 Set the number of commands which @value{GDBN} keeps in its history list.
19526 This defaults to the value of the environment variable
19527 @code{HISTSIZE}, or to 256 if this variable is not set.
19530 History expansion assigns special meaning to the character @kbd{!}.
19531 @ifset SYSTEM_READLINE
19532 @xref{Event Designators, , , history, GNU History Library},
19534 @ifclear SYSTEM_READLINE
19535 @xref{Event Designators},
19539 @cindex history expansion, turn on/off
19540 Since @kbd{!} is also the logical not operator in C, history expansion
19541 is off by default. If you decide to enable history expansion with the
19542 @code{set history expansion on} command, you may sometimes need to
19543 follow @kbd{!} (when it is used as logical not, in an expression) with
19544 a space or a tab to prevent it from being expanded. The readline
19545 history facilities do not attempt substitution on the strings
19546 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
19548 The commands to control history expansion are:
19551 @item set history expansion on
19552 @itemx set history expansion
19553 @kindex set history expansion
19554 Enable history expansion. History expansion is off by default.
19556 @item set history expansion off
19557 Disable history expansion.
19560 @kindex show history
19562 @itemx show history filename
19563 @itemx show history save
19564 @itemx show history size
19565 @itemx show history expansion
19566 These commands display the state of the @value{GDBN} history parameters.
19567 @code{show history} by itself displays all four states.
19572 @kindex show commands
19573 @cindex show last commands
19574 @cindex display command history
19575 @item show commands
19576 Display the last ten commands in the command history.
19578 @item show commands @var{n}
19579 Print ten commands centered on command number @var{n}.
19581 @item show commands +
19582 Print ten commands just after the commands last printed.
19586 @section Screen Size
19587 @cindex size of screen
19588 @cindex pauses in output
19590 Certain commands to @value{GDBN} may produce large amounts of
19591 information output to the screen. To help you read all of it,
19592 @value{GDBN} pauses and asks you for input at the end of each page of
19593 output. Type @key{RET} when you want to continue the output, or @kbd{q}
19594 to discard the remaining output. Also, the screen width setting
19595 determines when to wrap lines of output. Depending on what is being
19596 printed, @value{GDBN} tries to break the line at a readable place,
19597 rather than simply letting it overflow onto the following line.
19599 Normally @value{GDBN} knows the size of the screen from the terminal
19600 driver software. For example, on Unix @value{GDBN} uses the termcap data base
19601 together with the value of the @code{TERM} environment variable and the
19602 @code{stty rows} and @code{stty cols} settings. If this is not correct,
19603 you can override it with the @code{set height} and @code{set
19610 @kindex show height
19611 @item set height @var{lpp}
19613 @itemx set width @var{cpl}
19615 These @code{set} commands specify a screen height of @var{lpp} lines and
19616 a screen width of @var{cpl} characters. The associated @code{show}
19617 commands display the current settings.
19619 If you specify a height of zero lines, @value{GDBN} does not pause during
19620 output no matter how long the output is. This is useful if output is to a
19621 file or to an editor buffer.
19623 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
19624 from wrapping its output.
19626 @item set pagination on
19627 @itemx set pagination off
19628 @kindex set pagination
19629 Turn the output pagination on or off; the default is on. Turning
19630 pagination off is the alternative to @code{set height 0}. Note that
19631 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
19632 Options, -batch}) also automatically disables pagination.
19634 @item show pagination
19635 @kindex show pagination
19636 Show the current pagination mode.
19641 @cindex number representation
19642 @cindex entering numbers
19644 You can always enter numbers in octal, decimal, or hexadecimal in
19645 @value{GDBN} by the usual conventions: octal numbers begin with
19646 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
19647 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
19648 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
19649 10; likewise, the default display for numbers---when no particular
19650 format is specified---is base 10. You can change the default base for
19651 both input and output with the commands described below.
19654 @kindex set input-radix
19655 @item set input-radix @var{base}
19656 Set the default base for numeric input. Supported choices
19657 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
19658 specified either unambiguously or using the current input radix; for
19662 set input-radix 012
19663 set input-radix 10.
19664 set input-radix 0xa
19668 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
19669 leaves the input radix unchanged, no matter what it was, since
19670 @samp{10}, being without any leading or trailing signs of its base, is
19671 interpreted in the current radix. Thus, if the current radix is 16,
19672 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
19675 @kindex set output-radix
19676 @item set output-radix @var{base}
19677 Set the default base for numeric display. Supported choices
19678 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
19679 specified either unambiguously or using the current input radix.
19681 @kindex show input-radix
19682 @item show input-radix
19683 Display the current default base for numeric input.
19685 @kindex show output-radix
19686 @item show output-radix
19687 Display the current default base for numeric display.
19689 @item set radix @r{[}@var{base}@r{]}
19693 These commands set and show the default base for both input and output
19694 of numbers. @code{set radix} sets the radix of input and output to
19695 the same base; without an argument, it resets the radix back to its
19696 default value of 10.
19701 @section Configuring the Current ABI
19703 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
19704 application automatically. However, sometimes you need to override its
19705 conclusions. Use these commands to manage @value{GDBN}'s view of the
19712 One @value{GDBN} configuration can debug binaries for multiple operating
19713 system targets, either via remote debugging or native emulation.
19714 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
19715 but you can override its conclusion using the @code{set osabi} command.
19716 One example where this is useful is in debugging of binaries which use
19717 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
19718 not have the same identifying marks that the standard C library for your
19723 Show the OS ABI currently in use.
19726 With no argument, show the list of registered available OS ABI's.
19728 @item set osabi @var{abi}
19729 Set the current OS ABI to @var{abi}.
19732 @cindex float promotion
19734 Generally, the way that an argument of type @code{float} is passed to a
19735 function depends on whether the function is prototyped. For a prototyped
19736 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
19737 according to the architecture's convention for @code{float}. For unprototyped
19738 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
19739 @code{double} and then passed.
19741 Unfortunately, some forms of debug information do not reliably indicate whether
19742 a function is prototyped. If @value{GDBN} calls a function that is not marked
19743 as prototyped, it consults @kbd{set coerce-float-to-double}.
19746 @kindex set coerce-float-to-double
19747 @item set coerce-float-to-double
19748 @itemx set coerce-float-to-double on
19749 Arguments of type @code{float} will be promoted to @code{double} when passed
19750 to an unprototyped function. This is the default setting.
19752 @item set coerce-float-to-double off
19753 Arguments of type @code{float} will be passed directly to unprototyped
19756 @kindex show coerce-float-to-double
19757 @item show coerce-float-to-double
19758 Show the current setting of promoting @code{float} to @code{double}.
19762 @kindex show cp-abi
19763 @value{GDBN} needs to know the ABI used for your program's C@t{++}
19764 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
19765 used to build your application. @value{GDBN} only fully supports
19766 programs with a single C@t{++} ABI; if your program contains code using
19767 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
19768 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
19769 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
19770 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
19771 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
19772 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
19777 Show the C@t{++} ABI currently in use.
19780 With no argument, show the list of supported C@t{++} ABI's.
19782 @item set cp-abi @var{abi}
19783 @itemx set cp-abi auto
19784 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
19787 @node Messages/Warnings
19788 @section Optional Warnings and Messages
19790 @cindex verbose operation
19791 @cindex optional warnings
19792 By default, @value{GDBN} is silent about its inner workings. If you are
19793 running on a slow machine, you may want to use the @code{set verbose}
19794 command. This makes @value{GDBN} tell you when it does a lengthy
19795 internal operation, so you will not think it has crashed.
19797 Currently, the messages controlled by @code{set verbose} are those
19798 which announce that the symbol table for a source file is being read;
19799 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
19802 @kindex set verbose
19803 @item set verbose on
19804 Enables @value{GDBN} output of certain informational messages.
19806 @item set verbose off
19807 Disables @value{GDBN} output of certain informational messages.
19809 @kindex show verbose
19811 Displays whether @code{set verbose} is on or off.
19814 By default, if @value{GDBN} encounters bugs in the symbol table of an
19815 object file, it is silent; but if you are debugging a compiler, you may
19816 find this information useful (@pxref{Symbol Errors, ,Errors Reading
19821 @kindex set complaints
19822 @item set complaints @var{limit}
19823 Permits @value{GDBN} to output @var{limit} complaints about each type of
19824 unusual symbols before becoming silent about the problem. Set
19825 @var{limit} to zero to suppress all complaints; set it to a large number
19826 to prevent complaints from being suppressed.
19828 @kindex show complaints
19829 @item show complaints
19830 Displays how many symbol complaints @value{GDBN} is permitted to produce.
19834 @anchor{confirmation requests}
19835 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
19836 lot of stupid questions to confirm certain commands. For example, if
19837 you try to run a program which is already running:
19841 The program being debugged has been started already.
19842 Start it from the beginning? (y or n)
19845 If you are willing to unflinchingly face the consequences of your own
19846 commands, you can disable this ``feature'':
19850 @kindex set confirm
19852 @cindex confirmation
19853 @cindex stupid questions
19854 @item set confirm off
19855 Disables confirmation requests. Note that running @value{GDBN} with
19856 the @option{--batch} option (@pxref{Mode Options, -batch}) also
19857 automatically disables confirmation requests.
19859 @item set confirm on
19860 Enables confirmation requests (the default).
19862 @kindex show confirm
19864 Displays state of confirmation requests.
19868 @cindex command tracing
19869 If you need to debug user-defined commands or sourced files you may find it
19870 useful to enable @dfn{command tracing}. In this mode each command will be
19871 printed as it is executed, prefixed with one or more @samp{+} symbols, the
19872 quantity denoting the call depth of each command.
19875 @kindex set trace-commands
19876 @cindex command scripts, debugging
19877 @item set trace-commands on
19878 Enable command tracing.
19879 @item set trace-commands off
19880 Disable command tracing.
19881 @item show trace-commands
19882 Display the current state of command tracing.
19885 @node Debugging Output
19886 @section Optional Messages about Internal Happenings
19887 @cindex optional debugging messages
19889 @value{GDBN} has commands that enable optional debugging messages from
19890 various @value{GDBN} subsystems; normally these commands are of
19891 interest to @value{GDBN} maintainers, or when reporting a bug. This
19892 section documents those commands.
19895 @kindex set exec-done-display
19896 @item set exec-done-display
19897 Turns on or off the notification of asynchronous commands'
19898 completion. When on, @value{GDBN} will print a message when an
19899 asynchronous command finishes its execution. The default is off.
19900 @kindex show exec-done-display
19901 @item show exec-done-display
19902 Displays the current setting of asynchronous command completion
19905 @cindex gdbarch debugging info
19906 @cindex architecture debugging info
19907 @item set debug arch
19908 Turns on or off display of gdbarch debugging info. The default is off
19910 @item show debug arch
19911 Displays the current state of displaying gdbarch debugging info.
19912 @item set debug aix-thread
19913 @cindex AIX threads
19914 Display debugging messages about inner workings of the AIX thread
19916 @item show debug aix-thread
19917 Show the current state of AIX thread debugging info display.
19918 @item set debug dwarf2-die
19919 @cindex DWARF2 DIEs
19920 Dump DWARF2 DIEs after they are read in.
19921 The value is the number of nesting levels to print.
19922 A value of zero turns off the display.
19923 @item show debug dwarf2-die
19924 Show the current state of DWARF2 DIE debugging.
19925 @item set debug displaced
19926 @cindex displaced stepping debugging info
19927 Turns on or off display of @value{GDBN} debugging info for the
19928 displaced stepping support. The default is off.
19929 @item show debug displaced
19930 Displays the current state of displaying @value{GDBN} debugging info
19931 related to displaced stepping.
19932 @item set debug event
19933 @cindex event debugging info
19934 Turns on or off display of @value{GDBN} event debugging info. The
19936 @item show debug event
19937 Displays the current state of displaying @value{GDBN} event debugging
19939 @item set debug expression
19940 @cindex expression debugging info
19941 Turns on or off display of debugging info about @value{GDBN}
19942 expression parsing. The default is off.
19943 @item show debug expression
19944 Displays the current state of displaying debugging info about
19945 @value{GDBN} expression parsing.
19946 @item set debug frame
19947 @cindex frame debugging info
19948 Turns on or off display of @value{GDBN} frame debugging info. The
19950 @item show debug frame
19951 Displays the current state of displaying @value{GDBN} frame debugging
19953 @item set debug gnu-nat
19954 @cindex @sc{gnu}/Hurd debug messages
19955 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
19956 @item show debug gnu-nat
19957 Show the current state of @sc{gnu}/Hurd debugging messages.
19958 @item set debug infrun
19959 @cindex inferior debugging info
19960 Turns on or off display of @value{GDBN} debugging info for running the inferior.
19961 The default is off. @file{infrun.c} contains GDB's runtime state machine used
19962 for implementing operations such as single-stepping the inferior.
19963 @item show debug infrun
19964 Displays the current state of @value{GDBN} inferior debugging.
19965 @item set debug lin-lwp
19966 @cindex @sc{gnu}/Linux LWP debug messages
19967 @cindex Linux lightweight processes
19968 Turns on or off debugging messages from the Linux LWP debug support.
19969 @item show debug lin-lwp
19970 Show the current state of Linux LWP debugging messages.
19971 @item set debug lin-lwp-async
19972 @cindex @sc{gnu}/Linux LWP async debug messages
19973 @cindex Linux lightweight processes
19974 Turns on or off debugging messages from the Linux LWP async debug support.
19975 @item show debug lin-lwp-async
19976 Show the current state of Linux LWP async debugging messages.
19977 @item set debug observer
19978 @cindex observer debugging info
19979 Turns on or off display of @value{GDBN} observer debugging. This
19980 includes info such as the notification of observable events.
19981 @item show debug observer
19982 Displays the current state of observer debugging.
19983 @item set debug overload
19984 @cindex C@t{++} overload debugging info
19985 Turns on or off display of @value{GDBN} C@t{++} overload debugging
19986 info. This includes info such as ranking of functions, etc. The default
19988 @item show debug overload
19989 Displays the current state of displaying @value{GDBN} C@t{++} overload
19991 @cindex expression parser, debugging info
19992 @cindex debug expression parser
19993 @item set debug parser
19994 Turns on or off the display of expression parser debugging output.
19995 Internally, this sets the @code{yydebug} variable in the expression
19996 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
19997 details. The default is off.
19998 @item show debug parser
19999 Show the current state of expression parser debugging.
20000 @cindex packets, reporting on stdout
20001 @cindex serial connections, debugging
20002 @cindex debug remote protocol
20003 @cindex remote protocol debugging
20004 @cindex display remote packets
20005 @item set debug remote
20006 Turns on or off display of reports on all packets sent back and forth across
20007 the serial line to the remote machine. The info is printed on the
20008 @value{GDBN} standard output stream. The default is off.
20009 @item show debug remote
20010 Displays the state of display of remote packets.
20011 @item set debug serial
20012 Turns on or off display of @value{GDBN} serial debugging info. The
20014 @item show debug serial
20015 Displays the current state of displaying @value{GDBN} serial debugging
20017 @item set debug solib-frv
20018 @cindex FR-V shared-library debugging
20019 Turns on or off debugging messages for FR-V shared-library code.
20020 @item show debug solib-frv
20021 Display the current state of FR-V shared-library code debugging
20023 @item set debug target
20024 @cindex target debugging info
20025 Turns on or off display of @value{GDBN} target debugging info. This info
20026 includes what is going on at the target level of GDB, as it happens. The
20027 default is 0. Set it to 1 to track events, and to 2 to also track the
20028 value of large memory transfers. Changes to this flag do not take effect
20029 until the next time you connect to a target or use the @code{run} command.
20030 @item show debug target
20031 Displays the current state of displaying @value{GDBN} target debugging
20033 @item set debug timestamp
20034 @cindex timestampping debugging info
20035 Turns on or off display of timestamps with @value{GDBN} debugging info.
20036 When enabled, seconds and microseconds are displayed before each debugging
20038 @item show debug timestamp
20039 Displays the current state of displaying timestamps with @value{GDBN}
20041 @item set debugvarobj
20042 @cindex variable object debugging info
20043 Turns on or off display of @value{GDBN} variable object debugging
20044 info. The default is off.
20045 @item show debugvarobj
20046 Displays the current state of displaying @value{GDBN} variable object
20048 @item set debug xml
20049 @cindex XML parser debugging
20050 Turns on or off debugging messages for built-in XML parsers.
20051 @item show debug xml
20052 Displays the current state of XML debugging messages.
20055 @node Other Misc Settings
20056 @section Other Miscellaneous Settings
20057 @cindex miscellaneous settings
20060 @kindex set interactive-mode
20061 @item set interactive-mode
20062 If @code{on}, forces @value{GDBN} to operate interactively.
20063 If @code{off}, forces @value{GDBN} to operate non-interactively,
20064 If @code{auto} (the default), @value{GDBN} guesses which mode to use,
20065 based on whether the debugger was started in a terminal or not.
20067 In the vast majority of cases, the debugger should be able to guess
20068 correctly which mode should be used. But this setting can be useful
20069 in certain specific cases, such as running a MinGW @value{GDBN}
20070 inside a cygwin window.
20072 @kindex show interactive-mode
20073 @item show interactive-mode
20074 Displays whether the debugger is operating in interactive mode or not.
20077 @node Extending GDB
20078 @chapter Extending @value{GDBN}
20079 @cindex extending GDB
20081 @value{GDBN} provides two mechanisms for extension. The first is based
20082 on composition of @value{GDBN} commands, and the second is based on the
20083 Python scripting language.
20085 To facilitate the use of these extensions, @value{GDBN} is capable
20086 of evaluating the contents of a file. When doing so, @value{GDBN}
20087 can recognize which scripting language is being used by looking at
20088 the filename extension. Files with an unrecognized filename extension
20089 are always treated as a @value{GDBN} Command Files.
20090 @xref{Command Files,, Command files}.
20092 You can control how @value{GDBN} evaluates these files with the following
20096 @kindex set script-extension
20097 @kindex show script-extension
20098 @item set script-extension off
20099 All scripts are always evaluated as @value{GDBN} Command Files.
20101 @item set script-extension soft
20102 The debugger determines the scripting language based on filename
20103 extension. If this scripting language is supported, @value{GDBN}
20104 evaluates the script using that language. Otherwise, it evaluates
20105 the file as a @value{GDBN} Command File.
20107 @item set script-extension strict
20108 The debugger determines the scripting language based on filename
20109 extension, and evaluates the script using that language. If the
20110 language is not supported, then the evaluation fails.
20112 @item show script-extension
20113 Display the current value of the @code{script-extension} option.
20118 * Sequences:: Canned Sequences of Commands
20119 * Python:: Scripting @value{GDBN} using Python
20123 @section Canned Sequences of Commands
20125 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
20126 Command Lists}), @value{GDBN} provides two ways to store sequences of
20127 commands for execution as a unit: user-defined commands and command
20131 * Define:: How to define your own commands
20132 * Hooks:: Hooks for user-defined commands
20133 * Command Files:: How to write scripts of commands to be stored in a file
20134 * Output:: Commands for controlled output
20138 @subsection User-defined Commands
20140 @cindex user-defined command
20141 @cindex arguments, to user-defined commands
20142 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
20143 which you assign a new name as a command. This is done with the
20144 @code{define} command. User commands may accept up to 10 arguments
20145 separated by whitespace. Arguments are accessed within the user command
20146 via @code{$arg0@dots{}$arg9}. A trivial example:
20150 print $arg0 + $arg1 + $arg2
20155 To execute the command use:
20162 This defines the command @code{adder}, which prints the sum of
20163 its three arguments. Note the arguments are text substitutions, so they may
20164 reference variables, use complex expressions, or even perform inferior
20167 @cindex argument count in user-defined commands
20168 @cindex how many arguments (user-defined commands)
20169 In addition, @code{$argc} may be used to find out how many arguments have
20170 been passed. This expands to a number in the range 0@dots{}10.
20175 print $arg0 + $arg1
20178 print $arg0 + $arg1 + $arg2
20186 @item define @var{commandname}
20187 Define a command named @var{commandname}. If there is already a command
20188 by that name, you are asked to confirm that you want to redefine it.
20189 @var{commandname} may be a bare command name consisting of letters,
20190 numbers, dashes, and underscores. It may also start with any predefined
20191 prefix command. For example, @samp{define target my-target} creates
20192 a user-defined @samp{target my-target} command.
20194 The definition of the command is made up of other @value{GDBN} command lines,
20195 which are given following the @code{define} command. The end of these
20196 commands is marked by a line containing @code{end}.
20199 @kindex end@r{ (user-defined commands)}
20200 @item document @var{commandname}
20201 Document the user-defined command @var{commandname}, so that it can be
20202 accessed by @code{help}. The command @var{commandname} must already be
20203 defined. This command reads lines of documentation just as @code{define}
20204 reads the lines of the command definition, ending with @code{end}.
20205 After the @code{document} command is finished, @code{help} on command
20206 @var{commandname} displays the documentation you have written.
20208 You may use the @code{document} command again to change the
20209 documentation of a command. Redefining the command with @code{define}
20210 does not change the documentation.
20212 @kindex dont-repeat
20213 @cindex don't repeat command
20215 Used inside a user-defined command, this tells @value{GDBN} that this
20216 command should not be repeated when the user hits @key{RET}
20217 (@pxref{Command Syntax, repeat last command}).
20219 @kindex help user-defined
20220 @item help user-defined
20221 List all user-defined commands, with the first line of the documentation
20226 @itemx show user @var{commandname}
20227 Display the @value{GDBN} commands used to define @var{commandname} (but
20228 not its documentation). If no @var{commandname} is given, display the
20229 definitions for all user-defined commands.
20231 @cindex infinite recursion in user-defined commands
20232 @kindex show max-user-call-depth
20233 @kindex set max-user-call-depth
20234 @item show max-user-call-depth
20235 @itemx set max-user-call-depth
20236 The value of @code{max-user-call-depth} controls how many recursion
20237 levels are allowed in user-defined commands before @value{GDBN} suspects an
20238 infinite recursion and aborts the command.
20241 In addition to the above commands, user-defined commands frequently
20242 use control flow commands, described in @ref{Command Files}.
20244 When user-defined commands are executed, the
20245 commands of the definition are not printed. An error in any command
20246 stops execution of the user-defined command.
20248 If used interactively, commands that would ask for confirmation proceed
20249 without asking when used inside a user-defined command. Many @value{GDBN}
20250 commands that normally print messages to say what they are doing omit the
20251 messages when used in a user-defined command.
20254 @subsection User-defined Command Hooks
20255 @cindex command hooks
20256 @cindex hooks, for commands
20257 @cindex hooks, pre-command
20260 You may define @dfn{hooks}, which are a special kind of user-defined
20261 command. Whenever you run the command @samp{foo}, if the user-defined
20262 command @samp{hook-foo} exists, it is executed (with no arguments)
20263 before that command.
20265 @cindex hooks, post-command
20267 A hook may also be defined which is run after the command you executed.
20268 Whenever you run the command @samp{foo}, if the user-defined command
20269 @samp{hookpost-foo} exists, it is executed (with no arguments) after
20270 that command. Post-execution hooks may exist simultaneously with
20271 pre-execution hooks, for the same command.
20273 It is valid for a hook to call the command which it hooks. If this
20274 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
20276 @c It would be nice if hookpost could be passed a parameter indicating
20277 @c if the command it hooks executed properly or not. FIXME!
20279 @kindex stop@r{, a pseudo-command}
20280 In addition, a pseudo-command, @samp{stop} exists. Defining
20281 (@samp{hook-stop}) makes the associated commands execute every time
20282 execution stops in your program: before breakpoint commands are run,
20283 displays are printed, or the stack frame is printed.
20285 For example, to ignore @code{SIGALRM} signals while
20286 single-stepping, but treat them normally during normal execution,
20291 handle SIGALRM nopass
20295 handle SIGALRM pass
20298 define hook-continue
20299 handle SIGALRM pass
20303 As a further example, to hook at the beginning and end of the @code{echo}
20304 command, and to add extra text to the beginning and end of the message,
20312 define hookpost-echo
20316 (@value{GDBP}) echo Hello World
20317 <<<---Hello World--->>>
20322 You can define a hook for any single-word command in @value{GDBN}, but
20323 not for command aliases; you should define a hook for the basic command
20324 name, e.g.@: @code{backtrace} rather than @code{bt}.
20325 @c FIXME! So how does Joe User discover whether a command is an alias
20327 You can hook a multi-word command by adding @code{hook-} or
20328 @code{hookpost-} to the last word of the command, e.g.@:
20329 @samp{define target hook-remote} to add a hook to @samp{target remote}.
20331 If an error occurs during the execution of your hook, execution of
20332 @value{GDBN} commands stops and @value{GDBN} issues a prompt
20333 (before the command that you actually typed had a chance to run).
20335 If you try to define a hook which does not match any known command, you
20336 get a warning from the @code{define} command.
20338 @node Command Files
20339 @subsection Command Files
20341 @cindex command files
20342 @cindex scripting commands
20343 A command file for @value{GDBN} is a text file made of lines that are
20344 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
20345 also be included. An empty line in a command file does nothing; it
20346 does not mean to repeat the last command, as it would from the
20349 You can request the execution of a command file with the @code{source}
20350 command. Note that the @code{source} command is also used to evaluate
20351 scripts that are not Command Files. The exact behavior can be configured
20352 using the @code{script-extension} setting.
20353 @xref{Extending GDB,, Extending GDB}.
20357 @cindex execute commands from a file
20358 @item source [-s] [-v] @var{filename}
20359 Execute the command file @var{filename}.
20362 The lines in a command file are generally executed sequentially,
20363 unless the order of execution is changed by one of the
20364 @emph{flow-control commands} described below. The commands are not
20365 printed as they are executed. An error in any command terminates
20366 execution of the command file and control is returned to the console.
20368 @value{GDBN} first searches for @var{filename} in the current directory.
20369 If the file is not found there, and @var{filename} does not specify a
20370 directory, then @value{GDBN} also looks for the file on the source search path
20371 (specified with the @samp{directory} command);
20372 except that @file{$cdir} is not searched because the compilation directory
20373 is not relevant to scripts.
20375 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
20376 on the search path even if @var{filename} specifies a directory.
20377 The search is done by appending @var{filename} to each element of the
20378 search path. So, for example, if @var{filename} is @file{mylib/myscript}
20379 and the search path contains @file{/home/user} then @value{GDBN} will
20380 look for the script @file{/home/user/mylib/myscript}.
20381 The search is also done if @var{filename} is an absolute path.
20382 For example, if @var{filename} is @file{/tmp/myscript} and
20383 the search path contains @file{/home/user} then @value{GDBN} will
20384 look for the script @file{/home/user/tmp/myscript}.
20385 For DOS-like systems, if @var{filename} contains a drive specification,
20386 it is stripped before concatenation. For example, if @var{filename} is
20387 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
20388 will look for the script @file{c:/tmp/myscript}.
20390 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
20391 each command as it is executed. The option must be given before
20392 @var{filename}, and is interpreted as part of the filename anywhere else.
20394 Commands that would ask for confirmation if used interactively proceed
20395 without asking when used in a command file. Many @value{GDBN} commands that
20396 normally print messages to say what they are doing omit the messages
20397 when called from command files.
20399 @value{GDBN} also accepts command input from standard input. In this
20400 mode, normal output goes to standard output and error output goes to
20401 standard error. Errors in a command file supplied on standard input do
20402 not terminate execution of the command file---execution continues with
20406 gdb < cmds > log 2>&1
20409 (The syntax above will vary depending on the shell used.) This example
20410 will execute commands from the file @file{cmds}. All output and errors
20411 would be directed to @file{log}.
20413 Since commands stored on command files tend to be more general than
20414 commands typed interactively, they frequently need to deal with
20415 complicated situations, such as different or unexpected values of
20416 variables and symbols, changes in how the program being debugged is
20417 built, etc. @value{GDBN} provides a set of flow-control commands to
20418 deal with these complexities. Using these commands, you can write
20419 complex scripts that loop over data structures, execute commands
20420 conditionally, etc.
20427 This command allows to include in your script conditionally executed
20428 commands. The @code{if} command takes a single argument, which is an
20429 expression to evaluate. It is followed by a series of commands that
20430 are executed only if the expression is true (its value is nonzero).
20431 There can then optionally be an @code{else} line, followed by a series
20432 of commands that are only executed if the expression was false. The
20433 end of the list is marked by a line containing @code{end}.
20437 This command allows to write loops. Its syntax is similar to
20438 @code{if}: the command takes a single argument, which is an expression
20439 to evaluate, and must be followed by the commands to execute, one per
20440 line, terminated by an @code{end}. These commands are called the
20441 @dfn{body} of the loop. The commands in the body of @code{while} are
20442 executed repeatedly as long as the expression evaluates to true.
20446 This command exits the @code{while} loop in whose body it is included.
20447 Execution of the script continues after that @code{while}s @code{end}
20450 @kindex loop_continue
20451 @item loop_continue
20452 This command skips the execution of the rest of the body of commands
20453 in the @code{while} loop in whose body it is included. Execution
20454 branches to the beginning of the @code{while} loop, where it evaluates
20455 the controlling expression.
20457 @kindex end@r{ (if/else/while commands)}
20459 Terminate the block of commands that are the body of @code{if},
20460 @code{else}, or @code{while} flow-control commands.
20465 @subsection Commands for Controlled Output
20467 During the execution of a command file or a user-defined command, normal
20468 @value{GDBN} output is suppressed; the only output that appears is what is
20469 explicitly printed by the commands in the definition. This section
20470 describes three commands useful for generating exactly the output you
20475 @item echo @var{text}
20476 @c I do not consider backslash-space a standard C escape sequence
20477 @c because it is not in ANSI.
20478 Print @var{text}. Nonprinting characters can be included in
20479 @var{text} using C escape sequences, such as @samp{\n} to print a
20480 newline. @strong{No newline is printed unless you specify one.}
20481 In addition to the standard C escape sequences, a backslash followed
20482 by a space stands for a space. This is useful for displaying a
20483 string with spaces at the beginning or the end, since leading and
20484 trailing spaces are otherwise trimmed from all arguments.
20485 To print @samp{@w{ }and foo =@w{ }}, use the command
20486 @samp{echo \@w{ }and foo = \@w{ }}.
20488 A backslash at the end of @var{text} can be used, as in C, to continue
20489 the command onto subsequent lines. For example,
20492 echo This is some text\n\
20493 which is continued\n\
20494 onto several lines.\n
20497 produces the same output as
20500 echo This is some text\n
20501 echo which is continued\n
20502 echo onto several lines.\n
20506 @item output @var{expression}
20507 Print the value of @var{expression} and nothing but that value: no
20508 newlines, no @samp{$@var{nn} = }. The value is not entered in the
20509 value history either. @xref{Expressions, ,Expressions}, for more information
20512 @item output/@var{fmt} @var{expression}
20513 Print the value of @var{expression} in format @var{fmt}. You can use
20514 the same formats as for @code{print}. @xref{Output Formats,,Output
20515 Formats}, for more information.
20518 @item printf @var{template}, @var{expressions}@dots{}
20519 Print the values of one or more @var{expressions} under the control of
20520 the string @var{template}. To print several values, make
20521 @var{expressions} be a comma-separated list of individual expressions,
20522 which may be either numbers or pointers. Their values are printed as
20523 specified by @var{template}, exactly as a C program would do by
20524 executing the code below:
20527 printf (@var{template}, @var{expressions}@dots{});
20530 As in @code{C} @code{printf}, ordinary characters in @var{template}
20531 are printed verbatim, while @dfn{conversion specification} introduced
20532 by the @samp{%} character cause subsequent @var{expressions} to be
20533 evaluated, their values converted and formatted according to type and
20534 style information encoded in the conversion specifications, and then
20537 For example, you can print two values in hex like this:
20540 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
20543 @code{printf} supports all the standard @code{C} conversion
20544 specifications, including the flags and modifiers between the @samp{%}
20545 character and the conversion letter, with the following exceptions:
20549 The argument-ordering modifiers, such as @samp{2$}, are not supported.
20552 The modifier @samp{*} is not supported for specifying precision or
20556 The @samp{'} flag (for separation of digits into groups according to
20557 @code{LC_NUMERIC'}) is not supported.
20560 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
20564 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
20567 The conversion letters @samp{a} and @samp{A} are not supported.
20571 Note that the @samp{ll} type modifier is supported only if the
20572 underlying @code{C} implementation used to build @value{GDBN} supports
20573 the @code{long long int} type, and the @samp{L} type modifier is
20574 supported only if @code{long double} type is available.
20576 As in @code{C}, @code{printf} supports simple backslash-escape
20577 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
20578 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
20579 single character. Octal and hexadecimal escape sequences are not
20582 Additionally, @code{printf} supports conversion specifications for DFP
20583 (@dfn{Decimal Floating Point}) types using the following length modifiers
20584 together with a floating point specifier.
20589 @samp{H} for printing @code{Decimal32} types.
20592 @samp{D} for printing @code{Decimal64} types.
20595 @samp{DD} for printing @code{Decimal128} types.
20598 If the underlying @code{C} implementation used to build @value{GDBN} has
20599 support for the three length modifiers for DFP types, other modifiers
20600 such as width and precision will also be available for @value{GDBN} to use.
20602 In case there is no such @code{C} support, no additional modifiers will be
20603 available and the value will be printed in the standard way.
20605 Here's an example of printing DFP types using the above conversion letters:
20607 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
20611 @item eval @var{template}, @var{expressions}@dots{}
20612 Convert the values of one or more @var{expressions} under the control of
20613 the string @var{template} to a command line, and call it.
20618 @section Scripting @value{GDBN} using Python
20619 @cindex python scripting
20620 @cindex scripting with python
20622 You can script @value{GDBN} using the @uref{http://www.python.org/,
20623 Python programming language}. This feature is available only if
20624 @value{GDBN} was configured using @option{--with-python}.
20626 @cindex python directory
20627 Python scripts used by @value{GDBN} should be installed in
20628 @file{@var{data-directory}/python}, where @var{data-directory} is
20629 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
20630 This directory, known as the @dfn{python directory},
20631 is automatically added to the Python Search Path in order to allow
20632 the Python interpreter to locate all scripts installed at this location.
20635 * Python Commands:: Accessing Python from @value{GDBN}.
20636 * Python API:: Accessing @value{GDBN} from Python.
20637 * Auto-loading:: Automatically loading Python code.
20638 * Python modules:: Python modules provided by @value{GDBN}.
20641 @node Python Commands
20642 @subsection Python Commands
20643 @cindex python commands
20644 @cindex commands to access python
20646 @value{GDBN} provides one command for accessing the Python interpreter,
20647 and one related setting:
20651 @item python @r{[}@var{code}@r{]}
20652 The @code{python} command can be used to evaluate Python code.
20654 If given an argument, the @code{python} command will evaluate the
20655 argument as a Python command. For example:
20658 (@value{GDBP}) python print 23
20662 If you do not provide an argument to @code{python}, it will act as a
20663 multi-line command, like @code{define}. In this case, the Python
20664 script is made up of subsequent command lines, given after the
20665 @code{python} command. This command list is terminated using a line
20666 containing @code{end}. For example:
20669 (@value{GDBP}) python
20671 End with a line saying just "end".
20677 @kindex maint set python print-stack
20678 @item maint set python print-stack
20679 By default, @value{GDBN} will print a stack trace when an error occurs
20680 in a Python script. This can be controlled using @code{maint set
20681 python print-stack}: if @code{on}, the default, then Python stack
20682 printing is enabled; if @code{off}, then Python stack printing is
20686 It is also possible to execute a Python script from the @value{GDBN}
20690 @item source @file{script-name}
20691 The script name must end with @samp{.py} and @value{GDBN} must be configured
20692 to recognize the script language based on filename extension using
20693 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
20695 @item python execfile ("script-name")
20696 This method is based on the @code{execfile} Python built-in function,
20697 and thus is always available.
20701 @subsection Python API
20703 @cindex programming in python
20705 @cindex python stdout
20706 @cindex python pagination
20707 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
20708 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
20709 A Python program which outputs to one of these streams may have its
20710 output interrupted by the user (@pxref{Screen Size}). In this
20711 situation, a Python @code{KeyboardInterrupt} exception is thrown.
20714 * Basic Python:: Basic Python Functions.
20715 * Exception Handling::
20716 * Values From Inferior::
20717 * Types In Python:: Python representation of types.
20718 * Pretty Printing API:: Pretty-printing values.
20719 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
20720 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
20721 * Inferiors In Python:: Python representation of inferiors (processes)
20722 * Threads In Python:: Accessing inferior threads from Python.
20723 * Commands In Python:: Implementing new commands in Python.
20724 * Parameters In Python:: Adding new @value{GDBN} parameters.
20725 * Functions In Python:: Writing new convenience functions.
20726 * Progspaces In Python:: Program spaces.
20727 * Objfiles In Python:: Object files.
20728 * Frames In Python:: Accessing inferior stack frames from Python.
20729 * Blocks In Python:: Accessing frame blocks from Python.
20730 * Symbols In Python:: Python representation of symbols.
20731 * Symbol Tables In Python:: Python representation of symbol tables.
20732 * Lazy Strings In Python:: Python representation of lazy strings.
20733 * Breakpoints In Python:: Manipulating breakpoints using Python.
20737 @subsubsection Basic Python
20739 @cindex python functions
20740 @cindex python module
20742 @value{GDBN} introduces a new Python module, named @code{gdb}. All
20743 methods and classes added by @value{GDBN} are placed in this module.
20744 @value{GDBN} automatically @code{import}s the @code{gdb} module for
20745 use in all scripts evaluated by the @code{python} command.
20747 @findex gdb.PYTHONDIR
20749 A string containing the python directory (@pxref{Python}).
20752 @findex gdb.execute
20753 @defun execute command [from_tty] [to_string]
20754 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
20755 If a GDB exception happens while @var{command} runs, it is
20756 translated as described in @ref{Exception Handling,,Exception Handling}.
20758 @var{from_tty} specifies whether @value{GDBN} ought to consider this
20759 command as having originated from the user invoking it interactively.
20760 It must be a boolean value. If omitted, it defaults to @code{False}.
20762 By default, any output produced by @var{command} is sent to
20763 @value{GDBN}'s standard output. If the @var{to_string} parameter is
20764 @code{True}, then output will be collected by @code{gdb.execute} and
20765 returned as a string. The default is @code{False}, in which case the
20766 return value is @code{None}. If @var{to_string} is @code{True}, the
20767 @value{GDBN} virtual terminal will be temporarily set to unlimited width
20768 and height, and its pagination will be disabled; @pxref{Screen Size}.
20771 @findex gdb.breakpoints
20773 Return a sequence holding all of @value{GDBN}'s breakpoints.
20774 @xref{Breakpoints In Python}, for more information.
20777 @findex gdb.parameter
20778 @defun parameter parameter
20779 Return the value of a @value{GDBN} parameter. @var{parameter} is a
20780 string naming the parameter to look up; @var{parameter} may contain
20781 spaces if the parameter has a multi-part name. For example,
20782 @samp{print object} is a valid parameter name.
20784 If the named parameter does not exist, this function throws a
20785 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
20786 parameter's value is converted to a Python value of the appropriate
20787 type, and returned.
20790 @findex gdb.history
20791 @defun history number
20792 Return a value from @value{GDBN}'s value history (@pxref{Value
20793 History}). @var{number} indicates which history element to return.
20794 If @var{number} is negative, then @value{GDBN} will take its absolute value
20795 and count backward from the last element (i.e., the most recent element) to
20796 find the value to return. If @var{number} is zero, then @value{GDBN} will
20797 return the most recent element. If the element specified by @var{number}
20798 doesn't exist in the value history, a @code{gdb.error} exception will be
20801 If no exception is raised, the return value is always an instance of
20802 @code{gdb.Value} (@pxref{Values From Inferior}).
20805 @findex gdb.parse_and_eval
20806 @defun parse_and_eval expression
20807 Parse @var{expression} as an expression in the current language,
20808 evaluate it, and return the result as a @code{gdb.Value}.
20809 @var{expression} must be a string.
20811 This function can be useful when implementing a new command
20812 (@pxref{Commands In Python}), as it provides a way to parse the
20813 command's argument as an expression. It is also useful simply to
20814 compute values, for example, it is the only way to get the value of a
20815 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
20818 @findex gdb.post_event
20819 @defun post_event event
20820 Put @var{event}, a callable object taking no arguments, into
20821 @value{GDBN}'s internal event queue. This callable will be invoked at
20822 some later point, during @value{GDBN}'s event processing. Events
20823 posted using @code{post_event} will be run in the order in which they
20824 were posted; however, there is no way to know when they will be
20825 processed relative to other events inside @value{GDBN}.
20827 @value{GDBN} is not thread-safe. If your Python program uses multiple
20828 threads, you must be careful to only call @value{GDBN}-specific
20829 functions in the main @value{GDBN} thread. @code{post_event} ensures
20833 (@value{GDBP}) python
20837 > def __init__(self, message):
20838 > self.message = message;
20839 > def __call__(self):
20840 > gdb.write(self.message)
20842 >class MyThread1 (threading.Thread):
20844 > gdb.post_event(Writer("Hello "))
20846 >class MyThread2 (threading.Thread):
20848 > gdb.post_event(Writer("World\n"))
20850 >MyThread1().start()
20851 >MyThread2().start()
20853 (@value{GDBP}) Hello World
20858 @defun write string
20859 Print a string to @value{GDBN}'s paginated standard output stream.
20860 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
20861 call this function.
20866 Flush @value{GDBN}'s paginated standard output stream. Flushing
20867 @code{sys.stdout} or @code{sys.stderr} will automatically call this
20871 @findex gdb.target_charset
20872 @defun target_charset
20873 Return the name of the current target character set (@pxref{Character
20874 Sets}). This differs from @code{gdb.parameter('target-charset')} in
20875 that @samp{auto} is never returned.
20878 @findex gdb.target_wide_charset
20879 @defun target_wide_charset
20880 Return the name of the current target wide character set
20881 (@pxref{Character Sets}). This differs from
20882 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
20886 @findex gdb.solib_name
20887 @defun solib_name address
20888 Return the name of the shared library holding the given @var{address}
20889 as a string, or @code{None}.
20892 @findex gdb.decode_line
20893 @defun decode_line @r{[}expression@r{]}
20894 Return locations of the line specified by @var{expression}, or of the
20895 current line if no argument was given. This function returns a Python
20896 tuple containing two elements. The first element contains a string
20897 holding any unparsed section of @var{expression} (or @code{None} if
20898 the expression has been fully parsed). The second element contains
20899 either @code{None} or another tuple that contains all the locations
20900 that match the expression represented as @code{gdb.Symtab_and_line}
20901 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
20902 provided, it is decoded the way that @value{GDBN}'s inbuilt
20903 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
20906 @node Exception Handling
20907 @subsubsection Exception Handling
20908 @cindex python exceptions
20909 @cindex exceptions, python
20911 When executing the @code{python} command, Python exceptions
20912 uncaught within the Python code are translated to calls to
20913 @value{GDBN} error-reporting mechanism. If the command that called
20914 @code{python} does not handle the error, @value{GDBN} will
20915 terminate it and print an error message containing the Python
20916 exception name, the associated value, and the Python call stack
20917 backtrace at the point where the exception was raised. Example:
20920 (@value{GDBP}) python print foo
20921 Traceback (most recent call last):
20922 File "<string>", line 1, in <module>
20923 NameError: name 'foo' is not defined
20926 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
20927 Python code are converted to Python exceptions. The type of the
20928 Python exception depends on the error.
20932 This is the base class for most exceptions generated by @value{GDBN}.
20933 It is derived from @code{RuntimeError}, for compatibility with earlier
20934 versions of @value{GDBN}.
20936 If an error occurring in @value{GDBN} does not fit into some more
20937 specific category, then the generated exception will have this type.
20939 @item gdb.MemoryError
20940 This is a subclass of @code{gdb.error} which is thrown when an
20941 operation tried to access invalid memory in the inferior.
20943 @item KeyboardInterrupt
20944 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
20945 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
20948 In all cases, your exception handler will see the @value{GDBN} error
20949 message as its value and the Python call stack backtrace at the Python
20950 statement closest to where the @value{GDBN} error occured as the
20953 @findex gdb.GdbError
20954 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
20955 it is useful to be able to throw an exception that doesn't cause a
20956 traceback to be printed. For example, the user may have invoked the
20957 command incorrectly. Use the @code{gdb.GdbError} exception
20958 to handle this case. Example:
20962 >class HelloWorld (gdb.Command):
20963 > """Greet the whole world."""
20964 > def __init__ (self):
20965 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
20966 > def invoke (self, args, from_tty):
20967 > argv = gdb.string_to_argv (args)
20968 > if len (argv) != 0:
20969 > raise gdb.GdbError ("hello-world takes no arguments")
20970 > print "Hello, World!"
20973 (gdb) hello-world 42
20974 hello-world takes no arguments
20977 @node Values From Inferior
20978 @subsubsection Values From Inferior
20979 @cindex values from inferior, with Python
20980 @cindex python, working with values from inferior
20982 @cindex @code{gdb.Value}
20983 @value{GDBN} provides values it obtains from the inferior program in
20984 an object of type @code{gdb.Value}. @value{GDBN} uses this object
20985 for its internal bookkeeping of the inferior's values, and for
20986 fetching values when necessary.
20988 Inferior values that are simple scalars can be used directly in
20989 Python expressions that are valid for the value's data type. Here's
20990 an example for an integer or floating-point value @code{some_val}:
20997 As result of this, @code{bar} will also be a @code{gdb.Value} object
20998 whose values are of the same type as those of @code{some_val}.
21000 Inferior values that are structures or instances of some class can
21001 be accessed using the Python @dfn{dictionary syntax}. For example, if
21002 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
21003 can access its @code{foo} element with:
21006 bar = some_val['foo']
21009 Again, @code{bar} will also be a @code{gdb.Value} object.
21011 A @code{gdb.Value} that represents a function can be executed via
21012 inferior function call. Any arguments provided to the call must match
21013 the function's prototype, and must be provided in the order specified
21016 For example, @code{some_val} is a @code{gdb.Value} instance
21017 representing a function that takes two integers as arguments. To
21018 execute this function, call it like so:
21021 result = some_val (10,20)
21024 Any values returned from a function call will be stored as a
21027 The following attributes are provided:
21030 @defivar Value address
21031 If this object is addressable, this read-only attribute holds a
21032 @code{gdb.Value} object representing the address. Otherwise,
21033 this attribute holds @code{None}.
21036 @cindex optimized out value in Python
21037 @defivar Value is_optimized_out
21038 This read-only boolean attribute is true if the compiler optimized out
21039 this value, thus it is not available for fetching from the inferior.
21042 @defivar Value type
21043 The type of this @code{gdb.Value}. The value of this attribute is a
21044 @code{gdb.Type} object (@pxref{Types In Python}).
21047 @defivar Value dynamic_type
21048 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
21049 type information (@acronym{RTTI}) to determine the dynamic type of the
21050 value. If this value is of class type, it will return the class in
21051 which the value is embedded, if any. If this value is of pointer or
21052 reference to a class type, it will compute the dynamic type of the
21053 referenced object, and return a pointer or reference to that type,
21054 respectively. In all other cases, it will return the value's static
21057 Note that this feature will only work when debugging a C@t{++} program
21058 that includes @acronym{RTTI} for the object in question. Otherwise,
21059 it will just return the static type of the value as in @kbd{ptype foo}
21060 (@pxref{Symbols, ptype}).
21064 The following methods are provided:
21067 @defmethod Value __init__ @var{val}
21068 Many Python values can be converted directly to a @code{gdb.Value} via
21069 this object initializer. Specifically:
21072 @item Python boolean
21073 A Python boolean is converted to the boolean type from the current
21076 @item Python integer
21077 A Python integer is converted to the C @code{long} type for the
21078 current architecture.
21081 A Python long is converted to the C @code{long long} type for the
21082 current architecture.
21085 A Python float is converted to the C @code{double} type for the
21086 current architecture.
21088 @item Python string
21089 A Python string is converted to a target string, using the current
21092 @item @code{gdb.Value}
21093 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
21095 @item @code{gdb.LazyString}
21096 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
21097 Python}), then the lazy string's @code{value} method is called, and
21098 its result is used.
21102 @defmethod Value cast type
21103 Return a new instance of @code{gdb.Value} that is the result of
21104 casting this instance to the type described by @var{type}, which must
21105 be a @code{gdb.Type} object. If the cast cannot be performed for some
21106 reason, this method throws an exception.
21109 @defmethod Value dereference
21110 For pointer data types, this method returns a new @code{gdb.Value} object
21111 whose contents is the object pointed to by the pointer. For example, if
21112 @code{foo} is a C pointer to an @code{int}, declared in your C program as
21119 then you can use the corresponding @code{gdb.Value} to access what
21120 @code{foo} points to like this:
21123 bar = foo.dereference ()
21126 The result @code{bar} will be a @code{gdb.Value} object holding the
21127 value pointed to by @code{foo}.
21130 @defmethod Value dynamic_cast type
21131 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
21132 operator were used. Consult a C@t{++} reference for details.
21135 @defmethod Value reinterpret_cast type
21136 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
21137 operator were used. Consult a C@t{++} reference for details.
21140 @defmethod Value string @r{[}encoding@r{]} @r{[}errors@r{]} @r{[}length@r{]}
21141 If this @code{gdb.Value} represents a string, then this method
21142 converts the contents to a Python string. Otherwise, this method will
21143 throw an exception.
21145 Strings are recognized in a language-specific way; whether a given
21146 @code{gdb.Value} represents a string is determined by the current
21149 For C-like languages, a value is a string if it is a pointer to or an
21150 array of characters or ints. The string is assumed to be terminated
21151 by a zero of the appropriate width. However if the optional length
21152 argument is given, the string will be converted to that given length,
21153 ignoring any embedded zeros that the string may contain.
21155 If the optional @var{encoding} argument is given, it must be a string
21156 naming the encoding of the string in the @code{gdb.Value}, such as
21157 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
21158 the same encodings as the corresponding argument to Python's
21159 @code{string.decode} method, and the Python codec machinery will be used
21160 to convert the string. If @var{encoding} is not given, or if
21161 @var{encoding} is the empty string, then either the @code{target-charset}
21162 (@pxref{Character Sets}) will be used, or a language-specific encoding
21163 will be used, if the current language is able to supply one.
21165 The optional @var{errors} argument is the same as the corresponding
21166 argument to Python's @code{string.decode} method.
21168 If the optional @var{length} argument is given, the string will be
21169 fetched and converted to the given length.
21172 @defmethod Value lazy_string @r{[}encoding@r{]} @r{[}length@r{]}
21173 If this @code{gdb.Value} represents a string, then this method
21174 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
21175 In Python}). Otherwise, this method will throw an exception.
21177 If the optional @var{encoding} argument is given, it must be a string
21178 naming the encoding of the @code{gdb.LazyString}. Some examples are:
21179 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
21180 @var{encoding} argument is an encoding that @value{GDBN} does
21181 recognize, @value{GDBN} will raise an error.
21183 When a lazy string is printed, the @value{GDBN} encoding machinery is
21184 used to convert the string during printing. If the optional
21185 @var{encoding} argument is not provided, or is an empty string,
21186 @value{GDBN} will automatically select the encoding most suitable for
21187 the string type. For further information on encoding in @value{GDBN}
21188 please see @ref{Character Sets}.
21190 If the optional @var{length} argument is given, the string will be
21191 fetched and encoded to the length of characters specified. If
21192 the @var{length} argument is not provided, the string will be fetched
21193 and encoded until a null of appropriate width is found.
21197 @node Types In Python
21198 @subsubsection Types In Python
21199 @cindex types in Python
21200 @cindex Python, working with types
21203 @value{GDBN} represents types from the inferior using the class
21206 The following type-related functions are available in the @code{gdb}
21209 @findex gdb.lookup_type
21210 @defun lookup_type name [block]
21211 This function looks up a type by name. @var{name} is the name of the
21212 type to look up. It must be a string.
21214 If @var{block} is given, then @var{name} is looked up in that scope.
21215 Otherwise, it is searched for globally.
21217 Ordinarily, this function will return an instance of @code{gdb.Type}.
21218 If the named type cannot be found, it will throw an exception.
21221 An instance of @code{Type} has the following attributes:
21225 The type code for this type. The type code will be one of the
21226 @code{TYPE_CODE_} constants defined below.
21229 @defivar Type sizeof
21230 The size of this type, in target @code{char} units. Usually, a
21231 target's @code{char} type will be an 8-bit byte. However, on some
21232 unusual platforms, this type may have a different size.
21236 The tag name for this type. The tag name is the name after
21237 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
21238 languages have this concept. If this type has no tag name, then
21239 @code{None} is returned.
21243 The following methods are provided:
21246 @defmethod Type fields
21247 For structure and union types, this method returns the fields. Range
21248 types have two fields, the minimum and maximum values. Enum types
21249 have one field per enum constant. Function and method types have one
21250 field per parameter. The base types of C@t{++} classes are also
21251 represented as fields. If the type has no fields, or does not fit
21252 into one of these categories, an empty sequence will be returned.
21254 Each field is an object, with some pre-defined attributes:
21257 This attribute is not available for @code{static} fields (as in
21258 C@t{++} or Java). For non-@code{static} fields, the value is the bit
21259 position of the field.
21262 The name of the field, or @code{None} for anonymous fields.
21265 This is @code{True} if the field is artificial, usually meaning that
21266 it was provided by the compiler and not the user. This attribute is
21267 always provided, and is @code{False} if the field is not artificial.
21269 @item is_base_class
21270 This is @code{True} if the field represents a base class of a C@t{++}
21271 structure. This attribute is always provided, and is @code{False}
21272 if the field is not a base class of the type that is the argument of
21273 @code{fields}, or if that type was not a C@t{++} class.
21276 If the field is packed, or is a bitfield, then this will have a
21277 non-zero value, which is the size of the field in bits. Otherwise,
21278 this will be zero; in this case the field's size is given by its type.
21281 The type of the field. This is usually an instance of @code{Type},
21282 but it can be @code{None} in some situations.
21286 @defmethod Type array @var{n1} @r{[}@var{n2}@r{]}
21287 Return a new @code{gdb.Type} object which represents an array of this
21288 type. If one argument is given, it is the inclusive upper bound of
21289 the array; in this case the lower bound is zero. If two arguments are
21290 given, the first argument is the lower bound of the array, and the
21291 second argument is the upper bound of the array. An array's length
21292 must not be negative, but the bounds can be.
21295 @defmethod Type const
21296 Return a new @code{gdb.Type} object which represents a
21297 @code{const}-qualified variant of this type.
21300 @defmethod Type volatile
21301 Return a new @code{gdb.Type} object which represents a
21302 @code{volatile}-qualified variant of this type.
21305 @defmethod Type unqualified
21306 Return a new @code{gdb.Type} object which represents an unqualified
21307 variant of this type. That is, the result is neither @code{const} nor
21311 @defmethod Type range
21312 Return a Python @code{Tuple} object that contains two elements: the
21313 low bound of the argument type and the high bound of that type. If
21314 the type does not have a range, @value{GDBN} will raise a
21315 @code{gdb.error} exception (@pxref{Exception Handling}).
21318 @defmethod Type reference
21319 Return a new @code{gdb.Type} object which represents a reference to this
21323 @defmethod Type pointer
21324 Return a new @code{gdb.Type} object which represents a pointer to this
21328 @defmethod Type strip_typedefs
21329 Return a new @code{gdb.Type} that represents the real type,
21330 after removing all layers of typedefs.
21333 @defmethod Type target
21334 Return a new @code{gdb.Type} object which represents the target type
21337 For a pointer type, the target type is the type of the pointed-to
21338 object. For an array type (meaning C-like arrays), the target type is
21339 the type of the elements of the array. For a function or method type,
21340 the target type is the type of the return value. For a complex type,
21341 the target type is the type of the elements. For a typedef, the
21342 target type is the aliased type.
21344 If the type does not have a target, this method will throw an
21348 @defmethod Type template_argument n [block]
21349 If this @code{gdb.Type} is an instantiation of a template, this will
21350 return a new @code{gdb.Type} which represents the type of the
21351 @var{n}th template argument.
21353 If this @code{gdb.Type} is not a template type, this will throw an
21354 exception. Ordinarily, only C@t{++} code will have template types.
21356 If @var{block} is given, then @var{name} is looked up in that scope.
21357 Otherwise, it is searched for globally.
21362 Each type has a code, which indicates what category this type falls
21363 into. The available type categories are represented by constants
21364 defined in the @code{gdb} module:
21367 @findex TYPE_CODE_PTR
21368 @findex gdb.TYPE_CODE_PTR
21369 @item TYPE_CODE_PTR
21370 The type is a pointer.
21372 @findex TYPE_CODE_ARRAY
21373 @findex gdb.TYPE_CODE_ARRAY
21374 @item TYPE_CODE_ARRAY
21375 The type is an array.
21377 @findex TYPE_CODE_STRUCT
21378 @findex gdb.TYPE_CODE_STRUCT
21379 @item TYPE_CODE_STRUCT
21380 The type is a structure.
21382 @findex TYPE_CODE_UNION
21383 @findex gdb.TYPE_CODE_UNION
21384 @item TYPE_CODE_UNION
21385 The type is a union.
21387 @findex TYPE_CODE_ENUM
21388 @findex gdb.TYPE_CODE_ENUM
21389 @item TYPE_CODE_ENUM
21390 The type is an enum.
21392 @findex TYPE_CODE_FLAGS
21393 @findex gdb.TYPE_CODE_FLAGS
21394 @item TYPE_CODE_FLAGS
21395 A bit flags type, used for things such as status registers.
21397 @findex TYPE_CODE_FUNC
21398 @findex gdb.TYPE_CODE_FUNC
21399 @item TYPE_CODE_FUNC
21400 The type is a function.
21402 @findex TYPE_CODE_INT
21403 @findex gdb.TYPE_CODE_INT
21404 @item TYPE_CODE_INT
21405 The type is an integer type.
21407 @findex TYPE_CODE_FLT
21408 @findex gdb.TYPE_CODE_FLT
21409 @item TYPE_CODE_FLT
21410 A floating point type.
21412 @findex TYPE_CODE_VOID
21413 @findex gdb.TYPE_CODE_VOID
21414 @item TYPE_CODE_VOID
21415 The special type @code{void}.
21417 @findex TYPE_CODE_SET
21418 @findex gdb.TYPE_CODE_SET
21419 @item TYPE_CODE_SET
21422 @findex TYPE_CODE_RANGE
21423 @findex gdb.TYPE_CODE_RANGE
21424 @item TYPE_CODE_RANGE
21425 A range type, that is, an integer type with bounds.
21427 @findex TYPE_CODE_STRING
21428 @findex gdb.TYPE_CODE_STRING
21429 @item TYPE_CODE_STRING
21430 A string type. Note that this is only used for certain languages with
21431 language-defined string types; C strings are not represented this way.
21433 @findex TYPE_CODE_BITSTRING
21434 @findex gdb.TYPE_CODE_BITSTRING
21435 @item TYPE_CODE_BITSTRING
21438 @findex TYPE_CODE_ERROR
21439 @findex gdb.TYPE_CODE_ERROR
21440 @item TYPE_CODE_ERROR
21441 An unknown or erroneous type.
21443 @findex TYPE_CODE_METHOD
21444 @findex gdb.TYPE_CODE_METHOD
21445 @item TYPE_CODE_METHOD
21446 A method type, as found in C@t{++} or Java.
21448 @findex TYPE_CODE_METHODPTR
21449 @findex gdb.TYPE_CODE_METHODPTR
21450 @item TYPE_CODE_METHODPTR
21451 A pointer-to-member-function.
21453 @findex TYPE_CODE_MEMBERPTR
21454 @findex gdb.TYPE_CODE_MEMBERPTR
21455 @item TYPE_CODE_MEMBERPTR
21456 A pointer-to-member.
21458 @findex TYPE_CODE_REF
21459 @findex gdb.TYPE_CODE_REF
21460 @item TYPE_CODE_REF
21463 @findex TYPE_CODE_CHAR
21464 @findex gdb.TYPE_CODE_CHAR
21465 @item TYPE_CODE_CHAR
21468 @findex TYPE_CODE_BOOL
21469 @findex gdb.TYPE_CODE_BOOL
21470 @item TYPE_CODE_BOOL
21473 @findex TYPE_CODE_COMPLEX
21474 @findex gdb.TYPE_CODE_COMPLEX
21475 @item TYPE_CODE_COMPLEX
21476 A complex float type.
21478 @findex TYPE_CODE_TYPEDEF
21479 @findex gdb.TYPE_CODE_TYPEDEF
21480 @item TYPE_CODE_TYPEDEF
21481 A typedef to some other type.
21483 @findex TYPE_CODE_NAMESPACE
21484 @findex gdb.TYPE_CODE_NAMESPACE
21485 @item TYPE_CODE_NAMESPACE
21486 A C@t{++} namespace.
21488 @findex TYPE_CODE_DECFLOAT
21489 @findex gdb.TYPE_CODE_DECFLOAT
21490 @item TYPE_CODE_DECFLOAT
21491 A decimal floating point type.
21493 @findex TYPE_CODE_INTERNAL_FUNCTION
21494 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
21495 @item TYPE_CODE_INTERNAL_FUNCTION
21496 A function internal to @value{GDBN}. This is the type used to represent
21497 convenience functions.
21500 Further support for types is provided in the @code{gdb.types}
21501 Python module (@pxref{gdb.types}).
21503 @node Pretty Printing API
21504 @subsubsection Pretty Printing API
21506 An example output is provided (@pxref{Pretty Printing}).
21508 A pretty-printer is just an object that holds a value and implements a
21509 specific interface, defined here.
21511 @defop Operation {pretty printer} children (self)
21512 @value{GDBN} will call this method on a pretty-printer to compute the
21513 children of the pretty-printer's value.
21515 This method must return an object conforming to the Python iterator
21516 protocol. Each item returned by the iterator must be a tuple holding
21517 two elements. The first element is the ``name'' of the child; the
21518 second element is the child's value. The value can be any Python
21519 object which is convertible to a @value{GDBN} value.
21521 This method is optional. If it does not exist, @value{GDBN} will act
21522 as though the value has no children.
21525 @defop Operation {pretty printer} display_hint (self)
21526 The CLI may call this method and use its result to change the
21527 formatting of a value. The result will also be supplied to an MI
21528 consumer as a @samp{displayhint} attribute of the variable being
21531 This method is optional. If it does exist, this method must return a
21534 Some display hints are predefined by @value{GDBN}:
21538 Indicate that the object being printed is ``array-like''. The CLI
21539 uses this to respect parameters such as @code{set print elements} and
21540 @code{set print array}.
21543 Indicate that the object being printed is ``map-like'', and that the
21544 children of this value can be assumed to alternate between keys and
21548 Indicate that the object being printed is ``string-like''. If the
21549 printer's @code{to_string} method returns a Python string of some
21550 kind, then @value{GDBN} will call its internal language-specific
21551 string-printing function to format the string. For the CLI this means
21552 adding quotation marks, possibly escaping some characters, respecting
21553 @code{set print elements}, and the like.
21557 @defop Operation {pretty printer} to_string (self)
21558 @value{GDBN} will call this method to display the string
21559 representation of the value passed to the object's constructor.
21561 When printing from the CLI, if the @code{to_string} method exists,
21562 then @value{GDBN} will prepend its result to the values returned by
21563 @code{children}. Exactly how this formatting is done is dependent on
21564 the display hint, and may change as more hints are added. Also,
21565 depending on the print settings (@pxref{Print Settings}), the CLI may
21566 print just the result of @code{to_string} in a stack trace, omitting
21567 the result of @code{children}.
21569 If this method returns a string, it is printed verbatim.
21571 Otherwise, if this method returns an instance of @code{gdb.Value},
21572 then @value{GDBN} prints this value. This may result in a call to
21573 another pretty-printer.
21575 If instead the method returns a Python value which is convertible to a
21576 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
21577 the resulting value. Again, this may result in a call to another
21578 pretty-printer. Python scalars (integers, floats, and booleans) and
21579 strings are convertible to @code{gdb.Value}; other types are not.
21581 Finally, if this method returns @code{None} then no further operations
21582 are peformed in this method and nothing is printed.
21584 If the result is not one of these types, an exception is raised.
21587 @value{GDBN} provides a function which can be used to look up the
21588 default pretty-printer for a @code{gdb.Value}:
21590 @findex gdb.default_visualizer
21591 @defun default_visualizer value
21592 This function takes a @code{gdb.Value} object as an argument. If a
21593 pretty-printer for this value exists, then it is returned. If no such
21594 printer exists, then this returns @code{None}.
21597 @node Selecting Pretty-Printers
21598 @subsubsection Selecting Pretty-Printers
21600 The Python list @code{gdb.pretty_printers} contains an array of
21601 functions or callable objects that have been registered via addition
21602 as a pretty-printer. Printers in this list are called @code{global}
21603 printers, they're available when debugging all inferiors.
21604 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
21605 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
21608 Each function on these lists is passed a single @code{gdb.Value}
21609 argument and should return a pretty-printer object conforming to the
21610 interface definition above (@pxref{Pretty Printing API}). If a function
21611 cannot create a pretty-printer for the value, it should return
21614 @value{GDBN} first checks the @code{pretty_printers} attribute of each
21615 @code{gdb.Objfile} in the current program space and iteratively calls
21616 each enabled lookup routine in the list for that @code{gdb.Objfile}
21617 until it receives a pretty-printer object.
21618 If no pretty-printer is found in the objfile lists, @value{GDBN} then
21619 searches the pretty-printer list of the current program space,
21620 calling each enabled function until an object is returned.
21621 After these lists have been exhausted, it tries the global
21622 @code{gdb.pretty_printers} list, again calling each enabled function until an
21623 object is returned.
21625 The order in which the objfiles are searched is not specified. For a
21626 given list, functions are always invoked from the head of the list,
21627 and iterated over sequentially until the end of the list, or a printer
21628 object is returned.
21630 For various reasons a pretty-printer may not work.
21631 For example, the underlying data structure may have changed and
21632 the pretty-printer is out of date.
21634 The consequences of a broken pretty-printer are severe enough that
21635 @value{GDBN} provides support for enabling and disabling individual
21636 printers. For example, if @code{print frame-arguments} is on,
21637 a backtrace can become highly illegible if any argument is printed
21638 with a broken printer.
21640 Pretty-printers are enabled and disabled by attaching an @code{enabled}
21641 attribute to the registered function or callable object. If this attribute
21642 is present and its value is @code{False}, the printer is disabled, otherwise
21643 the printer is enabled.
21645 @node Writing a Pretty-Printer
21646 @subsubsection Writing a Pretty-Printer
21647 @cindex writing a pretty-printer
21649 A pretty-printer consists of two parts: a lookup function to detect
21650 if the type is supported, and the printer itself.
21652 Here is an example showing how a @code{std::string} printer might be
21653 written. @xref{Pretty Printing API}, for details on the API this class
21657 class StdStringPrinter(object):
21658 "Print a std::string"
21660 def __init__(self, val):
21663 def to_string(self):
21664 return self.val['_M_dataplus']['_M_p']
21666 def display_hint(self):
21670 And here is an example showing how a lookup function for the printer
21671 example above might be written.
21674 def str_lookup_function(val):
21675 lookup_tag = val.type.tag
21676 if lookup_tag == None:
21678 regex = re.compile("^std::basic_string<char,.*>$")
21679 if regex.match(lookup_tag):
21680 return StdStringPrinter(val)
21684 The example lookup function extracts the value's type, and attempts to
21685 match it to a type that it can pretty-print. If it is a type the
21686 printer can pretty-print, it will return a printer object. If not, it
21687 returns @code{None}.
21689 We recommend that you put your core pretty-printers into a Python
21690 package. If your pretty-printers are for use with a library, we
21691 further recommend embedding a version number into the package name.
21692 This practice will enable @value{GDBN} to load multiple versions of
21693 your pretty-printers at the same time, because they will have
21696 You should write auto-loaded code (@pxref{Auto-loading}) such that it
21697 can be evaluated multiple times without changing its meaning. An
21698 ideal auto-load file will consist solely of @code{import}s of your
21699 printer modules, followed by a call to a register pretty-printers with
21700 the current objfile.
21702 Taken as a whole, this approach will scale nicely to multiple
21703 inferiors, each potentially using a different library version.
21704 Embedding a version number in the Python package name will ensure that
21705 @value{GDBN} is able to load both sets of printers simultaneously.
21706 Then, because the search for pretty-printers is done by objfile, and
21707 because your auto-loaded code took care to register your library's
21708 printers with a specific objfile, @value{GDBN} will find the correct
21709 printers for the specific version of the library used by each
21712 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
21713 this code might appear in @code{gdb.libstdcxx.v6}:
21716 def register_printers(objfile):
21717 objfile.pretty_printers.add(str_lookup_function)
21721 And then the corresponding contents of the auto-load file would be:
21724 import gdb.libstdcxx.v6
21725 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
21728 The previous example illustrates a basic pretty-printer.
21729 There are a few things that can be improved on.
21730 The printer doesn't have a name, making it hard to identify in a
21731 list of installed printers. The lookup function has a name, but
21732 lookup functions can have arbitrary, even identical, names.
21734 Second, the printer only handles one type, whereas a library typically has
21735 several types. One could install a lookup function for each desired type
21736 in the library, but one could also have a single lookup function recognize
21737 several types. The latter is the conventional way this is handled.
21738 If a pretty-printer can handle multiple data types, then its
21739 @dfn{subprinters} are the printers for the individual data types.
21741 The @code{gdb.printing} module provides a formal way of solving these
21742 problems (@pxref{gdb.printing}).
21743 Here is another example that handles multiple types.
21745 These are the types we are going to pretty-print:
21748 struct foo @{ int a, b; @};
21749 struct bar @{ struct foo x, y; @};
21752 Here are the printers:
21756 """Print a foo object."""
21758 def __init__(self, val):
21761 def to_string(self):
21762 return ("a=<" + str(self.val["a"]) +
21763 "> b=<" + str(self.val["b"]) + ">")
21766 """Print a bar object."""
21768 def __init__(self, val):
21771 def to_string(self):
21772 return ("x=<" + str(self.val["x"]) +
21773 "> y=<" + str(self.val["y"]) + ">")
21776 This example doesn't need a lookup function, that is handled by the
21777 @code{gdb.printing} module. Instead a function is provided to build up
21778 the object that handles the lookup.
21781 import gdb.printing
21783 def build_pretty_printer():
21784 pp = gdb.printing.RegexpCollectionPrettyPrinter(
21786 pp.add_printer('foo', '^foo$', fooPrinter)
21787 pp.add_printer('bar', '^bar$', barPrinter)
21791 And here is the autoload support:
21794 import gdb.printing
21796 gdb.printing.register_pretty_printer(
21797 gdb.current_objfile(),
21798 my_library.build_pretty_printer())
21801 Finally, when this printer is loaded into @value{GDBN}, here is the
21802 corresponding output of @samp{info pretty-printer}:
21805 (gdb) info pretty-printer
21812 @node Inferiors In Python
21813 @subsubsection Inferiors In Python
21814 @cindex inferiors in python
21816 @findex gdb.Inferior
21817 Programs which are being run under @value{GDBN} are called inferiors
21818 (@pxref{Inferiors and Programs}). Python scripts can access
21819 information about and manipulate inferiors controlled by @value{GDBN}
21820 via objects of the @code{gdb.Inferior} class.
21822 The following inferior-related functions are available in the @code{gdb}
21826 Return a tuple containing all inferior objects.
21829 A @code{gdb.Inferior} object has the following attributes:
21832 @defivar Inferior num
21833 ID of inferior, as assigned by GDB.
21836 @defivar Inferior pid
21837 Process ID of the inferior, as assigned by the underlying operating
21841 @defivar Inferior was_attached
21842 Boolean signaling whether the inferior was created using `attach', or
21843 started by @value{GDBN} itself.
21847 A @code{gdb.Inferior} object has the following methods:
21850 @defmethod Inferior threads
21851 This method returns a tuple holding all the threads which are valid
21852 when it is called. If there are no valid threads, the method will
21853 return an empty tuple.
21856 @findex gdb.read_memory
21857 @defmethod Inferior read_memory address length
21858 Read @var{length} bytes of memory from the inferior, starting at
21859 @var{address}. Returns a buffer object, which behaves much like an array
21860 or a string. It can be modified and given to the @code{gdb.write_memory}
21864 @findex gdb.write_memory
21865 @defmethod Inferior write_memory address buffer @r{[}length@r{]}
21866 Write the contents of @var{buffer} to the inferior, starting at
21867 @var{address}. The @var{buffer} parameter must be a Python object
21868 which supports the buffer protocol, i.e., a string, an array or the
21869 object returned from @code{gdb.read_memory}. If given, @var{length}
21870 determines the number of bytes from @var{buffer} to be written.
21873 @findex gdb.search_memory
21874 @defmethod Inferior search_memory address length pattern
21875 Search a region of the inferior memory starting at @var{address} with
21876 the given @var{length} using the search pattern supplied in
21877 @var{pattern}. The @var{pattern} parameter must be a Python object
21878 which supports the buffer protocol, i.e., a string, an array or the
21879 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
21880 containing the address where the pattern was found, or @code{None} if
21881 the pattern could not be found.
21885 @node Threads In Python
21886 @subsubsection Threads In Python
21887 @cindex threads in python
21889 @findex gdb.InferiorThread
21890 Python scripts can access information about, and manipulate inferior threads
21891 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
21893 The following thread-related functions are available in the @code{gdb}
21896 @findex gdb.selected_thread
21897 @defun selected_thread
21898 This function returns the thread object for the selected thread. If there
21899 is no selected thread, this will return @code{None}.
21902 A @code{gdb.InferiorThread} object has the following attributes:
21905 @defivar InferiorThread num
21906 ID of the thread, as assigned by GDB.
21909 @defivar InferiorThread ptid
21910 ID of the thread, as assigned by the operating system. This attribute is a
21911 tuple containing three integers. The first is the Process ID (PID); the second
21912 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
21913 Either the LWPID or TID may be 0, which indicates that the operating system
21914 does not use that identifier.
21918 A @code{gdb.InferiorThread} object has the following methods:
21921 @defmethod InferiorThread switch
21922 This changes @value{GDBN}'s currently selected thread to the one represented
21926 @defmethod InferiorThread is_stopped
21927 Return a Boolean indicating whether the thread is stopped.
21930 @defmethod InferiorThread is_running
21931 Return a Boolean indicating whether the thread is running.
21934 @defmethod InferiorThread is_exited
21935 Return a Boolean indicating whether the thread is exited.
21939 @node Commands In Python
21940 @subsubsection Commands In Python
21942 @cindex commands in python
21943 @cindex python commands
21944 You can implement new @value{GDBN} CLI commands in Python. A CLI
21945 command is implemented using an instance of the @code{gdb.Command}
21946 class, most commonly using a subclass.
21948 @defmethod Command __init__ name @var{command_class} @r{[}@var{completer_class}@r{]} @r{[}@var{prefix}@r{]}
21949 The object initializer for @code{Command} registers the new command
21950 with @value{GDBN}. This initializer is normally invoked from the
21951 subclass' own @code{__init__} method.
21953 @var{name} is the name of the command. If @var{name} consists of
21954 multiple words, then the initial words are looked for as prefix
21955 commands. In this case, if one of the prefix commands does not exist,
21956 an exception is raised.
21958 There is no support for multi-line commands.
21960 @var{command_class} should be one of the @samp{COMMAND_} constants
21961 defined below. This argument tells @value{GDBN} how to categorize the
21962 new command in the help system.
21964 @var{completer_class} is an optional argument. If given, it should be
21965 one of the @samp{COMPLETE_} constants defined below. This argument
21966 tells @value{GDBN} how to perform completion for this command. If not
21967 given, @value{GDBN} will attempt to complete using the object's
21968 @code{complete} method (see below); if no such method is found, an
21969 error will occur when completion is attempted.
21971 @var{prefix} is an optional argument. If @code{True}, then the new
21972 command is a prefix command; sub-commands of this command may be
21975 The help text for the new command is taken from the Python
21976 documentation string for the command's class, if there is one. If no
21977 documentation string is provided, the default value ``This command is
21978 not documented.'' is used.
21981 @cindex don't repeat Python command
21982 @defmethod Command dont_repeat
21983 By default, a @value{GDBN} command is repeated when the user enters a
21984 blank line at the command prompt. A command can suppress this
21985 behavior by invoking the @code{dont_repeat} method. This is similar
21986 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
21989 @defmethod Command invoke argument from_tty
21990 This method is called by @value{GDBN} when this command is invoked.
21992 @var{argument} is a string. It is the argument to the command, after
21993 leading and trailing whitespace has been stripped.
21995 @var{from_tty} is a boolean argument. When true, this means that the
21996 command was entered by the user at the terminal; when false it means
21997 that the command came from elsewhere.
21999 If this method throws an exception, it is turned into a @value{GDBN}
22000 @code{error} call. Otherwise, the return value is ignored.
22002 @findex gdb.string_to_argv
22003 To break @var{argument} up into an argv-like string use
22004 @code{gdb.string_to_argv}. This function behaves identically to
22005 @value{GDBN}'s internal argument lexer @code{buildargv}.
22006 It is recommended to use this for consistency.
22007 Arguments are separated by spaces and may be quoted.
22011 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
22012 ['1', '2 "3', '4 "5', "6 '7"]
22017 @cindex completion of Python commands
22018 @defmethod Command complete text word
22019 This method is called by @value{GDBN} when the user attempts
22020 completion on this command. All forms of completion are handled by
22021 this method, that is, the @key{TAB} and @key{M-?} key bindings
22022 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
22025 The arguments @var{text} and @var{word} are both strings. @var{text}
22026 holds the complete command line up to the cursor's location.
22027 @var{word} holds the last word of the command line; this is computed
22028 using a word-breaking heuristic.
22030 The @code{complete} method can return several values:
22033 If the return value is a sequence, the contents of the sequence are
22034 used as the completions. It is up to @code{complete} to ensure that the
22035 contents actually do complete the word. A zero-length sequence is
22036 allowed, it means that there were no completions available. Only
22037 string elements of the sequence are used; other elements in the
22038 sequence are ignored.
22041 If the return value is one of the @samp{COMPLETE_} constants defined
22042 below, then the corresponding @value{GDBN}-internal completion
22043 function is invoked, and its result is used.
22046 All other results are treated as though there were no available
22051 When a new command is registered, it must be declared as a member of
22052 some general class of commands. This is used to classify top-level
22053 commands in the on-line help system; note that prefix commands are not
22054 listed under their own category but rather that of their top-level
22055 command. The available classifications are represented by constants
22056 defined in the @code{gdb} module:
22059 @findex COMMAND_NONE
22060 @findex gdb.COMMAND_NONE
22062 The command does not belong to any particular class. A command in
22063 this category will not be displayed in any of the help categories.
22065 @findex COMMAND_RUNNING
22066 @findex gdb.COMMAND_RUNNING
22067 @item COMMAND_RUNNING
22068 The command is related to running the inferior. For example,
22069 @code{start}, @code{step}, and @code{continue} are in this category.
22070 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
22071 commands in this category.
22073 @findex COMMAND_DATA
22074 @findex gdb.COMMAND_DATA
22076 The command is related to data or variables. For example,
22077 @code{call}, @code{find}, and @code{print} are in this category. Type
22078 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
22081 @findex COMMAND_STACK
22082 @findex gdb.COMMAND_STACK
22083 @item COMMAND_STACK
22084 The command has to do with manipulation of the stack. For example,
22085 @code{backtrace}, @code{frame}, and @code{return} are in this
22086 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
22087 list of commands in this category.
22089 @findex COMMAND_FILES
22090 @findex gdb.COMMAND_FILES
22091 @item COMMAND_FILES
22092 This class is used for file-related commands. For example,
22093 @code{file}, @code{list} and @code{section} are in this category.
22094 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
22095 commands in this category.
22097 @findex COMMAND_SUPPORT
22098 @findex gdb.COMMAND_SUPPORT
22099 @item COMMAND_SUPPORT
22100 This should be used for ``support facilities'', generally meaning
22101 things that are useful to the user when interacting with @value{GDBN},
22102 but not related to the state of the inferior. For example,
22103 @code{help}, @code{make}, and @code{shell} are in this category. Type
22104 @kbd{help support} at the @value{GDBN} prompt to see a list of
22105 commands in this category.
22107 @findex COMMAND_STATUS
22108 @findex gdb.COMMAND_STATUS
22109 @item COMMAND_STATUS
22110 The command is an @samp{info}-related command, that is, related to the
22111 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
22112 and @code{show} are in this category. Type @kbd{help status} at the
22113 @value{GDBN} prompt to see a list of commands in this category.
22115 @findex COMMAND_BREAKPOINTS
22116 @findex gdb.COMMAND_BREAKPOINTS
22117 @item COMMAND_BREAKPOINTS
22118 The command has to do with breakpoints. For example, @code{break},
22119 @code{clear}, and @code{delete} are in this category. Type @kbd{help
22120 breakpoints} at the @value{GDBN} prompt to see a list of commands in
22123 @findex COMMAND_TRACEPOINTS
22124 @findex gdb.COMMAND_TRACEPOINTS
22125 @item COMMAND_TRACEPOINTS
22126 The command has to do with tracepoints. For example, @code{trace},
22127 @code{actions}, and @code{tfind} are in this category. Type
22128 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
22129 commands in this category.
22131 @findex COMMAND_OBSCURE
22132 @findex gdb.COMMAND_OBSCURE
22133 @item COMMAND_OBSCURE
22134 The command is only used in unusual circumstances, or is not of
22135 general interest to users. For example, @code{checkpoint},
22136 @code{fork}, and @code{stop} are in this category. Type @kbd{help
22137 obscure} at the @value{GDBN} prompt to see a list of commands in this
22140 @findex COMMAND_MAINTENANCE
22141 @findex gdb.COMMAND_MAINTENANCE
22142 @item COMMAND_MAINTENANCE
22143 The command is only useful to @value{GDBN} maintainers. The
22144 @code{maintenance} and @code{flushregs} commands are in this category.
22145 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
22146 commands in this category.
22149 A new command can use a predefined completion function, either by
22150 specifying it via an argument at initialization, or by returning it
22151 from the @code{complete} method. These predefined completion
22152 constants are all defined in the @code{gdb} module:
22155 @findex COMPLETE_NONE
22156 @findex gdb.COMPLETE_NONE
22157 @item COMPLETE_NONE
22158 This constant means that no completion should be done.
22160 @findex COMPLETE_FILENAME
22161 @findex gdb.COMPLETE_FILENAME
22162 @item COMPLETE_FILENAME
22163 This constant means that filename completion should be performed.
22165 @findex COMPLETE_LOCATION
22166 @findex gdb.COMPLETE_LOCATION
22167 @item COMPLETE_LOCATION
22168 This constant means that location completion should be done.
22169 @xref{Specify Location}.
22171 @findex COMPLETE_COMMAND
22172 @findex gdb.COMPLETE_COMMAND
22173 @item COMPLETE_COMMAND
22174 This constant means that completion should examine @value{GDBN}
22177 @findex COMPLETE_SYMBOL
22178 @findex gdb.COMPLETE_SYMBOL
22179 @item COMPLETE_SYMBOL
22180 This constant means that completion should be done using symbol names
22184 The following code snippet shows how a trivial CLI command can be
22185 implemented in Python:
22188 class HelloWorld (gdb.Command):
22189 """Greet the whole world."""
22191 def __init__ (self):
22192 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_OBSCURE)
22194 def invoke (self, arg, from_tty):
22195 print "Hello, World!"
22200 The last line instantiates the class, and is necessary to trigger the
22201 registration of the command with @value{GDBN}. Depending on how the
22202 Python code is read into @value{GDBN}, you may need to import the
22203 @code{gdb} module explicitly.
22205 @node Parameters In Python
22206 @subsubsection Parameters In Python
22208 @cindex parameters in python
22209 @cindex python parameters
22210 @tindex gdb.Parameter
22212 You can implement new @value{GDBN} parameters using Python. A new
22213 parameter is implemented as an instance of the @code{gdb.Parameter}
22216 Parameters are exposed to the user via the @code{set} and
22217 @code{show} commands. @xref{Help}.
22219 There are many parameters that already exist and can be set in
22220 @value{GDBN}. Two examples are: @code{set follow fork} and
22221 @code{set charset}. Setting these parameters influences certain
22222 behavior in @value{GDBN}. Similarly, you can define parameters that
22223 can be used to influence behavior in custom Python scripts and commands.
22225 @defmethod Parameter __init__ name @var{command-class} @var{parameter-class} @r{[}@var{enum-sequence}@r{]}
22226 The object initializer for @code{Parameter} registers the new
22227 parameter with @value{GDBN}. This initializer is normally invoked
22228 from the subclass' own @code{__init__} method.
22230 @var{name} is the name of the new parameter. If @var{name} consists
22231 of multiple words, then the initial words are looked for as prefix
22232 parameters. An example of this can be illustrated with the
22233 @code{set print} set of parameters. If @var{name} is
22234 @code{print foo}, then @code{print} will be searched as the prefix
22235 parameter. In this case the parameter can subsequently be accessed in
22236 @value{GDBN} as @code{set print foo}.
22238 If @var{name} consists of multiple words, and no prefix parameter group
22239 can be found, an exception is raised.
22241 @var{command-class} should be one of the @samp{COMMAND_} constants
22242 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
22243 categorize the new parameter in the help system.
22245 @var{parameter-class} should be one of the @samp{PARAM_} constants
22246 defined below. This argument tells @value{GDBN} the type of the new
22247 parameter; this information is used for input validation and
22250 If @var{parameter-class} is @code{PARAM_ENUM}, then
22251 @var{enum-sequence} must be a sequence of strings. These strings
22252 represent the possible values for the parameter.
22254 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
22255 of a fourth argument will cause an exception to be thrown.
22257 The help text for the new parameter is taken from the Python
22258 documentation string for the parameter's class, if there is one. If
22259 there is no documentation string, a default value is used.
22262 @defivar Parameter set_doc
22263 If this attribute exists, and is a string, then its value is used as
22264 the help text for this parameter's @code{set} command. The value is
22265 examined when @code{Parameter.__init__} is invoked; subsequent changes
22269 @defivar Parameter show_doc
22270 If this attribute exists, and is a string, then its value is used as
22271 the help text for this parameter's @code{show} command. The value is
22272 examined when @code{Parameter.__init__} is invoked; subsequent changes
22276 @defivar Parameter value
22277 The @code{value} attribute holds the underlying value of the
22278 parameter. It can be read and assigned to just as any other
22279 attribute. @value{GDBN} does validation when assignments are made.
22283 When a new parameter is defined, its type must be specified. The
22284 available types are represented by constants defined in the @code{gdb}
22288 @findex PARAM_BOOLEAN
22289 @findex gdb.PARAM_BOOLEAN
22290 @item PARAM_BOOLEAN
22291 The value is a plain boolean. The Python boolean values, @code{True}
22292 and @code{False} are the only valid values.
22294 @findex PARAM_AUTO_BOOLEAN
22295 @findex gdb.PARAM_AUTO_BOOLEAN
22296 @item PARAM_AUTO_BOOLEAN
22297 The value has three possible states: true, false, and @samp{auto}. In
22298 Python, true and false are represented using boolean constants, and
22299 @samp{auto} is represented using @code{None}.
22301 @findex PARAM_UINTEGER
22302 @findex gdb.PARAM_UINTEGER
22303 @item PARAM_UINTEGER
22304 The value is an unsigned integer. The value of 0 should be
22305 interpreted to mean ``unlimited''.
22307 @findex PARAM_INTEGER
22308 @findex gdb.PARAM_INTEGER
22309 @item PARAM_INTEGER
22310 The value is a signed integer. The value of 0 should be interpreted
22311 to mean ``unlimited''.
22313 @findex PARAM_STRING
22314 @findex gdb.PARAM_STRING
22316 The value is a string. When the user modifies the string, any escape
22317 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
22318 translated into corresponding characters and encoded into the current
22321 @findex PARAM_STRING_NOESCAPE
22322 @findex gdb.PARAM_STRING_NOESCAPE
22323 @item PARAM_STRING_NOESCAPE
22324 The value is a string. When the user modifies the string, escapes are
22325 passed through untranslated.
22327 @findex PARAM_OPTIONAL_FILENAME
22328 @findex gdb.PARAM_OPTIONAL_FILENAME
22329 @item PARAM_OPTIONAL_FILENAME
22330 The value is a either a filename (a string), or @code{None}.
22332 @findex PARAM_FILENAME
22333 @findex gdb.PARAM_FILENAME
22334 @item PARAM_FILENAME
22335 The value is a filename. This is just like
22336 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
22338 @findex PARAM_ZINTEGER
22339 @findex gdb.PARAM_ZINTEGER
22340 @item PARAM_ZINTEGER
22341 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
22342 is interpreted as itself.
22345 @findex gdb.PARAM_ENUM
22347 The value is a string, which must be one of a collection string
22348 constants provided when the parameter is created.
22351 @node Functions In Python
22352 @subsubsection Writing new convenience functions
22354 @cindex writing convenience functions
22355 @cindex convenience functions in python
22356 @cindex python convenience functions
22357 @tindex gdb.Function
22359 You can implement new convenience functions (@pxref{Convenience Vars})
22360 in Python. A convenience function is an instance of a subclass of the
22361 class @code{gdb.Function}.
22363 @defmethod Function __init__ name
22364 The initializer for @code{Function} registers the new function with
22365 @value{GDBN}. The argument @var{name} is the name of the function,
22366 a string. The function will be visible to the user as a convenience
22367 variable of type @code{internal function}, whose name is the same as
22368 the given @var{name}.
22370 The documentation for the new function is taken from the documentation
22371 string for the new class.
22374 @defmethod Function invoke @var{*args}
22375 When a convenience function is evaluated, its arguments are converted
22376 to instances of @code{gdb.Value}, and then the function's
22377 @code{invoke} method is called. Note that @value{GDBN} does not
22378 predetermine the arity of convenience functions. Instead, all
22379 available arguments are passed to @code{invoke}, following the
22380 standard Python calling convention. In particular, a convenience
22381 function can have default values for parameters without ill effect.
22383 The return value of this method is used as its value in the enclosing
22384 expression. If an ordinary Python value is returned, it is converted
22385 to a @code{gdb.Value} following the usual rules.
22388 The following code snippet shows how a trivial convenience function can
22389 be implemented in Python:
22392 class Greet (gdb.Function):
22393 """Return string to greet someone.
22394 Takes a name as argument."""
22396 def __init__ (self):
22397 super (Greet, self).__init__ ("greet")
22399 def invoke (self, name):
22400 return "Hello, %s!" % name.string ()
22405 The last line instantiates the class, and is necessary to trigger the
22406 registration of the function with @value{GDBN}. Depending on how the
22407 Python code is read into @value{GDBN}, you may need to import the
22408 @code{gdb} module explicitly.
22410 @node Progspaces In Python
22411 @subsubsection Program Spaces In Python
22413 @cindex progspaces in python
22414 @tindex gdb.Progspace
22416 A program space, or @dfn{progspace}, represents a symbolic view
22417 of an address space.
22418 It consists of all of the objfiles of the program.
22419 @xref{Objfiles In Python}.
22420 @xref{Inferiors and Programs, program spaces}, for more details
22421 about program spaces.
22423 The following progspace-related functions are available in the
22426 @findex gdb.current_progspace
22427 @defun current_progspace
22428 This function returns the program space of the currently selected inferior.
22429 @xref{Inferiors and Programs}.
22432 @findex gdb.progspaces
22434 Return a sequence of all the progspaces currently known to @value{GDBN}.
22437 Each progspace is represented by an instance of the @code{gdb.Progspace}
22440 @defivar Progspace filename
22441 The file name of the progspace as a string.
22444 @defivar Progspace pretty_printers
22445 The @code{pretty_printers} attribute is a list of functions. It is
22446 used to look up pretty-printers. A @code{Value} is passed to each
22447 function in order; if the function returns @code{None}, then the
22448 search continues. Otherwise, the return value should be an object
22449 which is used to format the value. @xref{Pretty Printing API}, for more
22453 @node Objfiles In Python
22454 @subsubsection Objfiles In Python
22456 @cindex objfiles in python
22457 @tindex gdb.Objfile
22459 @value{GDBN} loads symbols for an inferior from various
22460 symbol-containing files (@pxref{Files}). These include the primary
22461 executable file, any shared libraries used by the inferior, and any
22462 separate debug info files (@pxref{Separate Debug Files}).
22463 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
22465 The following objfile-related functions are available in the
22468 @findex gdb.current_objfile
22469 @defun current_objfile
22470 When auto-loading a Python script (@pxref{Auto-loading}), @value{GDBN}
22471 sets the ``current objfile'' to the corresponding objfile. This
22472 function returns the current objfile. If there is no current objfile,
22473 this function returns @code{None}.
22476 @findex gdb.objfiles
22478 Return a sequence of all the objfiles current known to @value{GDBN}.
22479 @xref{Objfiles In Python}.
22482 Each objfile is represented by an instance of the @code{gdb.Objfile}
22485 @defivar Objfile filename
22486 The file name of the objfile as a string.
22489 @defivar Objfile pretty_printers
22490 The @code{pretty_printers} attribute is a list of functions. It is
22491 used to look up pretty-printers. A @code{Value} is passed to each
22492 function in order; if the function returns @code{None}, then the
22493 search continues. Otherwise, the return value should be an object
22494 which is used to format the value. @xref{Pretty Printing API}, for more
22498 @node Frames In Python
22499 @subsubsection Accessing inferior stack frames from Python.
22501 @cindex frames in python
22502 When the debugged program stops, @value{GDBN} is able to analyze its call
22503 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
22504 represents a frame in the stack. A @code{gdb.Frame} object is only valid
22505 while its corresponding frame exists in the inferior's stack. If you try
22506 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
22507 exception (@pxref{Exception Handling}).
22509 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
22513 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
22517 The following frame-related functions are available in the @code{gdb} module:
22519 @findex gdb.selected_frame
22520 @defun selected_frame
22521 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
22524 @defun frame_stop_reason_string reason
22525 Return a string explaining the reason why @value{GDBN} stopped unwinding
22526 frames, as expressed by the given @var{reason} code (an integer, see the
22527 @code{unwind_stop_reason} method further down in this section).
22530 A @code{gdb.Frame} object has the following methods:
22533 @defmethod Frame is_valid
22534 Returns true if the @code{gdb.Frame} object is valid, false if not.
22535 A frame object can become invalid if the frame it refers to doesn't
22536 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
22537 an exception if it is invalid at the time the method is called.
22540 @defmethod Frame name
22541 Returns the function name of the frame, or @code{None} if it can't be
22545 @defmethod Frame type
22546 Returns the type of the frame. The value can be one of
22547 @code{gdb.NORMAL_FRAME}, @code{gdb.DUMMY_FRAME}, @code{gdb.SIGTRAMP_FRAME}
22548 or @code{gdb.SENTINEL_FRAME}.
22551 @defmethod Frame unwind_stop_reason
22552 Return an integer representing the reason why it's not possible to find
22553 more frames toward the outermost frame. Use
22554 @code{gdb.frame_stop_reason_string} to convert the value returned by this
22555 function to a string.
22558 @defmethod Frame pc
22559 Returns the frame's resume address.
22562 @defmethod Frame block
22563 Return the frame's code block. @xref{Blocks In Python}.
22566 @defmethod Frame function
22567 Return the symbol for the function corresponding to this frame.
22568 @xref{Symbols In Python}.
22571 @defmethod Frame older
22572 Return the frame that called this frame.
22575 @defmethod Frame newer
22576 Return the frame called by this frame.
22579 @defmethod Frame find_sal
22580 Return the frame's symtab and line object.
22581 @xref{Symbol Tables In Python}.
22584 @defmethod Frame read_var variable @r{[}block@r{]}
22585 Return the value of @var{variable} in this frame. If the optional
22586 argument @var{block} is provided, search for the variable from that
22587 block; otherwise start at the frame's current block (which is
22588 determined by the frame's current program counter). @var{variable}
22589 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
22590 @code{gdb.Block} object.
22593 @defmethod Frame select
22594 Set this frame to be the selected frame. @xref{Stack, ,Examining the
22599 @node Blocks In Python
22600 @subsubsection Accessing frame blocks from Python.
22602 @cindex blocks in python
22605 Within each frame, @value{GDBN} maintains information on each block
22606 stored in that frame. These blocks are organized hierarchically, and
22607 are represented individually in Python as a @code{gdb.Block}.
22608 Please see @ref{Frames In Python}, for a more in-depth discussion on
22609 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
22610 detailed technical information on @value{GDBN}'s book-keeping of the
22613 The following block-related functions are available in the @code{gdb}
22616 @findex gdb.block_for_pc
22617 @defun block_for_pc pc
22618 Return the @code{gdb.Block} containing the given @var{pc} value. If the
22619 block cannot be found for the @var{pc} value specified, the function
22620 will return @code{None}.
22623 A @code{gdb.Block} object has the following attributes:
22626 @defivar Block start
22627 The start address of the block. This attribute is not writable.
22631 The end address of the block. This attribute is not writable.
22634 @defivar Block function
22635 The name of the block represented as a @code{gdb.Symbol}. If the
22636 block is not named, then this attribute holds @code{None}. This
22637 attribute is not writable.
22640 @defivar Block superblock
22641 The block containing this block. If this parent block does not exist,
22642 this attribute holds @code{None}. This attribute is not writable.
22646 @node Symbols In Python
22647 @subsubsection Python representation of Symbols.
22649 @cindex symbols in python
22652 @value{GDBN} represents every variable, function and type as an
22653 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
22654 Similarly, Python represents these symbols in @value{GDBN} with the
22655 @code{gdb.Symbol} object.
22657 The following symbol-related functions are available in the @code{gdb}
22660 @findex gdb.lookup_symbol
22661 @defun lookup_symbol name [block] [domain]
22662 This function searches for a symbol by name. The search scope can be
22663 restricted to the parameters defined in the optional domain and block
22666 @var{name} is the name of the symbol. It must be a string. The
22667 optional @var{block} argument restricts the search to symbols visible
22668 in that @var{block}. The @var{block} argument must be a
22669 @code{gdb.Block} object. The optional @var{domain} argument restricts
22670 the search to the domain type. The @var{domain} argument must be a
22671 domain constant defined in the @code{gdb} module and described later
22675 A @code{gdb.Symbol} object has the following attributes:
22678 @defivar Symbol symtab
22679 The symbol table in which the symbol appears. This attribute is
22680 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
22681 Python}. This attribute is not writable.
22684 @defivar Symbol name
22685 The name of the symbol as a string. This attribute is not writable.
22688 @defivar Symbol linkage_name
22689 The name of the symbol, as used by the linker (i.e., may be mangled).
22690 This attribute is not writable.
22693 @defivar Symbol print_name
22694 The name of the symbol in a form suitable for output. This is either
22695 @code{name} or @code{linkage_name}, depending on whether the user
22696 asked @value{GDBN} to display demangled or mangled names.
22699 @defivar Symbol addr_class
22700 The address class of the symbol. This classifies how to find the value
22701 of a symbol. Each address class is a constant defined in the
22702 @code{gdb} module and described later in this chapter.
22705 @defivar Symbol is_argument
22706 @code{True} if the symbol is an argument of a function.
22709 @defivar Symbol is_constant
22710 @code{True} if the symbol is a constant.
22713 @defivar Symbol is_function
22714 @code{True} if the symbol is a function or a method.
22717 @defivar Symbol is_variable
22718 @code{True} if the symbol is a variable.
22722 The available domain categories in @code{gdb.Symbol} are represented
22723 as constants in the @code{gdb} module:
22726 @findex SYMBOL_UNDEF_DOMAIN
22727 @findex gdb.SYMBOL_UNDEF_DOMAIN
22728 @item SYMBOL_UNDEF_DOMAIN
22729 This is used when a domain has not been discovered or none of the
22730 following domains apply. This usually indicates an error either
22731 in the symbol information or in @value{GDBN}'s handling of symbols.
22732 @findex SYMBOL_VAR_DOMAIN
22733 @findex gdb.SYMBOL_VAR_DOMAIN
22734 @item SYMBOL_VAR_DOMAIN
22735 This domain contains variables, function names, typedef names and enum
22737 @findex SYMBOL_STRUCT_DOMAIN
22738 @findex gdb.SYMBOL_STRUCT_DOMAIN
22739 @item SYMBOL_STRUCT_DOMAIN
22740 This domain holds struct, union and enum type names.
22741 @findex SYMBOL_LABEL_DOMAIN
22742 @findex gdb.SYMBOL_LABEL_DOMAIN
22743 @item SYMBOL_LABEL_DOMAIN
22744 This domain contains names of labels (for gotos).
22745 @findex SYMBOL_VARIABLES_DOMAIN
22746 @findex gdb.SYMBOL_VARIABLES_DOMAIN
22747 @item SYMBOL_VARIABLES_DOMAIN
22748 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
22749 contains everything minus functions and types.
22750 @findex SYMBOL_FUNCTIONS_DOMAIN
22751 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
22752 @item SYMBOL_FUNCTION_DOMAIN
22753 This domain contains all functions.
22754 @findex SYMBOL_TYPES_DOMAIN
22755 @findex gdb.SYMBOL_TYPES_DOMAIN
22756 @item SYMBOL_TYPES_DOMAIN
22757 This domain contains all types.
22760 The available address class categories in @code{gdb.Symbol} are represented
22761 as constants in the @code{gdb} module:
22764 @findex SYMBOL_LOC_UNDEF
22765 @findex gdb.SYMBOL_LOC_UNDEF
22766 @item SYMBOL_LOC_UNDEF
22767 If this is returned by address class, it indicates an error either in
22768 the symbol information or in @value{GDBN}'s handling of symbols.
22769 @findex SYMBOL_LOC_CONST
22770 @findex gdb.SYMBOL_LOC_CONST
22771 @item SYMBOL_LOC_CONST
22772 Value is constant int.
22773 @findex SYMBOL_LOC_STATIC
22774 @findex gdb.SYMBOL_LOC_STATIC
22775 @item SYMBOL_LOC_STATIC
22776 Value is at a fixed address.
22777 @findex SYMBOL_LOC_REGISTER
22778 @findex gdb.SYMBOL_LOC_REGISTER
22779 @item SYMBOL_LOC_REGISTER
22780 Value is in a register.
22781 @findex SYMBOL_LOC_ARG
22782 @findex gdb.SYMBOL_LOC_ARG
22783 @item SYMBOL_LOC_ARG
22784 Value is an argument. This value is at the offset stored within the
22785 symbol inside the frame's argument list.
22786 @findex SYMBOL_LOC_REF_ARG
22787 @findex gdb.SYMBOL_LOC_REF_ARG
22788 @item SYMBOL_LOC_REF_ARG
22789 Value address is stored in the frame's argument list. Just like
22790 @code{LOC_ARG} except that the value's address is stored at the
22791 offset, not the value itself.
22792 @findex SYMBOL_LOC_REGPARM_ADDR
22793 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
22794 @item SYMBOL_LOC_REGPARM_ADDR
22795 Value is a specified register. Just like @code{LOC_REGISTER} except
22796 the register holds the address of the argument instead of the argument
22798 @findex SYMBOL_LOC_LOCAL
22799 @findex gdb.SYMBOL_LOC_LOCAL
22800 @item SYMBOL_LOC_LOCAL
22801 Value is a local variable.
22802 @findex SYMBOL_LOC_TYPEDEF
22803 @findex gdb.SYMBOL_LOC_TYPEDEF
22804 @item SYMBOL_LOC_TYPEDEF
22805 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
22807 @findex SYMBOL_LOC_BLOCK
22808 @findex gdb.SYMBOL_LOC_BLOCK
22809 @item SYMBOL_LOC_BLOCK
22811 @findex SYMBOL_LOC_CONST_BYTES
22812 @findex gdb.SYMBOL_LOC_CONST_BYTES
22813 @item SYMBOL_LOC_CONST_BYTES
22814 Value is a byte-sequence.
22815 @findex SYMBOL_LOC_UNRESOLVED
22816 @findex gdb.SYMBOL_LOC_UNRESOLVED
22817 @item SYMBOL_LOC_UNRESOLVED
22818 Value is at a fixed address, but the address of the variable has to be
22819 determined from the minimal symbol table whenever the variable is
22821 @findex SYMBOL_LOC_OPTIMIZED_OUT
22822 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
22823 @item SYMBOL_LOC_OPTIMIZED_OUT
22824 The value does not actually exist in the program.
22825 @findex SYMBOL_LOC_COMPUTED
22826 @findex gdb.SYMBOL_LOC_COMPUTED
22827 @item SYMBOL_LOC_COMPUTED
22828 The value's address is a computed location.
22831 @node Symbol Tables In Python
22832 @subsubsection Symbol table representation in Python.
22834 @cindex symbol tables in python
22836 @tindex gdb.Symtab_and_line
22838 Access to symbol table data maintained by @value{GDBN} on the inferior
22839 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
22840 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
22841 from the @code{find_sal} method in @code{gdb.Frame} object.
22842 @xref{Frames In Python}.
22844 For more information on @value{GDBN}'s symbol table management, see
22845 @ref{Symbols, ,Examining the Symbol Table}, for more information.
22847 A @code{gdb.Symtab_and_line} object has the following attributes:
22850 @defivar Symtab_and_line symtab
22851 The symbol table object (@code{gdb.Symtab}) for this frame.
22852 This attribute is not writable.
22855 @defivar Symtab_and_line pc
22856 Indicates the current program counter address. This attribute is not
22860 @defivar Symtab_and_line line
22861 Indicates the current line number for this object. This
22862 attribute is not writable.
22866 A @code{gdb.Symtab} object has the following attributes:
22869 @defivar Symtab filename
22870 The symbol table's source filename. This attribute is not writable.
22873 @defivar Symtab objfile
22874 The symbol table's backing object file. @xref{Objfiles In Python}.
22875 This attribute is not writable.
22879 The following methods are provided:
22882 @defmethod Symtab fullname
22883 Return the symbol table's source absolute file name.
22887 @node Breakpoints In Python
22888 @subsubsection Manipulating breakpoints using Python
22890 @cindex breakpoints in python
22891 @tindex gdb.Breakpoint
22893 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
22896 @defmethod Breakpoint __init__ spec @r{[}type@r{]} @r{[}wp_class@r{]} @r{[}internal@r{]}
22897 Create a new breakpoint. @var{spec} is a string naming the
22898 location of the breakpoint, or an expression that defines a
22899 watchpoint. The contents can be any location recognized by the
22900 @code{break} command, or in the case of a watchpoint, by the @code{watch}
22901 command. The optional @var{type} denotes the breakpoint to create
22902 from the types defined later in this chapter. This argument can be
22903 either: @code{BP_BREAKPOINT} or @code{BP_WATCHPOINT}. @var{type}
22904 defaults to @code{BP_BREAKPOINT}. The optional @var{internal} argument
22905 allows the breakpoint to become invisible to the user. The breakpoint
22906 will neither be reported when created, nor will it be listed in the
22907 output from @code{info breakpoints} (but will be listed with the
22908 @code{maint info breakpoints} command). The optional @var{wp_class}
22909 argument defines the class of watchpoint to create, if @var{type} is
22910 @code{BP_WATCHPOINT}. If a watchpoint class is not provided, it is
22911 assumed to be a @var{WP_WRITE} class.
22914 The available watchpoint types represented by constants are defined in the
22919 @findex gdb.WP_READ
22921 Read only watchpoint.
22924 @findex gdb.WP_WRITE
22926 Write only watchpoint.
22929 @findex gdb.WP_ACCESS
22931 Read/Write watchpoint.
22934 @defmethod Breakpoint is_valid
22935 Return @code{True} if this @code{Breakpoint} object is valid,
22936 @code{False} otherwise. A @code{Breakpoint} object can become invalid
22937 if the user deletes the breakpoint. In this case, the object still
22938 exists, but the underlying breakpoint does not. In the cases of
22939 watchpoint scope, the watchpoint remains valid even if execution of the
22940 inferior leaves the scope of that watchpoint.
22943 @defmethod Breakpoint delete
22944 Permanently deletes the @value{GDBN} breakpoint. This also
22945 invalidates the Python @code{Breakpoint} object. Any further access
22946 to this object's attributes or methods will raise an error.
22949 @defivar Breakpoint enabled
22950 This attribute is @code{True} if the breakpoint is enabled, and
22951 @code{False} otherwise. This attribute is writable.
22954 @defivar Breakpoint silent
22955 This attribute is @code{True} if the breakpoint is silent, and
22956 @code{False} otherwise. This attribute is writable.
22958 Note that a breakpoint can also be silent if it has commands and the
22959 first command is @code{silent}. This is not reported by the
22960 @code{silent} attribute.
22963 @defivar Breakpoint thread
22964 If the breakpoint is thread-specific, this attribute holds the thread
22965 id. If the breakpoint is not thread-specific, this attribute is
22966 @code{None}. This attribute is writable.
22969 @defivar Breakpoint task
22970 If the breakpoint is Ada task-specific, this attribute holds the Ada task
22971 id. If the breakpoint is not task-specific (or the underlying
22972 language is not Ada), this attribute is @code{None}. This attribute
22976 @defivar Breakpoint ignore_count
22977 This attribute holds the ignore count for the breakpoint, an integer.
22978 This attribute is writable.
22981 @defivar Breakpoint number
22982 This attribute holds the breakpoint's number --- the identifier used by
22983 the user to manipulate the breakpoint. This attribute is not writable.
22986 @defivar Breakpoint type
22987 This attribute holds the breakpoint's type --- the identifier used to
22988 determine the actual breakpoint type or use-case. This attribute is not
22992 @defivar Breakpoint visible
22993 This attribute tells whether the breakpoint is visible to the user
22994 when set, or when the @samp{info breakpoints} command is run. This
22995 attribute is not writable.
22998 The available types are represented by constants defined in the @code{gdb}
23002 @findex BP_BREAKPOINT
23003 @findex gdb.BP_BREAKPOINT
23004 @item BP_BREAKPOINT
23005 Normal code breakpoint.
23007 @findex BP_WATCHPOINT
23008 @findex gdb.BP_WATCHPOINT
23009 @item BP_WATCHPOINT
23010 Watchpoint breakpoint.
23012 @findex BP_HARDWARE_WATCHPOINT
23013 @findex gdb.BP_HARDWARE_WATCHPOINT
23014 @item BP_HARDWARE_WATCHPOINT
23015 Hardware assisted watchpoint.
23017 @findex BP_READ_WATCHPOINT
23018 @findex gdb.BP_READ_WATCHPOINT
23019 @item BP_READ_WATCHPOINT
23020 Hardware assisted read watchpoint.
23022 @findex BP_ACCESS_WATCHPOINT
23023 @findex gdb.BP_ACCESS_WATCHPOINT
23024 @item BP_ACCESS_WATCHPOINT
23025 Hardware assisted access watchpoint.
23028 @defivar Breakpoint hit_count
23029 This attribute holds the hit count for the breakpoint, an integer.
23030 This attribute is writable, but currently it can only be set to zero.
23033 @defivar Breakpoint location
23034 This attribute holds the location of the breakpoint, as specified by
23035 the user. It is a string. If the breakpoint does not have a location
23036 (that is, it is a watchpoint) the attribute's value is @code{None}. This
23037 attribute is not writable.
23040 @defivar Breakpoint expression
23041 This attribute holds a breakpoint expression, as specified by
23042 the user. It is a string. If the breakpoint does not have an
23043 expression (the breakpoint is not a watchpoint) the attribute's value
23044 is @code{None}. This attribute is not writable.
23047 @defivar Breakpoint condition
23048 This attribute holds the condition of the breakpoint, as specified by
23049 the user. It is a string. If there is no condition, this attribute's
23050 value is @code{None}. This attribute is writable.
23053 @defivar Breakpoint commands
23054 This attribute holds the commands attached to the breakpoint. If
23055 there are commands, this attribute's value is a string holding all the
23056 commands, separated by newlines. If there are no commands, this
23057 attribute is @code{None}. This attribute is not writable.
23060 @node Lazy Strings In Python
23061 @subsubsection Python representation of lazy strings.
23063 @cindex lazy strings in python
23064 @tindex gdb.LazyString
23066 A @dfn{lazy string} is a string whose contents is not retrieved or
23067 encoded until it is needed.
23069 A @code{gdb.LazyString} is represented in @value{GDBN} as an
23070 @code{address} that points to a region of memory, an @code{encoding}
23071 that will be used to encode that region of memory, and a @code{length}
23072 to delimit the region of memory that represents the string. The
23073 difference between a @code{gdb.LazyString} and a string wrapped within
23074 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
23075 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
23076 retrieved and encoded during printing, while a @code{gdb.Value}
23077 wrapping a string is immediately retrieved and encoded on creation.
23079 A @code{gdb.LazyString} object has the following functions:
23081 @defmethod LazyString value
23082 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
23083 will point to the string in memory, but will lose all the delayed
23084 retrieval, encoding and handling that @value{GDBN} applies to a
23085 @code{gdb.LazyString}.
23088 @defivar LazyString address
23089 This attribute holds the address of the string. This attribute is not
23093 @defivar LazyString length
23094 This attribute holds the length of the string in characters. If the
23095 length is -1, then the string will be fetched and encoded up to the
23096 first null of appropriate width. This attribute is not writable.
23099 @defivar LazyString encoding
23100 This attribute holds the encoding that will be applied to the string
23101 when the string is printed by @value{GDBN}. If the encoding is not
23102 set, or contains an empty string, then @value{GDBN} will select the
23103 most appropriate encoding when the string is printed. This attribute
23107 @defivar LazyString type
23108 This attribute holds the type that is represented by the lazy string's
23109 type. For a lazy string this will always be a pointer type. To
23110 resolve this to the lazy string's character type, use the type's
23111 @code{target} method. @xref{Types In Python}. This attribute is not
23116 @subsection Auto-loading
23117 @cindex auto-loading, Python
23119 When a new object file is read (for example, due to the @code{file}
23120 command, or because the inferior has loaded a shared library),
23121 @value{GDBN} will look for Python support scripts in several ways:
23122 @file{@var{objfile}-gdb.py} and @code{.debug_gdb_scripts} section.
23125 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
23126 * .debug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
23127 * Which flavor to choose?::
23130 The auto-loading feature is useful for supplying application-specific
23131 debugging commands and scripts.
23133 Auto-loading can be enabled or disabled.
23136 @kindex set auto-load-scripts
23137 @item set auto-load-scripts [yes|no]
23138 Enable or disable the auto-loading of Python scripts.
23140 @kindex show auto-load-scripts
23141 @item show auto-load-scripts
23142 Show whether auto-loading of Python scripts is enabled or disabled.
23145 When reading an auto-loaded file, @value{GDBN} sets the
23146 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
23147 function (@pxref{Objfiles In Python}). This can be useful for
23148 registering objfile-specific pretty-printers.
23150 @node objfile-gdb.py file
23151 @subsubsection The @file{@var{objfile}-gdb.py} file
23152 @cindex @file{@var{objfile}-gdb.py}
23154 When a new object file is read, @value{GDBN} looks for
23155 a file named @file{@var{objfile}-gdb.py},
23156 where @var{objfile} is the object file's real name, formed by ensuring
23157 that the file name is absolute, following all symlinks, and resolving
23158 @code{.} and @code{..} components. If this file exists and is
23159 readable, @value{GDBN} will evaluate it as a Python script.
23161 If this file does not exist, and if the parameter
23162 @code{debug-file-directory} is set (@pxref{Separate Debug Files}),
23163 then @value{GDBN} will look for @var{real-name} in all of the
23164 directories mentioned in the value of @code{debug-file-directory}.
23166 Finally, if this file does not exist, then @value{GDBN} will look for
23167 a file named @file{@var{data-directory}/python/auto-load/@var{real-name}}, where
23168 @var{data-directory} is @value{GDBN}'s data directory (available via
23169 @code{show data-directory}, @pxref{Data Files}), and @var{real-name}
23170 is the object file's real name, as described above.
23172 @value{GDBN} does not track which files it has already auto-loaded this way.
23173 @value{GDBN} will load the associated script every time the corresponding
23174 @var{objfile} is opened.
23175 So your @file{-gdb.py} file should be careful to avoid errors if it
23176 is evaluated more than once.
23178 @node .debug_gdb_scripts section
23179 @subsubsection The @code{.debug_gdb_scripts} section
23180 @cindex @code{.debug_gdb_scripts} section
23182 For systems using file formats like ELF and COFF,
23183 when @value{GDBN} loads a new object file
23184 it will look for a special section named @samp{.debug_gdb_scripts}.
23185 If this section exists, its contents is a list of names of scripts to load.
23187 @value{GDBN} will look for each specified script file first in the
23188 current directory and then along the source search path
23189 (@pxref{Source Path, ,Specifying Source Directories}),
23190 except that @file{$cdir} is not searched, since the compilation
23191 directory is not relevant to scripts.
23193 Entries can be placed in section @code{.debug_gdb_scripts} with,
23194 for example, this GCC macro:
23197 /* Note: The "MS" section flags are to remove duplicates. */
23198 #define DEFINE_GDB_SCRIPT(script_name) \
23200 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
23202 .asciz \"" script_name "\"\n\
23208 Then one can reference the macro in a header or source file like this:
23211 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
23214 The script name may include directories if desired.
23216 If the macro is put in a header, any application or library
23217 using this header will get a reference to the specified script.
23219 @node Which flavor to choose?
23220 @subsubsection Which flavor to choose?
23222 Given the multiple ways of auto-loading Python scripts, it might not always
23223 be clear which one to choose. This section provides some guidance.
23225 Benefits of the @file{-gdb.py} way:
23229 Can be used with file formats that don't support multiple sections.
23232 Ease of finding scripts for public libraries.
23234 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
23235 in the source search path.
23236 For publicly installed libraries, e.g., @file{libstdc++}, there typically
23237 isn't a source directory in which to find the script.
23240 Doesn't require source code additions.
23243 Benefits of the @code{.debug_gdb_scripts} way:
23247 Works with static linking.
23249 Scripts for libraries done the @file{-gdb.py} way require an objfile to
23250 trigger their loading. When an application is statically linked the only
23251 objfile available is the executable, and it is cumbersome to attach all the
23252 scripts from all the input libraries to the executable's @file{-gdb.py} script.
23255 Works with classes that are entirely inlined.
23257 Some classes can be entirely inlined, and thus there may not be an associated
23258 shared library to attach a @file{-gdb.py} script to.
23261 Scripts needn't be copied out of the source tree.
23263 In some circumstances, apps can be built out of large collections of internal
23264 libraries, and the build infrastructure necessary to install the
23265 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
23266 cumbersome. It may be easier to specify the scripts in the
23267 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
23268 top of the source tree to the source search path.
23271 @node Python modules
23272 @subsection Python modules
23273 @cindex python modules
23275 @value{GDBN} comes with a module to assist writing Python code.
23278 * gdb.printing:: Building and registering pretty-printers.
23279 * gdb.types:: Utilities for working with types.
23283 @subsubsection gdb.printing
23284 @cindex gdb.printing
23286 This module provides a collection of utilities for working with
23290 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
23291 This class specifies the API that makes @samp{info pretty-printer},
23292 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
23293 Pretty-printers should generally inherit from this class.
23295 @item SubPrettyPrinter (@var{name})
23296 For printers that handle multiple types, this class specifies the
23297 corresponding API for the subprinters.
23299 @item RegexpCollectionPrettyPrinter (@var{name})
23300 Utility class for handling multiple printers, all recognized via
23301 regular expressions.
23302 @xref{Writing a Pretty-Printer}, for an example.
23304 @item register_pretty_printer (@var{obj}, @var{printer})
23305 Register @var{printer} with the pretty-printer list of @var{obj}.
23309 @subsubsection gdb.types
23312 This module provides a collection of utilities for working with
23313 @code{gdb.Types} objects.
23316 @item get_basic_type (@var{type})
23317 Return @var{type} with const and volatile qualifiers stripped,
23318 and with typedefs and C@t{++} references converted to the underlying type.
23323 typedef const int const_int;
23325 const_int& foo_ref (foo);
23326 int main () @{ return 0; @}
23333 (gdb) python import gdb.types
23334 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
23335 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
23339 @item has_field (@var{type}, @var{field})
23340 Return @code{True} if @var{type}, assumed to be a type with fields
23341 (e.g., a structure or union), has field @var{field}.
23343 @item make_enum_dict (@var{enum_type})
23344 Return a Python @code{dictionary} type produced from @var{enum_type}.
23348 @chapter Command Interpreters
23349 @cindex command interpreters
23351 @value{GDBN} supports multiple command interpreters, and some command
23352 infrastructure to allow users or user interface writers to switch
23353 between interpreters or run commands in other interpreters.
23355 @value{GDBN} currently supports two command interpreters, the console
23356 interpreter (sometimes called the command-line interpreter or @sc{cli})
23357 and the machine interface interpreter (or @sc{gdb/mi}). This manual
23358 describes both of these interfaces in great detail.
23360 By default, @value{GDBN} will start with the console interpreter.
23361 However, the user may choose to start @value{GDBN} with another
23362 interpreter by specifying the @option{-i} or @option{--interpreter}
23363 startup options. Defined interpreters include:
23367 @cindex console interpreter
23368 The traditional console or command-line interpreter. This is the most often
23369 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
23370 @value{GDBN} will use this interpreter.
23373 @cindex mi interpreter
23374 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
23375 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
23376 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
23380 @cindex mi2 interpreter
23381 The current @sc{gdb/mi} interface.
23384 @cindex mi1 interpreter
23385 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
23389 @cindex invoke another interpreter
23390 The interpreter being used by @value{GDBN} may not be dynamically
23391 switched at runtime. Although possible, this could lead to a very
23392 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
23393 enters the command "interpreter-set console" in a console view,
23394 @value{GDBN} would switch to using the console interpreter, rendering
23395 the IDE inoperable!
23397 @kindex interpreter-exec
23398 Although you may only choose a single interpreter at startup, you may execute
23399 commands in any interpreter from the current interpreter using the appropriate
23400 command. If you are running the console interpreter, simply use the
23401 @code{interpreter-exec} command:
23404 interpreter-exec mi "-data-list-register-names"
23407 @sc{gdb/mi} has a similar command, although it is only available in versions of
23408 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
23411 @chapter @value{GDBN} Text User Interface
23413 @cindex Text User Interface
23416 * TUI Overview:: TUI overview
23417 * TUI Keys:: TUI key bindings
23418 * TUI Single Key Mode:: TUI single key mode
23419 * TUI Commands:: TUI-specific commands
23420 * TUI Configuration:: TUI configuration variables
23423 The @value{GDBN} Text User Interface (TUI) is a terminal
23424 interface which uses the @code{curses} library to show the source
23425 file, the assembly output, the program registers and @value{GDBN}
23426 commands in separate text windows. The TUI mode is supported only
23427 on platforms where a suitable version of the @code{curses} library
23430 @pindex @value{GDBTUI}
23431 The TUI mode is enabled by default when you invoke @value{GDBN} as
23432 either @samp{@value{GDBTUI}} or @samp{@value{GDBP} -tui}.
23433 You can also switch in and out of TUI mode while @value{GDBN} runs by
23434 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
23435 @xref{TUI Keys, ,TUI Key Bindings}.
23438 @section TUI Overview
23440 In TUI mode, @value{GDBN} can display several text windows:
23444 This window is the @value{GDBN} command window with the @value{GDBN}
23445 prompt and the @value{GDBN} output. The @value{GDBN} input is still
23446 managed using readline.
23449 The source window shows the source file of the program. The current
23450 line and active breakpoints are displayed in this window.
23453 The assembly window shows the disassembly output of the program.
23456 This window shows the processor registers. Registers are highlighted
23457 when their values change.
23460 The source and assembly windows show the current program position
23461 by highlighting the current line and marking it with a @samp{>} marker.
23462 Breakpoints are indicated with two markers. The first marker
23463 indicates the breakpoint type:
23467 Breakpoint which was hit at least once.
23470 Breakpoint which was never hit.
23473 Hardware breakpoint which was hit at least once.
23476 Hardware breakpoint which was never hit.
23479 The second marker indicates whether the breakpoint is enabled or not:
23483 Breakpoint is enabled.
23486 Breakpoint is disabled.
23489 The source, assembly and register windows are updated when the current
23490 thread changes, when the frame changes, or when the program counter
23493 These windows are not all visible at the same time. The command
23494 window is always visible. The others can be arranged in several
23505 source and assembly,
23508 source and registers, or
23511 assembly and registers.
23514 A status line above the command window shows the following information:
23518 Indicates the current @value{GDBN} target.
23519 (@pxref{Targets, ,Specifying a Debugging Target}).
23522 Gives the current process or thread number.
23523 When no process is being debugged, this field is set to @code{No process}.
23526 Gives the current function name for the selected frame.
23527 The name is demangled if demangling is turned on (@pxref{Print Settings}).
23528 When there is no symbol corresponding to the current program counter,
23529 the string @code{??} is displayed.
23532 Indicates the current line number for the selected frame.
23533 When the current line number is not known, the string @code{??} is displayed.
23536 Indicates the current program counter address.
23540 @section TUI Key Bindings
23541 @cindex TUI key bindings
23543 The TUI installs several key bindings in the readline keymaps
23544 @ifset SYSTEM_READLINE
23545 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
23547 @ifclear SYSTEM_READLINE
23548 (@pxref{Command Line Editing}).
23550 The following key bindings are installed for both TUI mode and the
23551 @value{GDBN} standard mode.
23560 Enter or leave the TUI mode. When leaving the TUI mode,
23561 the curses window management stops and @value{GDBN} operates using
23562 its standard mode, writing on the terminal directly. When reentering
23563 the TUI mode, control is given back to the curses windows.
23564 The screen is then refreshed.
23568 Use a TUI layout with only one window. The layout will
23569 either be @samp{source} or @samp{assembly}. When the TUI mode
23570 is not active, it will switch to the TUI mode.
23572 Think of this key binding as the Emacs @kbd{C-x 1} binding.
23576 Use a TUI layout with at least two windows. When the current
23577 layout already has two windows, the next layout with two windows is used.
23578 When a new layout is chosen, one window will always be common to the
23579 previous layout and the new one.
23581 Think of it as the Emacs @kbd{C-x 2} binding.
23585 Change the active window. The TUI associates several key bindings
23586 (like scrolling and arrow keys) with the active window. This command
23587 gives the focus to the next TUI window.
23589 Think of it as the Emacs @kbd{C-x o} binding.
23593 Switch in and out of the TUI SingleKey mode that binds single
23594 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
23597 The following key bindings only work in the TUI mode:
23602 Scroll the active window one page up.
23606 Scroll the active window one page down.
23610 Scroll the active window one line up.
23614 Scroll the active window one line down.
23618 Scroll the active window one column left.
23622 Scroll the active window one column right.
23626 Refresh the screen.
23629 Because the arrow keys scroll the active window in the TUI mode, they
23630 are not available for their normal use by readline unless the command
23631 window has the focus. When another window is active, you must use
23632 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
23633 and @kbd{C-f} to control the command window.
23635 @node TUI Single Key Mode
23636 @section TUI Single Key Mode
23637 @cindex TUI single key mode
23639 The TUI also provides a @dfn{SingleKey} mode, which binds several
23640 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
23641 switch into this mode, where the following key bindings are used:
23644 @kindex c @r{(SingleKey TUI key)}
23648 @kindex d @r{(SingleKey TUI key)}
23652 @kindex f @r{(SingleKey TUI key)}
23656 @kindex n @r{(SingleKey TUI key)}
23660 @kindex q @r{(SingleKey TUI key)}
23662 exit the SingleKey mode.
23664 @kindex r @r{(SingleKey TUI key)}
23668 @kindex s @r{(SingleKey TUI key)}
23672 @kindex u @r{(SingleKey TUI key)}
23676 @kindex v @r{(SingleKey TUI key)}
23680 @kindex w @r{(SingleKey TUI key)}
23685 Other keys temporarily switch to the @value{GDBN} command prompt.
23686 The key that was pressed is inserted in the editing buffer so that
23687 it is possible to type most @value{GDBN} commands without interaction
23688 with the TUI SingleKey mode. Once the command is entered the TUI
23689 SingleKey mode is restored. The only way to permanently leave
23690 this mode is by typing @kbd{q} or @kbd{C-x s}.
23694 @section TUI-specific Commands
23695 @cindex TUI commands
23697 The TUI has specific commands to control the text windows.
23698 These commands are always available, even when @value{GDBN} is not in
23699 the TUI mode. When @value{GDBN} is in the standard mode, most
23700 of these commands will automatically switch to the TUI mode.
23702 Note that if @value{GDBN}'s @code{stdout} is not connected to a
23703 terminal, or @value{GDBN} has been started with the machine interface
23704 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
23705 these commands will fail with an error, because it would not be
23706 possible or desirable to enable curses window management.
23711 List and give the size of all displayed windows.
23715 Display the next layout.
23718 Display the previous layout.
23721 Display the source window only.
23724 Display the assembly window only.
23727 Display the source and assembly window.
23730 Display the register window together with the source or assembly window.
23734 Make the next window active for scrolling.
23737 Make the previous window active for scrolling.
23740 Make the source window active for scrolling.
23743 Make the assembly window active for scrolling.
23746 Make the register window active for scrolling.
23749 Make the command window active for scrolling.
23753 Refresh the screen. This is similar to typing @kbd{C-L}.
23755 @item tui reg float
23757 Show the floating point registers in the register window.
23759 @item tui reg general
23760 Show the general registers in the register window.
23763 Show the next register group. The list of register groups as well as
23764 their order is target specific. The predefined register groups are the
23765 following: @code{general}, @code{float}, @code{system}, @code{vector},
23766 @code{all}, @code{save}, @code{restore}.
23768 @item tui reg system
23769 Show the system registers in the register window.
23773 Update the source window and the current execution point.
23775 @item winheight @var{name} +@var{count}
23776 @itemx winheight @var{name} -@var{count}
23778 Change the height of the window @var{name} by @var{count}
23779 lines. Positive counts increase the height, while negative counts
23782 @item tabset @var{nchars}
23784 Set the width of tab stops to be @var{nchars} characters.
23787 @node TUI Configuration
23788 @section TUI Configuration Variables
23789 @cindex TUI configuration variables
23791 Several configuration variables control the appearance of TUI windows.
23794 @item set tui border-kind @var{kind}
23795 @kindex set tui border-kind
23796 Select the border appearance for the source, assembly and register windows.
23797 The possible values are the following:
23800 Use a space character to draw the border.
23803 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
23806 Use the Alternate Character Set to draw the border. The border is
23807 drawn using character line graphics if the terminal supports them.
23810 @item set tui border-mode @var{mode}
23811 @kindex set tui border-mode
23812 @itemx set tui active-border-mode @var{mode}
23813 @kindex set tui active-border-mode
23814 Select the display attributes for the borders of the inactive windows
23815 or the active window. The @var{mode} can be one of the following:
23818 Use normal attributes to display the border.
23824 Use reverse video mode.
23827 Use half bright mode.
23829 @item half-standout
23830 Use half bright and standout mode.
23833 Use extra bright or bold mode.
23835 @item bold-standout
23836 Use extra bright or bold and standout mode.
23841 @chapter Using @value{GDBN} under @sc{gnu} Emacs
23844 @cindex @sc{gnu} Emacs
23845 A special interface allows you to use @sc{gnu} Emacs to view (and
23846 edit) the source files for the program you are debugging with
23849 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
23850 executable file you want to debug as an argument. This command starts
23851 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
23852 created Emacs buffer.
23853 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
23855 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
23860 All ``terminal'' input and output goes through an Emacs buffer, called
23863 This applies both to @value{GDBN} commands and their output, and to the input
23864 and output done by the program you are debugging.
23866 This is useful because it means that you can copy the text of previous
23867 commands and input them again; you can even use parts of the output
23870 All the facilities of Emacs' Shell mode are available for interacting
23871 with your program. In particular, you can send signals the usual
23872 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
23876 @value{GDBN} displays source code through Emacs.
23878 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
23879 source file for that frame and puts an arrow (@samp{=>}) at the
23880 left margin of the current line. Emacs uses a separate buffer for
23881 source display, and splits the screen to show both your @value{GDBN} session
23884 Explicit @value{GDBN} @code{list} or search commands still produce output as
23885 usual, but you probably have no reason to use them from Emacs.
23888 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
23889 a graphical mode, enabled by default, which provides further buffers
23890 that can control the execution and describe the state of your program.
23891 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
23893 If you specify an absolute file name when prompted for the @kbd{M-x
23894 gdb} argument, then Emacs sets your current working directory to where
23895 your program resides. If you only specify the file name, then Emacs
23896 sets your current working directory to to the directory associated
23897 with the previous buffer. In this case, @value{GDBN} may find your
23898 program by searching your environment's @code{PATH} variable, but on
23899 some operating systems it might not find the source. So, although the
23900 @value{GDBN} input and output session proceeds normally, the auxiliary
23901 buffer does not display the current source and line of execution.
23903 The initial working directory of @value{GDBN} is printed on the top
23904 line of the GUD buffer and this serves as a default for the commands
23905 that specify files for @value{GDBN} to operate on. @xref{Files,
23906 ,Commands to Specify Files}.
23908 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
23909 need to call @value{GDBN} by a different name (for example, if you
23910 keep several configurations around, with different names) you can
23911 customize the Emacs variable @code{gud-gdb-command-name} to run the
23914 In the GUD buffer, you can use these special Emacs commands in
23915 addition to the standard Shell mode commands:
23919 Describe the features of Emacs' GUD Mode.
23922 Execute to another source line, like the @value{GDBN} @code{step} command; also
23923 update the display window to show the current file and location.
23926 Execute to next source line in this function, skipping all function
23927 calls, like the @value{GDBN} @code{next} command. Then update the display window
23928 to show the current file and location.
23931 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
23932 display window accordingly.
23935 Execute until exit from the selected stack frame, like the @value{GDBN}
23936 @code{finish} command.
23939 Continue execution of your program, like the @value{GDBN} @code{continue}
23943 Go up the number of frames indicated by the numeric argument
23944 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
23945 like the @value{GDBN} @code{up} command.
23948 Go down the number of frames indicated by the numeric argument, like the
23949 @value{GDBN} @code{down} command.
23952 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
23953 tells @value{GDBN} to set a breakpoint on the source line point is on.
23955 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
23956 separate frame which shows a backtrace when the GUD buffer is current.
23957 Move point to any frame in the stack and type @key{RET} to make it
23958 become the current frame and display the associated source in the
23959 source buffer. Alternatively, click @kbd{Mouse-2} to make the
23960 selected frame become the current one. In graphical mode, the
23961 speedbar displays watch expressions.
23963 If you accidentally delete the source-display buffer, an easy way to get
23964 it back is to type the command @code{f} in the @value{GDBN} buffer, to
23965 request a frame display; when you run under Emacs, this recreates
23966 the source buffer if necessary to show you the context of the current
23969 The source files displayed in Emacs are in ordinary Emacs buffers
23970 which are visiting the source files in the usual way. You can edit
23971 the files with these buffers if you wish; but keep in mind that @value{GDBN}
23972 communicates with Emacs in terms of line numbers. If you add or
23973 delete lines from the text, the line numbers that @value{GDBN} knows cease
23974 to correspond properly with the code.
23976 A more detailed description of Emacs' interaction with @value{GDBN} is
23977 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
23980 @c The following dropped because Epoch is nonstandard. Reactivate
23981 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
23983 @kindex Emacs Epoch environment
23987 Version 18 of @sc{gnu} Emacs has a built-in window system
23988 called the @code{epoch}
23989 environment. Users of this environment can use a new command,
23990 @code{inspect} which performs identically to @code{print} except that
23991 each value is printed in its own window.
23996 @chapter The @sc{gdb/mi} Interface
23998 @unnumberedsec Function and Purpose
24000 @cindex @sc{gdb/mi}, its purpose
24001 @sc{gdb/mi} is a line based machine oriented text interface to
24002 @value{GDBN} and is activated by specifying using the
24003 @option{--interpreter} command line option (@pxref{Mode Options}). It
24004 is specifically intended to support the development of systems which
24005 use the debugger as just one small component of a larger system.
24007 This chapter is a specification of the @sc{gdb/mi} interface. It is written
24008 in the form of a reference manual.
24010 Note that @sc{gdb/mi} is still under construction, so some of the
24011 features described below are incomplete and subject to change
24012 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
24014 @unnumberedsec Notation and Terminology
24016 @cindex notational conventions, for @sc{gdb/mi}
24017 This chapter uses the following notation:
24021 @code{|} separates two alternatives.
24024 @code{[ @var{something} ]} indicates that @var{something} is optional:
24025 it may or may not be given.
24028 @code{( @var{group} )*} means that @var{group} inside the parentheses
24029 may repeat zero or more times.
24032 @code{( @var{group} )+} means that @var{group} inside the parentheses
24033 may repeat one or more times.
24036 @code{"@var{string}"} means a literal @var{string}.
24040 @heading Dependencies
24044 * GDB/MI General Design::
24045 * GDB/MI Command Syntax::
24046 * GDB/MI Compatibility with CLI::
24047 * GDB/MI Development and Front Ends::
24048 * GDB/MI Output Records::
24049 * GDB/MI Simple Examples::
24050 * GDB/MI Command Description Format::
24051 * GDB/MI Breakpoint Commands::
24052 * GDB/MI Program Context::
24053 * GDB/MI Thread Commands::
24054 * GDB/MI Program Execution::
24055 * GDB/MI Stack Manipulation::
24056 * GDB/MI Variable Objects::
24057 * GDB/MI Data Manipulation::
24058 * GDB/MI Tracepoint Commands::
24059 * GDB/MI Symbol Query::
24060 * GDB/MI File Commands::
24062 * GDB/MI Kod Commands::
24063 * GDB/MI Memory Overlay Commands::
24064 * GDB/MI Signal Handling Commands::
24066 * GDB/MI Target Manipulation::
24067 * GDB/MI File Transfer Commands::
24068 * GDB/MI Miscellaneous Commands::
24071 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24072 @node GDB/MI General Design
24073 @section @sc{gdb/mi} General Design
24074 @cindex GDB/MI General Design
24076 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
24077 parts---commands sent to @value{GDBN}, responses to those commands
24078 and notifications. Each command results in exactly one response,
24079 indicating either successful completion of the command, or an error.
24080 For the commands that do not resume the target, the response contains the
24081 requested information. For the commands that resume the target, the
24082 response only indicates whether the target was successfully resumed.
24083 Notifications is the mechanism for reporting changes in the state of the
24084 target, or in @value{GDBN} state, that cannot conveniently be associated with
24085 a command and reported as part of that command response.
24087 The important examples of notifications are:
24091 Exec notifications. These are used to report changes in
24092 target state---when a target is resumed, or stopped. It would not
24093 be feasible to include this information in response of resuming
24094 commands, because one resume commands can result in multiple events in
24095 different threads. Also, quite some time may pass before any event
24096 happens in the target, while a frontend needs to know whether the resuming
24097 command itself was successfully executed.
24100 Console output, and status notifications. Console output
24101 notifications are used to report output of CLI commands, as well as
24102 diagnostics for other commands. Status notifications are used to
24103 report the progress of a long-running operation. Naturally, including
24104 this information in command response would mean no output is produced
24105 until the command is finished, which is undesirable.
24108 General notifications. Commands may have various side effects on
24109 the @value{GDBN} or target state beyond their official purpose. For example,
24110 a command may change the selected thread. Although such changes can
24111 be included in command response, using notification allows for more
24112 orthogonal frontend design.
24116 There's no guarantee that whenever an MI command reports an error,
24117 @value{GDBN} or the target are in any specific state, and especially,
24118 the state is not reverted to the state before the MI command was
24119 processed. Therefore, whenever an MI command results in an error,
24120 we recommend that the frontend refreshes all the information shown in
24121 the user interface.
24125 * Context management::
24126 * Asynchronous and non-stop modes::
24130 @node Context management
24131 @subsection Context management
24133 In most cases when @value{GDBN} accesses the target, this access is
24134 done in context of a specific thread and frame (@pxref{Frames}).
24135 Often, even when accessing global data, the target requires that a thread
24136 be specified. The CLI interface maintains the selected thread and frame,
24137 and supplies them to target on each command. This is convenient,
24138 because a command line user would not want to specify that information
24139 explicitly on each command, and because user interacts with
24140 @value{GDBN} via a single terminal, so no confusion is possible as
24141 to what thread and frame are the current ones.
24143 In the case of MI, the concept of selected thread and frame is less
24144 useful. First, a frontend can easily remember this information
24145 itself. Second, a graphical frontend can have more than one window,
24146 each one used for debugging a different thread, and the frontend might
24147 want to access additional threads for internal purposes. This
24148 increases the risk that by relying on implicitly selected thread, the
24149 frontend may be operating on a wrong one. Therefore, each MI command
24150 should explicitly specify which thread and frame to operate on. To
24151 make it possible, each MI command accepts the @samp{--thread} and
24152 @samp{--frame} options, the value to each is @value{GDBN} identifier
24153 for thread and frame to operate on.
24155 Usually, each top-level window in a frontend allows the user to select
24156 a thread and a frame, and remembers the user selection for further
24157 operations. However, in some cases @value{GDBN} may suggest that the
24158 current thread be changed. For example, when stopping on a breakpoint
24159 it is reasonable to switch to the thread where breakpoint is hit. For
24160 another example, if the user issues the CLI @samp{thread} command via
24161 the frontend, it is desirable to change the frontend's selected thread to the
24162 one specified by user. @value{GDBN} communicates the suggestion to
24163 change current thread using the @samp{=thread-selected} notification.
24164 No such notification is available for the selected frame at the moment.
24166 Note that historically, MI shares the selected thread with CLI, so
24167 frontends used the @code{-thread-select} to execute commands in the
24168 right context. However, getting this to work right is cumbersome. The
24169 simplest way is for frontend to emit @code{-thread-select} command
24170 before every command. This doubles the number of commands that need
24171 to be sent. The alternative approach is to suppress @code{-thread-select}
24172 if the selected thread in @value{GDBN} is supposed to be identical to the
24173 thread the frontend wants to operate on. However, getting this
24174 optimization right can be tricky. In particular, if the frontend
24175 sends several commands to @value{GDBN}, and one of the commands changes the
24176 selected thread, then the behaviour of subsequent commands will
24177 change. So, a frontend should either wait for response from such
24178 problematic commands, or explicitly add @code{-thread-select} for
24179 all subsequent commands. No frontend is known to do this exactly
24180 right, so it is suggested to just always pass the @samp{--thread} and
24181 @samp{--frame} options.
24183 @node Asynchronous and non-stop modes
24184 @subsection Asynchronous command execution and non-stop mode
24186 On some targets, @value{GDBN} is capable of processing MI commands
24187 even while the target is running. This is called @dfn{asynchronous
24188 command execution} (@pxref{Background Execution}). The frontend may
24189 specify a preferrence for asynchronous execution using the
24190 @code{-gdb-set target-async 1} command, which should be emitted before
24191 either running the executable or attaching to the target. After the
24192 frontend has started the executable or attached to the target, it can
24193 find if asynchronous execution is enabled using the
24194 @code{-list-target-features} command.
24196 Even if @value{GDBN} can accept a command while target is running,
24197 many commands that access the target do not work when the target is
24198 running. Therefore, asynchronous command execution is most useful
24199 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
24200 it is possible to examine the state of one thread, while other threads
24203 When a given thread is running, MI commands that try to access the
24204 target in the context of that thread may not work, or may work only on
24205 some targets. In particular, commands that try to operate on thread's
24206 stack will not work, on any target. Commands that read memory, or
24207 modify breakpoints, may work or not work, depending on the target. Note
24208 that even commands that operate on global state, such as @code{print},
24209 @code{set}, and breakpoint commands, still access the target in the
24210 context of a specific thread, so frontend should try to find a
24211 stopped thread and perform the operation on that thread (using the
24212 @samp{--thread} option).
24214 Which commands will work in the context of a running thread is
24215 highly target dependent. However, the two commands
24216 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
24217 to find the state of a thread, will always work.
24219 @node Thread groups
24220 @subsection Thread groups
24221 @value{GDBN} may be used to debug several processes at the same time.
24222 On some platfroms, @value{GDBN} may support debugging of several
24223 hardware systems, each one having several cores with several different
24224 processes running on each core. This section describes the MI
24225 mechanism to support such debugging scenarios.
24227 The key observation is that regardless of the structure of the
24228 target, MI can have a global list of threads, because most commands that
24229 accept the @samp{--thread} option do not need to know what process that
24230 thread belongs to. Therefore, it is not necessary to introduce
24231 neither additional @samp{--process} option, nor an notion of the
24232 current process in the MI interface. The only strictly new feature
24233 that is required is the ability to find how the threads are grouped
24236 To allow the user to discover such grouping, and to support arbitrary
24237 hierarchy of machines/cores/processes, MI introduces the concept of a
24238 @dfn{thread group}. Thread group is a collection of threads and other
24239 thread groups. A thread group always has a string identifier, a type,
24240 and may have additional attributes specific to the type. A new
24241 command, @code{-list-thread-groups}, returns the list of top-level
24242 thread groups, which correspond to processes that @value{GDBN} is
24243 debugging at the moment. By passing an identifier of a thread group
24244 to the @code{-list-thread-groups} command, it is possible to obtain
24245 the members of specific thread group.
24247 To allow the user to easily discover processes, and other objects, he
24248 wishes to debug, a concept of @dfn{available thread group} is
24249 introduced. Available thread group is an thread group that
24250 @value{GDBN} is not debugging, but that can be attached to, using the
24251 @code{-target-attach} command. The list of available top-level thread
24252 groups can be obtained using @samp{-list-thread-groups --available}.
24253 In general, the content of a thread group may be only retrieved only
24254 after attaching to that thread group.
24256 Thread groups are related to inferiors (@pxref{Inferiors and
24257 Programs}). Each inferior corresponds to a thread group of a special
24258 type @samp{process}, and some additional operations are permitted on
24259 such thread groups.
24261 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24262 @node GDB/MI Command Syntax
24263 @section @sc{gdb/mi} Command Syntax
24266 * GDB/MI Input Syntax::
24267 * GDB/MI Output Syntax::
24270 @node GDB/MI Input Syntax
24271 @subsection @sc{gdb/mi} Input Syntax
24273 @cindex input syntax for @sc{gdb/mi}
24274 @cindex @sc{gdb/mi}, input syntax
24276 @item @var{command} @expansion{}
24277 @code{@var{cli-command} | @var{mi-command}}
24279 @item @var{cli-command} @expansion{}
24280 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
24281 @var{cli-command} is any existing @value{GDBN} CLI command.
24283 @item @var{mi-command} @expansion{}
24284 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
24285 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
24287 @item @var{token} @expansion{}
24288 "any sequence of digits"
24290 @item @var{option} @expansion{}
24291 @code{"-" @var{parameter} [ " " @var{parameter} ]}
24293 @item @var{parameter} @expansion{}
24294 @code{@var{non-blank-sequence} | @var{c-string}}
24296 @item @var{operation} @expansion{}
24297 @emph{any of the operations described in this chapter}
24299 @item @var{non-blank-sequence} @expansion{}
24300 @emph{anything, provided it doesn't contain special characters such as
24301 "-", @var{nl}, """ and of course " "}
24303 @item @var{c-string} @expansion{}
24304 @code{""" @var{seven-bit-iso-c-string-content} """}
24306 @item @var{nl} @expansion{}
24315 The CLI commands are still handled by the @sc{mi} interpreter; their
24316 output is described below.
24319 The @code{@var{token}}, when present, is passed back when the command
24323 Some @sc{mi} commands accept optional arguments as part of the parameter
24324 list. Each option is identified by a leading @samp{-} (dash) and may be
24325 followed by an optional argument parameter. Options occur first in the
24326 parameter list and can be delimited from normal parameters using
24327 @samp{--} (this is useful when some parameters begin with a dash).
24334 We want easy access to the existing CLI syntax (for debugging).
24337 We want it to be easy to spot a @sc{mi} operation.
24340 @node GDB/MI Output Syntax
24341 @subsection @sc{gdb/mi} Output Syntax
24343 @cindex output syntax of @sc{gdb/mi}
24344 @cindex @sc{gdb/mi}, output syntax
24345 The output from @sc{gdb/mi} consists of zero or more out-of-band records
24346 followed, optionally, by a single result record. This result record
24347 is for the most recent command. The sequence of output records is
24348 terminated by @samp{(gdb)}.
24350 If an input command was prefixed with a @code{@var{token}} then the
24351 corresponding output for that command will also be prefixed by that same
24355 @item @var{output} @expansion{}
24356 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
24358 @item @var{result-record} @expansion{}
24359 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
24361 @item @var{out-of-band-record} @expansion{}
24362 @code{@var{async-record} | @var{stream-record}}
24364 @item @var{async-record} @expansion{}
24365 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
24367 @item @var{exec-async-output} @expansion{}
24368 @code{[ @var{token} ] "*" @var{async-output}}
24370 @item @var{status-async-output} @expansion{}
24371 @code{[ @var{token} ] "+" @var{async-output}}
24373 @item @var{notify-async-output} @expansion{}
24374 @code{[ @var{token} ] "=" @var{async-output}}
24376 @item @var{async-output} @expansion{}
24377 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
24379 @item @var{result-class} @expansion{}
24380 @code{"done" | "running" | "connected" | "error" | "exit"}
24382 @item @var{async-class} @expansion{}
24383 @code{"stopped" | @var{others}} (where @var{others} will be added
24384 depending on the needs---this is still in development).
24386 @item @var{result} @expansion{}
24387 @code{ @var{variable} "=" @var{value}}
24389 @item @var{variable} @expansion{}
24390 @code{ @var{string} }
24392 @item @var{value} @expansion{}
24393 @code{ @var{const} | @var{tuple} | @var{list} }
24395 @item @var{const} @expansion{}
24396 @code{@var{c-string}}
24398 @item @var{tuple} @expansion{}
24399 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
24401 @item @var{list} @expansion{}
24402 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
24403 @var{result} ( "," @var{result} )* "]" }
24405 @item @var{stream-record} @expansion{}
24406 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
24408 @item @var{console-stream-output} @expansion{}
24409 @code{"~" @var{c-string}}
24411 @item @var{target-stream-output} @expansion{}
24412 @code{"@@" @var{c-string}}
24414 @item @var{log-stream-output} @expansion{}
24415 @code{"&" @var{c-string}}
24417 @item @var{nl} @expansion{}
24420 @item @var{token} @expansion{}
24421 @emph{any sequence of digits}.
24429 All output sequences end in a single line containing a period.
24432 The @code{@var{token}} is from the corresponding request. Note that
24433 for all async output, while the token is allowed by the grammar and
24434 may be output by future versions of @value{GDBN} for select async
24435 output messages, it is generally omitted. Frontends should treat
24436 all async output as reporting general changes in the state of the
24437 target and there should be no need to associate async output to any
24441 @cindex status output in @sc{gdb/mi}
24442 @var{status-async-output} contains on-going status information about the
24443 progress of a slow operation. It can be discarded. All status output is
24444 prefixed by @samp{+}.
24447 @cindex async output in @sc{gdb/mi}
24448 @var{exec-async-output} contains asynchronous state change on the target
24449 (stopped, started, disappeared). All async output is prefixed by
24453 @cindex notify output in @sc{gdb/mi}
24454 @var{notify-async-output} contains supplementary information that the
24455 client should handle (e.g., a new breakpoint information). All notify
24456 output is prefixed by @samp{=}.
24459 @cindex console output in @sc{gdb/mi}
24460 @var{console-stream-output} is output that should be displayed as is in the
24461 console. It is the textual response to a CLI command. All the console
24462 output is prefixed by @samp{~}.
24465 @cindex target output in @sc{gdb/mi}
24466 @var{target-stream-output} is the output produced by the target program.
24467 All the target output is prefixed by @samp{@@}.
24470 @cindex log output in @sc{gdb/mi}
24471 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
24472 instance messages that should be displayed as part of an error log. All
24473 the log output is prefixed by @samp{&}.
24476 @cindex list output in @sc{gdb/mi}
24477 New @sc{gdb/mi} commands should only output @var{lists} containing
24483 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
24484 details about the various output records.
24486 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24487 @node GDB/MI Compatibility with CLI
24488 @section @sc{gdb/mi} Compatibility with CLI
24490 @cindex compatibility, @sc{gdb/mi} and CLI
24491 @cindex @sc{gdb/mi}, compatibility with CLI
24493 For the developers convenience CLI commands can be entered directly,
24494 but there may be some unexpected behaviour. For example, commands
24495 that query the user will behave as if the user replied yes, breakpoint
24496 command lists are not executed and some CLI commands, such as
24497 @code{if}, @code{when} and @code{define}, prompt for further input with
24498 @samp{>}, which is not valid MI output.
24500 This feature may be removed at some stage in the future and it is
24501 recommended that front ends use the @code{-interpreter-exec} command
24502 (@pxref{-interpreter-exec}).
24504 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24505 @node GDB/MI Development and Front Ends
24506 @section @sc{gdb/mi} Development and Front Ends
24507 @cindex @sc{gdb/mi} development
24509 The application which takes the MI output and presents the state of the
24510 program being debugged to the user is called a @dfn{front end}.
24512 Although @sc{gdb/mi} is still incomplete, it is currently being used
24513 by a variety of front ends to @value{GDBN}. This makes it difficult
24514 to introduce new functionality without breaking existing usage. This
24515 section tries to minimize the problems by describing how the protocol
24518 Some changes in MI need not break a carefully designed front end, and
24519 for these the MI version will remain unchanged. The following is a
24520 list of changes that may occur within one level, so front ends should
24521 parse MI output in a way that can handle them:
24525 New MI commands may be added.
24528 New fields may be added to the output of any MI command.
24531 The range of values for fields with specified values, e.g.,
24532 @code{in_scope} (@pxref{-var-update}) may be extended.
24534 @c The format of field's content e.g type prefix, may change so parse it
24535 @c at your own risk. Yes, in general?
24537 @c The order of fields may change? Shouldn't really matter but it might
24538 @c resolve inconsistencies.
24541 If the changes are likely to break front ends, the MI version level
24542 will be increased by one. This will allow the front end to parse the
24543 output according to the MI version. Apart from mi0, new versions of
24544 @value{GDBN} will not support old versions of MI and it will be the
24545 responsibility of the front end to work with the new one.
24547 @c Starting with mi3, add a new command -mi-version that prints the MI
24550 The best way to avoid unexpected changes in MI that might break your front
24551 end is to make your project known to @value{GDBN} developers and
24552 follow development on @email{gdb@@sourceware.org} and
24553 @email{gdb-patches@@sourceware.org}.
24554 @cindex mailing lists
24556 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24557 @node GDB/MI Output Records
24558 @section @sc{gdb/mi} Output Records
24561 * GDB/MI Result Records::
24562 * GDB/MI Stream Records::
24563 * GDB/MI Async Records::
24564 * GDB/MI Frame Information::
24565 * GDB/MI Thread Information::
24568 @node GDB/MI Result Records
24569 @subsection @sc{gdb/mi} Result Records
24571 @cindex result records in @sc{gdb/mi}
24572 @cindex @sc{gdb/mi}, result records
24573 In addition to a number of out-of-band notifications, the response to a
24574 @sc{gdb/mi} command includes one of the following result indications:
24578 @item "^done" [ "," @var{results} ]
24579 The synchronous operation was successful, @code{@var{results}} are the return
24584 This result record is equivalent to @samp{^done}. Historically, it
24585 was output instead of @samp{^done} if the command has resumed the
24586 target. This behaviour is maintained for backward compatibility, but
24587 all frontends should treat @samp{^done} and @samp{^running}
24588 identically and rely on the @samp{*running} output record to determine
24589 which threads are resumed.
24593 @value{GDBN} has connected to a remote target.
24595 @item "^error" "," @var{c-string}
24597 The operation failed. The @code{@var{c-string}} contains the corresponding
24602 @value{GDBN} has terminated.
24606 @node GDB/MI Stream Records
24607 @subsection @sc{gdb/mi} Stream Records
24609 @cindex @sc{gdb/mi}, stream records
24610 @cindex stream records in @sc{gdb/mi}
24611 @value{GDBN} internally maintains a number of output streams: the console, the
24612 target, and the log. The output intended for each of these streams is
24613 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
24615 Each stream record begins with a unique @dfn{prefix character} which
24616 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
24617 Syntax}). In addition to the prefix, each stream record contains a
24618 @code{@var{string-output}}. This is either raw text (with an implicit new
24619 line) or a quoted C string (which does not contain an implicit newline).
24622 @item "~" @var{string-output}
24623 The console output stream contains text that should be displayed in the
24624 CLI console window. It contains the textual responses to CLI commands.
24626 @item "@@" @var{string-output}
24627 The target output stream contains any textual output from the running
24628 target. This is only present when GDB's event loop is truly
24629 asynchronous, which is currently only the case for remote targets.
24631 @item "&" @var{string-output}
24632 The log stream contains debugging messages being produced by @value{GDBN}'s
24636 @node GDB/MI Async Records
24637 @subsection @sc{gdb/mi} Async Records
24639 @cindex async records in @sc{gdb/mi}
24640 @cindex @sc{gdb/mi}, async records
24641 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
24642 additional changes that have occurred. Those changes can either be a
24643 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
24644 target activity (e.g., target stopped).
24646 The following is the list of possible async records:
24650 @item *running,thread-id="@var{thread}"
24651 The target is now running. The @var{thread} field tells which
24652 specific thread is now running, and can be @samp{all} if all threads
24653 are running. The frontend should assume that no interaction with a
24654 running thread is possible after this notification is produced.
24655 The frontend should not assume that this notification is output
24656 only once for any command. @value{GDBN} may emit this notification
24657 several times, either for different threads, because it cannot resume
24658 all threads together, or even for a single thread, if the thread must
24659 be stepped though some code before letting it run freely.
24661 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
24662 The target has stopped. The @var{reason} field can have one of the
24666 @item breakpoint-hit
24667 A breakpoint was reached.
24668 @item watchpoint-trigger
24669 A watchpoint was triggered.
24670 @item read-watchpoint-trigger
24671 A read watchpoint was triggered.
24672 @item access-watchpoint-trigger
24673 An access watchpoint was triggered.
24674 @item function-finished
24675 An -exec-finish or similar CLI command was accomplished.
24676 @item location-reached
24677 An -exec-until or similar CLI command was accomplished.
24678 @item watchpoint-scope
24679 A watchpoint has gone out of scope.
24680 @item end-stepping-range
24681 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
24682 similar CLI command was accomplished.
24683 @item exited-signalled
24684 The inferior exited because of a signal.
24686 The inferior exited.
24687 @item exited-normally
24688 The inferior exited normally.
24689 @item signal-received
24690 A signal was received by the inferior.
24693 The @var{id} field identifies the thread that directly caused the stop
24694 -- for example by hitting a breakpoint. Depending on whether all-stop
24695 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
24696 stop all threads, or only the thread that directly triggered the stop.
24697 If all threads are stopped, the @var{stopped} field will have the
24698 value of @code{"all"}. Otherwise, the value of the @var{stopped}
24699 field will be a list of thread identifiers. Presently, this list will
24700 always include a single thread, but frontend should be prepared to see
24701 several threads in the list. The @var{core} field reports the
24702 processor core on which the stop event has happened. This field may be absent
24703 if such information is not available.
24705 @item =thread-group-added,id="@var{id}"
24706 @itemx =thread-group-removed,id="@var{id}"
24707 A thread group was either added or removed. The @var{id} field
24708 contains the @value{GDBN} identifier of the thread group. When a thread
24709 group is added, it generally might not be associated with a running
24710 process. When a thread group is removed, its id becomes invalid and
24711 cannot be used in any way.
24713 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
24714 A thread group became associated with a running program,
24715 either because the program was just started or the thread group
24716 was attached to a program. The @var{id} field contains the
24717 @value{GDBN} identifier of the thread group. The @var{pid} field
24718 contains process identifier, specific to the operating system.
24720 @itemx =thread-group-exited,id="@var{id}"
24721 A thread group is no longer associated with a running program,
24722 either because the program has exited, or because it was detached
24723 from. The @var{id} field contains the @value{GDBN} identifier of the
24726 @item =thread-created,id="@var{id}",group-id="@var{gid}"
24727 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
24728 A thread either was created, or has exited. The @var{id} field
24729 contains the @value{GDBN} identifier of the thread. The @var{gid}
24730 field identifies the thread group this thread belongs to.
24732 @item =thread-selected,id="@var{id}"
24733 Informs that the selected thread was changed as result of the last
24734 command. This notification is not emitted as result of @code{-thread-select}
24735 command but is emitted whenever an MI command that is not documented
24736 to change the selected thread actually changes it. In particular,
24737 invoking, directly or indirectly (via user-defined command), the CLI
24738 @code{thread} command, will generate this notification.
24740 We suggest that in response to this notification, front ends
24741 highlight the selected thread and cause subsequent commands to apply to
24744 @item =library-loaded,...
24745 Reports that a new library file was loaded by the program. This
24746 notification has 4 fields---@var{id}, @var{target-name},
24747 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
24748 opaque identifier of the library. For remote debugging case,
24749 @var{target-name} and @var{host-name} fields give the name of the
24750 library file on the target, and on the host respectively. For native
24751 debugging, both those fields have the same value. The
24752 @var{symbols-loaded} field reports if the debug symbols for this
24753 library are loaded. The @var{thread-group} field, if present,
24754 specifies the id of the thread group in whose context the library was loaded.
24755 If the field is absent, it means the library was loaded in the context
24756 of all present thread groups.
24758 @item =library-unloaded,...
24759 Reports that a library was unloaded by the program. This notification
24760 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
24761 the same meaning as for the @code{=library-loaded} notification.
24762 The @var{thread-group} field, if present, specifies the id of the
24763 thread group in whose context the library was unloaded. If the field is
24764 absent, it means the library was unloaded in the context of all present
24769 @node GDB/MI Frame Information
24770 @subsection @sc{gdb/mi} Frame Information
24772 Response from many MI commands includes an information about stack
24773 frame. This information is a tuple that may have the following
24778 The level of the stack frame. The innermost frame has the level of
24779 zero. This field is always present.
24782 The name of the function corresponding to the frame. This field may
24783 be absent if @value{GDBN} is unable to determine the function name.
24786 The code address for the frame. This field is always present.
24789 The name of the source files that correspond to the frame's code
24790 address. This field may be absent.
24793 The source line corresponding to the frames' code address. This field
24797 The name of the binary file (either executable or shared library) the
24798 corresponds to the frame's code address. This field may be absent.
24802 @node GDB/MI Thread Information
24803 @subsection @sc{gdb/mi} Thread Information
24805 Whenever @value{GDBN} has to report an information about a thread, it
24806 uses a tuple with the following fields:
24810 The numeric id assigned to the thread by @value{GDBN}. This field is
24814 Target-specific string identifying the thread. This field is always present.
24817 Additional information about the thread provided by the target.
24818 It is supposed to be human-readable and not interpreted by the
24819 frontend. This field is optional.
24822 Either @samp{stopped} or @samp{running}, depending on whether the
24823 thread is presently running. This field is always present.
24826 The value of this field is an integer number of the processor core the
24827 thread was last seen on. This field is optional.
24831 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24832 @node GDB/MI Simple Examples
24833 @section Simple Examples of @sc{gdb/mi} Interaction
24834 @cindex @sc{gdb/mi}, simple examples
24836 This subsection presents several simple examples of interaction using
24837 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
24838 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
24839 the output received from @sc{gdb/mi}.
24841 Note the line breaks shown in the examples are here only for
24842 readability, they don't appear in the real output.
24844 @subheading Setting a Breakpoint
24846 Setting a breakpoint generates synchronous output which contains detailed
24847 information of the breakpoint.
24850 -> -break-insert main
24851 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
24852 enabled="y",addr="0x08048564",func="main",file="myprog.c",
24853 fullname="/home/nickrob/myprog.c",line="68",times="0"@}
24857 @subheading Program Execution
24859 Program execution generates asynchronous records and MI gives the
24860 reason that execution stopped.
24866 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
24867 frame=@{addr="0x08048564",func="main",
24868 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
24869 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
24874 <- *stopped,reason="exited-normally"
24878 @subheading Quitting @value{GDBN}
24880 Quitting @value{GDBN} just prints the result class @samp{^exit}.
24888 Please note that @samp{^exit} is printed immediately, but it might
24889 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
24890 performs necessary cleanups, including killing programs being debugged
24891 or disconnecting from debug hardware, so the frontend should wait till
24892 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
24893 fails to exit in reasonable time.
24895 @subheading A Bad Command
24897 Here's what happens if you pass a non-existent command:
24901 <- ^error,msg="Undefined MI command: rubbish"
24906 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24907 @node GDB/MI Command Description Format
24908 @section @sc{gdb/mi} Command Description Format
24910 The remaining sections describe blocks of commands. Each block of
24911 commands is laid out in a fashion similar to this section.
24913 @subheading Motivation
24915 The motivation for this collection of commands.
24917 @subheading Introduction
24919 A brief introduction to this collection of commands as a whole.
24921 @subheading Commands
24923 For each command in the block, the following is described:
24925 @subsubheading Synopsis
24928 -command @var{args}@dots{}
24931 @subsubheading Result
24933 @subsubheading @value{GDBN} Command
24935 The corresponding @value{GDBN} CLI command(s), if any.
24937 @subsubheading Example
24939 Example(s) formatted for readability. Some of the described commands have
24940 not been implemented yet and these are labeled N.A.@: (not available).
24943 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
24944 @node GDB/MI Breakpoint Commands
24945 @section @sc{gdb/mi} Breakpoint Commands
24947 @cindex breakpoint commands for @sc{gdb/mi}
24948 @cindex @sc{gdb/mi}, breakpoint commands
24949 This section documents @sc{gdb/mi} commands for manipulating
24952 @subheading The @code{-break-after} Command
24953 @findex -break-after
24955 @subsubheading Synopsis
24958 -break-after @var{number} @var{count}
24961 The breakpoint number @var{number} is not in effect until it has been
24962 hit @var{count} times. To see how this is reflected in the output of
24963 the @samp{-break-list} command, see the description of the
24964 @samp{-break-list} command below.
24966 @subsubheading @value{GDBN} Command
24968 The corresponding @value{GDBN} command is @samp{ignore}.
24970 @subsubheading Example
24975 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
24976 enabled="y",addr="0x000100d0",func="main",file="hello.c",
24977 fullname="/home/foo/hello.c",line="5",times="0"@}
24984 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
24985 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
24986 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
24987 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
24988 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
24989 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
24990 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
24991 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
24992 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
24993 line="5",times="0",ignore="3"@}]@}
24998 @subheading The @code{-break-catch} Command
24999 @findex -break-catch
25002 @subheading The @code{-break-commands} Command
25003 @findex -break-commands
25005 @subsubheading Synopsis
25008 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
25011 Specifies the CLI commands that should be executed when breakpoint
25012 @var{number} is hit. The parameters @var{command1} to @var{commandN}
25013 are the commands. If no command is specified, any previously-set
25014 commands are cleared. @xref{Break Commands}. Typical use of this
25015 functionality is tracing a program, that is, printing of values of
25016 some variables whenever breakpoint is hit and then continuing.
25018 @subsubheading @value{GDBN} Command
25020 The corresponding @value{GDBN} command is @samp{commands}.
25022 @subsubheading Example
25027 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
25028 enabled="y",addr="0x000100d0",func="main",file="hello.c",
25029 fullname="/home/foo/hello.c",line="5",times="0"@}
25031 -break-commands 1 "print v" "continue"
25036 @subheading The @code{-break-condition} Command
25037 @findex -break-condition
25039 @subsubheading Synopsis
25042 -break-condition @var{number} @var{expr}
25045 Breakpoint @var{number} will stop the program only if the condition in
25046 @var{expr} is true. The condition becomes part of the
25047 @samp{-break-list} output (see the description of the @samp{-break-list}
25050 @subsubheading @value{GDBN} Command
25052 The corresponding @value{GDBN} command is @samp{condition}.
25054 @subsubheading Example
25058 -break-condition 1 1
25062 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25063 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25064 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25065 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25066 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25067 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25068 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25069 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25070 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25071 line="5",cond="1",times="0",ignore="3"@}]@}
25075 @subheading The @code{-break-delete} Command
25076 @findex -break-delete
25078 @subsubheading Synopsis
25081 -break-delete ( @var{breakpoint} )+
25084 Delete the breakpoint(s) whose number(s) are specified in the argument
25085 list. This is obviously reflected in the breakpoint list.
25087 @subsubheading @value{GDBN} Command
25089 The corresponding @value{GDBN} command is @samp{delete}.
25091 @subsubheading Example
25099 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
25100 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25101 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25102 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25103 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25104 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25105 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25110 @subheading The @code{-break-disable} Command
25111 @findex -break-disable
25113 @subsubheading Synopsis
25116 -break-disable ( @var{breakpoint} )+
25119 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
25120 break list is now set to @samp{n} for the named @var{breakpoint}(s).
25122 @subsubheading @value{GDBN} Command
25124 The corresponding @value{GDBN} command is @samp{disable}.
25126 @subsubheading Example
25134 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25135 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25136 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25137 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25138 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25139 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25140 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25141 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
25142 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25143 line="5",times="0"@}]@}
25147 @subheading The @code{-break-enable} Command
25148 @findex -break-enable
25150 @subsubheading Synopsis
25153 -break-enable ( @var{breakpoint} )+
25156 Enable (previously disabled) @var{breakpoint}(s).
25158 @subsubheading @value{GDBN} Command
25160 The corresponding @value{GDBN} command is @samp{enable}.
25162 @subsubheading Example
25170 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25171 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25172 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25173 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25174 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25175 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25176 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25177 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
25178 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
25179 line="5",times="0"@}]@}
25183 @subheading The @code{-break-info} Command
25184 @findex -break-info
25186 @subsubheading Synopsis
25189 -break-info @var{breakpoint}
25193 Get information about a single breakpoint.
25195 @subsubheading @value{GDBN} Command
25197 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
25199 @subsubheading Example
25202 @subheading The @code{-break-insert} Command
25203 @findex -break-insert
25205 @subsubheading Synopsis
25208 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
25209 [ -c @var{condition} ] [ -i @var{ignore-count} ]
25210 [ -p @var{thread} ] [ @var{location} ]
25214 If specified, @var{location}, can be one of:
25221 @item filename:linenum
25222 @item filename:function
25226 The possible optional parameters of this command are:
25230 Insert a temporary breakpoint.
25232 Insert a hardware breakpoint.
25233 @item -c @var{condition}
25234 Make the breakpoint conditional on @var{condition}.
25235 @item -i @var{ignore-count}
25236 Initialize the @var{ignore-count}.
25238 If @var{location} cannot be parsed (for example if it
25239 refers to unknown files or functions), create a pending
25240 breakpoint. Without this flag, @value{GDBN} will report
25241 an error, and won't create a breakpoint, if @var{location}
25244 Create a disabled breakpoint.
25246 Create a tracepoint. @xref{Tracepoints}. When this parameter
25247 is used together with @samp{-h}, a fast tracepoint is created.
25250 @subsubheading Result
25252 The result is in the form:
25255 ^done,bkpt=@{number="@var{number}",type="@var{type}",disp="del"|"keep",
25256 enabled="y"|"n",addr="@var{hex}",func="@var{funcname}",file="@var{filename}",
25257 fullname="@var{full_filename}",line="@var{lineno}",[thread="@var{threadno},]
25258 times="@var{times}"@}
25262 where @var{number} is the @value{GDBN} number for this breakpoint,
25263 @var{funcname} is the name of the function where the breakpoint was
25264 inserted, @var{filename} is the name of the source file which contains
25265 this function, @var{lineno} is the source line number within that file
25266 and @var{times} the number of times that the breakpoint has been hit
25267 (always 0 for -break-insert but may be greater for -break-info or -break-list
25268 which use the same output).
25270 Note: this format is open to change.
25271 @c An out-of-band breakpoint instead of part of the result?
25273 @subsubheading @value{GDBN} Command
25275 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
25276 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
25278 @subsubheading Example
25283 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
25284 fullname="/home/foo/recursive2.c,line="4",times="0"@}
25286 -break-insert -t foo
25287 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
25288 fullname="/home/foo/recursive2.c,line="11",times="0"@}
25291 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
25292 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25293 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25294 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25295 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25296 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25297 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25298 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25299 addr="0x0001072c", func="main",file="recursive2.c",
25300 fullname="/home/foo/recursive2.c,"line="4",times="0"@},
25301 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
25302 addr="0x00010774",func="foo",file="recursive2.c",
25303 fullname="/home/foo/recursive2.c",line="11",times="0"@}]@}
25305 -break-insert -r foo.*
25306 ~int foo(int, int);
25307 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
25308 "fullname="/home/foo/recursive2.c",line="11",times="0"@}
25312 @subheading The @code{-break-list} Command
25313 @findex -break-list
25315 @subsubheading Synopsis
25321 Displays the list of inserted breakpoints, showing the following fields:
25325 number of the breakpoint
25327 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
25329 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
25332 is the breakpoint enabled or no: @samp{y} or @samp{n}
25334 memory location at which the breakpoint is set
25336 logical location of the breakpoint, expressed by function name, file
25339 number of times the breakpoint has been hit
25342 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
25343 @code{body} field is an empty list.
25345 @subsubheading @value{GDBN} Command
25347 The corresponding @value{GDBN} command is @samp{info break}.
25349 @subsubheading Example
25354 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
25355 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25356 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25357 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25358 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25359 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25360 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25361 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25362 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
25363 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
25364 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
25365 line="13",times="0"@}]@}
25369 Here's an example of the result when there are no breakpoints:
25374 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
25375 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25376 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25377 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25378 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25379 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25380 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25385 @subheading The @code{-break-passcount} Command
25386 @findex -break-passcount
25388 @subsubheading Synopsis
25391 -break-passcount @var{tracepoint-number} @var{passcount}
25394 Set the passcount for tracepoint @var{tracepoint-number} to
25395 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
25396 is not a tracepoint, error is emitted. This corresponds to CLI
25397 command @samp{passcount}.
25399 @subheading The @code{-break-watch} Command
25400 @findex -break-watch
25402 @subsubheading Synopsis
25405 -break-watch [ -a | -r ]
25408 Create a watchpoint. With the @samp{-a} option it will create an
25409 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
25410 read from or on a write to the memory location. With the @samp{-r}
25411 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
25412 trigger only when the memory location is accessed for reading. Without
25413 either of the options, the watchpoint created is a regular watchpoint,
25414 i.e., it will trigger when the memory location is accessed for writing.
25415 @xref{Set Watchpoints, , Setting Watchpoints}.
25417 Note that @samp{-break-list} will report a single list of watchpoints and
25418 breakpoints inserted.
25420 @subsubheading @value{GDBN} Command
25422 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
25425 @subsubheading Example
25427 Setting a watchpoint on a variable in the @code{main} function:
25432 ^done,wpt=@{number="2",exp="x"@}
25437 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
25438 value=@{old="-268439212",new="55"@},
25439 frame=@{func="main",args=[],file="recursive2.c",
25440 fullname="/home/foo/bar/recursive2.c",line="5"@}
25444 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
25445 the program execution twice: first for the variable changing value, then
25446 for the watchpoint going out of scope.
25451 ^done,wpt=@{number="5",exp="C"@}
25456 *stopped,reason="watchpoint-trigger",
25457 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
25458 frame=@{func="callee4",args=[],
25459 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25460 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
25465 *stopped,reason="watchpoint-scope",wpnum="5",
25466 frame=@{func="callee3",args=[@{name="strarg",
25467 value="0x11940 \"A string argument.\""@}],
25468 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25469 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
25473 Listing breakpoints and watchpoints, at different points in the program
25474 execution. Note that once the watchpoint goes out of scope, it is
25480 ^done,wpt=@{number="2",exp="C"@}
25483 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
25484 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25485 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25486 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25487 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25488 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25489 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25490 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25491 addr="0x00010734",func="callee4",
25492 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25493 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"@},
25494 bkpt=@{number="2",type="watchpoint",disp="keep",
25495 enabled="y",addr="",what="C",times="0"@}]@}
25500 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
25501 value=@{old="-276895068",new="3"@},
25502 frame=@{func="callee4",args=[],
25503 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25504 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
25507 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
25508 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25509 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25510 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25511 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25512 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25513 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25514 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25515 addr="0x00010734",func="callee4",
25516 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25517 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
25518 bkpt=@{number="2",type="watchpoint",disp="keep",
25519 enabled="y",addr="",what="C",times="-5"@}]@}
25523 ^done,reason="watchpoint-scope",wpnum="2",
25524 frame=@{func="callee3",args=[@{name="strarg",
25525 value="0x11940 \"A string argument.\""@}],
25526 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25527 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
25530 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
25531 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
25532 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
25533 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
25534 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
25535 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
25536 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
25537 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
25538 addr="0x00010734",func="callee4",
25539 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
25540 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
25545 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25546 @node GDB/MI Program Context
25547 @section @sc{gdb/mi} Program Context
25549 @subheading The @code{-exec-arguments} Command
25550 @findex -exec-arguments
25553 @subsubheading Synopsis
25556 -exec-arguments @var{args}
25559 Set the inferior program arguments, to be used in the next
25562 @subsubheading @value{GDBN} Command
25564 The corresponding @value{GDBN} command is @samp{set args}.
25566 @subsubheading Example
25570 -exec-arguments -v word
25577 @subheading The @code{-exec-show-arguments} Command
25578 @findex -exec-show-arguments
25580 @subsubheading Synopsis
25583 -exec-show-arguments
25586 Print the arguments of the program.
25588 @subsubheading @value{GDBN} Command
25590 The corresponding @value{GDBN} command is @samp{show args}.
25592 @subsubheading Example
25597 @subheading The @code{-environment-cd} Command
25598 @findex -environment-cd
25600 @subsubheading Synopsis
25603 -environment-cd @var{pathdir}
25606 Set @value{GDBN}'s working directory.
25608 @subsubheading @value{GDBN} Command
25610 The corresponding @value{GDBN} command is @samp{cd}.
25612 @subsubheading Example
25616 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
25622 @subheading The @code{-environment-directory} Command
25623 @findex -environment-directory
25625 @subsubheading Synopsis
25628 -environment-directory [ -r ] [ @var{pathdir} ]+
25631 Add directories @var{pathdir} to beginning of search path for source files.
25632 If the @samp{-r} option is used, the search path is reset to the default
25633 search path. If directories @var{pathdir} are supplied in addition to the
25634 @samp{-r} option, the search path is first reset and then addition
25636 Multiple directories may be specified, separated by blanks. Specifying
25637 multiple directories in a single command
25638 results in the directories added to the beginning of the
25639 search path in the same order they were presented in the command.
25640 If blanks are needed as
25641 part of a directory name, double-quotes should be used around
25642 the name. In the command output, the path will show up separated
25643 by the system directory-separator character. The directory-separator
25644 character must not be used
25645 in any directory name.
25646 If no directories are specified, the current search path is displayed.
25648 @subsubheading @value{GDBN} Command
25650 The corresponding @value{GDBN} command is @samp{dir}.
25652 @subsubheading Example
25656 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
25657 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
25659 -environment-directory ""
25660 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
25662 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
25663 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
25665 -environment-directory -r
25666 ^done,source-path="$cdir:$cwd"
25671 @subheading The @code{-environment-path} Command
25672 @findex -environment-path
25674 @subsubheading Synopsis
25677 -environment-path [ -r ] [ @var{pathdir} ]+
25680 Add directories @var{pathdir} to beginning of search path for object files.
25681 If the @samp{-r} option is used, the search path is reset to the original
25682 search path that existed at gdb start-up. If directories @var{pathdir} are
25683 supplied in addition to the
25684 @samp{-r} option, the search path is first reset and then addition
25686 Multiple directories may be specified, separated by blanks. Specifying
25687 multiple directories in a single command
25688 results in the directories added to the beginning of the
25689 search path in the same order they were presented in the command.
25690 If blanks are needed as
25691 part of a directory name, double-quotes should be used around
25692 the name. In the command output, the path will show up separated
25693 by the system directory-separator character. The directory-separator
25694 character must not be used
25695 in any directory name.
25696 If no directories are specified, the current path is displayed.
25699 @subsubheading @value{GDBN} Command
25701 The corresponding @value{GDBN} command is @samp{path}.
25703 @subsubheading Example
25708 ^done,path="/usr/bin"
25710 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
25711 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
25713 -environment-path -r /usr/local/bin
25714 ^done,path="/usr/local/bin:/usr/bin"
25719 @subheading The @code{-environment-pwd} Command
25720 @findex -environment-pwd
25722 @subsubheading Synopsis
25728 Show the current working directory.
25730 @subsubheading @value{GDBN} Command
25732 The corresponding @value{GDBN} command is @samp{pwd}.
25734 @subsubheading Example
25739 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
25743 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25744 @node GDB/MI Thread Commands
25745 @section @sc{gdb/mi} Thread Commands
25748 @subheading The @code{-thread-info} Command
25749 @findex -thread-info
25751 @subsubheading Synopsis
25754 -thread-info [ @var{thread-id} ]
25757 Reports information about either a specific thread, if
25758 the @var{thread-id} parameter is present, or about all
25759 threads. When printing information about all threads,
25760 also reports the current thread.
25762 @subsubheading @value{GDBN} Command
25764 The @samp{info thread} command prints the same information
25767 @subsubheading Example
25772 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
25773 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
25774 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
25775 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
25776 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}],
25777 current-thread-id="1"
25781 The @samp{state} field may have the following values:
25785 The thread is stopped. Frame information is available for stopped
25789 The thread is running. There's no frame information for running
25794 @subheading The @code{-thread-list-ids} Command
25795 @findex -thread-list-ids
25797 @subsubheading Synopsis
25803 Produces a list of the currently known @value{GDBN} thread ids. At the
25804 end of the list it also prints the total number of such threads.
25806 This command is retained for historical reasons, the
25807 @code{-thread-info} command should be used instead.
25809 @subsubheading @value{GDBN} Command
25811 Part of @samp{info threads} supplies the same information.
25813 @subsubheading Example
25818 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
25819 current-thread-id="1",number-of-threads="3"
25824 @subheading The @code{-thread-select} Command
25825 @findex -thread-select
25827 @subsubheading Synopsis
25830 -thread-select @var{threadnum}
25833 Make @var{threadnum} the current thread. It prints the number of the new
25834 current thread, and the topmost frame for that thread.
25836 This command is deprecated in favor of explicitly using the
25837 @samp{--thread} option to each command.
25839 @subsubheading @value{GDBN} Command
25841 The corresponding @value{GDBN} command is @samp{thread}.
25843 @subsubheading Example
25850 *stopped,reason="end-stepping-range",thread-id="2",line="187",
25851 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
25855 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
25856 number-of-threads="3"
25859 ^done,new-thread-id="3",
25860 frame=@{level="0",func="vprintf",
25861 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
25862 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
25866 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
25867 @node GDB/MI Program Execution
25868 @section @sc{gdb/mi} Program Execution
25870 These are the asynchronous commands which generate the out-of-band
25871 record @samp{*stopped}. Currently @value{GDBN} only really executes
25872 asynchronously with remote targets and this interaction is mimicked in
25875 @subheading The @code{-exec-continue} Command
25876 @findex -exec-continue
25878 @subsubheading Synopsis
25881 -exec-continue [--reverse] [--all|--thread-group N]
25884 Resumes the execution of the inferior program, which will continue
25885 to execute until it reaches a debugger stop event. If the
25886 @samp{--reverse} option is specified, execution resumes in reverse until
25887 it reaches a stop event. Stop events may include
25890 breakpoints or watchpoints
25892 signals or exceptions
25894 the end of the process (or its beginning under @samp{--reverse})
25896 the end or beginning of a replay log if one is being used.
25898 In all-stop mode (@pxref{All-Stop
25899 Mode}), may resume only one thread, or all threads, depending on the
25900 value of the @samp{scheduler-locking} variable. If @samp{--all} is
25901 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
25902 ignored in all-stop mode. If the @samp{--thread-group} options is
25903 specified, then all threads in that thread group are resumed.
25905 @subsubheading @value{GDBN} Command
25907 The corresponding @value{GDBN} corresponding is @samp{continue}.
25909 @subsubheading Example
25916 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
25917 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
25923 @subheading The @code{-exec-finish} Command
25924 @findex -exec-finish
25926 @subsubheading Synopsis
25929 -exec-finish [--reverse]
25932 Resumes the execution of the inferior program until the current
25933 function is exited. Displays the results returned by the function.
25934 If the @samp{--reverse} option is specified, resumes the reverse
25935 execution of the inferior program until the point where current
25936 function was called.
25938 @subsubheading @value{GDBN} Command
25940 The corresponding @value{GDBN} command is @samp{finish}.
25942 @subsubheading Example
25944 Function returning @code{void}.
25951 *stopped,reason="function-finished",frame=@{func="main",args=[],
25952 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
25956 Function returning other than @code{void}. The name of the internal
25957 @value{GDBN} variable storing the result is printed, together with the
25964 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
25965 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
25966 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
25967 gdb-result-var="$1",return-value="0"
25972 @subheading The @code{-exec-interrupt} Command
25973 @findex -exec-interrupt
25975 @subsubheading Synopsis
25978 -exec-interrupt [--all|--thread-group N]
25981 Interrupts the background execution of the target. Note how the token
25982 associated with the stop message is the one for the execution command
25983 that has been interrupted. The token for the interrupt itself only
25984 appears in the @samp{^done} output. If the user is trying to
25985 interrupt a non-running program, an error message will be printed.
25987 Note that when asynchronous execution is enabled, this command is
25988 asynchronous just like other execution commands. That is, first the
25989 @samp{^done} response will be printed, and the target stop will be
25990 reported after that using the @samp{*stopped} notification.
25992 In non-stop mode, only the context thread is interrupted by default.
25993 All threads (in all inferiors) will be interrupted if the
25994 @samp{--all} option is specified. If the @samp{--thread-group}
25995 option is specified, all threads in that group will be interrupted.
25997 @subsubheading @value{GDBN} Command
25999 The corresponding @value{GDBN} command is @samp{interrupt}.
26001 @subsubheading Example
26012 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
26013 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
26014 fullname="/home/foo/bar/try.c",line="13"@}
26019 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
26023 @subheading The @code{-exec-jump} Command
26026 @subsubheading Synopsis
26029 -exec-jump @var{location}
26032 Resumes execution of the inferior program at the location specified by
26033 parameter. @xref{Specify Location}, for a description of the
26034 different forms of @var{location}.
26036 @subsubheading @value{GDBN} Command
26038 The corresponding @value{GDBN} command is @samp{jump}.
26040 @subsubheading Example
26043 -exec-jump foo.c:10
26044 *running,thread-id="all"
26049 @subheading The @code{-exec-next} Command
26052 @subsubheading Synopsis
26055 -exec-next [--reverse]
26058 Resumes execution of the inferior program, stopping when the beginning
26059 of the next source line is reached.
26061 If the @samp{--reverse} option is specified, resumes reverse execution
26062 of the inferior program, stopping at the beginning of the previous
26063 source line. If you issue this command on the first line of a
26064 function, it will take you back to the caller of that function, to the
26065 source line where the function was called.
26068 @subsubheading @value{GDBN} Command
26070 The corresponding @value{GDBN} command is @samp{next}.
26072 @subsubheading Example
26078 *stopped,reason="end-stepping-range",line="8",file="hello.c"
26083 @subheading The @code{-exec-next-instruction} Command
26084 @findex -exec-next-instruction
26086 @subsubheading Synopsis
26089 -exec-next-instruction [--reverse]
26092 Executes one machine instruction. If the instruction is a function
26093 call, continues until the function returns. If the program stops at an
26094 instruction in the middle of a source line, the address will be
26097 If the @samp{--reverse} option is specified, resumes reverse execution
26098 of the inferior program, stopping at the previous instruction. If the
26099 previously executed instruction was a return from another function,
26100 it will continue to execute in reverse until the call to that function
26101 (from the current stack frame) is reached.
26103 @subsubheading @value{GDBN} Command
26105 The corresponding @value{GDBN} command is @samp{nexti}.
26107 @subsubheading Example
26111 -exec-next-instruction
26115 *stopped,reason="end-stepping-range",
26116 addr="0x000100d4",line="5",file="hello.c"
26121 @subheading The @code{-exec-return} Command
26122 @findex -exec-return
26124 @subsubheading Synopsis
26130 Makes current function return immediately. Doesn't execute the inferior.
26131 Displays the new current frame.
26133 @subsubheading @value{GDBN} Command
26135 The corresponding @value{GDBN} command is @samp{return}.
26137 @subsubheading Example
26141 200-break-insert callee4
26142 200^done,bkpt=@{number="1",addr="0x00010734",
26143 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
26148 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
26149 frame=@{func="callee4",args=[],
26150 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26151 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
26157 111^done,frame=@{level="0",func="callee3",
26158 args=[@{name="strarg",
26159 value="0x11940 \"A string argument.\""@}],
26160 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26161 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
26166 @subheading The @code{-exec-run} Command
26169 @subsubheading Synopsis
26172 -exec-run [--all | --thread-group N]
26175 Starts execution of the inferior from the beginning. The inferior
26176 executes until either a breakpoint is encountered or the program
26177 exits. In the latter case the output will include an exit code, if
26178 the program has exited exceptionally.
26180 When no option is specified, the current inferior is started. If the
26181 @samp{--thread-group} option is specified, it should refer to a thread
26182 group of type @samp{process}, and that thread group will be started.
26183 If the @samp{--all} option is specified, then all inferiors will be started.
26185 @subsubheading @value{GDBN} Command
26187 The corresponding @value{GDBN} command is @samp{run}.
26189 @subsubheading Examples
26194 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
26199 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
26200 frame=@{func="main",args=[],file="recursive2.c",
26201 fullname="/home/foo/bar/recursive2.c",line="4"@}
26206 Program exited normally:
26214 *stopped,reason="exited-normally"
26219 Program exited exceptionally:
26227 *stopped,reason="exited",exit-code="01"
26231 Another way the program can terminate is if it receives a signal such as
26232 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
26236 *stopped,reason="exited-signalled",signal-name="SIGINT",
26237 signal-meaning="Interrupt"
26241 @c @subheading -exec-signal
26244 @subheading The @code{-exec-step} Command
26247 @subsubheading Synopsis
26250 -exec-step [--reverse]
26253 Resumes execution of the inferior program, stopping when the beginning
26254 of the next source line is reached, if the next source line is not a
26255 function call. If it is, stop at the first instruction of the called
26256 function. If the @samp{--reverse} option is specified, resumes reverse
26257 execution of the inferior program, stopping at the beginning of the
26258 previously executed source line.
26260 @subsubheading @value{GDBN} Command
26262 The corresponding @value{GDBN} command is @samp{step}.
26264 @subsubheading Example
26266 Stepping into a function:
26272 *stopped,reason="end-stepping-range",
26273 frame=@{func="foo",args=[@{name="a",value="10"@},
26274 @{name="b",value="0"@}],file="recursive2.c",
26275 fullname="/home/foo/bar/recursive2.c",line="11"@}
26285 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
26290 @subheading The @code{-exec-step-instruction} Command
26291 @findex -exec-step-instruction
26293 @subsubheading Synopsis
26296 -exec-step-instruction [--reverse]
26299 Resumes the inferior which executes one machine instruction. If the
26300 @samp{--reverse} option is specified, resumes reverse execution of the
26301 inferior program, stopping at the previously executed instruction.
26302 The output, once @value{GDBN} has stopped, will vary depending on
26303 whether we have stopped in the middle of a source line or not. In the
26304 former case, the address at which the program stopped will be printed
26307 @subsubheading @value{GDBN} Command
26309 The corresponding @value{GDBN} command is @samp{stepi}.
26311 @subsubheading Example
26315 -exec-step-instruction
26319 *stopped,reason="end-stepping-range",
26320 frame=@{func="foo",args=[],file="try.c",
26321 fullname="/home/foo/bar/try.c",line="10"@}
26323 -exec-step-instruction
26327 *stopped,reason="end-stepping-range",
26328 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
26329 fullname="/home/foo/bar/try.c",line="10"@}
26334 @subheading The @code{-exec-until} Command
26335 @findex -exec-until
26337 @subsubheading Synopsis
26340 -exec-until [ @var{location} ]
26343 Executes the inferior until the @var{location} specified in the
26344 argument is reached. If there is no argument, the inferior executes
26345 until a source line greater than the current one is reached. The
26346 reason for stopping in this case will be @samp{location-reached}.
26348 @subsubheading @value{GDBN} Command
26350 The corresponding @value{GDBN} command is @samp{until}.
26352 @subsubheading Example
26356 -exec-until recursive2.c:6
26360 *stopped,reason="location-reached",frame=@{func="main",args=[],
26361 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
26366 @subheading -file-clear
26367 Is this going away????
26370 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26371 @node GDB/MI Stack Manipulation
26372 @section @sc{gdb/mi} Stack Manipulation Commands
26375 @subheading The @code{-stack-info-frame} Command
26376 @findex -stack-info-frame
26378 @subsubheading Synopsis
26384 Get info on the selected frame.
26386 @subsubheading @value{GDBN} Command
26388 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
26389 (without arguments).
26391 @subsubheading Example
26396 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
26397 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26398 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
26402 @subheading The @code{-stack-info-depth} Command
26403 @findex -stack-info-depth
26405 @subsubheading Synopsis
26408 -stack-info-depth [ @var{max-depth} ]
26411 Return the depth of the stack. If the integer argument @var{max-depth}
26412 is specified, do not count beyond @var{max-depth} frames.
26414 @subsubheading @value{GDBN} Command
26416 There's no equivalent @value{GDBN} command.
26418 @subsubheading Example
26420 For a stack with frame levels 0 through 11:
26427 -stack-info-depth 4
26430 -stack-info-depth 12
26433 -stack-info-depth 11
26436 -stack-info-depth 13
26441 @subheading The @code{-stack-list-arguments} Command
26442 @findex -stack-list-arguments
26444 @subsubheading Synopsis
26447 -stack-list-arguments @var{print-values}
26448 [ @var{low-frame} @var{high-frame} ]
26451 Display a list of the arguments for the frames between @var{low-frame}
26452 and @var{high-frame} (inclusive). If @var{low-frame} and
26453 @var{high-frame} are not provided, list the arguments for the whole
26454 call stack. If the two arguments are equal, show the single frame
26455 at the corresponding level. It is an error if @var{low-frame} is
26456 larger than the actual number of frames. On the other hand,
26457 @var{high-frame} may be larger than the actual number of frames, in
26458 which case only existing frames will be returned.
26460 If @var{print-values} is 0 or @code{--no-values}, print only the names of
26461 the variables; if it is 1 or @code{--all-values}, print also their
26462 values; and if it is 2 or @code{--simple-values}, print the name,
26463 type and value for simple data types, and the name and type for arrays,
26464 structures and unions.
26466 Use of this command to obtain arguments in a single frame is
26467 deprecated in favor of the @samp{-stack-list-variables} command.
26469 @subsubheading @value{GDBN} Command
26471 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
26472 @samp{gdb_get_args} command which partially overlaps with the
26473 functionality of @samp{-stack-list-arguments}.
26475 @subsubheading Example
26482 frame=@{level="0",addr="0x00010734",func="callee4",
26483 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26484 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
26485 frame=@{level="1",addr="0x0001076c",func="callee3",
26486 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26487 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
26488 frame=@{level="2",addr="0x0001078c",func="callee2",
26489 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26490 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
26491 frame=@{level="3",addr="0x000107b4",func="callee1",
26492 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26493 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
26494 frame=@{level="4",addr="0x000107e0",func="main",
26495 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
26496 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
26498 -stack-list-arguments 0
26501 frame=@{level="0",args=[]@},
26502 frame=@{level="1",args=[name="strarg"]@},
26503 frame=@{level="2",args=[name="intarg",name="strarg"]@},
26504 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
26505 frame=@{level="4",args=[]@}]
26507 -stack-list-arguments 1
26510 frame=@{level="0",args=[]@},
26512 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
26513 frame=@{level="2",args=[
26514 @{name="intarg",value="2"@},
26515 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
26516 @{frame=@{level="3",args=[
26517 @{name="intarg",value="2"@},
26518 @{name="strarg",value="0x11940 \"A string argument.\""@},
26519 @{name="fltarg",value="3.5"@}]@},
26520 frame=@{level="4",args=[]@}]
26522 -stack-list-arguments 0 2 2
26523 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
26525 -stack-list-arguments 1 2 2
26526 ^done,stack-args=[frame=@{level="2",
26527 args=[@{name="intarg",value="2"@},
26528 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
26532 @c @subheading -stack-list-exception-handlers
26535 @subheading The @code{-stack-list-frames} Command
26536 @findex -stack-list-frames
26538 @subsubheading Synopsis
26541 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
26544 List the frames currently on the stack. For each frame it displays the
26549 The frame number, 0 being the topmost frame, i.e., the innermost function.
26551 The @code{$pc} value for that frame.
26555 File name of the source file where the function lives.
26556 @item @var{fullname}
26557 The full file name of the source file where the function lives.
26559 Line number corresponding to the @code{$pc}.
26561 The shared library where this function is defined. This is only given
26562 if the frame's function is not known.
26565 If invoked without arguments, this command prints a backtrace for the
26566 whole stack. If given two integer arguments, it shows the frames whose
26567 levels are between the two arguments (inclusive). If the two arguments
26568 are equal, it shows the single frame at the corresponding level. It is
26569 an error if @var{low-frame} is larger than the actual number of
26570 frames. On the other hand, @var{high-frame} may be larger than the
26571 actual number of frames, in which case only existing frames will be returned.
26573 @subsubheading @value{GDBN} Command
26575 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
26577 @subsubheading Example
26579 Full stack backtrace:
26585 [frame=@{level="0",addr="0x0001076c",func="foo",
26586 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
26587 frame=@{level="1",addr="0x000107a4",func="foo",
26588 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26589 frame=@{level="2",addr="0x000107a4",func="foo",
26590 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26591 frame=@{level="3",addr="0x000107a4",func="foo",
26592 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26593 frame=@{level="4",addr="0x000107a4",func="foo",
26594 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26595 frame=@{level="5",addr="0x000107a4",func="foo",
26596 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26597 frame=@{level="6",addr="0x000107a4",func="foo",
26598 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26599 frame=@{level="7",addr="0x000107a4",func="foo",
26600 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26601 frame=@{level="8",addr="0x000107a4",func="foo",
26602 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26603 frame=@{level="9",addr="0x000107a4",func="foo",
26604 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26605 frame=@{level="10",addr="0x000107a4",func="foo",
26606 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26607 frame=@{level="11",addr="0x00010738",func="main",
26608 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
26612 Show frames between @var{low_frame} and @var{high_frame}:
26616 -stack-list-frames 3 5
26618 [frame=@{level="3",addr="0x000107a4",func="foo",
26619 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26620 frame=@{level="4",addr="0x000107a4",func="foo",
26621 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
26622 frame=@{level="5",addr="0x000107a4",func="foo",
26623 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
26627 Show a single frame:
26631 -stack-list-frames 3 3
26633 [frame=@{level="3",addr="0x000107a4",func="foo",
26634 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
26639 @subheading The @code{-stack-list-locals} Command
26640 @findex -stack-list-locals
26642 @subsubheading Synopsis
26645 -stack-list-locals @var{print-values}
26648 Display the local variable names for the selected frame. If
26649 @var{print-values} is 0 or @code{--no-values}, print only the names of
26650 the variables; if it is 1 or @code{--all-values}, print also their
26651 values; and if it is 2 or @code{--simple-values}, print the name,
26652 type and value for simple data types, and the name and type for arrays,
26653 structures and unions. In this last case, a frontend can immediately
26654 display the value of simple data types and create variable objects for
26655 other data types when the user wishes to explore their values in
26658 This command is deprecated in favor of the
26659 @samp{-stack-list-variables} command.
26661 @subsubheading @value{GDBN} Command
26663 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
26665 @subsubheading Example
26669 -stack-list-locals 0
26670 ^done,locals=[name="A",name="B",name="C"]
26672 -stack-list-locals --all-values
26673 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
26674 @{name="C",value="@{1, 2, 3@}"@}]
26675 -stack-list-locals --simple-values
26676 ^done,locals=[@{name="A",type="int",value="1"@},
26677 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
26681 @subheading The @code{-stack-list-variables} Command
26682 @findex -stack-list-variables
26684 @subsubheading Synopsis
26687 -stack-list-variables @var{print-values}
26690 Display the names of local variables and function arguments for the selected frame. If
26691 @var{print-values} is 0 or @code{--no-values}, print only the names of
26692 the variables; if it is 1 or @code{--all-values}, print also their
26693 values; and if it is 2 or @code{--simple-values}, print the name,
26694 type and value for simple data types, and the name and type for arrays,
26695 structures and unions.
26697 @subsubheading Example
26701 -stack-list-variables --thread 1 --frame 0 --all-values
26702 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
26707 @subheading The @code{-stack-select-frame} Command
26708 @findex -stack-select-frame
26710 @subsubheading Synopsis
26713 -stack-select-frame @var{framenum}
26716 Change the selected frame. Select a different frame @var{framenum} on
26719 This command in deprecated in favor of passing the @samp{--frame}
26720 option to every command.
26722 @subsubheading @value{GDBN} Command
26724 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
26725 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
26727 @subsubheading Example
26731 -stack-select-frame 2
26736 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
26737 @node GDB/MI Variable Objects
26738 @section @sc{gdb/mi} Variable Objects
26742 @subheading Motivation for Variable Objects in @sc{gdb/mi}
26744 For the implementation of a variable debugger window (locals, watched
26745 expressions, etc.), we are proposing the adaptation of the existing code
26746 used by @code{Insight}.
26748 The two main reasons for that are:
26752 It has been proven in practice (it is already on its second generation).
26755 It will shorten development time (needless to say how important it is
26759 The original interface was designed to be used by Tcl code, so it was
26760 slightly changed so it could be used through @sc{gdb/mi}. This section
26761 describes the @sc{gdb/mi} operations that will be available and gives some
26762 hints about their use.
26764 @emph{Note}: In addition to the set of operations described here, we
26765 expect the @sc{gui} implementation of a variable window to require, at
26766 least, the following operations:
26769 @item @code{-gdb-show} @code{output-radix}
26770 @item @code{-stack-list-arguments}
26771 @item @code{-stack-list-locals}
26772 @item @code{-stack-select-frame}
26777 @subheading Introduction to Variable Objects
26779 @cindex variable objects in @sc{gdb/mi}
26781 Variable objects are "object-oriented" MI interface for examining and
26782 changing values of expressions. Unlike some other MI interfaces that
26783 work with expressions, variable objects are specifically designed for
26784 simple and efficient presentation in the frontend. A variable object
26785 is identified by string name. When a variable object is created, the
26786 frontend specifies the expression for that variable object. The
26787 expression can be a simple variable, or it can be an arbitrary complex
26788 expression, and can even involve CPU registers. After creating a
26789 variable object, the frontend can invoke other variable object
26790 operations---for example to obtain or change the value of a variable
26791 object, or to change display format.
26793 Variable objects have hierarchical tree structure. Any variable object
26794 that corresponds to a composite type, such as structure in C, has
26795 a number of child variable objects, for example corresponding to each
26796 element of a structure. A child variable object can itself have
26797 children, recursively. Recursion ends when we reach
26798 leaf variable objects, which always have built-in types. Child variable
26799 objects are created only by explicit request, so if a frontend
26800 is not interested in the children of a particular variable object, no
26801 child will be created.
26803 For a leaf variable object it is possible to obtain its value as a
26804 string, or set the value from a string. String value can be also
26805 obtained for a non-leaf variable object, but it's generally a string
26806 that only indicates the type of the object, and does not list its
26807 contents. Assignment to a non-leaf variable object is not allowed.
26809 A frontend does not need to read the values of all variable objects each time
26810 the program stops. Instead, MI provides an update command that lists all
26811 variable objects whose values has changed since the last update
26812 operation. This considerably reduces the amount of data that must
26813 be transferred to the frontend. As noted above, children variable
26814 objects are created on demand, and only leaf variable objects have a
26815 real value. As result, gdb will read target memory only for leaf
26816 variables that frontend has created.
26818 The automatic update is not always desirable. For example, a frontend
26819 might want to keep a value of some expression for future reference,
26820 and never update it. For another example, fetching memory is
26821 relatively slow for embedded targets, so a frontend might want
26822 to disable automatic update for the variables that are either not
26823 visible on the screen, or ``closed''. This is possible using so
26824 called ``frozen variable objects''. Such variable objects are never
26825 implicitly updated.
26827 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
26828 fixed variable object, the expression is parsed when the variable
26829 object is created, including associating identifiers to specific
26830 variables. The meaning of expression never changes. For a floating
26831 variable object the values of variables whose names appear in the
26832 expressions are re-evaluated every time in the context of the current
26833 frame. Consider this example:
26838 struct work_state state;
26845 If a fixed variable object for the @code{state} variable is created in
26846 this function, and we enter the recursive call, the the variable
26847 object will report the value of @code{state} in the top-level
26848 @code{do_work} invocation. On the other hand, a floating variable
26849 object will report the value of @code{state} in the current frame.
26851 If an expression specified when creating a fixed variable object
26852 refers to a local variable, the variable object becomes bound to the
26853 thread and frame in which the variable object is created. When such
26854 variable object is updated, @value{GDBN} makes sure that the
26855 thread/frame combination the variable object is bound to still exists,
26856 and re-evaluates the variable object in context of that thread/frame.
26858 The following is the complete set of @sc{gdb/mi} operations defined to
26859 access this functionality:
26861 @multitable @columnfractions .4 .6
26862 @item @strong{Operation}
26863 @tab @strong{Description}
26865 @item @code{-enable-pretty-printing}
26866 @tab enable Python-based pretty-printing
26867 @item @code{-var-create}
26868 @tab create a variable object
26869 @item @code{-var-delete}
26870 @tab delete the variable object and/or its children
26871 @item @code{-var-set-format}
26872 @tab set the display format of this variable
26873 @item @code{-var-show-format}
26874 @tab show the display format of this variable
26875 @item @code{-var-info-num-children}
26876 @tab tells how many children this object has
26877 @item @code{-var-list-children}
26878 @tab return a list of the object's children
26879 @item @code{-var-info-type}
26880 @tab show the type of this variable object
26881 @item @code{-var-info-expression}
26882 @tab print parent-relative expression that this variable object represents
26883 @item @code{-var-info-path-expression}
26884 @tab print full expression that this variable object represents
26885 @item @code{-var-show-attributes}
26886 @tab is this variable editable? does it exist here?
26887 @item @code{-var-evaluate-expression}
26888 @tab get the value of this variable
26889 @item @code{-var-assign}
26890 @tab set the value of this variable
26891 @item @code{-var-update}
26892 @tab update the variable and its children
26893 @item @code{-var-set-frozen}
26894 @tab set frozeness attribute
26895 @item @code{-var-set-update-range}
26896 @tab set range of children to display on update
26899 In the next subsection we describe each operation in detail and suggest
26900 how it can be used.
26902 @subheading Description And Use of Operations on Variable Objects
26904 @subheading The @code{-enable-pretty-printing} Command
26905 @findex -enable-pretty-printing
26908 -enable-pretty-printing
26911 @value{GDBN} allows Python-based visualizers to affect the output of the
26912 MI variable object commands. However, because there was no way to
26913 implement this in a fully backward-compatible way, a front end must
26914 request that this functionality be enabled.
26916 Once enabled, this feature cannot be disabled.
26918 Note that if Python support has not been compiled into @value{GDBN},
26919 this command will still succeed (and do nothing).
26921 This feature is currently (as of @value{GDBN} 7.0) experimental, and
26922 may work differently in future versions of @value{GDBN}.
26924 @subheading The @code{-var-create} Command
26925 @findex -var-create
26927 @subsubheading Synopsis
26930 -var-create @{@var{name} | "-"@}
26931 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
26934 This operation creates a variable object, which allows the monitoring of
26935 a variable, the result of an expression, a memory cell or a CPU
26938 The @var{name} parameter is the string by which the object can be
26939 referenced. It must be unique. If @samp{-} is specified, the varobj
26940 system will generate a string ``varNNNNNN'' automatically. It will be
26941 unique provided that one does not specify @var{name} of that format.
26942 The command fails if a duplicate name is found.
26944 The frame under which the expression should be evaluated can be
26945 specified by @var{frame-addr}. A @samp{*} indicates that the current
26946 frame should be used. A @samp{@@} indicates that a floating variable
26947 object must be created.
26949 @var{expression} is any expression valid on the current language set (must not
26950 begin with a @samp{*}), or one of the following:
26954 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
26957 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
26960 @samp{$@var{regname}} --- a CPU register name
26963 @cindex dynamic varobj
26964 A varobj's contents may be provided by a Python-based pretty-printer. In this
26965 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
26966 have slightly different semantics in some cases. If the
26967 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
26968 will never create a dynamic varobj. This ensures backward
26969 compatibility for existing clients.
26971 @subsubheading Result
26973 This operation returns attributes of the newly-created varobj. These
26978 The name of the varobj.
26981 The number of children of the varobj. This number is not necessarily
26982 reliable for a dynamic varobj. Instead, you must examine the
26983 @samp{has_more} attribute.
26986 The varobj's scalar value. For a varobj whose type is some sort of
26987 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
26988 will not be interesting.
26991 The varobj's type. This is a string representation of the type, as
26992 would be printed by the @value{GDBN} CLI.
26995 If a variable object is bound to a specific thread, then this is the
26996 thread's identifier.
26999 For a dynamic varobj, this indicates whether there appear to be any
27000 children available. For a non-dynamic varobj, this will be 0.
27003 This attribute will be present and have the value @samp{1} if the
27004 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
27005 then this attribute will not be present.
27008 A dynamic varobj can supply a display hint to the front end. The
27009 value comes directly from the Python pretty-printer object's
27010 @code{display_hint} method. @xref{Pretty Printing API}.
27013 Typical output will look like this:
27016 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
27017 has_more="@var{has_more}"
27021 @subheading The @code{-var-delete} Command
27022 @findex -var-delete
27024 @subsubheading Synopsis
27027 -var-delete [ -c ] @var{name}
27030 Deletes a previously created variable object and all of its children.
27031 With the @samp{-c} option, just deletes the children.
27033 Returns an error if the object @var{name} is not found.
27036 @subheading The @code{-var-set-format} Command
27037 @findex -var-set-format
27039 @subsubheading Synopsis
27042 -var-set-format @var{name} @var{format-spec}
27045 Sets the output format for the value of the object @var{name} to be
27048 @anchor{-var-set-format}
27049 The syntax for the @var{format-spec} is as follows:
27052 @var{format-spec} @expansion{}
27053 @{binary | decimal | hexadecimal | octal | natural@}
27056 The natural format is the default format choosen automatically
27057 based on the variable type (like decimal for an @code{int}, hex
27058 for pointers, etc.).
27060 For a variable with children, the format is set only on the
27061 variable itself, and the children are not affected.
27063 @subheading The @code{-var-show-format} Command
27064 @findex -var-show-format
27066 @subsubheading Synopsis
27069 -var-show-format @var{name}
27072 Returns the format used to display the value of the object @var{name}.
27075 @var{format} @expansion{}
27080 @subheading The @code{-var-info-num-children} Command
27081 @findex -var-info-num-children
27083 @subsubheading Synopsis
27086 -var-info-num-children @var{name}
27089 Returns the number of children of a variable object @var{name}:
27095 Note that this number is not completely reliable for a dynamic varobj.
27096 It will return the current number of children, but more children may
27100 @subheading The @code{-var-list-children} Command
27101 @findex -var-list-children
27103 @subsubheading Synopsis
27106 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
27108 @anchor{-var-list-children}
27110 Return a list of the children of the specified variable object and
27111 create variable objects for them, if they do not already exist. With
27112 a single argument or if @var{print-values} has a value of 0 or
27113 @code{--no-values}, print only the names of the variables; if
27114 @var{print-values} is 1 or @code{--all-values}, also print their
27115 values; and if it is 2 or @code{--simple-values} print the name and
27116 value for simple data types and just the name for arrays, structures
27119 @var{from} and @var{to}, if specified, indicate the range of children
27120 to report. If @var{from} or @var{to} is less than zero, the range is
27121 reset and all children will be reported. Otherwise, children starting
27122 at @var{from} (zero-based) and up to and excluding @var{to} will be
27125 If a child range is requested, it will only affect the current call to
27126 @code{-var-list-children}, but not future calls to @code{-var-update}.
27127 For this, you must instead use @code{-var-set-update-range}. The
27128 intent of this approach is to enable a front end to implement any
27129 update approach it likes; for example, scrolling a view may cause the
27130 front end to request more children with @code{-var-list-children}, and
27131 then the front end could call @code{-var-set-update-range} with a
27132 different range to ensure that future updates are restricted to just
27135 For each child the following results are returned:
27140 Name of the variable object created for this child.
27143 The expression to be shown to the user by the front end to designate this child.
27144 For example this may be the name of a structure member.
27146 For a dynamic varobj, this value cannot be used to form an
27147 expression. There is no way to do this at all with a dynamic varobj.
27149 For C/C@t{++} structures there are several pseudo children returned to
27150 designate access qualifiers. For these pseudo children @var{exp} is
27151 @samp{public}, @samp{private}, or @samp{protected}. In this case the
27152 type and value are not present.
27154 A dynamic varobj will not report the access qualifying
27155 pseudo-children, regardless of the language. This information is not
27156 available at all with a dynamic varobj.
27159 Number of children this child has. For a dynamic varobj, this will be
27163 The type of the child.
27166 If values were requested, this is the value.
27169 If this variable object is associated with a thread, this is the thread id.
27170 Otherwise this result is not present.
27173 If the variable object is frozen, this variable will be present with a value of 1.
27176 The result may have its own attributes:
27180 A dynamic varobj can supply a display hint to the front end. The
27181 value comes directly from the Python pretty-printer object's
27182 @code{display_hint} method. @xref{Pretty Printing API}.
27185 This is an integer attribute which is nonzero if there are children
27186 remaining after the end of the selected range.
27189 @subsubheading Example
27193 -var-list-children n
27194 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
27195 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
27197 -var-list-children --all-values n
27198 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
27199 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
27203 @subheading The @code{-var-info-type} Command
27204 @findex -var-info-type
27206 @subsubheading Synopsis
27209 -var-info-type @var{name}
27212 Returns the type of the specified variable @var{name}. The type is
27213 returned as a string in the same format as it is output by the
27217 type=@var{typename}
27221 @subheading The @code{-var-info-expression} Command
27222 @findex -var-info-expression
27224 @subsubheading Synopsis
27227 -var-info-expression @var{name}
27230 Returns a string that is suitable for presenting this
27231 variable object in user interface. The string is generally
27232 not valid expression in the current language, and cannot be evaluated.
27234 For example, if @code{a} is an array, and variable object
27235 @code{A} was created for @code{a}, then we'll get this output:
27238 (gdb) -var-info-expression A.1
27239 ^done,lang="C",exp="1"
27243 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
27245 Note that the output of the @code{-var-list-children} command also
27246 includes those expressions, so the @code{-var-info-expression} command
27249 @subheading The @code{-var-info-path-expression} Command
27250 @findex -var-info-path-expression
27252 @subsubheading Synopsis
27255 -var-info-path-expression @var{name}
27258 Returns an expression that can be evaluated in the current
27259 context and will yield the same value that a variable object has.
27260 Compare this with the @code{-var-info-expression} command, which
27261 result can be used only for UI presentation. Typical use of
27262 the @code{-var-info-path-expression} command is creating a
27263 watchpoint from a variable object.
27265 This command is currently not valid for children of a dynamic varobj,
27266 and will give an error when invoked on one.
27268 For example, suppose @code{C} is a C@t{++} class, derived from class
27269 @code{Base}, and that the @code{Base} class has a member called
27270 @code{m_size}. Assume a variable @code{c} is has the type of
27271 @code{C} and a variable object @code{C} was created for variable
27272 @code{c}. Then, we'll get this output:
27274 (gdb) -var-info-path-expression C.Base.public.m_size
27275 ^done,path_expr=((Base)c).m_size)
27278 @subheading The @code{-var-show-attributes} Command
27279 @findex -var-show-attributes
27281 @subsubheading Synopsis
27284 -var-show-attributes @var{name}
27287 List attributes of the specified variable object @var{name}:
27290 status=@var{attr} [ ( ,@var{attr} )* ]
27294 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
27296 @subheading The @code{-var-evaluate-expression} Command
27297 @findex -var-evaluate-expression
27299 @subsubheading Synopsis
27302 -var-evaluate-expression [-f @var{format-spec}] @var{name}
27305 Evaluates the expression that is represented by the specified variable
27306 object and returns its value as a string. The format of the string
27307 can be specified with the @samp{-f} option. The possible values of
27308 this option are the same as for @code{-var-set-format}
27309 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
27310 the current display format will be used. The current display format
27311 can be changed using the @code{-var-set-format} command.
27317 Note that one must invoke @code{-var-list-children} for a variable
27318 before the value of a child variable can be evaluated.
27320 @subheading The @code{-var-assign} Command
27321 @findex -var-assign
27323 @subsubheading Synopsis
27326 -var-assign @var{name} @var{expression}
27329 Assigns the value of @var{expression} to the variable object specified
27330 by @var{name}. The object must be @samp{editable}. If the variable's
27331 value is altered by the assign, the variable will show up in any
27332 subsequent @code{-var-update} list.
27334 @subsubheading Example
27342 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
27346 @subheading The @code{-var-update} Command
27347 @findex -var-update
27349 @subsubheading Synopsis
27352 -var-update [@var{print-values}] @{@var{name} | "*"@}
27355 Reevaluate the expressions corresponding to the variable object
27356 @var{name} and all its direct and indirect children, and return the
27357 list of variable objects whose values have changed; @var{name} must
27358 be a root variable object. Here, ``changed'' means that the result of
27359 @code{-var-evaluate-expression} before and after the
27360 @code{-var-update} is different. If @samp{*} is used as the variable
27361 object names, all existing variable objects are updated, except
27362 for frozen ones (@pxref{-var-set-frozen}). The option
27363 @var{print-values} determines whether both names and values, or just
27364 names are printed. The possible values of this option are the same
27365 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
27366 recommended to use the @samp{--all-values} option, to reduce the
27367 number of MI commands needed on each program stop.
27369 With the @samp{*} parameter, if a variable object is bound to a
27370 currently running thread, it will not be updated, without any
27373 If @code{-var-set-update-range} was previously used on a varobj, then
27374 only the selected range of children will be reported.
27376 @code{-var-update} reports all the changed varobjs in a tuple named
27379 Each item in the change list is itself a tuple holding:
27383 The name of the varobj.
27386 If values were requested for this update, then this field will be
27387 present and will hold the value of the varobj.
27390 @anchor{-var-update}
27391 This field is a string which may take one of three values:
27395 The variable object's current value is valid.
27398 The variable object does not currently hold a valid value but it may
27399 hold one in the future if its associated expression comes back into
27403 The variable object no longer holds a valid value.
27404 This can occur when the executable file being debugged has changed,
27405 either through recompilation or by using the @value{GDBN} @code{file}
27406 command. The front end should normally choose to delete these variable
27410 In the future new values may be added to this list so the front should
27411 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
27414 This is only present if the varobj is still valid. If the type
27415 changed, then this will be the string @samp{true}; otherwise it will
27419 If the varobj's type changed, then this field will be present and will
27422 @item new_num_children
27423 For a dynamic varobj, if the number of children changed, or if the
27424 type changed, this will be the new number of children.
27426 The @samp{numchild} field in other varobj responses is generally not
27427 valid for a dynamic varobj -- it will show the number of children that
27428 @value{GDBN} knows about, but because dynamic varobjs lazily
27429 instantiate their children, this will not reflect the number of
27430 children which may be available.
27432 The @samp{new_num_children} attribute only reports changes to the
27433 number of children known by @value{GDBN}. This is the only way to
27434 detect whether an update has removed children (which necessarily can
27435 only happen at the end of the update range).
27438 The display hint, if any.
27441 This is an integer value, which will be 1 if there are more children
27442 available outside the varobj's update range.
27445 This attribute will be present and have the value @samp{1} if the
27446 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
27447 then this attribute will not be present.
27450 If new children were added to a dynamic varobj within the selected
27451 update range (as set by @code{-var-set-update-range}), then they will
27452 be listed in this attribute.
27455 @subsubheading Example
27462 -var-update --all-values var1
27463 ^done,changelist=[@{name="var1",value="3",in_scope="true",
27464 type_changed="false"@}]
27468 @subheading The @code{-var-set-frozen} Command
27469 @findex -var-set-frozen
27470 @anchor{-var-set-frozen}
27472 @subsubheading Synopsis
27475 -var-set-frozen @var{name} @var{flag}
27478 Set the frozenness flag on the variable object @var{name}. The
27479 @var{flag} parameter should be either @samp{1} to make the variable
27480 frozen or @samp{0} to make it unfrozen. If a variable object is
27481 frozen, then neither itself, nor any of its children, are
27482 implicitly updated by @code{-var-update} of
27483 a parent variable or by @code{-var-update *}. Only
27484 @code{-var-update} of the variable itself will update its value and
27485 values of its children. After a variable object is unfrozen, it is
27486 implicitly updated by all subsequent @code{-var-update} operations.
27487 Unfreezing a variable does not update it, only subsequent
27488 @code{-var-update} does.
27490 @subsubheading Example
27494 -var-set-frozen V 1
27499 @subheading The @code{-var-set-update-range} command
27500 @findex -var-set-update-range
27501 @anchor{-var-set-update-range}
27503 @subsubheading Synopsis
27506 -var-set-update-range @var{name} @var{from} @var{to}
27509 Set the range of children to be returned by future invocations of
27510 @code{-var-update}.
27512 @var{from} and @var{to} indicate the range of children to report. If
27513 @var{from} or @var{to} is less than zero, the range is reset and all
27514 children will be reported. Otherwise, children starting at @var{from}
27515 (zero-based) and up to and excluding @var{to} will be reported.
27517 @subsubheading Example
27521 -var-set-update-range V 1 2
27525 @subheading The @code{-var-set-visualizer} command
27526 @findex -var-set-visualizer
27527 @anchor{-var-set-visualizer}
27529 @subsubheading Synopsis
27532 -var-set-visualizer @var{name} @var{visualizer}
27535 Set a visualizer for the variable object @var{name}.
27537 @var{visualizer} is the visualizer to use. The special value
27538 @samp{None} means to disable any visualizer in use.
27540 If not @samp{None}, @var{visualizer} must be a Python expression.
27541 This expression must evaluate to a callable object which accepts a
27542 single argument. @value{GDBN} will call this object with the value of
27543 the varobj @var{name} as an argument (this is done so that the same
27544 Python pretty-printing code can be used for both the CLI and MI).
27545 When called, this object must return an object which conforms to the
27546 pretty-printing interface (@pxref{Pretty Printing API}).
27548 The pre-defined function @code{gdb.default_visualizer} may be used to
27549 select a visualizer by following the built-in process
27550 (@pxref{Selecting Pretty-Printers}). This is done automatically when
27551 a varobj is created, and so ordinarily is not needed.
27553 This feature is only available if Python support is enabled. The MI
27554 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
27555 can be used to check this.
27557 @subsubheading Example
27559 Resetting the visualizer:
27563 -var-set-visualizer V None
27567 Reselecting the default (type-based) visualizer:
27571 -var-set-visualizer V gdb.default_visualizer
27575 Suppose @code{SomeClass} is a visualizer class. A lambda expression
27576 can be used to instantiate this class for a varobj:
27580 -var-set-visualizer V "lambda val: SomeClass()"
27584 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27585 @node GDB/MI Data Manipulation
27586 @section @sc{gdb/mi} Data Manipulation
27588 @cindex data manipulation, in @sc{gdb/mi}
27589 @cindex @sc{gdb/mi}, data manipulation
27590 This section describes the @sc{gdb/mi} commands that manipulate data:
27591 examine memory and registers, evaluate expressions, etc.
27593 @c REMOVED FROM THE INTERFACE.
27594 @c @subheading -data-assign
27595 @c Change the value of a program variable. Plenty of side effects.
27596 @c @subsubheading GDB Command
27598 @c @subsubheading Example
27601 @subheading The @code{-data-disassemble} Command
27602 @findex -data-disassemble
27604 @subsubheading Synopsis
27608 [ -s @var{start-addr} -e @var{end-addr} ]
27609 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
27617 @item @var{start-addr}
27618 is the beginning address (or @code{$pc})
27619 @item @var{end-addr}
27621 @item @var{filename}
27622 is the name of the file to disassemble
27623 @item @var{linenum}
27624 is the line number to disassemble around
27626 is the number of disassembly lines to be produced. If it is -1,
27627 the whole function will be disassembled, in case no @var{end-addr} is
27628 specified. If @var{end-addr} is specified as a non-zero value, and
27629 @var{lines} is lower than the number of disassembly lines between
27630 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
27631 displayed; if @var{lines} is higher than the number of lines between
27632 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
27635 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
27639 @subsubheading Result
27641 The output for each instruction is composed of four fields:
27650 Note that whatever included in the instruction field, is not manipulated
27651 directly by @sc{gdb/mi}, i.e., it is not possible to adjust its format.
27653 @subsubheading @value{GDBN} Command
27655 There's no direct mapping from this command to the CLI.
27657 @subsubheading Example
27659 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
27663 -data-disassemble -s $pc -e "$pc + 20" -- 0
27666 @{address="0x000107c0",func-name="main",offset="4",
27667 inst="mov 2, %o0"@},
27668 @{address="0x000107c4",func-name="main",offset="8",
27669 inst="sethi %hi(0x11800), %o2"@},
27670 @{address="0x000107c8",func-name="main",offset="12",
27671 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
27672 @{address="0x000107cc",func-name="main",offset="16",
27673 inst="sethi %hi(0x11800), %o2"@},
27674 @{address="0x000107d0",func-name="main",offset="20",
27675 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
27679 Disassemble the whole @code{main} function. Line 32 is part of
27683 -data-disassemble -f basics.c -l 32 -- 0
27685 @{address="0x000107bc",func-name="main",offset="0",
27686 inst="save %sp, -112, %sp"@},
27687 @{address="0x000107c0",func-name="main",offset="4",
27688 inst="mov 2, %o0"@},
27689 @{address="0x000107c4",func-name="main",offset="8",
27690 inst="sethi %hi(0x11800), %o2"@},
27692 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
27693 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
27697 Disassemble 3 instructions from the start of @code{main}:
27701 -data-disassemble -f basics.c -l 32 -n 3 -- 0
27703 @{address="0x000107bc",func-name="main",offset="0",
27704 inst="save %sp, -112, %sp"@},
27705 @{address="0x000107c0",func-name="main",offset="4",
27706 inst="mov 2, %o0"@},
27707 @{address="0x000107c4",func-name="main",offset="8",
27708 inst="sethi %hi(0x11800), %o2"@}]
27712 Disassemble 3 instructions from the start of @code{main} in mixed mode:
27716 -data-disassemble -f basics.c -l 32 -n 3 -- 1
27718 src_and_asm_line=@{line="31",
27719 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
27720 testsuite/gdb.mi/basics.c",line_asm_insn=[
27721 @{address="0x000107bc",func-name="main",offset="0",
27722 inst="save %sp, -112, %sp"@}]@},
27723 src_and_asm_line=@{line="32",
27724 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
27725 testsuite/gdb.mi/basics.c",line_asm_insn=[
27726 @{address="0x000107c0",func-name="main",offset="4",
27727 inst="mov 2, %o0"@},
27728 @{address="0x000107c4",func-name="main",offset="8",
27729 inst="sethi %hi(0x11800), %o2"@}]@}]
27734 @subheading The @code{-data-evaluate-expression} Command
27735 @findex -data-evaluate-expression
27737 @subsubheading Synopsis
27740 -data-evaluate-expression @var{expr}
27743 Evaluate @var{expr} as an expression. The expression could contain an
27744 inferior function call. The function call will execute synchronously.
27745 If the expression contains spaces, it must be enclosed in double quotes.
27747 @subsubheading @value{GDBN} Command
27749 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
27750 @samp{call}. In @code{gdbtk} only, there's a corresponding
27751 @samp{gdb_eval} command.
27753 @subsubheading Example
27755 In the following example, the numbers that precede the commands are the
27756 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
27757 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
27761 211-data-evaluate-expression A
27764 311-data-evaluate-expression &A
27765 311^done,value="0xefffeb7c"
27767 411-data-evaluate-expression A+3
27770 511-data-evaluate-expression "A + 3"
27776 @subheading The @code{-data-list-changed-registers} Command
27777 @findex -data-list-changed-registers
27779 @subsubheading Synopsis
27782 -data-list-changed-registers
27785 Display a list of the registers that have changed.
27787 @subsubheading @value{GDBN} Command
27789 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
27790 has the corresponding command @samp{gdb_changed_register_list}.
27792 @subsubheading Example
27794 On a PPC MBX board:
27802 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
27803 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
27806 -data-list-changed-registers
27807 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
27808 "10","11","13","14","15","16","17","18","19","20","21","22","23",
27809 "24","25","26","27","28","30","31","64","65","66","67","69"]
27814 @subheading The @code{-data-list-register-names} Command
27815 @findex -data-list-register-names
27817 @subsubheading Synopsis
27820 -data-list-register-names [ ( @var{regno} )+ ]
27823 Show a list of register names for the current target. If no arguments
27824 are given, it shows a list of the names of all the registers. If
27825 integer numbers are given as arguments, it will print a list of the
27826 names of the registers corresponding to the arguments. To ensure
27827 consistency between a register name and its number, the output list may
27828 include empty register names.
27830 @subsubheading @value{GDBN} Command
27832 @value{GDBN} does not have a command which corresponds to
27833 @samp{-data-list-register-names}. In @code{gdbtk} there is a
27834 corresponding command @samp{gdb_regnames}.
27836 @subsubheading Example
27838 For the PPC MBX board:
27841 -data-list-register-names
27842 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
27843 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
27844 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
27845 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
27846 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
27847 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
27848 "", "pc","ps","cr","lr","ctr","xer"]
27850 -data-list-register-names 1 2 3
27851 ^done,register-names=["r1","r2","r3"]
27855 @subheading The @code{-data-list-register-values} Command
27856 @findex -data-list-register-values
27858 @subsubheading Synopsis
27861 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
27864 Display the registers' contents. @var{fmt} is the format according to
27865 which the registers' contents are to be returned, followed by an optional
27866 list of numbers specifying the registers to display. A missing list of
27867 numbers indicates that the contents of all the registers must be returned.
27869 Allowed formats for @var{fmt} are:
27886 @subsubheading @value{GDBN} Command
27888 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
27889 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
27891 @subsubheading Example
27893 For a PPC MBX board (note: line breaks are for readability only, they
27894 don't appear in the actual output):
27898 -data-list-register-values r 64 65
27899 ^done,register-values=[@{number="64",value="0xfe00a300"@},
27900 @{number="65",value="0x00029002"@}]
27902 -data-list-register-values x
27903 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
27904 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
27905 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
27906 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
27907 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
27908 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
27909 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
27910 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
27911 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
27912 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
27913 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
27914 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
27915 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
27916 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
27917 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
27918 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
27919 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
27920 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
27921 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
27922 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
27923 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
27924 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
27925 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
27926 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
27927 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
27928 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
27929 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
27930 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
27931 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
27932 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
27933 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
27934 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
27935 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
27936 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
27937 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
27938 @{number="69",value="0x20002b03"@}]
27943 @subheading The @code{-data-read-memory} Command
27944 @findex -data-read-memory
27946 This command is deprecated, use @code{-data-read-memory-bytes} instead.
27948 @subsubheading Synopsis
27951 -data-read-memory [ -o @var{byte-offset} ]
27952 @var{address} @var{word-format} @var{word-size}
27953 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
27960 @item @var{address}
27961 An expression specifying the address of the first memory word to be
27962 read. Complex expressions containing embedded white space should be
27963 quoted using the C convention.
27965 @item @var{word-format}
27966 The format to be used to print the memory words. The notation is the
27967 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
27970 @item @var{word-size}
27971 The size of each memory word in bytes.
27973 @item @var{nr-rows}
27974 The number of rows in the output table.
27976 @item @var{nr-cols}
27977 The number of columns in the output table.
27980 If present, indicates that each row should include an @sc{ascii} dump. The
27981 value of @var{aschar} is used as a padding character when a byte is not a
27982 member of the printable @sc{ascii} character set (printable @sc{ascii}
27983 characters are those whose code is between 32 and 126, inclusively).
27985 @item @var{byte-offset}
27986 An offset to add to the @var{address} before fetching memory.
27989 This command displays memory contents as a table of @var{nr-rows} by
27990 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
27991 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
27992 (returned as @samp{total-bytes}). Should less than the requested number
27993 of bytes be returned by the target, the missing words are identified
27994 using @samp{N/A}. The number of bytes read from the target is returned
27995 in @samp{nr-bytes} and the starting address used to read memory in
27998 The address of the next/previous row or page is available in
27999 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
28002 @subsubheading @value{GDBN} Command
28004 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
28005 @samp{gdb_get_mem} memory read command.
28007 @subsubheading Example
28009 Read six bytes of memory starting at @code{bytes+6} but then offset by
28010 @code{-6} bytes. Format as three rows of two columns. One byte per
28011 word. Display each word in hex.
28015 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
28016 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
28017 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
28018 prev-page="0x0000138a",memory=[
28019 @{addr="0x00001390",data=["0x00","0x01"]@},
28020 @{addr="0x00001392",data=["0x02","0x03"]@},
28021 @{addr="0x00001394",data=["0x04","0x05"]@}]
28025 Read two bytes of memory starting at address @code{shorts + 64} and
28026 display as a single word formatted in decimal.
28030 5-data-read-memory shorts+64 d 2 1 1
28031 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
28032 next-row="0x00001512",prev-row="0x0000150e",
28033 next-page="0x00001512",prev-page="0x0000150e",memory=[
28034 @{addr="0x00001510",data=["128"]@}]
28038 Read thirty two bytes of memory starting at @code{bytes+16} and format
28039 as eight rows of four columns. Include a string encoding with @samp{x}
28040 used as the non-printable character.
28044 4-data-read-memory bytes+16 x 1 8 4 x
28045 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
28046 next-row="0x000013c0",prev-row="0x0000139c",
28047 next-page="0x000013c0",prev-page="0x00001380",memory=[
28048 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
28049 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
28050 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
28051 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
28052 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
28053 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
28054 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
28055 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
28059 @subheading The @code{-data-read-memory-bytes} Command
28060 @findex -data-read-memory-bytes
28062 @subsubheading Synopsis
28065 -data-read-memory-bytes [ -o @var{byte-offset} ]
28066 @var{address} @var{count}
28073 @item @var{address}
28074 An expression specifying the address of the first memory word to be
28075 read. Complex expressions containing embedded white space should be
28076 quoted using the C convention.
28079 The number of bytes to read. This should be an integer literal.
28081 @item @var{byte-offset}
28082 The offsets in bytes relative to @var{address} at which to start
28083 reading. This should be an integer literal. This option is provided
28084 so that a frontend is not required to first evaluate address and then
28085 perform address arithmetics itself.
28089 This command attempts to read all accessible memory regions in the
28090 specified range. First, all regions marked as unreadable in the memory
28091 map (if one is defined) will be skipped. @xref{Memory Region
28092 Attributes}. Second, @value{GDBN} will attempt to read the remaining
28093 regions. For each one, if reading full region results in an errors,
28094 @value{GDBN} will try to read a subset of the region.
28096 In general, every single byte in the region may be readable or not,
28097 and the only way to read every readable byte is to try a read at
28098 every address, which is not practical. Therefore, @value{GDBN} will
28099 attempt to read all accessible bytes at either beginning or the end
28100 of the region, using a binary division scheme. This heuristic works
28101 well for reading accross a memory map boundary. Note that if a region
28102 has a readable range that is neither at the beginning or the end,
28103 @value{GDBN} will not read it.
28105 The result record (@pxref{GDB/MI Result Records}) that is output of
28106 the command includes a field named @samp{memory} whose content is a
28107 list of tuples. Each tuple represent a successfully read memory block
28108 and has the following fields:
28112 The start address of the memory block, as hexadecimal literal.
28115 The end address of the memory block, as hexadecimal literal.
28118 The offset of the memory block, as hexadecimal literal, relative to
28119 the start address passed to @code{-data-read-memory-bytes}.
28122 The contents of the memory block, in hex.
28128 @subsubheading @value{GDBN} Command
28130 The corresponding @value{GDBN} command is @samp{x}.
28132 @subsubheading Example
28136 -data-read-memory-bytes &a 10
28137 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
28139 contents="01000000020000000300"@}]
28144 @subheading The @code{-data-write-memory-bytes} Command
28145 @findex -data-write-memory-bytes
28147 @subsubheading Synopsis
28150 -data-write-memory-bytes @var{address} @var{contents}
28157 @item @var{address}
28158 An expression specifying the address of the first memory word to be
28159 read. Complex expressions containing embedded white space should be
28160 quoted using the C convention.
28162 @item @var{contents}
28163 The hex-encoded bytes to write.
28167 @subsubheading @value{GDBN} Command
28169 There's no corresponding @value{GDBN} command.
28171 @subsubheading Example
28175 -data-write-memory-bytes &a "aabbccdd"
28181 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28182 @node GDB/MI Tracepoint Commands
28183 @section @sc{gdb/mi} Tracepoint Commands
28185 The commands defined in this section implement MI support for
28186 tracepoints. For detailed introduction, see @ref{Tracepoints}.
28188 @subheading The @code{-trace-find} Command
28189 @findex -trace-find
28191 @subsubheading Synopsis
28194 -trace-find @var{mode} [@var{parameters}@dots{}]
28197 Find a trace frame using criteria defined by @var{mode} and
28198 @var{parameters}. The following table lists permissible
28199 modes and their parameters. For details of operation, see @ref{tfind}.
28204 No parameters are required. Stops examining trace frames.
28207 An integer is required as parameter. Selects tracepoint frame with
28210 @item tracepoint-number
28211 An integer is required as parameter. Finds next
28212 trace frame that corresponds to tracepoint with the specified number.
28215 An address is required as parameter. Finds
28216 next trace frame that corresponds to any tracepoint at the specified
28219 @item pc-inside-range
28220 Two addresses are required as parameters. Finds next trace
28221 frame that corresponds to a tracepoint at an address inside the
28222 specified range. Both bounds are considered to be inside the range.
28224 @item pc-outside-range
28225 Two addresses are required as parameters. Finds
28226 next trace frame that corresponds to a tracepoint at an address outside
28227 the specified range. Both bounds are considered to be inside the range.
28230 Line specification is required as parameter. @xref{Specify Location}.
28231 Finds next trace frame that corresponds to a tracepoint at
28232 the specified location.
28236 If @samp{none} was passed as @var{mode}, the response does not
28237 have fields. Otherwise, the response may have the following fields:
28241 This field has either @samp{0} or @samp{1} as the value, depending
28242 on whether a matching tracepoint was found.
28245 The index of the found traceframe. This field is present iff
28246 the @samp{found} field has value of @samp{1}.
28249 The index of the found tracepoint. This field is present iff
28250 the @samp{found} field has value of @samp{1}.
28253 The information about the frame corresponding to the found trace
28254 frame. This field is present only if a trace frame was found.
28255 @xref{GDB/MI Frame Information}, for description of this field.
28259 @subsubheading @value{GDBN} Command
28261 The corresponding @value{GDBN} command is @samp{tfind}.
28263 @subheading -trace-define-variable
28264 @findex -trace-define-variable
28266 @subsubheading Synopsis
28269 -trace-define-variable @var{name} [ @var{value} ]
28272 Create trace variable @var{name} if it does not exist. If
28273 @var{value} is specified, sets the initial value of the specified
28274 trace variable to that value. Note that the @var{name} should start
28275 with the @samp{$} character.
28277 @subsubheading @value{GDBN} Command
28279 The corresponding @value{GDBN} command is @samp{tvariable}.
28281 @subheading -trace-list-variables
28282 @findex -trace-list-variables
28284 @subsubheading Synopsis
28287 -trace-list-variables
28290 Return a table of all defined trace variables. Each element of the
28291 table has the following fields:
28295 The name of the trace variable. This field is always present.
28298 The initial value. This is a 64-bit signed integer. This
28299 field is always present.
28302 The value the trace variable has at the moment. This is a 64-bit
28303 signed integer. This field is absent iff current value is
28304 not defined, for example if the trace was never run, or is
28309 @subsubheading @value{GDBN} Command
28311 The corresponding @value{GDBN} command is @samp{tvariables}.
28313 @subsubheading Example
28317 -trace-list-variables
28318 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
28319 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
28320 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
28321 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
28322 body=[variable=@{name="$trace_timestamp",initial="0"@}
28323 variable=@{name="$foo",initial="10",current="15"@}]@}
28327 @subheading -trace-save
28328 @findex -trace-save
28330 @subsubheading Synopsis
28333 -trace-save [-r ] @var{filename}
28336 Saves the collected trace data to @var{filename}. Without the
28337 @samp{-r} option, the data is downloaded from the target and saved
28338 in a local file. With the @samp{-r} option the target is asked
28339 to perform the save.
28341 @subsubheading @value{GDBN} Command
28343 The corresponding @value{GDBN} command is @samp{tsave}.
28346 @subheading -trace-start
28347 @findex -trace-start
28349 @subsubheading Synopsis
28355 Starts a tracing experiments. The result of this command does not
28358 @subsubheading @value{GDBN} Command
28360 The corresponding @value{GDBN} command is @samp{tstart}.
28362 @subheading -trace-status
28363 @findex -trace-status
28365 @subsubheading Synopsis
28371 Obtains the status of a tracing experiment. The result may include
28372 the following fields:
28377 May have a value of either @samp{0}, when no tracing operations are
28378 supported, @samp{1}, when all tracing operations are supported, or
28379 @samp{file} when examining trace file. In the latter case, examining
28380 of trace frame is possible but new tracing experiement cannot be
28381 started. This field is always present.
28384 May have a value of either @samp{0} or @samp{1} depending on whether
28385 tracing experiement is in progress on target. This field is present
28386 if @samp{supported} field is not @samp{0}.
28389 Report the reason why the tracing was stopped last time. This field
28390 may be absent iff tracing was never stopped on target yet. The
28391 value of @samp{request} means the tracing was stopped as result of
28392 the @code{-trace-stop} command. The value of @samp{overflow} means
28393 the tracing buffer is full. The value of @samp{disconnection} means
28394 tracing was automatically stopped when @value{GDBN} has disconnected.
28395 The value of @samp{passcount} means tracing was stopped when a
28396 tracepoint was passed a maximal number of times for that tracepoint.
28397 This field is present if @samp{supported} field is not @samp{0}.
28399 @item stopping-tracepoint
28400 The number of tracepoint whose passcount as exceeded. This field is
28401 present iff the @samp{stop-reason} field has the value of
28405 @itemx frames-created
28406 The @samp{frames} field is a count of the total number of trace frames
28407 in the trace buffer, while @samp{frames-created} is the total created
28408 during the run, including ones that were discarded, such as when a
28409 circular trace buffer filled up. Both fields are optional.
28413 These fields tell the current size of the tracing buffer and the
28414 remaining space. These fields are optional.
28417 The value of the circular trace buffer flag. @code{1} means that the
28418 trace buffer is circular and old trace frames will be discarded if
28419 necessary to make room, @code{0} means that the trace buffer is linear
28423 The value of the disconnected tracing flag. @code{1} means that
28424 tracing will continue after @value{GDBN} disconnects, @code{0} means
28425 that the trace run will stop.
28429 @subsubheading @value{GDBN} Command
28431 The corresponding @value{GDBN} command is @samp{tstatus}.
28433 @subheading -trace-stop
28434 @findex -trace-stop
28436 @subsubheading Synopsis
28442 Stops a tracing experiment. The result of this command has the same
28443 fields as @code{-trace-status}, except that the @samp{supported} and
28444 @samp{running} fields are not output.
28446 @subsubheading @value{GDBN} Command
28448 The corresponding @value{GDBN} command is @samp{tstop}.
28451 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28452 @node GDB/MI Symbol Query
28453 @section @sc{gdb/mi} Symbol Query Commands
28457 @subheading The @code{-symbol-info-address} Command
28458 @findex -symbol-info-address
28460 @subsubheading Synopsis
28463 -symbol-info-address @var{symbol}
28466 Describe where @var{symbol} is stored.
28468 @subsubheading @value{GDBN} Command
28470 The corresponding @value{GDBN} command is @samp{info address}.
28472 @subsubheading Example
28476 @subheading The @code{-symbol-info-file} Command
28477 @findex -symbol-info-file
28479 @subsubheading Synopsis
28485 Show the file for the symbol.
28487 @subsubheading @value{GDBN} Command
28489 There's no equivalent @value{GDBN} command. @code{gdbtk} has
28490 @samp{gdb_find_file}.
28492 @subsubheading Example
28496 @subheading The @code{-symbol-info-function} Command
28497 @findex -symbol-info-function
28499 @subsubheading Synopsis
28502 -symbol-info-function
28505 Show which function the symbol lives in.
28507 @subsubheading @value{GDBN} Command
28509 @samp{gdb_get_function} in @code{gdbtk}.
28511 @subsubheading Example
28515 @subheading The @code{-symbol-info-line} Command
28516 @findex -symbol-info-line
28518 @subsubheading Synopsis
28524 Show the core addresses of the code for a source line.
28526 @subsubheading @value{GDBN} Command
28528 The corresponding @value{GDBN} command is @samp{info line}.
28529 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
28531 @subsubheading Example
28535 @subheading The @code{-symbol-info-symbol} Command
28536 @findex -symbol-info-symbol
28538 @subsubheading Synopsis
28541 -symbol-info-symbol @var{addr}
28544 Describe what symbol is at location @var{addr}.
28546 @subsubheading @value{GDBN} Command
28548 The corresponding @value{GDBN} command is @samp{info symbol}.
28550 @subsubheading Example
28554 @subheading The @code{-symbol-list-functions} Command
28555 @findex -symbol-list-functions
28557 @subsubheading Synopsis
28560 -symbol-list-functions
28563 List the functions in the executable.
28565 @subsubheading @value{GDBN} Command
28567 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
28568 @samp{gdb_search} in @code{gdbtk}.
28570 @subsubheading Example
28575 @subheading The @code{-symbol-list-lines} Command
28576 @findex -symbol-list-lines
28578 @subsubheading Synopsis
28581 -symbol-list-lines @var{filename}
28584 Print the list of lines that contain code and their associated program
28585 addresses for the given source filename. The entries are sorted in
28586 ascending PC order.
28588 @subsubheading @value{GDBN} Command
28590 There is no corresponding @value{GDBN} command.
28592 @subsubheading Example
28595 -symbol-list-lines basics.c
28596 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
28602 @subheading The @code{-symbol-list-types} Command
28603 @findex -symbol-list-types
28605 @subsubheading Synopsis
28611 List all the type names.
28613 @subsubheading @value{GDBN} Command
28615 The corresponding commands are @samp{info types} in @value{GDBN},
28616 @samp{gdb_search} in @code{gdbtk}.
28618 @subsubheading Example
28622 @subheading The @code{-symbol-list-variables} Command
28623 @findex -symbol-list-variables
28625 @subsubheading Synopsis
28628 -symbol-list-variables
28631 List all the global and static variable names.
28633 @subsubheading @value{GDBN} Command
28635 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
28637 @subsubheading Example
28641 @subheading The @code{-symbol-locate} Command
28642 @findex -symbol-locate
28644 @subsubheading Synopsis
28650 @subsubheading @value{GDBN} Command
28652 @samp{gdb_loc} in @code{gdbtk}.
28654 @subsubheading Example
28658 @subheading The @code{-symbol-type} Command
28659 @findex -symbol-type
28661 @subsubheading Synopsis
28664 -symbol-type @var{variable}
28667 Show type of @var{variable}.
28669 @subsubheading @value{GDBN} Command
28671 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
28672 @samp{gdb_obj_variable}.
28674 @subsubheading Example
28679 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28680 @node GDB/MI File Commands
28681 @section @sc{gdb/mi} File Commands
28683 This section describes the GDB/MI commands to specify executable file names
28684 and to read in and obtain symbol table information.
28686 @subheading The @code{-file-exec-and-symbols} Command
28687 @findex -file-exec-and-symbols
28689 @subsubheading Synopsis
28692 -file-exec-and-symbols @var{file}
28695 Specify the executable file to be debugged. This file is the one from
28696 which the symbol table is also read. If no file is specified, the
28697 command clears the executable and symbol information. If breakpoints
28698 are set when using this command with no arguments, @value{GDBN} will produce
28699 error messages. Otherwise, no output is produced, except a completion
28702 @subsubheading @value{GDBN} Command
28704 The corresponding @value{GDBN} command is @samp{file}.
28706 @subsubheading Example
28710 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
28716 @subheading The @code{-file-exec-file} Command
28717 @findex -file-exec-file
28719 @subsubheading Synopsis
28722 -file-exec-file @var{file}
28725 Specify the executable file to be debugged. Unlike
28726 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
28727 from this file. If used without argument, @value{GDBN} clears the information
28728 about the executable file. No output is produced, except a completion
28731 @subsubheading @value{GDBN} Command
28733 The corresponding @value{GDBN} command is @samp{exec-file}.
28735 @subsubheading Example
28739 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
28746 @subheading The @code{-file-list-exec-sections} Command
28747 @findex -file-list-exec-sections
28749 @subsubheading Synopsis
28752 -file-list-exec-sections
28755 List the sections of the current executable file.
28757 @subsubheading @value{GDBN} Command
28759 The @value{GDBN} command @samp{info file} shows, among the rest, the same
28760 information as this command. @code{gdbtk} has a corresponding command
28761 @samp{gdb_load_info}.
28763 @subsubheading Example
28768 @subheading The @code{-file-list-exec-source-file} Command
28769 @findex -file-list-exec-source-file
28771 @subsubheading Synopsis
28774 -file-list-exec-source-file
28777 List the line number, the current source file, and the absolute path
28778 to the current source file for the current executable. The macro
28779 information field has a value of @samp{1} or @samp{0} depending on
28780 whether or not the file includes preprocessor macro information.
28782 @subsubheading @value{GDBN} Command
28784 The @value{GDBN} equivalent is @samp{info source}
28786 @subsubheading Example
28790 123-file-list-exec-source-file
28791 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
28796 @subheading The @code{-file-list-exec-source-files} Command
28797 @findex -file-list-exec-source-files
28799 @subsubheading Synopsis
28802 -file-list-exec-source-files
28805 List the source files for the current executable.
28807 It will always output the filename, but only when @value{GDBN} can find
28808 the absolute file name of a source file, will it output the fullname.
28810 @subsubheading @value{GDBN} Command
28812 The @value{GDBN} equivalent is @samp{info sources}.
28813 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
28815 @subsubheading Example
28818 -file-list-exec-source-files
28820 @{file=foo.c,fullname=/home/foo.c@},
28821 @{file=/home/bar.c,fullname=/home/bar.c@},
28822 @{file=gdb_could_not_find_fullpath.c@}]
28827 @subheading The @code{-file-list-shared-libraries} Command
28828 @findex -file-list-shared-libraries
28830 @subsubheading Synopsis
28833 -file-list-shared-libraries
28836 List the shared libraries in the program.
28838 @subsubheading @value{GDBN} Command
28840 The corresponding @value{GDBN} command is @samp{info shared}.
28842 @subsubheading Example
28846 @subheading The @code{-file-list-symbol-files} Command
28847 @findex -file-list-symbol-files
28849 @subsubheading Synopsis
28852 -file-list-symbol-files
28857 @subsubheading @value{GDBN} Command
28859 The corresponding @value{GDBN} command is @samp{info file} (part of it).
28861 @subsubheading Example
28866 @subheading The @code{-file-symbol-file} Command
28867 @findex -file-symbol-file
28869 @subsubheading Synopsis
28872 -file-symbol-file @var{file}
28875 Read symbol table info from the specified @var{file} argument. When
28876 used without arguments, clears @value{GDBN}'s symbol table info. No output is
28877 produced, except for a completion notification.
28879 @subsubheading @value{GDBN} Command
28881 The corresponding @value{GDBN} command is @samp{symbol-file}.
28883 @subsubheading Example
28887 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
28893 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28894 @node GDB/MI Memory Overlay Commands
28895 @section @sc{gdb/mi} Memory Overlay Commands
28897 The memory overlay commands are not implemented.
28899 @c @subheading -overlay-auto
28901 @c @subheading -overlay-list-mapping-state
28903 @c @subheading -overlay-list-overlays
28905 @c @subheading -overlay-map
28907 @c @subheading -overlay-off
28909 @c @subheading -overlay-on
28911 @c @subheading -overlay-unmap
28913 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28914 @node GDB/MI Signal Handling Commands
28915 @section @sc{gdb/mi} Signal Handling Commands
28917 Signal handling commands are not implemented.
28919 @c @subheading -signal-handle
28921 @c @subheading -signal-list-handle-actions
28923 @c @subheading -signal-list-signal-types
28927 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28928 @node GDB/MI Target Manipulation
28929 @section @sc{gdb/mi} Target Manipulation Commands
28932 @subheading The @code{-target-attach} Command
28933 @findex -target-attach
28935 @subsubheading Synopsis
28938 -target-attach @var{pid} | @var{gid} | @var{file}
28941 Attach to a process @var{pid} or a file @var{file} outside of
28942 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
28943 group, the id previously returned by
28944 @samp{-list-thread-groups --available} must be used.
28946 @subsubheading @value{GDBN} Command
28948 The corresponding @value{GDBN} command is @samp{attach}.
28950 @subsubheading Example
28954 =thread-created,id="1"
28955 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
28961 @subheading The @code{-target-compare-sections} Command
28962 @findex -target-compare-sections
28964 @subsubheading Synopsis
28967 -target-compare-sections [ @var{section} ]
28970 Compare data of section @var{section} on target to the exec file.
28971 Without the argument, all sections are compared.
28973 @subsubheading @value{GDBN} Command
28975 The @value{GDBN} equivalent is @samp{compare-sections}.
28977 @subsubheading Example
28982 @subheading The @code{-target-detach} Command
28983 @findex -target-detach
28985 @subsubheading Synopsis
28988 -target-detach [ @var{pid} | @var{gid} ]
28991 Detach from the remote target which normally resumes its execution.
28992 If either @var{pid} or @var{gid} is specified, detaches from either
28993 the specified process, or specified thread group. There's no output.
28995 @subsubheading @value{GDBN} Command
28997 The corresponding @value{GDBN} command is @samp{detach}.
28999 @subsubheading Example
29009 @subheading The @code{-target-disconnect} Command
29010 @findex -target-disconnect
29012 @subsubheading Synopsis
29018 Disconnect from the remote target. There's no output and the target is
29019 generally not resumed.
29021 @subsubheading @value{GDBN} Command
29023 The corresponding @value{GDBN} command is @samp{disconnect}.
29025 @subsubheading Example
29035 @subheading The @code{-target-download} Command
29036 @findex -target-download
29038 @subsubheading Synopsis
29044 Loads the executable onto the remote target.
29045 It prints out an update message every half second, which includes the fields:
29049 The name of the section.
29051 The size of what has been sent so far for that section.
29053 The size of the section.
29055 The total size of what was sent so far (the current and the previous sections).
29057 The size of the overall executable to download.
29061 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
29062 @sc{gdb/mi} Output Syntax}).
29064 In addition, it prints the name and size of the sections, as they are
29065 downloaded. These messages include the following fields:
29069 The name of the section.
29071 The size of the section.
29073 The size of the overall executable to download.
29077 At the end, a summary is printed.
29079 @subsubheading @value{GDBN} Command
29081 The corresponding @value{GDBN} command is @samp{load}.
29083 @subsubheading Example
29085 Note: each status message appears on a single line. Here the messages
29086 have been broken down so that they can fit onto a page.
29091 +download,@{section=".text",section-size="6668",total-size="9880"@}
29092 +download,@{section=".text",section-sent="512",section-size="6668",
29093 total-sent="512",total-size="9880"@}
29094 +download,@{section=".text",section-sent="1024",section-size="6668",
29095 total-sent="1024",total-size="9880"@}
29096 +download,@{section=".text",section-sent="1536",section-size="6668",
29097 total-sent="1536",total-size="9880"@}
29098 +download,@{section=".text",section-sent="2048",section-size="6668",
29099 total-sent="2048",total-size="9880"@}
29100 +download,@{section=".text",section-sent="2560",section-size="6668",
29101 total-sent="2560",total-size="9880"@}
29102 +download,@{section=".text",section-sent="3072",section-size="6668",
29103 total-sent="3072",total-size="9880"@}
29104 +download,@{section=".text",section-sent="3584",section-size="6668",
29105 total-sent="3584",total-size="9880"@}
29106 +download,@{section=".text",section-sent="4096",section-size="6668",
29107 total-sent="4096",total-size="9880"@}
29108 +download,@{section=".text",section-sent="4608",section-size="6668",
29109 total-sent="4608",total-size="9880"@}
29110 +download,@{section=".text",section-sent="5120",section-size="6668",
29111 total-sent="5120",total-size="9880"@}
29112 +download,@{section=".text",section-sent="5632",section-size="6668",
29113 total-sent="5632",total-size="9880"@}
29114 +download,@{section=".text",section-sent="6144",section-size="6668",
29115 total-sent="6144",total-size="9880"@}
29116 +download,@{section=".text",section-sent="6656",section-size="6668",
29117 total-sent="6656",total-size="9880"@}
29118 +download,@{section=".init",section-size="28",total-size="9880"@}
29119 +download,@{section=".fini",section-size="28",total-size="9880"@}
29120 +download,@{section=".data",section-size="3156",total-size="9880"@}
29121 +download,@{section=".data",section-sent="512",section-size="3156",
29122 total-sent="7236",total-size="9880"@}
29123 +download,@{section=".data",section-sent="1024",section-size="3156",
29124 total-sent="7748",total-size="9880"@}
29125 +download,@{section=".data",section-sent="1536",section-size="3156",
29126 total-sent="8260",total-size="9880"@}
29127 +download,@{section=".data",section-sent="2048",section-size="3156",
29128 total-sent="8772",total-size="9880"@}
29129 +download,@{section=".data",section-sent="2560",section-size="3156",
29130 total-sent="9284",total-size="9880"@}
29131 +download,@{section=".data",section-sent="3072",section-size="3156",
29132 total-sent="9796",total-size="9880"@}
29133 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
29140 @subheading The @code{-target-exec-status} Command
29141 @findex -target-exec-status
29143 @subsubheading Synopsis
29146 -target-exec-status
29149 Provide information on the state of the target (whether it is running or
29150 not, for instance).
29152 @subsubheading @value{GDBN} Command
29154 There's no equivalent @value{GDBN} command.
29156 @subsubheading Example
29160 @subheading The @code{-target-list-available-targets} Command
29161 @findex -target-list-available-targets
29163 @subsubheading Synopsis
29166 -target-list-available-targets
29169 List the possible targets to connect to.
29171 @subsubheading @value{GDBN} Command
29173 The corresponding @value{GDBN} command is @samp{help target}.
29175 @subsubheading Example
29179 @subheading The @code{-target-list-current-targets} Command
29180 @findex -target-list-current-targets
29182 @subsubheading Synopsis
29185 -target-list-current-targets
29188 Describe the current target.
29190 @subsubheading @value{GDBN} Command
29192 The corresponding information is printed by @samp{info file} (among
29195 @subsubheading Example
29199 @subheading The @code{-target-list-parameters} Command
29200 @findex -target-list-parameters
29202 @subsubheading Synopsis
29205 -target-list-parameters
29211 @subsubheading @value{GDBN} Command
29215 @subsubheading Example
29219 @subheading The @code{-target-select} Command
29220 @findex -target-select
29222 @subsubheading Synopsis
29225 -target-select @var{type} @var{parameters @dots{}}
29228 Connect @value{GDBN} to the remote target. This command takes two args:
29232 The type of target, for instance @samp{remote}, etc.
29233 @item @var{parameters}
29234 Device names, host names and the like. @xref{Target Commands, ,
29235 Commands for Managing Targets}, for more details.
29238 The output is a connection notification, followed by the address at
29239 which the target program is, in the following form:
29242 ^connected,addr="@var{address}",func="@var{function name}",
29243 args=[@var{arg list}]
29246 @subsubheading @value{GDBN} Command
29248 The corresponding @value{GDBN} command is @samp{target}.
29250 @subsubheading Example
29254 -target-select remote /dev/ttya
29255 ^connected,addr="0xfe00a300",func="??",args=[]
29259 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29260 @node GDB/MI File Transfer Commands
29261 @section @sc{gdb/mi} File Transfer Commands
29264 @subheading The @code{-target-file-put} Command
29265 @findex -target-file-put
29267 @subsubheading Synopsis
29270 -target-file-put @var{hostfile} @var{targetfile}
29273 Copy file @var{hostfile} from the host system (the machine running
29274 @value{GDBN}) to @var{targetfile} on the target system.
29276 @subsubheading @value{GDBN} Command
29278 The corresponding @value{GDBN} command is @samp{remote put}.
29280 @subsubheading Example
29284 -target-file-put localfile remotefile
29290 @subheading The @code{-target-file-get} Command
29291 @findex -target-file-get
29293 @subsubheading Synopsis
29296 -target-file-get @var{targetfile} @var{hostfile}
29299 Copy file @var{targetfile} from the target system to @var{hostfile}
29300 on the host system.
29302 @subsubheading @value{GDBN} Command
29304 The corresponding @value{GDBN} command is @samp{remote get}.
29306 @subsubheading Example
29310 -target-file-get remotefile localfile
29316 @subheading The @code{-target-file-delete} Command
29317 @findex -target-file-delete
29319 @subsubheading Synopsis
29322 -target-file-delete @var{targetfile}
29325 Delete @var{targetfile} from the target system.
29327 @subsubheading @value{GDBN} Command
29329 The corresponding @value{GDBN} command is @samp{remote delete}.
29331 @subsubheading Example
29335 -target-file-delete remotefile
29341 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29342 @node GDB/MI Miscellaneous Commands
29343 @section Miscellaneous @sc{gdb/mi} Commands
29345 @c @subheading -gdb-complete
29347 @subheading The @code{-gdb-exit} Command
29350 @subsubheading Synopsis
29356 Exit @value{GDBN} immediately.
29358 @subsubheading @value{GDBN} Command
29360 Approximately corresponds to @samp{quit}.
29362 @subsubheading Example
29372 @subheading The @code{-exec-abort} Command
29373 @findex -exec-abort
29375 @subsubheading Synopsis
29381 Kill the inferior running program.
29383 @subsubheading @value{GDBN} Command
29385 The corresponding @value{GDBN} command is @samp{kill}.
29387 @subsubheading Example
29392 @subheading The @code{-gdb-set} Command
29395 @subsubheading Synopsis
29401 Set an internal @value{GDBN} variable.
29402 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
29404 @subsubheading @value{GDBN} Command
29406 The corresponding @value{GDBN} command is @samp{set}.
29408 @subsubheading Example
29418 @subheading The @code{-gdb-show} Command
29421 @subsubheading Synopsis
29427 Show the current value of a @value{GDBN} variable.
29429 @subsubheading @value{GDBN} Command
29431 The corresponding @value{GDBN} command is @samp{show}.
29433 @subsubheading Example
29442 @c @subheading -gdb-source
29445 @subheading The @code{-gdb-version} Command
29446 @findex -gdb-version
29448 @subsubheading Synopsis
29454 Show version information for @value{GDBN}. Used mostly in testing.
29456 @subsubheading @value{GDBN} Command
29458 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
29459 default shows this information when you start an interactive session.
29461 @subsubheading Example
29463 @c This example modifies the actual output from GDB to avoid overfull
29469 ~Copyright 2000 Free Software Foundation, Inc.
29470 ~GDB is free software, covered by the GNU General Public License, and
29471 ~you are welcome to change it and/or distribute copies of it under
29472 ~ certain conditions.
29473 ~Type "show copying" to see the conditions.
29474 ~There is absolutely no warranty for GDB. Type "show warranty" for
29476 ~This GDB was configured as
29477 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
29482 @subheading The @code{-list-features} Command
29483 @findex -list-features
29485 Returns a list of particular features of the MI protocol that
29486 this version of gdb implements. A feature can be a command,
29487 or a new field in an output of some command, or even an
29488 important bugfix. While a frontend can sometimes detect presence
29489 of a feature at runtime, it is easier to perform detection at debugger
29492 The command returns a list of strings, with each string naming an
29493 available feature. Each returned string is just a name, it does not
29494 have any internal structure. The list of possible feature names
29500 (gdb) -list-features
29501 ^done,result=["feature1","feature2"]
29504 The current list of features is:
29507 @item frozen-varobjs
29508 Indicates presence of the @code{-var-set-frozen} command, as well
29509 as possible presense of the @code{frozen} field in the output
29510 of @code{-varobj-create}.
29511 @item pending-breakpoints
29512 Indicates presence of the @option{-f} option to the @code{-break-insert} command.
29514 Indicates presence of Python scripting support, Python-based
29515 pretty-printing commands, and possible presence of the
29516 @samp{display_hint} field in the output of @code{-var-list-children}
29518 Indicates presence of the @code{-thread-info} command.
29519 @item data-read-memory-bytes
29520 Indicates presense of the @code{-data-read-memory-bytes} and the
29521 @code{-data-write-memory-bytes} commands.
29525 @subheading The @code{-list-target-features} Command
29526 @findex -list-target-features
29528 Returns a list of particular features that are supported by the
29529 target. Those features affect the permitted MI commands, but
29530 unlike the features reported by the @code{-list-features} command, the
29531 features depend on which target GDB is using at the moment. Whenever
29532 a target can change, due to commands such as @code{-target-select},
29533 @code{-target-attach} or @code{-exec-run}, the list of target features
29534 may change, and the frontend should obtain it again.
29538 (gdb) -list-features
29539 ^done,result=["async"]
29542 The current list of features is:
29546 Indicates that the target is capable of asynchronous command
29547 execution, which means that @value{GDBN} will accept further commands
29548 while the target is running.
29551 Indicates that the target is capable of reverse execution.
29552 @xref{Reverse Execution}, for more information.
29556 @subheading The @code{-list-thread-groups} Command
29557 @findex -list-thread-groups
29559 @subheading Synopsis
29562 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
29565 Lists thread groups (@pxref{Thread groups}). When a single thread
29566 group is passed as the argument, lists the children of that group.
29567 When several thread group are passed, lists information about those
29568 thread groups. Without any parameters, lists information about all
29569 top-level thread groups.
29571 Normally, thread groups that are being debugged are reported.
29572 With the @samp{--available} option, @value{GDBN} reports thread groups
29573 available on the target.
29575 The output of this command may have either a @samp{threads} result or
29576 a @samp{groups} result. The @samp{thread} result has a list of tuples
29577 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
29578 Information}). The @samp{groups} result has a list of tuples as value,
29579 each tuple describing a thread group. If top-level groups are
29580 requested (that is, no parameter is passed), or when several groups
29581 are passed, the output always has a @samp{groups} result. The format
29582 of the @samp{group} result is described below.
29584 To reduce the number of roundtrips it's possible to list thread groups
29585 together with their children, by passing the @samp{--recurse} option
29586 and the recursion depth. Presently, only recursion depth of 1 is
29587 permitted. If this option is present, then every reported thread group
29588 will also include its children, either as @samp{group} or
29589 @samp{threads} field.
29591 In general, any combination of option and parameters is permitted, with
29592 the following caveats:
29596 When a single thread group is passed, the output will typically
29597 be the @samp{threads} result. Because threads may not contain
29598 anything, the @samp{recurse} option will be ignored.
29601 When the @samp{--available} option is passed, limited information may
29602 be available. In particular, the list of threads of a process might
29603 be inaccessible. Further, specifying specific thread groups might
29604 not give any performance advantage over listing all thread groups.
29605 The frontend should assume that @samp{-list-thread-groups --available}
29606 is always an expensive operation and cache the results.
29610 The @samp{groups} result is a list of tuples, where each tuple may
29611 have the following fields:
29615 Identifier of the thread group. This field is always present.
29616 The identifier is an opaque string; frontends should not try to
29617 convert it to an integer, even though it might look like one.
29620 The type of the thread group. At present, only @samp{process} is a
29624 The target-specific process identifier. This field is only present
29625 for thread groups of type @samp{process} and only if the process exists.
29628 The number of children this thread group has. This field may be
29629 absent for an available thread group.
29632 This field has a list of tuples as value, each tuple describing a
29633 thread. It may be present if the @samp{--recurse} option is
29634 specified, and it's actually possible to obtain the threads.
29637 This field is a list of integers, each identifying a core that one
29638 thread of the group is running on. This field may be absent if
29639 such information is not available.
29642 The name of the executable file that corresponds to this thread group.
29643 The field is only present for thread groups of type @samp{process},
29644 and only if there is a corresponding executable file.
29648 @subheading Example
29652 -list-thread-groups
29653 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
29654 -list-thread-groups 17
29655 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
29656 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
29657 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
29658 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
29659 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
29660 -list-thread-groups --available
29661 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
29662 -list-thread-groups --available --recurse 1
29663 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
29664 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
29665 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
29666 -list-thread-groups --available --recurse 1 17 18
29667 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
29668 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
29669 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
29673 @subheading The @code{-add-inferior} Command
29674 @findex -add-inferior
29676 @subheading Synopsis
29682 Creates a new inferior (@pxref{Inferiors and Programs}). The created
29683 inferior is not associated with any executable. Such association may
29684 be established with the @samp{-file-exec-and-symbols} command
29685 (@pxref{GDB/MI File Commands}). The command response has a single
29686 field, @samp{thread-group}, whose value is the identifier of the
29687 thread group corresponding to the new inferior.
29689 @subheading Example
29694 ^done,thread-group="i3"
29697 @subheading The @code{-interpreter-exec} Command
29698 @findex -interpreter-exec
29700 @subheading Synopsis
29703 -interpreter-exec @var{interpreter} @var{command}
29705 @anchor{-interpreter-exec}
29707 Execute the specified @var{command} in the given @var{interpreter}.
29709 @subheading @value{GDBN} Command
29711 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
29713 @subheading Example
29717 -interpreter-exec console "break main"
29718 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
29719 &"During symbol reading, bad structure-type format.\n"
29720 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
29725 @subheading The @code{-inferior-tty-set} Command
29726 @findex -inferior-tty-set
29728 @subheading Synopsis
29731 -inferior-tty-set /dev/pts/1
29734 Set terminal for future runs of the program being debugged.
29736 @subheading @value{GDBN} Command
29738 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
29740 @subheading Example
29744 -inferior-tty-set /dev/pts/1
29749 @subheading The @code{-inferior-tty-show} Command
29750 @findex -inferior-tty-show
29752 @subheading Synopsis
29758 Show terminal for future runs of program being debugged.
29760 @subheading @value{GDBN} Command
29762 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
29764 @subheading Example
29768 -inferior-tty-set /dev/pts/1
29772 ^done,inferior_tty_terminal="/dev/pts/1"
29776 @subheading The @code{-enable-timings} Command
29777 @findex -enable-timings
29779 @subheading Synopsis
29782 -enable-timings [yes | no]
29785 Toggle the printing of the wallclock, user and system times for an MI
29786 command as a field in its output. This command is to help frontend
29787 developers optimize the performance of their code. No argument is
29788 equivalent to @samp{yes}.
29790 @subheading @value{GDBN} Command
29794 @subheading Example
29802 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29803 addr="0x080484ed",func="main",file="myprog.c",
29804 fullname="/home/nickrob/myprog.c",line="73",times="0"@},
29805 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
29813 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
29814 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
29815 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
29816 fullname="/home/nickrob/myprog.c",line="73"@}
29821 @chapter @value{GDBN} Annotations
29823 This chapter describes annotations in @value{GDBN}. Annotations were
29824 designed to interface @value{GDBN} to graphical user interfaces or other
29825 similar programs which want to interact with @value{GDBN} at a
29826 relatively high level.
29828 The annotation mechanism has largely been superseded by @sc{gdb/mi}
29832 This is Edition @value{EDITION}, @value{DATE}.
29836 * Annotations Overview:: What annotations are; the general syntax.
29837 * Server Prefix:: Issuing a command without affecting user state.
29838 * Prompting:: Annotations marking @value{GDBN}'s need for input.
29839 * Errors:: Annotations for error messages.
29840 * Invalidation:: Some annotations describe things now invalid.
29841 * Annotations for Running::
29842 Whether the program is running, how it stopped, etc.
29843 * Source Annotations:: Annotations describing source code.
29846 @node Annotations Overview
29847 @section What is an Annotation?
29848 @cindex annotations
29850 Annotations start with a newline character, two @samp{control-z}
29851 characters, and the name of the annotation. If there is no additional
29852 information associated with this annotation, the name of the annotation
29853 is followed immediately by a newline. If there is additional
29854 information, the name of the annotation is followed by a space, the
29855 additional information, and a newline. The additional information
29856 cannot contain newline characters.
29858 Any output not beginning with a newline and two @samp{control-z}
29859 characters denotes literal output from @value{GDBN}. Currently there is
29860 no need for @value{GDBN} to output a newline followed by two
29861 @samp{control-z} characters, but if there was such a need, the
29862 annotations could be extended with an @samp{escape} annotation which
29863 means those three characters as output.
29865 The annotation @var{level}, which is specified using the
29866 @option{--annotate} command line option (@pxref{Mode Options}), controls
29867 how much information @value{GDBN} prints together with its prompt,
29868 values of expressions, source lines, and other types of output. Level 0
29869 is for no annotations, level 1 is for use when @value{GDBN} is run as a
29870 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
29871 for programs that control @value{GDBN}, and level 2 annotations have
29872 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
29873 Interface, annotate, GDB's Obsolete Annotations}).
29876 @kindex set annotate
29877 @item set annotate @var{level}
29878 The @value{GDBN} command @code{set annotate} sets the level of
29879 annotations to the specified @var{level}.
29881 @item show annotate
29882 @kindex show annotate
29883 Show the current annotation level.
29886 This chapter describes level 3 annotations.
29888 A simple example of starting up @value{GDBN} with annotations is:
29891 $ @kbd{gdb --annotate=3}
29893 Copyright 2003 Free Software Foundation, Inc.
29894 GDB is free software, covered by the GNU General Public License,
29895 and you are welcome to change it and/or distribute copies of it
29896 under certain conditions.
29897 Type "show copying" to see the conditions.
29898 There is absolutely no warranty for GDB. Type "show warranty"
29900 This GDB was configured as "i386-pc-linux-gnu"
29911 Here @samp{quit} is input to @value{GDBN}; the rest is output from
29912 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
29913 denotes a @samp{control-z} character) are annotations; the rest is
29914 output from @value{GDBN}.
29916 @node Server Prefix
29917 @section The Server Prefix
29918 @cindex server prefix
29920 If you prefix a command with @samp{server } then it will not affect
29921 the command history, nor will it affect @value{GDBN}'s notion of which
29922 command to repeat if @key{RET} is pressed on a line by itself. This
29923 means that commands can be run behind a user's back by a front-end in
29924 a transparent manner.
29926 The @code{server } prefix does not affect the recording of values into
29927 the value history; to print a value without recording it into the
29928 value history, use the @code{output} command instead of the
29929 @code{print} command.
29931 Using this prefix also disables confirmation requests
29932 (@pxref{confirmation requests}).
29935 @section Annotation for @value{GDBN} Input
29937 @cindex annotations for prompts
29938 When @value{GDBN} prompts for input, it annotates this fact so it is possible
29939 to know when to send output, when the output from a given command is
29942 Different kinds of input each have a different @dfn{input type}. Each
29943 input type has three annotations: a @code{pre-} annotation, which
29944 denotes the beginning of any prompt which is being output, a plain
29945 annotation, which denotes the end of the prompt, and then a @code{post-}
29946 annotation which denotes the end of any echo which may (or may not) be
29947 associated with the input. For example, the @code{prompt} input type
29948 features the following annotations:
29956 The input types are
29959 @findex pre-prompt annotation
29960 @findex prompt annotation
29961 @findex post-prompt annotation
29963 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
29965 @findex pre-commands annotation
29966 @findex commands annotation
29967 @findex post-commands annotation
29969 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
29970 command. The annotations are repeated for each command which is input.
29972 @findex pre-overload-choice annotation
29973 @findex overload-choice annotation
29974 @findex post-overload-choice annotation
29975 @item overload-choice
29976 When @value{GDBN} wants the user to select between various overloaded functions.
29978 @findex pre-query annotation
29979 @findex query annotation
29980 @findex post-query annotation
29982 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
29984 @findex pre-prompt-for-continue annotation
29985 @findex prompt-for-continue annotation
29986 @findex post-prompt-for-continue annotation
29987 @item prompt-for-continue
29988 When @value{GDBN} is asking the user to press return to continue. Note: Don't
29989 expect this to work well; instead use @code{set height 0} to disable
29990 prompting. This is because the counting of lines is buggy in the
29991 presence of annotations.
29996 @cindex annotations for errors, warnings and interrupts
29998 @findex quit annotation
30003 This annotation occurs right before @value{GDBN} responds to an interrupt.
30005 @findex error annotation
30010 This annotation occurs right before @value{GDBN} responds to an error.
30012 Quit and error annotations indicate that any annotations which @value{GDBN} was
30013 in the middle of may end abruptly. For example, if a
30014 @code{value-history-begin} annotation is followed by a @code{error}, one
30015 cannot expect to receive the matching @code{value-history-end}. One
30016 cannot expect not to receive it either, however; an error annotation
30017 does not necessarily mean that @value{GDBN} is immediately returning all the way
30020 @findex error-begin annotation
30021 A quit or error annotation may be preceded by
30027 Any output between that and the quit or error annotation is the error
30030 Warning messages are not yet annotated.
30031 @c If we want to change that, need to fix warning(), type_error(),
30032 @c range_error(), and possibly other places.
30035 @section Invalidation Notices
30037 @cindex annotations for invalidation messages
30038 The following annotations say that certain pieces of state may have
30042 @findex frames-invalid annotation
30043 @item ^Z^Zframes-invalid
30045 The frames (for example, output from the @code{backtrace} command) may
30048 @findex breakpoints-invalid annotation
30049 @item ^Z^Zbreakpoints-invalid
30051 The breakpoints may have changed. For example, the user just added or
30052 deleted a breakpoint.
30055 @node Annotations for Running
30056 @section Running the Program
30057 @cindex annotations for running programs
30059 @findex starting annotation
30060 @findex stopping annotation
30061 When the program starts executing due to a @value{GDBN} command such as
30062 @code{step} or @code{continue},
30068 is output. When the program stops,
30074 is output. Before the @code{stopped} annotation, a variety of
30075 annotations describe how the program stopped.
30078 @findex exited annotation
30079 @item ^Z^Zexited @var{exit-status}
30080 The program exited, and @var{exit-status} is the exit status (zero for
30081 successful exit, otherwise nonzero).
30083 @findex signalled annotation
30084 @findex signal-name annotation
30085 @findex signal-name-end annotation
30086 @findex signal-string annotation
30087 @findex signal-string-end annotation
30088 @item ^Z^Zsignalled
30089 The program exited with a signal. After the @code{^Z^Zsignalled}, the
30090 annotation continues:
30096 ^Z^Zsignal-name-end
30100 ^Z^Zsignal-string-end
30105 where @var{name} is the name of the signal, such as @code{SIGILL} or
30106 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
30107 as @code{Illegal Instruction} or @code{Segmentation fault}.
30108 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
30109 user's benefit and have no particular format.
30111 @findex signal annotation
30113 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
30114 just saying that the program received the signal, not that it was
30115 terminated with it.
30117 @findex breakpoint annotation
30118 @item ^Z^Zbreakpoint @var{number}
30119 The program hit breakpoint number @var{number}.
30121 @findex watchpoint annotation
30122 @item ^Z^Zwatchpoint @var{number}
30123 The program hit watchpoint number @var{number}.
30126 @node Source Annotations
30127 @section Displaying Source
30128 @cindex annotations for source display
30130 @findex source annotation
30131 The following annotation is used instead of displaying source code:
30134 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
30137 where @var{filename} is an absolute file name indicating which source
30138 file, @var{line} is the line number within that file (where 1 is the
30139 first line in the file), @var{character} is the character position
30140 within the file (where 0 is the first character in the file) (for most
30141 debug formats this will necessarily point to the beginning of a line),
30142 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
30143 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
30144 @var{addr} is the address in the target program associated with the
30145 source which is being displayed. @var{addr} is in the form @samp{0x}
30146 followed by one or more lowercase hex digits (note that this does not
30147 depend on the language).
30149 @node JIT Interface
30150 @chapter JIT Compilation Interface
30151 @cindex just-in-time compilation
30152 @cindex JIT compilation interface
30154 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
30155 interface. A JIT compiler is a program or library that generates native
30156 executable code at runtime and executes it, usually in order to achieve good
30157 performance while maintaining platform independence.
30159 Programs that use JIT compilation are normally difficult to debug because
30160 portions of their code are generated at runtime, instead of being loaded from
30161 object files, which is where @value{GDBN} normally finds the program's symbols
30162 and debug information. In order to debug programs that use JIT compilation,
30163 @value{GDBN} has an interface that allows the program to register in-memory
30164 symbol files with @value{GDBN} at runtime.
30166 If you are using @value{GDBN} to debug a program that uses this interface, then
30167 it should work transparently so long as you have not stripped the binary. If
30168 you are developing a JIT compiler, then the interface is documented in the rest
30169 of this chapter. At this time, the only known client of this interface is the
30172 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
30173 JIT compiler communicates with @value{GDBN} by writing data into a global
30174 variable and calling a fuction at a well-known symbol. When @value{GDBN}
30175 attaches, it reads a linked list of symbol files from the global variable to
30176 find existing code, and puts a breakpoint in the function so that it can find
30177 out about additional code.
30180 * Declarations:: Relevant C struct declarations
30181 * Registering Code:: Steps to register code
30182 * Unregistering Code:: Steps to unregister code
30186 @section JIT Declarations
30188 These are the relevant struct declarations that a C program should include to
30189 implement the interface:
30199 struct jit_code_entry
30201 struct jit_code_entry *next_entry;
30202 struct jit_code_entry *prev_entry;
30203 const char *symfile_addr;
30204 uint64_t symfile_size;
30207 struct jit_descriptor
30210 /* This type should be jit_actions_t, but we use uint32_t
30211 to be explicit about the bitwidth. */
30212 uint32_t action_flag;
30213 struct jit_code_entry *relevant_entry;
30214 struct jit_code_entry *first_entry;
30217 /* GDB puts a breakpoint in this function. */
30218 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
30220 /* Make sure to specify the version statically, because the
30221 debugger may check the version before we can set it. */
30222 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
30225 If the JIT is multi-threaded, then it is important that the JIT synchronize any
30226 modifications to this global data properly, which can easily be done by putting
30227 a global mutex around modifications to these structures.
30229 @node Registering Code
30230 @section Registering Code
30232 To register code with @value{GDBN}, the JIT should follow this protocol:
30236 Generate an object file in memory with symbols and other desired debug
30237 information. The file must include the virtual addresses of the sections.
30240 Create a code entry for the file, which gives the start and size of the symbol
30244 Add it to the linked list in the JIT descriptor.
30247 Point the relevant_entry field of the descriptor at the entry.
30250 Set @code{action_flag} to @code{JIT_REGISTER} and call
30251 @code{__jit_debug_register_code}.
30254 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
30255 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
30256 new code. However, the linked list must still be maintained in order to allow
30257 @value{GDBN} to attach to a running process and still find the symbol files.
30259 @node Unregistering Code
30260 @section Unregistering Code
30262 If code is freed, then the JIT should use the following protocol:
30266 Remove the code entry corresponding to the code from the linked list.
30269 Point the @code{relevant_entry} field of the descriptor at the code entry.
30272 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
30273 @code{__jit_debug_register_code}.
30276 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
30277 and the JIT will leak the memory used for the associated symbol files.
30280 @chapter Reporting Bugs in @value{GDBN}
30281 @cindex bugs in @value{GDBN}
30282 @cindex reporting bugs in @value{GDBN}
30284 Your bug reports play an essential role in making @value{GDBN} reliable.
30286 Reporting a bug may help you by bringing a solution to your problem, or it
30287 may not. But in any case the principal function of a bug report is to help
30288 the entire community by making the next version of @value{GDBN} work better. Bug
30289 reports are your contribution to the maintenance of @value{GDBN}.
30291 In order for a bug report to serve its purpose, you must include the
30292 information that enables us to fix the bug.
30295 * Bug Criteria:: Have you found a bug?
30296 * Bug Reporting:: How to report bugs
30300 @section Have You Found a Bug?
30301 @cindex bug criteria
30303 If you are not sure whether you have found a bug, here are some guidelines:
30306 @cindex fatal signal
30307 @cindex debugger crash
30308 @cindex crash of debugger
30310 If the debugger gets a fatal signal, for any input whatever, that is a
30311 @value{GDBN} bug. Reliable debuggers never crash.
30313 @cindex error on valid input
30315 If @value{GDBN} produces an error message for valid input, that is a
30316 bug. (Note that if you're cross debugging, the problem may also be
30317 somewhere in the connection to the target.)
30319 @cindex invalid input
30321 If @value{GDBN} does not produce an error message for invalid input,
30322 that is a bug. However, you should note that your idea of
30323 ``invalid input'' might be our idea of ``an extension'' or ``support
30324 for traditional practice''.
30327 If you are an experienced user of debugging tools, your suggestions
30328 for improvement of @value{GDBN} are welcome in any case.
30331 @node Bug Reporting
30332 @section How to Report Bugs
30333 @cindex bug reports
30334 @cindex @value{GDBN} bugs, reporting
30336 A number of companies and individuals offer support for @sc{gnu} products.
30337 If you obtained @value{GDBN} from a support organization, we recommend you
30338 contact that organization first.
30340 You can find contact information for many support companies and
30341 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
30343 @c should add a web page ref...
30346 @ifset BUGURL_DEFAULT
30347 In any event, we also recommend that you submit bug reports for
30348 @value{GDBN}. The preferred method is to submit them directly using
30349 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
30350 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
30353 @strong{Do not send bug reports to @samp{info-gdb}, or to
30354 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
30355 not want to receive bug reports. Those that do have arranged to receive
30358 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
30359 serves as a repeater. The mailing list and the newsgroup carry exactly
30360 the same messages. Often people think of posting bug reports to the
30361 newsgroup instead of mailing them. This appears to work, but it has one
30362 problem which can be crucial: a newsgroup posting often lacks a mail
30363 path back to the sender. Thus, if we need to ask for more information,
30364 we may be unable to reach you. For this reason, it is better to send
30365 bug reports to the mailing list.
30367 @ifclear BUGURL_DEFAULT
30368 In any event, we also recommend that you submit bug reports for
30369 @value{GDBN} to @value{BUGURL}.
30373 The fundamental principle of reporting bugs usefully is this:
30374 @strong{report all the facts}. If you are not sure whether to state a
30375 fact or leave it out, state it!
30377 Often people omit facts because they think they know what causes the
30378 problem and assume that some details do not matter. Thus, you might
30379 assume that the name of the variable you use in an example does not matter.
30380 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
30381 stray memory reference which happens to fetch from the location where that
30382 name is stored in memory; perhaps, if the name were different, the contents
30383 of that location would fool the debugger into doing the right thing despite
30384 the bug. Play it safe and give a specific, complete example. That is the
30385 easiest thing for you to do, and the most helpful.
30387 Keep in mind that the purpose of a bug report is to enable us to fix the
30388 bug. It may be that the bug has been reported previously, but neither
30389 you nor we can know that unless your bug report is complete and
30392 Sometimes people give a few sketchy facts and ask, ``Does this ring a
30393 bell?'' Those bug reports are useless, and we urge everyone to
30394 @emph{refuse to respond to them} except to chide the sender to report
30397 To enable us to fix the bug, you should include all these things:
30401 The version of @value{GDBN}. @value{GDBN} announces it if you start
30402 with no arguments; you can also print it at any time using @code{show
30405 Without this, we will not know whether there is any point in looking for
30406 the bug in the current version of @value{GDBN}.
30409 The type of machine you are using, and the operating system name and
30413 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
30414 ``@value{GCC}--2.8.1''.
30417 What compiler (and its version) was used to compile the program you are
30418 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
30419 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
30420 to get this information; for other compilers, see the documentation for
30424 The command arguments you gave the compiler to compile your example and
30425 observe the bug. For example, did you use @samp{-O}? To guarantee
30426 you will not omit something important, list them all. A copy of the
30427 Makefile (or the output from make) is sufficient.
30429 If we were to try to guess the arguments, we would probably guess wrong
30430 and then we might not encounter the bug.
30433 A complete input script, and all necessary source files, that will
30437 A description of what behavior you observe that you believe is
30438 incorrect. For example, ``It gets a fatal signal.''
30440 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
30441 will certainly notice it. But if the bug is incorrect output, we might
30442 not notice unless it is glaringly wrong. You might as well not give us
30443 a chance to make a mistake.
30445 Even if the problem you experience is a fatal signal, you should still
30446 say so explicitly. Suppose something strange is going on, such as, your
30447 copy of @value{GDBN} is out of synch, or you have encountered a bug in
30448 the C library on your system. (This has happened!) Your copy might
30449 crash and ours would not. If you told us to expect a crash, then when
30450 ours fails to crash, we would know that the bug was not happening for
30451 us. If you had not told us to expect a crash, then we would not be able
30452 to draw any conclusion from our observations.
30455 @cindex recording a session script
30456 To collect all this information, you can use a session recording program
30457 such as @command{script}, which is available on many Unix systems.
30458 Just run your @value{GDBN} session inside @command{script} and then
30459 include the @file{typescript} file with your bug report.
30461 Another way to record a @value{GDBN} session is to run @value{GDBN}
30462 inside Emacs and then save the entire buffer to a file.
30465 If you wish to suggest changes to the @value{GDBN} source, send us context
30466 diffs. If you even discuss something in the @value{GDBN} source, refer to
30467 it by context, not by line number.
30469 The line numbers in our development sources will not match those in your
30470 sources. Your line numbers would convey no useful information to us.
30474 Here are some things that are not necessary:
30478 A description of the envelope of the bug.
30480 Often people who encounter a bug spend a lot of time investigating
30481 which changes to the input file will make the bug go away and which
30482 changes will not affect it.
30484 This is often time consuming and not very useful, because the way we
30485 will find the bug is by running a single example under the debugger
30486 with breakpoints, not by pure deduction from a series of examples.
30487 We recommend that you save your time for something else.
30489 Of course, if you can find a simpler example to report @emph{instead}
30490 of the original one, that is a convenience for us. Errors in the
30491 output will be easier to spot, running under the debugger will take
30492 less time, and so on.
30494 However, simplification is not vital; if you do not want to do this,
30495 report the bug anyway and send us the entire test case you used.
30498 A patch for the bug.
30500 A patch for the bug does help us if it is a good one. But do not omit
30501 the necessary information, such as the test case, on the assumption that
30502 a patch is all we need. We might see problems with your patch and decide
30503 to fix the problem another way, or we might not understand it at all.
30505 Sometimes with a program as complicated as @value{GDBN} it is very hard to
30506 construct an example that will make the program follow a certain path
30507 through the code. If you do not send us the example, we will not be able
30508 to construct one, so we will not be able to verify that the bug is fixed.
30510 And if we cannot understand what bug you are trying to fix, or why your
30511 patch should be an improvement, we will not install it. A test case will
30512 help us to understand.
30515 A guess about what the bug is or what it depends on.
30517 Such guesses are usually wrong. Even we cannot guess right about such
30518 things without first using the debugger to find the facts.
30521 @c The readline documentation is distributed with the readline code
30522 @c and consists of the two following files:
30524 @c inc-hist.texinfo
30525 @c Use -I with makeinfo to point to the appropriate directory,
30526 @c environment var TEXINPUTS with TeX.
30527 @ifclear SYSTEM_READLINE
30528 @include rluser.texi
30529 @include inc-hist.texinfo
30533 @node Formatting Documentation
30534 @appendix Formatting Documentation
30536 @cindex @value{GDBN} reference card
30537 @cindex reference card
30538 The @value{GDBN} 4 release includes an already-formatted reference card, ready
30539 for printing with PostScript or Ghostscript, in the @file{gdb}
30540 subdirectory of the main source directory@footnote{In
30541 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
30542 release.}. If you can use PostScript or Ghostscript with your printer,
30543 you can print the reference card immediately with @file{refcard.ps}.
30545 The release also includes the source for the reference card. You
30546 can format it, using @TeX{}, by typing:
30552 The @value{GDBN} reference card is designed to print in @dfn{landscape}
30553 mode on US ``letter'' size paper;
30554 that is, on a sheet 11 inches wide by 8.5 inches
30555 high. You will need to specify this form of printing as an option to
30556 your @sc{dvi} output program.
30558 @cindex documentation
30560 All the documentation for @value{GDBN} comes as part of the machine-readable
30561 distribution. The documentation is written in Texinfo format, which is
30562 a documentation system that uses a single source file to produce both
30563 on-line information and a printed manual. You can use one of the Info
30564 formatting commands to create the on-line version of the documentation
30565 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
30567 @value{GDBN} includes an already formatted copy of the on-line Info
30568 version of this manual in the @file{gdb} subdirectory. The main Info
30569 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
30570 subordinate files matching @samp{gdb.info*} in the same directory. If
30571 necessary, you can print out these files, or read them with any editor;
30572 but they are easier to read using the @code{info} subsystem in @sc{gnu}
30573 Emacs or the standalone @code{info} program, available as part of the
30574 @sc{gnu} Texinfo distribution.
30576 If you want to format these Info files yourself, you need one of the
30577 Info formatting programs, such as @code{texinfo-format-buffer} or
30580 If you have @code{makeinfo} installed, and are in the top level
30581 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
30582 version @value{GDBVN}), you can make the Info file by typing:
30589 If you want to typeset and print copies of this manual, you need @TeX{},
30590 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
30591 Texinfo definitions file.
30593 @TeX{} is a typesetting program; it does not print files directly, but
30594 produces output files called @sc{dvi} files. To print a typeset
30595 document, you need a program to print @sc{dvi} files. If your system
30596 has @TeX{} installed, chances are it has such a program. The precise
30597 command to use depends on your system; @kbd{lpr -d} is common; another
30598 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
30599 require a file name without any extension or a @samp{.dvi} extension.
30601 @TeX{} also requires a macro definitions file called
30602 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
30603 written in Texinfo format. On its own, @TeX{} cannot either read or
30604 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
30605 and is located in the @file{gdb-@var{version-number}/texinfo}
30608 If you have @TeX{} and a @sc{dvi} printer program installed, you can
30609 typeset and print this manual. First switch to the @file{gdb}
30610 subdirectory of the main source directory (for example, to
30611 @file{gdb-@value{GDBVN}/gdb}) and type:
30617 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
30619 @node Installing GDB
30620 @appendix Installing @value{GDBN}
30621 @cindex installation
30624 * Requirements:: Requirements for building @value{GDBN}
30625 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
30626 * Separate Objdir:: Compiling @value{GDBN} in another directory
30627 * Config Names:: Specifying names for hosts and targets
30628 * Configure Options:: Summary of options for configure
30629 * System-wide configuration:: Having a system-wide init file
30633 @section Requirements for Building @value{GDBN}
30634 @cindex building @value{GDBN}, requirements for
30636 Building @value{GDBN} requires various tools and packages to be available.
30637 Other packages will be used only if they are found.
30639 @heading Tools/Packages Necessary for Building @value{GDBN}
30641 @item ISO C90 compiler
30642 @value{GDBN} is written in ISO C90. It should be buildable with any
30643 working C90 compiler, e.g.@: GCC.
30647 @heading Tools/Packages Optional for Building @value{GDBN}
30651 @value{GDBN} can use the Expat XML parsing library. This library may be
30652 included with your operating system distribution; if it is not, you
30653 can get the latest version from @url{http://expat.sourceforge.net}.
30654 The @file{configure} script will search for this library in several
30655 standard locations; if it is installed in an unusual path, you can
30656 use the @option{--with-libexpat-prefix} option to specify its location.
30662 Remote protocol memory maps (@pxref{Memory Map Format})
30664 Target descriptions (@pxref{Target Descriptions})
30666 Remote shared library lists (@pxref{Library List Format})
30668 MS-Windows shared libraries (@pxref{Shared Libraries})
30672 @cindex compressed debug sections
30673 @value{GDBN} will use the @samp{zlib} library, if available, to read
30674 compressed debug sections. Some linkers, such as GNU gold, are capable
30675 of producing binaries with compressed debug sections. If @value{GDBN}
30676 is compiled with @samp{zlib}, it will be able to read the debug
30677 information in such binaries.
30679 The @samp{zlib} library is likely included with your operating system
30680 distribution; if it is not, you can get the latest version from
30681 @url{http://zlib.net}.
30684 @value{GDBN}'s features related to character sets (@pxref{Character
30685 Sets}) require a functioning @code{iconv} implementation. If you are
30686 on a GNU system, then this is provided by the GNU C Library. Some
30687 other systems also provide a working @code{iconv}.
30689 On systems with @code{iconv}, you can install GNU Libiconv. If you
30690 have previously installed Libiconv, you can use the
30691 @option{--with-libiconv-prefix} option to configure.
30693 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
30694 arrange to build Libiconv if a directory named @file{libiconv} appears
30695 in the top-most source directory. If Libiconv is built this way, and
30696 if the operating system does not provide a suitable @code{iconv}
30697 implementation, then the just-built library will automatically be used
30698 by @value{GDBN}. One easy way to set this up is to download GNU
30699 Libiconv, unpack it, and then rename the directory holding the
30700 Libiconv source code to @samp{libiconv}.
30703 @node Running Configure
30704 @section Invoking the @value{GDBN} @file{configure} Script
30705 @cindex configuring @value{GDBN}
30706 @value{GDBN} comes with a @file{configure} script that automates the process
30707 of preparing @value{GDBN} for installation; you can then use @code{make} to
30708 build the @code{gdb} program.
30710 @c irrelevant in info file; it's as current as the code it lives with.
30711 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
30712 look at the @file{README} file in the sources; we may have improved the
30713 installation procedures since publishing this manual.}
30716 The @value{GDBN} distribution includes all the source code you need for
30717 @value{GDBN} in a single directory, whose name is usually composed by
30718 appending the version number to @samp{gdb}.
30720 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
30721 @file{gdb-@value{GDBVN}} directory. That directory contains:
30724 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
30725 script for configuring @value{GDBN} and all its supporting libraries
30727 @item gdb-@value{GDBVN}/gdb
30728 the source specific to @value{GDBN} itself
30730 @item gdb-@value{GDBVN}/bfd
30731 source for the Binary File Descriptor library
30733 @item gdb-@value{GDBVN}/include
30734 @sc{gnu} include files
30736 @item gdb-@value{GDBVN}/libiberty
30737 source for the @samp{-liberty} free software library
30739 @item gdb-@value{GDBVN}/opcodes
30740 source for the library of opcode tables and disassemblers
30742 @item gdb-@value{GDBVN}/readline
30743 source for the @sc{gnu} command-line interface
30745 @item gdb-@value{GDBVN}/glob
30746 source for the @sc{gnu} filename pattern-matching subroutine
30748 @item gdb-@value{GDBVN}/mmalloc
30749 source for the @sc{gnu} memory-mapped malloc package
30752 The simplest way to configure and build @value{GDBN} is to run @file{configure}
30753 from the @file{gdb-@var{version-number}} source directory, which in
30754 this example is the @file{gdb-@value{GDBVN}} directory.
30756 First switch to the @file{gdb-@var{version-number}} source directory
30757 if you are not already in it; then run @file{configure}. Pass the
30758 identifier for the platform on which @value{GDBN} will run as an
30764 cd gdb-@value{GDBVN}
30765 ./configure @var{host}
30770 where @var{host} is an identifier such as @samp{sun4} or
30771 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
30772 (You can often leave off @var{host}; @file{configure} tries to guess the
30773 correct value by examining your system.)
30775 Running @samp{configure @var{host}} and then running @code{make} builds the
30776 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
30777 libraries, then @code{gdb} itself. The configured source files, and the
30778 binaries, are left in the corresponding source directories.
30781 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
30782 system does not recognize this automatically when you run a different
30783 shell, you may need to run @code{sh} on it explicitly:
30786 sh configure @var{host}
30789 If you run @file{configure} from a directory that contains source
30790 directories for multiple libraries or programs, such as the
30791 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
30793 creates configuration files for every directory level underneath (unless
30794 you tell it not to, with the @samp{--norecursion} option).
30796 You should run the @file{configure} script from the top directory in the
30797 source tree, the @file{gdb-@var{version-number}} directory. If you run
30798 @file{configure} from one of the subdirectories, you will configure only
30799 that subdirectory. That is usually not what you want. In particular,
30800 if you run the first @file{configure} from the @file{gdb} subdirectory
30801 of the @file{gdb-@var{version-number}} directory, you will omit the
30802 configuration of @file{bfd}, @file{readline}, and other sibling
30803 directories of the @file{gdb} subdirectory. This leads to build errors
30804 about missing include files such as @file{bfd/bfd.h}.
30806 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
30807 However, you should make sure that the shell on your path (named by
30808 the @samp{SHELL} environment variable) is publicly readable. Remember
30809 that @value{GDBN} uses the shell to start your program---some systems refuse to
30810 let @value{GDBN} debug child processes whose programs are not readable.
30812 @node Separate Objdir
30813 @section Compiling @value{GDBN} in Another Directory
30815 If you want to run @value{GDBN} versions for several host or target machines,
30816 you need a different @code{gdb} compiled for each combination of
30817 host and target. @file{configure} is designed to make this easy by
30818 allowing you to generate each configuration in a separate subdirectory,
30819 rather than in the source directory. If your @code{make} program
30820 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
30821 @code{make} in each of these directories builds the @code{gdb}
30822 program specified there.
30824 To build @code{gdb} in a separate directory, run @file{configure}
30825 with the @samp{--srcdir} option to specify where to find the source.
30826 (You also need to specify a path to find @file{configure}
30827 itself from your working directory. If the path to @file{configure}
30828 would be the same as the argument to @samp{--srcdir}, you can leave out
30829 the @samp{--srcdir} option; it is assumed.)
30831 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
30832 separate directory for a Sun 4 like this:
30836 cd gdb-@value{GDBVN}
30839 ../gdb-@value{GDBVN}/configure sun4
30844 When @file{configure} builds a configuration using a remote source
30845 directory, it creates a tree for the binaries with the same structure
30846 (and using the same names) as the tree under the source directory. In
30847 the example, you'd find the Sun 4 library @file{libiberty.a} in the
30848 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
30849 @file{gdb-sun4/gdb}.
30851 Make sure that your path to the @file{configure} script has just one
30852 instance of @file{gdb} in it. If your path to @file{configure} looks
30853 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
30854 one subdirectory of @value{GDBN}, not the whole package. This leads to
30855 build errors about missing include files such as @file{bfd/bfd.h}.
30857 One popular reason to build several @value{GDBN} configurations in separate
30858 directories is to configure @value{GDBN} for cross-compiling (where
30859 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
30860 programs that run on another machine---the @dfn{target}).
30861 You specify a cross-debugging target by
30862 giving the @samp{--target=@var{target}} option to @file{configure}.
30864 When you run @code{make} to build a program or library, you must run
30865 it in a configured directory---whatever directory you were in when you
30866 called @file{configure} (or one of its subdirectories).
30868 The @code{Makefile} that @file{configure} generates in each source
30869 directory also runs recursively. If you type @code{make} in a source
30870 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
30871 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
30872 will build all the required libraries, and then build GDB.
30874 When you have multiple hosts or targets configured in separate
30875 directories, you can run @code{make} on them in parallel (for example,
30876 if they are NFS-mounted on each of the hosts); they will not interfere
30880 @section Specifying Names for Hosts and Targets
30882 The specifications used for hosts and targets in the @file{configure}
30883 script are based on a three-part naming scheme, but some short predefined
30884 aliases are also supported. The full naming scheme encodes three pieces
30885 of information in the following pattern:
30888 @var{architecture}-@var{vendor}-@var{os}
30891 For example, you can use the alias @code{sun4} as a @var{host} argument,
30892 or as the value for @var{target} in a @code{--target=@var{target}}
30893 option. The equivalent full name is @samp{sparc-sun-sunos4}.
30895 The @file{configure} script accompanying @value{GDBN} does not provide
30896 any query facility to list all supported host and target names or
30897 aliases. @file{configure} calls the Bourne shell script
30898 @code{config.sub} to map abbreviations to full names; you can read the
30899 script, if you wish, or you can use it to test your guesses on
30900 abbreviations---for example:
30903 % sh config.sub i386-linux
30905 % sh config.sub alpha-linux
30906 alpha-unknown-linux-gnu
30907 % sh config.sub hp9k700
30909 % sh config.sub sun4
30910 sparc-sun-sunos4.1.1
30911 % sh config.sub sun3
30912 m68k-sun-sunos4.1.1
30913 % sh config.sub i986v
30914 Invalid configuration `i986v': machine `i986v' not recognized
30918 @code{config.sub} is also distributed in the @value{GDBN} source
30919 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
30921 @node Configure Options
30922 @section @file{configure} Options
30924 Here is a summary of the @file{configure} options and arguments that
30925 are most often useful for building @value{GDBN}. @file{configure} also has
30926 several other options not listed here. @inforef{What Configure
30927 Does,,configure.info}, for a full explanation of @file{configure}.
30930 configure @r{[}--help@r{]}
30931 @r{[}--prefix=@var{dir}@r{]}
30932 @r{[}--exec-prefix=@var{dir}@r{]}
30933 @r{[}--srcdir=@var{dirname}@r{]}
30934 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
30935 @r{[}--target=@var{target}@r{]}
30940 You may introduce options with a single @samp{-} rather than
30941 @samp{--} if you prefer; but you may abbreviate option names if you use
30946 Display a quick summary of how to invoke @file{configure}.
30948 @item --prefix=@var{dir}
30949 Configure the source to install programs and files under directory
30952 @item --exec-prefix=@var{dir}
30953 Configure the source to install programs under directory
30956 @c avoid splitting the warning from the explanation:
30958 @item --srcdir=@var{dirname}
30959 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
30960 @code{make} that implements the @code{VPATH} feature.}@*
30961 Use this option to make configurations in directories separate from the
30962 @value{GDBN} source directories. Among other things, you can use this to
30963 build (or maintain) several configurations simultaneously, in separate
30964 directories. @file{configure} writes configuration-specific files in
30965 the current directory, but arranges for them to use the source in the
30966 directory @var{dirname}. @file{configure} creates directories under
30967 the working directory in parallel to the source directories below
30970 @item --norecursion
30971 Configure only the directory level where @file{configure} is executed; do not
30972 propagate configuration to subdirectories.
30974 @item --target=@var{target}
30975 Configure @value{GDBN} for cross-debugging programs running on the specified
30976 @var{target}. Without this option, @value{GDBN} is configured to debug
30977 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
30979 There is no convenient way to generate a list of all available targets.
30981 @item @var{host} @dots{}
30982 Configure @value{GDBN} to run on the specified @var{host}.
30984 There is no convenient way to generate a list of all available hosts.
30987 There are many other options available as well, but they are generally
30988 needed for special purposes only.
30990 @node System-wide configuration
30991 @section System-wide configuration and settings
30992 @cindex system-wide init file
30994 @value{GDBN} can be configured to have a system-wide init file;
30995 this file will be read and executed at startup (@pxref{Startup, , What
30996 @value{GDBN} does during startup}).
30998 Here is the corresponding configure option:
31001 @item --with-system-gdbinit=@var{file}
31002 Specify that the default location of the system-wide init file is
31006 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
31007 it may be subject to relocation. Two possible cases:
31011 If the default location of this init file contains @file{$prefix},
31012 it will be subject to relocation. Suppose that the configure options
31013 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
31014 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
31015 init file is looked for as @file{$install/etc/gdbinit} instead of
31016 @file{$prefix/etc/gdbinit}.
31019 By contrast, if the default location does not contain the prefix,
31020 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
31021 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
31022 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
31023 wherever @value{GDBN} is installed.
31026 @node Maintenance Commands
31027 @appendix Maintenance Commands
31028 @cindex maintenance commands
31029 @cindex internal commands
31031 In addition to commands intended for @value{GDBN} users, @value{GDBN}
31032 includes a number of commands intended for @value{GDBN} developers,
31033 that are not documented elsewhere in this manual. These commands are
31034 provided here for reference. (For commands that turn on debugging
31035 messages, see @ref{Debugging Output}.)
31038 @kindex maint agent
31039 @kindex maint agent-eval
31040 @item maint agent @var{expression}
31041 @itemx maint agent-eval @var{expression}
31042 Translate the given @var{expression} into remote agent bytecodes.
31043 This command is useful for debugging the Agent Expression mechanism
31044 (@pxref{Agent Expressions}). The @samp{agent} version produces an
31045 expression useful for data collection, such as by tracepoints, while
31046 @samp{maint agent-eval} produces an expression that evaluates directly
31047 to a result. For instance, a collection expression for @code{globa +
31048 globb} will include bytecodes to record four bytes of memory at each
31049 of the addresses of @code{globa} and @code{globb}, while discarding
31050 the result of the addition, while an evaluation expression will do the
31051 addition and return the sum.
31053 @kindex maint info breakpoints
31054 @item @anchor{maint info breakpoints}maint info breakpoints
31055 Using the same format as @samp{info breakpoints}, display both the
31056 breakpoints you've set explicitly, and those @value{GDBN} is using for
31057 internal purposes. Internal breakpoints are shown with negative
31058 breakpoint numbers. The type column identifies what kind of breakpoint
31063 Normal, explicitly set breakpoint.
31066 Normal, explicitly set watchpoint.
31069 Internal breakpoint, used to handle correctly stepping through
31070 @code{longjmp} calls.
31072 @item longjmp resume
31073 Internal breakpoint at the target of a @code{longjmp}.
31076 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
31079 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
31082 Shared library events.
31086 @kindex set displaced-stepping
31087 @kindex show displaced-stepping
31088 @cindex displaced stepping support
31089 @cindex out-of-line single-stepping
31090 @item set displaced-stepping
31091 @itemx show displaced-stepping
31092 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
31093 if the target supports it. Displaced stepping is a way to single-step
31094 over breakpoints without removing them from the inferior, by executing
31095 an out-of-line copy of the instruction that was originally at the
31096 breakpoint location. It is also known as out-of-line single-stepping.
31099 @item set displaced-stepping on
31100 If the target architecture supports it, @value{GDBN} will use
31101 displaced stepping to step over breakpoints.
31103 @item set displaced-stepping off
31104 @value{GDBN} will not use displaced stepping to step over breakpoints,
31105 even if such is supported by the target architecture.
31107 @cindex non-stop mode, and @samp{set displaced-stepping}
31108 @item set displaced-stepping auto
31109 This is the default mode. @value{GDBN} will use displaced stepping
31110 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
31111 architecture supports displaced stepping.
31114 @kindex maint check-symtabs
31115 @item maint check-symtabs
31116 Check the consistency of psymtabs and symtabs.
31118 @kindex maint cplus first_component
31119 @item maint cplus first_component @var{name}
31120 Print the first C@t{++} class/namespace component of @var{name}.
31122 @kindex maint cplus namespace
31123 @item maint cplus namespace
31124 Print the list of possible C@t{++} namespaces.
31126 @kindex maint demangle
31127 @item maint demangle @var{name}
31128 Demangle a C@t{++} or Objective-C mangled @var{name}.
31130 @kindex maint deprecate
31131 @kindex maint undeprecate
31132 @cindex deprecated commands
31133 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
31134 @itemx maint undeprecate @var{command}
31135 Deprecate or undeprecate the named @var{command}. Deprecated commands
31136 cause @value{GDBN} to issue a warning when you use them. The optional
31137 argument @var{replacement} says which newer command should be used in
31138 favor of the deprecated one; if it is given, @value{GDBN} will mention
31139 the replacement as part of the warning.
31141 @kindex maint dump-me
31142 @item maint dump-me
31143 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
31144 Cause a fatal signal in the debugger and force it to dump its core.
31145 This is supported only on systems which support aborting a program
31146 with the @code{SIGQUIT} signal.
31148 @kindex maint internal-error
31149 @kindex maint internal-warning
31150 @item maint internal-error @r{[}@var{message-text}@r{]}
31151 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
31152 Cause @value{GDBN} to call the internal function @code{internal_error}
31153 or @code{internal_warning} and hence behave as though an internal error
31154 or internal warning has been detected. In addition to reporting the
31155 internal problem, these functions give the user the opportunity to
31156 either quit @value{GDBN} or create a core file of the current
31157 @value{GDBN} session.
31159 These commands take an optional parameter @var{message-text} that is
31160 used as the text of the error or warning message.
31162 Here's an example of using @code{internal-error}:
31165 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
31166 @dots{}/maint.c:121: internal-error: testing, 1, 2
31167 A problem internal to GDB has been detected. Further
31168 debugging may prove unreliable.
31169 Quit this debugging session? (y or n) @kbd{n}
31170 Create a core file? (y or n) @kbd{n}
31174 @cindex @value{GDBN} internal error
31175 @cindex internal errors, control of @value{GDBN} behavior
31177 @kindex maint set internal-error
31178 @kindex maint show internal-error
31179 @kindex maint set internal-warning
31180 @kindex maint show internal-warning
31181 @item maint set internal-error @var{action} [ask|yes|no]
31182 @itemx maint show internal-error @var{action}
31183 @itemx maint set internal-warning @var{action} [ask|yes|no]
31184 @itemx maint show internal-warning @var{action}
31185 When @value{GDBN} reports an internal problem (error or warning) it
31186 gives the user the opportunity to both quit @value{GDBN} and create a
31187 core file of the current @value{GDBN} session. These commands let you
31188 override the default behaviour for each particular @var{action},
31189 described in the table below.
31193 You can specify that @value{GDBN} should always (yes) or never (no)
31194 quit. The default is to ask the user what to do.
31197 You can specify that @value{GDBN} should always (yes) or never (no)
31198 create a core file. The default is to ask the user what to do.
31201 @kindex maint packet
31202 @item maint packet @var{text}
31203 If @value{GDBN} is talking to an inferior via the serial protocol,
31204 then this command sends the string @var{text} to the inferior, and
31205 displays the response packet. @value{GDBN} supplies the initial
31206 @samp{$} character, the terminating @samp{#} character, and the
31209 @kindex maint print architecture
31210 @item maint print architecture @r{[}@var{file}@r{]}
31211 Print the entire architecture configuration. The optional argument
31212 @var{file} names the file where the output goes.
31214 @kindex maint print c-tdesc
31215 @item maint print c-tdesc
31216 Print the current target description (@pxref{Target Descriptions}) as
31217 a C source file. The created source file can be used in @value{GDBN}
31218 when an XML parser is not available to parse the description.
31220 @kindex maint print dummy-frames
31221 @item maint print dummy-frames
31222 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
31225 (@value{GDBP}) @kbd{b add}
31227 (@value{GDBP}) @kbd{print add(2,3)}
31228 Breakpoint 2, add (a=2, b=3) at @dots{}
31230 The program being debugged stopped while in a function called from GDB.
31232 (@value{GDBP}) @kbd{maint print dummy-frames}
31233 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
31234 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
31235 call_lo=0x01014000 call_hi=0x01014001
31239 Takes an optional file parameter.
31241 @kindex maint print registers
31242 @kindex maint print raw-registers
31243 @kindex maint print cooked-registers
31244 @kindex maint print register-groups
31245 @item maint print registers @r{[}@var{file}@r{]}
31246 @itemx maint print raw-registers @r{[}@var{file}@r{]}
31247 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
31248 @itemx maint print register-groups @r{[}@var{file}@r{]}
31249 Print @value{GDBN}'s internal register data structures.
31251 The command @code{maint print raw-registers} includes the contents of
31252 the raw register cache; the command @code{maint print cooked-registers}
31253 includes the (cooked) value of all registers, including registers which
31254 aren't available on the target nor visible to user; and the
31255 command @code{maint print register-groups} includes the groups that each
31256 register is a member of. @xref{Registers,, Registers, gdbint,
31257 @value{GDBN} Internals}.
31259 These commands take an optional parameter, a file name to which to
31260 write the information.
31262 @kindex maint print reggroups
31263 @item maint print reggroups @r{[}@var{file}@r{]}
31264 Print @value{GDBN}'s internal register group data structures. The
31265 optional argument @var{file} tells to what file to write the
31268 The register groups info looks like this:
31271 (@value{GDBP}) @kbd{maint print reggroups}
31284 This command forces @value{GDBN} to flush its internal register cache.
31286 @kindex maint print objfiles
31287 @cindex info for known object files
31288 @item maint print objfiles
31289 Print a dump of all known object files. For each object file, this
31290 command prints its name, address in memory, and all of its psymtabs
31293 @kindex maint print section-scripts
31294 @cindex info for known .debug_gdb_scripts-loaded scripts
31295 @item maint print section-scripts [@var{regexp}]
31296 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
31297 If @var{regexp} is specified, only print scripts loaded by object files
31298 matching @var{regexp}.
31299 For each script, this command prints its name as specified in the objfile,
31300 and the full path if known.
31301 @xref{.debug_gdb_scripts section}.
31303 @kindex maint print statistics
31304 @cindex bcache statistics
31305 @item maint print statistics
31306 This command prints, for each object file in the program, various data
31307 about that object file followed by the byte cache (@dfn{bcache})
31308 statistics for the object file. The objfile data includes the number
31309 of minimal, partial, full, and stabs symbols, the number of types
31310 defined by the objfile, the number of as yet unexpanded psym tables,
31311 the number of line tables and string tables, and the amount of memory
31312 used by the various tables. The bcache statistics include the counts,
31313 sizes, and counts of duplicates of all and unique objects, max,
31314 average, and median entry size, total memory used and its overhead and
31315 savings, and various measures of the hash table size and chain
31318 @kindex maint print target-stack
31319 @cindex target stack description
31320 @item maint print target-stack
31321 A @dfn{target} is an interface between the debugger and a particular
31322 kind of file or process. Targets can be stacked in @dfn{strata},
31323 so that more than one target can potentially respond to a request.
31324 In particular, memory accesses will walk down the stack of targets
31325 until they find a target that is interested in handling that particular
31328 This command prints a short description of each layer that was pushed on
31329 the @dfn{target stack}, starting from the top layer down to the bottom one.
31331 @kindex maint print type
31332 @cindex type chain of a data type
31333 @item maint print type @var{expr}
31334 Print the type chain for a type specified by @var{expr}. The argument
31335 can be either a type name or a symbol. If it is a symbol, the type of
31336 that symbol is described. The type chain produced by this command is
31337 a recursive definition of the data type as stored in @value{GDBN}'s
31338 data structures, including its flags and contained types.
31340 @kindex maint set dwarf2 always-disassemble
31341 @kindex maint show dwarf2 always-disassemble
31342 @item maint set dwarf2 always-disassemble
31343 @item maint show dwarf2 always-disassemble
31344 Control the behavior of @code{info address} when using DWARF debugging
31347 The default is @code{off}, which means that @value{GDBN} should try to
31348 describe a variable's location in an easily readable format. When
31349 @code{on}, @value{GDBN} will instead display the DWARF location
31350 expression in an assembly-like format. Note that some locations are
31351 too complex for @value{GDBN} to describe simply; in this case you will
31352 always see the disassembly form.
31354 Here is an example of the resulting disassembly:
31357 (gdb) info addr argc
31358 Symbol "argc" is a complex DWARF expression:
31362 For more information on these expressions, see
31363 @uref{http://www.dwarfstd.org/, the DWARF standard}.
31365 @kindex maint set dwarf2 max-cache-age
31366 @kindex maint show dwarf2 max-cache-age
31367 @item maint set dwarf2 max-cache-age
31368 @itemx maint show dwarf2 max-cache-age
31369 Control the DWARF 2 compilation unit cache.
31371 @cindex DWARF 2 compilation units cache
31372 In object files with inter-compilation-unit references, such as those
31373 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
31374 reader needs to frequently refer to previously read compilation units.
31375 This setting controls how long a compilation unit will remain in the
31376 cache if it is not referenced. A higher limit means that cached
31377 compilation units will be stored in memory longer, and more total
31378 memory will be used. Setting it to zero disables caching, which will
31379 slow down @value{GDBN} startup, but reduce memory consumption.
31381 @kindex maint set profile
31382 @kindex maint show profile
31383 @cindex profiling GDB
31384 @item maint set profile
31385 @itemx maint show profile
31386 Control profiling of @value{GDBN}.
31388 Profiling will be disabled until you use the @samp{maint set profile}
31389 command to enable it. When you enable profiling, the system will begin
31390 collecting timing and execution count data; when you disable profiling or
31391 exit @value{GDBN}, the results will be written to a log file. Remember that
31392 if you use profiling, @value{GDBN} will overwrite the profiling log file
31393 (often called @file{gmon.out}). If you have a record of important profiling
31394 data in a @file{gmon.out} file, be sure to move it to a safe location.
31396 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
31397 compiled with the @samp{-pg} compiler option.
31399 @kindex maint set show-debug-regs
31400 @kindex maint show show-debug-regs
31401 @cindex hardware debug registers
31402 @item maint set show-debug-regs
31403 @itemx maint show show-debug-regs
31404 Control whether to show variables that mirror the hardware debug
31405 registers. Use @code{ON} to enable, @code{OFF} to disable. If
31406 enabled, the debug registers values are shown when @value{GDBN} inserts or
31407 removes a hardware breakpoint or watchpoint, and when the inferior
31408 triggers a hardware-assisted breakpoint or watchpoint.
31410 @kindex maint set show-all-tib
31411 @kindex maint show show-all-tib
31412 @item maint set show-all-tib
31413 @itemx maint show show-all-tib
31414 Control whether to show all non zero areas within a 1k block starting
31415 at thread local base, when using the @samp{info w32 thread-information-block}
31418 @kindex maint space
31419 @cindex memory used by commands
31421 Control whether to display memory usage for each command. If set to a
31422 nonzero value, @value{GDBN} will display how much memory each command
31423 took, following the command's own output. This can also be requested
31424 by invoking @value{GDBN} with the @option{--statistics} command-line
31425 switch (@pxref{Mode Options}).
31428 @cindex time of command execution
31430 Control whether to display the execution time for each command. If
31431 set to a nonzero value, @value{GDBN} will display how much time it
31432 took to execute each command, following the command's own output.
31433 The time is not printed for the commands that run the target, since
31434 there's no mechanism currently to compute how much time was spend
31435 by @value{GDBN} and how much time was spend by the program been debugged.
31436 it's not possibly currently
31437 This can also be requested by invoking @value{GDBN} with the
31438 @option{--statistics} command-line switch (@pxref{Mode Options}).
31440 @kindex maint translate-address
31441 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
31442 Find the symbol stored at the location specified by the address
31443 @var{addr} and an optional section name @var{section}. If found,
31444 @value{GDBN} prints the name of the closest symbol and an offset from
31445 the symbol's location to the specified address. This is similar to
31446 the @code{info address} command (@pxref{Symbols}), except that this
31447 command also allows to find symbols in other sections.
31449 If section was not specified, the section in which the symbol was found
31450 is also printed. For dynamically linked executables, the name of
31451 executable or shared library containing the symbol is printed as well.
31455 The following command is useful for non-interactive invocations of
31456 @value{GDBN}, such as in the test suite.
31459 @item set watchdog @var{nsec}
31460 @kindex set watchdog
31461 @cindex watchdog timer
31462 @cindex timeout for commands
31463 Set the maximum number of seconds @value{GDBN} will wait for the
31464 target operation to finish. If this time expires, @value{GDBN}
31465 reports and error and the command is aborted.
31467 @item show watchdog
31468 Show the current setting of the target wait timeout.
31471 @node Remote Protocol
31472 @appendix @value{GDBN} Remote Serial Protocol
31477 * Stop Reply Packets::
31478 * General Query Packets::
31479 * Architecture-Specific Protocol Details::
31480 * Tracepoint Packets::
31481 * Host I/O Packets::
31483 * Notification Packets::
31484 * Remote Non-Stop::
31485 * Packet Acknowledgment::
31487 * File-I/O Remote Protocol Extension::
31488 * Library List Format::
31489 * Memory Map Format::
31490 * Thread List Format::
31496 There may be occasions when you need to know something about the
31497 protocol---for example, if there is only one serial port to your target
31498 machine, you might want your program to do something special if it
31499 recognizes a packet meant for @value{GDBN}.
31501 In the examples below, @samp{->} and @samp{<-} are used to indicate
31502 transmitted and received data, respectively.
31504 @cindex protocol, @value{GDBN} remote serial
31505 @cindex serial protocol, @value{GDBN} remote
31506 @cindex remote serial protocol
31507 All @value{GDBN} commands and responses (other than acknowledgments
31508 and notifications, see @ref{Notification Packets}) are sent as a
31509 @var{packet}. A @var{packet} is introduced with the character
31510 @samp{$}, the actual @var{packet-data}, and the terminating character
31511 @samp{#} followed by a two-digit @var{checksum}:
31514 @code{$}@var{packet-data}@code{#}@var{checksum}
31518 @cindex checksum, for @value{GDBN} remote
31520 The two-digit @var{checksum} is computed as the modulo 256 sum of all
31521 characters between the leading @samp{$} and the trailing @samp{#} (an
31522 eight bit unsigned checksum).
31524 Implementors should note that prior to @value{GDBN} 5.0 the protocol
31525 specification also included an optional two-digit @var{sequence-id}:
31528 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
31531 @cindex sequence-id, for @value{GDBN} remote
31533 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
31534 has never output @var{sequence-id}s. Stubs that handle packets added
31535 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
31537 When either the host or the target machine receives a packet, the first
31538 response expected is an acknowledgment: either @samp{+} (to indicate
31539 the package was received correctly) or @samp{-} (to request
31543 -> @code{$}@var{packet-data}@code{#}@var{checksum}
31548 The @samp{+}/@samp{-} acknowledgments can be disabled
31549 once a connection is established.
31550 @xref{Packet Acknowledgment}, for details.
31552 The host (@value{GDBN}) sends @var{command}s, and the target (the
31553 debugging stub incorporated in your program) sends a @var{response}. In
31554 the case of step and continue @var{command}s, the response is only sent
31555 when the operation has completed, and the target has again stopped all
31556 threads in all attached processes. This is the default all-stop mode
31557 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
31558 execution mode; see @ref{Remote Non-Stop}, for details.
31560 @var{packet-data} consists of a sequence of characters with the
31561 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
31564 @cindex remote protocol, field separator
31565 Fields within the packet should be separated using @samp{,} @samp{;} or
31566 @samp{:}. Except where otherwise noted all numbers are represented in
31567 @sc{hex} with leading zeros suppressed.
31569 Implementors should note that prior to @value{GDBN} 5.0, the character
31570 @samp{:} could not appear as the third character in a packet (as it
31571 would potentially conflict with the @var{sequence-id}).
31573 @cindex remote protocol, binary data
31574 @anchor{Binary Data}
31575 Binary data in most packets is encoded either as two hexadecimal
31576 digits per byte of binary data. This allowed the traditional remote
31577 protocol to work over connections which were only seven-bit clean.
31578 Some packets designed more recently assume an eight-bit clean
31579 connection, and use a more efficient encoding to send and receive
31582 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
31583 as an escape character. Any escaped byte is transmitted as the escape
31584 character followed by the original character XORed with @code{0x20}.
31585 For example, the byte @code{0x7d} would be transmitted as the two
31586 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
31587 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
31588 @samp{@}}) must always be escaped. Responses sent by the stub
31589 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
31590 is not interpreted as the start of a run-length encoded sequence
31593 Response @var{data} can be run-length encoded to save space.
31594 Run-length encoding replaces runs of identical characters with one
31595 instance of the repeated character, followed by a @samp{*} and a
31596 repeat count. The repeat count is itself sent encoded, to avoid
31597 binary characters in @var{data}: a value of @var{n} is sent as
31598 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
31599 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
31600 code 32) for a repeat count of 3. (This is because run-length
31601 encoding starts to win for counts 3 or more.) Thus, for example,
31602 @samp{0* } is a run-length encoding of ``0000'': the space character
31603 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
31606 The printable characters @samp{#} and @samp{$} or with a numeric value
31607 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
31608 seven repeats (@samp{$}) can be expanded using a repeat count of only
31609 five (@samp{"}). For example, @samp{00000000} can be encoded as
31612 The error response returned for some packets includes a two character
31613 error number. That number is not well defined.
31615 @cindex empty response, for unsupported packets
31616 For any @var{command} not supported by the stub, an empty response
31617 (@samp{$#00}) should be returned. That way it is possible to extend the
31618 protocol. A newer @value{GDBN} can tell if a packet is supported based
31621 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
31622 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
31628 The following table provides a complete list of all currently defined
31629 @var{command}s and their corresponding response @var{data}.
31630 @xref{File-I/O Remote Protocol Extension}, for details about the File
31631 I/O extension of the remote protocol.
31633 Each packet's description has a template showing the packet's overall
31634 syntax, followed by an explanation of the packet's meaning. We
31635 include spaces in some of the templates for clarity; these are not
31636 part of the packet's syntax. No @value{GDBN} packet uses spaces to
31637 separate its components. For example, a template like @samp{foo
31638 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
31639 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
31640 @var{baz}. @value{GDBN} does not transmit a space character between the
31641 @samp{foo} and the @var{bar}, or between the @var{bar} and the
31644 @cindex @var{thread-id}, in remote protocol
31645 @anchor{thread-id syntax}
31646 Several packets and replies include a @var{thread-id} field to identify
31647 a thread. Normally these are positive numbers with a target-specific
31648 interpretation, formatted as big-endian hex strings. A @var{thread-id}
31649 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
31652 In addition, the remote protocol supports a multiprocess feature in
31653 which the @var{thread-id} syntax is extended to optionally include both
31654 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
31655 The @var{pid} (process) and @var{tid} (thread) components each have the
31656 format described above: a positive number with target-specific
31657 interpretation formatted as a big-endian hex string, literal @samp{-1}
31658 to indicate all processes or threads (respectively), or @samp{0} to
31659 indicate an arbitrary process or thread. Specifying just a process, as
31660 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
31661 error to specify all processes but a specific thread, such as
31662 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
31663 for those packets and replies explicitly documented to include a process
31664 ID, rather than a @var{thread-id}.
31666 The multiprocess @var{thread-id} syntax extensions are only used if both
31667 @value{GDBN} and the stub report support for the @samp{multiprocess}
31668 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
31671 Note that all packet forms beginning with an upper- or lower-case
31672 letter, other than those described here, are reserved for future use.
31674 Here are the packet descriptions.
31679 @cindex @samp{!} packet
31680 @anchor{extended mode}
31681 Enable extended mode. In extended mode, the remote server is made
31682 persistent. The @samp{R} packet is used to restart the program being
31688 The remote target both supports and has enabled extended mode.
31692 @cindex @samp{?} packet
31693 Indicate the reason the target halted. The reply is the same as for
31694 step and continue. This packet has a special interpretation when the
31695 target is in non-stop mode; see @ref{Remote Non-Stop}.
31698 @xref{Stop Reply Packets}, for the reply specifications.
31700 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
31701 @cindex @samp{A} packet
31702 Initialized @code{argv[]} array passed into program. @var{arglen}
31703 specifies the number of bytes in the hex encoded byte stream
31704 @var{arg}. See @code{gdbserver} for more details.
31709 The arguments were set.
31715 @cindex @samp{b} packet
31716 (Don't use this packet; its behavior is not well-defined.)
31717 Change the serial line speed to @var{baud}.
31719 JTC: @emph{When does the transport layer state change? When it's
31720 received, or after the ACK is transmitted. In either case, there are
31721 problems if the command or the acknowledgment packet is dropped.}
31723 Stan: @emph{If people really wanted to add something like this, and get
31724 it working for the first time, they ought to modify ser-unix.c to send
31725 some kind of out-of-band message to a specially-setup stub and have the
31726 switch happen "in between" packets, so that from remote protocol's point
31727 of view, nothing actually happened.}
31729 @item B @var{addr},@var{mode}
31730 @cindex @samp{B} packet
31731 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
31732 breakpoint at @var{addr}.
31734 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
31735 (@pxref{insert breakpoint or watchpoint packet}).
31737 @cindex @samp{bc} packet
31740 Backward continue. Execute the target system in reverse. No parameter.
31741 @xref{Reverse Execution}, for more information.
31744 @xref{Stop Reply Packets}, for the reply specifications.
31746 @cindex @samp{bs} packet
31749 Backward single step. Execute one instruction in reverse. No parameter.
31750 @xref{Reverse Execution}, for more information.
31753 @xref{Stop Reply Packets}, for the reply specifications.
31755 @item c @r{[}@var{addr}@r{]}
31756 @cindex @samp{c} packet
31757 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
31758 resume at current address.
31761 @xref{Stop Reply Packets}, for the reply specifications.
31763 @item C @var{sig}@r{[};@var{addr}@r{]}
31764 @cindex @samp{C} packet
31765 Continue with signal @var{sig} (hex signal number). If
31766 @samp{;@var{addr}} is omitted, resume at same address.
31769 @xref{Stop Reply Packets}, for the reply specifications.
31772 @cindex @samp{d} packet
31775 Don't use this packet; instead, define a general set packet
31776 (@pxref{General Query Packets}).
31780 @cindex @samp{D} packet
31781 The first form of the packet is used to detach @value{GDBN} from the
31782 remote system. It is sent to the remote target
31783 before @value{GDBN} disconnects via the @code{detach} command.
31785 The second form, including a process ID, is used when multiprocess
31786 protocol extensions are enabled (@pxref{multiprocess extensions}), to
31787 detach only a specific process. The @var{pid} is specified as a
31788 big-endian hex string.
31798 @item F @var{RC},@var{EE},@var{CF};@var{XX}
31799 @cindex @samp{F} packet
31800 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
31801 This is part of the File-I/O protocol extension. @xref{File-I/O
31802 Remote Protocol Extension}, for the specification.
31805 @anchor{read registers packet}
31806 @cindex @samp{g} packet
31807 Read general registers.
31811 @item @var{XX@dots{}}
31812 Each byte of register data is described by two hex digits. The bytes
31813 with the register are transmitted in target byte order. The size of
31814 each register and their position within the @samp{g} packet are
31815 determined by the @value{GDBN} internal gdbarch functions
31816 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
31817 specification of several standard @samp{g} packets is specified below.
31819 When reading registers from a trace frame (@pxref{Analyze Collected
31820 Data,,Using the Collected Data}), the stub may also return a string of
31821 literal @samp{x}'s in place of the register data digits, to indicate
31822 that the corresponding register has not been collected, thus its value
31823 is unavailable. For example, for an architecture with 4 registers of
31824 4 bytes each, the following reply indicates to @value{GDBN} that
31825 registers 0 and 2 have not been collected, while registers 1 and 3
31826 have been collected, and both have zero value:
31830 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
31837 @item G @var{XX@dots{}}
31838 @cindex @samp{G} packet
31839 Write general registers. @xref{read registers packet}, for a
31840 description of the @var{XX@dots{}} data.
31850 @item H @var{c} @var{thread-id}
31851 @cindex @samp{H} packet
31852 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
31853 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
31854 should be @samp{c} for step and continue operations, @samp{g} for other
31855 operations. The thread designator @var{thread-id} has the format and
31856 interpretation described in @ref{thread-id syntax}.
31867 @c 'H': How restrictive (or permissive) is the thread model. If a
31868 @c thread is selected and stopped, are other threads allowed
31869 @c to continue to execute? As I mentioned above, I think the
31870 @c semantics of each command when a thread is selected must be
31871 @c described. For example:
31873 @c 'g': If the stub supports threads and a specific thread is
31874 @c selected, returns the register block from that thread;
31875 @c otherwise returns current registers.
31877 @c 'G' If the stub supports threads and a specific thread is
31878 @c selected, sets the registers of the register block of
31879 @c that thread; otherwise sets current registers.
31881 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
31882 @anchor{cycle step packet}
31883 @cindex @samp{i} packet
31884 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
31885 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
31886 step starting at that address.
31889 @cindex @samp{I} packet
31890 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
31894 @cindex @samp{k} packet
31897 FIXME: @emph{There is no description of how to operate when a specific
31898 thread context has been selected (i.e.@: does 'k' kill only that
31901 @item m @var{addr},@var{length}
31902 @cindex @samp{m} packet
31903 Read @var{length} bytes of memory starting at address @var{addr}.
31904 Note that @var{addr} may not be aligned to any particular boundary.
31906 The stub need not use any particular size or alignment when gathering
31907 data from memory for the response; even if @var{addr} is word-aligned
31908 and @var{length} is a multiple of the word size, the stub is free to
31909 use byte accesses, or not. For this reason, this packet may not be
31910 suitable for accessing memory-mapped I/O devices.
31911 @cindex alignment of remote memory accesses
31912 @cindex size of remote memory accesses
31913 @cindex memory, alignment and size of remote accesses
31917 @item @var{XX@dots{}}
31918 Memory contents; each byte is transmitted as a two-digit hexadecimal
31919 number. The reply may contain fewer bytes than requested if the
31920 server was able to read only part of the region of memory.
31925 @item M @var{addr},@var{length}:@var{XX@dots{}}
31926 @cindex @samp{M} packet
31927 Write @var{length} bytes of memory starting at address @var{addr}.
31928 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
31929 hexadecimal number.
31936 for an error (this includes the case where only part of the data was
31941 @cindex @samp{p} packet
31942 Read the value of register @var{n}; @var{n} is in hex.
31943 @xref{read registers packet}, for a description of how the returned
31944 register value is encoded.
31948 @item @var{XX@dots{}}
31949 the register's value
31953 Indicating an unrecognized @var{query}.
31956 @item P @var{n@dots{}}=@var{r@dots{}}
31957 @anchor{write register packet}
31958 @cindex @samp{P} packet
31959 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
31960 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
31961 digits for each byte in the register (target byte order).
31971 @item q @var{name} @var{params}@dots{}
31972 @itemx Q @var{name} @var{params}@dots{}
31973 @cindex @samp{q} packet
31974 @cindex @samp{Q} packet
31975 General query (@samp{q}) and set (@samp{Q}). These packets are
31976 described fully in @ref{General Query Packets}.
31979 @cindex @samp{r} packet
31980 Reset the entire system.
31982 Don't use this packet; use the @samp{R} packet instead.
31985 @cindex @samp{R} packet
31986 Restart the program being debugged. @var{XX}, while needed, is ignored.
31987 This packet is only available in extended mode (@pxref{extended mode}).
31989 The @samp{R} packet has no reply.
31991 @item s @r{[}@var{addr}@r{]}
31992 @cindex @samp{s} packet
31993 Single step. @var{addr} is the address at which to resume. If
31994 @var{addr} is omitted, resume at same address.
31997 @xref{Stop Reply Packets}, for the reply specifications.
31999 @item S @var{sig}@r{[};@var{addr}@r{]}
32000 @anchor{step with signal packet}
32001 @cindex @samp{S} packet
32002 Step with signal. This is analogous to the @samp{C} packet, but
32003 requests a single-step, rather than a normal resumption of execution.
32006 @xref{Stop Reply Packets}, for the reply specifications.
32008 @item t @var{addr}:@var{PP},@var{MM}
32009 @cindex @samp{t} packet
32010 Search backwards starting at address @var{addr} for a match with pattern
32011 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
32012 @var{addr} must be at least 3 digits.
32014 @item T @var{thread-id}
32015 @cindex @samp{T} packet
32016 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
32021 thread is still alive
32027 Packets starting with @samp{v} are identified by a multi-letter name,
32028 up to the first @samp{;} or @samp{?} (or the end of the packet).
32030 @item vAttach;@var{pid}
32031 @cindex @samp{vAttach} packet
32032 Attach to a new process with the specified process ID @var{pid}.
32033 The process ID is a
32034 hexadecimal integer identifying the process. In all-stop mode, all
32035 threads in the attached process are stopped; in non-stop mode, it may be
32036 attached without being stopped if that is supported by the target.
32038 @c In non-stop mode, on a successful vAttach, the stub should set the
32039 @c current thread to a thread of the newly-attached process. After
32040 @c attaching, GDB queries for the attached process's thread ID with qC.
32041 @c Also note that, from a user perspective, whether or not the
32042 @c target is stopped on attach in non-stop mode depends on whether you
32043 @c use the foreground or background version of the attach command, not
32044 @c on what vAttach does; GDB does the right thing with respect to either
32045 @c stopping or restarting threads.
32047 This packet is only available in extended mode (@pxref{extended mode}).
32053 @item @r{Any stop packet}
32054 for success in all-stop mode (@pxref{Stop Reply Packets})
32056 for success in non-stop mode (@pxref{Remote Non-Stop})
32059 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
32060 @cindex @samp{vCont} packet
32061 Resume the inferior, specifying different actions for each thread.
32062 If an action is specified with no @var{thread-id}, then it is applied to any
32063 threads that don't have a specific action specified; if no default action is
32064 specified then other threads should remain stopped in all-stop mode and
32065 in their current state in non-stop mode.
32066 Specifying multiple
32067 default actions is an error; specifying no actions is also an error.
32068 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
32070 Currently supported actions are:
32076 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
32080 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
32085 The optional argument @var{addr} normally associated with the
32086 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
32087 not supported in @samp{vCont}.
32089 The @samp{t} action is only relevant in non-stop mode
32090 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
32091 A stop reply should be generated for any affected thread not already stopped.
32092 When a thread is stopped by means of a @samp{t} action,
32093 the corresponding stop reply should indicate that the thread has stopped with
32094 signal @samp{0}, regardless of whether the target uses some other signal
32095 as an implementation detail.
32098 @xref{Stop Reply Packets}, for the reply specifications.
32101 @cindex @samp{vCont?} packet
32102 Request a list of actions supported by the @samp{vCont} packet.
32106 @item vCont@r{[};@var{action}@dots{}@r{]}
32107 The @samp{vCont} packet is supported. Each @var{action} is a supported
32108 command in the @samp{vCont} packet.
32110 The @samp{vCont} packet is not supported.
32113 @item vFile:@var{operation}:@var{parameter}@dots{}
32114 @cindex @samp{vFile} packet
32115 Perform a file operation on the target system. For details,
32116 see @ref{Host I/O Packets}.
32118 @item vFlashErase:@var{addr},@var{length}
32119 @cindex @samp{vFlashErase} packet
32120 Direct the stub to erase @var{length} bytes of flash starting at
32121 @var{addr}. The region may enclose any number of flash blocks, but
32122 its start and end must fall on block boundaries, as indicated by the
32123 flash block size appearing in the memory map (@pxref{Memory Map
32124 Format}). @value{GDBN} groups flash memory programming operations
32125 together, and sends a @samp{vFlashDone} request after each group; the
32126 stub is allowed to delay erase operation until the @samp{vFlashDone}
32127 packet is received.
32129 The stub must support @samp{vCont} if it reports support for
32130 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
32131 this case @samp{vCont} actions can be specified to apply to all threads
32132 in a process by using the @samp{p@var{pid}.-1} form of the
32143 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
32144 @cindex @samp{vFlashWrite} packet
32145 Direct the stub to write data to flash address @var{addr}. The data
32146 is passed in binary form using the same encoding as for the @samp{X}
32147 packet (@pxref{Binary Data}). The memory ranges specified by
32148 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
32149 not overlap, and must appear in order of increasing addresses
32150 (although @samp{vFlashErase} packets for higher addresses may already
32151 have been received; the ordering is guaranteed only between
32152 @samp{vFlashWrite} packets). If a packet writes to an address that was
32153 neither erased by a preceding @samp{vFlashErase} packet nor by some other
32154 target-specific method, the results are unpredictable.
32162 for vFlashWrite addressing non-flash memory
32168 @cindex @samp{vFlashDone} packet
32169 Indicate to the stub that flash programming operation is finished.
32170 The stub is permitted to delay or batch the effects of a group of
32171 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
32172 @samp{vFlashDone} packet is received. The contents of the affected
32173 regions of flash memory are unpredictable until the @samp{vFlashDone}
32174 request is completed.
32176 @item vKill;@var{pid}
32177 @cindex @samp{vKill} packet
32178 Kill the process with the specified process ID. @var{pid} is a
32179 hexadecimal integer identifying the process. This packet is used in
32180 preference to @samp{k} when multiprocess protocol extensions are
32181 supported; see @ref{multiprocess extensions}.
32191 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
32192 @cindex @samp{vRun} packet
32193 Run the program @var{filename}, passing it each @var{argument} on its
32194 command line. The file and arguments are hex-encoded strings. If
32195 @var{filename} is an empty string, the stub may use a default program
32196 (e.g.@: the last program run). The program is created in the stopped
32199 @c FIXME: What about non-stop mode?
32201 This packet is only available in extended mode (@pxref{extended mode}).
32207 @item @r{Any stop packet}
32208 for success (@pxref{Stop Reply Packets})
32212 @anchor{vStopped packet}
32213 @cindex @samp{vStopped} packet
32215 In non-stop mode (@pxref{Remote Non-Stop}), acknowledge a previous stop
32216 reply and prompt for the stub to report another one.
32220 @item @r{Any stop packet}
32221 if there is another unreported stop event (@pxref{Stop Reply Packets})
32223 if there are no unreported stop events
32226 @item X @var{addr},@var{length}:@var{XX@dots{}}
32228 @cindex @samp{X} packet
32229 Write data to memory, where the data is transmitted in binary.
32230 @var{addr} is address, @var{length} is number of bytes,
32231 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
32241 @item z @var{type},@var{addr},@var{kind}
32242 @itemx Z @var{type},@var{addr},@var{kind}
32243 @anchor{insert breakpoint or watchpoint packet}
32244 @cindex @samp{z} packet
32245 @cindex @samp{Z} packets
32246 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
32247 watchpoint starting at address @var{address} of kind @var{kind}.
32249 Each breakpoint and watchpoint packet @var{type} is documented
32252 @emph{Implementation notes: A remote target shall return an empty string
32253 for an unrecognized breakpoint or watchpoint packet @var{type}. A
32254 remote target shall support either both or neither of a given
32255 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
32256 avoid potential problems with duplicate packets, the operations should
32257 be implemented in an idempotent way.}
32259 @item z0,@var{addr},@var{kind}
32260 @itemx Z0,@var{addr},@var{kind}
32261 @cindex @samp{z0} packet
32262 @cindex @samp{Z0} packet
32263 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
32264 @var{addr} of type @var{kind}.
32266 A memory breakpoint is implemented by replacing the instruction at
32267 @var{addr} with a software breakpoint or trap instruction. The
32268 @var{kind} is target-specific and typically indicates the size of
32269 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
32270 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
32271 architectures have additional meanings for @var{kind};
32272 see @ref{Architecture-Specific Protocol Details}.
32274 @emph{Implementation note: It is possible for a target to copy or move
32275 code that contains memory breakpoints (e.g., when implementing
32276 overlays). The behavior of this packet, in the presence of such a
32277 target, is not defined.}
32289 @item z1,@var{addr},@var{kind}
32290 @itemx Z1,@var{addr},@var{kind}
32291 @cindex @samp{z1} packet
32292 @cindex @samp{Z1} packet
32293 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
32294 address @var{addr}.
32296 A hardware breakpoint is implemented using a mechanism that is not
32297 dependant on being able to modify the target's memory. @var{kind}
32298 has the same meaning as in @samp{Z0} packets.
32300 @emph{Implementation note: A hardware breakpoint is not affected by code
32313 @item z2,@var{addr},@var{kind}
32314 @itemx Z2,@var{addr},@var{kind}
32315 @cindex @samp{z2} packet
32316 @cindex @samp{Z2} packet
32317 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
32318 @var{kind} is interpreted as the number of bytes to watch.
32330 @item z3,@var{addr},@var{kind}
32331 @itemx Z3,@var{addr},@var{kind}
32332 @cindex @samp{z3} packet
32333 @cindex @samp{Z3} packet
32334 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
32335 @var{kind} is interpreted as the number of bytes to watch.
32347 @item z4,@var{addr},@var{kind}
32348 @itemx Z4,@var{addr},@var{kind}
32349 @cindex @samp{z4} packet
32350 @cindex @samp{Z4} packet
32351 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
32352 @var{kind} is interpreted as the number of bytes to watch.
32366 @node Stop Reply Packets
32367 @section Stop Reply Packets
32368 @cindex stop reply packets
32370 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
32371 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
32372 receive any of the below as a reply. Except for @samp{?}
32373 and @samp{vStopped}, that reply is only returned
32374 when the target halts. In the below the exact meaning of @dfn{signal
32375 number} is defined by the header @file{include/gdb/signals.h} in the
32376 @value{GDBN} source code.
32378 As in the description of request packets, we include spaces in the
32379 reply templates for clarity; these are not part of the reply packet's
32380 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
32386 The program received signal number @var{AA} (a two-digit hexadecimal
32387 number). This is equivalent to a @samp{T} response with no
32388 @var{n}:@var{r} pairs.
32390 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
32391 @cindex @samp{T} packet reply
32392 The program received signal number @var{AA} (a two-digit hexadecimal
32393 number). This is equivalent to an @samp{S} response, except that the
32394 @samp{@var{n}:@var{r}} pairs can carry values of important registers
32395 and other information directly in the stop reply packet, reducing
32396 round-trip latency. Single-step and breakpoint traps are reported
32397 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
32401 If @var{n} is a hexadecimal number, it is a register number, and the
32402 corresponding @var{r} gives that register's value. @var{r} is a
32403 series of bytes in target byte order, with each byte given by a
32404 two-digit hex number.
32407 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
32408 the stopped thread, as specified in @ref{thread-id syntax}.
32411 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
32412 the core on which the stop event was detected.
32415 If @var{n} is a recognized @dfn{stop reason}, it describes a more
32416 specific event that stopped the target. The currently defined stop
32417 reasons are listed below. @var{aa} should be @samp{05}, the trap
32418 signal. At most one stop reason should be present.
32421 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
32422 and go on to the next; this allows us to extend the protocol in the
32426 The currently defined stop reasons are:
32432 The packet indicates a watchpoint hit, and @var{r} is the data address, in
32435 @cindex shared library events, remote reply
32437 The packet indicates that the loaded libraries have changed.
32438 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
32439 list of loaded libraries. @var{r} is ignored.
32441 @cindex replay log events, remote reply
32443 The packet indicates that the target cannot continue replaying
32444 logged execution events, because it has reached the end (or the
32445 beginning when executing backward) of the log. The value of @var{r}
32446 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
32447 for more information.
32451 @itemx W @var{AA} ; process:@var{pid}
32452 The process exited, and @var{AA} is the exit status. This is only
32453 applicable to certain targets.
32455 The second form of the response, including the process ID of the exited
32456 process, can be used only when @value{GDBN} has reported support for
32457 multiprocess protocol extensions; see @ref{multiprocess extensions}.
32458 The @var{pid} is formatted as a big-endian hex string.
32461 @itemx X @var{AA} ; process:@var{pid}
32462 The process terminated with signal @var{AA}.
32464 The second form of the response, including the process ID of the
32465 terminated process, can be used only when @value{GDBN} has reported
32466 support for multiprocess protocol extensions; see @ref{multiprocess
32467 extensions}. The @var{pid} is formatted as a big-endian hex string.
32469 @item O @var{XX}@dots{}
32470 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
32471 written as the program's console output. This can happen at any time
32472 while the program is running and the debugger should continue to wait
32473 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
32475 @item F @var{call-id},@var{parameter}@dots{}
32476 @var{call-id} is the identifier which says which host system call should
32477 be called. This is just the name of the function. Translation into the
32478 correct system call is only applicable as it's defined in @value{GDBN}.
32479 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
32482 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
32483 this very system call.
32485 The target replies with this packet when it expects @value{GDBN} to
32486 call a host system call on behalf of the target. @value{GDBN} replies
32487 with an appropriate @samp{F} packet and keeps up waiting for the next
32488 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
32489 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
32490 Protocol Extension}, for more details.
32494 @node General Query Packets
32495 @section General Query Packets
32496 @cindex remote query requests
32498 Packets starting with @samp{q} are @dfn{general query packets};
32499 packets starting with @samp{Q} are @dfn{general set packets}. General
32500 query and set packets are a semi-unified form for retrieving and
32501 sending information to and from the stub.
32503 The initial letter of a query or set packet is followed by a name
32504 indicating what sort of thing the packet applies to. For example,
32505 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
32506 definitions with the stub. These packet names follow some
32511 The name must not contain commas, colons or semicolons.
32513 Most @value{GDBN} query and set packets have a leading upper case
32516 The names of custom vendor packets should use a company prefix, in
32517 lower case, followed by a period. For example, packets designed at
32518 the Acme Corporation might begin with @samp{qacme.foo} (for querying
32519 foos) or @samp{Qacme.bar} (for setting bars).
32522 The name of a query or set packet should be separated from any
32523 parameters by a @samp{:}; the parameters themselves should be
32524 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
32525 full packet name, and check for a separator or the end of the packet,
32526 in case two packet names share a common prefix. New packets should not begin
32527 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
32528 packets predate these conventions, and have arguments without any terminator
32529 for the packet name; we suspect they are in widespread use in places that
32530 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
32531 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
32534 Like the descriptions of the other packets, each description here
32535 has a template showing the packet's overall syntax, followed by an
32536 explanation of the packet's meaning. We include spaces in some of the
32537 templates for clarity; these are not part of the packet's syntax. No
32538 @value{GDBN} packet uses spaces to separate its components.
32540 Here are the currently defined query and set packets:
32544 @item QAllow:@var{op}:@var{val}@dots{}
32545 @cindex @samp{QAllow} packet
32546 Specify which operations @value{GDBN} expects to request of the
32547 target, as a semicolon-separated list of operation name and value
32548 pairs. Possible values for @var{op} include @samp{WriteReg},
32549 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
32550 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
32551 indicating that @value{GDBN} will not request the operation, or 1,
32552 indicating that it may. (The target can then use this to set up its
32553 own internals optimally, for instance if the debugger never expects to
32554 insert breakpoints, it may not need to install its own trap handler.)
32557 @cindex current thread, remote request
32558 @cindex @samp{qC} packet
32559 Return the current thread ID.
32563 @item QC @var{thread-id}
32564 Where @var{thread-id} is a thread ID as documented in
32565 @ref{thread-id syntax}.
32566 @item @r{(anything else)}
32567 Any other reply implies the old thread ID.
32570 @item qCRC:@var{addr},@var{length}
32571 @cindex CRC of memory block, remote request
32572 @cindex @samp{qCRC} packet
32573 Compute the CRC checksum of a block of memory using CRC-32 defined in
32574 IEEE 802.3. The CRC is computed byte at a time, taking the most
32575 significant bit of each byte first. The initial pattern code
32576 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
32578 @emph{Note:} This is the same CRC used in validating separate debug
32579 files (@pxref{Separate Debug Files, , Debugging Information in Separate
32580 Files}). However the algorithm is slightly different. When validating
32581 separate debug files, the CRC is computed taking the @emph{least}
32582 significant bit of each byte first, and the final result is inverted to
32583 detect trailing zeros.
32588 An error (such as memory fault)
32589 @item C @var{crc32}
32590 The specified memory region's checksum is @var{crc32}.
32594 @itemx qsThreadInfo
32595 @cindex list active threads, remote request
32596 @cindex @samp{qfThreadInfo} packet
32597 @cindex @samp{qsThreadInfo} packet
32598 Obtain a list of all active thread IDs from the target (OS). Since there
32599 may be too many active threads to fit into one reply packet, this query
32600 works iteratively: it may require more than one query/reply sequence to
32601 obtain the entire list of threads. The first query of the sequence will
32602 be the @samp{qfThreadInfo} query; subsequent queries in the
32603 sequence will be the @samp{qsThreadInfo} query.
32605 NOTE: This packet replaces the @samp{qL} query (see below).
32609 @item m @var{thread-id}
32611 @item m @var{thread-id},@var{thread-id}@dots{}
32612 a comma-separated list of thread IDs
32614 (lower case letter @samp{L}) denotes end of list.
32617 In response to each query, the target will reply with a list of one or
32618 more thread IDs, separated by commas.
32619 @value{GDBN} will respond to each reply with a request for more thread
32620 ids (using the @samp{qs} form of the query), until the target responds
32621 with @samp{l} (lower-case ell, for @dfn{last}).
32622 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
32625 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
32626 @cindex get thread-local storage address, remote request
32627 @cindex @samp{qGetTLSAddr} packet
32628 Fetch the address associated with thread local storage specified
32629 by @var{thread-id}, @var{offset}, and @var{lm}.
32631 @var{thread-id} is the thread ID associated with the
32632 thread for which to fetch the TLS address. @xref{thread-id syntax}.
32634 @var{offset} is the (big endian, hex encoded) offset associated with the
32635 thread local variable. (This offset is obtained from the debug
32636 information associated with the variable.)
32638 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
32639 the load module associated with the thread local storage. For example,
32640 a @sc{gnu}/Linux system will pass the link map address of the shared
32641 object associated with the thread local storage under consideration.
32642 Other operating environments may choose to represent the load module
32643 differently, so the precise meaning of this parameter will vary.
32647 @item @var{XX}@dots{}
32648 Hex encoded (big endian) bytes representing the address of the thread
32649 local storage requested.
32652 An error occurred. @var{nn} are hex digits.
32655 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
32658 @item qGetTIBAddr:@var{thread-id}
32659 @cindex get thread information block address
32660 @cindex @samp{qGetTIBAddr} packet
32661 Fetch address of the Windows OS specific Thread Information Block.
32663 @var{thread-id} is the thread ID associated with the thread.
32667 @item @var{XX}@dots{}
32668 Hex encoded (big endian) bytes representing the linear address of the
32669 thread information block.
32672 An error occured. This means that either the thread was not found, or the
32673 address could not be retrieved.
32676 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
32679 @item qL @var{startflag} @var{threadcount} @var{nextthread}
32680 Obtain thread information from RTOS. Where: @var{startflag} (one hex
32681 digit) is one to indicate the first query and zero to indicate a
32682 subsequent query; @var{threadcount} (two hex digits) is the maximum
32683 number of threads the response packet can contain; and @var{nextthread}
32684 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
32685 returned in the response as @var{argthread}.
32687 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
32691 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
32692 Where: @var{count} (two hex digits) is the number of threads being
32693 returned; @var{done} (one hex digit) is zero to indicate more threads
32694 and one indicates no further threads; @var{argthreadid} (eight hex
32695 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
32696 is a sequence of thread IDs from the target. @var{threadid} (eight hex
32697 digits). See @code{remote.c:parse_threadlist_response()}.
32701 @cindex section offsets, remote request
32702 @cindex @samp{qOffsets} packet
32703 Get section offsets that the target used when relocating the downloaded
32708 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
32709 Relocate the @code{Text} section by @var{xxx} from its original address.
32710 Relocate the @code{Data} section by @var{yyy} from its original address.
32711 If the object file format provides segment information (e.g.@: @sc{elf}
32712 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
32713 segments by the supplied offsets.
32715 @emph{Note: while a @code{Bss} offset may be included in the response,
32716 @value{GDBN} ignores this and instead applies the @code{Data} offset
32717 to the @code{Bss} section.}
32719 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
32720 Relocate the first segment of the object file, which conventionally
32721 contains program code, to a starting address of @var{xxx}. If
32722 @samp{DataSeg} is specified, relocate the second segment, which
32723 conventionally contains modifiable data, to a starting address of
32724 @var{yyy}. @value{GDBN} will report an error if the object file
32725 does not contain segment information, or does not contain at least
32726 as many segments as mentioned in the reply. Extra segments are
32727 kept at fixed offsets relative to the last relocated segment.
32730 @item qP @var{mode} @var{thread-id}
32731 @cindex thread information, remote request
32732 @cindex @samp{qP} packet
32733 Returns information on @var{thread-id}. Where: @var{mode} is a hex
32734 encoded 32 bit mode; @var{thread-id} is a thread ID
32735 (@pxref{thread-id syntax}).
32737 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
32740 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
32744 @cindex non-stop mode, remote request
32745 @cindex @samp{QNonStop} packet
32747 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
32748 @xref{Remote Non-Stop}, for more information.
32753 The request succeeded.
32756 An error occurred. @var{nn} are hex digits.
32759 An empty reply indicates that @samp{QNonStop} is not supported by
32763 This packet is not probed by default; the remote stub must request it,
32764 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32765 Use of this packet is controlled by the @code{set non-stop} command;
32766 @pxref{Non-Stop Mode}.
32768 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
32769 @cindex pass signals to inferior, remote request
32770 @cindex @samp{QPassSignals} packet
32771 @anchor{QPassSignals}
32772 Each listed @var{signal} should be passed directly to the inferior process.
32773 Signals are numbered identically to continue packets and stop replies
32774 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
32775 strictly greater than the previous item. These signals do not need to stop
32776 the inferior, or be reported to @value{GDBN}. All other signals should be
32777 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
32778 combine; any earlier @samp{QPassSignals} list is completely replaced by the
32779 new list. This packet improves performance when using @samp{handle
32780 @var{signal} nostop noprint pass}.
32785 The request succeeded.
32788 An error occurred. @var{nn} are hex digits.
32791 An empty reply indicates that @samp{QPassSignals} is not supported by
32795 Use of this packet is controlled by the @code{set remote pass-signals}
32796 command (@pxref{Remote Configuration, set remote pass-signals}).
32797 This packet is not probed by default; the remote stub must request it,
32798 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
32800 @item qRcmd,@var{command}
32801 @cindex execute remote command, remote request
32802 @cindex @samp{qRcmd} packet
32803 @var{command} (hex encoded) is passed to the local interpreter for
32804 execution. Invalid commands should be reported using the output
32805 string. Before the final result packet, the target may also respond
32806 with a number of intermediate @samp{O@var{output}} console output
32807 packets. @emph{Implementors should note that providing access to a
32808 stubs's interpreter may have security implications}.
32813 A command response with no output.
32815 A command response with the hex encoded output string @var{OUTPUT}.
32817 Indicate a badly formed request.
32819 An empty reply indicates that @samp{qRcmd} is not recognized.
32822 (Note that the @code{qRcmd} packet's name is separated from the
32823 command by a @samp{,}, not a @samp{:}, contrary to the naming
32824 conventions above. Please don't use this packet as a model for new
32827 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
32828 @cindex searching memory, in remote debugging
32829 @cindex @samp{qSearch:memory} packet
32830 @anchor{qSearch memory}
32831 Search @var{length} bytes at @var{address} for @var{search-pattern}.
32832 @var{address} and @var{length} are encoded in hex.
32833 @var{search-pattern} is a sequence of bytes, hex encoded.
32838 The pattern was not found.
32840 The pattern was found at @var{address}.
32842 A badly formed request or an error was encountered while searching memory.
32844 An empty reply indicates that @samp{qSearch:memory} is not recognized.
32847 @item QStartNoAckMode
32848 @cindex @samp{QStartNoAckMode} packet
32849 @anchor{QStartNoAckMode}
32850 Request that the remote stub disable the normal @samp{+}/@samp{-}
32851 protocol acknowledgments (@pxref{Packet Acknowledgment}).
32856 The stub has switched to no-acknowledgment mode.
32857 @value{GDBN} acknowledges this reponse,
32858 but neither the stub nor @value{GDBN} shall send or expect further
32859 @samp{+}/@samp{-} acknowledgments in the current connection.
32861 An empty reply indicates that the stub does not support no-acknowledgment mode.
32864 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
32865 @cindex supported packets, remote query
32866 @cindex features of the remote protocol
32867 @cindex @samp{qSupported} packet
32868 @anchor{qSupported}
32869 Tell the remote stub about features supported by @value{GDBN}, and
32870 query the stub for features it supports. This packet allows
32871 @value{GDBN} and the remote stub to take advantage of each others'
32872 features. @samp{qSupported} also consolidates multiple feature probes
32873 at startup, to improve @value{GDBN} performance---a single larger
32874 packet performs better than multiple smaller probe packets on
32875 high-latency links. Some features may enable behavior which must not
32876 be on by default, e.g.@: because it would confuse older clients or
32877 stubs. Other features may describe packets which could be
32878 automatically probed for, but are not. These features must be
32879 reported before @value{GDBN} will use them. This ``default
32880 unsupported'' behavior is not appropriate for all packets, but it
32881 helps to keep the initial connection time under control with new
32882 versions of @value{GDBN} which support increasing numbers of packets.
32886 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
32887 The stub supports or does not support each returned @var{stubfeature},
32888 depending on the form of each @var{stubfeature} (see below for the
32891 An empty reply indicates that @samp{qSupported} is not recognized,
32892 or that no features needed to be reported to @value{GDBN}.
32895 The allowed forms for each feature (either a @var{gdbfeature} in the
32896 @samp{qSupported} packet, or a @var{stubfeature} in the response)
32900 @item @var{name}=@var{value}
32901 The remote protocol feature @var{name} is supported, and associated
32902 with the specified @var{value}. The format of @var{value} depends
32903 on the feature, but it must not include a semicolon.
32905 The remote protocol feature @var{name} is supported, and does not
32906 need an associated value.
32908 The remote protocol feature @var{name} is not supported.
32910 The remote protocol feature @var{name} may be supported, and
32911 @value{GDBN} should auto-detect support in some other way when it is
32912 needed. This form will not be used for @var{gdbfeature} notifications,
32913 but may be used for @var{stubfeature} responses.
32916 Whenever the stub receives a @samp{qSupported} request, the
32917 supplied set of @value{GDBN} features should override any previous
32918 request. This allows @value{GDBN} to put the stub in a known
32919 state, even if the stub had previously been communicating with
32920 a different version of @value{GDBN}.
32922 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
32927 This feature indicates whether @value{GDBN} supports multiprocess
32928 extensions to the remote protocol. @value{GDBN} does not use such
32929 extensions unless the stub also reports that it supports them by
32930 including @samp{multiprocess+} in its @samp{qSupported} reply.
32931 @xref{multiprocess extensions}, for details.
32934 This feature indicates that @value{GDBN} supports the XML target
32935 description. If the stub sees @samp{xmlRegisters=} with target
32936 specific strings separated by a comma, it will report register
32940 This feature indicates whether @value{GDBN} supports the
32941 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
32942 instruction reply packet}).
32945 Stubs should ignore any unknown values for
32946 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
32947 packet supports receiving packets of unlimited length (earlier
32948 versions of @value{GDBN} may reject overly long responses). Additional values
32949 for @var{gdbfeature} may be defined in the future to let the stub take
32950 advantage of new features in @value{GDBN}, e.g.@: incompatible
32951 improvements in the remote protocol---the @samp{multiprocess} feature is
32952 an example of such a feature. The stub's reply should be independent
32953 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
32954 describes all the features it supports, and then the stub replies with
32955 all the features it supports.
32957 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
32958 responses, as long as each response uses one of the standard forms.
32960 Some features are flags. A stub which supports a flag feature
32961 should respond with a @samp{+} form response. Other features
32962 require values, and the stub should respond with an @samp{=}
32965 Each feature has a default value, which @value{GDBN} will use if
32966 @samp{qSupported} is not available or if the feature is not mentioned
32967 in the @samp{qSupported} response. The default values are fixed; a
32968 stub is free to omit any feature responses that match the defaults.
32970 Not all features can be probed, but for those which can, the probing
32971 mechanism is useful: in some cases, a stub's internal
32972 architecture may not allow the protocol layer to know some information
32973 about the underlying target in advance. This is especially common in
32974 stubs which may be configured for multiple targets.
32976 These are the currently defined stub features and their properties:
32978 @multitable @columnfractions 0.35 0.2 0.12 0.2
32979 @c NOTE: The first row should be @headitem, but we do not yet require
32980 @c a new enough version of Texinfo (4.7) to use @headitem.
32982 @tab Value Required
32986 @item @samp{PacketSize}
32991 @item @samp{qXfer:auxv:read}
32996 @item @samp{qXfer:features:read}
33001 @item @samp{qXfer:libraries:read}
33006 @item @samp{qXfer:memory-map:read}
33011 @item @samp{qXfer:sdata:read}
33016 @item @samp{qXfer:spu:read}
33021 @item @samp{qXfer:spu:write}
33026 @item @samp{qXfer:siginfo:read}
33031 @item @samp{qXfer:siginfo:write}
33036 @item @samp{qXfer:threads:read}
33042 @item @samp{QNonStop}
33047 @item @samp{QPassSignals}
33052 @item @samp{QStartNoAckMode}
33057 @item @samp{multiprocess}
33062 @item @samp{ConditionalTracepoints}
33067 @item @samp{ReverseContinue}
33072 @item @samp{ReverseStep}
33077 @item @samp{TracepointSource}
33082 @item @samp{QAllow}
33089 These are the currently defined stub features, in more detail:
33092 @cindex packet size, remote protocol
33093 @item PacketSize=@var{bytes}
33094 The remote stub can accept packets up to at least @var{bytes} in
33095 length. @value{GDBN} will send packets up to this size for bulk
33096 transfers, and will never send larger packets. This is a limit on the
33097 data characters in the packet, including the frame and checksum.
33098 There is no trailing NUL byte in a remote protocol packet; if the stub
33099 stores packets in a NUL-terminated format, it should allow an extra
33100 byte in its buffer for the NUL. If this stub feature is not supported,
33101 @value{GDBN} guesses based on the size of the @samp{g} packet response.
33103 @item qXfer:auxv:read
33104 The remote stub understands the @samp{qXfer:auxv:read} packet
33105 (@pxref{qXfer auxiliary vector read}).
33107 @item qXfer:features:read
33108 The remote stub understands the @samp{qXfer:features:read} packet
33109 (@pxref{qXfer target description read}).
33111 @item qXfer:libraries:read
33112 The remote stub understands the @samp{qXfer:libraries:read} packet
33113 (@pxref{qXfer library list read}).
33115 @item qXfer:memory-map:read
33116 The remote stub understands the @samp{qXfer:memory-map:read} packet
33117 (@pxref{qXfer memory map read}).
33119 @item qXfer:sdata:read
33120 The remote stub understands the @samp{qXfer:sdata:read} packet
33121 (@pxref{qXfer sdata read}).
33123 @item qXfer:spu:read
33124 The remote stub understands the @samp{qXfer:spu:read} packet
33125 (@pxref{qXfer spu read}).
33127 @item qXfer:spu:write
33128 The remote stub understands the @samp{qXfer:spu:write} packet
33129 (@pxref{qXfer spu write}).
33131 @item qXfer:siginfo:read
33132 The remote stub understands the @samp{qXfer:siginfo:read} packet
33133 (@pxref{qXfer siginfo read}).
33135 @item qXfer:siginfo:write
33136 The remote stub understands the @samp{qXfer:siginfo:write} packet
33137 (@pxref{qXfer siginfo write}).
33139 @item qXfer:threads:read
33140 The remote stub understands the @samp{qXfer:threads:read} packet
33141 (@pxref{qXfer threads read}).
33144 The remote stub understands the @samp{QNonStop} packet
33145 (@pxref{QNonStop}).
33148 The remote stub understands the @samp{QPassSignals} packet
33149 (@pxref{QPassSignals}).
33151 @item QStartNoAckMode
33152 The remote stub understands the @samp{QStartNoAckMode} packet and
33153 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
33156 @anchor{multiprocess extensions}
33157 @cindex multiprocess extensions, in remote protocol
33158 The remote stub understands the multiprocess extensions to the remote
33159 protocol syntax. The multiprocess extensions affect the syntax of
33160 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
33161 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
33162 replies. Note that reporting this feature indicates support for the
33163 syntactic extensions only, not that the stub necessarily supports
33164 debugging of more than one process at a time. The stub must not use
33165 multiprocess extensions in packet replies unless @value{GDBN} has also
33166 indicated it supports them in its @samp{qSupported} request.
33168 @item qXfer:osdata:read
33169 The remote stub understands the @samp{qXfer:osdata:read} packet
33170 ((@pxref{qXfer osdata read}).
33172 @item ConditionalTracepoints
33173 The remote stub accepts and implements conditional expressions defined
33174 for tracepoints (@pxref{Tracepoint Conditions}).
33176 @item ReverseContinue
33177 The remote stub accepts and implements the reverse continue packet
33181 The remote stub accepts and implements the reverse step packet
33184 @item TracepointSource
33185 The remote stub understands the @samp{QTDPsrc} packet that supplies
33186 the source form of tracepoint definitions.
33189 The remote stub understands the @samp{QAllow} packet.
33191 @item StaticTracepoint
33192 @cindex static tracepoints, in remote protocol
33193 The remote stub supports static tracepoints.
33198 @cindex symbol lookup, remote request
33199 @cindex @samp{qSymbol} packet
33200 Notify the target that @value{GDBN} is prepared to serve symbol lookup
33201 requests. Accept requests from the target for the values of symbols.
33206 The target does not need to look up any (more) symbols.
33207 @item qSymbol:@var{sym_name}
33208 The target requests the value of symbol @var{sym_name} (hex encoded).
33209 @value{GDBN} may provide the value by using the
33210 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
33214 @item qSymbol:@var{sym_value}:@var{sym_name}
33215 Set the value of @var{sym_name} to @var{sym_value}.
33217 @var{sym_name} (hex encoded) is the name of a symbol whose value the
33218 target has previously requested.
33220 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
33221 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
33227 The target does not need to look up any (more) symbols.
33228 @item qSymbol:@var{sym_name}
33229 The target requests the value of a new symbol @var{sym_name} (hex
33230 encoded). @value{GDBN} will continue to supply the values of symbols
33231 (if available), until the target ceases to request them.
33236 @item QTDisconnected
33243 @xref{Tracepoint Packets}.
33245 @item qThreadExtraInfo,@var{thread-id}
33246 @cindex thread attributes info, remote request
33247 @cindex @samp{qThreadExtraInfo} packet
33248 Obtain a printable string description of a thread's attributes from
33249 the target OS. @var{thread-id} is a thread ID;
33250 see @ref{thread-id syntax}. This
33251 string may contain anything that the target OS thinks is interesting
33252 for @value{GDBN} to tell the user about the thread. The string is
33253 displayed in @value{GDBN}'s @code{info threads} display. Some
33254 examples of possible thread extra info strings are @samp{Runnable}, or
33255 @samp{Blocked on Mutex}.
33259 @item @var{XX}@dots{}
33260 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
33261 comprising the printable string containing the extra information about
33262 the thread's attributes.
33265 (Note that the @code{qThreadExtraInfo} packet's name is separated from
33266 the command by a @samp{,}, not a @samp{:}, contrary to the naming
33267 conventions above. Please don't use this packet as a model for new
33282 @xref{Tracepoint Packets}.
33284 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
33285 @cindex read special object, remote request
33286 @cindex @samp{qXfer} packet
33287 @anchor{qXfer read}
33288 Read uninterpreted bytes from the target's special data area
33289 identified by the keyword @var{object}. Request @var{length} bytes
33290 starting at @var{offset} bytes into the data. The content and
33291 encoding of @var{annex} is specific to @var{object}; it can supply
33292 additional details about what data to access.
33294 Here are the specific requests of this form defined so far. All
33295 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
33296 formats, listed below.
33299 @item qXfer:auxv:read::@var{offset},@var{length}
33300 @anchor{qXfer auxiliary vector read}
33301 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
33302 auxiliary vector}. Note @var{annex} must be empty.
33304 This packet is not probed by default; the remote stub must request it,
33305 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33307 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
33308 @anchor{qXfer target description read}
33309 Access the @dfn{target description}. @xref{Target Descriptions}. The
33310 annex specifies which XML document to access. The main description is
33311 always loaded from the @samp{target.xml} annex.
33313 This packet is not probed by default; the remote stub must request it,
33314 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33316 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
33317 @anchor{qXfer library list read}
33318 Access the target's list of loaded libraries. @xref{Library List Format}.
33319 The annex part of the generic @samp{qXfer} packet must be empty
33320 (@pxref{qXfer read}).
33322 Targets which maintain a list of libraries in the program's memory do
33323 not need to implement this packet; it is designed for platforms where
33324 the operating system manages the list of loaded libraries.
33326 This packet is not probed by default; the remote stub must request it,
33327 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33329 @item qXfer:memory-map:read::@var{offset},@var{length}
33330 @anchor{qXfer memory map read}
33331 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
33332 annex part of the generic @samp{qXfer} packet must be empty
33333 (@pxref{qXfer read}).
33335 This packet is not probed by default; the remote stub must request it,
33336 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33338 @item qXfer:sdata:read::@var{offset},@var{length}
33339 @anchor{qXfer sdata read}
33341 Read contents of the extra collected static tracepoint marker
33342 information. The annex part of the generic @samp{qXfer} packet must
33343 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
33346 This packet is not probed by default; the remote stub must request it,
33347 by supplying an appropriate @samp{qSupported} response
33348 (@pxref{qSupported}).
33350 @item qXfer:siginfo:read::@var{offset},@var{length}
33351 @anchor{qXfer siginfo read}
33352 Read contents of the extra signal information on the target
33353 system. The annex part of the generic @samp{qXfer} packet must be
33354 empty (@pxref{qXfer read}).
33356 This packet is not probed by default; the remote stub must request it,
33357 by supplying an appropriate @samp{qSupported} response
33358 (@pxref{qSupported}).
33360 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
33361 @anchor{qXfer spu read}
33362 Read contents of an @code{spufs} file on the target system. The
33363 annex specifies which file to read; it must be of the form
33364 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
33365 in the target process, and @var{name} identifes the @code{spufs} file
33366 in that context to be accessed.
33368 This packet is not probed by default; the remote stub must request it,
33369 by supplying an appropriate @samp{qSupported} response
33370 (@pxref{qSupported}).
33372 @item qXfer:threads:read::@var{offset},@var{length}
33373 @anchor{qXfer threads read}
33374 Access the list of threads on target. @xref{Thread List Format}. The
33375 annex part of the generic @samp{qXfer} packet must be empty
33376 (@pxref{qXfer read}).
33378 This packet is not probed by default; the remote stub must request it,
33379 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33381 @item qXfer:osdata:read::@var{offset},@var{length}
33382 @anchor{qXfer osdata read}
33383 Access the target's @dfn{operating system information}.
33384 @xref{Operating System Information}.
33391 Data @var{data} (@pxref{Binary Data}) has been read from the
33392 target. There may be more data at a higher address (although
33393 it is permitted to return @samp{m} even for the last valid
33394 block of data, as long as at least one byte of data was read).
33395 @var{data} may have fewer bytes than the @var{length} in the
33399 Data @var{data} (@pxref{Binary Data}) has been read from the target.
33400 There is no more data to be read. @var{data} may have fewer bytes
33401 than the @var{length} in the request.
33404 The @var{offset} in the request is at the end of the data.
33405 There is no more data to be read.
33408 The request was malformed, or @var{annex} was invalid.
33411 The offset was invalid, or there was an error encountered reading the data.
33412 @var{nn} is a hex-encoded @code{errno} value.
33415 An empty reply indicates the @var{object} string was not recognized by
33416 the stub, or that the object does not support reading.
33419 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
33420 @cindex write data into object, remote request
33421 @anchor{qXfer write}
33422 Write uninterpreted bytes into the target's special data area
33423 identified by the keyword @var{object}, starting at @var{offset} bytes
33424 into the data. @var{data}@dots{} is the binary-encoded data
33425 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
33426 is specific to @var{object}; it can supply additional details about what data
33429 Here are the specific requests of this form defined so far. All
33430 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
33431 formats, listed below.
33434 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
33435 @anchor{qXfer siginfo write}
33436 Write @var{data} to the extra signal information on the target system.
33437 The annex part of the generic @samp{qXfer} packet must be
33438 empty (@pxref{qXfer write}).
33440 This packet is not probed by default; the remote stub must request it,
33441 by supplying an appropriate @samp{qSupported} response
33442 (@pxref{qSupported}).
33444 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
33445 @anchor{qXfer spu write}
33446 Write @var{data} to an @code{spufs} file on the target system. The
33447 annex specifies which file to write; it must be of the form
33448 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
33449 in the target process, and @var{name} identifes the @code{spufs} file
33450 in that context to be accessed.
33452 This packet is not probed by default; the remote stub must request it,
33453 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
33459 @var{nn} (hex encoded) is the number of bytes written.
33460 This may be fewer bytes than supplied in the request.
33463 The request was malformed, or @var{annex} was invalid.
33466 The offset was invalid, or there was an error encountered writing the data.
33467 @var{nn} is a hex-encoded @code{errno} value.
33470 An empty reply indicates the @var{object} string was not
33471 recognized by the stub, or that the object does not support writing.
33474 @item qXfer:@var{object}:@var{operation}:@dots{}
33475 Requests of this form may be added in the future. When a stub does
33476 not recognize the @var{object} keyword, or its support for
33477 @var{object} does not recognize the @var{operation} keyword, the stub
33478 must respond with an empty packet.
33480 @item qAttached:@var{pid}
33481 @cindex query attached, remote request
33482 @cindex @samp{qAttached} packet
33483 Return an indication of whether the remote server attached to an
33484 existing process or created a new process. When the multiprocess
33485 protocol extensions are supported (@pxref{multiprocess extensions}),
33486 @var{pid} is an integer in hexadecimal format identifying the target
33487 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
33488 the query packet will be simplified as @samp{qAttached}.
33490 This query is used, for example, to know whether the remote process
33491 should be detached or killed when a @value{GDBN} session is ended with
33492 the @code{quit} command.
33497 The remote server attached to an existing process.
33499 The remote server created a new process.
33501 A badly formed request or an error was encountered.
33506 @node Architecture-Specific Protocol Details
33507 @section Architecture-Specific Protocol Details
33509 This section describes how the remote protocol is applied to specific
33510 target architectures. Also see @ref{Standard Target Features}, for
33511 details of XML target descriptions for each architecture.
33515 @subsubsection Breakpoint Kinds
33517 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
33522 16-bit Thumb mode breakpoint.
33525 32-bit Thumb mode (Thumb-2) breakpoint.
33528 32-bit ARM mode breakpoint.
33534 @subsubsection Register Packet Format
33536 The following @code{g}/@code{G} packets have previously been defined.
33537 In the below, some thirty-two bit registers are transferred as
33538 sixty-four bits. Those registers should be zero/sign extended (which?)
33539 to fill the space allocated. Register bytes are transferred in target
33540 byte order. The two nibbles within a register byte are transferred
33541 most-significant - least-significant.
33547 All registers are transferred as thirty-two bit quantities in the order:
33548 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
33549 registers; fsr; fir; fp.
33553 All registers are transferred as sixty-four bit quantities (including
33554 thirty-two bit registers such as @code{sr}). The ordering is the same
33559 @node Tracepoint Packets
33560 @section Tracepoint Packets
33561 @cindex tracepoint packets
33562 @cindex packets, tracepoint
33564 Here we describe the packets @value{GDBN} uses to implement
33565 tracepoints (@pxref{Tracepoints}).
33569 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
33570 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
33571 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
33572 the tracepoint is disabled. @var{step} is the tracepoint's step
33573 count, and @var{pass} is its pass count. If an @samp{F} is present,
33574 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
33575 the number of bytes that the target should copy elsewhere to make room
33576 for the tracepoint. If an @samp{X} is present, it introduces a
33577 tracepoint condition, which consists of a hexadecimal length, followed
33578 by a comma and hex-encoded bytes, in a manner similar to action
33579 encodings as described below. If the trailing @samp{-} is present,
33580 further @samp{QTDP} packets will follow to specify this tracepoint's
33586 The packet was understood and carried out.
33588 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
33590 The packet was not recognized.
33593 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
33594 Define actions to be taken when a tracepoint is hit. @var{n} and
33595 @var{addr} must be the same as in the initial @samp{QTDP} packet for
33596 this tracepoint. This packet may only be sent immediately after
33597 another @samp{QTDP} packet that ended with a @samp{-}. If the
33598 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
33599 specifying more actions for this tracepoint.
33601 In the series of action packets for a given tracepoint, at most one
33602 can have an @samp{S} before its first @var{action}. If such a packet
33603 is sent, it and the following packets define ``while-stepping''
33604 actions. Any prior packets define ordinary actions --- that is, those
33605 taken when the tracepoint is first hit. If no action packet has an
33606 @samp{S}, then all the packets in the series specify ordinary
33607 tracepoint actions.
33609 The @samp{@var{action}@dots{}} portion of the packet is a series of
33610 actions, concatenated without separators. Each action has one of the
33616 Collect the registers whose bits are set in @var{mask}. @var{mask} is
33617 a hexadecimal number whose @var{i}'th bit is set if register number
33618 @var{i} should be collected. (The least significant bit is numbered
33619 zero.) Note that @var{mask} may be any number of digits long; it may
33620 not fit in a 32-bit word.
33622 @item M @var{basereg},@var{offset},@var{len}
33623 Collect @var{len} bytes of memory starting at the address in register
33624 number @var{basereg}, plus @var{offset}. If @var{basereg} is
33625 @samp{-1}, then the range has a fixed address: @var{offset} is the
33626 address of the lowest byte to collect. The @var{basereg},
33627 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
33628 values (the @samp{-1} value for @var{basereg} is a special case).
33630 @item X @var{len},@var{expr}
33631 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
33632 it directs. @var{expr} is an agent expression, as described in
33633 @ref{Agent Expressions}. Each byte of the expression is encoded as a
33634 two-digit hex number in the packet; @var{len} is the number of bytes
33635 in the expression (and thus one-half the number of hex digits in the
33640 Any number of actions may be packed together in a single @samp{QTDP}
33641 packet, as long as the packet does not exceed the maximum packet
33642 length (400 bytes, for many stubs). There may be only one @samp{R}
33643 action per tracepoint, and it must precede any @samp{M} or @samp{X}
33644 actions. Any registers referred to by @samp{M} and @samp{X} actions
33645 must be collected by a preceding @samp{R} action. (The
33646 ``while-stepping'' actions are treated as if they were attached to a
33647 separate tracepoint, as far as these restrictions are concerned.)
33652 The packet was understood and carried out.
33654 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
33656 The packet was not recognized.
33659 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
33660 @cindex @samp{QTDPsrc} packet
33661 Specify a source string of tracepoint @var{n} at address @var{addr}.
33662 This is useful to get accurate reproduction of the tracepoints
33663 originally downloaded at the beginning of the trace run. @var{type}
33664 is the name of the tracepoint part, such as @samp{cond} for the
33665 tracepoint's conditional expression (see below for a list of types), while
33666 @var{bytes} is the string, encoded in hexadecimal.
33668 @var{start} is the offset of the @var{bytes} within the overall source
33669 string, while @var{slen} is the total length of the source string.
33670 This is intended for handling source strings that are longer than will
33671 fit in a single packet.
33672 @c Add detailed example when this info is moved into a dedicated
33673 @c tracepoint descriptions section.
33675 The available string types are @samp{at} for the location,
33676 @samp{cond} for the conditional, and @samp{cmd} for an action command.
33677 @value{GDBN} sends a separate packet for each command in the action
33678 list, in the same order in which the commands are stored in the list.
33680 The target does not need to do anything with source strings except
33681 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
33684 Although this packet is optional, and @value{GDBN} will only send it
33685 if the target replies with @samp{TracepointSource} @xref{General
33686 Query Packets}, it makes both disconnected tracing and trace files
33687 much easier to use. Otherwise the user must be careful that the
33688 tracepoints in effect while looking at trace frames are identical to
33689 the ones in effect during the trace run; even a small discrepancy
33690 could cause @samp{tdump} not to work, or a particular trace frame not
33693 @item QTDV:@var{n}:@var{value}
33694 @cindex define trace state variable, remote request
33695 @cindex @samp{QTDV} packet
33696 Create a new trace state variable, number @var{n}, with an initial
33697 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
33698 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
33699 the option of not using this packet for initial values of zero; the
33700 target should simply create the trace state variables as they are
33701 mentioned in expressions.
33703 @item QTFrame:@var{n}
33704 Select the @var{n}'th tracepoint frame from the buffer, and use the
33705 register and memory contents recorded there to answer subsequent
33706 request packets from @value{GDBN}.
33708 A successful reply from the stub indicates that the stub has found the
33709 requested frame. The response is a series of parts, concatenated
33710 without separators, describing the frame we selected. Each part has
33711 one of the following forms:
33715 The selected frame is number @var{n} in the trace frame buffer;
33716 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
33717 was no frame matching the criteria in the request packet.
33720 The selected trace frame records a hit of tracepoint number @var{t};
33721 @var{t} is a hexadecimal number.
33725 @item QTFrame:pc:@var{addr}
33726 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
33727 currently selected frame whose PC is @var{addr};
33728 @var{addr} is a hexadecimal number.
33730 @item QTFrame:tdp:@var{t}
33731 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
33732 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
33733 is a hexadecimal number.
33735 @item QTFrame:range:@var{start}:@var{end}
33736 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
33737 currently selected frame whose PC is between @var{start} (inclusive)
33738 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
33741 @item QTFrame:outside:@var{start}:@var{end}
33742 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
33743 frame @emph{outside} the given range of addresses (exclusive).
33746 Begin the tracepoint experiment. Begin collecting data from
33747 tracepoint hits in the trace frame buffer. This packet supports the
33748 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
33749 instruction reply packet}).
33752 End the tracepoint experiment. Stop collecting trace frames.
33755 Clear the table of tracepoints, and empty the trace frame buffer.
33757 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
33758 Establish the given ranges of memory as ``transparent''. The stub
33759 will answer requests for these ranges from memory's current contents,
33760 if they were not collected as part of the tracepoint hit.
33762 @value{GDBN} uses this to mark read-only regions of memory, like those
33763 containing program code. Since these areas never change, they should
33764 still have the same contents they did when the tracepoint was hit, so
33765 there's no reason for the stub to refuse to provide their contents.
33767 @item QTDisconnected:@var{value}
33768 Set the choice to what to do with the tracing run when @value{GDBN}
33769 disconnects from the target. A @var{value} of 1 directs the target to
33770 continue the tracing run, while 0 tells the target to stop tracing if
33771 @value{GDBN} is no longer in the picture.
33774 Ask the stub if there is a trace experiment running right now.
33776 The reply has the form:
33780 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
33781 @var{running} is a single digit @code{1} if the trace is presently
33782 running, or @code{0} if not. It is followed by semicolon-separated
33783 optional fields that an agent may use to report additional status.
33787 If the trace is not running, the agent may report any of several
33788 explanations as one of the optional fields:
33793 No trace has been run yet.
33796 The trace was stopped by a user-originated stop command.
33799 The trace stopped because the trace buffer filled up.
33801 @item tdisconnected:0
33802 The trace stopped because @value{GDBN} disconnected from the target.
33804 @item tpasscount:@var{tpnum}
33805 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
33807 @item terror:@var{text}:@var{tpnum}
33808 The trace stopped because tracepoint @var{tpnum} had an error. The
33809 string @var{text} is available to describe the nature of the error
33810 (for instance, a divide by zero in the condition expression).
33811 @var{text} is hex encoded.
33814 The trace stopped for some other reason.
33818 Additional optional fields supply statistical and other information.
33819 Although not required, they are extremely useful for users monitoring
33820 the progress of a trace run. If a trace has stopped, and these
33821 numbers are reported, they must reflect the state of the just-stopped
33826 @item tframes:@var{n}
33827 The number of trace frames in the buffer.
33829 @item tcreated:@var{n}
33830 The total number of trace frames created during the run. This may
33831 be larger than the trace frame count, if the buffer is circular.
33833 @item tsize:@var{n}
33834 The total size of the trace buffer, in bytes.
33836 @item tfree:@var{n}
33837 The number of bytes still unused in the buffer.
33839 @item circular:@var{n}
33840 The value of the circular trace buffer flag. @code{1} means that the
33841 trace buffer is circular and old trace frames will be discarded if
33842 necessary to make room, @code{0} means that the trace buffer is linear
33845 @item disconn:@var{n}
33846 The value of the disconnected tracing flag. @code{1} means that
33847 tracing will continue after @value{GDBN} disconnects, @code{0} means
33848 that the trace run will stop.
33852 @item qTV:@var{var}
33853 @cindex trace state variable value, remote request
33854 @cindex @samp{qTV} packet
33855 Ask the stub for the value of the trace state variable number @var{var}.
33860 The value of the variable is @var{value}. This will be the current
33861 value of the variable if the user is examining a running target, or a
33862 saved value if the variable was collected in the trace frame that the
33863 user is looking at. Note that multiple requests may result in
33864 different reply values, such as when requesting values while the
33865 program is running.
33868 The value of the variable is unknown. This would occur, for example,
33869 if the user is examining a trace frame in which the requested variable
33875 These packets request data about tracepoints that are being used by
33876 the target. @value{GDBN} sends @code{qTfP} to get the first piece
33877 of data, and multiple @code{qTsP} to get additional pieces. Replies
33878 to these packets generally take the form of the @code{QTDP} packets
33879 that define tracepoints. (FIXME add detailed syntax)
33883 These packets request data about trace state variables that are on the
33884 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
33885 and multiple @code{qTsV} to get additional variables. Replies to
33886 these packets follow the syntax of the @code{QTDV} packets that define
33887 trace state variables.
33891 These packets request data about static tracepoint markers that exist
33892 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
33893 first piece of data, and multiple @code{qTsSTM} to get additional
33894 pieces. Replies to these packets take the following form:
33898 @item m @var{address}:@var{id}:@var{extra}
33900 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
33901 a comma-separated list of markers
33903 (lower case letter @samp{L}) denotes end of list.
33905 An error occurred. @var{nn} are hex digits.
33907 An empty reply indicates that the request is not supported by the
33911 @var{address} is encoded in hex.
33912 @var{id} and @var{extra} are strings encoded in hex.
33914 In response to each query, the target will reply with a list of one or
33915 more markers, separated by commas. @value{GDBN} will respond to each
33916 reply with a request for more markers (using the @samp{qs} form of the
33917 query), until the target responds with @samp{l} (lower-case ell, for
33920 @item qTSTMat:@var{address}
33921 This packets requests data about static tracepoint markers in the
33922 target program at @var{address}. Replies to this packet follow the
33923 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
33924 tracepoint markers.
33926 @item QTSave:@var{filename}
33927 This packet directs the target to save trace data to the file name
33928 @var{filename} in the target's filesystem. @var{filename} is encoded
33929 as a hex string; the interpretation of the file name (relative vs
33930 absolute, wild cards, etc) is up to the target.
33932 @item qTBuffer:@var{offset},@var{len}
33933 Return up to @var{len} bytes of the current contents of trace buffer,
33934 starting at @var{offset}. The trace buffer is treated as if it were
33935 a contiguous collection of traceframes, as per the trace file format.
33936 The reply consists as many hex-encoded bytes as the target can deliver
33937 in a packet; it is not an error to return fewer than were asked for.
33938 A reply consisting of just @code{l} indicates that no bytes are
33941 @item QTBuffer:circular:@var{value}
33942 This packet directs the target to use a circular trace buffer if
33943 @var{value} is 1, or a linear buffer if the value is 0.
33947 @subsection Relocate instruction reply packet
33948 When installing fast tracepoints in memory, the target may need to
33949 relocate the instruction currently at the tracepoint address to a
33950 different address in memory. For most instructions, a simple copy is
33951 enough, but, for example, call instructions that implicitly push the
33952 return address on the stack, and relative branches or other
33953 PC-relative instructions require offset adjustment, so that the effect
33954 of executing the instruction at a different address is the same as if
33955 it had executed in the original location.
33957 In response to several of the tracepoint packets, the target may also
33958 respond with a number of intermediate @samp{qRelocInsn} request
33959 packets before the final result packet, to have @value{GDBN} handle
33960 this relocation operation. If a packet supports this mechanism, its
33961 documentation will explicitly say so. See for example the above
33962 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
33963 format of the request is:
33966 @item qRelocInsn:@var{from};@var{to}
33968 This requests @value{GDBN} to copy instruction at address @var{from}
33969 to address @var{to}, possibly adjusted so that executing the
33970 instruction at @var{to} has the same effect as executing it at
33971 @var{from}. @value{GDBN} writes the adjusted instruction to target
33972 memory starting at @var{to}.
33977 @item qRelocInsn:@var{adjusted_size}
33978 Informs the stub the relocation is complete. @var{adjusted_size} is
33979 the length in bytes of resulting relocated instruction sequence.
33981 A badly formed request was detected, or an error was encountered while
33982 relocating the instruction.
33985 @node Host I/O Packets
33986 @section Host I/O Packets
33987 @cindex Host I/O, remote protocol
33988 @cindex file transfer, remote protocol
33990 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
33991 operations on the far side of a remote link. For example, Host I/O is
33992 used to upload and download files to a remote target with its own
33993 filesystem. Host I/O uses the same constant values and data structure
33994 layout as the target-initiated File-I/O protocol. However, the
33995 Host I/O packets are structured differently. The target-initiated
33996 protocol relies on target memory to store parameters and buffers.
33997 Host I/O requests are initiated by @value{GDBN}, and the
33998 target's memory is not involved. @xref{File-I/O Remote Protocol
33999 Extension}, for more details on the target-initiated protocol.
34001 The Host I/O request packets all encode a single operation along with
34002 its arguments. They have this format:
34006 @item vFile:@var{operation}: @var{parameter}@dots{}
34007 @var{operation} is the name of the particular request; the target
34008 should compare the entire packet name up to the second colon when checking
34009 for a supported operation. The format of @var{parameter} depends on
34010 the operation. Numbers are always passed in hexadecimal. Negative
34011 numbers have an explicit minus sign (i.e.@: two's complement is not
34012 used). Strings (e.g.@: filenames) are encoded as a series of
34013 hexadecimal bytes. The last argument to a system call may be a
34014 buffer of escaped binary data (@pxref{Binary Data}).
34018 The valid responses to Host I/O packets are:
34022 @item F @var{result} [, @var{errno}] [; @var{attachment}]
34023 @var{result} is the integer value returned by this operation, usually
34024 non-negative for success and -1 for errors. If an error has occured,
34025 @var{errno} will be included in the result. @var{errno} will have a
34026 value defined by the File-I/O protocol (@pxref{Errno Values}). For
34027 operations which return data, @var{attachment} supplies the data as a
34028 binary buffer. Binary buffers in response packets are escaped in the
34029 normal way (@pxref{Binary Data}). See the individual packet
34030 documentation for the interpretation of @var{result} and
34034 An empty response indicates that this operation is not recognized.
34038 These are the supported Host I/O operations:
34041 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
34042 Open a file at @var{pathname} and return a file descriptor for it, or
34043 return -1 if an error occurs. @var{pathname} is a string,
34044 @var{flags} is an integer indicating a mask of open flags
34045 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
34046 of mode bits to use if the file is created (@pxref{mode_t Values}).
34047 @xref{open}, for details of the open flags and mode values.
34049 @item vFile:close: @var{fd}
34050 Close the open file corresponding to @var{fd} and return 0, or
34051 -1 if an error occurs.
34053 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
34054 Read data from the open file corresponding to @var{fd}. Up to
34055 @var{count} bytes will be read from the file, starting at @var{offset}
34056 relative to the start of the file. The target may read fewer bytes;
34057 common reasons include packet size limits and an end-of-file
34058 condition. The number of bytes read is returned. Zero should only be
34059 returned for a successful read at the end of the file, or if
34060 @var{count} was zero.
34062 The data read should be returned as a binary attachment on success.
34063 If zero bytes were read, the response should include an empty binary
34064 attachment (i.e.@: a trailing semicolon). The return value is the
34065 number of target bytes read; the binary attachment may be longer if
34066 some characters were escaped.
34068 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
34069 Write @var{data} (a binary buffer) to the open file corresponding
34070 to @var{fd}. Start the write at @var{offset} from the start of the
34071 file. Unlike many @code{write} system calls, there is no
34072 separate @var{count} argument; the length of @var{data} in the
34073 packet is used. @samp{vFile:write} returns the number of bytes written,
34074 which may be shorter than the length of @var{data}, or -1 if an
34077 @item vFile:unlink: @var{pathname}
34078 Delete the file at @var{pathname} on the target. Return 0,
34079 or -1 if an error occurs. @var{pathname} is a string.
34084 @section Interrupts
34085 @cindex interrupts (remote protocol)
34087 When a program on the remote target is running, @value{GDBN} may
34088 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
34089 a @code{BREAK} followed by @code{g},
34090 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
34092 The precise meaning of @code{BREAK} is defined by the transport
34093 mechanism and may, in fact, be undefined. @value{GDBN} does not
34094 currently define a @code{BREAK} mechanism for any of the network
34095 interfaces except for TCP, in which case @value{GDBN} sends the
34096 @code{telnet} BREAK sequence.
34098 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
34099 transport mechanisms. It is represented by sending the single byte
34100 @code{0x03} without any of the usual packet overhead described in
34101 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
34102 transmitted as part of a packet, it is considered to be packet data
34103 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
34104 (@pxref{X packet}), used for binary downloads, may include an unescaped
34105 @code{0x03} as part of its packet.
34107 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
34108 When Linux kernel receives this sequence from serial port,
34109 it stops execution and connects to gdb.
34111 Stubs are not required to recognize these interrupt mechanisms and the
34112 precise meaning associated with receipt of the interrupt is
34113 implementation defined. If the target supports debugging of multiple
34114 threads and/or processes, it should attempt to interrupt all
34115 currently-executing threads and processes.
34116 If the stub is successful at interrupting the
34117 running program, it should send one of the stop
34118 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
34119 of successfully stopping the program in all-stop mode, and a stop reply
34120 for each stopped thread in non-stop mode.
34121 Interrupts received while the
34122 program is stopped are discarded.
34124 @node Notification Packets
34125 @section Notification Packets
34126 @cindex notification packets
34127 @cindex packets, notification
34129 The @value{GDBN} remote serial protocol includes @dfn{notifications},
34130 packets that require no acknowledgment. Both the GDB and the stub
34131 may send notifications (although the only notifications defined at
34132 present are sent by the stub). Notifications carry information
34133 without incurring the round-trip latency of an acknowledgment, and so
34134 are useful for low-impact communications where occasional packet loss
34137 A notification packet has the form @samp{% @var{data} #
34138 @var{checksum}}, where @var{data} is the content of the notification,
34139 and @var{checksum} is a checksum of @var{data}, computed and formatted
34140 as for ordinary @value{GDBN} packets. A notification's @var{data}
34141 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
34142 receiving a notification, the recipient sends no @samp{+} or @samp{-}
34143 to acknowledge the notification's receipt or to report its corruption.
34145 Every notification's @var{data} begins with a name, which contains no
34146 colon characters, followed by a colon character.
34148 Recipients should silently ignore corrupted notifications and
34149 notifications they do not understand. Recipients should restart
34150 timeout periods on receipt of a well-formed notification, whether or
34151 not they understand it.
34153 Senders should only send the notifications described here when this
34154 protocol description specifies that they are permitted. In the
34155 future, we may extend the protocol to permit existing notifications in
34156 new contexts; this rule helps older senders avoid confusing newer
34159 (Older versions of @value{GDBN} ignore bytes received until they see
34160 the @samp{$} byte that begins an ordinary packet, so new stubs may
34161 transmit notifications without fear of confusing older clients. There
34162 are no notifications defined for @value{GDBN} to send at the moment, but we
34163 assume that most older stubs would ignore them, as well.)
34165 The following notification packets from the stub to @value{GDBN} are
34169 @item Stop: @var{reply}
34170 Report an asynchronous stop event in non-stop mode.
34171 The @var{reply} has the form of a stop reply, as
34172 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
34173 for information on how these notifications are acknowledged by
34177 @node Remote Non-Stop
34178 @section Remote Protocol Support for Non-Stop Mode
34180 @value{GDBN}'s remote protocol supports non-stop debugging of
34181 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
34182 supports non-stop mode, it should report that to @value{GDBN} by including
34183 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
34185 @value{GDBN} typically sends a @samp{QNonStop} packet only when
34186 establishing a new connection with the stub. Entering non-stop mode
34187 does not alter the state of any currently-running threads, but targets
34188 must stop all threads in any already-attached processes when entering
34189 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
34190 probe the target state after a mode change.
34192 In non-stop mode, when an attached process encounters an event that
34193 would otherwise be reported with a stop reply, it uses the
34194 asynchronous notification mechanism (@pxref{Notification Packets}) to
34195 inform @value{GDBN}. In contrast to all-stop mode, where all threads
34196 in all processes are stopped when a stop reply is sent, in non-stop
34197 mode only the thread reporting the stop event is stopped. That is,
34198 when reporting a @samp{S} or @samp{T} response to indicate completion
34199 of a step operation, hitting a breakpoint, or a fault, only the
34200 affected thread is stopped; any other still-running threads continue
34201 to run. When reporting a @samp{W} or @samp{X} response, all running
34202 threads belonging to other attached processes continue to run.
34204 Only one stop reply notification at a time may be pending; if
34205 additional stop events occur before @value{GDBN} has acknowledged the
34206 previous notification, they must be queued by the stub for later
34207 synchronous transmission in response to @samp{vStopped} packets from
34208 @value{GDBN}. Because the notification mechanism is unreliable,
34209 the stub is permitted to resend a stop reply notification
34210 if it believes @value{GDBN} may not have received it. @value{GDBN}
34211 ignores additional stop reply notifications received before it has
34212 finished processing a previous notification and the stub has completed
34213 sending any queued stop events.
34215 Otherwise, @value{GDBN} must be prepared to receive a stop reply
34216 notification at any time. Specifically, they may appear when
34217 @value{GDBN} is not otherwise reading input from the stub, or when
34218 @value{GDBN} is expecting to read a normal synchronous response or a
34219 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
34220 Notification packets are distinct from any other communication from
34221 the stub so there is no ambiguity.
34223 After receiving a stop reply notification, @value{GDBN} shall
34224 acknowledge it by sending a @samp{vStopped} packet (@pxref{vStopped packet})
34225 as a regular, synchronous request to the stub. Such acknowledgment
34226 is not required to happen immediately, as @value{GDBN} is permitted to
34227 send other, unrelated packets to the stub first, which the stub should
34230 Upon receiving a @samp{vStopped} packet, if the stub has other queued
34231 stop events to report to @value{GDBN}, it shall respond by sending a
34232 normal stop reply response. @value{GDBN} shall then send another
34233 @samp{vStopped} packet to solicit further responses; again, it is
34234 permitted to send other, unrelated packets as well which the stub
34235 should process normally.
34237 If the stub receives a @samp{vStopped} packet and there are no
34238 additional stop events to report, the stub shall return an @samp{OK}
34239 response. At this point, if further stop events occur, the stub shall
34240 send a new stop reply notification, @value{GDBN} shall accept the
34241 notification, and the process shall be repeated.
34243 In non-stop mode, the target shall respond to the @samp{?} packet as
34244 follows. First, any incomplete stop reply notification/@samp{vStopped}
34245 sequence in progress is abandoned. The target must begin a new
34246 sequence reporting stop events for all stopped threads, whether or not
34247 it has previously reported those events to @value{GDBN}. The first
34248 stop reply is sent as a synchronous reply to the @samp{?} packet, and
34249 subsequent stop replies are sent as responses to @samp{vStopped} packets
34250 using the mechanism described above. The target must not send
34251 asynchronous stop reply notifications until the sequence is complete.
34252 If all threads are running when the target receives the @samp{?} packet,
34253 or if the target is not attached to any process, it shall respond
34256 @node Packet Acknowledgment
34257 @section Packet Acknowledgment
34259 @cindex acknowledgment, for @value{GDBN} remote
34260 @cindex packet acknowledgment, for @value{GDBN} remote
34261 By default, when either the host or the target machine receives a packet,
34262 the first response expected is an acknowledgment: either @samp{+} (to indicate
34263 the package was received correctly) or @samp{-} (to request retransmission).
34264 This mechanism allows the @value{GDBN} remote protocol to operate over
34265 unreliable transport mechanisms, such as a serial line.
34267 In cases where the transport mechanism is itself reliable (such as a pipe or
34268 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
34269 It may be desirable to disable them in that case to reduce communication
34270 overhead, or for other reasons. This can be accomplished by means of the
34271 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
34273 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
34274 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
34275 and response format still includes the normal checksum, as described in
34276 @ref{Overview}, but the checksum may be ignored by the receiver.
34278 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
34279 no-acknowledgment mode, it should report that to @value{GDBN}
34280 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
34281 @pxref{qSupported}.
34282 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
34283 disabled via the @code{set remote noack-packet off} command
34284 (@pxref{Remote Configuration}),
34285 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
34286 Only then may the stub actually turn off packet acknowledgments.
34287 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
34288 response, which can be safely ignored by the stub.
34290 Note that @code{set remote noack-packet} command only affects negotiation
34291 between @value{GDBN} and the stub when subsequent connections are made;
34292 it does not affect the protocol acknowledgment state for any current
34294 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
34295 new connection is established,
34296 there is also no protocol request to re-enable the acknowledgments
34297 for the current connection, once disabled.
34302 Example sequence of a target being re-started. Notice how the restart
34303 does not get any direct output:
34308 @emph{target restarts}
34311 <- @code{T001:1234123412341234}
34315 Example sequence of a target being stepped by a single instruction:
34318 -> @code{G1445@dots{}}
34323 <- @code{T001:1234123412341234}
34327 <- @code{1455@dots{}}
34331 @node File-I/O Remote Protocol Extension
34332 @section File-I/O Remote Protocol Extension
34333 @cindex File-I/O remote protocol extension
34336 * File-I/O Overview::
34337 * Protocol Basics::
34338 * The F Request Packet::
34339 * The F Reply Packet::
34340 * The Ctrl-C Message::
34342 * List of Supported Calls::
34343 * Protocol-specific Representation of Datatypes::
34345 * File-I/O Examples::
34348 @node File-I/O Overview
34349 @subsection File-I/O Overview
34350 @cindex file-i/o overview
34352 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
34353 target to use the host's file system and console I/O to perform various
34354 system calls. System calls on the target system are translated into a
34355 remote protocol packet to the host system, which then performs the needed
34356 actions and returns a response packet to the target system.
34357 This simulates file system operations even on targets that lack file systems.
34359 The protocol is defined to be independent of both the host and target systems.
34360 It uses its own internal representation of datatypes and values. Both
34361 @value{GDBN} and the target's @value{GDBN} stub are responsible for
34362 translating the system-dependent value representations into the internal
34363 protocol representations when data is transmitted.
34365 The communication is synchronous. A system call is possible only when
34366 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
34367 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
34368 the target is stopped to allow deterministic access to the target's
34369 memory. Therefore File-I/O is not interruptible by target signals. On
34370 the other hand, it is possible to interrupt File-I/O by a user interrupt
34371 (@samp{Ctrl-C}) within @value{GDBN}.
34373 The target's request to perform a host system call does not finish
34374 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
34375 after finishing the system call, the target returns to continuing the
34376 previous activity (continue, step). No additional continue or step
34377 request from @value{GDBN} is required.
34380 (@value{GDBP}) continue
34381 <- target requests 'system call X'
34382 target is stopped, @value{GDBN} executes system call
34383 -> @value{GDBN} returns result
34384 ... target continues, @value{GDBN} returns to wait for the target
34385 <- target hits breakpoint and sends a Txx packet
34388 The protocol only supports I/O on the console and to regular files on
34389 the host file system. Character or block special devices, pipes,
34390 named pipes, sockets or any other communication method on the host
34391 system are not supported by this protocol.
34393 File I/O is not supported in non-stop mode.
34395 @node Protocol Basics
34396 @subsection Protocol Basics
34397 @cindex protocol basics, file-i/o
34399 The File-I/O protocol uses the @code{F} packet as the request as well
34400 as reply packet. Since a File-I/O system call can only occur when
34401 @value{GDBN} is waiting for a response from the continuing or stepping target,
34402 the File-I/O request is a reply that @value{GDBN} has to expect as a result
34403 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
34404 This @code{F} packet contains all information needed to allow @value{GDBN}
34405 to call the appropriate host system call:
34409 A unique identifier for the requested system call.
34412 All parameters to the system call. Pointers are given as addresses
34413 in the target memory address space. Pointers to strings are given as
34414 pointer/length pair. Numerical values are given as they are.
34415 Numerical control flags are given in a protocol-specific representation.
34419 At this point, @value{GDBN} has to perform the following actions.
34423 If the parameters include pointer values to data needed as input to a
34424 system call, @value{GDBN} requests this data from the target with a
34425 standard @code{m} packet request. This additional communication has to be
34426 expected by the target implementation and is handled as any other @code{m}
34430 @value{GDBN} translates all value from protocol representation to host
34431 representation as needed. Datatypes are coerced into the host types.
34434 @value{GDBN} calls the system call.
34437 It then coerces datatypes back to protocol representation.
34440 If the system call is expected to return data in buffer space specified
34441 by pointer parameters to the call, the data is transmitted to the
34442 target using a @code{M} or @code{X} packet. This packet has to be expected
34443 by the target implementation and is handled as any other @code{M} or @code{X}
34448 Eventually @value{GDBN} replies with another @code{F} packet which contains all
34449 necessary information for the target to continue. This at least contains
34456 @code{errno}, if has been changed by the system call.
34463 After having done the needed type and value coercion, the target continues
34464 the latest continue or step action.
34466 @node The F Request Packet
34467 @subsection The @code{F} Request Packet
34468 @cindex file-i/o request packet
34469 @cindex @code{F} request packet
34471 The @code{F} request packet has the following format:
34474 @item F@var{call-id},@var{parameter@dots{}}
34476 @var{call-id} is the identifier to indicate the host system call to be called.
34477 This is just the name of the function.
34479 @var{parameter@dots{}} are the parameters to the system call.
34480 Parameters are hexadecimal integer values, either the actual values in case
34481 of scalar datatypes, pointers to target buffer space in case of compound
34482 datatypes and unspecified memory areas, or pointer/length pairs in case
34483 of string parameters. These are appended to the @var{call-id} as a
34484 comma-delimited list. All values are transmitted in ASCII
34485 string representation, pointer/length pairs separated by a slash.
34491 @node The F Reply Packet
34492 @subsection The @code{F} Reply Packet
34493 @cindex file-i/o reply packet
34494 @cindex @code{F} reply packet
34496 The @code{F} reply packet has the following format:
34500 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
34502 @var{retcode} is the return code of the system call as hexadecimal value.
34504 @var{errno} is the @code{errno} set by the call, in protocol-specific
34506 This parameter can be omitted if the call was successful.
34508 @var{Ctrl-C flag} is only sent if the user requested a break. In this
34509 case, @var{errno} must be sent as well, even if the call was successful.
34510 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
34517 or, if the call was interrupted before the host call has been performed:
34524 assuming 4 is the protocol-specific representation of @code{EINTR}.
34529 @node The Ctrl-C Message
34530 @subsection The @samp{Ctrl-C} Message
34531 @cindex ctrl-c message, in file-i/o protocol
34533 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
34534 reply packet (@pxref{The F Reply Packet}),
34535 the target should behave as if it had
34536 gotten a break message. The meaning for the target is ``system call
34537 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
34538 (as with a break message) and return to @value{GDBN} with a @code{T02}
34541 It's important for the target to know in which
34542 state the system call was interrupted. There are two possible cases:
34546 The system call hasn't been performed on the host yet.
34549 The system call on the host has been finished.
34553 These two states can be distinguished by the target by the value of the
34554 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
34555 call hasn't been performed. This is equivalent to the @code{EINTR} handling
34556 on POSIX systems. In any other case, the target may presume that the
34557 system call has been finished --- successfully or not --- and should behave
34558 as if the break message arrived right after the system call.
34560 @value{GDBN} must behave reliably. If the system call has not been called
34561 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
34562 @code{errno} in the packet. If the system call on the host has been finished
34563 before the user requests a break, the full action must be finished by
34564 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
34565 The @code{F} packet may only be sent when either nothing has happened
34566 or the full action has been completed.
34569 @subsection Console I/O
34570 @cindex console i/o as part of file-i/o
34572 By default and if not explicitly closed by the target system, the file
34573 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
34574 on the @value{GDBN} console is handled as any other file output operation
34575 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
34576 by @value{GDBN} so that after the target read request from file descriptor
34577 0 all following typing is buffered until either one of the following
34582 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
34584 system call is treated as finished.
34587 The user presses @key{RET}. This is treated as end of input with a trailing
34591 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
34592 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
34596 If the user has typed more characters than fit in the buffer given to
34597 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
34598 either another @code{read(0, @dots{})} is requested by the target, or debugging
34599 is stopped at the user's request.
34602 @node List of Supported Calls
34603 @subsection List of Supported Calls
34604 @cindex list of supported file-i/o calls
34621 @unnumberedsubsubsec open
34622 @cindex open, file-i/o system call
34627 int open(const char *pathname, int flags);
34628 int open(const char *pathname, int flags, mode_t mode);
34632 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
34635 @var{flags} is the bitwise @code{OR} of the following values:
34639 If the file does not exist it will be created. The host
34640 rules apply as far as file ownership and time stamps
34644 When used with @code{O_CREAT}, if the file already exists it is
34645 an error and open() fails.
34648 If the file already exists and the open mode allows
34649 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
34650 truncated to zero length.
34653 The file is opened in append mode.
34656 The file is opened for reading only.
34659 The file is opened for writing only.
34662 The file is opened for reading and writing.
34666 Other bits are silently ignored.
34670 @var{mode} is the bitwise @code{OR} of the following values:
34674 User has read permission.
34677 User has write permission.
34680 Group has read permission.
34683 Group has write permission.
34686 Others have read permission.
34689 Others have write permission.
34693 Other bits are silently ignored.
34696 @item Return value:
34697 @code{open} returns the new file descriptor or -1 if an error
34704 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
34707 @var{pathname} refers to a directory.
34710 The requested access is not allowed.
34713 @var{pathname} was too long.
34716 A directory component in @var{pathname} does not exist.
34719 @var{pathname} refers to a device, pipe, named pipe or socket.
34722 @var{pathname} refers to a file on a read-only filesystem and
34723 write access was requested.
34726 @var{pathname} is an invalid pointer value.
34729 No space on device to create the file.
34732 The process already has the maximum number of files open.
34735 The limit on the total number of files open on the system
34739 The call was interrupted by the user.
34745 @unnumberedsubsubsec close
34746 @cindex close, file-i/o system call
34755 @samp{Fclose,@var{fd}}
34757 @item Return value:
34758 @code{close} returns zero on success, or -1 if an error occurred.
34764 @var{fd} isn't a valid open file descriptor.
34767 The call was interrupted by the user.
34773 @unnumberedsubsubsec read
34774 @cindex read, file-i/o system call
34779 int read(int fd, void *buf, unsigned int count);
34783 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
34785 @item Return value:
34786 On success, the number of bytes read is returned.
34787 Zero indicates end of file. If count is zero, read
34788 returns zero as well. On error, -1 is returned.
34794 @var{fd} is not a valid file descriptor or is not open for
34798 @var{bufptr} is an invalid pointer value.
34801 The call was interrupted by the user.
34807 @unnumberedsubsubsec write
34808 @cindex write, file-i/o system call
34813 int write(int fd, const void *buf, unsigned int count);
34817 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
34819 @item Return value:
34820 On success, the number of bytes written are returned.
34821 Zero indicates nothing was written. On error, -1
34828 @var{fd} is not a valid file descriptor or is not open for
34832 @var{bufptr} is an invalid pointer value.
34835 An attempt was made to write a file that exceeds the
34836 host-specific maximum file size allowed.
34839 No space on device to write the data.
34842 The call was interrupted by the user.
34848 @unnumberedsubsubsec lseek
34849 @cindex lseek, file-i/o system call
34854 long lseek (int fd, long offset, int flag);
34858 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
34860 @var{flag} is one of:
34864 The offset is set to @var{offset} bytes.
34867 The offset is set to its current location plus @var{offset}
34871 The offset is set to the size of the file plus @var{offset}
34875 @item Return value:
34876 On success, the resulting unsigned offset in bytes from
34877 the beginning of the file is returned. Otherwise, a
34878 value of -1 is returned.
34884 @var{fd} is not a valid open file descriptor.
34887 @var{fd} is associated with the @value{GDBN} console.
34890 @var{flag} is not a proper value.
34893 The call was interrupted by the user.
34899 @unnumberedsubsubsec rename
34900 @cindex rename, file-i/o system call
34905 int rename(const char *oldpath, const char *newpath);
34909 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
34911 @item Return value:
34912 On success, zero is returned. On error, -1 is returned.
34918 @var{newpath} is an existing directory, but @var{oldpath} is not a
34922 @var{newpath} is a non-empty directory.
34925 @var{oldpath} or @var{newpath} is a directory that is in use by some
34929 An attempt was made to make a directory a subdirectory
34933 A component used as a directory in @var{oldpath} or new
34934 path is not a directory. Or @var{oldpath} is a directory
34935 and @var{newpath} exists but is not a directory.
34938 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
34941 No access to the file or the path of the file.
34945 @var{oldpath} or @var{newpath} was too long.
34948 A directory component in @var{oldpath} or @var{newpath} does not exist.
34951 The file is on a read-only filesystem.
34954 The device containing the file has no room for the new
34958 The call was interrupted by the user.
34964 @unnumberedsubsubsec unlink
34965 @cindex unlink, file-i/o system call
34970 int unlink(const char *pathname);
34974 @samp{Funlink,@var{pathnameptr}/@var{len}}
34976 @item Return value:
34977 On success, zero is returned. On error, -1 is returned.
34983 No access to the file or the path of the file.
34986 The system does not allow unlinking of directories.
34989 The file @var{pathname} cannot be unlinked because it's
34990 being used by another process.
34993 @var{pathnameptr} is an invalid pointer value.
34996 @var{pathname} was too long.
34999 A directory component in @var{pathname} does not exist.
35002 A component of the path is not a directory.
35005 The file is on a read-only filesystem.
35008 The call was interrupted by the user.
35014 @unnumberedsubsubsec stat/fstat
35015 @cindex fstat, file-i/o system call
35016 @cindex stat, file-i/o system call
35021 int stat(const char *pathname, struct stat *buf);
35022 int fstat(int fd, struct stat *buf);
35026 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
35027 @samp{Ffstat,@var{fd},@var{bufptr}}
35029 @item Return value:
35030 On success, zero is returned. On error, -1 is returned.
35036 @var{fd} is not a valid open file.
35039 A directory component in @var{pathname} does not exist or the
35040 path is an empty string.
35043 A component of the path is not a directory.
35046 @var{pathnameptr} is an invalid pointer value.
35049 No access to the file or the path of the file.
35052 @var{pathname} was too long.
35055 The call was interrupted by the user.
35061 @unnumberedsubsubsec gettimeofday
35062 @cindex gettimeofday, file-i/o system call
35067 int gettimeofday(struct timeval *tv, void *tz);
35071 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
35073 @item Return value:
35074 On success, 0 is returned, -1 otherwise.
35080 @var{tz} is a non-NULL pointer.
35083 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
35089 @unnumberedsubsubsec isatty
35090 @cindex isatty, file-i/o system call
35095 int isatty(int fd);
35099 @samp{Fisatty,@var{fd}}
35101 @item Return value:
35102 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
35108 The call was interrupted by the user.
35113 Note that the @code{isatty} call is treated as a special case: it returns
35114 1 to the target if the file descriptor is attached
35115 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
35116 would require implementing @code{ioctl} and would be more complex than
35121 @unnumberedsubsubsec system
35122 @cindex system, file-i/o system call
35127 int system(const char *command);
35131 @samp{Fsystem,@var{commandptr}/@var{len}}
35133 @item Return value:
35134 If @var{len} is zero, the return value indicates whether a shell is
35135 available. A zero return value indicates a shell is not available.
35136 For non-zero @var{len}, the value returned is -1 on error and the
35137 return status of the command otherwise. Only the exit status of the
35138 command is returned, which is extracted from the host's @code{system}
35139 return value by calling @code{WEXITSTATUS(retval)}. In case
35140 @file{/bin/sh} could not be executed, 127 is returned.
35146 The call was interrupted by the user.
35151 @value{GDBN} takes over the full task of calling the necessary host calls
35152 to perform the @code{system} call. The return value of @code{system} on
35153 the host is simplified before it's returned
35154 to the target. Any termination signal information from the child process
35155 is discarded, and the return value consists
35156 entirely of the exit status of the called command.
35158 Due to security concerns, the @code{system} call is by default refused
35159 by @value{GDBN}. The user has to allow this call explicitly with the
35160 @code{set remote system-call-allowed 1} command.
35163 @item set remote system-call-allowed
35164 @kindex set remote system-call-allowed
35165 Control whether to allow the @code{system} calls in the File I/O
35166 protocol for the remote target. The default is zero (disabled).
35168 @item show remote system-call-allowed
35169 @kindex show remote system-call-allowed
35170 Show whether the @code{system} calls are allowed in the File I/O
35174 @node Protocol-specific Representation of Datatypes
35175 @subsection Protocol-specific Representation of Datatypes
35176 @cindex protocol-specific representation of datatypes, in file-i/o protocol
35179 * Integral Datatypes::
35181 * Memory Transfer::
35186 @node Integral Datatypes
35187 @unnumberedsubsubsec Integral Datatypes
35188 @cindex integral datatypes, in file-i/o protocol
35190 The integral datatypes used in the system calls are @code{int},
35191 @code{unsigned int}, @code{long}, @code{unsigned long},
35192 @code{mode_t}, and @code{time_t}.
35194 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
35195 implemented as 32 bit values in this protocol.
35197 @code{long} and @code{unsigned long} are implemented as 64 bit types.
35199 @xref{Limits}, for corresponding MIN and MAX values (similar to those
35200 in @file{limits.h}) to allow range checking on host and target.
35202 @code{time_t} datatypes are defined as seconds since the Epoch.
35204 All integral datatypes transferred as part of a memory read or write of a
35205 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
35208 @node Pointer Values
35209 @unnumberedsubsubsec Pointer Values
35210 @cindex pointer values, in file-i/o protocol
35212 Pointers to target data are transmitted as they are. An exception
35213 is made for pointers to buffers for which the length isn't
35214 transmitted as part of the function call, namely strings. Strings
35215 are transmitted as a pointer/length pair, both as hex values, e.g.@:
35222 which is a pointer to data of length 18 bytes at position 0x1aaf.
35223 The length is defined as the full string length in bytes, including
35224 the trailing null byte. For example, the string @code{"hello world"}
35225 at address 0x123456 is transmitted as
35231 @node Memory Transfer
35232 @unnumberedsubsubsec Memory Transfer
35233 @cindex memory transfer, in file-i/o protocol
35235 Structured data which is transferred using a memory read or write (for
35236 example, a @code{struct stat}) is expected to be in a protocol-specific format
35237 with all scalar multibyte datatypes being big endian. Translation to
35238 this representation needs to be done both by the target before the @code{F}
35239 packet is sent, and by @value{GDBN} before
35240 it transfers memory to the target. Transferred pointers to structured
35241 data should point to the already-coerced data at any time.
35245 @unnumberedsubsubsec struct stat
35246 @cindex struct stat, in file-i/o protocol
35248 The buffer of type @code{struct stat} used by the target and @value{GDBN}
35249 is defined as follows:
35253 unsigned int st_dev; /* device */
35254 unsigned int st_ino; /* inode */
35255 mode_t st_mode; /* protection */
35256 unsigned int st_nlink; /* number of hard links */
35257 unsigned int st_uid; /* user ID of owner */
35258 unsigned int st_gid; /* group ID of owner */
35259 unsigned int st_rdev; /* device type (if inode device) */
35260 unsigned long st_size; /* total size, in bytes */
35261 unsigned long st_blksize; /* blocksize for filesystem I/O */
35262 unsigned long st_blocks; /* number of blocks allocated */
35263 time_t st_atime; /* time of last access */
35264 time_t st_mtime; /* time of last modification */
35265 time_t st_ctime; /* time of last change */
35269 The integral datatypes conform to the definitions given in the
35270 appropriate section (see @ref{Integral Datatypes}, for details) so this
35271 structure is of size 64 bytes.
35273 The values of several fields have a restricted meaning and/or
35279 A value of 0 represents a file, 1 the console.
35282 No valid meaning for the target. Transmitted unchanged.
35285 Valid mode bits are described in @ref{Constants}. Any other
35286 bits have currently no meaning for the target.
35291 No valid meaning for the target. Transmitted unchanged.
35296 These values have a host and file system dependent
35297 accuracy. Especially on Windows hosts, the file system may not
35298 support exact timing values.
35301 The target gets a @code{struct stat} of the above representation and is
35302 responsible for coercing it to the target representation before
35305 Note that due to size differences between the host, target, and protocol
35306 representations of @code{struct stat} members, these members could eventually
35307 get truncated on the target.
35309 @node struct timeval
35310 @unnumberedsubsubsec struct timeval
35311 @cindex struct timeval, in file-i/o protocol
35313 The buffer of type @code{struct timeval} used by the File-I/O protocol
35314 is defined as follows:
35318 time_t tv_sec; /* second */
35319 long tv_usec; /* microsecond */
35323 The integral datatypes conform to the definitions given in the
35324 appropriate section (see @ref{Integral Datatypes}, for details) so this
35325 structure is of size 8 bytes.
35328 @subsection Constants
35329 @cindex constants, in file-i/o protocol
35331 The following values are used for the constants inside of the
35332 protocol. @value{GDBN} and target are responsible for translating these
35333 values before and after the call as needed.
35344 @unnumberedsubsubsec Open Flags
35345 @cindex open flags, in file-i/o protocol
35347 All values are given in hexadecimal representation.
35359 @node mode_t Values
35360 @unnumberedsubsubsec mode_t Values
35361 @cindex mode_t values, in file-i/o protocol
35363 All values are given in octal representation.
35380 @unnumberedsubsubsec Errno Values
35381 @cindex errno values, in file-i/o protocol
35383 All values are given in decimal representation.
35408 @code{EUNKNOWN} is used as a fallback error value if a host system returns
35409 any error value not in the list of supported error numbers.
35412 @unnumberedsubsubsec Lseek Flags
35413 @cindex lseek flags, in file-i/o protocol
35422 @unnumberedsubsubsec Limits
35423 @cindex limits, in file-i/o protocol
35425 All values are given in decimal representation.
35428 INT_MIN -2147483648
35430 UINT_MAX 4294967295
35431 LONG_MIN -9223372036854775808
35432 LONG_MAX 9223372036854775807
35433 ULONG_MAX 18446744073709551615
35436 @node File-I/O Examples
35437 @subsection File-I/O Examples
35438 @cindex file-i/o examples
35440 Example sequence of a write call, file descriptor 3, buffer is at target
35441 address 0x1234, 6 bytes should be written:
35444 <- @code{Fwrite,3,1234,6}
35445 @emph{request memory read from target}
35448 @emph{return "6 bytes written"}
35452 Example sequence of a read call, file descriptor 3, buffer is at target
35453 address 0x1234, 6 bytes should be read:
35456 <- @code{Fread,3,1234,6}
35457 @emph{request memory write to target}
35458 -> @code{X1234,6:XXXXXX}
35459 @emph{return "6 bytes read"}
35463 Example sequence of a read call, call fails on the host due to invalid
35464 file descriptor (@code{EBADF}):
35467 <- @code{Fread,3,1234,6}
35471 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
35475 <- @code{Fread,3,1234,6}
35480 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
35484 <- @code{Fread,3,1234,6}
35485 -> @code{X1234,6:XXXXXX}
35489 @node Library List Format
35490 @section Library List Format
35491 @cindex library list format, remote protocol
35493 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
35494 same process as your application to manage libraries. In this case,
35495 @value{GDBN} can use the loader's symbol table and normal memory
35496 operations to maintain a list of shared libraries. On other
35497 platforms, the operating system manages loaded libraries.
35498 @value{GDBN} can not retrieve the list of currently loaded libraries
35499 through memory operations, so it uses the @samp{qXfer:libraries:read}
35500 packet (@pxref{qXfer library list read}) instead. The remote stub
35501 queries the target's operating system and reports which libraries
35504 The @samp{qXfer:libraries:read} packet returns an XML document which
35505 lists loaded libraries and their offsets. Each library has an
35506 associated name and one or more segment or section base addresses,
35507 which report where the library was loaded in memory.
35509 For the common case of libraries that are fully linked binaries, the
35510 library should have a list of segments. If the target supports
35511 dynamic linking of a relocatable object file, its library XML element
35512 should instead include a list of allocated sections. The segment or
35513 section bases are start addresses, not relocation offsets; they do not
35514 depend on the library's link-time base addresses.
35516 @value{GDBN} must be linked with the Expat library to support XML
35517 library lists. @xref{Expat}.
35519 A simple memory map, with one loaded library relocated by a single
35520 offset, looks like this:
35524 <library name="/lib/libc.so.6">
35525 <segment address="0x10000000"/>
35530 Another simple memory map, with one loaded library with three
35531 allocated sections (.text, .data, .bss), looks like this:
35535 <library name="sharedlib.o">
35536 <section address="0x10000000"/>
35537 <section address="0x20000000"/>
35538 <section address="0x30000000"/>
35543 The format of a library list is described by this DTD:
35546 <!-- library-list: Root element with versioning -->
35547 <!ELEMENT library-list (library)*>
35548 <!ATTLIST library-list version CDATA #FIXED "1.0">
35549 <!ELEMENT library (segment*, section*)>
35550 <!ATTLIST library name CDATA #REQUIRED>
35551 <!ELEMENT segment EMPTY>
35552 <!ATTLIST segment address CDATA #REQUIRED>
35553 <!ELEMENT section EMPTY>
35554 <!ATTLIST section address CDATA #REQUIRED>
35557 In addition, segments and section descriptors cannot be mixed within a
35558 single library element, and you must supply at least one segment or
35559 section for each library.
35561 @node Memory Map Format
35562 @section Memory Map Format
35563 @cindex memory map format
35565 To be able to write into flash memory, @value{GDBN} needs to obtain a
35566 memory map from the target. This section describes the format of the
35569 The memory map is obtained using the @samp{qXfer:memory-map:read}
35570 (@pxref{qXfer memory map read}) packet and is an XML document that
35571 lists memory regions.
35573 @value{GDBN} must be linked with the Expat library to support XML
35574 memory maps. @xref{Expat}.
35576 The top-level structure of the document is shown below:
35579 <?xml version="1.0"?>
35580 <!DOCTYPE memory-map
35581 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
35582 "http://sourceware.org/gdb/gdb-memory-map.dtd">
35588 Each region can be either:
35593 A region of RAM starting at @var{addr} and extending for @var{length}
35597 <memory type="ram" start="@var{addr}" length="@var{length}"/>
35602 A region of read-only memory:
35605 <memory type="rom" start="@var{addr}" length="@var{length}"/>
35610 A region of flash memory, with erasure blocks @var{blocksize}
35614 <memory type="flash" start="@var{addr}" length="@var{length}">
35615 <property name="blocksize">@var{blocksize}</property>
35621 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
35622 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
35623 packets to write to addresses in such ranges.
35625 The formal DTD for memory map format is given below:
35628 <!-- ................................................... -->
35629 <!-- Memory Map XML DTD ................................ -->
35630 <!-- File: memory-map.dtd .............................. -->
35631 <!-- .................................... .............. -->
35632 <!-- memory-map.dtd -->
35633 <!-- memory-map: Root element with versioning -->
35634 <!ELEMENT memory-map (memory | property)>
35635 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
35636 <!ELEMENT memory (property)>
35637 <!-- memory: Specifies a memory region,
35638 and its type, or device. -->
35639 <!ATTLIST memory type CDATA #REQUIRED
35640 start CDATA #REQUIRED
35641 length CDATA #REQUIRED
35642 device CDATA #IMPLIED>
35643 <!-- property: Generic attribute tag -->
35644 <!ELEMENT property (#PCDATA | property)*>
35645 <!ATTLIST property name CDATA #REQUIRED>
35648 @node Thread List Format
35649 @section Thread List Format
35650 @cindex thread list format
35652 To efficiently update the list of threads and their attributes,
35653 @value{GDBN} issues the @samp{qXfer:threads:read} packet
35654 (@pxref{qXfer threads read}) and obtains the XML document with
35655 the following structure:
35658 <?xml version="1.0"?>
35660 <thread id="id" core="0">
35661 ... description ...
35666 Each @samp{thread} element must have the @samp{id} attribute that
35667 identifies the thread (@pxref{thread-id syntax}). The
35668 @samp{core} attribute, if present, specifies which processor core
35669 the thread was last executing on. The content of the of @samp{thread}
35670 element is interpreted as human-readable auxilliary information.
35672 @include agentexpr.texi
35674 @node Trace File Format
35675 @appendix Trace File Format
35676 @cindex trace file format
35678 The trace file comes in three parts: a header, a textual description
35679 section, and a trace frame section with binary data.
35681 The header has the form @code{\x7fTRACE0\n}. The first byte is
35682 @code{0x7f} so as to indicate that the file contains binary data,
35683 while the @code{0} is a version number that may have different values
35686 The description section consists of multiple lines of @sc{ascii} text
35687 separated by newline characters (@code{0xa}). The lines may include a
35688 variety of optional descriptive or context-setting information, such
35689 as tracepoint definitions or register set size. @value{GDBN} will
35690 ignore any line that it does not recognize. An empty line marks the end
35693 @c FIXME add some specific types of data
35695 The trace frame section consists of a number of consecutive frames.
35696 Each frame begins with a two-byte tracepoint number, followed by a
35697 four-byte size giving the amount of data in the frame. The data in
35698 the frame consists of a number of blocks, each introduced by a
35699 character indicating its type (at least register, memory, and trace
35700 state variable). The data in this section is raw binary, not a
35701 hexadecimal or other encoding; its endianness matches the target's
35704 @c FIXME bi-arch may require endianness/arch info in description section
35707 @item R @var{bytes}
35708 Register block. The number and ordering of bytes matches that of a
35709 @code{g} packet in the remote protocol. Note that these are the
35710 actual bytes, in target order and @value{GDBN} register order, not a
35711 hexadecimal encoding.
35713 @item M @var{address} @var{length} @var{bytes}...
35714 Memory block. This is a contiguous block of memory, at the 8-byte
35715 address @var{address}, with a 2-byte length @var{length}, followed by
35716 @var{length} bytes.
35718 @item V @var{number} @var{value}
35719 Trace state variable block. This records the 8-byte signed value
35720 @var{value} of trace state variable numbered @var{number}.
35724 Future enhancements of the trace file format may include additional types
35727 @node Target Descriptions
35728 @appendix Target Descriptions
35729 @cindex target descriptions
35731 @strong{Warning:} target descriptions are still under active development,
35732 and the contents and format may change between @value{GDBN} releases.
35733 The format is expected to stabilize in the future.
35735 One of the challenges of using @value{GDBN} to debug embedded systems
35736 is that there are so many minor variants of each processor
35737 architecture in use. It is common practice for vendors to start with
35738 a standard processor core --- ARM, PowerPC, or MIPS, for example ---
35739 and then make changes to adapt it to a particular market niche. Some
35740 architectures have hundreds of variants, available from dozens of
35741 vendors. This leads to a number of problems:
35745 With so many different customized processors, it is difficult for
35746 the @value{GDBN} maintainers to keep up with the changes.
35748 Since individual variants may have short lifetimes or limited
35749 audiences, it may not be worthwhile to carry information about every
35750 variant in the @value{GDBN} source tree.
35752 When @value{GDBN} does support the architecture of the embedded system
35753 at hand, the task of finding the correct architecture name to give the
35754 @command{set architecture} command can be error-prone.
35757 To address these problems, the @value{GDBN} remote protocol allows a
35758 target system to not only identify itself to @value{GDBN}, but to
35759 actually describe its own features. This lets @value{GDBN} support
35760 processor variants it has never seen before --- to the extent that the
35761 descriptions are accurate, and that @value{GDBN} understands them.
35763 @value{GDBN} must be linked with the Expat library to support XML
35764 target descriptions. @xref{Expat}.
35767 * Retrieving Descriptions:: How descriptions are fetched from a target.
35768 * Target Description Format:: The contents of a target description.
35769 * Predefined Target Types:: Standard types available for target
35771 * Standard Target Features:: Features @value{GDBN} knows about.
35774 @node Retrieving Descriptions
35775 @section Retrieving Descriptions
35777 Target descriptions can be read from the target automatically, or
35778 specified by the user manually. The default behavior is to read the
35779 description from the target. @value{GDBN} retrieves it via the remote
35780 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
35781 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
35782 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
35783 XML document, of the form described in @ref{Target Description
35786 Alternatively, you can specify a file to read for the target description.
35787 If a file is set, the target will not be queried. The commands to
35788 specify a file are:
35791 @cindex set tdesc filename
35792 @item set tdesc filename @var{path}
35793 Read the target description from @var{path}.
35795 @cindex unset tdesc filename
35796 @item unset tdesc filename
35797 Do not read the XML target description from a file. @value{GDBN}
35798 will use the description supplied by the current target.
35800 @cindex show tdesc filename
35801 @item show tdesc filename
35802 Show the filename to read for a target description, if any.
35806 @node Target Description Format
35807 @section Target Description Format
35808 @cindex target descriptions, XML format
35810 A target description annex is an @uref{http://www.w3.org/XML/, XML}
35811 document which complies with the Document Type Definition provided in
35812 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
35813 means you can use generally available tools like @command{xmllint} to
35814 check that your feature descriptions are well-formed and valid.
35815 However, to help people unfamiliar with XML write descriptions for
35816 their targets, we also describe the grammar here.
35818 Target descriptions can identify the architecture of the remote target
35819 and (for some architectures) provide information about custom register
35820 sets. They can also identify the OS ABI of the remote target.
35821 @value{GDBN} can use this information to autoconfigure for your
35822 target, or to warn you if you connect to an unsupported target.
35824 Here is a simple target description:
35827 <target version="1.0">
35828 <architecture>i386:x86-64</architecture>
35833 This minimal description only says that the target uses
35834 the x86-64 architecture.
35836 A target description has the following overall form, with [ ] marking
35837 optional elements and @dots{} marking repeatable elements. The elements
35838 are explained further below.
35841 <?xml version="1.0"?>
35842 <!DOCTYPE target SYSTEM "gdb-target.dtd">
35843 <target version="1.0">
35844 @r{[}@var{architecture}@r{]}
35845 @r{[}@var{osabi}@r{]}
35846 @r{[}@var{compatible}@r{]}
35847 @r{[}@var{feature}@dots{}@r{]}
35852 The description is generally insensitive to whitespace and line
35853 breaks, under the usual common-sense rules. The XML version
35854 declaration and document type declaration can generally be omitted
35855 (@value{GDBN} does not require them), but specifying them may be
35856 useful for XML validation tools. The @samp{version} attribute for
35857 @samp{<target>} may also be omitted, but we recommend
35858 including it; if future versions of @value{GDBN} use an incompatible
35859 revision of @file{gdb-target.dtd}, they will detect and report
35860 the version mismatch.
35862 @subsection Inclusion
35863 @cindex target descriptions, inclusion
35866 @cindex <xi:include>
35869 It can sometimes be valuable to split a target description up into
35870 several different annexes, either for organizational purposes, or to
35871 share files between different possible target descriptions. You can
35872 divide a description into multiple files by replacing any element of
35873 the target description with an inclusion directive of the form:
35876 <xi:include href="@var{document}"/>
35880 When @value{GDBN} encounters an element of this form, it will retrieve
35881 the named XML @var{document}, and replace the inclusion directive with
35882 the contents of that document. If the current description was read
35883 using @samp{qXfer}, then so will be the included document;
35884 @var{document} will be interpreted as the name of an annex. If the
35885 current description was read from a file, @value{GDBN} will look for
35886 @var{document} as a file in the same directory where it found the
35887 original description.
35889 @subsection Architecture
35890 @cindex <architecture>
35892 An @samp{<architecture>} element has this form:
35895 <architecture>@var{arch}</architecture>
35898 @var{arch} is one of the architectures from the set accepted by
35899 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
35902 @cindex @code{<osabi>}
35904 This optional field was introduced in @value{GDBN} version 7.0.
35905 Previous versions of @value{GDBN} ignore it.
35907 An @samp{<osabi>} element has this form:
35910 <osabi>@var{abi-name}</osabi>
35913 @var{abi-name} is an OS ABI name from the same selection accepted by
35914 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
35916 @subsection Compatible Architecture
35917 @cindex @code{<compatible>}
35919 This optional field was introduced in @value{GDBN} version 7.0.
35920 Previous versions of @value{GDBN} ignore it.
35922 A @samp{<compatible>} element has this form:
35925 <compatible>@var{arch}</compatible>
35928 @var{arch} is one of the architectures from the set accepted by
35929 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
35931 A @samp{<compatible>} element is used to specify that the target
35932 is able to run binaries in some other than the main target architecture
35933 given by the @samp{<architecture>} element. For example, on the
35934 Cell Broadband Engine, the main architecture is @code{powerpc:common}
35935 or @code{powerpc:common64}, but the system is able to run binaries
35936 in the @code{spu} architecture as well. The way to describe this
35937 capability with @samp{<compatible>} is as follows:
35940 <architecture>powerpc:common</architecture>
35941 <compatible>spu</compatible>
35944 @subsection Features
35947 Each @samp{<feature>} describes some logical portion of the target
35948 system. Features are currently used to describe available CPU
35949 registers and the types of their contents. A @samp{<feature>} element
35953 <feature name="@var{name}">
35954 @r{[}@var{type}@dots{}@r{]}
35960 Each feature's name should be unique within the description. The name
35961 of a feature does not matter unless @value{GDBN} has some special
35962 knowledge of the contents of that feature; if it does, the feature
35963 should have its standard name. @xref{Standard Target Features}.
35967 Any register's value is a collection of bits which @value{GDBN} must
35968 interpret. The default interpretation is a two's complement integer,
35969 but other types can be requested by name in the register description.
35970 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
35971 Target Types}), and the description can define additional composite types.
35973 Each type element must have an @samp{id} attribute, which gives
35974 a unique (within the containing @samp{<feature>}) name to the type.
35975 Types must be defined before they are used.
35978 Some targets offer vector registers, which can be treated as arrays
35979 of scalar elements. These types are written as @samp{<vector>} elements,
35980 specifying the array element type, @var{type}, and the number of elements,
35984 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
35988 If a register's value is usefully viewed in multiple ways, define it
35989 with a union type containing the useful representations. The
35990 @samp{<union>} element contains one or more @samp{<field>} elements,
35991 each of which has a @var{name} and a @var{type}:
35994 <union id="@var{id}">
35995 <field name="@var{name}" type="@var{type}"/>
36001 If a register's value is composed from several separate values, define
36002 it with a structure type. There are two forms of the @samp{<struct>}
36003 element; a @samp{<struct>} element must either contain only bitfields
36004 or contain no bitfields. If the structure contains only bitfields,
36005 its total size in bytes must be specified, each bitfield must have an
36006 explicit start and end, and bitfields are automatically assigned an
36007 integer type. The field's @var{start} should be less than or
36008 equal to its @var{end}, and zero represents the least significant bit.
36011 <struct id="@var{id}" size="@var{size}">
36012 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
36017 If the structure contains no bitfields, then each field has an
36018 explicit type, and no implicit padding is added.
36021 <struct id="@var{id}">
36022 <field name="@var{name}" type="@var{type}"/>
36028 If a register's value is a series of single-bit flags, define it with
36029 a flags type. The @samp{<flags>} element has an explicit @var{size}
36030 and contains one or more @samp{<field>} elements. Each field has a
36031 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
36035 <flags id="@var{id}" size="@var{size}">
36036 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
36041 @subsection Registers
36044 Each register is represented as an element with this form:
36047 <reg name="@var{name}"
36048 bitsize="@var{size}"
36049 @r{[}regnum="@var{num}"@r{]}
36050 @r{[}save-restore="@var{save-restore}"@r{]}
36051 @r{[}type="@var{type}"@r{]}
36052 @r{[}group="@var{group}"@r{]}/>
36056 The components are as follows:
36061 The register's name; it must be unique within the target description.
36064 The register's size, in bits.
36067 The register's number. If omitted, a register's number is one greater
36068 than that of the previous register (either in the current feature or in
36069 a preceeding feature); the first register in the target description
36070 defaults to zero. This register number is used to read or write
36071 the register; e.g.@: it is used in the remote @code{p} and @code{P}
36072 packets, and registers appear in the @code{g} and @code{G} packets
36073 in order of increasing register number.
36076 Whether the register should be preserved across inferior function
36077 calls; this must be either @code{yes} or @code{no}. The default is
36078 @code{yes}, which is appropriate for most registers except for
36079 some system control registers; this is not related to the target's
36083 The type of the register. @var{type} may be a predefined type, a type
36084 defined in the current feature, or one of the special types @code{int}
36085 and @code{float}. @code{int} is an integer type of the correct size
36086 for @var{bitsize}, and @code{float} is a floating point type (in the
36087 architecture's normal floating point format) of the correct size for
36088 @var{bitsize}. The default is @code{int}.
36091 The register group to which this register belongs. @var{group} must
36092 be either @code{general}, @code{float}, or @code{vector}. If no
36093 @var{group} is specified, @value{GDBN} will not display the register
36094 in @code{info registers}.
36098 @node Predefined Target Types
36099 @section Predefined Target Types
36100 @cindex target descriptions, predefined types
36102 Type definitions in the self-description can build up composite types
36103 from basic building blocks, but can not define fundamental types. Instead,
36104 standard identifiers are provided by @value{GDBN} for the fundamental
36105 types. The currently supported types are:
36114 Signed integer types holding the specified number of bits.
36121 Unsigned integer types holding the specified number of bits.
36125 Pointers to unspecified code and data. The program counter and
36126 any dedicated return address register may be marked as code
36127 pointers; printing a code pointer converts it into a symbolic
36128 address. The stack pointer and any dedicated address registers
36129 may be marked as data pointers.
36132 Single precision IEEE floating point.
36135 Double precision IEEE floating point.
36138 The 12-byte extended precision format used by ARM FPA registers.
36141 The 10-byte extended precision format used by x87 registers.
36144 32bit @sc{eflags} register used by x86.
36147 32bit @sc{mxcsr} register used by x86.
36151 @node Standard Target Features
36152 @section Standard Target Features
36153 @cindex target descriptions, standard features
36155 A target description must contain either no registers or all the
36156 target's registers. If the description contains no registers, then
36157 @value{GDBN} will assume a default register layout, selected based on
36158 the architecture. If the description contains any registers, the
36159 default layout will not be used; the standard registers must be
36160 described in the target description, in such a way that @value{GDBN}
36161 can recognize them.
36163 This is accomplished by giving specific names to feature elements
36164 which contain standard registers. @value{GDBN} will look for features
36165 with those names and verify that they contain the expected registers;
36166 if any known feature is missing required registers, or if any required
36167 feature is missing, @value{GDBN} will reject the target
36168 description. You can add additional registers to any of the
36169 standard features --- @value{GDBN} will display them just as if
36170 they were added to an unrecognized feature.
36172 This section lists the known features and their expected contents.
36173 Sample XML documents for these features are included in the
36174 @value{GDBN} source tree, in the directory @file{gdb/features}.
36176 Names recognized by @value{GDBN} should include the name of the
36177 company or organization which selected the name, and the overall
36178 architecture to which the feature applies; so e.g.@: the feature
36179 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
36181 The names of registers are not case sensitive for the purpose
36182 of recognizing standard features, but @value{GDBN} will only display
36183 registers using the capitalization used in the description.
36190 * PowerPC Features::
36195 @subsection ARM Features
36196 @cindex target descriptions, ARM features
36198 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
36200 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
36201 @samp{lr}, @samp{pc}, and @samp{cpsr}.
36203 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
36204 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
36205 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
36208 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
36209 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
36211 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
36212 it should contain at least registers @samp{wR0} through @samp{wR15} and
36213 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
36214 @samp{wCSSF}, and @samp{wCASF} registers are optional.
36216 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
36217 should contain at least registers @samp{d0} through @samp{d15}. If
36218 they are present, @samp{d16} through @samp{d31} should also be included.
36219 @value{GDBN} will synthesize the single-precision registers from
36220 halves of the double-precision registers.
36222 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
36223 need to contain registers; it instructs @value{GDBN} to display the
36224 VFP double-precision registers as vectors and to synthesize the
36225 quad-precision registers from pairs of double-precision registers.
36226 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
36227 be present and include 32 double-precision registers.
36229 @node i386 Features
36230 @subsection i386 Features
36231 @cindex target descriptions, i386 features
36233 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
36234 targets. It should describe the following registers:
36238 @samp{eax} through @samp{edi} plus @samp{eip} for i386
36240 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
36242 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
36243 @samp{fs}, @samp{gs}
36245 @samp{st0} through @samp{st7}
36247 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
36248 @samp{foseg}, @samp{fooff} and @samp{fop}
36251 The register sets may be different, depending on the target.
36253 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
36254 describe registers:
36258 @samp{xmm0} through @samp{xmm7} for i386
36260 @samp{xmm0} through @samp{xmm15} for amd64
36265 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
36266 @samp{org.gnu.gdb.i386.sse} feature. It should
36267 describe the upper 128 bits of @sc{ymm} registers:
36271 @samp{ymm0h} through @samp{ymm7h} for i386
36273 @samp{ymm0h} through @samp{ymm15h} for amd64
36276 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
36277 describe a single register, @samp{orig_eax}.
36279 @node MIPS Features
36280 @subsection MIPS Features
36281 @cindex target descriptions, MIPS features
36283 The @samp{org.gnu.gdb.mips.cpu} feature is required for MIPS targets.
36284 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
36285 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
36288 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
36289 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
36290 registers. They may be 32-bit or 64-bit depending on the target.
36292 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
36293 it may be optional in a future version of @value{GDBN}. It should
36294 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
36295 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
36297 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
36298 contain a single register, @samp{restart}, which is used by the
36299 Linux kernel to control restartable syscalls.
36301 @node M68K Features
36302 @subsection M68K Features
36303 @cindex target descriptions, M68K features
36306 @item @samp{org.gnu.gdb.m68k.core}
36307 @itemx @samp{org.gnu.gdb.coldfire.core}
36308 @itemx @samp{org.gnu.gdb.fido.core}
36309 One of those features must be always present.
36310 The feature that is present determines which flavor of m68k is
36311 used. The feature that is present should contain registers
36312 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
36313 @samp{sp}, @samp{ps} and @samp{pc}.
36315 @item @samp{org.gnu.gdb.coldfire.fp}
36316 This feature is optional. If present, it should contain registers
36317 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
36321 @node PowerPC Features
36322 @subsection PowerPC Features
36323 @cindex target descriptions, PowerPC features
36325 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
36326 targets. It should contain registers @samp{r0} through @samp{r31},
36327 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
36328 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
36330 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
36331 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
36333 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
36334 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
36337 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
36338 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
36339 will combine these registers with the floating point registers
36340 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
36341 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
36342 through @samp{vs63}, the set of vector registers for POWER7.
36344 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
36345 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
36346 @samp{spefscr}. SPE targets should provide 32-bit registers in
36347 @samp{org.gnu.gdb.power.core} and provide the upper halves in
36348 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
36349 these to present registers @samp{ev0} through @samp{ev31} to the
36352 @node Operating System Information
36353 @appendix Operating System Information
36354 @cindex operating system information
36360 Users of @value{GDBN} often wish to obtain information about the state of
36361 the operating system running on the target---for example the list of
36362 processes, or the list of open files. This section describes the
36363 mechanism that makes it possible. This mechanism is similar to the
36364 target features mechanism (@pxref{Target Descriptions}), but focuses
36365 on a different aspect of target.
36367 Operating system information is retrived from the target via the
36368 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
36369 read}). The object name in the request should be @samp{osdata}, and
36370 the @var{annex} identifies the data to be fetched.
36373 @appendixsection Process list
36374 @cindex operating system information, process list
36376 When requesting the process list, the @var{annex} field in the
36377 @samp{qXfer} request should be @samp{processes}. The returned data is
36378 an XML document. The formal syntax of this document is defined in
36379 @file{gdb/features/osdata.dtd}.
36381 An example document is:
36384 <?xml version="1.0"?>
36385 <!DOCTYPE target SYSTEM "osdata.dtd">
36386 <osdata type="processes">
36388 <column name="pid">1</column>
36389 <column name="user">root</column>
36390 <column name="command">/sbin/init</column>
36391 <column name="cores">1,2,3</column>
36396 Each item should include a column whose name is @samp{pid}. The value
36397 of that column should identify the process on the target. The
36398 @samp{user} and @samp{command} columns are optional, and will be
36399 displayed by @value{GDBN}. The @samp{cores} column, if present,
36400 should contain a comma-separated list of cores that this process
36401 is running on. Target may provide additional columns,
36402 which @value{GDBN} currently ignores.
36406 @node GNU Free Documentation License
36407 @appendix GNU Free Documentation License
36416 % I think something like @colophon should be in texinfo. In the
36418 \long\def\colophon{\hbox to0pt{}\vfill
36419 \centerline{The body of this manual is set in}
36420 \centerline{\fontname\tenrm,}
36421 \centerline{with headings in {\bf\fontname\tenbf}}
36422 \centerline{and examples in {\tt\fontname\tentt}.}
36423 \centerline{{\it\fontname\tenit\/},}
36424 \centerline{{\bf\fontname\tenbf}, and}
36425 \centerline{{\sl\fontname\tensl\/}}
36426 \centerline{are used for emphasis.}\vfill}
36428 % Blame: doc@cygnus.com, 1991.